text: //===--- SemaExpr.cpp - Semantic Analysis for Expressions -----------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file implements semantic analysis for expressions.
  //
  //===----------------------------------------------------------------------===//
  
  #include "TreeTransform.h"
  #include "UsedDeclVisitor.h"
  #include "clang/AST/ASTConsumer.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/ASTLambda.h"
  #include "clang/AST/ASTMutationListener.h"
  #include "clang/AST/CXXInheritance.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/DeclTemplate.h"
  #include "clang/AST/EvaluatedExprVisitor.h"
  #include "clang/AST/Expr.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/AST/ExprObjC.h"
  #include "clang/AST/ExprOpenMP.h"
  #include "clang/AST/OperationKinds.h"
  #include "clang/AST/ParentMapContext.h"
  #include "clang/AST/RecursiveASTVisitor.h"
  #include "clang/AST/TypeLoc.h"
  #include "clang/Basic/Builtins.h"
  #include "clang/Basic/DiagnosticSema.h"
  #include "clang/Basic/PartialDiagnostic.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/Lex/LiteralSupport.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Sema/AnalysisBasedWarnings.h"
  #include "clang/Sema/DeclSpec.h"
  #include "clang/Sema/DelayedDiagnostic.h"
  #include "clang/Sema/Designator.h"
  #include "clang/Sema/Initialization.h"
  #include "clang/Sema/Lookup.h"
  #include "clang/Sema/Overload.h"
  #include "clang/Sema/ParsedTemplate.h"
  #include "clang/Sema/Scope.h"
  #include "clang/Sema/ScopeInfo.h"
  #include "clang/Sema/SemaFixItUtils.h"
  #include "clang/Sema/SemaInternal.h"
  #include "clang/Sema/Template.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/Support/ConvertUTF.h"
  #include "llvm/Support/SaveAndRestore.h"
  
  using namespace clang;
  using namespace sema;
  
  /// Determine whether the use of this declaration is valid, without
  /// emitting diagnostics.
  bool Sema::CanUseDecl(NamedDecl *D, bool TreatUnavailableAsInvalid) {
    // See if this is an auto-typed variable whose initializer we are parsing.
    if (ParsingInitForAutoVars.count(D))
      return false;
  
    // See if this is a deleted function.
    if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
      if (FD->isDeleted())
        return false;
  
      // If the function has a deduced return type, and we can't deduce it,
      // then we can't use it either.
      if (getLangOpts().CPlusPlus14 && FD->getReturnType()->isUndeducedType() &&
          DeduceReturnType(FD, SourceLocation(), /*Diagnose*/ false))
        return false;
  
      // See if this is an aligned allocation/deallocation function that is
      // unavailable.
      if (TreatUnavailableAsInvalid &&
          isUnavailableAlignedAllocationFunction(*FD))
        return false;
    }
  
    // See if this function is unavailable.
    if (TreatUnavailableAsInvalid && D->getAvailability() == AR_Unavailable &&
        cast<Decl>(CurContext)->getAvailability() != AR_Unavailable)
      return false;
  
    if (isa<UnresolvedUsingIfExistsDecl>(D))
      return false;
  
    return true;
  }
  
  static void DiagnoseUnusedOfDecl(Sema &S, NamedDecl *D, SourceLocation Loc) {
    // Warn if this is used but marked unused.
    if (const auto *A = D->getAttr<UnusedAttr>()) {
      // [[maybe_unused]] should not diagnose uses, but __attribute__((unused))
      // should diagnose them.
      if (A->getSemanticSpelling() != UnusedAttr::CXX11_maybe_unused &&
          A->getSemanticSpelling() != UnusedAttr::C2x_maybe_unused) {
        const Decl *DC = cast_or_null<Decl>(S.getCurObjCLexicalContext());
        if (DC && !DC->hasAttr<UnusedAttr>())
          S.Diag(Loc, diag::warn_used_but_marked_unused) << D;
      }
    }
  }
  
  /// Emit a note explaining that this function is deleted.
  void Sema::NoteDeletedFunction(FunctionDecl *Decl) {
    assert(Decl && Decl->isDeleted());
  
    if (Decl->isDefaulted()) {
      // If the method was explicitly defaulted, point at that declaration.
      if (!Decl->isImplicit())
        Diag(Decl->getLocation(), diag::note_implicitly_deleted);
  
      // Try to diagnose why this special member function was implicitly
      // deleted. This might fail, if that reason no longer applies.
      DiagnoseDeletedDefaultedFunction(Decl);
      return;
    }
  
    auto *Ctor = dyn_cast<CXXConstructorDecl>(Decl);
    if (Ctor && Ctor->isInheritingConstructor())
      return NoteDeletedInheritingConstructor(Ctor);
  
    Diag(Decl->getLocation(), diag::note_availability_specified_here)
      << Decl << 1;
  }
  
  /// Determine whether a FunctionDecl was ever declared with an
  /// explicit storage class.
  static bool hasAnyExplicitStorageClass(const FunctionDecl *D) {
    for (auto I : D->redecls()) {
      if (I->getStorageClass() != SC_None)
        return true;
    }
    return false;
  }
  
  /// Check whether we're in an extern inline function and referring to a
  /// variable or function with internal linkage (C11 6.7.4p3).
  ///
  /// This is only a warning because we used to silently accept this code, but
  /// in many cases it will not behave correctly. This is not enabled in C++ mode
  /// because the restriction language is a bit weaker (C++11 [basic.def.odr]p6)
  /// and so while there may still be user mistakes, most of the time we can't
  /// prove that there are errors.
  static void diagnoseUseOfInternalDeclInInlineFunction(Sema &S,
                                                        const NamedDecl *D,
                                                        SourceLocation Loc) {
    // This is disabled under C++; there are too many ways for this to fire in
    // contexts where the warning is a false positive, or where it is technically
    // correct but benign.
    if (S.getLangOpts().CPlusPlus)
      return;
  
    // Check if this is an inlined function or method.
    FunctionDecl *Current = S.getCurFunctionDecl();
    if (!Current)
      return;
    if (!Current->isInlined())
      return;
    if (!Current->isExternallyVisible())
      return;
  
    // Check if the decl has internal linkage.
    if (D->getFormalLinkage() != InternalLinkage)
      return;
  
    // Downgrade from ExtWarn to Extension if
    //  (1) the supposedly external inline function is in the main file,
    //      and probably won't be included anywhere else.
    //  (2) the thing we're referencing is a pure function.
    //  (3) the thing we're referencing is another inline function.
    // This last can give us false negatives, but it's better than warning on
    // wrappers for simple C library functions.
    const FunctionDecl *UsedFn = dyn_cast<FunctionDecl>(D);
    bool DowngradeWarning = S.getSourceManager().isInMainFile(Loc);
    if (!DowngradeWarning && UsedFn)
      DowngradeWarning = UsedFn->isInlined() || UsedFn->hasAttr<ConstAttr>();
  
    S.Diag(Loc, DowngradeWarning ? diag::ext_internal_in_extern_inline_quiet
                                 : diag::ext_internal_in_extern_inline)
      << /*IsVar=*/!UsedFn << D;
  
    S.MaybeSuggestAddingStaticToDecl(Current);
  
    S.Diag(D->getCanonicalDecl()->getLocation(), diag::note_entity_declared_at)
        << D;
  }
  
  void Sema::MaybeSuggestAddingStaticToDecl(const FunctionDecl *Cur) {
    const FunctionDecl *First = Cur->getFirstDecl();
  
    // Suggest "static" on the function, if possible.
    if (!hasAnyExplicitStorageClass(First)) {
      SourceLocation DeclBegin = First->getSourceRange().getBegin();
      Diag(DeclBegin, diag::note_convert_inline_to_static)
        << Cur << FixItHint::CreateInsertion(DeclBegin, "static ");
    }
  }
  
  /// Determine whether the use of this declaration is valid, and
  /// emit any corresponding diagnostics.
  ///
  /// This routine diagnoses various problems with referencing
  /// declarations that can occur when using a declaration. For example,
  /// it might warn if a deprecated or unavailable declaration is being
  /// used, or produce an error (and return true) if a C++0x deleted
  /// function is being used.
  ///
  /// \returns true if there was an error (this declaration cannot be
  /// referenced), false otherwise.
  ///
  bool Sema::DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
                               const ObjCInterfaceDecl *UnknownObjCClass,
                               bool ObjCPropertyAccess,
                               bool AvoidPartialAvailabilityChecks,
                               ObjCInterfaceDecl *ClassReceiver) {
    SourceLocation Loc = Locs.front();
    if (getLangOpts().CPlusPlus && isa<FunctionDecl>(D)) {
      // If there were any diagnostics suppressed by template argument deduction,
      // emit them now.
      auto Pos = SuppressedDiagnostics.find(D->getCanonicalDecl());
      if (Pos != SuppressedDiagnostics.end()) {
        for (const PartialDiagnosticAt &Suppressed : Pos->second)
          Diag(Suppressed.first, Suppressed.second);
  
        // Clear out the list of suppressed diagnostics, so that we don't emit
        // them again for this specialization. However, we don't obsolete this
        // entry from the table, because we want to avoid ever emitting these
        // diagnostics again.
        Pos->second.clear();
      }
  
      // C++ [basic.start.main]p3:
      //   The function 'main' shall not be used within a program.
      if (cast<FunctionDecl>(D)->isMain())
        Diag(Loc, diag::ext_main_used);
  
      diagnoseUnavailableAlignedAllocation(*cast<FunctionDecl>(D), Loc);
    }
  
    // See if this is an auto-typed variable whose initializer we are parsing.
    if (ParsingInitForAutoVars.count(D)) {
      if (isa<BindingDecl>(D)) {
        Diag(Loc, diag::err_binding_cannot_appear_in_own_initializer)
          << D->getDeclName();
      } else {
        Diag(Loc, diag::err_auto_variable_cannot_appear_in_own_initializer)
          << D->getDeclName() << cast<VarDecl>(D)->getType();
      }
      return true;
    }
  
    if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
      // See if this is a deleted function.
      if (FD->isDeleted()) {
        auto *Ctor = dyn_cast<CXXConstructorDecl>(FD);
        if (Ctor && Ctor->isInheritingConstructor())
          Diag(Loc, diag::err_deleted_inherited_ctor_use)
              << Ctor->getParent()
              << Ctor->getInheritedConstructor().getConstructor()->getParent();
        else
          Diag(Loc, diag::err_deleted_function_use);
        NoteDeletedFunction(FD);
        return true;
      }
  
      // [expr.prim.id]p4
      //   A program that refers explicitly or implicitly to a function with a
      //   trailing requires-clause whose constraint-expression is not satisfied,
      //   other than to declare it, is ill-formed. [...]
      //
      // See if this is a function with constraints that need to be satisfied.
      // Check this before deducing the return type, as it might instantiate the
      // definition.
      if (FD->getTrailingRequiresClause()) {
        ConstraintSatisfaction Satisfaction;
        if (CheckFunctionConstraints(FD, Satisfaction, Loc))
          // A diagnostic will have already been generated (non-constant
          // constraint expression, for example)
          return true;
        if (!Satisfaction.IsSatisfied) {
          Diag(Loc,
               diag::err_reference_to_function_with_unsatisfied_constraints)
              << D;
          DiagnoseUnsatisfiedConstraint(Satisfaction);
          return true;
        }
      }
  
      // If the function has a deduced return type, and we can't deduce it,
      // then we can't use it either.
      if (getLangOpts().CPlusPlus14 && FD->getReturnType()->isUndeducedType() &&
          DeduceReturnType(FD, Loc))
        return true;
  
      if (getLangOpts().CUDA && !CheckCUDACall(Loc, FD))
        return true;
  
      if (getLangOpts().SYCLIsDevice && !checkSYCLDeviceFunction(Loc, FD))
        return true;
    }
  
    if (auto *MD = dyn_cast<CXXMethodDecl>(D)) {
      // Lambdas are only default-constructible or assignable in C++2a onwards.
      if (MD->getParent()->isLambda() &&
          ((isa<CXXConstructorDecl>(MD) &&
            cast<CXXConstructorDecl>(MD)->isDefaultConstructor()) ||
           MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator())) {
        Diag(Loc, diag::warn_cxx17_compat_lambda_def_ctor_assign)
          << !isa<CXXConstructorDecl>(MD);
      }
    }
  
    auto getReferencedObjCProp = [](const NamedDecl *D) ->
                                        const ObjCPropertyDecl * {
      if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
        return MD->findPropertyDecl();
      return nullptr;
    };
    if (const ObjCPropertyDecl *ObjCPDecl = getReferencedObjCProp(D)) {
      if (diagnoseArgIndependentDiagnoseIfAttrs(ObjCPDecl, Loc))
        return true;
    } else if (diagnoseArgIndependentDiagnoseIfAttrs(D, Loc)) {
        return true;
    }
  
    // [OpenMP 4.0], 2.15 declare reduction Directive, Restrictions
    // Only the variables omp_in and omp_out are allowed in the combiner.
    // Only the variables omp_priv and omp_orig are allowed in the
    // initializer-clause.
    auto *DRD = dyn_cast<OMPDeclareReductionDecl>(CurContext);
    if (LangOpts.OpenMP && DRD && !CurContext->containsDecl(D) &&
        isa<VarDecl>(D)) {
      Diag(Loc, diag::err_omp_wrong_var_in_declare_reduction)
          << getCurFunction()->HasOMPDeclareReductionCombiner;
      Diag(D->getLocation(), diag::note_entity_declared_at) << D;
      return true;
    }
  
    // [OpenMP 5.0], 2.19.7.3. declare mapper Directive, Restrictions
    //  List-items in map clauses on this construct may only refer to the declared
    //  variable var and entities that could be referenced by a procedure defined
    //  at the same location
    if (LangOpts.OpenMP && isa<VarDecl>(D) &&
        !isOpenMPDeclareMapperVarDeclAllowed(cast<VarDecl>(D))) {
      Diag(Loc, diag::err_omp_declare_mapper_wrong_var)
          << getOpenMPDeclareMapperVarName();
      Diag(D->getLocation(), diag::note_entity_declared_at) << D;
      return true;
    }
  
    if (const auto *EmptyD = dyn_cast<UnresolvedUsingIfExistsDecl>(D)) {
      Diag(Loc, diag::err_use_of_empty_using_if_exists);
      Diag(EmptyD->getLocation(), diag::note_empty_using_if_exists_here);
      return true;
    }
  
    DiagnoseAvailabilityOfDecl(D, Locs, UnknownObjCClass, ObjCPropertyAccess,
                               AvoidPartialAvailabilityChecks, ClassReceiver);
  
    DiagnoseUnusedOfDecl(*this, D, Loc);
  
    diagnoseUseOfInternalDeclInInlineFunction(*this, D, Loc);
  
    if (auto *VD = dyn_cast<ValueDecl>(D))
      checkTypeSupport(VD->getType(), Loc, VD);
  
    if (LangOpts.SYCLIsDevice || (LangOpts.OpenMP && LangOpts.OpenMPIsDevice)) {
      if (!Context.getTargetInfo().isTLSSupported())
        if (const auto *VD = dyn_cast<VarDecl>(D))
          if (VD->getTLSKind() != VarDecl::TLS_None)
            targetDiag(*Locs.begin(), diag::err_thread_unsupported);
    }
  
    if (isa<ParmVarDecl>(D) && isa<RequiresExprBodyDecl>(D->getDeclContext()) &&
        !isUnevaluatedContext()) {
      // C++ [expr.prim.req.nested] p3
      //   A local parameter shall only appear as an unevaluated operand
      //   (Clause 8) within the constraint-expression.
      Diag(Loc, diag::err_requires_expr_parameter_referenced_in_evaluated_context)
          << D;
      Diag(D->getLocation(), diag::note_entity_declared_at) << D;
      return true;
    }
  
    return false;
  }
  
  /// DiagnoseSentinelCalls - This routine checks whether a call or
  /// message-send is to a declaration with the sentinel attribute, and
  /// if so, it checks that the requirements of the sentinel are
  /// satisfied.
  void Sema::DiagnoseSentinelCalls(NamedDecl *D, SourceLocation Loc,
                                   ArrayRef<Expr *> Args) {
    const SentinelAttr *attr = D->getAttr<SentinelAttr>();
    if (!attr)
      return;
  
    // The number of formal parameters of the declaration.
    unsigned numFormalParams;
  
    // The kind of declaration.  This is also an index into a %select in
    // the diagnostic.
    enum CalleeType { CT_Function, CT_Method, CT_Block } calleeType;
  
    if (ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
      numFormalParams = MD->param_size();
      calleeType = CT_Method;
    } else if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
      numFormalParams = FD->param_size();
      calleeType = CT_Function;
    } else if (isa<VarDecl>(D)) {
      QualType type = cast<ValueDecl>(D)->getType();
      const FunctionType *fn = nullptr;
      if (const PointerType *ptr = type->getAs<PointerType>()) {
        fn = ptr->getPointeeType()->getAs<FunctionType>();
        if (!fn) return;
        calleeType = CT_Function;
      } else if (const BlockPointerType *ptr = type->getAs<BlockPointerType>()) {
        fn = ptr->getPointeeType()->castAs<FunctionType>();
        calleeType = CT_Block;
      } else {
        return;
      }
  
      if (const FunctionProtoType *proto = dyn_cast<FunctionProtoType>(fn)) {
        numFormalParams = proto->getNumParams();
      } else {
        numFormalParams = 0;
      }
    } else {
      return;
    }
  
    // "nullPos" is the number of formal parameters at the end which
    // effectively count as part of the variadic arguments.  This is
    // useful if you would prefer to not have *any* formal parameters,
    // but the language forces you to have at least one.
    unsigned nullPos = attr->getNullPos();
    assert((nullPos == 0 || nullPos == 1) && "invalid null position on sentinel");
    numFormalParams = (nullPos > numFormalParams ? 0 : numFormalParams - nullPos);
  
    // The number of arguments which should follow the sentinel.
    unsigned numArgsAfterSentinel = attr->getSentinel();
  
    // If there aren't enough arguments for all the formal parameters,
    // the sentinel, and the args after the sentinel, complain.
    if (Args.size() < numFormalParams + numArgsAfterSentinel + 1) {
      Diag(Loc, diag::warn_not_enough_argument) << D->getDeclName();
      Diag(D->getLocation(), diag::note_sentinel_here) << int(calleeType);
      return;
    }
  
    // Otherwise, find the sentinel expression.
    Expr *sentinelExpr = Args[Args.size() - numArgsAfterSentinel - 1];
    if (!sentinelExpr) return;
    if (sentinelExpr->isValueDependent()) return;
    if (Context.isSentinelNullExpr(sentinelExpr)) return;
  
    // Pick a reasonable string to insert.  Optimistically use 'nil', 'nullptr',
    // or 'NULL' if those are actually defined in the context.  Only use
    // 'nil' for ObjC methods, where it's much more likely that the
    // variadic arguments form a list of object pointers.
    SourceLocation MissingNilLoc = getLocForEndOfToken(sentinelExpr->getEndLoc());
    std::string NullValue;
    if (calleeType == CT_Method && PP.isMacroDefined("nil"))
      NullValue = "nil";
    else if (getLangOpts().CPlusPlus11)
      NullValue = "nullptr";
    else if (PP.isMacroDefined("NULL"))
      NullValue = "NULL";
    else
      NullValue = "(void*) 0";
  
    if (MissingNilLoc.isInvalid())
      Diag(Loc, diag::warn_missing_sentinel) << int(calleeType);
    else
      Diag(MissingNilLoc, diag::warn_missing_sentinel)
        << int(calleeType)
        << FixItHint::CreateInsertion(MissingNilLoc, ", " + NullValue);
    Diag(D->getLocation(), diag::note_sentinel_here) << int(calleeType);
  }
  
  SourceRange Sema::getExprRange(Expr *E) const {
    return E ? E->getSourceRange() : SourceRange();
  }
  
  //===----------------------------------------------------------------------===//
  //  Standard Promotions and Conversions
  //===----------------------------------------------------------------------===//
  
  /// DefaultFunctionArrayConversion (C99 6.3.2.1p3, C99 6.3.2.1p4).
  ExprResult Sema::DefaultFunctionArrayConversion(Expr *E, bool Diagnose) {
    // Handle any placeholder expressions which made it here.
    if (E->hasPlaceholderType()) {
      ExprResult result = CheckPlaceholderExpr(E);
      if (result.isInvalid()) return ExprError();
      E = result.get();
    }
  
    QualType Ty = E->getType();
    assert(!Ty.isNull() && "DefaultFunctionArrayConversion - missing type");
  
    if (Ty->isFunctionType()) {
      if (auto *DRE = dyn_cast<DeclRefExpr>(E->IgnoreParenCasts()))
        if (auto *FD = dyn_cast<FunctionDecl>(DRE->getDecl()))
          if (!checkAddressOfFunctionIsAvailable(FD, Diagnose, E->getExprLoc()))
            return ExprError();
  
      E = ImpCastExprToType(E, Context.getPointerType(Ty),
                            CK_FunctionToPointerDecay).get();
    } else if (Ty->isArrayType()) {
      // In C90 mode, arrays only promote to pointers if the array expression is
      // an lvalue.  The relevant legalese is C90 6.2.2.1p3: "an lvalue that has
      // type 'array of type' is converted to an expression that has type 'pointer
      // to type'...".  In C99 this was changed to: C99 6.3.2.1p3: "an expression
      // that has type 'array of type' ...".  The relevant change is "an lvalue"
      // (C90) to "an expression" (C99).
      //
      // C++ 4.2p1:
      // An lvalue or rvalue of type "array of N T" or "array of unknown bound of
      // T" can be converted to an rvalue of type "pointer to T".
      //
      if (getLangOpts().C99 || getLangOpts().CPlusPlus || E->isLValue()) {
        ExprResult Res = ImpCastExprToType(E, Context.getArrayDecayedType(Ty),
                                           CK_ArrayToPointerDecay);
        if (Res.isInvalid())
          return ExprError();
        E = Res.get();
      }
    }
    return E;
  }
  
  static void CheckForNullPointerDereference(Sema &S, Expr *E) {
    // Check to see if we are dereferencing a null pointer.  If so,
    // and if not volatile-qualified, this is undefined behavior that the
    // optimizer will delete, so warn about it.  People sometimes try to use this
    // to get a deterministic trap and are surprised by clang's behavior.  This
    // only handles the pattern "*null", which is a very syntactic check.
    const auto *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts());
    if (UO && UO->getOpcode() == UO_Deref &&
        UO->getSubExpr()->getType()->isPointerType()) {
      const LangAS AS =
          UO->getSubExpr()->getType()->getPointeeType().getAddressSpace();
      if ((!isTargetAddressSpace(AS) ||
           (isTargetAddressSpace(AS) && toTargetAddressSpace(AS) == 0)) &&
          UO->getSubExpr()->IgnoreParenCasts()->isNullPointerConstant(
              S.Context, Expr::NPC_ValueDependentIsNotNull) &&
          !UO->getType().isVolatileQualified()) {
        S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
                              S.PDiag(diag::warn_indirection_through_null)
                                  << UO->getSubExpr()->getSourceRange());
        S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
                              S.PDiag(diag::note_indirection_through_null));
      }
    }
  }
  
  static void DiagnoseDirectIsaAccess(Sema &S, const ObjCIvarRefExpr *OIRE,
                                      SourceLocation AssignLoc,
                                      const Expr* RHS) {
    const ObjCIvarDecl *IV = OIRE->getDecl();
    if (!IV)
      return;
  
    DeclarationName MemberName = IV->getDeclName();
    IdentifierInfo *Member = MemberName.getAsIdentifierInfo();
    if (!Member || !Member->isStr("isa"))
      return;
  
    const Expr *Base = OIRE->getBase();
    QualType BaseType = Base->getType();
    if (OIRE->isArrow())
      BaseType = BaseType->getPointeeType();
    if (const ObjCObjectType *OTy = BaseType->getAs<ObjCObjectType>())
      if (ObjCInterfaceDecl *IDecl = OTy->getInterface()) {
        ObjCInterfaceDecl *ClassDeclared = nullptr;
        ObjCIvarDecl *IV = IDecl->lookupInstanceVariable(Member, ClassDeclared);
        if (!ClassDeclared->getSuperClass()
            && (*ClassDeclared->ivar_begin()) == IV) {
          if (RHS) {
            NamedDecl *ObjectSetClass =
              S.LookupSingleName(S.TUScope,
                                 &S.Context.Idents.get("object_setClass"),
                                 SourceLocation(), S.LookupOrdinaryName);
            if (ObjectSetClass) {
              SourceLocation RHSLocEnd = S.getLocForEndOfToken(RHS->getEndLoc());
              S.Diag(OIRE->getExprLoc(), diag::warn_objc_isa_assign)
                  << FixItHint::CreateInsertion(OIRE->getBeginLoc(),
                                                "object_setClass(")
                  << FixItHint::CreateReplacement(
                         SourceRange(OIRE->getOpLoc(), AssignLoc), ",")
                  << FixItHint::CreateInsertion(RHSLocEnd, ")");
            }
            else
              S.Diag(OIRE->getLocation(), diag::warn_objc_isa_assign);
          } else {
            NamedDecl *ObjectGetClass =
              S.LookupSingleName(S.TUScope,
                                 &S.Context.Idents.get("object_getClass"),
                                 SourceLocation(), S.LookupOrdinaryName);
            if (ObjectGetClass)
              S.Diag(OIRE->getExprLoc(), diag::warn_objc_isa_use)
                  << FixItHint::CreateInsertion(OIRE->getBeginLoc(),
                                                "object_getClass(")
                  << FixItHint::CreateReplacement(
                         SourceRange(OIRE->getOpLoc(), OIRE->getEndLoc()), ")");
            else
              S.Diag(OIRE->getLocation(), diag::warn_objc_isa_use);
          }
          S.Diag(IV->getLocation(), diag::note_ivar_decl);
        }
      }
  }
  
  ExprResult Sema::DefaultLvalueConversion(Expr *E) {
    // Handle any placeholder expressions which made it here.
    if (E->hasPlaceholderType()) {
      ExprResult result = CheckPlaceholderExpr(E);
      if (result.isInvalid()) return ExprError();
      E = result.get();
    }
  
    // C++ [conv.lval]p1:
    //   A glvalue of a non-function, non-array type T can be
    //   converted to a prvalue.
    if (!E->isGLValue()) return E;
  
    QualType T = E->getType();
    assert(!T.isNull() && "r-value conversion on typeless expression?");
  
    // lvalue-to-rvalue conversion cannot be applied to function or array types.
    if (T->isFunctionType() || T->isArrayType())
      return E;
  
    // We don't want to throw lvalue-to-rvalue casts on top of
    // expressions of certain types in C++.
    if (getLangOpts().CPlusPlus &&
        (E->getType() == Context.OverloadTy ||
         T->isDependentType() ||
         T->isRecordType()))
      return E;
  
    // The C standard is actually really unclear on this point, and
    // DR106 tells us what the result should be but not why.  It's
    // generally best to say that void types just doesn't undergo
    // lvalue-to-rvalue at all.  Note that expressions of unqualified
    // 'void' type are never l-values, but qualified void can be.
    if (T->isVoidType())
      return E;
  
    // OpenCL usually rejects direct accesses to values of 'half' type.
    if (getLangOpts().OpenCL &&
        !getOpenCLOptions().isAvailableOption("cl_khr_fp16", getLangOpts()) &&
        T->isHalfType()) {
      Diag(E->getExprLoc(), diag::err_opencl_half_load_store)
        << 0 << T;
      return ExprError();
    }
  
    CheckForNullPointerDereference(*this, E);
    if (const ObjCIsaExpr *OISA = dyn_cast<ObjCIsaExpr>(E->IgnoreParenCasts())) {
      NamedDecl *ObjectGetClass = LookupSingleName(TUScope,
                                       &Context.Idents.get("object_getClass"),
                                       SourceLocation(), LookupOrdinaryName);
      if (ObjectGetClass)
        Diag(E->getExprLoc(), diag::warn_objc_isa_use)
            << FixItHint::CreateInsertion(OISA->getBeginLoc(), "object_getClass(")
            << FixItHint::CreateReplacement(
                   SourceRange(OISA->getOpLoc(), OISA->getIsaMemberLoc()), ")");
      else
        Diag(E->getExprLoc(), diag::warn_objc_isa_use);
    }
    else if (const ObjCIvarRefExpr *OIRE =
              dyn_cast<ObjCIvarRefExpr>(E->IgnoreParenCasts()))
      DiagnoseDirectIsaAccess(*this, OIRE, SourceLocation(), /* Expr*/nullptr);
  
    // C++ [conv.lval]p1:
    //   [...] If T is a non-class type, the type of the prvalue is the
    //   cv-unqualified version of T. Otherwise, the type of the
    //   rvalue is T.
    //
    // C99 6.3.2.1p2:
    //   If the lvalue has qualified type, the value has the unqualified
    //   version of the type of the lvalue; otherwise, the value has the
    //   type of the lvalue.
    if (T.hasQualifiers())
      T = T.getUnqualifiedType();
  
    // Under the MS ABI, lock down the inheritance model now.
    if (T->isMemberPointerType() &&
        Context.getTargetInfo().getCXXABI().isMicrosoft())
      (void)isCompleteType(E->getExprLoc(), T);
  
    ExprResult Res = CheckLValueToRValueConversionOperand(E);
    if (Res.isInvalid())
      return Res;
    E = Res.get();
  
    // Loading a __weak object implicitly retains the value, so we need a cleanup to
    // balance that.
    if (E->getType().getObjCLifetime() == Qualifiers::OCL_Weak)
      Cleanup.setExprNeedsCleanups(true);
  
    if (E->getType().isDestructedType() == QualType::DK_nontrivial_c_struct)
      Cleanup.setExprNeedsCleanups(true);
  
    // C++ [conv.lval]p3:
    //   If T is cv std::nullptr_t, the result is a null pointer constant.
    CastKind CK = T->isNullPtrType() ? CK_NullToPointer : CK_LValueToRValue;
    Res = ImplicitCastExpr::Create(Context, T, CK, E, nullptr, VK_PRValue,
                                   CurFPFeatureOverrides());
  
    // C11 6.3.2.1p2:
    //   ... if the lvalue has atomic type, the value has the non-atomic version
    //   of the type of the lvalue ...
    if (const AtomicType *Atomic = T->getAs<AtomicType>()) {
      T = Atomic->getValueType().getUnqualifiedType();
      Res = ImplicitCastExpr::Create(Context, T, CK_AtomicToNonAtomic, Res.get(),
                                     nullptr, VK_PRValue, FPOptionsOverride());
    }
  
    return Res;
  }
  
  ExprResult Sema::DefaultFunctionArrayLvalueConversion(Expr *E, bool Diagnose) {
    ExprResult Res = DefaultFunctionArrayConversion(E, Diagnose);
    if (Res.isInvalid())
      return ExprError();
    Res = DefaultLvalueConversion(Res.get());
    if (Res.isInvalid())
      return ExprError();
    return Res;
  }
  
  /// CallExprUnaryConversions - a special case of an unary conversion
  /// performed on a function designator of a call expression.
  ExprResult Sema::CallExprUnaryConversions(Expr *E) {
    QualType Ty = E->getType();
    ExprResult Res = E;
    // Only do implicit cast for a function type, but not for a pointer
    // to function type.
    if (Ty->isFunctionType()) {
      Res = ImpCastExprToType(E, Context.getPointerType(Ty),
                              CK_FunctionToPointerDecay);
      if (Res.isInvalid())
        return ExprError();
    }
    Res = DefaultLvalueConversion(Res.get());
    if (Res.isInvalid())
      return ExprError();
    return Res.get();
  }
  
  /// UsualUnaryConversions - Performs various conversions that are common to most
  /// operators (C99 6.3). The conversions of array and function types are
  /// sometimes suppressed. For example, the array->pointer conversion doesn't
  /// apply if the array is an argument to the sizeof or address (&) operators.
  /// In these instances, this routine should *not* be called.
  ExprResult Sema::UsualUnaryConversions(Expr *E) {
    // First, convert to an r-value.
    ExprResult Res = DefaultFunctionArrayLvalueConversion(E);
    if (Res.isInvalid())
      return ExprError();
    E = Res.get();
  
    QualType Ty = E->getType();
    assert(!Ty.isNull() && "UsualUnaryConversions - missing type");
  
    LangOptions::FPEvalMethodKind EvalMethod = CurFPFeatures.getFPEvalMethod();
    if (EvalMethod != LangOptions::FEM_Source && Ty->isFloatingType() &&
        (getLangOpts().getFPEvalMethod() !=
             LangOptions::FPEvalMethodKind::FEM_UnsetOnCommandLine ||
         PP.getLastFPEvalPragmaLocation().isValid())) {
      switch (EvalMethod) {
      default:
        llvm_unreachable("Unrecognized float evaluation method");
        break;
      case LangOptions::FEM_UnsetOnCommandLine:
        llvm_unreachable("Float evaluation method should be set by now");
        break;
      case LangOptions::FEM_Double:
        if (Context.getFloatingTypeOrder(Context.DoubleTy, Ty) > 0)
          // Widen the expression to double.
          return Ty->isComplexType()
                     ? ImpCastExprToType(E,
                                         Context.getComplexType(Context.DoubleTy),
                                         CK_FloatingComplexCast)
                     : ImpCastExprToType(E, Context.DoubleTy, CK_FloatingCast);
        break;
      case LangOptions::FEM_Extended:
        if (Context.getFloatingTypeOrder(Context.LongDoubleTy, Ty) > 0)
          // Widen the expression to long double.
          return Ty->isComplexType()
                     ? ImpCastExprToType(
                           E, Context.getComplexType(Context.LongDoubleTy),
                           CK_FloatingComplexCast)
                     : ImpCastExprToType(E, Context.LongDoubleTy,
                                         CK_FloatingCast);
        break;
      }
    }
  
    // Half FP have to be promoted to float unless it is natively supported
    if (Ty->isHalfType() && !getLangOpts().NativeHalfType)
      return ImpCastExprToType(Res.get(), Context.FloatTy, CK_FloatingCast);
  
    // Try to perform integral promotions if the object has a theoretically
    // promotable type.
    if (Ty->isIntegralOrUnscopedEnumerationType()) {
      // C99 6.3.1.1p2:
      //
      //   The following may be used in an expression wherever an int or
      //   unsigned int may be used:
      //     - an object or expression with an integer type whose integer
      //       conversion rank is less than or equal to the rank of int
      //       and unsigned int.
      //     - A bit-field of type _Bool, int, signed int, or unsigned int.
      //
      //   If an int can represent all values of the original type, the
      //   value is converted to an int; otherwise, it is converted to an
      //   unsigned int. These are called the integer promotions. All
      //   other types are unchanged by the integer promotions.
  
      QualType PTy = Context.isPromotableBitField(E);
      if (!PTy.isNull()) {
        E = ImpCastExprToType(E, PTy, CK_IntegralCast).get();
        return E;
      }
      if (Ty->isPromotableIntegerType()) {
        QualType PT = Context.getPromotedIntegerType(Ty);
        E = ImpCastExprToType(E, PT, CK_IntegralCast).get();
        return E;
      }
    }
    return E;
  }
  
  /// DefaultArgumentPromotion (C99 6.5.2.2p6). Used for function calls that
  /// do not have a prototype. Arguments that have type float or __fp16
  /// are promoted to double. All other argument types are converted by
  /// UsualUnaryConversions().
  ExprResult Sema::DefaultArgumentPromotion(Expr *E) {
    QualType Ty = E->getType();
    assert(!Ty.isNull() && "DefaultArgumentPromotion - missing type");
  
    ExprResult Res = UsualUnaryConversions(E);
    if (Res.isInvalid())
      return ExprError();
    E = Res.get();
  
    // If this is a 'float'  or '__fp16' (CVR qualified or typedef)
    // promote to double.
    // Note that default argument promotion applies only to float (and
    // half/fp16); it does not apply to _Float16.
    const BuiltinType *BTy = Ty->getAs<BuiltinType>();
    if (BTy && (BTy->getKind() == BuiltinType::Half ||
                BTy->getKind() == BuiltinType::Float)) {
      if (getLangOpts().OpenCL &&
          !getOpenCLOptions().isAvailableOption("cl_khr_fp64", getLangOpts())) {
        if (BTy->getKind() == BuiltinType::Half) {
          E = ImpCastExprToType(E, Context.FloatTy, CK_FloatingCast).get();
        }
      } else {
        E = ImpCastExprToType(E, Context.DoubleTy, CK_FloatingCast).get();
      }
    }
    if (BTy &&
        getLangOpts().getExtendIntArgs() ==
            LangOptions::ExtendArgsKind::ExtendTo64 &&
        Context.getTargetInfo().supportsExtendIntArgs() && Ty->isIntegerType() &&
        Context.getTypeSizeInChars(BTy) <
            Context.getTypeSizeInChars(Context.LongLongTy)) {
      E = (Ty->isUnsignedIntegerType())
              ? ImpCastExprToType(E, Context.UnsignedLongLongTy, CK_IntegralCast)
                    .get()
              : ImpCastExprToType(E, Context.LongLongTy, CK_IntegralCast).get();
      assert(8 == Context.getTypeSizeInChars(Context.LongLongTy).getQuantity() &&
             "Unexpected typesize for LongLongTy");
    }
  
    // C++ performs lvalue-to-rvalue conversion as a default argument
    // promotion, even on class types, but note:
    //   C++11 [conv.lval]p2:
    //     When an lvalue-to-rvalue conversion occurs in an unevaluated
    //     operand or a subexpression thereof the value contained in the
    //     referenced object is not accessed. Otherwise, if the glvalue
    //     has a class type, the conversion copy-initializes a temporary
    //     of type T from the glvalue and the result of the conversion
    //     is a prvalue for the temporary.
    // FIXME: add some way to gate this entire thing for correctness in
    // potentially potentially evaluated contexts.
    if (getLangOpts().CPlusPlus && E->isGLValue() && !isUnevaluatedContext()) {
      ExprResult Temp = PerformCopyInitialization(
                         InitializedEntity::InitializeTemporary(E->getType()),
                                                  E->getExprLoc(), E);
      if (Temp.isInvalid())
        return ExprError();
      E = Temp.get();
    }
  
    return E;
  }
  
  /// Determine the degree of POD-ness for an expression.
  /// Incomplete types are considered POD, since this check can be performed
  /// when we're in an unevaluated context.
  Sema::VarArgKind Sema::isValidVarArgType(const QualType &Ty) {
    if (Ty->isIncompleteType()) {
      // C++11 [expr.call]p7:
      //   After these conversions, if the argument does not have arithmetic,
      //   enumeration, pointer, pointer to member, or class type, the program
      //   is ill-formed.
      //
      // Since we've already performed array-to-pointer and function-to-pointer
      // decay, the only such type in C++ is cv void. This also handles
      // initializer lists as variadic arguments.
      if (Ty->isVoidType())
        return VAK_Invalid;
  
      if (Ty->isObjCObjectType())
        return VAK_Invalid;
      return VAK_Valid;
    }
  
    if (Ty.isDestructedType() == QualType::DK_nontrivial_c_struct)
      return VAK_Invalid;
  
    if (Ty.isCXX98PODType(Context))
      return VAK_Valid;
  
    // C++11 [expr.call]p7:
    //   Passing a potentially-evaluated argument of class type (Clause 9)
    //   having a non-trivial copy constructor, a non-trivial move constructor,
    //   or a non-trivial destructor, with no corresponding parameter,
    //   is conditionally-supported with implementation-defined semantics.
    if (getLangOpts().CPlusPlus11 && !Ty->isDependentType())
      if (CXXRecordDecl *Record = Ty->getAsCXXRecordDecl())
        if (!Record->hasNonTrivialCopyConstructor() &&
            !Record->hasNonTrivialMoveConstructor() &&
            !Record->hasNonTrivialDestructor())
          return VAK_ValidInCXX11;
  
    if (getLangOpts().ObjCAutoRefCount && Ty->isObjCLifetimeType())
      return VAK_Valid;
  
    if (Ty->isObjCObjectType())
      return VAK_Invalid;
  
    if (getLangOpts().MSVCCompat)
      return VAK_MSVCUndefined;
  
    // FIXME: In C++11, these cases are conditionally-supported, meaning we're
    // permitted to reject them. We should consider doing so.
    return VAK_Undefined;
  }
  
  void Sema::checkVariadicArgument(const Expr *E, VariadicCallType CT) {
    // Don't allow one to pass an Objective-C interface to a vararg.
    const QualType &Ty = E->getType();
    VarArgKind VAK = isValidVarArgType(Ty);
  
    // Complain about passing non-POD types through varargs.
    switch (VAK) {
    case VAK_ValidInCXX11:
      DiagRuntimeBehavior(
          E->getBeginLoc(), nullptr,
          PDiag(diag::warn_cxx98_compat_pass_non_pod_arg_to_vararg) << Ty << CT);
      LLVM_FALLTHROUGH;
    case VAK_Valid:
      if (Ty->isRecordType()) {
        // This is unlikely to be what the user intended. If the class has a
        // 'c_str' member function, the user probably meant to call that.
        DiagRuntimeBehavior(E->getBeginLoc(), nullptr,
                            PDiag(diag::warn_pass_class_arg_to_vararg)
                                << Ty << CT << hasCStrMethod(E) << ".c_str()");
      }
      break;
  
    case VAK_Undefined:
    case VAK_MSVCUndefined:
      DiagRuntimeBehavior(E->getBeginLoc(), nullptr,
                          PDiag(diag::warn_cannot_pass_non_pod_arg_to_vararg)
                              << getLangOpts().CPlusPlus11 << Ty << CT);
      break;
  
    case VAK_Invalid:
      if (Ty.isDestructedType() == QualType::DK_nontrivial_c_struct)
        Diag(E->getBeginLoc(),
             diag::err_cannot_pass_non_trivial_c_struct_to_vararg)
            << Ty << CT;
      else if (Ty->isObjCObjectType())
        DiagRuntimeBehavior(E->getBeginLoc(), nullptr,
                            PDiag(diag::err_cannot_pass_objc_interface_to_vararg)
                                << Ty << CT);
      else
        Diag(E->getBeginLoc(), diag::err_cannot_pass_to_vararg)
            << isa<InitListExpr>(E) << Ty << CT;
      break;
    }
  }
  
  /// DefaultVariadicArgumentPromotion - Like DefaultArgumentPromotion, but
  /// will create a trap if the resulting type is not a POD type.
  ExprResult Sema::DefaultVariadicArgumentPromotion(Expr *E, VariadicCallType CT,
                                                    FunctionDecl *FDecl) {
    if (const BuiltinType *PlaceholderTy = E->getType()->getAsPlaceholderType()) {
      // Strip the unbridged-cast placeholder expression off, if applicable.
      if (PlaceholderTy->getKind() == BuiltinType::ARCUnbridgedCast &&
          (CT == VariadicMethod ||
           (FDecl && FDecl->hasAttr<CFAuditedTransferAttr>()))) {
        E = stripARCUnbridgedCast(E);
  
      // Otherwise, do normal placeholder checking.
      } else {
        ExprResult ExprRes = CheckPlaceholderExpr(E);
        if (ExprRes.isInvalid())
          return ExprError();
        E = ExprRes.get();
      }
    }
  
    ExprResult ExprRes = DefaultArgumentPromotion(E);
    if (ExprRes.isInvalid())
      return ExprError();
  
    // Copy blocks to the heap.
    if (ExprRes.get()->getType()->isBlockPointerType())
      maybeExtendBlockObject(ExprRes);
  
    E = ExprRes.get();
  
    // Diagnostics regarding non-POD argument types are
    // emitted along with format string checking in Sema::CheckFunctionCall().
    if (isValidVarArgType(E->getType()) == VAK_Undefined) {
      // Turn this into a trap.
      CXXScopeSpec SS;
      SourceLocation TemplateKWLoc;
      UnqualifiedId Name;
      Name.setIdentifier(PP.getIdentifierInfo("__builtin_trap"),
                         E->getBeginLoc());
      ExprResult TrapFn = ActOnIdExpression(TUScope, SS, TemplateKWLoc, Name,
                                            /*HasTrailingLParen=*/true,
                                            /*IsAddressOfOperand=*/false);
      if (TrapFn.isInvalid())
        return ExprError();
  
      ExprResult Call = BuildCallExpr(TUScope, TrapFn.get(), E->getBeginLoc(),
                                      None, E->getEndLoc());
      if (Call.isInvalid())
        return ExprError();
  
      ExprResult Comma =
          ActOnBinOp(TUScope, E->getBeginLoc(), tok::comma, Call.get(), E);
      if (Comma.isInvalid())
        return ExprError();
      return Comma.get();
    }
  
    if (!getLangOpts().CPlusPlus &&
        RequireCompleteType(E->getExprLoc(), E->getType(),
                            diag::err_call_incomplete_argument))
      return ExprError();
  
    return E;
  }
  
  /// Converts an integer to complex float type.  Helper function of
  /// UsualArithmeticConversions()
  ///
  /// \return false if the integer expression is an integer type and is
  /// successfully converted to the complex type.
  static bool handleIntegerToComplexFloatConversion(Sema &S, ExprResult &IntExpr,
                                                    ExprResult &ComplexExpr,
                                                    QualType IntTy,
                                                    QualType ComplexTy,
                                                    bool SkipCast) {
    if (IntTy->isComplexType() || IntTy->isRealFloatingType()) return true;
    if (SkipCast) return false;
    if (IntTy->isIntegerType()) {
      QualType fpTy = cast<ComplexType>(ComplexTy)->getElementType();
      IntExpr = S.ImpCastExprToType(IntExpr.get(), fpTy, CK_IntegralToFloating);
      IntExpr = S.ImpCastExprToType(IntExpr.get(), ComplexTy,
                                    CK_FloatingRealToComplex);
    } else {
      assert(IntTy->isComplexIntegerType());
      IntExpr = S.ImpCastExprToType(IntExpr.get(), ComplexTy,
                                    CK_IntegralComplexToFloatingComplex);
    }
    return false;
  }
  
  /// Handle arithmetic conversion with complex types.  Helper function of
  /// UsualArithmeticConversions()
  static QualType handleComplexFloatConversion(Sema &S, ExprResult &LHS,
                                               ExprResult &RHS, QualType LHSType,
                                               QualType RHSType,
                                               bool IsCompAssign) {
    // if we have an integer operand, the result is the complex type.
    if (!handleIntegerToComplexFloatConversion(S, RHS, LHS, RHSType, LHSType,
                                               /*skipCast*/false))
      return LHSType;
    if (!handleIntegerToComplexFloatConversion(S, LHS, RHS, LHSType, RHSType,
                                               /*skipCast*/IsCompAssign))
      return RHSType;
  
    // This handles complex/complex, complex/float, or float/complex.
    // When both operands are complex, the shorter operand is converted to the
    // type of the longer, and that is the type of the result. This corresponds
    // to what is done when combining two real floating-point operands.
    // The fun begins when size promotion occur across type domains.
    // From H&S 6.3.4: When one operand is complex and the other is a real
    // floating-point type, the less precise type is converted, within it's
    // real or complex domain, to the precision of the other type. For example,
    // when combining a "long double" with a "double _Complex", the
    // "double _Complex" is promoted to "long double _Complex".
  
    // Compute the rank of the two types, regardless of whether they are complex.
    int Order = S.Context.getFloatingTypeOrder(LHSType, RHSType);
  
    auto *LHSComplexType = dyn_cast<ComplexType>(LHSType);
    auto *RHSComplexType = dyn_cast<ComplexType>(RHSType);
    QualType LHSElementType =
        LHSComplexType ? LHSComplexType->getElementType() : LHSType;
    QualType RHSElementType =
        RHSComplexType ? RHSComplexType->getElementType() : RHSType;
  
    QualType ResultType = S.Context.getComplexType(LHSElementType);
    if (Order < 0) {
      // Promote the precision of the LHS if not an assignment.
      ResultType = S.Context.getComplexType(RHSElementType);
      if (!IsCompAssign) {
        if (LHSComplexType)
          LHS =
              S.ImpCastExprToType(LHS.get(), ResultType, CK_FloatingComplexCast);
        else
          LHS = S.ImpCastExprToType(LHS.get(), RHSElementType, CK_FloatingCast);
      }
    } else if (Order > 0) {
      // Promote the precision of the RHS.
      if (RHSComplexType)
        RHS = S.ImpCastExprToType(RHS.get(), ResultType, CK_FloatingComplexCast);
      else
        RHS = S.ImpCastExprToType(RHS.get(), LHSElementType, CK_FloatingCast);
    }
    return ResultType;
  }
  
  /// Handle arithmetic conversion from integer to float.  Helper function
  /// of UsualArithmeticConversions()
  static QualType handleIntToFloatConversion(Sema &S, ExprResult &FloatExpr,
                                             ExprResult &IntExpr,
                                             QualType FloatTy, QualType IntTy,
                                             bool ConvertFloat, bool ConvertInt) {
    if (IntTy->isIntegerType()) {
      if (ConvertInt)
        // Convert intExpr to the lhs floating point type.
        IntExpr = S.ImpCastExprToType(IntExpr.get(), FloatTy,
                                      CK_IntegralToFloating);
      return FloatTy;
    }
  
    // Convert both sides to the appropriate complex float.
    assert(IntTy->isComplexIntegerType());
    QualType result = S.Context.getComplexType(FloatTy);
  
    // _Complex int -> _Complex float
    if (ConvertInt)
      IntExpr = S.ImpCastExprToType(IntExpr.get(), result,
                                    CK_IntegralComplexToFloatingComplex);
  
    // float -> _Complex float
    if (ConvertFloat)
      FloatExpr = S.ImpCastExprToType(FloatExpr.get(), result,
                                      CK_FloatingRealToComplex);
  
    return result;
  }
  
  /// Handle arithmethic conversion with floating point types.  Helper
  /// function of UsualArithmeticConversions()
  static QualType handleFloatConversion(Sema &S, ExprResult &LHS,
                                        ExprResult &RHS, QualType LHSType,
                                        QualType RHSType, bool IsCompAssign) {
    bool LHSFloat = LHSType->isRealFloatingType();
    bool RHSFloat = RHSType->isRealFloatingType();
  
    // N1169 4.1.4: If one of the operands has a floating type and the other
    //              operand has a fixed-point type, the fixed-point operand
    //              is converted to the floating type [...]
    if (LHSType->isFixedPointType() || RHSType->isFixedPointType()) {
      if (LHSFloat)
        RHS = S.ImpCastExprToType(RHS.get(), LHSType, CK_FixedPointToFloating);
      else if (!IsCompAssign)
        LHS = S.ImpCastExprToType(LHS.get(), RHSType, CK_FixedPointToFloating);
      return LHSFloat ? LHSType : RHSType;
    }
  
    // If we have two real floating types, convert the smaller operand
    // to the bigger result.
    if (LHSFloat && RHSFloat) {
      int order = S.Context.getFloatingTypeOrder(LHSType, RHSType);
      if (order > 0) {
        RHS = S.ImpCastExprToType(RHS.get(), LHSType, CK_FloatingCast);
        return LHSType;
      }
  
      assert(order < 0 && "illegal float comparison");
      if (!IsCompAssign)
        LHS = S.ImpCastExprToType(LHS.get(), RHSType, CK_FloatingCast);
      return RHSType;
    }
  
    if (LHSFloat) {
      // Half FP has to be promoted to float unless it is natively supported
      if (LHSType->isHalfType() && !S.getLangOpts().NativeHalfType)
        LHSType = S.Context.FloatTy;
  
      return handleIntToFloatConversion(S, LHS, RHS, LHSType, RHSType,
                                        /*ConvertFloat=*/!IsCompAssign,
                                        /*ConvertInt=*/ true);
    }
    assert(RHSFloat);
    return handleIntToFloatConversion(S, RHS, LHS, RHSType, LHSType,
                                      /*ConvertFloat=*/ true,
                                      /*ConvertInt=*/!IsCompAssign);
  }
  
  /// Diagnose attempts to convert between __float128, __ibm128 and
  /// long double if there is no support for such conversion.
  /// Helper function of UsualArithmeticConversions().
  static bool unsupportedTypeConversion(const Sema &S, QualType LHSType,
                                        QualType RHSType) {
    // No issue if either is not a floating point type.
    if (!LHSType->isFloatingType() || !RHSType->isFloatingType())
      return false;
  
    // No issue if both have the same 128-bit float semantics.
    auto *LHSComplex = LHSType->getAs<ComplexType>();
    auto *RHSComplex = RHSType->getAs<ComplexType>();
  
    QualType LHSElem = LHSComplex ? LHSComplex->getElementType() : LHSType;
    QualType RHSElem = RHSComplex ? RHSComplex->getElementType() : RHSType;
  
    const llvm::fltSemantics &LHSSem = S.Context.getFloatTypeSemantics(LHSElem);
    const llvm::fltSemantics &RHSSem = S.Context.getFloatTypeSemantics(RHSElem);
  
    if ((&LHSSem != &llvm::APFloat::PPCDoubleDouble() ||
         &RHSSem != &llvm::APFloat::IEEEquad()) &&
        (&LHSSem != &llvm::APFloat::IEEEquad() ||
         &RHSSem != &llvm::APFloat::PPCDoubleDouble()))
      return false;
  
    return true;
  }
  
  typedef ExprResult PerformCastFn(Sema &S, Expr *operand, QualType toType);
  
  namespace {
  /// These helper callbacks are placed in an anonymous namespace to
  /// permit their use as function template parameters.
  ExprResult doIntegralCast(Sema &S, Expr *op, QualType toType) {
    return S.ImpCastExprToType(op, toType, CK_IntegralCast);
  }
  
  ExprResult doComplexIntegralCast(Sema &S, Expr *op, QualType toType) {
    return S.ImpCastExprToType(op, S.Context.getComplexType(toType),
                               CK_IntegralComplexCast);
  }
  }
  
  /// Handle integer arithmetic conversions.  Helper function of
  /// UsualArithmeticConversions()
  template <PerformCastFn doLHSCast, PerformCastFn doRHSCast>
  static QualType handleIntegerConversion(Sema &S, ExprResult &LHS,
                                          ExprResult &RHS, QualType LHSType,
                                          QualType RHSType, bool IsCompAssign) {
    // The rules for this case are in C99 6.3.1.8
    int order = S.Context.getIntegerTypeOrder(LHSType, RHSType);
    bool LHSSigned = LHSType->hasSignedIntegerRepresentation();
    bool RHSSigned = RHSType->hasSignedIntegerRepresentation();
    if (LHSSigned == RHSSigned) {
      // Same signedness; use the higher-ranked type
      if (order >= 0) {
        RHS = (*doRHSCast)(S, RHS.get(), LHSType);
        return LHSType;
      } else if (!IsCompAssign)
        LHS = (*doLHSCast)(S, LHS.get(), RHSType);
      return RHSType;
    } else if (order != (LHSSigned ? 1 : -1)) {
      // The unsigned type has greater than or equal rank to the
      // signed type, so use the unsigned type
      if (RHSSigned) {
        RHS = (*doRHSCast)(S, RHS.get(), LHSType);
        return LHSType;
      } else if (!IsCompAssign)
        LHS = (*doLHSCast)(S, LHS.get(), RHSType);
      return RHSType;
    } else if (S.Context.getIntWidth(LHSType) != S.Context.getIntWidth(RHSType)) {
      // The two types are different widths; if we are here, that
      // means the signed type is larger than the unsigned type, so
      // use the signed type.
      if (LHSSigned) {
        RHS = (*doRHSCast)(S, RHS.get(), LHSType);
        return LHSType;
      } else if (!IsCompAssign)
        LHS = (*doLHSCast)(S, LHS.get(), RHSType);
      return RHSType;
    } else {
      // The signed type is higher-ranked than the unsigned type,
      // but isn't actually any bigger (like unsigned int and long
      // on most 32-bit systems).  Use the unsigned type corresponding
      // to the signed type.
      QualType result =
        S.Context.getCorrespondingUnsignedType(LHSSigned ? LHSType : RHSType);
      RHS = (*doRHSCast)(S, RHS.get(), result);
      if (!IsCompAssign)
        LHS = (*doLHSCast)(S, LHS.get(), result);
      return result;
    }
  }
  
  /// Handle conversions with GCC complex int extension.  Helper function
  /// of UsualArithmeticConversions()
  static QualType handleComplexIntConversion(Sema &S, ExprResult &LHS,
                                             ExprResult &RHS, QualType LHSType,
                                             QualType RHSType,
                                             bool IsCompAssign) {
    const ComplexType *LHSComplexInt = LHSType->getAsComplexIntegerType();
    const ComplexType *RHSComplexInt = RHSType->getAsComplexIntegerType();
  
    if (LHSComplexInt && RHSComplexInt) {
      QualType LHSEltType = LHSComplexInt->getElementType();
      QualType RHSEltType = RHSComplexInt->getElementType();
      QualType ScalarType =
        handleIntegerConversion<doComplexIntegralCast, doComplexIntegralCast>
          (S, LHS, RHS, LHSEltType, RHSEltType, IsCompAssign);
  
      return S.Context.getComplexType(ScalarType);
    }
  
    if (LHSComplexInt) {
      QualType LHSEltType = LHSComplexInt->getElementType();
      QualType ScalarType =
        handleIntegerConversion<doComplexIntegralCast, doIntegralCast>
          (S, LHS, RHS, LHSEltType, RHSType, IsCompAssign);
      QualType ComplexType = S.Context.getComplexType(ScalarType);
      RHS = S.ImpCastExprToType(RHS.get(), ComplexType,
                                CK_IntegralRealToComplex);
  
      return ComplexType;
    }
  
    assert(RHSComplexInt);
  
    QualType RHSEltType = RHSComplexInt->getElementType();
    QualType ScalarType =
      handleIntegerConversion<doIntegralCast, doComplexIntegralCast>
        (S, LHS, RHS, LHSType, RHSEltType, IsCompAssign);
    QualType ComplexType = S.Context.getComplexType(ScalarType);
  
    if (!IsCompAssign)
      LHS = S.ImpCastExprToType(LHS.get(), ComplexType,
                                CK_IntegralRealToComplex);
    return ComplexType;
  }
  
  /// Return the rank of a given fixed point or integer type. The value itself
  /// doesn't matter, but the values must be increasing with proper increasing
  /// rank as described in N1169 4.1.1.
  static unsigned GetFixedPointRank(QualType Ty) {
    const auto *BTy = Ty->getAs<BuiltinType>();
    assert(BTy && "Expected a builtin type.");
  
    switch (BTy->getKind()) {
    case BuiltinType::ShortFract:
    case BuiltinType::UShortFract:
    case BuiltinType::SatShortFract:
    case BuiltinType::SatUShortFract:
      return 1;
    case BuiltinType::Fract:
    case BuiltinType::UFract:
    case BuiltinType::SatFract:
    case BuiltinType::SatUFract:
      return 2;
    case BuiltinType::LongFract:
    case BuiltinType::ULongFract:
    case BuiltinType::SatLongFract:
    case BuiltinType::SatULongFract:
      return 3;
    case BuiltinType::ShortAccum:
    case BuiltinType::UShortAccum:
    case BuiltinType::SatShortAccum:
    case BuiltinType::SatUShortAccum:
      return 4;
    case BuiltinType::Accum:
    case BuiltinType::UAccum:
    case BuiltinType::SatAccum:
    case BuiltinType::SatUAccum:
      return 5;
    case BuiltinType::LongAccum:
    case BuiltinType::ULongAccum:
    case BuiltinType::SatLongAccum:
    case BuiltinType::SatULongAccum:
      return 6;
    default:
      if (BTy->isInteger())
        return 0;
      llvm_unreachable("Unexpected fixed point or integer type");
    }
  }
  
  /// handleFixedPointConversion - Fixed point operations between fixed
  /// point types and integers or other fixed point types do not fall under
  /// usual arithmetic conversion since these conversions could result in loss
  /// of precsision (N1169 4.1.4). These operations should be calculated with
  /// the full precision of their result type (N1169 4.1.6.2.1).
  static QualType handleFixedPointConversion(Sema &S, QualType LHSTy,
                                             QualType RHSTy) {
    assert((LHSTy->isFixedPointType() || RHSTy->isFixedPointType()) &&
           "Expected at least one of the operands to be a fixed point type");
    assert((LHSTy->isFixedPointOrIntegerType() ||
            RHSTy->isFixedPointOrIntegerType()) &&
           "Special fixed point arithmetic operation conversions are only "
           "applied to ints or other fixed point types");
  
    // If one operand has signed fixed-point type and the other operand has
    // unsigned fixed-point type, then the unsigned fixed-point operand is
    // converted to its corresponding signed fixed-point type and the resulting
    // type is the type of the converted operand.
    if (RHSTy->isSignedFixedPointType() && LHSTy->isUnsignedFixedPointType())
      LHSTy = S.Context.getCorrespondingSignedFixedPointType(LHSTy);
    else if (RHSTy->isUnsignedFixedPointType() && LHSTy->isSignedFixedPointType())
      RHSTy = S.Context.getCorrespondingSignedFixedPointType(RHSTy);
  
    // The result type is the type with the highest rank, whereby a fixed-point
    // conversion rank is always greater than an integer conversion rank; if the
    // type of either of the operands is a saturating fixedpoint type, the result
    // type shall be the saturating fixed-point type corresponding to the type
    // with the highest rank; the resulting value is converted (taking into
    // account rounding and overflow) to the precision of the resulting type.
    // Same ranks between signed and unsigned types are resolved earlier, so both
    // types are either signed or both unsigned at this point.
    unsigned LHSTyRank = GetFixedPointRank(LHSTy);
    unsigned RHSTyRank = GetFixedPointRank(RHSTy);
  
    QualType ResultTy = LHSTyRank > RHSTyRank ? LHSTy : RHSTy;
  
    if (LHSTy->isSaturatedFixedPointType() || RHSTy->isSaturatedFixedPointType())
      ResultTy = S.Context.getCorrespondingSaturatedType(ResultTy);
  
    return ResultTy;
  }
  
  /// Check that the usual arithmetic conversions can be performed on this pair of
  /// expressions that might be of enumeration type.
  static void checkEnumArithmeticConversions(Sema &S, Expr *LHS, Expr *RHS,
                                             SourceLocation Loc,
                                             Sema::ArithConvKind ACK) {
    // C++2a [expr.arith.conv]p1:
    //   If one operand is of enumeration type and the other operand is of a
    //   different enumeration type or a floating-point type, this behavior is
    //   deprecated ([depr.arith.conv.enum]).
    //
    // Warn on this in all language modes. Produce a deprecation warning in C++20.
    // Eventually we will presumably reject these cases (in C++23 onwards?).
    QualType L = LHS->getType(), R = RHS->getType();
    bool LEnum = L->isUnscopedEnumerationType(),
         REnum = R->isUnscopedEnumerationType();
    bool IsCompAssign = ACK == Sema::ACK_CompAssign;
    if ((!IsCompAssign && LEnum && R->isFloatingType()) ||
        (REnum && L->isFloatingType())) {
      S.Diag(Loc, S.getLangOpts().CPlusPlus20
                      ? diag::warn_arith_conv_enum_float_cxx20
                      : diag::warn_arith_conv_enum_float)
          << LHS->getSourceRange() << RHS->getSourceRange()
          << (int)ACK << LEnum << L << R;
    } else if (!IsCompAssign && LEnum && REnum &&
               !S.Context.hasSameUnqualifiedType(L, R)) {
      unsigned DiagID;
      if (!L->castAs<EnumType>()->getDecl()->hasNameForLinkage() ||
          !R->castAs<EnumType>()->getDecl()->hasNameForLinkage()) {
        // If either enumeration type is unnamed, it's less likely that the
        // user cares about this, but this situation is still deprecated in
        // C++2a. Use a different warning group.
        DiagID = S.getLangOpts().CPlusPlus20
                      ? diag::warn_arith_conv_mixed_anon_enum_types_cxx20
                      : diag::warn_arith_conv_mixed_anon_enum_types;
      } else if (ACK == Sema::ACK_Conditional) {
        // Conditional expressions are separated out because they have
        // historically had a different warning flag.
        DiagID = S.getLangOpts().CPlusPlus20
                     ? diag::warn_conditional_mixed_enum_types_cxx20
                     : diag::warn_conditional_mixed_enum_types;
      } else if (ACK == Sema::ACK_Comparison) {
        // Comparison expressions are separated out because they have
        // historically had a different warning flag.
        DiagID = S.getLangOpts().CPlusPlus20
                     ? diag::warn_comparison_mixed_enum_types_cxx20
                     : diag::warn_comparison_mixed_enum_types;
      } else {
        DiagID = S.getLangOpts().CPlusPlus20
                     ? diag::warn_arith_conv_mixed_enum_types_cxx20
                     : diag::warn_arith_conv_mixed_enum_types;
      }
      S.Diag(Loc, DiagID) << LHS->getSourceRange() << RHS->getSourceRange()
                          << (int)ACK << L << R;
    }
  }
  
  /// UsualArithmeticConversions - Performs various conversions that are common to
  /// binary operators (C99 6.3.1.8). If both operands aren't arithmetic, this
  /// routine returns the first non-arithmetic type found. The client is
  /// responsible for emitting appropriate error diagnostics.
  QualType Sema::UsualArithmeticConversions(ExprResult &LHS, ExprResult &RHS,
                                            SourceLocation Loc,
                                            ArithConvKind ACK) {
    checkEnumArithmeticConversions(*this, LHS.get(), RHS.get(), Loc, ACK);
  
    if (ACK != ACK_CompAssign) {
      LHS = UsualUnaryConversions(LHS.get());
      if (LHS.isInvalid())
        return QualType();
    }
  
    RHS = UsualUnaryConversions(RHS.get());
    if (RHS.isInvalid())
      return QualType();
  
    // For conversion purposes, we ignore any qualifiers.
    // For example, "const float" and "float" are equivalent.
    QualType LHSType =
      Context.getCanonicalType(LHS.get()->getType()).getUnqualifiedType();
    QualType RHSType =
      Context.getCanonicalType(RHS.get()->getType()).getUnqualifiedType();
  
    // For conversion purposes, we ignore any atomic qualifier on the LHS.
    if (const AtomicType *AtomicLHS = LHSType->getAs<AtomicType>())
      LHSType = AtomicLHS->getValueType();
  
    // If both types are identical, no conversion is needed.
    if (LHSType == RHSType)
      return LHSType;
  
    // If either side is a non-arithmetic type (e.g. a pointer), we are done.
    // The caller can deal with this (e.g. pointer + int).
    if (!LHSType->isArithmeticType() || !RHSType->isArithmeticType())
      return QualType();
  
    // Apply unary and bitfield promotions to the LHS's type.
    QualType LHSUnpromotedType = LHSType;
    if (LHSType->isPromotableIntegerType())
      LHSType = Context.getPromotedIntegerType(LHSType);
    QualType LHSBitfieldPromoteTy = Context.isPromotableBitField(LHS.get());
    if (!LHSBitfieldPromoteTy.isNull())
      LHSType = LHSBitfieldPromoteTy;
    if (LHSType != LHSUnpromotedType && ACK != ACK_CompAssign)
      LHS = ImpCastExprToType(LHS.get(), LHSType, CK_IntegralCast);
  
    // If both types are identical, no conversion is needed.
    if (LHSType == RHSType)
      return LHSType;
  
    // At this point, we have two different arithmetic types.
  
    // Diagnose attempts to convert between __ibm128, __float128 and long double
    // where such conversions currently can't be handled.
    if (unsupportedTypeConversion(*this, LHSType, RHSType))
      return QualType();
  
    // Handle complex types first (C99 6.3.1.8p1).
    if (LHSType->isComplexType() || RHSType->isComplexType())
      return handleComplexFloatConversion(*this, LHS, RHS, LHSType, RHSType,
                                          ACK == ACK_CompAssign);
  
    // Now handle "real" floating types (i.e. float, double, long double).
    if (LHSType->isRealFloatingType() || RHSType->isRealFloatingType())
      return handleFloatConversion(*this, LHS, RHS, LHSType, RHSType,
                                   ACK == ACK_CompAssign);
  
    // Handle GCC complex int extension.
    if (LHSType->isComplexIntegerType() || RHSType->isComplexIntegerType())
      return handleComplexIntConversion(*this, LHS, RHS, LHSType, RHSType,
                                        ACK == ACK_CompAssign);
  
    if (LHSType->isFixedPointType() || RHSType->isFixedPointType())
      return handleFixedPointConversion(*this, LHSType, RHSType);
  
    // Finally, we have two differing integer types.
    return handleIntegerConversion<doIntegralCast, doIntegralCast>
             (*this, LHS, RHS, LHSType, RHSType, ACK == ACK_CompAssign);
  }
  
  //===----------------------------------------------------------------------===//
  //  Semantic Analysis for various Expression Types
  //===----------------------------------------------------------------------===//
  
  
  ExprResult
  Sema::ActOnGenericSelectionExpr(SourceLocation KeyLoc,
                                  SourceLocation DefaultLoc,
                                  SourceLocation RParenLoc,
                                  Expr *ControllingExpr,
                                  ArrayRef<ParsedType> ArgTypes,
                                  ArrayRef<Expr *> ArgExprs) {
    unsigned NumAssocs = ArgTypes.size();
    assert(NumAssocs == ArgExprs.size());
  
    TypeSourceInfo **Types = new TypeSourceInfo*[NumAssocs];
    for (unsigned i = 0; i < NumAssocs; ++i) {
      if (ArgTypes[i])
        (void) GetTypeFromParser(ArgTypes[i], &Types[i]);
      else
        Types[i] = nullptr;
    }
  
    ExprResult ER = CreateGenericSelectionExpr(KeyLoc, DefaultLoc, RParenLoc,
                                               ControllingExpr,
                                               llvm::makeArrayRef(Types, NumAssocs),
                                               ArgExprs);
    delete [] Types;
    return ER;
  }
  
  ExprResult
  Sema::CreateGenericSelectionExpr(SourceLocation KeyLoc,
                                   SourceLocation DefaultLoc,
                                   SourceLocation RParenLoc,
                                   Expr *ControllingExpr,
                                   ArrayRef<TypeSourceInfo *> Types,
                                   ArrayRef<Expr *> Exprs) {
    unsigned NumAssocs = Types.size();
    assert(NumAssocs == Exprs.size());
  
    // Decay and strip qualifiers for the controlling expression type, and handle
    // placeholder type replacement. See committee discussion from WG14 DR423.
    {
      EnterExpressionEvaluationContext Unevaluated(
          *this, Sema::ExpressionEvaluationContext::Unevaluated);
      ExprResult R = DefaultFunctionArrayLvalueConversion(ControllingExpr);
      if (R.isInvalid())
        return ExprError();
      ControllingExpr = R.get();
    }
  
    // The controlling expression is an unevaluated operand, so side effects are
    // likely unintended.
    if (!inTemplateInstantiation() &&
        ControllingExpr->HasSideEffects(Context, false))
      Diag(ControllingExpr->getExprLoc(),
           diag::warn_side_effects_unevaluated_context);
  
    bool TypeErrorFound = false,
         IsResultDependent = ControllingExpr->isTypeDependent(),
         ContainsUnexpandedParameterPack
           = ControllingExpr->containsUnexpandedParameterPack();
  
    for (unsigned i = 0; i < NumAssocs; ++i) {
      if (Exprs[i]->containsUnexpandedParameterPack())
        ContainsUnexpandedParameterPack = true;
  
      if (Types[i]) {
        if (Types[i]->getType()->containsUnexpandedParameterPack())
          ContainsUnexpandedParameterPack = true;
  
        if (Types[i]->getType()->isDependentType()) {
          IsResultDependent = true;
        } else {
          // C11 6.5.1.1p2 "The type name in a generic association shall specify a
          // complete object type other than a variably modified type."
          unsigned D = 0;
          if (Types[i]->getType()->isIncompleteType())
            D = diag::err_assoc_type_incomplete;
          else if (!Types[i]->getType()->isObjectType())
            D = diag::err_assoc_type_nonobject;
          else if (Types[i]->getType()->isVariablyModifiedType())
            D = diag::err_assoc_type_variably_modified;
  
          if (D != 0) {
            Diag(Types[i]->getTypeLoc().getBeginLoc(), D)
              << Types[i]->getTypeLoc().getSourceRange()
              << Types[i]->getType();
            TypeErrorFound = true;
          }
  
          // C11 6.5.1.1p2 "No two generic associations in the same generic
          // selection shall specify compatible types."
          for (unsigned j = i+1; j < NumAssocs; ++j)
            if (Types[j] && !Types[j]->getType()->isDependentType() &&
                Context.typesAreCompatible(Types[i]->getType(),
                                           Types[j]->getType())) {
              Diag(Types[j]->getTypeLoc().getBeginLoc(),
                   diag::err_assoc_compatible_types)
                << Types[j]->getTypeLoc().getSourceRange()
                << Types[j]->getType()
                << Types[i]->getType();
              Diag(Types[i]->getTypeLoc().getBeginLoc(),
                   diag::note_compat_assoc)
                << Types[i]->getTypeLoc().getSourceRange()
                << Types[i]->getType();
              TypeErrorFound = true;
            }
        }
      }
    }
    if (TypeErrorFound)
      return ExprError();
  
    // If we determined that the generic selection is result-dependent, don't
    // try to compute the result expression.
    if (IsResultDependent)
      return GenericSelectionExpr::Create(Context, KeyLoc, ControllingExpr, Types,
                                          Exprs, DefaultLoc, RParenLoc,
                                          ContainsUnexpandedParameterPack);
  
    SmallVector<unsigned, 1> CompatIndices;
    unsigned DefaultIndex = -1U;
    for (unsigned i = 0; i < NumAssocs; ++i) {
      if (!Types[i])
        DefaultIndex = i;
      else if (Context.typesAreCompatible(ControllingExpr->getType(),
                                          Types[i]->getType()))
        CompatIndices.push_back(i);
    }
  
    // C11 6.5.1.1p2 "The controlling expression of a generic selection shall have
    // type compatible with at most one of the types named in its generic
    // association list."
    if (CompatIndices.size() > 1) {
      // We strip parens here because the controlling expression is typically
      // parenthesized in macro definitions.
      ControllingExpr = ControllingExpr->IgnoreParens();
      Diag(ControllingExpr->getBeginLoc(), diag::err_generic_sel_multi_match)
          << ControllingExpr->getSourceRange() << ControllingExpr->getType()
          << (unsigned)CompatIndices.size();
      for (unsigned I : CompatIndices) {
        Diag(Types[I]->getTypeLoc().getBeginLoc(),
             diag::note_compat_assoc)
          << Types[I]->getTypeLoc().getSourceRange()
          << Types[I]->getType();
      }
      return ExprError();
    }
  
    // C11 6.5.1.1p2 "If a generic selection has no default generic association,
    // its controlling expression shall have type compatible with exactly one of
    // the types named in its generic association list."
    if (DefaultIndex == -1U && CompatIndices.size() == 0) {
      // We strip parens here because the controlling expression is typically
      // parenthesized in macro definitions.
      ControllingExpr = ControllingExpr->IgnoreParens();
      Diag(ControllingExpr->getBeginLoc(), diag::err_generic_sel_no_match)
          << ControllingExpr->getSourceRange() << ControllingExpr->getType();
      return ExprError();
    }
  
    // C11 6.5.1.1p3 "If a generic selection has a generic association with a
    // type name that is compatible with the type of the controlling expression,
    // then the result expression of the generic selection is the expression
    // in that generic association. Otherwise, the result expression of the
    // generic selection is the expression in the default generic association."
    unsigned ResultIndex =
      CompatIndices.size() ? CompatIndices[0] : DefaultIndex;
  
    return GenericSelectionExpr::Create(
        Context, KeyLoc, ControllingExpr, Types, Exprs, DefaultLoc, RParenLoc,
        ContainsUnexpandedParameterPack, ResultIndex);
  }
  
  /// getUDSuffixLoc - Create a SourceLocation for a ud-suffix, given the
  /// location of the token and the offset of the ud-suffix within it.
  static SourceLocation getUDSuffixLoc(Sema &S, SourceLocation TokLoc,
                                       unsigned Offset) {
    return Lexer::AdvanceToTokenCharacter(TokLoc, Offset, S.getSourceManager(),
                                          S.getLangOpts());
  }
  
  /// BuildCookedLiteralOperatorCall - A user-defined literal was found. Look up
  /// the corresponding cooked (non-raw) literal operator, and build a call to it.
  static ExprResult BuildCookedLiteralOperatorCall(Sema &S, Scope *Scope,
                                                   IdentifierInfo *UDSuffix,
                                                   SourceLocation UDSuffixLoc,
                                                   ArrayRef<Expr*> Args,
                                                   SourceLocation LitEndLoc) {
    assert(Args.size() <= 2 && "too many arguments for literal operator");
  
    QualType ArgTy[2];
    for (unsigned ArgIdx = 0; ArgIdx != Args.size(); ++ArgIdx) {
      ArgTy[ArgIdx] = Args[ArgIdx]->getType();
      if (ArgTy[ArgIdx]->isArrayType())
        ArgTy[ArgIdx] = S.Context.getArrayDecayedType(ArgTy[ArgIdx]);
    }
  
    DeclarationName OpName =
      S.Context.DeclarationNames.getCXXLiteralOperatorName(UDSuffix);
    DeclarationNameInfo OpNameInfo(OpName, UDSuffixLoc);
    OpNameInfo.setCXXLiteralOperatorNameLoc(UDSuffixLoc);
  
    LookupResult R(S, OpName, UDSuffixLoc, Sema::LookupOrdinaryName);
    if (S.LookupLiteralOperator(Scope, R, llvm::makeArrayRef(ArgTy, Args.size()),
                                /*AllowRaw*/ false, /*AllowTemplate*/ false,
                                /*AllowStringTemplatePack*/ false,
                                /*DiagnoseMissing*/ true) == Sema::LOLR_Error)
      return ExprError();
  
    return S.BuildLiteralOperatorCall(R, OpNameInfo, Args, LitEndLoc);
  }
  
  /// ActOnStringLiteral - The specified tokens were lexed as pasted string
  /// fragments (e.g. "foo" "bar" L"baz").  The result string has to handle string
  /// concatenation ([C99 5.1.1.2, translation phase #6]), so it may come from
  /// multiple tokens.  However, the common case is that StringToks points to one
  /// string.
  ///
  ExprResult
  Sema::ActOnStringLiteral(ArrayRef<Token> StringToks, Scope *UDLScope) {
    assert(!StringToks.empty() && "Must have at least one string!");
  
    StringLiteralParser Literal(StringToks, PP);
    if (Literal.hadError)
      return ExprError();
  
    SmallVector<SourceLocation, 4> StringTokLocs;
    for (const Token &Tok : StringToks)
      StringTokLocs.push_back(Tok.getLocation());
  
    QualType CharTy = Context.CharTy;
    StringLiteral::StringKind Kind = StringLiteral::Ascii;
    if (Literal.isWide()) {
      CharTy = Context.getWideCharType();
      Kind = StringLiteral::Wide;
    } else if (Literal.isUTF8()) {
      if (getLangOpts().Char8)
        CharTy = Context.Char8Ty;
      Kind = StringLiteral::UTF8;
    } else if (Literal.isUTF16()) {
      CharTy = Context.Char16Ty;
      Kind = StringLiteral::UTF16;
    } else if (Literal.isUTF32()) {
      CharTy = Context.Char32Ty;
      Kind = StringLiteral::UTF32;
    } else if (Literal.isPascal()) {
      CharTy = Context.UnsignedCharTy;
    }
  
    // Warn on initializing an array of char from a u8 string literal; this
    // becomes ill-formed in C++2a.
    if (getLangOpts().CPlusPlus && !getLangOpts().CPlusPlus20 &&
        !getLangOpts().Char8 && Kind == StringLiteral::UTF8) {
      Diag(StringTokLocs.front(), diag::warn_cxx20_compat_utf8_string);
  
      // Create removals for all 'u8' prefixes in the string literal(s). This
      // ensures C++2a compatibility (but may change the program behavior when
      // built by non-Clang compilers for which the execution character set is
      // not always UTF-8).
      auto RemovalDiag = PDiag(diag::note_cxx20_compat_utf8_string_remove_u8);
      SourceLocation RemovalDiagLoc;
      for (const Token &Tok : StringToks) {
        if (Tok.getKind() == tok::utf8_string_literal) {
          if (RemovalDiagLoc.isInvalid())
            RemovalDiagLoc = Tok.getLocation();
          RemovalDiag << FixItHint::CreateRemoval(CharSourceRange::getCharRange(
              Tok.getLocation(),
              Lexer::AdvanceToTokenCharacter(Tok.getLocation(), 2,
                                             getSourceManager(), getLangOpts())));
        }
      }
      Diag(RemovalDiagLoc, RemovalDiag);
    }
  
    QualType StrTy =
        Context.getStringLiteralArrayType(CharTy, Literal.GetNumStringChars());
  
    // Pass &StringTokLocs[0], StringTokLocs.size() to factory!
    StringLiteral *Lit = StringLiteral::Create(Context, Literal.GetString(),
                                               Kind, Literal.Pascal, StrTy,
                                               &StringTokLocs[0],
                                               StringTokLocs.size());
    if (Literal.getUDSuffix().empty())
      return Lit;
  
    // We're building a user-defined literal.
    IdentifierInfo *UDSuffix = &Context.Idents.get(Literal.getUDSuffix());
    SourceLocation UDSuffixLoc =
      getUDSuffixLoc(*this, StringTokLocs[Literal.getUDSuffixToken()],
                     Literal.getUDSuffixOffset());
  
    // Make sure we're allowed user-defined literals here.
    if (!UDLScope)
      return ExprError(Diag(UDSuffixLoc, diag::err_invalid_string_udl));
  
    // C++11 [lex.ext]p5: The literal L is treated as a call of the form
    //   operator "" X (str, len)
    QualType SizeType = Context.getSizeType();
  
    DeclarationName OpName =
      Context.DeclarationNames.getCXXLiteralOperatorName(UDSuffix);
    DeclarationNameInfo OpNameInfo(OpName, UDSuffixLoc);
    OpNameInfo.setCXXLiteralOperatorNameLoc(UDSuffixLoc);
  
    QualType ArgTy[] = {
      Context.getArrayDecayedType(StrTy), SizeType
    };
  
    LookupResult R(*this, OpName, UDSuffixLoc, LookupOrdinaryName);
    switch (LookupLiteralOperator(UDLScope, R, ArgTy,
                                  /*AllowRaw*/ false, /*AllowTemplate*/ true,
                                  /*AllowStringTemplatePack*/ true,
                                  /*DiagnoseMissing*/ true, Lit)) {
  
    case LOLR_Cooked: {
      llvm::APInt Len(Context.getIntWidth(SizeType), Literal.GetNumStringChars());
      IntegerLiteral *LenArg = IntegerLiteral::Create(Context, Len, SizeType,
                                                      StringTokLocs[0]);
      Expr *Args[] = { Lit, LenArg };
  
      return BuildLiteralOperatorCall(R, OpNameInfo, Args, StringTokLocs.back());
    }
  
    case LOLR_Template: {
      TemplateArgumentListInfo ExplicitArgs;
      TemplateArgument Arg(Lit);
      TemplateArgumentLocInfo ArgInfo(Lit);
      ExplicitArgs.addArgument(TemplateArgumentLoc(Arg, ArgInfo));
      return BuildLiteralOperatorCall(R, OpNameInfo, None, StringTokLocs.back(),
                                      &ExplicitArgs);
    }
  
    case LOLR_StringTemplatePack: {
      TemplateArgumentListInfo ExplicitArgs;
  
      unsigned CharBits = Context.getIntWidth(CharTy);
      bool CharIsUnsigned = CharTy->isUnsignedIntegerType();
      llvm::APSInt Value(CharBits, CharIsUnsigned);
  
      TemplateArgument TypeArg(CharTy);
      TemplateArgumentLocInfo TypeArgInfo(Context.getTrivialTypeSourceInfo(CharTy));
      ExplicitArgs.addArgument(TemplateArgumentLoc(TypeArg, TypeArgInfo));
  
      for (unsigned I = 0, N = Lit->getLength(); I != N; ++I) {
        Value = Lit->getCodeUnit(I);
        TemplateArgument Arg(Context, Value, CharTy);
        TemplateArgumentLocInfo ArgInfo;
        ExplicitArgs.addArgument(TemplateArgumentLoc(Arg, ArgInfo));
      }
      return BuildLiteralOperatorCall(R, OpNameInfo, None, StringTokLocs.back(),
                                      &ExplicitArgs);
    }
    case LOLR_Raw:
    case LOLR_ErrorNoDiagnostic:
      llvm_unreachable("unexpected literal operator lookup result");
    case LOLR_Error:
      return ExprError();
    }
    llvm_unreachable("unexpected literal operator lookup result");
  }
  
  DeclRefExpr *
  Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
                         SourceLocation Loc,
                         const CXXScopeSpec *SS) {
    DeclarationNameInfo NameInfo(D->getDeclName(), Loc);
    return BuildDeclRefExpr(D, Ty, VK, NameInfo, SS);
  }
  
  DeclRefExpr *
  Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
                         const DeclarationNameInfo &NameInfo,
                         const CXXScopeSpec *SS, NamedDecl *FoundD,
                         SourceLocation TemplateKWLoc,
                         const TemplateArgumentListInfo *TemplateArgs) {
    NestedNameSpecifierLoc NNS =
        SS ? SS->getWithLocInContext(Context) : NestedNameSpecifierLoc();
    return BuildDeclRefExpr(D, Ty, VK, NameInfo, NNS, FoundD, TemplateKWLoc,
                            TemplateArgs);
  }
  
  // CUDA/HIP: Check whether a captured reference variable is referencing a
  // host variable in a device or host device lambda.
  static bool isCapturingReferenceToHostVarInCUDADeviceLambda(const Sema &S,
                                                              VarDecl *VD) {
    if (!S.getLangOpts().CUDA || !VD->hasInit())
      return false;
    assert(VD->getType()->isReferenceType());
  
    // Check whether the reference variable is referencing a host variable.
    auto *DRE = dyn_cast<DeclRefExpr>(VD->getInit());
    if (!DRE)
      return false;
    auto *Referee = dyn_cast<VarDecl>(DRE->getDecl());
    if (!Referee || !Referee->hasGlobalStorage() ||
        Referee->hasAttr<CUDADeviceAttr>())
      return false;
  
    // Check whether the current function is a device or host device lambda.
    // Check whether the reference variable is a capture by getDeclContext()
    // since refersToEnclosingVariableOrCapture() is not ready at this point.
    auto *MD = dyn_cast_or_null<CXXMethodDecl>(S.CurContext);
    if (MD && MD->getParent()->isLambda() &&
        MD->getOverloadedOperator() == OO_Call && MD->hasAttr<CUDADeviceAttr>() &&
        VD->getDeclContext() != MD)
      return true;
  
    return false;
  }
  
  NonOdrUseReason Sema::getNonOdrUseReasonInCurrentContext(ValueDecl *D) {
    // A declaration named in an unevaluated operand never constitutes an odr-use.
    if (isUnevaluatedContext())
      return NOUR_Unevaluated;
  
    // C++2a [basic.def.odr]p4:
    //   A variable x whose name appears as a potentially-evaluated expression e
    //   is odr-used by e unless [...] x is a reference that is usable in
    //   constant expressions.
    // CUDA/HIP:
    //   If a reference variable referencing a host variable is captured in a
    //   device or host device lambda, the value of the referee must be copied
    //   to the capture and the reference variable must be treated as odr-use
    //   since the value of the referee is not known at compile time and must
    //   be loaded from the captured.
    if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
      if (VD->getType()->isReferenceType() &&
          !(getLangOpts().OpenMP && isOpenMPCapturedDecl(D)) &&
          !isCapturingReferenceToHostVarInCUDADeviceLambda(*this, VD) &&
          VD->isUsableInConstantExpressions(Context))
        return NOUR_Constant;
    }
  
    // All remaining non-variable cases constitute an odr-use. For variables, we
    // need to wait and see how the expression is used.
    return NOUR_None;
  }
  
  /// BuildDeclRefExpr - Build an expression that references a
  /// declaration that does not require a closure capture.
  DeclRefExpr *
  Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
                         const DeclarationNameInfo &NameInfo,
                         NestedNameSpecifierLoc NNS, NamedDecl *FoundD,
                         SourceLocation TemplateKWLoc,
                         const TemplateArgumentListInfo *TemplateArgs) {
    bool RefersToCapturedVariable =
        isa<VarDecl>(D) &&
        NeedToCaptureVariable(cast<VarDecl>(D), NameInfo.getLoc());
  
    DeclRefExpr *E = DeclRefExpr::Create(
        Context, NNS, TemplateKWLoc, D, RefersToCapturedVariable, NameInfo, Ty,
        VK, FoundD, TemplateArgs, getNonOdrUseReasonInCurrentContext(D));
    MarkDeclRefReferenced(E);
  
    // C++ [except.spec]p17:
    //   An exception-specification is considered to be needed when:
    //   - in an expression, the function is the unique lookup result or
    //     the selected member of a set of overloaded functions.
    //
    // We delay doing this until after we've built the function reference and
    // marked it as used so that:
    //  a) if the function is defaulted, we get errors from defining it before /
    //     instead of errors from computing its exception specification, and
    //  b) if the function is a defaulted comparison, we can use the body we
    //     build when defining it as input to the exception specification
    //     computation rather than computing a new body.
    if (auto *FPT = Ty->getAs<FunctionProtoType>()) {
      if (isUnresolvedExceptionSpec(FPT->getExceptionSpecType())) {
        if (auto *NewFPT = ResolveExceptionSpec(NameInfo.getLoc(), FPT))
          E->setType(Context.getQualifiedType(NewFPT, Ty.getQualifiers()));
      }
    }
  
    if (getLangOpts().ObjCWeak && isa<VarDecl>(D) &&
        Ty.getObjCLifetime() == Qualifiers::OCL_Weak && !isUnevaluatedContext() &&
        !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, E->getBeginLoc()))
      getCurFunction()->recordUseOfWeak(E);
  
    FieldDecl *FD = dyn_cast<FieldDecl>(D);
    if (IndirectFieldDecl *IFD = dyn_cast<IndirectFieldDecl>(D))
      FD = IFD->getAnonField();
    if (FD) {
      UnusedPrivateFields.remove(FD);
      // Just in case we're building an illegal pointer-to-member.
      if (FD->isBitField())
        E->setObjectKind(OK_BitField);
    }
  
    // C++ [expr.prim]/8: The expression [...] is a bit-field if the identifier
    // designates a bit-field.
    if (auto *BD = dyn_cast<BindingDecl>(D))
      if (auto *BE = BD->getBinding())
        E->setObjectKind(BE->getObjectKind());
  
    return E;
  }
  
  /// Decomposes the given name into a DeclarationNameInfo, its location, and
  /// possibly a list of template arguments.
  ///
  /// If this produces template arguments, it is permitted to call
  /// DecomposeTemplateName.
  ///
  /// This actually loses a lot of source location information for
  /// non-standard name kinds; we should consider preserving that in
  /// some way.
  void
  Sema::DecomposeUnqualifiedId(const UnqualifiedId &Id,
                               TemplateArgumentListInfo &Buffer,
                               DeclarationNameInfo &NameInfo,
                               const TemplateArgumentListInfo *&TemplateArgs) {
    if (Id.getKind() == UnqualifiedIdKind::IK_TemplateId) {
      Buffer.setLAngleLoc(Id.TemplateId->LAngleLoc);
      Buffer.setRAngleLoc(Id.TemplateId->RAngleLoc);
  
      ASTTemplateArgsPtr TemplateArgsPtr(Id.TemplateId->getTemplateArgs(),
                                         Id.TemplateId->NumArgs);
      translateTemplateArguments(TemplateArgsPtr, Buffer);
  
      TemplateName TName = Id.TemplateId->Template.get();
      SourceLocation TNameLoc = Id.TemplateId->TemplateNameLoc;
      NameInfo = Context.getNameForTemplate(TName, TNameLoc);
      TemplateArgs = &Buffer;
    } else {
      NameInfo = GetNameFromUnqualifiedId(Id);
      TemplateArgs = nullptr;
    }
  }
  
  static void emitEmptyLookupTypoDiagnostic(
      const TypoCorrection &TC, Sema &SemaRef, const CXXScopeSpec &SS,
      DeclarationName Typo, SourceLocation TypoLoc, ArrayRef<Expr *> Args,
      unsigned DiagnosticID, unsigned DiagnosticSuggestID) {
    DeclContext *Ctx =
        SS.isEmpty() ? nullptr : SemaRef.computeDeclContext(SS, false);
    if (!TC) {
      // Emit a special diagnostic for failed member lookups.
      // FIXME: computing the declaration context might fail here (?)
      if (Ctx)
        SemaRef.Diag(TypoLoc, diag::err_no_member) << Typo << Ctx
                                                   << SS.getRange();
      else
        SemaRef.Diag(TypoLoc, DiagnosticID) << Typo;
      return;
    }
  
    std::string CorrectedStr = TC.getAsString(SemaRef.getLangOpts());
    bool DroppedSpecifier =
        TC.WillReplaceSpecifier() && Typo.getAsString() == CorrectedStr;
    unsigned NoteID = TC.getCorrectionDeclAs<ImplicitParamDecl>()
                          ? diag::note_implicit_param_decl
                          : diag::note_previous_decl;
    if (!Ctx)
      SemaRef.diagnoseTypo(TC, SemaRef.PDiag(DiagnosticSuggestID) << Typo,
                           SemaRef.PDiag(NoteID));
    else
      SemaRef.diagnoseTypo(TC, SemaRef.PDiag(diag::err_no_member_suggest)
                                   << Typo << Ctx << DroppedSpecifier
                                   << SS.getRange(),
                           SemaRef.PDiag(NoteID));
  }
  
  /// Diagnose a lookup that found results in an enclosing class during error
  /// recovery. This usually indicates that the results were found in a dependent
  /// base class that could not be searched as part of a template definition.
  /// Always issues a diagnostic (though this may be only a warning in MS
  /// compatibility mode).
  ///
  /// Return \c true if the error is unrecoverable, or \c false if the caller
  /// should attempt to recover using these lookup results.
  bool Sema::DiagnoseDependentMemberLookup(LookupResult &R) {
    // During a default argument instantiation the CurContext points
    // to a CXXMethodDecl; but we can't apply a this-> fixit inside a
    // function parameter list, hence add an explicit check.
    bool isDefaultArgument =
        !CodeSynthesisContexts.empty() &&
        CodeSynthesisContexts.back().Kind ==
            CodeSynthesisContext::DefaultFunctionArgumentInstantiation;
    CXXMethodDecl *CurMethod = dyn_cast<CXXMethodDecl>(CurContext);
    bool isInstance = CurMethod && CurMethod->isInstance() &&
                      R.getNamingClass() == CurMethod->getParent() &&
                      !isDefaultArgument;
  
    // There are two ways we can find a class-scope declaration during template
    // instantiation that we did not find in the template definition: if it is a
    // member of a dependent base class, or if it is declared after the point of
    // use in the same class. Distinguish these by comparing the class in which
    // the member was found to the naming class of the lookup.
    unsigned DiagID = diag::err_found_in_dependent_base;
    unsigned NoteID = diag::note_member_declared_at;
    if (R.getRepresentativeDecl()->getDeclContext()->Equals(R.getNamingClass())) {
      DiagID = getLangOpts().MSVCCompat ? diag::ext_found_later_in_class
                                        : diag::err_found_later_in_class;
    } else if (getLangOpts().MSVCCompat) {
      DiagID = diag::ext_found_in_dependent_base;
      NoteID = diag::note_dependent_member_use;
    }
  
    if (isInstance) {
      // Give a code modification hint to insert 'this->'.
      Diag(R.getNameLoc(), DiagID)
          << R.getLookupName()
          << FixItHint::CreateInsertion(R.getNameLoc(), "this->");
      CheckCXXThisCapture(R.getNameLoc());
    } else {
      // FIXME: Add a FixItHint to insert 'Base::' or 'Derived::' (assuming
      // they're not shadowed).
      Diag(R.getNameLoc(), DiagID) << R.getLookupName();
    }
  
    for (NamedDecl *D : R)
      Diag(D->getLocation(), NoteID);
  
    // Return true if we are inside a default argument instantiation
    // and the found name refers to an instance member function, otherwise
    // the caller will try to create an implicit member call and this is wrong
    // for default arguments.
    //
    // FIXME: Is this special case necessary? We could allow the caller to
    // diagnose this.
    if (isDefaultArgument && ((*R.begin())->isCXXInstanceMember())) {
      Diag(R.getNameLoc(), diag::err_member_call_without_object);
      return true;
    }
  
    // Tell the callee to try to recover.
    return false;
  }
  
  /// Diagnose an empty lookup.
  ///
  /// \return false if new lookup candidates were found
  bool Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
                                 CorrectionCandidateCallback &CCC,
                                 TemplateArgumentListInfo *ExplicitTemplateArgs,
                                 ArrayRef<Expr *> Args, TypoExpr **Out) {
    DeclarationName Name = R.getLookupName();
  
    unsigned diagnostic = diag::err_undeclared_var_use;
    unsigned diagnostic_suggest = diag::err_undeclared_var_use_suggest;
    if (Name.getNameKind() == DeclarationName::CXXOperatorName ||
        Name.getNameKind() == DeclarationName::CXXLiteralOperatorName ||
        Name.getNameKind() == DeclarationName::CXXConversionFunctionName) {
      diagnostic = diag::err_undeclared_use;
      diagnostic_suggest = diag::err_undeclared_use_suggest;
    }
  
    // If the original lookup was an unqualified lookup, fake an
    // unqualified lookup.  This is useful when (for example) the
    // original lookup would not have found something because it was a
    // dependent name.
    DeclContext *DC = SS.isEmpty() ? CurContext : nullptr;
    while (DC) {
      if (isa<CXXRecordDecl>(DC)) {
        LookupQualifiedName(R, DC);
  
        if (!R.empty()) {
          // Don't give errors about ambiguities in this lookup.
          R.suppressDiagnostics();
  
          // If there's a best viable function among the results, only mention
          // that one in the notes.
          OverloadCandidateSet Candidates(R.getNameLoc(),
                                          OverloadCandidateSet::CSK_Normal);
          AddOverloadedCallCandidates(R, ExplicitTemplateArgs, Args, Candidates);
          OverloadCandidateSet::iterator Best;
          if (Candidates.BestViableFunction(*this, R.getNameLoc(), Best) ==
              OR_Success) {
            R.clear();
            R.addDecl(Best->FoundDecl.getDecl(), Best->FoundDecl.getAccess());
            R.resolveKind();
          }
  
          return DiagnoseDependentMemberLookup(R);
        }
  
        R.clear();
      }
  
      DC = DC->getLookupParent();
    }
  
    // We didn't find anything, so try to correct for a typo.
    TypoCorrection Corrected;
    if (S && Out) {
      SourceLocation TypoLoc = R.getNameLoc();
      assert(!ExplicitTemplateArgs &&
             "Diagnosing an empty lookup with explicit template args!");
      *Out = CorrectTypoDelayed(
          R.getLookupNameInfo(), R.getLookupKind(), S, &SS, CCC,
          [=](const TypoCorrection &TC) {
            emitEmptyLookupTypoDiagnostic(TC, *this, SS, Name, TypoLoc, Args,
                                          diagnostic, diagnostic_suggest);
          },
          nullptr, CTK_ErrorRecovery);
      if (*Out)
        return true;
    } else if (S &&
               (Corrected = CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(),
                                        S, &SS, CCC, CTK_ErrorRecovery))) {
      std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
      bool DroppedSpecifier =
          Corrected.WillReplaceSpecifier() && Name.getAsString() == CorrectedStr;
      R.setLookupName(Corrected.getCorrection());
  
      bool AcceptableWithRecovery = false;
      bool AcceptableWithoutRecovery = false;
      NamedDecl *ND = Corrected.getFoundDecl();
      if (ND) {
        if (Corrected.isOverloaded()) {
          OverloadCandidateSet OCS(R.getNameLoc(),
                                   OverloadCandidateSet::CSK_Normal);
          OverloadCandidateSet::iterator Best;
          for (NamedDecl *CD : Corrected) {
            if (FunctionTemplateDecl *FTD =
                     dyn_cast<FunctionTemplateDecl>(CD))
              AddTemplateOverloadCandidate(
                  FTD, DeclAccessPair::make(FTD, AS_none), ExplicitTemplateArgs,
                  Args, OCS);
            else if (FunctionDecl *FD = dyn_cast<FunctionDecl>(CD))
              if (!ExplicitTemplateArgs || ExplicitTemplateArgs->size() == 0)
                AddOverloadCandidate(FD, DeclAccessPair::make(FD, AS_none),
                                     Args, OCS);
          }
          switch (OCS.BestViableFunction(*this, R.getNameLoc(), Best)) {
          case OR_Success:
            ND = Best->FoundDecl;
            Corrected.setCorrectionDecl(ND);
            break;
          default:
            // FIXME: Arbitrarily pick the first declaration for the note.
            Corrected.setCorrectionDecl(ND);
            break;
          }
        }
        R.addDecl(ND);
        if (getLangOpts().CPlusPlus && ND->isCXXClassMember()) {
          CXXRecordDecl *Record = nullptr;
          if (Corrected.getCorrectionSpecifier()) {
            const Type *Ty = Corrected.getCorrectionSpecifier()->getAsType();
            Record = Ty->getAsCXXRecordDecl();
          }
          if (!Record)
            Record = cast<CXXRecordDecl>(
                ND->getDeclContext()->getRedeclContext());
          R.setNamingClass(Record);
        }
  
        auto *UnderlyingND = ND->getUnderlyingDecl();
        AcceptableWithRecovery = isa<ValueDecl>(UnderlyingND) ||
                                 isa<FunctionTemplateDecl>(UnderlyingND);
        // FIXME: If we ended up with a typo for a type name or
        // Objective-C class name, we're in trouble because the parser
        // is in the wrong place to recover. Suggest the typo
        // correction, but don't make it a fix-it since we're not going
        // to recover well anyway.
        AcceptableWithoutRecovery = isa<TypeDecl>(UnderlyingND) ||
                                    getAsTypeTemplateDecl(UnderlyingND) ||
                                    isa<ObjCInterfaceDecl>(UnderlyingND);
      } else {
        // FIXME: We found a keyword. Suggest it, but don't provide a fix-it
        // because we aren't able to recover.
        AcceptableWithoutRecovery = true;
      }
  
      if (AcceptableWithRecovery || AcceptableWithoutRecovery) {
        unsigned NoteID = Corrected.getCorrectionDeclAs<ImplicitParamDecl>()
                              ? diag::note_implicit_param_decl
                              : diag::note_previous_decl;
        if (SS.isEmpty())
          diagnoseTypo(Corrected, PDiag(diagnostic_suggest) << Name,
                       PDiag(NoteID), AcceptableWithRecovery);
        else
          diagnoseTypo(Corrected, PDiag(diag::err_no_member_suggest)
                                    << Name << computeDeclContext(SS, false)
                                    << DroppedSpecifier << SS.getRange(),
                       PDiag(NoteID), AcceptableWithRecovery);
  
        // Tell the callee whether to try to recover.
        return !AcceptableWithRecovery;
      }
    }
    R.clear();
  
    // Emit a special diagnostic for failed member lookups.
    // FIXME: computing the declaration context might fail here (?)
    if (!SS.isEmpty()) {
      Diag(R.getNameLoc(), diag::err_no_member)
        << Name << computeDeclContext(SS, false)
        << SS.getRange();
      return true;
    }
  
    // Give up, we can't recover.
    Diag(R.getNameLoc(), diagnostic) << Name;
    return true;
  }
  
  /// In Microsoft mode, if we are inside a template class whose parent class has
  /// dependent base classes, and we can't resolve an unqualified identifier, then
  /// assume the identifier is a member of a dependent base class.  We can only
  /// recover successfully in static methods, instance methods, and other contexts
  /// where 'this' is available.  This doesn't precisely match MSVC's
  /// instantiation model, but it's close enough.
  static Expr *
  recoverFromMSUnqualifiedLookup(Sema &S, ASTContext &Context,
                                 DeclarationNameInfo &NameInfo,
                                 SourceLocation TemplateKWLoc,
                                 const TemplateArgumentListInfo *TemplateArgs) {
    // Only try to recover from lookup into dependent bases in static methods or
    // contexts where 'this' is available.
    QualType ThisType = S.getCurrentThisType();
    const CXXRecordDecl *RD = nullptr;
    if (!ThisType.isNull())
      RD = ThisType->getPointeeType()->getAsCXXRecordDecl();
    else if (auto *MD = dyn_cast<CXXMethodDecl>(S.CurContext))
      RD = MD->getParent();
    if (!RD || !RD->hasAnyDependentBases())
      return nullptr;
  
    // Diagnose this as unqualified lookup into a dependent base class.  If 'this'
    // is available, suggest inserting 'this->' as a fixit.
    SourceLocation Loc = NameInfo.getLoc();
    auto DB = S.Diag(Loc, diag::ext_undeclared_unqual_id_with_dependent_base);
    DB << NameInfo.getName() << RD;
  
    if (!ThisType.isNull()) {
      DB << FixItHint::CreateInsertion(Loc, "this->");
      return CXXDependentScopeMemberExpr::Create(
          Context, /*This=*/nullptr, ThisType, /*IsArrow=*/true,
          /*Op=*/SourceLocation(), NestedNameSpecifierLoc(), TemplateKWLoc,
          /*FirstQualifierFoundInScope=*/nullptr, NameInfo, TemplateArgs);
    }
  
    // Synthesize a fake NNS that points to the derived class.  This will
    // perform name lookup during template instantiation.
    CXXScopeSpec SS;
    auto *NNS =
        NestedNameSpecifier::Create(Context, nullptr, true, RD->getTypeForDecl());
    SS.MakeTrivial(Context, NNS, SourceRange(Loc, Loc));
    return DependentScopeDeclRefExpr::Create(
        Context, SS.getWithLocInContext(Context), TemplateKWLoc, NameInfo,
        TemplateArgs);
  }
  
  ExprResult
  Sema::ActOnIdExpression(Scope *S, CXXScopeSpec &SS,
                          SourceLocation TemplateKWLoc, UnqualifiedId &Id,
                          bool HasTrailingLParen, bool IsAddressOfOperand,
                          CorrectionCandidateCallback *CCC,
                          bool IsInlineAsmIdentifier, Token *KeywordReplacement) {
    assert(!(IsAddressOfOperand && HasTrailingLParen) &&
           "cannot be direct & operand and have a trailing lparen");
    if (SS.isInvalid())
      return ExprError();
  
    TemplateArgumentListInfo TemplateArgsBuffer;
  
    // Decompose the UnqualifiedId into the following data.
    DeclarationNameInfo NameInfo;
    const TemplateArgumentListInfo *TemplateArgs;
    DecomposeUnqualifiedId(Id, TemplateArgsBuffer, NameInfo, TemplateArgs);
  
    DeclarationName Name = NameInfo.getName();
    IdentifierInfo *II = Name.getAsIdentifierInfo();
    SourceLocation NameLoc = NameInfo.getLoc();
  
    if (II && II->isEditorPlaceholder()) {
      // FIXME: When typed placeholders are supported we can create a typed
      // placeholder expression node.
      return ExprError();
    }
  
    // C++ [temp.dep.expr]p3:
    //   An id-expression is type-dependent if it contains:
    //     -- an identifier that was declared with a dependent type,
    //        (note: handled after lookup)
    //     -- a template-id that is dependent,
    //        (note: handled in BuildTemplateIdExpr)
    //     -- a conversion-function-id that specifies a dependent type,
    //     -- a nested-name-specifier that contains a class-name that
    //        names a dependent type.
    // Determine whether this is a member of an unknown specialization;
    // we need to handle these differently.
    bool DependentID = false;
    if (Name.getNameKind() == DeclarationName::CXXConversionFunctionName &&
        Name.getCXXNameType()->isDependentType()) {
      DependentID = true;
    } else if (SS.isSet()) {
      if (DeclContext *DC = computeDeclContext(SS, false)) {
        if (RequireCompleteDeclContext(SS, DC))
          return ExprError();
      } else {
        DependentID = true;
      }
    }
  
    if (DependentID)
      return ActOnDependentIdExpression(SS, TemplateKWLoc, NameInfo,
                                        IsAddressOfOperand, TemplateArgs);
  
    // Perform the required lookup.
    LookupResult R(*this, NameInfo,
                   (Id.getKind() == UnqualifiedIdKind::IK_ImplicitSelfParam)
                       ? LookupObjCImplicitSelfParam
                       : LookupOrdinaryName);
    if (TemplateKWLoc.isValid() || TemplateArgs) {
      // Lookup the template name again to correctly establish the context in
      // which it was found. This is really unfortunate as we already did the
      // lookup to determine that it was a template name in the first place. If
      // this becomes a performance hit, we can work harder to preserve those
      // results until we get here but it's likely not worth it.
      bool MemberOfUnknownSpecialization;
      AssumedTemplateKind AssumedTemplate;
      if (LookupTemplateName(R, S, SS, QualType(), /*EnteringContext=*/false,
                             MemberOfUnknownSpecialization, TemplateKWLoc,
                             &AssumedTemplate))
        return ExprError();
  
      if (MemberOfUnknownSpecialization ||
          (R.getResultKind() == LookupResult::NotFoundInCurrentInstantiation))
        return ActOnDependentIdExpression(SS, TemplateKWLoc, NameInfo,
                                          IsAddressOfOperand, TemplateArgs);
    } else {
      bool IvarLookupFollowUp = II && !SS.isSet() && getCurMethodDecl();
      LookupParsedName(R, S, &SS, !IvarLookupFollowUp);
  
      // If the result might be in a dependent base class, this is a dependent
      // id-expression.
      if (R.getResultKind() == LookupResult::NotFoundInCurrentInstantiation)
        return ActOnDependentIdExpression(SS, TemplateKWLoc, NameInfo,
                                          IsAddressOfOperand, TemplateArgs);
  
      // If this reference is in an Objective-C method, then we need to do
      // some special Objective-C lookup, too.
      if (IvarLookupFollowUp) {
        ExprResult E(LookupInObjCMethod(R, S, II, true));
        if (E.isInvalid())
          return ExprError();
  
        if (Expr *Ex = E.getAs<Expr>())
          return Ex;
      }
    }
  
    if (R.isAmbiguous())
      return ExprError();
  
    // This could be an implicitly declared function reference (legal in C90,
    // extension in C99, forbidden in C++).
    if (R.empty() && HasTrailingLParen && II && !getLangOpts().CPlusPlus) {
      NamedDecl *D = ImplicitlyDefineFunction(NameLoc, *II, S);
      if (D) R.addDecl(D);
    }
  
    // Determine whether this name might be a candidate for
    // argument-dependent lookup.
    bool ADL = UseArgumentDependentLookup(SS, R, HasTrailingLParen);
  
    if (R.empty() && !ADL) {
      if (SS.isEmpty() && getLangOpts().MSVCCompat) {
        if (Expr *E = recoverFromMSUnqualifiedLookup(*this, Context, NameInfo,
                                                     TemplateKWLoc, TemplateArgs))
          return E;
      }
  
      // Don't diagnose an empty lookup for inline assembly.
      if (IsInlineAsmIdentifier)
        return ExprError();
  
      // If this name wasn't predeclared and if this is not a function
      // call, diagnose the problem.
      TypoExpr *TE = nullptr;
      DefaultFilterCCC DefaultValidator(II, SS.isValid() ? SS.getScopeRep()
                                                         : nullptr);
      DefaultValidator.IsAddressOfOperand = IsAddressOfOperand;
      assert((!CCC || CCC->IsAddressOfOperand == IsAddressOfOperand) &&
             "Typo correction callback misconfigured");
      if (CCC) {
        // Make sure the callback knows what the typo being diagnosed is.
        CCC->setTypoName(II);
        if (SS.isValid())
          CCC->setTypoNNS(SS.getScopeRep());
      }
      // FIXME: DiagnoseEmptyLookup produces bad diagnostics if we're looking for
      // a template name, but we happen to have always already looked up the name
      // before we get here if it must be a template name.
      if (DiagnoseEmptyLookup(S, SS, R, CCC ? *CCC : DefaultValidator, nullptr,
                              None, &TE)) {
        if (TE && KeywordReplacement) {
          auto &State = getTypoExprState(TE);
          auto BestTC = State.Consumer->getNextCorrection();
          if (BestTC.isKeyword()) {
            auto *II = BestTC.getCorrectionAsIdentifierInfo();
            if (State.DiagHandler)
              State.DiagHandler(BestTC);
            KeywordReplacement->startToken();
            KeywordReplacement->setKind(II->getTokenID());
            KeywordReplacement->setIdentifierInfo(II);
            KeywordReplacement->setLocation(BestTC.getCorrectionRange().getBegin());
            // Clean up the state associated with the TypoExpr, since it has
            // now been diagnosed (without a call to CorrectDelayedTyposInExpr).
            clearDelayedTypo(TE);
            // Signal that a correction to a keyword was performed by returning a
            // valid-but-null ExprResult.
            return (Expr*)nullptr;
          }
          State.Consumer->resetCorrectionStream();
        }
        return TE ? TE : ExprError();
      }
  
      assert(!R.empty() &&
             "DiagnoseEmptyLookup returned false but added no results");
  
      // If we found an Objective-C instance variable, let
      // LookupInObjCMethod build the appropriate expression to
      // reference the ivar.
      if (ObjCIvarDecl *Ivar = R.getAsSingle<ObjCIvarDecl>()) {
        R.clear();
        ExprResult E(LookupInObjCMethod(R, S, Ivar->getIdentifier()));
        // In a hopelessly buggy code, Objective-C instance variable
        // lookup fails and no expression will be built to reference it.
        if (!E.isInvalid() && !E.get())
          return ExprError();
        return E;
      }
    }
  
    // This is guaranteed from this point on.
    assert(!R.empty() || ADL);
  
    // Check whether this might be a C++ implicit instance member access.
    // C++ [class.mfct.non-static]p3:
    //   When an id-expression that is not part of a class member access
    //   syntax and not used to form a pointer to member is used in the
    //   body of a non-static member function of class X, if name lookup
    //   resolves the name in the id-expression to a non-static non-type
    //   member of some class C, the id-expression is transformed into a
    //   class member access expression using (*this) as the
    //   postfix-expression to the left of the . operator.
    //
    // But we don't actually need to do this for '&' operands if R
    // resolved to a function or overloaded function set, because the
    // expression is ill-formed if it actually works out to be a
    // non-static member function:
    //
    // C++ [expr.ref]p4:
    //   Otherwise, if E1.E2 refers to a non-static member function. . .
    //   [t]he expression can be used only as the left-hand operand of a
    //   member function call.
    //
    // There are other safeguards against such uses, but it's important
    // to get this right here so that we don't end up making a
    // spuriously dependent expression if we're inside a dependent
    // instance method.
    if (!R.empty() && (*R.begin())->isCXXClassMember()) {
      bool MightBeImplicitMember;
      if (!IsAddressOfOperand)
        MightBeImplicitMember = true;
      else if (!SS.isEmpty())
        MightBeImplicitMember = false;
      else if (R.isOverloadedResult())
        MightBeImplicitMember = false;
      else if (R.isUnresolvableResult())
        MightBeImplicitMember = true;
      else
        MightBeImplicitMember = isa<FieldDecl>(R.getFoundDecl()) ||
                                isa<IndirectFieldDecl>(R.getFoundDecl()) ||
                                isa<MSPropertyDecl>(R.getFoundDecl());
  
      if (MightBeImplicitMember)
        return BuildPossibleImplicitMemberExpr(SS, TemplateKWLoc,
                                               R, TemplateArgs, S);
    }
  
    if (TemplateArgs || TemplateKWLoc.isValid()) {
  
      // In C++1y, if this is a variable template id, then check it
      // in BuildTemplateIdExpr().
      // The single lookup result must be a variable template declaration.
      if (Id.getKind() == UnqualifiedIdKind::IK_TemplateId && Id.TemplateId &&
          Id.TemplateId->Kind == TNK_Var_template) {
        assert(R.getAsSingle<VarTemplateDecl>() &&
               "There should only be one declaration found.");
      }
  
      return BuildTemplateIdExpr(SS, TemplateKWLoc, R, ADL, TemplateArgs);
    }
  
    return BuildDeclarationNameExpr(SS, R, ADL);
  }
  
  /// BuildQualifiedDeclarationNameExpr - Build a C++ qualified
  /// declaration name, generally during template instantiation.
  /// There's a large number of things which don't need to be done along
  /// this path.
  ExprResult Sema::BuildQualifiedDeclarationNameExpr(
      CXXScopeSpec &SS, const DeclarationNameInfo &NameInfo,
      bool IsAddressOfOperand, const Scope *S, TypeSourceInfo **RecoveryTSI) {
    DeclContext *DC = computeDeclContext(SS, false);
    if (!DC)
      return BuildDependentDeclRefExpr(SS, /*TemplateKWLoc=*/SourceLocation(),
                                       NameInfo, /*TemplateArgs=*/nullptr);
  
    if (RequireCompleteDeclContext(SS, DC))
      return ExprError();
  
    LookupResult R(*this, NameInfo, LookupOrdinaryName);
    LookupQualifiedName(R, DC);
  
    if (R.isAmbiguous())
      return ExprError();
  
    if (R.getResultKind() == LookupResult::NotFoundInCurrentInstantiation)
      return BuildDependentDeclRefExpr(SS, /*TemplateKWLoc=*/SourceLocation(),
                                       NameInfo, /*TemplateArgs=*/nullptr);
  
    if (R.empty()) {
      // Don't diagnose problems with invalid record decl, the secondary no_member
      // diagnostic during template instantiation is likely bogus, e.g. if a class
      // is invalid because it's derived from an invalid base class, then missing
      // members were likely supposed to be inherited.
      if (const auto *CD = dyn_cast<CXXRecordDecl>(DC))
        if (CD->isInvalidDecl())
          return ExprError();
      Diag(NameInfo.getLoc(), diag::err_no_member)
        << NameInfo.getName() << DC << SS.getRange();
      return ExprError();
    }
  
    if (const TypeDecl *TD = R.getAsSingle<TypeDecl>()) {
      // Diagnose a missing typename if this resolved unambiguously to a type in
      // a dependent context.  If we can recover with a type, downgrade this to
      // a warning in Microsoft compatibility mode.
      unsigned DiagID = diag::err_typename_missing;
      if (RecoveryTSI && getLangOpts().MSVCCompat)
        DiagID = diag::ext_typename_missing;
      SourceLocation Loc = SS.getBeginLoc();
      auto D = Diag(Loc, DiagID);
      D << SS.getScopeRep() << NameInfo.getName().getAsString()
        << SourceRange(Loc, NameInfo.getEndLoc());
  
      // Don't recover if the caller isn't expecting us to or if we're in a SFINAE
      // context.
      if (!RecoveryTSI)
        return ExprError();
  
      // Only issue the fixit if we're prepared to recover.
      D << FixItHint::CreateInsertion(Loc, "typename ");
  
      // Recover by pretending this was an elaborated type.
      QualType Ty = Context.getTypeDeclType(TD);
      TypeLocBuilder TLB;
      TLB.pushTypeSpec(Ty).setNameLoc(NameInfo.getLoc());
  
      QualType ET = getElaboratedType(ETK_None, SS, Ty);
      ElaboratedTypeLoc QTL = TLB.push<ElaboratedTypeLoc>(ET);
      QTL.setElaboratedKeywordLoc(SourceLocation());
      QTL.setQualifierLoc(SS.getWithLocInContext(Context));
  
      *RecoveryTSI = TLB.getTypeSourceInfo(Context, ET);
  
      return ExprEmpty();
    }
  
    // Defend against this resolving to an implicit member access. We usually
    // won't get here if this might be a legitimate a class member (we end up in
    // BuildMemberReferenceExpr instead), but this can be valid if we're forming
    // a pointer-to-member or in an unevaluated context in C++11.
    if (!R.empty() && (*R.begin())->isCXXClassMember() && !IsAddressOfOperand)
      return BuildPossibleImplicitMemberExpr(SS,
                                             /*TemplateKWLoc=*/SourceLocation(),
                                             R, /*TemplateArgs=*/nullptr, S);
  
    return BuildDeclarationNameExpr(SS, R, /* ADL */ false);
  }
  
  /// The parser has read a name in, and Sema has detected that we're currently
  /// inside an ObjC method. Perform some additional checks and determine if we
  /// should form a reference to an ivar.
  ///
  /// Ideally, most of this would be done by lookup, but there's
  /// actually quite a lot of extra work involved.
  DeclResult Sema::LookupIvarInObjCMethod(LookupResult &Lookup, Scope *S,
                                          IdentifierInfo *II) {
    SourceLocation Loc = Lookup.getNameLoc();
    ObjCMethodDecl *CurMethod = getCurMethodDecl();
  
    // Check for error condition which is already reported.
    if (!CurMethod)
      return DeclResult(true);
  
    // There are two cases to handle here.  1) scoped lookup could have failed,
    // in which case we should look for an ivar.  2) scoped lookup could have
    // found a decl, but that decl is outside the current instance method (i.e.
    // a global variable).  In these two cases, we do a lookup for an ivar with
    // this name, if the lookup sucedes, we replace it our current decl.
  
    // If we're in a class method, we don't normally want to look for
    // ivars.  But if we don't find anything else, and there's an
    // ivar, that's an error.
    bool IsClassMethod = CurMethod->isClassMethod();
  
    bool LookForIvars;
    if (Lookup.empty())
      LookForIvars = true;
    else if (IsClassMethod)
      LookForIvars = false;
    else
      LookForIvars = (Lookup.isSingleResult() &&
                      Lookup.getFoundDecl()->isDefinedOutsideFunctionOrMethod());
    ObjCInterfaceDecl *IFace = nullptr;
    if (LookForIvars) {
      IFace = CurMethod->getClassInterface();
      ObjCInterfaceDecl *ClassDeclared;
      ObjCIvarDecl *IV = nullptr;
      if (IFace && (IV = IFace->lookupInstanceVariable(II, ClassDeclared))) {
        // Diagnose using an ivar in a class method.
        if (IsClassMethod) {
          Diag(Loc, diag::err_ivar_use_in_class_method) << IV->getDeclName();
          return DeclResult(true);
        }
  
        // Diagnose the use of an ivar outside of the declaring class.
        if (IV->getAccessControl() == ObjCIvarDecl::Private &&
            !declaresSameEntity(ClassDeclared, IFace) &&
            !getLangOpts().DebuggerSupport)
          Diag(Loc, diag::err_private_ivar_access) << IV->getDeclName();
  
        // Success.
        return IV;
      }
    } else if (CurMethod->isInstanceMethod()) {
      // We should warn if a local variable hides an ivar.
      if (ObjCInterfaceDecl *IFace = CurMethod->getClassInterface()) {
        ObjCInterfaceDecl *ClassDeclared;
        if (ObjCIvarDecl *IV = IFace->lookupInstanceVariable(II, ClassDeclared)) {
          if (IV->getAccessControl() != ObjCIvarDecl::Private ||
              declaresSameEntity(IFace, ClassDeclared))
            Diag(Loc, diag::warn_ivar_use_hidden) << IV->getDeclName();
        }
      }
    } else if (Lookup.isSingleResult() &&
               Lookup.getFoundDecl()->isDefinedOutsideFunctionOrMethod()) {
      // If accessing a stand-alone ivar in a class method, this is an error.
      if (const ObjCIvarDecl *IV =
              dyn_cast<ObjCIvarDecl>(Lookup.getFoundDecl())) {
        Diag(Loc, diag::err_ivar_use_in_class_method) << IV->getDeclName();
        return DeclResult(true);
      }
    }
  
    // Didn't encounter an error, didn't find an ivar.
    return DeclResult(false);
  }
  
  ExprResult Sema::BuildIvarRefExpr(Scope *S, SourceLocation Loc,
                                    ObjCIvarDecl *IV) {
    ObjCMethodDecl *CurMethod = getCurMethodDecl();
    assert(CurMethod && CurMethod->isInstanceMethod() &&
           "should not reference ivar from this context");
  
    ObjCInterfaceDecl *IFace = CurMethod->getClassInterface();
    assert(IFace && "should not reference ivar from this context");
  
    // If we're referencing an invalid decl, just return this as a silent
    // error node.  The error diagnostic was already emitted on the decl.
    if (IV->isInvalidDecl())
      return ExprError();
  
    // Check if referencing a field with __attribute__((deprecated)).
    if (DiagnoseUseOfDecl(IV, Loc))
      return ExprError();
  
    // FIXME: This should use a new expr for a direct reference, don't
    // turn this into Self->ivar, just return a BareIVarExpr or something.
    IdentifierInfo &II = Context.Idents.get("self");
    UnqualifiedId SelfName;
    SelfName.setImplicitSelfParam(&II);
    CXXScopeSpec SelfScopeSpec;
    SourceLocation TemplateKWLoc;
    ExprResult SelfExpr =
        ActOnIdExpression(S, SelfScopeSpec, TemplateKWLoc, SelfName,
                          /*HasTrailingLParen=*/false,
                          /*IsAddressOfOperand=*/false);
    if (SelfExpr.isInvalid())
      return ExprError();
  
    SelfExpr = DefaultLvalueConversion(SelfExpr.get());
    if (SelfExpr.isInvalid())
      return ExprError();
  
    MarkAnyDeclReferenced(Loc, IV, true);
  
    ObjCMethodFamily MF = CurMethod->getMethodFamily();
    if (MF != OMF_init && MF != OMF_dealloc && MF != OMF_finalize &&
        !IvarBacksCurrentMethodAccessor(IFace, CurMethod, IV))
      Diag(Loc, diag::warn_direct_ivar_access) << IV->getDeclName();
  
    ObjCIvarRefExpr *Result = new (Context)
        ObjCIvarRefExpr(IV, IV->getUsageType(SelfExpr.get()->getType()), Loc,
                        IV->getLocation(), SelfExpr.get(), true, true);
  
    if (IV->getType().getObjCLifetime() == Qualifiers::OCL_Weak) {
      if (!isUnevaluatedContext() &&
          !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, Loc))
        getCurFunction()->recordUseOfWeak(Result);
    }
    if (getLangOpts().ObjCAutoRefCount)
      if (const BlockDecl *BD = CurContext->getInnermostBlockDecl())
        ImplicitlyRetainedSelfLocs.push_back({Loc, BD});
  
    return Result;
  }
  
  /// The parser has read a name in, and Sema has detected that we're currently
  /// inside an ObjC method. Perform some additional checks and determine if we
  /// should form a reference to an ivar. If so, build an expression referencing
  /// that ivar.
  ExprResult
  Sema::LookupInObjCMethod(LookupResult &Lookup, Scope *S,
                           IdentifierInfo *II, bool AllowBuiltinCreation) {
    // FIXME: Integrate this lookup step into LookupParsedName.
    DeclResult Ivar = LookupIvarInObjCMethod(Lookup, S, II);
    if (Ivar.isInvalid())
      return ExprError();
    if (Ivar.isUsable())
      return BuildIvarRefExpr(S, Lookup.getNameLoc(),
                              cast<ObjCIvarDecl>(Ivar.get()));
  
    if (Lookup.empty() && II && AllowBuiltinCreation)
      LookupBuiltin(Lookup);
  
    // Sentinel value saying that we didn't do anything special.
    return ExprResult(false);
  }
  
  /// Cast a base object to a member's actual type.
  ///
  /// There are two relevant checks:
  ///
  /// C++ [class.access.base]p7:
  ///
  ///   If a class member access operator [...] is used to access a non-static
  ///   data member or non-static member function, the reference is ill-formed if
  ///   the left operand [...] cannot be implicitly converted to a pointer to the
  ///   naming class of the right operand.
  ///
  /// C++ [expr.ref]p7:
  ///
  ///   If E2 is a non-static data member or a non-static member function, the
  ///   program is ill-formed if the class of which E2 is directly a member is an
  ///   ambiguous base (11.8) of the naming class (11.9.3) of E2.
  ///
  /// Note that the latter check does not consider access; the access of the
  /// "real" base class is checked as appropriate when checking the access of the
  /// member name.
  ExprResult
  Sema::PerformObjectMemberConversion(Expr *From,
                                      NestedNameSpecifier *Qualifier,
                                      NamedDecl *FoundDecl,
                                      NamedDecl *Member) {
    CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Member->getDeclContext());
    if (!RD)
      return From;
  
    QualType DestRecordType;
    QualType DestType;
    QualType FromRecordType;
    QualType FromType = From->getType();
    bool PointerConversions = false;
    if (isa<FieldDecl>(Member)) {
      DestRecordType = Context.getCanonicalType(Context.getTypeDeclType(RD));
      auto FromPtrType = FromType->getAs<PointerType>();
      DestRecordType = Context.getAddrSpaceQualType(
          DestRecordType, FromPtrType
                              ? FromType->getPointeeType().getAddressSpace()
                              : FromType.getAddressSpace());
  
      if (FromPtrType) {
        DestType = Context.getPointerType(DestRecordType);
        FromRecordType = FromPtrType->getPointeeType();
        PointerConversions = true;
      } else {
        DestType = DestRecordType;
        FromRecordType = FromType;
      }
    } else if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) {
      if (Method->isStatic())
        return From;
  
      DestType = Method->getThisType();
      DestRecordType = DestType->getPointeeType();
  
      if (FromType->getAs<PointerType>()) {
        FromRecordType = FromType->getPointeeType();
        PointerConversions = true;
      } else {
        FromRecordType = FromType;
        DestType = DestRecordType;
      }
  
      LangAS FromAS = FromRecordType.getAddressSpace();
      LangAS DestAS = DestRecordType.getAddressSpace();
      if (FromAS != DestAS) {
        QualType FromRecordTypeWithoutAS =
            Context.removeAddrSpaceQualType(FromRecordType);
        QualType FromTypeWithDestAS =
            Context.getAddrSpaceQualType(FromRecordTypeWithoutAS, DestAS);
        if (PointerConversions)
          FromTypeWithDestAS = Context.getPointerType(FromTypeWithDestAS);
        From = ImpCastExprToType(From, FromTypeWithDestAS,
                                 CK_AddressSpaceConversion, From->getValueKind())
                   .get();
      }
    } else {
      // No conversion necessary.
      return From;
    }
  
    if (DestType->isDependentType() || FromType->isDependentType())
      return From;
  
    // If the unqualified types are the same, no conversion is necessary.
    if (Context.hasSameUnqualifiedType(FromRecordType, DestRecordType))
      return From;
  
    SourceRange FromRange = From->getSourceRange();
    SourceLocation FromLoc = FromRange.getBegin();
  
    ExprValueKind VK = From->getValueKind();
  
    // C++ [class.member.lookup]p8:
    //   [...] Ambiguities can often be resolved by qualifying a name with its
    //   class name.
    //
    // If the member was a qualified name and the qualified referred to a
    // specific base subobject type, we'll cast to that intermediate type
    // first and then to the object in which the member is declared. That allows
    // one to resolve ambiguities in, e.g., a diamond-shaped hierarchy such as:
    //
    //   class Base { public: int x; };
    //   class Derived1 : public Base { };
    //   class Derived2 : public Base { };
    //   class VeryDerived : public Derived1, public Derived2 { void f(); };
    //
    //   void VeryDerived::f() {
    //     x = 17; // error: ambiguous base subobjects
    //     Derived1::x = 17; // okay, pick the Base subobject of Derived1
    //   }
    if (Qualifier && Qualifier->getAsType()) {
      QualType QType = QualType(Qualifier->getAsType(), 0);
      assert(QType->isRecordType() && "lookup done with non-record type");
  
      QualType QRecordType = QualType(QType->castAs<RecordType>(), 0);
  
      // In C++98, the qualifier type doesn't actually have to be a base
      // type of the object type, in which case we just ignore it.
      // Otherwise build the appropriate casts.
      if (IsDerivedFrom(FromLoc, FromRecordType, QRecordType)) {
        CXXCastPath BasePath;
        if (CheckDerivedToBaseConversion(FromRecordType, QRecordType,
                                         FromLoc, FromRange, &BasePath))
          return ExprError();
  
        if (PointerConversions)
          QType = Context.getPointerType(QType);
        From = ImpCastExprToType(From, QType, CK_UncheckedDerivedToBase,
                                 VK, &BasePath).get();
  
        FromType = QType;
        FromRecordType = QRecordType;
  
        // If the qualifier type was the same as the destination type,
        // we're done.
        if (Context.hasSameUnqualifiedType(FromRecordType, DestRecordType))
          return From;
      }
    }
  
    CXXCastPath BasePath;
    if (CheckDerivedToBaseConversion(FromRecordType, DestRecordType,
                                     FromLoc, FromRange, &BasePath,
                                     /*IgnoreAccess=*/true))
      return ExprError();
  
    return ImpCastExprToType(From, DestType, CK_UncheckedDerivedToBase,
                             VK, &BasePath);
  }
  
  bool Sema::UseArgumentDependentLookup(const CXXScopeSpec &SS,
                                        const LookupResult &R,
                                        bool HasTrailingLParen) {
    // Only when used directly as the postfix-expression of a call.
    if (!HasTrailingLParen)
      return false;
  
    // Never if a scope specifier was provided.
    if (SS.isSet())
      return false;
  
    // Only in C++ or ObjC++.
    if (!getLangOpts().CPlusPlus)
      return false;
  
    // Turn off ADL when we find certain kinds of declarations during
    // normal lookup:
    for (NamedDecl *D : R) {
      // C++0x [basic.lookup.argdep]p3:
      //     -- a declaration of a class member
      // Since using decls preserve this property, we check this on the
      // original decl.
      if (D->isCXXClassMember())
        return false;
  
      // C++0x [basic.lookup.argdep]p3:
      //     -- a block-scope function declaration that is not a
      //        using-declaration
      // NOTE: we also trigger this for function templates (in fact, we
      // don't check the decl type at all, since all other decl types
      // turn off ADL anyway).
      if (isa<UsingShadowDecl>(D))
        D = cast<UsingShadowDecl>(D)->getTargetDecl();
      else if (D->getLexicalDeclContext()->isFunctionOrMethod())
        return false;
  
      // C++0x [basic.lookup.argdep]p3:
      //     -- a declaration that is neither a function or a function
      //        template
      // And also for builtin functions.
      if (isa<FunctionDecl>(D)) {
        FunctionDecl *FDecl = cast<FunctionDecl>(D);
  
        // But also builtin functions.
        if (FDecl->getBuiltinID() && FDecl->isImplicit())
          return false;
      } else if (!isa<FunctionTemplateDecl>(D))
        return false;
    }
  
    return true;
  }
  
  
  /// Diagnoses obvious problems with the use of the given declaration
  /// as an expression.  This is only actually called for lookups that
  /// were not overloaded, and it doesn't promise that the declaration
  /// will in fact be used.
  static bool CheckDeclInExpr(Sema &S, SourceLocation Loc, NamedDecl *D) {
    if (D->isInvalidDecl())
      return true;
  
    if (isa<TypedefNameDecl>(D)) {
      S.Diag(Loc, diag::err_unexpected_typedef) << D->getDeclName();
      return true;
    }
  
    if (isa<ObjCInterfaceDecl>(D)) {
      S.Diag(Loc, diag::err_unexpected_interface) << D->getDeclName();
      return true;
    }
  
    if (isa<NamespaceDecl>(D)) {
      S.Diag(Loc, diag::err_unexpected_namespace) << D->getDeclName();
      return true;
    }
  
    return false;
  }
  
  // Certain multiversion types should be treated as overloaded even when there is
  // only one result.
  static bool ShouldLookupResultBeMultiVersionOverload(const LookupResult &R) {
    assert(R.isSingleResult() && "Expected only a single result");
    const auto *FD = dyn_cast<FunctionDecl>(R.getFoundDecl());
    return FD &&
           (FD->isCPUDispatchMultiVersion() || FD->isCPUSpecificMultiVersion());
  }
  
  ExprResult Sema::BuildDeclarationNameExpr(const CXXScopeSpec &SS,
                                            LookupResult &R, bool NeedsADL,
                                            bool AcceptInvalidDecl) {
    // If this is a single, fully-resolved result and we don't need ADL,
    // just build an ordinary singleton decl ref.
    if (!NeedsADL && R.isSingleResult() &&
        !R.getAsSingle<FunctionTemplateDecl>() &&
        !ShouldLookupResultBeMultiVersionOverload(R))
      return BuildDeclarationNameExpr(SS, R.getLookupNameInfo(), R.getFoundDecl(),
                                      R.getRepresentativeDecl(), nullptr,
                                      AcceptInvalidDecl);
  
    // We only need to check the declaration if there's exactly one
    // result, because in the overloaded case the results can only be
    // functions and function templates.
    if (R.isSingleResult() && !ShouldLookupResultBeMultiVersionOverload(R) &&
        CheckDeclInExpr(*this, R.getNameLoc(), R.getFoundDecl()))
      return ExprError();
  
    // Otherwise, just build an unresolved lookup expression.  Suppress
    // any lookup-related diagnostics; we'll hash these out later, when
    // we've picked a target.
    R.suppressDiagnostics();
  
    UnresolvedLookupExpr *ULE
      = UnresolvedLookupExpr::Create(Context, R.getNamingClass(),
                                     SS.getWithLocInContext(Context),
                                     R.getLookupNameInfo(),
                                     NeedsADL, R.isOverloadedResult(),
                                     R.begin(), R.end());
  
    return ULE;
  }
  
  static void diagnoseUncapturableValueReference(Sema &S, SourceLocation loc,
                                                 ValueDecl *var);
  
  /// Complete semantic analysis for a reference to the given declaration.
  ExprResult Sema::BuildDeclarationNameExpr(
      const CXXScopeSpec &SS, const DeclarationNameInfo &NameInfo, NamedDecl *D,
      NamedDecl *FoundD, const TemplateArgumentListInfo *TemplateArgs,
      bool AcceptInvalidDecl) {
    assert(D && "Cannot refer to a NULL declaration");
    assert(!isa<FunctionTemplateDecl>(D) &&
           "Cannot refer unambiguously to a function template");
  
    SourceLocation Loc = NameInfo.getLoc();
    if (CheckDeclInExpr(*this, Loc, D)) {
      // Recovery from invalid cases (e.g. D is an invalid Decl).
      // We use the dependent type for the RecoveryExpr to prevent bogus follow-up
      // diagnostics, as invalid decls use int as a fallback type.
      return CreateRecoveryExpr(NameInfo.getBeginLoc(), NameInfo.getEndLoc(), {});
    }
  
    if (TemplateDecl *Template = dyn_cast<TemplateDecl>(D)) {
      // Specifically diagnose references to class templates that are missing
      // a template argument list.
      diagnoseMissingTemplateArguments(TemplateName(Template), Loc);
      return ExprError();
    }
  
    // Make sure that we're referring to a value.
    if (!isa<ValueDecl, UnresolvedUsingIfExistsDecl>(D)) {
      Diag(Loc, diag::err_ref_non_value) << D << SS.getRange();
      Diag(D->getLocation(), diag::note_declared_at);
      return ExprError();
    }
  
    // Check whether this declaration can be used. Note that we suppress
    // this check when we're going to perform argument-dependent lookup
    // on this function name, because this might not be the function
    // that overload resolution actually selects.
    if (DiagnoseUseOfDecl(D, Loc))
      return ExprError();
  
    auto *VD = cast<ValueDecl>(D);
  
    // Only create DeclRefExpr's for valid Decl's.
    if (VD->isInvalidDecl() && !AcceptInvalidDecl)
      return ExprError();
  
    // Handle members of anonymous structs and unions.  If we got here,
    // and the reference is to a class member indirect field, then this
    // must be the subject of a pointer-to-member expression.
    if (IndirectFieldDecl *indirectField = dyn_cast<IndirectFieldDecl>(VD))
      if (!indirectField->isCXXClassMember())
        return BuildAnonymousStructUnionMemberReference(SS, NameInfo.getLoc(),
                                                        indirectField);
  
    QualType type = VD->getType();
    if (type.isNull())
      return ExprError();
    ExprValueKind valueKind = VK_PRValue;
  
    // In 'T ...V;', the type of the declaration 'V' is 'T...', but the type of
    // a reference to 'V' is simply (unexpanded) 'T'. The type, like the value,
    // is expanded by some outer '...' in the context of the use.
    type = type.getNonPackExpansionType();
  
    switch (D->getKind()) {
      // Ignore all the non-ValueDecl kinds.
  #define ABSTRACT_DECL(kind)
  #define VALUE(type, base)
  #define DECL(type, base) case Decl::type:
  #include "clang/AST/DeclNodes.inc"
      llvm_unreachable("invalid value decl kind");
  
    // These shouldn't make it here.
    case Decl::ObjCAtDefsField:
      llvm_unreachable("forming non-member reference to ivar?");
  
    // Enum constants are always r-values and never references.
    // Unresolved using declarations are dependent.
    case Decl::EnumConstant:
    case Decl::UnresolvedUsingValue:
    case Decl::OMPDeclareReduction:
    case Decl::OMPDeclareMapper:
      valueKind = VK_PRValue;
      break;
  
    // Fields and indirect fields that got here must be for
    // pointer-to-member expressions; we just call them l-values for
    // internal consistency, because this subexpression doesn't really
    // exist in the high-level semantics.
    case Decl::Field:
    case Decl::IndirectField:
    case Decl::ObjCIvar:
      assert(getLangOpts().CPlusPlus && "building reference to field in C?");
  
      // These can't have reference type in well-formed programs, but
      // for internal consistency we do this anyway.
      type = type.getNonReferenceType();
      valueKind = VK_LValue;
      break;
  
    // Non-type template parameters are either l-values or r-values
    // depending on the type.
    case Decl::NonTypeTemplateParm: {
      if (const ReferenceType *reftype = type->getAs<ReferenceType>()) {
        type = reftype->getPointeeType();
        valueKind = VK_LValue; // even if the parameter is an r-value reference
        break;
      }
  
      // [expr.prim.id.unqual]p2:
      //   If the entity is a template parameter object for a template
      //   parameter of type T, the type of the expression is const T.
      //   [...] The expression is an lvalue if the entity is a [...] template
      //   parameter object.
      if (type->isRecordType()) {
        type = type.getUnqualifiedType().withConst();
        valueKind = VK_LValue;
        break;
      }
  
      // For non-references, we need to strip qualifiers just in case
      // the template parameter was declared as 'const int' or whatever.
      valueKind = VK_PRValue;
      type = type.getUnqualifiedType();
      break;
    }
  
    case Decl::Var:
    case Decl::VarTemplateSpecialization:
    case Decl::VarTemplatePartialSpecialization:
    case Decl::Decomposition:
    case Decl::OMPCapturedExpr:
      // In C, "extern void blah;" is valid and is an r-value.
      if (!getLangOpts().CPlusPlus && !type.hasQualifiers() &&
          type->isVoidType()) {
        valueKind = VK_PRValue;
        break;
      }
      LLVM_FALLTHROUGH;
  
    case Decl::ImplicitParam:
    case Decl::ParmVar: {
      // These are always l-values.
      valueKind = VK_LValue;
      type = type.getNonReferenceType();
  
      // FIXME: Does the addition of const really only apply in
      // potentially-evaluated contexts? Since the variable isn't actually
      // captured in an unevaluated context, it seems that the answer is no.
      if (!isUnevaluatedContext()) {
        QualType CapturedType = getCapturedDeclRefType(cast<VarDecl>(VD), Loc);
        if (!CapturedType.isNull())
          type = CapturedType;
      }
  
      break;
    }
  
    case Decl::Binding: {
      // These are always lvalues.
      valueKind = VK_LValue;
      type = type.getNonReferenceType();
      // FIXME: Support lambda-capture of BindingDecls, once CWG actually
      // decides how that's supposed to work.
      auto *BD = cast<BindingDecl>(VD);
      if (BD->getDeclContext() != CurContext) {
        auto *DD = dyn_cast_or_null<VarDecl>(BD->getDecomposedDecl());
        if (DD && DD->hasLocalStorage())
          diagnoseUncapturableValueReference(*this, Loc, BD);
      }
      break;
    }
  
    case Decl::Function: {
      if (unsigned BID = cast<FunctionDecl>(VD)->getBuiltinID()) {
        if (!Context.BuiltinInfo.isPredefinedLibFunction(BID)) {
          type = Context.BuiltinFnTy;
          valueKind = VK_PRValue;
          break;
        }
      }
  
      const FunctionType *fty = type->castAs<FunctionType>();
  
      // If we're referring to a function with an __unknown_anytype
      // result type, make the entire expression __unknown_anytype.
      if (fty->getReturnType() == Context.UnknownAnyTy) {
        type = Context.UnknownAnyTy;
        valueKind = VK_PRValue;
        break;
      }
  
      // Functions are l-values in C++.
      if (getLangOpts().CPlusPlus) {
        valueKind = VK_LValue;
        break;
      }
  
      // C99 DR 316 says that, if a function type comes from a
      // function definition (without a prototype), that type is only
      // used for checking compatibility. Therefore, when referencing
      // the function, we pretend that we don't have the full function
      // type.
      if (!cast<FunctionDecl>(VD)->hasPrototype() && isa<FunctionProtoType>(fty))
        type = Context.getFunctionNoProtoType(fty->getReturnType(),
                                              fty->getExtInfo());
  
      // Functions are r-values in C.
      valueKind = VK_PRValue;
      break;
    }
  
    case Decl::CXXDeductionGuide:
      llvm_unreachable("building reference to deduction guide");
  
    case Decl::MSProperty:
    case Decl::MSGuid:
    case Decl::TemplateParamObject:
      // FIXME: Should MSGuidDecl and template parameter objects be subject to
      // capture in OpenMP, or duplicated between host and device?
      valueKind = VK_LValue;
      break;
  
    case Decl::CXXMethod:
      // If we're referring to a method with an __unknown_anytype
      // result type, make the entire expression __unknown_anytype.
      // This should only be possible with a type written directly.
      if (const FunctionProtoType *proto =
              dyn_cast<FunctionProtoType>(VD->getType()))
        if (proto->getReturnType() == Context.UnknownAnyTy) {
          type = Context.UnknownAnyTy;
          valueKind = VK_PRValue;
          break;
        }
  
      // C++ methods are l-values if static, r-values if non-static.
      if (cast<CXXMethodDecl>(VD)->isStatic()) {
        valueKind = VK_LValue;
        break;
      }
      LLVM_FALLTHROUGH;
  
    case Decl::CXXConversion:
    case Decl::CXXDestructor:
    case Decl::CXXConstructor:
      valueKind = VK_PRValue;
      break;
    }
  
    return BuildDeclRefExpr(VD, type, valueKind, NameInfo, &SS, FoundD,
                            /*FIXME: TemplateKWLoc*/ SourceLocation(),
                            TemplateArgs);
  }
  
  static void ConvertUTF8ToWideString(unsigned CharByteWidth, StringRef Source,
                                      SmallString<32> &Target) {
    Target.resize(CharByteWidth * (Source.size() + 1));
    char *ResultPtr = &Target[0];
    const llvm::UTF8 *ErrorPtr;
    bool success =
        llvm::ConvertUTF8toWide(CharByteWidth, Source, ResultPtr, ErrorPtr);
    (void)success;
    assert(success);
    Target.resize(ResultPtr - &Target[0]);
  }
  
  ExprResult Sema::BuildPredefinedExpr(SourceLocation Loc,
                                       PredefinedExpr::IdentKind IK) {
    // Pick the current block, lambda, captured statement or function.
    Decl *currentDecl = nullptr;
    if (const BlockScopeInfo *BSI = getCurBlock())
      currentDecl = BSI->TheDecl;
    else if (const LambdaScopeInfo *LSI = getCurLambda())
      currentDecl = LSI->CallOperator;
    else if (const CapturedRegionScopeInfo *CSI = getCurCapturedRegion())
      currentDecl = CSI->TheCapturedDecl;
    else
      currentDecl = getCurFunctionOrMethodDecl();
  
    if (!currentDecl) {
      Diag(Loc, diag::ext_predef_outside_function);
      currentDecl = Context.getTranslationUnitDecl();
    }
  
    QualType ResTy;
    StringLiteral *SL = nullptr;
    if (cast<DeclContext>(currentDecl)->isDependentContext())
      ResTy = Context.DependentTy;
    else {
      // Pre-defined identifiers are of type char[x], where x is the length of
      // the string.
      auto Str = PredefinedExpr::ComputeName(IK, currentDecl);
      unsigned Length = Str.length();
  
      llvm::APInt LengthI(32, Length + 1);
      if (IK == PredefinedExpr::LFunction || IK == PredefinedExpr::LFuncSig) {
        ResTy =
            Context.adjustStringLiteralBaseType(Context.WideCharTy.withConst());
        SmallString<32> RawChars;
        ConvertUTF8ToWideString(Context.getTypeSizeInChars(ResTy).getQuantity(),
                                Str, RawChars);
        ResTy = Context.getConstantArrayType(ResTy, LengthI, nullptr,
                                             ArrayType::Normal,
                                             /*IndexTypeQuals*/ 0);
        SL = StringLiteral::Create(Context, RawChars, StringLiteral::Wide,
                                   /*Pascal*/ false, ResTy, Loc);
      } else {
        ResTy = Context.adjustStringLiteralBaseType(Context.CharTy.withConst());
        ResTy = Context.getConstantArrayType(ResTy, LengthI, nullptr,
                                             ArrayType::Normal,
                                             /*IndexTypeQuals*/ 0);
        SL = StringLiteral::Create(Context, Str, StringLiteral::Ascii,
                                   /*Pascal*/ false, ResTy, Loc);
      }
    }
  
    return PredefinedExpr::Create(Context, Loc, ResTy, IK, SL);
  }
  
  ExprResult Sema::BuildSYCLUniqueStableNameExpr(SourceLocation OpLoc,
                                                 SourceLocation LParen,
                                                 SourceLocation RParen,
                                                 TypeSourceInfo *TSI) {
    return SYCLUniqueStableNameExpr::Create(Context, OpLoc, LParen, RParen, TSI);
  }
  
  ExprResult Sema::ActOnSYCLUniqueStableNameExpr(SourceLocation OpLoc,
                                                 SourceLocation LParen,
                                                 SourceLocation RParen,
                                                 ParsedType ParsedTy) {
    TypeSourceInfo *TSI = nullptr;
    QualType Ty = GetTypeFromParser(ParsedTy, &TSI);
  
    if (Ty.isNull())
      return ExprError();
    if (!TSI)
      TSI = Context.getTrivialTypeSourceInfo(Ty, LParen);
  
    return BuildSYCLUniqueStableNameExpr(OpLoc, LParen, RParen, TSI);
  }
  
  ExprResult Sema::ActOnPredefinedExpr(SourceLocation Loc, tok::TokenKind Kind) {
    PredefinedExpr::IdentKind IK;
  
    switch (Kind) {
    default: llvm_unreachable("Unknown simple primary expr!");
    case tok::kw___func__: IK = PredefinedExpr::Func; break; // [C99 6.4.2.2]
    case tok::kw___FUNCTION__: IK = PredefinedExpr::Function; break;
    case tok::kw___FUNCDNAME__: IK = PredefinedExpr::FuncDName; break; // [MS]
    case tok::kw___FUNCSIG__: IK = PredefinedExpr::FuncSig; break; // [MS]
    case tok::kw_L__FUNCTION__: IK = PredefinedExpr::LFunction; break; // [MS]
    case tok::kw_L__FUNCSIG__: IK = PredefinedExpr::LFuncSig; break; // [MS]
    case tok::kw___PRETTY_FUNCTION__: IK = PredefinedExpr::PrettyFunction; break;
    }
  
    return BuildPredefinedExpr(Loc, IK);
  }
  
  ExprResult Sema::ActOnCharacterConstant(const Token &Tok, Scope *UDLScope) {
    SmallString<16> CharBuffer;
    bool Invalid = false;
    StringRef ThisTok = PP.getSpelling(Tok, CharBuffer, &Invalid);
    if (Invalid)
      return ExprError();
  
    CharLiteralParser Literal(ThisTok.begin(), ThisTok.end(), Tok.getLocation(),
                              PP, Tok.getKind());
    if (Literal.hadError())
      return ExprError();
  
    QualType Ty;
    if (Literal.isWide())
      Ty = Context.WideCharTy; // L'x' -> wchar_t in C and C++.
    else if (Literal.isUTF8() && getLangOpts().Char8)
      Ty = Context.Char8Ty; // u8'x' -> char8_t when it exists.
    else if (Literal.isUTF16())
      Ty = Context.Char16Ty; // u'x' -> char16_t in C11 and C++11.
    else if (Literal.isUTF32())
      Ty = Context.Char32Ty; // U'x' -> char32_t in C11 and C++11.
    else if (!getLangOpts().CPlusPlus || Literal.isMultiChar())
      Ty = Context.IntTy;   // 'x' -> int in C, 'wxyz' -> int in C++.
    else
      Ty = Context.CharTy;  // 'x' -> char in C++
  
    CharacterLiteral::CharacterKind Kind = CharacterLiteral::Ascii;
    if (Literal.isWide())
      Kind = CharacterLiteral::Wide;
    else if (Literal.isUTF16())
      Kind = CharacterLiteral::UTF16;
    else if (Literal.isUTF32())
      Kind = CharacterLiteral::UTF32;
    else if (Literal.isUTF8())
      Kind = CharacterLiteral::UTF8;
  
    Expr *Lit = new (Context) CharacterLiteral(Literal.getValue(), Kind, Ty,
                                               Tok.getLocation());
  
    if (Literal.getUDSuffix().empty())
      return Lit;
  
    // We're building a user-defined literal.
    IdentifierInfo *UDSuffix = &Context.Idents.get(Literal.getUDSuffix());
    SourceLocation UDSuffixLoc =
      getUDSuffixLoc(*this, Tok.getLocation(), Literal.getUDSuffixOffset());
  
    // Make sure we're allowed user-defined literals here.
    if (!UDLScope)
      return ExprError(Diag(UDSuffixLoc, diag::err_invalid_character_udl));
  
    // C++11 [lex.ext]p6: The literal L is treated as a call of the form
    //   operator "" X (ch)
    return BuildCookedLiteralOperatorCall(*this, UDLScope, UDSuffix, UDSuffixLoc,
                                          Lit, Tok.getLocation());
  }
  
  ExprResult Sema::ActOnIntegerConstant(SourceLocation Loc, uint64_t Val) {
    unsigned IntSize = Context.getTargetInfo().getIntWidth();
    return IntegerLiteral::Create(Context, llvm::APInt(IntSize, Val),
                                  Context.IntTy, Loc);
  }
  
  static Expr *BuildFloatingLiteral(Sema &S, NumericLiteralParser &Literal,
                                    QualType Ty, SourceLocation Loc) {
    const llvm::fltSemantics &Format = S.Context.getFloatTypeSemantics(Ty);
  
    using llvm::APFloat;
    APFloat Val(Format);
  
    APFloat::opStatus result = Literal.GetFloatValue(Val);
  
    // Overflow is always an error, but underflow is only an error if
    // we underflowed to zero (APFloat reports denormals as underflow).
    if ((result & APFloat::opOverflow) ||
        ((result & APFloat::opUnderflow) && Val.isZero())) {
      unsigned diagnostic;
      SmallString<20> buffer;
      if (result & APFloat::opOverflow) {
        diagnostic = diag::warn_float_overflow;
        APFloat::getLargest(Format).toString(buffer);
      } else {
        diagnostic = diag::warn_float_underflow;
        APFloat::getSmallest(Format).toString(buffer);
      }
  
      S.Diag(Loc, diagnostic)
        << Ty
        << StringRef(buffer.data(), buffer.size());
    }
  
    bool isExact = (result == APFloat::opOK);
    return FloatingLiteral::Create(S.Context, Val, isExact, Ty, Loc);
  }
  
  bool Sema::CheckLoopHintExpr(Expr *E, SourceLocation Loc) {
    assert(E && "Invalid expression");
  
    if (E->isValueDependent())
      return false;
  
    QualType QT = E->getType();
    if (!QT->isIntegerType() || QT->isBooleanType() || QT->isCharType()) {
      Diag(E->getExprLoc(), diag::err_pragma_loop_invalid_argument_type) << QT;
      return true;
    }
  
    llvm::APSInt ValueAPS;
    ExprResult R = VerifyIntegerConstantExpression(E, &ValueAPS);
  
    if (R.isInvalid())
      return true;
  
    bool ValueIsPositive = ValueAPS.isStrictlyPositive();
    if (!ValueIsPositive || ValueAPS.getActiveBits() > 31) {
      Diag(E->getExprLoc(), diag::err_pragma_loop_invalid_argument_value)
          << toString(ValueAPS, 10) << ValueIsPositive;
      return true;
    }
  
    return false;
  }
  
  ExprResult Sema::ActOnNumericConstant(const Token &Tok, Scope *UDLScope) {
    // Fast path for a single digit (which is quite common).  A single digit
    // cannot have a trigraph, escaped newline, radix prefix, or suffix.
    if (Tok.getLength() == 1) {
      const char Val = PP.getSpellingOfSingleCharacterNumericConstant(Tok);
      return ActOnIntegerConstant(Tok.getLocation(), Val-'0');
    }
  
    SmallString<128> SpellingBuffer;
    // NumericLiteralParser wants to overread by one character.  Add padding to
    // the buffer in case the token is copied to the buffer.  If getSpelling()
    // returns a StringRef to the memory buffer, it should have a null char at
    // the EOF, so it is also safe.
    SpellingBuffer.resize(Tok.getLength() + 1);
  
    // Get the spelling of the token, which eliminates trigraphs, etc.
    bool Invalid = false;
    StringRef TokSpelling = PP.getSpelling(Tok, SpellingBuffer, &Invalid);
    if (Invalid)
      return ExprError();
  
    NumericLiteralParser Literal(TokSpelling, Tok.getLocation(),
                                 PP.getSourceManager(), PP.getLangOpts(),
                                 PP.getTargetInfo(), PP.getDiagnostics());
    if (Literal.hadError)
      return ExprError();
  
    if (Literal.hasUDSuffix()) {
      // We're building a user-defined literal.
      IdentifierInfo *UDSuffix = &Context.Idents.get(Literal.getUDSuffix());
      SourceLocation UDSuffixLoc =
        getUDSuffixLoc(*this, Tok.getLocation(), Literal.getUDSuffixOffset());
  
      // Make sure we're allowed user-defined literals here.
      if (!UDLScope)
        return ExprError(Diag(UDSuffixLoc, diag::err_invalid_numeric_udl));
  
      QualType CookedTy;
      if (Literal.isFloatingLiteral()) {
        // C++11 [lex.ext]p4: If S contains a literal operator with parameter type
        // long double, the literal is treated as a call of the form
        //   operator "" X (f L)
        CookedTy = Context.LongDoubleTy;
      } else {
        // C++11 [lex.ext]p3: If S contains a literal operator with parameter type
        // unsigned long long, the literal is treated as a call of the form
        //   operator "" X (n ULL)
        CookedTy = Context.UnsignedLongLongTy;
      }
  
      DeclarationName OpName =
        Context.DeclarationNames.getCXXLiteralOperatorName(UDSuffix);
      DeclarationNameInfo OpNameInfo(OpName, UDSuffixLoc);
      OpNameInfo.setCXXLiteralOperatorNameLoc(UDSuffixLoc);
  
      SourceLocation TokLoc = Tok.getLocation();
  
      // Perform literal operator lookup to determine if we're building a raw
      // literal or a cooked one.
      LookupResult R(*this, OpName, UDSuffixLoc, LookupOrdinaryName);
      switch (LookupLiteralOperator(UDLScope, R, CookedTy,
                                    /*AllowRaw*/ true, /*AllowTemplate*/ true,
                                    /*AllowStringTemplatePack*/ false,
                                    /*DiagnoseMissing*/ !Literal.isImaginary)) {
      case LOLR_ErrorNoDiagnostic:
        // Lookup failure for imaginary constants isn't fatal, there's still the
        // GNU extension producing _Complex types.
        break;
      case LOLR_Error:
        return ExprError();
      case LOLR_Cooked: {
        Expr *Lit;
        if (Literal.isFloatingLiteral()) {
          Lit = BuildFloatingLiteral(*this, Literal, CookedTy, Tok.getLocation());
        } else {
          llvm::APInt ResultVal(Context.getTargetInfo().getLongLongWidth(), 0);
          if (Literal.GetIntegerValue(ResultVal))
            Diag(Tok.getLocation(), diag::err_integer_literal_too_large)
                << /* Unsigned */ 1;
          Lit = IntegerLiteral::Create(Context, ResultVal, CookedTy,
                                       Tok.getLocation());
        }
        return BuildLiteralOperatorCall(R, OpNameInfo, Lit, TokLoc);
      }
  
      case LOLR_Raw: {
        // C++11 [lit.ext]p3, p4: If S contains a raw literal operator, the
        // literal is treated as a call of the form
        //   operator "" X ("n")
        unsigned Length = Literal.getUDSuffixOffset();
        QualType StrTy = Context.getConstantArrayType(
            Context.adjustStringLiteralBaseType(Context.CharTy.withConst()),
            llvm::APInt(32, Length + 1), nullptr, ArrayType::Normal, 0);
        Expr *Lit = StringLiteral::Create(
            Context, StringRef(TokSpelling.data(), Length), StringLiteral::Ascii,
            /*Pascal*/false, StrTy, &TokLoc, 1);
        return BuildLiteralOperatorCall(R, OpNameInfo, Lit, TokLoc);
      }
  
      case LOLR_Template: {
        // C++11 [lit.ext]p3, p4: Otherwise (S contains a literal operator
        // template), L is treated as a call fo the form
        //   operator "" X <'c1', 'c2', ... 'ck'>()
        // where n is the source character sequence c1 c2 ... ck.
        TemplateArgumentListInfo ExplicitArgs;
        unsigned CharBits = Context.getIntWidth(Context.CharTy);
        bool CharIsUnsigned = Context.CharTy->isUnsignedIntegerType();
        llvm::APSInt Value(CharBits, CharIsUnsigned);
        for (unsigned I = 0, N = Literal.getUDSuffixOffset(); I != N; ++I) {
          Value = TokSpelling[I];
          TemplateArgument Arg(Context, Value, Context.CharTy);
          TemplateArgumentLocInfo ArgInfo;
          ExplicitArgs.addArgument(TemplateArgumentLoc(Arg, ArgInfo));
        }
        return BuildLiteralOperatorCall(R, OpNameInfo, None, TokLoc,
                                        &ExplicitArgs);
      }
      case LOLR_StringTemplatePack:
        llvm_unreachable("unexpected literal operator lookup result");
      }
    }
  
    Expr *Res;
  
    if (Literal.isFixedPointLiteral()) {
      QualType Ty;
  
      if (Literal.isAccum) {
        if (Literal.isHalf) {
          Ty = Context.ShortAccumTy;
        } else if (Literal.isLong) {
          Ty = Context.LongAccumTy;
        } else {
          Ty = Context.AccumTy;
        }
      } else if (Literal.isFract) {
        if (Literal.isHalf) {
          Ty = Context.ShortFractTy;
        } else if (Literal.isLong) {
          Ty = Context.LongFractTy;
        } else {
          Ty = Context.FractTy;
        }
      }
  
      if (Literal.isUnsigned) Ty = Context.getCorrespondingUnsignedType(Ty);
  
      bool isSigned = !Literal.isUnsigned;
      unsigned scale = Context.getFixedPointScale(Ty);
      unsigned bit_width = Context.getTypeInfo(Ty).Width;
  
      llvm::APInt Val(bit_width, 0, isSigned);
      bool Overflowed = Literal.GetFixedPointValue(Val, scale);
      bool ValIsZero = Val.isZero() && !Overflowed;
  
      auto MaxVal = Context.getFixedPointMax(Ty).getValue();
      if (Literal.isFract && Val == MaxVal + 1 && !ValIsZero)
        // Clause 6.4.4 - The value of a constant shall be in the range of
        // representable values for its type, with exception for constants of a
        // fract type with a value of exactly 1; such a constant shall denote
        // the maximal value for the type.
        --Val;
      else if (Val.ugt(MaxVal) || Overflowed)
        Diag(Tok.getLocation(), diag::err_too_large_for_fixed_point);
  
      Res = FixedPointLiteral::CreateFromRawInt(Context, Val, Ty,
                                                Tok.getLocation(), scale);
    } else if (Literal.isFloatingLiteral()) {
      QualType Ty;
      if (Literal.isHalf){
        if (getOpenCLOptions().isAvailableOption("cl_khr_fp16", getLangOpts()))
          Ty = Context.HalfTy;
        else {
          Diag(Tok.getLocation(), diag::err_half_const_requires_fp16);
          return ExprError();
        }
      } else if (Literal.isFloat)
        Ty = Context.FloatTy;
      else if (Literal.isLong)
        Ty = Context.LongDoubleTy;
      else if (Literal.isFloat16)
        Ty = Context.Float16Ty;
      else if (Literal.isFloat128)
        Ty = Context.Float128Ty;
      else
        Ty = Context.DoubleTy;
  
      Res = BuildFloatingLiteral(*this, Literal, Ty, Tok.getLocation());
  
      if (Ty == Context.DoubleTy) {
        if (getLangOpts().SinglePrecisionConstants) {
          if (Ty->castAs<BuiltinType>()->getKind() != BuiltinType::Float) {
            Res = ImpCastExprToType(Res, Context.FloatTy, CK_FloatingCast).get();
          }
        } else if (getLangOpts().OpenCL && !getOpenCLOptions().isAvailableOption(
                                               "cl_khr_fp64", getLangOpts())) {
          // Impose single-precision float type when cl_khr_fp64 is not enabled.
          Diag(Tok.getLocation(), diag::warn_double_const_requires_fp64)
              << (getLangOpts().getOpenCLCompatibleVersion() >= 300);
          Res = ImpCastExprToType(Res, Context.FloatTy, CK_FloatingCast).get();
        }
      }
    } else if (!Literal.isIntegerLiteral()) {
      return ExprError();
    } else {
      QualType Ty;
  
      // 'long long' is a C99 or C++11 feature.
      if (!getLangOpts().C99 && Literal.isLongLong) {
        if (getLangOpts().CPlusPlus)
          Diag(Tok.getLocation(),
               getLangOpts().CPlusPlus11 ?
               diag::warn_cxx98_compat_longlong : diag::ext_cxx11_longlong);
        else
          Diag(Tok.getLocation(), diag::ext_c99_longlong);
      }
  
      // 'z/uz' literals are a C++2b feature.
      if (Literal.isSizeT)
        Diag(Tok.getLocation(), getLangOpts().CPlusPlus
                                    ? getLangOpts().CPlusPlus2b
                                          ? diag::warn_cxx20_compat_size_t_suffix
                                          : diag::ext_cxx2b_size_t_suffix
                                    : diag::err_cxx2b_size_t_suffix);
  
      // Get the value in the widest-possible width.
      unsigned MaxWidth = Context.getTargetInfo().getIntMaxTWidth();
      llvm::APInt ResultVal(MaxWidth, 0);
  
      if (Literal.GetIntegerValue(ResultVal)) {
        // If this value didn't fit into uintmax_t, error and force to ull.
        Diag(Tok.getLocation(), diag::err_integer_literal_too_large)
            << /* Unsigned */ 1;
        Ty = Context.UnsignedLongLongTy;
        assert(Context.getTypeSize(Ty) == ResultVal.getBitWidth() &&
               "long long is not intmax_t?");
      } else {
        // If this value fits into a ULL, try to figure out what else it fits into
        // according to the rules of C99 6.4.4.1p5.
  
        // Octal, Hexadecimal, and integers with a U suffix are allowed to
        // be an unsigned int.
        bool AllowUnsigned = Literal.isUnsigned || Literal.getRadix() != 10;
  
        // Check from smallest to largest, picking the smallest type we can.
        unsigned Width = 0;
  
        // Microsoft specific integer suffixes are explicitly sized.
        if (Literal.MicrosoftInteger) {
          if (Literal.MicrosoftInteger == 8 && !Literal.isUnsigned) {
            Width = 8;
            Ty = Context.CharTy;
          } else {
            Width = Literal.MicrosoftInteger;
            Ty = Context.getIntTypeForBitwidth(Width,
                                               /*Signed=*/!Literal.isUnsigned);
          }
        }
  
        // Check C++2b size_t literals.
        if (Literal.isSizeT) {
          assert(!Literal.MicrosoftInteger &&
                 "size_t literals can't be Microsoft literals");
          unsigned SizeTSize = Context.getTargetInfo().getTypeWidth(
              Context.getTargetInfo().getSizeType());
  
          // Does it fit in size_t?
          if (ResultVal.isIntN(SizeTSize)) {
            // Does it fit in ssize_t?
            if (!Literal.isUnsigned && ResultVal[SizeTSize - 1] == 0)
              Ty = Context.getSignedSizeType();
            else if (AllowUnsigned)
              Ty = Context.getSizeType();
            Width = SizeTSize;
          }
        }
  
        if (Ty.isNull() && !Literal.isLong && !Literal.isLongLong &&
            !Literal.isSizeT) {
          // Are int/unsigned possibilities?
          unsigned IntSize = Context.getTargetInfo().getIntWidth();
  
          // Does it fit in a unsigned int?
          if (ResultVal.isIntN(IntSize)) {
            // Does it fit in a signed int?
            if (!Literal.isUnsigned && ResultVal[IntSize-1] == 0)
              Ty = Context.IntTy;
            else if (AllowUnsigned)
              Ty = Context.UnsignedIntTy;
            Width = IntSize;
          }
        }
  
        // Are long/unsigned long possibilities?
        if (Ty.isNull() && !Literal.isLongLong && !Literal.isSizeT) {
          unsigned LongSize = Context.getTargetInfo().getLongWidth();
  
          // Does it fit in a unsigned long?
          if (ResultVal.isIntN(LongSize)) {
            // Does it fit in a signed long?
            if (!Literal.isUnsigned && ResultVal[LongSize-1] == 0)
              Ty = Context.LongTy;
            else if (AllowUnsigned)
              Ty = Context.UnsignedLongTy;
            // Check according to the rules of C90 6.1.3.2p5. C++03 [lex.icon]p2
            // is compatible.
            else if (!getLangOpts().C99 && !getLangOpts().CPlusPlus11) {
              const unsigned LongLongSize =
                  Context.getTargetInfo().getLongLongWidth();
              Diag(Tok.getLocation(),
                   getLangOpts().CPlusPlus
                       ? Literal.isLong
                             ? diag::warn_old_implicitly_unsigned_long_cxx
                             : /*C++98 UB*/ diag::
                                   ext_old_implicitly_unsigned_long_cxx
                       : diag::warn_old_implicitly_unsigned_long)
                  << (LongLongSize > LongSize ? /*will have type 'long long'*/ 0
                                              : /*will be ill-formed*/ 1);
              Ty = Context.UnsignedLongTy;
            }
            Width = LongSize;
          }
        }
  
        // Check long long if needed.
        if (Ty.isNull() && !Literal.isSizeT) {
          unsigned LongLongSize = Context.getTargetInfo().getLongLongWidth();
  
          // Does it fit in a unsigned long long?
          if (ResultVal.isIntN(LongLongSize)) {
            // Does it fit in a signed long long?
            // To be compatible with MSVC, hex integer literals ending with the
            // LL or i64 suffix are always signed in Microsoft mode.
            if (!Literal.isUnsigned && (ResultVal[LongLongSize-1] == 0 ||
                (getLangOpts().MSVCCompat && Literal.isLongLong)))
              Ty = Context.LongLongTy;
            else if (AllowUnsigned)
              Ty = Context.UnsignedLongLongTy;
            Width = LongLongSize;
          }
        }
  
        // If we still couldn't decide a type, we either have 'size_t' literal
        // that is out of range, or a decimal literal that does not fit in a
        // signed long long and has no U suffix.
        if (Ty.isNull()) {
          if (Literal.isSizeT)
            Diag(Tok.getLocation(), diag::err_size_t_literal_too_large)
                << Literal.isUnsigned;
          else
            Diag(Tok.getLocation(),
                 diag::ext_integer_literal_too_large_for_signed);
          Ty = Context.UnsignedLongLongTy;
          Width = Context.getTargetInfo().getLongLongWidth();
        }
  
        if (ResultVal.getBitWidth() != Width)
          ResultVal = ResultVal.trunc(Width);
      }
      Res = IntegerLiteral::Create(Context, ResultVal, Ty, Tok.getLocation());
    }
  
    // If this is an imaginary literal, create the ImaginaryLiteral wrapper.
    if (Literal.isImaginary) {
      Res = new (Context) ImaginaryLiteral(Res,
                                          Context.getComplexType(Res->getType()));
  
      Diag(Tok.getLocation(), diag::ext_imaginary_constant);
    }
    return Res;
  }
  
  ExprResult Sema::ActOnParenExpr(SourceLocation L, SourceLocation R, Expr *E) {
    assert(E && "ActOnParenExpr() missing expr");
    QualType ExprTy = E->getType();
    if (getLangOpts().ProtectParens && CurFPFeatures.getAllowFPReassociate() &&
        !E->isLValue() && ExprTy->hasFloatingRepresentation())
      return BuildBuiltinCallExpr(R, Builtin::BI__arithmetic_fence, E);
    return new (Context) ParenExpr(L, R, E);
  }
  
  static bool CheckVecStepTraitOperandType(Sema &S, QualType T,
                                           SourceLocation Loc,
                                           SourceRange ArgRange) {
    // [OpenCL 1.1 6.11.12] "The vec_step built-in function takes a built-in
    // scalar or vector data type argument..."
    // Every built-in scalar type (OpenCL 1.1 6.1.1) is either an arithmetic
    // type (C99 6.2.5p18) or void.
    if (!(T->isArithmeticType() || T->isVoidType() || T->isVectorType())) {
      S.Diag(Loc, diag::err_vecstep_non_scalar_vector_type)
        << T << ArgRange;
      return true;
    }
  
    assert((T->isVoidType() || !T->isIncompleteType()) &&
           "Scalar types should always be complete");
    return false;
  }
  
  static bool CheckPtrAuthTypeDiscriminatorOperandType(Sema &S, QualType T,
                                                       SourceLocation Loc,
                                                       SourceRange ArgRange) {
    if (T->isVariablyModifiedType()) {
      S.Diag(Loc, diag::err_ptrauth_type_disc_variably_modified) << T << ArgRange;
      return true;
    }
  
    return false;
  }
  
  static bool CheckExtensionTraitOperandType(Sema &S, QualType T,
                                             SourceLocation Loc,
                                             SourceRange ArgRange,
                                             UnaryExprOrTypeTrait TraitKind) {
    // Invalid types must be hard errors for SFINAE in C++.
    if (S.LangOpts.CPlusPlus)
      return true;
  
    // C99 6.5.3.4p1:
    if (T->isFunctionType() &&
        (TraitKind == UETT_SizeOf || TraitKind == UETT_AlignOf ||
         TraitKind == UETT_PreferredAlignOf)) {
      // sizeof(function)/alignof(function) is allowed as an extension.
      S.Diag(Loc, diag::ext_sizeof_alignof_function_type)
          << getTraitSpelling(TraitKind) << ArgRange;
      return false;
    }
  
    // Allow sizeof(void)/alignof(void) as an extension, unless in OpenCL where
    // this is an error (OpenCL v1.1 s6.3.k)
    if (T->isVoidType()) {
      unsigned DiagID = S.LangOpts.OpenCL ? diag::err_opencl_sizeof_alignof_type
                                          : diag::ext_sizeof_alignof_void_type;
      S.Diag(Loc, DiagID) << getTraitSpelling(TraitKind) << ArgRange;
      return false;
    }
  
    return true;
  }
  
  static bool CheckObjCTraitOperandConstraints(Sema &S, QualType T,
                                               SourceLocation Loc,
                                               SourceRange ArgRange,
                                               UnaryExprOrTypeTrait TraitKind) {
    // Reject sizeof(interface) and sizeof(interface<proto>) if the
    // runtime doesn't allow it.
    if (!S.LangOpts.ObjCRuntime.allowsSizeofAlignof() && T->isObjCObjectType()) {
      S.Diag(Loc, diag::err_sizeof_nonfragile_interface)
        << T << (TraitKind == UETT_SizeOf)
        << ArgRange;
      return true;
    }
  
    return false;
  }
  
  /// Check whether E is a pointer from a decayed array type (the decayed
  /// pointer type is equal to T) and emit a warning if it is.
  static void warnOnSizeofOnArrayDecay(Sema &S, SourceLocation Loc, QualType T,
                                       Expr *E) {
    // Don't warn if the operation changed the type.
    if (T != E->getType())
      return;
  
    // Now look for array decays.
    ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E);
    if (!ICE || ICE->getCastKind() != CK_ArrayToPointerDecay)
      return;
  
    S.Diag(Loc, diag::warn_sizeof_array_decay) << ICE->getSourceRange()
                                               << ICE->getType()
                                               << ICE->getSubExpr()->getType();
  }
  
  /// Check the constraints on expression operands to unary type expression
  /// and type traits.
  ///
  /// Completes any types necessary and validates the constraints on the operand
  /// expression. The logic mostly mirrors the type-based overload, but may modify
  /// the expression as it completes the type for that expression through template
  /// instantiation, etc.
  bool Sema::CheckUnaryExprOrTypeTraitOperand(Expr *E,
                                              UnaryExprOrTypeTrait ExprKind) {
    QualType ExprTy = E->getType();
    assert(!ExprTy->isReferenceType());
  
    bool IsUnevaluatedOperand =
        (ExprKind == UETT_SizeOf || ExprKind == UETT_AlignOf ||
         ExprKind == UETT_PreferredAlignOf || ExprKind == UETT_VecStep);
    if (IsUnevaluatedOperand) {
      ExprResult Result = CheckUnevaluatedOperand(E);
      if (Result.isInvalid())
        return true;
      E = Result.get();
    }
  
    // The operand for sizeof and alignof is in an unevaluated expression context,
    // so side effects could result in unintended consequences.
    // Exclude instantiation-dependent expressions, because 'sizeof' is sometimes
    // used to build SFINAE gadgets.
    // FIXME: Should we consider instantiation-dependent operands to 'alignof'?
    if (IsUnevaluatedOperand && !inTemplateInstantiation() &&
        !E->isInstantiationDependent() &&
        E->HasSideEffects(Context, false))
      Diag(E->getExprLoc(), diag::warn_side_effects_unevaluated_context);
  
    if (ExprKind == UETT_VecStep)
      return CheckVecStepTraitOperandType(*this, ExprTy, E->getExprLoc(),
                                          E->getSourceRange());
  
    // Explicitly list some types as extensions.
    if (!CheckExtensionTraitOperandType(*this, ExprTy, E->getExprLoc(),
                                        E->getSourceRange(), ExprKind))
      return false;
  
    // 'alignof' applied to an expression only requires the base element type of
    // the expression to be complete. 'sizeof' requires the expression's type to
    // be complete (and will attempt to complete it if it's an array of unknown
    // bound).
    if (ExprKind == UETT_AlignOf || ExprKind == UETT_PreferredAlignOf) {
      if (RequireCompleteSizedType(
              E->getExprLoc(), Context.getBaseElementType(E->getType()),
              diag::err_sizeof_alignof_incomplete_or_sizeless_type,
              getTraitSpelling(ExprKind), E->getSourceRange()))
        return true;
    } else {
      if (RequireCompleteSizedExprType(
              E, diag::err_sizeof_alignof_incomplete_or_sizeless_type,
              getTraitSpelling(ExprKind), E->getSourceRange()))
        return true;
    }
  
    // Completing the expression's type may have changed it.
    ExprTy = E->getType();
    assert(!ExprTy->isReferenceType());
  
    if (ExprTy->isFunctionType()) {
      Diag(E->getExprLoc(), diag::err_sizeof_alignof_function_type)
          << getTraitSpelling(ExprKind) << E->getSourceRange();
      return true;
    }
  
    if (CheckObjCTraitOperandConstraints(*this, ExprTy, E->getExprLoc(),
                                         E->getSourceRange(), ExprKind))
      return true;
  
    if (ExprKind == UETT_SizeOf) {
      if (DeclRefExpr *DeclRef = dyn_cast<DeclRefExpr>(E->IgnoreParens())) {
        if (ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(DeclRef->getFoundDecl())) {
          QualType OType = PVD->getOriginalType();
          QualType Type = PVD->getType();
          if (Type->isPointerType() && OType->isArrayType()) {
            Diag(E->getExprLoc(), diag::warn_sizeof_array_param)
              << Type << OType;
            Diag(PVD->getLocation(), diag::note_declared_at);
          }
        }
      }
  
      // Warn on "sizeof(array op x)" and "sizeof(x op array)", where the array
      // decays into a pointer and returns an unintended result. This is most
      // likely a typo for "sizeof(array) op x".
      if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E->IgnoreParens())) {
        warnOnSizeofOnArrayDecay(*this, BO->getOperatorLoc(), BO->getType(),
                                 BO->getLHS());
        warnOnSizeofOnArrayDecay(*this, BO->getOperatorLoc(), BO->getType(),
                                 BO->getRHS());
      }
    }
  
    return false;
  }
  
  /// Check the constraints on operands to unary expression and type
  /// traits.
  ///
  /// This will complete any types necessary, and validate the various constraints
  /// on those operands.
  ///
  /// The UsualUnaryConversions() function is *not* called by this routine.
  /// C99 6.3.2.1p[2-4] all state:
  ///   Except when it is the operand of the sizeof operator ...
  ///
  /// C++ [expr.sizeof]p4
  ///   The lvalue-to-rvalue, array-to-pointer, and function-to-pointer
  ///   standard conversions are not applied to the operand of sizeof.
  ///
  /// This policy is followed for all of the unary trait expressions.
  bool Sema::CheckUnaryExprOrTypeTraitOperand(QualType ExprType,
                                              SourceLocation OpLoc,
                                              SourceRange ExprRange,
                                              UnaryExprOrTypeTrait ExprKind) {
    if (ExprType->isDependentType())
      return false;
  
    // C++ [expr.sizeof]p2:
    //     When applied to a reference or a reference type, the result
    //     is the size of the referenced type.
    // C++11 [expr.alignof]p3:
    //     When alignof is applied to a reference type, the result
    //     shall be the alignment of the referenced type.
    if (const ReferenceType *Ref = ExprType->getAs<ReferenceType>())
      ExprType = Ref->getPointeeType();
  
    // C11 6.5.3.4/3, C++11 [expr.alignof]p3:
    //   When alignof or _Alignof is applied to an array type, the result
    //   is the alignment of the element type.
    if (ExprKind == UETT_AlignOf || ExprKind == UETT_PreferredAlignOf ||
        ExprKind == UETT_OpenMPRequiredSimdAlign)
      ExprType = Context.getBaseElementType(ExprType);
  
    if (ExprKind == UETT_VecStep)
      return CheckVecStepTraitOperandType(*this, ExprType, OpLoc, ExprRange);
  
    if (ExprKind == UETT_PtrAuthTypeDiscriminator)
      return CheckPtrAuthTypeDiscriminatorOperandType(
          *this, ExprType, OpLoc, ExprRange);
  
    // Explicitly list some types as extensions.
    if (!CheckExtensionTraitOperandType(*this, ExprType, OpLoc, ExprRange,
                                        ExprKind))
      return false;
  
    if (RequireCompleteSizedType(
            OpLoc, ExprType, diag::err_sizeof_alignof_incomplete_or_sizeless_type,
            getTraitSpelling(ExprKind), ExprRange))
      return true;
  
    if (ExprType->isFunctionType()) {
      Diag(OpLoc, diag::err_sizeof_alignof_function_type)
          << getTraitSpelling(ExprKind) << ExprRange;
      return true;
    }
  
    if (CheckObjCTraitOperandConstraints(*this, ExprType, OpLoc, ExprRange,
                                         ExprKind))
      return true;
  
    return false;
  }
  
  static bool CheckAlignOfExpr(Sema &S, Expr *E, UnaryExprOrTypeTrait ExprKind) {
    // Cannot know anything else if the expression is dependent.
    if (E->isTypeDependent())
      return false;
  
    if (E->getObjectKind() == OK_BitField) {
      S.Diag(E->getExprLoc(), diag::err_sizeof_alignof_typeof_bitfield)
         << 1 << E->getSourceRange();
      return true;
    }
  
    ValueDecl *D = nullptr;
    Expr *Inner = E->IgnoreParens();
    if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Inner)) {
      D = DRE->getDecl();
    } else if (MemberExpr *ME = dyn_cast<MemberExpr>(Inner)) {
      D = ME->getMemberDecl();
    }
  
    // If it's a field, require the containing struct to have a
    // complete definition so that we can compute the layout.
    //
    // This can happen in C++11 onwards, either by naming the member
    // in a way that is not transformed into a member access expression
    // (in an unevaluated operand, for instance), or by naming the member
    // in a trailing-return-type.
    //
    // For the record, since __alignof__ on expressions is a GCC
    // extension, GCC seems to permit this but always gives the
    // nonsensical answer 0.
    //
    // We don't really need the layout here --- we could instead just
    // directly check for all the appropriate alignment-lowing
    // attributes --- but that would require duplicating a lot of
    // logic that just isn't worth duplicating for such a marginal
    // use-case.
    if (FieldDecl *FD = dyn_cast_or_null<FieldDecl>(D)) {
      // Fast path this check, since we at least know the record has a
      // definition if we can find a member of it.
      if (!FD->getParent()->isCompleteDefinition()) {
        S.Diag(E->getExprLoc(), diag::err_alignof_member_of_incomplete_type)
          << E->getSourceRange();
        return true;
      }
  
      // Otherwise, if it's a field, and the field doesn't have
      // reference type, then it must have a complete type (or be a
      // flexible array member, which we explicitly want to
      // white-list anyway), which makes the following checks trivial.
      if (!FD->getType()->isReferenceType())
        return false;
    }
  
    return S.CheckUnaryExprOrTypeTraitOperand(E, ExprKind);
  }
  
  bool Sema::CheckVecStepExpr(Expr *E) {
    E = E->IgnoreParens();
  
    // Cannot know anything else if the expression is dependent.
    if (E->isTypeDependent())
      return false;
  
    return CheckUnaryExprOrTypeTraitOperand(E, UETT_VecStep);
  }
  
  static void captureVariablyModifiedType(ASTContext &Context, QualType T,
                                          CapturingScopeInfo *CSI) {
    assert(T->isVariablyModifiedType());
    assert(CSI != nullptr);
  
    // We're going to walk down into the type and look for VLA expressions.
    do {
      const Type *Ty = T.getTypePtr();
      switch (Ty->getTypeClass()) {
  #define TYPE(Class, Base)
  #define ABSTRACT_TYPE(Class, Base)
  #define NON_CANONICAL_TYPE(Class, Base)
  #define DEPENDENT_TYPE(Class, Base) case Type::Class:
  #define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base)
  #include "clang/AST/TypeNodes.inc"
        T = QualType();
        break;
      // These types are never variably-modified.
      case Type::Builtin:
      case Type::Complex:
      case Type::Vector:
      case Type::ExtVector:
      case Type::ConstantMatrix:
      case Type::Record:
      case Type::Enum:
      case Type::Elaborated:
      case Type::TemplateSpecialization:
      case Type::ObjCObject:
      case Type::ObjCInterface:
      case Type::ObjCObjectPointer:
      case Type::ObjCTypeParam:
      case Type::Pipe:
      case Type::BitInt:
        llvm_unreachable("type class is never variably-modified!");
      case Type::Adjusted:
        T = cast<AdjustedType>(Ty)->getOriginalType();
        break;
      case Type::Decayed:
        T = cast<DecayedType>(Ty)->getPointeeType();
        break;
      case Type::Pointer:
        T = cast<PointerType>(Ty)->getPointeeType();
        break;
      case Type::BlockPointer:
        T = cast<BlockPointerType>(Ty)->getPointeeType();
        break;
      case Type::LValueReference:
      case Type::RValueReference:
        T = cast<ReferenceType>(Ty)->getPointeeType();
        break;
      case Type::MemberPointer:
        T = cast<MemberPointerType>(Ty)->getPointeeType();
        break;
      case Type::ConstantArray:
      case Type::IncompleteArray:
        // Losing element qualification here is fine.
        T = cast<ArrayType>(Ty)->getElementType();
        break;
      case Type::VariableArray: {
        // Losing element qualification here is fine.
        const VariableArrayType *VAT = cast<VariableArrayType>(Ty);
  
        // Unknown size indication requires no size computation.
        // Otherwise, evaluate and record it.
        auto Size = VAT->getSizeExpr();
        if (Size && !CSI->isVLATypeCaptured(VAT) &&
            (isa<CapturedRegionScopeInfo>(CSI) || isa<LambdaScopeInfo>(CSI)))
          CSI->addVLATypeCapture(Size->getExprLoc(), VAT, Context.getSizeType());
  
        T = VAT->getElementType();
        break;
      }
      case Type::FunctionProto:
      case Type::FunctionNoProto:
        T = cast<FunctionType>(Ty)->getReturnType();
        break;
      case Type::Paren:
      case Type::TypeOf:
      case Type::UnaryTransform:
      case Type::Attributed:
      case Type::SubstTemplateTypeParm:
      case Type::MacroQualified:
        // Keep walking after single level desugaring.
        T = T.getSingleStepDesugaredType(Context);
        break;
      case Type::Typedef:
        T = cast<TypedefType>(Ty)->desugar();
        break;
      case Type::Decltype:
        T = cast<DecltypeType>(Ty)->desugar();
        break;
      case Type::Using:
        T = cast<UsingType>(Ty)->desugar();
        break;
      case Type::Auto:
      case Type::DeducedTemplateSpecialization:
        T = cast<DeducedType>(Ty)->getDeducedType();
        break;
      case Type::TypeOfExpr:
        T = cast<TypeOfExprType>(Ty)->getUnderlyingExpr()->getType();
        break;
      case Type::Atomic:
        T = cast<AtomicType>(Ty)->getValueType();
        break;
      }
    } while (!T.isNull() && T->isVariablyModifiedType());
  }
  
  /// Build a sizeof or alignof expression given a type operand.
  ExprResult
  Sema::CreateUnaryExprOrTypeTraitExpr(TypeSourceInfo *TInfo,
                                       SourceLocation OpLoc,
                                       UnaryExprOrTypeTrait ExprKind,
                                       SourceRange R) {
    if (!TInfo)
      return ExprError();
  
    QualType T = TInfo->getType();
  
    if (!T->isDependentType() &&
        CheckUnaryExprOrTypeTraitOperand(T, OpLoc, R, ExprKind))
      return ExprError();
  
    if (T->isVariablyModifiedType() && FunctionScopes.size() > 1) {
      if (auto *TT = T->getAs<TypedefType>()) {
        for (auto I = FunctionScopes.rbegin(),
                  E = std::prev(FunctionScopes.rend());
             I != E; ++I) {
          auto *CSI = dyn_cast<CapturingScopeInfo>(*I);
          if (CSI == nullptr)
            break;
          DeclContext *DC = nullptr;
          if (auto *LSI = dyn_cast<LambdaScopeInfo>(CSI))
            DC = LSI->CallOperator;
          else if (auto *CRSI = dyn_cast<CapturedRegionScopeInfo>(CSI))
            DC = CRSI->TheCapturedDecl;
          else if (auto *BSI = dyn_cast<BlockScopeInfo>(CSI))
            DC = BSI->TheDecl;
          if (DC) {
            if (DC->containsDecl(TT->getDecl()))
              break;
            captureVariablyModifiedType(Context, T, CSI);
          }
        }
      }
    }
  
    // C99 6.5.3.4p4: the type (an unsigned integer type) is size_t.
    if (isUnevaluatedContext() && ExprKind == UETT_SizeOf &&
        TInfo->getType()->isVariablyModifiedType())
      TInfo = TransformToPotentiallyEvaluated(TInfo);
  
    return new (Context) UnaryExprOrTypeTraitExpr(
        ExprKind, TInfo, Context.getSizeType(), OpLoc, R.getEnd());
  }
  
  /// Build a sizeof or alignof expression given an expression
  /// operand.
  ExprResult
  Sema::CreateUnaryExprOrTypeTraitExpr(Expr *E, SourceLocation OpLoc,
                                       UnaryExprOrTypeTrait ExprKind) {
    ExprResult PE = CheckPlaceholderExpr(E);
    if (PE.isInvalid())
      return ExprError();
  
    E = PE.get();
  
    // Verify that the operand is valid.
    bool isInvalid = false;
    if (E->isTypeDependent()) {
      // Delay type-checking for type-dependent expressions.
    } else if (ExprKind == UETT_AlignOf || ExprKind == UETT_PreferredAlignOf) {
      isInvalid = CheckAlignOfExpr(*this, E, ExprKind);
    } else if (ExprKind == UETT_VecStep) {
      isInvalid = CheckVecStepExpr(E);
    } else if (ExprKind == UETT_OpenMPRequiredSimdAlign) {
        Diag(E->getExprLoc(), diag::err_openmp_default_simd_align_expr);
        isInvalid = true;
    } else if (E->refersToBitField()) {  // C99 6.5.3.4p1.
      Diag(E->getExprLoc(), diag::err_sizeof_alignof_typeof_bitfield) << 0;
      isInvalid = true;
    } else {
      isInvalid = CheckUnaryExprOrTypeTraitOperand(E, UETT_SizeOf);
    }
  
    if (isInvalid)
      return ExprError();
  
    if (ExprKind == UETT_SizeOf && E->getType()->isVariableArrayType()) {
      PE = TransformToPotentiallyEvaluated(E);
      if (PE.isInvalid()) return ExprError();
      E = PE.get();
    }
  
    // C99 6.5.3.4p4: the type (an unsigned integer type) is size_t.
    return new (Context) UnaryExprOrTypeTraitExpr(
        ExprKind, E, Context.getSizeType(), OpLoc, E->getSourceRange().getEnd());
  }
  
  /// ActOnUnaryExprOrTypeTraitExpr - Handle @c sizeof(type) and @c sizeof @c
  /// expr and the same for @c alignof and @c __alignof
  /// Note that the ArgRange is invalid if isType is false.
  ExprResult
  Sema::ActOnUnaryExprOrTypeTraitExpr(SourceLocation OpLoc,
                                      UnaryExprOrTypeTrait ExprKind, bool IsType,
                                      void *TyOrEx, SourceRange ArgRange) {
    // If error parsing type, ignore.
    if (!TyOrEx) return ExprError();
  
    if (IsType) {
      TypeSourceInfo *TInfo;
      (void) GetTypeFromParser(ParsedType::getFromOpaquePtr(TyOrEx), &TInfo);
      return CreateUnaryExprOrTypeTraitExpr(TInfo, OpLoc, ExprKind, ArgRange);
    }
  
    Expr *ArgEx = (Expr *)TyOrEx;
    ExprResult Result = CreateUnaryExprOrTypeTraitExpr(ArgEx, OpLoc, ExprKind);
    return Result;
  }
  
  static QualType CheckRealImagOperand(Sema &S, ExprResult &V, SourceLocation Loc,
                                       bool IsReal) {
    if (V.get()->isTypeDependent())
      return S.Context.DependentTy;
  
    // _Real and _Imag are only l-values for normal l-values.
    if (V.get()->getObjectKind() != OK_Ordinary) {
      V = S.DefaultLvalueConversion(V.get());
      if (V.isInvalid())
        return QualType();
    }
  
    // These operators return the element type of a complex type.
    if (const ComplexType *CT = V.get()->getType()->getAs<ComplexType>())
      return CT->getElementType();
  
    // Otherwise they pass through real integer and floating point types here.
    if (V.get()->getType()->isArithmeticType())
      return V.get()->getType();
  
    // Test for placeholders.
    ExprResult PR = S.CheckPlaceholderExpr(V.get());
    if (PR.isInvalid()) return QualType();
    if (PR.get() != V.get()) {
      V = PR;
      return CheckRealImagOperand(S, V, Loc, IsReal);
    }
  
    // Reject anything else.
    S.Diag(Loc, diag::err_realimag_invalid_type) << V.get()->getType()
      << (IsReal ? "__real" : "__imag");
    return QualType();
  }
  
  
  
  ExprResult
  Sema::ActOnPostfixUnaryOp(Scope *S, SourceLocation OpLoc,
                            tok::TokenKind Kind, Expr *Input) {
    UnaryOperatorKind Opc;
    switch (Kind) {
    default: llvm_unreachable("Unknown unary op!");
    case tok::plusplus:   Opc = UO_PostInc; break;
    case tok::minusminus: Opc = UO_PostDec; break;
    }
  
    // Since this might is a postfix expression, get rid of ParenListExprs.
    ExprResult Result = MaybeConvertParenListExprToParenExpr(S, Input);
    if (Result.isInvalid()) return ExprError();
    Input = Result.get();
  
    return BuildUnaryOp(S, OpLoc, Opc, Input);
  }
  
  /// Diagnose if arithmetic on the given ObjC pointer is illegal.
  ///
  /// \return true on error
  static bool checkArithmeticOnObjCPointer(Sema &S,
                                           SourceLocation opLoc,
                                           Expr *op) {
    assert(op->getType()->isObjCObjectPointerType());
    if (S.LangOpts.ObjCRuntime.allowsPointerArithmetic() &&
        !S.LangOpts.ObjCSubscriptingLegacyRuntime)
      return false;
  
    S.Diag(opLoc, diag::err_arithmetic_nonfragile_interface)
      << op->getType()->castAs<ObjCObjectPointerType>()->getPointeeType()
      << op->getSourceRange();
    return true;
  }
  
  static bool isMSPropertySubscriptExpr(Sema &S, Expr *Base) {
    auto *BaseNoParens = Base->IgnoreParens();
    if (auto *MSProp = dyn_cast<MSPropertyRefExpr>(BaseNoParens))
      return MSProp->getPropertyDecl()->getType()->isArrayType();
    return isa<MSPropertySubscriptExpr>(BaseNoParens);
  }
  
  // Returns the type used for LHS[RHS], given one of LHS, RHS is type-dependent.
  // Typically this is DependentTy, but can sometimes be more precise.
  //
  // There are cases when we could determine a non-dependent type:
  //  - LHS and RHS may have non-dependent types despite being type-dependent
  //    (e.g. unbounded array static members of the current instantiation)
  //  - one may be a dependent-sized array with known element type
  //  - one may be a dependent-typed valid index (enum in current instantiation)
  //
  // We *always* return a dependent type, in such cases it is DependentTy.
  // This avoids creating type-dependent expressions with non-dependent types.
  // FIXME: is this important to avoid? See https://reviews.llvm.org/D107275
  static QualType getDependentArraySubscriptType(Expr *LHS, Expr *RHS,
                                                 const ASTContext &Ctx) {
    assert(LHS->isTypeDependent() || RHS->isTypeDependent());
    QualType LTy = LHS->getType(), RTy = RHS->getType();
    QualType Result = Ctx.DependentTy;
    if (RTy->isIntegralOrUnscopedEnumerationType()) {
      if (const PointerType *PT = LTy->getAs<PointerType>())
        Result = PT->getPointeeType();
      else if (const ArrayType *AT = LTy->getAsArrayTypeUnsafe())
        Result = AT->getElementType();
    } else if (LTy->isIntegralOrUnscopedEnumerationType()) {
      if (const PointerType *PT = RTy->getAs<PointerType>())
        Result = PT->getPointeeType();
      else if (const ArrayType *AT = RTy->getAsArrayTypeUnsafe())
        Result = AT->getElementType();
    }
    // Ensure we return a dependent type.
    return Result->isDependentType() ? Result : Ctx.DependentTy;
  }
  
  static bool checkArgsForPlaceholders(Sema &S, MultiExprArg args);
  
  ExprResult Sema::ActOnArraySubscriptExpr(Scope *S, Expr *base,
                                           SourceLocation lbLoc,
                                           MultiExprArg ArgExprs,
                                           SourceLocation rbLoc) {
  
    if (base && !base->getType().isNull() &&
        base->hasPlaceholderType(BuiltinType::OMPArraySection))
      return ActOnOMPArraySectionExpr(base, lbLoc, ArgExprs.front(), SourceLocation(),
                                      SourceLocation(), /*Length*/ nullptr,
                                      /*Stride=*/nullptr, rbLoc);
  
    // Since this might be a postfix expression, get rid of ParenListExprs.
    if (isa<ParenListExpr>(base)) {
      ExprResult result = MaybeConvertParenListExprToParenExpr(S, base);
      if (result.isInvalid())
        return ExprError();
      base = result.get();
    }
  
    // Check if base and idx form a MatrixSubscriptExpr.
    //
    // Helper to check for comma expressions, which are not allowed as indices for
    // matrix subscript expressions.
    auto CheckAndReportCommaError = [this, base, rbLoc](Expr *E) {
      if (isa<BinaryOperator>(E) && cast<BinaryOperator>(E)->isCommaOp()) {
        Diag(E->getExprLoc(), diag::err_matrix_subscript_comma)
            << SourceRange(base->getBeginLoc(), rbLoc);
        return true;
      }
      return false;
    };
    // The matrix subscript operator ([][])is considered a single operator.
    // Separating the index expressions by parenthesis is not allowed.
    if (base->hasPlaceholderType(BuiltinType::IncompleteMatrixIdx) &&
        !isa<MatrixSubscriptExpr>(base)) {
      Diag(base->getExprLoc(), diag::err_matrix_separate_incomplete_index)
          << SourceRange(base->getBeginLoc(), rbLoc);
      return ExprError();
    }
    // If the base is a MatrixSubscriptExpr, try to create a new
    // MatrixSubscriptExpr.
    auto *matSubscriptE = dyn_cast<MatrixSubscriptExpr>(base);
    if (matSubscriptE) {
      assert(ArgExprs.size() == 1);
      if (CheckAndReportCommaError(ArgExprs.front()))
        return ExprError();
  
      assert(matSubscriptE->isIncomplete() &&
             "base has to be an incomplete matrix subscript");
      return CreateBuiltinMatrixSubscriptExpr(matSubscriptE->getBase(),
                                              matSubscriptE->getRowIdx(),
                                              ArgExprs.front(), rbLoc);
    }
  
    // Handle any non-overload placeholder types in the base and index
    // expressions.  We can't handle overloads here because the other
    // operand might be an overloadable type, in which case the overload
    // resolution for the operator overload should get the first crack
    // at the overload.
    bool IsMSPropertySubscript = false;
    if (base->getType()->isNonOverloadPlaceholderType()) {
      IsMSPropertySubscript = isMSPropertySubscriptExpr(*this, base);
      if (!IsMSPropertySubscript) {
        ExprResult result = CheckPlaceholderExpr(base);
        if (result.isInvalid())
          return ExprError();
        base = result.get();
      }
    }
  
    // If the base is a matrix type, try to create a new MatrixSubscriptExpr.
    if (base->getType()->isMatrixType()) {
      assert(ArgExprs.size() == 1);
      if (CheckAndReportCommaError(ArgExprs.front()))
        return ExprError();
  
      return CreateBuiltinMatrixSubscriptExpr(base, ArgExprs.front(), nullptr,
                                              rbLoc);
    }
  
    if (ArgExprs.size() == 1 && getLangOpts().CPlusPlus20) {
      Expr *idx = ArgExprs[0];
      if ((isa<BinaryOperator>(idx) && cast<BinaryOperator>(idx)->isCommaOp()) ||
          (isa<CXXOperatorCallExpr>(idx) &&
           cast<CXXOperatorCallExpr>(idx)->getOperator() == OO_Comma)) {
        Diag(idx->getExprLoc(), diag::warn_deprecated_comma_subscript)
            << SourceRange(base->getBeginLoc(), rbLoc);
      }
    }
  
    if (ArgExprs.size() == 1 &&
        ArgExprs[0]->getType()->isNonOverloadPlaceholderType()) {
      ExprResult result = CheckPlaceholderExpr(ArgExprs[0]);
      if (result.isInvalid())
        return ExprError();
      ArgExprs[0] = result.get();
    } else {
      if (checkArgsForPlaceholders(*this, ArgExprs))
        return ExprError();
    }
  
    // Build an unanalyzed expression if either operand is type-dependent.
    if (getLangOpts().CPlusPlus && ArgExprs.size() == 1 &&
        (base->isTypeDependent() ||
         Expr::hasAnyTypeDependentArguments(ArgExprs))) {
      return new (Context) ArraySubscriptExpr(
          base, ArgExprs.front(),
          getDependentArraySubscriptType(base, ArgExprs.front(), getASTContext()),
          VK_LValue, OK_Ordinary, rbLoc);
    }
  
    // MSDN, property (C++)
    // https://msdn.microsoft.com/en-us/library/yhfk0thd(v=vs.120).aspx
    // This attribute can also be used in the declaration of an empty array in a
    // class or structure definition. For example:
    // __declspec(property(get=GetX, put=PutX)) int x[];
    // The above statement indicates that x[] can be used with one or more array
    // indices. In this case, i=p->x[a][b] will be turned into i=p->GetX(a, b),
    // and p->x[a][b] = i will be turned into p->PutX(a, b, i);
    if (IsMSPropertySubscript) {
      assert(ArgExprs.size() == 1);
      // Build MS property subscript expression if base is MS property reference
      // or MS property subscript.
      return new (Context)
          MSPropertySubscriptExpr(base, ArgExprs.front(), Context.PseudoObjectTy,
                                  VK_LValue, OK_Ordinary, rbLoc);
    }
  
    // Use C++ overloaded-operator rules if either operand has record
    // type.  The spec says to do this if either type is *overloadable*,
    // but enum types can't declare subscript operators or conversion
    // operators, so there's nothing interesting for overload resolution
    // to do if there aren't any record types involved.
    //
    // ObjC pointers have their own subscripting logic that is not tied
    // to overload resolution and so should not take this path.
    if (getLangOpts().CPlusPlus && !base->getType()->isObjCObjectPointerType() &&
        ((base->getType()->isRecordType() ||
          (ArgExprs.size() != 1 || ArgExprs[0]->getType()->isRecordType())))) {
      return CreateOverloadedArraySubscriptExpr(lbLoc, rbLoc, base, ArgExprs);
    }
  
    ExprResult Res =
        CreateBuiltinArraySubscriptExpr(base, lbLoc, ArgExprs.front(), rbLoc);
  
    if (!Res.isInvalid() && isa<ArraySubscriptExpr>(Res.get()))
      CheckSubscriptAccessOfNoDeref(cast<ArraySubscriptExpr>(Res.get()));
  
    return Res;
  }
  
  ExprResult Sema::tryConvertExprToType(Expr *E, QualType Ty) {
    InitializedEntity Entity = InitializedEntity::InitializeTemporary(Ty);
    InitializationKind Kind =
        InitializationKind::CreateCopy(E->getBeginLoc(), SourceLocation());
    InitializationSequence InitSeq(*this, Entity, Kind, E);
    return InitSeq.Perform(*this, Entity, Kind, E);
  }
  
  ExprResult Sema::CreateBuiltinMatrixSubscriptExpr(Expr *Base, Expr *RowIdx,
                                                    Expr *ColumnIdx,
                                                    SourceLocation RBLoc) {
    ExprResult BaseR = CheckPlaceholderExpr(Base);
    if (BaseR.isInvalid())
      return BaseR;
    Base = BaseR.get();
  
    ExprResult RowR = CheckPlaceholderExpr(RowIdx);
    if (RowR.isInvalid())
      return RowR;
    RowIdx = RowR.get();
  
    if (!ColumnIdx)
      return new (Context) MatrixSubscriptExpr(
          Base, RowIdx, ColumnIdx, Context.IncompleteMatrixIdxTy, RBLoc);
  
    // Build an unanalyzed expression if any of the operands is type-dependent.
    if (Base->isTypeDependent() || RowIdx->isTypeDependent() ||
        ColumnIdx->isTypeDependent())
      return new (Context) MatrixSubscriptExpr(Base, RowIdx, ColumnIdx,
                                               Context.DependentTy, RBLoc);
  
    ExprResult ColumnR = CheckPlaceholderExpr(ColumnIdx);
    if (ColumnR.isInvalid())
      return ColumnR;
    ColumnIdx = ColumnR.get();
  
    // Check that IndexExpr is an integer expression. If it is a constant
    // expression, check that it is less than Dim (= the number of elements in the
    // corresponding dimension).
    auto IsIndexValid = [&](Expr *IndexExpr, unsigned Dim,
                            bool IsColumnIdx) -> Expr * {
      if (!IndexExpr->getType()->isIntegerType() &&
          !IndexExpr->isTypeDependent()) {
        Diag(IndexExpr->getBeginLoc(), diag::err_matrix_index_not_integer)
            << IsColumnIdx;
        return nullptr;
      }
  
      if (Optional<llvm::APSInt> Idx =
              IndexExpr->getIntegerConstantExpr(Context)) {
        if ((*Idx < 0 || *Idx >= Dim)) {
          Diag(IndexExpr->getBeginLoc(), diag::err_matrix_index_outside_range)
              << IsColumnIdx << Dim;
          return nullptr;
        }
      }
  
      ExprResult ConvExpr =
          tryConvertExprToType(IndexExpr, Context.getSizeType());
      assert(!ConvExpr.isInvalid() &&
             "should be able to convert any integer type to size type");
      return ConvExpr.get();
    };
  
    auto *MTy = Base->getType()->getAs<ConstantMatrixType>();
    RowIdx = IsIndexValid(RowIdx, MTy->getNumRows(), false);
    ColumnIdx = IsIndexValid(ColumnIdx, MTy->getNumColumns(), true);
    if (!RowIdx || !ColumnIdx)
      return ExprError();
  
    return new (Context) MatrixSubscriptExpr(Base, RowIdx, ColumnIdx,
                                             MTy->getElementType(), RBLoc);
  }
  
  void Sema::CheckAddressOfNoDeref(const Expr *E) {
    ExpressionEvaluationContextRecord &LastRecord = ExprEvalContexts.back();
    const Expr *StrippedExpr = E->IgnoreParenImpCasts();
  
    // For expressions like `&(*s).b`, the base is recorded and what should be
    // checked.
    const MemberExpr *Member = nullptr;
    while ((Member = dyn_cast<MemberExpr>(StrippedExpr)) && !Member->isArrow())
      StrippedExpr = Member->getBase()->IgnoreParenImpCasts();
  
    LastRecord.PossibleDerefs.erase(StrippedExpr);
  }
  
  void Sema::CheckSubscriptAccessOfNoDeref(const ArraySubscriptExpr *E) {
    if (isUnevaluatedContext())
      return;
  
    QualType ResultTy = E->getType();
    ExpressionEvaluationContextRecord &LastRecord = ExprEvalContexts.back();
  
    // Bail if the element is an array since it is not memory access.
    if (isa<ArrayType>(ResultTy))
      return;
  
    if (ResultTy->hasAttr(attr::NoDeref)) {
      LastRecord.PossibleDerefs.insert(E);
      return;
    }
  
    // Check if the base type is a pointer to a member access of a struct
    // marked with noderef.
    const Expr *Base = E->getBase();
    QualType BaseTy = Base->getType();
    if (!(isa<ArrayType>(BaseTy) || isa<PointerType>(BaseTy)))
      // Not a pointer access
      return;
  
    const MemberExpr *Member = nullptr;
    while ((Member = dyn_cast<MemberExpr>(Base->IgnoreParenCasts())) &&
           Member->isArrow())
      Base = Member->getBase();
  
    if (const auto *Ptr = dyn_cast<PointerType>(Base->getType())) {
      if (Ptr->getPointeeType()->hasAttr(attr::NoDeref))
        LastRecord.PossibleDerefs.insert(E);
    }
  }
  
  ExprResult Sema::ActOnOMPArraySectionExpr(Expr *Base, SourceLocation LBLoc,
                                            Expr *LowerBound,
                                            SourceLocation ColonLocFirst,
                                            SourceLocation ColonLocSecond,
                                            Expr *Length, Expr *Stride,
                                            SourceLocation RBLoc) {
    if (Base->hasPlaceholderType() &&
        !Base->hasPlaceholderType(BuiltinType::OMPArraySection)) {
      ExprResult Result = CheckPlaceholderExpr(Base);
      if (Result.isInvalid())
        return ExprError();
      Base = Result.get();
    }
    if (LowerBound && LowerBound->getType()->isNonOverloadPlaceholderType()) {
      ExprResult Result = CheckPlaceholderExpr(LowerBound);
      if (Result.isInvalid())
        return ExprError();
      Result = DefaultLvalueConversion(Result.get());
      if (Result.isInvalid())
        return ExprError();
      LowerBound = Result.get();
    }
    if (Length && Length->getType()->isNonOverloadPlaceholderType()) {
      ExprResult Result = CheckPlaceholderExpr(Length);
      if (Result.isInvalid())
        return ExprError();
      Result = DefaultLvalueConversion(Result.get());
      if (Result.isInvalid())
        return ExprError();
      Length = Result.get();
    }
    if (Stride && Stride->getType()->isNonOverloadPlaceholderType()) {
      ExprResult Result = CheckPlaceholderExpr(Stride);
      if (Result.isInvalid())
        return ExprError();
      Result = DefaultLvalueConversion(Result.get());
      if (Result.isInvalid())
        return ExprError();
      Stride = Result.get();
    }
  
    // Build an unanalyzed expression if either operand is type-dependent.
    if (Base->isTypeDependent() ||
        (LowerBound &&
         (LowerBound->isTypeDependent() || LowerBound->isValueDependent())) ||
        (Length && (Length->isTypeDependent() || Length->isValueDependent())) ||
        (Stride && (Stride->isTypeDependent() || Stride->isValueDependent()))) {
      return new (Context) OMPArraySectionExpr(
          Base, LowerBound, Length, Stride, Context.DependentTy, VK_LValue,
          OK_Ordinary, ColonLocFirst, ColonLocSecond, RBLoc);
    }
  
    // Perform default conversions.
    QualType OriginalTy = OMPArraySectionExpr::getBaseOriginalType(Base);
    QualType ResultTy;
    if (OriginalTy->isAnyPointerType()) {
      ResultTy = OriginalTy->getPointeeType();
    } else if (OriginalTy->isArrayType()) {
      ResultTy = OriginalTy->getAsArrayTypeUnsafe()->getElementType();
    } else {
      return ExprError(
          Diag(Base->getExprLoc(), diag::err_omp_typecheck_section_value)
          << Base->getSourceRange());
    }
    // C99 6.5.2.1p1
    if (LowerBound) {
      auto Res = PerformOpenMPImplicitIntegerConversion(LowerBound->getExprLoc(),
                                                        LowerBound);
      if (Res.isInvalid())
        return ExprError(Diag(LowerBound->getExprLoc(),
                              diag::err_omp_typecheck_section_not_integer)
                         << 0 << LowerBound->getSourceRange());
      LowerBound = Res.get();
  
      if (LowerBound->getType()->isSpecificBuiltinType(BuiltinType::Char_S) ||
          LowerBound->getType()->isSpecificBuiltinType(BuiltinType::Char_U))
        Diag(LowerBound->getExprLoc(), diag::warn_omp_section_is_char)
            << 0 << LowerBound->getSourceRange();
    }
    if (Length) {
      auto Res =
          PerformOpenMPImplicitIntegerConversion(Length->getExprLoc(), Length);
      if (Res.isInvalid())
        return ExprError(Diag(Length->getExprLoc(),
                              diag::err_omp_typecheck_section_not_integer)
                         << 1 << Length->getSourceRange());
      Length = Res.get();
  
      if (Length->getType()->isSpecificBuiltinType(BuiltinType::Char_S) ||
          Length->getType()->isSpecificBuiltinType(BuiltinType::Char_U))
        Diag(Length->getExprLoc(), diag::warn_omp_section_is_char)
            << 1 << Length->getSourceRange();
    }
    if (Stride) {
      ExprResult Res =
          PerformOpenMPImplicitIntegerConversion(Stride->getExprLoc(), Stride);
      if (Res.isInvalid())
        return ExprError(Diag(Stride->getExprLoc(),
                              diag::err_omp_typecheck_section_not_integer)
                         << 1 << Stride->getSourceRange());
      Stride = Res.get();
  
      if (Stride->getType()->isSpecificBuiltinType(BuiltinType::Char_S) ||
          Stride->getType()->isSpecificBuiltinType(BuiltinType::Char_U))
        Diag(Stride->getExprLoc(), diag::warn_omp_section_is_char)
            << 1 << Stride->getSourceRange();
    }
  
    // C99 6.5.2.1p1: "shall have type "pointer to *object* type". Similarly,
    // C++ [expr.sub]p1: The type "T" shall be a completely-defined object
    // type. Note that functions are not objects, and that (in C99 parlance)
    // incomplete types are not object types.
    if (ResultTy->isFunctionType()) {
      Diag(Base->getExprLoc(), diag::err_omp_section_function_type)
          << ResultTy << Base->getSourceRange();
      return ExprError();
    }
  
    if (RequireCompleteType(Base->getExprLoc(), ResultTy,
                            diag::err_omp_section_incomplete_type, Base))
      return ExprError();
  
    if (LowerBound && !OriginalTy->isAnyPointerType()) {
      Expr::EvalResult Result;
      if (LowerBound->EvaluateAsInt(Result, Context)) {
        // OpenMP 5.0, [2.1.5 Array Sections]
        // The array section must be a subset of the original array.
        llvm::APSInt LowerBoundValue = Result.Val.getInt();
        if (LowerBoundValue.isNegative()) {
          Diag(LowerBound->getExprLoc(), diag::err_omp_section_not_subset_of_array)
              << LowerBound->getSourceRange();
          return ExprError();
        }
      }
    }
  
    if (Length) {
      Expr::EvalResult Result;
      if (Length->EvaluateAsInt(Result, Context)) {
        // OpenMP 5.0, [2.1.5 Array Sections]
        // The length must evaluate to non-negative integers.
        llvm::APSInt LengthValue = Result.Val.getInt();
        if (LengthValue.isNegative()) {
          Diag(Length->getExprLoc(), diag::err_omp_section_length_negative)
              << toString(LengthValue, /*Radix=*/10, /*Signed=*/true)
              << Length->getSourceRange();
          return ExprError();
        }
      }
    } else if (ColonLocFirst.isValid() &&
               (OriginalTy.isNull() || (!OriginalTy->isConstantArrayType() &&
                                        !OriginalTy->isVariableArrayType()))) {
      // OpenMP 5.0, [2.1.5 Array Sections]
      // When the size of the array dimension is not known, the length must be
      // specified explicitly.
      Diag(ColonLocFirst, diag::err_omp_section_length_undefined)
          << (!OriginalTy.isNull() && OriginalTy->isArrayType());
      return ExprError();
    }
  
    if (Stride) {
      Expr::EvalResult Result;
      if (Stride->EvaluateAsInt(Result, Context)) {
        // OpenMP 5.0, [2.1.5 Array Sections]
        // The stride must evaluate to a positive integer.
        llvm::APSInt StrideValue = Result.Val.getInt();
        if (!StrideValue.isStrictlyPositive()) {
          Diag(Stride->getExprLoc(), diag::err_omp_section_stride_non_positive)
              << toString(StrideValue, /*Radix=*/10, /*Signed=*/true)
              << Stride->getSourceRange();
          return ExprError();
        }
      }
    }
  
    if (!Base->hasPlaceholderType(BuiltinType::OMPArraySection)) {
      ExprResult Result = DefaultFunctionArrayLvalueConversion(Base);
      if (Result.isInvalid())
        return ExprError();
      Base = Result.get();
    }
    return new (Context) OMPArraySectionExpr(
        Base, LowerBound, Length, Stride, Context.OMPArraySectionTy, VK_LValue,
        OK_Ordinary, ColonLocFirst, ColonLocSecond, RBLoc);
  }
  
  ExprResult Sema::ActOnOMPArrayShapingExpr(Expr *Base, SourceLocation LParenLoc,
                                            SourceLocation RParenLoc,
                                            ArrayRef<Expr *> Dims,
                                            ArrayRef<SourceRange> Brackets) {
    if (Base->hasPlaceholderType()) {
      ExprResult Result = CheckPlaceholderExpr(Base);
      if (Result.isInvalid())
        return ExprError();
      Result = DefaultLvalueConversion(Result.get());
      if (Result.isInvalid())
        return ExprError();
      Base = Result.get();
    }
    QualType BaseTy = Base->getType();
    // Delay analysis of the types/expressions if instantiation/specialization is
    // required.
    if (!BaseTy->isPointerType() && Base->isTypeDependent())
      return OMPArrayShapingExpr::Create(Context, Context.DependentTy, Base,
                                         LParenLoc, RParenLoc, Dims, Brackets);
    if (!BaseTy->isPointerType() ||
        (!Base->isTypeDependent() &&
         BaseTy->getPointeeType()->isIncompleteType()))
      return ExprError(Diag(Base->getExprLoc(),
                            diag::err_omp_non_pointer_type_array_shaping_base)
                       << Base->getSourceRange());
  
    SmallVector<Expr *, 4> NewDims;
    bool ErrorFound = false;
    for (Expr *Dim : Dims) {
      if (Dim->hasPlaceholderType()) {
        ExprResult Result = CheckPlaceholderExpr(Dim);
        if (Result.isInvalid()) {
          ErrorFound = true;
          continue;
        }
        Result = DefaultLvalueConversion(Result.get());
        if (Result.isInvalid()) {
          ErrorFound = true;
          continue;
        }
        Dim = Result.get();
      }
      if (!Dim->isTypeDependent()) {
        ExprResult Result =
            PerformOpenMPImplicitIntegerConversion(Dim->getExprLoc(), Dim);
        if (Result.isInvalid()) {
          ErrorFound = true;
          Diag(Dim->getExprLoc(), diag::err_omp_typecheck_shaping_not_integer)
              << Dim->getSourceRange();
          continue;
        }
        Dim = Result.get();
        Expr::EvalResult EvResult;
        if (!Dim->isValueDependent() && Dim->EvaluateAsInt(EvResult, Context)) {
          // OpenMP 5.0, [2.1.4 Array Shaping]
          // Each si is an integral type expression that must evaluate to a
          // positive integer.
          llvm::APSInt Value = EvResult.Val.getInt();
          if (!Value.isStrictlyPositive()) {
            Diag(Dim->getExprLoc(), diag::err_omp_shaping_dimension_not_positive)
                << toString(Value, /*Radix=*/10, /*Signed=*/true)
                << Dim->getSourceRange();
            ErrorFound = true;
            continue;
          }
        }
      }
      NewDims.push_back(Dim);
    }
    if (ErrorFound)
      return ExprError();
    return OMPArrayShapingExpr::Create(Context, Context.OMPArrayShapingTy, Base,
                                       LParenLoc, RParenLoc, NewDims, Brackets);
  }
  
  ExprResult Sema::ActOnOMPIteratorExpr(Scope *S, SourceLocation IteratorKwLoc,
                                        SourceLocation LLoc, SourceLocation RLoc,
                                        ArrayRef<OMPIteratorData> Data) {
    SmallVector<OMPIteratorExpr::IteratorDefinition, 4> ID;
    bool IsCorrect = true;
    for (const OMPIteratorData &D : Data) {
      TypeSourceInfo *TInfo = nullptr;
      SourceLocation StartLoc;
      QualType DeclTy;
      if (!D.Type.getAsOpaquePtr()) {
        // OpenMP 5.0, 2.1.6 Iterators
        // In an iterator-specifier, if the iterator-type is not specified then
        // the type of that iterator is of int type.
        DeclTy = Context.IntTy;
        StartLoc = D.DeclIdentLoc;
      } else {
        DeclTy = GetTypeFromParser(D.Type, &TInfo);
        StartLoc = TInfo->getTypeLoc().getBeginLoc();
      }
  
      bool IsDeclTyDependent = DeclTy->isDependentType() ||
                               DeclTy->containsUnexpandedParameterPack() ||
                               DeclTy->isInstantiationDependentType();
      if (!IsDeclTyDependent) {
        if (!DeclTy->isIntegralType(Context) && !DeclTy->isAnyPointerType()) {
          // OpenMP 5.0, 2.1.6 Iterators, Restrictions, C/C++
          // The iterator-type must be an integral or pointer type.
          Diag(StartLoc, diag::err_omp_iterator_not_integral_or_pointer)
              << DeclTy;
          IsCorrect = false;
          continue;
        }
        if (DeclTy.isConstant(Context)) {
          // OpenMP 5.0, 2.1.6 Iterators, Restrictions, C/C++
          // The iterator-type must not be const qualified.
          Diag(StartLoc, diag::err_omp_iterator_not_integral_or_pointer)
              << DeclTy;
          IsCorrect = false;
          continue;
        }
      }
  
      // Iterator declaration.
      assert(D.DeclIdent && "Identifier expected.");
      // Always try to create iterator declarator to avoid extra error messages
      // about unknown declarations use.
      auto *VD = VarDecl::Create(Context, CurContext, StartLoc, D.DeclIdentLoc,
                                 D.DeclIdent, DeclTy, TInfo, SC_None);
      VD->setImplicit();
      if (S) {
        // Check for conflicting previous declaration.
        DeclarationNameInfo NameInfo(VD->getDeclName(), D.DeclIdentLoc);
        LookupResult Previous(*this, NameInfo, LookupOrdinaryName,
                              ForVisibleRedeclaration);
        Previous.suppressDiagnostics();
        LookupName(Previous, S);
  
        FilterLookupForScope(Previous, CurContext, S, /*ConsiderLinkage=*/false,
                             /*AllowInlineNamespace=*/false);
        if (!Previous.empty()) {
          NamedDecl *Old = Previous.getRepresentativeDecl();
          Diag(D.DeclIdentLoc, diag::err_redefinition) << VD->getDeclName();
          Diag(Old->getLocation(), diag::note_previous_definition);
        } else {
          PushOnScopeChains(VD, S);
        }
      } else {
        CurContext->addDecl(VD);
      }
      Expr *Begin = D.Range.Begin;
      if (!IsDeclTyDependent && Begin && !Begin->isTypeDependent()) {
        ExprResult BeginRes =
            PerformImplicitConversion(Begin, DeclTy, AA_Converting);
        Begin = BeginRes.get();
      }
      Expr *End = D.Range.End;
      if (!IsDeclTyDependent && End && !End->isTypeDependent()) {
        ExprResult EndRes = PerformImplicitConversion(End, DeclTy, AA_Converting);
        End = EndRes.get();
      }
      Expr *Step = D.Range.Step;
      if (!IsDeclTyDependent && Step && !Step->isTypeDependent()) {
        if (!Step->getType()->isIntegralType(Context)) {
          Diag(Step->getExprLoc(), diag::err_omp_iterator_step_not_integral)
              << Step << Step->getSourceRange();
          IsCorrect = false;
          continue;
        }
        Optional<llvm::APSInt> Result = Step->getIntegerConstantExpr(Context);
        // OpenMP 5.0, 2.1.6 Iterators, Restrictions
        // If the step expression of a range-specification equals zero, the
        // behavior is unspecified.
        if (Result && Result->isZero()) {
          Diag(Step->getExprLoc(), diag::err_omp_iterator_step_constant_zero)
              << Step << Step->getSourceRange();
          IsCorrect = false;
          continue;
        }
      }
      if (!Begin || !End || !IsCorrect) {
        IsCorrect = false;
        continue;
      }
      OMPIteratorExpr::IteratorDefinition &IDElem = ID.emplace_back();
      IDElem.IteratorDecl = VD;
      IDElem.AssignmentLoc = D.AssignLoc;
      IDElem.Range.Begin = Begin;
      IDElem.Range.End = End;
      IDElem.Range.Step = Step;
      IDElem.ColonLoc = D.ColonLoc;
      IDElem.SecondColonLoc = D.SecColonLoc;
    }
    if (!IsCorrect) {
      // Invalidate all created iterator declarations if error is found.
      for (const OMPIteratorExpr::IteratorDefinition &D : ID) {
        if (Decl *ID = D.IteratorDecl)
          ID->setInvalidDecl();
      }
      return ExprError();
    }
    SmallVector<OMPIteratorHelperData, 4> Helpers;
    if (!CurContext->isDependentContext()) {
      // Build number of ityeration for each iteration range.
      // Ni = ((Stepi > 0) ? ((Endi + Stepi -1 - Begini)/Stepi) :
      // ((Begini-Stepi-1-Endi) / -Stepi);
      for (OMPIteratorExpr::IteratorDefinition &D : ID) {
        // (Endi - Begini)
        ExprResult Res = CreateBuiltinBinOp(D.AssignmentLoc, BO_Sub, D.Range.End,
                                            D.Range.Begin);
        if(!Res.isUsable()) {
          IsCorrect = false;
          continue;
        }
        ExprResult St, St1;
        if (D.Range.Step) {
          St = D.Range.Step;
          // (Endi - Begini) + Stepi
          Res = CreateBuiltinBinOp(D.AssignmentLoc, BO_Add, Res.get(), St.get());
          if (!Res.isUsable()) {
            IsCorrect = false;
            continue;
          }
          // (Endi - Begini) + Stepi - 1
          Res =
              CreateBuiltinBinOp(D.AssignmentLoc, BO_Sub, Res.get(),
                                 ActOnIntegerConstant(D.AssignmentLoc, 1).get());
          if (!Res.isUsable()) {
            IsCorrect = false;
            continue;
          }
          // ((Endi - Begini) + Stepi - 1) / Stepi
          Res = CreateBuiltinBinOp(D.AssignmentLoc, BO_Div, Res.get(), St.get());
          if (!Res.isUsable()) {
            IsCorrect = false;
            continue;
          }
          St1 = CreateBuiltinUnaryOp(D.AssignmentLoc, UO_Minus, D.Range.Step);
          // (Begini - Endi)
          ExprResult Res1 = CreateBuiltinBinOp(D.AssignmentLoc, BO_Sub,
                                               D.Range.Begin, D.Range.End);
          if (!Res1.isUsable()) {
            IsCorrect = false;
            continue;
          }
          // (Begini - Endi) - Stepi
          Res1 =
              CreateBuiltinBinOp(D.AssignmentLoc, BO_Add, Res1.get(), St1.get());
          if (!Res1.isUsable()) {
            IsCorrect = false;
            continue;
          }
          // (Begini - Endi) - Stepi - 1
          Res1 =
              CreateBuiltinBinOp(D.AssignmentLoc, BO_Sub, Res1.get(),
                                 ActOnIntegerConstant(D.AssignmentLoc, 1).get());
          if (!Res1.isUsable()) {
            IsCorrect = false;
            continue;
          }
          // ((Begini - Endi) - Stepi - 1) / (-Stepi)
          Res1 =
              CreateBuiltinBinOp(D.AssignmentLoc, BO_Div, Res1.get(), St1.get());
          if (!Res1.isUsable()) {
            IsCorrect = false;
            continue;
          }
          // Stepi > 0.
          ExprResult CmpRes =
              CreateBuiltinBinOp(D.AssignmentLoc, BO_GT, D.Range.Step,
                                 ActOnIntegerConstant(D.AssignmentLoc, 0).get());
          if (!CmpRes.isUsable()) {
            IsCorrect = false;
            continue;
          }
          Res = ActOnConditionalOp(D.AssignmentLoc, D.AssignmentLoc, CmpRes.get(),
                                   Res.get(), Res1.get());
          if (!Res.isUsable()) {
            IsCorrect = false;
            continue;
          }
        }
        Res = ActOnFinishFullExpr(Res.get(), /*DiscardedValue=*/false);
        if (!Res.isUsable()) {
          IsCorrect = false;
          continue;
        }
  
        // Build counter update.
        // Build counter.
        auto *CounterVD =
            VarDecl::Create(Context, CurContext, D.IteratorDecl->getBeginLoc(),
                            D.IteratorDecl->getBeginLoc(), nullptr,
                            Res.get()->getType(), nullptr, SC_None);
        CounterVD->setImplicit();
        ExprResult RefRes =
            BuildDeclRefExpr(CounterVD, CounterVD->getType(), VK_LValue,
                             D.IteratorDecl->getBeginLoc());
        // Build counter update.
        // I = Begini + counter * Stepi;
        ExprResult UpdateRes;
        if (D.Range.Step) {
          UpdateRes = CreateBuiltinBinOp(
              D.AssignmentLoc, BO_Mul,
              DefaultLvalueConversion(RefRes.get()).get(), St.get());
        } else {
          UpdateRes = DefaultLvalueConversion(RefRes.get());
        }
        if (!UpdateRes.isUsable()) {
          IsCorrect = false;
          continue;
        }
        UpdateRes = CreateBuiltinBinOp(D.AssignmentLoc, BO_Add, D.Range.Begin,
                                       UpdateRes.get());
        if (!UpdateRes.isUsable()) {
          IsCorrect = false;
          continue;
        }
        ExprResult VDRes =
            BuildDeclRefExpr(cast<VarDecl>(D.IteratorDecl),
                             cast<VarDecl>(D.IteratorDecl)->getType(), VK_LValue,
                             D.IteratorDecl->getBeginLoc());
        UpdateRes = CreateBuiltinBinOp(D.AssignmentLoc, BO_Assign, VDRes.get(),
                                       UpdateRes.get());
        if (!UpdateRes.isUsable()) {
          IsCorrect = false;
          continue;
        }
        UpdateRes =
            ActOnFinishFullExpr(UpdateRes.get(), /*DiscardedValue=*/true);
        if (!UpdateRes.isUsable()) {
          IsCorrect = false;
          continue;
        }
        ExprResult CounterUpdateRes =
            CreateBuiltinUnaryOp(D.AssignmentLoc, UO_PreInc, RefRes.get());
        if (!CounterUpdateRes.isUsable()) {
          IsCorrect = false;
          continue;
        }
        CounterUpdateRes =
            ActOnFinishFullExpr(CounterUpdateRes.get(), /*DiscardedValue=*/true);
        if (!CounterUpdateRes.isUsable()) {
          IsCorrect = false;
          continue;
        }
        OMPIteratorHelperData &HD = Helpers.emplace_back();
        HD.CounterVD = CounterVD;
        HD.Upper = Res.get();
        HD.Update = UpdateRes.get();
        HD.CounterUpdate = CounterUpdateRes.get();
      }
    } else {
      Helpers.assign(ID.size(), {});
    }
    if (!IsCorrect) {
      // Invalidate all created iterator declarations if error is found.
      for (const OMPIteratorExpr::IteratorDefinition &D : ID) {
        if (Decl *ID = D.IteratorDecl)
          ID->setInvalidDecl();
      }
      return ExprError();
    }
    return OMPIteratorExpr::Create(Context, Context.OMPIteratorTy, IteratorKwLoc,
                                   LLoc, RLoc, ID, Helpers);
  }
  
  ExprResult
  Sema::CreateBuiltinArraySubscriptExpr(Expr *Base, SourceLocation LLoc,
                                        Expr *Idx, SourceLocation RLoc) {
    Expr *LHSExp = Base;
    Expr *RHSExp = Idx;
  
    ExprValueKind VK = VK_LValue;
    ExprObjectKind OK = OK_Ordinary;
  
    // Per C++ core issue 1213, the result is an xvalue if either operand is
    // a non-lvalue array, and an lvalue otherwise.
    if (getLangOpts().CPlusPlus11) {
      for (auto *Op : {LHSExp, RHSExp}) {
        Op = Op->IgnoreImplicit();
        if (Op->getType()->isArrayType() && !Op->isLValue())
          VK = VK_XValue;
      }
    }
  
    // Perform default conversions.
    if (!LHSExp->getType()->getAs<VectorType>()) {
      ExprResult Result = DefaultFunctionArrayLvalueConversion(LHSExp);
      if (Result.isInvalid())
        return ExprError();
      LHSExp = Result.get();
    }
    ExprResult Result = DefaultFunctionArrayLvalueConversion(RHSExp);
    if (Result.isInvalid())
      return ExprError();
    RHSExp = Result.get();
  
    QualType LHSTy = LHSExp->getType(), RHSTy = RHSExp->getType();
  
    // C99 6.5.2.1p2: the expression e1[e2] is by definition precisely equivalent
    // to the expression *((e1)+(e2)). This means the array "Base" may actually be
    // in the subscript position. As a result, we need to derive the array base
    // and index from the expression types.
    Expr *BaseExpr, *IndexExpr;
    QualType ResultType;
    if (LHSTy->isDependentType() || RHSTy->isDependentType()) {
      BaseExpr = LHSExp;
      IndexExpr = RHSExp;
      ResultType =
          getDependentArraySubscriptType(LHSExp, RHSExp, getASTContext());
    } else if (const PointerType *PTy = LHSTy->getAs<PointerType>()) {
      BaseExpr = LHSExp;
      IndexExpr = RHSExp;
      ResultType = PTy->getPointeeType();
    } else if (const ObjCObjectPointerType *PTy =
                 LHSTy->getAs<ObjCObjectPointerType>()) {
      BaseExpr = LHSExp;
      IndexExpr = RHSExp;
  
      // Use custom logic if this should be the pseudo-object subscript
      // expression.
      if (!LangOpts.isSubscriptPointerArithmetic())
        return BuildObjCSubscriptExpression(RLoc, BaseExpr, IndexExpr, nullptr,
                                            nullptr);
  
      ResultType = PTy->getPointeeType();
    } else if (const PointerType *PTy = RHSTy->getAs<PointerType>()) {
       // Handle the uncommon case of "123[Ptr]".
      BaseExpr = RHSExp;
      IndexExpr = LHSExp;
      ResultType = PTy->getPointeeType();
    } else if (const ObjCObjectPointerType *PTy =
                 RHSTy->getAs<ObjCObjectPointerType>()) {
       // Handle the uncommon case of "123[Ptr]".
      BaseExpr = RHSExp;
      IndexExpr = LHSExp;
      ResultType = PTy->getPointeeType();
      if (!LangOpts.isSubscriptPointerArithmetic()) {
        Diag(LLoc, diag::err_subscript_nonfragile_interface)
          << ResultType << BaseExpr->getSourceRange();
        return ExprError();
      }
    } else if (const VectorType *VTy = LHSTy->getAs<VectorType>()) {
      BaseExpr = LHSExp;    // vectors: V[123]
      IndexExpr = RHSExp;
      // We apply C++ DR1213 to vector subscripting too.
      if (getLangOpts().CPlusPlus11 && LHSExp->isPRValue()) {
        ExprResult Materialized = TemporaryMaterializationConversion(LHSExp);
        if (Materialized.isInvalid())
          return ExprError();
        LHSExp = Materialized.get();
      }
      VK = LHSExp->getValueKind();
      if (VK != VK_PRValue)
        OK = OK_VectorComponent;
  
      ResultType = VTy->getElementType();
      QualType BaseType = BaseExpr->getType();
      Qualifiers BaseQuals = BaseType.getQualifiers();
      Qualifiers MemberQuals = ResultType.getQualifiers();
      Qualifiers Combined = BaseQuals + MemberQuals;
      if (Combined != MemberQuals)
        ResultType = Context.getQualifiedType(ResultType, Combined);
    } else if (LHSTy->isArrayType()) {
      // If we see an array that wasn't promoted by
      // DefaultFunctionArrayLvalueConversion, it must be an array that
      // wasn't promoted because of the C90 rule that doesn't
      // allow promoting non-lvalue arrays.  Warn, then
      // force the promotion here.
      Diag(LHSExp->getBeginLoc(), diag::ext_subscript_non_lvalue)
          << LHSExp->getSourceRange();
      LHSExp = ImpCastExprToType(LHSExp, Context.getArrayDecayedType(LHSTy),
                                 CK_ArrayToPointerDecay).get();
      LHSTy = LHSExp->getType();
  
      BaseExpr = LHSExp;
      IndexExpr = RHSExp;
      ResultType = LHSTy->castAs<PointerType>()->getPointeeType();
    } else if (RHSTy->isArrayType()) {
      // Same as previous, except for 123[f().a] case
      Diag(RHSExp->getBeginLoc(), diag::ext_subscript_non_lvalue)
          << RHSExp->getSourceRange();
      RHSExp = ImpCastExprToType(RHSExp, Context.getArrayDecayedType(RHSTy),
                                 CK_ArrayToPointerDecay).get();
      RHSTy = RHSExp->getType();
  
      BaseExpr = RHSExp;
      IndexExpr = LHSExp;
      ResultType = RHSTy->castAs<PointerType>()->getPointeeType();
    } else {
      return ExprError(Diag(LLoc, diag::err_typecheck_subscript_value)
         << LHSExp->getSourceRange() << RHSExp->getSourceRange());
    }
    // C99 6.5.2.1p1
    if (!IndexExpr->getType()->isIntegerType() && !IndexExpr->isTypeDependent())
      return ExprError(Diag(LLoc, diag::err_typecheck_subscript_not_integer)
                       << IndexExpr->getSourceRange());
  
    if ((IndexExpr->getType()->isSpecificBuiltinType(BuiltinType::Char_S) ||
         IndexExpr->getType()->isSpecificBuiltinType(BuiltinType::Char_U))
           && !IndexExpr->isTypeDependent())
      Diag(LLoc, diag::warn_subscript_is_char) << IndexExpr->getSourceRange();
  
    // C99 6.5.2.1p1: "shall have type "pointer to *object* type". Similarly,
    // C++ [expr.sub]p1: The type "T" shall be a completely-defined object
    // type. Note that Functions are not objects, and that (in C99 parlance)
    // incomplete types are not object types.
    if (ResultType->isFunctionType()) {
      Diag(BaseExpr->getBeginLoc(), diag::err_subscript_function_type)
          << ResultType << BaseExpr->getSourceRange();
      return ExprError();
    }
  
    if (ResultType->isVoidType() && !getLangOpts().CPlusPlus) {
      // GNU extension: subscripting on pointer to void
      Diag(LLoc, diag::ext_gnu_subscript_void_type)
        << BaseExpr->getSourceRange();
  
      // C forbids expressions of unqualified void type from being l-values.
      // See IsCForbiddenLValueType.
      if (!ResultType.hasQualifiers())
        VK = VK_PRValue;
    } else if (!ResultType->isDependentType() &&
               RequireCompleteSizedType(
                   LLoc, ResultType,
                   diag::err_subscript_incomplete_or_sizeless_type, BaseExpr))
      return ExprError();
  
    assert(VK == VK_PRValue || LangOpts.CPlusPlus ||
           !ResultType.isCForbiddenLValueType());
  
    if (LHSExp->IgnoreParenImpCasts()->getType()->isVariablyModifiedType() &&
        FunctionScopes.size() > 1) {
      if (auto *TT =
              LHSExp->IgnoreParenImpCasts()->getType()->getAs<TypedefType>()) {
        for (auto I = FunctionScopes.rbegin(),
                  E = std::prev(FunctionScopes.rend());
             I != E; ++I) {
          auto *CSI = dyn_cast<CapturingScopeInfo>(*I);
          if (CSI == nullptr)
            break;
          DeclContext *DC = nullptr;
          if (auto *LSI = dyn_cast<LambdaScopeInfo>(CSI))
            DC = LSI->CallOperator;
          else if (auto *CRSI = dyn_cast<CapturedRegionScopeInfo>(CSI))
            DC = CRSI->TheCapturedDecl;
          else if (auto *BSI = dyn_cast<BlockScopeInfo>(CSI))
            DC = BSI->TheDecl;
          if (DC) {
            if (DC->containsDecl(TT->getDecl()))
              break;
            captureVariablyModifiedType(
                Context, LHSExp->IgnoreParenImpCasts()->getType(), CSI);
          }
        }
      }
    }
  
    return new (Context)
        ArraySubscriptExpr(LHSExp, RHSExp, ResultType, VK, OK, RLoc);
  }
  
  bool Sema::CheckCXXDefaultArgExpr(SourceLocation CallLoc, FunctionDecl *FD,
                                    ParmVarDecl *Param) {
    if (Param->hasUnparsedDefaultArg()) {
      // If we've already cleared out the location for the default argument,
      // that means we're parsing it right now.
      if (!UnparsedDefaultArgLocs.count(Param)) {
        Diag(Param->getBeginLoc(), diag::err_recursive_default_argument) << FD;
        Diag(CallLoc, diag::note_recursive_default_argument_used_here);
        Param->setInvalidDecl();
        return true;
      }
  
      Diag(CallLoc, diag::err_use_of_default_argument_to_function_declared_later)
          << FD << cast<CXXRecordDecl>(FD->getDeclContext());
      Diag(UnparsedDefaultArgLocs[Param],
           diag::note_default_argument_declared_here);
      return true;
    }
  
    if (Param->hasUninstantiatedDefaultArg() &&
        InstantiateDefaultArgument(CallLoc, FD, Param))
      return true;
  
    assert(Param->hasInit() && "default argument but no initializer?");
  
    // If the default expression creates temporaries, we need to
    // push them to the current stack of expression temporaries so they'll
    // be properly destroyed.
    // FIXME: We should really be rebuilding the default argument with new
    // bound temporaries; see the comment in PR5810.
    // We don't need to do that with block decls, though, because
    // blocks in default argument expression can never capture anything.
    if (auto Init = dyn_cast<ExprWithCleanups>(Param->getInit())) {
      // Set the "needs cleanups" bit regardless of whether there are
      // any explicit objects.
      Cleanup.setExprNeedsCleanups(Init->cleanupsHaveSideEffects());
  
      // Append all the objects to the cleanup list.  Right now, this
      // should always be a no-op, because blocks in default argument
      // expressions should never be able to capture anything.
      assert(!Init->getNumObjects() &&
             "default argument expression has capturing blocks?");
    }
  
    // We already type-checked the argument, so we know it works.
    // Just mark all of the declarations in this potentially-evaluated expression
    // as being "referenced".
    EnterExpressionEvaluationContext EvalContext(
        *this, ExpressionEvaluationContext::PotentiallyEvaluated, Param);
    MarkDeclarationsReferencedInExpr(Param->getDefaultArg(),
                                     /*SkipLocalVariables=*/true);
    return false;
  }
  
  ExprResult Sema::BuildCXXDefaultArgExpr(SourceLocation CallLoc,
                                          FunctionDecl *FD, ParmVarDecl *Param) {
    assert(Param->hasDefaultArg() && "can't build nonexistent default arg");
    if (CheckCXXDefaultArgExpr(CallLoc, FD, Param))
      return ExprError();
    return CXXDefaultArgExpr::Create(Context, CallLoc, Param, CurContext);
  }
  
  Sema::VariadicCallType
  Sema::getVariadicCallType(FunctionDecl *FDecl, const FunctionProtoType *Proto,
                            Expr *Fn) {
    if (Proto && Proto->isVariadic()) {
      if (isa_and_nonnull<CXXConstructorDecl>(FDecl))
        return VariadicConstructor;
      else if (Fn && Fn->getType()->isBlockPointerType())
        return VariadicBlock;
      else if (FDecl) {
        if (CXXMethodDecl *Method = dyn_cast_or_null<CXXMethodDecl>(FDecl))
          if (Method->isInstance())
            return VariadicMethod;
      } else if (Fn && Fn->getType() == Context.BoundMemberTy)
        return VariadicMethod;
      return VariadicFunction;
    }
    return VariadicDoesNotApply;
  }
  
  namespace {
  class FunctionCallCCC final : public FunctionCallFilterCCC {
  public:
    FunctionCallCCC(Sema &SemaRef, const IdentifierInfo *FuncName,
                    unsigned NumArgs, MemberExpr *ME)
        : FunctionCallFilterCCC(SemaRef, NumArgs, false, ME),
          FunctionName(FuncName) {}
  
    bool ValidateCandidate(const TypoCorrection &candidate) override {
      if (!candidate.getCorrectionSpecifier() ||
          candidate.getCorrectionAsIdentifierInfo() != FunctionName) {
        return false;
      }
  
      return FunctionCallFilterCCC::ValidateCandidate(candidate);
    }
  
    std::unique_ptr<CorrectionCandidateCallback> clone() override {
      return std::make_unique<FunctionCallCCC>(*this);
    }
  
  private:
    const IdentifierInfo *const FunctionName;
  };
  }
  
  static TypoCorrection TryTypoCorrectionForCall(Sema &S, Expr *Fn,
                                                 FunctionDecl *FDecl,
                                                 ArrayRef<Expr *> Args) {
    MemberExpr *ME = dyn_cast<MemberExpr>(Fn);
    DeclarationName FuncName = FDecl->getDeclName();
    SourceLocation NameLoc = ME ? ME->getMemberLoc() : Fn->getBeginLoc();
  
    FunctionCallCCC CCC(S, FuncName.getAsIdentifierInfo(), Args.size(), ME);
    if (TypoCorrection Corrected = S.CorrectTypo(
            DeclarationNameInfo(FuncName, NameLoc), Sema::LookupOrdinaryName,
            S.getScopeForContext(S.CurContext), nullptr, CCC,
            Sema::CTK_ErrorRecovery)) {
      if (NamedDecl *ND = Corrected.getFoundDecl()) {
        if (Corrected.isOverloaded()) {
          OverloadCandidateSet OCS(NameLoc, OverloadCandidateSet::CSK_Normal);
          OverloadCandidateSet::iterator Best;
          for (NamedDecl *CD : Corrected) {
            if (FunctionDecl *FD = dyn_cast<FunctionDecl>(CD))
              S.AddOverloadCandidate(FD, DeclAccessPair::make(FD, AS_none), Args,
                                     OCS);
          }
          switch (OCS.BestViableFunction(S, NameLoc, Best)) {
          case OR_Success:
            ND = Best->FoundDecl;
            Corrected.setCorrectionDecl(ND);
            break;
          default:
            break;
          }
        }
        ND = ND->getUnderlyingDecl();
        if (isa<ValueDecl>(ND) || isa<FunctionTemplateDecl>(ND))
          return Corrected;
      }
    }
    return TypoCorrection();
  }
  
  /// ConvertArgumentsForCall - Converts the arguments specified in
  /// Args/NumArgs to the parameter types of the function FDecl with
  /// function prototype Proto. Call is the call expression itself, and
  /// Fn is the function expression. For a C++ member function, this
  /// routine does not attempt to convert the object argument. Returns
  /// true if the call is ill-formed.
  bool
  Sema::ConvertArgumentsForCall(CallExpr *Call, Expr *Fn,
                                FunctionDecl *FDecl,
                                const FunctionProtoType *Proto,
                                ArrayRef<Expr *> Args,
                                SourceLocation RParenLoc,
                                bool IsExecConfig) {
    // Bail out early if calling a builtin with custom typechecking.
    if (FDecl)
      if (unsigned ID = FDecl->getBuiltinID())
        if (Context.BuiltinInfo.hasCustomTypechecking(ID))
          return false;
  
    // C99 6.5.2.2p7 - the arguments are implicitly converted, as if by
    // assignment, to the types of the corresponding parameter, ...
    unsigned NumParams = Proto->getNumParams();
    bool Invalid = false;
    unsigned MinArgs = FDecl ? FDecl->getMinRequiredArguments() : NumParams;
    unsigned FnKind = Fn->getType()->isBlockPointerType()
                         ? 1 /* block */
                         : (IsExecConfig ? 3 /* kernel function (exec config) */
                                         : 0 /* function */);
  
    // If too few arguments are available (and we don't have default
    // arguments for the remaining parameters), don't make the call.
    if (Args.size() < NumParams) {
      if (Args.size() < MinArgs) {
        TypoCorrection TC;
        if (FDecl && (TC = TryTypoCorrectionForCall(*this, Fn, FDecl, Args))) {
          unsigned diag_id =
              MinArgs == NumParams && !Proto->isVariadic()
                  ? diag::err_typecheck_call_too_few_args_suggest
                  : diag::err_typecheck_call_too_few_args_at_least_suggest;
          diagnoseTypo(TC, PDiag(diag_id) << FnKind << MinArgs
                                          << static_cast<unsigned>(Args.size())
                                          << TC.getCorrectionRange());
        } else if (MinArgs == 1 && FDecl && FDecl->getParamDecl(0)->getDeclName())
          Diag(RParenLoc,
               MinArgs == NumParams && !Proto->isVariadic()
                   ? diag::err_typecheck_call_too_few_args_one
                   : diag::err_typecheck_call_too_few_args_at_least_one)
              << FnKind << FDecl->getParamDecl(0) << Fn->getSourceRange();
        else
          Diag(RParenLoc, MinArgs == NumParams && !Proto->isVariadic()
                              ? diag::err_typecheck_call_too_few_args
                              : diag::err_typecheck_call_too_few_args_at_least)
              << FnKind << MinArgs << static_cast<unsigned>(Args.size())
              << Fn->getSourceRange();
  
        // Emit the location of the prototype.
        if (!TC && FDecl && !FDecl->getBuiltinID() && !IsExecConfig)
          Diag(FDecl->getLocation(), diag::note_callee_decl) << FDecl;
  
        return true;
      }
      // We reserve space for the default arguments when we create
      // the call expression, before calling ConvertArgumentsForCall.
      assert((Call->getNumArgs() == NumParams) &&
             "We should have reserved space for the default arguments before!");
    }
  
    // If too many are passed and not variadic, error on the extras and drop
    // them.
    if (Args.size() > NumParams) {
      if (!Proto->isVariadic()) {
        TypoCorrection TC;
        if (FDecl && (TC = TryTypoCorrectionForCall(*this, Fn, FDecl, Args))) {
          unsigned diag_id =
              MinArgs == NumParams && !Proto->isVariadic()
                  ? diag::err_typecheck_call_too_many_args_suggest
                  : diag::err_typecheck_call_too_many_args_at_most_suggest;
          diagnoseTypo(TC, PDiag(diag_id) << FnKind << NumParams
                                          << static_cast<unsigned>(Args.size())
                                          << TC.getCorrectionRange());
        } else if (NumParams == 1 && FDecl &&
                   FDecl->getParamDecl(0)->getDeclName())
          Diag(Args[NumParams]->getBeginLoc(),
               MinArgs == NumParams
                   ? diag::err_typecheck_call_too_many_args_one
                   : diag::err_typecheck_call_too_many_args_at_most_one)
              << FnKind << FDecl->getParamDecl(0)
              << static_cast<unsigned>(Args.size()) << Fn->getSourceRange()
              << SourceRange(Args[NumParams]->getBeginLoc(),
                             Args.back()->getEndLoc());
        else
          Diag(Args[NumParams]->getBeginLoc(),
               MinArgs == NumParams
                   ? diag::err_typecheck_call_too_many_args
                   : diag::err_typecheck_call_too_many_args_at_most)
              << FnKind << NumParams << static_cast<unsigned>(Args.size())
              << Fn->getSourceRange()
              << SourceRange(Args[NumParams]->getBeginLoc(),
                             Args.back()->getEndLoc());
  
        // Emit the location of the prototype.
        if (!TC && FDecl && !FDecl->getBuiltinID() && !IsExecConfig)
          Diag(FDecl->getLocation(), diag::note_callee_decl) << FDecl;
  
        // This deletes the extra arguments.
        Call->shrinkNumArgs(NumParams);
        return true;
      }
    }
    SmallVector<Expr *, 8> AllArgs;
    VariadicCallType CallType = getVariadicCallType(FDecl, Proto, Fn);
  
    Invalid = GatherArgumentsForCall(Call->getBeginLoc(), FDecl, Proto, 0, Args,
                                     AllArgs, CallType);
    if (Invalid)
      return true;
    unsigned TotalNumArgs = AllArgs.size();
    for (unsigned i = 0; i < TotalNumArgs; ++i)
      Call->setArg(i, AllArgs[i]);
  
    Call->computeDependence();
    return false;
  }
  
  bool Sema::GatherArgumentsForCall(SourceLocation CallLoc, FunctionDecl *FDecl,
                                    const FunctionProtoType *Proto,
                                    unsigned FirstParam, ArrayRef<Expr *> Args,
                                    SmallVectorImpl<Expr *> &AllArgs,
                                    VariadicCallType CallType, bool AllowExplicit,
                                    bool IsListInitialization) {
    unsigned NumParams = Proto->getNumParams();
    bool Invalid = false;
    size_t ArgIx = 0;
    // Continue to check argument types (even if we have too few/many args).
    for (unsigned i = FirstParam; i < NumParams; i++) {
      QualType ProtoArgType = Proto->getParamType(i);
  
      Expr *Arg;
      ParmVarDecl *Param = FDecl ? FDecl->getParamDecl(i) : nullptr;
      if (ArgIx < Args.size()) {
        Arg = Args[ArgIx++];
  
        if (RequireCompleteType(Arg->getBeginLoc(), ProtoArgType,
                                diag::err_call_incomplete_argument, Arg))
          return true;
  
        // Strip the unbridged-cast placeholder expression off, if applicable.
        bool CFAudited = false;
        if (Arg->getType() == Context.ARCUnbridgedCastTy &&
            FDecl && FDecl->hasAttr<CFAuditedTransferAttr>() &&
            (!Param || !Param->hasAttr<CFConsumedAttr>()))
          Arg = stripARCUnbridgedCast(Arg);
        else if (getLangOpts().ObjCAutoRefCount &&
                 FDecl && FDecl->hasAttr<CFAuditedTransferAttr>() &&
                 (!Param || !Param->hasAttr<CFConsumedAttr>()))
          CFAudited = true;
  
        if (Proto->getExtParameterInfo(i).isNoEscape() &&
            ProtoArgType->isBlockPointerType())
          if (auto *BE = dyn_cast<BlockExpr>(Arg->IgnoreParenNoopCasts(Context)))
            BE->getBlockDecl()->setDoesNotEscape();
  
        InitializedEntity Entity =
            Param ? InitializedEntity::InitializeParameter(Context, Param,
                                                           ProtoArgType)
                  : InitializedEntity::InitializeParameter(
                        Context, ProtoArgType, Proto->isParamConsumed(i));
  
        // Remember that parameter belongs to a CF audited API.
        if (CFAudited)
          Entity.setParameterCFAudited();
  
        ExprResult ArgE = PerformCopyInitialization(
            Entity, SourceLocation(), Arg, IsListInitialization, AllowExplicit);
        if (ArgE.isInvalid())
          return true;
  
        Arg = ArgE.getAs<Expr>();
      } else {
        assert(Param && "can't use default arguments without a known callee");
  
        ExprResult ArgExpr = BuildCXXDefaultArgExpr(CallLoc, FDecl, Param);
        if (ArgExpr.isInvalid())
          return true;
  
        Arg = ArgExpr.getAs<Expr>();
      }
  
      // Check for array bounds violations for each argument to the call. This
      // check only triggers warnings when the argument isn't a more complex Expr
      // with its own checking, such as a BinaryOperator.
      CheckArrayAccess(Arg);
  
      // Check for violations of C99 static array rules (C99 6.7.5.3p7).
      CheckStaticArrayArgument(CallLoc, Param, Arg);
  
      AllArgs.push_back(Arg);
    }
  
    // If this is a variadic call, handle args passed through "...".
    if (CallType != VariadicDoesNotApply) {
      // Assume that extern "C" functions with variadic arguments that
      // return __unknown_anytype aren't *really* variadic.
      if (Proto->getReturnType() == Context.UnknownAnyTy && FDecl &&
          FDecl->isExternC()) {
        for (Expr *A : Args.slice(ArgIx)) {
          QualType paramType; // ignored
          ExprResult arg = checkUnknownAnyArg(CallLoc, A, paramType);
          Invalid |= arg.isInvalid();
          AllArgs.push_back(arg.get());
        }
  
      // Otherwise do argument promotion, (C99 6.5.2.2p7).
      } else {
        for (Expr *A : Args.slice(ArgIx)) {
          ExprResult Arg = DefaultVariadicArgumentPromotion(A, CallType, FDecl);
          Invalid |= Arg.isInvalid();
          AllArgs.push_back(Arg.get());
        }
      }
  
      // Check for array bounds violations.
      for (Expr *A : Args.slice(ArgIx))
        CheckArrayAccess(A);
    }
    return Invalid;
  }
  
  static void DiagnoseCalleeStaticArrayParam(Sema &S, ParmVarDecl *PVD) {
    TypeLoc TL = PVD->getTypeSourceInfo()->getTypeLoc();
    if (DecayedTypeLoc DTL = TL.getAs<DecayedTypeLoc>())
      TL = DTL.getOriginalLoc();
    if (ArrayTypeLoc ATL = TL.getAs<ArrayTypeLoc>())
      S.Diag(PVD->getLocation(), diag::note_callee_static_array)
        << ATL.getLocalSourceRange();
  }
  
  /// CheckStaticArrayArgument - If the given argument corresponds to a static
  /// array parameter, check that it is non-null, and that if it is formed by
  /// array-to-pointer decay, the underlying array is sufficiently large.
  ///
  /// C99 6.7.5.3p7: If the keyword static also appears within the [ and ] of the
  /// array type derivation, then for each call to the function, the value of the
  /// corresponding actual argument shall provide access to the first element of
  /// an array with at least as many elements as specified by the size expression.
  void
  Sema::CheckStaticArrayArgument(SourceLocation CallLoc,
                                 ParmVarDecl *Param,
                                 const Expr *ArgExpr) {
    // Static array parameters are not supported in C++.
    if (!Param || getLangOpts().CPlusPlus)
      return;
  
    QualType OrigTy = Param->getOriginalType();
  
    const ArrayType *AT = Context.getAsArrayType(OrigTy);
    if (!AT || AT->getSizeModifier() != ArrayType::Static)
      return;
  
    if (ArgExpr->isNullPointerConstant(Context,
                                       Expr::NPC_NeverValueDependent)) {
      Diag(CallLoc, diag::warn_null_arg) << ArgExpr->getSourceRange();
      DiagnoseCalleeStaticArrayParam(*this, Param);
      return;
    }
  
    const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(AT);
    if (!CAT)
      return;
  
    const ConstantArrayType *ArgCAT =
      Context.getAsConstantArrayType(ArgExpr->IgnoreParenCasts()->getType());
    if (!ArgCAT)
      return;
  
    if (getASTContext().hasSameUnqualifiedType(CAT->getElementType(),
                                               ArgCAT->getElementType())) {
      if (ArgCAT->getSize().ult(CAT->getSize())) {
        Diag(CallLoc, diag::warn_static_array_too_small)
            << ArgExpr->getSourceRange()
            << (unsigned)ArgCAT->getSize().getZExtValue()
            << (unsigned)CAT->getSize().getZExtValue() << 0;
        DiagnoseCalleeStaticArrayParam(*this, Param);
      }
      return;
    }
  
    Optional<CharUnits> ArgSize =
        getASTContext().getTypeSizeInCharsIfKnown(ArgCAT);
    Optional<CharUnits> ParmSize = getASTContext().getTypeSizeInCharsIfKnown(CAT);
    if (ArgSize && ParmSize && *ArgSize < *ParmSize) {
      Diag(CallLoc, diag::warn_static_array_too_small)
          << ArgExpr->getSourceRange() << (unsigned)ArgSize->getQuantity()
          << (unsigned)ParmSize->getQuantity() << 1;
      DiagnoseCalleeStaticArrayParam(*this, Param);
    }
  }
  
  /// Given a function expression of unknown-any type, try to rebuild it
  /// to have a function type.
  static ExprResult rebuildUnknownAnyFunction(Sema &S, Expr *fn);
  
  /// Is the given type a placeholder that we need to lower out
  /// immediately during argument processing?
  static bool isPlaceholderToRemoveAsArg(QualType type) {
    // Placeholders are never sugared.
    const BuiltinType *placeholder = dyn_cast<BuiltinType>(type);
    if (!placeholder) return false;
  
    switch (placeholder->getKind()) {
    // Ignore all the non-placeholder types.
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
    case BuiltinType::Id:
  #include "clang/Basic/OpenCLImageTypes.def"
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
    case BuiltinType::Id:
  #include "clang/Basic/OpenCLExtensionTypes.def"
    // In practice we'll never use this, since all SVE types are sugared
    // via TypedefTypes rather than exposed directly as BuiltinTypes.
  #define SVE_TYPE(Name, Id, SingletonId) \
    case BuiltinType::Id:
  #include "clang/Basic/AArch64SVEACLETypes.def"
  #define PPC_VECTOR_TYPE(Name, Id, Size) \
    case BuiltinType::Id:
  #include "clang/Basic/PPCTypes.def"
  #define RVV_TYPE(Name, Id, SingletonId) case BuiltinType::Id:
  #include "clang/Basic/RISCVVTypes.def"
  #define PLACEHOLDER_TYPE(ID, SINGLETON_ID)
  #define BUILTIN_TYPE(ID, SINGLETON_ID) case BuiltinType::ID:
  #include "clang/AST/BuiltinTypes.def"
      return false;
  
    // We cannot lower out overload sets; they might validly be resolved
    // by the call machinery.
    case BuiltinType::Overload:
      return false;
  
    // Unbridged casts in ARC can be handled in some call positions and
    // should be left in place.
    case BuiltinType::ARCUnbridgedCast:
      return false;
  
    // Pseudo-objects should be converted as soon as possible.
    case BuiltinType::PseudoObject:
      return true;
  
    // The debugger mode could theoretically but currently does not try
    // to resolve unknown-typed arguments based on known parameter types.
    case BuiltinType::UnknownAny:
      return true;
  
    // These are always invalid as call arguments and should be reported.
    case BuiltinType::BoundMember:
    case BuiltinType::BuiltinFn:
    case BuiltinType::IncompleteMatrixIdx:
    case BuiltinType::OMPArraySection:
    case BuiltinType::OMPArrayShaping:
    case BuiltinType::OMPIterator:
      return true;
  
    }
    llvm_unreachable("bad builtin type kind");
  }
  
  /// Check an argument list for placeholders that we won't try to
  /// handle later.
  static bool checkArgsForPlaceholders(Sema &S, MultiExprArg args) {
    // Apply this processing to all the arguments at once instead of
    // dying at the first failure.
    bool hasInvalid = false;
    for (size_t i = 0, e = args.size(); i != e; i++) {
      if (isPlaceholderToRemoveAsArg(args[i]->getType())) {
        ExprResult result = S.CheckPlaceholderExpr(args[i]);
        if (result.isInvalid()) hasInvalid = true;
        else args[i] = result.get();
      }
    }
    return hasInvalid;
  }
  
  /// If a builtin function has a pointer argument with no explicit address
  /// space, then it should be able to accept a pointer to any address
  /// space as input.  In order to do this, we need to replace the
  /// standard builtin declaration with one that uses the same address space
  /// as the call.
  ///
  /// \returns nullptr If this builtin is not a candidate for a rewrite i.e.
  ///                  it does not contain any pointer arguments without
  ///                  an address space qualifer.  Otherwise the rewritten
  ///                  FunctionDecl is returned.
  /// TODO: Handle pointer return types.
  static FunctionDecl *rewriteBuiltinFunctionDecl(Sema *Sema, ASTContext &Context,
                                                  FunctionDecl *FDecl,
                                                  MultiExprArg ArgExprs) {
  
    QualType DeclType = FDecl->getType();
    const FunctionProtoType *FT = dyn_cast<FunctionProtoType>(DeclType);
  
    if (!Context.BuiltinInfo.hasPtrArgsOrResult(FDecl->getBuiltinID()) || !FT ||
        ArgExprs.size() < FT->getNumParams())
      return nullptr;
  
    bool NeedsNewDecl = false;
    unsigned i = 0;
    SmallVector<QualType, 8> OverloadParams;
  
    for (QualType ParamType : FT->param_types()) {
  
      // Convert array arguments to pointer to simplify type lookup.
      ExprResult ArgRes =
          Sema->DefaultFunctionArrayLvalueConversion(ArgExprs[i++]);
      if (ArgRes.isInvalid())
        return nullptr;
      Expr *Arg = ArgRes.get();
      QualType ArgType = Arg->getType();
      if (!ParamType->isPointerType() ||
          ParamType.hasAddressSpace() ||
          !ArgType->isPointerType() ||
          !ArgType->getPointeeType().hasAddressSpace()) {
        OverloadParams.push_back(ParamType);
        continue;
      }
  
      QualType PointeeType = ParamType->getPointeeType();
      if (PointeeType.hasAddressSpace())
        continue;
  
      NeedsNewDecl = true;
      LangAS AS = ArgType->getPointeeType().getAddressSpace();
  
      PointeeType = Context.getAddrSpaceQualType(PointeeType, AS);
      OverloadParams.push_back(Context.getPointerType(PointeeType));
    }
  
    if (!NeedsNewDecl)
      return nullptr;
  
    FunctionProtoType::ExtProtoInfo EPI;
    EPI.Variadic = FT->isVariadic();
    QualType OverloadTy = Context.getFunctionType(FT->getReturnType(),
                                                  OverloadParams, EPI);
    DeclContext *Parent = FDecl->getParent();
    FunctionDecl *OverloadDecl = FunctionDecl::Create(
        Context, Parent, FDecl->getLocation(), FDecl->getLocation(),
        FDecl->getIdentifier(), OverloadTy,
        /*TInfo=*/nullptr, SC_Extern, Sema->getCurFPFeatures().isFPConstrained(),
        false,
        /*hasPrototype=*/true);
    SmallVector<ParmVarDecl*, 16> Params;
    FT = cast<FunctionProtoType>(OverloadTy);
    for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i) {
      QualType ParamType = FT->getParamType(i);
      ParmVarDecl *Parm =
          ParmVarDecl::Create(Context, OverloadDecl, SourceLocation(),
                                  SourceLocation(), nullptr, ParamType,
                                  /*TInfo=*/nullptr, SC_None, nullptr);
      Parm->setScopeInfo(0, i);
      Params.push_back(Parm);
    }
    OverloadDecl->setParams(Params);
    Sema->mergeDeclAttributes(OverloadDecl, FDecl);
    return OverloadDecl;
  }
  
  static void checkDirectCallValidity(Sema &S, const Expr *Fn,
                                      FunctionDecl *Callee,
                                      MultiExprArg ArgExprs) {
    // `Callee` (when called with ArgExprs) may be ill-formed. enable_if (and
    // similar attributes) really don't like it when functions are called with an
    // invalid number of args.
    if (S.TooManyArguments(Callee->getNumParams(), ArgExprs.size(),
                           /*PartialOverloading=*/false) &&
        !Callee->isVariadic())
      return;
    if (Callee->getMinRequiredArguments() > ArgExprs.size())
      return;
  
    if (const EnableIfAttr *Attr =
            S.CheckEnableIf(Callee, Fn->getBeginLoc(), ArgExprs, true)) {
      S.Diag(Fn->getBeginLoc(),
             isa<CXXMethodDecl>(Callee)
                 ? diag::err_ovl_no_viable_member_function_in_call
                 : diag::err_ovl_no_viable_function_in_call)
          << Callee << Callee->getSourceRange();
      S.Diag(Callee->getLocation(),
             diag::note_ovl_candidate_disabled_by_function_cond_attr)
          << Attr->getCond()->getSourceRange() << Attr->getMessage();
      return;
    }
  }
  
  static bool enclosingClassIsRelatedToClassInWhichMembersWereFound(
      const UnresolvedMemberExpr *const UME, Sema &S) {
  
    const auto GetFunctionLevelDCIfCXXClass =
        [](Sema &S) -> const CXXRecordDecl * {
      const DeclContext *const DC = S.getFunctionLevelDeclContext();
      if (!DC || !DC->getParent())
        return nullptr;
  
      // If the call to some member function was made from within a member
      // function body 'M' return return 'M's parent.
      if (const auto *MD = dyn_cast<CXXMethodDecl>(DC))
        return MD->getParent()->getCanonicalDecl();
      // else the call was made from within a default member initializer of a
      // class, so return the class.
      if (const auto *RD = dyn_cast<CXXRecordDecl>(DC))
        return RD->getCanonicalDecl();
      return nullptr;
    };
    // If our DeclContext is neither a member function nor a class (in the
    // case of a lambda in a default member initializer), we can't have an
    // enclosing 'this'.
  
    const CXXRecordDecl *const CurParentClass = GetFunctionLevelDCIfCXXClass(S);
    if (!CurParentClass)
      return false;
  
    // The naming class for implicit member functions call is the class in which
    // name lookup starts.
    const CXXRecordDecl *const NamingClass =
        UME->getNamingClass()->getCanonicalDecl();
    assert(NamingClass && "Must have naming class even for implicit access");
  
    // If the unresolved member functions were found in a 'naming class' that is
    // related (either the same or derived from) to the class that contains the
    // member function that itself contained the implicit member access.
  
    return CurParentClass == NamingClass ||
           CurParentClass->isDerivedFrom(NamingClass);
  }
  
  static void
  tryImplicitlyCaptureThisIfImplicitMemberFunctionAccessWithDependentArgs(
      Sema &S, const UnresolvedMemberExpr *const UME, SourceLocation CallLoc) {
  
    if (!UME)
      return;
  
    LambdaScopeInfo *const CurLSI = S.getCurLambda();
    // Only try and implicitly capture 'this' within a C++ Lambda if it hasn't
    // already been captured, or if this is an implicit member function call (if
    // it isn't, an attempt to capture 'this' should already have been made).
    if (!CurLSI || CurLSI->ImpCaptureStyle == CurLSI->ImpCap_None ||
        !UME->isImplicitAccess() || CurLSI->isCXXThisCaptured())
      return;
  
    // Check if the naming class in which the unresolved members were found is
    // related (same as or is a base of) to the enclosing class.
  
    if (!enclosingClassIsRelatedToClassInWhichMembersWereFound(UME, S))
      return;
  
  
    DeclContext *EnclosingFunctionCtx = S.CurContext->getParent()->getParent();
    // If the enclosing function is not dependent, then this lambda is
    // capture ready, so if we can capture this, do so.
    if (!EnclosingFunctionCtx->isDependentContext()) {
      // If the current lambda and all enclosing lambdas can capture 'this' -
      // then go ahead and capture 'this' (since our unresolved overload set
      // contains at least one non-static member function).
      if (!S.CheckCXXThisCapture(CallLoc, /*Explcit*/ false, /*Diagnose*/ false))
        S.CheckCXXThisCapture(CallLoc);
    } else if (S.CurContext->isDependentContext()) {
      // ... since this is an implicit member reference, that might potentially
      // involve a 'this' capture, mark 'this' for potential capture in
      // enclosing lambdas.
      if (CurLSI->ImpCaptureStyle != CurLSI->ImpCap_None)
        CurLSI->addPotentialThisCapture(CallLoc);
    }
  }
  
  // Once a call is fully resolved, warn for unqualified calls to specific
  // C++ standard functions, like move and forward.
  static void DiagnosedUnqualifiedCallsToStdFunctions(Sema &S, CallExpr *Call) {
    // We are only checking unary move and forward so exit early here.
    if (Call->getNumArgs() != 1)
      return;
  
    Expr *E = Call->getCallee()->IgnoreParenImpCasts();
    if (!E || isa<UnresolvedLookupExpr>(E))
      return;
    DeclRefExpr *DRE = dyn_cast_or_null<DeclRefExpr>(E);
    if (!DRE || !DRE->getLocation().isValid())
      return;
  
    if (DRE->getQualifier())
      return;
  
    NamedDecl *D = dyn_cast_or_null<NamedDecl>(Call->getCalleeDecl());
    if (!D || !D->isInStdNamespace())
      return;
  
    // Only warn for some functions deemed more frequent or problematic.
    static constexpr llvm::StringRef SpecialFunctions[] = {"move", "forward"};
    auto it = llvm::find(SpecialFunctions, D->getName());
    if (it == std::end(SpecialFunctions))
      return;
  
    S.Diag(DRE->getLocation(), diag::warn_unqualified_call_to_std_cast_function)
        << D->getQualifiedNameAsString()
        << FixItHint::CreateInsertion(DRE->getLocation(), "std::");
  }
  
  ExprResult Sema::ActOnCallExpr(Scope *Scope, Expr *Fn, SourceLocation LParenLoc,
                                 MultiExprArg ArgExprs, SourceLocation RParenLoc,
                                 Expr *ExecConfig) {
    ExprResult Call =
        BuildCallExpr(Scope, Fn, LParenLoc, ArgExprs, RParenLoc, ExecConfig,
                      /*IsExecConfig=*/false, /*AllowRecovery=*/true);
    if (Call.isInvalid())
      return Call;
  
    // Diagnose uses of the C++20 "ADL-only template-id call" feature in earlier
    // language modes.
    if (auto *ULE = dyn_cast<UnresolvedLookupExpr>(Fn)) {
      if (ULE->hasExplicitTemplateArgs() &&
          ULE->decls_begin() == ULE->decls_end()) {
        Diag(Fn->getExprLoc(), getLangOpts().CPlusPlus20
                                   ? diag::warn_cxx17_compat_adl_only_template_id
                                   : diag::ext_adl_only_template_id)
            << ULE->getName();
      }
    }
  
    if (LangOpts.OpenMP)
      Call = ActOnOpenMPCall(Call, Scope, LParenLoc, ArgExprs, RParenLoc,
                             ExecConfig);
    if (LangOpts.CPlusPlus) {
      CallExpr *CE = dyn_cast<CallExpr>(Call.get());
      if (CE)
        DiagnosedUnqualifiedCallsToStdFunctions(*this, CE);
    }
    return Call;
  }
  
  /// BuildCallExpr - Handle a call to Fn with the specified array of arguments.
  /// This provides the location of the left/right parens and a list of comma
  /// locations.
  ExprResult Sema::BuildCallExpr(Scope *Scope, Expr *Fn, SourceLocation LParenLoc,
                                 MultiExprArg ArgExprs, SourceLocation RParenLoc,
                                 Expr *ExecConfig, bool IsExecConfig,
                                 bool AllowRecovery) {
    // Since this might be a postfix expression, get rid of ParenListExprs.
    ExprResult Result = MaybeConvertParenListExprToParenExpr(Scope, Fn);
    if (Result.isInvalid()) return ExprError();
    Fn = Result.get();
  
    if (checkArgsForPlaceholders(*this, ArgExprs))
      return ExprError();
  
    if (getLangOpts().CPlusPlus) {
      // If this is a pseudo-destructor expression, build the call immediately.
      if (isa<CXXPseudoDestructorExpr>(Fn)) {
        if (!ArgExprs.empty()) {
          // Pseudo-destructor calls should not have any arguments.
          Diag(Fn->getBeginLoc(), diag::err_pseudo_dtor_call_with_args)
              << FixItHint::CreateRemoval(
                     SourceRange(ArgExprs.front()->getBeginLoc(),
                                 ArgExprs.back()->getEndLoc()));
        }
  
        return CallExpr::Create(Context, Fn, /*Args=*/{}, Context.VoidTy,
                                VK_PRValue, RParenLoc, CurFPFeatureOverrides());
      }
      if (Fn->getType() == Context.PseudoObjectTy) {
        ExprResult result = CheckPlaceholderExpr(Fn);
        if (result.isInvalid()) return ExprError();
        Fn = result.get();
      }
  
      // Determine whether this is a dependent call inside a C++ template,
      // in which case we won't do any semantic analysis now.
      if (Fn->isTypeDependent() || Expr::hasAnyTypeDependentArguments(ArgExprs)) {
        if (ExecConfig) {
          return CUDAKernelCallExpr::Create(Context, Fn,
                                            cast<CallExpr>(ExecConfig), ArgExprs,
                                            Context.DependentTy, VK_PRValue,
                                            RParenLoc, CurFPFeatureOverrides());
        } else {
  
          tryImplicitlyCaptureThisIfImplicitMemberFunctionAccessWithDependentArgs(
              *this, dyn_cast<UnresolvedMemberExpr>(Fn->IgnoreParens()),
              Fn->getBeginLoc());
  
          return CallExpr::Create(Context, Fn, ArgExprs, Context.DependentTy,
                                  VK_PRValue, RParenLoc, CurFPFeatureOverrides());
        }
      }
  
      // Determine whether this is a call to an object (C++ [over.call.object]).
      if (Fn->getType()->isRecordType())
        return BuildCallToObjectOfClassType(Scope, Fn, LParenLoc, ArgExprs,
                                            RParenLoc);
  
      if (Fn->getType() == Context.UnknownAnyTy) {
        ExprResult result = rebuildUnknownAnyFunction(*this, Fn);
        if (result.isInvalid()) return ExprError();
        Fn = result.get();
      }
  
      if (Fn->getType() == Context.BoundMemberTy) {
        return BuildCallToMemberFunction(Scope, Fn, LParenLoc, ArgExprs,
                                         RParenLoc, ExecConfig, IsExecConfig,
                                         AllowRecovery);
      }
    }
  
    // Check for overloaded calls.  This can happen even in C due to extensions.
    if (Fn->getType() == Context.OverloadTy) {
      OverloadExpr::FindResult find = OverloadExpr::find(Fn);
  
      // We aren't supposed to apply this logic if there's an '&' involved.
      if (!find.HasFormOfMemberPointer) {
        if (Expr::hasAnyTypeDependentArguments(ArgExprs))
          return CallExpr::Create(Context, Fn, ArgExprs, Context.DependentTy,
                                  VK_PRValue, RParenLoc, CurFPFeatureOverrides());
        OverloadExpr *ovl = find.Expression;
        if (UnresolvedLookupExpr *ULE = dyn_cast<UnresolvedLookupExpr>(ovl))
          return BuildOverloadedCallExpr(
              Scope, Fn, ULE, LParenLoc, ArgExprs, RParenLoc, ExecConfig,
              /*AllowTypoCorrection=*/true, find.IsAddressOfOperand);
        return BuildCallToMemberFunction(Scope, Fn, LParenLoc, ArgExprs,
                                         RParenLoc, ExecConfig, IsExecConfig,
                                         AllowRecovery);
      }
    }
  
    // If we're directly calling a function, get the appropriate declaration.
    if (Fn->getType() == Context.UnknownAnyTy) {
      ExprResult result = rebuildUnknownAnyFunction(*this, Fn);
      if (result.isInvalid()) return ExprError();
      Fn = result.get();
    }
  
    Expr *NakedFn = Fn->IgnoreParens();
  
    bool CallingNDeclIndirectly = false;
    NamedDecl *NDecl = nullptr;
    if (UnaryOperator *UnOp = dyn_cast<UnaryOperator>(NakedFn)) {
      if (UnOp->getOpcode() == UO_AddrOf) {
        CallingNDeclIndirectly = true;
        NakedFn = UnOp->getSubExpr()->IgnoreParens();
      }
    }
  
    if (auto *DRE = dyn_cast<DeclRefExpr>(NakedFn)) {
      NDecl = DRE->getDecl();
  
      FunctionDecl *FDecl = dyn_cast<FunctionDecl>(NDecl);
      if (FDecl && FDecl->getBuiltinID()) {
        // Rewrite the function decl for this builtin by replacing parameters
        // with no explicit address space with the address space of the arguments
        // in ArgExprs.
        if ((FDecl =
                 rewriteBuiltinFunctionDecl(this, Context, FDecl, ArgExprs))) {
          NDecl = FDecl;
          Fn = DeclRefExpr::Create(
              Context, FDecl->getQualifierLoc(), SourceLocation(), FDecl, false,
              SourceLocation(), FDecl->getType(), Fn->getValueKind(), FDecl,
              nullptr, DRE->isNonOdrUse());
        }
      }
    } else if (isa<MemberExpr>(NakedFn))
      NDecl = cast<MemberExpr>(NakedFn)->getMemberDecl();
  
    if (FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(NDecl)) {
      if (CallingNDeclIndirectly && !checkAddressOfFunctionIsAvailable(
                                        FD, /*Complain=*/true, Fn->getBeginLoc()))
        return ExprError();
  
      checkDirectCallValidity(*this, Fn, FD, ArgExprs);
  
      // If this expression is a call to a builtin function in HIP device
      // compilation, allow a pointer-type argument to default address space to be
      // passed as a pointer-type parameter to a non-default address space.
      // If Arg is declared in the default address space and Param is declared
      // in a non-default address space, perform an implicit address space cast to
      // the parameter type.
      if (getLangOpts().HIP && getLangOpts().CUDAIsDevice && FD &&
          FD->getBuiltinID()) {
        for (unsigned Idx = 0; Idx < FD->param_size(); ++Idx) {
          ParmVarDecl *Param = FD->getParamDecl(Idx);
          if (!ArgExprs[Idx] || !Param || !Param->getType()->isPointerType() ||
              !ArgExprs[Idx]->getType()->isPointerType())
            continue;
  
          auto ParamAS = Param->getType()->getPointeeType().getAddressSpace();
          auto ArgTy = ArgExprs[Idx]->getType();
          auto ArgPtTy = ArgTy->getPointeeType();
          auto ArgAS = ArgPtTy.getAddressSpace();
  
          // Add address space cast if target address spaces are different
          bool NeedImplicitASC =
            ParamAS != LangAS::Default &&       // Pointer params in generic AS don't need special handling.
            ( ArgAS == LangAS::Default  ||      // We do allow implicit conversion from generic AS
                                                // or from specific AS which has target AS matching that of Param.
            getASTContext().getTargetAddressSpace(ArgAS) == getASTContext().getTargetAddressSpace(ParamAS));
          if (!NeedImplicitASC)
            continue;
  
          // First, ensure that the Arg is an RValue.
          if (ArgExprs[Idx]->isGLValue()) {
            ArgExprs[Idx] = ImplicitCastExpr::Create(
                Context, ArgExprs[Idx]->getType(), CK_NoOp, ArgExprs[Idx],
                nullptr, VK_PRValue, FPOptionsOverride());
          }
  
          // Construct a new arg type with address space of Param
          Qualifiers ArgPtQuals = ArgPtTy.getQualifiers();
          ArgPtQuals.setAddressSpace(ParamAS);
          auto NewArgPtTy =
              Context.getQualifiedType(ArgPtTy.getUnqualifiedType(), ArgPtQuals);
          auto NewArgTy =
              Context.getQualifiedType(Context.getPointerType(NewArgPtTy),
                                       ArgTy.getQualifiers());
  
          // Finally perform an implicit address space cast
          ArgExprs[Idx] = ImpCastExprToType(ArgExprs[Idx], NewArgTy,
                                            CK_AddressSpaceConversion)
                              .get();
        }
      }
    }
  
    if (Context.isDependenceAllowed() &&
        (Fn->isTypeDependent() || Expr::hasAnyTypeDependentArguments(ArgExprs))) {
      assert(!getLangOpts().CPlusPlus);
      assert((Fn->containsErrors() ||
              llvm::any_of(ArgExprs,
                           [](clang::Expr *E) { return E->containsErrors(); })) &&
             "should only occur in error-recovery path.");
      QualType ReturnType =
          llvm::isa_and_nonnull<FunctionDecl>(NDecl)
              ? cast<FunctionDecl>(NDecl)->getCallResultType()
              : Context.DependentTy;
      return CallExpr::Create(Context, Fn, ArgExprs, ReturnType,
                              Expr::getValueKindForType(ReturnType), RParenLoc,
                              CurFPFeatureOverrides());
    }
    return BuildResolvedCallExpr(Fn, NDecl, LParenLoc, ArgExprs, RParenLoc,
                                 ExecConfig, IsExecConfig);
  }
  
  /// BuildBuiltinCallExpr - Create a call to a builtin function specified by Id
  //  with the specified CallArgs
  Expr *Sema::BuildBuiltinCallExpr(SourceLocation Loc, Builtin::ID Id,
                                   MultiExprArg CallArgs) {
    StringRef Name = Context.BuiltinInfo.getName(Id);
    LookupResult R(*this, &Context.Idents.get(Name), Loc,
                   Sema::LookupOrdinaryName);
    LookupName(R, TUScope, /*AllowBuiltinCreation=*/true);
  
    auto *BuiltInDecl = R.getAsSingle<FunctionDecl>();
    assert(BuiltInDecl && "failed to find builtin declaration");
  
    ExprResult DeclRef =
        BuildDeclRefExpr(BuiltInDecl, BuiltInDecl->getType(), VK_LValue, Loc);
    assert(DeclRef.isUsable() && "Builtin reference cannot fail");
  
    ExprResult Call =
        BuildCallExpr(/*Scope=*/nullptr, DeclRef.get(), Loc, CallArgs, Loc);
  
    assert(!Call.isInvalid() && "Call to builtin cannot fail!");
    return Call.get();
  }
  
  /// Parse a __builtin_astype expression.
  ///
  /// __builtin_astype( value, dst type )
  ///
  ExprResult Sema::ActOnAsTypeExpr(Expr *E, ParsedType ParsedDestTy,
                                   SourceLocation BuiltinLoc,
                                   SourceLocation RParenLoc) {
    QualType DstTy = GetTypeFromParser(ParsedDestTy);
    return BuildAsTypeExpr(E, DstTy, BuiltinLoc, RParenLoc);
  }
  
  /// Create a new AsTypeExpr node (bitcast) from the arguments.
  ExprResult Sema::BuildAsTypeExpr(Expr *E, QualType DestTy,
                                   SourceLocation BuiltinLoc,
                                   SourceLocation RParenLoc) {
    ExprValueKind VK = VK_PRValue;
    ExprObjectKind OK = OK_Ordinary;
    QualType SrcTy = E->getType();
    if (!SrcTy->isDependentType() &&
        Context.getTypeSize(DestTy) != Context.getTypeSize(SrcTy))
      return ExprError(
          Diag(BuiltinLoc, diag::err_invalid_astype_of_different_size)
          << DestTy << SrcTy << E->getSourceRange());
    return new (Context) AsTypeExpr(E, DestTy, VK, OK, BuiltinLoc, RParenLoc);
  }
  
  /// ActOnConvertVectorExpr - create a new convert-vector expression from the
  /// provided arguments.
  ///
  /// __builtin_convertvector( value, dst type )
  ///
  ExprResult Sema::ActOnConvertVectorExpr(Expr *E, ParsedType ParsedDestTy,
                                          SourceLocation BuiltinLoc,
                                          SourceLocation RParenLoc) {
    TypeSourceInfo *TInfo;
    GetTypeFromParser(ParsedDestTy, &TInfo);
    return SemaConvertVectorExpr(E, TInfo, BuiltinLoc, RParenLoc);
  }
  
  /// BuildResolvedCallExpr - Build a call to a resolved expression,
  /// i.e. an expression not of \p OverloadTy.  The expression should
  /// unary-convert to an expression of function-pointer or
  /// block-pointer type.
  ///
  /// \param NDecl the declaration being called, if available
  ExprResult Sema::BuildResolvedCallExpr(Expr *Fn, NamedDecl *NDecl,
                                         SourceLocation LParenLoc,
                                         ArrayRef<Expr *> Args,
                                         SourceLocation RParenLoc, Expr *Config,
                                         bool IsExecConfig, ADLCallKind UsesADL) {
    FunctionDecl *FDecl = dyn_cast_or_null<FunctionDecl>(NDecl);
    unsigned BuiltinID = (FDecl ? FDecl->getBuiltinID() : 0);
  
    // Functions with 'interrupt' attribute cannot be called directly.
    if (FDecl && FDecl->hasAttr<AnyX86InterruptAttr>()) {
      Diag(Fn->getExprLoc(), diag::err_anyx86_interrupt_called);
      return ExprError();
    }
  
    // Interrupt handlers don't save off the VFP regs automatically on ARM,
    // so there's some risk when calling out to non-interrupt handler functions
    // that the callee might not preserve them. This is easy to diagnose here,
    // but can be very challenging to debug.
    // Likewise, X86 interrupt handlers may only call routines with attribute
    // no_caller_saved_registers since there is no efficient way to
    // save and restore the non-GPR state.
    if (auto *Caller = getCurFunctionDecl()) {
      if (Caller->hasAttr<ARMInterruptAttr>()) {
        bool VFP = Context.getTargetInfo().hasFeature("vfp");
        if (VFP && (!FDecl || !FDecl->hasAttr<ARMInterruptAttr>())) {
          Diag(Fn->getExprLoc(), diag::warn_arm_interrupt_calling_convention);
          if (FDecl)
            Diag(FDecl->getLocation(), diag::note_callee_decl) << FDecl;
        }
      }
      if (Caller->hasAttr<AnyX86InterruptAttr>() &&
          ((!FDecl || !FDecl->hasAttr<AnyX86NoCallerSavedRegistersAttr>()))) {
        Diag(Fn->getExprLoc(), diag::warn_anyx86_interrupt_regsave);
        if (FDecl)
          Diag(FDecl->getLocation(), diag::note_callee_decl) << FDecl;
      }
    }
  
    // Promote the function operand.
    // We special-case function promotion here because we only allow promoting
    // builtin functions to function pointers in the callee of a call.
    ExprResult Result;
    QualType ResultTy;
    if (BuiltinID &&
        Fn->getType()->isSpecificBuiltinType(BuiltinType::BuiltinFn)) {
      // Extract the return type from the (builtin) function pointer type.
      // FIXME Several builtins still have setType in
      // Sema::CheckBuiltinFunctionCall. One should review their definitions in
      // Builtins.def to ensure they are correct before removing setType calls.
      QualType FnPtrTy = Context.getPointerType(FDecl->getType());
      Result = ImpCastExprToType(Fn, FnPtrTy, CK_BuiltinFnToFnPtr).get();
      ResultTy = FDecl->getCallResultType();
    } else {
      Result = CallExprUnaryConversions(Fn);
      ResultTy = Context.BoolTy;
    }
    if (Result.isInvalid())
      return ExprError();
    Fn = Result.get();
  
    // Check for a valid function type, but only if it is not a builtin which
    // requires custom type checking. These will be handled by
    // CheckBuiltinFunctionCall below just after creation of the call expression.
    const FunctionType *FuncT = nullptr;
    if (!BuiltinID || !Context.BuiltinInfo.hasCustomTypechecking(BuiltinID)) {
    retry:
      if (const PointerType *PT = Fn->getType()->getAs<PointerType>()) {
        // C99 6.5.2.2p1 - "The expression that denotes the called function shall
        // have type pointer to function".
        FuncT = PT->getPointeeType()->getAs<FunctionType>();
        if (!FuncT)
          return ExprError(Diag(LParenLoc, diag::err_typecheck_call_not_function)
                           << Fn->getType() << Fn->getSourceRange());
      } else if (const BlockPointerType *BPT =
                     Fn->getType()->getAs<BlockPointerType>()) {
        FuncT = BPT->getPointeeType()->castAs<FunctionType>();
      } else {
        // Handle calls to expressions of unknown-any type.
        if (Fn->getType() == Context.UnknownAnyTy) {
          ExprResult rewrite = rebuildUnknownAnyFunction(*this, Fn);
          if (rewrite.isInvalid())
            return ExprError();
          Fn = rewrite.get();
          goto retry;
        }
  
        return ExprError(Diag(LParenLoc, diag::err_typecheck_call_not_function)
                         << Fn->getType() << Fn->getSourceRange());
      }
    }
  
    // Get the number of parameters in the function prototype, if any.
    // We will allocate space for max(Args.size(), NumParams) arguments
    // in the call expression.
    const auto *Proto = dyn_cast_or_null<FunctionProtoType>(FuncT);
    unsigned NumParams = Proto ? Proto->getNumParams() : 0;
  
    CallExpr *TheCall;
    if (Config) {
      assert(UsesADL == ADLCallKind::NotADL &&
             "CUDAKernelCallExpr should not use ADL");
      TheCall = CUDAKernelCallExpr::Create(Context, Fn, cast<CallExpr>(Config),
                                           Args, ResultTy, VK_PRValue, RParenLoc,
                                           CurFPFeatureOverrides(), NumParams);
    } else {
      TheCall =
          CallExpr::Create(Context, Fn, Args, ResultTy, VK_PRValue, RParenLoc,
                           CurFPFeatureOverrides(), NumParams, UsesADL);
    }
  
    if (!Context.isDependenceAllowed()) {
      // Forget about the nulled arguments since typo correction
      // do not handle them well.
      TheCall->shrinkNumArgs(Args.size());
      // C cannot always handle TypoExpr nodes in builtin calls and direct
      // function calls as their argument checking don't necessarily handle
      // dependent types properly, so make sure any TypoExprs have been
      // dealt with.
      ExprResult Result = CorrectDelayedTyposInExpr(TheCall);
      if (!Result.isUsable()) return ExprError();
      CallExpr *TheOldCall = TheCall;
      TheCall = dyn_cast<CallExpr>(Result.get());
      bool CorrectedTypos = TheCall != TheOldCall;
      if (!TheCall) return Result;
      Args = llvm::makeArrayRef(TheCall->getArgs(), TheCall->getNumArgs());
  
      // A new call expression node was created if some typos were corrected.
      // However it may not have been constructed with enough storage. In this
      // case, rebuild the node with enough storage. The waste of space is
      // immaterial since this only happens when some typos were corrected.
      if (CorrectedTypos && Args.size() < NumParams) {
        if (Config)
          TheCall = CUDAKernelCallExpr::Create(
              Context, Fn, cast<CallExpr>(Config), Args, ResultTy, VK_PRValue,
              RParenLoc, CurFPFeatureOverrides(), NumParams);
        else
          TheCall =
              CallExpr::Create(Context, Fn, Args, ResultTy, VK_PRValue, RParenLoc,
                               CurFPFeatureOverrides(), NumParams, UsesADL);
      }
      // We can now handle the nulled arguments for the default arguments.
      TheCall->setNumArgsUnsafe(std::max<unsigned>(Args.size(), NumParams));
    }
  
    // Bail out early if calling a builtin with custom type checking.
    if (BuiltinID && Context.BuiltinInfo.hasCustomTypechecking(BuiltinID))
      return CheckBuiltinFunctionCall(FDecl, BuiltinID, TheCall);
  
    if (getLangOpts().CUDA) {
      if (Config) {
        // CUDA: Kernel calls must be to global functions
        if (FDecl && !FDecl->hasAttr<CUDAGlobalAttr>())
          return ExprError(Diag(LParenLoc,diag::err_kern_call_not_global_function)
              << FDecl << Fn->getSourceRange());
  
        // CUDA: Kernel function must have 'void' return type
        if (!FuncT->getReturnType()->isVoidType() &&
            !FuncT->getReturnType()->getAs<AutoType>() &&
            !FuncT->getReturnType()->isInstantiationDependentType())
          return ExprError(Diag(LParenLoc, diag::err_kern_type_not_void_return)
              << Fn->getType() << Fn->getSourceRange());
      } else {
        // CUDA: Calls to global functions must be configured
        if (FDecl && FDecl->hasAttr<CUDAGlobalAttr>())
          return ExprError(Diag(LParenLoc, diag::err_global_call_not_config)
              << FDecl << Fn->getSourceRange());
      }
    }
  
    // Check for a valid return type
    if (CheckCallReturnType(FuncT->getReturnType(), Fn->getBeginLoc(), TheCall,
                            FDecl))
      return ExprError();
  
    // We know the result type of the call, set it.
    TheCall->setType(FuncT->getCallResultType(Context));
    TheCall->setValueKind(Expr::getValueKindForType(FuncT->getReturnType()));
  
    if (Proto) {
      if (ConvertArgumentsForCall(TheCall, Fn, FDecl, Proto, Args, RParenLoc,
                                  IsExecConfig))
        return ExprError();
    } else {
      assert(isa<FunctionNoProtoType>(FuncT) && "Unknown FunctionType!");
  
      if (FDecl) {
        // Check if we have too few/too many template arguments, based
        // on our knowledge of the function definition.
        const FunctionDecl *Def = nullptr;
        if (FDecl->hasBody(Def) && Args.size() != Def->param_size()) {
          Proto = Def->getType()->getAs<FunctionProtoType>();
         if (!Proto || !(Proto->isVariadic() && Args.size() >= Def->param_size()))
            Diag(RParenLoc, diag::warn_call_wrong_number_of_arguments)
            << (Args.size() > Def->param_size()) << FDecl << Fn->getSourceRange();
        }
  
        // If the function we're calling isn't a function prototype, but we have
        // a function prototype from a prior declaratiom, use that prototype.
        if (!FDecl->hasPrototype())
          Proto = FDecl->getType()->getAs<FunctionProtoType>();
      }
  
      // Promote the arguments (C99 6.5.2.2p6).
      for (unsigned i = 0, e = Args.size(); i != e; i++) {
        Expr *Arg = Args[i];
  
        if (Proto && i < Proto->getNumParams()) {
          InitializedEntity Entity = InitializedEntity::InitializeParameter(
              Context, Proto->getParamType(i), Proto->isParamConsumed(i));
          ExprResult ArgE =
              PerformCopyInitialization(Entity, SourceLocation(), Arg);
          if (ArgE.isInvalid())
            return true;
  
          Arg = ArgE.getAs<Expr>();
  
        } else {
          ExprResult ArgE = DefaultArgumentPromotion(Arg);
  
          if (ArgE.isInvalid())
            return true;
  
          Arg = ArgE.getAs<Expr>();
        }
  
        if (RequireCompleteType(Arg->getBeginLoc(), Arg->getType(),
                                diag::err_call_incomplete_argument, Arg))
          return ExprError();
  
        TheCall->setArg(i, Arg);
      }
      TheCall->computeDependence();
    }
  
    if (CXXMethodDecl *Method = dyn_cast_or_null<CXXMethodDecl>(FDecl))
      if (!Method->isStatic())
        return ExprError(Diag(LParenLoc, diag::err_member_call_without_object)
          << Fn->getSourceRange());
  
    // Check for sentinels
    if (NDecl)
      DiagnoseSentinelCalls(NDecl, LParenLoc, Args);
  
    // Warn for unions passing across security boundary (CMSE).
    if (FuncT != nullptr && FuncT->getCmseNSCallAttr()) {
      for (unsigned i = 0, e = Args.size(); i != e; i++) {
        if (const auto *RT =
                dyn_cast<RecordType>(Args[i]->getType().getCanonicalType())) {
          if (RT->getDecl()->isOrContainsUnion())
            Diag(Args[i]->getBeginLoc(), diag::warn_cmse_nonsecure_union)
                << 0 << i;
        }
      }
    }
  
    // Do special checking on direct calls to functions.
    if (FDecl) {
      if (CheckFunctionCall(FDecl, TheCall, Proto))
        return ExprError();
  
      checkFortifiedBuiltinMemoryFunction(FDecl, TheCall);
  
      if (BuiltinID)
        return CheckBuiltinFunctionCall(FDecl, BuiltinID, TheCall);
    } else if (NDecl) {
      if (CheckPointerCall(NDecl, TheCall, Proto))
        return ExprError();
    } else {
      if (CheckOtherCall(TheCall, Proto))
        return ExprError();
    }
  
    return CheckForImmediateInvocation(MaybeBindToTemporary(TheCall), FDecl);
  }
  
  ExprResult
  Sema::ActOnCompoundLiteral(SourceLocation LParenLoc, ParsedType Ty,
                             SourceLocation RParenLoc, Expr *InitExpr) {
    assert(Ty && "ActOnCompoundLiteral(): missing type");
    assert(InitExpr && "ActOnCompoundLiteral(): missing expression");
  
    TypeSourceInfo *TInfo;
    QualType literalType = GetTypeFromParser(Ty, &TInfo);
    if (!TInfo)
      TInfo = Context.getTrivialTypeSourceInfo(literalType);
  
    return BuildCompoundLiteralExpr(LParenLoc, TInfo, RParenLoc, InitExpr);
  }
  
  ExprResult
  Sema::BuildCompoundLiteralExpr(SourceLocation LParenLoc, TypeSourceInfo *TInfo,
                                 SourceLocation RParenLoc, Expr *LiteralExpr) {
    QualType literalType = TInfo->getType();
  
    if (literalType->isArrayType()) {
      if (RequireCompleteSizedType(
              LParenLoc, Context.getBaseElementType(literalType),
              diag::err_array_incomplete_or_sizeless_type,
              SourceRange(LParenLoc, LiteralExpr->getSourceRange().getEnd())))
        return ExprError();
      if (literalType->isVariableArrayType()) {
        if (!tryToFixVariablyModifiedVarType(TInfo, literalType, LParenLoc,
                                             diag::err_variable_object_no_init)) {
          return ExprError();
        }
      }
    } else if (!literalType->isDependentType() &&
               RequireCompleteType(LParenLoc, literalType,
                 diag::err_typecheck_decl_incomplete_type,
                 SourceRange(LParenLoc, LiteralExpr->getSourceRange().getEnd())))
      return ExprError();
  
    InitializedEntity Entity
      = InitializedEntity::InitializeCompoundLiteralInit(TInfo);
    InitializationKind Kind
      = InitializationKind::CreateCStyleCast(LParenLoc,
                                             SourceRange(LParenLoc, RParenLoc),
                                             /*InitList=*/true);
    InitializationSequence InitSeq(*this, Entity, Kind, LiteralExpr);
    ExprResult Result = InitSeq.Perform(*this, Entity, Kind, LiteralExpr,
                                        &literalType);
    if (Result.isInvalid())
      return ExprError();
    LiteralExpr = Result.get();
  
    bool isFileScope = !CurContext->isFunctionOrMethod();
  
    // In C, compound literals are l-values for some reason.
    // For GCC compatibility, in C++, file-scope array compound literals with
    // constant initializers are also l-values, and compound literals are
    // otherwise prvalues.
    //
    // (GCC also treats C++ list-initialized file-scope array prvalues with
    // constant initializers as l-values, but that's non-conforming, so we don't
    // follow it there.)
    //
    // FIXME: It would be better to handle the lvalue cases as materializing and
    // lifetime-extending a temporary object, but our materialized temporaries
    // representation only supports lifetime extension from a variable, not "out
    // of thin air".
    // FIXME: For C++, we might want to instead lifetime-extend only if a pointer
    // is bound to the result of applying array-to-pointer decay to the compound
    // literal.
    // FIXME: GCC supports compound literals of reference type, which should
    // obviously have a value kind derived from the kind of reference involved.
    ExprValueKind VK =
        (getLangOpts().CPlusPlus && !(isFileScope && literalType->isArrayType()))
            ? VK_PRValue
            : VK_LValue;
  
    if (isFileScope)
      if (auto ILE = dyn_cast<InitListExpr>(LiteralExpr))
        for (unsigned i = 0, j = ILE->getNumInits(); i != j; i++) {
          Expr *Init = ILE->getInit(i);
          ILE->setInit(i, ConstantExpr::Create(Context, Init));
        }
  
    auto *E = new (Context) CompoundLiteralExpr(LParenLoc, TInfo, literalType,
                                                VK, LiteralExpr, isFileScope);
    if (isFileScope) {
      if (!LiteralExpr->isTypeDependent() &&
          !LiteralExpr->isValueDependent() &&
          !literalType->isDependentType()) // C99 6.5.2.5p3
        if (CheckForConstantInitializer(LiteralExpr, literalType))
          return ExprError();
    } else if (literalType.getAddressSpace() != LangAS::opencl_private &&
               literalType.getAddressSpace() != LangAS::Default) {
      // Embedded-C extensions to C99 6.5.2.5:
      //   "If the compound literal occurs inside the body of a function, the
      //   type name shall not be qualified by an address-space qualifier."
      Diag(LParenLoc, diag::err_compound_literal_with_address_space)
        << SourceRange(LParenLoc, LiteralExpr->getSourceRange().getEnd());
      return ExprError();
    }
  
    if (!isFileScope && !getLangOpts().CPlusPlus) {
      // Compound literals that have automatic storage duration are destroyed at
      // the end of the scope in C; in C++, they're just temporaries.
  
      // Emit diagnostics if it is or contains a C union type that is non-trivial
      // to destruct.
      if (E->getType().hasNonTrivialToPrimitiveDestructCUnion())
        checkNonTrivialCUnion(E->getType(), E->getExprLoc(),
                              NTCUC_CompoundLiteral, NTCUK_Destruct);
  
      // Diagnose jumps that enter or exit the lifetime of the compound literal.
      if (literalType.isDestructedType()) {
        Cleanup.setExprNeedsCleanups(true);
        ExprCleanupObjects.push_back(E);
        getCurFunction()->setHasBranchProtectedScope();
      }
    }
  
    if (E->getType().hasNonTrivialToPrimitiveDefaultInitializeCUnion() ||
        E->getType().hasNonTrivialToPrimitiveCopyCUnion())
      checkNonTrivialCUnionInInitializer(E->getInitializer(),
                                         E->getInitializer()->getExprLoc());
  
    return MaybeBindToTemporary(E);
  }
  
  ExprResult
  Sema::ActOnInitList(SourceLocation LBraceLoc, MultiExprArg InitArgList,
                      SourceLocation RBraceLoc) {
    // Only produce each kind of designated initialization diagnostic once.
    SourceLocation FirstDesignator;
    bool DiagnosedArrayDesignator = false;
    bool DiagnosedNestedDesignator = false;
    bool DiagnosedMixedDesignator = false;
  
    // Check that any designated initializers are syntactically valid in the
    // current language mode.
    for (unsigned I = 0, E = InitArgList.size(); I != E; ++I) {
      if (auto *DIE = dyn_cast<DesignatedInitExpr>(InitArgList[I])) {
        if (FirstDesignator.isInvalid())
          FirstDesignator = DIE->getBeginLoc();
  
        if (!getLangOpts().CPlusPlus)
          break;
  
        if (!DiagnosedNestedDesignator && DIE->size() > 1) {
          DiagnosedNestedDesignator = true;
          Diag(DIE->getBeginLoc(), diag::ext_designated_init_nested)
            << DIE->getDesignatorsSourceRange();
        }
  
        for (auto &Desig : DIE->designators()) {
          if (!Desig.isFieldDesignator() && !DiagnosedArrayDesignator) {
            DiagnosedArrayDesignator = true;
            Diag(Desig.getBeginLoc(), diag::ext_designated_init_array)
              << Desig.getSourceRange();
          }
        }
  
        if (!DiagnosedMixedDesignator &&
            !isa<DesignatedInitExpr>(InitArgList[0])) {
          DiagnosedMixedDesignator = true;
          Diag(DIE->getBeginLoc(), diag::ext_designated_init_mixed)
            << DIE->getSourceRange();
          Diag(InitArgList[0]->getBeginLoc(), diag::note_designated_init_mixed)
            << InitArgList[0]->getSourceRange();
        }
      } else if (getLangOpts().CPlusPlus && !DiagnosedMixedDesignator &&
                 isa<DesignatedInitExpr>(InitArgList[0])) {
        DiagnosedMixedDesignator = true;
        auto *DIE = cast<DesignatedInitExpr>(InitArgList[0]);
        Diag(DIE->getBeginLoc(), diag::ext_designated_init_mixed)
          << DIE->getSourceRange();
        Diag(InitArgList[I]->getBeginLoc(), diag::note_designated_init_mixed)
          << InitArgList[I]->getSourceRange();
      }
    }
  
    if (FirstDesignator.isValid()) {
      // Only diagnose designated initiaization as a C++20 extension if we didn't
      // already diagnose use of (non-C++20) C99 designator syntax.
      if (getLangOpts().CPlusPlus && !DiagnosedArrayDesignator &&
          !DiagnosedNestedDesignator && !DiagnosedMixedDesignator) {
        Diag(FirstDesignator, getLangOpts().CPlusPlus20
                                  ? diag::warn_cxx17_compat_designated_init
                                  : diag::ext_cxx_designated_init);
      } else if (!getLangOpts().CPlusPlus && !getLangOpts().C99) {
        Diag(FirstDesignator, diag::ext_designated_init);
      }
    }
  
    return BuildInitList(LBraceLoc, InitArgList, RBraceLoc);
  }
  
  ExprResult
  Sema::BuildInitList(SourceLocation LBraceLoc, MultiExprArg InitArgList,
                      SourceLocation RBraceLoc) {
    // Semantic analysis for initializers is done by ActOnDeclarator() and
    // CheckInitializer() - it requires knowledge of the object being initialized.
  
    // Immediately handle non-overload placeholders.  Overloads can be
    // resolved contextually, but everything else here can't.
    for (unsigned I = 0, E = InitArgList.size(); I != E; ++I) {
      if (InitArgList[I]->getType()->isNonOverloadPlaceholderType()) {
        ExprResult result = CheckPlaceholderExpr(InitArgList[I]);
  
        // Ignore failures; dropping the entire initializer list because
        // of one failure would be terrible for indexing/etc.
        if (result.isInvalid()) continue;
  
        InitArgList[I] = result.get();
      }
    }
  
    InitListExpr *E = new (Context) InitListExpr(Context, LBraceLoc, InitArgList,
                                                 RBraceLoc);
    E->setType(Context.VoidTy); // FIXME: just a place holder for now.
    return E;
  }
  
  /// Do an explicit extend of the given block pointer if we're in ARC.
  void Sema::maybeExtendBlockObject(ExprResult &E) {
    assert(E.get()->getType()->isBlockPointerType());
    assert(E.get()->isPRValue());
  
    // Only do this in an r-value context.
    if (!getLangOpts().ObjCAutoRefCount) return;
  
    E = ImplicitCastExpr::Create(
        Context, E.get()->getType(), CK_ARCExtendBlockObject, E.get(),
        /*base path*/ nullptr, VK_PRValue, FPOptionsOverride());
    Cleanup.setExprNeedsCleanups(true);
  }
  
  /// Prepare a conversion of the given expression to an ObjC object
  /// pointer type.
  CastKind Sema::PrepareCastToObjCObjectPointer(ExprResult &E) {
    QualType type = E.get()->getType();
    if (type->isObjCObjectPointerType()) {
      return CK_BitCast;
    } else if (type->isBlockPointerType()) {
      maybeExtendBlockObject(E);
      return CK_BlockPointerToObjCPointerCast;
    } else {
      assert(type->isPointerType());
      return CK_CPointerToObjCPointerCast;
    }
  }
  
  /// Prepares for a scalar cast, performing all the necessary stages
  /// except the final cast and returning the kind required.
  CastKind Sema::PrepareScalarCast(ExprResult &Src, QualType DestTy) {
    // Both Src and Dest are scalar types, i.e. arithmetic or pointer.
    // Also, callers should have filtered out the invalid cases with
    // pointers.  Everything else should be possible.
  
    QualType SrcTy = Src.get()->getType();
    if (Context.hasSameUnqualifiedType(SrcTy, DestTy))
      return CK_NoOp;
  
    switch (Type::ScalarTypeKind SrcKind = SrcTy->getScalarTypeKind()) {
    case Type::STK_MemberPointer:
      llvm_unreachable("member pointer type in C");
  
    case Type::STK_CPointer:
    case Type::STK_BlockPointer:
    case Type::STK_ObjCObjectPointer:
      switch (DestTy->getScalarTypeKind()) {
      case Type::STK_CPointer: {
        LangAS SrcAS = SrcTy->getPointeeType().getAddressSpace();
        LangAS DestAS = DestTy->getPointeeType().getAddressSpace();
        if (SrcAS != DestAS)
          return CK_AddressSpaceConversion;
        if (Context.hasCvrSimilarType(SrcTy, DestTy))
          return CK_NoOp;
        return CK_BitCast;
      }
      case Type::STK_BlockPointer:
        return (SrcKind == Type::STK_BlockPointer
                  ? CK_BitCast : CK_AnyPointerToBlockPointerCast);
      case Type::STK_ObjCObjectPointer:
        if (SrcKind == Type::STK_ObjCObjectPointer)
          return CK_BitCast;
        if (SrcKind == Type::STK_CPointer)
          return CK_CPointerToObjCPointerCast;
        maybeExtendBlockObject(Src);
        return CK_BlockPointerToObjCPointerCast;
      case Type::STK_Bool:
        return CK_PointerToBoolean;
      case Type::STK_Integral:
        return CK_PointerToIntegral;
      case Type::STK_Floating:
      case Type::STK_FloatingComplex:
      case Type::STK_IntegralComplex:
      case Type::STK_MemberPointer:
      case Type::STK_FixedPoint:
        llvm_unreachable("illegal cast from pointer");
      }
      llvm_unreachable("Should have returned before this");
  
    case Type::STK_FixedPoint:
      switch (DestTy->getScalarTypeKind()) {
      case Type::STK_FixedPoint:
        return CK_FixedPointCast;
      case Type::STK_Bool:
        return CK_FixedPointToBoolean;
      case Type::STK_Integral:
        return CK_FixedPointToIntegral;
      case Type::STK_Floating:
        return CK_FixedPointToFloating;
      case Type::STK_IntegralComplex:
      case Type::STK_FloatingComplex:
        Diag(Src.get()->getExprLoc(),
             diag::err_unimplemented_conversion_with_fixed_point_type)
            << DestTy;
        return CK_IntegralCast;
      case Type::STK_CPointer:
      case Type::STK_ObjCObjectPointer:
      case Type::STK_BlockPointer:
      case Type::STK_MemberPointer:
        llvm_unreachable("illegal cast to pointer type");
      }
      llvm_unreachable("Should have returned before this");
  
    case Type::STK_Bool: // casting from bool is like casting from an integer
    case Type::STK_Integral:
      switch (DestTy->getScalarTypeKind()) {
      case Type::STK_CPointer:
      case Type::STK_ObjCObjectPointer:
      case Type::STK_BlockPointer:
        if (Src.get()->isNullPointerConstant(Context,
                                             Expr::NPC_ValueDependentIsNull))
          return CK_NullToPointer;
        return CK_IntegralToPointer;
      case Type::STK_Bool:
        return CK_IntegralToBoolean;
      case Type::STK_Integral:
        return CK_IntegralCast;
      case Type::STK_Floating:
        return CK_IntegralToFloating;
      case Type::STK_IntegralComplex:
        Src = ImpCastExprToType(Src.get(),
                        DestTy->castAs<ComplexType>()->getElementType(),
                        CK_IntegralCast);
        return CK_IntegralRealToComplex;
      case Type::STK_FloatingComplex:
        Src = ImpCastExprToType(Src.get(),
                        DestTy->castAs<ComplexType>()->getElementType(),
                        CK_IntegralToFloating);
        return CK_FloatingRealToComplex;
      case Type::STK_MemberPointer:
        llvm_unreachable("member pointer type in C");
      case Type::STK_FixedPoint:
        return CK_IntegralToFixedPoint;
      }
      llvm_unreachable("Should have returned before this");
  
    case Type::STK_Floating:
      switch (DestTy->getScalarTypeKind()) {
      case Type::STK_Floating:
        return CK_FloatingCast;
      case Type::STK_Bool:
        return CK_FloatingToBoolean;
      case Type::STK_Integral:
        return CK_FloatingToIntegral;
      case Type::STK_FloatingComplex:
        Src = ImpCastExprToType(Src.get(),
                                DestTy->castAs<ComplexType>()->getElementType(),
                                CK_FloatingCast);
        return CK_FloatingRealToComplex;
      case Type::STK_IntegralComplex:
        Src = ImpCastExprToType(Src.get(),
                                DestTy->castAs<ComplexType>()->getElementType(),
                                CK_FloatingToIntegral);
        return CK_IntegralRealToComplex;
      case Type::STK_CPointer:
      case Type::STK_ObjCObjectPointer:
      case Type::STK_BlockPointer:
        llvm_unreachable("valid float->pointer cast?");
      case Type::STK_MemberPointer:
        llvm_unreachable("member pointer type in C");
      case Type::STK_FixedPoint:
        return CK_FloatingToFixedPoint;
      }
      llvm_unreachable("Should have returned before this");
  
    case Type::STK_FloatingComplex:
      switch (DestTy->getScalarTypeKind()) {
      case Type::STK_FloatingComplex:
        return CK_FloatingComplexCast;
      case Type::STK_IntegralComplex:
        return CK_FloatingComplexToIntegralComplex;
      case Type::STK_Floating: {
        QualType ET = SrcTy->castAs<ComplexType>()->getElementType();
        if (Context.hasSameType(ET, DestTy))
          return CK_FloatingComplexToReal;
        Src = ImpCastExprToType(Src.get(), ET, CK_FloatingComplexToReal);
        return CK_FloatingCast;
      }
      case Type::STK_Bool:
        return CK_FloatingComplexToBoolean;
      case Type::STK_Integral:
        Src = ImpCastExprToType(Src.get(),
                                SrcTy->castAs<ComplexType>()->getElementType(),
                                CK_FloatingComplexToReal);
        return CK_FloatingToIntegral;
      case Type::STK_CPointer:
      case Type::STK_ObjCObjectPointer:
      case Type::STK_BlockPointer:
        llvm_unreachable("valid complex float->pointer cast?");
      case Type::STK_MemberPointer:
        llvm_unreachable("member pointer type in C");
      case Type::STK_FixedPoint:
        Diag(Src.get()->getExprLoc(),
             diag::err_unimplemented_conversion_with_fixed_point_type)
            << SrcTy;
        return CK_IntegralCast;
      }
      llvm_unreachable("Should have returned before this");
  
    case Type::STK_IntegralComplex:
      switch (DestTy->getScalarTypeKind()) {
      case Type::STK_FloatingComplex:
        return CK_IntegralComplexToFloatingComplex;
      case Type::STK_IntegralComplex:
        return CK_IntegralComplexCast;
      case Type::STK_Integral: {
        QualType ET = SrcTy->castAs<ComplexType>()->getElementType();
        if (Context.hasSameType(ET, DestTy))
          return CK_IntegralComplexToReal;
        Src = ImpCastExprToType(Src.get(), ET, CK_IntegralComplexToReal);
        return CK_IntegralCast;
      }
      case Type::STK_Bool:
        return CK_IntegralComplexToBoolean;
      case Type::STK_Floating:
        Src = ImpCastExprToType(Src.get(),
                                SrcTy->castAs<ComplexType>()->getElementType(),
                                CK_IntegralComplexToReal);
        return CK_IntegralToFloating;
      case Type::STK_CPointer:
      case Type::STK_ObjCObjectPointer:
      case Type::STK_BlockPointer:
        llvm_unreachable("valid complex int->pointer cast?");
      case Type::STK_MemberPointer:
        llvm_unreachable("member pointer type in C");
      case Type::STK_FixedPoint:
        Diag(Src.get()->getExprLoc(),
             diag::err_unimplemented_conversion_with_fixed_point_type)
            << SrcTy;
        return CK_IntegralCast;
      }
      llvm_unreachable("Should have returned before this");
    }
  
    llvm_unreachable("Unhandled scalar cast");
  }
  
  static bool breakDownVectorType(QualType type, uint64_t &len,
                                  QualType &eltType) {
    // Vectors are simple.
    if (const VectorType *vecType = type->getAs<VectorType>()) {
      len = vecType->getNumElements();
      eltType = vecType->getElementType();
      assert(eltType->isScalarType());
      return true;
    }
  
    // We allow lax conversion to and from non-vector types, but only if
    // they're real types (i.e. non-complex, non-pointer scalar types).
    if (!type->isRealType()) return false;
  
    len = 1;
    eltType = type;
    return true;
  }
  
  /// Are the two types SVE-bitcast-compatible types? I.e. is bitcasting from the
  /// first SVE type (e.g. an SVE VLAT) to the second type (e.g. an SVE VLST)
  /// allowed?
  ///
  /// This will also return false if the two given types do not make sense from
  /// the perspective of SVE bitcasts.
  bool Sema::isValidSveBitcast(QualType srcTy, QualType destTy) {
    assert(srcTy->isVectorType() || destTy->isVectorType());
  
    auto ValidScalableConversion = [](QualType FirstType, QualType SecondType) {
      if (!FirstType->isSizelessBuiltinType())
        return false;
  
      const auto *VecTy = SecondType->getAs<VectorType>();
      return VecTy &&
             VecTy->getVectorKind() == VectorType::SveFixedLengthDataVector;
    };
  
    return ValidScalableConversion(srcTy, destTy) ||
           ValidScalableConversion(destTy, srcTy);
  }
  
  /// Are the two types matrix types and do they have the same dimensions i.e.
  /// do they have the same number of rows and the same number of columns?
  bool Sema::areMatrixTypesOfTheSameDimension(QualType srcTy, QualType destTy) {
    if (!destTy->isMatrixType() || !srcTy->isMatrixType())
      return false;
  
    const ConstantMatrixType *matSrcType = srcTy->getAs<ConstantMatrixType>();
    const ConstantMatrixType *matDestType = destTy->getAs<ConstantMatrixType>();
  
    return matSrcType->getNumRows() == matDestType->getNumRows() &&
           matSrcType->getNumColumns() == matDestType->getNumColumns();
  }
  
  bool Sema::areVectorTypesSameSize(QualType SrcTy, QualType DestTy) {
    assert(DestTy->isVectorType() || SrcTy->isVectorType());
  
    uint64_t SrcLen, DestLen;
    QualType SrcEltTy, DestEltTy;
    if (!breakDownVectorType(SrcTy, SrcLen, SrcEltTy))
      return false;
    if (!breakDownVectorType(DestTy, DestLen, DestEltTy))
      return false;
  
    // ASTContext::getTypeSize will return the size rounded up to a
    // power of 2, so instead of using that, we need to use the raw
    // element size multiplied by the element count.
    uint64_t SrcEltSize = Context.getTypeSize(SrcEltTy);
    uint64_t DestEltSize = Context.getTypeSize(DestEltTy);
  
    return (SrcLen * SrcEltSize == DestLen * DestEltSize);
  }
  
  /// Are the two types lax-compatible vector types?  That is, given
  /// that one of them is a vector, do they have equal storage sizes,
  /// where the storage size is the number of elements times the element
  /// size?
  ///
  /// This will also return false if either of the types is neither a
  /// vector nor a real type.
  bool Sema::areLaxCompatibleVectorTypes(QualType srcTy, QualType destTy) {
    assert(destTy->isVectorType() || srcTy->isVectorType());
  
    // Disallow lax conversions between scalars and ExtVectors (these
    // conversions are allowed for other vector types because common headers
    // depend on them).  Most scalar OP ExtVector cases are handled by the
    // splat path anyway, which does what we want (convert, not bitcast).
    // What this rules out for ExtVectors is crazy things like char4*float.
    if (srcTy->isScalarType() && destTy->isExtVectorType()) return false;
    if (destTy->isScalarType() && srcTy->isExtVectorType()) return false;
  
    return areVectorTypesSameSize(srcTy, destTy);
  }
  
  /// Is this a legal conversion between two types, one of which is
  /// known to be a vector type?
  bool Sema::isLaxVectorConversion(QualType srcTy, QualType destTy) {
    assert(destTy->isVectorType() || srcTy->isVectorType());
  
    switch (Context.getLangOpts().getLaxVectorConversions()) {
    case LangOptions::LaxVectorConversionKind::None:
      return false;
  
    case LangOptions::LaxVectorConversionKind::Integer:
      if (!srcTy->isIntegralOrEnumerationType()) {
        auto *Vec = srcTy->getAs<VectorType>();
        if (!Vec || !Vec->getElementType()->isIntegralOrEnumerationType())
          return false;
      }
      if (!destTy->isIntegralOrEnumerationType()) {
        auto *Vec = destTy->getAs<VectorType>();
        if (!Vec || !Vec->getElementType()->isIntegralOrEnumerationType())
          return false;
      }
      // OK, integer (vector) -> integer (vector) bitcast.
      break;
  
      case LangOptions::LaxVectorConversionKind::All:
      break;
    }
  
    return areLaxCompatibleVectorTypes(srcTy, destTy);
  }
  
  bool Sema::CheckMatrixCast(SourceRange R, QualType DestTy, QualType SrcTy,
                             CastKind &Kind) {
    if (SrcTy->isMatrixType() && DestTy->isMatrixType()) {
      if (!areMatrixTypesOfTheSameDimension(SrcTy, DestTy)) {
        return Diag(R.getBegin(), diag::err_invalid_conversion_between_matrixes)
               << DestTy << SrcTy << R;
      }
    } else if (SrcTy->isMatrixType()) {
      return Diag(R.getBegin(),
                  diag::err_invalid_conversion_between_matrix_and_type)
             << SrcTy << DestTy << R;
    } else if (DestTy->isMatrixType()) {
      return Diag(R.getBegin(),
                  diag::err_invalid_conversion_between_matrix_and_type)
             << DestTy << SrcTy << R;
    }
  
    Kind = CK_MatrixCast;
    return false;
  }
  
  bool Sema::CheckVectorCast(SourceRange R, QualType VectorTy, QualType Ty,
                             CastKind &Kind) {
    assert(VectorTy->isVectorType() && "Not a vector type!");
  
    if (Ty->isVectorType() || Ty->isIntegralType(Context)) {
      if (!areLaxCompatibleVectorTypes(Ty, VectorTy))
        return Diag(R.getBegin(),
                    Ty->isVectorType() ?
                    diag::err_invalid_conversion_between_vectors :
                    diag::err_invalid_conversion_between_vector_and_integer)
          << VectorTy << Ty << R;
    } else
      return Diag(R.getBegin(),
                  diag::err_invalid_conversion_between_vector_and_scalar)
        << VectorTy << Ty << R;
  
    Kind = CK_BitCast;
    return false;
  }
  
  ExprResult Sema::prepareVectorSplat(QualType VectorTy, Expr *SplattedExpr) {
    QualType DestElemTy = VectorTy->castAs<VectorType>()->getElementType();
  
    if (DestElemTy == SplattedExpr->getType())
      return SplattedExpr;
  
    assert(DestElemTy->isFloatingType() ||
           DestElemTy->isIntegralOrEnumerationType());
  
    CastKind CK;
    if (VectorTy->isExtVectorType() && SplattedExpr->getType()->isBooleanType()) {
      // OpenCL requires that we convert `true` boolean expressions to -1, but
      // only when splatting vectors.
      if (DestElemTy->isFloatingType()) {
        // To avoid having to have a CK_BooleanToSignedFloating cast kind, we cast
        // in two steps: boolean to signed integral, then to floating.
        ExprResult CastExprRes = ImpCastExprToType(SplattedExpr, Context.IntTy,
                                                   CK_BooleanToSignedIntegral);
        SplattedExpr = CastExprRes.get();
        CK = CK_IntegralToFloating;
      } else {
        CK = CK_BooleanToSignedIntegral;
      }
    } else {
      ExprResult CastExprRes = SplattedExpr;
      CK = PrepareScalarCast(CastExprRes, DestElemTy);
      if (CastExprRes.isInvalid())
        return ExprError();
      SplattedExpr = CastExprRes.get();
    }
    return ImpCastExprToType(SplattedExpr, DestElemTy, CK);
  }
  
  ExprResult Sema::CheckExtVectorCast(SourceRange R, QualType DestTy,
                                      Expr *CastExpr, CastKind &Kind) {
    assert(DestTy->isExtVectorType() && "Not an extended vector type!");
  
    QualType SrcTy = CastExpr->getType();
  
    // If SrcTy is a VectorType, the total size must match to explicitly cast to
    // an ExtVectorType.
    // In OpenCL, casts between vectors of different types are not allowed.
    // (See OpenCL 6.2).
    if (SrcTy->isVectorType()) {
      if (!areLaxCompatibleVectorTypes(SrcTy, DestTy) ||
          (getLangOpts().OpenCL &&
           !Context.hasSameUnqualifiedType(DestTy, SrcTy))) {
        Diag(R.getBegin(),diag::err_invalid_conversion_between_ext_vectors)
          << DestTy << SrcTy << R;
        return ExprError();
      }
      Kind = CK_BitCast;
      return CastExpr;
    }
  
    // All non-pointer scalars can be cast to ExtVector type.  The appropriate
    // conversion will take place first from scalar to elt type, and then
    // splat from elt type to vector.
    if (SrcTy->isPointerType())
      return Diag(R.getBegin(),
                  diag::err_invalid_conversion_between_vector_and_scalar)
        << DestTy << SrcTy << R;
  
    Kind = CK_VectorSplat;
    return prepareVectorSplat(DestTy, CastExpr);
  }
  
  ExprResult
  Sema::ActOnCastExpr(Scope *S, SourceLocation LParenLoc,
                      Declarator &D, ParsedType &Ty,
                      SourceLocation RParenLoc, Expr *CastExpr) {
    assert(!D.isInvalidType() && (CastExpr != nullptr) &&
           "ActOnCastExpr(): missing type or expr");
  
    TypeSourceInfo *castTInfo = GetTypeForDeclaratorCast(D, CastExpr->getType());
    if (D.isInvalidType())
      return ExprError();
  
    if (getLangOpts().CPlusPlus) {
      // Check that there are no default arguments (C++ only).
      CheckExtraCXXDefaultArguments(D);
    } else {
      // Make sure any TypoExprs have been dealt with.
      ExprResult Res = CorrectDelayedTyposInExpr(CastExpr);
      if (!Res.isUsable())
        return ExprError();
      CastExpr = Res.get();
    }
  
    checkUnusedDeclAttributes(D);
  
    QualType castType = castTInfo->getType();
    Ty = CreateParsedType(castType, castTInfo);
  
    bool isVectorLiteral = false;
  
    // Check for an altivec or OpenCL literal,
    // i.e. all the elements are integer constants.
    ParenExpr *PE = dyn_cast<ParenExpr>(CastExpr);
    ParenListExpr *PLE = dyn_cast<ParenListExpr>(CastExpr);
    if ((getLangOpts().AltiVec || getLangOpts().ZVector || getLangOpts().OpenCL)
         && castType->isVectorType() && (PE || PLE)) {
      if (PLE && PLE->getNumExprs() == 0) {
        Diag(PLE->getExprLoc(), diag::err_altivec_empty_initializer);
        return ExprError();
      }
      if (PE || PLE->getNumExprs() == 1) {
        Expr *E = (PE ? PE->getSubExpr() : PLE->getExpr(0));
        if (!E->isTypeDependent() && !E->getType()->isVectorType())
          isVectorLiteral = true;
      }
      else
        isVectorLiteral = true;
    }
  
    // If this is a vector initializer, '(' type ')' '(' init, ..., init ')'
    // then handle it as such.
    if (isVectorLiteral)
      return BuildVectorLiteral(LParenLoc, RParenLoc, CastExpr, castTInfo);
  
    // If the Expr being casted is a ParenListExpr, handle it specially.
    // This is not an AltiVec-style cast, so turn the ParenListExpr into a
    // sequence of BinOp comma operators.
    if (isa<ParenListExpr>(CastExpr)) {
      ExprResult Result = MaybeConvertParenListExprToParenExpr(S, CastExpr);
      if (Result.isInvalid()) return ExprError();
      CastExpr = Result.get();
    }
  
    if (getLangOpts().CPlusPlus && !castType->isVoidType())
      Diag(LParenLoc, diag::warn_old_style_cast) << CastExpr->getSourceRange();
  
    CheckTollFreeBridgeCast(castType, CastExpr);
  
    CheckObjCBridgeRelatedCast(castType, CastExpr);
  
    DiscardMisalignedMemberAddress(castType.getTypePtr(), CastExpr);
  
    return BuildCStyleCastExpr(LParenLoc, castTInfo, RParenLoc, CastExpr);
  }
  
  ExprResult Sema::BuildVectorLiteral(SourceLocation LParenLoc,
                                      SourceLocation RParenLoc, Expr *E,
                                      TypeSourceInfo *TInfo) {
    assert((isa<ParenListExpr>(E) || isa<ParenExpr>(E)) &&
           "Expected paren or paren list expression");
  
    Expr **exprs;
    unsigned numExprs;
    Expr *subExpr;
    SourceLocation LiteralLParenLoc, LiteralRParenLoc;
    if (ParenListExpr *PE = dyn_cast<ParenListExpr>(E)) {
      LiteralLParenLoc = PE->getLParenLoc();
      LiteralRParenLoc = PE->getRParenLoc();
      exprs = PE->getExprs();
      numExprs = PE->getNumExprs();
    } else { // isa<ParenExpr> by assertion at function entrance
      LiteralLParenLoc = cast<ParenExpr>(E)->getLParen();
      LiteralRParenLoc = cast<ParenExpr>(E)->getRParen();
      subExpr = cast<ParenExpr>(E)->getSubExpr();
      exprs = &subExpr;
      numExprs = 1;
    }
  
    QualType Ty = TInfo->getType();
    assert(Ty->isVectorType() && "Expected vector type");
  
    SmallVector<Expr *, 8> initExprs;
    const VectorType *VTy = Ty->castAs<VectorType>();
    unsigned numElems = VTy->getNumElements();
  
    // '(...)' form of vector initialization in AltiVec: the number of
    // initializers must be one or must match the size of the vector.
    // If a single value is specified in the initializer then it will be
    // replicated to all the components of the vector
    if (CheckAltivecInitFromScalar(E->getSourceRange(), Ty,
                                   VTy->getElementType()))
      return ExprError();
    if (ShouldSplatAltivecScalarInCast(VTy)) {
      // The number of initializers must be one or must match the size of the
      // vector. If a single value is specified in the initializer then it will
      // be replicated to all the components of the vector
      if (numExprs == 1) {
        QualType ElemTy = VTy->getElementType();
        ExprResult Literal = DefaultLvalueConversion(exprs[0]);
        if (Literal.isInvalid())
          return ExprError();
        Literal = ImpCastExprToType(Literal.get(), ElemTy,
                                    PrepareScalarCast(Literal, ElemTy));
        return BuildCStyleCastExpr(LParenLoc, TInfo, RParenLoc, Literal.get());
      }
      else if (numExprs < numElems) {
        Diag(E->getExprLoc(),
             diag::err_incorrect_number_of_vector_initializers);
        return ExprError();
      }
      else
        initExprs.append(exprs, exprs + numExprs);
    }
    else {
      // For OpenCL, when the number of initializers is a single value,
      // it will be replicated to all components of the vector.
      if (getLangOpts().OpenCL &&
          VTy->getVectorKind() == VectorType::GenericVector &&
          numExprs == 1) {
          QualType ElemTy = VTy->getElementType();
          ExprResult Literal = DefaultLvalueConversion(exprs[0]);
          if (Literal.isInvalid())
            return ExprError();
          Literal = ImpCastExprToType(Literal.get(), ElemTy,
                                      PrepareScalarCast(Literal, ElemTy));
          return BuildCStyleCastExpr(LParenLoc, TInfo, RParenLoc, Literal.get());
      }
  
      initExprs.append(exprs, exprs + numExprs);
    }
    // FIXME: This means that pretty-printing the final AST will produce curly
    // braces instead of the original commas.
    InitListExpr *initE = new (Context) InitListExpr(Context, LiteralLParenLoc,
                                                     initExprs, LiteralRParenLoc);
    initE->setType(Ty);
    return BuildCompoundLiteralExpr(LParenLoc, TInfo, RParenLoc, initE);
  }
  
  /// This is not an AltiVec-style cast or or C++ direct-initialization, so turn
  /// the ParenListExpr into a sequence of comma binary operators.
  ExprResult
  Sema::MaybeConvertParenListExprToParenExpr(Scope *S, Expr *OrigExpr) {
    ParenListExpr *E = dyn_cast<ParenListExpr>(OrigExpr);
    if (!E)
      return OrigExpr;
  
    ExprResult Result(E->getExpr(0));
  
    for (unsigned i = 1, e = E->getNumExprs(); i != e && !Result.isInvalid(); ++i)
      Result = ActOnBinOp(S, E->getExprLoc(), tok::comma, Result.get(),
                          E->getExpr(i));
  
    if (Result.isInvalid()) return ExprError();
  
    return ActOnParenExpr(E->getLParenLoc(), E->getRParenLoc(), Result.get());
  }
  
  ExprResult Sema::ActOnParenListExpr(SourceLocation L,
                                      SourceLocation R,
                                      MultiExprArg Val) {
    return ParenListExpr::Create(Context, L, Val, R);
  }
  
  /// Emit a specialized diagnostic when one expression is a null pointer
  /// constant and the other is not a pointer.  Returns true if a diagnostic is
  /// emitted.
  bool Sema::DiagnoseConditionalForNull(Expr *LHSExpr, Expr *RHSExpr,
                                        SourceLocation QuestionLoc) {
    Expr *NullExpr = LHSExpr;
    Expr *NonPointerExpr = RHSExpr;
    Expr::NullPointerConstantKind NullKind =
        NullExpr->isNullPointerConstant(Context,
                                        Expr::NPC_ValueDependentIsNotNull);
  
    if (NullKind == Expr::NPCK_NotNull) {
      NullExpr = RHSExpr;
      NonPointerExpr = LHSExpr;
      NullKind =
          NullExpr->isNullPointerConstant(Context,
                                          Expr::NPC_ValueDependentIsNotNull);
    }
  
    if (NullKind == Expr::NPCK_NotNull)
      return false;
  
    if (NullKind == Expr::NPCK_ZeroExpression)
      return false;
  
    if (NullKind == Expr::NPCK_ZeroLiteral) {
      // In this case, check to make sure that we got here from a "NULL"
      // string in the source code.
      NullExpr = NullExpr->IgnoreParenImpCasts();
      SourceLocation loc = NullExpr->getExprLoc();
      if (!findMacroSpelling(loc, "NULL"))
        return false;
    }
  
    int DiagType = (NullKind == Expr::NPCK_CXX11_nullptr);
    Diag(QuestionLoc, diag::err_typecheck_cond_incompatible_operands_null)
        << NonPointerExpr->getType() << DiagType
        << NonPointerExpr->getSourceRange();
    return true;
  }
  
  /// Return false if the condition expression is valid, true otherwise.
  static bool checkCondition(Sema &S, Expr *Cond, SourceLocation QuestionLoc) {
    QualType CondTy = Cond->getType();
  
    // OpenCL v1.1 s6.3.i says the condition cannot be a floating point type.
    if (S.getLangOpts().OpenCL && CondTy->isFloatingType()) {
      S.Diag(QuestionLoc, diag::err_typecheck_cond_expect_nonfloat)
        << CondTy << Cond->getSourceRange();
      return true;
    }
  
    // C99 6.5.15p2
    if (CondTy->isScalarType()) return false;
  
    S.Diag(QuestionLoc, diag::err_typecheck_cond_expect_scalar)
      << CondTy << Cond->getSourceRange();
    return true;
  }
  
  /// Handle when one or both operands are void type.
  static QualType checkConditionalVoidType(Sema &S, ExprResult &LHS,
                                           ExprResult &RHS) {
      Expr *LHSExpr = LHS.get();
      Expr *RHSExpr = RHS.get();
  
      if (!LHSExpr->getType()->isVoidType())
        S.Diag(RHSExpr->getBeginLoc(), diag::ext_typecheck_cond_one_void)
            << RHSExpr->getSourceRange();
      if (!RHSExpr->getType()->isVoidType())
        S.Diag(LHSExpr->getBeginLoc(), diag::ext_typecheck_cond_one_void)
            << LHSExpr->getSourceRange();
      LHS = S.ImpCastExprToType(LHS.get(), S.Context.VoidTy, CK_ToVoid);
      RHS = S.ImpCastExprToType(RHS.get(), S.Context.VoidTy, CK_ToVoid);
      return S.Context.VoidTy;
  }
  
  /// Return false if the NullExpr can be promoted to PointerTy,
  /// true otherwise.
  static bool checkConditionalNullPointer(Sema &S, ExprResult &NullExpr,
                                          QualType PointerTy) {
    if ((!PointerTy->isAnyPointerType() && !PointerTy->isBlockPointerType()) ||
        !NullExpr.get()->isNullPointerConstant(S.Context,
                                              Expr::NPC_ValueDependentIsNull))
      return true;
  
    NullExpr = S.ImpCastExprToType(NullExpr.get(), PointerTy, CK_NullToPointer);
    return false;
  }
  
  /// Checks compatibility between two pointers and return the resulting
  /// type.
  static QualType checkConditionalPointerCompatibility(Sema &S, ExprResult &LHS,
                                                       ExprResult &RHS,
                                                       SourceLocation Loc) {
    QualType LHSTy = LHS.get()->getType();
    QualType RHSTy = RHS.get()->getType();
  
    if (S.Context.hasSameType(LHSTy, RHSTy)) {
      // Two identical pointers types are always compatible.
      return LHSTy;
    }
  
    QualType lhptee, rhptee;
  
    // Get the pointee types.
    bool IsBlockPointer = false;
    if (const BlockPointerType *LHSBTy = LHSTy->getAs<BlockPointerType>()) {
      lhptee = LHSBTy->getPointeeType();
      rhptee = RHSTy->castAs<BlockPointerType>()->getPointeeType();
      IsBlockPointer = true;
    } else {
      lhptee = LHSTy->castAs<PointerType>()->getPointeeType();
      rhptee = RHSTy->castAs<PointerType>()->getPointeeType();
    }
  
    // C99 6.5.15p6: If both operands are pointers to compatible types or to
    // differently qualified versions of compatible types, the result type is
    // a pointer to an appropriately qualified version of the composite
    // type.
  
    // Only CVR-qualifiers exist in the standard, and the differently-qualified
    // clause doesn't make sense for our extensions. E.g. address space 2 should
    // be incompatible with address space 3: they may live on different devices or
    // anything.
    Qualifiers lhQual = lhptee.getQualifiers();
    Qualifiers rhQual = rhptee.getQualifiers();
  
    LangAS ResultAddrSpace = LangAS::Default;
    LangAS LAddrSpace = lhQual.getAddressSpace();
    LangAS RAddrSpace = rhQual.getAddressSpace();
  
    // OpenCL v1.1 s6.5 - Conversion between pointers to distinct address
    // spaces is disallowed.
    if (lhQual.isAddressSpaceSupersetOf(rhQual))
      ResultAddrSpace = LAddrSpace;
    else if (rhQual.isAddressSpaceSupersetOf(lhQual))
      ResultAddrSpace = RAddrSpace;
    else {
      S.Diag(Loc, diag::err_typecheck_op_on_nonoverlapping_address_space_pointers)
          << LHSTy << RHSTy << 2 << LHS.get()->getSourceRange()
          << RHS.get()->getSourceRange();
      return QualType();
    }
  
    unsigned MergedCVRQual = lhQual.getCVRQualifiers() | rhQual.getCVRQualifiers();
    auto LHSCastKind = CK_BitCast, RHSCastKind = CK_BitCast;
    lhQual.removeCVRQualifiers();
    rhQual.removeCVRQualifiers();
  
    if (lhQual.getPointerAuth() != rhQual.getPointerAuth()) {
      S.Diag(Loc, diag::err_typecheck_cond_incompatible_ptrauth)
        << LHSTy << RHSTy
        << LHS.get()->getSourceRange()
        << RHS.get()->getSourceRange();
      return QualType();
    }
  
    // OpenCL v2.0 specification doesn't extend compatibility of type qualifiers
    // (C99 6.7.3) for address spaces. We assume that the check should behave in
    // the same manner as it's defined for CVR qualifiers, so for OpenCL two
    // qual types are compatible iff
    //  * corresponded types are compatible
    //  * CVR qualifiers are equal
    //  * address spaces are equal
    // Thus for conditional operator we merge CVR and address space unqualified
    // pointees and if there is a composite type we return a pointer to it with
    // merged qualifiers.
    LHSCastKind =
        LAddrSpace == ResultAddrSpace ? CK_BitCast : CK_AddressSpaceConversion;
    RHSCastKind =
        RAddrSpace == ResultAddrSpace ? CK_BitCast : CK_AddressSpaceConversion;
    lhQual.removeAddressSpace();
    rhQual.removeAddressSpace();
  
    lhptee = S.Context.getQualifiedType(lhptee.getUnqualifiedType(), lhQual);
    rhptee = S.Context.getQualifiedType(rhptee.getUnqualifiedType(), rhQual);
  
    QualType CompositeTy = S.Context.mergeTypes(lhptee, rhptee);
  
    if (CompositeTy.isNull()) {
      // In this situation, we assume void* type. No especially good
      // reason, but this is what gcc does, and we do have to pick
      // to get a consistent AST.
      QualType incompatTy;
      incompatTy = S.Context.getPointerType(
          S.Context.getAddrSpaceQualType(S.Context.VoidTy, ResultAddrSpace));
      LHS = S.ImpCastExprToType(LHS.get(), incompatTy, LHSCastKind);
      RHS = S.ImpCastExprToType(RHS.get(), incompatTy, RHSCastKind);
  
      // FIXME: For OpenCL the warning emission and cast to void* leaves a room
      // for casts between types with incompatible address space qualifiers.
      // For the following code the compiler produces casts between global and
      // local address spaces of the corresponded innermost pointees:
      // local int *global *a;
      // global int *global *b;
      // a = (0 ? a : b); // see C99 6.5.16.1.p1.
      S.Diag(Loc, diag::ext_typecheck_cond_incompatible_pointers)
          << LHSTy << RHSTy << LHS.get()->getSourceRange()
          << RHS.get()->getSourceRange();
  
      return incompatTy;
    }
  
    // The pointer types are compatible.
    // In case of OpenCL ResultTy should have the address space qualifier
    // which is a superset of address spaces of both the 2nd and the 3rd
    // operands of the conditional operator.
    QualType ResultTy = [&, ResultAddrSpace]() {
      if (S.getLangOpts().OpenCL) {
        Qualifiers CompositeQuals = CompositeTy.getQualifiers();
        CompositeQuals.setAddressSpace(ResultAddrSpace);
        return S.Context
            .getQualifiedType(CompositeTy.getUnqualifiedType(), CompositeQuals)
            .withCVRQualifiers(MergedCVRQual);
      }
      return CompositeTy.withCVRQualifiers(MergedCVRQual);
    }();
    if (IsBlockPointer)
      ResultTy = S.Context.getBlockPointerType(ResultTy);
    else
      ResultTy = S.Context.getPointerType(ResultTy);
  
    LHS = S.ImpCastExprToType(LHS.get(), ResultTy, LHSCastKind);
    RHS = S.ImpCastExprToType(RHS.get(), ResultTy, RHSCastKind);
    return ResultTy;
  }
  
  /// Return the resulting type when the operands are both block pointers.
  static QualType checkConditionalBlockPointerCompatibility(Sema &S,
                                                            ExprResult &LHS,
                                                            ExprResult &RHS,
                                                            SourceLocation Loc) {
    QualType LHSTy = LHS.get()->getType();
    QualType RHSTy = RHS.get()->getType();
  
    if (!LHSTy->isBlockPointerType() || !RHSTy->isBlockPointerType()) {
      if (LHSTy->isVoidPointerType() || RHSTy->isVoidPointerType()) {
        QualType destType = S.Context.getPointerType(S.Context.VoidTy);
        LHS = S.ImpCastExprToType(LHS.get(), destType, CK_BitCast);
        RHS = S.ImpCastExprToType(RHS.get(), destType, CK_BitCast);
        return destType;
      }
      S.Diag(Loc, diag::err_typecheck_cond_incompatible_operands)
        << LHSTy << RHSTy << LHS.get()->getSourceRange()
        << RHS.get()->getSourceRange();
      return QualType();
    }
  
    // We have 2 block pointer types.
    return checkConditionalPointerCompatibility(S, LHS, RHS, Loc);
  }
  
  /// Return the resulting type when the operands are both pointers.
  static QualType
  checkConditionalObjectPointersCompatibility(Sema &S, ExprResult &LHS,
                                              ExprResult &RHS,
                                              SourceLocation Loc) {
    // get the pointer types
    QualType LHSTy = LHS.get()->getType();
    QualType RHSTy = RHS.get()->getType();
  
    // get the "pointed to" types
    QualType lhptee = LHSTy->castAs<PointerType>()->getPointeeType();
    QualType rhptee = RHSTy->castAs<PointerType>()->getPointeeType();
  
    // ignore qualifiers on void (C99 6.5.15p3, clause 6)
    if (lhptee->isVoidType() && rhptee->isIncompleteOrObjectType()) {
      // Figure out necessary qualifiers (C99 6.5.15p6)
      QualType destPointee
        = S.Context.getQualifiedType(lhptee, rhptee.getQualifiers());
      QualType destType = S.Context.getPointerType(destPointee);
      // Add qualifiers if necessary.
      LHS = S.ImpCastExprToType(LHS.get(), destType, CK_NoOp);
      // Promote to void*.
      RHS = S.ImpCastExprToType(RHS.get(), destType, CK_BitCast);
      return destType;
    }
    if (rhptee->isVoidType() && lhptee->isIncompleteOrObjectType()) {
      QualType destPointee
        = S.Context.getQualifiedType(rhptee, lhptee.getQualifiers());
      QualType destType = S.Context.getPointerType(destPointee);
      // Add qualifiers if necessary.
      RHS = S.ImpCastExprToType(RHS.get(), destType, CK_NoOp);
      // Promote to void*.
      LHS = S.ImpCastExprToType(LHS.get(), destType, CK_BitCast);
      return destType;
    }
  
    return checkConditionalPointerCompatibility(S, LHS, RHS, Loc);
  }
  
  /// Return false if the first expression is not an integer and the second
  /// expression is not a pointer, true otherwise.
  static bool checkPointerIntegerMismatch(Sema &S, ExprResult &Int,
                                          Expr* PointerExpr, SourceLocation Loc,
                                          bool IsIntFirstExpr) {
    if (!PointerExpr->getType()->isPointerType() ||
        !Int.get()->getType()->isIntegerType())
      return false;
  
    Expr *Expr1 = IsIntFirstExpr ? Int.get() : PointerExpr;
    Expr *Expr2 = IsIntFirstExpr ? PointerExpr : Int.get();
  
    S.Diag(Loc, diag::ext_typecheck_cond_pointer_integer_mismatch)
      << Expr1->getType() << Expr2->getType()
      << Expr1->getSourceRange() << Expr2->getSourceRange();
    Int = S.ImpCastExprToType(Int.get(), PointerExpr->getType(),
                              CK_IntegralToPointer);
    return true;
  }
  
  /// Simple conversion between integer and floating point types.
  ///
  /// Used when handling the OpenCL conditional operator where the
  /// condition is a vector while the other operands are scalar.
  ///
  /// OpenCL v1.1 s6.3.i and s6.11.6 together require that the scalar
  /// types are either integer or floating type. Between the two
  /// operands, the type with the higher rank is defined as the "result
  /// type". The other operand needs to be promoted to the same type. No
  /// other type promotion is allowed. We cannot use
  /// UsualArithmeticConversions() for this purpose, since it always
  /// promotes promotable types.
  static QualType OpenCLArithmeticConversions(Sema &S, ExprResult &LHS,
                                              ExprResult &RHS,
                                              SourceLocation QuestionLoc) {
    LHS = S.DefaultFunctionArrayLvalueConversion(LHS.get());
    if (LHS.isInvalid())
      return QualType();
    RHS = S.DefaultFunctionArrayLvalueConversion(RHS.get());
    if (RHS.isInvalid())
      return QualType();
  
    // For conversion purposes, we ignore any qualifiers.
    // For example, "const float" and "float" are equivalent.
    QualType LHSType =
      S.Context.getCanonicalType(LHS.get()->getType()).getUnqualifiedType();
    QualType RHSType =
      S.Context.getCanonicalType(RHS.get()->getType()).getUnqualifiedType();
  
    if (!LHSType->isIntegerType() && !LHSType->isRealFloatingType()) {
      S.Diag(QuestionLoc, diag::err_typecheck_cond_expect_int_float)
        << LHSType << LHS.get()->getSourceRange();
      return QualType();
    }
  
    if (!RHSType->isIntegerType() && !RHSType->isRealFloatingType()) {
      S.Diag(QuestionLoc, diag::err_typecheck_cond_expect_int_float)
        << RHSType << RHS.get()->getSourceRange();
      return QualType();
    }
  
    // If both types are identical, no conversion is needed.
    if (LHSType == RHSType)
      return LHSType;
  
    // Now handle "real" floating types (i.e. float, double, long double).
    if (LHSType->isRealFloatingType() || RHSType->isRealFloatingType())
      return handleFloatConversion(S, LHS, RHS, LHSType, RHSType,
                                   /*IsCompAssign = */ false);
  
    // Finally, we have two differing integer types.
    return handleIntegerConversion<doIntegralCast, doIntegralCast>
    (S, LHS, RHS, LHSType, RHSType, /*IsCompAssign = */ false);
  }
  
  /// Convert scalar operands to a vector that matches the
  ///        condition in length.
  ///
  /// Used when handling the OpenCL conditional operator where the
  /// condition is a vector while the other operands are scalar.
  ///
  /// We first compute the "result type" for the scalar operands
  /// according to OpenCL v1.1 s6.3.i. Both operands are then converted
  /// into a vector of that type where the length matches the condition
  /// vector type. s6.11.6 requires that the element types of the result
  /// and the condition must have the same number of bits.
  static QualType
  OpenCLConvertScalarsToVectors(Sema &S, ExprResult &LHS, ExprResult &RHS,
                                QualType CondTy, SourceLocation QuestionLoc) {
    QualType ResTy = OpenCLArithmeticConversions(S, LHS, RHS, QuestionLoc);
    if (ResTy.isNull()) return QualType();
  
    const VectorType *CV = CondTy->getAs<VectorType>();
    assert(CV);
  
    // Determine the vector result type
    unsigned NumElements = CV->getNumElements();
    QualType VectorTy = S.Context.getExtVectorType(ResTy, NumElements);
  
    // Ensure that all types have the same number of bits
    if (S.Context.getTypeSize(CV->getElementType())
        != S.Context.getTypeSize(ResTy)) {
      // Since VectorTy is created internally, it does not pretty print
      // with an OpenCL name. Instead, we just print a description.
      std::string EleTyName = ResTy.getUnqualifiedType().getAsString();
      SmallString<64> Str;
      llvm::raw_svector_ostream OS(Str);
      OS << "(vector of " << NumElements << " '" << EleTyName << "' values)";
      S.Diag(QuestionLoc, diag::err_conditional_vector_element_size)
        << CondTy << OS.str();
      return QualType();
    }
  
    // Convert operands to the vector result type
    LHS = S.ImpCastExprToType(LHS.get(), VectorTy, CK_VectorSplat);
    RHS = S.ImpCastExprToType(RHS.get(), VectorTy, CK_VectorSplat);
  
    return VectorTy;
  }
  
  /// Return false if this is a valid OpenCL condition vector
  static bool checkOpenCLConditionVector(Sema &S, Expr *Cond,
                                         SourceLocation QuestionLoc) {
    // OpenCL v1.1 s6.11.6 says the elements of the vector must be of
    // integral type.
    const VectorType *CondTy = Cond->getType()->getAs<VectorType>();
    assert(CondTy);
    QualType EleTy = CondTy->getElementType();
    if (EleTy->isIntegerType()) return false;
  
    S.Diag(QuestionLoc, diag::err_typecheck_cond_expect_nonfloat)
      << Cond->getType() << Cond->getSourceRange();
    return true;
  }
  
  /// Return false if the vector condition type and the vector
  ///        result type are compatible.
  ///
  /// OpenCL v1.1 s6.11.6 requires that both vector types have the same
  /// number of elements, and their element types have the same number
  /// of bits.
  static bool checkVectorResult(Sema &S, QualType CondTy, QualType VecResTy,
                                SourceLocation QuestionLoc) {
    const VectorType *CV = CondTy->getAs<VectorType>();
    const VectorType *RV = VecResTy->getAs<VectorType>();
    assert(CV && RV);
  
    if (CV->getNumElements() != RV->getNumElements()) {
      S.Diag(QuestionLoc, diag::err_conditional_vector_size)
        << CondTy << VecResTy;
      return true;
    }
  
    QualType CVE = CV->getElementType();
    QualType RVE = RV->getElementType();
  
    if (S.Context.getTypeSize(CVE) != S.Context.getTypeSize(RVE)) {
      S.Diag(QuestionLoc, diag::err_conditional_vector_element_size)
        << CondTy << VecResTy;
      return true;
    }
  
    return false;
  }
  
  /// Return the resulting type for the conditional operator in
  ///        OpenCL (aka "ternary selection operator", OpenCL v1.1
  ///        s6.3.i) when the condition is a vector type.
  static QualType
  OpenCLCheckVectorConditional(Sema &S, ExprResult &Cond,
                               ExprResult &LHS, ExprResult &RHS,
                               SourceLocation QuestionLoc) {
    Cond = S.DefaultFunctionArrayLvalueConversion(Cond.get());
    if (Cond.isInvalid())
      return QualType();
    QualType CondTy = Cond.get()->getType();
  
    if (checkOpenCLConditionVector(S, Cond.get(), QuestionLoc))
      return QualType();
  
    // If either operand is a vector then find the vector type of the
    // result as specified in OpenCL v1.1 s6.3.i.
    if (LHS.get()->getType()->isVectorType() ||
        RHS.get()->getType()->isVectorType()) {
      QualType VecResTy = S.CheckVectorOperands(LHS, RHS, QuestionLoc,
                                                /*isCompAssign*/false,
                                                /*AllowBothBool*/true,
                                                /*AllowBoolConversions*/false);
      if (VecResTy.isNull()) return QualType();
      // The result type must match the condition type as specified in
      // OpenCL v1.1 s6.11.6.
      if (checkVectorResult(S, CondTy, VecResTy, QuestionLoc))
        return QualType();
      return VecResTy;
    }
  
    // Both operands are scalar.
    return OpenCLConvertScalarsToVectors(S, LHS, RHS, CondTy, QuestionLoc);
  }
  
  /// Return true if the Expr is block type
  static bool checkBlockType(Sema &S, const Expr *E) {
    if (const CallExpr *CE = dyn_cast<CallExpr>(E)) {
      QualType Ty = CE->getCallee()->getType();
      if (Ty->isBlockPointerType()) {
        S.Diag(E->getExprLoc(), diag::err_opencl_ternary_with_block);
        return true;
      }
    }
    return false;
  }
  
  /// Note that LHS is not null here, even if this is the gnu "x ?: y" extension.
  /// In that case, LHS = cond.
  /// C99 6.5.15
  QualType Sema::CheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
                                          ExprResult &RHS, ExprValueKind &VK,
                                          ExprObjectKind &OK,
                                          SourceLocation QuestionLoc) {
  
    ExprResult LHSResult = CheckPlaceholderExpr(LHS.get());
    if (!LHSResult.isUsable()) return QualType();
    LHS = LHSResult;
  
    ExprResult RHSResult = CheckPlaceholderExpr(RHS.get());
    if (!RHSResult.isUsable()) return QualType();
    RHS = RHSResult;
  
    // C++ is sufficiently different to merit its own checker.
    if (getLangOpts().CPlusPlus)
      return CXXCheckConditionalOperands(Cond, LHS, RHS, VK, OK, QuestionLoc);
  
    VK = VK_PRValue;
    OK = OK_Ordinary;
  
    if (Context.isDependenceAllowed() &&
        (Cond.get()->isTypeDependent() || LHS.get()->isTypeDependent() ||
         RHS.get()->isTypeDependent())) {
      assert(!getLangOpts().CPlusPlus);
      assert((Cond.get()->containsErrors() || LHS.get()->containsErrors() ||
              RHS.get()->containsErrors()) &&
             "should only occur in error-recovery path.");
      return Context.DependentTy;
    }
  
    // The OpenCL operator with a vector condition is sufficiently
    // different to merit its own checker.
    if ((getLangOpts().OpenCL && Cond.get()->getType()->isVectorType()) ||
        Cond.get()->getType()->isExtVectorType())
      return OpenCLCheckVectorConditional(*this, Cond, LHS, RHS, QuestionLoc);
  
    // First, check the condition.
    Cond = UsualUnaryConversions(Cond.get());
    if (Cond.isInvalid())
      return QualType();
    if (checkCondition(*this, Cond.get(), QuestionLoc))
      return QualType();
  
    // Now check the two expressions.
    if (LHS.get()->getType()->isVectorType() ||
        RHS.get()->getType()->isVectorType())
      return CheckVectorOperands(LHS, RHS, QuestionLoc, /*isCompAssign*/false,
                                 /*AllowBothBool*/true,
                                 /*AllowBoolConversions*/false);
  
    QualType ResTy =
        UsualArithmeticConversions(LHS, RHS, QuestionLoc, ACK_Conditional);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
  
    QualType LHSTy = LHS.get()->getType();
    QualType RHSTy = RHS.get()->getType();
  
    // Diagnose attempts to convert between __ibm128, __float128 and long double
    // where such conversions currently can't be handled.
    if (unsupportedTypeConversion(*this, LHSTy, RHSTy)) {
      Diag(QuestionLoc,
           diag::err_typecheck_cond_incompatible_operands) << LHSTy << RHSTy
        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
      return QualType();
    }
  
    // OpenCL v2.0 s6.12.5 - Blocks cannot be used as expressions of the ternary
    // selection operator (?:).
    if (getLangOpts().OpenCL &&
        ((int)checkBlockType(*this, LHS.get()) | (int)checkBlockType(*this, RHS.get()))) {
      return QualType();
    }
  
    // If both operands have arithmetic type, do the usual arithmetic conversions
    // to find a common type: C99 6.5.15p3,5.
    if (LHSTy->isArithmeticType() && RHSTy->isArithmeticType()) {
      // Disallow invalid arithmetic conversions, such as those between bit-
      // precise integers types of different sizes, or between a bit-precise
      // integer and another type.
      if (ResTy.isNull() && (LHSTy->isBitIntType() || RHSTy->isBitIntType())) {
        Diag(QuestionLoc, diag::err_typecheck_cond_incompatible_operands)
            << LHSTy << RHSTy << LHS.get()->getSourceRange()
            << RHS.get()->getSourceRange();
        return QualType();
      }
  
      LHS = ImpCastExprToType(LHS.get(), ResTy, PrepareScalarCast(LHS, ResTy));
      RHS = ImpCastExprToType(RHS.get(), ResTy, PrepareScalarCast(RHS, ResTy));
  
      return ResTy;
    }
  
    // And if they're both bfloat (which isn't arithmetic), that's fine too.
    if (LHSTy->isBFloat16Type() && RHSTy->isBFloat16Type()) {
      return LHSTy;
    }
  
    // If both operands are the same structure or union type, the result is that
    // type.
    if (const RecordType *LHSRT = LHSTy->getAs<RecordType>()) {    // C99 6.5.15p3
      if (const RecordType *RHSRT = RHSTy->getAs<RecordType>())
        if (LHSRT->getDecl() == RHSRT->getDecl())
          // "If both the operands have structure or union type, the result has
          // that type."  This implies that CV qualifiers are dropped.
          return LHSTy.getUnqualifiedType();
      // FIXME: Type of conditional expression must be complete in C mode.
    }
  
    // C99 6.5.15p5: "If both operands have void type, the result has void type."
    // The following || allows only one side to be void (a GCC-ism).
    if (LHSTy->isVoidType() || RHSTy->isVoidType()) {
      return checkConditionalVoidType(*this, LHS, RHS);
    }
  
    // C99 6.5.15p6 - "if one operand is a null pointer constant, the result has
    // the type of the other operand."
    if (!checkConditionalNullPointer(*this, RHS, LHSTy)) return LHSTy;
    if (!checkConditionalNullPointer(*this, LHS, RHSTy)) return RHSTy;
  
    // All objective-c pointer type analysis is done here.
    QualType compositeType = FindCompositeObjCPointerType(LHS, RHS,
                                                          QuestionLoc);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
    if (!compositeType.isNull())
      return compositeType;
  
  
    // Handle block pointer types.
    if (LHSTy->isBlockPointerType() || RHSTy->isBlockPointerType())
      return checkConditionalBlockPointerCompatibility(*this, LHS, RHS,
                                                       QuestionLoc);
  
    // Check constraints for C object pointers types (C99 6.5.15p3,6).
    if (LHSTy->isPointerType() && RHSTy->isPointerType())
      return checkConditionalObjectPointersCompatibility(*this, LHS, RHS,
                                                         QuestionLoc);
  
    // GCC compatibility: soften pointer/integer mismatch.  Note that
    // null pointers have been filtered out by this point.
    if (checkPointerIntegerMismatch(*this, LHS, RHS.get(), QuestionLoc,
        /*IsIntFirstExpr=*/true))
      return RHSTy;
    if (checkPointerIntegerMismatch(*this, RHS, LHS.get(), QuestionLoc,
        /*IsIntFirstExpr=*/false))
      return LHSTy;
  
    // Allow ?: operations in which both operands have the same
    // built-in sizeless type.
    if (LHSTy->isSizelessBuiltinType() && Context.hasSameType(LHSTy, RHSTy))
      return LHSTy;
  
    // Emit a better diagnostic if one of the expressions is a null pointer
    // constant and the other is not a pointer type. In this case, the user most
    // likely forgot to take the address of the other expression.
    if (DiagnoseConditionalForNull(LHS.get(), RHS.get(), QuestionLoc))
      return QualType();
  
    // Otherwise, the operands are not compatible.
    Diag(QuestionLoc, diag::err_typecheck_cond_incompatible_operands)
      << LHSTy << RHSTy << LHS.get()->getSourceRange()
      << RHS.get()->getSourceRange();
    return QualType();
  }
  
  /// FindCompositeObjCPointerType - Helper method to find composite type of
  /// two objective-c pointer types of the two input expressions.
  QualType Sema::FindCompositeObjCPointerType(ExprResult &LHS, ExprResult &RHS,
                                              SourceLocation QuestionLoc) {
    QualType LHSTy = LHS.get()->getType();
    QualType RHSTy = RHS.get()->getType();
  
    // Handle things like Class and struct objc_class*.  Here we case the result
    // to the pseudo-builtin, because that will be implicitly cast back to the
    // redefinition type if an attempt is made to access its fields.
    if (LHSTy->isObjCClassType() &&
        (Context.hasSameType(RHSTy, Context.getObjCClassRedefinitionType()))) {
      RHS = ImpCastExprToType(RHS.get(), LHSTy, CK_CPointerToObjCPointerCast);
      return LHSTy;
    }
    if (RHSTy->isObjCClassType() &&
        (Context.hasSameType(LHSTy, Context.getObjCClassRedefinitionType()))) {
      LHS = ImpCastExprToType(LHS.get(), RHSTy, CK_CPointerToObjCPointerCast);
      return RHSTy;
    }
    // And the same for struct objc_object* / id
    if (LHSTy->isObjCIdType() &&
        (Context.hasSameType(RHSTy, Context.getObjCIdRedefinitionType()))) {
      RHS = ImpCastExprToType(RHS.get(), LHSTy, CK_CPointerToObjCPointerCast);
      return LHSTy;
    }
    if (RHSTy->isObjCIdType() &&
        (Context.hasSameType(LHSTy, Context.getObjCIdRedefinitionType()))) {
      LHS = ImpCastExprToType(LHS.get(), RHSTy, CK_CPointerToObjCPointerCast);
      return RHSTy;
    }
    // And the same for struct objc_selector* / SEL
    if (Context.isObjCSelType(LHSTy) &&
        (Context.hasSameType(RHSTy, Context.getObjCSelRedefinitionType()))) {
      RHS = ImpCastExprToType(RHS.get(), LHSTy, CK_BitCast);
      return LHSTy;
    }
    if (Context.isObjCSelType(RHSTy) &&
        (Context.hasSameType(LHSTy, Context.getObjCSelRedefinitionType()))) {
      LHS = ImpCastExprToType(LHS.get(), RHSTy, CK_BitCast);
      return RHSTy;
    }
    // Check constraints for Objective-C object pointers types.
    if (LHSTy->isObjCObjectPointerType() && RHSTy->isObjCObjectPointerType()) {
  
      if (Context.getCanonicalType(LHSTy) == Context.getCanonicalType(RHSTy)) {
        // Two identical object pointer types are always compatible.
        return LHSTy;
      }
      const ObjCObjectPointerType *LHSOPT = LHSTy->castAs<ObjCObjectPointerType>();
      const ObjCObjectPointerType *RHSOPT = RHSTy->castAs<ObjCObjectPointerType>();
      QualType compositeType = LHSTy;
  
      // If both operands are interfaces and either operand can be
      // assigned to the other, use that type as the composite
      // type. This allows
      //   xxx ? (A*) a : (B*) b
      // where B is a subclass of A.
      //
      // Additionally, as for assignment, if either type is 'id'
      // allow silent coercion. Finally, if the types are
      // incompatible then make sure to use 'id' as the composite
      // type so the result is acceptable for sending messages to.
  
      // FIXME: Consider unifying with 'areComparableObjCPointerTypes'.
      // It could return the composite type.
      if (!(compositeType =
            Context.areCommonBaseCompatible(LHSOPT, RHSOPT)).isNull()) {
        // Nothing more to do.
      } else if (Context.canAssignObjCInterfaces(LHSOPT, RHSOPT)) {
        compositeType = RHSOPT->isObjCBuiltinType() ? RHSTy : LHSTy;
      } else if (Context.canAssignObjCInterfaces(RHSOPT, LHSOPT)) {
        compositeType = LHSOPT->isObjCBuiltinType() ? LHSTy : RHSTy;
      } else if ((LHSOPT->isObjCQualifiedIdType() ||
                  RHSOPT->isObjCQualifiedIdType()) &&
                 Context.ObjCQualifiedIdTypesAreCompatible(LHSOPT, RHSOPT,
                                                           true)) {
        // Need to handle "id<xx>" explicitly.
        // GCC allows qualified id and any Objective-C type to devolve to
        // id. Currently localizing to here until clear this should be
        // part of ObjCQualifiedIdTypesAreCompatible.
        compositeType = Context.getObjCIdType();
      } else if (LHSTy->isObjCIdType() || RHSTy->isObjCIdType()) {
        compositeType = Context.getObjCIdType();
      } else {
        Diag(QuestionLoc, diag::ext_typecheck_cond_incompatible_operands)
        << LHSTy << RHSTy
        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
        QualType incompatTy = Context.getObjCIdType();
        LHS = ImpCastExprToType(LHS.get(), incompatTy, CK_BitCast);
        RHS = ImpCastExprToType(RHS.get(), incompatTy, CK_BitCast);
        return incompatTy;
      }
      // The object pointer types are compatible.
      LHS = ImpCastExprToType(LHS.get(), compositeType, CK_BitCast);
      RHS = ImpCastExprToType(RHS.get(), compositeType, CK_BitCast);
      return compositeType;
    }
    // Check Objective-C object pointer types and 'void *'
    if (LHSTy->isVoidPointerType() && RHSTy->isObjCObjectPointerType()) {
      if (getLangOpts().ObjCAutoRefCount) {
        // ARC forbids the implicit conversion of object pointers to 'void *',
        // so these types are not compatible.
        Diag(QuestionLoc, diag::err_cond_voidptr_arc) << LHSTy << RHSTy
            << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
        LHS = RHS = true;
        return QualType();
      }
      QualType lhptee = LHSTy->castAs<PointerType>()->getPointeeType();
      QualType rhptee = RHSTy->castAs<ObjCObjectPointerType>()->getPointeeType();
      QualType destPointee
      = Context.getQualifiedType(lhptee, rhptee.getQualifiers());
      QualType destType = Context.getPointerType(destPointee);
      // Add qualifiers if necessary.
      LHS = ImpCastExprToType(LHS.get(), destType, CK_NoOp);
      // Promote to void*.
      RHS = ImpCastExprToType(RHS.get(), destType, CK_BitCast);
      return destType;
    }
    if (LHSTy->isObjCObjectPointerType() && RHSTy->isVoidPointerType()) {
      if (getLangOpts().ObjCAutoRefCount) {
        // ARC forbids the implicit conversion of object pointers to 'void *',
        // so these types are not compatible.
        Diag(QuestionLoc, diag::err_cond_voidptr_arc) << LHSTy << RHSTy
            << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
        LHS = RHS = true;
        return QualType();
      }
      QualType lhptee = LHSTy->castAs<ObjCObjectPointerType>()->getPointeeType();
      QualType rhptee = RHSTy->castAs<PointerType>()->getPointeeType();
      QualType destPointee
      = Context.getQualifiedType(rhptee, lhptee.getQualifiers());
      QualType destType = Context.getPointerType(destPointee);
      // Add qualifiers if necessary.
      RHS = ImpCastExprToType(RHS.get(), destType, CK_NoOp);
      // Promote to void*.
      LHS = ImpCastExprToType(LHS.get(), destType, CK_BitCast);
      return destType;
    }
    return QualType();
  }
  
  /// SuggestParentheses - Emit a note with a fixit hint that wraps
  /// ParenRange in parentheses.
  static void SuggestParentheses(Sema &Self, SourceLocation Loc,
                                 const PartialDiagnostic &Note,
                                 SourceRange ParenRange) {
    SourceLocation EndLoc = Self.getLocForEndOfToken(ParenRange.getEnd());
    if (ParenRange.getBegin().isFileID() && ParenRange.getEnd().isFileID() &&
        EndLoc.isValid()) {
      Self.Diag(Loc, Note)
        << FixItHint::CreateInsertion(ParenRange.getBegin(), "(")
        << FixItHint::CreateInsertion(EndLoc, ")");
    } else {
      // We can't display the parentheses, so just show the bare note.
      Self.Diag(Loc, Note) << ParenRange;
    }
  }
  
  static bool IsArithmeticOp(BinaryOperatorKind Opc) {
    return BinaryOperator::isAdditiveOp(Opc) ||
           BinaryOperator::isMultiplicativeOp(Opc) ||
           BinaryOperator::isShiftOp(Opc) || Opc == BO_And || Opc == BO_Or;
    // This only checks for bitwise-or and bitwise-and, but not bitwise-xor and
    // not any of the logical operators.  Bitwise-xor is commonly used as a
    // logical-xor because there is no logical-xor operator.  The logical
    // operators, including uses of xor, have a high false positive rate for
    // precedence warnings.
  }
  
  /// IsArithmeticBinaryExpr - Returns true if E is an arithmetic binary
  /// expression, either using a built-in or overloaded operator,
  /// and sets *OpCode to the opcode and *RHSExprs to the right-hand side
  /// expression.
  static bool IsArithmeticBinaryExpr(Expr *E, BinaryOperatorKind *Opcode,
                                     Expr **RHSExprs) {
    // Don't strip parenthesis: we should not warn if E is in parenthesis.
    E = E->IgnoreImpCasts();
    E = E->IgnoreConversionOperatorSingleStep();
    E = E->IgnoreImpCasts();
    if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E)) {
      E = MTE->getSubExpr();
      E = E->IgnoreImpCasts();
    }
  
    // Built-in binary operator.
    if (BinaryOperator *OP = dyn_cast<BinaryOperator>(E)) {
      if (IsArithmeticOp(OP->getOpcode())) {
        *Opcode = OP->getOpcode();
        *RHSExprs = OP->getRHS();
        return true;
      }
    }
  
    // Overloaded operator.
    if (CXXOperatorCallExpr *Call = dyn_cast<CXXOperatorCallExpr>(E)) {
      if (Call->getNumArgs() != 2)
        return false;
  
      // Make sure this is really a binary operator that is safe to pass into
      // BinaryOperator::getOverloadedOpcode(), e.g. it's not a subscript op.
      OverloadedOperatorKind OO = Call->getOperator();
      if (OO < OO_Plus || OO > OO_Arrow ||
          OO == OO_PlusPlus || OO == OO_MinusMinus)
        return false;
  
      BinaryOperatorKind OpKind = BinaryOperator::getOverloadedOpcode(OO);
      if (IsArithmeticOp(OpKind)) {
        *Opcode = OpKind;
        *RHSExprs = Call->getArg(1);
        return true;
      }
    }
  
    return false;
  }
  
  /// ExprLooksBoolean - Returns true if E looks boolean, i.e. it has boolean type
  /// or is a logical expression such as (x==y) which has int type, but is
  /// commonly interpreted as boolean.
  static bool ExprLooksBoolean(Expr *E) {
    E = E->IgnoreParenImpCasts();
  
    if (E->getType()->isBooleanType())
      return true;
    if (BinaryOperator *OP = dyn_cast<BinaryOperator>(E))
      return OP->isComparisonOp() || OP->isLogicalOp();
    if (UnaryOperator *OP = dyn_cast<UnaryOperator>(E))
      return OP->getOpcode() == UO_LNot;
    if (E->getType()->isPointerType())
      return true;
    // FIXME: What about overloaded operator calls returning "unspecified boolean
    // type"s (commonly pointer-to-members)?
  
    return false;
  }
  
  /// DiagnoseConditionalPrecedence - Emit a warning when a conditional operator
  /// and binary operator are mixed in a way that suggests the programmer assumed
  /// the conditional operator has higher precedence, for example:
  /// "int x = a + someBinaryCondition ? 1 : 2".
  static void DiagnoseConditionalPrecedence(Sema &Self,
                                            SourceLocation OpLoc,
                                            Expr *Condition,
                                            Expr *LHSExpr,
                                            Expr *RHSExpr) {
    BinaryOperatorKind CondOpcode;
    Expr *CondRHS;
  
    if (!IsArithmeticBinaryExpr(Condition, &CondOpcode, &CondRHS))
      return;
    if (!ExprLooksBoolean(CondRHS))
      return;
  
    // The condition is an arithmetic binary expression, with a right-
    // hand side that looks boolean, so warn.
  
    unsigned DiagID = BinaryOperator::isBitwiseOp(CondOpcode)
                          ? diag::warn_precedence_bitwise_conditional
                          : diag::warn_precedence_conditional;
  
    Self.Diag(OpLoc, DiagID)
        << Condition->getSourceRange()
        << BinaryOperator::getOpcodeStr(CondOpcode);
  
    SuggestParentheses(
        Self, OpLoc,
        Self.PDiag(diag::note_precedence_silence)
            << BinaryOperator::getOpcodeStr(CondOpcode),
        SourceRange(Condition->getBeginLoc(), Condition->getEndLoc()));
  
    SuggestParentheses(Self, OpLoc,
                       Self.PDiag(diag::note_precedence_conditional_first),
                       SourceRange(CondRHS->getBeginLoc(), RHSExpr->getEndLoc()));
  }
  
  /// Compute the nullability of a conditional expression.
  static QualType computeConditionalNullability(QualType ResTy, bool IsBin,
                                                QualType LHSTy, QualType RHSTy,
                                                ASTContext &Ctx) {
    if (!ResTy->isAnyPointerType())
      return ResTy;
  
    auto GetNullability = [&Ctx](QualType Ty) {
      Optional<NullabilityKind> Kind = Ty->getNullability(Ctx);
      if (Kind) {
        // For our purposes, treat _Nullable_result as _Nullable.
        if (*Kind == NullabilityKind::NullableResult)
          return NullabilityKind::Nullable;
        return *Kind;
      }
      return NullabilityKind::Unspecified;
    };
  
    auto LHSKind = GetNullability(LHSTy), RHSKind = GetNullability(RHSTy);
    NullabilityKind MergedKind;
  
    // Compute nullability of a binary conditional expression.
    if (IsBin) {
      if (LHSKind == NullabilityKind::NonNull)
        MergedKind = NullabilityKind::NonNull;
      else
        MergedKind = RHSKind;
    // Compute nullability of a normal conditional expression.
    } else {
      if (LHSKind == NullabilityKind::Nullable ||
          RHSKind == NullabilityKind::Nullable)
        MergedKind = NullabilityKind::Nullable;
      else if (LHSKind == NullabilityKind::NonNull)
        MergedKind = RHSKind;
      else if (RHSKind == NullabilityKind::NonNull)
        MergedKind = LHSKind;
      else
        MergedKind = NullabilityKind::Unspecified;
    }
  
    // Return if ResTy already has the correct nullability.
    if (GetNullability(ResTy) == MergedKind)
      return ResTy;
  
    // Strip all nullability from ResTy.
    while (ResTy->getNullability(Ctx))
      ResTy = ResTy.getSingleStepDesugaredType(Ctx);
  
    // Create a new AttributedType with the new nullability kind.
    auto NewAttr = AttributedType::getNullabilityAttrKind(MergedKind);
    return Ctx.getAttributedType(NewAttr, ResTy, ResTy);
  }
  
  /// ActOnConditionalOp - Parse a ?: operation.  Note that 'LHS' may be null
  /// in the case of a the GNU conditional expr extension.
  ExprResult Sema::ActOnConditionalOp(SourceLocation QuestionLoc,
                                      SourceLocation ColonLoc,
                                      Expr *CondExpr, Expr *LHSExpr,
                                      Expr *RHSExpr) {
    if (!Context.isDependenceAllowed()) {
      // C cannot handle TypoExpr nodes in the condition because it
      // doesn't handle dependent types properly, so make sure any TypoExprs have
      // been dealt with before checking the operands.
      ExprResult CondResult = CorrectDelayedTyposInExpr(CondExpr);
      ExprResult LHSResult = CorrectDelayedTyposInExpr(LHSExpr);
      ExprResult RHSResult = CorrectDelayedTyposInExpr(RHSExpr);
  
      if (!CondResult.isUsable())
        return ExprError();
  
      if (LHSExpr) {
        if (!LHSResult.isUsable())
          return ExprError();
      }
  
      if (!RHSResult.isUsable())
        return ExprError();
  
      CondExpr = CondResult.get();
      LHSExpr = LHSResult.get();
      RHSExpr = RHSResult.get();
    }
  
    // If this is the gnu "x ?: y" extension, analyze the types as though the LHS
    // was the condition.
    OpaqueValueExpr *opaqueValue = nullptr;
    Expr *commonExpr = nullptr;
    if (!LHSExpr) {
      commonExpr = CondExpr;
      // Lower out placeholder types first.  This is important so that we don't
      // try to capture a placeholder. This happens in few cases in C++; such
      // as Objective-C++'s dictionary subscripting syntax.
      if (commonExpr->hasPlaceholderType()) {
        ExprResult result = CheckPlaceholderExpr(commonExpr);
        if (!result.isUsable()) return ExprError();
        commonExpr = result.get();
      }
      // We usually want to apply unary conversions *before* saving, except
      // in the special case of a C++ l-value conditional.
      if (!(getLangOpts().CPlusPlus
            && !commonExpr->isTypeDependent()
            && commonExpr->getValueKind() == RHSExpr->getValueKind()
            && commonExpr->isGLValue()
            && commonExpr->isOrdinaryOrBitFieldObject()
            && RHSExpr->isOrdinaryOrBitFieldObject()
            && Context.hasSameType(commonExpr->getType(), RHSExpr->getType()))) {
        ExprResult commonRes = UsualUnaryConversions(commonExpr);
        if (commonRes.isInvalid())
          return ExprError();
        commonExpr = commonRes.get();
      }
  
      // If the common expression is a class or array prvalue, materialize it
      // so that we can safely refer to it multiple times.
      if (commonExpr->isPRValue() && (commonExpr->getType()->isRecordType() ||
                                      commonExpr->getType()->isArrayType())) {
        ExprResult MatExpr = TemporaryMaterializationConversion(commonExpr);
        if (MatExpr.isInvalid())
          return ExprError();
        commonExpr = MatExpr.get();
      }
  
      opaqueValue = new (Context) OpaqueValueExpr(commonExpr->getExprLoc(),
                                                  commonExpr->getType(),
                                                  commonExpr->getValueKind(),
                                                  commonExpr->getObjectKind(),
                                                  commonExpr);
      LHSExpr = CondExpr = opaqueValue;
    }
  
    QualType LHSTy = LHSExpr->getType(), RHSTy = RHSExpr->getType();
    ExprValueKind VK = VK_PRValue;
    ExprObjectKind OK = OK_Ordinary;
    ExprResult Cond = CondExpr, LHS = LHSExpr, RHS = RHSExpr;
    QualType result = CheckConditionalOperands(Cond, LHS, RHS,
                                               VK, OK, QuestionLoc);
    if (result.isNull() || Cond.isInvalid() || LHS.isInvalid() ||
        RHS.isInvalid())
      return ExprError();
  
    DiagnoseConditionalPrecedence(*this, QuestionLoc, Cond.get(), LHS.get(),
                                  RHS.get());
  
    CheckBoolLikeConversion(Cond.get(), QuestionLoc);
  
    result = computeConditionalNullability(result, commonExpr, LHSTy, RHSTy,
                                           Context);
  
    if (!commonExpr)
      return new (Context)
          ConditionalOperator(Cond.get(), QuestionLoc, LHS.get(), ColonLoc,
                              RHS.get(), result, VK, OK);
  
    return new (Context) BinaryConditionalOperator(
        commonExpr, opaqueValue, Cond.get(), LHS.get(), RHS.get(), QuestionLoc,
        ColonLoc, result, VK, OK);
  }
  
  // Check if we have a conversion between incompatible cmse function pointer
  // types, that is, a conversion between a function pointer with the
  // cmse_nonsecure_call attribute and one without.
  static bool IsInvalidCmseNSCallConversion(Sema &S, QualType FromType,
                                            QualType ToType) {
    if (const auto *ToFn =
            dyn_cast<FunctionType>(S.Context.getCanonicalType(ToType))) {
      if (const auto *FromFn =
              dyn_cast<FunctionType>(S.Context.getCanonicalType(FromType))) {
        FunctionType::ExtInfo ToEInfo = ToFn->getExtInfo();
        FunctionType::ExtInfo FromEInfo = FromFn->getExtInfo();
  
        return ToEInfo.getCmseNSCall() != FromEInfo.getCmseNSCall();
      }
    }
    return false;
  }
  
  // checkPointerTypesForAssignment - This is a very tricky routine (despite
  // being closely modeled after the C99 spec:-). The odd characteristic of this
  // routine is it effectively iqnores the qualifiers on the top level pointee.
  // This circumvents the usual type rules specified in 6.2.7p1 & 6.7.5.[1-3].
  // FIXME: add a couple examples in this comment.
  static Sema::AssignConvertType
  checkPointerTypesForAssignment(Sema &S, QualType LHSType, QualType RHSType) {
    assert(LHSType.isCanonical() && "LHS not canonicalized!");
    assert(RHSType.isCanonical() && "RHS not canonicalized!");
  
    // get the "pointed to" type (ignoring qualifiers at the top level)
    const Type *lhptee, *rhptee;
    Qualifiers lhq, rhq;
    std::tie(lhptee, lhq) =
        cast<PointerType>(LHSType)->getPointeeType().split().asPair();
    std::tie(rhptee, rhq) =
        cast<PointerType>(RHSType)->getPointeeType().split().asPair();
  
    Sema::AssignConvertType ConvTy = Sema::Compatible;
  
    // C99 6.5.16.1p1: This following citation is common to constraints
    // 3 & 4 (below). ...and the type *pointed to* by the left has all the
    // qualifiers of the type *pointed to* by the right;
  
    // As a special case, 'non-__weak A *' -> 'non-__weak const *' is okay.
    if (lhq.getObjCLifetime() != rhq.getObjCLifetime() &&
        lhq.compatiblyIncludesObjCLifetime(rhq)) {
      // Ignore lifetime for further calculation.
      lhq.removeObjCLifetime();
      rhq.removeObjCLifetime();
    }
  
    if (!lhq.compatiblyIncludes(rhq)) {
      // Treat address-space mismatches as fatal.
      if (!lhq.isAddressSpaceSupersetOf(rhq))
        return Sema::IncompatiblePointerDiscardsQualifiers;
  
      // It's okay to add or remove GC or lifetime qualifiers when converting to
      // and from void*.
      else if (lhq.withoutObjCGCAttr().withoutObjCLifetime()
                          .compatiblyIncludes(
                                  rhq.withoutObjCGCAttr().withoutObjCLifetime())
               && (lhptee->isVoidType() || rhptee->isVoidType()))
        ; // keep old
  
      // Treat lifetime mismatches as fatal.
      else if (lhq.getObjCLifetime() != rhq.getObjCLifetime())
        ConvTy = Sema::IncompatiblePointerDiscardsQualifiers;
  
      // Treat pointer-auth mismatches as fatal.
      else if (lhq.getPointerAuth() != rhq.getPointerAuth())
        ConvTy = Sema::IncompatiblePointerDiscardsQualifiers;
  
      // For GCC/MS compatibility, other qualifier mismatches are treated
      // as still compatible in C.
      else ConvTy = Sema::CompatiblePointerDiscardsQualifiers;
    }
  
    // C99 6.5.16.1p1 (constraint 4): If one operand is a pointer to an object or
    // incomplete type and the other is a pointer to a qualified or unqualified
    // version of void...
    if (lhptee->isVoidType()) {
      if (rhptee->isIncompleteOrObjectType())
        return ConvTy;
  
      // As an extension, we allow cast to/from void* to function pointer.
      assert(rhptee->isFunctionType());
      return Sema::FunctionVoidPointer;
    }
  
    if (rhptee->isVoidType()) {
      if (lhptee->isIncompleteOrObjectType())
        return ConvTy;
  
      // As an extension, we allow cast to/from void* to function pointer.
      assert(lhptee->isFunctionType());
      return Sema::FunctionVoidPointer;
    }
  
    // C99 6.5.16.1p1 (constraint 3): both operands are pointers to qualified or
    // unqualified versions of compatible types, ...
    QualType ltrans = QualType(lhptee, 0), rtrans = QualType(rhptee, 0);
    if (!S.Context.typesAreCompatible(ltrans, rtrans)) {
      // Check if the pointee types are compatible ignoring the sign.
      // We explicitly check for char so that we catch "char" vs
      // "unsigned char" on systems where "char" is unsigned.
      if (lhptee->isCharType())
        ltrans = S.Context.UnsignedCharTy;
      else if (lhptee->hasSignedIntegerRepresentation())
        ltrans = S.Context.getCorrespondingUnsignedType(ltrans);
  
      if (rhptee->isCharType())
        rtrans = S.Context.UnsignedCharTy;
      else if (rhptee->hasSignedIntegerRepresentation())
        rtrans = S.Context.getCorrespondingUnsignedType(rtrans);
  
      if (ltrans == rtrans) {
        // Types are compatible ignoring the sign. Qualifier incompatibility
        // takes priority over sign incompatibility because the sign
        // warning can be disabled.
        if (ConvTy != Sema::Compatible)
          return ConvTy;
  
        return Sema::IncompatiblePointerSign;
      }
  
      // If we are a multi-level pointer, it's possible that our issue is simply
      // one of qualification - e.g. char ** -> const char ** is not allowed. If
      // the eventual target type is the same and the pointers have the same
      // level of indirection, this must be the issue.
      if (isa<PointerType>(lhptee) && isa<PointerType>(rhptee)) {
        do {
          std::tie(lhptee, lhq) =
            cast<PointerType>(lhptee)->getPointeeType().split().asPair();
          std::tie(rhptee, rhq) =
            cast<PointerType>(rhptee)->getPointeeType().split().asPair();
  
          // Inconsistent address spaces at this point is invalid, even if the
          // address spaces would be compatible.
          // FIXME: This doesn't catch address space mismatches for pointers of
          // different nesting levels, like:
          //   __local int *** a;
          //   int ** b = a;
          // It's not clear how to actually determine when such pointers are
          // invalidly incompatible.
          if (lhq.getAddressSpace() != rhq.getAddressSpace())
            return Sema::IncompatibleNestedPointerAddressSpaceMismatch;
  
        } while (isa<PointerType>(lhptee) && isa<PointerType>(rhptee));
  
        if (lhptee == rhptee)
          return Sema::IncompatibleNestedPointerQualifiers;
      }
  
      // General pointer incompatibility takes priority over qualifiers.
      if (RHSType->isFunctionPointerType() && LHSType->isFunctionPointerType())
        return Sema::IncompatibleFunctionPointer;
      return Sema::IncompatiblePointer;
    }
    if (!S.getLangOpts().CPlusPlus &&
        S.IsFunctionConversion(ltrans, rtrans, ltrans))
      return Sema::IncompatibleFunctionPointer;
    if (IsInvalidCmseNSCallConversion(S, ltrans, rtrans))
      return Sema::IncompatibleFunctionPointer;
    return ConvTy;
  }
  
  /// checkBlockPointerTypesForAssignment - This routine determines whether two
  /// block pointer types are compatible or whether a block and normal pointer
  /// are compatible. It is more restrict than comparing two function pointer
  // types.
  static Sema::AssignConvertType
  checkBlockPointerTypesForAssignment(Sema &S, QualType LHSType,
                                      QualType RHSType) {
    assert(LHSType.isCanonical() && "LHS not canonicalized!");
    assert(RHSType.isCanonical() && "RHS not canonicalized!");
  
    QualType lhptee, rhptee;
  
    // get the "pointed to" type (ignoring qualifiers at the top level)
    lhptee = cast<BlockPointerType>(LHSType)->getPointeeType();
    rhptee = cast<BlockPointerType>(RHSType)->getPointeeType();
  
    // In C++, the types have to match exactly.
    if (S.getLangOpts().CPlusPlus)
      return Sema::IncompatibleBlockPointer;
  
    Sema::AssignConvertType ConvTy = Sema::Compatible;
  
    // For blocks we enforce that qualifiers are identical.
    Qualifiers LQuals = lhptee.getLocalQualifiers();
    Qualifiers RQuals = rhptee.getLocalQualifiers();
    if (S.getLangOpts().OpenCL) {
      LQuals.removeAddressSpace();
      RQuals.removeAddressSpace();
    }
    if (LQuals != RQuals)
      ConvTy = Sema::CompatiblePointerDiscardsQualifiers;
  
    // FIXME: OpenCL doesn't define the exact compile time semantics for a block
    // assignment.
    // The current behavior is similar to C++ lambdas. A block might be
    // assigned to a variable iff its return type and parameters are compatible
    // (C99 6.2.7) with the corresponding return type and parameters of the LHS of
    // an assignment. Presumably it should behave in way that a function pointer
    // assignment does in C, so for each parameter and return type:
    //  * CVR and address space of LHS should be a superset of CVR and address
    //  space of RHS.
    //  * unqualified types should be compatible.
    if (S.getLangOpts().OpenCL) {
      if (!S.Context.typesAreBlockPointerCompatible(
              S.Context.getQualifiedType(LHSType.getUnqualifiedType(), LQuals),
              S.Context.getQualifiedType(RHSType.getUnqualifiedType(), RQuals)))
        return Sema::IncompatibleBlockPointer;
    } else if (!S.Context.typesAreBlockPointerCompatible(LHSType, RHSType))
      return Sema::IncompatibleBlockPointer;
  
    return ConvTy;
  }
  
  /// checkObjCPointerTypesForAssignment - Compares two objective-c pointer types
  /// for assignment compatibility.
  static Sema::AssignConvertType
  checkObjCPointerTypesForAssignment(Sema &S, QualType LHSType,
                                     QualType RHSType) {
    assert(LHSType.isCanonical() && "LHS was not canonicalized!");
    assert(RHSType.isCanonical() && "RHS was not canonicalized!");
  
    if (LHSType->isObjCBuiltinType()) {
      // Class is not compatible with ObjC object pointers.
      if (LHSType->isObjCClassType() && !RHSType->isObjCBuiltinType() &&
          !RHSType->isObjCQualifiedClassType())
        return Sema::IncompatiblePointer;
      return Sema::Compatible;
    }
    if (RHSType->isObjCBuiltinType()) {
      if (RHSType->isObjCClassType() && !LHSType->isObjCBuiltinType() &&
          !LHSType->isObjCQualifiedClassType())
        return Sema::IncompatiblePointer;
      return Sema::Compatible;
    }
    QualType lhptee = LHSType->castAs<ObjCObjectPointerType>()->getPointeeType();
    QualType rhptee = RHSType->castAs<ObjCObjectPointerType>()->getPointeeType();
  
    if (!lhptee.isAtLeastAsQualifiedAs(rhptee) &&
        // make an exception for id<P>
        !LHSType->isObjCQualifiedIdType())
      return Sema::CompatiblePointerDiscardsQualifiers;
  
    if (S.Context.typesAreCompatible(LHSType, RHSType))
      return Sema::Compatible;
    if (LHSType->isObjCQualifiedIdType() || RHSType->isObjCQualifiedIdType())
      return Sema::IncompatibleObjCQualifiedId;
    return Sema::IncompatiblePointer;
  }
  
  Sema::AssignConvertType
  Sema::CheckAssignmentConstraints(SourceLocation Loc,
                                   QualType LHSType, QualType RHSType) {
    // Fake up an opaque expression.  We don't actually care about what
    // cast operations are required, so if CheckAssignmentConstraints
    // adds casts to this they'll be wasted, but fortunately that doesn't
    // usually happen on valid code.
    OpaqueValueExpr RHSExpr(Loc, RHSType, VK_PRValue);
    ExprResult RHSPtr = &RHSExpr;
    CastKind K;
  
    return CheckAssignmentConstraints(LHSType, RHSPtr, K, /*ConvertRHS=*/false);
  }
  
  /// This helper function returns true if QT is a vector type that has element
  /// type ElementType.
  static bool isVector(QualType QT, QualType ElementType) {
    if (const VectorType *VT = QT->getAs<VectorType>())
      return VT->getElementType().getCanonicalType() == ElementType;
    return false;
  }
  
  /// CheckAssignmentConstraints (C99 6.5.16) - This routine currently
  /// has code to accommodate several GCC extensions when type checking
  /// pointers. Here are some objectionable examples that GCC considers warnings:
  ///
  ///  int a, *pint;
  ///  short *pshort;
  ///  struct foo *pfoo;
  ///
  ///  pint = pshort; // warning: assignment from incompatible pointer type
  ///  a = pint; // warning: assignment makes integer from pointer without a cast
  ///  pint = a; // warning: assignment makes pointer from integer without a cast
  ///  pint = pfoo; // warning: assignment from incompatible pointer type
  ///
  /// As a result, the code for dealing with pointers is more complex than the
  /// C99 spec dictates.
  ///
  /// Sets 'Kind' for any result kind except Incompatible.
  Sema::AssignConvertType
  Sema::CheckAssignmentConstraints(QualType LHSType, ExprResult &RHS,
                                   CastKind &Kind, bool ConvertRHS) {
    QualType RHSType = RHS.get()->getType();
    QualType OrigLHSType = LHSType;
  
    // Get canonical types.  We're not formatting these types, just comparing
    // them.
    LHSType = Context.getCanonicalType(LHSType).getUnqualifiedType();
    RHSType = Context.getCanonicalType(RHSType).getUnqualifiedType();
  
    // Common case: no conversion required.
    if (LHSType == RHSType) {
      Kind = CK_NoOp;
      return Compatible;
    }
  
    // If we have an atomic type, try a non-atomic assignment, then just add an
    // atomic qualification step.
    if (const AtomicType *AtomicTy = dyn_cast<AtomicType>(LHSType)) {
      Sema::AssignConvertType result =
        CheckAssignmentConstraints(AtomicTy->getValueType(), RHS, Kind);
      if (result != Compatible)
        return result;
      if (Kind != CK_NoOp && ConvertRHS)
        RHS = ImpCastExprToType(RHS.get(), AtomicTy->getValueType(), Kind);
      Kind = CK_NonAtomicToAtomic;
      return Compatible;
    }
  
    // If the left-hand side is a reference type, then we are in a
    // (rare!) case where we've allowed the use of references in C,
    // e.g., as a parameter type in a built-in function. In this case,
    // just make sure that the type referenced is compatible with the
    // right-hand side type. The caller is responsible for adjusting
    // LHSType so that the resulting expression does not have reference
    // type.
    if (const ReferenceType *LHSTypeRef = LHSType->getAs<ReferenceType>()) {
      if (Context.typesAreCompatible(LHSTypeRef->getPointeeType(), RHSType)) {
        Kind = CK_LValueBitCast;
        return Compatible;
      }
      return Incompatible;
    }
  
    // Allow scalar to ExtVector assignments, and assignments of an ExtVector type
    // to the same ExtVector type.
    if (LHSType->isExtVectorType()) {
      if (RHSType->isExtVectorType())
        return Incompatible;
      if (RHSType->isArithmeticType()) {
        // CK_VectorSplat does T -> vector T, so first cast to the element type.
        if (ConvertRHS)
          RHS = prepareVectorSplat(LHSType, RHS.get());
        Kind = CK_VectorSplat;
        return Compatible;
      }
    }
  
    // Conversions to or from vector type.
    if (LHSType->isVectorType() || RHSType->isVectorType()) {
      if (LHSType->isVectorType() && RHSType->isVectorType()) {
        // Allow assignments of an AltiVec vector type to an equivalent GCC
        // vector type and vice versa
        if (Context.areCompatibleVectorTypes(LHSType, RHSType)) {
          Kind = CK_BitCast;
          return Compatible;
        }
  
        // If we are allowing lax vector conversions, and LHS and RHS are both
        // vectors, the total size only needs to be the same. This is a bitcast;
        // no bits are changed but the result type is different.
        if (isLaxVectorConversion(RHSType, LHSType)) {
          Kind = CK_BitCast;
          return IncompatibleVectors;
        }
      }
  
      // When the RHS comes from another lax conversion (e.g. binops between
      // scalars and vectors) the result is canonicalized as a vector. When the
      // LHS is also a vector, the lax is allowed by the condition above. Handle
      // the case where LHS is a scalar.
      if (LHSType->isScalarType()) {
        const VectorType *VecType = RHSType->getAs<VectorType>();
        if (VecType && VecType->getNumElements() == 1 &&
            isLaxVectorConversion(RHSType, LHSType)) {
          ExprResult *VecExpr = &RHS;
          *VecExpr = ImpCastExprToType(VecExpr->get(), LHSType, CK_BitCast);
          Kind = CK_BitCast;
          return Compatible;
        }
      }
  
      // Allow assignments between fixed-length and sizeless SVE vectors.
      if ((LHSType->isSizelessBuiltinType() && RHSType->isVectorType()) ||
          (LHSType->isVectorType() && RHSType->isSizelessBuiltinType()))
        if (Context.areCompatibleSveTypes(LHSType, RHSType) ||
            Context.areLaxCompatibleSveTypes(LHSType, RHSType)) {
          Kind = CK_BitCast;
          return Compatible;
        }
  
      return Incompatible;
    }
  
    // Diagnose attempts to convert between __ibm128, __float128 and long double
    // where such conversions currently can't be handled.
    if (unsupportedTypeConversion(*this, LHSType, RHSType))
      return Incompatible;
  
    // Disallow assigning a _Complex to a real type in C++ mode since it simply
    // discards the imaginary part.
    if (getLangOpts().CPlusPlus && RHSType->getAs<ComplexType>() &&
        !LHSType->getAs<ComplexType>())
      return Incompatible;
  
    // Arithmetic conversions.
    if (LHSType->isArithmeticType() && RHSType->isArithmeticType() &&
        !(getLangOpts().CPlusPlus && LHSType->isEnumeralType())) {
      if (ConvertRHS)
        Kind = PrepareScalarCast(RHS, LHSType);
      return Compatible;
    }
  
    // Conversions to normal pointers.
    if (const PointerType *LHSPointer = dyn_cast<PointerType>(LHSType)) {
      // U* -> T*
      if (isa<PointerType>(RHSType)) {
        LangAS AddrSpaceL = LHSPointer->getPointeeType().getAddressSpace();
        LangAS AddrSpaceR = RHSType->getPointeeType().getAddressSpace();
        if (AddrSpaceL != AddrSpaceR)
          Kind = CK_AddressSpaceConversion;
        else if (Context.hasCvrSimilarType(RHSType, LHSType))
          Kind = CK_NoOp;
        else
          Kind = CK_BitCast;
        return checkPointerTypesForAssignment(*this, LHSType, RHSType);
      }
  
      // int -> T*
      if (RHSType->isIntegerType()) {
        Kind = CK_IntegralToPointer; // FIXME: null?
        return IntToPointer;
      }
  
      // C pointers are not compatible with ObjC object pointers,
      // with two exceptions:
      if (isa<ObjCObjectPointerType>(RHSType)) {
        //  - conversions to void*
        if (LHSPointer->getPointeeType()->isVoidType()) {
          Kind = CK_BitCast;
          return Compatible;
        }
  
        //  - conversions from 'Class' to the redefinition type
        if (RHSType->isObjCClassType() &&
            Context.hasSameType(LHSType,
                                Context.getObjCClassRedefinitionType())) {
          Kind = CK_BitCast;
          return Compatible;
        }
  
        Kind = CK_BitCast;
        return IncompatiblePointer;
      }
  
      // U^ -> void*
      if (RHSType->getAs<BlockPointerType>()) {
        if (LHSPointer->getPointeeType()->isVoidType()) {
          LangAS AddrSpaceL = LHSPointer->getPointeeType().getAddressSpace();
          LangAS AddrSpaceR = RHSType->getAs<BlockPointerType>()
                                  ->getPointeeType()
                                  .getAddressSpace();
          Kind =
              AddrSpaceL != AddrSpaceR ? CK_AddressSpaceConversion : CK_BitCast;
          return Compatible;
        }
      }
  
      return Incompatible;
    }
  
    // Conversions to block pointers.
    if (isa<BlockPointerType>(LHSType)) {
      // U^ -> T^
      if (RHSType->isBlockPointerType()) {
        LangAS AddrSpaceL = LHSType->getAs<BlockPointerType>()
                                ->getPointeeType()
                                .getAddressSpace();
        LangAS AddrSpaceR = RHSType->getAs<BlockPointerType>()
                                ->getPointeeType()
                                .getAddressSpace();
        Kind = AddrSpaceL != AddrSpaceR ? CK_AddressSpaceConversion : CK_BitCast;
        return checkBlockPointerTypesForAssignment(*this, LHSType, RHSType);
      }
  
      // int or null -> T^
      if (RHSType->isIntegerType()) {
        Kind = CK_IntegralToPointer; // FIXME: null
        return IntToBlockPointer;
      }
  
      // id -> T^
      if (getLangOpts().ObjC && RHSType->isObjCIdType()) {
        Kind = CK_AnyPointerToBlockPointerCast;
        return Compatible;
      }
  
      // void* -> T^
      if (const PointerType *RHSPT = RHSType->getAs<PointerType>())
        if (RHSPT->getPointeeType()->isVoidType()) {
          Kind = CK_AnyPointerToBlockPointerCast;
          return Compatible;
        }
  
      return Incompatible;
    }
  
    // Conversions to Objective-C pointers.
    if (isa<ObjCObjectPointerType>(LHSType)) {
      // A* -> B*
      if (RHSType->isObjCObjectPointerType()) {
        Kind = CK_BitCast;
        Sema::AssignConvertType result =
          checkObjCPointerTypesForAssignment(*this, LHSType, RHSType);
        if (getLangOpts().allowsNonTrivialObjCLifetimeQualifiers() &&
            result == Compatible &&
            !CheckObjCARCUnavailableWeakConversion(OrigLHSType, RHSType))
          result = IncompatibleObjCWeakRef;
        return result;
      }
  
      // int or null -> A*
      if (RHSType->isIntegerType()) {
        Kind = CK_IntegralToPointer; // FIXME: null
        return IntToPointer;
      }
  
      // In general, C pointers are not compatible with ObjC object pointers,
      // with two exceptions:
      if (isa<PointerType>(RHSType)) {
        Kind = CK_CPointerToObjCPointerCast;
  
        //  - conversions from 'void*'
        if (RHSType->isVoidPointerType()) {
          return Compatible;
        }
  
        //  - conversions to 'Class' from its redefinition type
        if (LHSType->isObjCClassType() &&
            Context.hasSameType(RHSType,
                                Context.getObjCClassRedefinitionType())) {
          return Compatible;
        }
  
        return IncompatiblePointer;
      }
  
      // Only under strict condition T^ is compatible with an Objective-C pointer.
      if (RHSType->isBlockPointerType() &&
          LHSType->isBlockCompatibleObjCPointerType(Context)) {
        if (ConvertRHS)
          maybeExtendBlockObject(RHS);
        Kind = CK_BlockPointerToObjCPointerCast;
        return Compatible;
      }
  
      return Incompatible;
    }
  
    // Conversions from pointers that are not covered by the above.
    if (isa<PointerType>(RHSType)) {
      // T* -> _Bool
      if (LHSType == Context.BoolTy) {
        Kind = CK_PointerToBoolean;
        return Compatible;
      }
  
      // T* -> int
      if (LHSType->isIntegerType()) {
        Kind = CK_PointerToIntegral;
        return PointerToInt;
      }
  
      return Incompatible;
    }
  
    // Conversions from Objective-C pointers that are not covered by the above.
    if (isa<ObjCObjectPointerType>(RHSType)) {
      // T* -> _Bool
      if (LHSType == Context.BoolTy) {
        Kind = CK_PointerToBoolean;
        return Compatible;
      }
  
      // T* -> int
      if (LHSType->isIntegerType()) {
        Kind = CK_PointerToIntegral;
        return PointerToInt;
      }
  
      return Incompatible;
    }
  
    // struct A -> struct B
    if (isa<TagType>(LHSType) && isa<TagType>(RHSType)) {
      if (Context.typesAreCompatible(LHSType, RHSType)) {
        Kind = CK_NoOp;
        return Compatible;
      }
    }
  
    if (LHSType->isSamplerT() && RHSType->isIntegerType()) {
      Kind = CK_IntToOCLSampler;
      return Compatible;
    }
  
    return Incompatible;
  }
  
  /// Constructs a transparent union from an expression that is
  /// used to initialize the transparent union.
  static void ConstructTransparentUnion(Sema &S, ASTContext &C,
                                        ExprResult &EResult, QualType UnionType,
                                        FieldDecl *Field) {
    // Build an initializer list that designates the appropriate member
    // of the transparent union.
    Expr *E = EResult.get();
    InitListExpr *Initializer = new (C) InitListExpr(C, SourceLocation(),
                                                     E, SourceLocation());
    Initializer->setType(UnionType);
    Initializer->setInitializedFieldInUnion(Field);
  
    // Build a compound literal constructing a value of the transparent
    // union type from this initializer list.
    TypeSourceInfo *unionTInfo = C.getTrivialTypeSourceInfo(UnionType);
    EResult = new (C) CompoundLiteralExpr(SourceLocation(), unionTInfo, UnionType,
                                          VK_PRValue, Initializer, false);
  }
  
  Sema::AssignConvertType
  Sema::CheckTransparentUnionArgumentConstraints(QualType ArgType,
                                                 ExprResult &RHS) {
    QualType RHSType = RHS.get()->getType();
  
    // If the ArgType is a Union type, we want to handle a potential
    // transparent_union GCC extension.
    const RecordType *UT = ArgType->getAsUnionType();
    if (!UT || !UT->getDecl()->hasAttr<TransparentUnionAttr>())
      return Incompatible;
  
    // The field to initialize within the transparent union.
    RecordDecl *UD = UT->getDecl();
    FieldDecl *InitField = nullptr;
    // It's compatible if the expression matches any of the fields.
    for (auto *it : UD->fields()) {
      if (it->getType()->isPointerType()) {
        // If the transparent union contains a pointer type, we allow:
        // 1) void pointer
        // 2) null pointer constant
        if (RHSType->isPointerType())
          if (RHSType->castAs<PointerType>()->getPointeeType()->isVoidType()) {
            RHS = ImpCastExprToType(RHS.get(), it->getType(), CK_BitCast);
            InitField = it;
            break;
          }
  
        if (RHS.get()->isNullPointerConstant(Context,
                                             Expr::NPC_ValueDependentIsNull)) {
          RHS = ImpCastExprToType(RHS.get(), it->getType(),
                                  CK_NullToPointer);
          InitField = it;
          break;
        }
      }
  
      CastKind Kind;
      if (CheckAssignmentConstraints(it->getType(), RHS, Kind)
            == Compatible) {
        RHS = ImpCastExprToType(RHS.get(), it->getType(), Kind);
        InitField = it;
        break;
      }
    }
  
    if (!InitField)
      return Incompatible;
  
    ConstructTransparentUnion(*this, Context, RHS, ArgType, InitField);
    return Compatible;
  }
  
  Sema::AssignConvertType
  Sema::CheckSingleAssignmentConstraints(QualType LHSType, ExprResult &CallerRHS,
                                         bool Diagnose,
                                         bool DiagnoseCFAudited,
                                         bool ConvertRHS) {
    // We need to be able to tell the caller whether we diagnosed a problem, if
    // they ask us to issue diagnostics.
    assert((ConvertRHS || !Diagnose) && "can't indicate whether we diagnosed");
  
    // If ConvertRHS is false, we want to leave the caller's RHS untouched. Sadly,
    // we can't avoid *all* modifications at the moment, so we need some somewhere
    // to put the updated value.
    ExprResult LocalRHS = CallerRHS;
    ExprResult &RHS = ConvertRHS ? CallerRHS : LocalRHS;
  
    if (const auto *LHSPtrType = LHSType->getAs<PointerType>()) {
      if (const auto *RHSPtrType = RHS.get()->getType()->getAs<PointerType>()) {
        if (RHSPtrType->getPointeeType()->hasAttr(attr::NoDeref) &&
            !LHSPtrType->getPointeeType()->hasAttr(attr::NoDeref)) {
          Diag(RHS.get()->getExprLoc(),
               diag::warn_noderef_to_dereferenceable_pointer)
              << RHS.get()->getSourceRange();
        }
      }
    }
  
    if (getLangOpts().CPlusPlus) {
      if (!LHSType->isRecordType() && !LHSType->isAtomicType()) {
        // C++ 5.17p3: If the left operand is not of class type, the
        // expression is implicitly converted (C++ 4) to the
        // cv-unqualified type of the left operand.
        QualType RHSType = RHS.get()->getType();
        if (Diagnose) {
          RHS = PerformImplicitConversion(RHS.get(), LHSType.getUnqualifiedType(),
                                          AA_Assigning);
        } else {
          ImplicitConversionSequence ICS =
              TryImplicitConversion(RHS.get(), LHSType.getUnqualifiedType(),
                                    /*SuppressUserConversions=*/false,
                                    AllowedExplicit::None,
                                    /*InOverloadResolution=*/false,
                                    /*CStyle=*/false,
                                    /*AllowObjCWritebackConversion=*/false);
          if (ICS.isFailure())
            return Incompatible;
          RHS = PerformImplicitConversion(RHS.get(), LHSType.getUnqualifiedType(),
                                          ICS, AA_Assigning);
        }
        if (RHS.isInvalid())
          return Incompatible;
        Sema::AssignConvertType result = Compatible;
        if (getLangOpts().allowsNonTrivialObjCLifetimeQualifiers() &&
            !CheckObjCARCUnavailableWeakConversion(LHSType, RHSType))
          result = IncompatibleObjCWeakRef;
        return result;
      }
  
      // FIXME: Currently, we fall through and treat C++ classes like C
      // structures.
      // FIXME: We also fall through for atomics; not sure what should
      // happen there, though.
    } else if (RHS.get()->getType() == Context.OverloadTy) {
      // As a set of extensions to C, we support overloading on functions. These
      // functions need to be resolved here.
      DeclAccessPair DAP;
      if (FunctionDecl *FD = ResolveAddressOfOverloadedFunction(
              RHS.get(), LHSType, /*Complain=*/false, DAP))
        RHS = FixOverloadedFunctionReference(RHS.get(), DAP, FD);
      else
        return Incompatible;
    }
  
    // C99 6.5.16.1p1: the left operand is a pointer and the right is
    // a null pointer constant.
    if ((LHSType->isPointerType() || LHSType->isObjCObjectPointerType() ||
         LHSType->isBlockPointerType()) &&
        RHS.get()->isNullPointerConstant(Context,
                                         Expr::NPC_ValueDependentIsNull)) {
      if (Diagnose || ConvertRHS) {
        CastKind Kind;
        CXXCastPath Path;
        CheckPointerConversion(RHS.get(), LHSType, Kind, Path,
                               /*IgnoreBaseAccess=*/false, Diagnose);
        if (ConvertRHS)
          RHS = ImpCastExprToType(RHS.get(), LHSType, Kind, VK_PRValue, &Path);
      }
      return Compatible;
    }
  
    // OpenCL queue_t type assignment.
    if (LHSType->isQueueT() && RHS.get()->isNullPointerConstant(
                                   Context, Expr::NPC_ValueDependentIsNull)) {
      RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
      return Compatible;
    }
  
    // This check seems unnatural, however it is necessary to ensure the proper
    // conversion of functions/arrays. If the conversion were done for all
    // DeclExpr's (created by ActOnIdExpression), it would mess up the unary
    // expressions that suppress this implicit conversion (&, sizeof).
    //
    // Suppress this for references: C++ 8.5.3p5.
    if (!LHSType->isReferenceType()) {
      // FIXME: We potentially allocate here even if ConvertRHS is false.
      RHS = DefaultFunctionArrayLvalueConversion(RHS.get(), Diagnose);
      if (RHS.isInvalid())
        return Incompatible;
    }
  
    Expr *PRE = RHS.get()->IgnoreParenCasts();
    if (Diagnose && isa<ObjCProtocolExpr>(PRE)) {
      ObjCProtocolDecl *PDecl = cast<ObjCProtocolExpr>(PRE)->getProtocol();
      if (PDecl && !PDecl->hasDefinition()) {
        Diag(PRE->getExprLoc(), diag::warn_atprotocol_protocol) << PDecl;
        Diag(PDecl->getLocation(), diag::note_entity_declared_at) << PDecl;
      }
    }
  
    CastKind Kind;
    Sema::AssignConvertType result =
      CheckAssignmentConstraints(LHSType, RHS, Kind, ConvertRHS);
  
    // C99 6.5.16.1p2: The value of the right operand is converted to the
    // type of the assignment expression.
    // CheckAssignmentConstraints allows the left-hand side to be a reference,
    // so that we can use references in built-in functions even in C.
    // The getNonReferenceType() call makes sure that the resulting expression
    // does not have reference type.
    if (result != Incompatible && RHS.get()->getType() != LHSType) {
      QualType Ty = LHSType.getNonLValueExprType(Context);
      Expr *E = RHS.get();
  
      // Check for various Objective-C errors. If we are not reporting
      // diagnostics and just checking for errors, e.g., during overload
      // resolution, return Incompatible to indicate the failure.
      if (getLangOpts().allowsNonTrivialObjCLifetimeQualifiers() &&
          CheckObjCConversion(SourceRange(), Ty, E, CCK_ImplicitConversion,
                              Diagnose, DiagnoseCFAudited) != ACR_okay) {
        if (!Diagnose)
          return Incompatible;
      }
      if (getLangOpts().ObjC &&
          (CheckObjCBridgeRelatedConversions(E->getBeginLoc(), LHSType,
                                             E->getType(), E, Diagnose) ||
           CheckConversionToObjCLiteral(LHSType, E, Diagnose))) {
        if (!Diagnose)
          return Incompatible;
        // Replace the expression with a corrected version and continue so we
        // can find further errors.
        RHS = E;
        return Compatible;
      }
  
      if (ConvertRHS)
        RHS = ImpCastExprToType(E, Ty, Kind);
    }
  
    return result;
  }
  
  namespace {
  /// The original operand to an operator, prior to the application of the usual
  /// arithmetic conversions and converting the arguments of a builtin operator
  /// candidate.
  struct OriginalOperand {
    explicit OriginalOperand(Expr *Op) : Orig(Op), Conversion(nullptr) {
      if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Op))
        Op = MTE->getSubExpr();
      if (auto *BTE = dyn_cast<CXXBindTemporaryExpr>(Op))
        Op = BTE->getSubExpr();
      if (auto *ICE = dyn_cast<ImplicitCastExpr>(Op)) {
        Orig = ICE->getSubExprAsWritten();
        Conversion = ICE->getConversionFunction();
      }
    }
  
    QualType getType() const { return Orig->getType(); }
  
    Expr *Orig;
    NamedDecl *Conversion;
  };
  }
  
  QualType Sema::InvalidOperands(SourceLocation Loc, ExprResult &LHS,
                                 ExprResult &RHS) {
    OriginalOperand OrigLHS(LHS.get()), OrigRHS(RHS.get());
  
    Diag(Loc, diag::err_typecheck_invalid_operands)
      << OrigLHS.getType() << OrigRHS.getType()
      << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
  
    // If a user-defined conversion was applied to either of the operands prior
    // to applying the built-in operator rules, tell the user about it.
    if (OrigLHS.Conversion) {
      Diag(OrigLHS.Conversion->getLocation(),
           diag::note_typecheck_invalid_operands_converted)
        << 0 << LHS.get()->getType();
    }
    if (OrigRHS.Conversion) {
      Diag(OrigRHS.Conversion->getLocation(),
           diag::note_typecheck_invalid_operands_converted)
        << 1 << RHS.get()->getType();
    }
  
    return QualType();
  }
  
  // Diagnose cases where a scalar was implicitly converted to a vector and
  // diagnose the underlying types. Otherwise, diagnose the error
  // as invalid vector logical operands for non-C++ cases.
  QualType Sema::InvalidLogicalVectorOperands(SourceLocation Loc, ExprResult &LHS,
                                              ExprResult &RHS) {
    QualType LHSType = LHS.get()->IgnoreImpCasts()->getType();
    QualType RHSType = RHS.get()->IgnoreImpCasts()->getType();
  
    bool LHSNatVec = LHSType->isVectorType();
    bool RHSNatVec = RHSType->isVectorType();
  
    if (!(LHSNatVec && RHSNatVec)) {
      Expr *Vector = LHSNatVec ? LHS.get() : RHS.get();
      Expr *NonVector = !LHSNatVec ? LHS.get() : RHS.get();
      Diag(Loc, diag::err_typecheck_logical_vector_expr_gnu_cpp_restrict)
          << 0 << Vector->getType() << NonVector->IgnoreImpCasts()->getType()
          << Vector->getSourceRange();
      return QualType();
    }
  
    Diag(Loc, diag::err_typecheck_logical_vector_expr_gnu_cpp_restrict)
        << 1 << LHSType << RHSType << LHS.get()->getSourceRange()
        << RHS.get()->getSourceRange();
  
    return QualType();
  }
  
  /// Try to convert a value of non-vector type to a vector type by converting
  /// the type to the element type of the vector and then performing a splat.
  /// If the language is OpenCL, we only use conversions that promote scalar
  /// rank; for C, Obj-C, and C++ we allow any real scalar conversion except
  /// for float->int.
  ///
  /// OpenCL V2.0 6.2.6.p2:
  /// An error shall occur if any scalar operand type has greater rank
  /// than the type of the vector element.
  ///
  /// \param scalar - if non-null, actually perform the conversions
  /// \return true if the operation fails (but without diagnosing the failure)
  static bool tryVectorConvertAndSplat(Sema &S, ExprResult *scalar,
                                       QualType scalarTy,
                                       QualType vectorEltTy,
                                       QualType vectorTy,
                                       unsigned &DiagID) {
    // The conversion to apply to the scalar before splatting it,
    // if necessary.
    CastKind scalarCast = CK_NoOp;
  
    if (vectorEltTy->isIntegralType(S.Context)) {
      if (S.getLangOpts().OpenCL && (scalarTy->isRealFloatingType() ||
          (scalarTy->isIntegerType() &&
           S.Context.getIntegerTypeOrder(vectorEltTy, scalarTy) < 0))) {
        DiagID = diag::err_opencl_scalar_type_rank_greater_than_vector_type;
        return true;
      }
      if (!scalarTy->isIntegralType(S.Context))
        return true;
      scalarCast = CK_IntegralCast;
    } else if (vectorEltTy->isRealFloatingType()) {
      if (scalarTy->isRealFloatingType()) {
        if (S.getLangOpts().OpenCL &&
            S.Context.getFloatingTypeOrder(vectorEltTy, scalarTy) < 0) {
          DiagID = diag::err_opencl_scalar_type_rank_greater_than_vector_type;
          return true;
        }
        scalarCast = CK_FloatingCast;
      }
      else if (scalarTy->isIntegralType(S.Context))
        scalarCast = CK_IntegralToFloating;
      else
        return true;
    } else {
      return true;
    }
  
    // Adjust scalar if desired.
    if (scalar) {
      if (scalarCast != CK_NoOp)
        *scalar = S.ImpCastExprToType(scalar->get(), vectorEltTy, scalarCast);
      *scalar = S.ImpCastExprToType(scalar->get(), vectorTy, CK_VectorSplat);
    }
    return false;
  }
  
  /// Convert vector E to a vector with the same number of elements but different
  /// element type.
  static ExprResult convertVector(Expr *E, QualType ElementType, Sema &S) {
    const auto *VecTy = E->getType()->getAs<VectorType>();
    assert(VecTy && "Expression E must be a vector");
    QualType NewVecTy = S.Context.getVectorType(ElementType,
                                                VecTy->getNumElements(),
                                                VecTy->getVectorKind());
  
    // Look through the implicit cast. Return the subexpression if its type is
    // NewVecTy.
    if (auto *ICE = dyn_cast<ImplicitCastExpr>(E))
      if (ICE->getSubExpr()->getType() == NewVecTy)
        return ICE->getSubExpr();
  
    auto Cast = ElementType->isIntegerType() ? CK_IntegralCast : CK_FloatingCast;
    return S.ImpCastExprToType(E, NewVecTy, Cast);
  }
  
  /// Test if a (constant) integer Int can be casted to another integer type
  /// IntTy without losing precision.
  static bool canConvertIntToOtherIntTy(Sema &S, ExprResult *Int,
                                        QualType OtherIntTy) {
    QualType IntTy = Int->get()->getType().getUnqualifiedType();
  
    // Reject cases where the value of the Int is unknown as that would
    // possibly cause truncation, but accept cases where the scalar can be
    // demoted without loss of precision.
    Expr::EvalResult EVResult;
    bool CstInt = Int->get()->EvaluateAsInt(EVResult, S.Context);
    int Order = S.Context.getIntegerTypeOrder(OtherIntTy, IntTy);
    bool IntSigned = IntTy->hasSignedIntegerRepresentation();
    bool OtherIntSigned = OtherIntTy->hasSignedIntegerRepresentation();
  
    if (CstInt) {
      // If the scalar is constant and is of a higher order and has more active
      // bits that the vector element type, reject it.
      llvm::APSInt Result = EVResult.Val.getInt();
      unsigned NumBits = IntSigned
                             ? (Result.isNegative() ? Result.getMinSignedBits()
                                                    : Result.getActiveBits())
                             : Result.getActiveBits();
      if (Order < 0 && S.Context.getIntWidth(OtherIntTy) < NumBits)
        return true;
  
      // If the signedness of the scalar type and the vector element type
      // differs and the number of bits is greater than that of the vector
      // element reject it.
      return (IntSigned != OtherIntSigned &&
              NumBits > S.Context.getIntWidth(OtherIntTy));
    }
  
    // Reject cases where the value of the scalar is not constant and it's
    // order is greater than that of the vector element type.
    return (Order < 0);
  }
  
  /// Test if a (constant) integer Int can be casted to floating point type
  /// FloatTy without losing precision.
  static bool canConvertIntTyToFloatTy(Sema &S, ExprResult *Int,
                                       QualType FloatTy) {
    QualType IntTy = Int->get()->getType().getUnqualifiedType();
  
    // Determine if the integer constant can be expressed as a floating point
    // number of the appropriate type.
    Expr::EvalResult EVResult;
    bool CstInt = Int->get()->EvaluateAsInt(EVResult, S.Context);
  
    uint64_t Bits = 0;
    if (CstInt) {
      // Reject constants that would be truncated if they were converted to
      // the floating point type. Test by simple to/from conversion.
      // FIXME: Ideally the conversion to an APFloat and from an APFloat
      //        could be avoided if there was a convertFromAPInt method
      //        which could signal back if implicit truncation occurred.
      llvm::APSInt Result = EVResult.Val.getInt();
      llvm::APFloat Float(S.Context.getFloatTypeSemantics(FloatTy));
      Float.convertFromAPInt(Result, IntTy->hasSignedIntegerRepresentation(),
                             llvm::APFloat::rmTowardZero);
      llvm::APSInt ConvertBack(S.Context.getIntWidth(IntTy),
                               !IntTy->hasSignedIntegerRepresentation());
      bool Ignored = false;
      Float.convertToInteger(ConvertBack, llvm::APFloat::rmNearestTiesToEven,
                             &Ignored);
      if (Result != ConvertBack)
        return true;
    } else {
      // Reject types that cannot be fully encoded into the mantissa of
      // the float.
      Bits = S.Context.getTypeSize(IntTy);
      unsigned FloatPrec = llvm::APFloat::semanticsPrecision(
          S.Context.getFloatTypeSemantics(FloatTy));
      if (Bits > FloatPrec)
        return true;
    }
  
    return false;
  }
  
  /// Attempt to convert and splat Scalar into a vector whose types matches
  /// Vector following GCC conversion rules. The rule is that implicit
  /// conversion can occur when Scalar can be casted to match Vector's element
  /// type without causing truncation of Scalar.
  static bool tryGCCVectorConvertAndSplat(Sema &S, ExprResult *Scalar,
                                          ExprResult *Vector) {
    QualType ScalarTy = Scalar->get()->getType().getUnqualifiedType();
    QualType VectorTy = Vector->get()->getType().getUnqualifiedType();
    const auto *VT = VectorTy->castAs<VectorType>();
  
    assert(!isa<ExtVectorType>(VT) &&
           "ExtVectorTypes should not be handled here!");
  
    QualType VectorEltTy = VT->getElementType();
  
    // Reject cases where the vector element type or the scalar element type are
    // not integral or floating point types.
    if (!VectorEltTy->isArithmeticType() || !ScalarTy->isArithmeticType())
      return true;
  
    // The conversion to apply to the scalar before splatting it,
    // if necessary.
    CastKind ScalarCast = CK_NoOp;
  
    // Accept cases where the vector elements are integers and the scalar is
    // an integer.
    // FIXME: Notionally if the scalar was a floating point value with a precise
    //        integral representation, we could cast it to an appropriate integer
    //        type and then perform the rest of the checks here. GCC will perform
    //        this conversion in some cases as determined by the input language.
    //        We should accept it on a language independent basis.
    if (VectorEltTy->isIntegralType(S.Context) &&
        ScalarTy->isIntegralType(S.Context) &&
        S.Context.getIntegerTypeOrder(VectorEltTy, ScalarTy)) {
  
      if (canConvertIntToOtherIntTy(S, Scalar, VectorEltTy))
        return true;
  
      ScalarCast = CK_IntegralCast;
    } else if (VectorEltTy->isIntegralType(S.Context) &&
               ScalarTy->isRealFloatingType()) {
      if (S.Context.getTypeSize(VectorEltTy) == S.Context.getTypeSize(ScalarTy))
        ScalarCast = CK_FloatingToIntegral;
      else
        return true;
    } else if (VectorEltTy->isRealFloatingType()) {
      if (ScalarTy->isRealFloatingType()) {
  
        // Reject cases where the scalar type is not a constant and has a higher
        // Order than the vector element type.
        llvm::APFloat Result(0.0);
  
        // Determine whether this is a constant scalar. In the event that the
        // value is dependent (and thus cannot be evaluated by the constant
        // evaluator), skip the evaluation. This will then diagnose once the
        // expression is instantiated.
        bool CstScalar = Scalar->get()->isValueDependent() ||
                         Scalar->get()->EvaluateAsFloat(Result, S.Context);
        int Order = S.Context.getFloatingTypeOrder(VectorEltTy, ScalarTy);
        if (!CstScalar && Order < 0)
          return true;
  
        // If the scalar cannot be safely casted to the vector element type,
        // reject it.
        if (CstScalar) {
          bool Truncated = false;
          Result.convert(S.Context.getFloatTypeSemantics(VectorEltTy),
                         llvm::APFloat::rmNearestTiesToEven, &Truncated);
          if (Truncated)
            return true;
        }
  
        ScalarCast = CK_FloatingCast;
      } else if (ScalarTy->isIntegralType(S.Context)) {
        if (canConvertIntTyToFloatTy(S, Scalar, VectorEltTy))
          return true;
  
        ScalarCast = CK_IntegralToFloating;
      } else
        return true;
    } else if (ScalarTy->isEnumeralType())
      return true;
  
    // Adjust scalar if desired.
    if (Scalar) {
      if (ScalarCast != CK_NoOp)
        *Scalar = S.ImpCastExprToType(Scalar->get(), VectorEltTy, ScalarCast);
      *Scalar = S.ImpCastExprToType(Scalar->get(), VectorTy, CK_VectorSplat);
    }
    return false;
  }
  
  QualType Sema::CheckVectorOperands(ExprResult &LHS, ExprResult &RHS,
                                     SourceLocation Loc, bool IsCompAssign,
                                     bool AllowBothBool,
                                     bool AllowBoolConversions) {
    if (!IsCompAssign) {
      LHS = DefaultFunctionArrayLvalueConversion(LHS.get());
      if (LHS.isInvalid())
        return QualType();
    }
    RHS = DefaultFunctionArrayLvalueConversion(RHS.get());
    if (RHS.isInvalid())
      return QualType();
  
    // For conversion purposes, we ignore any qualifiers.
    // For example, "const float" and "float" are equivalent.
    QualType LHSType = LHS.get()->getType().getUnqualifiedType();
    QualType RHSType = RHS.get()->getType().getUnqualifiedType();
  
    const VectorType *LHSVecType = LHSType->getAs<VectorType>();
    const VectorType *RHSVecType = RHSType->getAs<VectorType>();
    assert(LHSVecType || RHSVecType);
  
    if ((LHSVecType && LHSVecType->getElementType()->isBFloat16Type()) ||
        (RHSVecType && RHSVecType->getElementType()->isBFloat16Type()))
      return InvalidOperands(Loc, LHS, RHS);
  
    // AltiVec-style "vector bool op vector bool" combinations are allowed
    // for some operators but not others.
    if (!AllowBothBool &&
        LHSVecType && LHSVecType->getVectorKind() == VectorType::AltiVecBool &&
        RHSVecType && RHSVecType->getVectorKind() == VectorType::AltiVecBool)
      return InvalidOperands(Loc, LHS, RHS);
  
    // If the vector types are identical, return.
    if (Context.hasSameType(LHSType, RHSType))
      return LHSType;
  
    // If we have compatible AltiVec and GCC vector types, use the AltiVec type.
    if (LHSVecType && RHSVecType &&
        Context.areCompatibleVectorTypes(LHSType, RHSType)) {
      if (isa<ExtVectorType>(LHSVecType)) {
        RHS = ImpCastExprToType(RHS.get(), LHSType, CK_BitCast);
        return LHSType;
      }
  
      if (!IsCompAssign)
        LHS = ImpCastExprToType(LHS.get(), RHSType, CK_BitCast);
      return RHSType;
    }
  
    // AllowBoolConversions says that bool and non-bool AltiVec vectors
    // can be mixed, with the result being the non-bool type.  The non-bool
    // operand must have integer element type.
    if (AllowBoolConversions && LHSVecType && RHSVecType &&
        LHSVecType->getNumElements() == RHSVecType->getNumElements() &&
        (Context.getTypeSize(LHSVecType->getElementType()) ==
         Context.getTypeSize(RHSVecType->getElementType()))) {
      if (LHSVecType->getVectorKind() == VectorType::AltiVecVector &&
          LHSVecType->getElementType()->isIntegerType() &&
          RHSVecType->getVectorKind() == VectorType::AltiVecBool) {
        RHS = ImpCastExprToType(RHS.get(), LHSType, CK_BitCast);
        return LHSType;
      }
      if (!IsCompAssign &&
          LHSVecType->getVectorKind() == VectorType::AltiVecBool &&
          RHSVecType->getVectorKind() == VectorType::AltiVecVector &&
          RHSVecType->getElementType()->isIntegerType()) {
        LHS = ImpCastExprToType(LHS.get(), RHSType, CK_BitCast);
        return RHSType;
      }
    }
  
    // Expressions containing fixed-length and sizeless SVE vectors are invalid
    // since the ambiguity can affect the ABI.
    auto IsSveConversion = [](QualType FirstType, QualType SecondType) {
      const VectorType *VecType = SecondType->getAs<VectorType>();
      return FirstType->isSizelessBuiltinType() && VecType &&
             (VecType->getVectorKind() == VectorType::SveFixedLengthDataVector ||
              VecType->getVectorKind() ==
                  VectorType::SveFixedLengthPredicateVector);
    };
  
    if (IsSveConversion(LHSType, RHSType) || IsSveConversion(RHSType, LHSType)) {
      Diag(Loc, diag::err_typecheck_sve_ambiguous) << LHSType << RHSType;
      return QualType();
    }
  
    // Expressions containing GNU and SVE (fixed or sizeless) vectors are invalid
    // since the ambiguity can affect the ABI.
    auto IsSveGnuConversion = [](QualType FirstType, QualType SecondType) {
      const VectorType *FirstVecType = FirstType->getAs<VectorType>();
      const VectorType *SecondVecType = SecondType->getAs<VectorType>();
  
      if (FirstVecType && SecondVecType)
        return FirstVecType->getVectorKind() == VectorType::GenericVector &&
               (SecondVecType->getVectorKind() ==
                    VectorType::SveFixedLengthDataVector ||
                SecondVecType->getVectorKind() ==
                    VectorType::SveFixedLengthPredicateVector);
  
      return FirstType->isSizelessBuiltinType() && SecondVecType &&
             SecondVecType->getVectorKind() == VectorType::GenericVector;
    };
  
    if (IsSveGnuConversion(LHSType, RHSType) ||
        IsSveGnuConversion(RHSType, LHSType)) {
      Diag(Loc, diag::err_typecheck_sve_gnu_ambiguous) << LHSType << RHSType;
      return QualType();
    }
  
    // If there's a vector type and a scalar, try to convert the scalar to
    // the vector element type and splat.
    unsigned DiagID = diag::err_typecheck_vector_not_convertable;
    if (!RHSVecType) {
      if (isa<ExtVectorType>(LHSVecType)) {
        if (!tryVectorConvertAndSplat(*this, &RHS, RHSType,
                                      LHSVecType->getElementType(), LHSType,
                                      DiagID))
          return LHSType;
      } else {
        if (!tryGCCVectorConvertAndSplat(*this, &RHS, &LHS))
          return LHSType;
      }
    }
    if (!LHSVecType) {
      if (isa<ExtVectorType>(RHSVecType)) {
        if (!tryVectorConvertAndSplat(*this, (IsCompAssign ? nullptr : &LHS),
                                      LHSType, RHSVecType->getElementType(),
                                      RHSType, DiagID))
          return RHSType;
      } else {
        if (LHS.get()->isLValue() ||
            !tryGCCVectorConvertAndSplat(*this, &LHS, &RHS))
          return RHSType;
      }
    }
  
    // FIXME: The code below also handles conversion between vectors and
    // non-scalars, we should break this down into fine grained specific checks
    // and emit proper diagnostics.
    QualType VecType = LHSVecType ? LHSType : RHSType;
    const VectorType *VT = LHSVecType ? LHSVecType : RHSVecType;
    QualType OtherType = LHSVecType ? RHSType : LHSType;
    ExprResult *OtherExpr = LHSVecType ? &RHS : &LHS;
    if (isLaxVectorConversion(OtherType, VecType)) {
      // If we're allowing lax vector conversions, only the total (data) size
      // needs to be the same. For non compound assignment, if one of the types is
      // scalar, the result is always the vector type.
      if (!IsCompAssign) {
        *OtherExpr = ImpCastExprToType(OtherExpr->get(), VecType, CK_BitCast);
        return VecType;
      // In a compound assignment, lhs += rhs, 'lhs' is a lvalue src, forbidding
      // any implicit cast. Here, the 'rhs' should be implicit casted to 'lhs'
      // type. Note that this is already done by non-compound assignments in
      // CheckAssignmentConstraints. If it's a scalar type, only bitcast for
      // <1 x T> -> T. The result is also a vector type.
      } else if (OtherType->isExtVectorType() || OtherType->isVectorType() ||
                 (OtherType->isScalarType() && VT->getNumElements() == 1)) {
        ExprResult *RHSExpr = &RHS;
        *RHSExpr = ImpCastExprToType(RHSExpr->get(), LHSType, CK_BitCast);
        return VecType;
      }
    }
  
    // Okay, the expression is invalid.
  
    // If there's a non-vector, non-real operand, diagnose that.
    if ((!RHSVecType && !RHSType->isRealType()) ||
        (!LHSVecType && !LHSType->isRealType())) {
      Diag(Loc, diag::err_typecheck_vector_not_convertable_non_scalar)
        << LHSType << RHSType
        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
      return QualType();
    }
  
    // OpenCL V1.1 6.2.6.p1:
    // If the operands are of more than one vector type, then an error shall
    // occur. Implicit conversions between vector types are not permitted, per
    // section 6.2.1.
    if (getLangOpts().OpenCL &&
        RHSVecType && isa<ExtVectorType>(RHSVecType) &&
        LHSVecType && isa<ExtVectorType>(LHSVecType)) {
      Diag(Loc, diag::err_opencl_implicit_vector_conversion) << LHSType
                                                             << RHSType;
      return QualType();
    }
  
  
    // If there is a vector type that is not a ExtVector and a scalar, we reach
    // this point if scalar could not be converted to the vector's element type
    // without truncation.
    if ((RHSVecType && !isa<ExtVectorType>(RHSVecType)) ||
        (LHSVecType && !isa<ExtVectorType>(LHSVecType))) {
      QualType Scalar = LHSVecType ? RHSType : LHSType;
      QualType Vector = LHSVecType ? LHSType : RHSType;
      unsigned ScalarOrVector = LHSVecType && RHSVecType ? 1 : 0;
      Diag(Loc,
           diag::err_typecheck_vector_not_convertable_implict_truncation)
          << ScalarOrVector << Scalar << Vector;
  
      return QualType();
    }
  
    // Otherwise, use the generic diagnostic.
    Diag(Loc, DiagID)
      << LHSType << RHSType
      << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
    return QualType();
  }
  
  QualType Sema::CheckSizelessVectorOperands(ExprResult &LHS, ExprResult &RHS,
                                             SourceLocation Loc) {
    QualType LHSType = LHS.get()->getType().getUnqualifiedType();
    QualType RHSType = RHS.get()->getType().getUnqualifiedType();
  
    const BuiltinType *LHSVecType = LHSType->getAs<BuiltinType>();
    const BuiltinType *RHSVecType = RHSType->getAs<BuiltinType>();
  
    unsigned DiagID = diag::err_typecheck_invalid_operands;
    if (LHSVecType->isSVEBool() || RHSVecType->isSVEBool()) {
      Diag(Loc, DiagID) << LHSType << RHSType << LHS.get()->getSourceRange()
                        << RHS.get()->getSourceRange();
      return QualType();
    }
  
    if (Context.hasSameType(LHSType, RHSType))
      return LHSType;
  
    Diag(Loc, DiagID) << LHSType << RHSType << LHS.get()->getSourceRange()
                      << RHS.get()->getSourceRange();
    return QualType();
  }
  
  // checkArithmeticNull - Detect when a NULL constant is used improperly in an
  // expression.  These are mainly cases where the null pointer is used as an
  // integer instead of a pointer.
  static void checkArithmeticNull(Sema &S, ExprResult &LHS, ExprResult &RHS,
                                  SourceLocation Loc, bool IsCompare) {
    // The canonical way to check for a GNU null is with isNullPointerConstant,
    // but we use a bit of a hack here for speed; this is a relatively
    // hot path, and isNullPointerConstant is slow.
    bool LHSNull = isa<GNUNullExpr>(LHS.get()->IgnoreParenImpCasts());
    bool RHSNull = isa<GNUNullExpr>(RHS.get()->IgnoreParenImpCasts());
  
    QualType NonNullType = LHSNull ? RHS.get()->getType() : LHS.get()->getType();
  
    // Avoid analyzing cases where the result will either be invalid (and
    // diagnosed as such) or entirely valid and not something to warn about.
    if ((!LHSNull && !RHSNull) || NonNullType->isBlockPointerType() ||
        NonNullType->isMemberPointerType() || NonNullType->isFunctionType())
      return;
  
    // Comparison operations would not make sense with a null pointer no matter
    // what the other expression is.
    if (!IsCompare) {
      S.Diag(Loc, diag::warn_null_in_arithmetic_operation)
          << (LHSNull ? LHS.get()->getSourceRange() : SourceRange())
          << (RHSNull ? RHS.get()->getSourceRange() : SourceRange());
      return;
    }
  
    // The rest of the operations only make sense with a null pointer
    // if the other expression is a pointer.
    if (LHSNull == RHSNull || NonNullType->isAnyPointerType() ||
        NonNullType->canDecayToPointerType())
      return;
  
    S.Diag(Loc, diag::warn_null_in_comparison_operation)
        << LHSNull /* LHS is NULL */ << NonNullType
        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
  }
  
  static void DiagnoseDivisionSizeofPointerOrArray(Sema &S, Expr *LHS, Expr *RHS,
                                            SourceLocation Loc) {
    const auto *LUE = dyn_cast<UnaryExprOrTypeTraitExpr>(LHS);
    const auto *RUE = dyn_cast<UnaryExprOrTypeTraitExpr>(RHS);
    if (!LUE || !RUE)
      return;
    if (LUE->getKind() != UETT_SizeOf || LUE->isArgumentType() ||
        RUE->getKind() != UETT_SizeOf)
      return;
  
    const Expr *LHSArg = LUE->getArgumentExpr()->IgnoreParens();
    QualType LHSTy = LHSArg->getType();
    QualType RHSTy;
  
    if (RUE->isArgumentType())
      RHSTy = RUE->getArgumentType().getNonReferenceType();
    else
      RHSTy = RUE->getArgumentExpr()->IgnoreParens()->getType();
  
    if (LHSTy->isPointerType() && !RHSTy->isPointerType()) {
      if (!S.Context.hasSameUnqualifiedType(LHSTy->getPointeeType(), RHSTy))
        return;
  
      S.Diag(Loc, diag::warn_division_sizeof_ptr) << LHS << LHS->getSourceRange();
      if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSArg)) {
        if (const ValueDecl *LHSArgDecl = DRE->getDecl())
          S.Diag(LHSArgDecl->getLocation(), diag::note_pointer_declared_here)
              << LHSArgDecl;
      }
    } else if (const auto *ArrayTy = S.Context.getAsArrayType(LHSTy)) {
      QualType ArrayElemTy = ArrayTy->getElementType();
      if (ArrayElemTy != S.Context.getBaseElementType(ArrayTy) ||
          ArrayElemTy->isDependentType() || RHSTy->isDependentType() ||
          RHSTy->isReferenceType() || ArrayElemTy->isCharType() ||
          S.Context.getTypeSize(ArrayElemTy) == S.Context.getTypeSize(RHSTy))
        return;
      S.Diag(Loc, diag::warn_division_sizeof_array)
          << LHSArg->getSourceRange() << ArrayElemTy << RHSTy;
      if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSArg)) {
        if (const ValueDecl *LHSArgDecl = DRE->getDecl())
          S.Diag(LHSArgDecl->getLocation(), diag::note_array_declared_here)
              << LHSArgDecl;
      }
  
      S.Diag(Loc, diag::note_precedence_silence) << RHS;
    }
  }
  
  static void DiagnoseBadDivideOrRemainderValues(Sema& S, ExprResult &LHS,
                                                 ExprResult &RHS,
                                                 SourceLocation Loc, bool IsDiv) {
    // Check for division/remainder by zero.
    Expr::EvalResult RHSValue;
    if (!RHS.get()->isValueDependent() &&
        RHS.get()->EvaluateAsInt(RHSValue, S.Context) &&
        RHSValue.Val.getInt() == 0)
      S.DiagRuntimeBehavior(Loc, RHS.get(),
                            S.PDiag(diag::warn_remainder_division_by_zero)
                              << IsDiv << RHS.get()->getSourceRange());
  }
  
  QualType Sema::CheckMultiplyDivideOperands(ExprResult &LHS, ExprResult &RHS,
                                             SourceLocation Loc,
                                             bool IsCompAssign, bool IsDiv) {
    checkArithmeticNull(*this, LHS, RHS, Loc, /*IsCompare=*/false);
  
    QualType LHSTy = LHS.get()->getType();
    QualType RHSTy = RHS.get()->getType();
    if (LHSTy->isVectorType() || RHSTy->isVectorType())
      return CheckVectorOperands(LHS, RHS, Loc, IsCompAssign,
                                 /*AllowBothBool*/ getLangOpts().AltiVec,
                                 /*AllowBoolConversions*/ false);
    if (LHSTy->isVLSTBuiltinType() || RHSTy->isVLSTBuiltinType())
      return CheckSizelessVectorOperands(LHS, RHS, Loc);
    if (!IsDiv &&
        (LHSTy->isConstantMatrixType() || RHSTy->isConstantMatrixType()))
      return CheckMatrixMultiplyOperands(LHS, RHS, Loc, IsCompAssign);
    // For division, only matrix-by-scalar is supported. Other combinations with
    // matrix types are invalid.
    if (IsDiv && LHSTy->isConstantMatrixType() && RHSTy->isArithmeticType())
      return CheckMatrixElementwiseOperands(LHS, RHS, Loc, IsCompAssign);
  
    QualType compType = UsualArithmeticConversions(
        LHS, RHS, Loc, IsCompAssign ? ACK_CompAssign : ACK_Arithmetic);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
  
  
    if (compType.isNull() || !compType->isArithmeticType())
      return InvalidOperands(Loc, LHS, RHS);
    if (IsDiv) {
      DiagnoseBadDivideOrRemainderValues(*this, LHS, RHS, Loc, IsDiv);
      DiagnoseDivisionSizeofPointerOrArray(*this, LHS.get(), RHS.get(), Loc);
    }
    return compType;
  }
  
  QualType Sema::CheckRemainderOperands(
    ExprResult &LHS, ExprResult &RHS, SourceLocation Loc, bool IsCompAssign) {
    checkArithmeticNull(*this, LHS, RHS, Loc, /*IsCompare=*/false);
  
    if (LHS.get()->getType()->isVectorType() ||
        RHS.get()->getType()->isVectorType()) {
      if (LHS.get()->getType()->hasIntegerRepresentation() &&
          RHS.get()->getType()->hasIntegerRepresentation())
        return CheckVectorOperands(LHS, RHS, Loc, IsCompAssign,
                                   /*AllowBothBool*/getLangOpts().AltiVec,
                                   /*AllowBoolConversions*/false);
      return InvalidOperands(Loc, LHS, RHS);
    }
  
    if (LHS.get()->getType()->isVLSTBuiltinType() &&
        RHS.get()->getType()->isVLSTBuiltinType()) {
      if (LHS.get()
              ->getType()
              ->getSveEltType(Context)
              ->hasIntegerRepresentation() &&
          RHS.get()
              ->getType()
              ->getSveEltType(Context)
              ->hasIntegerRepresentation())
        return CheckSizelessVectorOperands(LHS, RHS, Loc);
  
      return InvalidOperands(Loc, LHS, RHS);
    }
  
    QualType compType = UsualArithmeticConversions(
        LHS, RHS, Loc, IsCompAssign ? ACK_CompAssign : ACK_Arithmetic);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
  
    if (compType.isNull() || !compType->isIntegerType())
      return InvalidOperands(Loc, LHS, RHS);
    DiagnoseBadDivideOrRemainderValues(*this, LHS, RHS, Loc, false /* IsDiv */);
    return compType;
  }
  
  /// Diagnose invalid arithmetic on two void pointers.
  static void diagnoseArithmeticOnTwoVoidPointers(Sema &S, SourceLocation Loc,
                                                  Expr *LHSExpr, Expr *RHSExpr) {
    S.Diag(Loc, S.getLangOpts().CPlusPlus
                  ? diag::err_typecheck_pointer_arith_void_type
                  : diag::ext_gnu_void_ptr)
      << 1 /* two pointers */ << LHSExpr->getSourceRange()
                              << RHSExpr->getSourceRange();
  }
  
  /// Diagnose invalid arithmetic on a void pointer.
  static void diagnoseArithmeticOnVoidPointer(Sema &S, SourceLocation Loc,
                                              Expr *Pointer) {
    S.Diag(Loc, S.getLangOpts().CPlusPlus
                  ? diag::err_typecheck_pointer_arith_void_type
                  : diag::ext_gnu_void_ptr)
      << 0 /* one pointer */ << Pointer->getSourceRange();
  }
  
  /// Diagnose invalid arithmetic on a null pointer.
  ///
  /// If \p IsGNUIdiom is true, the operation is using the 'p = (i8*)nullptr + n'
  /// idiom, which we recognize as a GNU extension.
  ///
  static void diagnoseArithmeticOnNullPointer(Sema &S, SourceLocation Loc,
                                              Expr *Pointer, bool IsGNUIdiom) {
    if (IsGNUIdiom)
      S.Diag(Loc, diag::warn_gnu_null_ptr_arith)
        << Pointer->getSourceRange();
    else
      S.Diag(Loc, diag::warn_pointer_arith_null_ptr)
        << S.getLangOpts().CPlusPlus << Pointer->getSourceRange();
  }
  
  /// Diagnose invalid subraction on a null pointer.
  ///
  static void diagnoseSubtractionOnNullPointer(Sema &S, SourceLocation Loc,
                                               Expr *Pointer, bool BothNull) {
    // Null - null is valid in C++ [expr.add]p7
    if (BothNull && S.getLangOpts().CPlusPlus)
      return;
  
    // Is this s a macro from a system header?
    if (S.Diags.getSuppressSystemWarnings() && S.SourceMgr.isInSystemMacro(Loc))
      return;
  
    S.Diag(Loc, diag::warn_pointer_sub_null_ptr)
        << S.getLangOpts().CPlusPlus << Pointer->getSourceRange();
  }
  
  /// Diagnose invalid arithmetic on two function pointers.
  static void diagnoseArithmeticOnTwoFunctionPointers(Sema &S, SourceLocation Loc,
                                                      Expr *LHS, Expr *RHS) {
    assert(LHS->getType()->isAnyPointerType());
    assert(RHS->getType()->isAnyPointerType());
    S.Diag(Loc, S.getLangOpts().CPlusPlus
                  ? diag::err_typecheck_pointer_arith_function_type
                  : diag::ext_gnu_ptr_func_arith)
      << 1 /* two pointers */ << LHS->getType()->getPointeeType()
      // We only show the second type if it differs from the first.
      << (unsigned)!S.Context.hasSameUnqualifiedType(LHS->getType(),
                                                     RHS->getType())
      << RHS->getType()->getPointeeType()
      << LHS->getSourceRange() << RHS->getSourceRange();
  }
  
  /// Diagnose invalid arithmetic on a function pointer.
  static void diagnoseArithmeticOnFunctionPointer(Sema &S, SourceLocation Loc,
                                                  Expr *Pointer) {
    assert(Pointer->getType()->isAnyPointerType());
    S.Diag(Loc, S.getLangOpts().CPlusPlus
                  ? diag::err_typecheck_pointer_arith_function_type
                  : diag::ext_gnu_ptr_func_arith)
      << 0 /* one pointer */ << Pointer->getType()->getPointeeType()
      << 0 /* one pointer, so only one type */
      << Pointer->getSourceRange();
  }
  
  /// Emit error if Operand is incomplete pointer type
  ///
  /// \returns True if pointer has incomplete type
  static bool checkArithmeticIncompletePointerType(Sema &S, SourceLocation Loc,
                                                   Expr *Operand) {
    QualType ResType = Operand->getType();
    if (const AtomicType *ResAtomicType = ResType->getAs<AtomicType>())
      ResType = ResAtomicType->getValueType();
  
    assert(ResType->isAnyPointerType() && !ResType->isDependentType());
    QualType PointeeTy = ResType->getPointeeType();
    return S.RequireCompleteSizedType(
        Loc, PointeeTy,
        diag::err_typecheck_arithmetic_incomplete_or_sizeless_type,
        Operand->getSourceRange());
  }
  
  /// Check the validity of an arithmetic pointer operand.
  ///
  /// If the operand has pointer type, this code will check for pointer types
  /// which are invalid in arithmetic operations. These will be diagnosed
  /// appropriately, including whether or not the use is supported as an
  /// extension.
  ///
  /// \returns True when the operand is valid to use (even if as an extension).
  static bool checkArithmeticOpPointerOperand(Sema &S, SourceLocation Loc,
                                              Expr *Operand) {
    QualType ResType = Operand->getType();
    if (const AtomicType *ResAtomicType = ResType->getAs<AtomicType>())
      ResType = ResAtomicType->getValueType();
  
    if (!ResType->isAnyPointerType()) return true;
  
    QualType PointeeTy = ResType->getPointeeType();
    if (PointeeTy->isVoidType()) {
      diagnoseArithmeticOnVoidPointer(S, Loc, Operand);
      return !S.getLangOpts().CPlusPlus;
    }
    if (PointeeTy->isFunctionType()) {
      diagnoseArithmeticOnFunctionPointer(S, Loc, Operand);
      return !S.getLangOpts().CPlusPlus;
    }
  
    if (checkArithmeticIncompletePointerType(S, Loc, Operand)) return false;
  
    return true;
  }
  
  /// Check the validity of a binary arithmetic operation w.r.t. pointer
  /// operands.
  ///
  /// This routine will diagnose any invalid arithmetic on pointer operands much
  /// like \see checkArithmeticOpPointerOperand. However, it has special logic
  /// for emitting a single diagnostic even for operations where both LHS and RHS
  /// are (potentially problematic) pointers.
  ///
  /// \returns True when the operand is valid to use (even if as an extension).
  static bool checkArithmeticBinOpPointerOperands(Sema &S, SourceLocation Loc,
                                                  Expr *LHSExpr, Expr *RHSExpr) {
    bool isLHSPointer = LHSExpr->getType()->isAnyPointerType();
    bool isRHSPointer = RHSExpr->getType()->isAnyPointerType();
    if (!isLHSPointer && !isRHSPointer) return true;
  
    QualType LHSPointeeTy, RHSPointeeTy;
    if (isLHSPointer) LHSPointeeTy = LHSExpr->getType()->getPointeeType();
    if (isRHSPointer) RHSPointeeTy = RHSExpr->getType()->getPointeeType();
  
    // if both are pointers check if operation is valid wrt address spaces
    if (isLHSPointer && isRHSPointer) {
      if (!LHSPointeeTy.isAddressSpaceOverlapping(RHSPointeeTy)) {
        S.Diag(Loc,
               diag::err_typecheck_op_on_nonoverlapping_address_space_pointers)
            << LHSExpr->getType() << RHSExpr->getType() << 1 /*arithmetic op*/
            << LHSExpr->getSourceRange() << RHSExpr->getSourceRange();
        return false;
      }
    }
  
    // Check for arithmetic on pointers to incomplete types.
    bool isLHSVoidPtr = isLHSPointer && LHSPointeeTy->isVoidType();
    bool isRHSVoidPtr = isRHSPointer && RHSPointeeTy->isVoidType();
    if (isLHSVoidPtr || isRHSVoidPtr) {
      if (!isRHSVoidPtr) diagnoseArithmeticOnVoidPointer(S, Loc, LHSExpr);
      else if (!isLHSVoidPtr) diagnoseArithmeticOnVoidPointer(S, Loc, RHSExpr);
      else diagnoseArithmeticOnTwoVoidPointers(S, Loc, LHSExpr, RHSExpr);
  
      return !S.getLangOpts().CPlusPlus;
    }
  
    bool isLHSFuncPtr = isLHSPointer && LHSPointeeTy->isFunctionType();
    bool isRHSFuncPtr = isRHSPointer && RHSPointeeTy->isFunctionType();
    if (isLHSFuncPtr || isRHSFuncPtr) {
      if (!isRHSFuncPtr) diagnoseArithmeticOnFunctionPointer(S, Loc, LHSExpr);
      else if (!isLHSFuncPtr) diagnoseArithmeticOnFunctionPointer(S, Loc,
                                                                  RHSExpr);
      else diagnoseArithmeticOnTwoFunctionPointers(S, Loc, LHSExpr, RHSExpr);
  
      return !S.getLangOpts().CPlusPlus;
    }
  
    if (isLHSPointer && checkArithmeticIncompletePointerType(S, Loc, LHSExpr))
      return false;
    if (isRHSPointer && checkArithmeticIncompletePointerType(S, Loc, RHSExpr))
      return false;
  
    return true;
  }
  
  /// diagnoseStringPlusInt - Emit a warning when adding an integer to a string
  /// literal.
  static void diagnoseStringPlusInt(Sema &Self, SourceLocation OpLoc,
                                    Expr *LHSExpr, Expr *RHSExpr) {
    StringLiteral* StrExpr = dyn_cast<StringLiteral>(LHSExpr->IgnoreImpCasts());
    Expr* IndexExpr = RHSExpr;
    if (!StrExpr) {
      StrExpr = dyn_cast<StringLiteral>(RHSExpr->IgnoreImpCasts());
      IndexExpr = LHSExpr;
    }
  
    bool IsStringPlusInt = StrExpr &&
        IndexExpr->getType()->isIntegralOrUnscopedEnumerationType();
    if (!IsStringPlusInt || IndexExpr->isValueDependent())
      return;
  
    SourceRange DiagRange(LHSExpr->getBeginLoc(), RHSExpr->getEndLoc());
    Self.Diag(OpLoc, diag::warn_string_plus_int)
        << DiagRange << IndexExpr->IgnoreImpCasts()->getType();
  
    // Only print a fixit for "str" + int, not for int + "str".
    if (IndexExpr == RHSExpr) {
      SourceLocation EndLoc = Self.getLocForEndOfToken(RHSExpr->getEndLoc());
      Self.Diag(OpLoc, diag::note_string_plus_scalar_silence)
          << FixItHint::CreateInsertion(LHSExpr->getBeginLoc(), "&")
          << FixItHint::CreateReplacement(SourceRange(OpLoc), "[")
          << FixItHint::CreateInsertion(EndLoc, "]");
    } else
      Self.Diag(OpLoc, diag::note_string_plus_scalar_silence);
  }
  
  /// Emit a warning when adding a char literal to a string.
  static void diagnoseStringPlusChar(Sema &Self, SourceLocation OpLoc,
                                     Expr *LHSExpr, Expr *RHSExpr) {
    const Expr *StringRefExpr = LHSExpr;
    const CharacterLiteral *CharExpr =
        dyn_cast<CharacterLiteral>(RHSExpr->IgnoreImpCasts());
  
    if (!CharExpr) {
      CharExpr = dyn_cast<CharacterLiteral>(LHSExpr->IgnoreImpCasts());
      StringRefExpr = RHSExpr;
    }
  
    if (!CharExpr || !StringRefExpr)
      return;
  
    const QualType StringType = StringRefExpr->getType();
  
    // Return if not a PointerType.
    if (!StringType->isAnyPointerType())
      return;
  
    // Return if not a CharacterType.
    if (!StringType->getPointeeType()->isAnyCharacterType())
      return;
  
    ASTContext &Ctx = Self.getASTContext();
    SourceRange DiagRange(LHSExpr->getBeginLoc(), RHSExpr->getEndLoc());
  
    const QualType CharType = CharExpr->getType();
    if (!CharType->isAnyCharacterType() &&
        CharType->isIntegerType() &&
        llvm::isUIntN(Ctx.getCharWidth(), CharExpr->getValue())) {
      Self.Diag(OpLoc, diag::warn_string_plus_char)
          << DiagRange << Ctx.CharTy;
    } else {
      Self.Diag(OpLoc, diag::warn_string_plus_char)
          << DiagRange << CharExpr->getType();
    }
  
    // Only print a fixit for str + char, not for char + str.
    if (isa<CharacterLiteral>(RHSExpr->IgnoreImpCasts())) {
      SourceLocation EndLoc = Self.getLocForEndOfToken(RHSExpr->getEndLoc());
      Self.Diag(OpLoc, diag::note_string_plus_scalar_silence)
          << FixItHint::CreateInsertion(LHSExpr->getBeginLoc(), "&")
          << FixItHint::CreateReplacement(SourceRange(OpLoc), "[")
          << FixItHint::CreateInsertion(EndLoc, "]");
    } else {
      Self.Diag(OpLoc, diag::note_string_plus_scalar_silence);
    }
  }
  
  /// Emit error when two pointers are incompatible.
  static void diagnosePointerIncompatibility(Sema &S, SourceLocation Loc,
                                             Expr *LHSExpr, Expr *RHSExpr) {
    assert(LHSExpr->getType()->isAnyPointerType());
    assert(RHSExpr->getType()->isAnyPointerType());
    S.Diag(Loc, diag::err_typecheck_sub_ptr_compatible)
      << LHSExpr->getType() << RHSExpr->getType() << LHSExpr->getSourceRange()
      << RHSExpr->getSourceRange();
  }
  
  // C99 6.5.6
  QualType Sema::CheckAdditionOperands(ExprResult &LHS, ExprResult &RHS,
                                       SourceLocation Loc, BinaryOperatorKind Opc,
                                       QualType* CompLHSTy) {
    checkArithmeticNull(*this, LHS, RHS, Loc, /*IsCompare=*/false);
  
    if (LHS.get()->getType()->isVectorType() ||
        RHS.get()->getType()->isVectorType()) {
      QualType compType = CheckVectorOperands(
          LHS, RHS, Loc, CompLHSTy,
          /*AllowBothBool*/getLangOpts().AltiVec,
          /*AllowBoolConversions*/getLangOpts().ZVector);
      if (CompLHSTy) *CompLHSTy = compType;
      return compType;
    }
  
    if (LHS.get()->getType()->isVLSTBuiltinType() ||
        RHS.get()->getType()->isVLSTBuiltinType()) {
      QualType compType = CheckSizelessVectorOperands(LHS, RHS, Loc);
      if (CompLHSTy)
        *CompLHSTy = compType;
      return compType;
    }
  
    if (LHS.get()->getType()->isConstantMatrixType() ||
        RHS.get()->getType()->isConstantMatrixType()) {
      QualType compType =
          CheckMatrixElementwiseOperands(LHS, RHS, Loc, CompLHSTy);
      if (CompLHSTy)
        *CompLHSTy = compType;
      return compType;
    }
  
    QualType compType = UsualArithmeticConversions(
        LHS, RHS, Loc, CompLHSTy ? ACK_CompAssign : ACK_Arithmetic);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
  
    // Diagnose "string literal" '+' int and string '+' "char literal".
    if (Opc == BO_Add) {
      diagnoseStringPlusInt(*this, Loc, LHS.get(), RHS.get());
      diagnoseStringPlusChar(*this, Loc, LHS.get(), RHS.get());
    }
  
    // handle the common case first (both operands are arithmetic).
    if (!compType.isNull() && compType->isArithmeticType()) {
      if (CompLHSTy) *CompLHSTy = compType;
      return compType;
    }
  
    // Type-checking.  Ultimately the pointer's going to be in PExp;
    // note that we bias towards the LHS being the pointer.
    Expr *PExp = LHS.get(), *IExp = RHS.get();
  
    bool isObjCPointer;
    if (PExp->getType()->isPointerType()) {
      isObjCPointer = false;
    } else if (PExp->getType()->isObjCObjectPointerType()) {
      isObjCPointer = true;
    } else {
      std::swap(PExp, IExp);
      if (PExp->getType()->isPointerType()) {
        isObjCPointer = false;
      } else if (PExp->getType()->isObjCObjectPointerType()) {
        isObjCPointer = true;
      } else {
        return InvalidOperands(Loc, LHS, RHS);
      }
    }
    assert(PExp->getType()->isAnyPointerType());
  
    if (!IExp->getType()->isIntegerType())
      return InvalidOperands(Loc, LHS, RHS);
  
    // Adding to a null pointer results in undefined behavior.
    if (PExp->IgnoreParenCasts()->isNullPointerConstant(
            Context, Expr::NPC_ValueDependentIsNotNull)) {
      // In C++ adding zero to a null pointer is defined.
      Expr::EvalResult KnownVal;
      if (!getLangOpts().CPlusPlus ||
          (!IExp->isValueDependent() &&
           (!IExp->EvaluateAsInt(KnownVal, Context) ||
            KnownVal.Val.getInt() != 0))) {
        // Check the conditions to see if this is the 'p = nullptr + n' idiom.
        bool IsGNUIdiom = BinaryOperator::isNullPointerArithmeticExtension(
            Context, BO_Add, PExp, IExp);
        diagnoseArithmeticOnNullPointer(*this, Loc, PExp, IsGNUIdiom);
      }
    }
  
    if (!checkArithmeticOpPointerOperand(*this, Loc, PExp))
      return QualType();
  
    if (isObjCPointer && checkArithmeticOnObjCPointer(*this, Loc, PExp))
      return QualType();
  
    // Check array bounds for pointer arithemtic
    CheckArrayAccess(PExp, IExp);
  
    if (CompLHSTy) {
      QualType LHSTy = Context.isPromotableBitField(LHS.get());
      if (LHSTy.isNull()) {
        LHSTy = LHS.get()->getType();
        if (LHSTy->isPromotableIntegerType())
          LHSTy = Context.getPromotedIntegerType(LHSTy);
      }
      *CompLHSTy = LHSTy;
    }
  
    return PExp->getType();
  }
  
  // C99 6.5.6
  QualType Sema::CheckSubtractionOperands(ExprResult &LHS, ExprResult &RHS,
                                          SourceLocation Loc,
                                          QualType* CompLHSTy) {
    checkArithmeticNull(*this, LHS, RHS, Loc, /*IsCompare=*/false);
  
    if (LHS.get()->getType()->isVectorType() ||
        RHS.get()->getType()->isVectorType()) {
      QualType compType = CheckVectorOperands(
          LHS, RHS, Loc, CompLHSTy,
          /*AllowBothBool*/getLangOpts().AltiVec,
          /*AllowBoolConversions*/getLangOpts().ZVector);
      if (CompLHSTy) *CompLHSTy = compType;
      return compType;
    }
  
    if (LHS.get()->getType()->isVLSTBuiltinType() ||
        RHS.get()->getType()->isVLSTBuiltinType()) {
      QualType compType = CheckSizelessVectorOperands(LHS, RHS, Loc);
      if (CompLHSTy)
        *CompLHSTy = compType;
      return compType;
    }
  
    if (LHS.get()->getType()->isConstantMatrixType() ||
        RHS.get()->getType()->isConstantMatrixType()) {
      QualType compType =
          CheckMatrixElementwiseOperands(LHS, RHS, Loc, CompLHSTy);
      if (CompLHSTy)
        *CompLHSTy = compType;
      return compType;
    }
  
    QualType compType = UsualArithmeticConversions(
        LHS, RHS, Loc, CompLHSTy ? ACK_CompAssign : ACK_Arithmetic);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
  
    // Enforce type constraints: C99 6.5.6p3.
  
    // Handle the common case first (both operands are arithmetic).
    if (!compType.isNull() && compType->isArithmeticType()) {
      if (CompLHSTy) *CompLHSTy = compType;
      return compType;
    }
  
    // Either ptr - int   or   ptr - ptr.
    if (LHS.get()->getType()->isAnyPointerType()) {
      QualType lpointee = LHS.get()->getType()->getPointeeType();
  
      // Diagnose bad cases where we step over interface counts.
      if (LHS.get()->getType()->isObjCObjectPointerType() &&
          checkArithmeticOnObjCPointer(*this, Loc, LHS.get()))
        return QualType();
  
      // The result type of a pointer-int computation is the pointer type.
      if (RHS.get()->getType()->isIntegerType()) {
        // Subtracting from a null pointer should produce a warning.
        // The last argument to the diagnose call says this doesn't match the
        // GNU int-to-pointer idiom.
        if (LHS.get()->IgnoreParenCasts()->isNullPointerConstant(Context,
                                             Expr::NPC_ValueDependentIsNotNull)) {
          // In C++ adding zero to a null pointer is defined.
          Expr::EvalResult KnownVal;
          if (!getLangOpts().CPlusPlus ||
              (!RHS.get()->isValueDependent() &&
               (!RHS.get()->EvaluateAsInt(KnownVal, Context) ||
                KnownVal.Val.getInt() != 0))) {
            diagnoseArithmeticOnNullPointer(*this, Loc, LHS.get(), false);
          }
        }
  
        if (!checkArithmeticOpPointerOperand(*this, Loc, LHS.get()))
          return QualType();
  
        // Check array bounds for pointer arithemtic
        CheckArrayAccess(LHS.get(), RHS.get(), /*ArraySubscriptExpr*/nullptr,
                         /*AllowOnePastEnd*/true, /*IndexNegated*/true);
  
        if (CompLHSTy) *CompLHSTy = LHS.get()->getType();
        return LHS.get()->getType();
      }
  
      // Handle pointer-pointer subtractions.
      if (const PointerType *RHSPTy
            = RHS.get()->getType()->getAs<PointerType>()) {
        QualType rpointee = RHSPTy->getPointeeType();
  
        if (getLangOpts().CPlusPlus) {
          // Pointee types must be the same: C++ [expr.add]
          if (!Context.hasSameUnqualifiedType(lpointee, rpointee)) {
            diagnosePointerIncompatibility(*this, Loc, LHS.get(), RHS.get());
          }
        } else {
          // Pointee types must be compatible C99 6.5.6p3
          if (!Context.typesAreCompatible(
                  Context.getCanonicalType(lpointee).getUnqualifiedType(),
                  Context.getCanonicalType(rpointee).getUnqualifiedType())) {
            diagnosePointerIncompatibility(*this, Loc, LHS.get(), RHS.get());
            return QualType();
          }
        }
  
        if (!checkArithmeticBinOpPointerOperands(*this, Loc,
                                                 LHS.get(), RHS.get()))
          return QualType();
  
        bool LHSIsNullPtr = LHS.get()->IgnoreParenCasts()->isNullPointerConstant(
            Context, Expr::NPC_ValueDependentIsNotNull);
        bool RHSIsNullPtr = RHS.get()->IgnoreParenCasts()->isNullPointerConstant(
            Context, Expr::NPC_ValueDependentIsNotNull);
  
        // Subtracting nullptr or from nullptr is suspect
        if (LHSIsNullPtr)
          diagnoseSubtractionOnNullPointer(*this, Loc, LHS.get(), RHSIsNullPtr);
        if (RHSIsNullPtr)
          diagnoseSubtractionOnNullPointer(*this, Loc, RHS.get(), LHSIsNullPtr);
  
        // The pointee type may have zero size.  As an extension, a structure or
        // union may have zero size or an array may have zero length.  In this
        // case subtraction does not make sense.
        if (!rpointee->isVoidType() && !rpointee->isFunctionType()) {
          CharUnits ElementSize = Context.getTypeSizeInChars(rpointee);
          if (ElementSize.isZero()) {
            Diag(Loc,diag::warn_sub_ptr_zero_size_types)
              << rpointee.getUnqualifiedType()
              << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
          }
        }
  
        if (CompLHSTy) *CompLHSTy = LHS.get()->getType();
        return Context.getPointerDiffType();
      }
    }
  
    return InvalidOperands(Loc, LHS, RHS);
  }
  
  static bool isScopedEnumerationType(QualType T) {
    if (const EnumType *ET = T->getAs<EnumType>())
      return ET->getDecl()->isScoped();
    return false;
  }
  
  static void DiagnoseBadShiftValues(Sema& S, ExprResult &LHS, ExprResult &RHS,
                                     SourceLocation Loc, BinaryOperatorKind Opc,
                                     QualType LHSType) {
    // OpenCL 6.3j: shift values are effectively % word size of LHS (more defined),
    // so skip remaining warnings as we don't want to modify values within Sema.
    if (S.getLangOpts().OpenCL)
      return;
  
    // Check right/shifter operand
    Expr::EvalResult RHSResult;
    if (RHS.get()->isValueDependent() ||
        !RHS.get()->EvaluateAsInt(RHSResult, S.Context))
      return;
    llvm::APSInt Right = RHSResult.Val.getInt();
  
    if (Right.isNegative()) {
      S.DiagRuntimeBehavior(Loc, RHS.get(),
                            S.PDiag(diag::warn_shift_negative)
                              << RHS.get()->getSourceRange());
      return;
    }
  
    QualType LHSExprType = LHS.get()->getType();
    uint64_t LeftSize = S.Context.getTypeSize(LHSExprType);
    if (LHSExprType->isBitIntType())
      LeftSize = S.Context.getIntWidth(LHSExprType);
    else if (LHSExprType->isFixedPointType()) {
      auto FXSema = S.Context.getFixedPointSemantics(LHSExprType);
      LeftSize = FXSema.getWidth() - (unsigned)FXSema.hasUnsignedPadding();
    }
    llvm::APInt LeftBits(Right.getBitWidth(), LeftSize);
    if (Right.uge(LeftBits)) {
      S.DiagRuntimeBehavior(Loc, RHS.get(),
                            S.PDiag(diag::warn_shift_gt_typewidth)
                              << RHS.get()->getSourceRange());
      return;
    }
  
    // FIXME: We probably need to handle fixed point types specially here.
    if (Opc != BO_Shl || LHSExprType->isFixedPointType())
      return;
  
    // When left shifting an ICE which is signed, we can check for overflow which
    // according to C++ standards prior to C++2a has undefined behavior
    // ([expr.shift] 5.8/2). Unsigned integers have defined behavior modulo one
    // more than the maximum value representable in the result type, so never
    // warn for those. (FIXME: Unsigned left-shift overflow in a constant
    // expression is still probably a bug.)
    Expr::EvalResult LHSResult;
    if (LHS.get()->isValueDependent() ||
        LHSType->hasUnsignedIntegerRepresentation() ||
        !LHS.get()->EvaluateAsInt(LHSResult, S.Context))
      return;
    llvm::APSInt Left = LHSResult.Val.getInt();
  
    // If LHS does not have a signed type and non-negative value
    // then, the behavior is undefined before C++2a. Warn about it.
    if (Left.isNegative() && !S.getLangOpts().isSignedOverflowDefined() &&
        !S.getLangOpts().CPlusPlus20) {
      S.DiagRuntimeBehavior(Loc, LHS.get(),
                            S.PDiag(diag::warn_shift_lhs_negative)
                              << LHS.get()->getSourceRange());
      return;
    }
  
    llvm::APInt ResultBits =
        static_cast<llvm::APInt&>(Right) + Left.getMinSignedBits();
    if (LeftBits.uge(ResultBits))
      return;
    llvm::APSInt Result = Left.extend(ResultBits.getLimitedValue());
    Result = Result.shl(Right);
  
    // Print the bit representation of the signed integer as an unsigned
    // hexadecimal number.
    SmallString<40> HexResult;
    Result.toString(HexResult, 16, /*Signed =*/false, /*Literal =*/true);
  
    // If we are only missing a sign bit, this is less likely to result in actual
    // bugs -- if the result is cast back to an unsigned type, it will have the
    // expected value. Thus we place this behind a different warning that can be
    // turned off separately if needed.
    if (LeftBits == ResultBits - 1) {
      S.Diag(Loc, diag::warn_shift_result_sets_sign_bit)
          << HexResult << LHSType
          << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
      return;
    }
  
    S.Diag(Loc, diag::warn_shift_result_gt_typewidth)
      << HexResult.str() << Result.getMinSignedBits() << LHSType
      << Left.getBitWidth() << LHS.get()->getSourceRange()
      << RHS.get()->getSourceRange();
  }
  
  /// Return the resulting type when a vector is shifted
  ///        by a scalar or vector shift amount.
  static QualType checkVectorShift(Sema &S, ExprResult &LHS, ExprResult &RHS,
                                   SourceLocation Loc, bool IsCompAssign) {
    // OpenCL v1.1 s6.3.j says RHS can be a vector only if LHS is a vector.
    if ((S.LangOpts.OpenCL || S.LangOpts.ZVector) &&
        !LHS.get()->getType()->isVectorType()) {
      S.Diag(Loc, diag::err_shift_rhs_only_vector)
        << RHS.get()->getType() << LHS.get()->getType()
        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
      return QualType();
    }
  
    if (!IsCompAssign) {
      LHS = S.UsualUnaryConversions(LHS.get());
      if (LHS.isInvalid()) return QualType();
    }
  
    RHS = S.UsualUnaryConversions(RHS.get());
    if (RHS.isInvalid()) return QualType();
  
    QualType LHSType = LHS.get()->getType();
    // Note that LHS might be a scalar because the routine calls not only in
    // OpenCL case.
    const VectorType *LHSVecTy = LHSType->getAs<VectorType>();
    QualType LHSEleType = LHSVecTy ? LHSVecTy->getElementType() : LHSType;
  
    // Note that RHS might not be a vector.
    QualType RHSType = RHS.get()->getType();
    const VectorType *RHSVecTy = RHSType->getAs<VectorType>();
    QualType RHSEleType = RHSVecTy ? RHSVecTy->getElementType() : RHSType;
  
    // The operands need to be integers.
    if (!LHSEleType->isIntegerType()) {
      S.Diag(Loc, diag::err_typecheck_expect_int)
        << LHS.get()->getType() << LHS.get()->getSourceRange();
      return QualType();
    }
  
    if (!RHSEleType->isIntegerType()) {
      S.Diag(Loc, diag::err_typecheck_expect_int)
        << RHS.get()->getType() << RHS.get()->getSourceRange();
      return QualType();
    }
  
    if (!LHSVecTy) {
      assert(RHSVecTy);
      if (IsCompAssign)
        return RHSType;
      if (LHSEleType != RHSEleType) {
        LHS = S.ImpCastExprToType(LHS.get(),RHSEleType, CK_IntegralCast);
        LHSEleType = RHSEleType;
      }
      QualType VecTy =
          S.Context.getExtVectorType(LHSEleType, RHSVecTy->getNumElements());
      LHS = S.ImpCastExprToType(LHS.get(), VecTy, CK_VectorSplat);
      LHSType = VecTy;
    } else if (RHSVecTy) {
      // OpenCL v1.1 s6.3.j says that for vector types, the operators
      // are applied component-wise. So if RHS is a vector, then ensure
      // that the number of elements is the same as LHS...
      if (RHSVecTy->getNumElements() != LHSVecTy->getNumElements()) {
        S.Diag(Loc, diag::err_typecheck_vector_lengths_not_equal)
          << LHS.get()->getType() << RHS.get()->getType()
          << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
        return QualType();
      }
      if (!S.LangOpts.OpenCL && !S.LangOpts.ZVector) {
        const BuiltinType *LHSBT = LHSEleType->getAs<clang::BuiltinType>();
        const BuiltinType *RHSBT = RHSEleType->getAs<clang::BuiltinType>();
        if (LHSBT != RHSBT &&
            S.Context.getTypeSize(LHSBT) != S.Context.getTypeSize(RHSBT)) {
          S.Diag(Loc, diag::warn_typecheck_vector_element_sizes_not_equal)
              << LHS.get()->getType() << RHS.get()->getType()
              << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
        }
      }
    } else {
      // ...else expand RHS to match the number of elements in LHS.
      QualType VecTy =
        S.Context.getExtVectorType(RHSEleType, LHSVecTy->getNumElements());
      RHS = S.ImpCastExprToType(RHS.get(), VecTy, CK_VectorSplat);
    }
  
    return LHSType;
  }
  
  // C99 6.5.7
  QualType Sema::CheckShiftOperands(ExprResult &LHS, ExprResult &RHS,
                                    SourceLocation Loc, BinaryOperatorKind Opc,
                                    bool IsCompAssign) {
    checkArithmeticNull(*this, LHS, RHS, Loc, /*IsCompare=*/false);
  
    // Vector shifts promote their scalar inputs to vector type.
    if (LHS.get()->getType()->isVectorType() ||
        RHS.get()->getType()->isVectorType()) {
      if (LangOpts.ZVector) {
        // The shift operators for the z vector extensions work basically
        // like general shifts, except that neither the LHS nor the RHS is
        // allowed to be a "vector bool".
        if (auto LHSVecType = LHS.get()->getType()->getAs<VectorType>())
          if (LHSVecType->getVectorKind() == VectorType::AltiVecBool)
            return InvalidOperands(Loc, LHS, RHS);
        if (auto RHSVecType = RHS.get()->getType()->getAs<VectorType>())
          if (RHSVecType->getVectorKind() == VectorType::AltiVecBool)
            return InvalidOperands(Loc, LHS, RHS);
      }
      return checkVectorShift(*this, LHS, RHS, Loc, IsCompAssign);
    }
  
    // Shifts don't perform usual arithmetic conversions, they just do integer
    // promotions on each operand. C99 6.5.7p3
  
    // For the LHS, do usual unary conversions, but then reset them away
    // if this is a compound assignment.
    ExprResult OldLHS = LHS;
    LHS = UsualUnaryConversions(LHS.get());
    if (LHS.isInvalid())
      return QualType();
    QualType LHSType = LHS.get()->getType();
    if (IsCompAssign) LHS = OldLHS;
  
    // The RHS is simpler.
    RHS = UsualUnaryConversions(RHS.get());
    if (RHS.isInvalid())
      return QualType();
    QualType RHSType = RHS.get()->getType();
  
    // C99 6.5.7p2: Each of the operands shall have integer type.
    // Embedded-C 4.1.6.2.2: The LHS may also be fixed-point.
    if ((!LHSType->isFixedPointOrIntegerType() &&
         !LHSType->hasIntegerRepresentation()) ||
        !RHSType->hasIntegerRepresentation())
      return InvalidOperands(Loc, LHS, RHS);
  
    // C++0x: Don't allow scoped enums. FIXME: Use something better than
    // hasIntegerRepresentation() above instead of this.
    if (isScopedEnumerationType(LHSType) ||
        isScopedEnumerationType(RHSType)) {
      return InvalidOperands(Loc, LHS, RHS);
    }
    DiagnoseBadShiftValues(*this, LHS, RHS, Loc, Opc, LHSType);
  
    // "The type of the result is that of the promoted left operand."
    return LHSType;
  }
  
  /// Diagnose bad pointer comparisons.
  static void diagnoseDistinctPointerComparison(Sema &S, SourceLocation Loc,
                                                ExprResult &LHS, ExprResult &RHS,
                                                bool IsError) {
    S.Diag(Loc, IsError ? diag::err_typecheck_comparison_of_distinct_pointers
                        : diag::ext_typecheck_comparison_of_distinct_pointers)
      << LHS.get()->getType() << RHS.get()->getType()
      << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
  }
  
  /// Returns false if the pointers are converted to a composite type,
  /// true otherwise.
  static bool convertPointersToCompositeType(Sema &S, SourceLocation Loc,
                                             ExprResult &LHS, ExprResult &RHS) {
    // C++ [expr.rel]p2:
    //   [...] Pointer conversions (4.10) and qualification
    //   conversions (4.4) are performed on pointer operands (or on
    //   a pointer operand and a null pointer constant) to bring
    //   them to their composite pointer type. [...]
    //
    // C++ [expr.eq]p1 uses the same notion for (in)equality
    // comparisons of pointers.
  
    QualType LHSType = LHS.get()->getType();
    QualType RHSType = RHS.get()->getType();
    assert(LHSType->isPointerType() || RHSType->isPointerType() ||
           LHSType->isMemberPointerType() || RHSType->isMemberPointerType());
  
    QualType T = S.FindCompositePointerType(Loc, LHS, RHS);
    if (T.isNull()) {
      if ((LHSType->isAnyPointerType() || LHSType->isMemberPointerType()) &&
          (RHSType->isAnyPointerType() || RHSType->isMemberPointerType()))
        diagnoseDistinctPointerComparison(S, Loc, LHS, RHS, /*isError*/true);
      else
        S.InvalidOperands(Loc, LHS, RHS);
      return true;
    }
  
    return false;
  }
  
  static void diagnoseFunctionPointerToVoidComparison(Sema &S, SourceLocation Loc,
                                                      ExprResult &LHS,
                                                      ExprResult &RHS,
                                                      bool IsError) {
    S.Diag(Loc, IsError ? diag::err_typecheck_comparison_of_fptr_to_void
                        : diag::ext_typecheck_comparison_of_fptr_to_void)
      << LHS.get()->getType() << RHS.get()->getType()
      << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
  }
  
  static bool isObjCObjectLiteral(ExprResult &E) {
    switch (E.get()->IgnoreParenImpCasts()->getStmtClass()) {
    case Stmt::ObjCArrayLiteralClass:
    case Stmt::ObjCDictionaryLiteralClass:
    case Stmt::ObjCStringLiteralClass:
    case Stmt::ObjCBoxedExprClass:
      return true;
    default:
      // Note that ObjCBoolLiteral is NOT an object literal!
      return false;
    }
  }
  
  static bool hasIsEqualMethod(Sema &S, const Expr *LHS, const Expr *RHS) {
    const ObjCObjectPointerType *Type =
      LHS->getType()->getAs<ObjCObjectPointerType>();
  
    // If this is not actually an Objective-C object, bail out.
    if (!Type)
      return false;
  
    // Get the LHS object's interface type.
    QualType InterfaceType = Type->getPointeeType();
  
    // If the RHS isn't an Objective-C object, bail out.
    if (!RHS->getType()->isObjCObjectPointerType())
      return false;
  
    // Try to find the -isEqual: method.
    Selector IsEqualSel = S.NSAPIObj->getIsEqualSelector();
    ObjCMethodDecl *Method = S.LookupMethodInObjectType(IsEqualSel,
                                                        InterfaceType,
                                                        /*IsInstance=*/true);
    if (!Method) {
      if (Type->isObjCIdType()) {
        // For 'id', just check the global pool.
        Method = S.LookupInstanceMethodInGlobalPool(IsEqualSel, SourceRange(),
                                                    /*receiverId=*/true);
      } else {
        // Check protocols.
        Method = S.LookupMethodInQualifiedType(IsEqualSel, Type,
                                               /*IsInstance=*/true);
      }
    }
  
    if (!Method)
      return false;
  
    QualType T = Method->parameters()[0]->getType();
    if (!T->isObjCObjectPointerType())
      return false;
  
    QualType R = Method->getReturnType();
    if (!R->isScalarType())
      return false;
  
    return true;
  }
  
  Sema::ObjCLiteralKind Sema::CheckLiteralKind(Expr *FromE) {
    FromE = FromE->IgnoreParenImpCasts();
    switch (FromE->getStmtClass()) {
      default:
        break;
      case Stmt::ObjCStringLiteralClass:
        // "string literal"
        return LK_String;
      case Stmt::ObjCArrayLiteralClass:
        // "array literal"
        return LK_Array;
      case Stmt::ObjCDictionaryLiteralClass:
        // "dictionary literal"
        return LK_Dictionary;
      case Stmt::BlockExprClass:
        return LK_Block;
      case Stmt::ObjCBoxedExprClass: {
        Expr *Inner = cast<ObjCBoxedExpr>(FromE)->getSubExpr()->IgnoreParens();
        switch (Inner->getStmtClass()) {
          case Stmt::IntegerLiteralClass:
          case Stmt::FloatingLiteralClass:
          case Stmt::CharacterLiteralClass:
          case Stmt::ObjCBoolLiteralExprClass:
          case Stmt::CXXBoolLiteralExprClass:
            // "numeric literal"
            return LK_Numeric;
          case Stmt::ImplicitCastExprClass: {
            CastKind CK = cast<CastExpr>(Inner)->getCastKind();
            // Boolean literals can be represented by implicit casts.
            if (CK == CK_IntegralToBoolean || CK == CK_IntegralCast)
              return LK_Numeric;
            break;
          }
          default:
            break;
        }
        return LK_Boxed;
      }
    }
    return LK_None;
  }
  
  static void diagnoseObjCLiteralComparison(Sema &S, SourceLocation Loc,
                                            ExprResult &LHS, ExprResult &RHS,
                                            BinaryOperator::Opcode Opc){
    Expr *Literal;
    Expr *Other;
    if (isObjCObjectLiteral(LHS)) {
      Literal = LHS.get();
      Other = RHS.get();
    } else {
      Literal = RHS.get();
      Other = LHS.get();
    }
  
    // Don't warn on comparisons against nil.
    Other = Other->IgnoreParenCasts();
    if (Other->isNullPointerConstant(S.getASTContext(),
                                     Expr::NPC_ValueDependentIsNotNull))
      return;
  
    // This should be kept in sync with warn_objc_literal_comparison.
    // LK_String should always be after the other literals, since it has its own
    // warning flag.
    Sema::ObjCLiteralKind LiteralKind = S.CheckLiteralKind(Literal);
    assert(LiteralKind != Sema::LK_Block);
    if (LiteralKind == Sema::LK_None) {
      llvm_unreachable("Unknown Objective-C object literal kind");
    }
  
    if (LiteralKind == Sema::LK_String)
      S.Diag(Loc, diag::warn_objc_string_literal_comparison)
        << Literal->getSourceRange();
    else
      S.Diag(Loc, diag::warn_objc_literal_comparison)
        << LiteralKind << Literal->getSourceRange();
  
    if (BinaryOperator::isEqualityOp(Opc) &&
        hasIsEqualMethod(S, LHS.get(), RHS.get())) {
      SourceLocation Start = LHS.get()->getBeginLoc();
      SourceLocation End = S.getLocForEndOfToken(RHS.get()->getEndLoc());
      CharSourceRange OpRange =
        CharSourceRange::getCharRange(Loc, S.getLocForEndOfToken(Loc));
  
      S.Diag(Loc, diag::note_objc_literal_comparison_isequal)
        << FixItHint::CreateInsertion(Start, Opc == BO_EQ ? "[" : "![")
        << FixItHint::CreateReplacement(OpRange, " isEqual:")
        << FixItHint::CreateInsertion(End, "]");
    }
  }
  
  /// Warns on !x < y, !x & y where !(x < y), !(x & y) was probably intended.
  static void diagnoseLogicalNotOnLHSofCheck(Sema &S, ExprResult &LHS,
                                             ExprResult &RHS, SourceLocation Loc,
                                             BinaryOperatorKind Opc) {
    // Check that left hand side is !something.
    UnaryOperator *UO = dyn_cast<UnaryOperator>(LHS.get()->IgnoreImpCasts());
    if (!UO || UO->getOpcode() != UO_LNot) return;
  
    // Only check if the right hand side is non-bool arithmetic type.
    if (RHS.get()->isKnownToHaveBooleanValue()) return;
  
    // Make sure that the something in !something is not bool.
    Expr *SubExpr = UO->getSubExpr()->IgnoreImpCasts();
    if (SubExpr->isKnownToHaveBooleanValue()) return;
  
    // Emit warning.
    bool IsBitwiseOp = Opc == BO_And || Opc == BO_Or || Opc == BO_Xor;
    S.Diag(UO->getOperatorLoc(), diag::warn_logical_not_on_lhs_of_check)
        << Loc << IsBitwiseOp;
  
    // First note suggest !(x < y)
    SourceLocation FirstOpen = SubExpr->getBeginLoc();
    SourceLocation FirstClose = RHS.get()->getEndLoc();
    FirstClose = S.getLocForEndOfToken(FirstClose);
    if (FirstClose.isInvalid())
      FirstOpen = SourceLocation();
    S.Diag(UO->getOperatorLoc(), diag::note_logical_not_fix)
        << IsBitwiseOp
        << FixItHint::CreateInsertion(FirstOpen, "(")
        << FixItHint::CreateInsertion(FirstClose, ")");
  
    // Second note suggests (!x) < y
    SourceLocation SecondOpen = LHS.get()->getBeginLoc();
    SourceLocation SecondClose = LHS.get()->getEndLoc();
    SecondClose = S.getLocForEndOfToken(SecondClose);
    if (SecondClose.isInvalid())
      SecondOpen = SourceLocation();
    S.Diag(UO->getOperatorLoc(), diag::note_logical_not_silence_with_parens)
        << FixItHint::CreateInsertion(SecondOpen, "(")
        << FixItHint::CreateInsertion(SecondClose, ")");
  }
  
  // Returns true if E refers to a non-weak array.
  static bool checkForArray(const Expr *E) {
    const ValueDecl *D = nullptr;
    if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(E)) {
      D = DR->getDecl();
    } else if (const MemberExpr *Mem = dyn_cast<MemberExpr>(E)) {
      if (Mem->isImplicitAccess())
        D = Mem->getMemberDecl();
    }
    if (!D)
      return false;
    return D->getType()->isArrayType() && !D->isWeak();
  }
  
  /// Diagnose some forms of syntactically-obvious tautological comparison.
  static void diagnoseTautologicalComparison(Sema &S, SourceLocation Loc,
                                             Expr *LHS, Expr *RHS,
                                             BinaryOperatorKind Opc) {
    Expr *LHSStripped = LHS->IgnoreParenImpCasts();
    Expr *RHSStripped = RHS->IgnoreParenImpCasts();
  
    QualType LHSType = LHS->getType();
    QualType RHSType = RHS->getType();
    if (LHSType->hasFloatingRepresentation() ||
        (LHSType->isBlockPointerType() && !BinaryOperator::isEqualityOp(Opc)) ||
        S.inTemplateInstantiation())
      return;
  
    // Comparisons between two array types are ill-formed for operator<=>, so
    // we shouldn't emit any additional warnings about it.
    if (Opc == BO_Cmp && LHSType->isArrayType() && RHSType->isArrayType())
      return;
  
    // For non-floating point types, check for self-comparisons of the form
    // x == x, x != x, x < x, etc.  These always evaluate to a constant, and
    // often indicate logic errors in the program.
    //
    // NOTE: Don't warn about comparison expressions resulting from macro
    // expansion. Also don't warn about comparisons which are only self
    // comparisons within a template instantiation. The warnings should catch
    // obvious cases in the definition of the template anyways. The idea is to
    // warn when the typed comparison operator will always evaluate to the same
    // result.
  
    // Used for indexing into %select in warn_comparison_always
    enum {
      AlwaysConstant,
      AlwaysTrue,
      AlwaysFalse,
      AlwaysEqual, // std::strong_ordering::equal from operator<=>
    };
  
    // C++2a [depr.array.comp]:
    //   Equality and relational comparisons ([expr.eq], [expr.rel]) between two
    //   operands of array type are deprecated.
    if (S.getLangOpts().CPlusPlus20 && LHSStripped->getType()->isArrayType() &&
        RHSStripped->getType()->isArrayType()) {
      S.Diag(Loc, diag::warn_depr_array_comparison)
          << LHS->getSourceRange() << RHS->getSourceRange()
          << LHSStripped->getType() << RHSStripped->getType();
      // Carry on to produce the tautological comparison warning, if this
      // expression is potentially-evaluated, we can resolve the array to a
      // non-weak declaration, and so on.
    }
  
    if (!LHS->getBeginLoc().isMacroID() && !RHS->getBeginLoc().isMacroID()) {
      if (Expr::isSameComparisonOperand(LHS, RHS)) {
        unsigned Result;
        switch (Opc) {
        case BO_EQ:
        case BO_LE:
        case BO_GE:
          Result = AlwaysTrue;
          break;
        case BO_NE:
        case BO_LT:
        case BO_GT:
          Result = AlwaysFalse;
          break;
        case BO_Cmp:
          Result = AlwaysEqual;
          break;
        default:
          Result = AlwaysConstant;
          break;
        }
        S.DiagRuntimeBehavior(Loc, nullptr,
                              S.PDiag(diag::warn_comparison_always)
                                  << 0 /*self-comparison*/
                                  << Result);
      } else if (checkForArray(LHSStripped) && checkForArray(RHSStripped)) {
        // What is it always going to evaluate to?
        unsigned Result;
        switch (Opc) {
        case BO_EQ: // e.g. array1 == array2
          Result = AlwaysFalse;
          break;
        case BO_NE: // e.g. array1 != array2
          Result = AlwaysTrue;
          break;
        default: // e.g. array1 <= array2
          // The best we can say is 'a constant'
          Result = AlwaysConstant;
          break;
        }
        S.DiagRuntimeBehavior(Loc, nullptr,
                              S.PDiag(diag::warn_comparison_always)
                                  << 1 /*array comparison*/
                                  << Result);
      }
    }
  
    if (isa<CastExpr>(LHSStripped))
      LHSStripped = LHSStripped->IgnoreParenCasts();
    if (isa<CastExpr>(RHSStripped))
      RHSStripped = RHSStripped->IgnoreParenCasts();
  
    // Warn about comparisons against a string constant (unless the other
    // operand is null); the user probably wants string comparison function.
    Expr *LiteralString = nullptr;
    Expr *LiteralStringStripped = nullptr;
    if ((isa<StringLiteral>(LHSStripped) || isa<ObjCEncodeExpr>(LHSStripped)) &&
        !RHSStripped->isNullPointerConstant(S.Context,
                                            Expr::NPC_ValueDependentIsNull)) {
      LiteralString = LHS;
      LiteralStringStripped = LHSStripped;
    } else if ((isa<StringLiteral>(RHSStripped) ||
                isa<ObjCEncodeExpr>(RHSStripped)) &&
               !LHSStripped->isNullPointerConstant(S.Context,
                                            Expr::NPC_ValueDependentIsNull)) {
      LiteralString = RHS;
      LiteralStringStripped = RHSStripped;
    }
  
    if (LiteralString) {
      S.DiagRuntimeBehavior(Loc, nullptr,
                            S.PDiag(diag::warn_stringcompare)
                                << isa<ObjCEncodeExpr>(LiteralStringStripped)
                                << LiteralString->getSourceRange());
    }
  }
  
  static ImplicitConversionKind castKindToImplicitConversionKind(CastKind CK) {
    switch (CK) {
    default: {
  #ifndef NDEBUG
      llvm::errs() << "unhandled cast kind: " << CastExpr::getCastKindName(CK)
                   << "\n";
  #endif
      llvm_unreachable("unhandled cast kind");
    }
    case CK_UserDefinedConversion:
      return ICK_Identity;
    case CK_LValueToRValue:
      return ICK_Lvalue_To_Rvalue;
    case CK_ArrayToPointerDecay:
      return ICK_Array_To_Pointer;
    case CK_FunctionToPointerDecay:
      return ICK_Function_To_Pointer;
    case CK_IntegralCast:
      return ICK_Integral_Conversion;
    case CK_FloatingCast:
      return ICK_Floating_Conversion;
    case CK_IntegralToFloating:
    case CK_FloatingToIntegral:
      return ICK_Floating_Integral;
    case CK_IntegralComplexCast:
    case CK_FloatingComplexCast:
    case CK_FloatingComplexToIntegralComplex:
    case CK_IntegralComplexToFloatingComplex:
      return ICK_Complex_Conversion;
    case CK_FloatingComplexToReal:
    case CK_FloatingRealToComplex:
    case CK_IntegralComplexToReal:
    case CK_IntegralRealToComplex:
      return ICK_Complex_Real;
    }
  }
  
  static bool checkThreeWayNarrowingConversion(Sema &S, QualType ToType, Expr *E,
                                               QualType FromType,
                                               SourceLocation Loc) {
    // Check for a narrowing implicit conversion.
    StandardConversionSequence SCS;
    SCS.setAsIdentityConversion();
    SCS.setToType(0, FromType);
    SCS.setToType(1, ToType);
    if (const auto *ICE = dyn_cast<ImplicitCastExpr>(E))
      SCS.Second = castKindToImplicitConversionKind(ICE->getCastKind());
  
    APValue PreNarrowingValue;
    QualType PreNarrowingType;
    switch (SCS.getNarrowingKind(S.Context, E, PreNarrowingValue,
                                 PreNarrowingType,
                                 /*IgnoreFloatToIntegralConversion*/ true)) {
    case NK_Dependent_Narrowing:
      // Implicit conversion to a narrower type, but the expression is
      // value-dependent so we can't tell whether it's actually narrowing.
    case NK_Not_Narrowing:
      return false;
  
    case NK_Constant_Narrowing:
      // Implicit conversion to a narrower type, and the value is not a constant
      // expression.
      S.Diag(E->getBeginLoc(), diag::err_spaceship_argument_narrowing)
          << /*Constant*/ 1
          << PreNarrowingValue.getAsString(S.Context, PreNarrowingType) << ToType;
      return true;
  
    case NK_Variable_Narrowing:
      // Implicit conversion to a narrower type, and the value is not a constant
      // expression.
    case NK_Type_Narrowing:
      S.Diag(E->getBeginLoc(), diag::err_spaceship_argument_narrowing)
          << /*Constant*/ 0 << FromType << ToType;
      // TODO: It's not a constant expression, but what if the user intended it
      // to be? Can we produce notes to help them figure out why it isn't?
      return true;
    }
    llvm_unreachable("unhandled case in switch");
  }
  
  static QualType checkArithmeticOrEnumeralThreeWayCompare(Sema &S,
                                                           ExprResult &LHS,
                                                           ExprResult &RHS,
                                                           SourceLocation Loc) {
    QualType LHSType = LHS.get()->getType();
    QualType RHSType = RHS.get()->getType();
    // Dig out the original argument type and expression before implicit casts
    // were applied. These are the types/expressions we need to check the
    // [expr.spaceship] requirements against.
    ExprResult LHSStripped = LHS.get()->IgnoreParenImpCasts();
    ExprResult RHSStripped = RHS.get()->IgnoreParenImpCasts();
    QualType LHSStrippedType = LHSStripped.get()->getType();
    QualType RHSStrippedType = RHSStripped.get()->getType();
  
    // C++2a [expr.spaceship]p3: If one of the operands is of type bool and the
    // other is not, the program is ill-formed.
    if (LHSStrippedType->isBooleanType() != RHSStrippedType->isBooleanType()) {
      S.InvalidOperands(Loc, LHSStripped, RHSStripped);
      return QualType();
    }
  
    // FIXME: Consider combining this with checkEnumArithmeticConversions.
    int NumEnumArgs = (int)LHSStrippedType->isEnumeralType() +
                      RHSStrippedType->isEnumeralType();
    if (NumEnumArgs == 1) {
      bool LHSIsEnum = LHSStrippedType->isEnumeralType();
      QualType OtherTy = LHSIsEnum ? RHSStrippedType : LHSStrippedType;
      if (OtherTy->hasFloatingRepresentation()) {
        S.InvalidOperands(Loc, LHSStripped, RHSStripped);
        return QualType();
      }
    }
    if (NumEnumArgs == 2) {
      // C++2a [expr.spaceship]p5: If both operands have the same enumeration
      // type E, the operator yields the result of converting the operands
      // to the underlying type of E and applying <=> to the converted operands.
      if (!S.Context.hasSameUnqualifiedType(LHSStrippedType, RHSStrippedType)) {
        S.InvalidOperands(Loc, LHS, RHS);
        return QualType();
      }
      QualType IntType =
          LHSStrippedType->castAs<EnumType>()->getDecl()->getIntegerType();
      assert(IntType->isArithmeticType());
  
      // We can't use `CK_IntegralCast` when the underlying type is 'bool', so we
      // promote the boolean type, and all other promotable integer types, to
      // avoid this.
      if (IntType->isPromotableIntegerType())
        IntType = S.Context.getPromotedIntegerType(IntType);
  
      LHS = S.ImpCastExprToType(LHS.get(), IntType, CK_IntegralCast);
      RHS = S.ImpCastExprToType(RHS.get(), IntType, CK_IntegralCast);
      LHSType = RHSType = IntType;
    }
  
    // C++2a [expr.spaceship]p4: If both operands have arithmetic types, the
    // usual arithmetic conversions are applied to the operands.
    QualType Type =
        S.UsualArithmeticConversions(LHS, RHS, Loc, Sema::ACK_Comparison);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
    if (Type.isNull())
      return S.InvalidOperands(Loc, LHS, RHS);
  
    Optional<ComparisonCategoryType> CCT =
        getComparisonCategoryForBuiltinCmp(Type);
    if (!CCT)
      return S.InvalidOperands(Loc, LHS, RHS);
  
    bool HasNarrowing = checkThreeWayNarrowingConversion(
        S, Type, LHS.get(), LHSType, LHS.get()->getBeginLoc());
    HasNarrowing |= checkThreeWayNarrowingConversion(S, Type, RHS.get(), RHSType,
                                                     RHS.get()->getBeginLoc());
    if (HasNarrowing)
      return QualType();
  
    assert(!Type.isNull() && "composite type for <=> has not been set");
  
    return S.CheckComparisonCategoryType(
        *CCT, Loc, Sema::ComparisonCategoryUsage::OperatorInExpression);
  }
  
  static QualType checkArithmeticOrEnumeralCompare(Sema &S, ExprResult &LHS,
                                                   ExprResult &RHS,
                                                   SourceLocation Loc,
                                                   BinaryOperatorKind Opc) {
    if (Opc == BO_Cmp)
      return checkArithmeticOrEnumeralThreeWayCompare(S, LHS, RHS, Loc);
  
    // C99 6.5.8p3 / C99 6.5.9p4
    QualType Type =
        S.UsualArithmeticConversions(LHS, RHS, Loc, Sema::ACK_Comparison);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
    if (Type.isNull())
      return S.InvalidOperands(Loc, LHS, RHS);
    assert(Type->isArithmeticType() || Type->isEnumeralType());
  
    if (Type->isAnyComplexType() && BinaryOperator::isRelationalOp(Opc))
      return S.InvalidOperands(Loc, LHS, RHS);
  
    // Check for comparisons of floating point operands using != and ==.
    if (Type->hasFloatingRepresentation() && BinaryOperator::isEqualityOp(Opc))
      S.CheckFloatComparison(Loc, LHS.get(), RHS.get());
  
    // The result of comparisons is 'bool' in C++, 'int' in C.
    return S.Context.getLogicalOperationType();
  }
  
  void Sema::CheckPtrComparisonWithNullChar(ExprResult &E, ExprResult &NullE) {
    if (!NullE.get()->getType()->isAnyPointerType())
      return;
    int NullValue = PP.isMacroDefined("NULL") ? 0 : 1;
    if (!E.get()->getType()->isAnyPointerType() &&
        E.get()->isNullPointerConstant(Context,
                                       Expr::NPC_ValueDependentIsNotNull) ==
          Expr::NPCK_ZeroExpression) {
      if (const auto *CL = dyn_cast<CharacterLiteral>(E.get())) {
        if (CL->getValue() == 0)
          Diag(E.get()->getExprLoc(), diag::warn_pointer_compare)
              << NullValue
              << FixItHint::CreateReplacement(E.get()->getExprLoc(),
                                              NullValue ? "NULL" : "(void *)0");
      } else if (const auto *CE = dyn_cast<CStyleCastExpr>(E.get())) {
          TypeSourceInfo *TI = CE->getTypeInfoAsWritten();
          QualType T = Context.getCanonicalType(TI->getType()).getUnqualifiedType();
          if (T == Context.CharTy)
            Diag(E.get()->getExprLoc(), diag::warn_pointer_compare)
                << NullValue
                << FixItHint::CreateReplacement(E.get()->getExprLoc(),
                                                NullValue ? "NULL" : "(void *)0");
        }
    }
  }
  
  // C99 6.5.8, C++ [expr.rel]
  QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
                                      SourceLocation Loc,
                                      BinaryOperatorKind Opc) {
    bool IsRelational = BinaryOperator::isRelationalOp(Opc);
    bool IsThreeWay = Opc == BO_Cmp;
    bool IsOrdered = IsRelational || IsThreeWay;
    auto IsAnyPointerType = [](ExprResult E) {
      QualType Ty = E.get()->getType();
      return Ty->isPointerType() || Ty->isMemberPointerType();
    };
  
    // C++2a [expr.spaceship]p6: If at least one of the operands is of pointer
    // type, array-to-pointer, ..., conversions are performed on both operands to
    // bring them to their composite type.
    // Otherwise, all comparisons expect an rvalue, so convert to rvalue before
    // any type-related checks.
    if (!IsThreeWay || IsAnyPointerType(LHS) || IsAnyPointerType(RHS)) {
      LHS = DefaultFunctionArrayLvalueConversion(LHS.get());
      if (LHS.isInvalid())
        return QualType();
      RHS = DefaultFunctionArrayLvalueConversion(RHS.get());
      if (RHS.isInvalid())
        return QualType();
    } else {
      LHS = DefaultLvalueConversion(LHS.get());
      if (LHS.isInvalid())
        return QualType();
      RHS = DefaultLvalueConversion(RHS.get());
      if (RHS.isInvalid())
        return QualType();
    }
  
    checkArithmeticNull(*this, LHS, RHS, Loc, /*IsCompare=*/true);
    if (!getLangOpts().CPlusPlus && BinaryOperator::isEqualityOp(Opc)) {
      CheckPtrComparisonWithNullChar(LHS, RHS);
      CheckPtrComparisonWithNullChar(RHS, LHS);
    }
  
    // Handle vector comparisons separately.
    if (LHS.get()->getType()->isVectorType() ||
        RHS.get()->getType()->isVectorType())
      return CheckVectorCompareOperands(LHS, RHS, Loc, Opc);
  
    diagnoseLogicalNotOnLHSofCheck(*this, LHS, RHS, Loc, Opc);
    diagnoseTautologicalComparison(*this, Loc, LHS.get(), RHS.get(), Opc);
  
    QualType LHSType = LHS.get()->getType();
    QualType RHSType = RHS.get()->getType();
    if ((LHSType->isArithmeticType() || LHSType->isEnumeralType()) &&
        (RHSType->isArithmeticType() || RHSType->isEnumeralType()))
      return checkArithmeticOrEnumeralCompare(*this, LHS, RHS, Loc, Opc);
  
    const Expr::NullPointerConstantKind LHSNullKind =
        LHS.get()->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNull);
    const Expr::NullPointerConstantKind RHSNullKind =
        RHS.get()->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNull);
    bool LHSIsNull = LHSNullKind != Expr::NPCK_NotNull;
    bool RHSIsNull = RHSNullKind != Expr::NPCK_NotNull;
  
    auto computeResultTy = [&]() {
      if (Opc != BO_Cmp)
        return Context.getLogicalOperationType();
      assert(getLangOpts().CPlusPlus);
      assert(Context.hasSameType(LHS.get()->getType(), RHS.get()->getType()));
  
      QualType CompositeTy = LHS.get()->getType();
      assert(!CompositeTy->isReferenceType());
  
      Optional<ComparisonCategoryType> CCT =
          getComparisonCategoryForBuiltinCmp(CompositeTy);
      if (!CCT)
        return InvalidOperands(Loc, LHS, RHS);
  
      if (CompositeTy->isPointerType() && LHSIsNull != RHSIsNull) {
        // P0946R0: Comparisons between a null pointer constant and an object
        // pointer result in std::strong_equality, which is ill-formed under
        // P1959R0.
        Diag(Loc, diag::err_typecheck_three_way_comparison_of_pointer_and_zero)
            << (LHSIsNull ? LHS.get()->getSourceRange()
                          : RHS.get()->getSourceRange());
        return QualType();
      }
  
      return CheckComparisonCategoryType(
          *CCT, Loc, ComparisonCategoryUsage::OperatorInExpression);
    };
  
    if (!IsOrdered && LHSIsNull != RHSIsNull) {
      bool IsEquality = Opc == BO_EQ;
      if (RHSIsNull)
        DiagnoseAlwaysNonNullPointer(LHS.get(), RHSNullKind, IsEquality,
                                     RHS.get()->getSourceRange());
      else
        DiagnoseAlwaysNonNullPointer(RHS.get(), LHSNullKind, IsEquality,
                                     LHS.get()->getSourceRange());
    }
  
    if (IsOrdered && LHSType->isFunctionPointerType() &&
        RHSType->isFunctionPointerType()) {
      // Valid unless a relational comparison of function pointers
      bool IsError = Opc == BO_Cmp;
      auto DiagID =
          IsError ? diag::err_typecheck_ordered_comparison_of_function_pointers
          : getLangOpts().CPlusPlus
              ? diag::warn_typecheck_ordered_comparison_of_function_pointers
              : diag::ext_typecheck_ordered_comparison_of_function_pointers;
      Diag(Loc, DiagID) << LHSType << RHSType << LHS.get()->getSourceRange()
                        << RHS.get()->getSourceRange();
      if (IsError)
        return QualType();
    }
  
    if ((LHSType->isIntegerType() && !LHSIsNull) ||
        (RHSType->isIntegerType() && !RHSIsNull)) {
      // Skip normal pointer conversion checks in this case; we have better
      // diagnostics for this below.
    } else if (getLangOpts().CPlusPlus) {
      // Equality comparison of a function pointer to a void pointer is invalid,
      // but we allow it as an extension.
      // FIXME: If we really want to allow this, should it be part of composite
      // pointer type computation so it works in conditionals too?
      if (!IsOrdered &&
          ((LHSType->isFunctionPointerType() && RHSType->isVoidPointerType()) ||
           (RHSType->isFunctionPointerType() && LHSType->isVoidPointerType()))) {
        // This is a gcc extension compatibility comparison.
        // In a SFINAE context, we treat this as a hard error to maintain
        // conformance with the C++ standard.
        diagnoseFunctionPointerToVoidComparison(
            *this, Loc, LHS, RHS, /*isError*/ (bool)isSFINAEContext());
  
        if (isSFINAEContext())
          return QualType();
  
        RHS = ImpCastExprToType(RHS.get(), LHSType, CK_BitCast);
        return computeResultTy();
      }
  
      // C++ [expr.eq]p2:
      //   If at least one operand is a pointer [...] bring them to their
      //   composite pointer type.
      // C++ [expr.spaceship]p6
      //  If at least one of the operands is of pointer type, [...] bring them
      //  to their composite pointer type.
      // C++ [expr.rel]p2:
      //   If both operands are pointers, [...] bring them to their composite
      //   pointer type.
      // For <=>, the only valid non-pointer types are arrays and functions, and
      // we already decayed those, so this is really the same as the relational
      // comparison rule.
      if ((int)LHSType->isPointerType() + (int)RHSType->isPointerType() >=
              (IsOrdered ? 2 : 1) &&
          (!LangOpts.ObjCAutoRefCount || !(LHSType->isObjCObjectPointerType() ||
                                           RHSType->isObjCObjectPointerType()))) {
        if (convertPointersToCompositeType(*this, Loc, LHS, RHS))
          return QualType();
        return computeResultTy();
      }
    } else if (LHSType->isPointerType() &&
               RHSType->isPointerType()) { // C99 6.5.8p2
      // All of the following pointer-related warnings are GCC extensions, except
      // when handling null pointer constants.
      QualType LCanPointeeTy =
        LHSType->castAs<PointerType>()->getPointeeType().getCanonicalType();
      QualType RCanPointeeTy =
        RHSType->castAs<PointerType>()->getPointeeType().getCanonicalType();
  
      // C99 6.5.9p2 and C99 6.5.8p2
      if (Context.typesAreCompatible(LCanPointeeTy.getUnqualifiedType(),
                                     RCanPointeeTy.getUnqualifiedType())) {
        if (IsRelational) {
          // Pointers both need to point to complete or incomplete types
          if ((LCanPointeeTy->isIncompleteType() !=
               RCanPointeeTy->isIncompleteType()) &&
              !getLangOpts().C11) {
            Diag(Loc, diag::ext_typecheck_compare_complete_incomplete_pointers)
                << LHS.get()->getSourceRange() << RHS.get()->getSourceRange()
                << LHSType << RHSType << LCanPointeeTy->isIncompleteType()
                << RCanPointeeTy->isIncompleteType();
          }
        }
      } else if (!IsRelational &&
                 (LCanPointeeTy->isVoidType() || RCanPointeeTy->isVoidType())) {
        // Valid unless comparison between non-null pointer and function pointer
        if ((LCanPointeeTy->isFunctionType() || RCanPointeeTy->isFunctionType())
            && !LHSIsNull && !RHSIsNull)
          diagnoseFunctionPointerToVoidComparison(*this, Loc, LHS, RHS,
                                                  /*isError*/false);
      } else {
        // Invalid
        diagnoseDistinctPointerComparison(*this, Loc, LHS, RHS, /*isError*/false);
      }
      if (LCanPointeeTy != RCanPointeeTy) {
        // Treat NULL constant as a special case in OpenCL.
        if (getLangOpts().OpenCL && !LHSIsNull && !RHSIsNull) {
          if (!LCanPointeeTy.isAddressSpaceOverlapping(RCanPointeeTy)) {
            Diag(Loc,
                 diag::err_typecheck_op_on_nonoverlapping_address_space_pointers)
                << LHSType << RHSType << 0 /* comparison */
                << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
          }
        }
        LangAS AddrSpaceL = LCanPointeeTy.getAddressSpace();
        LangAS AddrSpaceR = RCanPointeeTy.getAddressSpace();
        CastKind Kind = AddrSpaceL != AddrSpaceR ? CK_AddressSpaceConversion
                                                 : CK_BitCast;
        if (LHSIsNull && !RHSIsNull)
          LHS = ImpCastExprToType(LHS.get(), RHSType, Kind);
        else
          RHS = ImpCastExprToType(RHS.get(), LHSType, Kind);
      }
      return computeResultTy();
    }
  
    if (getLangOpts().CPlusPlus) {
      // C++ [expr.eq]p4:
      //   Two operands of type std::nullptr_t or one operand of type
      //   std::nullptr_t and the other a null pointer constant compare equal.
      if (!IsOrdered && LHSIsNull && RHSIsNull) {
        if (LHSType->isNullPtrType()) {
          RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
          return computeResultTy();
        }
        if (RHSType->isNullPtrType()) {
          LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
          return computeResultTy();
        }
      }
  
      // Comparison of Objective-C pointers and block pointers against nullptr_t.
      // These aren't covered by the composite pointer type rules.
      if (!IsOrdered && RHSType->isNullPtrType() &&
          (LHSType->isObjCObjectPointerType() || LHSType->isBlockPointerType())) {
        RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
        return computeResultTy();
      }
      if (!IsOrdered && LHSType->isNullPtrType() &&
          (RHSType->isObjCObjectPointerType() || RHSType->isBlockPointerType())) {
        LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
        return computeResultTy();
      }
  
      if (IsRelational &&
          ((LHSType->isNullPtrType() && RHSType->isPointerType()) ||
           (RHSType->isNullPtrType() && LHSType->isPointerType()))) {
        // HACK: Relational comparison of nullptr_t against a pointer type is
        // invalid per DR583, but we allow it within std::less<> and friends,
        // since otherwise common uses of it break.
        // FIXME: Consider removing this hack once LWG fixes std::less<> and
        // friends to have std::nullptr_t overload candidates.
        DeclContext *DC = CurContext;
        if (isa<FunctionDecl>(DC))
          DC = DC->getParent();
        if (auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(DC)) {
          if (CTSD->isInStdNamespace() &&
              llvm::StringSwitch<bool>(CTSD->getName())
                  .Cases("less", "less_equal", "greater", "greater_equal", true)
                  .Default(false)) {
            if (RHSType->isNullPtrType())
              RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
            else
              LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
            return computeResultTy();
          }
        }
      }
  
      // C++ [expr.eq]p2:
      //   If at least one operand is a pointer to member, [...] bring them to
      //   their composite pointer type.
      if (!IsOrdered &&
          (LHSType->isMemberPointerType() || RHSType->isMemberPointerType())) {
        if (convertPointersToCompositeType(*this, Loc, LHS, RHS))
          return QualType();
        else
          return computeResultTy();
      }
    }
  
    // Handle block pointer types.
    if (!IsOrdered && LHSType->isBlockPointerType() &&
        RHSType->isBlockPointerType()) {
      QualType lpointee = LHSType->castAs<BlockPointerType>()->getPointeeType();
      QualType rpointee = RHSType->castAs<BlockPointerType>()->getPointeeType();
  
      if (!LHSIsNull && !RHSIsNull &&
          !Context.typesAreCompatible(lpointee, rpointee)) {
        Diag(Loc, diag::err_typecheck_comparison_of_distinct_blocks)
          << LHSType << RHSType << LHS.get()->getSourceRange()
          << RHS.get()->getSourceRange();
      }
      RHS = ImpCastExprToType(RHS.get(), LHSType, CK_BitCast);
      return computeResultTy();
    }
  
    // Allow block pointers to be compared with null pointer constants.
    if (!IsOrdered
        && ((LHSType->isBlockPointerType() && RHSType->isPointerType())
            || (LHSType->isPointerType() && RHSType->isBlockPointerType()))) {
      if (!LHSIsNull && !RHSIsNull) {
        if (!((RHSType->isPointerType() && RHSType->castAs<PointerType>()
               ->getPointeeType()->isVoidType())
              || (LHSType->isPointerType() && LHSType->castAs<PointerType>()
                  ->getPointeeType()->isVoidType())))
          Diag(Loc, diag::err_typecheck_comparison_of_distinct_blocks)
            << LHSType << RHSType << LHS.get()->getSourceRange()
            << RHS.get()->getSourceRange();
      }
      if (LHSIsNull && !RHSIsNull)
        LHS = ImpCastExprToType(LHS.get(), RHSType,
                                RHSType->isPointerType() ? CK_BitCast
                                  : CK_AnyPointerToBlockPointerCast);
      else
        RHS = ImpCastExprToType(RHS.get(), LHSType,
                                LHSType->isPointerType() ? CK_BitCast
                                  : CK_AnyPointerToBlockPointerCast);
      return computeResultTy();
    }
  
    if (LHSType->isObjCObjectPointerType() ||
        RHSType->isObjCObjectPointerType()) {
      const PointerType *LPT = LHSType->getAs<PointerType>();
      const PointerType *RPT = RHSType->getAs<PointerType>();
      if (LPT || RPT) {
        bool LPtrToVoid = LPT ? LPT->getPointeeType()->isVoidType() : false;
        bool RPtrToVoid = RPT ? RPT->getPointeeType()->isVoidType() : false;
  
        if (!LPtrToVoid && !RPtrToVoid &&
            !Context.typesAreCompatible(LHSType, RHSType)) {
          diagnoseDistinctPointerComparison(*this, Loc, LHS, RHS,
                                            /*isError*/false);
        }
        // FIXME: If LPtrToVoid, we should presumably convert the LHS rather than
        // the RHS, but we have test coverage for this behavior.
        // FIXME: Consider using convertPointersToCompositeType in C++.
        if (LHSIsNull && !RHSIsNull) {
          Expr *E = LHS.get();
          if (getLangOpts().ObjCAutoRefCount)
            CheckObjCConversion(SourceRange(), RHSType, E,
                                CCK_ImplicitConversion);
          LHS = ImpCastExprToType(E, RHSType,
                                  RPT ? CK_BitCast :CK_CPointerToObjCPointerCast);
        }
        else {
          Expr *E = RHS.get();
          if (getLangOpts().ObjCAutoRefCount)
            CheckObjCConversion(SourceRange(), LHSType, E, CCK_ImplicitConversion,
                                /*Diagnose=*/true,
                                /*DiagnoseCFAudited=*/false, Opc);
          RHS = ImpCastExprToType(E, LHSType,
                                  LPT ? CK_BitCast :CK_CPointerToObjCPointerCast);
        }
        return computeResultTy();
      }
      if (LHSType->isObjCObjectPointerType() &&
          RHSType->isObjCObjectPointerType()) {
        if (!Context.areComparableObjCPointerTypes(LHSType, RHSType))
          diagnoseDistinctPointerComparison(*this, Loc, LHS, RHS,
                                            /*isError*/false);
        if (isObjCObjectLiteral(LHS) || isObjCObjectLiteral(RHS))
          diagnoseObjCLiteralComparison(*this, Loc, LHS, RHS, Opc);
  
        if (LHSIsNull && !RHSIsNull)
          LHS = ImpCastExprToType(LHS.get(), RHSType, CK_BitCast);
        else
          RHS = ImpCastExprToType(RHS.get(), LHSType, CK_BitCast);
        return computeResultTy();
      }
  
      if (!IsOrdered && LHSType->isBlockPointerType() &&
          RHSType->isBlockCompatibleObjCPointerType(Context)) {
        LHS = ImpCastExprToType(LHS.get(), RHSType,
                                CK_BlockPointerToObjCPointerCast);
        return computeResultTy();
      } else if (!IsOrdered &&
                 LHSType->isBlockCompatibleObjCPointerType(Context) &&
                 RHSType->isBlockPointerType()) {
        RHS = ImpCastExprToType(RHS.get(), LHSType,
                                CK_BlockPointerToObjCPointerCast);
        return computeResultTy();
      }
    }
    if ((LHSType->isAnyPointerType() && RHSType->isIntegerType()) ||
        (LHSType->isIntegerType() && RHSType->isAnyPointerType())) {
      unsigned DiagID = 0;
      bool isError = false;
      if (LangOpts.DebuggerSupport) {
        // Under a debugger, allow the comparison of pointers to integers,
        // since users tend to want to compare addresses.
      } else if ((LHSIsNull && LHSType->isIntegerType()) ||
                 (RHSIsNull && RHSType->isIntegerType())) {
        if (IsOrdered) {
          isError = getLangOpts().CPlusPlus;
          DiagID =
            isError ? diag::err_typecheck_ordered_comparison_of_pointer_and_zero
                    : diag::ext_typecheck_ordered_comparison_of_pointer_and_zero;
        }
      } else if (getLangOpts().CPlusPlus) {
        DiagID = diag::err_typecheck_comparison_of_pointer_integer;
        isError = true;
      } else if (IsOrdered)
        DiagID = diag::ext_typecheck_ordered_comparison_of_pointer_integer;
      else
        DiagID = diag::ext_typecheck_comparison_of_pointer_integer;
  
      if (DiagID) {
        Diag(Loc, DiagID)
          << LHSType << RHSType << LHS.get()->getSourceRange()
          << RHS.get()->getSourceRange();
        if (isError)
          return QualType();
      }
  
      if (LHSType->isIntegerType())
        LHS = ImpCastExprToType(LHS.get(), RHSType,
                          LHSIsNull ? CK_NullToPointer : CK_IntegralToPointer);
      else
        RHS = ImpCastExprToType(RHS.get(), LHSType,
                          RHSIsNull ? CK_NullToPointer : CK_IntegralToPointer);
      return computeResultTy();
    }
  
    // Handle block pointers.
    if (!IsOrdered && RHSIsNull
        && LHSType->isBlockPointerType() && RHSType->isIntegerType()) {
      RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
      return computeResultTy();
    }
    if (!IsOrdered && LHSIsNull
        && LHSType->isIntegerType() && RHSType->isBlockPointerType()) {
      LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
      return computeResultTy();
    }
  
    if (getLangOpts().getOpenCLCompatibleVersion() >= 200) {
      if (LHSType->isClkEventT() && RHSType->isClkEventT()) {
        return computeResultTy();
      }
  
      if (LHSType->isQueueT() && RHSType->isQueueT()) {
        return computeResultTy();
      }
  
      if (LHSIsNull && RHSType->isQueueT()) {
        LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
        return computeResultTy();
      }
  
      if (LHSType->isQueueT() && RHSIsNull) {
        RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
        return computeResultTy();
      }
    }
  
    return InvalidOperands(Loc, LHS, RHS);
  }
  
  // Return a signed ext_vector_type that is of identical size and number of
  // elements. For floating point vectors, return an integer type of identical
  // size and number of elements. In the non ext_vector_type case, search from
  // the largest type to the smallest type to avoid cases where long long == long,
  // where long gets picked over long long.
  QualType Sema::GetSignedVectorType(QualType V) {
    const VectorType *VTy = V->castAs<VectorType>();
    unsigned TypeSize = Context.getTypeSize(VTy->getElementType());
  
    if (isa<ExtVectorType>(VTy)) {
      if (TypeSize == Context.getTypeSize(Context.CharTy))
        return Context.getExtVectorType(Context.CharTy, VTy->getNumElements());
      if (TypeSize == Context.getTypeSize(Context.ShortTy))
        return Context.getExtVectorType(Context.ShortTy, VTy->getNumElements());
      if (TypeSize == Context.getTypeSize(Context.IntTy))
        return Context.getExtVectorType(Context.IntTy, VTy->getNumElements());
      if (TypeSize == Context.getTypeSize(Context.Int128Ty))
        return Context.getExtVectorType(Context.Int128Ty, VTy->getNumElements());
      if (TypeSize == Context.getTypeSize(Context.LongTy))
        return Context.getExtVectorType(Context.LongTy, VTy->getNumElements());
      assert(TypeSize == Context.getTypeSize(Context.LongLongTy) &&
             "Unhandled vector element size in vector compare");
      return Context.getExtVectorType(Context.LongLongTy, VTy->getNumElements());
    }
  
    if (TypeSize == Context.getTypeSize(Context.Int128Ty))
      return Context.getVectorType(Context.Int128Ty, VTy->getNumElements(),
                                   VectorType::GenericVector);
    if (TypeSize == Context.getTypeSize(Context.LongLongTy))
      return Context.getVectorType(Context.LongLongTy, VTy->getNumElements(),
                                   VectorType::GenericVector);
    if (TypeSize == Context.getTypeSize(Context.LongTy))
      return Context.getVectorType(Context.LongTy, VTy->getNumElements(),
                                   VectorType::GenericVector);
    if (TypeSize == Context.getTypeSize(Context.IntTy))
      return Context.getVectorType(Context.IntTy, VTy->getNumElements(),
                                   VectorType::GenericVector);
    if (TypeSize == Context.getTypeSize(Context.ShortTy))
      return Context.getVectorType(Context.ShortTy, VTy->getNumElements(),
                                   VectorType::GenericVector);
    assert(TypeSize == Context.getTypeSize(Context.CharTy) &&
           "Unhandled vector element size in vector compare");
    return Context.getVectorType(Context.CharTy, VTy->getNumElements(),
                                 VectorType::GenericVector);
  }
  
  /// CheckVectorCompareOperands - vector comparisons are a clang extension that
  /// operates on extended vector types.  Instead of producing an IntTy result,
  /// like a scalar comparison, a vector comparison produces a vector of integer
  /// types.
  QualType Sema::CheckVectorCompareOperands(ExprResult &LHS, ExprResult &RHS,
                                            SourceLocation Loc,
                                            BinaryOperatorKind Opc) {
    if (Opc == BO_Cmp) {
      Diag(Loc, diag::err_three_way_vector_comparison);
      return QualType();
    }
  
    // Check to make sure we're operating on vectors of the same type and width,
    // Allowing one side to be a scalar of element type.
    QualType vType = CheckVectorOperands(LHS, RHS, Loc, /*isCompAssign*/false,
                                /*AllowBothBool*/true,
                                /*AllowBoolConversions*/getLangOpts().ZVector);
    if (vType.isNull())
      return vType;
  
    QualType LHSType = LHS.get()->getType();
  
    // Determine the return type of a vector compare. By default clang will return
    // a scalar for all vector compares except vector bool and vector pixel.
    // With the gcc compiler we will always return a vector type and with the xl
    // compiler we will always return a scalar type. This switch allows choosing
    // which behavior is prefered.
    if (getLangOpts().AltiVec) {
      switch (getLangOpts().getAltivecSrcCompat()) {
      case LangOptions::AltivecSrcCompatKind::Mixed:
        // If AltiVec, the comparison results in a numeric type, i.e.
        // bool for C++, int for C
        if (vType->castAs<VectorType>()->getVectorKind() ==
            VectorType::AltiVecVector)
          return Context.getLogicalOperationType();
        else
          Diag(Loc, diag::warn_deprecated_altivec_src_compat);
        break;
      case LangOptions::AltivecSrcCompatKind::GCC:
        // For GCC we always return the vector type.
        break;
      case LangOptions::AltivecSrcCompatKind::XL:
        return Context.getLogicalOperationType();
        break;
      }
    }
  
    // For non-floating point types, check for self-comparisons of the form
    // x == x, x != x, x < x, etc.  These always evaluate to a constant, and
    // often indicate logic errors in the program.
    diagnoseTautologicalComparison(*this, Loc, LHS.get(), RHS.get(), Opc);
  
    // Check for comparisons of floating point operands using != and ==.
    if (BinaryOperator::isEqualityOp(Opc) &&
        LHSType->hasFloatingRepresentation()) {
      assert(RHS.get()->getType()->hasFloatingRepresentation());
      CheckFloatComparison(Loc, LHS.get(), RHS.get());
    }
  
    // Return a signed type for the vector.
    return GetSignedVectorType(vType);
  }
  
  static void diagnoseXorMisusedAsPow(Sema &S, const ExprResult &XorLHS,
                                      const ExprResult &XorRHS,
                                      const SourceLocation Loc) {
    // Do not diagnose macros.
    if (Loc.isMacroID())
      return;
  
    // Do not diagnose if both LHS and RHS are macros.
    if (XorLHS.get()->getExprLoc().isMacroID() &&
        XorRHS.get()->getExprLoc().isMacroID())
      return;
  
    bool Negative = false;
    bool ExplicitPlus = false;
    const auto *LHSInt = dyn_cast<IntegerLiteral>(XorLHS.get());
    const auto *RHSInt = dyn_cast<IntegerLiteral>(XorRHS.get());
  
    if (!LHSInt)
      return;
    if (!RHSInt) {
      // Check negative literals.
      if (const auto *UO = dyn_cast<UnaryOperator>(XorRHS.get())) {
        UnaryOperatorKind Opc = UO->getOpcode();
        if (Opc != UO_Minus && Opc != UO_Plus)
          return;
        RHSInt = dyn_cast<IntegerLiteral>(UO->getSubExpr());
        if (!RHSInt)
          return;
        Negative = (Opc == UO_Minus);
        ExplicitPlus = !Negative;
      } else {
        return;
      }
    }
  
    const llvm::APInt &LeftSideValue = LHSInt->getValue();
    llvm::APInt RightSideValue = RHSInt->getValue();
    if (LeftSideValue != 2 && LeftSideValue != 10)
      return;
  
    if (LeftSideValue.getBitWidth() != RightSideValue.getBitWidth())
      return;
  
    CharSourceRange ExprRange = CharSourceRange::getCharRange(
        LHSInt->getBeginLoc(), S.getLocForEndOfToken(RHSInt->getLocation()));
    llvm::StringRef ExprStr =
        Lexer::getSourceText(ExprRange, S.getSourceManager(), S.getLangOpts());
  
    CharSourceRange XorRange =
        CharSourceRange::getCharRange(Loc, S.getLocForEndOfToken(Loc));
    llvm::StringRef XorStr =
        Lexer::getSourceText(XorRange, S.getSourceManager(), S.getLangOpts());
    // Do not diagnose if xor keyword/macro is used.
    if (XorStr == "xor")
      return;
  
    std::string LHSStr = std::string(Lexer::getSourceText(
        CharSourceRange::getTokenRange(LHSInt->getSourceRange()),
        S.getSourceManager(), S.getLangOpts()));
    std::string RHSStr = std::string(Lexer::getSourceText(
        CharSourceRange::getTokenRange(RHSInt->getSourceRange()),
        S.getSourceManager(), S.getLangOpts()));
  
    if (Negative) {
      RightSideValue = -RightSideValue;
      RHSStr = "-" + RHSStr;
    } else if (ExplicitPlus) {
      RHSStr = "+" + RHSStr;
    }
  
    StringRef LHSStrRef = LHSStr;
    StringRef RHSStrRef = RHSStr;
    // Do not diagnose literals with digit separators, binary, hexadecimal, octal
    // literals.
    if (LHSStrRef.startswith("0b") || LHSStrRef.startswith("0B") ||
        RHSStrRef.startswith("0b") || RHSStrRef.startswith("0B") ||
        LHSStrRef.startswith("0x") || LHSStrRef.startswith("0X") ||
        RHSStrRef.startswith("0x") || RHSStrRef.startswith("0X") ||
        (LHSStrRef.size() > 1 && LHSStrRef.startswith("0")) ||
        (RHSStrRef.size() > 1 && RHSStrRef.startswith("0")) ||
        LHSStrRef.contains('\'') || RHSStrRef.contains('\''))
      return;
  
    bool SuggestXor =
        S.getLangOpts().CPlusPlus || S.getPreprocessor().isMacroDefined("xor");
    const llvm::APInt XorValue = LeftSideValue ^ RightSideValue;
    int64_t RightSideIntValue = RightSideValue.getSExtValue();
    if (LeftSideValue == 2 && RightSideIntValue >= 0) {
      std::string SuggestedExpr = "1 << " + RHSStr;
      bool Overflow = false;
      llvm::APInt One = (LeftSideValue - 1);
      llvm::APInt PowValue = One.sshl_ov(RightSideValue, Overflow);
      if (Overflow) {
        if (RightSideIntValue < 64)
          S.Diag(Loc, diag::warn_xor_used_as_pow_base)
              << ExprStr << toString(XorValue, 10, true) << ("1LL << " + RHSStr)
              << FixItHint::CreateReplacement(ExprRange, "1LL << " + RHSStr);
        else if (RightSideIntValue == 64)
          S.Diag(Loc, diag::warn_xor_used_as_pow)
              << ExprStr << toString(XorValue, 10, true);
        else
          return;
      } else {
        S.Diag(Loc, diag::warn_xor_used_as_pow_base_extra)
            << ExprStr << toString(XorValue, 10, true) << SuggestedExpr
            << toString(PowValue, 10, true)
            << FixItHint::CreateReplacement(
                   ExprRange, (RightSideIntValue == 0) ? "1" : SuggestedExpr);
      }
  
      S.Diag(Loc, diag::note_xor_used_as_pow_silence)
          << ("0x2 ^ " + RHSStr) << SuggestXor;
    } else if (LeftSideValue == 10) {
      std::string SuggestedValue = "1e" + std::to_string(RightSideIntValue);
      S.Diag(Loc, diag::warn_xor_used_as_pow_base)
          << ExprStr << toString(XorValue, 10, true) << SuggestedValue
          << FixItHint::CreateReplacement(ExprRange, SuggestedValue);
      S.Diag(Loc, diag::note_xor_used_as_pow_silence)
          << ("0xA ^ " + RHSStr) << SuggestXor;
    }
  }
  
  QualType Sema::CheckVectorLogicalOperands(ExprResult &LHS, ExprResult &RHS,
                                            SourceLocation Loc) {
    // Ensure that either both operands are of the same vector type, or
    // one operand is of a vector type and the other is of its element type.
    QualType vType = CheckVectorOperands(LHS, RHS, Loc, false,
                                         /*AllowBothBool*/true,
                                         /*AllowBoolConversions*/false);
    if (vType.isNull())
      return InvalidOperands(Loc, LHS, RHS);
    if (getLangOpts().OpenCL &&
        getLangOpts().getOpenCLCompatibleVersion() < 120 &&
        vType->hasFloatingRepresentation())
      return InvalidOperands(Loc, LHS, RHS);
    // FIXME: The check for C++ here is for GCC compatibility. GCC rejects the
    //        usage of the logical operators && and || with vectors in C. This
    //        check could be notionally dropped.
    if (!getLangOpts().CPlusPlus &&
        !(isa<ExtVectorType>(vType->getAs<VectorType>())))
      return InvalidLogicalVectorOperands(Loc, LHS, RHS);
  
    return GetSignedVectorType(LHS.get()->getType());
  }
  
  QualType Sema::CheckMatrixElementwiseOperands(ExprResult &LHS, ExprResult &RHS,
                                                SourceLocation Loc,
                                                bool IsCompAssign) {
    if (!IsCompAssign) {
      LHS = DefaultFunctionArrayLvalueConversion(LHS.get());
      if (LHS.isInvalid())
        return QualType();
    }
    RHS = DefaultFunctionArrayLvalueConversion(RHS.get());
    if (RHS.isInvalid())
      return QualType();
  
    // For conversion purposes, we ignore any qualifiers.
    // For example, "const float" and "float" are equivalent.
    QualType LHSType = LHS.get()->getType().getUnqualifiedType();
    QualType RHSType = RHS.get()->getType().getUnqualifiedType();
  
    const MatrixType *LHSMatType = LHSType->getAs<MatrixType>();
    const MatrixType *RHSMatType = RHSType->getAs<MatrixType>();
    assert((LHSMatType || RHSMatType) && "At least one operand must be a matrix");
  
    if (Context.hasSameType(LHSType, RHSType))
      return LHSType;
  
    // Type conversion may change LHS/RHS. Keep copies to the original results, in
    // case we have to return InvalidOperands.
    ExprResult OriginalLHS = LHS;
    ExprResult OriginalRHS = RHS;
    if (LHSMatType && !RHSMatType) {
      RHS = tryConvertExprToType(RHS.get(), LHSMatType->getElementType());
      if (!RHS.isInvalid())
        return LHSType;
  
      return InvalidOperands(Loc, OriginalLHS, OriginalRHS);
    }
  
    if (!LHSMatType && RHSMatType) {
      LHS = tryConvertExprToType(LHS.get(), RHSMatType->getElementType());
      if (!LHS.isInvalid())
        return RHSType;
      return InvalidOperands(Loc, OriginalLHS, OriginalRHS);
    }
  
    return InvalidOperands(Loc, LHS, RHS);
  }
  
  QualType Sema::CheckMatrixMultiplyOperands(ExprResult &LHS, ExprResult &RHS,
                                             SourceLocation Loc,
                                             bool IsCompAssign) {
    if (!IsCompAssign) {
      LHS = DefaultFunctionArrayLvalueConversion(LHS.get());
      if (LHS.isInvalid())
        return QualType();
    }
    RHS = DefaultFunctionArrayLvalueConversion(RHS.get());
    if (RHS.isInvalid())
      return QualType();
  
    auto *LHSMatType = LHS.get()->getType()->getAs<ConstantMatrixType>();
    auto *RHSMatType = RHS.get()->getType()->getAs<ConstantMatrixType>();
    assert((LHSMatType || RHSMatType) && "At least one operand must be a matrix");
  
    if (LHSMatType && RHSMatType) {
      if (LHSMatType->getNumColumns() != RHSMatType->getNumRows())
        return InvalidOperands(Loc, LHS, RHS);
  
      if (!Context.hasSameType(LHSMatType->getElementType(),
                               RHSMatType->getElementType()))
        return InvalidOperands(Loc, LHS, RHS);
  
      return Context.getConstantMatrixType(LHSMatType->getElementType(),
                                           LHSMatType->getNumRows(),
                                           RHSMatType->getNumColumns());
    }
    return CheckMatrixElementwiseOperands(LHS, RHS, Loc, IsCompAssign);
  }
  
  inline QualType Sema::CheckBitwiseOperands(ExprResult &LHS, ExprResult &RHS,
                                             SourceLocation Loc,
                                             BinaryOperatorKind Opc) {
    checkArithmeticNull(*this, LHS, RHS, Loc, /*IsCompare=*/false);
  
    bool IsCompAssign =
        Opc == BO_AndAssign || Opc == BO_OrAssign || Opc == BO_XorAssign;
  
    if (LHS.get()->getType()->isVectorType() ||
        RHS.get()->getType()->isVectorType()) {
      if (LHS.get()->getType()->hasIntegerRepresentation() &&
          RHS.get()->getType()->hasIntegerRepresentation())
        return CheckVectorOperands(LHS, RHS, Loc, IsCompAssign,
                          /*AllowBothBool*/true,
                          /*AllowBoolConversions*/getLangOpts().ZVector);
      return InvalidOperands(Loc, LHS, RHS);
    }
  
    if (Opc == BO_And)
      diagnoseLogicalNotOnLHSofCheck(*this, LHS, RHS, Loc, Opc);
  
    if (LHS.get()->getType()->hasFloatingRepresentation() ||
        RHS.get()->getType()->hasFloatingRepresentation())
      return InvalidOperands(Loc, LHS, RHS);
  
    ExprResult LHSResult = LHS, RHSResult = RHS;
    QualType compType = UsualArithmeticConversions(
        LHSResult, RHSResult, Loc, IsCompAssign ? ACK_CompAssign : ACK_BitwiseOp);
    if (LHSResult.isInvalid() || RHSResult.isInvalid())
      return QualType();
    LHS = LHSResult.get();
    RHS = RHSResult.get();
  
    if (Opc == BO_Xor)
      diagnoseXorMisusedAsPow(*this, LHS, RHS, Loc);
  
    if (!compType.isNull() && compType->isIntegralOrUnscopedEnumerationType())
      return compType;
    return InvalidOperands(Loc, LHS, RHS);
  }
  
  // C99 6.5.[13,14]
  inline QualType Sema::CheckLogicalOperands(ExprResult &LHS, ExprResult &RHS,
                                             SourceLocation Loc,
                                             BinaryOperatorKind Opc) {
    // Check vector operands differently.
    if (LHS.get()->getType()->isVectorType() || RHS.get()->getType()->isVectorType())
      return CheckVectorLogicalOperands(LHS, RHS, Loc);
  
    bool EnumConstantInBoolContext = false;
    for (const ExprResult &HS : {LHS, RHS}) {
      if (const auto *DREHS = dyn_cast<DeclRefExpr>(HS.get())) {
        const auto *ECDHS = dyn_cast<EnumConstantDecl>(DREHS->getDecl());
        if (ECDHS && ECDHS->getInitVal() != 0 && ECDHS->getInitVal() != 1)
          EnumConstantInBoolContext = true;
      }
    }
  
    if (EnumConstantInBoolContext)
      Diag(Loc, diag::warn_enum_constant_in_bool_context);
  
    // Diagnose cases where the user write a logical and/or but probably meant a
    // bitwise one.  We do this when the LHS is a non-bool integer and the RHS
    // is a constant.
    if (!EnumConstantInBoolContext && LHS.get()->getType()->isIntegerType() &&
        !LHS.get()->getType()->isBooleanType() &&
        RHS.get()->getType()->isIntegerType() && !RHS.get()->isValueDependent() &&
        // Don't warn in macros or template instantiations.
        !Loc.isMacroID() && !inTemplateInstantiation()) {
      // If the RHS can be constant folded, and if it constant folds to something
      // that isn't 0 or 1 (which indicate a potential logical operation that
      // happened to fold to true/false) then warn.
      // Parens on the RHS are ignored.
      Expr::EvalResult EVResult;
      if (RHS.get()->EvaluateAsInt(EVResult, Context)) {
        llvm::APSInt Result = EVResult.Val.getInt();
        if ((getLangOpts().Bool && !RHS.get()->getType()->isBooleanType() &&
             !RHS.get()->getExprLoc().isMacroID()) ||
            (Result != 0 && Result != 1)) {
          Diag(Loc, diag::warn_logical_instead_of_bitwise)
            << RHS.get()->getSourceRange()
            << (Opc == BO_LAnd ? "&&" : "||");
          // Suggest replacing the logical operator with the bitwise version
          Diag(Loc, diag::note_logical_instead_of_bitwise_change_operator)
              << (Opc == BO_LAnd ? "&" : "|")
              << FixItHint::CreateReplacement(SourceRange(
                                                   Loc, getLocForEndOfToken(Loc)),
                                              Opc == BO_LAnd ? "&" : "|");
          if (Opc == BO_LAnd)
            // Suggest replacing "Foo() && kNonZero" with "Foo()"
            Diag(Loc, diag::note_logical_instead_of_bitwise_remove_constant)
                << FixItHint::CreateRemoval(
                       SourceRange(getLocForEndOfToken(LHS.get()->getEndLoc()),
                                   RHS.get()->getEndLoc()));
        }
      }
    }
  
    if (!Context.getLangOpts().CPlusPlus) {
      // OpenCL v1.1 s6.3.g: The logical operators and (&&), or (||) do
      // not operate on the built-in scalar and vector float types.
      if (Context.getLangOpts().OpenCL &&
          Context.getLangOpts().OpenCLVersion < 120) {
        if (LHS.get()->getType()->isFloatingType() ||
            RHS.get()->getType()->isFloatingType())
          return InvalidOperands(Loc, LHS, RHS);
      }
  
      LHS = UsualUnaryConversions(LHS.get());
      if (LHS.isInvalid())
        return QualType();
  
      RHS = UsualUnaryConversions(RHS.get());
      if (RHS.isInvalid())
        return QualType();
  
      if (!LHS.get()->getType()->isScalarType() ||
          !RHS.get()->getType()->isScalarType())
        return InvalidOperands(Loc, LHS, RHS);
  
      return Context.IntTy;
    }
  
    // The following is safe because we only use this method for
    // non-overloadable operands.
  
    // C++ [expr.log.and]p1
    // C++ [expr.log.or]p1
    // The operands are both contextually converted to type bool.
    ExprResult LHSRes = PerformContextuallyConvertToBool(LHS.get());
    if (LHSRes.isInvalid())
      return InvalidOperands(Loc, LHS, RHS);
    LHS = LHSRes;
  
    ExprResult RHSRes = PerformContextuallyConvertToBool(RHS.get());
    if (RHSRes.isInvalid())
      return InvalidOperands(Loc, LHS, RHS);
    RHS = RHSRes;
  
    // C++ [expr.log.and]p2
    // C++ [expr.log.or]p2
    // The result is a bool.
    return Context.BoolTy;
  }
  
  static bool IsReadonlyMessage(Expr *E, Sema &S) {
    const MemberExpr *ME = dyn_cast<MemberExpr>(E);
    if (!ME) return false;
    if (!isa<FieldDecl>(ME->getMemberDecl())) return false;
    ObjCMessageExpr *Base = dyn_cast<ObjCMessageExpr>(
        ME->getBase()->IgnoreImplicit()->IgnoreParenImpCasts());
    if (!Base) return false;
    return Base->getMethodDecl() != nullptr;
  }
  
  /// Is the given expression (which must be 'const') a reference to a
  /// variable which was originally non-const, but which has become
  /// 'const' due to being captured within a block?
  enum NonConstCaptureKind { NCCK_None, NCCK_Block, NCCK_Lambda };
  static NonConstCaptureKind isReferenceToNonConstCapture(Sema &S, Expr *E) {
    assert(E->isLValue() && E->getType().isConstQualified());
    E = E->IgnoreParens();
  
    // Must be a reference to a declaration from an enclosing scope.
    DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E);
    if (!DRE) return NCCK_None;
    if (!DRE->refersToEnclosingVariableOrCapture()) return NCCK_None;
  
    // The declaration must be a variable which is not declared 'const'.
    VarDecl *var = dyn_cast<VarDecl>(DRE->getDecl());
    if (!var) return NCCK_None;
    if (var->getType().isConstQualified()) return NCCK_None;
    assert(var->hasLocalStorage() && "capture added 'const' to non-local?");
  
    // Decide whether the first capture was for a block or a lambda.
    DeclContext *DC = S.CurContext, *Prev = nullptr;
    // Decide whether the first capture was for a block or a lambda.
    while (DC) {
      // For init-capture, it is possible that the variable belongs to the
      // template pattern of the current context.
      if (auto *FD = dyn_cast<FunctionDecl>(DC))
        if (var->isInitCapture() &&
            FD->getTemplateInstantiationPattern() == var->getDeclContext())
          break;
      if (DC == var->getDeclContext())
        break;
      Prev = DC;
      DC = DC->getParent();
    }
    // Unless we have an init-capture, we've gone one step too far.
    if (!var->isInitCapture())
      DC = Prev;
    return (isa<BlockDecl>(DC) ? NCCK_Block : NCCK_Lambda);
  }
  
  static bool IsTypeModifiable(QualType Ty, bool IsDereference) {
    Ty = Ty.getNonReferenceType();
    if (IsDereference && Ty->isPointerType())
      Ty = Ty->getPointeeType();
    return !Ty.isConstQualified();
  }
  
  // Update err_typecheck_assign_const and note_typecheck_assign_const
  // when this enum is changed.
  enum {
    ConstFunction,
    ConstVariable,
    ConstMember,
    ConstMethod,
    NestedConstMember,
    ConstUnknown,  // Keep as last element
  };
  
  /// Emit the "read-only variable not assignable" error and print notes to give
  /// more information about why the variable is not assignable, such as pointing
  /// to the declaration of a const variable, showing that a method is const, or
  /// that the function is returning a const reference.
  static void DiagnoseConstAssignment(Sema &S, const Expr *E,
                                      SourceLocation Loc) {
    SourceRange ExprRange = E->getSourceRange();
  
    // Only emit one error on the first const found.  All other consts will emit
    // a note to the error.
    bool DiagnosticEmitted = false;
  
    // Track if the current expression is the result of a dereference, and if the
    // next checked expression is the result of a dereference.
    bool IsDereference = false;
    bool NextIsDereference = false;
  
    // Loop to process MemberExpr chains.
    while (true) {
      IsDereference = NextIsDereference;
  
      E = E->IgnoreImplicit()->IgnoreParenImpCasts();
      if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
        NextIsDereference = ME->isArrow();
        const ValueDecl *VD = ME->getMemberDecl();
        if (const FieldDecl *Field = dyn_cast<FieldDecl>(VD)) {
          // Mutable fields can be modified even if the class is const.
          if (Field->isMutable()) {
            assert(DiagnosticEmitted && "Expected diagnostic not emitted.");
            break;
          }
  
          if (!IsTypeModifiable(Field->getType(), IsDereference)) {
            if (!DiagnosticEmitted) {
              S.Diag(Loc, diag::err_typecheck_assign_const)
                  << ExprRange << ConstMember << false /*static*/ << Field
                  << Field->getType();
              DiagnosticEmitted = true;
            }
            S.Diag(VD->getLocation(), diag::note_typecheck_assign_const)
                << ConstMember << false /*static*/ << Field << Field->getType()
                << Field->getSourceRange();
          }
          E = ME->getBase();
          continue;
        } else if (const VarDecl *VDecl = dyn_cast<VarDecl>(VD)) {
          if (VDecl->getType().isConstQualified()) {
            if (!DiagnosticEmitted) {
              S.Diag(Loc, diag::err_typecheck_assign_const)
                  << ExprRange << ConstMember << true /*static*/ << VDecl
                  << VDecl->getType();
              DiagnosticEmitted = true;
            }
            S.Diag(VD->getLocation(), diag::note_typecheck_assign_const)
                << ConstMember << true /*static*/ << VDecl << VDecl->getType()
                << VDecl->getSourceRange();
          }
          // Static fields do not inherit constness from parents.
          break;
        }
        break; // End MemberExpr
      } else if (const ArraySubscriptExpr *ASE =
                     dyn_cast<ArraySubscriptExpr>(E)) {
        E = ASE->getBase()->IgnoreParenImpCasts();
        continue;
      } else if (const ExtVectorElementExpr *EVE =
                     dyn_cast<ExtVectorElementExpr>(E)) {
        E = EVE->getBase()->IgnoreParenImpCasts();
        continue;
      }
      break;
    }
  
    if (const CallExpr *CE = dyn_cast<CallExpr>(E)) {
      // Function calls
      const FunctionDecl *FD = CE->getDirectCallee();
      if (FD && !IsTypeModifiable(FD->getReturnType(), IsDereference)) {
        if (!DiagnosticEmitted) {
          S.Diag(Loc, diag::err_typecheck_assign_const) << ExprRange
                                                        << ConstFunction << FD;
          DiagnosticEmitted = true;
        }
        S.Diag(FD->getReturnTypeSourceRange().getBegin(),
               diag::note_typecheck_assign_const)
            << ConstFunction << FD << FD->getReturnType()
            << FD->getReturnTypeSourceRange();
      }
    } else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
      // Point to variable declaration.
      if (const ValueDecl *VD = DRE->getDecl()) {
        if (!IsTypeModifiable(VD->getType(), IsDereference)) {
          if (!DiagnosticEmitted) {
            S.Diag(Loc, diag::err_typecheck_assign_const)
                << ExprRange << ConstVariable << VD << VD->getType();
            DiagnosticEmitted = true;
          }
          S.Diag(VD->getLocation(), diag::note_typecheck_assign_const)
              << ConstVariable << VD << VD->getType() << VD->getSourceRange();
        }
      }
    } else if (isa<CXXThisExpr>(E)) {
      if (const DeclContext *DC = S.getFunctionLevelDeclContext()) {
        if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(DC)) {
          if (MD->isConst()) {
            if (!DiagnosticEmitted) {
              S.Diag(Loc, diag::err_typecheck_assign_const) << ExprRange
                                                            << ConstMethod << MD;
              DiagnosticEmitted = true;
            }
            S.Diag(MD->getLocation(), diag::note_typecheck_assign_const)
                << ConstMethod << MD << MD->getSourceRange();
          }
        }
      }
    }
  
    if (DiagnosticEmitted)
      return;
  
    // Can't determine a more specific message, so display the generic error.
    S.Diag(Loc, diag::err_typecheck_assign_const) << ExprRange << ConstUnknown;
  }
  
  enum OriginalExprKind {
    OEK_Variable,
    OEK_Member,
    OEK_LValue
  };
  
  static void DiagnoseRecursiveConstFields(Sema &S, const ValueDecl *VD,
                                           const RecordType *Ty,
                                           SourceLocation Loc, SourceRange Range,
                                           OriginalExprKind OEK,
                                           bool &DiagnosticEmitted) {
    std::vector<const RecordType *> RecordTypeList;
    RecordTypeList.push_back(Ty);
    unsigned NextToCheckIndex = 0;
    // We walk the record hierarchy breadth-first to ensure that we print
    // diagnostics in field nesting order.
    while (RecordTypeList.size() > NextToCheckIndex) {
      bool IsNested = NextToCheckIndex > 0;
      for (const FieldDecl *Field :
           RecordTypeList[NextToCheckIndex]->getDecl()->fields()) {
        // First, check every field for constness.
        QualType FieldTy = Field->getType();
        if (FieldTy.isConstQualified()) {
          if (!DiagnosticEmitted) {
            S.Diag(Loc, diag::err_typecheck_assign_const)
                << Range << NestedConstMember << OEK << VD
                << IsNested << Field;
            DiagnosticEmitted = true;
          }
          S.Diag(Field->getLocation(), diag::note_typecheck_assign_const)
              << NestedConstMember << IsNested << Field
              << FieldTy << Field->getSourceRange();
        }
  
        // Then we append it to the list to check next in order.
        FieldTy = FieldTy.getCanonicalType();
        if (const auto *FieldRecTy = FieldTy->getAs<RecordType>()) {
          if (!llvm::is_contained(RecordTypeList, FieldRecTy))
            RecordTypeList.push_back(FieldRecTy);
        }
      }
      ++NextToCheckIndex;
    }
  }
  
  /// Emit an error for the case where a record we are trying to assign to has a
  /// const-qualified field somewhere in its hierarchy.
  static void DiagnoseRecursiveConstFields(Sema &S, const Expr *E,
                                           SourceLocation Loc) {
    QualType Ty = E->getType();
    assert(Ty->isRecordType() && "lvalue was not record?");
    SourceRange Range = E->getSourceRange();
    const RecordType *RTy = Ty.getCanonicalType()->getAs<RecordType>();
    bool DiagEmitted = false;
  
    if (const MemberExpr *ME = dyn_cast<MemberExpr>(E))
      DiagnoseRecursiveConstFields(S, ME->getMemberDecl(), RTy, Loc,
              Range, OEK_Member, DiagEmitted);
    else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
      DiagnoseRecursiveConstFields(S, DRE->getDecl(), RTy, Loc,
              Range, OEK_Variable, DiagEmitted);
    else
      DiagnoseRecursiveConstFields(S, nullptr, RTy, Loc,
              Range, OEK_LValue, DiagEmitted);
    if (!DiagEmitted)
      DiagnoseConstAssignment(S, E, Loc);
  }
  
  /// CheckForModifiableLvalue - Verify that E is a modifiable lvalue.  If not,
  /// emit an error and return true.  If so, return false.
  static bool CheckForModifiableLvalue(Expr *E, SourceLocation Loc, Sema &S) {
    assert(!E->hasPlaceholderType(BuiltinType::PseudoObject));
  
    S.CheckShadowingDeclModification(E, Loc);
  
    SourceLocation OrigLoc = Loc;
    Expr::isModifiableLvalueResult IsLV = E->isModifiableLvalue(S.Context,
                                                                &Loc);
    if (IsLV == Expr::MLV_ClassTemporary && IsReadonlyMessage(E, S))
      IsLV = Expr::MLV_InvalidMessageExpression;
    if (IsLV == Expr::MLV_Valid)
      return false;
  
    unsigned DiagID = 0;
    bool NeedType = false;
    switch (IsLV) { // C99 6.5.16p2
    case Expr::MLV_ConstQualified:
      // Use a specialized diagnostic when we're assigning to an object
      // from an enclosing function or block.
      if (NonConstCaptureKind NCCK = isReferenceToNonConstCapture(S, E)) {
        if (NCCK == NCCK_Block)
          DiagID = diag::err_block_decl_ref_not_modifiable_lvalue;
        else
          DiagID = diag::err_lambda_decl_ref_not_modifiable_lvalue;
        break;
      }
  
      // In ARC, use some specialized diagnostics for occasions where we
      // infer 'const'.  These are always pseudo-strong variables.
      if (S.getLangOpts().ObjCAutoRefCount) {
        DeclRefExpr *declRef = dyn_cast<DeclRefExpr>(E->IgnoreParenCasts());
        if (declRef && isa<VarDecl>(declRef->getDecl())) {
          VarDecl *var = cast<VarDecl>(declRef->getDecl());
  
          // Use the normal diagnostic if it's pseudo-__strong but the
          // user actually wrote 'const'.
          if (var->isARCPseudoStrong() &&
              (!var->getTypeSourceInfo() ||
               !var->getTypeSourceInfo()->getType().isConstQualified())) {
            // There are three pseudo-strong cases:
            //  - self
            ObjCMethodDecl *method = S.getCurMethodDecl();
            if (method && var == method->getSelfDecl()) {
              DiagID = method->isClassMethod()
                ? diag::err_typecheck_arc_assign_self_class_method
                : diag::err_typecheck_arc_assign_self;
  
            //  - Objective-C externally_retained attribute.
            } else if (var->hasAttr<ObjCExternallyRetainedAttr>() ||
                       isa<ParmVarDecl>(var)) {
              DiagID = diag::err_typecheck_arc_assign_externally_retained;
  
            //  - fast enumeration variables
            } else {
              DiagID = diag::err_typecheck_arr_assign_enumeration;
            }
  
            SourceRange Assign;
            if (Loc != OrigLoc)
              Assign = SourceRange(OrigLoc, OrigLoc);
            S.Diag(Loc, DiagID) << E->getSourceRange() << Assign;
            // We need to preserve the AST regardless, so migration tool
            // can do its job.
            return false;
          }
        }
      }
  
      // If none of the special cases above are triggered, then this is a
      // simple const assignment.
      if (DiagID == 0) {
        DiagnoseConstAssignment(S, E, Loc);
        return true;
      }
  
      break;
    case Expr::MLV_ConstAddrSpace:
      DiagnoseConstAssignment(S, E, Loc);
      return true;
    case Expr::MLV_ConstQualifiedField:
      DiagnoseRecursiveConstFields(S, E, Loc);
      return true;
    case Expr::MLV_ArrayType:
    case Expr::MLV_ArrayTemporary:
      DiagID = diag::err_typecheck_array_not_modifiable_lvalue;
      NeedType = true;
      break;
    case Expr::MLV_NotObjectType:
      DiagID = diag::err_typecheck_non_object_not_modifiable_lvalue;
      NeedType = true;
      break;
    case Expr::MLV_LValueCast:
      DiagID = diag::err_typecheck_lvalue_casts_not_supported;
      break;
    case Expr::MLV_Valid:
      llvm_unreachable("did not take early return for MLV_Valid");
    case Expr::MLV_InvalidExpression:
    case Expr::MLV_MemberFunction:
    case Expr::MLV_ClassTemporary:
      DiagID = diag::err_typecheck_expression_not_modifiable_lvalue;
      break;
    case Expr::MLV_IncompleteType:
    case Expr::MLV_IncompleteVoidType:
      return S.RequireCompleteType(Loc, E->getType(),
               diag::err_typecheck_incomplete_type_not_modifiable_lvalue, E);
    case Expr::MLV_DuplicateVectorComponents:
      DiagID = diag::err_typecheck_duplicate_vector_components_not_mlvalue;
      break;
    case Expr::MLV_NoSetterProperty:
      llvm_unreachable("readonly properties should be processed differently");
    case Expr::MLV_InvalidMessageExpression:
      DiagID = diag::err_readonly_message_assignment;
      break;
    case Expr::MLV_SubObjCPropertySetting:
      DiagID = diag::err_no_subobject_property_setting;
      break;
    }
  
    SourceRange Assign;
    if (Loc != OrigLoc)
      Assign = SourceRange(OrigLoc, OrigLoc);
    if (NeedType)
      S.Diag(Loc, DiagID) << E->getType() << E->getSourceRange() << Assign;
    else
      S.Diag(Loc, DiagID) << E->getSourceRange() << Assign;
    return true;
  }
  
  static void CheckIdentityFieldAssignment(Expr *LHSExpr, Expr *RHSExpr,
                                           SourceLocation Loc,
                                           Sema &Sema) {
    if (Sema.inTemplateInstantiation())
      return;
    if (Sema.isUnevaluatedContext())
      return;
    if (Loc.isInvalid() || Loc.isMacroID())
      return;
    if (LHSExpr->getExprLoc().isMacroID() || RHSExpr->getExprLoc().isMacroID())
      return;
  
    // C / C++ fields
    MemberExpr *ML = dyn_cast<MemberExpr>(LHSExpr);
    MemberExpr *MR = dyn_cast<MemberExpr>(RHSExpr);
    if (ML && MR) {
      if (!(isa<CXXThisExpr>(ML->getBase()) && isa<CXXThisExpr>(MR->getBase())))
        return;
      const ValueDecl *LHSDecl =
          cast<ValueDecl>(ML->getMemberDecl()->getCanonicalDecl());
      const ValueDecl *RHSDecl =
          cast<ValueDecl>(MR->getMemberDecl()->getCanonicalDecl());
      if (LHSDecl != RHSDecl)
        return;
      if (LHSDecl->getType().isVolatileQualified())
        return;
      if (const ReferenceType *RefTy = LHSDecl->getType()->getAs<ReferenceType>())
        if (RefTy->getPointeeType().isVolatileQualified())
          return;
  
      Sema.Diag(Loc, diag::warn_identity_field_assign) << 0;
    }
  
    // Objective-C instance variables
    ObjCIvarRefExpr *OL = dyn_cast<ObjCIvarRefExpr>(LHSExpr);
    ObjCIvarRefExpr *OR = dyn_cast<ObjCIvarRefExpr>(RHSExpr);
    if (OL && OR && OL->getDecl() == OR->getDecl()) {
      DeclRefExpr *RL = dyn_cast<DeclRefExpr>(OL->getBase()->IgnoreImpCasts());
      DeclRefExpr *RR = dyn_cast<DeclRefExpr>(OR->getBase()->IgnoreImpCasts());
      if (RL && RR && RL->getDecl() == RR->getDecl())
        Sema.Diag(Loc, diag::warn_identity_field_assign) << 1;
    }
  }
  
  // C99 6.5.16.1
  QualType Sema::CheckAssignmentOperands(Expr *LHSExpr, ExprResult &RHS,
                                         SourceLocation Loc,
                                         QualType CompoundType) {
    assert(!LHSExpr->hasPlaceholderType(BuiltinType::PseudoObject));
  
    // Verify that LHS is a modifiable lvalue, and emit error if not.
    if (CheckForModifiableLvalue(LHSExpr, Loc, *this))
      return QualType();
  
    QualType LHSType = LHSExpr->getType();
    QualType RHSType = CompoundType.isNull() ? RHS.get()->getType() :
                                               CompoundType;
    // OpenCL v1.2 s6.1.1.1 p2:
    // The half data type can only be used to declare a pointer to a buffer that
    // contains half values
    if (getLangOpts().OpenCL &&
        !getOpenCLOptions().isAvailableOption("cl_khr_fp16", getLangOpts()) &&
        LHSType->isHalfType()) {
      Diag(Loc, diag::err_opencl_half_load_store) << 1
          << LHSType.getUnqualifiedType();
      return QualType();
    }
  
    AssignConvertType ConvTy;
    if (CompoundType.isNull()) {
      Expr *RHSCheck = RHS.get();
  
      CheckIdentityFieldAssignment(LHSExpr, RHSCheck, Loc, *this);
  
      QualType LHSTy(LHSType);
      ConvTy = CheckSingleAssignmentConstraints(LHSTy, RHS);
      if (RHS.isInvalid())
        return QualType();
      // Special case of NSObject attributes on c-style pointer types.
      if (ConvTy == IncompatiblePointer &&
          ((Context.isObjCNSObjectType(LHSType) &&
            RHSType->isObjCObjectPointerType()) ||
           (Context.isObjCNSObjectType(RHSType) &&
            LHSType->isObjCObjectPointerType())))
        ConvTy = Compatible;
  
      if (ConvTy == Compatible &&
          LHSType->isObjCObjectType())
          Diag(Loc, diag::err_objc_object_assignment)
            << LHSType;
  
      // If the RHS is a unary plus or minus, check to see if they = and + are
      // right next to each other.  If so, the user may have typo'd "x =+ 4"
      // instead of "x += 4".
      if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(RHSCheck))
        RHSCheck = ICE->getSubExpr();
      if (UnaryOperator *UO = dyn_cast<UnaryOperator>(RHSCheck)) {
        if ((UO->getOpcode() == UO_Plus || UO->getOpcode() == UO_Minus) &&
            Loc.isFileID() && UO->getOperatorLoc().isFileID() &&
            // Only if the two operators are exactly adjacent.
            Loc.getLocWithOffset(1) == UO->getOperatorLoc() &&
            // And there is a space or other character before the subexpr of the
            // unary +/-.  We don't want to warn on "x=-1".
            Loc.getLocWithOffset(2) != UO->getSubExpr()->getBeginLoc() &&
            UO->getSubExpr()->getBeginLoc().isFileID()) {
          Diag(Loc, diag::warn_not_compound_assign)
            << (UO->getOpcode() == UO_Plus ? "+" : "-")
            << SourceRange(UO->getOperatorLoc(), UO->getOperatorLoc());
        }
      }
  
      if (ConvTy == Compatible) {
        if (LHSType.getObjCLifetime() == Qualifiers::OCL_Strong) {
          // Warn about retain cycles where a block captures the LHS, but
          // not if the LHS is a simple variable into which the block is
          // being stored...unless that variable can be captured by reference!
          const Expr *InnerLHS = LHSExpr->IgnoreParenCasts();
          const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(InnerLHS);
          if (!DRE || DRE->getDecl()->hasAttr<BlocksAttr>())
            checkRetainCycles(LHSExpr, RHS.get());
        }
  
        if (LHSType.getObjCLifetime() == Qualifiers::OCL_Strong ||
            LHSType.isNonWeakInMRRWithObjCWeak(Context)) {
          // It is safe to assign a weak reference into a strong variable.
          // Although this code can still have problems:
          //   id x = self.weakProp;
          //   id y = self.weakProp;
          // we do not warn to warn spuriously when 'x' and 'y' are on separate
          // paths through the function. This should be revisited if
          // -Wrepeated-use-of-weak is made flow-sensitive.
          // For ObjCWeak only, we do not warn if the assign is to a non-weak
          // variable, which will be valid for the current autorelease scope.
          if (!Diags.isIgnored(diag::warn_arc_repeated_use_of_weak,
                               RHS.get()->getBeginLoc()))
            getCurFunction()->markSafeWeakUse(RHS.get());
  
        } else if (getLangOpts().ObjCAutoRefCount || getLangOpts().ObjCWeak) {
          checkUnsafeExprAssigns(Loc, LHSExpr, RHS.get());
        }
      }
    } else {
      // Compound assignment "x += y"
      ConvTy = CheckAssignmentConstraints(Loc, LHSType, RHSType);
    }
  
    if (DiagnoseAssignmentResult(ConvTy, Loc, LHSType, RHSType,
                                 RHS.get(), AA_Assigning))
      return QualType();
  
    CheckForNullPointerDereference(*this, LHSExpr);
  
    if (getLangOpts().CPlusPlus20 && LHSType.isVolatileQualified()) {
      if (CompoundType.isNull()) {
        // C++2a [expr.ass]p5:
        //   A simple-assignment whose left operand is of a volatile-qualified
        //   type is deprecated unless the assignment is either a discarded-value
        //   expression or an unevaluated operand
        ExprEvalContexts.back().VolatileAssignmentLHSs.push_back(LHSExpr);
      } else {
        // C++2a [expr.ass]p6:
        //   [Compound-assignment] expressions are deprecated if E1 has
        //   volatile-qualified type
        Diag(Loc, diag::warn_deprecated_compound_assign_volatile) << LHSType;
      }
    }
  
    // C99 6.5.16p3: The type of an assignment expression is the type of the
    // left operand unless the left operand has qualified type, in which case
    // it is the unqualified version of the type of the left operand.
    // C99 6.5.16.1p2: In simple assignment, the value of the right operand
    // is converted to the type of the assignment expression (above).
    // C++ 5.17p1: the type of the assignment expression is that of its left
    // operand.
    return (getLangOpts().CPlusPlus
            ? LHSType : LHSType.getUnqualifiedType());
  }
  
  // Only ignore explicit casts to void.
  static bool IgnoreCommaOperand(const Expr *E) {
    E = E->IgnoreParens();
  
    if (const CastExpr *CE = dyn_cast<CastExpr>(E)) {
      if (CE->getCastKind() == CK_ToVoid) {
        return true;
      }
  
      // static_cast<void> on a dependent type will not show up as CK_ToVoid.
      if (CE->getCastKind() == CK_Dependent && E->getType()->isVoidType() &&
          CE->getSubExpr()->getType()->isDependentType()) {
        return true;
      }
    }
  
    return false;
  }
  
  // Look for instances where it is likely the comma operator is confused with
  // another operator.  There is an explicit list of acceptable expressions for
  // the left hand side of the comma operator, otherwise emit a warning.
  void Sema::DiagnoseCommaOperator(const Expr *LHS, SourceLocation Loc) {
    // No warnings in macros
    if (Loc.isMacroID())
      return;
  
    // Don't warn in template instantiations.
    if (inTemplateInstantiation())
      return;
  
    // Scope isn't fine-grained enough to explicitly list the specific cases, so
    // instead, skip more than needed, then call back into here with the
    // CommaVisitor in SemaStmt.cpp.
    // The listed locations are the initialization and increment portions
    // of a for loop.  The additional checks are on the condition of
    // if statements, do/while loops, and for loops.
    // Differences in scope flags for C89 mode requires the extra logic.
    const unsigned ForIncrementFlags =
        getLangOpts().C99 || getLangOpts().CPlusPlus
            ? Scope::ControlScope | Scope::ContinueScope | Scope::BreakScope
            : Scope::ContinueScope | Scope::BreakScope;
    const unsigned ForInitFlags = Scope::ControlScope | Scope::DeclScope;
    const unsigned ScopeFlags = getCurScope()->getFlags();
    if ((ScopeFlags & ForIncrementFlags) == ForIncrementFlags ||
        (ScopeFlags & ForInitFlags) == ForInitFlags)
      return;
  
    // If there are multiple comma operators used together, get the RHS of the
    // of the comma operator as the LHS.
    while (const BinaryOperator *BO = dyn_cast<BinaryOperator>(LHS)) {
      if (BO->getOpcode() != BO_Comma)
        break;
      LHS = BO->getRHS();
    }
  
    // Only allow some expressions on LHS to not warn.
    if (IgnoreCommaOperand(LHS))
      return;
  
    Diag(Loc, diag::warn_comma_operator);
    Diag(LHS->getBeginLoc(), diag::note_cast_to_void)
        << LHS->getSourceRange()
        << FixItHint::CreateInsertion(LHS->getBeginLoc(),
                                      LangOpts.CPlusPlus ? "static_cast<void>("
                                                         : "(void)(")
        << FixItHint::CreateInsertion(PP.getLocForEndOfToken(LHS->getEndLoc()),
                                      ")");
  }
  
  // C99 6.5.17
  static QualType CheckCommaOperands(Sema &S, ExprResult &LHS, ExprResult &RHS,
                                     SourceLocation Loc) {
    LHS = S.CheckPlaceholderExpr(LHS.get());
    RHS = S.CheckPlaceholderExpr(RHS.get());
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();
  
    // C's comma performs lvalue conversion (C99 6.3.2.1) on both its
    // operands, but not unary promotions.
    // C++'s comma does not do any conversions at all (C++ [expr.comma]p1).
  
    // So we treat the LHS as a ignored value, and in C++ we allow the
    // containing site to determine what should be done with the RHS.
    LHS = S.IgnoredValueConversions(LHS.get());
    if (LHS.isInvalid())
      return QualType();
  
    S.DiagnoseUnusedExprResult(LHS.get(), diag::warn_unused_comma_left_operand);
  
    if (!S.getLangOpts().CPlusPlus) {
      RHS = S.DefaultFunctionArrayLvalueConversion(RHS.get());
      if (RHS.isInvalid())
        return QualType();
      if (!RHS.get()->getType()->isVoidType())
        S.RequireCompleteType(Loc, RHS.get()->getType(),
                              diag::err_incomplete_type);
    }
  
    if (!S.getDiagnostics().isIgnored(diag::warn_comma_operator, Loc))
      S.DiagnoseCommaOperator(LHS.get(), Loc);
  
    return RHS.get()->getType();
  }
  
  /// CheckIncrementDecrementOperand - unlike most "Check" methods, this routine
  /// doesn't need to call UsualUnaryConversions or UsualArithmeticConversions.
  static QualType CheckIncrementDecrementOperand(Sema &S, Expr *Op,
                                                 ExprValueKind &VK,
                                                 ExprObjectKind &OK,
                                                 SourceLocation OpLoc,
                                                 bool IsInc, bool IsPrefix) {
    if (Op->isTypeDependent())
      return S.Context.DependentTy;
  
    QualType ResType = Op->getType();
    // Atomic types can be used for increment / decrement where the non-atomic
    // versions can, so ignore the _Atomic() specifier for the purpose of
    // checking.
    if (const AtomicType *ResAtomicType = ResType->getAs<AtomicType>())
      ResType = ResAtomicType->getValueType();
  
    assert(!ResType.isNull() && "no type for increment/decrement expression");
  
    if (S.getLangOpts().CPlusPlus && ResType->isBooleanType()) {
      // Decrement of bool is not allowed.
      if (!IsInc) {
        S.Diag(OpLoc, diag::err_decrement_bool) << Op->getSourceRange();
        return QualType();
      }
      // Increment of bool sets it to true, but is deprecated.
      S.Diag(OpLoc, S.getLangOpts().CPlusPlus17 ? diag::ext_increment_bool
                                                : diag::warn_increment_bool)
        << Op->getSourceRange();
    } else if (S.getLangOpts().CPlusPlus && ResType->isEnumeralType()) {
      // Error on enum increments and decrements in C++ mode
      S.Diag(OpLoc, diag::err_increment_decrement_enum) << IsInc << ResType;
      return QualType();
    } else if (ResType->isRealType()) {
      // OK!
    } else if (ResType->isPointerType()) {
      // C99 6.5.2.4p2, 6.5.6p2
      if (!checkArithmeticOpPointerOperand(S, OpLoc, Op))
        return QualType();
    } else if (ResType->isObjCObjectPointerType()) {
      // On modern runtimes, ObjC pointer arithmetic is forbidden.
      // Otherwise, we just need a complete type.
      if (checkArithmeticIncompletePointerType(S, OpLoc, Op) ||
          checkArithmeticOnObjCPointer(S, OpLoc, Op))
        return QualType();
    } else if (ResType->isAnyComplexType()) {
      // C99 does not support ++/-- on complex types, we allow as an extension.
      S.Diag(OpLoc, diag::ext_integer_increment_complex)
        << ResType << Op->getSourceRange();
    } else if (ResType->isPlaceholderType()) {
      ExprResult PR = S.CheckPlaceholderExpr(Op);
      if (PR.isInvalid()) return QualType();
      return CheckIncrementDecrementOperand(S, PR.get(), VK, OK, OpLoc,
                                            IsInc, IsPrefix);
    } else if (S.getLangOpts().AltiVec && ResType->isVectorType()) {
      // OK! ( C/C++ Language Extensions for CBEA(Version 2.6) 10.3 )
    } else if (S.getLangOpts().ZVector && ResType->isVectorType() &&
               (ResType->castAs<VectorType>()->getVectorKind() !=
                VectorType::AltiVecBool)) {
      // The z vector extensions allow ++ and -- for non-bool vectors.
    } else if(S.getLangOpts().OpenCL && ResType->isVectorType() &&
              ResType->castAs<VectorType>()->getElementType()->isIntegerType()) {
      // OpenCL V1.2 6.3 says dec/inc ops operate on integer vector types.
    } else {
      S.Diag(OpLoc, diag::err_typecheck_illegal_increment_decrement)
        << ResType << int(IsInc) << Op->getSourceRange();
      return QualType();
    }
    // At this point, we know we have a real, complex or pointer type.
    // Now make sure the operand is a modifiable lvalue.
    if (CheckForModifiableLvalue(Op, OpLoc, S))
      return QualType();
    if (S.getLangOpts().CPlusPlus20 && ResType.isVolatileQualified()) {
      // C++2a [expr.pre.inc]p1, [expr.post.inc]p1:
      //   An operand with volatile-qualified type is deprecated
      S.Diag(OpLoc, diag::warn_deprecated_increment_decrement_volatile)
          << IsInc << ResType;
    }
    // In C++, a prefix increment is the same type as the operand. Otherwise
    // (in C or with postfix), the increment is the unqualified type of the
    // operand.
    if (IsPrefix && S.getLangOpts().CPlusPlus) {
      VK = VK_LValue;
      OK = Op->getObjectKind();
      return ResType;
    } else {
      VK = VK_PRValue;
      return ResType.getUnqualifiedType();
    }
  }
  
  
  /// getPrimaryDecl - Helper function for CheckAddressOfOperand().
  /// This routine allows us to typecheck complex/recursive expressions
  /// where the declaration is needed for type checking. We only need to
  /// handle cases when the expression references a function designator
  /// or is an lvalue. Here are some examples:
  ///  - &(x) => x
  ///  - &*****f => f for f a function designator.
  ///  - &s.xx => s
  ///  - &s.zz[1].yy -> s, if zz is an array
  ///  - *(x + 1) -> x, if x is an array
  ///  - &"123"[2] -> 0
  ///  - & __real__ x -> x
  ///
  /// FIXME: We don't recurse to the RHS of a comma, nor handle pointers to
  /// members.
  static ValueDecl *getPrimaryDecl(Expr *E) {
    switch (E->getStmtClass()) {
    case Stmt::DeclRefExprClass:
      return cast<DeclRefExpr>(E)->getDecl();
    case Stmt::MemberExprClass:
      // If this is an arrow operator, the address is an offset from
      // the base's value, so the object the base refers to is
      // irrelevant.
      if (cast<MemberExpr>(E)->isArrow())
        return nullptr;
      // Otherwise, the expression refers to a part of the base
      return getPrimaryDecl(cast<MemberExpr>(E)->getBase());
    case Stmt::ArraySubscriptExprClass: {
      // FIXME: This code shouldn't be necessary!  We should catch the implicit
      // promotion of register arrays earlier.
      Expr* Base = cast<ArraySubscriptExpr>(E)->getBase();
      if (ImplicitCastExpr* ICE = dyn_cast<ImplicitCastExpr>(Base)) {
        if (ICE->getSubExpr()->getType()->isArrayType())
          return getPrimaryDecl(ICE->getSubExpr());
      }
      return nullptr;
    }
    case Stmt::UnaryOperatorClass: {
      UnaryOperator *UO = cast<UnaryOperator>(E);
  
      switch(UO->getOpcode()) {
      case UO_Real:
      case UO_Imag:
      case UO_Extension:
        return getPrimaryDecl(UO->getSubExpr());
      default:
        return nullptr;
      }
    }
    case Stmt::ParenExprClass:
      return getPrimaryDecl(cast<ParenExpr>(E)->getSubExpr());
    case Stmt::ImplicitCastExprClass:
      // If the result of an implicit cast is an l-value, we care about
      // the sub-expression; otherwise, the result here doesn't matter.
      return getPrimaryDecl(cast<ImplicitCastExpr>(E)->getSubExpr());
    case Stmt::CXXUuidofExprClass:
      return cast<CXXUuidofExpr>(E)->getGuidDecl();
    default:
      return nullptr;
    }
  }
  
  namespace {
  enum {
    AO_Bit_Field = 0,
    AO_Vector_Element = 1,
    AO_Property_Expansion = 2,
    AO_Register_Variable = 3,
    AO_Matrix_Element = 4,
    AO_No_Error = 5
  };
  }
  /// Diagnose invalid operand for address of operations.
  ///
  /// \param Type The type of operand which cannot have its address taken.
  static void diagnoseAddressOfInvalidType(Sema &S, SourceLocation Loc,
                                           Expr *E, unsigned Type) {
    S.Diag(Loc, diag::err_typecheck_address_of) << Type << E->getSourceRange();
  }
  
  /// CheckAddressOfOperand - The operand of & must be either a function
  /// designator or an lvalue designating an object. If it is an lvalue, the
  /// object cannot be declared with storage class register or be a bit field.
  /// Note: The usual conversions are *not* applied to the operand of the &
  /// operator (C99 6.3.2.1p[2-4]), and its result is never an lvalue.
  /// In C++, the operand might be an overloaded function name, in which case
  /// we allow the '&' but retain the overloaded-function type.
  QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc) {
    if (const BuiltinType *PTy = OrigOp.get()->getType()->getAsPlaceholderType()){
      if (PTy->getKind() == BuiltinType::Overload) {
        Expr *E = OrigOp.get()->IgnoreParens();
        if (!isa<OverloadExpr>(E)) {
          assert(cast<UnaryOperator>(E)->getOpcode() == UO_AddrOf);
          Diag(OpLoc, diag::err_typecheck_invalid_lvalue_addrof_addrof_function)
            << OrigOp.get()->getSourceRange();
          return QualType();
        }
  
        OverloadExpr *Ovl = cast<OverloadExpr>(E);
        if (isa<UnresolvedMemberExpr>(Ovl))
          if (!ResolveSingleFunctionTemplateSpecialization(Ovl)) {
            Diag(OpLoc, diag::err_invalid_form_pointer_member_function)
              << OrigOp.get()->getSourceRange();
            return QualType();
          }
  
        return Context.OverloadTy;
      }
  
      if (PTy->getKind() == BuiltinType::UnknownAny)
        return Context.UnknownAnyTy;
  
      if (PTy->getKind() == BuiltinType::BoundMember) {
        Diag(OpLoc, diag::err_invalid_form_pointer_member_function)
          << OrigOp.get()->getSourceRange();
        return QualType();
      }
  
      OrigOp = CheckPlaceholderExpr(OrigOp.get());
      if (OrigOp.isInvalid()) return QualType();
    }
  
    if (OrigOp.get()->isTypeDependent())
      return Context.DependentTy;
  
    assert(!OrigOp.get()->hasPlaceholderType());
  
    // Make sure to ignore parentheses in subsequent checks
    Expr *op = OrigOp.get()->IgnoreParens();
  
    // In OpenCL captures for blocks called as lambda functions
    // are located in the private address space. Blocks used in
    // enqueue_kernel can be located in a different address space
    // depending on a vendor implementation. Thus preventing
    // taking an address of the capture to avoid invalid AS casts.
    if (LangOpts.OpenCL) {
      auto* VarRef = dyn_cast<DeclRefExpr>(op);
      if (VarRef && VarRef->refersToEnclosingVariableOrCapture()) {
        Diag(op->getExprLoc(), diag::err_opencl_taking_address_capture);
        return QualType();
      }
    }
  
    if (getLangOpts().C99) {
      // Implement C99-only parts of addressof rules.
      if (UnaryOperator* uOp = dyn_cast<UnaryOperator>(op)) {
        if (uOp->getOpcode() == UO_Deref)
          // Per C99 6.5.3.2, the address of a deref always returns a valid result
          // (assuming the deref expression is valid).
          return uOp->getSubExpr()->getType();
      }
      // Technically, there should be a check for array subscript
      // expressions here, but the result of one is always an lvalue anyway.
    }
    ValueDecl *dcl = getPrimaryDecl(op);
  
    if (auto *FD = dyn_cast_or_null<FunctionDecl>(dcl))
      if (!checkAddressOfFunctionIsAvailable(FD, /*Complain=*/true,
                                             op->getBeginLoc()))
        return QualType();
  
    Expr::LValueClassification lval = op->ClassifyLValue(Context);
    unsigned AddressOfError = AO_No_Error;
  
    if (lval == Expr::LV_ClassTemporary || lval == Expr::LV_ArrayTemporary) {
      bool sfinae = (bool)isSFINAEContext();
      Diag(OpLoc, isSFINAEContext() ? diag::err_typecheck_addrof_temporary
                                    : diag::ext_typecheck_addrof_temporary)
        << op->getType() << op->getSourceRange();
      if (sfinae)
        return QualType();
      // Materialize the temporary as an lvalue so that we can take its address.
      OrigOp = op =
          CreateMaterializeTemporaryExpr(op->getType(), OrigOp.get(), true);
    } else if (isa<ObjCSelectorExpr>(op)) {
      return Context.getPointerType(op->getType());
    } else if (lval == Expr::LV_MemberFunction) {
      // If it's an instance method, make a member pointer.
      // The expression must have exactly the form &A::foo.
  
      // If the underlying expression isn't a decl ref, give up.
      if (!isa<DeclRefExpr>(op)) {
        Diag(OpLoc, diag::err_invalid_form_pointer_member_function)
          << OrigOp.get()->getSourceRange();
        return QualType();
      }
      DeclRefExpr *DRE = cast<DeclRefExpr>(op);
      CXXMethodDecl *MD = cast<CXXMethodDecl>(DRE->getDecl());
  
      // The id-expression was parenthesized.
      if (OrigOp.get() != DRE) {
        Diag(OpLoc, diag::err_parens_pointer_member_function)
          << OrigOp.get()->getSourceRange();
  
      // The method was named without a qualifier.
      } else if (!DRE->getQualifier()) {
        if (MD->getParent()->getName().empty())
          Diag(OpLoc, diag::err_unqualified_pointer_member_function)
            << op->getSourceRange();
        else {
          SmallString<32> Str;
          StringRef Qual = (MD->getParent()->getName() + "::").toStringRef(Str);
          Diag(OpLoc, diag::err_unqualified_pointer_member_function)
            << op->getSourceRange()
            << FixItHint::CreateInsertion(op->getSourceRange().getBegin(), Qual);
        }
      }
  
      // Taking the address of a dtor is illegal per C++ [class.dtor]p2.
      if (isa<CXXDestructorDecl>(MD))
        Diag(OpLoc, diag::err_typecheck_addrof_dtor) << op->getSourceRange();
  
      QualType MPTy = Context.getMemberPointerType(
          op->getType(), Context.getTypeDeclType(MD->getParent()).getTypePtr());
  
      if (getLangOpts().PointerAuthCalls && MD->isVirtual() &&
          !isUnevaluatedContext() && !MPTy->isDependentType()) {
        // When pointer authentication is enabled, argument and return types of
        // vitual member functions must be complete. This is because vitrual
        // member function pointers are implemented using virtual dispatch
        // thunks and the thunks cannot be emitted if the argument or return
        // types are incomplete.
        auto ReturnOrParamTypeIsIncomplete = [&](QualType T,
                                                 SourceLocation DeclRefLoc,
                                                 SourceLocation RetArgTypeLoc) {
          if (RequireCompleteType(DeclRefLoc, T, diag::err_incomplete_type)) {
            Diag(DeclRefLoc,
                 diag::note_ptrauth_virtual_function_pointer_incomplete_arg_ret);
            Diag(RetArgTypeLoc,
                 diag::note_ptrauth_virtual_function_incomplete_arg_ret_type)
                << T;
            return true;
          }
          return false;
        };
        QualType RetTy = MD->getReturnType();
        bool IsIncomplete =
            !RetTy->isVoidType() &&
            ReturnOrParamTypeIsIncomplete(
                RetTy, OpLoc, MD->getReturnTypeSourceRange().getBegin());
        for (auto *PVD : MD->parameters())
          IsIncomplete |= ReturnOrParamTypeIsIncomplete(PVD->getType(), OpLoc,
                                                        PVD->getBeginLoc());
        if (IsIncomplete)
          return QualType();
      }
  
      // Under the MS ABI, lock down the inheritance model now.
      if (Context.getTargetInfo().getCXXABI().isMicrosoft())
        (void)isCompleteType(OpLoc, MPTy);
      return MPTy;
    } else if (lval != Expr::LV_Valid && lval != Expr::LV_IncompleteVoidType) {
      // C99 6.5.3.2p1
      // The operand must be either an l-value or a function designator
      if (!op->getType()->isFunctionType()) {
        // Use a special diagnostic for loads from property references.
        if (isa<PseudoObjectExpr>(op)) {
          AddressOfError = AO_Property_Expansion;
        } else {
          Diag(OpLoc, diag::err_typecheck_invalid_lvalue_addrof)
            << op->getType() << op->getSourceRange();
          return QualType();
        }
      }
    } else if (op->getObjectKind() == OK_BitField) { // C99 6.5.3.2p1
      // The operand cannot be a bit-field
      AddressOfError = AO_Bit_Field;
    } else if (op->getObjectKind() == OK_VectorComponent) {
      // The operand cannot be an element of a vector
      AddressOfError = AO_Vector_Element;
    } else if (op->getObjectKind() == OK_MatrixComponent) {
      // The operand cannot be an element of a matrix.
      AddressOfError = AO_Matrix_Element;
    } else if (dcl) { // C99 6.5.3.2p1
      // We have an lvalue with a decl. Make sure the decl is not declared
      // with the register storage-class specifier.
      if (const VarDecl *vd = dyn_cast<VarDecl>(dcl)) {
        // in C++ it is not error to take address of a register
        // variable (c++03 7.1.1P3)
        if (vd->getStorageClass() == SC_Register &&
            !getLangOpts().CPlusPlus) {
          AddressOfError = AO_Register_Variable;
        }
      } else if (isa<MSPropertyDecl>(dcl)) {
        AddressOfError = AO_Property_Expansion;
      } else if (isa<FunctionTemplateDecl>(dcl)) {
        return Context.OverloadTy;
      } else if (isa<FieldDecl>(dcl) || isa<IndirectFieldDecl>(dcl)) {
        // Okay: we can take the address of a field.
        // Could be a pointer to member, though, if there is an explicit
        // scope qualifier for the class.
        if (isa<DeclRefExpr>(op) && cast<DeclRefExpr>(op)->getQualifier()) {
          DeclContext *Ctx = dcl->getDeclContext();
          if (Ctx && Ctx->isRecord()) {
            if (dcl->getType()->isReferenceType()) {
              Diag(OpLoc,
                   diag::err_cannot_form_pointer_to_member_of_reference_type)
                << dcl->getDeclName() << dcl->getType();
              return QualType();
            }
  
            while (cast<RecordDecl>(Ctx)->isAnonymousStructOrUnion())
              Ctx = Ctx->getParent();
  
            QualType MPTy = Context.getMemberPointerType(
                op->getType(),
                Context.getTypeDeclType(cast<RecordDecl>(Ctx)).getTypePtr());
            // Under the MS ABI, lock down the inheritance model now.
            if (Context.getTargetInfo().getCXXABI().isMicrosoft())
              (void)isCompleteType(OpLoc, MPTy);
            return MPTy;
          }
        }
      } else if (!isa<FunctionDecl>(dcl) && !isa<NonTypeTemplateParmDecl>(dcl) &&
                 !isa<BindingDecl>(dcl) && !isa<MSGuidDecl>(dcl))
        llvm_unreachable("Unknown/unexpected decl type");
    }
  
    if (AddressOfError != AO_No_Error) {
      diagnoseAddressOfInvalidType(*this, OpLoc, op, AddressOfError);
      return QualType();
    }
  
    if (lval == Expr::LV_IncompleteVoidType) {
      // Taking the address of a void variable is technically illegal, but we
      // allow it in cases which are otherwise valid.
      // Example: "extern void x; void* y = &x;".
      Diag(OpLoc, diag::ext_typecheck_addrof_void) << op->getSourceRange();
    }
  
    // If the operand has type "type", the result has type "pointer to type".
    if (op->getType()->isObjCObjectType())
      return Context.getObjCObjectPointerType(op->getType());
  
    CheckAddressOfPackedMember(op);
  
    return Context.getPointerType(op->getType());
  }
  
  static void RecordModifiableNonNullParam(Sema &S, const Expr *Exp) {
    const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Exp);
    if (!DRE)
      return;
    const Decl *D = DRE->getDecl();
    if (!D)
      return;
    const ParmVarDecl *Param = dyn_cast<ParmVarDecl>(D);
    if (!Param)
      return;
    if (const FunctionDecl* FD = dyn_cast<FunctionDecl>(Param->getDeclContext()))
      if (!FD->hasAttr<NonNullAttr>() && !Param->hasAttr<NonNullAttr>())
        return;
    if (FunctionScopeInfo *FD = S.getCurFunction())
      if (!FD->ModifiedNonNullParams.count(Param))
        FD->ModifiedNonNullParams.insert(Param);
  }
  
  /// CheckIndirectionOperand - Type check unary indirection (prefix '*').
  static QualType CheckIndirectionOperand(Sema &S, Expr *Op, ExprValueKind &VK,
                                          SourceLocation OpLoc) {
    if (Op->isTypeDependent())
      return S.Context.DependentTy;
  
    ExprResult ConvResult = S.UsualUnaryConversions(Op);
    if (ConvResult.isInvalid())
      return QualType();
    Op = ConvResult.get();
    QualType OpTy = Op->getType();
    QualType Result;
  
    if (isa<CXXReinterpretCastExpr>(Op)) {
      QualType OpOrigType = Op->IgnoreParenCasts()->getType();
      S.CheckCompatibleReinterpretCast(OpOrigType, OpTy, /*IsDereference*/true,
                                       Op->getSourceRange());
    }
  
    if (const PointerType *PT = OpTy->getAs<PointerType>())
    {
      Result = PT->getPointeeType();
    }
    else if (const ObjCObjectPointerType *OPT =
               OpTy->getAs<ObjCObjectPointerType>())
      Result = OPT->getPointeeType();
    else {
      ExprResult PR = S.CheckPlaceholderExpr(Op);
      if (PR.isInvalid()) return QualType();
      if (PR.get() != Op)
        return CheckIndirectionOperand(S, PR.get(), VK, OpLoc);
    }
  
    if (Result.isNull()) {
      S.Diag(OpLoc, diag::err_typecheck_indirection_requires_pointer)
        << OpTy << Op->getSourceRange();
      return QualType();
    }
  
    // Note that per both C89 and C99, indirection is always legal, even if Result
    // is an incomplete type or void.  It would be possible to warn about
    // dereferencing a void pointer, but it's completely well-defined, and such a
    // warning is unlikely to catch any mistakes. In C++, indirection is not valid
    // for pointers to 'void' but is fine for any other pointer type:
    //
    // C++ [expr.unary.op]p1:
    //   [...] the expression to which [the unary * operator] is applied shall
    //   be a pointer to an object type, or a pointer to a function type
    if (S.getLangOpts().CPlusPlus && Result->isVoidType())
      S.Diag(OpLoc, diag::ext_typecheck_indirection_through_void_pointer)
        << OpTy << Op->getSourceRange();
  
    // Dereferences are usually l-values...
    VK = VK_LValue;
  
    // ...except that certain expressions are never l-values in C.
    if (!S.getLangOpts().CPlusPlus && Result.isCForbiddenLValueType())
      VK = VK_PRValue;
  
    return Result;
  }
  
  BinaryOperatorKind Sema::ConvertTokenKindToBinaryOpcode(tok::TokenKind Kind) {
    BinaryOperatorKind Opc;
    switch (Kind) {
    default: llvm_unreachable("Unknown binop!");
    case tok::periodstar:           Opc = BO_PtrMemD; break;
    case tok::arrowstar:            Opc = BO_PtrMemI; break;
    case tok::star:                 Opc = BO_Mul; break;
    case tok::slash:                Opc = BO_Div; break;
    case tok::percent:              Opc = BO_Rem; break;
    case tok::plus:                 Opc = BO_Add; break;
    case tok::minus:                Opc = BO_Sub; break;
    case tok::lessless:             Opc = BO_Shl; break;
    case tok::greatergreater:       Opc = BO_Shr; break;
    case tok::lessequal:            Opc = BO_LE; break;
    case tok::less:                 Opc = BO_LT; break;
    case tok::greaterequal:         Opc = BO_GE; break;
    case tok::greater:              Opc = BO_GT; break;
    case tok::exclaimequal:         Opc = BO_NE; break;
    case tok::equalequal:           Opc = BO_EQ; break;
    case tok::spaceship:            Opc = BO_Cmp; break;
    case tok::amp:                  Opc = BO_And; break;
    case tok::caret:                Opc = BO_Xor; break;
    case tok::pipe:                 Opc = BO_Or; break;
    case tok::ampamp:               Opc = BO_LAnd; break;
    case tok::pipepipe:             Opc = BO_LOr; break;
    case tok::equal:                Opc = BO_Assign; break;
    case tok::starequal:            Opc = BO_MulAssign; break;
    case tok::slashequal:           Opc = BO_DivAssign; break;
    case tok::percentequal:         Opc = BO_RemAssign; break;
    case tok::plusequal:            Opc = BO_AddAssign; break;
    case tok::minusequal:           Opc = BO_SubAssign; break;
    case tok::lesslessequal:        Opc = BO_ShlAssign; break;
    case tok::greatergreaterequal:  Opc = BO_ShrAssign; break;
    case tok::ampequal:             Opc = BO_AndAssign; break;
    case tok::caretequal:           Opc = BO_XorAssign; break;
    case tok::pipeequal:            Opc = BO_OrAssign; break;
    case tok::comma:                Opc = BO_Comma; break;
    }
    return Opc;
  }
  
  static inline UnaryOperatorKind ConvertTokenKindToUnaryOpcode(
    tok::TokenKind Kind) {
    UnaryOperatorKind Opc;
    switch (Kind) {
    default: llvm_unreachable("Unknown unary op!");
    case tok::plusplus:     Opc = UO_PreInc; break;
    case tok::minusminus:   Opc = UO_PreDec; break;
    case tok::amp:          Opc = UO_AddrOf; break;
    case tok::star:         Opc = UO_Deref; break;
    case tok::plus:         Opc = UO_Plus; break;
    case tok::minus:        Opc = UO_Minus; break;
    case tok::tilde:        Opc = UO_Not; break;
    case tok::exclaim:      Opc = UO_LNot; break;
    case tok::kw___real:    Opc = UO_Real; break;
    case tok::kw___imag:    Opc = UO_Imag; break;
    case tok::kw___extension__: Opc = UO_Extension; break;
    }
    return Opc;
  }
  
  /// DiagnoseSelfAssignment - Emits a warning if a value is assigned to itself.
  /// This warning suppressed in the event of macro expansions.
  static void DiagnoseSelfAssignment(Sema &S, Expr *LHSExpr, Expr *RHSExpr,
                                     SourceLocation OpLoc, bool IsBuiltin) {
    if (S.inTemplateInstantiation())
      return;
    if (S.isUnevaluatedContext())
      return;
    if (OpLoc.isInvalid() || OpLoc.isMacroID())
      return;
    LHSExpr = LHSExpr->IgnoreParenImpCasts();
    RHSExpr = RHSExpr->IgnoreParenImpCasts();
    const DeclRefExpr *LHSDeclRef = dyn_cast<DeclRefExpr>(LHSExpr);
    const DeclRefExpr *RHSDeclRef = dyn_cast<DeclRefExpr>(RHSExpr);
    if (!LHSDeclRef || !RHSDeclRef ||
        LHSDeclRef->getLocation().isMacroID() ||
        RHSDeclRef->getLocation().isMacroID())
      return;
    const ValueDecl *LHSDecl =
      cast<ValueDecl>(LHSDeclRef->getDecl()->getCanonicalDecl());
    const ValueDecl *RHSDecl =
      cast<ValueDecl>(RHSDeclRef->getDecl()->getCanonicalDecl());
    if (LHSDecl != RHSDecl)
      return;
    if (LHSDecl->getType().isVolatileQualified())
      return;
    if (const ReferenceType *RefTy = LHSDecl->getType()->getAs<ReferenceType>())
      if (RefTy->getPointeeType().isVolatileQualified())
        return;
  
    S.Diag(OpLoc, IsBuiltin ? diag::warn_self_assignment_builtin
                            : diag::warn_self_assignment_overloaded)
        << LHSDeclRef->getType() << LHSExpr->getSourceRange()
        << RHSExpr->getSourceRange();
  }
  
  /// Check if a bitwise-& is performed on an Objective-C pointer.  This
  /// is usually indicative of introspection within the Objective-C pointer.
  static void checkObjCPointerIntrospection(Sema &S, ExprResult &L, ExprResult &R,
                                            SourceLocation OpLoc) {
    if (!S.getLangOpts().ObjC)
      return;
  
    const Expr *ObjCPointerExpr = nullptr, *OtherExpr = nullptr;
    const Expr *LHS = L.get();
    const Expr *RHS = R.get();
  
    if (LHS->IgnoreParenCasts()->getType()->isObjCObjectPointerType()) {
      ObjCPointerExpr = LHS;
      OtherExpr = RHS;
    }
    else if (RHS->IgnoreParenCasts()->getType()->isObjCObjectPointerType()) {
      ObjCPointerExpr = RHS;
      OtherExpr = LHS;
    }
  
    // This warning is deliberately made very specific to reduce false
    // positives with logic that uses '&' for hashing.  This logic mainly
    // looks for code trying to introspect into tagged pointers, which
    // code should generally never do.
    if (ObjCPointerExpr && isa<IntegerLiteral>(OtherExpr->IgnoreParenCasts())) {
      unsigned Diag = diag::warn_objc_pointer_masking;
      // Determine if we are introspecting the result of performSelectorXXX.
      const Expr *Ex = ObjCPointerExpr->IgnoreParenCasts();
      // Special case messages to -performSelector and friends, which
      // can return non-pointer values boxed in a pointer value.
      // Some clients may wish to silence warnings in this subcase.
      if (const ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(Ex)) {
        Selector S = ME->getSelector();
        StringRef SelArg0 = S.getNameForSlot(0);
        if (SelArg0.startswith("performSelector"))
          Diag = diag::warn_objc_pointer_masking_performSelector;
      }
  
      S.Diag(OpLoc, Diag)
        << ObjCPointerExpr->getSourceRange();
    }
  }
  
  static NamedDecl *getDeclFromExpr(Expr *E) {
    if (!E)
      return nullptr;
    if (auto *DRE = dyn_cast<DeclRefExpr>(E))
      return DRE->getDecl();
    if (auto *ME = dyn_cast<MemberExpr>(E))
      return ME->getMemberDecl();
    if (auto *IRE = dyn_cast<ObjCIvarRefExpr>(E))
      return IRE->getDecl();
    return nullptr;
  }
  
  // This helper function promotes a binary operator's operands (which are of a
  // half vector type) to a vector of floats and then truncates the result to
  // a vector of either half or short.
  static ExprResult convertHalfVecBinOp(Sema &S, ExprResult LHS, ExprResult RHS,
                                        BinaryOperatorKind Opc, QualType ResultTy,
                                        ExprValueKind VK, ExprObjectKind OK,
                                        bool IsCompAssign, SourceLocation OpLoc,
                                        FPOptionsOverride FPFeatures) {
    auto &Context = S.getASTContext();
    assert((isVector(ResultTy, Context.HalfTy) ||
            isVector(ResultTy, Context.ShortTy)) &&
           "Result must be a vector of half or short");
    assert(isVector(LHS.get()->getType(), Context.HalfTy) &&
           isVector(RHS.get()->getType(), Context.HalfTy) &&
           "both operands expected to be a half vector");
  
    RHS = convertVector(RHS.get(), Context.FloatTy, S);
    QualType BinOpResTy = RHS.get()->getType();
  
    // If Opc is a comparison, ResultType is a vector of shorts. In that case,
    // change BinOpResTy to a vector of ints.
    if (isVector(ResultTy, Context.ShortTy))
      BinOpResTy = S.GetSignedVectorType(BinOpResTy);
  
    if (IsCompAssign)
      return CompoundAssignOperator::Create(Context, LHS.get(), RHS.get(), Opc,
                                            ResultTy, VK, OK, OpLoc, FPFeatures,
                                            BinOpResTy, BinOpResTy);
  
    LHS = convertVector(LHS.get(), Context.FloatTy, S);
    auto *BO = BinaryOperator::Create(Context, LHS.get(), RHS.get(), Opc,
                                      BinOpResTy, VK, OK, OpLoc, FPFeatures);
    return convertVector(BO, ResultTy->castAs<VectorType>()->getElementType(), S);
  }
  
  static std::pair<ExprResult, ExprResult>
  CorrectDelayedTyposInBinOp(Sema &S, BinaryOperatorKind Opc, Expr *LHSExpr,
                             Expr *RHSExpr) {
    ExprResult LHS = LHSExpr, RHS = RHSExpr;
    if (!S.Context.isDependenceAllowed()) {
      // C cannot handle TypoExpr nodes on either side of a binop because it
      // doesn't handle dependent types properly, so make sure any TypoExprs have
      // been dealt with before checking the operands.
      LHS = S.CorrectDelayedTyposInExpr(LHS);
      RHS = S.CorrectDelayedTyposInExpr(
          RHS, /*InitDecl=*/nullptr, /*RecoverUncorrectedTypos=*/false,
          [Opc, LHS](Expr *E) {
            if (Opc != BO_Assign)
              return ExprResult(E);
            // Avoid correcting the RHS to the same Expr as the LHS.
            Decl *D = getDeclFromExpr(E);
            return (D && D == getDeclFromExpr(LHS.get())) ? ExprError() : E;
          });
    }
    return std::make_pair(LHS, RHS);
  }
  
  /// Returns true if conversion between vectors of halfs and vectors of floats
  /// is needed.
  static bool needsConversionOfHalfVec(bool OpRequiresConversion, ASTContext &Ctx,
                                       Expr *E0, Expr *E1 = nullptr) {
    if (!OpRequiresConversion || Ctx.getLangOpts().NativeHalfType ||
        Ctx.getTargetInfo().useFP16ConversionIntrinsics())
      return false;
  
    auto HasVectorOfHalfType = [&Ctx](Expr *E) {
      QualType Ty = E->IgnoreImplicit()->getType();
  
      // Don't promote half precision neon vectors like float16x4_t in arm_neon.h
      // to vectors of floats. Although the element type of the vectors is __fp16,
      // the vectors shouldn't be treated as storage-only types. See the
      // discussion here: https://reviews.llvm.org/rG825235c140e7
      if (const VectorType *VT = Ty->getAs<VectorType>()) {
        if (VT->getVectorKind() == VectorType::NeonVector)
          return false;
        return VT->getElementType().getCanonicalType() == Ctx.HalfTy;
      }
      return false;
    };
  
    return HasVectorOfHalfType(E0) && (!E1 || HasVectorOfHalfType(E1));
  }
  
  /// CreateBuiltinBinOp - Creates a new built-in binary operation with
  /// operator @p Opc at location @c TokLoc. This routine only supports
  /// built-in operations; ActOnBinOp handles overloaded operators.
  ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
                                      BinaryOperatorKind Opc,
                                      Expr *LHSExpr, Expr *RHSExpr) {
    if (getLangOpts().CPlusPlus11 && isa<InitListExpr>(RHSExpr)) {
      // The syntax only allows initializer lists on the RHS of assignment,
      // so we don't need to worry about accepting invalid code for
      // non-assignment operators.
      // C++11 5.17p9:
      //   The meaning of x = {v} [...] is that of x = T(v) [...]. The meaning
      //   of x = {} is x = T().
      InitializationKind Kind = InitializationKind::CreateDirectList(
          RHSExpr->getBeginLoc(), RHSExpr->getBeginLoc(), RHSExpr->getEndLoc());
      InitializedEntity Entity =
          InitializedEntity::InitializeTemporary(LHSExpr->getType());
      InitializationSequence InitSeq(*this, Entity, Kind, RHSExpr);
      ExprResult Init = InitSeq.Perform(*this, Entity, Kind, RHSExpr);
      if (Init.isInvalid())
        return Init;
      RHSExpr = Init.get();
    }
  
    ExprResult LHS = LHSExpr, RHS = RHSExpr;
    QualType ResultTy;     // Result type of the binary operator.
    // The following two variables are used for compound assignment operators
    QualType CompLHSTy;    // Type of LHS after promotions for computation
    QualType CompResultTy; // Type of computation result
    ExprValueKind VK = VK_PRValue;
    ExprObjectKind OK = OK_Ordinary;
    bool ConvertHalfVec = false;
  
    std::tie(LHS, RHS) = CorrectDelayedTyposInBinOp(*this, Opc, LHSExpr, RHSExpr);
    if (!LHS.isUsable() || !RHS.isUsable())
      return ExprError();
  
    if (getLangOpts().OpenCL) {
      QualType LHSTy = LHSExpr->getType();
      QualType RHSTy = RHSExpr->getType();
      // OpenCLC v2.0 s6.13.11.1 allows atomic variables to be initialized by
      // the ATOMIC_VAR_INIT macro.
      if (LHSTy->isAtomicType() || RHSTy->isAtomicType()) {
        SourceRange SR(LHSExpr->getBeginLoc(), RHSExpr->getEndLoc());
        if (BO_Assign == Opc)
          Diag(OpLoc, diag::err_opencl_atomic_init) << 0 << SR;
        else
          ResultTy = InvalidOperands(OpLoc, LHS, RHS);
        return ExprError();
      }
  
      // OpenCL special types - image, sampler, pipe, and blocks are to be used
      // only with a builtin functions and therefore should be disallowed here.
      if (LHSTy->isImageType() || RHSTy->isImageType() ||
          LHSTy->isSamplerT() || RHSTy->isSamplerT() ||
          LHSTy->isPipeType() || RHSTy->isPipeType() ||
          LHSTy->isBlockPointerType() || RHSTy->isBlockPointerType()) {
        ResultTy = InvalidOperands(OpLoc, LHS, RHS);
        return ExprError();
      }
    }
  
    checkTypeSupport(LHSExpr->getType(), OpLoc, /*ValueDecl*/ nullptr);
    checkTypeSupport(RHSExpr->getType(), OpLoc, /*ValueDecl*/ nullptr);
  
    switch (Opc) {
    case BO_Assign:
      ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, QualType());
      if (getLangOpts().CPlusPlus &&
          LHS.get()->getObjectKind() != OK_ObjCProperty) {
        VK = LHS.get()->getValueKind();
        OK = LHS.get()->getObjectKind();
      }
      if (!ResultTy.isNull()) {
        DiagnoseSelfAssignment(*this, LHS.get(), RHS.get(), OpLoc, true);
        DiagnoseSelfMove(LHS.get(), RHS.get(), OpLoc);
  
        // Avoid copying a block to the heap if the block is assigned to a local
        // auto variable that is declared in the same scope as the block. This
        // optimization is unsafe if the local variable is declared in an outer
        // scope. For example:
        //
        // BlockTy b;
        // {
        //   b = ^{...};
        // }
        // // It is unsafe to invoke the block here if it wasn't copied to the
        // // heap.
        // b();
  
        if (auto *BE = dyn_cast<BlockExpr>(RHS.get()->IgnoreParens()))
          if (auto *DRE = dyn_cast<DeclRefExpr>(LHS.get()->IgnoreParens()))
            if (auto *VD = dyn_cast<VarDecl>(DRE->getDecl()))
              if (VD->hasLocalStorage() && getCurScope()->isDeclScope(VD))
                BE->getBlockDecl()->setCanAvoidCopyToHeap();
  
        if (LHS.get()->getType().hasNonTrivialToPrimitiveCopyCUnion())
          checkNonTrivialCUnion(LHS.get()->getType(), LHS.get()->getExprLoc(),
                                NTCUC_Assignment, NTCUK_Copy);
      }
      RecordModifiableNonNullParam(*this, LHS.get());
      break;
    case BO_PtrMemD:
    case BO_PtrMemI:
      ResultTy = CheckPointerToMemberOperands(LHS, RHS, VK, OpLoc,
                                              Opc == BO_PtrMemI);
      break;
    case BO_Mul:
    case BO_Div:
      ConvertHalfVec = true;
      ResultTy = CheckMultiplyDivideOperands(LHS, RHS, OpLoc, false,
                                             Opc == BO_Div);
      break;
    case BO_Rem:
      ResultTy = CheckRemainderOperands(LHS, RHS, OpLoc);
      break;
    case BO_Add:
      ConvertHalfVec = true;
      ResultTy = CheckAdditionOperands(LHS, RHS, OpLoc, Opc);
      break;
    case BO_Sub:
      ConvertHalfVec = true;
      ResultTy = CheckSubtractionOperands(LHS, RHS, OpLoc);
      break;
    case BO_Shl:
    case BO_Shr:
      ResultTy = CheckShiftOperands(LHS, RHS, OpLoc, Opc);
      break;
    case BO_LE:
    case BO_LT:
    case BO_GE:
    case BO_GT:
      ConvertHalfVec = true;
      ResultTy = CheckCompareOperands(LHS, RHS, OpLoc, Opc);
      break;
    case BO_EQ:
    case BO_NE:
      ConvertHalfVec = true;
      ResultTy = CheckCompareOperands(LHS, RHS, OpLoc, Opc);
      break;
    case BO_Cmp:
      ConvertHalfVec = true;
      ResultTy = CheckCompareOperands(LHS, RHS, OpLoc, Opc);
      assert(ResultTy.isNull() || ResultTy->getAsCXXRecordDecl());
      break;
    case BO_And:
      checkObjCPointerIntrospection(*this, LHS, RHS, OpLoc);
      LLVM_FALLTHROUGH;
    case BO_Xor:
    case BO_Or:
      ResultTy = CheckBitwiseOperands(LHS, RHS, OpLoc, Opc);
      break;
    case BO_LAnd:
    case BO_LOr:
      ConvertHalfVec = true;
      ResultTy = CheckLogicalOperands(LHS, RHS, OpLoc, Opc);
      break;
    case BO_MulAssign:
    case BO_DivAssign:
      ConvertHalfVec = true;
      CompResultTy = CheckMultiplyDivideOperands(LHS, RHS, OpLoc, true,
                                                 Opc == BO_DivAssign);
      CompLHSTy = CompResultTy;
      if (!CompResultTy.isNull() && !LHS.isInvalid() && !RHS.isInvalid())
        ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, CompResultTy);
      break;
    case BO_RemAssign:
      CompResultTy = CheckRemainderOperands(LHS, RHS, OpLoc, true);
      CompLHSTy = CompResultTy;
      if (!CompResultTy.isNull() && !LHS.isInvalid() && !RHS.isInvalid())
        ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, CompResultTy);
      break;
    case BO_AddAssign:
      ConvertHalfVec = true;
      CompResultTy = CheckAdditionOperands(LHS, RHS, OpLoc, Opc, &CompLHSTy);
      if (!CompResultTy.isNull() && !LHS.isInvalid() && !RHS.isInvalid())
        ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, CompResultTy);
      break;
    case BO_SubAssign:
      ConvertHalfVec = true;
      CompResultTy = CheckSubtractionOperands(LHS, RHS, OpLoc, &CompLHSTy);
      if (!CompResultTy.isNull() && !LHS.isInvalid() && !RHS.isInvalid())
        ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, CompResultTy);
      break;
    case BO_ShlAssign:
    case BO_ShrAssign:
      CompResultTy = CheckShiftOperands(LHS, RHS, OpLoc, Opc, true);
      CompLHSTy = CompResultTy;
      if (!CompResultTy.isNull() && !LHS.isInvalid() && !RHS.isInvalid())
        ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, CompResultTy);
      break;
    case BO_AndAssign:
    case BO_OrAssign: // fallthrough
      DiagnoseSelfAssignment(*this, LHS.get(), RHS.get(), OpLoc, true);
      LLVM_FALLTHROUGH;
    case BO_XorAssign:
      CompResultTy = CheckBitwiseOperands(LHS, RHS, OpLoc, Opc);
      CompLHSTy = CompResultTy;
      if (!CompResultTy.isNull() && !LHS.isInvalid() && !RHS.isInvalid())
        ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, CompResultTy);
      break;
    case BO_Comma:
      ResultTy = CheckCommaOperands(*this, LHS, RHS, OpLoc);
      if (getLangOpts().CPlusPlus && !RHS.isInvalid()) {
        VK = RHS.get()->getValueKind();
        OK = RHS.get()->getObjectKind();
      }
      break;
    }
    if (ResultTy.isNull() || LHS.isInvalid() || RHS.isInvalid())
      return ExprError();
  
    // Some of the binary operations require promoting operands of half vector to
    // float vectors and truncating the result back to half vector. For now, we do
    // this only when HalfArgsAndReturn is set (that is, when the target is arm or
    // arm64).
    assert(
        (Opc == BO_Comma || isVector(RHS.get()->getType(), Context.HalfTy) ==
                                isVector(LHS.get()->getType(), Context.HalfTy)) &&
        "both sides are half vectors or neither sides are");
    ConvertHalfVec =
        needsConversionOfHalfVec(ConvertHalfVec, Context, LHS.get(), RHS.get());
  
    // Check for array bounds violations for both sides of the BinaryOperator
    CheckArrayAccess(LHS.get());
    CheckArrayAccess(RHS.get());
  
    if (const ObjCIsaExpr *OISA = dyn_cast<ObjCIsaExpr>(LHS.get()->IgnoreParenCasts())) {
      NamedDecl *ObjectSetClass = LookupSingleName(TUScope,
                                                   &Context.Idents.get("object_setClass"),
                                                   SourceLocation(), LookupOrdinaryName);
      if (ObjectSetClass && isa<ObjCIsaExpr>(LHS.get())) {
        SourceLocation RHSLocEnd = getLocForEndOfToken(RHS.get()->getEndLoc());
        Diag(LHS.get()->getExprLoc(), diag::warn_objc_isa_assign)
            << FixItHint::CreateInsertion(LHS.get()->getBeginLoc(),
                                          "object_setClass(")
            << FixItHint::CreateReplacement(SourceRange(OISA->getOpLoc(), OpLoc),
                                            ",")
            << FixItHint::CreateInsertion(RHSLocEnd, ")");
      }
      else
        Diag(LHS.get()->getExprLoc(), diag::warn_objc_isa_assign);
    }
    else if (const ObjCIvarRefExpr *OIRE =
             dyn_cast<ObjCIvarRefExpr>(LHS.get()->IgnoreParenCasts()))
      DiagnoseDirectIsaAccess(*this, OIRE, OpLoc, RHS.get());
  
    // Opc is not a compound assignment if CompResultTy is null.
    if (CompResultTy.isNull()) {
      if (ConvertHalfVec)
        return convertHalfVecBinOp(*this, LHS, RHS, Opc, ResultTy, VK, OK, false,
                                   OpLoc, CurFPFeatureOverrides());
      return BinaryOperator::Create(Context, LHS.get(), RHS.get(), Opc, ResultTy,
                                    VK, OK, OpLoc, CurFPFeatureOverrides());
    }
  
    // Handle compound assignments.
    if (getLangOpts().CPlusPlus && LHS.get()->getObjectKind() !=
        OK_ObjCProperty) {
      VK = VK_LValue;
      OK = LHS.get()->getObjectKind();
    }
  
    // The LHS is not converted to the result type for fixed-point compound
    // assignment as the common type is computed on demand. Reset the CompLHSTy
    // to the LHS type we would have gotten after unary conversions.
    if (CompResultTy->isFixedPointType())
      CompLHSTy = UsualUnaryConversions(LHS.get()).get()->getType();
  
    if (ConvertHalfVec)
      return convertHalfVecBinOp(*this, LHS, RHS, Opc, ResultTy, VK, OK, true,
                                 OpLoc, CurFPFeatureOverrides());
  
    return CompoundAssignOperator::Create(
        Context, LHS.get(), RHS.get(), Opc, ResultTy, VK, OK, OpLoc,
        CurFPFeatureOverrides(), CompLHSTy, CompResultTy);
  }
  
  /// DiagnoseBitwisePrecedence - Emit a warning when bitwise and comparison
  /// operators are mixed in a way that suggests that the programmer forgot that
  /// comparison operators have higher precedence. The most typical example of
  /// such code is "flags & 0x0020 != 0", which is equivalent to "flags & 1".
  static void DiagnoseBitwisePrecedence(Sema &Self, BinaryOperatorKind Opc,
                                        SourceLocation OpLoc, Expr *LHSExpr,
                                        Expr *RHSExpr) {
    BinaryOperator *LHSBO = dyn_cast<BinaryOperator>(LHSExpr);
    BinaryOperator *RHSBO = dyn_cast<BinaryOperator>(RHSExpr);
  
    // Check that one of the sides is a comparison operator and the other isn't.
    bool isLeftComp = LHSBO && LHSBO->isComparisonOp();
    bool isRightComp = RHSBO && RHSBO->isComparisonOp();
    if (isLeftComp == isRightComp)
      return;
  
    // Bitwise operations are sometimes used as eager logical ops.
    // Don't diagnose this.
    bool isLeftBitwise = LHSBO && LHSBO->isBitwiseOp();
    bool isRightBitwise = RHSBO && RHSBO->isBitwiseOp();
    if (isLeftBitwise || isRightBitwise)
      return;
  
    SourceRange DiagRange = isLeftComp
                                ? SourceRange(LHSExpr->getBeginLoc(), OpLoc)
                                : SourceRange(OpLoc, RHSExpr->getEndLoc());
    StringRef OpStr = isLeftComp ? LHSBO->getOpcodeStr() : RHSBO->getOpcodeStr();
    SourceRange ParensRange =
        isLeftComp
            ? SourceRange(LHSBO->getRHS()->getBeginLoc(), RHSExpr->getEndLoc())
            : SourceRange(LHSExpr->getBeginLoc(), RHSBO->getLHS()->getEndLoc());
  
    Self.Diag(OpLoc, diag::warn_precedence_bitwise_rel)
      << DiagRange << BinaryOperator::getOpcodeStr(Opc) << OpStr;
    SuggestParentheses(Self, OpLoc,
      Self.PDiag(diag::note_precedence_silence) << OpStr,
      (isLeftComp ? LHSExpr : RHSExpr)->getSourceRange());
    SuggestParentheses(Self, OpLoc,
      Self.PDiag(diag::note_precedence_bitwise_first)
        << BinaryOperator::getOpcodeStr(Opc),
      ParensRange);
  }
  
  /// It accepts a '&&' expr that is inside a '||' one.
  /// Emit a diagnostic together with a fixit hint that wraps the '&&' expression
  /// in parentheses.
  static void
  EmitDiagnosticForLogicalAndInLogicalOr(Sema &Self, SourceLocation OpLoc,
                                         BinaryOperator *Bop) {
    assert(Bop->getOpcode() == BO_LAnd);
    Self.Diag(Bop->getOperatorLoc(), diag::warn_logical_and_in_logical_or)
        << Bop->getSourceRange() << OpLoc;
    SuggestParentheses(Self, Bop->getOperatorLoc(),
      Self.PDiag(diag::note_precedence_silence)
        << Bop->getOpcodeStr(),
      Bop->getSourceRange());
  }
  
  /// Returns true if the given expression can be evaluated as a constant
  /// 'true'.
  static bool EvaluatesAsTrue(Sema &S, Expr *E) {
    bool Res;
    return !E->isValueDependent() &&
           E->EvaluateAsBooleanCondition(Res, S.getASTContext()) && Res;
  }
  
  /// Returns true if the given expression can be evaluated as a constant
  /// 'false'.
  static bool EvaluatesAsFalse(Sema &S, Expr *E) {
    bool Res;
    return !E->isValueDependent() &&
           E->EvaluateAsBooleanCondition(Res, S.getASTContext()) && !Res;
  }
  
  /// Look for '&&' in the left hand of a '||' expr.
  static void DiagnoseLogicalAndInLogicalOrLHS(Sema &S, SourceLocation OpLoc,
                                               Expr *LHSExpr, Expr *RHSExpr) {
    if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(LHSExpr)) {
      if (Bop->getOpcode() == BO_LAnd) {
        // If it's "a && b || 0" don't warn since the precedence doesn't matter.
        if (EvaluatesAsFalse(S, RHSExpr))
          return;
        // If it's "1 && a || b" don't warn since the precedence doesn't matter.
        if (!EvaluatesAsTrue(S, Bop->getLHS()))
          return EmitDiagnosticForLogicalAndInLogicalOr(S, OpLoc, Bop);
      } else if (Bop->getOpcode() == BO_LOr) {
        if (BinaryOperator *RBop = dyn_cast<BinaryOperator>(Bop->getRHS())) {
          // If it's "a || b && 1 || c" we didn't warn earlier for
          // "a || b && 1", but warn now.
          if (RBop->getOpcode() == BO_LAnd && EvaluatesAsTrue(S, RBop->getRHS()))
            return EmitDiagnosticForLogicalAndInLogicalOr(S, OpLoc, RBop);
        }
      }
    }
  }
  
  /// Look for '&&' in the right hand of a '||' expr.
  static void DiagnoseLogicalAndInLogicalOrRHS(Sema &S, SourceLocation OpLoc,
                                               Expr *LHSExpr, Expr *RHSExpr) {
    if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(RHSExpr)) {
      if (Bop->getOpcode() == BO_LAnd) {
        // If it's "0 || a && b" don't warn since the precedence doesn't matter.
        if (EvaluatesAsFalse(S, LHSExpr))
          return;
        // If it's "a || b && 1" don't warn since the precedence doesn't matter.
        if (!EvaluatesAsTrue(S, Bop->getRHS()))
          return EmitDiagnosticForLogicalAndInLogicalOr(S, OpLoc, Bop);
      }
    }
  }
  
  /// Look for bitwise op in the left or right hand of a bitwise op with
  /// lower precedence and emit a diagnostic together with a fixit hint that wraps
  /// the '&' expression in parentheses.
  static void DiagnoseBitwiseOpInBitwiseOp(Sema &S, BinaryOperatorKind Opc,
                                           SourceLocation OpLoc, Expr *SubExpr) {
    if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(SubExpr)) {
      if (Bop->isBitwiseOp() && Bop->getOpcode() < Opc) {
        S.Diag(Bop->getOperatorLoc(), diag::warn_bitwise_op_in_bitwise_op)
          << Bop->getOpcodeStr() << BinaryOperator::getOpcodeStr(Opc)
          << Bop->getSourceRange() << OpLoc;
        SuggestParentheses(S, Bop->getOperatorLoc(),
          S.PDiag(diag::note_precedence_silence)
            << Bop->getOpcodeStr(),
          Bop->getSourceRange());
      }
    }
  }
  
  static void DiagnoseAdditionInShift(Sema &S, SourceLocation OpLoc,
                                      Expr *SubExpr, StringRef Shift) {
    if (BinaryOperator *Bop = dyn_cast<BinaryOperator>(SubExpr)) {
      if (Bop->getOpcode() == BO_Add || Bop->getOpcode() == BO_Sub) {
        StringRef Op = Bop->getOpcodeStr();
        S.Diag(Bop->getOperatorLoc(), diag::warn_addition_in_bitshift)
            << Bop->getSourceRange() << OpLoc << Shift << Op;
        SuggestParentheses(S, Bop->getOperatorLoc(),
            S.PDiag(diag::note_precedence_silence) << Op,
            Bop->getSourceRange());
      }
    }
  }
  
  static void DiagnoseShiftCompare(Sema &S, SourceLocation OpLoc,
                                   Expr *LHSExpr, Expr *RHSExpr) {
    CXXOperatorCallExpr *OCE = dyn_cast<CXXOperatorCallExpr>(LHSExpr);
    if (!OCE)
      return;
  
    FunctionDecl *FD = OCE->getDirectCallee();
    if (!FD || !FD->isOverloadedOperator())
      return;
  
    OverloadedOperatorKind Kind = FD->getOverloadedOperator();
    if (Kind != OO_LessLess && Kind != OO_GreaterGreater)
      return;
  
    S.Diag(OpLoc, diag::warn_overloaded_shift_in_comparison)
        << LHSExpr->getSourceRange() << RHSExpr->getSourceRange()
        << (Kind == OO_LessLess);
    SuggestParentheses(S, OCE->getOperatorLoc(),
                       S.PDiag(diag::note_precedence_silence)
                           << (Kind == OO_LessLess ? "<<" : ">>"),
                       OCE->getSourceRange());
    SuggestParentheses(
        S, OpLoc, S.PDiag(diag::note_evaluate_comparison_first),
        SourceRange(OCE->getArg(1)->getBeginLoc(), RHSExpr->getEndLoc()));
  }
  
  /// DiagnoseBinOpPrecedence - Emit warnings for expressions with tricky
  /// precedence.
  static void DiagnoseBinOpPrecedence(Sema &Self, BinaryOperatorKind Opc,
                                      SourceLocation OpLoc, Expr *LHSExpr,
                                      Expr *RHSExpr){
    // Diagnose "arg1 'bitwise' arg2 'eq' arg3".
    if (BinaryOperator::isBitwiseOp(Opc))
      DiagnoseBitwisePrecedence(Self, Opc, OpLoc, LHSExpr, RHSExpr);
  
    // Diagnose "arg1 & arg2 | arg3"
    if ((Opc == BO_Or || Opc == BO_Xor) &&
        !OpLoc.isMacroID()/* Don't warn in macros. */) {
      DiagnoseBitwiseOpInBitwiseOp(Self, Opc, OpLoc, LHSExpr);
      DiagnoseBitwiseOpInBitwiseOp(Self, Opc, OpLoc, RHSExpr);
    }
  
    // Warn about arg1 || arg2 && arg3, as GCC 4.3+ does.
    // We don't warn for 'assert(a || b && "bad")' since this is safe.
    if (Opc == BO_LOr && !OpLoc.isMacroID()/* Don't warn in macros. */) {
      DiagnoseLogicalAndInLogicalOrLHS(Self, OpLoc, LHSExpr, RHSExpr);
      DiagnoseLogicalAndInLogicalOrRHS(Self, OpLoc, LHSExpr, RHSExpr);
    }
  
    if ((Opc == BO_Shl && LHSExpr->getType()->isIntegralType(Self.getASTContext()))
        || Opc == BO_Shr) {
      StringRef Shift = BinaryOperator::getOpcodeStr(Opc);
      DiagnoseAdditionInShift(Self, OpLoc, LHSExpr, Shift);
      DiagnoseAdditionInShift(Self, OpLoc, RHSExpr, Shift);
    }
  
    // Warn on overloaded shift operators and comparisons, such as:
    // cout << 5 == 4;
    if (BinaryOperator::isComparisonOp(Opc))
      DiagnoseShiftCompare(Self, OpLoc, LHSExpr, RHSExpr);
  }
  
  // Binary Operators.  'Tok' is the token for the operator.
  ExprResult Sema::ActOnBinOp(Scope *S, SourceLocation TokLoc,
                              tok::TokenKind Kind,
                              Expr *LHSExpr, Expr *RHSExpr) {
    BinaryOperatorKind Opc = ConvertTokenKindToBinaryOpcode(Kind);
    assert(LHSExpr && "ActOnBinOp(): missing left expression");
    assert(RHSExpr && "ActOnBinOp(): missing right expression");
  
    // Emit warnings for tricky precedence issues, e.g. "bitfield & 0x4 == 0"
    DiagnoseBinOpPrecedence(*this, Opc, TokLoc, LHSExpr, RHSExpr);
  
    return BuildBinOp(S, TokLoc, Opc, LHSExpr, RHSExpr);
  }
  
  void Sema::LookupBinOp(Scope *S, SourceLocation OpLoc, BinaryOperatorKind Opc,
                         UnresolvedSetImpl &Functions) {
    OverloadedOperatorKind OverOp = BinaryOperator::getOverloadedOperator(Opc);
    if (OverOp != OO_None && OverOp != OO_Equal)
      LookupOverloadedOperatorName(OverOp, S, Functions);
  
    // In C++20 onwards, we may have a second operator to look up.
    if (getLangOpts().CPlusPlus20) {
      if (OverloadedOperatorKind ExtraOp = getRewrittenOverloadedOperator(OverOp))
        LookupOverloadedOperatorName(ExtraOp, S, Functions);
    }
  }
  
  /// Build an overloaded binary operator expression in the given scope.
  static ExprResult BuildOverloadedBinOp(Sema &S, Scope *Sc, SourceLocation OpLoc,
                                         BinaryOperatorKind Opc,
                                         Expr *LHS, Expr *RHS) {
    switch (Opc) {
    case BO_Assign:
    case BO_DivAssign:
    case BO_RemAssign:
    case BO_SubAssign:
    case BO_AndAssign:
    case BO_OrAssign:
    case BO_XorAssign:
      DiagnoseSelfAssignment(S, LHS, RHS, OpLoc, false);
      CheckIdentityFieldAssignment(LHS, RHS, OpLoc, S);
      break;
    default:
      break;
    }
  
    // Find all of the overloaded operators visible from this point.
    UnresolvedSet<16> Functions;
    S.LookupBinOp(Sc, OpLoc, Opc, Functions);
  
    // Build the (potentially-overloaded, potentially-dependent)
    // binary operation.
    return S.CreateOverloadedBinOp(OpLoc, Opc, Functions, LHS, RHS);
  }
  
  ExprResult Sema::BuildBinOp(Scope *S, SourceLocation OpLoc,
                              BinaryOperatorKind Opc,
                              Expr *LHSExpr, Expr *RHSExpr) {
    ExprResult LHS, RHS;
    std::tie(LHS, RHS) = CorrectDelayedTyposInBinOp(*this, Opc, LHSExpr, RHSExpr);
    if (!LHS.isUsable() || !RHS.isUsable())
      return ExprError();
    LHSExpr = LHS.get();
    RHSExpr = RHS.get();
  
    // We want to end up calling one of checkPseudoObjectAssignment
    // (if the LHS is a pseudo-object), BuildOverloadedBinOp (if
    // both expressions are overloadable or either is type-dependent),
    // or CreateBuiltinBinOp (in any other case).  We also want to get
    // any placeholder types out of the way.
  
    // Handle pseudo-objects in the LHS.
    if (const BuiltinType *pty = LHSExpr->getType()->getAsPlaceholderType()) {
      // Assignments with a pseudo-object l-value need special analysis.
      if (pty->getKind() == BuiltinType::PseudoObject &&
          BinaryOperator::isAssignmentOp(Opc))
        return checkPseudoObjectAssignment(S, OpLoc, Opc, LHSExpr, RHSExpr);
  
      // Don't resolve overloads if the other type is overloadable.
      if (getLangOpts().CPlusPlus && pty->getKind() == BuiltinType::Overload) {
        // We can't actually test that if we still have a placeholder,
        // though.  Fortunately, none of the exceptions we see in that
        // code below are valid when the LHS is an overload set.  Note
        // that an overload set can be dependently-typed, but it never
        // instantiates to having an overloadable type.
        ExprResult resolvedRHS = CheckPlaceholderExpr(RHSExpr);
        if (resolvedRHS.isInvalid()) return ExprError();
        RHSExpr = resolvedRHS.get();
  
        if (RHSExpr->isTypeDependent() ||
            RHSExpr->getType()->isOverloadableType())
          return BuildOverloadedBinOp(*this, S, OpLoc, Opc, LHSExpr, RHSExpr);
      }
  
      // If we're instantiating "a.x < b" or "A::x < b" and 'x' names a function
      // template, diagnose the missing 'template' keyword instead of diagnosing
      // an invalid use of a bound member function.
      //
      // Note that "A::x < b" might be valid if 'b' has an overloadable type due
      // to C++1z [over.over]/1.4, but we already checked for that case above.
      if (Opc == BO_LT && inTemplateInstantiation() &&
          (pty->getKind() == BuiltinType::BoundMember ||
           pty->getKind() == BuiltinType::Overload)) {
        auto *OE = dyn_cast<OverloadExpr>(LHSExpr);
        if (OE && !OE->hasTemplateKeyword() && !OE->hasExplicitTemplateArgs() &&
            std::any_of(OE->decls_begin(), OE->decls_end(), [](NamedDecl *ND) {
              return isa<FunctionTemplateDecl>(ND);
            })) {
          Diag(OE->getQualifier() ? OE->getQualifierLoc().getBeginLoc()
                                  : OE->getNameLoc(),
               diag::err_template_kw_missing)
            << OE->getName().getAsString() << "";
          return ExprError();
        }
      }
  
      ExprResult LHS = CheckPlaceholderExpr(LHSExpr);
      if (LHS.isInvalid()) return ExprError();
      LHSExpr = LHS.get();
    }
  
    // Handle pseudo-objects in the RHS.
    if (const BuiltinType *pty = RHSExpr->getType()->getAsPlaceholderType()) {
      // An overload in the RHS can potentially be resolved by the type
      // being assigned to.
      if (Opc == BO_Assign && pty->getKind() == BuiltinType::Overload) {
        if (getLangOpts().CPlusPlus &&
            (LHSExpr->isTypeDependent() || RHSExpr->isTypeDependent() ||
             LHSExpr->getType()->isOverloadableType()))
          return BuildOverloadedBinOp(*this, S, OpLoc, Opc, LHSExpr, RHSExpr);
  
        return CreateBuiltinBinOp(OpLoc, Opc, LHSExpr, RHSExpr);
      }
  
      // Don't resolve overloads if the other type is overloadable.
      if (getLangOpts().CPlusPlus && pty->getKind() == BuiltinType::Overload &&
          LHSExpr->getType()->isOverloadableType())
        return BuildOverloadedBinOp(*this, S, OpLoc, Opc, LHSExpr, RHSExpr);
  
      ExprResult resolvedRHS = CheckPlaceholderExpr(RHSExpr);
      if (!resolvedRHS.isUsable()) return ExprError();
      RHSExpr = resolvedRHS.get();
    }
  
    if (getLangOpts().CPlusPlus) {
      // If either expression is type-dependent, always build an
      // overloaded op.
      if (LHSExpr->isTypeDependent() || RHSExpr->isTypeDependent())
        return BuildOverloadedBinOp(*this, S, OpLoc, Opc, LHSExpr, RHSExpr);
  
      // Otherwise, build an overloaded op if either expression has an
      // overloadable type.
      if (LHSExpr->getType()->isOverloadableType() ||
          RHSExpr->getType()->isOverloadableType())
        return BuildOverloadedBinOp(*this, S, OpLoc, Opc, LHSExpr, RHSExpr);
    }
  
    if (getLangOpts().RecoveryAST &&
        (LHSExpr->isTypeDependent() || RHSExpr->isTypeDependent())) {
      assert(!getLangOpts().CPlusPlus);
      assert((LHSExpr->containsErrors() || RHSExpr->containsErrors()) &&
             "Should only occur in error-recovery path.");
      if (BinaryOperator::isCompoundAssignmentOp(Opc))
        // C [6.15.16] p3:
        // An assignment expression has the value of the left operand after the
        // assignment, but is not an lvalue.
        return CompoundAssignOperator::Create(
            Context, LHSExpr, RHSExpr, Opc,
            LHSExpr->getType().getUnqualifiedType(), VK_PRValue, OK_Ordinary,
            OpLoc, CurFPFeatureOverrides());
      QualType ResultType;
      switch (Opc) {
      case BO_Assign:
        ResultType = LHSExpr->getType().getUnqualifiedType();
        break;
      case BO_LT:
      case BO_GT:
      case BO_LE:
      case BO_GE:
      case BO_EQ:
      case BO_NE:
      case BO_LAnd:
      case BO_LOr:
        // These operators have a fixed result type regardless of operands.
        ResultType = Context.IntTy;
        break;
      case BO_Comma:
        ResultType = RHSExpr->getType();
        break;
      default:
        ResultType = Context.DependentTy;
        break;
      }
      return BinaryOperator::Create(Context, LHSExpr, RHSExpr, Opc, ResultType,
                                    VK_PRValue, OK_Ordinary, OpLoc,
                                    CurFPFeatureOverrides());
    }
  
    // Build a built-in binary operation.
    return CreateBuiltinBinOp(OpLoc, Opc, LHSExpr, RHSExpr);
  }
  
  static bool isOverflowingIntegerType(ASTContext &Ctx, QualType T) {
    if (T.isNull() || T->isDependentType())
      return false;
  
    if (!T->isPromotableIntegerType())
      return true;
  
    return Ctx.getIntWidth(T) >= Ctx.getIntWidth(Ctx.IntTy);
  }
  
  ExprResult Sema::CreateBuiltinUnaryOp(SourceLocation OpLoc,
                                        UnaryOperatorKind Opc,
                                        Expr *InputExpr) {
    ExprResult Input = InputExpr;
    ExprValueKind VK = VK_PRValue;
    ExprObjectKind OK = OK_Ordinary;
    QualType resultType;
    bool CanOverflow = false;
  
    bool ConvertHalfVec = false;
    if (getLangOpts().OpenCL) {
      QualType Ty = InputExpr->getType();
      // The only legal unary operation for atomics is '&'.
      if ((Opc != UO_AddrOf && Ty->isAtomicType()) ||
      // OpenCL special types - image, sampler, pipe, and blocks are to be used
      // only with a builtin functions and therefore should be disallowed here.
          (Ty->isImageType() || Ty->isSamplerT() || Ty->isPipeType()
          || Ty->isBlockPointerType())) {
        return ExprError(Diag(OpLoc, diag::err_typecheck_unary_expr)
                         << InputExpr->getType()
                         << Input.get()->getSourceRange());
      }
    }
  
    switch (Opc) {
    case UO_PreInc:
    case UO_PreDec:
    case UO_PostInc:
    case UO_PostDec:
      resultType = CheckIncrementDecrementOperand(*this, Input.get(), VK, OK,
                                                  OpLoc,
                                                  Opc == UO_PreInc ||
                                                  Opc == UO_PostInc,
                                                  Opc == UO_PreInc ||
                                                  Opc == UO_PreDec);
      CanOverflow = isOverflowingIntegerType(Context, resultType);
      break;
    case UO_AddrOf:
      resultType = CheckAddressOfOperand(Input, OpLoc);
      CheckAddressOfNoDeref(InputExpr);
      RecordModifiableNonNullParam(*this, InputExpr);
      break;
    case UO_Deref: {
      Input = DefaultFunctionArrayLvalueConversion(Input.get());
      if (Input.isInvalid()) return ExprError();
      resultType = CheckIndirectionOperand(*this, Input.get(), VK, OpLoc);
      break;
    }
    case UO_Plus:
    case UO_Minus:
      CanOverflow = Opc == UO_Minus &&
                    isOverflowingIntegerType(Context, Input.get()->getType());
      Input = UsualUnaryConversions(Input.get());
      if (Input.isInvalid()) return ExprError();
      // Unary plus and minus require promoting an operand of half vector to a
      // float vector and truncating the result back to a half vector. For now, we
      // do this only when HalfArgsAndReturns is set (that is, when the target is
      // arm or arm64).
      ConvertHalfVec = needsConversionOfHalfVec(true, Context, Input.get());
  
      // If the operand is a half vector, promote it to a float vector.
      if (ConvertHalfVec)
        Input = convertVector(Input.get(), Context.FloatTy, *this);
      resultType = Input.get()->getType();
      if (resultType->isDependentType())
        break;
      if (resultType->isArithmeticType()) // C99 6.5.3.3p1
        break;
      else if (resultType->isVectorType() &&
               // The z vector extensions don't allow + or - with bool vectors.
               (!Context.getLangOpts().ZVector ||
                resultType->castAs<VectorType>()->getVectorKind() !=
                VectorType::AltiVecBool))
        break;
      else if (getLangOpts().CPlusPlus && // C++ [expr.unary.op]p6
               Opc == UO_Plus &&
               resultType->isPointerType())
        break;
  
      return ExprError(Diag(OpLoc, diag::err_typecheck_unary_expr)
        << resultType << Input.get()->getSourceRange());
  
    case UO_Not: // bitwise complement
      Input = UsualUnaryConversions(Input.get());
      if (Input.isInvalid())
        return ExprError();
      resultType = Input.get()->getType();
      if (resultType->isDependentType())
        break;
      // C99 6.5.3.3p1. We allow complex int and float as a GCC extension.
      if (resultType->isComplexType() || resultType->isComplexIntegerType())
        // C99 does not support '~' for complex conjugation.
        Diag(OpLoc, diag::ext_integer_complement_complex)
            << resultType << Input.get()->getSourceRange();
      else if (resultType->hasIntegerRepresentation())
        break;
      else if (resultType->isExtVectorType() && Context.getLangOpts().OpenCL) {
        // OpenCL v1.1 s6.3.f: The bitwise operator not (~) does not operate
        // on vector float types.
        QualType T = resultType->castAs<ExtVectorType>()->getElementType();
        if (!T->isIntegerType())
          return ExprError(Diag(OpLoc, diag::err_typecheck_unary_expr)
                            << resultType << Input.get()->getSourceRange());
      } else {
        return ExprError(Diag(OpLoc, diag::err_typecheck_unary_expr)
                         << resultType << Input.get()->getSourceRange());
      }
      break;
  
    case UO_LNot: // logical negation
      // Unlike +/-/~, integer promotions aren't done here (C99 6.5.3.3p5).
      Input = DefaultFunctionArrayLvalueConversion(Input.get());
      if (Input.isInvalid()) return ExprError();
      resultType = Input.get()->getType();
  
      // Though we still have to promote half FP to float...
      if (resultType->isHalfType() && !Context.getLangOpts().NativeHalfType) {
        Input = ImpCastExprToType(Input.get(), Context.FloatTy, CK_FloatingCast).get();
        resultType = Context.FloatTy;
      }
  
      if (resultType->isDependentType())
        break;
      if (resultType->isScalarType() && !isScopedEnumerationType(resultType)) {
        // C99 6.5.3.3p1: ok, fallthrough;
        if (Context.getLangOpts().CPlusPlus) {
          // C++03 [expr.unary.op]p8, C++0x [expr.unary.op]p9:
          // operand contextually converted to bool.
          Input = ImpCastExprToType(Input.get(), Context.BoolTy,
                                    ScalarTypeToBooleanCastKind(resultType));
        } else if (Context.getLangOpts().OpenCL &&
                   Context.getLangOpts().OpenCLVersion < 120) {
          // OpenCL v1.1 6.3.h: The logical operator not (!) does not
          // operate on scalar float types.
          if (!resultType->isIntegerType() && !resultType->isPointerType())
            return ExprError(Diag(OpLoc, diag::err_typecheck_unary_expr)
                             << resultType << Input.get()->getSourceRange());
        }
      } else if (resultType->isExtVectorType()) {
        if (Context.getLangOpts().OpenCL &&
            Context.getLangOpts().getOpenCLCompatibleVersion() < 120) {
          // OpenCL v1.1 6.3.h: The logical operator not (!) does not
          // operate on vector float types.
          QualType T = resultType->castAs<ExtVectorType>()->getElementType();
          if (!T->isIntegerType())
            return ExprError(Diag(OpLoc, diag::err_typecheck_unary_expr)
                             << resultType << Input.get()->getSourceRange());
        }
        // Vector logical not returns the signed variant of the operand type.
        resultType = GetSignedVectorType(resultType);
        break;
      } else if (Context.getLangOpts().CPlusPlus && resultType->isVectorType()) {
        const VectorType *VTy = resultType->castAs<VectorType>();
        if (VTy->getVectorKind() != VectorType::GenericVector)
          return ExprError(Diag(OpLoc, diag::err_typecheck_unary_expr)
                           << resultType << Input.get()->getSourceRange());
  
        // Vector logical not returns the signed variant of the operand type.
        resultType = GetSignedVectorType(resultType);
        break;
      } else {
        return ExprError(Diag(OpLoc, diag::err_typecheck_unary_expr)
          << resultType << Input.get()->getSourceRange());
      }
  
      // LNot always has type int. C99 6.5.3.3p5.
      // In C++, it's bool. C++ 5.3.1p8
      resultType = Context.getLogicalOperationType();
      break;
    case UO_Real:
    case UO_Imag:
      resultType = CheckRealImagOperand(*this, Input, OpLoc, Opc == UO_Real);
      // _Real maps ordinary l-values into ordinary l-values. _Imag maps ordinary
      // complex l-values to ordinary l-values and all other values to r-values.
      if (Input.isInvalid()) return ExprError();
      if (Opc == UO_Real || Input.get()->getType()->isAnyComplexType()) {
        if (Input.get()->isGLValue() &&
            Input.get()->getObjectKind() == OK_Ordinary)
          VK = Input.get()->getValueKind();
      } else if (!getLangOpts().CPlusPlus) {
        // In C, a volatile scalar is read by __imag. In C++, it is not.
        Input = DefaultLvalueConversion(Input.get());
      }
      break;
    case UO_Extension:
      resultType = Input.get()->getType();
      VK = Input.get()->getValueKind();
      OK = Input.get()->getObjectKind();
      break;
    case UO_Coawait:
      // It's unnecessary to represent the pass-through operator co_await in the
      // AST; just return the input expression instead.
      assert(!Input.get()->getType()->isDependentType() &&
                     "the co_await expression must be non-dependant before "
                     "building operator co_await");
      return Input;
    }
    if (resultType.isNull() || Input.isInvalid())
      return ExprError();
  
    // Check for array bounds violations in the operand of the UnaryOperator,
    // except for the '*' and '&' operators that have to be handled specially
    // by CheckArrayAccess (as there are special cases like &array[arraysize]
    // that are explicitly defined as valid by the standard).
    if (Opc != UO_AddrOf && Opc != UO_Deref)
      CheckArrayAccess(Input.get());
  
    auto *UO =
        UnaryOperator::Create(Context, Input.get(), Opc, resultType, VK, OK,
                              OpLoc, CanOverflow, CurFPFeatureOverrides());
  
    if (Opc == UO_Deref && UO->getType()->hasAttr(attr::NoDeref) &&
        !isa<ArrayType>(UO->getType().getDesugaredType(Context)) &&
        !isUnevaluatedContext())
      ExprEvalContexts.back().PossibleDerefs.insert(UO);
  
    // Convert the result back to a half vector.
    if (ConvertHalfVec)
      return convertVector(UO, Context.HalfTy, *this);
    return UO;
  }
  
  /// Determine whether the given expression is a qualified member
  /// access expression, of a form that could be turned into a pointer to member
  /// with the address-of operator.
  bool Sema::isQualifiedMemberAccess(Expr *E) {
    if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
      if (!DRE->getQualifier())
        return false;
  
      ValueDecl *VD = DRE->getDecl();
      if (!VD->isCXXClassMember())
        return false;
  
      if (isa<FieldDecl>(VD) || isa<IndirectFieldDecl>(VD))
        return true;
      if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(VD))
        return Method->isInstance();
  
      return false;
    }
  
    if (UnresolvedLookupExpr *ULE = dyn_cast<UnresolvedLookupExpr>(E)) {
      if (!ULE->getQualifier())
        return false;
  
      for (NamedDecl *D : ULE->decls()) {
        if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(D)) {
          if (Method->isInstance())
            return true;
        } else {
          // Overload set does not contain methods.
          break;
        }
      }
  
      return false;
    }
  
    return false;
  }
  
  ExprResult Sema::BuildUnaryOp(Scope *S, SourceLocation OpLoc,
                                UnaryOperatorKind Opc, Expr *Input) {
    // First things first: handle placeholders so that the
    // overloaded-operator check considers the right type.
    if (const BuiltinType *pty = Input->getType()->getAsPlaceholderType()) {
      // Increment and decrement of pseudo-object references.
      if (pty->getKind() == BuiltinType::PseudoObject &&
          UnaryOperator::isIncrementDecrementOp(Opc))
        return checkPseudoObjectIncDec(S, OpLoc, Opc, Input);
  
      // extension is always a builtin operator.
      if (Opc == UO_Extension)
        return CreateBuiltinUnaryOp(OpLoc, Opc, Input);
  
      // & gets special logic for several kinds of placeholder.
      // The builtin code knows what to do.
      if (Opc == UO_AddrOf &&
          (pty->getKind() == BuiltinType::Overload ||
           pty->getKind() == BuiltinType::UnknownAny ||
           pty->getKind() == BuiltinType::BoundMember))
        return CreateBuiltinUnaryOp(OpLoc, Opc, Input);
  
      // Anything else needs to be handled now.
      ExprResult Result = CheckPlaceholderExpr(Input);
      if (Result.isInvalid()) return ExprError();
      Input = Result.get();
    }
  
    if (getLangOpts().CPlusPlus && Input->getType()->isOverloadableType() &&
        UnaryOperator::getOverloadedOperator(Opc) != OO_None &&
        !(Opc == UO_AddrOf && isQualifiedMemberAccess(Input))) {
      // Find all of the overloaded operators visible from this point.
      UnresolvedSet<16> Functions;
      OverloadedOperatorKind OverOp = UnaryOperator::getOverloadedOperator(Opc);
      if (S && OverOp != OO_None)
        LookupOverloadedOperatorName(OverOp, S, Functions);
  
      return CreateOverloadedUnaryOp(OpLoc, Opc, Functions, Input);
    }
  
    return CreateBuiltinUnaryOp(OpLoc, Opc, Input);
  }
  
  // Unary Operators.  'Tok' is the token for the operator.
  ExprResult Sema::ActOnUnaryOp(Scope *S, SourceLocation OpLoc,
                                tok::TokenKind Op, Expr *Input) {
    return BuildUnaryOp(S, OpLoc, ConvertTokenKindToUnaryOpcode(Op), Input);
  }
  
  /// ActOnAddrLabel - Parse the GNU address of label extension: "&&foo".
  ExprResult Sema::ActOnAddrLabel(SourceLocation OpLoc, SourceLocation LabLoc,
                                  LabelDecl *TheDecl) {
    TheDecl->markUsed(Context);
    // Create the AST node.  The address of a label always has type 'void*'.
    return new (Context) AddrLabelExpr(OpLoc, LabLoc, TheDecl,
                                       Context.getPointerType(Context.VoidTy));
  }
  
  void Sema::ActOnStartStmtExpr() {
    PushExpressionEvaluationContext(ExprEvalContexts.back().Context);
  }
  
  void Sema::ActOnStmtExprError() {
    // Note that function is also called by TreeTransform when leaving a
    // StmtExpr scope without rebuilding anything.
  
    DiscardCleanupsInEvaluationContext();
    PopExpressionEvaluationContext();
  }
  
  ExprResult Sema::ActOnStmtExpr(Scope *S, SourceLocation LPLoc, Stmt *SubStmt,
                                 SourceLocation RPLoc) {
    return BuildStmtExpr(LPLoc, SubStmt, RPLoc, getTemplateDepth(S));
  }
  
  ExprResult Sema::BuildStmtExpr(SourceLocation LPLoc, Stmt *SubStmt,
                                 SourceLocation RPLoc, unsigned TemplateDepth) {
    assert(SubStmt && isa<CompoundStmt>(SubStmt) && "Invalid action invocation!");
    CompoundStmt *Compound = cast<CompoundStmt>(SubStmt);
  
    if (hasAnyUnrecoverableErrorsInThisFunction())
      DiscardCleanupsInEvaluationContext();
    assert(!Cleanup.exprNeedsCleanups() &&
           "cleanups within StmtExpr not correctly bound!");
    PopExpressionEvaluationContext();
  
    // FIXME: there are a variety of strange constraints to enforce here, for
    // example, it is not possible to goto into a stmt expression apparently.
    // More semantic analysis is needed.
  
    // If there are sub-stmts in the compound stmt, take the type of the last one
    // as the type of the stmtexpr.
    QualType Ty = Context.VoidTy;
    bool StmtExprMayBindToTemp = false;
    if (!Compound->body_empty()) {
      // For GCC compatibility we get the last Stmt excluding trailing NullStmts.
      if (const auto *LastStmt =
              dyn_cast<ValueStmt>(Compound->getStmtExprResult())) {
        if (const Expr *Value = LastStmt->getExprStmt()) {
          StmtExprMayBindToTemp = true;
          Ty = Value->getType();
        }
      }
    }
  
    // FIXME: Check that expression type is complete/non-abstract; statement
    // expressions are not lvalues.
    Expr *ResStmtExpr =
        new (Context) StmtExpr(Compound, Ty, LPLoc, RPLoc, TemplateDepth);
    if (StmtExprMayBindToTemp)
      return MaybeBindToTemporary(ResStmtExpr);
    return ResStmtExpr;
  }
  
  ExprResult Sema::ActOnStmtExprResult(ExprResult ER) {
    if (ER.isInvalid())
      return ExprError();
  
    // Do function/array conversion on the last expression, but not
    // lvalue-to-rvalue.  However, initialize an unqualified type.
    ER = DefaultFunctionArrayConversion(ER.get());
    if (ER.isInvalid())
      return ExprError();
    Expr *E = ER.get();
  
    if (E->isTypeDependent())
      return E;
  
    // In ARC, if the final expression ends in a consume, splice
    // the consume out and bind it later.  In the alternate case
    // (when dealing with a retainable type), the result
    // initialization will create a produce.  In both cases the
    // result will be +1, and we'll need to balance that out with
    // a bind.
    auto *Cast = dyn_cast<ImplicitCastExpr>(E);
    if (Cast && Cast->getCastKind() == CK_ARCConsumeObject)
      return Cast->getSubExpr();
  
    // FIXME: Provide a better location for the initialization.
    return PerformCopyInitialization(
        InitializedEntity::InitializeStmtExprResult(
            E->getBeginLoc(), E->getType().getUnqualifiedType()),
        SourceLocation(), E);
  }
  
  ExprResult Sema::BuildBuiltinOffsetOf(SourceLocation BuiltinLoc,
                                        TypeSourceInfo *TInfo,
                                        ArrayRef<OffsetOfComponent> Components,
                                        SourceLocation RParenLoc) {
    QualType ArgTy = TInfo->getType();
    bool Dependent = ArgTy->isDependentType();
    SourceRange TypeRange = TInfo->getTypeLoc().getLocalSourceRange();
  
    // We must have at least one component that refers to the type, and the first
    // one is known to be a field designator.  Verify that the ArgTy represents
    // a struct/union/class.
    if (!Dependent && !ArgTy->isRecordType())
      return ExprError(Diag(BuiltinLoc, diag::err_offsetof_record_type)
                         << ArgTy << TypeRange);
  
    // Type must be complete per C99 7.17p3 because a declaring a variable
    // with an incomplete type would be ill-formed.
    if (!Dependent
        && RequireCompleteType(BuiltinLoc, ArgTy,
                               diag::err_offsetof_incomplete_type, TypeRange))
      return ExprError();
  
    bool DidWarnAboutNonPOD = false;
    QualType CurrentType = ArgTy;
    SmallVector<OffsetOfNode, 4> Comps;
    SmallVector<Expr*, 4> Exprs;
    for (const OffsetOfComponent &OC : Components) {
      if (OC.isBrackets) {
        // Offset of an array sub-field.  TODO: Should we allow vector elements?
        if (!CurrentType->isDependentType()) {
          const ArrayType *AT = Context.getAsArrayType(CurrentType);
          if(!AT)
            return ExprError(Diag(OC.LocEnd, diag::err_offsetof_array_type)
                             << CurrentType);
          CurrentType = AT->getElementType();
        } else
          CurrentType = Context.DependentTy;
  
        ExprResult IdxRval = DefaultLvalueConversion(static_cast<Expr*>(OC.U.E));
        if (IdxRval.isInvalid())
          return ExprError();
        Expr *Idx = IdxRval.get();
  
        // The expression must be an integral expression.
        // FIXME: An integral constant expression?
        if (!Idx->isTypeDependent() && !Idx->isValueDependent() &&
            !Idx->getType()->isIntegerType())
          return ExprError(
              Diag(Idx->getBeginLoc(), diag::err_typecheck_subscript_not_integer)
              << Idx->getSourceRange());
  
        // Record this array index.
        Comps.push_back(OffsetOfNode(OC.LocStart, Exprs.size(), OC.LocEnd));
        Exprs.push_back(Idx);
        continue;
      }
  
      // Offset of a field.
      if (CurrentType->isDependentType()) {
        // We have the offset of a field, but we can't look into the dependent
        // type. Just record the identifier of the field.
        Comps.push_back(OffsetOfNode(OC.LocStart, OC.U.IdentInfo, OC.LocEnd));
        CurrentType = Context.DependentTy;
        continue;
      }
  
      // We need to have a complete type to look into.
      if (RequireCompleteType(OC.LocStart, CurrentType,
                              diag::err_offsetof_incomplete_type))
        return ExprError();
  
      // Look for the designated field.
      const RecordType *RC = CurrentType->getAs<RecordType>();
      if (!RC)
        return ExprError(Diag(OC.LocEnd, diag::err_offsetof_record_type)
                         << CurrentType);
      RecordDecl *RD = RC->getDecl();
  
      // C++ [lib.support.types]p5:
      //   The macro offsetof accepts a restricted set of type arguments in this
      //   International Standard. type shall be a POD structure or a POD union
      //   (clause 9).
      // C++11 [support.types]p4:
      //   If type is not a standard-layout class (Clause 9), the results are
      //   undefined.
      if (CXXRecordDecl *CRD = dyn_cast<CXXRecordDecl>(RD)) {
        bool IsSafe = LangOpts.CPlusPlus11? CRD->isStandardLayout() : CRD->isPOD();
        unsigned DiagID =
          LangOpts.CPlusPlus11? diag::ext_offsetof_non_standardlayout_type
                              : diag::ext_offsetof_non_pod_type;
  
        if (!IsSafe && !DidWarnAboutNonPOD &&
            DiagRuntimeBehavior(BuiltinLoc, nullptr,
                                PDiag(DiagID)
                                << SourceRange(Components[0].LocStart, OC.LocEnd)
                                << CurrentType))
          DidWarnAboutNonPOD = true;
      }
  
      // Look for the field.
      LookupResult R(*this, OC.U.IdentInfo, OC.LocStart, LookupMemberName);
      LookupQualifiedName(R, RD);
      FieldDecl *MemberDecl = R.getAsSingle<FieldDecl>();
      IndirectFieldDecl *IndirectMemberDecl = nullptr;
      if (!MemberDecl) {
        if ((IndirectMemberDecl = R.getAsSingle<IndirectFieldDecl>()))
          MemberDecl = IndirectMemberDecl->getAnonField();
      }
  
      if (!MemberDecl)
        return ExprError(Diag(BuiltinLoc, diag::err_no_member)
                         << OC.U.IdentInfo << RD << SourceRange(OC.LocStart,
                                                                OC.LocEnd));
  
      // C99 7.17p3:
      //   (If the specified member is a bit-field, the behavior is undefined.)
      //
      // We diagnose this as an error.
      if (MemberDecl->isBitField()) {
        Diag(OC.LocEnd, diag::err_offsetof_bitfield)
          << MemberDecl->getDeclName()
          << SourceRange(BuiltinLoc, RParenLoc);
        Diag(MemberDecl->getLocation(), diag::note_bitfield_decl);
        return ExprError();
      }
  
      RecordDecl *Parent = MemberDecl->getParent();
      if (IndirectMemberDecl)
        Parent = cast<RecordDecl>(IndirectMemberDecl->getDeclContext());
  
      // If the member was found in a base class, introduce OffsetOfNodes for
      // the base class indirections.
      CXXBasePaths Paths;
      if (IsDerivedFrom(OC.LocStart, CurrentType, Context.getTypeDeclType(Parent),
                        Paths)) {
        if (Paths.getDetectedVirtual()) {
          Diag(OC.LocEnd, diag::err_offsetof_field_of_virtual_base)
            << MemberDecl->getDeclName()
            << SourceRange(BuiltinLoc, RParenLoc);
          return ExprError();
        }
  
        CXXBasePath &Path = Paths.front();
        for (const CXXBasePathElement &B : Path)
          Comps.push_back(OffsetOfNode(B.Base));
      }
  
      if (IndirectMemberDecl) {
        for (auto *FI : IndirectMemberDecl->chain()) {
          assert(isa<FieldDecl>(FI));
          Comps.push_back(OffsetOfNode(OC.LocStart,
                                       cast<FieldDecl>(FI), OC.LocEnd));
        }
      } else
        Comps.push_back(OffsetOfNode(OC.LocStart, MemberDecl, OC.LocEnd));
  
      CurrentType = MemberDecl->getType().getNonReferenceType();
    }
  
    return OffsetOfExpr::Create(Context, Context.getSizeType(), BuiltinLoc, TInfo,
                                Comps, Exprs, RParenLoc);
  }
  
  ExprResult Sema::ActOnBuiltinOffsetOf(Scope *S,
                                        SourceLocation BuiltinLoc,
                                        SourceLocation TypeLoc,
                                        ParsedType ParsedArgTy,
                                        ArrayRef<OffsetOfComponent> Components,
                                        SourceLocation RParenLoc) {
  
    TypeSourceInfo *ArgTInfo;
    QualType ArgTy = GetTypeFromParser(ParsedArgTy, &ArgTInfo);
    if (ArgTy.isNull())
      return ExprError();
  
    if (!ArgTInfo)
      ArgTInfo = Context.getTrivialTypeSourceInfo(ArgTy, TypeLoc);
  
    return BuildBuiltinOffsetOf(BuiltinLoc, ArgTInfo, Components, RParenLoc);
  }
  
  
  ExprResult Sema::ActOnChooseExpr(SourceLocation BuiltinLoc,
                                   Expr *CondExpr,
                                   Expr *LHSExpr, Expr *RHSExpr,
                                   SourceLocation RPLoc) {
    assert((CondExpr && LHSExpr && RHSExpr) && "Missing type argument(s)");
  
    ExprValueKind VK = VK_PRValue;
    ExprObjectKind OK = OK_Ordinary;
    QualType resType;
    bool CondIsTrue = false;
    if (CondExpr->isTypeDependent() || CondExpr->isValueDependent()) {
      resType = Context.DependentTy;
    } else {
      // The conditional expression is required to be a constant expression.
      llvm::APSInt condEval(32);
      ExprResult CondICE = VerifyIntegerConstantExpression(
          CondExpr, &condEval, diag::err_typecheck_choose_expr_requires_constant);
      if (CondICE.isInvalid())
        return ExprError();
      CondExpr = CondICE.get();
      CondIsTrue = condEval.getZExtValue();
  
      // If the condition is > zero, then the AST type is the same as the LHSExpr.
      Expr *ActiveExpr = CondIsTrue ? LHSExpr : RHSExpr;
  
      resType = ActiveExpr->getType();
      VK = ActiveExpr->getValueKind();
      OK = ActiveExpr->getObjectKind();
    }
  
    return new (Context) ChooseExpr(BuiltinLoc, CondExpr, LHSExpr, RHSExpr,
                                    resType, VK, OK, RPLoc, CondIsTrue);
  }
  
  //===----------------------------------------------------------------------===//
  // Clang Extensions.
  //===----------------------------------------------------------------------===//
  
  /// ActOnBlockStart - This callback is invoked when a block literal is started.
  void Sema::ActOnBlockStart(SourceLocation CaretLoc, Scope *CurScope) {
    BlockDecl *Block = BlockDecl::Create(Context, CurContext, CaretLoc);
  
    if (LangOpts.CPlusPlus) {
      MangleNumberingContext *MCtx;
      Decl *ManglingContextDecl;
      std::tie(MCtx, ManglingContextDecl) =
          getCurrentMangleNumberContext(Block->getDeclContext());
      if (MCtx) {
        unsigned ManglingNumber = MCtx->getManglingNumber(Block);
        Block->setBlockMangling(ManglingNumber, ManglingContextDecl);
      }
    }
  
    PushBlockScope(CurScope, Block);
    CurContext->addDecl(Block);
    if (CurScope)
      PushDeclContext(CurScope, Block);
    else
      CurContext = Block;
  
    getCurBlock()->HasImplicitReturnType = true;
  
    // Enter a new evaluation context to insulate the block from any
    // cleanups from the enclosing full-expression.
    PushExpressionEvaluationContext(
        ExpressionEvaluationContext::PotentiallyEvaluated);
  }
  
  void Sema::ActOnBlockArguments(SourceLocation CaretLoc, Declarator &ParamInfo,
                                 Scope *CurScope) {
    assert(ParamInfo.getIdentifier() == nullptr &&
           "block-id should have no identifier!");
    assert(ParamInfo.getContext() == DeclaratorContext::BlockLiteral);
    BlockScopeInfo *CurBlock = getCurBlock();
  
    TypeSourceInfo *Sig = GetTypeForDeclarator(ParamInfo, CurScope);
    QualType T = Sig->getType();
  
    // FIXME: We should allow unexpanded parameter packs here, but that would,
    // in turn, make the block expression contain unexpanded parameter packs.
    if (DiagnoseUnexpandedParameterPack(CaretLoc, Sig, UPPC_Block)) {
      // Drop the parameters.
      FunctionProtoType::ExtProtoInfo EPI;
      EPI.HasTrailingReturn = false;
      EPI.TypeQuals.addConst();
      T = Context.getFunctionType(Context.DependentTy, None, EPI);
      Sig = Context.getTrivialTypeSourceInfo(T);
    }
  
    // GetTypeForDeclarator always produces a function type for a block
    // literal signature.  Furthermore, it is always a FunctionProtoType
    // unless the function was written with a typedef.
    assert(T->isFunctionType() &&
           "GetTypeForDeclarator made a non-function block signature");
  
    // Look for an explicit signature in that function type.
    FunctionProtoTypeLoc ExplicitSignature;
  
    if ((ExplicitSignature = Sig->getTypeLoc()
                                 .getAsAdjusted<FunctionProtoTypeLoc>())) {
  
      // Check whether that explicit signature was synthesized by
      // GetTypeForDeclarator.  If so, don't save that as part of the
      // written signature.
      if (ExplicitSignature.getLocalRangeBegin() ==
          ExplicitSignature.getLocalRangeEnd()) {
        // This would be much cheaper if we stored TypeLocs instead of
        // TypeSourceInfos.
        TypeLoc Result = ExplicitSignature.getReturnLoc();
        unsigned Size = Result.getFullDataSize();
        Sig = Context.CreateTypeSourceInfo(Result.getType(), Size);
        Sig->getTypeLoc().initializeFullCopy(Result, Size);
  
        ExplicitSignature = FunctionProtoTypeLoc();
      }
    }
  
    CurBlock->TheDecl->setSignatureAsWritten(Sig);
    CurBlock->FunctionType = T;
  
    const auto *Fn = T->castAs<FunctionType>();
    QualType RetTy = Fn->getReturnType();
    bool isVariadic =
        (isa<FunctionProtoType>(Fn) && cast<FunctionProtoType>(Fn)->isVariadic());
  
    CurBlock->TheDecl->setIsVariadic(isVariadic);
  
    // Context.DependentTy is used as a placeholder for a missing block
    // return type.  TODO:  what should we do with declarators like:
    //   ^ * { ... }
    // If the answer is "apply template argument deduction"....
    if (RetTy != Context.DependentTy) {
      CurBlock->ReturnType = RetTy;
      CurBlock->TheDecl->setBlockMissingReturnType(false);
      CurBlock->HasImplicitReturnType = false;
    }
  
    // Push block parameters from the declarator if we had them.
    SmallVector<ParmVarDecl*, 8> Params;
    if (ExplicitSignature) {
      for (unsigned I = 0, E = ExplicitSignature.getNumParams(); I != E; ++I) {
        ParmVarDecl *Param = ExplicitSignature.getParam(I);
        if (Param->getIdentifier() == nullptr && !Param->isImplicit() &&
            !Param->isInvalidDecl() && !getLangOpts().CPlusPlus) {
          // Diagnose this as an extension in C17 and earlier.
          if (!getLangOpts().C2x)
            Diag(Param->getLocation(), diag::ext_parameter_name_omitted_c2x);
        }
        Params.push_back(Param);
      }
  
    // Fake up parameter variables if we have a typedef, like
    //   ^ fntype { ... }
    } else if (const FunctionProtoType *Fn = T->getAs<FunctionProtoType>()) {
      for (const auto &I : Fn->param_types()) {
        ParmVarDecl *Param = BuildParmVarDeclForTypedef(
            CurBlock->TheDecl, ParamInfo.getBeginLoc(), I);
        Params.push_back(Param);
      }
    }
  
    // Set the parameters on the block decl.
    if (!Params.empty()) {
      CurBlock->TheDecl->setParams(Params);
      CheckParmsForFunctionDef(CurBlock->TheDecl->parameters(),
                               /*CheckParameterNames=*/false);
    }
  
    // Finally we can process decl attributes.
    ProcessDeclAttributes(CurScope, CurBlock->TheDecl, ParamInfo);
  
    // Put the parameter variables in scope.
    for (auto AI : CurBlock->TheDecl->parameters()) {
      AI->setOwningFunction(CurBlock->TheDecl);
  
      // If this has an identifier, add it to the scope stack.
      if (AI->getIdentifier()) {
        CheckShadow(CurBlock->TheScope, AI);
  
        PushOnScopeChains(AI, CurBlock->TheScope);
      }
    }
  }
  
  /// ActOnBlockError - If there is an error parsing a block, this callback
  /// is invoked to pop the information about the block from the action impl.
  void Sema::ActOnBlockError(SourceLocation CaretLoc, Scope *CurScope) {
    // Leave the expression-evaluation context.
    DiscardCleanupsInEvaluationContext();
    PopExpressionEvaluationContext();
  
    // Pop off CurBlock, handle nested blocks.
    PopDeclContext();
    PopFunctionScopeInfo();
  }
  
  /// ActOnBlockStmtExpr - This is called when the body of a block statement
  /// literal was successfully completed.  ^(int x){...}
  ExprResult Sema::ActOnBlockStmtExpr(SourceLocation CaretLoc,
                                      Stmt *Body, Scope *CurScope) {
    // If blocks are disabled, emit an error.
    if (!LangOpts.Blocks)
      Diag(CaretLoc, diag::err_blocks_disable) << LangOpts.OpenCL;
  
    // Leave the expression-evaluation context.
    if (hasAnyUnrecoverableErrorsInThisFunction())
      DiscardCleanupsInEvaluationContext();
    assert(!Cleanup.exprNeedsCleanups() &&
           "cleanups within block not correctly bound!");
    PopExpressionEvaluationContext();
  
    BlockScopeInfo *BSI = cast<BlockScopeInfo>(FunctionScopes.back());
    BlockDecl *BD = BSI->TheDecl;
  
    if (BSI->HasImplicitReturnType)
      deduceClosureReturnType(*BSI);
  
    QualType RetTy = Context.VoidTy;
    if (!BSI->ReturnType.isNull())
      RetTy = BSI->ReturnType;
  
    bool NoReturn = BD->hasAttr<NoReturnAttr>();
    QualType BlockTy;
  
    // If the user wrote a function type in some form, try to use that.
    if (!BSI->FunctionType.isNull()) {
      const FunctionType *FTy = BSI->FunctionType->castAs<FunctionType>();
  
      FunctionType::ExtInfo Ext = FTy->getExtInfo();
      if (NoReturn && !Ext.getNoReturn()) Ext = Ext.withNoReturn(true);
  
      // Turn protoless block types into nullary block types.
      if (isa<FunctionNoProtoType>(FTy)) {
        FunctionProtoType::ExtProtoInfo EPI;
        EPI.ExtInfo = Ext;
        BlockTy = Context.getFunctionType(RetTy, None, EPI);
  
      // Otherwise, if we don't need to change anything about the function type,
      // preserve its sugar structure.
      } else if (FTy->getReturnType() == RetTy &&
                 (!NoReturn || FTy->getNoReturnAttr())) {
        BlockTy = BSI->FunctionType;
  
      // Otherwise, make the minimal modifications to the function type.
      } else {
        const FunctionProtoType *FPT = cast<FunctionProtoType>(FTy);
        FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
        EPI.TypeQuals = Qualifiers();
        EPI.ExtInfo = Ext;
        BlockTy = Context.getFunctionType(RetTy, FPT->getParamTypes(), EPI);
      }
  
    // If we don't have a function type, just build one from nothing.
    } else {
      FunctionProtoType::ExtProtoInfo EPI;
      EPI.ExtInfo = FunctionType::ExtInfo().withNoReturn(NoReturn);
      BlockTy = Context.getFunctionType(RetTy, None, EPI);
    }
  
    DiagnoseUnusedParameters(BD->parameters());
    BlockTy = Context.getBlockPointerType(BlockTy);
  
    // If needed, diagnose invalid gotos and switches in the block.
    if (getCurFunction()->NeedsScopeChecking() &&
        !PP.isCodeCompletionEnabled())
      DiagnoseInvalidJumps(cast<CompoundStmt>(Body));
  
    BD->setBody(cast<CompoundStmt>(Body));
  
    if (Body && getCurFunction()->HasPotentialAvailabilityViolations)
      DiagnoseUnguardedAvailabilityViolations(BD);
  
    // Try to apply the named return value optimization. We have to check again
    // if we can do this, though, because blocks keep return statements around
    // to deduce an implicit return type.
    if (getLangOpts().CPlusPlus && RetTy->isRecordType() &&
        !BD->isDependentContext())
      computeNRVO(Body, BSI);
  
    if (RetTy.hasNonTrivialToPrimitiveDestructCUnion() ||
        RetTy.hasNonTrivialToPrimitiveCopyCUnion())
      checkNonTrivialCUnion(RetTy, BD->getCaretLocation(), NTCUC_FunctionReturn,
                            NTCUK_Destruct|NTCUK_Copy);
  
    PopDeclContext();
  
    // Set the captured variables on the block.
    SmallVector<BlockDecl::Capture, 4> Captures;
    for (Capture &Cap : BSI->Captures) {
      if (Cap.isInvalid() || Cap.isThisCapture())
        continue;
  
      VarDecl *Var = Cap.getVariable();
      Expr *CopyExpr = nullptr;
      if (getLangOpts().CPlusPlus && Cap.isCopyCapture()) {
        if (const RecordType *Record =
                Cap.getCaptureType()->getAs<RecordType>()) {
          // The capture logic needs the destructor, so make sure we mark it.
          // Usually this is unnecessary because most local variables have
          // their destructors marked at declaration time, but parameters are
          // an exception because it's technically only the call site that
          // actually requires the destructor.
          if (isa<ParmVarDecl>(Var))
            FinalizeVarWithDestructor(Var, Record);
  
          // Enter a separate potentially-evaluated context while building block
          // initializers to isolate their cleanups from those of the block
          // itself.
          // FIXME: Is this appropriate even when the block itself occurs in an
          // unevaluated operand?
          EnterExpressionEvaluationContext EvalContext(
              *this, ExpressionEvaluationContext::PotentiallyEvaluated);
  
          SourceLocation Loc = Cap.getLocation();
  
          ExprResult Result = BuildDeclarationNameExpr(
              CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
  
          // According to the blocks spec, the capture of a variable from
          // the stack requires a const copy constructor.  This is not true
          // of the copy/move done to move a __block variable to the heap.
          if (!Result.isInvalid() &&
              !Result.get()->getType().isConstQualified()) {
            Result = ImpCastExprToType(Result.get(),
                                       Result.get()->getType().withConst(),
                                       CK_NoOp, VK_LValue);
          }
  
          if (!Result.isInvalid()) {
            Result = PerformCopyInitialization(
                InitializedEntity::InitializeBlock(Var->getLocation(),
                                                   Cap.getCaptureType()),
                Loc, Result.get());
          }
  
          // Build a full-expression copy expression if initialization
          // succeeded and used a non-trivial constructor.  Recover from
          // errors by pretending that the copy isn't necessary.
          if (!Result.isInvalid() &&
              !cast<CXXConstructExpr>(Result.get())->getConstructor()
                  ->isTrivial()) {
            Result = MaybeCreateExprWithCleanups(Result);
            CopyExpr = Result.get();
          }
        }
      }
  
      BlockDecl::Capture NewCap(Var, Cap.isBlockCapture(), Cap.isNested(),
                                CopyExpr);
      Captures.push_back(NewCap);
    }
    BD->setCaptures(Context, Captures, BSI->CXXThisCaptureIndex != 0);
  
    // Pop the block scope now but keep it alive to the end of this function.
    AnalysisBasedWarnings::Policy WP = AnalysisWarnings.getDefaultPolicy();
    PoppedFunctionScopePtr ScopeRAII = PopFunctionScopeInfo(&WP, BD, BlockTy);
  
    BlockExpr *Result = new (Context) BlockExpr(BD, BlockTy);
  
    // If the block isn't obviously global, i.e. it captures anything at
    // all, then we need to do a few things in the surrounding context:
    if (Result->getBlockDecl()->hasCaptures()) {
      // First, this expression has a new cleanup object.
      ExprCleanupObjects.push_back(Result->getBlockDecl());
      Cleanup.setExprNeedsCleanups(true);
  
      // It also gets a branch-protected scope if any of the captured
      // variables needs destruction.
      for (const auto &CI : Result->getBlockDecl()->captures()) {
        const VarDecl *var = CI.getVariable();
        if (var->getType().isDestructedType() != QualType::DK_none) {
          setFunctionHasBranchProtectedScope();
          break;
        }
      }
    }
  
    if (getCurFunction())
      getCurFunction()->addBlock(BD);
  
    return Result;
  }
  
  ExprResult Sema::ActOnVAArg(SourceLocation BuiltinLoc, Expr *E, ParsedType Ty,
                              SourceLocation RPLoc) {
    TypeSourceInfo *TInfo;
    GetTypeFromParser(Ty, &TInfo);
    return BuildVAArgExpr(BuiltinLoc, E, TInfo, RPLoc);
  }
  
  ExprResult Sema::BuildVAArgExpr(SourceLocation BuiltinLoc,
                                  Expr *E, TypeSourceInfo *TInfo,
                                  SourceLocation RPLoc) {
    Expr *OrigExpr = E;
    bool IsMS = false;
  
    // CUDA device code does not support varargs.
    if (getLangOpts().CUDA && getLangOpts().CUDAIsDevice) {
      if (const FunctionDecl *F = dyn_cast<FunctionDecl>(CurContext)) {
        CUDAFunctionTarget T = IdentifyCUDATarget(F);
        if (T == CFT_Global || T == CFT_Device || T == CFT_HostDevice)
          return ExprError(Diag(E->getBeginLoc(), diag::err_va_arg_in_device));
      }
    }
  
    // NVPTX does not support va_arg expression.
    if (getLangOpts().OpenMP && getLangOpts().OpenMPIsDevice &&
        Context.getTargetInfo().getTriple().isNVPTX())
      targetDiag(E->getBeginLoc(), diag::err_va_arg_in_device);
  
    // It might be a __builtin_ms_va_list. (But don't ever mark a va_arg()
    // as Microsoft ABI on an actual Microsoft platform, where
    // __builtin_ms_va_list and __builtin_va_list are the same.)
    if (!E->isTypeDependent() && Context.getTargetInfo().hasBuiltinMSVaList() &&
        Context.getTargetInfo().getBuiltinVaListKind() != TargetInfo::CharPtrBuiltinVaList) {
      QualType MSVaListType = Context.getBuiltinMSVaListType();
      if (Context.hasSameType(MSVaListType, E->getType())) {
        if (CheckForModifiableLvalue(E, BuiltinLoc, *this))
          return ExprError();
        IsMS = true;
      }
    }
  
    // Get the va_list type
    QualType VaListType = Context.getBuiltinVaListType();
    if (!IsMS) {
      if (VaListType->isArrayType()) {
        // Deal with implicit array decay; for example, on x86-64,
        // va_list is an array, but it's supposed to decay to
        // a pointer for va_arg.
        VaListType = Context.getArrayDecayedType(VaListType);
        // Make sure the input expression also decays appropriately.
        ExprResult Result = UsualUnaryConversions(E);
        if (Result.isInvalid())
          return ExprError();
        E = Result.get();
      } else if (VaListType->isRecordType() && getLangOpts().CPlusPlus) {
        // If va_list is a record type and we are compiling in C++ mode,
        // check the argument using reference binding.
        InitializedEntity Entity = InitializedEntity::InitializeParameter(
            Context, Context.getLValueReferenceType(VaListType), false);
        ExprResult Init = PerformCopyInitialization(Entity, SourceLocation(), E);
        if (Init.isInvalid())
          return ExprError();
        E = Init.getAs<Expr>();
      } else {
        // Otherwise, the va_list argument must be an l-value because
        // it is modified by va_arg.
        if (!E->isTypeDependent() &&
            CheckForModifiableLvalue(E, BuiltinLoc, *this))
          return ExprError();
      }
    }
  
    if (!IsMS && !E->isTypeDependent() &&
        !Context.hasSameType(VaListType, E->getType()))
      return ExprError(
          Diag(E->getBeginLoc(),
               diag::err_first_argument_to_va_arg_not_of_type_va_list)
          << OrigExpr->getType() << E->getSourceRange());
  
    if (!TInfo->getType()->isDependentType()) {
      if (RequireCompleteType(TInfo->getTypeLoc().getBeginLoc(), TInfo->getType(),
                              diag::err_second_parameter_to_va_arg_incomplete,
                              TInfo->getTypeLoc()))
        return ExprError();
  
      if (RequireNonAbstractType(TInfo->getTypeLoc().getBeginLoc(),
                                 TInfo->getType(),
                                 diag::err_second_parameter_to_va_arg_abstract,
                                 TInfo->getTypeLoc()))
        return ExprError();
  
      if (!TInfo->getType().isPODType(Context)) {
        Diag(TInfo->getTypeLoc().getBeginLoc(),
             TInfo->getType()->isObjCLifetimeType()
               ? diag::warn_second_parameter_to_va_arg_ownership_qualified
               : diag::warn_second_parameter_to_va_arg_not_pod)
          << TInfo->getType()
          << TInfo->getTypeLoc().getSourceRange();
      }
  
      // Check for va_arg where arguments of the given type will be promoted
      // (i.e. this va_arg is guaranteed to have undefined behavior).
      QualType PromoteType;
      if (TInfo->getType()->isPromotableIntegerType()) {
        PromoteType = Context.getPromotedIntegerType(TInfo->getType());
        // [cstdarg.syn]p1 defers the C++ behavior to what the C standard says,
        // and C2x 7.16.1.1p2 says, in part:
        //   If type is not compatible with the type of the actual next argument
        //   (as promoted according to the default argument promotions), the
        //   behavior is undefined, except for the following cases:
        //     - both types are pointers to qualified or unqualified versions of
        //       compatible types;
        //     - one type is a signed integer type, the other type is the
        //       corresponding unsigned integer type, and the value is
        //       representable in both types;
        //     - one type is pointer to qualified or unqualified void and the
        //       other is a pointer to a qualified or unqualified character type.
        // Given that type compatibility is the primary requirement (ignoring
        // qualifications), you would think we could call typesAreCompatible()
        // directly to test this. However, in C++, that checks for *same type*,
        // which causes false positives when passing an enumeration type to
        // va_arg. Instead, get the underlying type of the enumeration and pass
        // that.
        QualType UnderlyingType = TInfo->getType();
        if (const auto *ET = UnderlyingType->getAs<EnumType>())
          UnderlyingType = ET->getDecl()->getIntegerType();
        if (Context.typesAreCompatible(PromoteType, UnderlyingType,
                                       /*CompareUnqualified*/ true))
          PromoteType = QualType();
  
        // If the types are still not compatible, we need to test whether the
        // promoted type and the underlying type are the same except for
        // signedness. Ask the AST for the correctly corresponding type and see
        // if that's compatible.
        if (!PromoteType.isNull() && !UnderlyingType->isBooleanType() &&
            PromoteType->isUnsignedIntegerType() !=
                UnderlyingType->isUnsignedIntegerType()) {
          UnderlyingType =
              UnderlyingType->isUnsignedIntegerType()
                  ? Context.getCorrespondingSignedType(UnderlyingType)
                  : Context.getCorrespondingUnsignedType(UnderlyingType);
          if (Context.typesAreCompatible(PromoteType, UnderlyingType,
                                         /*CompareUnqualified*/ true))
            PromoteType = QualType();
        }
      }
      if (TInfo->getType()->isSpecificBuiltinType(BuiltinType::Float))
        PromoteType = Context.DoubleTy;
      if (!PromoteType.isNull())
        DiagRuntimeBehavior(TInfo->getTypeLoc().getBeginLoc(), E,
                    PDiag(diag::warn_second_parameter_to_va_arg_never_compatible)
                            << TInfo->getType()
                            << PromoteType
                            << TInfo->getTypeLoc().getSourceRange());
    }
  
    QualType T = TInfo->getType().getNonLValueExprType(Context);
    return new (Context) VAArgExpr(BuiltinLoc, E, TInfo, RPLoc, T, IsMS);
  }
  
  ExprResult Sema::ActOnGNUNullExpr(SourceLocation TokenLoc) {
    // The type of __null will be int or long, depending on the size of
    // pointers on the target.
    QualType Ty;
    unsigned pw = Context.getTargetInfo().getPointerWidth(0);
    if (pw == Context.getTargetInfo().getIntWidth())
      Ty = Context.IntTy;
    else if (pw == Context.getTargetInfo().getLongWidth())
      Ty = Context.LongTy;
    else if (pw == Context.getTargetInfo().getLongLongWidth())
      Ty = Context.LongLongTy;
    else {
      llvm_unreachable("I don't know size of pointer!");
    }
  
    return new (Context) GNUNullExpr(Ty, TokenLoc);
  }
  
  ExprResult Sema::ActOnSourceLocExpr(SourceLocExpr::IdentKind Kind,
                                      SourceLocation BuiltinLoc,
                                      SourceLocation RPLoc) {
    return BuildSourceLocExpr(Kind, BuiltinLoc, RPLoc, CurContext);
  }
  
  ExprResult Sema::BuildSourceLocExpr(SourceLocExpr::IdentKind Kind,
                                      SourceLocation BuiltinLoc,
                                      SourceLocation RPLoc,
                                      DeclContext *ParentContext) {
    return new (Context)
        SourceLocExpr(Context, Kind, BuiltinLoc, RPLoc, ParentContext);
  }
  
  bool Sema::CheckConversionToObjCLiteral(QualType DstType, Expr *&Exp,
                                          bool Diagnose) {
    if (!getLangOpts().ObjC)
      return false;
  
    const ObjCObjectPointerType *PT = DstType->getAs<ObjCObjectPointerType>();
    if (!PT)
      return false;
    const ObjCInterfaceDecl *ID = PT->getInterfaceDecl();
  
    // Ignore any parens, implicit casts (should only be
    // array-to-pointer decays), and not-so-opaque values.  The last is
    // important for making this trigger for property assignments.
    Expr *SrcExpr = Exp->IgnoreParenImpCasts();
    if (OpaqueValueExpr *OV = dyn_cast<OpaqueValueExpr>(SrcExpr))
      if (OV->getSourceExpr())
        SrcExpr = OV->getSourceExpr()->IgnoreParenImpCasts();
  
    if (auto *SL = dyn_cast<StringLiteral>(SrcExpr)) {
      if (!PT->isObjCIdType() &&
          !(ID && ID->getIdentifier()->isStr("NSString")))
        return false;
      if (!SL->isAscii())
        return false;
  
      if (Diagnose) {
        Diag(SL->getBeginLoc(), diag::err_missing_atsign_prefix)
            << /*string*/0 << FixItHint::CreateInsertion(SL->getBeginLoc(), "@");
        Exp = BuildObjCStringLiteral(SL->getBeginLoc(), SL).get();
      }
      return true;
    }
  
    if ((isa<IntegerLiteral>(SrcExpr) || isa<CharacterLiteral>(SrcExpr) ||
        isa<FloatingLiteral>(SrcExpr) || isa<ObjCBoolLiteralExpr>(SrcExpr) ||
        isa<CXXBoolLiteralExpr>(SrcExpr)) &&
        !SrcExpr->isNullPointerConstant(
            getASTContext(), Expr::NPC_NeverValueDependent)) {
      if (!ID || !ID->getIdentifier()->isStr("NSNumber"))
        return false;
      if (Diagnose) {
        Diag(SrcExpr->getBeginLoc(), diag::err_missing_atsign_prefix)
            << /*number*/1
            << FixItHint::CreateInsertion(SrcExpr->getBeginLoc(), "@");
        Expr *NumLit =
            BuildObjCNumericLiteral(SrcExpr->getBeginLoc(), SrcExpr).get();
        if (NumLit)
          Exp = NumLit;
      }
      return true;
    }
  
    return false;
  }
  
  static bool maybeDiagnoseAssignmentToFunction(Sema &S, QualType DstType,
                                                const Expr *SrcExpr) {
    if (!DstType->isFunctionPointerType() ||
        !SrcExpr->getType()->isFunctionType())
      return false;
  
    auto *DRE = dyn_cast<DeclRefExpr>(SrcExpr->IgnoreParenImpCasts());
    if (!DRE)
      return false;
  
    auto *FD = dyn_cast<FunctionDecl>(DRE->getDecl());
    if (!FD)
      return false;
  
    return !S.checkAddressOfFunctionIsAvailable(FD,
                                                /*Complain=*/true,
                                                SrcExpr->getBeginLoc());
  }
  
  bool Sema::DiagnoseAssignmentResult(AssignConvertType ConvTy,
                                      SourceLocation Loc,
                                      QualType DstType, QualType SrcType,
                                      Expr *SrcExpr, AssignmentAction Action,
                                      bool *Complained) {
    if (Complained)
      *Complained = false;
  
    // Decode the result (notice that AST's are still created for extensions).
    bool CheckInferredResultType = false;
    bool isInvalid = false;
    unsigned DiagKind = 0;
    ConversionFixItGenerator ConvHints;
    bool MayHaveConvFixit = false;
    bool MayHaveFunctionDiff = false;
    const ObjCInterfaceDecl *IFace = nullptr;
    const ObjCProtocolDecl *PDecl = nullptr;
  
    switch (ConvTy) {
    case Compatible:
        DiagnoseAssignmentEnum(DstType, SrcType, SrcExpr);
        return false;
  
    case PointerToInt:
      if (getLangOpts().CPlusPlus) {
        DiagKind = diag::err_typecheck_convert_pointer_int;
        isInvalid = true;
      } else {
        DiagKind = diag::ext_typecheck_convert_pointer_int;
      }
      ConvHints.tryToFixConversion(SrcExpr, SrcType, DstType, *this);
      MayHaveConvFixit = true;
      break;
    case IntToPointer:
      if (getLangOpts().CPlusPlus) {
        DiagKind = diag::err_typecheck_convert_int_pointer;
        isInvalid = true;
      } else {
        DiagKind = diag::ext_typecheck_convert_int_pointer;
      }
      ConvHints.tryToFixConversion(SrcExpr, SrcType, DstType, *this);
      MayHaveConvFixit = true;
      break;
    case IncompatibleFunctionPointer:
      if (getLangOpts().CPlusPlus) {
        DiagKind = diag::err_typecheck_convert_incompatible_function_pointer;
        isInvalid = true;
      } else {
        DiagKind = diag::ext_typecheck_convert_incompatible_function_pointer;
      }
      ConvHints.tryToFixConversion(SrcExpr, SrcType, DstType, *this);
      MayHaveConvFixit = true;
      break;
    case IncompatiblePointer:
      if (Action == AA_Passing_CFAudited) {
        DiagKind = diag::err_arc_typecheck_convert_incompatible_pointer;
      } else if (getLangOpts().CPlusPlus) {
        DiagKind = diag::err_typecheck_convert_incompatible_pointer;
        isInvalid = true;
      } else {
        DiagKind = diag::ext_typecheck_convert_incompatible_pointer;
      }
      CheckInferredResultType = DstType->isObjCObjectPointerType() &&
        SrcType->isObjCObjectPointerType();
      if (!CheckInferredResultType) {
        ConvHints.tryToFixConversion(SrcExpr, SrcType, DstType, *this);
      } else if (CheckInferredResultType) {
        SrcType = SrcType.getUnqualifiedType();
        DstType = DstType.getUnqualifiedType();
      }
      MayHaveConvFixit = true;
      break;
    case IncompatiblePointerSign:
      if (getLangOpts().CPlusPlus) {
        DiagKind = diag::err_typecheck_convert_incompatible_pointer_sign;
        isInvalid = true;
      } else {
        DiagKind = diag::ext_typecheck_convert_incompatible_pointer_sign;
      }
      break;
    case FunctionVoidPointer:
      if (getLangOpts().CPlusPlus) {
        DiagKind = diag::err_typecheck_convert_pointer_void_func;
        isInvalid = true;
      } else {
        DiagKind = diag::ext_typecheck_convert_pointer_void_func;
      }
      break;
    case IncompatiblePointerDiscardsQualifiers: {
      // Perform array-to-pointer decay if necessary.
      if (SrcType->isArrayType()) SrcType = Context.getArrayDecayedType(SrcType);
  
      isInvalid = true;
  
      Qualifiers lhq = SrcType->getPointeeType().getQualifiers();
      Qualifiers rhq = DstType->getPointeeType().getQualifiers();
      if (lhq.getAddressSpace() != rhq.getAddressSpace()) {
        DiagKind = diag::err_typecheck_incompatible_address_space;
        break;
      } else if (lhq.getPointerAuth() != rhq.getPointerAuth()) {
        DiagKind = diag::err_typecheck_incompatible_ptrauth;
        break;
      } else if (lhq.getObjCLifetime() != rhq.getObjCLifetime()) {
        DiagKind = diag::err_typecheck_incompatible_ownership;
        break;
      }
  
      llvm_unreachable("unknown error case for discarding qualifiers!");
      // fallthrough
    }
    case CompatiblePointerDiscardsQualifiers:
      // If the qualifiers lost were because we were applying the
      // (deprecated) C++ conversion from a string literal to a char*
      // (or wchar_t*), then there was no error (C++ 4.2p2).  FIXME:
      // Ideally, this check would be performed in
      // checkPointerTypesForAssignment. However, that would require a
      // bit of refactoring (so that the second argument is an
      // expression, rather than a type), which should be done as part
      // of a larger effort to fix checkPointerTypesForAssignment for
      // C++ semantics.
      if (getLangOpts().CPlusPlus &&
          IsStringLiteralToNonConstPointerConversion(SrcExpr, DstType))
        return false;
      if (getLangOpts().CPlusPlus) {
        DiagKind =  diag::err_typecheck_convert_discards_qualifiers;
        isInvalid = true;
      } else {
        DiagKind =  diag::ext_typecheck_convert_discards_qualifiers;
      }
  
      break;
    case IncompatibleNestedPointerQualifiers:
      if (getLangOpts().CPlusPlus) {
        isInvalid = true;
        DiagKind = diag::err_nested_pointer_qualifier_mismatch;
      } else {
        DiagKind = diag::ext_nested_pointer_qualifier_mismatch;
      }
      break;
    case IncompatibleNestedPointerAddressSpaceMismatch:
      DiagKind = diag::err_typecheck_incompatible_nested_address_space;
      isInvalid = true;
      break;
    case IntToBlockPointer:
      DiagKind = diag::err_int_to_block_pointer;
      isInvalid = true;
      break;
    case IncompatibleBlockPointer:
      DiagKind = diag::err_typecheck_convert_incompatible_block_pointer;
      isInvalid = true;
      break;
    case IncompatibleObjCQualifiedId: {
      if (SrcType->isObjCQualifiedIdType()) {
        const ObjCObjectPointerType *srcOPT =
                  SrcType->castAs<ObjCObjectPointerType>();
        for (auto *srcProto : srcOPT->quals()) {
          PDecl = srcProto;
          break;
        }
        if (const ObjCInterfaceType *IFaceT =
              DstType->castAs<ObjCObjectPointerType>()->getInterfaceType())
          IFace = IFaceT->getDecl();
      }
      else if (DstType->isObjCQualifiedIdType()) {
        const ObjCObjectPointerType *dstOPT =
          DstType->castAs<ObjCObjectPointerType>();
        for (auto *dstProto : dstOPT->quals()) {
          PDecl = dstProto;
          break;
        }
        if (const ObjCInterfaceType *IFaceT =
              SrcType->castAs<ObjCObjectPointerType>()->getInterfaceType())
          IFace = IFaceT->getDecl();
      }
      if (getLangOpts().CPlusPlus) {
        DiagKind = diag::err_incompatible_qualified_id;
        isInvalid = true;
      } else {
        DiagKind = diag::warn_incompatible_qualified_id;
      }
      break;
    }
    case IncompatibleVectors:
      if (getLangOpts().CPlusPlus) {
        DiagKind = diag::err_incompatible_vectors;
        isInvalid = true;
      } else {
        DiagKind = diag::warn_incompatible_vectors;
      }
      break;
    case IncompatibleObjCWeakRef:
      DiagKind = diag::err_arc_weak_unavailable_assign;
      isInvalid = true;
      break;
    case Incompatible:
      if (maybeDiagnoseAssignmentToFunction(*this, DstType, SrcExpr)) {
        if (Complained)
          *Complained = true;
        return true;
      }
  
      DiagKind = diag::err_typecheck_convert_incompatible;
      ConvHints.tryToFixConversion(SrcExpr, SrcType, DstType, *this);
      MayHaveConvFixit = true;
      isInvalid = true;
      MayHaveFunctionDiff = true;
      break;
    }
  
    QualType FirstType, SecondType;
    switch (Action) {
    case AA_Assigning:
    case AA_Initializing:
      // The destination type comes first.
      FirstType = DstType;
      SecondType = SrcType;
      break;
  
    case AA_Returning:
    case AA_Passing:
    case AA_Passing_CFAudited:
    case AA_Converting:
    case AA_Sending:
    case AA_Casting:
      // The source type comes first.
      FirstType = SrcType;
      SecondType = DstType;
      break;
    }
  
    PartialDiagnostic FDiag = PDiag(DiagKind);
    if (Action == AA_Passing_CFAudited)
      FDiag << FirstType << SecondType << AA_Passing << SrcExpr->getSourceRange();
    else
      FDiag << FirstType << SecondType << Action << SrcExpr->getSourceRange();
  
    if (DiagKind == diag::ext_typecheck_convert_incompatible_pointer_sign ||
        DiagKind == diag::err_typecheck_convert_incompatible_pointer_sign) {
      auto isPlainChar = [](const clang::Type *Type) {
        return Type->isSpecificBuiltinType(BuiltinType::Char_S) ||
               Type->isSpecificBuiltinType(BuiltinType::Char_U);
      };
      FDiag << (isPlainChar(FirstType->getPointeeOrArrayElementType()) ||
                isPlainChar(SecondType->getPointeeOrArrayElementType()));
    }
  
    // If we can fix the conversion, suggest the FixIts.
    if (!ConvHints.isNull()) {
      for (FixItHint &H : ConvHints.Hints)
        FDiag << H;
    }
  
    if (MayHaveConvFixit) { FDiag << (unsigned) (ConvHints.Kind); }
  
    if (MayHaveFunctionDiff)
      HandleFunctionTypeMismatch(FDiag, SecondType, FirstType);
  
    Diag(Loc, FDiag);
    if ((DiagKind == diag::warn_incompatible_qualified_id ||
         DiagKind == diag::err_incompatible_qualified_id) &&
        PDecl && IFace && !IFace->hasDefinition())
      Diag(IFace->getLocation(), diag::note_incomplete_class_and_qualified_id)
          << IFace << PDecl;
  
    if (SecondType == Context.OverloadTy)
      NoteAllOverloadCandidates(OverloadExpr::find(SrcExpr).Expression,
                                FirstType, /*TakingAddress=*/true);
  
    if (CheckInferredResultType)
      EmitRelatedResultTypeNote(SrcExpr);
  
    if (Action == AA_Returning && ConvTy == IncompatiblePointer)
      EmitRelatedResultTypeNoteForReturn(DstType);
  
    if (Complained)
      *Complained = true;
    return isInvalid;
  }
  
  ExprResult Sema::VerifyIntegerConstantExpression(Expr *E,
                                                   llvm::APSInt *Result,
                                                   AllowFoldKind CanFold) {
    class SimpleICEDiagnoser : public VerifyICEDiagnoser {
    public:
      SemaDiagnosticBuilder diagnoseNotICEType(Sema &S, SourceLocation Loc,
                                               QualType T) override {
        return S.Diag(Loc, diag::err_ice_not_integral)
               << T << S.LangOpts.CPlusPlus;
      }
      SemaDiagnosticBuilder diagnoseNotICE(Sema &S, SourceLocation Loc) override {
        return S.Diag(Loc, diag::err_expr_not_ice) << S.LangOpts.CPlusPlus;
      }
    } Diagnoser;
  
    return VerifyIntegerConstantExpression(E, Result, Diagnoser, CanFold);
  }
  
  ExprResult Sema::VerifyIntegerConstantExpression(Expr *E,
                                                   llvm::APSInt *Result,
                                                   unsigned DiagID,
                                                   AllowFoldKind CanFold) {
    class IDDiagnoser : public VerifyICEDiagnoser {
      unsigned DiagID;
  
    public:
      IDDiagnoser(unsigned DiagID)
        : VerifyICEDiagnoser(DiagID == 0), DiagID(DiagID) { }
  
      SemaDiagnosticBuilder diagnoseNotICE(Sema &S, SourceLocation Loc) override {
        return S.Diag(Loc, DiagID);
      }
    } Diagnoser(DiagID);
  
    return VerifyIntegerConstantExpression(E, Result, Diagnoser, CanFold);
  }
  
  Sema::SemaDiagnosticBuilder
  Sema::VerifyICEDiagnoser::diagnoseNotICEType(Sema &S, SourceLocation Loc,
                                               QualType T) {
    return diagnoseNotICE(S, Loc);
  }
  
  Sema::SemaDiagnosticBuilder
  Sema::VerifyICEDiagnoser::diagnoseFold(Sema &S, SourceLocation Loc) {
    return S.Diag(Loc, diag::ext_expr_not_ice) << S.LangOpts.CPlusPlus;
  }
  
  ExprResult
  Sema::VerifyIntegerConstantExpression(Expr *E, llvm::APSInt *Result,
                                        VerifyICEDiagnoser &Diagnoser,
                                        AllowFoldKind CanFold) {
    SourceLocation DiagLoc = E->getBeginLoc();
  
    if (getLangOpts().CPlusPlus11) {
      // C++11 [expr.const]p5:
      //   If an expression of literal class type is used in a context where an
      //   integral constant expression is required, then that class type shall
      //   have a single non-explicit conversion function to an integral or
      //   unscoped enumeration type
      ExprResult Converted;
      class CXX11ConvertDiagnoser : public ICEConvertDiagnoser {
        VerifyICEDiagnoser &BaseDiagnoser;
      public:
        CXX11ConvertDiagnoser(VerifyICEDiagnoser &BaseDiagnoser)
            : ICEConvertDiagnoser(/*AllowScopedEnumerations*/ false,
                                  BaseDiagnoser.Suppress, true),
              BaseDiagnoser(BaseDiagnoser) {}
  
        SemaDiagnosticBuilder diagnoseNotInt(Sema &S, SourceLocation Loc,
                                             QualType T) override {
          return BaseDiagnoser.diagnoseNotICEType(S, Loc, T);
        }
  
        SemaDiagnosticBuilder diagnoseIncomplete(
            Sema &S, SourceLocation Loc, QualType T) override {
          return S.Diag(Loc, diag::err_ice_incomplete_type) << T;
        }
  
        SemaDiagnosticBuilder diagnoseExplicitConv(
            Sema &S, SourceLocation Loc, QualType T, QualType ConvTy) override {
          return S.Diag(Loc, diag::err_ice_explicit_conversion) << T << ConvTy;
        }
  
        SemaDiagnosticBuilder noteExplicitConv(
            Sema &S, CXXConversionDecl *Conv, QualType ConvTy) override {
          return S.Diag(Conv->getLocation(), diag::note_ice_conversion_here)
                   << ConvTy->isEnumeralType() << ConvTy;
        }
  
        SemaDiagnosticBuilder diagnoseAmbiguous(
            Sema &S, SourceLocation Loc, QualType T) override {
          return S.Diag(Loc, diag::err_ice_ambiguous_conversion) << T;
        }
  
        SemaDiagnosticBuilder noteAmbiguous(
            Sema &S, CXXConversionDecl *Conv, QualType ConvTy) override {
          return S.Diag(Conv->getLocation(), diag::note_ice_conversion_here)
                   << ConvTy->isEnumeralType() << ConvTy;
        }
  
        SemaDiagnosticBuilder diagnoseConversion(
            Sema &S, SourceLocation Loc, QualType T, QualType ConvTy) override {
          llvm_unreachable("conversion functions are permitted");
        }
      } ConvertDiagnoser(Diagnoser);
  
      Converted = PerformContextualImplicitConversion(DiagLoc, E,
                                                      ConvertDiagnoser);
      if (Converted.isInvalid())
        return Converted;
      E = Converted.get();
      if (!E->getType()->isIntegralOrUnscopedEnumerationType())
        return ExprError();
    } else if (!E->getType()->isIntegralOrUnscopedEnumerationType()) {
      // An ICE must be of integral or unscoped enumeration type.
      if (!Diagnoser.Suppress)
        Diagnoser.diagnoseNotICEType(*this, DiagLoc, E->getType())
            << E->getSourceRange();
      return ExprError();
    }
  
    ExprResult RValueExpr = DefaultLvalueConversion(E);
    if (RValueExpr.isInvalid())
      return ExprError();
  
    E = RValueExpr.get();
  
    // Circumvent ICE checking in C++11 to avoid evaluating the expression twice
    // in the non-ICE case.
    if (!getLangOpts().CPlusPlus11 && E->isIntegerConstantExpr(Context)) {
      if (Result)
        *Result = E->EvaluateKnownConstIntCheckOverflow(Context);
      if (!isa<ConstantExpr>(E))
        E = Result ? ConstantExpr::Create(Context, E, APValue(*Result))
                   : ConstantExpr::Create(Context, E);
      return E;
    }
  
    Expr::EvalResult EvalResult;
    SmallVector<PartialDiagnosticAt, 8> Notes;
    EvalResult.Diag = &Notes;
  
    // Try to evaluate the expression, and produce diagnostics explaining why it's
    // not a constant expression as a side-effect.
    bool Folded =
        E->EvaluateAsRValue(EvalResult, Context, /*isConstantContext*/ true) &&
        EvalResult.Val.isInt() && !EvalResult.HasSideEffects;
  
    if (!isa<ConstantExpr>(E))
      E = ConstantExpr::Create(Context, E, EvalResult.Val);
  
    // In C++11, we can rely on diagnostics being produced for any expression
    // which is not a constant expression. If no diagnostics were produced, then
    // this is a constant expression.
    if (Folded && getLangOpts().CPlusPlus11 && Notes.empty()) {
      if (Result)
        *Result = EvalResult.Val.getInt();
      return E;
    }
  
    // If our only note is the usual "invalid subexpression" note, just point
    // the caret at its location rather than producing an essentially
    // redundant note.
    if (Notes.size() == 1 && Notes[0].second.getDiagID() ==
          diag::note_invalid_subexpr_in_const_expr) {
      DiagLoc = Notes[0].first;
      Notes.clear();
    }
  
    if (!Folded || !CanFold) {
      if (!Diagnoser.Suppress) {
        Diagnoser.diagnoseNotICE(*this, DiagLoc) << E->getSourceRange();
        for (const PartialDiagnosticAt &Note : Notes)
          Diag(Note.first, Note.second);
      }
  
      return ExprError();
    }
  
    Diagnoser.diagnoseFold(*this, DiagLoc) << E->getSourceRange();
    for (const PartialDiagnosticAt &Note : Notes)
      Diag(Note.first, Note.second);
  
    if (Result)
      *Result = EvalResult.Val.getInt();
    return E;
  }
  
  namespace {
    // Handle the case where we conclude a expression which we speculatively
    // considered to be unevaluated is actually evaluated.
    class TransformToPE : public TreeTransform<TransformToPE> {
      typedef TreeTransform<TransformToPE> BaseTransform;
  
    public:
      TransformToPE(Sema &SemaRef) : BaseTransform(SemaRef) { }
  
      // Make sure we redo semantic analysis
      bool AlwaysRebuild() { return true; }
      bool ReplacingOriginal() { return true; }
  
      // We need to special-case DeclRefExprs referring to FieldDecls which
      // are not part of a member pointer formation; normal TreeTransforming
      // doesn't catch this case because of the way we represent them in the AST.
      // FIXME: This is a bit ugly; is it really the best way to handle this
      // case?
      //
      // Error on DeclRefExprs referring to FieldDecls.
      ExprResult TransformDeclRefExpr(DeclRefExpr *E) {
        if (isa<FieldDecl>(E->getDecl()) &&
            !SemaRef.isUnevaluatedContext())
          return SemaRef.Diag(E->getLocation(),
                              diag::err_invalid_non_static_member_use)
              << E->getDecl() << E->getSourceRange();
  
        return BaseTransform::TransformDeclRefExpr(E);
      }
  
      // Exception: filter out member pointer formation
      ExprResult TransformUnaryOperator(UnaryOperator *E) {
        if (E->getOpcode() == UO_AddrOf && E->getType()->isMemberPointerType())
          return E;
  
        return BaseTransform::TransformUnaryOperator(E);
      }
  
      // The body of a lambda-expression is in a separate expression evaluation
      // context so never needs to be transformed.
      // FIXME: Ideally we wouldn't transform the closure type either, and would
      // just recreate the capture expressions and lambda expression.
      StmtResult TransformLambdaBody(LambdaExpr *E, Stmt *Body) {
        return SkipLambdaBody(E, Body);
      }
    };
  }
  
  ExprResult Sema::TransformToPotentiallyEvaluated(Expr *E) {
    assert(isUnevaluatedContext() &&
           "Should only transform unevaluated expressions");
    ExprEvalContexts.back().Context =
        ExprEvalContexts[ExprEvalContexts.size()-2].Context;
    if (isUnevaluatedContext())
      return E;
    return TransformToPE(*this).TransformExpr(E);
  }
  
  TypeSourceInfo *Sema::TransformToPotentiallyEvaluated(TypeSourceInfo *TInfo) {
    assert(isUnevaluatedContext() &&
           "Should only transform unevaluated expressions");
    ExprEvalContexts.back().Context =
        ExprEvalContexts[ExprEvalContexts.size() - 2].Context;
    if (isUnevaluatedContext())
      return TInfo;
    return TransformToPE(*this).TransformType(TInfo);
  }
  
  void
  Sema::PushExpressionEvaluationContext(
      ExpressionEvaluationContext NewContext, Decl *LambdaContextDecl,
      ExpressionEvaluationContextRecord::ExpressionKind ExprContext) {
    ExprEvalContexts.emplace_back(NewContext, ExprCleanupObjects.size(), Cleanup,
                                  LambdaContextDecl, ExprContext);
  
    // Discarded statements and immediate contexts nested in other
    // discarded statements or immediate context are themselves
    // a discarded statement or an immediate context, respectively.
    ExprEvalContexts.back().InDiscardedStatement =
        ExprEvalContexts[ExprEvalContexts.size() - 2]
            .isDiscardedStatementContext();
    ExprEvalContexts.back().InImmediateFunctionContext =
        ExprEvalContexts[ExprEvalContexts.size() - 2]
            .isImmediateFunctionContext();
  
    Cleanup.reset();
    if (!MaybeODRUseExprs.empty())
      std::swap(MaybeODRUseExprs, ExprEvalContexts.back().SavedMaybeODRUseExprs);
  }
  
  void
  Sema::PushExpressionEvaluationContext(
      ExpressionEvaluationContext NewContext, ReuseLambdaContextDecl_t,
      ExpressionEvaluationContextRecord::ExpressionKind ExprContext) {
    Decl *ClosureContextDecl = ExprEvalContexts.back().ManglingContextDecl;
    PushExpressionEvaluationContext(NewContext, ClosureContextDecl, ExprContext);
  }
  
  namespace {
  
  const DeclRefExpr *CheckPossibleDeref(Sema &S, const Expr *PossibleDeref) {
    PossibleDeref = PossibleDeref->IgnoreParenImpCasts();
    if (const auto *E = dyn_cast<UnaryOperator>(PossibleDeref)) {
      if (E->getOpcode() == UO_Deref)
        return CheckPossibleDeref(S, E->getSubExpr());
    } else if (const auto *E = dyn_cast<ArraySubscriptExpr>(PossibleDeref)) {
      return CheckPossibleDeref(S, E->getBase());
    } else if (const auto *E = dyn_cast<MemberExpr>(PossibleDeref)) {
      return CheckPossibleDeref(S, E->getBase());
    } else if (const auto E = dyn_cast<DeclRefExpr>(PossibleDeref)) {
      QualType Inner;
      QualType Ty = E->getType();
      if (const auto *Ptr = Ty->getAs<PointerType>())
        Inner = Ptr->getPointeeType();
      else if (const auto *Arr = S.Context.getAsArrayType(Ty))
        Inner = Arr->getElementType();
      else
        return nullptr;
  
      if (Inner->hasAttr(attr::NoDeref))
        return E;
    }
    return nullptr;
  }
  
  } // namespace
  
  void Sema::WarnOnPendingNoDerefs(ExpressionEvaluationContextRecord &Rec) {
    for (const Expr *E : Rec.PossibleDerefs) {
      const DeclRefExpr *DeclRef = CheckPossibleDeref(*this, E);
      if (DeclRef) {
        const ValueDecl *Decl = DeclRef->getDecl();
        Diag(E->getExprLoc(), diag::warn_dereference_of_noderef_type)
            << Decl->getName() << E->getSourceRange();
        Diag(Decl->getLocation(), diag::note_previous_decl) << Decl->getName();
      } else {
        Diag(E->getExprLoc(), diag::warn_dereference_of_noderef_type_no_decl)
            << E->getSourceRange();
      }
    }
    Rec.PossibleDerefs.clear();
  }
  
  /// Check whether E, which is either a discarded-value expression or an
  /// unevaluated operand, is a simple-assignment to a volatlie-qualified lvalue,
  /// and if so, remove it from the list of volatile-qualified assignments that
  /// we are going to warn are deprecated.
  void Sema::CheckUnusedVolatileAssignment(Expr *E) {
    if (!E->getType().isVolatileQualified() || !getLangOpts().CPlusPlus20)
      return;
  
    // Note: ignoring parens here is not justified by the standard rules, but
    // ignoring parentheses seems like a more reasonable approach, and this only
    // drives a deprecation warning so doesn't affect conformance.
    if (auto *BO = dyn_cast<BinaryOperator>(E->IgnoreParenImpCasts())) {
      if (BO->getOpcode() == BO_Assign) {
        auto &LHSs = ExprEvalContexts.back().VolatileAssignmentLHSs;
        llvm::erase_value(LHSs, BO->getLHS());
      }
    }
  }
  
  ExprResult Sema::CheckForImmediateInvocation(ExprResult E, FunctionDecl *Decl) {
    if (isUnevaluatedContext() || !E.isUsable() || !Decl ||
        !Decl->isConsteval() || isConstantEvaluated() ||
        RebuildingImmediateInvocation || isImmediateFunctionContext())
      return E;
  
    /// Opportunistically remove the callee from ReferencesToConsteval if we can.
    /// It's OK if this fails; we'll also remove this in
    /// HandleImmediateInvocations, but catching it here allows us to avoid
    /// walking the AST looking for it in simple cases.
    if (auto *Call = dyn_cast<CallExpr>(E.get()->IgnoreImplicit()))
      if (auto *DeclRef =
              dyn_cast<DeclRefExpr>(Call->getCallee()->IgnoreImplicit()))
        ExprEvalContexts.back().ReferenceToConsteval.erase(DeclRef);
  
    E = MaybeCreateExprWithCleanups(E);
  
    ConstantExpr *Res = ConstantExpr::Create(
        getASTContext(), E.get(),
        ConstantExpr::getStorageKind(Decl->getReturnType().getTypePtr(),
                                     getASTContext()),
        /*IsImmediateInvocation*/ true);
    /// Value-dependent constant expressions should not be immediately
    /// evaluated until they are instantiated.
    if (!Res->isValueDependent())
      ExprEvalContexts.back().ImmediateInvocationCandidates.emplace_back(Res, 0);
    return Res;
  }
  
  static void EvaluateAndDiagnoseImmediateInvocation(
      Sema &SemaRef, Sema::ImmediateInvocationCandidate Candidate) {
    llvm::SmallVector<PartialDiagnosticAt, 8> Notes;
    Expr::EvalResult Eval;
    Eval.Diag = &Notes;
    ConstantExpr *CE = Candidate.getPointer();
    bool Result = CE->EvaluateAsConstantExpr(
        Eval, SemaRef.getASTContext(), ConstantExprKind::ImmediateInvocation);
    if (!Result || !Notes.empty()) {
      Expr *InnerExpr = CE->getSubExpr()->IgnoreImplicit();
      if (auto *FunctionalCast = dyn_cast<CXXFunctionalCastExpr>(InnerExpr))
        InnerExpr = FunctionalCast->getSubExpr();
      FunctionDecl *FD = nullptr;
      if (auto *Call = dyn_cast<CallExpr>(InnerExpr))
        FD = cast<FunctionDecl>(Call->getCalleeDecl());
      else if (auto *Call = dyn_cast<CXXConstructExpr>(InnerExpr))
        FD = Call->getConstructor();
      else
        llvm_unreachable("unhandled decl kind");
      assert(FD->isConsteval());
      SemaRef.Diag(CE->getBeginLoc(), diag::err_invalid_consteval_call) << FD;
      for (auto &Note : Notes)
        SemaRef.Diag(Note.first, Note.second);
      return;
    }
    CE->MoveIntoResult(Eval.Val, SemaRef.getASTContext());
  }
  
  static void RemoveNestedImmediateInvocation(
      Sema &SemaRef, Sema::ExpressionEvaluationContextRecord &Rec,
      SmallVector<Sema::ImmediateInvocationCandidate, 4>::reverse_iterator It) {
    struct ComplexRemove : TreeTransform<ComplexRemove> {
      using Base = TreeTransform<ComplexRemove>;
      llvm::SmallPtrSetImpl<DeclRefExpr *> &DRSet;
      SmallVector<Sema::ImmediateInvocationCandidate, 4> &IISet;
      SmallVector<Sema::ImmediateInvocationCandidate, 4>::reverse_iterator
          CurrentII;
      ComplexRemove(Sema &SemaRef, llvm::SmallPtrSetImpl<DeclRefExpr *> &DR,
                    SmallVector<Sema::ImmediateInvocationCandidate, 4> &II,
                    SmallVector<Sema::ImmediateInvocationCandidate,
                                4>::reverse_iterator Current)
          : Base(SemaRef), DRSet(DR), IISet(II), CurrentII(Current) {}
      void RemoveImmediateInvocation(ConstantExpr* E) {
        auto It = std::find_if(CurrentII, IISet.rend(),
                               [E](Sema::ImmediateInvocationCandidate Elem) {
                                 return Elem.getPointer() == E;
                               });
        assert(It != IISet.rend() &&
               "ConstantExpr marked IsImmediateInvocation should "
               "be present");
        It->setInt(1); // Mark as deleted
      }
      ExprResult TransformConstantExpr(ConstantExpr *E) {
        if (!E->isImmediateInvocation())
          return Base::TransformConstantExpr(E);
        RemoveImmediateInvocation(E);
        return Base::TransformExpr(E->getSubExpr());
      }
      /// Base::TransfromCXXOperatorCallExpr doesn't traverse the callee so
      /// we need to remove its DeclRefExpr from the DRSet.
      ExprResult TransformCXXOperatorCallExpr(CXXOperatorCallExpr *E) {
        DRSet.erase(cast<DeclRefExpr>(E->getCallee()->IgnoreImplicit()));
        return Base::TransformCXXOperatorCallExpr(E);
      }
      /// Base::TransformInitializer skip ConstantExpr so we need to visit them
      /// here.
      ExprResult TransformInitializer(Expr *Init, bool NotCopyInit) {
        if (!Init)
          return Init;
        /// ConstantExpr are the first layer of implicit node to be removed so if
        /// Init isn't a ConstantExpr, no ConstantExpr will be skipped.
        if (auto *CE = dyn_cast<ConstantExpr>(Init))
          if (CE->isImmediateInvocation())
            RemoveImmediateInvocation(CE);
        return Base::TransformInitializer(Init, NotCopyInit);
      }
      ExprResult TransformDeclRefExpr(DeclRefExpr *E) {
        DRSet.erase(E);
        return E;
      }
      bool AlwaysRebuild() { return false; }
      bool ReplacingOriginal() { return true; }
      bool AllowSkippingCXXConstructExpr() {
        bool Res = AllowSkippingFirstCXXConstructExpr;
        AllowSkippingFirstCXXConstructExpr = true;
        return Res;
      }
      bool AllowSkippingFirstCXXConstructExpr = true;
    } Transformer(SemaRef, Rec.ReferenceToConsteval,
                  Rec.ImmediateInvocationCandidates, It);
  
    /// CXXConstructExpr with a single argument are getting skipped by
    /// TreeTransform in some situtation because they could be implicit. This
    /// can only occur for the top-level CXXConstructExpr because it is used
    /// nowhere in the expression being transformed therefore will not be rebuilt.
    /// Setting AllowSkippingFirstCXXConstructExpr to false will prevent from
    /// skipping the first CXXConstructExpr.
    if (isa<CXXConstructExpr>(It->getPointer()->IgnoreImplicit()))
      Transformer.AllowSkippingFirstCXXConstructExpr = false;
  
    ExprResult Res = Transformer.TransformExpr(It->getPointer()->getSubExpr());
    assert(Res.isUsable());
    Res = SemaRef.MaybeCreateExprWithCleanups(Res);
    It->getPointer()->setSubExpr(Res.get());
  }
  
  static void
  HandleImmediateInvocations(Sema &SemaRef,
                             Sema::ExpressionEvaluationContextRecord &Rec) {
    if ((Rec.ImmediateInvocationCandidates.size() == 0 &&
         Rec.ReferenceToConsteval.size() == 0) ||
        SemaRef.RebuildingImmediateInvocation)
      return;
  
    /// When we have more then 1 ImmediateInvocationCandidates we need to check
    /// for nested ImmediateInvocationCandidates. when we have only 1 we only
    /// need to remove ReferenceToConsteval in the immediate invocation.
    if (Rec.ImmediateInvocationCandidates.size() > 1) {
  
      /// Prevent sema calls during the tree transform from adding pointers that
      /// are already in the sets.
      llvm::SaveAndRestore<bool> DisableIITracking(
          SemaRef.RebuildingImmediateInvocation, true);
  
      /// Prevent diagnostic during tree transfrom as they are duplicates
      Sema::TentativeAnalysisScope DisableDiag(SemaRef);
  
      for (auto It = Rec.ImmediateInvocationCandidates.rbegin();
           It != Rec.ImmediateInvocationCandidates.rend(); It++)
        if (!It->getInt())
          RemoveNestedImmediateInvocation(SemaRef, Rec, It);
    } else if (Rec.ImmediateInvocationCandidates.size() == 1 &&
               Rec.ReferenceToConsteval.size()) {
      struct SimpleRemove : RecursiveASTVisitor<SimpleRemove> {
        llvm::SmallPtrSetImpl<DeclRefExpr *> &DRSet;
        SimpleRemove(llvm::SmallPtrSetImpl<DeclRefExpr *> &S) : DRSet(S) {}
        bool VisitDeclRefExpr(DeclRefExpr *E) {
          DRSet.erase(E);
          return DRSet.size();
        }
      } Visitor(Rec.ReferenceToConsteval);
      Visitor.TraverseStmt(
          Rec.ImmediateInvocationCandidates.front().getPointer()->getSubExpr());
    }
    for (auto CE : Rec.ImmediateInvocationCandidates)
      if (!CE.getInt())
        EvaluateAndDiagnoseImmediateInvocation(SemaRef, CE);
    for (auto DR : Rec.ReferenceToConsteval) {
      auto *FD = cast<FunctionDecl>(DR->getDecl());
      SemaRef.Diag(DR->getBeginLoc(), diag::err_invalid_consteval_take_address)
          << FD;
      SemaRef.Diag(FD->getLocation(), diag::note_declared_at);
    }
  }
  
  void Sema::PopExpressionEvaluationContext() {
    ExpressionEvaluationContextRecord& Rec = ExprEvalContexts.back();
    unsigned NumTypos = Rec.NumTypos;
  
    if (!Rec.Lambdas.empty()) {
      using ExpressionKind = ExpressionEvaluationContextRecord::ExpressionKind;
      if (!getLangOpts().CPlusPlus20 &&
          (Rec.ExprContext == ExpressionKind::EK_TemplateArgument ||
           Rec.isUnevaluated() ||
           (Rec.isConstantEvaluated() && !getLangOpts().CPlusPlus17))) {
        unsigned D;
        if (Rec.isUnevaluated()) {
          // C++11 [expr.prim.lambda]p2:
          //   A lambda-expression shall not appear in an unevaluated operand
          //   (Clause 5).
          D = diag::err_lambda_unevaluated_operand;
        } else if (Rec.isConstantEvaluated() && !getLangOpts().CPlusPlus17) {
          // C++1y [expr.const]p2:
          //   A conditional-expression e is a core constant expression unless the
          //   evaluation of e, following the rules of the abstract machine, would
          //   evaluate [...] a lambda-expression.
          D = diag::err_lambda_in_constant_expression;
        } else if (Rec.ExprContext == ExpressionKind::EK_TemplateArgument) {
          // C++17 [expr.prim.lamda]p2:
          // A lambda-expression shall not appear [...] in a template-argument.
          D = diag::err_lambda_in_invalid_context;
        } else
          llvm_unreachable("Couldn't infer lambda error message.");
  
        for (const auto *L : Rec.Lambdas)
          Diag(L->getBeginLoc(), D);
      }
    }
  
    WarnOnPendingNoDerefs(Rec);
    HandleImmediateInvocations(*this, Rec);
  
    // Warn on any volatile-qualified simple-assignments that are not discarded-
    // value expressions nor unevaluated operands (those cases get removed from
    // this list by CheckUnusedVolatileAssignment).
    for (auto *BO : Rec.VolatileAssignmentLHSs)
      Diag(BO->getBeginLoc(), diag::warn_deprecated_simple_assign_volatile)
          << BO->getType();
  
    // When are coming out of an unevaluated context, clear out any
    // temporaries that we may have created as part of the evaluation of
    // the expression in that context: they aren't relevant because they
    // will never be constructed.
    if (Rec.isUnevaluated() || Rec.isConstantEvaluated()) {
      ExprCleanupObjects.erase(ExprCleanupObjects.begin() + Rec.NumCleanupObjects,
                               ExprCleanupObjects.end());
      Cleanup = Rec.ParentCleanup;
      CleanupVarDeclMarking();
      std::swap(MaybeODRUseExprs, Rec.SavedMaybeODRUseExprs);
    // Otherwise, merge the contexts together.
    } else {
      Cleanup.mergeFrom(Rec.ParentCleanup);
      MaybeODRUseExprs.insert(Rec.SavedMaybeODRUseExprs.begin(),
                              Rec.SavedMaybeODRUseExprs.end());
    }
  
    // Pop the current expression evaluation context off the stack.
    ExprEvalContexts.pop_back();
  
    // The global expression evaluation context record is never popped.
    ExprEvalContexts.back().NumTypos += NumTypos;
  }
  
  void Sema::DiscardCleanupsInEvaluationContext() {
    ExprCleanupObjects.erase(
           ExprCleanupObjects.begin() + ExprEvalContexts.back().NumCleanupObjects,
           ExprCleanupObjects.end());
    Cleanup.reset();
    MaybeODRUseExprs.clear();
  }
  
  ExprResult Sema::HandleExprEvaluationContextForTypeof(Expr *E) {
    ExprResult Result = CheckPlaceholderExpr(E);
    if (Result.isInvalid())
      return ExprError();
    E = Result.get();
    if (!E->getType()->isVariablyModifiedType())
      return E;
    return TransformToPotentiallyEvaluated(E);
  }
  
  /// Are we in a context that is potentially constant evaluated per C++20
  /// [expr.const]p12?
  static bool isPotentiallyConstantEvaluatedContext(Sema &SemaRef) {
    /// C++2a [expr.const]p12:
    //   An expression or conversion is potentially constant evaluated if it is
    switch (SemaRef.ExprEvalContexts.back().Context) {
      case Sema::ExpressionEvaluationContext::ConstantEvaluated:
      case Sema::ExpressionEvaluationContext::ImmediateFunctionContext:
  
        // -- a manifestly constant-evaluated expression,
      case Sema::ExpressionEvaluationContext::PotentiallyEvaluated:
      case Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
      case Sema::ExpressionEvaluationContext::DiscardedStatement:
        // -- a potentially-evaluated expression,
      case Sema::ExpressionEvaluationContext::UnevaluatedList:
        // -- an immediate subexpression of a braced-init-list,
  
        // -- [FIXME] an expression of the form & cast-expression that occurs
        //    within a templated entity
        // -- a subexpression of one of the above that is not a subexpression of
        // a nested unevaluated operand.
        return true;
  
      case Sema::ExpressionEvaluationContext::Unevaluated:
      case Sema::ExpressionEvaluationContext::UnevaluatedAbstract:
        // Expressions in this context are never evaluated.
        return false;
    }
    llvm_unreachable("Invalid context");
  }
  
  /// Return true if this function has a calling convention that requires mangling
  /// in the size of the parameter pack.
  static bool funcHasParameterSizeMangling(Sema &S, FunctionDecl *FD) {
    // These manglings don't do anything on non-Windows or non-x86 platforms, so
    // we don't need parameter type sizes.
    const llvm::Triple &TT = S.Context.getTargetInfo().getTriple();
    if (!TT.isOSWindows() || !TT.isX86())
      return false;
  
    // If this is C++ and this isn't an extern "C" function, parameters do not
    // need to be complete. In this case, C++ mangling will apply, which doesn't
    // use the size of the parameters.
    if (S.getLangOpts().CPlusPlus && !FD->isExternC())
      return false;
  
    // Stdcall, fastcall, and vectorcall need this special treatment.
    CallingConv CC = FD->getType()->castAs<FunctionType>()->getCallConv();
    switch (CC) {
    case CC_X86StdCall:
    case CC_X86FastCall:
    case CC_X86VectorCall:
      return true;
    default:
      break;
    }
    return false;
  }
  
  /// Require that all of the parameter types of function be complete. Normally,
  /// parameter types are only required to be complete when a function is called
  /// or defined, but to mangle functions with certain calling conventions, the
  /// mangler needs to know the size of the parameter list. In this situation,
  /// MSVC doesn't emit an error or instantiate templates. Instead, MSVC mangles
  /// the function as _foo@0, i.e. zero bytes of parameters, which will usually
  /// result in a linker error. Clang doesn't implement this behavior, and instead
  /// attempts to error at compile time.
  static void CheckCompleteParameterTypesForMangler(Sema &S, FunctionDecl *FD,
                                                    SourceLocation Loc) {
    class ParamIncompleteTypeDiagnoser : public Sema::TypeDiagnoser {
      FunctionDecl *FD;
      ParmVarDecl *Param;
  
    public:
      ParamIncompleteTypeDiagnoser(FunctionDecl *FD, ParmVarDecl *Param)
          : FD(FD), Param(Param) {}
  
      void diagnose(Sema &S, SourceLocation Loc, QualType T) override {
        CallingConv CC = FD->getType()->castAs<FunctionType>()->getCallConv();
        StringRef CCName;
        switch (CC) {
        case CC_X86StdCall:
          CCName = "stdcall";
          break;
        case CC_X86FastCall:
          CCName = "fastcall";
          break;
        case CC_X86VectorCall:
          CCName = "vectorcall";
          break;
        default:
          llvm_unreachable("CC does not need mangling");
        }
  
        S.Diag(Loc, diag::err_cconv_incomplete_param_type)
            << Param->getDeclName() << FD->getDeclName() << CCName;
      }
    };
  
    for (ParmVarDecl *Param : FD->parameters()) {
      ParamIncompleteTypeDiagnoser Diagnoser(FD, Param);
      S.RequireCompleteType(Loc, Param->getType(), Diagnoser);
    }
  }
  
  namespace {
  enum class OdrUseContext {
    /// Declarations in this context are not odr-used.
    None,
    /// Declarations in this context are formally odr-used, but this is a
    /// dependent context.
    Dependent,
    /// Declarations in this context are odr-used but not actually used (yet).
    FormallyOdrUsed,
    /// Declarations in this context are used.
    Used
  };
  }
  
  /// Are we within a context in which references to resolved functions or to
  /// variables result in odr-use?
  static OdrUseContext isOdrUseContext(Sema &SemaRef) {
    OdrUseContext Result;
  
    switch (SemaRef.ExprEvalContexts.back().Context) {
      case Sema::ExpressionEvaluationContext::Unevaluated:
      case Sema::ExpressionEvaluationContext::UnevaluatedList:
      case Sema::ExpressionEvaluationContext::UnevaluatedAbstract:
        return OdrUseContext::None;
  
      case Sema::ExpressionEvaluationContext::ConstantEvaluated:
      case Sema::ExpressionEvaluationContext::ImmediateFunctionContext:
      case Sema::ExpressionEvaluationContext::PotentiallyEvaluated:
        Result = OdrUseContext::Used;
        break;
  
      case Sema::ExpressionEvaluationContext::DiscardedStatement:
        Result = OdrUseContext::FormallyOdrUsed;
        break;
  
      case Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
        // A default argument formally results in odr-use, but doesn't actually
        // result in a use in any real sense until it itself is used.
        Result = OdrUseContext::FormallyOdrUsed;
        break;
    }
  
    if (SemaRef.CurContext->isDependentContext())
      return OdrUseContext::Dependent;
  
    return Result;
  }
  
  static bool isImplicitlyDefinableConstexprFunction(FunctionDecl *Func) {
    if (!Func->isConstexpr())
      return false;
  
    if (Func->isImplicitlyInstantiable() || !Func->isUserProvided())
      return true;
    auto *CCD = dyn_cast<CXXConstructorDecl>(Func);
    return CCD && CCD->getInheritedConstructor();
  }
  
  /// Mark a function referenced, and check whether it is odr-used
  /// (C++ [basic.def.odr]p2, C99 6.9p3)
  void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
                                    bool MightBeOdrUse) {
    assert(Func && "No function?");
  
    Func->setReferenced();
  
    // Recursive functions aren't really used until they're used from some other
    // context.
    bool IsRecursiveCall = CurContext == Func;
  
    // C++11 [basic.def.odr]p3:
    //   A function whose name appears as a potentially-evaluated expression is
    //   odr-used if it is the unique lookup result or the selected member of a
    //   set of overloaded functions [...].
    //
    // We (incorrectly) mark overload resolution as an unevaluated context, so we
    // can just check that here.
    OdrUseContext OdrUse =
        MightBeOdrUse ? isOdrUseContext(*this) : OdrUseContext::None;
    if (IsRecursiveCall && OdrUse == OdrUseContext::Used)
      OdrUse = OdrUseContext::FormallyOdrUsed;
  
    // Trivial default constructors and destructors are never actually used.
    // FIXME: What about other special members?
    if (Func->isTrivial() && !Func->hasAttr<DLLExportAttr>() &&
        OdrUse == OdrUseContext::Used) {
      if (auto *Constructor = dyn_cast<CXXConstructorDecl>(Func))
        if (Constructor->isDefaultConstructor())
          OdrUse = OdrUseContext::FormallyOdrUsed;
      if (isa<CXXDestructorDecl>(Func))
        OdrUse = OdrUseContext::FormallyOdrUsed;
    }
  
    // C++20 [expr.const]p12:
    //   A function [...] is needed for constant evaluation if it is [...] a
    //   constexpr function that is named by an expression that is potentially
    //   constant evaluated
    bool NeededForConstantEvaluation =
        isPotentiallyConstantEvaluatedContext(*this) &&
        isImplicitlyDefinableConstexprFunction(Func);
  
    // Determine whether we require a function definition to exist, per
    // C++11 [temp.inst]p3:
    //   Unless a function template specialization has been explicitly
    //   instantiated or explicitly specialized, the function template
    //   specialization is implicitly instantiated when the specialization is
    //   referenced in a context that requires a function definition to exist.
    // C++20 [temp.inst]p7:
    //   The existence of a definition of a [...] function is considered to
    //   affect the semantics of the program if the [...] function is needed for
    //   constant evaluation by an expression
    // C++20 [basic.def.odr]p10:
    //   Every program shall contain exactly one definition of every non-inline
    //   function or variable that is odr-used in that program outside of a
    //   discarded statement
    // C++20 [special]p1:
    //   The implementation will implicitly define [defaulted special members]
    //   if they are odr-used or needed for constant evaluation.
    //
    // Note that we skip the implicit instantiation of templates that are only
    // used in unused default arguments or by recursive calls to themselves.
    // This is formally non-conforming, but seems reasonable in practice.
    bool NeedDefinition = !IsRecursiveCall && (OdrUse == OdrUseContext::Used ||
                                               NeededForConstantEvaluation);
  
    // C++14 [temp.expl.spec]p6:
    //   If a template [...] is explicitly specialized then that specialization
    //   shall be declared before the first use of that specialization that would
    //   cause an implicit instantiation to take place, in every translation unit
    //   in which such a use occurs
    if (NeedDefinition &&
        (Func->getTemplateSpecializationKind() != TSK_Undeclared ||
         Func->getMemberSpecializationInfo()))
      checkSpecializationVisibility(Loc, Func);
  
    if (getLangOpts().CUDA)
      CheckCUDACall(Loc, Func);
  
    if (getLangOpts().SYCLIsDevice)
      checkSYCLDeviceFunction(Loc, Func);
  
    // If we need a definition, try to create one.
    if (NeedDefinition && !Func->getBody()) {
      runWithSufficientStackSpace(Loc, [&] {
        if (CXXConstructorDecl *Constructor =
                dyn_cast<CXXConstructorDecl>(Func)) {
          Constructor = cast<CXXConstructorDecl>(Constructor->getFirstDecl());
          if (Constructor->isDefaulted() && !Constructor->isDeleted()) {
            if (Constructor->isDefaultConstructor()) {
              if (Constructor->isTrivial() &&
                  !Constructor->hasAttr<DLLExportAttr>())
                return;
              DefineImplicitDefaultConstructor(Loc, Constructor);
            } else if (Constructor->isCopyConstructor()) {
              DefineImplicitCopyConstructor(Loc, Constructor);
            } else if (Constructor->isMoveConstructor()) {
              DefineImplicitMoveConstructor(Loc, Constructor);
            }
          } else if (Constructor->getInheritedConstructor()) {
            DefineInheritingConstructor(Loc, Constructor);
          }
        } else if (CXXDestructorDecl *Destructor =
                       dyn_cast<CXXDestructorDecl>(Func)) {
          Destructor = cast<CXXDestructorDecl>(Destructor->getFirstDecl());
          if (Destructor->isDefaulted() && !Destructor->isDeleted()) {
            if (Destructor->isTrivial() && !Destructor->hasAttr<DLLExportAttr>())
              return;
            DefineImplicitDestructor(Loc, Destructor);
          }
          if (Destructor->isVirtual() && getLangOpts().AppleKext)
            MarkVTableUsed(Loc, Destructor->getParent());
        } else if (CXXMethodDecl *MethodDecl = dyn_cast<CXXMethodDecl>(Func)) {
          if (MethodDecl->isOverloadedOperator() &&
              MethodDecl->getOverloadedOperator() == OO_Equal) {
            MethodDecl = cast<CXXMethodDecl>(MethodDecl->getFirstDecl());
            if (MethodDecl->isDefaulted() && !MethodDecl->isDeleted()) {
              if (MethodDecl->isCopyAssignmentOperator())
                DefineImplicitCopyAssignment(Loc, MethodDecl);
              else if (MethodDecl->isMoveAssignmentOperator())
                DefineImplicitMoveAssignment(Loc, MethodDecl);
            }
          } else if (isa<CXXConversionDecl>(MethodDecl) &&
                     MethodDecl->getParent()->isLambda()) {
            CXXConversionDecl *Conversion =
                cast<CXXConversionDecl>(MethodDecl->getFirstDecl());
            if (Conversion->isLambdaToBlockPointerConversion())
              DefineImplicitLambdaToBlockPointerConversion(Loc, Conversion);
            else
              DefineImplicitLambdaToFunctionPointerConversion(Loc, Conversion);
          } else if (MethodDecl->isVirtual() && getLangOpts().AppleKext)
            MarkVTableUsed(Loc, MethodDecl->getParent());
        }
  
        if (Func->isDefaulted() && !Func->isDeleted()) {
          DefaultedComparisonKind DCK = getDefaultedComparisonKind(Func);
          if (DCK != DefaultedComparisonKind::None)
            DefineDefaultedComparison(Loc, Func, DCK);
        }
  
        // Implicit instantiation of function templates and member functions of
        // class templates.
        if (Func->isImplicitlyInstantiable()) {
          TemplateSpecializationKind TSK =
              Func->getTemplateSpecializationKindForInstantiation();
          SourceLocation PointOfInstantiation = Func->getPointOfInstantiation();
          bool FirstInstantiation = PointOfInstantiation.isInvalid();
          if (FirstInstantiation) {
            PointOfInstantiation = Loc;
            if (auto *MSI = Func->getMemberSpecializationInfo())
              MSI->setPointOfInstantiation(Loc);
              // FIXME: Notify listener.
            else
              Func->setTemplateSpecializationKind(TSK, PointOfInstantiation);
          } else if (TSK != TSK_ImplicitInstantiation) {
            // Use the point of use as the point of instantiation, instead of the
            // point of explicit instantiation (which we track as the actual point
            // of instantiation). This gives better backtraces in diagnostics.
            PointOfInstantiation = Loc;
          }
  
          if (FirstInstantiation || TSK != TSK_ImplicitInstantiation ||
              Func->isConstexpr()) {
            if (isa<CXXRecordDecl>(Func->getDeclContext()) &&
                cast<CXXRecordDecl>(Func->getDeclContext())->isLocalClass() &&
                CodeSynthesisContexts.size())
              PendingLocalImplicitInstantiations.push_back(
                  std::make_pair(Func, PointOfInstantiation));
            else if (Func->isConstexpr())
              // Do not defer instantiations of constexpr functions, to avoid the
              // expression evaluator needing to call back into Sema if it sees a
              // call to such a function.
              InstantiateFunctionDefinition(PointOfInstantiation, Func);
            else {
              Func->setInstantiationIsPending(true);
              PendingInstantiations.push_back(
                  std::make_pair(Func, PointOfInstantiation));
              // Notify the consumer that a function was implicitly instantiated.
              Consumer.HandleCXXImplicitFunctionInstantiation(Func);
            }
          }
        } else {
          // Walk redefinitions, as some of them may be instantiable.
          for (auto i : Func->redecls()) {
            if (!i->isUsed(false) && i->isImplicitlyInstantiable())
              MarkFunctionReferenced(Loc, i, MightBeOdrUse);
          }
        }
      });
    }
  
    // C++14 [except.spec]p17:
    //   An exception-specification is considered to be needed when:
    //   - the function is odr-used or, if it appears in an unevaluated operand,
    //     would be odr-used if the expression were potentially-evaluated;
    //
    // Note, we do this even if MightBeOdrUse is false. That indicates that the
    // function is a pure virtual function we're calling, and in that case the
    // function was selected by overload resolution and we need to resolve its
    // exception specification for a different reason.
    const FunctionProtoType *FPT = Func->getType()->getAs<FunctionProtoType>();
    if (FPT && isUnresolvedExceptionSpec(FPT->getExceptionSpecType()))
      ResolveExceptionSpec(Loc, FPT);
  
    // If this is the first "real" use, act on that.
    if (OdrUse == OdrUseContext::Used && !Func->isUsed(/*CheckUsedAttr=*/false)) {
      // Keep track of used but undefined functions.
      if (!Func->isDefined()) {
        if (mightHaveNonExternalLinkage(Func))
          UndefinedButUsed.insert(std::make_pair(Func->getCanonicalDecl(), Loc));
        else if (Func->getMostRecentDecl()->isInlined() &&
                 !LangOpts.GNUInline &&
                 !Func->getMostRecentDecl()->hasAttr<GNUInlineAttr>())
          UndefinedButUsed.insert(std::make_pair(Func->getCanonicalDecl(), Loc));
        else if (isExternalWithNoLinkageType(Func))
          UndefinedButUsed.insert(std::make_pair(Func->getCanonicalDecl(), Loc));
      }
  
      // Some x86 Windows calling conventions mangle the size of the parameter
      // pack into the name. Computing the size of the parameters requires the
      // parameter types to be complete. Check that now.
      if (funcHasParameterSizeMangling(*this, Func))
        CheckCompleteParameterTypesForMangler(*this, Func, Loc);
  
      // In the MS C++ ABI, the compiler emits destructor variants where they are
      // used. If the destructor is used here but defined elsewhere, mark the
      // virtual base destructors referenced. If those virtual base destructors
      // are inline, this will ensure they are defined when emitting the complete
      // destructor variant. This checking may be redundant if the destructor is
      // provided later in this TU.
      if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
        if (auto *Dtor = dyn_cast<CXXDestructorDecl>(Func)) {
          CXXRecordDecl *Parent = Dtor->getParent();
          if (Parent->getNumVBases() > 0 && !Dtor->getBody())
            CheckCompleteDestructorVariant(Loc, Dtor);
        }
      }
  
      Func->markUsed(Context);
    }
  }
  
  /// Directly mark a variable odr-used. Given a choice, prefer to use
  /// MarkVariableReferenced since it does additional checks and then
  /// calls MarkVarDeclODRUsed.
  /// If the variable must be captured:
  ///  - if FunctionScopeIndexToStopAt is null, capture it in the CurContext
  ///  - else capture it in the DeclContext that maps to the
  ///    *FunctionScopeIndexToStopAt on the FunctionScopeInfo stack.
  static void
  MarkVarDeclODRUsed(VarDecl *Var, SourceLocation Loc, Sema &SemaRef,
                     const unsigned *const FunctionScopeIndexToStopAt = nullptr) {
    // Keep track of used but undefined variables.
    // FIXME: We shouldn't suppress this warning for static data members.
    if (Var->hasDefinition(SemaRef.Context) == VarDecl::DeclarationOnly &&
        (!Var->isExternallyVisible() || Var->isInline() ||
         SemaRef.isExternalWithNoLinkageType(Var)) &&
        !(Var->isStaticDataMember() && Var->hasInit())) {
      SourceLocation &old = SemaRef.UndefinedButUsed[Var->getCanonicalDecl()];
      if (old.isInvalid())
        old = Loc;
    }
    QualType CaptureType, DeclRefType;
    if (SemaRef.LangOpts.OpenMP)
      SemaRef.tryCaptureOpenMPLambdas(Var);
    SemaRef.tryCaptureVariable(Var, Loc, Sema::TryCapture_Implicit,
      /*EllipsisLoc*/ SourceLocation(),
      /*BuildAndDiagnose*/ true,
      CaptureType, DeclRefType,
      FunctionScopeIndexToStopAt);
  
    if (SemaRef.LangOpts.CUDA && Var->hasGlobalStorage()) {
      auto *FD = dyn_cast_or_null<FunctionDecl>(SemaRef.CurContext);
      auto VarTarget = SemaRef.IdentifyCUDATarget(Var);
      auto UserTarget = SemaRef.IdentifyCUDATarget(FD);
      if (VarTarget == Sema::CVT_Host &&
          (UserTarget == Sema::CFT_Device || UserTarget == Sema::CFT_HostDevice ||
           UserTarget == Sema::CFT_Global)) {
        // Diagnose ODR-use of host global variables in device functions.
        // Reference of device global variables in host functions is allowed
        // through shadow variables therefore it is not diagnosed.
        if (SemaRef.LangOpts.CUDAIsDevice) {
          SemaRef.targetDiag(Loc, diag::err_ref_bad_target)
              << /*host*/ 2 << /*variable*/ 1 << Var << UserTarget;
          SemaRef.targetDiag(Var->getLocation(),
                             Var->getType().isConstQualified()
                                 ? diag::note_cuda_const_var_unpromoted
                                 : diag::note_cuda_host_var);
        }
      } else if (VarTarget == Sema::CVT_Device &&
                 (UserTarget == Sema::CFT_Host ||
                  UserTarget == Sema::CFT_HostDevice) &&
                 !Var->hasExternalStorage()) {
        // Record a CUDA/HIP device side variable if it is ODR-used
        // by host code. This is done conservatively, when the variable is
        // referenced in any of the following contexts:
        //   - a non-function context
        //   - a host function
        //   - a host device function
        // This makes the ODR-use of the device side variable by host code to
        // be visible in the device compilation for the compiler to be able to
        // emit template variables instantiated by host code only and to
        // externalize the static device side variable ODR-used by host code.
        SemaRef.getASTContext().CUDADeviceVarODRUsedByHost.insert(Var);
      }
    }
  
    Var->markUsed(SemaRef.Context);
  }
  
  void Sema::MarkCaptureUsedInEnclosingContext(VarDecl *Capture,
                                               SourceLocation Loc,
                                               unsigned CapturingScopeIndex) {
    MarkVarDeclODRUsed(Capture, Loc, *this, &CapturingScopeIndex);
  }
  
  static void diagnoseUncapturableValueReference(Sema &S, SourceLocation loc,
                                                 ValueDecl *var) {
    DeclContext *VarDC = var->getDeclContext();
  
    //  If the parameter still belongs to the translation unit, then
    //  we're actually just using one parameter in the declaration of
    //  the next.
    if (isa<ParmVarDecl>(var) &&
        isa<TranslationUnitDecl>(VarDC))
      return;
  
    // For C code, don't diagnose about capture if we're not actually in code
    // right now; it's impossible to write a non-constant expression outside of
    // function context, so we'll get other (more useful) diagnostics later.
    //
    // For C++, things get a bit more nasty... it would be nice to suppress this
    // diagnostic for certain cases like using a local variable in an array bound
    // for a member of a local class, but the correct predicate is not obvious.
    if (!S.getLangOpts().CPlusPlus && !S.CurContext->isFunctionOrMethod())
      return;
  
    unsigned ValueKind = isa<BindingDecl>(var) ? 1 : 0;
    unsigned ContextKind = 3; // unknown
    if (isa<CXXMethodDecl>(VarDC) &&
        cast<CXXRecordDecl>(VarDC->getParent())->isLambda()) {
      ContextKind = 2;
    } else if (isa<FunctionDecl>(VarDC)) {
      ContextKind = 0;
    } else if (isa<BlockDecl>(VarDC)) {
      ContextKind = 1;
    }
  
    S.Diag(loc, diag::err_reference_to_local_in_enclosing_context)
      << var << ValueKind << ContextKind << VarDC;
    S.Diag(var->getLocation(), diag::note_entity_declared_at)
        << var;
  
    // FIXME: Add additional diagnostic info about class etc. which prevents
    // capture.
  }
  
  
  static bool isVariableAlreadyCapturedInScopeInfo(CapturingScopeInfo *CSI, VarDecl *Var,
                                        bool &SubCapturesAreNested,
                                        QualType &CaptureType,
                                        QualType &DeclRefType) {
     // Check whether we've already captured it.
    if (CSI->CaptureMap.count(Var)) {
      // If we found a capture, any subcaptures are nested.
      SubCapturesAreNested = true;
  
      // Retrieve the capture type for this variable.
      CaptureType = CSI->getCapture(Var).getCaptureType();
  
      // Compute the type of an expression that refers to this variable.
      DeclRefType = CaptureType.getNonReferenceType();
  
      // Similarly to mutable captures in lambda, all the OpenMP captures by copy
      // are mutable in the sense that user can change their value - they are
      // private instances of the captured declarations.
      const Capture &Cap = CSI->getCapture(Var);
      if (Cap.isCopyCapture() &&
          !(isa<LambdaScopeInfo>(CSI) && cast<LambdaScopeInfo>(CSI)->Mutable) &&
          !(isa<CapturedRegionScopeInfo>(CSI) &&
            cast<CapturedRegionScopeInfo>(CSI)->CapRegionKind == CR_OpenMP))
        DeclRefType.addConst();
      return true;
    }
    return false;
  }
  
  // Only block literals, captured statements, and lambda expressions can
  // capture; other scopes don't work.
  static DeclContext *getParentOfCapturingContextOrNull(DeclContext *DC, VarDecl *Var,
                                   SourceLocation Loc,
                                   const bool Diagnose, Sema &S) {
    if (isa<BlockDecl>(DC) || isa<CapturedDecl>(DC) || isLambdaCallOperator(DC))
      return getLambdaAwareParentOfDeclContext(DC);
    else if (Var->hasLocalStorage()) {
      if (Diagnose)
         diagnoseUncapturableValueReference(S, Loc, Var);
    }
    return nullptr;
  }
  
  // Certain capturing entities (lambdas, blocks etc.) are not allowed to capture
  // certain types of variables (unnamed, variably modified types etc.)
  // so check for eligibility.
  static bool isVariableCapturable(CapturingScopeInfo *CSI, VarDecl *Var,
                                   SourceLocation Loc,
                                   const bool Diagnose, Sema &S) {
  
    bool IsBlock = isa<BlockScopeInfo>(CSI);
    bool IsLambda = isa<LambdaScopeInfo>(CSI);
  
    // Lambdas are not allowed to capture unnamed variables
    // (e.g. anonymous unions).
    // FIXME: The C++11 rule don't actually state this explicitly, but I'm
    // assuming that's the intent.
    if (IsLambda && !Var->getDeclName()) {
      if (Diagnose) {
        S.Diag(Loc, diag::err_lambda_capture_anonymous_var);
        S.Diag(Var->getLocation(), diag::note_declared_at);
      }
      return false;
    }
  
    // Prohibit variably-modified types in blocks; they're difficult to deal with.
    if (Var->getType()->isVariablyModifiedType() && IsBlock) {
      if (Diagnose) {
        S.Diag(Loc, diag::err_ref_vm_type);
        S.Diag(Var->getLocation(), diag::note_previous_decl) << Var;
      }
      return false;
    }
    // Prohibit structs with flexible array members too.
    // We cannot capture what is in the tail end of the struct.
    if (const RecordType *VTTy = Var->getType()->getAs<RecordType>()) {
      if (VTTy->getDecl()->hasFlexibleArrayMember()) {
        if (Diagnose) {
          if (IsBlock)
            S.Diag(Loc, diag::err_ref_flexarray_type);
          else
            S.Diag(Loc, diag::err_lambda_capture_flexarray_type) << Var;
          S.Diag(Var->getLocation(), diag::note_previous_decl) << Var;
        }
        return false;
      }
    }
    const bool HasBlocksAttr = Var->hasAttr<BlocksAttr>();
    // Lambdas and captured statements are not allowed to capture __block
    // variables; they don't support the expected semantics.
    if (HasBlocksAttr && (IsLambda || isa<CapturedRegionScopeInfo>(CSI))) {
      if (Diagnose) {
        S.Diag(Loc, diag::err_capture_block_variable) << Var << !IsLambda;
        S.Diag(Var->getLocation(), diag::note_previous_decl) << Var;
      }
      return false;
    }
    // OpenCL v2.0 s6.12.5: Blocks cannot reference/capture other blocks
    if (S.getLangOpts().OpenCL && IsBlock &&
        Var->getType()->isBlockPointerType()) {
      if (Diagnose)
        S.Diag(Loc, diag::err_opencl_block_ref_block);
      return false;
    }
  
    return true;
  }
  
  // Returns true if the capture by block was successful.
  static bool captureInBlock(BlockScopeInfo *BSI, VarDecl *Var,
                                   SourceLocation Loc,
                                   const bool BuildAndDiagnose,
                                   QualType &CaptureType,
                                   QualType &DeclRefType,
                                   const bool Nested,
                                   Sema &S, bool Invalid) {
    bool ByRef = false;
  
    // Blocks are not allowed to capture arrays, excepting OpenCL.
    // OpenCL v2.0 s1.12.5 (revision 40): arrays are captured by reference
    // (decayed to pointers).
    if (!Invalid && !S.getLangOpts().OpenCL && CaptureType->isArrayType()) {
      if (BuildAndDiagnose) {
        S.Diag(Loc, diag::err_ref_array_type);
        S.Diag(Var->getLocation(), diag::note_previous_decl) << Var;
        Invalid = true;
      } else {
        return false;
      }
    }
  
    // Forbid the block-capture of autoreleasing variables.
    if (!Invalid &&
        CaptureType.getObjCLifetime() == Qualifiers::OCL_Autoreleasing) {
      if (BuildAndDiagnose) {
        S.Diag(Loc, diag::err_arc_autoreleasing_capture)
          << /*block*/ 0;
        S.Diag(Var->getLocation(), diag::note_previous_decl) << Var;
        Invalid = true;
      } else {
        return false;
      }
    }
  
    // Warn about implicitly autoreleasing indirect parameters captured by blocks.
    if (const auto *PT = CaptureType->getAs<PointerType>()) {
      QualType PointeeTy = PT->getPointeeType();
  
      if (!Invalid && PointeeTy->getAs<ObjCObjectPointerType>() &&
          PointeeTy.getObjCLifetime() == Qualifiers::OCL_Autoreleasing &&
          !S.Context.hasDirectOwnershipQualifier(PointeeTy)) {
        if (BuildAndDiagnose) {
          SourceLocation VarLoc = Var->getLocation();
          S.Diag(Loc, diag::warn_block_capture_autoreleasing);
          S.Diag(VarLoc, diag::note_declare_parameter_strong);
        }
      }
    }
  
    const bool HasBlocksAttr = Var->hasAttr<BlocksAttr>();
    if (HasBlocksAttr || CaptureType->isReferenceType() ||
        (S.getLangOpts().OpenMP && S.isOpenMPCapturedDecl(Var))) {
      // Block capture by reference does not change the capture or
      // declaration reference types.
      ByRef = true;
    } else {
      // Block capture by copy introduces 'const'.
      CaptureType = CaptureType.getNonReferenceType().withConst();
      DeclRefType = CaptureType;
    }
  
    // Actually capture the variable.
    if (BuildAndDiagnose)
      BSI->addCapture(Var, HasBlocksAttr, ByRef, Nested, Loc, SourceLocation(),
                      CaptureType, Invalid);
  
    return !Invalid;
  }
  
  
  /// Capture the given variable in the captured region.
  static bool captureInCapturedRegion(
      CapturedRegionScopeInfo *RSI, VarDecl *Var, SourceLocation Loc,
      const bool BuildAndDiagnose, QualType &CaptureType, QualType &DeclRefType,
      const bool RefersToCapturedVariable, Sema::TryCaptureKind Kind,
      bool IsTopScope, Sema &S, bool Invalid) {
    // By default, capture variables by reference.
    bool ByRef = true;
    if (IsTopScope && Kind != Sema::TryCapture_Implicit) {
      ByRef = (Kind == Sema::TryCapture_ExplicitByRef);
    } else if (S.getLangOpts().OpenMP && RSI->CapRegionKind == CR_OpenMP) {
      // Using an LValue reference type is consistent with Lambdas (see below).
      if (S.isOpenMPCapturedDecl(Var)) {
        bool HasConst = DeclRefType.isConstQualified();
        DeclRefType = DeclRefType.getUnqualifiedType();
        // Don't lose diagnostics about assignments to const.
        if (HasConst)
          DeclRefType.addConst();
      }
      // Do not capture firstprivates in tasks.
      if (S.isOpenMPPrivateDecl(Var, RSI->OpenMPLevel, RSI->OpenMPCaptureLevel) !=
          OMPC_unknown)
        return true;
      ByRef = S.isOpenMPCapturedByRef(Var, RSI->OpenMPLevel,
                                      RSI->OpenMPCaptureLevel);
    }
  
    if (ByRef)
      CaptureType = S.Context.getLValueReferenceType(DeclRefType);
    else
      CaptureType = DeclRefType;
  
    // Actually capture the variable.
    if (BuildAndDiagnose)
      RSI->addCapture(Var, /*isBlock*/ false, ByRef, RefersToCapturedVariable,
                      Loc, SourceLocation(), CaptureType, Invalid);
  
    return !Invalid;
  }
  
  /// Capture the given variable in the lambda.
  static bool captureInLambda(LambdaScopeInfo *LSI,
                              VarDecl *Var,
                              SourceLocation Loc,
                              const bool BuildAndDiagnose,
                              QualType &CaptureType,
                              QualType &DeclRefType,
                              const bool RefersToCapturedVariable,
                              const Sema::TryCaptureKind Kind,
                              SourceLocation EllipsisLoc,
                              const bool IsTopScope,
                              Sema &S, bool Invalid) {
    // Determine whether we are capturing by reference or by value.
    bool ByRef = false;
    if (IsTopScope && Kind != Sema::TryCapture_Implicit) {
      ByRef = (Kind == Sema::TryCapture_ExplicitByRef);
    } else {
      ByRef = (LSI->ImpCaptureStyle == LambdaScopeInfo::ImpCap_LambdaByref);
    }
  
    // Compute the type of the field that will capture this variable.
    if (ByRef) {
      // C++11 [expr.prim.lambda]p15:
      //   An entity is captured by reference if it is implicitly or
      //   explicitly captured but not captured by copy. It is
      //   unspecified whether additional unnamed non-static data
      //   members are declared in the closure type for entities
      //   captured by reference.
      //
      // FIXME: It is not clear whether we want to build an lvalue reference
      // to the DeclRefType or to CaptureType.getNonReferenceType(). GCC appears
      // to do the former, while EDG does the latter. Core issue 1249 will
      // clarify, but for now we follow GCC because it's a more permissive and
      // easily defensible position.
      CaptureType = S.Context.getLValueReferenceType(DeclRefType);
    } else {
      // C++11 [expr.prim.lambda]p14:
      //   For each entity captured by copy, an unnamed non-static
      //   data member is declared in the closure type. The
      //   declaration order of these members is unspecified. The type
      //   of such a data member is the type of the corresponding
      //   captured entity if the entity is not a reference to an
      //   object, or the referenced type otherwise. [Note: If the
      //   captured entity is a reference to a function, the
      //   corresponding data member is also a reference to a
      //   function. - end note ]
      if (const ReferenceType *RefType = CaptureType->getAs<ReferenceType>()){
        if (!RefType->getPointeeType()->isFunctionType())
          CaptureType = RefType->getPointeeType();
      }
  
      // Forbid the lambda copy-capture of autoreleasing variables.
      if (!Invalid &&
          CaptureType.getObjCLifetime() == Qualifiers::OCL_Autoreleasing) {
        if (BuildAndDiagnose) {
          S.Diag(Loc, diag::err_arc_autoreleasing_capture) << /*lambda*/ 1;
          S.Diag(Var->getLocation(), diag::note_previous_decl)
            << Var->getDeclName();
          Invalid = true;
        } else {
          return false;
        }
      }
  
      // Make sure that by-copy captures are of a complete and non-abstract type.
      if (!Invalid && BuildAndDiagnose) {
        if (!CaptureType->isDependentType() &&
            S.RequireCompleteSizedType(
                Loc, CaptureType,
                diag::err_capture_of_incomplete_or_sizeless_type,
                Var->getDeclName()))
          Invalid = true;
        else if (S.RequireNonAbstractType(Loc, CaptureType,
                                          diag::err_capture_of_abstract_type))
          Invalid = true;
      }
    }
  
    // Compute the type of a reference to this captured variable.
    if (ByRef)
      DeclRefType = CaptureType.getNonReferenceType();
    else {
      // C++ [expr.prim.lambda]p5:
      //   The closure type for a lambda-expression has a public inline
      //   function call operator [...]. This function call operator is
      //   declared const (9.3.1) if and only if the lambda-expression's
      //   parameter-declaration-clause is not followed by mutable.
      DeclRefType = CaptureType.getNonReferenceType();
      if (!LSI->Mutable && !CaptureType->isReferenceType())
        DeclRefType.addConst();
    }
  
    // Add the capture.
    if (BuildAndDiagnose)
      LSI->addCapture(Var, /*isBlock=*/false, ByRef, RefersToCapturedVariable,
                      Loc, EllipsisLoc, CaptureType, Invalid);
  
    return !Invalid;
  }
  
  static bool canCaptureVariableByCopy(VarDecl *Var, const ASTContext &Context) {
    // Offer a Copy fix even if the type is dependent.
    if (Var->getType()->isDependentType())
      return true;
    QualType T = Var->getType().getNonReferenceType();
    if (T.isTriviallyCopyableType(Context))
      return true;
    if (CXXRecordDecl *RD = T->getAsCXXRecordDecl()) {
  
      if (!(RD = RD->getDefinition()))
        return false;
      if (RD->hasSimpleCopyConstructor())
        return true;
      if (RD->hasUserDeclaredCopyConstructor())
        for (CXXConstructorDecl *Ctor : RD->ctors())
          if (Ctor->isCopyConstructor())
            return !Ctor->isDeleted();
    }
    return false;
  }
  
  /// Create up to 4 fix-its for explicit reference and value capture of \p Var or
  /// default capture. Fixes may be omitted if they aren't allowed by the
  /// standard, for example we can't emit a default copy capture fix-it if we
  /// already explicitly copy capture capture another variable.
  static void buildLambdaCaptureFixit(Sema &Sema, LambdaScopeInfo *LSI,
                                      VarDecl *Var) {
    assert(LSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_None);
    // Don't offer Capture by copy of default capture by copy fixes if Var is
    // known not to be copy constructible.
    bool ShouldOfferCopyFix = canCaptureVariableByCopy(Var, Sema.getASTContext());
  
    SmallString<32> FixBuffer;
    StringRef Separator = LSI->NumExplicitCaptures > 0 ? ", " : "";
    if (Var->getDeclName().isIdentifier() && !Var->getName().empty()) {
      SourceLocation VarInsertLoc = LSI->IntroducerRange.getEnd();
      if (ShouldOfferCopyFix) {
        // Offer fixes to insert an explicit capture for the variable.
        // [] -> [VarName]
        // [OtherCapture] -> [OtherCapture, VarName]
        FixBuffer.assign({Separator, Var->getName()});
        Sema.Diag(VarInsertLoc, diag::note_lambda_variable_capture_fixit)
            << Var << /*value*/ 0
            << FixItHint::CreateInsertion(VarInsertLoc, FixBuffer);
      }
      // As above but capture by reference.
      FixBuffer.assign({Separator, "&", Var->getName()});
      Sema.Diag(VarInsertLoc, diag::note_lambda_variable_capture_fixit)
          << Var << /*reference*/ 1
          << FixItHint::CreateInsertion(VarInsertLoc, FixBuffer);
    }
  
    // Only try to offer default capture if there are no captures excluding this
    // and init captures.
    // [this]: OK.
    // [X = Y]: OK.
    // [&A, &B]: Don't offer.
    // [A, B]: Don't offer.
    if (llvm::any_of(LSI->Captures, [](Capture &C) {
          return !C.isThisCapture() && !C.isInitCapture();
        }))
      return;
  
    // The default capture specifiers, '=' or '&', must appear first in the
    // capture body.
    SourceLocation DefaultInsertLoc =
        LSI->IntroducerRange.getBegin().getLocWithOffset(1);
  
    if (ShouldOfferCopyFix) {
      bool CanDefaultCopyCapture = true;
      // [=, *this] OK since c++17
      // [=, this] OK since c++20
      if (LSI->isCXXThisCaptured() && !Sema.getLangOpts().CPlusPlus20)
        CanDefaultCopyCapture = Sema.getLangOpts().CPlusPlus17
                                    ? LSI->getCXXThisCapture().isCopyCapture()
                                    : false;
      // We can't use default capture by copy if any captures already specified
      // capture by copy.
      if (CanDefaultCopyCapture && llvm::none_of(LSI->Captures, [](Capture &C) {
            return !C.isThisCapture() && !C.isInitCapture() && C.isCopyCapture();
          })) {
        FixBuffer.assign({"=", Separator});
        Sema.Diag(DefaultInsertLoc, diag::note_lambda_default_capture_fixit)
            << /*value*/ 0
            << FixItHint::CreateInsertion(DefaultInsertLoc, FixBuffer);
      }
    }
  
    // We can't use default capture by reference if any captures already specified
    // capture by reference.
    if (llvm::none_of(LSI->Captures, [](Capture &C) {
          return !C.isInitCapture() && C.isReferenceCapture() &&
                 !C.isThisCapture();
        })) {
      FixBuffer.assign({"&", Separator});
      Sema.Diag(DefaultInsertLoc, diag::note_lambda_default_capture_fixit)
          << /*reference*/ 1
          << FixItHint::CreateInsertion(DefaultInsertLoc, FixBuffer);
    }
  }
  
  bool Sema::tryCaptureVariable(
      VarDecl *Var, SourceLocation ExprLoc, TryCaptureKind Kind,
      SourceLocation EllipsisLoc, bool BuildAndDiagnose, QualType &CaptureType,
      QualType &DeclRefType, const unsigned *const FunctionScopeIndexToStopAt) {
    // An init-capture is notionally from the context surrounding its
    // declaration, but its parent DC is the lambda class.
    DeclContext *VarDC = Var->getDeclContext();
    if (Var->isInitCapture())
      VarDC = VarDC->getParent();
  
    DeclContext *DC = CurContext;
    const unsigned MaxFunctionScopesIndex = FunctionScopeIndexToStopAt
        ? *FunctionScopeIndexToStopAt : FunctionScopes.size() - 1;
    // We need to sync up the Declaration Context with the
    // FunctionScopeIndexToStopAt
    if (FunctionScopeIndexToStopAt) {
      unsigned FSIndex = FunctionScopes.size() - 1;
      while (FSIndex != MaxFunctionScopesIndex) {
        DC = getLambdaAwareParentOfDeclContext(DC);
        --FSIndex;
      }
    }
  
  
    // If the variable is declared in the current context, there is no need to
    // capture it.
    if (VarDC == DC) return true;
  
    // Capture global variables if it is required to use private copy of this
    // variable.
    bool IsGlobal = !Var->hasLocalStorage();
    if (IsGlobal &&
        !(LangOpts.OpenMP && isOpenMPCapturedDecl(Var, /*CheckScopeInfo=*/true,
                                                  MaxFunctionScopesIndex)))
      return true;
    Var = Var->getCanonicalDecl();
  
    // Walk up the stack to determine whether we can capture the variable,
    // performing the "simple" checks that don't depend on type. We stop when
    // we've either hit the declared scope of the variable or find an existing
    // capture of that variable.  We start from the innermost capturing-entity
    // (the DC) and ensure that all intervening capturing-entities
    // (blocks/lambdas etc.) between the innermost capturer and the variable`s
    // declcontext can either capture the variable or have already captured
    // the variable.
    CaptureType = Var->getType();
    DeclRefType = CaptureType.getNonReferenceType();
    bool Nested = false;
    bool Explicit = (Kind != TryCapture_Implicit);
    unsigned FunctionScopesIndex = MaxFunctionScopesIndex;
    do {
      // Only block literals, captured statements, and lambda expressions can
      // capture; other scopes don't work.
      DeclContext *ParentDC = getParentOfCapturingContextOrNull(DC, Var,
                                                                ExprLoc,
                                                                BuildAndDiagnose,
                                                                *this);
      // We need to check for the parent *first* because, if we *have*
      // private-captured a global variable, we need to recursively capture it in
      // intermediate blocks, lambdas, etc.
      if (!ParentDC) {
        if (IsGlobal) {
          FunctionScopesIndex = MaxFunctionScopesIndex - 1;
          break;
        }
        return true;
      }
  
      FunctionScopeInfo  *FSI = FunctionScopes[FunctionScopesIndex];
      CapturingScopeInfo *CSI = cast<CapturingScopeInfo>(FSI);
  
  
      // Check whether we've already captured it.
      if (isVariableAlreadyCapturedInScopeInfo(CSI, Var, Nested, CaptureType,
                                               DeclRefType)) {
        CSI->getCapture(Var).markUsed(BuildAndDiagnose);
        break;
      }
      // If we are instantiating a generic lambda call operator body,
      // we do not want to capture new variables.  What was captured
      // during either a lambdas transformation or initial parsing
      // should be used.
      if (isGenericLambdaCallOperatorSpecialization(DC)) {
        if (BuildAndDiagnose) {
          LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(CSI);
          if (LSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_None) {
            Diag(ExprLoc, diag::err_lambda_impcap) << Var;
            Diag(Var->getLocation(), diag::note_previous_decl) << Var;
            Diag(LSI->Lambda->getBeginLoc(), diag::note_lambda_decl);
            buildLambdaCaptureFixit(*this, LSI, Var);
          } else
            diagnoseUncapturableValueReference(*this, ExprLoc, Var);
        }
        return true;
      }
  
      // Try to capture variable-length arrays types.
      if (Var->getType()->isVariablyModifiedType()) {
        // We're going to walk down into the type and look for VLA
        // expressions.
        QualType QTy = Var->getType();
        if (ParmVarDecl *PVD = dyn_cast_or_null<ParmVarDecl>(Var))
          QTy = PVD->getOriginalType();
        captureVariablyModifiedType(Context, QTy, CSI);
      }
  
      if (getLangOpts().OpenMP) {
        if (auto *RSI = dyn_cast<CapturedRegionScopeInfo>(CSI)) {
          // OpenMP private variables should not be captured in outer scope, so
          // just break here. Similarly, global variables that are captured in a
          // target region should not be captured outside the scope of the region.
          if (RSI->CapRegionKind == CR_OpenMP) {
            OpenMPClauseKind IsOpenMPPrivateDecl = isOpenMPPrivateDecl(
                Var, RSI->OpenMPLevel, RSI->OpenMPCaptureLevel);
            // If the variable is private (i.e. not captured) and has variably
            // modified type, we still need to capture the type for correct
            // codegen in all regions, associated with the construct. Currently,
            // it is captured in the innermost captured region only.
            if (IsOpenMPPrivateDecl != OMPC_unknown &&
                Var->getType()->isVariablyModifiedType()) {
              QualType QTy = Var->getType();
              if (ParmVarDecl *PVD = dyn_cast_or_null<ParmVarDecl>(Var))
                QTy = PVD->getOriginalType();
              for (int I = 1, E = getNumberOfConstructScopes(RSI->OpenMPLevel);
                   I < E; ++I) {
                auto *OuterRSI = cast<CapturedRegionScopeInfo>(
                    FunctionScopes[FunctionScopesIndex - I]);
                assert(RSI->OpenMPLevel == OuterRSI->OpenMPLevel &&
                       "Wrong number of captured regions associated with the "
                       "OpenMP construct.");
                captureVariablyModifiedType(Context, QTy, OuterRSI);
              }
            }
            bool IsTargetCap =
                IsOpenMPPrivateDecl != OMPC_private &&
                isOpenMPTargetCapturedDecl(Var, RSI->OpenMPLevel,
                                           RSI->OpenMPCaptureLevel);
            // Do not capture global if it is not privatized in outer regions.
            bool IsGlobalCap =
                IsGlobal && isOpenMPGlobalCapturedDecl(Var, RSI->OpenMPLevel,
                                                       RSI->OpenMPCaptureLevel);
  
            // When we detect target captures we are looking from inside the
            // target region, therefore we need to propagate the capture from the
            // enclosing region. Therefore, the capture is not initially nested.
            if (IsTargetCap)
              adjustOpenMPTargetScopeIndex(FunctionScopesIndex, RSI->OpenMPLevel);
  
            if (IsTargetCap || IsOpenMPPrivateDecl == OMPC_private ||
                (IsGlobal && !IsGlobalCap)) {
              Nested = !IsTargetCap;
              bool HasConst = DeclRefType.isConstQualified();
              DeclRefType = DeclRefType.getUnqualifiedType();
              // Don't lose diagnostics about assignments to const.
              if (HasConst)
                DeclRefType.addConst();
              CaptureType = Context.getLValueReferenceType(DeclRefType);
              break;
            }
          }
        }
      }
      if (CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_None && !Explicit) {
        // No capture-default, and this is not an explicit capture
        // so cannot capture this variable.
        if (BuildAndDiagnose) {
          Diag(ExprLoc, diag::err_lambda_impcap) << Var;
          Diag(Var->getLocation(), diag::note_previous_decl) << Var;
          auto *LSI = cast<LambdaScopeInfo>(CSI);
          if (LSI->Lambda) {
            Diag(LSI->Lambda->getBeginLoc(), diag::note_lambda_decl);
            buildLambdaCaptureFixit(*this, LSI, Var);
          }
          // FIXME: If we error out because an outer lambda can not implicitly
          // capture a variable that an inner lambda explicitly captures, we
          // should have the inner lambda do the explicit capture - because
          // it makes for cleaner diagnostics later.  This would purely be done
          // so that the diagnostic does not misleadingly claim that a variable
          // can not be captured by a lambda implicitly even though it is captured
          // explicitly.  Suggestion:
          //  - create const bool VariableCaptureWasInitiallyExplicit = Explicit
          //    at the function head
          //  - cache the StartingDeclContext - this must be a lambda
          //  - captureInLambda in the innermost lambda the variable.
        }
        return true;
      }
  
      FunctionScopesIndex--;
      DC = ParentDC;
      Explicit = false;
    } while (!VarDC->Equals(DC));
  
    // Walk back down the scope stack, (e.g. from outer lambda to inner lambda)
    // computing the type of the capture at each step, checking type-specific
    // requirements, and adding captures if requested.
    // If the variable had already been captured previously, we start capturing
    // at the lambda nested within that one.
    bool Invalid = false;
    for (unsigned I = ++FunctionScopesIndex, N = MaxFunctionScopesIndex + 1; I != N;
         ++I) {
      CapturingScopeInfo *CSI = cast<CapturingScopeInfo>(FunctionScopes[I]);
  
      // Certain capturing entities (lambdas, blocks etc.) are not allowed to capture
      // certain types of variables (unnamed, variably modified types etc.)
      // so check for eligibility.
      if (!Invalid)
        Invalid =
            !isVariableCapturable(CSI, Var, ExprLoc, BuildAndDiagnose, *this);
  
      // After encountering an error, if we're actually supposed to capture, keep
      // capturing in nested contexts to suppress any follow-on diagnostics.
      if (Invalid && !BuildAndDiagnose)
        return true;
  
      if (BlockScopeInfo *BSI = dyn_cast<BlockScopeInfo>(CSI)) {
        Invalid = !captureInBlock(BSI, Var, ExprLoc, BuildAndDiagnose, CaptureType,
                                 DeclRefType, Nested, *this, Invalid);
        Nested = true;
      } else if (CapturedRegionScopeInfo *RSI = dyn_cast<CapturedRegionScopeInfo>(CSI)) {
        Invalid = !captureInCapturedRegion(
            RSI, Var, ExprLoc, BuildAndDiagnose, CaptureType, DeclRefType, Nested,
            Kind, /*IsTopScope*/ I == N - 1, *this, Invalid);
        Nested = true;
      } else {
        LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(CSI);
        Invalid =
            !captureInLambda(LSI, Var, ExprLoc, BuildAndDiagnose, CaptureType,
                             DeclRefType, Nested, Kind, EllipsisLoc,
                             /*IsTopScope*/ I == N - 1, *this, Invalid);
        Nested = true;
      }
  
      if (Invalid && !BuildAndDiagnose)
        return true;
    }
    return Invalid;
  }
  
  bool Sema::tryCaptureVariable(VarDecl *Var, SourceLocation Loc,
                                TryCaptureKind Kind, SourceLocation EllipsisLoc) {
    QualType CaptureType;
    QualType DeclRefType;
    return tryCaptureVariable(Var, Loc, Kind, EllipsisLoc,
                              /*BuildAndDiagnose=*/true, CaptureType,
                              DeclRefType, nullptr);
  }
  
  bool Sema::NeedToCaptureVariable(VarDecl *Var, SourceLocation Loc) {
    QualType CaptureType;
    QualType DeclRefType;
    return !tryCaptureVariable(Var, Loc, TryCapture_Implicit, SourceLocation(),
                               /*BuildAndDiagnose=*/false, CaptureType,
                               DeclRefType, nullptr);
  }
  
  QualType Sema::getCapturedDeclRefType(VarDecl *Var, SourceLocation Loc) {
    QualType CaptureType;
    QualType DeclRefType;
  
    // Determine whether we can capture this variable.
    if (tryCaptureVariable(Var, Loc, TryCapture_Implicit, SourceLocation(),
                           /*BuildAndDiagnose=*/false, CaptureType,
                           DeclRefType, nullptr))
      return QualType();
  
    return DeclRefType;
  }
  
  namespace {
  // Helper to copy the template arguments from a DeclRefExpr or MemberExpr.
  // The produced TemplateArgumentListInfo* points to data stored within this
  // object, so should only be used in contexts where the pointer will not be
  // used after the CopiedTemplateArgs object is destroyed.
  class CopiedTemplateArgs {
    bool HasArgs;
    TemplateArgumentListInfo TemplateArgStorage;
  public:
    template<typename RefExpr>
    CopiedTemplateArgs(RefExpr *E) : HasArgs(E->hasExplicitTemplateArgs()) {
      if (HasArgs)
        E->copyTemplateArgumentsInto(TemplateArgStorage);
    }
    operator TemplateArgumentListInfo*()
  #ifdef __has_cpp_attribute
  #if __has_cpp_attribute(clang::lifetimebound)
    [[clang::lifetimebound]]
  #endif
  #endif
    {
      return HasArgs ? &TemplateArgStorage : nullptr;
    }
  };
  }
  
  /// Walk the set of potential results of an expression and mark them all as
  /// non-odr-uses if they satisfy the side-conditions of the NonOdrUseReason.
  ///
  /// \return A new expression if we found any potential results, ExprEmpty() if
  ///         not, and ExprError() if we diagnosed an error.
  static ExprResult rebuildPotentialResultsAsNonOdrUsed(Sema &S, Expr *E,
                                                        NonOdrUseReason NOUR) {
    // Per C++11 [basic.def.odr], a variable is odr-used "unless it is
    // an object that satisfies the requirements for appearing in a
    // constant expression (5.19) and the lvalue-to-rvalue conversion (4.1)
    // is immediately applied."  This function handles the lvalue-to-rvalue
    // conversion part.
    //
    // If we encounter a node that claims to be an odr-use but shouldn't be, we
    // transform it into the relevant kind of non-odr-use node and rebuild the
    // tree of nodes leading to it.
    //
    // This is a mini-TreeTransform that only transforms a restricted subset of
    // nodes (and only certain operands of them).
  
    // Rebuild a subexpression.
    auto Rebuild = [&](Expr *Sub) {
      return rebuildPotentialResultsAsNonOdrUsed(S, Sub, NOUR);
    };
  
    // Check whether a potential result satisfies the requirements of NOUR.
    auto IsPotentialResultOdrUsed = [&](NamedDecl *D) {
      // Any entity other than a VarDecl is always odr-used whenever it's named
      // in a potentially-evaluated expression.
      auto *VD = dyn_cast<VarDecl>(D);
      if (!VD)
        return true;
  
      // C++2a [basic.def.odr]p4:
      //   A variable x whose name appears as a potentially-evalauted expression
      //   e is odr-used by e unless
      //   -- x is a reference that is usable in constant expressions, or
      //   -- x is a variable of non-reference type that is usable in constant
      //      expressions and has no mutable subobjects, and e is an element of
      //      the set of potential results of an expression of
      //      non-volatile-qualified non-class type to which the lvalue-to-rvalue
      //      conversion is applied, or
      //   -- x is a variable of non-reference type, and e is an element of the
      //      set of potential results of a discarded-value expression to which
      //      the lvalue-to-rvalue conversion is not applied
      //
      // We check the first bullet and the "potentially-evaluated" condition in
      // BuildDeclRefExpr. We check the type requirements in the second bullet
      // in CheckLValueToRValueConversionOperand below.
      switch (NOUR) {
      case NOUR_None:
      case NOUR_Unevaluated:
        llvm_unreachable("unexpected non-odr-use-reason");
  
      case NOUR_Constant:
        // Constant references were handled when they were built.
        if (VD->getType()->isReferenceType())
          return true;
        if (auto *RD = VD->getType()->getAsCXXRecordDecl())
          if (RD->hasMutableFields())
            return true;
        if (!VD->isUsableInConstantExpressions(S.Context))
          return true;
        break;
  
      case NOUR_Discarded:
        if (VD->getType()->isReferenceType())
          return true;
        break;
      }
      return false;
    };
  
    // Mark that this expression does not constitute an odr-use.
    auto MarkNotOdrUsed = [&] {
      S.MaybeODRUseExprs.remove(E);
      if (LambdaScopeInfo *LSI = S.getCurLambda())
        LSI->markVariableExprAsNonODRUsed(E);
    };
  
    // C++2a [basic.def.odr]p2:
    //   The set of potential results of an expression e is defined as follows:
    switch (E->getStmtClass()) {
    //   -- If e is an id-expression, ...
    case Expr::DeclRefExprClass: {
      auto *DRE = cast<DeclRefExpr>(E);
      if (DRE->isNonOdrUse() || IsPotentialResultOdrUsed(DRE->getDecl()))
        break;
  
      // Rebuild as a non-odr-use DeclRefExpr.
      MarkNotOdrUsed();
      return DeclRefExpr::Create(
          S.Context, DRE->getQualifierLoc(), DRE->getTemplateKeywordLoc(),
          DRE->getDecl(), DRE->refersToEnclosingVariableOrCapture(),
          DRE->getNameInfo(), DRE->getType(), DRE->getValueKind(),
          DRE->getFoundDecl(), CopiedTemplateArgs(DRE), NOUR);
    }
  
    case Expr::FunctionParmPackExprClass: {
      auto *FPPE = cast<FunctionParmPackExpr>(E);
      // If any of the declarations in the pack is odr-used, then the expression
      // as a whole constitutes an odr-use.
      for (VarDecl *D : *FPPE)
        if (IsPotentialResultOdrUsed(D))
          return ExprEmpty();
  
      // FIXME: Rebuild as a non-odr-use FunctionParmPackExpr? In practice,
      // nothing cares about whether we marked this as an odr-use, but it might
      // be useful for non-compiler tools.
      MarkNotOdrUsed();
      break;
    }
  
    //   -- If e is a subscripting operation with an array operand...
    case Expr::ArraySubscriptExprClass: {
      auto *ASE = cast<ArraySubscriptExpr>(E);
      Expr *OldBase = ASE->getBase()->IgnoreImplicit();
      if (!OldBase->getType()->isArrayType())
        break;
      ExprResult Base = Rebuild(OldBase);
      if (!Base.isUsable())
        return Base;
      Expr *LHS = ASE->getBase() == ASE->getLHS() ? Base.get() : ASE->getLHS();
      Expr *RHS = ASE->getBase() == ASE->getRHS() ? Base.get() : ASE->getRHS();
      SourceLocation LBracketLoc = ASE->getBeginLoc(); // FIXME: Not stored.
      return S.ActOnArraySubscriptExpr(nullptr, LHS, LBracketLoc, RHS,
                                       ASE->getRBracketLoc());
    }
  
    case Expr::MemberExprClass: {
      auto *ME = cast<MemberExpr>(E);
      // -- If e is a class member access expression [...] naming a non-static
      //    data member...
      if (isa<FieldDecl>(ME->getMemberDecl())) {
        ExprResult Base = Rebuild(ME->getBase());
        if (!Base.isUsable())
          return Base;
        return MemberExpr::Create(
            S.Context, Base.get(), ME->isArrow(), ME->getOperatorLoc(),
            ME->getQualifierLoc(), ME->getTemplateKeywordLoc(),
            ME->getMemberDecl(), ME->getFoundDecl(), ME->getMemberNameInfo(),
            CopiedTemplateArgs(ME), ME->getType(), ME->getValueKind(),
            ME->getObjectKind(), ME->isNonOdrUse());
      }
  
      if (ME->getMemberDecl()->isCXXInstanceMember())
        break;
  
      // -- If e is a class member access expression naming a static data member,
      //    ...
      if (ME->isNonOdrUse() || IsPotentialResultOdrUsed(ME->getMemberDecl()))
        break;
  
      // Rebuild as a non-odr-use MemberExpr.
      MarkNotOdrUsed();
      return MemberExpr::Create(
          S.Context, ME->getBase(), ME->isArrow(), ME->getOperatorLoc(),
          ME->getQualifierLoc(), ME->getTemplateKeywordLoc(), ME->getMemberDecl(),
          ME->getFoundDecl(), ME->getMemberNameInfo(), CopiedTemplateArgs(ME),
          ME->getType(), ME->getValueKind(), ME->getObjectKind(), NOUR);
    }
  
    case Expr::BinaryOperatorClass: {
      auto *BO = cast<BinaryOperator>(E);
      Expr *LHS = BO->getLHS();
      Expr *RHS = BO->getRHS();
      // -- If e is a pointer-to-member expression of the form e1 .* e2 ...
      if (BO->getOpcode() == BO_PtrMemD) {
        ExprResult Sub = Rebuild(LHS);
        if (!Sub.isUsable())
          return Sub;
        LHS = Sub.get();
      //   -- If e is a comma expression, ...
      } else if (BO->getOpcode() == BO_Comma) {
        ExprResult Sub = Rebuild(RHS);
        if (!Sub.isUsable())
          return Sub;
        RHS = Sub.get();
      } else {
        break;
      }
      return S.BuildBinOp(nullptr, BO->getOperatorLoc(), BO->getOpcode(),
                          LHS, RHS);
    }
  
    //   -- If e has the form (e1)...
    case Expr::ParenExprClass: {
      auto *PE = cast<ParenExpr>(E);
      ExprResult Sub = Rebuild(PE->getSubExpr());
      if (!Sub.isUsable())
        return Sub;
      return S.ActOnParenExpr(PE->getLParen(), PE->getRParen(), Sub.get());
    }
  
    //   -- If e is a glvalue conditional expression, ...
    // We don't apply this to a binary conditional operator. FIXME: Should we?
    case Expr::ConditionalOperatorClass: {
      auto *CO = cast<ConditionalOperator>(E);
      ExprResult LHS = Rebuild(CO->getLHS());
      if (LHS.isInvalid())
        return ExprError();
      ExprResult RHS = Rebuild(CO->getRHS());
      if (RHS.isInvalid())
        return ExprError();
      if (!LHS.isUsable() && !RHS.isUsable())
        return ExprEmpty();
      if (!LHS.isUsable())
        LHS = CO->getLHS();
      if (!RHS.isUsable())
        RHS = CO->getRHS();
      return S.ActOnConditionalOp(CO->getQuestionLoc(), CO->getColonLoc(),
                                  CO->getCond(), LHS.get(), RHS.get());
    }
  
    // [Clang extension]
    //   -- If e has the form __extension__ e1...
    case Expr::UnaryOperatorClass: {
      auto *UO = cast<UnaryOperator>(E);
      if (UO->getOpcode() != UO_Extension)
        break;
      ExprResult Sub = Rebuild(UO->getSubExpr());
      if (!Sub.isUsable())
        return Sub;
      return S.BuildUnaryOp(nullptr, UO->getOperatorLoc(), UO_Extension,
                            Sub.get());
    }
  
    // [Clang extension]
    //   -- If e has the form _Generic(...), the set of potential results is the
    //      union of the sets of potential results of the associated expressions.
    case Expr::GenericSelectionExprClass: {
      auto *GSE = cast<GenericSelectionExpr>(E);
  
      SmallVector<Expr *, 4> AssocExprs;
      bool AnyChanged = false;
      for (Expr *OrigAssocExpr : GSE->getAssocExprs()) {
        ExprResult AssocExpr = Rebuild(OrigAssocExpr);
        if (AssocExpr.isInvalid())
          return ExprError();
        if (AssocExpr.isUsable()) {
          AssocExprs.push_back(AssocExpr.get());
          AnyChanged = true;
        } else {
          AssocExprs.push_back(OrigAssocExpr);
        }
      }
  
      return AnyChanged ? S.CreateGenericSelectionExpr(
                              GSE->getGenericLoc(), GSE->getDefaultLoc(),
                              GSE->getRParenLoc(), GSE->getControllingExpr(),
                              GSE->getAssocTypeSourceInfos(), AssocExprs)
                        : ExprEmpty();
    }
  
    // [Clang extension]
    //   -- If e has the form __builtin_choose_expr(...), the set of potential
    //      results is the union of the sets of potential results of the
    //      second and third subexpressions.
    case Expr::ChooseExprClass: {
      auto *CE = cast<ChooseExpr>(E);
  
      ExprResult LHS = Rebuild(CE->getLHS());
      if (LHS.isInvalid())
        return ExprError();
  
      ExprResult RHS = Rebuild(CE->getLHS());
      if (RHS.isInvalid())
        return ExprError();
  
      if (!LHS.get() && !RHS.get())
        return ExprEmpty();
      if (!LHS.isUsable())
        LHS = CE->getLHS();
      if (!RHS.isUsable())
        RHS = CE->getRHS();
  
      return S.ActOnChooseExpr(CE->getBuiltinLoc(), CE->getCond(), LHS.get(),
                               RHS.get(), CE->getRParenLoc());
    }
  
    // Step through non-syntactic nodes.
    case Expr::ConstantExprClass: {
      auto *CE = cast<ConstantExpr>(E);
      ExprResult Sub = Rebuild(CE->getSubExpr());
      if (!Sub.isUsable())
        return Sub;
      return ConstantExpr::Create(S.Context, Sub.get());
    }
  
    // We could mostly rely on the recursive rebuilding to rebuild implicit
    // casts, but not at the top level, so rebuild them here.
    case Expr::ImplicitCastExprClass: {
      auto *ICE = cast<ImplicitCastExpr>(E);
      // Only step through the narrow set of cast kinds we expect to encounter.
      // Anything else suggests we've left the region in which potential results
      // can be found.
      switch (ICE->getCastKind()) {
      case CK_NoOp:
      case CK_DerivedToBase:
      case CK_UncheckedDerivedToBase: {
        ExprResult Sub = Rebuild(ICE->getSubExpr());
        if (!Sub.isUsable())
          return Sub;
        CXXCastPath Path(ICE->path());
        return S.ImpCastExprToType(Sub.get(), ICE->getType(), ICE->getCastKind(),
                                   ICE->getValueKind(), &Path);
      }
  
      default:
        break;
      }
      break;
    }
  
    default:
      break;
    }
  
    // Can't traverse through this node. Nothing to do.
    return ExprEmpty();
  }
  
  ExprResult Sema::CheckLValueToRValueConversionOperand(Expr *E) {
    // Check whether the operand is or contains an object of non-trivial C union
    // type.
    if (E->getType().isVolatileQualified() &&
        (E->getType().hasNonTrivialToPrimitiveDestructCUnion() ||
         E->getType().hasNonTrivialToPrimitiveCopyCUnion()))
      checkNonTrivialCUnion(E->getType(), E->getExprLoc(),
                            Sema::NTCUC_LValueToRValueVolatile,
                            NTCUK_Destruct|NTCUK_Copy);
  
    // C++2a [basic.def.odr]p4:
    //   [...] an expression of non-volatile-qualified non-class type to which
    //   the lvalue-to-rvalue conversion is applied [...]
    if (E->getType().isVolatileQualified() || E->getType()->getAs<RecordType>())
      return E;
  
    ExprResult Result =
        rebuildPotentialResultsAsNonOdrUsed(*this, E, NOUR_Constant);
    if (Result.isInvalid())
      return ExprError();
    return Result.get() ? Result : E;
  }
  
  ExprResult Sema::ActOnConstantExpression(ExprResult Res) {
    Res = CorrectDelayedTyposInExpr(Res);
  
    if (!Res.isUsable())
      return Res;
  
    // If a constant-expression is a reference to a variable where we delay
    // deciding whether it is an odr-use, just assume we will apply the
    // lvalue-to-rvalue conversion.  In the one case where this doesn't happen
    // (a non-type template argument), we have special handling anyway.
    return CheckLValueToRValueConversionOperand(Res.get());
  }
  
  void Sema::CleanupVarDeclMarking() {
    // Iterate through a local copy in case MarkVarDeclODRUsed makes a recursive
    // call.
    MaybeODRUseExprSet LocalMaybeODRUseExprs;
    std::swap(LocalMaybeODRUseExprs, MaybeODRUseExprs);
  
    for (Expr *E : LocalMaybeODRUseExprs) {
      if (auto *DRE = dyn_cast<DeclRefExpr>(E)) {
        MarkVarDeclODRUsed(cast<VarDecl>(DRE->getDecl()),
                           DRE->getLocation(), *this);
      } else if (auto *ME = dyn_cast<MemberExpr>(E)) {
        MarkVarDeclODRUsed(cast<VarDecl>(ME->getMemberDecl()), ME->getMemberLoc(),
                           *this);
      } else if (auto *FP = dyn_cast<FunctionParmPackExpr>(E)) {
        for (VarDecl *VD : *FP)
          MarkVarDeclODRUsed(VD, FP->getParameterPackLocation(), *this);
      } else {
        llvm_unreachable("Unexpected expression");
      }
    }
  
    assert(MaybeODRUseExprs.empty() &&
           "MarkVarDeclODRUsed failed to cleanup MaybeODRUseExprs?");
  }
  
  static void DoMarkVarDeclReferenced(
      Sema &SemaRef, SourceLocation Loc, VarDecl *Var, Expr *E,
      llvm::DenseMap<const VarDecl *, int> &RefsMinusAssignments) {
    assert((!E || isa<DeclRefExpr>(E) || isa<MemberExpr>(E) ||
            isa<FunctionParmPackExpr>(E)) &&
           "Invalid Expr argument to DoMarkVarDeclReferenced");
    Var->setReferenced();
  
    if (Var->isInvalidDecl())
      return;
  
    auto *MSI = Var->getMemberSpecializationInfo();
    TemplateSpecializationKind TSK = MSI ? MSI->getTemplateSpecializationKind()
                                         : Var->getTemplateSpecializationKind();
  
    OdrUseContext OdrUse = isOdrUseContext(SemaRef);
    bool UsableInConstantExpr =
        Var->mightBeUsableInConstantExpressions(SemaRef.Context);
  
    if (Var->isLocalVarDeclOrParm() && !Var->hasExternalStorage()) {
      RefsMinusAssignments.insert({Var, 0}).first->getSecond()++;
    }
  
    // C++20 [expr.const]p12:
    //   A variable [...] is needed for constant evaluation if it is [...] a
    //   variable whose name appears as a potentially constant evaluated
    //   expression that is either a contexpr variable or is of non-volatile
    //   const-qualified integral type or of reference type
    bool NeededForConstantEvaluation =
        isPotentiallyConstantEvaluatedContext(SemaRef) && UsableInConstantExpr;
  
    bool NeedDefinition =
        OdrUse == OdrUseContext::Used || NeededForConstantEvaluation;
  
    assert(!isa<VarTemplatePartialSpecializationDecl>(Var) &&
           "Can't instantiate a partial template specialization.");
  
    // If this might be a member specialization of a static data member, check
    // the specialization is visible. We already did the checks for variable
    // template specializations when we created them.
    if (NeedDefinition && TSK != TSK_Undeclared &&
        !isa<VarTemplateSpecializationDecl>(Var))
      SemaRef.checkSpecializationVisibility(Loc, Var);
  
    // Perform implicit instantiation of static data members, static data member
    // templates of class templates, and variable template specializations. Delay
    // instantiations of variable templates, except for those that could be used
    // in a constant expression.
    if (NeedDefinition && isTemplateInstantiation(TSK)) {
      // Per C++17 [temp.explicit]p10, we may instantiate despite an explicit
      // instantiation declaration if a variable is usable in a constant
      // expression (among other cases).
      bool TryInstantiating =
          TSK == TSK_ImplicitInstantiation ||
          (TSK == TSK_ExplicitInstantiationDeclaration && UsableInConstantExpr);
  
      if (TryInstantiating) {
        SourceLocation PointOfInstantiation =
            MSI ? MSI->getPointOfInstantiation() : Var->getPointOfInstantiation();
        bool FirstInstantiation = PointOfInstantiation.isInvalid();
        if (FirstInstantiation) {
          PointOfInstantiation = Loc;
          if (MSI)
            MSI->setPointOfInstantiation(PointOfInstantiation);
            // FIXME: Notify listener.
          else
            Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
        }
  
        if (UsableInConstantExpr) {
          // Do not defer instantiations of variables that could be used in a
          // constant expression.
          SemaRef.runWithSufficientStackSpace(PointOfInstantiation, [&] {
            SemaRef.InstantiateVariableDefinition(PointOfInstantiation, Var);
          });
  
          // Re-set the member to trigger a recomputation of the dependence bits
          // for the expression.
          if (auto *DRE = dyn_cast_or_null<DeclRefExpr>(E))
            DRE->setDecl(DRE->getDecl());
          else if (auto *ME = dyn_cast_or_null<MemberExpr>(E))
            ME->setMemberDecl(ME->getMemberDecl());
        } else if (FirstInstantiation ||
                   isa<VarTemplateSpecializationDecl>(Var)) {
          // FIXME: For a specialization of a variable template, we don't
          // distinguish between "declaration and type implicitly instantiated"
          // and "implicit instantiation of definition requested", so we have
          // no direct way to avoid enqueueing the pending instantiation
          // multiple times.
          SemaRef.PendingInstantiations
              .push_back(std::make_pair(Var, PointOfInstantiation));
        }
      }
    }
  
    // C++2a [basic.def.odr]p4:
    //   A variable x whose name appears as a potentially-evaluated expression e
    //   is odr-used by e unless
    //   -- x is a reference that is usable in constant expressions
    //   -- x is a variable of non-reference type that is usable in constant
    //      expressions and has no mutable subobjects [FIXME], and e is an
    //      element of the set of potential results of an expression of
    //      non-volatile-qualified non-class type to which the lvalue-to-rvalue
    //      conversion is applied
    //   -- x is a variable of non-reference type, and e is an element of the set
    //      of potential results of a discarded-value expression to which the
    //      lvalue-to-rvalue conversion is not applied [FIXME]
    //
    // We check the first part of the second bullet here, and
    // Sema::CheckLValueToRValueConversionOperand deals with the second part.
    // FIXME: To get the third bullet right, we need to delay this even for
    // variables that are not usable in constant expressions.
  
    // If we already know this isn't an odr-use, there's nothing more to do.
    if (DeclRefExpr *DRE = dyn_cast_or_null<DeclRefExpr>(E))
      if (DRE->isNonOdrUse())
        return;
    if (MemberExpr *ME = dyn_cast_or_null<MemberExpr>(E))
      if (ME->isNonOdrUse())
        return;
  
    switch (OdrUse) {
    case OdrUseContext::None:
      assert((!E || isa<FunctionParmPackExpr>(E)) &&
             "missing non-odr-use marking for unevaluated decl ref");
      break;
  
    case OdrUseContext::FormallyOdrUsed:
      // FIXME: Ignoring formal odr-uses results in incorrect lambda capture
      // behavior.
      break;
  
    case OdrUseContext::Used:
      // If we might later find that this expression isn't actually an odr-use,
      // delay the marking.
      if (E && Var->isUsableInConstantExpressions(SemaRef.Context))
        SemaRef.MaybeODRUseExprs.insert(E);
      else
        MarkVarDeclODRUsed(Var, Loc, SemaRef);
      break;
  
    case OdrUseContext::Dependent:
      // If this is a dependent context, we don't need to mark variables as
      // odr-used, but we may still need to track them for lambda capture.
      // FIXME: Do we also need to do this inside dependent typeid expressions
      // (which are modeled as unevaluated at this point)?
      const bool RefersToEnclosingScope =
          (SemaRef.CurContext != Var->getDeclContext() &&
           Var->getDeclContext()->isFunctionOrMethod() && Var->hasLocalStorage());
      if (RefersToEnclosingScope) {
        LambdaScopeInfo *const LSI =
            SemaRef.getCurLambda(/*IgnoreNonLambdaCapturingScope=*/true);
        if (LSI && (!LSI->CallOperator ||
                    !LSI->CallOperator->Encloses(Var->getDeclContext()))) {
          // If a variable could potentially be odr-used, defer marking it so
          // until we finish analyzing the full expression for any
          // lvalue-to-rvalue
          // or discarded value conversions that would obviate odr-use.
          // Add it to the list of potential captures that will be analyzed
          // later (ActOnFinishFullExpr) for eventual capture and odr-use marking
          // unless the variable is a reference that was initialized by a constant
          // expression (this will never need to be captured or odr-used).
          //
          // FIXME: We can simplify this a lot after implementing P0588R1.
          assert(E && "Capture variable should be used in an expression.");
          if (!Var->getType()->isReferenceType() ||
              !Var->isUsableInConstantExpressions(SemaRef.Context))
            LSI->addPotentialCapture(E->IgnoreParens());
        }
      }
      break;
    }
  }
  
  /// Mark a variable referenced, and check whether it is odr-used
  /// (C++ [basic.def.odr]p2, C99 6.9p3).  Note that this should not be
  /// used directly for normal expressions referring to VarDecl.
  void Sema::MarkVariableReferenced(SourceLocation Loc, VarDecl *Var) {
    DoMarkVarDeclReferenced(*this, Loc, Var, nullptr, RefsMinusAssignments);
  }
  
  static void
  MarkExprReferenced(Sema &SemaRef, SourceLocation Loc, Decl *D, Expr *E,
                     bool MightBeOdrUse,
                     llvm::DenseMap<const VarDecl *, int> &RefsMinusAssignments) {
    if (SemaRef.isInOpenMPDeclareTargetContext())
      SemaRef.checkDeclIsAllowedInOpenMPTarget(E, D);
  
    if (VarDecl *Var = dyn_cast<VarDecl>(D)) {
      DoMarkVarDeclReferenced(SemaRef, Loc, Var, E, RefsMinusAssignments);
      return;
    }
  
    SemaRef.MarkAnyDeclReferenced(Loc, D, MightBeOdrUse);
  
    // If this is a call to a method via a cast, also mark the method in the
    // derived class used in case codegen can devirtualize the call.
    const MemberExpr *ME = dyn_cast<MemberExpr>(E);
    if (!ME)
      return;
    CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(ME->getMemberDecl());
    if (!MD)
      return;
    // Only attempt to devirtualize if this is truly a virtual call.
    bool IsVirtualCall = MD->isVirtual() &&
                            ME->performsVirtualDispatch(SemaRef.getLangOpts());
    if (!IsVirtualCall)
      return;
  
    // If it's possible to devirtualize the call, mark the called function
    // referenced.
    CXXMethodDecl *DM = MD->getDevirtualizedMethod(
        ME->getBase(), SemaRef.getLangOpts().AppleKext);
    if (DM)
      SemaRef.MarkAnyDeclReferenced(Loc, DM, MightBeOdrUse);
  }
  
  /// Perform reference-marking and odr-use handling for a DeclRefExpr.
  ///
  /// Note, this may change the dependence of the DeclRefExpr, and so needs to be
  /// handled with care if the DeclRefExpr is not newly-created.
  void Sema::MarkDeclRefReferenced(DeclRefExpr *E, const Expr *Base) {
    // TODO: update this with DR# once a defect report is filed.
    // C++11 defect. The address of a pure member should not be an ODR use, even
    // if it's a qualified reference.
    bool OdrUse = true;
    if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(E->getDecl()))
      if (Method->isVirtual() &&
          !Method->getDevirtualizedMethod(Base, getLangOpts().AppleKext))
        OdrUse = false;
  
    if (auto *FD = dyn_cast<FunctionDecl>(E->getDecl()))
      if (!isUnevaluatedContext() && !isConstantEvaluated() &&
          FD->isConsteval() && !RebuildingImmediateInvocation)
        ExprEvalContexts.back().ReferenceToConsteval.insert(E);
    MarkExprReferenced(*this, E->getLocation(), E->getDecl(), E, OdrUse,
                       RefsMinusAssignments);
  }
  
  /// Perform reference-marking and odr-use handling for a MemberExpr.
  void Sema::MarkMemberReferenced(MemberExpr *E) {
    // C++11 [basic.def.odr]p2:
    //   A non-overloaded function whose name appears as a potentially-evaluated
    //   expression or a member of a set of candidate functions, if selected by
    //   overload resolution when referred to from a potentially-evaluated
    //   expression, is odr-used, unless it is a pure virtual function and its
    //   name is not explicitly qualified.
    bool MightBeOdrUse = true;
    if (E->performsVirtualDispatch(getLangOpts())) {
      if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(E->getMemberDecl()))
        if (Method->isPure())
          MightBeOdrUse = false;
    }
    SourceLocation Loc =
        E->getMemberLoc().isValid() ? E->getMemberLoc() : E->getBeginLoc();
    MarkExprReferenced(*this, Loc, E->getMemberDecl(), E, MightBeOdrUse,
                       RefsMinusAssignments);
  }
  
  /// Perform reference-marking and odr-use handling for a FunctionParmPackExpr.
  void Sema::MarkFunctionParmPackReferenced(FunctionParmPackExpr *E) {
    for (VarDecl *VD : *E)
      MarkExprReferenced(*this, E->getParameterPackLocation(), VD, E, true,
                         RefsMinusAssignments);
  }
  
  /// Perform marking for a reference to an arbitrary declaration.  It
  /// marks the declaration referenced, and performs odr-use checking for
  /// functions and variables. This method should not be used when building a
  /// normal expression which refers to a variable.
  void Sema::MarkAnyDeclReferenced(SourceLocation Loc, Decl *D,
                                   bool MightBeOdrUse) {
    if (MightBeOdrUse) {
      if (auto *VD = dyn_cast<VarDecl>(D)) {
        MarkVariableReferenced(Loc, VD);
        return;
      }
    }
    if (auto *FD = dyn_cast<FunctionDecl>(D)) {
      MarkFunctionReferenced(Loc, FD, MightBeOdrUse);
      return;
    }
    D->setReferenced();
  }
  
  namespace {
    // Mark all of the declarations used by a type as referenced.
    // FIXME: Not fully implemented yet! We need to have a better understanding
    // of when we're entering a context we should not recurse into.
    // FIXME: This is and EvaluatedExprMarker are more-or-less equivalent to
    // TreeTransforms rebuilding the type in a new context. Rather than
    // duplicating the TreeTransform logic, we should consider reusing it here.
    // Currently that causes problems when rebuilding LambdaExprs.
    class MarkReferencedDecls : public RecursiveASTVisitor<MarkReferencedDecls> {
      Sema &S;
      SourceLocation Loc;
  
    public:
      typedef RecursiveASTVisitor<MarkReferencedDecls> Inherited;
  
      MarkReferencedDecls(Sema &S, SourceLocation Loc) : S(S), Loc(Loc) { }
  
      bool TraverseTemplateArgument(const TemplateArgument &Arg);
    };
  }
  
  bool MarkReferencedDecls::TraverseTemplateArgument(
      const TemplateArgument &Arg) {
    {
      // A non-type template argument is a constant-evaluated context.
      EnterExpressionEvaluationContext Evaluated(
          S, Sema::ExpressionEvaluationContext::ConstantEvaluated);
      if (Arg.getKind() == TemplateArgument::Declaration) {
        if (Decl *D = Arg.getAsDecl())
          S.MarkAnyDeclReferenced(Loc, D, true);
      } else if (Arg.getKind() == TemplateArgument::Expression) {
        S.MarkDeclarationsReferencedInExpr(Arg.getAsExpr(), false);
      }
    }
  
    return Inherited::TraverseTemplateArgument(Arg);
  }
  
  void Sema::MarkDeclarationsReferencedInType(SourceLocation Loc, QualType T) {
    MarkReferencedDecls Marker(*this, Loc);
    Marker.TraverseType(T);
  }
  
  namespace {
  /// Helper class that marks all of the declarations referenced by
  /// potentially-evaluated subexpressions as "referenced".
  class EvaluatedExprMarker : public UsedDeclVisitor<EvaluatedExprMarker> {
  public:
    typedef UsedDeclVisitor<EvaluatedExprMarker> Inherited;
    bool SkipLocalVariables;
    ArrayRef<const Expr *> StopAt;
  
    EvaluatedExprMarker(Sema &S, bool SkipLocalVariables,
                        ArrayRef<const Expr *> StopAt)
        : Inherited(S), SkipLocalVariables(SkipLocalVariables), StopAt(StopAt) {}
  
    void visitUsedDecl(SourceLocation Loc, Decl *D) {
      S.MarkFunctionReferenced(Loc, cast<FunctionDecl>(D));
    }
  
    void Visit(Expr *E) {
      if (std::find(StopAt.begin(), StopAt.end(), E) != StopAt.end())
        return;
      Inherited::Visit(E);
    }
  
    void VisitDeclRefExpr(DeclRefExpr *E) {
      // If we were asked not to visit local variables, don't.
      if (SkipLocalVariables) {
        if (VarDecl *VD = dyn_cast<VarDecl>(E->getDecl()))
          if (VD->hasLocalStorage())
            return;
      }
  
      // FIXME: This can trigger the instantiation of the initializer of a
      // variable, which can cause the expression to become value-dependent
      // or error-dependent. Do we need to propagate the new dependence bits?
      S.MarkDeclRefReferenced(E);
    }
  
    void VisitMemberExpr(MemberExpr *E) {
      S.MarkMemberReferenced(E);
      Visit(E->getBase());
    }
  };
  } // namespace
  
  /// Mark any declarations that appear within this expression or any
  /// potentially-evaluated subexpressions as "referenced".
  ///
  /// \param SkipLocalVariables If true, don't mark local variables as
  /// 'referenced'.
  /// \param StopAt Subexpressions that we shouldn't recurse into.
  void Sema::MarkDeclarationsReferencedInExpr(Expr *E,
                                              bool SkipLocalVariables,
                                              ArrayRef<const Expr*> StopAt) {
    EvaluatedExprMarker(*this, SkipLocalVariables, StopAt).Visit(E);
  }
  
  /// Emit a diagnostic when statements are reachable.
  /// FIXME: check for reachability even in expressions for which we don't build a
  ///        CFG (eg, in the initializer of a global or in a constant expression).
  ///        For example,
  ///        namespace { auto *p = new double[3][false ? (1, 2) : 3]; }
  bool Sema::DiagIfReachable(SourceLocation Loc, ArrayRef<const Stmt *> Stmts,
                             const PartialDiagnostic &PD) {
    if (!Stmts.empty() && getCurFunctionOrMethodDecl()) {
      if (!FunctionScopes.empty())
        FunctionScopes.back()->PossiblyUnreachableDiags.push_back(
            sema::PossiblyUnreachableDiag(PD, Loc, Stmts));
      return true;
    }
  
    // The initializer of a constexpr variable or of the first declaration of a
    // static data member is not syntactically a constant evaluated constant,
    // but nonetheless is always required to be a constant expression, so we
    // can skip diagnosing.
    // FIXME: Using the mangling context here is a hack.
    if (auto *VD = dyn_cast_or_null<VarDecl>(
            ExprEvalContexts.back().ManglingContextDecl)) {
      if (VD->isConstexpr() ||
          (VD->isStaticDataMember() && VD->isFirstDecl() && !VD->isInline()))
        return false;
      // FIXME: For any other kind of variable, we should build a CFG for its
      // initializer and check whether the context in question is reachable.
    }
  
    Diag(Loc, PD);
    return true;
  }
  
  /// Emit a diagnostic that describes an effect on the run-time behavior
  /// of the program being compiled.
  ///
  /// This routine emits the given diagnostic when the code currently being
  /// type-checked is "potentially evaluated", meaning that there is a
  /// possibility that the code will actually be executable. Code in sizeof()
  /// expressions, code used only during overload resolution, etc., are not
  /// potentially evaluated. This routine will suppress such diagnostics or,
  /// in the absolutely nutty case of potentially potentially evaluated
  /// expressions (C++ typeid), queue the diagnostic to potentially emit it
  /// later.
  ///
  /// This routine should be used for all diagnostics that describe the run-time
  /// behavior of a program, such as passing a non-POD value through an ellipsis.
  /// Failure to do so will likely result in spurious diagnostics or failures
  /// during overload resolution or within sizeof/alignof/typeof/typeid.
  bool Sema::DiagRuntimeBehavior(SourceLocation Loc, ArrayRef<const Stmt*> Stmts,
                                 const PartialDiagnostic &PD) {
  
    if (ExprEvalContexts.back().isDiscardedStatementContext())
      return false;
  
    switch (ExprEvalContexts.back().Context) {
    case ExpressionEvaluationContext::Unevaluated:
    case ExpressionEvaluationContext::UnevaluatedList:
    case ExpressionEvaluationContext::UnevaluatedAbstract:
    case ExpressionEvaluationContext::DiscardedStatement:
      // The argument will never be evaluated, so don't complain.
      break;
  
    case ExpressionEvaluationContext::ConstantEvaluated:
    case ExpressionEvaluationContext::ImmediateFunctionContext:
      // Relevant diagnostics should be produced by constant evaluation.
      break;
  
    case ExpressionEvaluationContext::PotentiallyEvaluated:
    case ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
      return DiagIfReachable(Loc, Stmts, PD);
    }
  
    return false;
  }
  
  bool Sema::DiagRuntimeBehavior(SourceLocation Loc, const Stmt *Statement,
                                 const PartialDiagnostic &PD) {
    return DiagRuntimeBehavior(
        Loc, Statement ? llvm::makeArrayRef(Statement) : llvm::None, PD);
  }
  
  bool Sema::CheckCallReturnType(QualType ReturnType, SourceLocation Loc,
                                 CallExpr *CE, FunctionDecl *FD) {
    if (ReturnType->isVoidType() || !ReturnType->isIncompleteType())
      return false;
  
    // If we're inside a decltype's expression, don't check for a valid return
    // type or construct temporaries until we know whether this is the last call.
    if (ExprEvalContexts.back().ExprContext ==
        ExpressionEvaluationContextRecord::EK_Decltype) {
      ExprEvalContexts.back().DelayedDecltypeCalls.push_back(CE);
      return false;
    }
  
    class CallReturnIncompleteDiagnoser : public TypeDiagnoser {
      FunctionDecl *FD;
      CallExpr *CE;
  
    public:
      CallReturnIncompleteDiagnoser(FunctionDecl *FD, CallExpr *CE)
        : FD(FD), CE(CE) { }
  
      void diagnose(Sema &S, SourceLocation Loc, QualType T) override {
        if (!FD) {
          S.Diag(Loc, diag::err_call_incomplete_return)
            << T << CE->getSourceRange();
          return;
        }
  
        S.Diag(Loc, diag::err_call_function_incomplete_return)
            << CE->getSourceRange() << FD << T;
        S.Diag(FD->getLocation(), diag::note_entity_declared_at)
            << FD->getDeclName();
      }
    } Diagnoser(FD, CE);
  
    if (RequireCompleteType(Loc, ReturnType, Diagnoser))
      return true;
  
    return false;
  }
  
  // Diagnose the s/=/==/ and s/\|=/!=/ typos. Note that adding parentheses
  // will prevent this condition from triggering, which is what we want.
  void Sema::DiagnoseAssignmentAsCondition(Expr *E) {
    SourceLocation Loc;
  
    unsigned diagnostic = diag::warn_condition_is_assignment;
    bool IsOrAssign = false;
  
    if (BinaryOperator *Op = dyn_cast<BinaryOperator>(E)) {
      if (Op->getOpcode() != BO_Assign && Op->getOpcode() != BO_OrAssign)
        return;
  
      IsOrAssign = Op->getOpcode() == BO_OrAssign;
  
      // Greylist some idioms by putting them into a warning subcategory.
      if (ObjCMessageExpr *ME
            = dyn_cast<ObjCMessageExpr>(Op->getRHS()->IgnoreParenCasts())) {
        Selector Sel = ME->getSelector();
  
        // self = [<foo> init...]
        if (isSelfExpr(Op->getLHS()) && ME->getMethodFamily() == OMF_init)
          diagnostic = diag::warn_condition_is_idiomatic_assignment;
  
        // <foo> = [<bar> nextObject]
        else if (Sel.isUnarySelector() && Sel.getNameForSlot(0) == "nextObject")
          diagnostic = diag::warn_condition_is_idiomatic_assignment;
      }
  
      Loc = Op->getOperatorLoc();
    } else if (CXXOperatorCallExpr *Op = dyn_cast<CXXOperatorCallExpr>(E)) {
      if (Op->getOperator() != OO_Equal && Op->getOperator() != OO_PipeEqual)
        return;
  
      IsOrAssign = Op->getOperator() == OO_PipeEqual;
      Loc = Op->getOperatorLoc();
    } else if (PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(E))
      return DiagnoseAssignmentAsCondition(POE->getSyntacticForm());
    else {
      // Not an assignment.
      return;
    }
  
    Diag(Loc, diagnostic) << E->getSourceRange();
  
    SourceLocation Open = E->getBeginLoc();
    SourceLocation Close = getLocForEndOfToken(E->getSourceRange().getEnd());
    Diag(Loc, diag::note_condition_assign_silence)
          << FixItHint::CreateInsertion(Open, "(")
          << FixItHint::CreateInsertion(Close, ")");
  
    if (IsOrAssign)
      Diag(Loc, diag::note_condition_or_assign_to_comparison)
        << FixItHint::CreateReplacement(Loc, "!=");
    else
      Diag(Loc, diag::note_condition_assign_to_comparison)
        << FixItHint::CreateReplacement(Loc, "==");
  }
  
  /// Redundant parentheses over an equality comparison can indicate
  /// that the user intended an assignment used as condition.
  void Sema::DiagnoseEqualityWithExtraParens(ParenExpr *ParenE) {
    // Don't warn if the parens came from a macro.
    SourceLocation parenLoc = ParenE->getBeginLoc();
    if (parenLoc.isInvalid() || parenLoc.isMacroID())
      return;
    // Don't warn for dependent expressions.
    if (ParenE->isTypeDependent())
      return;
  
    Expr *E = ParenE->IgnoreParens();
  
    if (BinaryOperator *opE = dyn_cast<BinaryOperator>(E))
      if (opE->getOpcode() == BO_EQ &&
          opE->getLHS()->IgnoreParenImpCasts()->isModifiableLvalue(Context)
                                                             == Expr::MLV_Valid) {
        SourceLocation Loc = opE->getOperatorLoc();
  
        Diag(Loc, diag::warn_equality_with_extra_parens) << E->getSourceRange();
        SourceRange ParenERange = ParenE->getSourceRange();
        Diag(Loc, diag::note_equality_comparison_silence)
          << FixItHint::CreateRemoval(ParenERange.getBegin())
          << FixItHint::CreateRemoval(ParenERange.getEnd());
        Diag(Loc, diag::note_equality_comparison_to_assign)
          << FixItHint::CreateReplacement(Loc, "=");
      }
  }
  
  ExprResult Sema::CheckBooleanCondition(SourceLocation Loc, Expr *E,
                                         bool IsConstexpr) {
    DiagnoseAssignmentAsCondition(E);
    if (ParenExpr *parenE = dyn_cast<ParenExpr>(E))
      DiagnoseEqualityWithExtraParens(parenE);
  
    ExprResult result = CheckPlaceholderExpr(E);
    if (result.isInvalid()) return ExprError();
    E = result.get();
  
    if (!E->isTypeDependent()) {
      if (getLangOpts().CPlusPlus)
        return CheckCXXBooleanCondition(E, IsConstexpr); // C++ 6.4p4
  
      ExprResult ERes = DefaultFunctionArrayLvalueConversion(E);
      if (ERes.isInvalid())
        return ExprError();
      E = ERes.get();
  
      QualType T = E->getType();
      if (!T->isScalarType()) { // C99 6.8.4.1p1
        Diag(Loc, diag::err_typecheck_statement_requires_scalar)
          << T << E->getSourceRange();
        return ExprError();
      }
      CheckBoolLikeConversion(E, Loc);
    }
  
    return E;
  }
  
  Sema::ConditionResult Sema::ActOnCondition(Scope *S, SourceLocation Loc,
                                             Expr *SubExpr, ConditionKind CK,
                                             bool MissingOK) {
    // MissingOK indicates whether having no condition expression is valid
    // (for loop) or invalid (e.g. while loop).
    if (!SubExpr)
      return MissingOK ? ConditionResult() : ConditionError();
  
    ExprResult Cond;
    switch (CK) {
    case ConditionKind::Boolean:
      Cond = CheckBooleanCondition(Loc, SubExpr);
      break;
  
    case ConditionKind::ConstexprIf:
      Cond = CheckBooleanCondition(Loc, SubExpr, true);
      break;
  
    case ConditionKind::Switch:
      Cond = CheckSwitchCondition(Loc, SubExpr);
      break;
    }
    if (Cond.isInvalid()) {
      Cond = CreateRecoveryExpr(SubExpr->getBeginLoc(), SubExpr->getEndLoc(),
                                {SubExpr}, PreferredConditionType(CK));
      if (!Cond.get())
        return ConditionError();
    }
    // FIXME: FullExprArg doesn't have an invalid bit, so check nullness instead.
    FullExprArg FullExpr = MakeFullExpr(Cond.get(), Loc);
    if (!FullExpr.get())
      return ConditionError();
  
    return ConditionResult(*this, nullptr, FullExpr,
                           CK == ConditionKind::ConstexprIf);
  }
  
  namespace {
    /// A visitor for rebuilding a call to an __unknown_any expression
    /// to have an appropriate type.
    struct RebuildUnknownAnyFunction
      : StmtVisitor<RebuildUnknownAnyFunction, ExprResult> {
  
      Sema &S;
  
      RebuildUnknownAnyFunction(Sema &S) : S(S) {}
  
      ExprResult VisitStmt(Stmt *S) {
        llvm_unreachable("unexpected statement!");
      }
  
      ExprResult VisitExpr(Expr *E) {
        S.Diag(E->getExprLoc(), diag::err_unsupported_unknown_any_call)
          << E->getSourceRange();
        return ExprError();
      }
  
      /// Rebuild an expression which simply semantically wraps another
      /// expression which it shares the type and value kind of.
      template <class T> ExprResult rebuildSugarExpr(T *E) {
        ExprResult SubResult = Visit(E->getSubExpr());
        if (SubResult.isInvalid()) return ExprError();
  
        Expr *SubExpr = SubResult.get();
        E->setSubExpr(SubExpr);
        E->setType(SubExpr->getType());
        E->setValueKind(SubExpr->getValueKind());
        assert(E->getObjectKind() == OK_Ordinary);
        return E;
      }
  
      ExprResult VisitParenExpr(ParenExpr *E) {
        return rebuildSugarExpr(E);
      }
  
      ExprResult VisitUnaryExtension(UnaryOperator *E) {
        return rebuildSugarExpr(E);
      }
  
      ExprResult VisitUnaryAddrOf(UnaryOperator *E) {
        ExprResult SubResult = Visit(E->getSubExpr());
        if (SubResult.isInvalid()) return ExprError();
  
        Expr *SubExpr = SubResult.get();
        E->setSubExpr(SubExpr);
        E->setType(S.Context.getPointerType(SubExpr->getType()));
        assert(E->isPRValue());
        assert(E->getObjectKind() == OK_Ordinary);
        return E;
      }
  
      ExprResult resolveDecl(Expr *E, ValueDecl *VD) {
        if (!isa<FunctionDecl>(VD)) return VisitExpr(E);
  
        E->setType(VD->getType());
  
        assert(E->isPRValue());
        if (S.getLangOpts().CPlusPlus &&
            !(isa<CXXMethodDecl>(VD) &&
              cast<CXXMethodDecl>(VD)->isInstance()))
          E->setValueKind(VK_LValue);
  
        return E;
      }
  
      ExprResult VisitMemberExpr(MemberExpr *E) {
        return resolveDecl(E, E->getMemberDecl());
      }
  
      ExprResult VisitDeclRefExpr(DeclRefExpr *E) {
        return resolveDecl(E, E->getDecl());
      }
    };
  }
  
  /// Given a function expression of unknown-any type, try to rebuild it
  /// to have a function type.
  static ExprResult rebuildUnknownAnyFunction(Sema &S, Expr *FunctionExpr) {
    ExprResult Result = RebuildUnknownAnyFunction(S).Visit(FunctionExpr);
    if (Result.isInvalid()) return ExprError();
    return S.DefaultFunctionArrayConversion(Result.get());
  }
  
  namespace {
    /// A visitor for rebuilding an expression of type __unknown_anytype
    /// into one which resolves the type directly on the referring
    /// expression.  Strict preservation of the original source
    /// structure is not a goal.
    struct RebuildUnknownAnyExpr
      : StmtVisitor<RebuildUnknownAnyExpr, ExprResult> {
  
      Sema &S;
  
      /// The current destination type.
      QualType DestType;
  
      RebuildUnknownAnyExpr(Sema &S, QualType CastType)
        : S(S), DestType(CastType) {}
  
      ExprResult VisitStmt(Stmt *S) {
        llvm_unreachable("unexpected statement!");
      }
  
      ExprResult VisitExpr(Expr *E) {
        S.Diag(E->getExprLoc(), diag::err_unsupported_unknown_any_expr)
          << E->getSourceRange();
        return ExprError();
      }
  
      ExprResult VisitCallExpr(CallExpr *E);
      ExprResult VisitObjCMessageExpr(ObjCMessageExpr *E);
  
      /// Rebuild an expression which simply semantically wraps another
      /// expression which it shares the type and value kind of.
      template <class T> ExprResult rebuildSugarExpr(T *E) {
        ExprResult SubResult = Visit(E->getSubExpr());
        if (SubResult.isInvalid()) return ExprError();
        Expr *SubExpr = SubResult.get();
        E->setSubExpr(SubExpr);
        E->setType(SubExpr->getType());
        E->setValueKind(SubExpr->getValueKind());
        assert(E->getObjectKind() == OK_Ordinary);
        return E;
      }
  
      ExprResult VisitParenExpr(ParenExpr *E) {
        return rebuildSugarExpr(E);
      }
  
      ExprResult VisitUnaryExtension(UnaryOperator *E) {
        return rebuildSugarExpr(E);
      }
  
      ExprResult VisitUnaryAddrOf(UnaryOperator *E) {
        const PointerType *Ptr = DestType->getAs<PointerType>();
        if (!Ptr) {
          S.Diag(E->getOperatorLoc(), diag::err_unknown_any_addrof)
            << E->getSourceRange();
          return ExprError();
        }
  
        if (isa<CallExpr>(E->getSubExpr())) {
          S.Diag(E->getOperatorLoc(), diag::err_unknown_any_addrof_call)
            << E->getSourceRange();
          return ExprError();
        }
  
        assert(E->isPRValue());
        assert(E->getObjectKind() == OK_Ordinary);
        E->setType(DestType);
  
        // Build the sub-expression as if it were an object of the pointee type.
        DestType = Ptr->getPointeeType();
        ExprResult SubResult = Visit(E->getSubExpr());
        if (SubResult.isInvalid()) return ExprError();
        E->setSubExpr(SubResult.get());
        return E;
      }
  
      ExprResult VisitImplicitCastExpr(ImplicitCastExpr *E);
  
      ExprResult resolveDecl(Expr *E, ValueDecl *VD);
  
      ExprResult VisitMemberExpr(MemberExpr *E) {
        return resolveDecl(E, E->getMemberDecl());
      }
  
      ExprResult VisitDeclRefExpr(DeclRefExpr *E) {
        return resolveDecl(E, E->getDecl());
      }
    };
  }
  
  /// Rebuilds a call expression which yielded __unknown_anytype.
  ExprResult RebuildUnknownAnyExpr::VisitCallExpr(CallExpr *E) {
    Expr *CalleeExpr = E->getCallee();
  
    enum FnKind {
      FK_MemberFunction,
      FK_FunctionPointer,
      FK_BlockPointer
    };
  
    FnKind Kind;
    QualType CalleeType = CalleeExpr->getType();
    if (CalleeType == S.Context.BoundMemberTy) {
      assert(isa<CXXMemberCallExpr>(E) || isa<CXXOperatorCallExpr>(E));
      Kind = FK_MemberFunction;
      CalleeType = Expr::findBoundMemberType(CalleeExpr);
    } else if (const PointerType *Ptr = CalleeType->getAs<PointerType>()) {
      CalleeType = Ptr->getPointeeType();
      Kind = FK_FunctionPointer;
    } else {
      CalleeType = CalleeType->castAs<BlockPointerType>()->getPointeeType();
      Kind = FK_BlockPointer;
    }
    const FunctionType *FnType = CalleeType->castAs<FunctionType>();
  
    // Verify that this is a legal result type of a function.
    if (DestType->isArrayType() || DestType->isFunctionType()) {
      unsigned diagID = diag::err_func_returning_array_function;
      if (Kind == FK_BlockPointer)
        diagID = diag::err_block_returning_array_function;
  
      S.Diag(E->getExprLoc(), diagID)
        << DestType->isFunctionType() << DestType;
      return ExprError();
    }
  
    // Otherwise, go ahead and set DestType as the call's result.
    E->setType(DestType.getNonLValueExprType(S.Context));
    E->setValueKind(Expr::getValueKindForType(DestType));
    assert(E->getObjectKind() == OK_Ordinary);
  
    // Rebuild the function type, replacing the result type with DestType.
    const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(FnType);
    if (Proto) {
      // __unknown_anytype(...) is a special case used by the debugger when
      // it has no idea what a function's signature is.
      //
      // We want to build this call essentially under the K&R
      // unprototyped rules, but making a FunctionNoProtoType in C++
      // would foul up all sorts of assumptions.  However, we cannot
      // simply pass all arguments as variadic arguments, nor can we
      // portably just call the function under a non-variadic type; see
      // the comment on IR-gen's TargetInfo::isNoProtoCallVariadic.
      // However, it turns out that in practice it is generally safe to
      // call a function declared as "A foo(B,C,D);" under the prototype
      // "A foo(B,C,D,...);".  The only known exception is with the
      // Windows ABI, where any variadic function is implicitly cdecl
      // regardless of its normal CC.  Therefore we change the parameter
      // types to match the types of the arguments.
      //
      // This is a hack, but it is far superior to moving the
      // corresponding target-specific code from IR-gen to Sema/AST.
  
      ArrayRef<QualType> ParamTypes = Proto->getParamTypes();
      SmallVector<QualType, 8> ArgTypes;
      if (ParamTypes.empty() && Proto->isVariadic()) { // the special case
        ArgTypes.reserve(E->getNumArgs());
        for (unsigned i = 0, e = E->getNumArgs(); i != e; ++i) {
          ArgTypes.push_back(S.Context.getReferenceQualifiedType(E->getArg(i)));
        }
        ParamTypes = ArgTypes;
      }
      DestType = S.Context.getFunctionType(DestType, ParamTypes,
                                           Proto->getExtProtoInfo());
    } else {
      DestType = S.Context.getFunctionNoProtoType(DestType,
                                                  FnType->getExtInfo());
    }
  
    // Rebuild the appropriate pointer-to-function type.
    switch (Kind) {
    case FK_MemberFunction:
      // Nothing to do.
      break;
  
    case FK_FunctionPointer:
      DestType = S.Context.getPointerType(DestType);
      break;
  
    case FK_BlockPointer:
      DestType = S.Context.getBlockPointerType(DestType);
      break;
    }
  
    // Finally, we can recurse.
    ExprResult CalleeResult = Visit(CalleeExpr);
    if (!CalleeResult.isUsable()) return ExprError();
    E->setCallee(CalleeResult.get());
  
    // Bind a temporary if necessary.
    return S.MaybeBindToTemporary(E);
  }
  
  ExprResult RebuildUnknownAnyExpr::VisitObjCMessageExpr(ObjCMessageExpr *E) {
    // Verify that this is a legal result type of a call.
    if (DestType->isArrayType() || DestType->isFunctionType()) {
      S.Diag(E->getExprLoc(), diag::err_func_returning_array_function)
        << DestType->isFunctionType() << DestType;
      return ExprError();
    }
  
    // Rewrite the method result type if available.
    if (ObjCMethodDecl *Method = E->getMethodDecl()) {
      assert(Method->getReturnType() == S.Context.UnknownAnyTy);
      Method->setReturnType(DestType);
    }
  
    // Change the type of the message.
    E->setType(DestType.getNonReferenceType());
    E->setValueKind(Expr::getValueKindForType(DestType));
  
    return S.MaybeBindToTemporary(E);
  }
  
  ExprResult RebuildUnknownAnyExpr::VisitImplicitCastExpr(ImplicitCastExpr *E) {
    // The only case we should ever see here is a function-to-pointer decay.
    if (E->getCastKind() == CK_FunctionToPointerDecay) {
      assert(E->isPRValue());
      assert(E->getObjectKind() == OK_Ordinary);
  
      E->setType(DestType);
  
      // Rebuild the sub-expression as the pointee (function) type.
      DestType = DestType->castAs<PointerType>()->getPointeeType();
  
      ExprResult Result = Visit(E->getSubExpr());
      if (!Result.isUsable()) return ExprError();
  
      E->setSubExpr(Result.get());
      return E;
    } else if (E->getCastKind() == CK_LValueToRValue) {
      assert(E->isPRValue());
      assert(E->getObjectKind() == OK_Ordinary);
  
      assert(isa<BlockPointerType>(E->getType()));
  
      E->setType(DestType);
  
      // The sub-expression has to be a lvalue reference, so rebuild it as such.
      DestType = S.Context.getLValueReferenceType(DestType);
  
      ExprResult Result = Visit(E->getSubExpr());
      if (!Result.isUsable()) return ExprError();
  
      E->setSubExpr(Result.get());
      return E;
    } else {
      llvm_unreachable("Unhandled cast type!");
    }
  }
  
  ExprResult RebuildUnknownAnyExpr::resolveDecl(Expr *E, ValueDecl *VD) {
    ExprValueKind ValueKind = VK_LValue;
    QualType Type = DestType;
  
    // We know how to make this work for certain kinds of decls:
  
    //  - functions
    if (FunctionDecl *FD = dyn_cast<FunctionDecl>(VD)) {
      if (const PointerType *Ptr = Type->getAs<PointerType>()) {
        DestType = Ptr->getPointeeType();
        ExprResult Result = resolveDecl(E, VD);
        if (Result.isInvalid()) return ExprError();
        return S.ImpCastExprToType(Result.get(), Type, CK_FunctionToPointerDecay,
                                   VK_PRValue);
      }
  
      if (!Type->isFunctionType()) {
        S.Diag(E->getExprLoc(), diag::err_unknown_any_function)
          << VD << E->getSourceRange();
        return ExprError();
      }
      if (const FunctionProtoType *FT = Type->getAs<FunctionProtoType>()) {
        // We must match the FunctionDecl's type to the hack introduced in
        // RebuildUnknownAnyExpr::VisitCallExpr to vararg functions of unknown
        // type. See the lengthy commentary in that routine.
        QualType FDT = FD->getType();
        const FunctionType *FnType = FDT->castAs<FunctionType>();
        const FunctionProtoType *Proto = dyn_cast_or_null<FunctionProtoType>(FnType);
        DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E);
        if (DRE && Proto && Proto->getParamTypes().empty() && Proto->isVariadic()) {
          SourceLocation Loc = FD->getLocation();
          FunctionDecl *NewFD = FunctionDecl::Create(
              S.Context, FD->getDeclContext(), Loc, Loc,
              FD->getNameInfo().getName(), DestType, FD->getTypeSourceInfo(),
              SC_None, S.getCurFPFeatures().isFPConstrained(),
              false /*isInlineSpecified*/, FD->hasPrototype(),
              /*ConstexprKind*/ ConstexprSpecKind::Unspecified);
  
          if (FD->getQualifier())
            NewFD->setQualifierInfo(FD->getQualifierLoc());
  
          SmallVector<ParmVarDecl*, 16> Params;
          for (const auto &AI : FT->param_types()) {
            ParmVarDecl *Param =
              S.BuildParmVarDeclForTypedef(FD, Loc, AI);
            Param->setScopeInfo(0, Params.size());
            Params.push_back(Param);
          }
          NewFD->setParams(Params);
          DRE->setDecl(NewFD);
          VD = DRE->getDecl();
        }
      }
  
      if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD))
        if (MD->isInstance()) {
          ValueKind = VK_PRValue;
          Type = S.Context.BoundMemberTy;
        }
  
      // Function references aren't l-values in C.
      if (!S.getLangOpts().CPlusPlus)
        ValueKind = VK_PRValue;
  
    //  - variables
    } else if (isa<VarDecl>(VD)) {
      if (const ReferenceType *RefTy = Type->getAs<ReferenceType>()) {
        Type = RefTy->getPointeeType();
      } else if (Type->isFunctionType()) {
        S.Diag(E->getExprLoc(), diag::err_unknown_any_var_function_type)
          << VD << E->getSourceRange();
        return ExprError();
      }
  
    //  - nothing else
    } else {
      S.Diag(E->getExprLoc(), diag::err_unsupported_unknown_any_decl)
        << VD << E->getSourceRange();
      return ExprError();
    }
  
    // Modifying the declaration like this is friendly to IR-gen but
    // also really dangerous.
    VD->setType(DestType);
    E->setType(Type);
    E->setValueKind(ValueKind);
    return E;
  }
  
  /// Check a cast of an unknown-any type.  We intentionally only
  /// trigger this for C-style casts.
  ExprResult Sema::checkUnknownAnyCast(SourceRange TypeRange, QualType CastType,
                                       Expr *CastExpr, CastKind &CastKind,
                                       ExprValueKind &VK, CXXCastPath &Path) {
    // The type we're casting to must be either void or complete.
    if (!CastType->isVoidType() &&
        RequireCompleteType(TypeRange.getBegin(), CastType,
                            diag::err_typecheck_cast_to_incomplete))
      return ExprError();
  
    // Rewrite the casted expression from scratch.
    ExprResult result = RebuildUnknownAnyExpr(*this, CastType).Visit(CastExpr);
    if (!result.isUsable()) return ExprError();
  
    CastExpr = result.get();
    VK = CastExpr->getValueKind();
    CastKind = CK_NoOp;
  
    return CastExpr;
  }
  
  ExprResult Sema::forceUnknownAnyToType(Expr *E, QualType ToType) {
    return RebuildUnknownAnyExpr(*this, ToType).Visit(E);
  }
  
  ExprResult Sema::checkUnknownAnyArg(SourceLocation callLoc,
                                      Expr *arg, QualType &paramType) {
    // If the syntactic form of the argument is not an explicit cast of
    // any sort, just do default argument promotion.
    ExplicitCastExpr *castArg = dyn_cast<ExplicitCastExpr>(arg->IgnoreParens());
    if (!castArg) {
      ExprResult result = DefaultArgumentPromotion(arg);
      if (result.isInvalid()) return ExprError();
      paramType = result.get()->getType();
      return result;
    }
  
    // Otherwise, use the type that was written in the explicit cast.
    assert(!arg->hasPlaceholderType());
    paramType = castArg->getTypeAsWritten();
  
    // Copy-initialize a parameter of that type.
    InitializedEntity entity =
      InitializedEntity::InitializeParameter(Context, paramType,
                                             /*consumed*/ false);
    return PerformCopyInitialization(entity, callLoc, arg);
  }
  
  static ExprResult diagnoseUnknownAnyExpr(Sema &S, Expr *E) {
    Expr *orig = E;
    unsigned diagID = diag::err_uncasted_use_of_unknown_any;
    while (true) {
      E = E->IgnoreParenImpCasts();
      if (CallExpr *call = dyn_cast<CallExpr>(E)) {
        E = call->getCallee();
        diagID = diag::err_uncasted_call_of_unknown_any;
      } else {
        break;
      }
    }
  
    SourceLocation loc;
    NamedDecl *d;
    if (DeclRefExpr *ref = dyn_cast<DeclRefExpr>(E)) {
      loc = ref->getLocation();
      d = ref->getDecl();
    } else if (MemberExpr *mem = dyn_cast<MemberExpr>(E)) {
      loc = mem->getMemberLoc();
      d = mem->getMemberDecl();
    } else if (ObjCMessageExpr *msg = dyn_cast<ObjCMessageExpr>(E)) {
      diagID = diag::err_uncasted_call_of_unknown_any;
      loc = msg->getSelectorStartLoc();
      d = msg->getMethodDecl();
      if (!d) {
        S.Diag(loc, diag::err_uncasted_send_to_unknown_any_method)
          << static_cast<unsigned>(msg->isClassMessage()) << msg->getSelector()
          << orig->getSourceRange();
        return ExprError();
      }
    } else {
      S.Diag(E->getExprLoc(), diag::err_unsupported_unknown_any_expr)
        << E->getSourceRange();
      return ExprError();
    }
  
    S.Diag(loc, diagID) << d << orig->getSourceRange();
  
    // Never recoverable.
    return ExprError();
  }
  
  /// Check for operands with placeholder types and complain if found.
  /// Returns ExprError() if there was an error and no recovery was possible.
  ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
    if (!Context.isDependenceAllowed()) {
      // C cannot handle TypoExpr nodes on either side of a binop because it
      // doesn't handle dependent types properly, so make sure any TypoExprs have
      // been dealt with before checking the operands.
      ExprResult Result = CorrectDelayedTyposInExpr(E);
      if (!Result.isUsable()) return ExprError();
      E = Result.get();
    }
  
    const BuiltinType *placeholderType = E->getType()->getAsPlaceholderType();
    if (!placeholderType) return E;
  
    switch (placeholderType->getKind()) {
  
    // Overloaded expressions.
    case BuiltinType::Overload: {
      // Try to resolve a single function template specialization.
      // This is obligatory.
      ExprResult Result = E;
      if (ResolveAndFixSingleFunctionTemplateSpecialization(Result, false))
        return Result;
  
      // No guarantees that ResolveAndFixSingleFunctionTemplateSpecialization
      // leaves Result unchanged on failure.
      Result = E;
      if (resolveAndFixAddressOfSingleOverloadCandidate(Result))
        return Result;
  
      // If that failed, try to recover with a call.
      tryToRecoverWithCall(Result, PDiag(diag::err_ovl_unresolvable),
                           /*complain*/ true);
      return Result;
    }
  
    // Bound member functions.
    case BuiltinType::BoundMember: {
      ExprResult result = E;
      const Expr *BME = E->IgnoreParens();
      PartialDiagnostic PD = PDiag(diag::err_bound_member_function);
      // Try to give a nicer diagnostic if it is a bound member that we recognize.
      if (isa<CXXPseudoDestructorExpr>(BME)) {
        PD = PDiag(diag::err_dtor_expr_without_call) << /*pseudo-destructor*/ 1;
      } else if (const auto *ME = dyn_cast<MemberExpr>(BME)) {
        if (ME->getMemberNameInfo().getName().getNameKind() ==
            DeclarationName::CXXDestructorName)
          PD = PDiag(diag::err_dtor_expr_without_call) << /*destructor*/ 0;
      }
      tryToRecoverWithCall(result, PD,
                           /*complain*/ true);
      return result;
    }
  
    // ARC unbridged casts.
    case BuiltinType::ARCUnbridgedCast: {
      Expr *realCast = stripARCUnbridgedCast(E);
      diagnoseARCUnbridgedCast(realCast);
      return realCast;
    }
  
    // Expressions of unknown type.
    case BuiltinType::UnknownAny:
      return diagnoseUnknownAnyExpr(*this, E);
  
    // Pseudo-objects.
    case BuiltinType::PseudoObject:
      return checkPseudoObjectRValue(E);
  
    case BuiltinType::BuiltinFn: {
      // Accept __noop without parens by implicitly converting it to a call expr.
      auto *DRE = dyn_cast<DeclRefExpr>(E->IgnoreParenImpCasts());
      if (DRE) {
        auto *FD = cast<FunctionDecl>(DRE->getDecl());
        if (FD->getBuiltinID() == Builtin::BI__noop) {
          E = ImpCastExprToType(E, Context.getPointerType(FD->getType()),
                                CK_BuiltinFnToFnPtr)
                  .get();
          return CallExpr::Create(Context, E, /*Args=*/{}, Context.IntTy,
                                  VK_PRValue, SourceLocation(),
                                  FPOptionsOverride());
        }
      }
  
      Diag(E->getBeginLoc(), diag::err_builtin_fn_use);
      return ExprError();
    }
  
    case BuiltinType::IncompleteMatrixIdx:
      Diag(cast<MatrixSubscriptExpr>(E->IgnoreParens())
               ->getRowIdx()
               ->getBeginLoc(),
           diag::err_matrix_incomplete_index);
      return ExprError();
  
    // Expressions of unknown type.
    case BuiltinType::OMPArraySection:
      Diag(E->getBeginLoc(), diag::err_omp_array_section_use);
      return ExprError();
  
    // Expressions of unknown type.
    case BuiltinType::OMPArrayShaping:
      return ExprError(Diag(E->getBeginLoc(), diag::err_omp_array_shaping_use));
  
    case BuiltinType::OMPIterator:
      return ExprError(Diag(E->getBeginLoc(), diag::err_omp_iterator_use));
  
    // Everything else should be impossible.
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
    case BuiltinType::Id:
  #include "clang/Basic/OpenCLImageTypes.def"
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
    case BuiltinType::Id:
  #include "clang/Basic/OpenCLExtensionTypes.def"
  #define SVE_TYPE(Name, Id, SingletonId) \
    case BuiltinType::Id:
  #include "clang/Basic/AArch64SVEACLETypes.def"
  #define PPC_VECTOR_TYPE(Name, Id, Size) \
    case BuiltinType::Id:
  #include "clang/Basic/PPCTypes.def"
  #define RVV_TYPE(Name, Id, SingletonId) case BuiltinType::Id:
  #include "clang/Basic/RISCVVTypes.def"
  #define BUILTIN_TYPE(Id, SingletonId) case BuiltinType::Id:
  #define PLACEHOLDER_TYPE(Id, SingletonId)
  #include "clang/AST/BuiltinTypes.def"
      break;
    }
  
    llvm_unreachable("invalid placeholder type!");
  }
  
  bool Sema::CheckCaseExpression(Expr *E) {
    if (E->isTypeDependent())
      return true;
    if (E->isValueDependent() || E->isIntegerConstantExpr(Context))
      return E->getType()->isIntegralOrEnumerationType();
    return false;
  }
  
  /// ActOnObjCBoolLiteral - Parse {__objc_yes,__objc_no} literals.
  ExprResult
  Sema::ActOnObjCBoolLiteral(SourceLocation OpLoc, tok::TokenKind Kind) {
    assert((Kind == tok::kw___objc_yes || Kind == tok::kw___objc_no) &&
           "Unknown Objective-C Boolean value!");
    QualType BoolT = Context.ObjCBuiltinBoolTy;
    if (!Context.getBOOLDecl()) {
      LookupResult Result(*this, &Context.Idents.get("BOOL"), OpLoc,
                          Sema::LookupOrdinaryName);
      if (LookupName(Result, getCurScope()) && Result.isSingleResult()) {
        NamedDecl *ND = Result.getFoundDecl();
        if (TypedefDecl *TD = dyn_cast<TypedefDecl>(ND))
          Context.setBOOLDecl(TD);
      }
    }
    if (Context.getBOOLDecl())
      BoolT = Context.getBOOLType();
    return new (Context)
        ObjCBoolLiteralExpr(Kind == tok::kw___objc_yes, BoolT, OpLoc);
  }
  
  ExprResult Sema::ActOnObjCAvailabilityCheckExpr(
      llvm::ArrayRef<AvailabilitySpec> AvailSpecs, SourceLocation AtLoc,
      SourceLocation RParen) {
  
    auto FindSpecVersion = [&](StringRef Platform)
        -> Optional<ObjCAvailabilityCheckExpr::VersionAsWritten> {
      auto Spec = llvm::find_if(AvailSpecs, [&](const AvailabilitySpec &Spec) {
        return Spec.getPlatform() == Platform;
      });
      // Transcribe the "ios" availability check to "maccatalyst" when compiling
      // for "maccatalyst" if "maccatalyst" is not specified.
      if (Spec == AvailSpecs.end() && Platform == "maccatalyst") {
        Spec = llvm::find_if(AvailSpecs, [&](const AvailabilitySpec &Spec) {
          return Spec.getPlatform() == "ios";
        });
      }
      if (Spec == AvailSpecs.end())
        return None;
      if (Platform == "macos") {
        return ObjCAvailabilityCheckExpr::VersionAsWritten{
            llvm::Triple::getCanonicalVersionForOS(llvm::Triple::MacOSX,
                                                   Spec->getVersion()),
            Spec->getVersion()};
      }
      return ObjCAvailabilityCheckExpr::VersionAsWritten{Spec->getVersion(),
                                                         Spec->getVersion()};
    };
  
    auto MaybeVersion =
        FindSpecVersion(Context.getTargetInfo().getPlatformName());
    ObjCAvailabilityCheckExpr::VersionAsWritten Version;
    if (MaybeVersion)
      Version = *MaybeVersion;
  
    // The use of `@available` in the enclosing context should be analyzed to
    // warn when it's used inappropriately (i.e. not if(@available)).
    if (FunctionScopeInfo *Context = getCurFunctionAvailabilityContext())
      Context->HasPotentialAvailabilityViolations = true;
  
    return new (Context)
        ObjCAvailabilityCheckExpr(Version, AtLoc, RParen, Context.BoolTy);
  }
  
  ExprResult Sema::CreateRecoveryExpr(SourceLocation Begin, SourceLocation End,
                                      ArrayRef<Expr *> SubExprs, QualType T) {
    if (!Context.getLangOpts().RecoveryAST)
      return ExprError();
  
    if (isSFINAEContext())
      return ExprError();
  
    if (T.isNull() || T->isUndeducedType() ||
        !Context.getLangOpts().RecoveryASTType)
      // We don't know the concrete type, fallback to dependent type.
      T = Context.DependentTy;
  
    return RecoveryExpr::Create(Context, T, Begin, End, SubExprs);
  }
  