text: //===--- SemaStmt.cpp - Semantic Analysis for Statements ------------------===//
  //
  // 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 statements.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Sema/Ownership.h"
  #include "clang/Sema/SemaInternal.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/ASTDiagnostic.h"
  #include "clang/AST/ASTLambda.h"
  #include "clang/AST/CharUnits.h"
  #include "clang/AST/CXXInheritance.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/EvaluatedExprVisitor.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/AST/ExprObjC.h"
  #include "clang/AST/RecursiveASTVisitor.h"
  #include "clang/AST/StmtCXX.h"
  #include "clang/AST/StmtObjC.h"
  #include "clang/AST/TypeLoc.h"
  #include "clang/AST/TypeOrdering.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Sema/Initialization.h"
  #include "clang/Sema/Lookup.h"
  #include "clang/Sema/Scope.h"
  #include "clang/Sema/ScopeInfo.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallPtrSet.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/SmallVector.h"
  
  using namespace clang;
  using namespace sema;
  
  StmtResult Sema::ActOnExprStmt(ExprResult FE, bool DiscardedValue) {
    if (FE.isInvalid())
      return StmtError();
  
    FE = ActOnFinishFullExpr(FE.get(), FE.get()->getExprLoc(), DiscardedValue);
    if (FE.isInvalid())
      return StmtError();
  
    // C99 6.8.3p2: The expression in an expression statement is evaluated as a
    // void expression for its side effects.  Conversion to void allows any
    // operand, even incomplete types.
  
    // Same thing in for stmt first clause (when expr) and third clause.
    return StmtResult(FE.getAs<Stmt>());
  }
  
  
  StmtResult Sema::ActOnExprStmtError() {
    DiscardCleanupsInEvaluationContext();
    return StmtError();
  }
  
  StmtResult Sema::ActOnNullStmt(SourceLocation SemiLoc,
                                 bool HasLeadingEmptyMacro) {
    return new (Context) NullStmt(SemiLoc, HasLeadingEmptyMacro);
  }
  
  StmtResult Sema::ActOnDeclStmt(DeclGroupPtrTy dg, SourceLocation StartLoc,
                                 SourceLocation EndLoc) {
    DeclGroupRef DG = dg.get();
  
    // If we have an invalid decl, just return an error.
    if (DG.isNull()) return StmtError();
  
    return new (Context) DeclStmt(DG, StartLoc, EndLoc);
  }
  
  void Sema::ActOnForEachDeclStmt(DeclGroupPtrTy dg) {
    DeclGroupRef DG = dg.get();
  
    // If we don't have a declaration, or we have an invalid declaration,
    // just return.
    if (DG.isNull() || !DG.isSingleDecl())
      return;
  
    Decl *decl = DG.getSingleDecl();
    if (!decl || decl->isInvalidDecl())
      return;
  
    // Only variable declarations are permitted.
    VarDecl *var = dyn_cast<VarDecl>(decl);
    if (!var) {
      Diag(decl->getLocation(), diag::err_non_variable_decl_in_for);
      decl->setInvalidDecl();
      return;
    }
  
    // foreach variables are never actually initialized in the way that
    // the parser came up with.
    var->setInit(nullptr);
  
    // In ARC, we don't need to retain the iteration variable of a fast
    // enumeration loop.  Rather than actually trying to catch that
    // during declaration processing, we remove the consequences here.
    if (getLangOpts().ObjCAutoRefCount) {
      QualType type = var->getType();
  
      // Only do this if we inferred the lifetime.  Inferred lifetime
      // will show up as a local qualifier because explicit lifetime
      // should have shown up as an AttributedType instead.
      if (type.getLocalQualifiers().getObjCLifetime() == Qualifiers::OCL_Strong) {
        // Add 'const' and mark the variable as pseudo-strong.
        var->setType(type.withConst());
        var->setARCPseudoStrong(true);
      }
    }
  }
  
  /// Diagnose unused comparisons, both builtin and overloaded operators.
  /// For '==' and '!=', suggest fixits for '=' or '|='.
  ///
  /// Adding a cast to void (or other expression wrappers) will prevent the
  /// warning from firing.
  static bool DiagnoseUnusedComparison(Sema &S, const Expr *E) {
    SourceLocation Loc;
    bool CanAssign;
    enum { Equality, Inequality, Relational, ThreeWay } Kind;
  
    if (const BinaryOperator *Op = dyn_cast<BinaryOperator>(E)) {
      if (!Op->isComparisonOp())
        return false;
  
      if (Op->getOpcode() == BO_EQ)
        Kind = Equality;
      else if (Op->getOpcode() == BO_NE)
        Kind = Inequality;
      else if (Op->getOpcode() == BO_Cmp)
        Kind = ThreeWay;
      else {
        assert(Op->isRelationalOp());
        Kind = Relational;
      }
      Loc = Op->getOperatorLoc();
      CanAssign = Op->getLHS()->IgnoreParenImpCasts()->isLValue();
    } else if (const CXXOperatorCallExpr *Op = dyn_cast<CXXOperatorCallExpr>(E)) {
      switch (Op->getOperator()) {
      case OO_EqualEqual:
        Kind = Equality;
        break;
      case OO_ExclaimEqual:
        Kind = Inequality;
        break;
      case OO_Less:
      case OO_Greater:
      case OO_GreaterEqual:
      case OO_LessEqual:
        Kind = Relational;
        break;
      case OO_Spaceship:
        Kind = ThreeWay;
        break;
      default:
        return false;
      }
  
      Loc = Op->getOperatorLoc();
      CanAssign = Op->getArg(0)->IgnoreParenImpCasts()->isLValue();
    } else {
      // Not a typo-prone comparison.
      return false;
    }
  
    // Suppress warnings when the operator, suspicious as it may be, comes from
    // a macro expansion.
    if (S.SourceMgr.isMacroBodyExpansion(Loc))
      return false;
  
    S.Diag(Loc, diag::warn_unused_comparison)
      << (unsigned)Kind << E->getSourceRange();
  
    // If the LHS is a plausible entity to assign to, provide a fixit hint to
    // correct common typos.
    if (CanAssign) {
      if (Kind == Inequality)
        S.Diag(Loc, diag::note_inequality_comparison_to_or_assign)
          << FixItHint::CreateReplacement(Loc, "|=");
      else if (Kind == Equality)
        S.Diag(Loc, diag::note_equality_comparison_to_assign)
          << FixItHint::CreateReplacement(Loc, "=");
    }
  
    return true;
  }
  
  static bool DiagnoseNoDiscard(Sema &S, const WarnUnusedResultAttr *A,
                                SourceLocation Loc, SourceRange R1,
                                SourceRange R2, bool IsCtor) {
    if (!A)
      return false;
    StringRef Msg = A->getMessage();
  
    if (Msg.empty()) {
      if (IsCtor)
        return S.Diag(Loc, diag::warn_unused_constructor) << A << R1 << R2;
      return S.Diag(Loc, diag::warn_unused_result) << A << R1 << R2;
    }
  
    if (IsCtor)
      return S.Diag(Loc, diag::warn_unused_constructor_msg) << A << Msg << R1
                                                            << R2;
    return S.Diag(Loc, diag::warn_unused_result_msg) << A << Msg << R1 << R2;
  }
  
  void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
    if (const LabelStmt *Label = dyn_cast_or_null<LabelStmt>(S))
      return DiagnoseUnusedExprResult(Label->getSubStmt());
  
    const Expr *E = dyn_cast_or_null<Expr>(S);
    if (!E)
      return;
  
    // If we are in an unevaluated expression context, then there can be no unused
    // results because the results aren't expected to be used in the first place.
    if (isUnevaluatedContext())
      return;
  
    SourceLocation ExprLoc = E->IgnoreParenImpCasts()->getExprLoc();
    // In most cases, we don't want to warn if the expression is written in a
    // macro body, or if the macro comes from a system header. If the offending
    // expression is a call to a function with the warn_unused_result attribute,
    // we warn no matter the location. Because of the order in which the various
    // checks need to happen, we factor out the macro-related test here.
    bool ShouldSuppress =
        SourceMgr.isMacroBodyExpansion(ExprLoc) ||
        SourceMgr.isInSystemMacro(ExprLoc);
  
    const Expr *WarnExpr;
    SourceLocation Loc;
    SourceRange R1, R2;
    if (!E->isUnusedResultAWarning(WarnExpr, Loc, R1, R2, Context))
      return;
  
    // If this is a GNU statement expression expanded from a macro, it is probably
    // unused because it is a function-like macro that can be used as either an
    // expression or statement.  Don't warn, because it is almost certainly a
    // false positive.
    if (isa<StmtExpr>(E) && Loc.isMacroID())
      return;
  
    // Check if this is the UNREFERENCED_PARAMETER from the Microsoft headers.
    // That macro is frequently used to suppress "unused parameter" warnings,
    // but its implementation makes clang's -Wunused-value fire.  Prevent this.
    if (isa<ParenExpr>(E->IgnoreImpCasts()) && Loc.isMacroID()) {
      SourceLocation SpellLoc = Loc;
      if (findMacroSpelling(SpellLoc, "UNREFERENCED_PARAMETER"))
        return;
    }
  
    // Okay, we have an unused result.  Depending on what the base expression is,
    // we might want to make a more specific diagnostic.  Check for one of these
    // cases now.
    unsigned DiagID = diag::warn_unused_expr;
    if (const FullExpr *Temps = dyn_cast<FullExpr>(E))
      E = Temps->getSubExpr();
    if (const CXXBindTemporaryExpr *TempExpr = dyn_cast<CXXBindTemporaryExpr>(E))
      E = TempExpr->getSubExpr();
  
    if (DiagnoseUnusedComparison(*this, E))
      return;
  
    E = WarnExpr;
    if (const auto *Cast = dyn_cast<CastExpr>(E))
      if (Cast->getCastKind() == CK_NoOp ||
          Cast->getCastKind() == CK_ConstructorConversion)
        E = Cast->getSubExpr()->IgnoreImpCasts();
  
    if (const CallExpr *CE = dyn_cast<CallExpr>(E)) {
      if (E->getType()->isVoidType())
        return;
  
      if (DiagnoseNoDiscard(*this, cast_or_null<WarnUnusedResultAttr>(
                                       CE->getUnusedResultAttr(Context)),
                            Loc, R1, R2, /*isCtor=*/false))
        return;
  
      // If the callee has attribute pure, const, or warn_unused_result, warn with
      // a more specific message to make it clear what is happening. If the call
      // is written in a macro body, only warn if it has the warn_unused_result
      // attribute.
      if (const Decl *FD = CE->getCalleeDecl()) {
        if (ShouldSuppress)
          return;
        if (FD->hasAttr<PureAttr>()) {
          Diag(Loc, diag::warn_unused_call) << R1 << R2 << "pure";
          return;
        }
        if (FD->hasAttr<ConstAttr>()) {
          Diag(Loc, diag::warn_unused_call) << R1 << R2 << "const";
          return;
        }
      }
    } else if (const auto *CE = dyn_cast<CXXConstructExpr>(E)) {
      if (const CXXConstructorDecl *Ctor = CE->getConstructor()) {
        const auto *A = Ctor->getAttr<WarnUnusedResultAttr>();
        A = A ? A : Ctor->getParent()->getAttr<WarnUnusedResultAttr>();
        if (DiagnoseNoDiscard(*this, A, Loc, R1, R2, /*isCtor=*/true))
          return;
      }
    } else if (const auto *ILE = dyn_cast<InitListExpr>(E)) {
      if (const TagDecl *TD = ILE->getType()->getAsTagDecl()) {
  
        if (DiagnoseNoDiscard(*this, TD->getAttr<WarnUnusedResultAttr>(), Loc, R1,
                              R2, /*isCtor=*/false))
          return;
      }
    } else if (ShouldSuppress)
      return;
  
    E = WarnExpr;
    if (const ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(E)) {
      if (getLangOpts().ObjCAutoRefCount && ME->isDelegateInitCall()) {
        Diag(Loc, diag::err_arc_unused_init_message) << R1;
        return;
      }
      const ObjCMethodDecl *MD = ME->getMethodDecl();
      if (MD) {
        if (DiagnoseNoDiscard(*this, MD->getAttr<WarnUnusedResultAttr>(), Loc, R1,
                              R2, /*isCtor=*/false))
          return;
      }
    } else if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(E)) {
      const Expr *Source = POE->getSyntacticForm();
      if (isa<ObjCSubscriptRefExpr>(Source))
        DiagID = diag::warn_unused_container_subscript_expr;
      else
        DiagID = diag::warn_unused_property_expr;
    } else if (const CXXFunctionalCastExpr *FC
                                         = dyn_cast<CXXFunctionalCastExpr>(E)) {
      const Expr *E = FC->getSubExpr();
      if (const CXXBindTemporaryExpr *TE = dyn_cast<CXXBindTemporaryExpr>(E))
        E = TE->getSubExpr();
      if (isa<CXXTemporaryObjectExpr>(E))
        return;
      if (const CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(E))
        if (const CXXRecordDecl *RD = CE->getType()->getAsCXXRecordDecl())
          if (!RD->getAttr<WarnUnusedAttr>())
            return;
    }
    // Diagnose "(void*) blah" as a typo for "(void) blah".
    else if (const CStyleCastExpr *CE = dyn_cast<CStyleCastExpr>(E)) {
      TypeSourceInfo *TI = CE->getTypeInfoAsWritten();
      QualType T = TI->getType();
  
      // We really do want to use the non-canonical type here.
      if (T == Context.VoidPtrTy) {
        PointerTypeLoc TL = TI->getTypeLoc().castAs<PointerTypeLoc>();
  
        Diag(Loc, diag::warn_unused_voidptr)
          << FixItHint::CreateRemoval(TL.getStarLoc());
        return;
      }
    }
  
    if (E->isGLValue() && E->getType().isVolatileQualified()) {
      Diag(Loc, diag::warn_unused_volatile) << R1 << R2;
      return;
    }
  
    DiagRuntimeBehavior(Loc, nullptr, PDiag(DiagID) << R1 << R2);
  }
  
  void Sema::ActOnStartOfCompoundStmt(bool IsStmtExpr) {
    PushCompoundScope(IsStmtExpr);
  }
  
  void Sema::ActOnFinishOfCompoundStmt() {
    PopCompoundScope();
  }
  
  sema::CompoundScopeInfo &Sema::getCurCompoundScope() const {
    return getCurFunction()->CompoundScopes.back();
  }
  
  StmtResult Sema::ActOnCompoundStmt(SourceLocation L, SourceLocation R,
                                     ArrayRef<Stmt *> Elts, bool isStmtExpr) {
    const unsigned NumElts = Elts.size();
  
    // If we're in C89 mode, check that we don't have any decls after stmts.  If
    // so, emit an extension diagnostic.
    if (!getLangOpts().C99 && !getLangOpts().CPlusPlus) {
      // Note that __extension__ can be around a decl.
      unsigned i = 0;
      // Skip over all declarations.
      for (; i != NumElts && isa<DeclStmt>(Elts[i]); ++i)
        /*empty*/;
  
      // We found the end of the list or a statement.  Scan for another declstmt.
      for (; i != NumElts && !isa<DeclStmt>(Elts[i]); ++i)
        /*empty*/;
  
      if (i != NumElts) {
        Decl *D = *cast<DeclStmt>(Elts[i])->decl_begin();
        Diag(D->getLocation(), diag::ext_mixed_decls_code);
      }
    }
  
    // Check for suspicious empty body (null statement) in `for' and `while'
    // statements.  Don't do anything for template instantiations, this just adds
    // noise.
    if (NumElts != 0 && !CurrentInstantiationScope &&
        getCurCompoundScope().HasEmptyLoopBodies) {
      for (unsigned i = 0; i != NumElts - 1; ++i)
        DiagnoseEmptyLoopBody(Elts[i], Elts[i + 1]);
    }
  
    return CompoundStmt::Create(Context, Elts, L, R);
  }
  
  ExprResult
  Sema::ActOnCaseExpr(SourceLocation CaseLoc, ExprResult Val) {
    if (!Val.get())
      return Val;
  
    if (DiagnoseUnexpandedParameterPack(Val.get()))
      return ExprError();
  
    // If we're not inside a switch, let the 'case' statement handling diagnose
    // this. Just clean up after the expression as best we can.
    if (getCurFunction()->SwitchStack.empty())
      return ActOnFinishFullExpr(Val.get(), Val.get()->getExprLoc(), false,
                                 getLangOpts().CPlusPlus11);
  
    Expr *CondExpr =
        getCurFunction()->SwitchStack.back().getPointer()->getCond();
    if (!CondExpr)
      return ExprError();
    QualType CondType = CondExpr->getType();
  
    auto CheckAndFinish = [&](Expr *E) {
      if (CondType->isDependentType() || E->isTypeDependent())
        return ExprResult(E);
  
      if (getLangOpts().CPlusPlus11) {
        // C++11 [stmt.switch]p2: the constant-expression shall be a converted
        // constant expression of the promoted type of the switch condition.
        llvm::APSInt TempVal;
        return CheckConvertedConstantExpression(E, CondType, TempVal,
                                                CCEK_CaseValue);
      }
  
      ExprResult ER = E;
      if (!E->isValueDependent())
        ER = VerifyIntegerConstantExpression(E);
      if (!ER.isInvalid())
        ER = DefaultLvalueConversion(ER.get());
      if (!ER.isInvalid())
        ER = ImpCastExprToType(ER.get(), CondType, CK_IntegralCast);
      if (!ER.isInvalid())
        ER = ActOnFinishFullExpr(ER.get(), ER.get()->getExprLoc(), false);
      return ER;
    };
  
    ExprResult Converted = CorrectDelayedTyposInExpr(Val, CheckAndFinish);
    if (Converted.get() == Val.get())
      Converted = CheckAndFinish(Val.get());
    return Converted;
  }
  
  StmtResult
  Sema::ActOnCaseStmt(SourceLocation CaseLoc, ExprResult LHSVal,
                      SourceLocation DotDotDotLoc, ExprResult RHSVal,
                      SourceLocation ColonLoc) {
    assert((LHSVal.isInvalid() || LHSVal.get()) && "missing LHS value");
    assert((DotDotDotLoc.isInvalid() ? RHSVal.isUnset()
                                     : RHSVal.isInvalid() || RHSVal.get()) &&
           "missing RHS value");
  
    if (getCurFunction()->SwitchStack.empty()) {
      Diag(CaseLoc, diag::err_case_not_in_switch);
      return StmtError();
    }
  
    if (LHSVal.isInvalid() || RHSVal.isInvalid()) {
      getCurFunction()->SwitchStack.back().setInt(true);
      return StmtError();
    }
  
    auto *CS = CaseStmt::Create(Context, LHSVal.get(), RHSVal.get(),
                                CaseLoc, DotDotDotLoc, ColonLoc);
    getCurFunction()->SwitchStack.back().getPointer()->addSwitchCase(CS);
    return CS;
  }
  
  /// ActOnCaseStmtBody - This installs a statement as the body of a case.
  void Sema::ActOnCaseStmtBody(Stmt *S, Stmt *SubStmt) {
    cast<CaseStmt>(S)->setSubStmt(SubStmt);
  }
  
  StmtResult
  Sema::ActOnDefaultStmt(SourceLocation DefaultLoc, SourceLocation ColonLoc,
                         Stmt *SubStmt, Scope *CurScope) {
    if (getCurFunction()->SwitchStack.empty()) {
      Diag(DefaultLoc, diag::err_default_not_in_switch);
      return SubStmt;
    }
  
    DefaultStmt *DS = new (Context) DefaultStmt(DefaultLoc, ColonLoc, SubStmt);
    getCurFunction()->SwitchStack.back().getPointer()->addSwitchCase(DS);
    return DS;
  }
  
  StmtResult
  Sema::ActOnLabelStmt(SourceLocation IdentLoc, LabelDecl *TheDecl,
                       SourceLocation ColonLoc, Stmt *SubStmt) {
    // If the label was multiply defined, reject it now.
    if (TheDecl->getStmt()) {
      Diag(IdentLoc, diag::err_redefinition_of_label) << TheDecl->getDeclName();
      Diag(TheDecl->getLocation(), diag::note_previous_definition);
      return SubStmt;
    }
  
    // Otherwise, things are good.  Fill in the declaration and return it.
    LabelStmt *LS = new (Context) LabelStmt(IdentLoc, TheDecl, SubStmt);
    TheDecl->setStmt(LS);
    if (!TheDecl->isGnuLocal()) {
      TheDecl->setLocStart(IdentLoc);
      if (!TheDecl->isMSAsmLabel()) {
        // Don't update the location of MS ASM labels.  These will result in
        // a diagnostic, and changing the location here will mess that up.
        TheDecl->setLocation(IdentLoc);
      }
    }
    return LS;
  }
  
  StmtResult Sema::ActOnAttributedStmt(SourceLocation AttrLoc,
                                       ArrayRef<const Attr*> Attrs,
                                       Stmt *SubStmt) {
    // Fill in the declaration and return it.
    AttributedStmt *LS = AttributedStmt::Create(Context, AttrLoc, Attrs, SubStmt);
    return LS;
  }
  
  namespace {
  class CommaVisitor : public EvaluatedExprVisitor<CommaVisitor> {
    typedef EvaluatedExprVisitor<CommaVisitor> Inherited;
    Sema &SemaRef;
  public:
    CommaVisitor(Sema &SemaRef) : Inherited(SemaRef.Context), SemaRef(SemaRef) {}
    void VisitBinaryOperator(BinaryOperator *E) {
      if (E->getOpcode() == BO_Comma)
        SemaRef.DiagnoseCommaOperator(E->getLHS(), E->getExprLoc());
      EvaluatedExprVisitor<CommaVisitor>::VisitBinaryOperator(E);
    }
  };
  }
  
  StmtResult
  Sema::ActOnIfStmt(SourceLocation IfLoc, bool IsConstexpr, Stmt *InitStmt,
                    ConditionResult Cond,
                    Stmt *thenStmt, SourceLocation ElseLoc,
                    Stmt *elseStmt) {
    if (Cond.isInvalid())
      Cond = ConditionResult(
          *this, nullptr,
          MakeFullExpr(new (Context) OpaqueValueExpr(SourceLocation(),
                                                     Context.BoolTy, VK_RValue),
                       IfLoc),
          false);
  
    Expr *CondExpr = Cond.get().second;
    // Only call the CommaVisitor when not C89 due to differences in scope flags.
    if ((getLangOpts().C99 || getLangOpts().CPlusPlus) &&
        !Diags.isIgnored(diag::warn_comma_operator, CondExpr->getExprLoc()))
      CommaVisitor(*this).Visit(CondExpr);
  
    if (!elseStmt)
      DiagnoseEmptyStmtBody(CondExpr->getEndLoc(), thenStmt,
                            diag::warn_empty_if_body);
  
    return BuildIfStmt(IfLoc, IsConstexpr, InitStmt, Cond, thenStmt, ElseLoc,
                       elseStmt);
  }
  
  StmtResult Sema::BuildIfStmt(SourceLocation IfLoc, bool IsConstexpr,
                               Stmt *InitStmt, ConditionResult Cond,
                               Stmt *thenStmt, SourceLocation ElseLoc,
                               Stmt *elseStmt) {
    if (Cond.isInvalid())
      return StmtError();
  
    if (IsConstexpr || isa<ObjCAvailabilityCheckExpr>(Cond.get().second))
      setFunctionHasBranchProtectedScope();
  
    return IfStmt::Create(Context, IfLoc, IsConstexpr, InitStmt, Cond.get().first,
                          Cond.get().second, thenStmt, ElseLoc, elseStmt);
  }
  
  namespace {
    struct CaseCompareFunctor {
      bool operator()(const std::pair<llvm::APSInt, CaseStmt*> &LHS,
                      const llvm::APSInt &RHS) {
        return LHS.first < RHS;
      }
      bool operator()(const std::pair<llvm::APSInt, CaseStmt*> &LHS,
                      const std::pair<llvm::APSInt, CaseStmt*> &RHS) {
        return LHS.first < RHS.first;
      }
      bool operator()(const llvm::APSInt &LHS,
                      const std::pair<llvm::APSInt, CaseStmt*> &RHS) {
        return LHS < RHS.first;
      }
    };
  }
  
  /// CmpCaseVals - Comparison predicate for sorting case values.
  ///
  static bool CmpCaseVals(const std::pair<llvm::APSInt, CaseStmt*>& lhs,
                          const std::pair<llvm::APSInt, CaseStmt*>& rhs) {
    if (lhs.first < rhs.first)
      return true;
  
    if (lhs.first == rhs.first &&
        lhs.second->getCaseLoc().getRawEncoding()
         < rhs.second->getCaseLoc().getRawEncoding())
      return true;
    return false;
  }
  
  /// CmpEnumVals - Comparison predicate for sorting enumeration values.
  ///
  static bool CmpEnumVals(const std::pair<llvm::APSInt, EnumConstantDecl*>& lhs,
                          const std::pair<llvm::APSInt, EnumConstantDecl*>& rhs)
  {
    return lhs.first < rhs.first;
  }
  
  /// EqEnumVals - Comparison preficate for uniqing enumeration values.
  ///
  static bool EqEnumVals(const std::pair<llvm::APSInt, EnumConstantDecl*>& lhs,
                         const std::pair<llvm::APSInt, EnumConstantDecl*>& rhs)
  {
    return lhs.first == rhs.first;
  }
  
  /// GetTypeBeforeIntegralPromotion - Returns the pre-promotion type of
  /// potentially integral-promoted expression @p expr.
  static QualType GetTypeBeforeIntegralPromotion(const Expr *&E) {
    if (const auto *FE = dyn_cast<FullExpr>(E))
      E = FE->getSubExpr();
    while (const auto *ImpCast = dyn_cast<ImplicitCastExpr>(E)) {
      if (ImpCast->getCastKind() != CK_IntegralCast) break;
      E = ImpCast->getSubExpr();
    }
    return E->getType();
  }
  
  ExprResult Sema::CheckSwitchCondition(SourceLocation SwitchLoc, Expr *Cond) {
    class SwitchConvertDiagnoser : public ICEConvertDiagnoser {
      Expr *Cond;
  
    public:
      SwitchConvertDiagnoser(Expr *Cond)
          : ICEConvertDiagnoser(/*AllowScopedEnumerations*/true, false, true),
            Cond(Cond) {}
  
      SemaDiagnosticBuilder diagnoseNotInt(Sema &S, SourceLocation Loc,
                                           QualType T) override {
        return S.Diag(Loc, diag::err_typecheck_statement_requires_integer) << T;
      }
  
      SemaDiagnosticBuilder diagnoseIncomplete(
          Sema &S, SourceLocation Loc, QualType T) override {
        return S.Diag(Loc, diag::err_switch_incomplete_class_type)
                 << T << Cond->getSourceRange();
      }
  
      SemaDiagnosticBuilder diagnoseExplicitConv(
          Sema &S, SourceLocation Loc, QualType T, QualType ConvTy) override {
        return S.Diag(Loc, diag::err_switch_explicit_conversion) << T << ConvTy;
      }
  
      SemaDiagnosticBuilder noteExplicitConv(
          Sema &S, CXXConversionDecl *Conv, QualType ConvTy) override {
        return S.Diag(Conv->getLocation(), diag::note_switch_conversion)
          << ConvTy->isEnumeralType() << ConvTy;
      }
  
      SemaDiagnosticBuilder diagnoseAmbiguous(Sema &S, SourceLocation Loc,
                                              QualType T) override {
        return S.Diag(Loc, diag::err_switch_multiple_conversions) << T;
      }
  
      SemaDiagnosticBuilder noteAmbiguous(
          Sema &S, CXXConversionDecl *Conv, QualType ConvTy) override {
        return S.Diag(Conv->getLocation(), diag::note_switch_conversion)
        << ConvTy->isEnumeralType() << ConvTy;
      }
  
      SemaDiagnosticBuilder diagnoseConversion(
          Sema &S, SourceLocation Loc, QualType T, QualType ConvTy) override {
        llvm_unreachable("conversion functions are permitted");
      }
    } SwitchDiagnoser(Cond);
  
    ExprResult CondResult =
        PerformContextualImplicitConversion(SwitchLoc, Cond, SwitchDiagnoser);
    if (CondResult.isInvalid())
      return ExprError();
  
    // FIXME: PerformContextualImplicitConversion doesn't always tell us if it
    // failed and produced a diagnostic.
    Cond = CondResult.get();
    if (!Cond->isTypeDependent() &&
        !Cond->getType()->isIntegralOrEnumerationType())
      return ExprError();
  
    // C99 6.8.4.2p5 - Integer promotions are performed on the controlling expr.
    return UsualUnaryConversions(Cond);
  }
  
  StmtResult Sema::ActOnStartOfSwitchStmt(SourceLocation SwitchLoc,
                                          Stmt *InitStmt, ConditionResult Cond) {
    Expr *CondExpr = Cond.get().second;
    assert((Cond.isInvalid() || CondExpr) && "switch with no condition");
  
    if (CondExpr && !CondExpr->isTypeDependent()) {
      // We have already converted the expression to an integral or enumeration
      // type, when we parsed the switch condition. If we don't have an
      // appropriate type now, enter the switch scope but remember that it's
      // invalid.
      assert(CondExpr->getType()->isIntegralOrEnumerationType() &&
             "invalid condition type");
      if (CondExpr->isKnownToHaveBooleanValue()) {
        // switch(bool_expr) {...} is often a programmer error, e.g.
        //   switch(n && mask) { ... }  // Doh - should be "n & mask".
        // One can always use an if statement instead of switch(bool_expr).
        Diag(SwitchLoc, diag::warn_bool_switch_condition)
            << CondExpr->getSourceRange();
      }
    }
  
    setFunctionHasBranchIntoScope();
  
    auto *SS = SwitchStmt::Create(Context, InitStmt, Cond.get().first, CondExpr);
    getCurFunction()->SwitchStack.push_back(
        FunctionScopeInfo::SwitchInfo(SS, false));
    return SS;
  }
  
  static void AdjustAPSInt(llvm::APSInt &Val, unsigned BitWidth, bool IsSigned) {
    Val = Val.extOrTrunc(BitWidth);
    Val.setIsSigned(IsSigned);
  }
  
  /// Check the specified case value is in range for the given unpromoted switch
  /// type.
  static void checkCaseValue(Sema &S, SourceLocation Loc, const llvm::APSInt &Val,
                             unsigned UnpromotedWidth, bool UnpromotedSign) {
    // In C++11 onwards, this is checked by the language rules.
    if (S.getLangOpts().CPlusPlus11)
      return;
  
    // If the case value was signed and negative and the switch expression is
    // unsigned, don't bother to warn: this is implementation-defined behavior.
    // FIXME: Introduce a second, default-ignored warning for this case?
    if (UnpromotedWidth < Val.getBitWidth()) {
      llvm::APSInt ConvVal(Val);
      AdjustAPSInt(ConvVal, UnpromotedWidth, UnpromotedSign);
      AdjustAPSInt(ConvVal, Val.getBitWidth(), Val.isSigned());
      // FIXME: Use different diagnostics for overflow  in conversion to promoted
      // type versus "switch expression cannot have this value". Use proper
      // IntRange checking rather than just looking at the unpromoted type here.
      if (ConvVal != Val)
        S.Diag(Loc, diag::warn_case_value_overflow) << Val.toString(10)
                                                    << ConvVal.toString(10);
    }
  }
  
  typedef SmallVector<std::pair<llvm::APSInt, EnumConstantDecl*>, 64> EnumValsTy;
  
  /// Returns true if we should emit a diagnostic about this case expression not
  /// being a part of the enum used in the switch controlling expression.
  static bool ShouldDiagnoseSwitchCaseNotInEnum(const Sema &S,
                                                const EnumDecl *ED,
                                                const Expr *CaseExpr,
                                                EnumValsTy::iterator &EI,
                                                EnumValsTy::iterator &EIEnd,
                                                const llvm::APSInt &Val) {
    if (!ED->isClosed())
      return false;
  
    if (const DeclRefExpr *DRE =
            dyn_cast<DeclRefExpr>(CaseExpr->IgnoreParenImpCasts())) {
      if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
        QualType VarType = VD->getType();
        QualType EnumType = S.Context.getTypeDeclType(ED);
        if (VD->hasGlobalStorage() && VarType.isConstQualified() &&
            S.Context.hasSameUnqualifiedType(EnumType, VarType))
          return false;
      }
    }
  
    if (ED->hasAttr<FlagEnumAttr>())
      return !S.IsValueInFlagEnum(ED, Val, false);
  
    while (EI != EIEnd && EI->first < Val)
      EI++;
  
    if (EI != EIEnd && EI->first == Val)
      return false;
  
    return true;
  }
  
  static void checkEnumTypesInSwitchStmt(Sema &S, const Expr *Cond,
                                         const Expr *Case) {
    QualType CondType = Cond->getType();
    QualType CaseType = Case->getType();
  
    const EnumType *CondEnumType = CondType->getAs<EnumType>();
    const EnumType *CaseEnumType = CaseType->getAs<EnumType>();
    if (!CondEnumType || !CaseEnumType)
      return;
  
    // Ignore anonymous enums.
    if (!CondEnumType->getDecl()->getIdentifier() &&
        !CondEnumType->getDecl()->getTypedefNameForAnonDecl())
      return;
    if (!CaseEnumType->getDecl()->getIdentifier() &&
        !CaseEnumType->getDecl()->getTypedefNameForAnonDecl())
      return;
  
    if (S.Context.hasSameUnqualifiedType(CondType, CaseType))
      return;
  
    S.Diag(Case->getExprLoc(), diag::warn_comparison_of_mixed_enum_types_switch)
        << CondType << CaseType << Cond->getSourceRange()
        << Case->getSourceRange();
  }
  
  StmtResult
  Sema::ActOnFinishSwitchStmt(SourceLocation SwitchLoc, Stmt *Switch,
                              Stmt *BodyStmt) {
    SwitchStmt *SS = cast<SwitchStmt>(Switch);
    bool CaseListIsIncomplete = getCurFunction()->SwitchStack.back().getInt();
    assert(SS == getCurFunction()->SwitchStack.back().getPointer() &&
           "switch stack missing push/pop!");
  
    getCurFunction()->SwitchStack.pop_back();
  
    if (!BodyStmt) return StmtError();
    SS->setBody(BodyStmt, SwitchLoc);
  
    Expr *CondExpr = SS->getCond();
    if (!CondExpr) return StmtError();
  
    QualType CondType = CondExpr->getType();
  
    // C++ 6.4.2.p2:
    // Integral promotions are performed (on the switch condition).
    //
    // A case value unrepresentable by the original switch condition
    // type (before the promotion) doesn't make sense, even when it can
    // be represented by the promoted type.  Therefore we need to find
    // the pre-promotion type of the switch condition.
    const Expr *CondExprBeforePromotion = CondExpr;
    QualType CondTypeBeforePromotion =
        GetTypeBeforeIntegralPromotion(CondExprBeforePromotion);
  
    // Get the bitwidth of the switched-on value after promotions. We must
    // convert the integer case values to this width before comparison.
    bool HasDependentValue
      = CondExpr->isTypeDependent() || CondExpr->isValueDependent();
    unsigned CondWidth = HasDependentValue ? 0 : Context.getIntWidth(CondType);
    bool CondIsSigned = CondType->isSignedIntegerOrEnumerationType();
  
    // Get the width and signedness that the condition might actually have, for
    // warning purposes.
    // FIXME: Grab an IntRange for the condition rather than using the unpromoted
    // type.
    unsigned CondWidthBeforePromotion
      = HasDependentValue ? 0 : Context.getIntWidth(CondTypeBeforePromotion);
    bool CondIsSignedBeforePromotion
      = CondTypeBeforePromotion->isSignedIntegerOrEnumerationType();
  
    // Accumulate all of the case values in a vector so that we can sort them
    // and detect duplicates.  This vector contains the APInt for the case after
    // it has been converted to the condition type.
    typedef SmallVector<std::pair<llvm::APSInt, CaseStmt*>, 64> CaseValsTy;
    CaseValsTy CaseVals;
  
    // Keep track of any GNU case ranges we see.  The APSInt is the low value.
    typedef std::vector<std::pair<llvm::APSInt, CaseStmt*> > CaseRangesTy;
    CaseRangesTy CaseRanges;
  
    DefaultStmt *TheDefaultStmt = nullptr;
  
    bool CaseListIsErroneous = false;
  
    for (SwitchCase *SC = SS->getSwitchCaseList(); SC && !HasDependentValue;
         SC = SC->getNextSwitchCase()) {
  
      if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SC)) {
        if (TheDefaultStmt) {
          Diag(DS->getDefaultLoc(), diag::err_multiple_default_labels_defined);
          Diag(TheDefaultStmt->getDefaultLoc(), diag::note_duplicate_case_prev);
  
          // FIXME: Remove the default statement from the switch block so that
          // we'll return a valid AST.  This requires recursing down the AST and
          // finding it, not something we are set up to do right now.  For now,
          // just lop the entire switch stmt out of the AST.
          CaseListIsErroneous = true;
        }
        TheDefaultStmt = DS;
  
      } else {
        CaseStmt *CS = cast<CaseStmt>(SC);
  
        Expr *Lo = CS->getLHS();
  
        if (Lo->isValueDependent()) {
          HasDependentValue = true;
          break;
        }
  
        // We already verified that the expression has a constant value;
        // get that value (prior to conversions).
        const Expr *LoBeforePromotion = Lo;
        GetTypeBeforeIntegralPromotion(LoBeforePromotion);
        llvm::APSInt LoVal = LoBeforePromotion->EvaluateKnownConstInt(Context);
  
        // Check the unconverted value is within the range of possible values of
        // the switch expression.
        checkCaseValue(*this, Lo->getBeginLoc(), LoVal, CondWidthBeforePromotion,
                       CondIsSignedBeforePromotion);
  
        // FIXME: This duplicates the check performed for warn_not_in_enum below.
        checkEnumTypesInSwitchStmt(*this, CondExprBeforePromotion,
                                   LoBeforePromotion);
  
        // Convert the value to the same width/sign as the condition.
        AdjustAPSInt(LoVal, CondWidth, CondIsSigned);
  
        // If this is a case range, remember it in CaseRanges, otherwise CaseVals.
        if (CS->getRHS()) {
          if (CS->getRHS()->isValueDependent()) {
            HasDependentValue = true;
            break;
          }
          CaseRanges.push_back(std::make_pair(LoVal, CS));
        } else
          CaseVals.push_back(std::make_pair(LoVal, CS));
      }
    }
  
    if (!HasDependentValue) {
      // If we don't have a default statement, check whether the
      // condition is constant.
      llvm::APSInt ConstantCondValue;
      bool HasConstantCond = false;
      if (!TheDefaultStmt) {
        Expr::EvalResult Result;
        HasConstantCond = CondExpr->EvaluateAsInt(Result, Context,
                                                  Expr::SE_AllowSideEffects);
        if (Result.Val.isInt())
          ConstantCondValue = Result.Val.getInt();
        assert(!HasConstantCond ||
               (ConstantCondValue.getBitWidth() == CondWidth &&
                ConstantCondValue.isSigned() == CondIsSigned));
      }
      bool ShouldCheckConstantCond = HasConstantCond;
  
      // Sort all the scalar case values so we can easily detect duplicates.
      llvm::stable_sort(CaseVals, CmpCaseVals);
  
      if (!CaseVals.empty()) {
        for (unsigned i = 0, e = CaseVals.size(); i != e; ++i) {
          if (ShouldCheckConstantCond &&
              CaseVals[i].first == ConstantCondValue)
            ShouldCheckConstantCond = false;
  
          if (i != 0 && CaseVals[i].first == CaseVals[i-1].first) {
            // If we have a duplicate, report it.
            // First, determine if either case value has a name
            StringRef PrevString, CurrString;
            Expr *PrevCase = CaseVals[i-1].second->getLHS()->IgnoreParenCasts();
            Expr *CurrCase = CaseVals[i].second->getLHS()->IgnoreParenCasts();
            if (DeclRefExpr *DeclRef = dyn_cast<DeclRefExpr>(PrevCase)) {
              PrevString = DeclRef->getDecl()->getName();
            }
            if (DeclRefExpr *DeclRef = dyn_cast<DeclRefExpr>(CurrCase)) {
              CurrString = DeclRef->getDecl()->getName();
            }
            SmallString<16> CaseValStr;
            CaseVals[i-1].first.toString(CaseValStr);
  
            if (PrevString == CurrString)
              Diag(CaseVals[i].second->getLHS()->getBeginLoc(),
                   diag::err_duplicate_case)
                  << (PrevString.empty() ? StringRef(CaseValStr) : PrevString);
            else
              Diag(CaseVals[i].second->getLHS()->getBeginLoc(),
                   diag::err_duplicate_case_differing_expr)
                  << (PrevString.empty() ? StringRef(CaseValStr) : PrevString)
                  << (CurrString.empty() ? StringRef(CaseValStr) : CurrString)
                  << CaseValStr;
  
            Diag(CaseVals[i - 1].second->getLHS()->getBeginLoc(),
                 diag::note_duplicate_case_prev);
            // FIXME: We really want to remove the bogus case stmt from the
            // substmt, but we have no way to do this right now.
            CaseListIsErroneous = true;
          }
        }
      }
  
      // Detect duplicate case ranges, which usually don't exist at all in
      // the first place.
      if (!CaseRanges.empty()) {
        // Sort all the case ranges by their low value so we can easily detect
        // overlaps between ranges.
        llvm::stable_sort(CaseRanges);
  
        // Scan the ranges, computing the high values and removing empty ranges.
        std::vector<llvm::APSInt> HiVals;
        for (unsigned i = 0, e = CaseRanges.size(); i != e; ++i) {
          llvm::APSInt &LoVal = CaseRanges[i].first;
          CaseStmt *CR = CaseRanges[i].second;
          Expr *Hi = CR->getRHS();
  
          const Expr *HiBeforePromotion = Hi;
          GetTypeBeforeIntegralPromotion(HiBeforePromotion);
          llvm::APSInt HiVal = HiBeforePromotion->EvaluateKnownConstInt(Context);
  
          // Check the unconverted value is within the range of possible values of
          // the switch expression.
          checkCaseValue(*this, Hi->getBeginLoc(), HiVal,
                         CondWidthBeforePromotion, CondIsSignedBeforePromotion);
  
          // Convert the value to the same width/sign as the condition.
          AdjustAPSInt(HiVal, CondWidth, CondIsSigned);
  
          // If the low value is bigger than the high value, the case is empty.
          if (LoVal > HiVal) {
            Diag(CR->getLHS()->getBeginLoc(), diag::warn_case_empty_range)
                << SourceRange(CR->getLHS()->getBeginLoc(), Hi->getEndLoc());
            CaseRanges.erase(CaseRanges.begin()+i);
            --i;
            --e;
            continue;
          }
  
          if (ShouldCheckConstantCond &&
              LoVal <= ConstantCondValue &&
              ConstantCondValue <= HiVal)
            ShouldCheckConstantCond = false;
  
          HiVals.push_back(HiVal);
        }
  
        // Rescan the ranges, looking for overlap with singleton values and other
        // ranges.  Since the range list is sorted, we only need to compare case
        // ranges with their neighbors.
        for (unsigned i = 0, e = CaseRanges.size(); i != e; ++i) {
          llvm::APSInt &CRLo = CaseRanges[i].first;
          llvm::APSInt &CRHi = HiVals[i];
          CaseStmt *CR = CaseRanges[i].second;
  
          // Check to see whether the case range overlaps with any
          // singleton cases.
          CaseStmt *OverlapStmt = nullptr;
          llvm::APSInt OverlapVal(32);
  
          // Find the smallest value >= the lower bound.  If I is in the
          // case range, then we have overlap.
          CaseValsTy::iterator I =
              llvm::lower_bound(CaseVals, CRLo, CaseCompareFunctor());
          if (I != CaseVals.end() && I->first < CRHi) {
            OverlapVal  = I->first;   // Found overlap with scalar.
            OverlapStmt = I->second;
          }
  
          // Find the smallest value bigger than the upper bound.
          I = std::upper_bound(I, CaseVals.end(), CRHi, CaseCompareFunctor());
          if (I != CaseVals.begin() && (I-1)->first >= CRLo) {
            OverlapVal  = (I-1)->first;      // Found overlap with scalar.
            OverlapStmt = (I-1)->second;
          }
  
          // Check to see if this case stmt overlaps with the subsequent
          // case range.
          if (i && CRLo <= HiVals[i-1]) {
            OverlapVal  = HiVals[i-1];       // Found overlap with range.
            OverlapStmt = CaseRanges[i-1].second;
          }
  
          if (OverlapStmt) {
            // If we have a duplicate, report it.
            Diag(CR->getLHS()->getBeginLoc(), diag::err_duplicate_case)
                << OverlapVal.toString(10);
            Diag(OverlapStmt->getLHS()->getBeginLoc(),
                 diag::note_duplicate_case_prev);
            // FIXME: We really want to remove the bogus case stmt from the
            // substmt, but we have no way to do this right now.
            CaseListIsErroneous = true;
          }
        }
      }
  
      // Complain if we have a constant condition and we didn't find a match.
      if (!CaseListIsErroneous && !CaseListIsIncomplete &&
          ShouldCheckConstantCond) {
        // TODO: it would be nice if we printed enums as enums, chars as
        // chars, etc.
        Diag(CondExpr->getExprLoc(), diag::warn_missing_case_for_condition)
          << ConstantCondValue.toString(10)
          << CondExpr->getSourceRange();
      }
  
      // Check to see if switch is over an Enum and handles all of its
      // values.  We only issue a warning if there is not 'default:', but
      // we still do the analysis to preserve this information in the AST
      // (which can be used by flow-based analyes).
      //
      const EnumType *ET = CondTypeBeforePromotion->getAs<EnumType>();
  
      // If switch has default case, then ignore it.
      if (!CaseListIsErroneous && !CaseListIsIncomplete && !HasConstantCond &&
          ET && ET->getDecl()->isCompleteDefinition()) {
        const EnumDecl *ED = ET->getDecl();
        EnumValsTy EnumVals;
  
        // Gather all enum values, set their type and sort them,
        // allowing easier comparison with CaseVals.
        for (auto *EDI : ED->enumerators()) {
          llvm::APSInt Val = EDI->getInitVal();
          AdjustAPSInt(Val, CondWidth, CondIsSigned);
          EnumVals.push_back(std::make_pair(Val, EDI));
        }
        llvm::stable_sort(EnumVals, CmpEnumVals);
        auto EI = EnumVals.begin(), EIEnd =
          std::unique(EnumVals.begin(), EnumVals.end(), EqEnumVals);
  
        // See which case values aren't in enum.
        for (CaseValsTy::const_iterator CI = CaseVals.begin();
            CI != CaseVals.end(); CI++) {
          Expr *CaseExpr = CI->second->getLHS();
          if (ShouldDiagnoseSwitchCaseNotInEnum(*this, ED, CaseExpr, EI, EIEnd,
                                                CI->first))
            Diag(CaseExpr->getExprLoc(), diag::warn_not_in_enum)
              << CondTypeBeforePromotion;
        }
  
        // See which of case ranges aren't in enum
        EI = EnumVals.begin();
        for (CaseRangesTy::const_iterator RI = CaseRanges.begin();
            RI != CaseRanges.end(); RI++) {
          Expr *CaseExpr = RI->second->getLHS();
          if (ShouldDiagnoseSwitchCaseNotInEnum(*this, ED, CaseExpr, EI, EIEnd,
                                                RI->first))
            Diag(CaseExpr->getExprLoc(), diag::warn_not_in_enum)
              << CondTypeBeforePromotion;
  
          llvm::APSInt Hi =
            RI->second->getRHS()->EvaluateKnownConstInt(Context);
          AdjustAPSInt(Hi, CondWidth, CondIsSigned);
  
          CaseExpr = RI->second->getRHS();
          if (ShouldDiagnoseSwitchCaseNotInEnum(*this, ED, CaseExpr, EI, EIEnd,
                                                Hi))
            Diag(CaseExpr->getExprLoc(), diag::warn_not_in_enum)
              << CondTypeBeforePromotion;
        }
  
        // Check which enum vals aren't in switch
        auto CI = CaseVals.begin();
        auto RI = CaseRanges.begin();
        bool hasCasesNotInSwitch = false;
  
        SmallVector<DeclarationName,8> UnhandledNames;
  
        for (EI = EnumVals.begin(); EI != EIEnd; EI++) {
          // Don't warn about omitted unavailable EnumConstantDecls.
          switch (EI->second->getAvailability()) {
          case AR_Deprecated:
            // Omitting a deprecated constant is ok; it should never materialize.
          case AR_Unavailable:
            continue;
  
          case AR_NotYetIntroduced:
            // Partially available enum constants should be present. Note that we
            // suppress -Wunguarded-availability diagnostics for such uses.
          case AR_Available:
            break;
          }
  
          if (EI->second->hasAttr<UnusedAttr>())
            continue;
  
          // Drop unneeded case values
          while (CI != CaseVals.end() && CI->first < EI->first)
            CI++;
  
          if (CI != CaseVals.end() && CI->first == EI->first)
            continue;
  
          // Drop unneeded case ranges
          for (; RI != CaseRanges.end(); RI++) {
            llvm::APSInt Hi =
              RI->second->getRHS()->EvaluateKnownConstInt(Context);
            AdjustAPSInt(Hi, CondWidth, CondIsSigned);
            if (EI->first <= Hi)
              break;
          }
  
          if (RI == CaseRanges.end() || EI->first < RI->first) {
            hasCasesNotInSwitch = true;
            UnhandledNames.push_back(EI->second->getDeclName());
          }
        }
  
        if (TheDefaultStmt && UnhandledNames.empty() && ED->isClosedNonFlag())
          Diag(TheDefaultStmt->getDefaultLoc(), diag::warn_unreachable_default);
  
        // Produce a nice diagnostic if multiple values aren't handled.
        if (!UnhandledNames.empty()) {
          DiagnosticBuilder DB = Diag(CondExpr->getExprLoc(),
                                      TheDefaultStmt ? diag::warn_def_missing_case
                                                     : diag::warn_missing_case)
                                 << (int)UnhandledNames.size();
  
          for (size_t I = 0, E = std::min(UnhandledNames.size(), (size_t)3);
               I != E; ++I)
            DB << UnhandledNames[I];
        }
  
        if (!hasCasesNotInSwitch)
          SS->setAllEnumCasesCovered();
      }
    }
  
    if (BodyStmt)
      DiagnoseEmptyStmtBody(CondExpr->getEndLoc(), BodyStmt,
                            diag::warn_empty_switch_body);
  
    // FIXME: If the case list was broken is some way, we don't have a good system
    // to patch it up.  Instead, just return the whole substmt as broken.
    if (CaseListIsErroneous)
      return StmtError();
  
    return SS;
  }
  
  void
  Sema::DiagnoseAssignmentEnum(QualType DstType, QualType SrcType,
                               Expr *SrcExpr) {
    if (Diags.isIgnored(diag::warn_not_in_enum_assignment, SrcExpr->getExprLoc()))
      return;
  
    if (const EnumType *ET = DstType->getAs<EnumType>())
      if (!Context.hasSameUnqualifiedType(SrcType, DstType) &&
          SrcType->isIntegerType()) {
        if (!SrcExpr->isTypeDependent() && !SrcExpr->isValueDependent() &&
            SrcExpr->isIntegerConstantExpr(Context)) {
          // Get the bitwidth of the enum value before promotions.
          unsigned DstWidth = Context.getIntWidth(DstType);
          bool DstIsSigned = DstType->isSignedIntegerOrEnumerationType();
  
          llvm::APSInt RhsVal = SrcExpr->EvaluateKnownConstInt(Context);
          AdjustAPSInt(RhsVal, DstWidth, DstIsSigned);
          const EnumDecl *ED = ET->getDecl();
  
          if (!ED->isClosed())
            return;
  
          if (ED->hasAttr<FlagEnumAttr>()) {
            if (!IsValueInFlagEnum(ED, RhsVal, true))
              Diag(SrcExpr->getExprLoc(), diag::warn_not_in_enum_assignment)
                << DstType.getUnqualifiedType();
          } else {
            typedef SmallVector<std::pair<llvm::APSInt, EnumConstantDecl *>, 64>
                EnumValsTy;
            EnumValsTy EnumVals;
  
            // Gather all enum values, set their type and sort them,
            // allowing easier comparison with rhs constant.
            for (auto *EDI : ED->enumerators()) {
              llvm::APSInt Val = EDI->getInitVal();
              AdjustAPSInt(Val, DstWidth, DstIsSigned);
              EnumVals.push_back(std::make_pair(Val, EDI));
            }
            if (EnumVals.empty())
              return;
            llvm::stable_sort(EnumVals, CmpEnumVals);
            EnumValsTy::iterator EIend =
                std::unique(EnumVals.begin(), EnumVals.end(), EqEnumVals);
  
            // See which values aren't in the enum.
            EnumValsTy::const_iterator EI = EnumVals.begin();
            while (EI != EIend && EI->first < RhsVal)
              EI++;
            if (EI == EIend || EI->first != RhsVal) {
              Diag(SrcExpr->getExprLoc(), diag::warn_not_in_enum_assignment)
                  << DstType.getUnqualifiedType();
            }
          }
        }
      }
  }
  
  StmtResult Sema::ActOnWhileStmt(SourceLocation WhileLoc, ConditionResult Cond,
                                  Stmt *Body) {
    if (Cond.isInvalid())
      return StmtError();
  
    auto CondVal = Cond.get();
    CheckBreakContinueBinding(CondVal.second);
  
    if (CondVal.second &&
        !Diags.isIgnored(diag::warn_comma_operator, CondVal.second->getExprLoc()))
      CommaVisitor(*this).Visit(CondVal.second);
  
    if (isa<NullStmt>(Body))
      getCurCompoundScope().setHasEmptyLoopBodies();
  
    return WhileStmt::Create(Context, CondVal.first, CondVal.second, Body,
                             WhileLoc);
  }
  
  StmtResult
  Sema::ActOnDoStmt(SourceLocation DoLoc, Stmt *Body,
                    SourceLocation WhileLoc, SourceLocation CondLParen,
                    Expr *Cond, SourceLocation CondRParen) {
    assert(Cond && "ActOnDoStmt(): missing expression");
  
    CheckBreakContinueBinding(Cond);
    ExprResult CondResult = CheckBooleanCondition(DoLoc, Cond);
    if (CondResult.isInvalid())
      return StmtError();
    Cond = CondResult.get();
  
    CondResult = ActOnFinishFullExpr(Cond, DoLoc, /*DiscardedValue*/ false);
    if (CondResult.isInvalid())
      return StmtError();
    Cond = CondResult.get();
  
    // Only call the CommaVisitor for C89 due to differences in scope flags.
    if (Cond && !getLangOpts().C99 && !getLangOpts().CPlusPlus &&
        !Diags.isIgnored(diag::warn_comma_operator, Cond->getExprLoc()))
      CommaVisitor(*this).Visit(Cond);
  
    return new (Context) DoStmt(Body, Cond, DoLoc, WhileLoc, CondRParen);
  }
  
  namespace {
    // Use SetVector since the diagnostic cares about the ordering of the Decl's.
    using DeclSetVector =
        llvm::SetVector<VarDecl *, llvm::SmallVector<VarDecl *, 8>,
                        llvm::SmallPtrSet<VarDecl *, 8>>;
  
    // This visitor will traverse a conditional statement and store all
    // the evaluated decls into a vector.  Simple is set to true if none
    // of the excluded constructs are used.
    class DeclExtractor : public EvaluatedExprVisitor<DeclExtractor> {
      DeclSetVector &Decls;
      SmallVectorImpl<SourceRange> &Ranges;
      bool Simple;
    public:
      typedef EvaluatedExprVisitor<DeclExtractor> Inherited;
  
      DeclExtractor(Sema &S, DeclSetVector &Decls,
                    SmallVectorImpl<SourceRange> &Ranges) :
          Inherited(S.Context),
          Decls(Decls),
          Ranges(Ranges),
          Simple(true) {}
  
      bool isSimple() { return Simple; }
  
      // Replaces the method in EvaluatedExprVisitor.
      void VisitMemberExpr(MemberExpr* E) {
        Simple = false;
      }
  
      // Any Stmt not whitelisted will cause the condition to be marked complex.
      void VisitStmt(Stmt *S) {
        Simple = false;
      }
  
      void VisitBinaryOperator(BinaryOperator *E) {
        Visit(E->getLHS());
        Visit(E->getRHS());
      }
  
      void VisitCastExpr(CastExpr *E) {
        Visit(E->getSubExpr());
      }
  
      void VisitUnaryOperator(UnaryOperator *E) {
        // Skip checking conditionals with derefernces.
        if (E->getOpcode() == UO_Deref)
          Simple = false;
        else
          Visit(E->getSubExpr());
      }
  
      void VisitConditionalOperator(ConditionalOperator *E) {
        Visit(E->getCond());
        Visit(E->getTrueExpr());
        Visit(E->getFalseExpr());
      }
  
      void VisitParenExpr(ParenExpr *E) {
        Visit(E->getSubExpr());
      }
  
      void VisitBinaryConditionalOperator(BinaryConditionalOperator *E) {
        Visit(E->getOpaqueValue()->getSourceExpr());
        Visit(E->getFalseExpr());
      }
  
      void VisitIntegerLiteral(IntegerLiteral *E) { }
      void VisitFloatingLiteral(FloatingLiteral *E) { }
      void VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *E) { }
      void VisitCharacterLiteral(CharacterLiteral *E) { }
      void VisitGNUNullExpr(GNUNullExpr *E) { }
      void VisitImaginaryLiteral(ImaginaryLiteral *E) { }
  
      void VisitDeclRefExpr(DeclRefExpr *E) {
        VarDecl *VD = dyn_cast<VarDecl>(E->getDecl());
        if (!VD) {
          // Don't allow unhandled Decl types.
          Simple = false;
          return;
        }
  
        Ranges.push_back(E->getSourceRange());
  
        Decls.insert(VD);
      }
  
    }; // end class DeclExtractor
  
    // DeclMatcher checks to see if the decls are used in a non-evaluated
    // context.
    class DeclMatcher : public EvaluatedExprVisitor<DeclMatcher> {
      DeclSetVector &Decls;
      bool FoundDecl;
  
    public:
      typedef EvaluatedExprVisitor<DeclMatcher> Inherited;
  
      DeclMatcher(Sema &S, DeclSetVector &Decls, Stmt *Statement) :
          Inherited(S.Context), Decls(Decls), FoundDecl(false) {
        if (!Statement) return;
  
        Visit(Statement);
      }
  
      void VisitReturnStmt(ReturnStmt *S) {
        FoundDecl = true;
      }
  
      void VisitBreakStmt(BreakStmt *S) {
        FoundDecl = true;
      }
  
      void VisitGotoStmt(GotoStmt *S) {
        FoundDecl = true;
      }
  
      void VisitCastExpr(CastExpr *E) {
        if (E->getCastKind() == CK_LValueToRValue)
          CheckLValueToRValueCast(E->getSubExpr());
        else
          Visit(E->getSubExpr());
      }
  
      void CheckLValueToRValueCast(Expr *E) {
        E = E->IgnoreParenImpCasts();
  
        if (isa<DeclRefExpr>(E)) {
          return;
        }
  
        if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
          Visit(CO->getCond());
          CheckLValueToRValueCast(CO->getTrueExpr());
          CheckLValueToRValueCast(CO->getFalseExpr());
          return;
        }
  
        if (BinaryConditionalOperator *BCO =
                dyn_cast<BinaryConditionalOperator>(E)) {
          CheckLValueToRValueCast(BCO->getOpaqueValue()->getSourceExpr());
          CheckLValueToRValueCast(BCO->getFalseExpr());
          return;
        }
  
        Visit(E);
      }
  
      void VisitDeclRefExpr(DeclRefExpr *E) {
        if (VarDecl *VD = dyn_cast<VarDecl>(E->getDecl()))
          if (Decls.count(VD))
            FoundDecl = true;
      }
  
      void VisitPseudoObjectExpr(PseudoObjectExpr *POE) {
        // Only need to visit the semantics for POE.
        // SyntaticForm doesn't really use the Decal.
        for (auto *S : POE->semantics()) {
          if (auto *OVE = dyn_cast<OpaqueValueExpr>(S))
            // Look past the OVE into the expression it binds.
            Visit(OVE->getSourceExpr());
          else
            Visit(S);
        }
      }
  
      bool FoundDeclInUse() { return FoundDecl; }
  
    };  // end class DeclMatcher
  
    void CheckForLoopConditionalStatement(Sema &S, Expr *Second,
                                          Expr *Third, Stmt *Body) {
      // Condition is empty
      if (!Second) return;
  
      if (S.Diags.isIgnored(diag::warn_variables_not_in_loop_body,
                            Second->getBeginLoc()))
        return;
  
      PartialDiagnostic PDiag = S.PDiag(diag::warn_variables_not_in_loop_body);
      DeclSetVector Decls;
      SmallVector<SourceRange, 10> Ranges;
      DeclExtractor DE(S, Decls, Ranges);
      DE.Visit(Second);
  
      // Don't analyze complex conditionals.
      if (!DE.isSimple()) return;
  
      // No decls found.
      if (Decls.size() == 0) return;
  
      // Don't warn on volatile, static, or global variables.
      for (auto *VD : Decls)
        if (VD->getType().isVolatileQualified() || VD->hasGlobalStorage())
          return;
  
      if (DeclMatcher(S, Decls, Second).FoundDeclInUse() ||
          DeclMatcher(S, Decls, Third).FoundDeclInUse() ||
          DeclMatcher(S, Decls, Body).FoundDeclInUse())
        return;
  
      // Load decl names into diagnostic.
      if (Decls.size() > 4) {
        PDiag << 0;
      } else {
        PDiag << (unsigned)Decls.size();
        for (auto *VD : Decls)
          PDiag << VD->getDeclName();
      }
  
      for (auto Range : Ranges)
        PDiag << Range;
  
      S.Diag(Ranges.begin()->getBegin(), PDiag);
    }
  
    // If Statement is an incemement or decrement, return true and sets the
    // variables Increment and DRE.
    bool ProcessIterationStmt(Sema &S, Stmt* Statement, bool &Increment,
                              DeclRefExpr *&DRE) {
      if (auto Cleanups = dyn_cast<ExprWithCleanups>(Statement))
        if (!Cleanups->cleanupsHaveSideEffects())
          Statement = Cleanups->getSubExpr();
  
      if (UnaryOperator *UO = dyn_cast<UnaryOperator>(Statement)) {
        switch (UO->getOpcode()) {
          default: return false;
          case UO_PostInc:
          case UO_PreInc:
            Increment = true;
            break;
          case UO_PostDec:
          case UO_PreDec:
            Increment = false;
            break;
        }
        DRE = dyn_cast<DeclRefExpr>(UO->getSubExpr());
        return DRE;
      }
  
      if (CXXOperatorCallExpr *Call = dyn_cast<CXXOperatorCallExpr>(Statement)) {
        FunctionDecl *FD = Call->getDirectCallee();
        if (!FD || !FD->isOverloadedOperator()) return false;
        switch (FD->getOverloadedOperator()) {
          default: return false;
          case OO_PlusPlus:
            Increment = true;
            break;
          case OO_MinusMinus:
            Increment = false;
            break;
        }
        DRE = dyn_cast<DeclRefExpr>(Call->getArg(0));
        return DRE;
      }
  
      return false;
    }
  
    // A visitor to determine if a continue or break statement is a
    // subexpression.
    class BreakContinueFinder : public ConstEvaluatedExprVisitor<BreakContinueFinder> {
      SourceLocation BreakLoc;
      SourceLocation ContinueLoc;
      bool InSwitch = false;
  
    public:
      BreakContinueFinder(Sema &S, const Stmt* Body) :
          Inherited(S.Context) {
        Visit(Body);
      }
  
      typedef ConstEvaluatedExprVisitor<BreakContinueFinder> Inherited;
  
      void VisitContinueStmt(const ContinueStmt* E) {
        ContinueLoc = E->getContinueLoc();
      }
  
      void VisitBreakStmt(const BreakStmt* E) {
        if (!InSwitch)
          BreakLoc = E->getBreakLoc();
      }
  
      void VisitSwitchStmt(const SwitchStmt* S) {
        if (const Stmt *Init = S->getInit())
          Visit(Init);
        if (const Stmt *CondVar = S->getConditionVariableDeclStmt())
          Visit(CondVar);
        if (const Stmt *Cond = S->getCond())
          Visit(Cond);
  
        // Don't return break statements from the body of a switch.
        InSwitch = true;
        if (const Stmt *Body = S->getBody())
          Visit(Body);
        InSwitch = false;
      }
  
      void VisitForStmt(const ForStmt *S) {
        // Only visit the init statement of a for loop; the body
        // has a different break/continue scope.
        if (const Stmt *Init = S->getInit())
          Visit(Init);
      }
  
      void VisitWhileStmt(const WhileStmt *) {
        // Do nothing; the children of a while loop have a different
        // break/continue scope.
      }
  
      void VisitDoStmt(const DoStmt *) {
        // Do nothing; the children of a while loop have a different
        // break/continue scope.
      }
  
      void VisitCXXForRangeStmt(const CXXForRangeStmt *S) {
        // Only visit the initialization of a for loop; the body
        // has a different break/continue scope.
        if (const Stmt *Init = S->getInit())
          Visit(Init);
        if (const Stmt *Range = S->getRangeStmt())
          Visit(Range);
        if (const Stmt *Begin = S->getBeginStmt())
          Visit(Begin);
        if (const Stmt *End = S->getEndStmt())
          Visit(End);
      }
  
      void VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S) {
        // Only visit the initialization of a for loop; the body
        // has a different break/continue scope.
        if (const Stmt *Element = S->getElement())
          Visit(Element);
        if (const Stmt *Collection = S->getCollection())
          Visit(Collection);
      }
  
      bool ContinueFound() { return ContinueLoc.isValid(); }
      bool BreakFound() { return BreakLoc.isValid(); }
      SourceLocation GetContinueLoc() { return ContinueLoc; }
      SourceLocation GetBreakLoc() { return BreakLoc; }
  
    };  // end class BreakContinueFinder
  
    // Emit a warning when a loop increment/decrement appears twice per loop
    // iteration.  The conditions which trigger this warning are:
    // 1) The last statement in the loop body and the third expression in the
    //    for loop are both increment or both decrement of the same variable
    // 2) No continue statements in the loop body.
    void CheckForRedundantIteration(Sema &S, Expr *Third, Stmt *Body) {
      // Return when there is nothing to check.
      if (!Body || !Third) return;
  
      if (S.Diags.isIgnored(diag::warn_redundant_loop_iteration,
                            Third->getBeginLoc()))
        return;
  
      // Get the last statement from the loop body.
      CompoundStmt *CS = dyn_cast<CompoundStmt>(Body);
      if (!CS || CS->body_empty()) return;
      Stmt *LastStmt = CS->body_back();
      if (!LastStmt) return;
  
      bool LoopIncrement, LastIncrement;
      DeclRefExpr *LoopDRE, *LastDRE;
  
      if (!ProcessIterationStmt(S, Third, LoopIncrement, LoopDRE)) return;
      if (!ProcessIterationStmt(S, LastStmt, LastIncrement, LastDRE)) return;
  
      // Check that the two statements are both increments or both decrements
      // on the same variable.
      if (LoopIncrement != LastIncrement ||
          LoopDRE->getDecl() != LastDRE->getDecl()) return;
  
      if (BreakContinueFinder(S, Body).ContinueFound()) return;
  
      S.Diag(LastDRE->getLocation(), diag::warn_redundant_loop_iteration)
           << LastDRE->getDecl() << LastIncrement;
      S.Diag(LoopDRE->getLocation(), diag::note_loop_iteration_here)
           << LoopIncrement;
    }
  
  } // end namespace
  
  
  void Sema::CheckBreakContinueBinding(Expr *E) {
    if (!E || getLangOpts().CPlusPlus)
      return;
    BreakContinueFinder BCFinder(*this, E);
    Scope *BreakParent = CurScope->getBreakParent();
    if (BCFinder.BreakFound() && BreakParent) {
      if (BreakParent->getFlags() & Scope::SwitchScope) {
        Diag(BCFinder.GetBreakLoc(), diag::warn_break_binds_to_switch);
      } else {
        Diag(BCFinder.GetBreakLoc(), diag::warn_loop_ctrl_binds_to_inner)
            << "break";
      }
    } else if (BCFinder.ContinueFound() && CurScope->getContinueParent()) {
      Diag(BCFinder.GetContinueLoc(), diag::warn_loop_ctrl_binds_to_inner)
          << "continue";
    }
  }
  
  StmtResult Sema::ActOnForStmt(SourceLocation ForLoc, SourceLocation LParenLoc,
                                Stmt *First, ConditionResult Second,
                                FullExprArg third, SourceLocation RParenLoc,
                                Stmt *Body) {
    if (Second.isInvalid())
      return StmtError();
  
    if (!getLangOpts().CPlusPlus) {
      if (DeclStmt *DS = dyn_cast_or_null<DeclStmt>(First)) {
        // C99 6.8.5p3: The declaration part of a 'for' statement shall only
        // declare identifiers for objects having storage class 'auto' or
        // 'register'.
        for (auto *DI : DS->decls()) {
          VarDecl *VD = dyn_cast<VarDecl>(DI);
          if (VD && VD->isLocalVarDecl() && !VD->hasLocalStorage())
            VD = nullptr;
          if (!VD) {
            Diag(DI->getLocation(), diag::err_non_local_variable_decl_in_for);
            DI->setInvalidDecl();
          }
        }
      }
    }
  
    CheckBreakContinueBinding(Second.get().second);
    CheckBreakContinueBinding(third.get());
  
    if (!Second.get().first)
      CheckForLoopConditionalStatement(*this, Second.get().second, third.get(),
                                       Body);
    CheckForRedundantIteration(*this, third.get(), Body);
  
    if (Second.get().second &&
        !Diags.isIgnored(diag::warn_comma_operator,
                         Second.get().second->getExprLoc()))
      CommaVisitor(*this).Visit(Second.get().second);
  
    Expr *Third  = third.release().getAs<Expr>();
    if (isa<NullStmt>(Body))
      getCurCompoundScope().setHasEmptyLoopBodies();
  
    return new (Context)
        ForStmt(Context, First, Second.get().second, Second.get().first, Third,
                Body, ForLoc, LParenLoc, RParenLoc);
  }
  
  /// In an Objective C collection iteration statement:
  ///   for (x in y)
  /// x can be an arbitrary l-value expression.  Bind it up as a
  /// full-expression.
  StmtResult Sema::ActOnForEachLValueExpr(Expr *E) {
    // Reduce placeholder expressions here.  Note that this rejects the
    // use of pseudo-object l-values in this position.
    ExprResult result = CheckPlaceholderExpr(E);
    if (result.isInvalid()) return StmtError();
    E = result.get();
  
    ExprResult FullExpr = ActOnFinishFullExpr(E, /*DiscardedValue*/ false);
    if (FullExpr.isInvalid())
      return StmtError();
    return StmtResult(static_cast<Stmt*>(FullExpr.get()));
  }
  
  ExprResult
  Sema::CheckObjCForCollectionOperand(SourceLocation forLoc, Expr *collection) {
    if (!collection)
      return ExprError();
  
    ExprResult result = CorrectDelayedTyposInExpr(collection);
    if (!result.isUsable())
      return ExprError();
    collection = result.get();
  
    // Bail out early if we've got a type-dependent expression.
    if (collection->isTypeDependent()) return collection;
  
    // Perform normal l-value conversion.
    result = DefaultFunctionArrayLvalueConversion(collection);
    if (result.isInvalid())
      return ExprError();
    collection = result.get();
  
    // The operand needs to have object-pointer type.
    // TODO: should we do a contextual conversion?
    const ObjCObjectPointerType *pointerType =
      collection->getType()->getAs<ObjCObjectPointerType>();
    if (!pointerType)
      return Diag(forLoc, diag::err_collection_expr_type)
               << collection->getType() << collection->getSourceRange();
  
    // Check that the operand provides
    //   - countByEnumeratingWithState:objects:count:
    const ObjCObjectType *objectType = pointerType->getObjectType();
    ObjCInterfaceDecl *iface = objectType->getInterface();
  
    // If we have a forward-declared type, we can't do this check.
    // Under ARC, it is an error not to have a forward-declared class.
    if (iface &&
        (getLangOpts().ObjCAutoRefCount
             ? RequireCompleteType(forLoc, QualType(objectType, 0),
                                   diag::err_arc_collection_forward, collection)
             : !isCompleteType(forLoc, QualType(objectType, 0)))) {
      // Otherwise, if we have any useful type information, check that
      // the type declares the appropriate method.
    } else if (iface || !objectType->qual_empty()) {
      IdentifierInfo *selectorIdents[] = {
        &Context.Idents.get("countByEnumeratingWithState"),
        &Context.Idents.get("objects"),
        &Context.Idents.get("count")
      };
      Selector selector = Context.Selectors.getSelector(3, &selectorIdents[0]);
  
      ObjCMethodDecl *method = nullptr;
  
      // If there's an interface, look in both the public and private APIs.
      if (iface) {
        method = iface->lookupInstanceMethod(selector);
        if (!method) method = iface->lookupPrivateMethod(selector);
      }
  
      // Also check protocol qualifiers.
      if (!method)
        method = LookupMethodInQualifiedType(selector, pointerType,
                                             /*instance*/ true);
  
      // If we didn't find it anywhere, give up.
      if (!method) {
        Diag(forLoc, diag::warn_collection_expr_type)
          << collection->getType() << selector << collection->getSourceRange();
      }
  
      // TODO: check for an incompatible signature?
    }
  
    // Wrap up any cleanups in the expression.
    return collection;
  }
  
  StmtResult
  Sema::ActOnObjCForCollectionStmt(SourceLocation ForLoc,
                                   Stmt *First, Expr *collection,
                                   SourceLocation RParenLoc) {
    setFunctionHasBranchProtectedScope();
  
    ExprResult CollectionExprResult =
      CheckObjCForCollectionOperand(ForLoc, collection);
  
    if (First) {
      QualType FirstType;
      if (DeclStmt *DS = dyn_cast<DeclStmt>(First)) {
        if (!DS->isSingleDecl())
          return StmtError(Diag((*DS->decl_begin())->getLocation(),
                           diag::err_toomany_element_decls));
  
        VarDecl *D = dyn_cast<VarDecl>(DS->getSingleDecl());
        if (!D || D->isInvalidDecl())
          return StmtError();
  
        FirstType = D->getType();
        // C99 6.8.5p3: The declaration part of a 'for' statement shall only
        // declare identifiers for objects having storage class 'auto' or
        // 'register'.
        if (!D->hasLocalStorage())
          return StmtError(Diag(D->getLocation(),
                                diag::err_non_local_variable_decl_in_for));
  
        // If the type contained 'auto', deduce the 'auto' to 'id'.
        if (FirstType->getContainedAutoType()) {
          OpaqueValueExpr OpaqueId(D->getLocation(), Context.getObjCIdType(),
                                   VK_RValue);
          Expr *DeducedInit = &OpaqueId;
          if (DeduceAutoType(D->getTypeSourceInfo(), DeducedInit, FirstType) ==
                  DAR_Failed)
            DiagnoseAutoDeductionFailure(D, DeducedInit);
          if (FirstType.isNull()) {
            D->setInvalidDecl();
            return StmtError();
          }
  
          D->setType(FirstType);
  
          if (!inTemplateInstantiation()) {
            SourceLocation Loc =
                D->getTypeSourceInfo()->getTypeLoc().getBeginLoc();
            Diag(Loc, diag::warn_auto_var_is_id)
              << D->getDeclName();
          }
        }
  
      } else {
        Expr *FirstE = cast<Expr>(First);
        if (!FirstE->isTypeDependent() && !FirstE->isLValue())
          return StmtError(
              Diag(First->getBeginLoc(), diag::err_selector_element_not_lvalue)
              << First->getSourceRange());
  
        FirstType = static_cast<Expr*>(First)->getType();
        if (FirstType.isConstQualified())
          Diag(ForLoc, diag::err_selector_element_const_type)
            << FirstType << First->getSourceRange();
      }
      if (!FirstType->isDependentType() &&
          !FirstType->isObjCObjectPointerType() &&
          !FirstType->isBlockPointerType())
          return StmtError(Diag(ForLoc, diag::err_selector_element_type)
                             << FirstType << First->getSourceRange());
    }
  
    if (CollectionExprResult.isInvalid())
      return StmtError();
  
    CollectionExprResult =
        ActOnFinishFullExpr(CollectionExprResult.get(), /*DiscardedValue*/ false);
    if (CollectionExprResult.isInvalid())
      return StmtError();
  
    return new (Context) ObjCForCollectionStmt(First, CollectionExprResult.get(),
                                               nullptr, ForLoc, RParenLoc);
  }
  
  /// Finish building a variable declaration for a for-range statement.
  /// \return true if an error occurs.
  static bool FinishForRangeVarDecl(Sema &SemaRef, VarDecl *Decl, Expr *Init,
                                    SourceLocation Loc, int DiagID) {
    if (Decl->getType()->isUndeducedType()) {
      ExprResult Res = SemaRef.CorrectDelayedTyposInExpr(Init);
      if (!Res.isUsable()) {
        Decl->setInvalidDecl();
        return true;
      }
      Init = Res.get();
    }
  
    // Deduce the type for the iterator variable now rather than leaving it to
    // AddInitializerToDecl, so we can produce a more suitable diagnostic.
    QualType InitType;
    if ((!isa<InitListExpr>(Init) && Init->getType()->isVoidType()) ||
        SemaRef.DeduceAutoType(Decl->getTypeSourceInfo(), Init, InitType) ==
            Sema::DAR_Failed)
      SemaRef.Diag(Loc, DiagID) << Init->getType();
    if (InitType.isNull()) {
      Decl->setInvalidDecl();
      return true;
    }
    Decl->setType(InitType);
  
    // In ARC, infer lifetime.
    // FIXME: ARC may want to turn this into 'const __unsafe_unretained' if
    // we're doing the equivalent of fast iteration.
    if (SemaRef.getLangOpts().ObjCAutoRefCount &&
        SemaRef.inferObjCARCLifetime(Decl))
      Decl->setInvalidDecl();
  
    SemaRef.AddInitializerToDecl(Decl, Init, /*DirectInit=*/false);
    SemaRef.FinalizeDeclaration(Decl);
    SemaRef.CurContext->addHiddenDecl(Decl);
    return false;
  }
  
  namespace {
  // An enum to represent whether something is dealing with a call to begin()
  // or a call to end() in a range-based for loop.
  enum BeginEndFunction {
    BEF_begin,
    BEF_end
  };
  
  /// Produce a note indicating which begin/end function was implicitly called
  /// by a C++11 for-range statement. This is often not obvious from the code,
  /// nor from the diagnostics produced when analysing the implicit expressions
  /// required in a for-range statement.
  void NoteForRangeBeginEndFunction(Sema &SemaRef, Expr *E,
                                    BeginEndFunction BEF) {
    CallExpr *CE = dyn_cast<CallExpr>(E);
    if (!CE)
      return;
    FunctionDecl *D = dyn_cast<FunctionDecl>(CE->getCalleeDecl());
    if (!D)
      return;
    SourceLocation Loc = D->getLocation();
  
    std::string Description;
    bool IsTemplate = false;
    if (FunctionTemplateDecl *FunTmpl = D->getPrimaryTemplate()) {
      Description = SemaRef.getTemplateArgumentBindingsText(
        FunTmpl->getTemplateParameters(), *D->getTemplateSpecializationArgs());
      IsTemplate = true;
    }
  
    SemaRef.Diag(Loc, diag::note_for_range_begin_end)
      << BEF << IsTemplate << Description << E->getType();
  }
  
  /// Build a variable declaration for a for-range statement.
  VarDecl *BuildForRangeVarDecl(Sema &SemaRef, SourceLocation Loc,
                                QualType Type, StringRef Name) {
    DeclContext *DC = SemaRef.CurContext;
    IdentifierInfo *II = &SemaRef.PP.getIdentifierTable().get(Name);
    TypeSourceInfo *TInfo = SemaRef.Context.getTrivialTypeSourceInfo(Type, Loc);
    VarDecl *Decl = VarDecl::Create(SemaRef.Context, DC, Loc, Loc, II, Type,
                                    TInfo, SC_None);
    Decl->setImplicit();
    return Decl;
  }
  
  }
  
  static bool ObjCEnumerationCollection(Expr *Collection) {
    return !Collection->isTypeDependent()
            && Collection->getType()->getAs<ObjCObjectPointerType>() != nullptr;
  }
  
  /// ActOnCXXForRangeStmt - Check and build a C++11 for-range statement.
  ///
  /// C++11 [stmt.ranged]:
  ///   A range-based for statement is equivalent to
  ///
  ///   {
  ///     auto && __range = range-init;
  ///     for ( auto __begin = begin-expr,
  ///           __end = end-expr;
  ///           __begin != __end;
  ///           ++__begin ) {
  ///       for-range-declaration = *__begin;
  ///       statement
  ///     }
  ///   }
  ///
  /// The body of the loop is not available yet, since it cannot be analysed until
  /// we have determined the type of the for-range-declaration.
  StmtResult Sema::ActOnCXXForRangeStmt(Scope *S, SourceLocation ForLoc,
                                        SourceLocation CoawaitLoc, Stmt *InitStmt,
                                        Stmt *First, SourceLocation ColonLoc,
                                        Expr *Range, SourceLocation RParenLoc,
                                        BuildForRangeKind Kind) {
    if (!First)
      return StmtError();
  
    if (Range && ObjCEnumerationCollection(Range)) {
      // FIXME: Support init-statements in Objective-C++20 ranged for statement.
      if (InitStmt)
        return Diag(InitStmt->getBeginLoc(), diag::err_objc_for_range_init_stmt)
                   << InitStmt->getSourceRange();
      return ActOnObjCForCollectionStmt(ForLoc, First, Range, RParenLoc);
    }
  
    DeclStmt *DS = dyn_cast<DeclStmt>(First);
    assert(DS && "first part of for range not a decl stmt");
  
    if (!DS->isSingleDecl()) {
      Diag(DS->getBeginLoc(), diag::err_type_defined_in_for_range);
      return StmtError();
    }
  
    Decl *LoopVar = DS->getSingleDecl();
    if (LoopVar->isInvalidDecl() || !Range ||
        DiagnoseUnexpandedParameterPack(Range, UPPC_Expression)) {
      LoopVar->setInvalidDecl();
      return StmtError();
    }
  
    // Build the coroutine state immediately and not later during template
    // instantiation
    if (!CoawaitLoc.isInvalid()) {
      if (!ActOnCoroutineBodyStart(S, CoawaitLoc, "co_await"))
        return StmtError();
    }
  
    // Build  auto && __range = range-init
    // Divide by 2, since the variables are in the inner scope (loop body).
    const auto DepthStr = std::to_string(S->getDepth() / 2);
    SourceLocation RangeLoc = Range->getBeginLoc();
    VarDecl *RangeVar = BuildForRangeVarDecl(*this, RangeLoc,
                                             Context.getAutoRRefDeductType(),
                                             std::string("__range") + DepthStr);
    if (FinishForRangeVarDecl(*this, RangeVar, Range, RangeLoc,
                              diag::err_for_range_deduction_failure)) {
      LoopVar->setInvalidDecl();
      return StmtError();
    }
  
    // Claim the type doesn't contain auto: we've already done the checking.
    DeclGroupPtrTy RangeGroup =
        BuildDeclaratorGroup(MutableArrayRef<Decl *>((Decl **)&RangeVar, 1));
    StmtResult RangeDecl = ActOnDeclStmt(RangeGroup, RangeLoc, RangeLoc);
    if (RangeDecl.isInvalid()) {
      LoopVar->setInvalidDecl();
      return StmtError();
    }
  
    return BuildCXXForRangeStmt(
        ForLoc, CoawaitLoc, InitStmt, ColonLoc, RangeDecl.get(),
        /*BeginStmt=*/nullptr, /*EndStmt=*/nullptr,
        /*Cond=*/nullptr, /*Inc=*/nullptr, DS, RParenLoc, Kind);
  }
  
  /// Create the initialization, compare, and increment steps for
  /// the range-based for loop expression.
  /// This function does not handle array-based for loops,
  /// which are created in Sema::BuildCXXForRangeStmt.
  ///
  /// \returns a ForRangeStatus indicating success or what kind of error occurred.
  /// BeginExpr and EndExpr are set and FRS_Success is returned on success;
  /// CandidateSet and BEF are set and some non-success value is returned on
  /// failure.
  static Sema::ForRangeStatus
  BuildNonArrayForRange(Sema &SemaRef, Expr *BeginRange, Expr *EndRange,
                        QualType RangeType, VarDecl *BeginVar, VarDecl *EndVar,
                        SourceLocation ColonLoc, SourceLocation CoawaitLoc,
                        OverloadCandidateSet *CandidateSet, ExprResult *BeginExpr,
                        ExprResult *EndExpr, BeginEndFunction *BEF) {
    DeclarationNameInfo BeginNameInfo(
        &SemaRef.PP.getIdentifierTable().get("begin"), ColonLoc);
    DeclarationNameInfo EndNameInfo(&SemaRef.PP.getIdentifierTable().get("end"),
                                    ColonLoc);
  
    LookupResult BeginMemberLookup(SemaRef, BeginNameInfo,
                                   Sema::LookupMemberName);
    LookupResult EndMemberLookup(SemaRef, EndNameInfo, Sema::LookupMemberName);
  
    auto BuildBegin = [&] {
      *BEF = BEF_begin;
      Sema::ForRangeStatus RangeStatus =
          SemaRef.BuildForRangeBeginEndCall(ColonLoc, ColonLoc, BeginNameInfo,
                                            BeginMemberLookup, CandidateSet,
                                            BeginRange, BeginExpr);
  
      if (RangeStatus != Sema::FRS_Success) {
        if (RangeStatus == Sema::FRS_DiagnosticIssued)
          SemaRef.Diag(BeginRange->getBeginLoc(), diag::note_in_for_range)
              << ColonLoc << BEF_begin << BeginRange->getType();
        return RangeStatus;
      }
      if (!CoawaitLoc.isInvalid()) {
        // FIXME: getCurScope() should not be used during template instantiation.
        // We should pick up the set of unqualified lookup results for operator
        // co_await during the initial parse.
        *BeginExpr = SemaRef.ActOnCoawaitExpr(SemaRef.getCurScope(), ColonLoc,
                                              BeginExpr->get());
        if (BeginExpr->isInvalid())
          return Sema::FRS_DiagnosticIssued;
      }
      if (FinishForRangeVarDecl(SemaRef, BeginVar, BeginExpr->get(), ColonLoc,
                                diag::err_for_range_iter_deduction_failure)) {
        NoteForRangeBeginEndFunction(SemaRef, BeginExpr->get(), *BEF);
        return Sema::FRS_DiagnosticIssued;
      }
      return Sema::FRS_Success;
    };
  
    auto BuildEnd = [&] {
      *BEF = BEF_end;
      Sema::ForRangeStatus RangeStatus =
          SemaRef.BuildForRangeBeginEndCall(ColonLoc, ColonLoc, EndNameInfo,
                                            EndMemberLookup, CandidateSet,
                                            EndRange, EndExpr);
      if (RangeStatus != Sema::FRS_Success) {
        if (RangeStatus == Sema::FRS_DiagnosticIssued)
          SemaRef.Diag(EndRange->getBeginLoc(), diag::note_in_for_range)
              << ColonLoc << BEF_end << EndRange->getType();
        return RangeStatus;
      }
      if (FinishForRangeVarDecl(SemaRef, EndVar, EndExpr->get(), ColonLoc,
                                diag::err_for_range_iter_deduction_failure)) {
        NoteForRangeBeginEndFunction(SemaRef, EndExpr->get(), *BEF);
        return Sema::FRS_DiagnosticIssued;
      }
      return Sema::FRS_Success;
    };
  
    if (CXXRecordDecl *D = RangeType->getAsCXXRecordDecl()) {
      // - if _RangeT is a class type, the unqualified-ids begin and end are
      //   looked up in the scope of class _RangeT as if by class member access
      //   lookup (3.4.5), and if either (or both) finds at least one
      //   declaration, begin-expr and end-expr are __range.begin() and
      //   __range.end(), respectively;
      SemaRef.LookupQualifiedName(BeginMemberLookup, D);
      if (BeginMemberLookup.isAmbiguous())
        return Sema::FRS_DiagnosticIssued;
  
      SemaRef.LookupQualifiedName(EndMemberLookup, D);
      if (EndMemberLookup.isAmbiguous())
        return Sema::FRS_DiagnosticIssued;
  
      if (BeginMemberLookup.empty() != EndMemberLookup.empty()) {
        // Look up the non-member form of the member we didn't find, first.
        // This way we prefer a "no viable 'end'" diagnostic over a "i found
        // a 'begin' but ignored it because there was no member 'end'"
        // diagnostic.
        auto BuildNonmember = [&](
            BeginEndFunction BEFFound, LookupResult &Found,
            llvm::function_ref<Sema::ForRangeStatus()> BuildFound,
            llvm::function_ref<Sema::ForRangeStatus()> BuildNotFound) {
          LookupResult OldFound = std::move(Found);
          Found.clear();
  
          if (Sema::ForRangeStatus Result = BuildNotFound())
            return Result;
  
          switch (BuildFound()) {
          case Sema::FRS_Success:
            return Sema::FRS_Success;
  
          case Sema::FRS_NoViableFunction:
            CandidateSet->NoteCandidates(
                PartialDiagnosticAt(BeginRange->getBeginLoc(),
                                    SemaRef.PDiag(diag::err_for_range_invalid)
                                        << BeginRange->getType() << BEFFound),
                SemaRef, OCD_AllCandidates, BeginRange);
            LLVM_FALLTHROUGH;
  
          case Sema::FRS_DiagnosticIssued:
            for (NamedDecl *D : OldFound) {
              SemaRef.Diag(D->getLocation(),
                           diag::note_for_range_member_begin_end_ignored)
                  << BeginRange->getType() << BEFFound;
            }
            return Sema::FRS_DiagnosticIssued;
          }
          llvm_unreachable("unexpected ForRangeStatus");
        };
        if (BeginMemberLookup.empty())
          return BuildNonmember(BEF_end, EndMemberLookup, BuildEnd, BuildBegin);
        return BuildNonmember(BEF_begin, BeginMemberLookup, BuildBegin, BuildEnd);
      }
    } else {
      // - otherwise, begin-expr and end-expr are begin(__range) and
      //   end(__range), respectively, where begin and end are looked up with
      //   argument-dependent lookup (3.4.2). For the purposes of this name
      //   lookup, namespace std is an associated namespace.
    }
  
    if (Sema::ForRangeStatus Result = BuildBegin())
      return Result;
    return BuildEnd();
  }
  
  /// Speculatively attempt to dereference an invalid range expression.
  /// If the attempt fails, this function will return a valid, null StmtResult
  /// and emit no diagnostics.
  static StmtResult RebuildForRangeWithDereference(Sema &SemaRef, Scope *S,
                                                   SourceLocation ForLoc,
                                                   SourceLocation CoawaitLoc,
                                                   Stmt *InitStmt,
                                                   Stmt *LoopVarDecl,
                                                   SourceLocation ColonLoc,
                                                   Expr *Range,
                                                   SourceLocation RangeLoc,
                                                   SourceLocation RParenLoc) {
    // Determine whether we can rebuild the for-range statement with a
    // dereferenced range expression.
    ExprResult AdjustedRange;
    {
      Sema::SFINAETrap Trap(SemaRef);
  
      AdjustedRange = SemaRef.BuildUnaryOp(S, RangeLoc, UO_Deref, Range);
      if (AdjustedRange.isInvalid())
        return StmtResult();
  
      StmtResult SR = SemaRef.ActOnCXXForRangeStmt(
          S, ForLoc, CoawaitLoc, InitStmt, LoopVarDecl, ColonLoc,
          AdjustedRange.get(), RParenLoc, Sema::BFRK_Check);
      if (SR.isInvalid())
        return StmtResult();
    }
  
    // The attempt to dereference worked well enough that it could produce a valid
    // loop. Produce a fixit, and rebuild the loop with diagnostics enabled, in
    // case there are any other (non-fatal) problems with it.
    SemaRef.Diag(RangeLoc, diag::err_for_range_dereference)
      << Range->getType() << FixItHint::CreateInsertion(RangeLoc, "*");
    return SemaRef.ActOnCXXForRangeStmt(
        S, ForLoc, CoawaitLoc, InitStmt, LoopVarDecl, ColonLoc,
        AdjustedRange.get(), RParenLoc, Sema::BFRK_Rebuild);
  }
  
  namespace {
  /// RAII object to automatically invalidate a declaration if an error occurs.
  struct InvalidateOnErrorScope {
    InvalidateOnErrorScope(Sema &SemaRef, Decl *D, bool Enabled)
        : Trap(SemaRef.Diags), D(D), Enabled(Enabled) {}
    ~InvalidateOnErrorScope() {
      if (Enabled && Trap.hasErrorOccurred())
        D->setInvalidDecl();
    }
  
    DiagnosticErrorTrap Trap;
    Decl *D;
    bool Enabled;
  };
  }
  
  /// BuildCXXForRangeStmt - Build or instantiate a C++11 for-range statement.
  StmtResult Sema::BuildCXXForRangeStmt(SourceLocation ForLoc,
                                        SourceLocation CoawaitLoc, Stmt *InitStmt,
                                        SourceLocation ColonLoc, Stmt *RangeDecl,
                                        Stmt *Begin, Stmt *End, Expr *Cond,
                                        Expr *Inc, Stmt *LoopVarDecl,
                                        SourceLocation RParenLoc,
                                        BuildForRangeKind Kind) {
    // FIXME: This should not be used during template instantiation. We should
    // pick up the set of unqualified lookup results for the != and + operators
    // in the initial parse.
    //
    // Testcase (accepts-invalid):
    //   template<typename T> void f() { for (auto x : T()) {} }
    //   namespace N { struct X { X begin(); X end(); int operator*(); }; }
    //   bool operator!=(N::X, N::X); void operator++(N::X);
    //   void g() { f<N::X>(); }
    Scope *S = getCurScope();
  
    DeclStmt *RangeDS = cast<DeclStmt>(RangeDecl);
    VarDecl *RangeVar = cast<VarDecl>(RangeDS->getSingleDecl());
    QualType RangeVarType = RangeVar->getType();
  
    DeclStmt *LoopVarDS = cast<DeclStmt>(LoopVarDecl);
    VarDecl *LoopVar = cast<VarDecl>(LoopVarDS->getSingleDecl());
  
    // If we hit any errors, mark the loop variable as invalid if its type
    // contains 'auto'.
    InvalidateOnErrorScope Invalidate(*this, LoopVar,
                                      LoopVar->getType()->isUndeducedType());
  
    StmtResult BeginDeclStmt = Begin;
    StmtResult EndDeclStmt = End;
    ExprResult NotEqExpr = Cond, IncrExpr = Inc;
  
    if (RangeVarType->isDependentType()) {
      // The range is implicitly used as a placeholder when it is dependent.
      RangeVar->markUsed(Context);
  
      // Deduce any 'auto's in the loop variable as 'DependentTy'. We'll fill
      // them in properly when we instantiate the loop.
      if (!LoopVar->isInvalidDecl() && Kind != BFRK_Check) {
        if (auto *DD = dyn_cast<DecompositionDecl>(LoopVar))
          for (auto *Binding : DD->bindings())
            Binding->setType(Context.DependentTy);
        LoopVar->setType(SubstAutoType(LoopVar->getType(), Context.DependentTy));
      }
    } else if (!BeginDeclStmt.get()) {
      SourceLocation RangeLoc = RangeVar->getLocation();
  
      const QualType RangeVarNonRefType = RangeVarType.getNonReferenceType();
  
      ExprResult BeginRangeRef = BuildDeclRefExpr(RangeVar, RangeVarNonRefType,
                                                  VK_LValue, ColonLoc);
      if (BeginRangeRef.isInvalid())
        return StmtError();
  
      ExprResult EndRangeRef = BuildDeclRefExpr(RangeVar, RangeVarNonRefType,
                                                VK_LValue, ColonLoc);
      if (EndRangeRef.isInvalid())
        return StmtError();
  
      QualType AutoType = Context.getAutoDeductType();
      Expr *Range = RangeVar->getInit();
      if (!Range)
        return StmtError();
      QualType RangeType = Range->getType();
  
      if (RequireCompleteType(RangeLoc, RangeType,
                              diag::err_for_range_incomplete_type))
        return StmtError();
  
      // Build auto __begin = begin-expr, __end = end-expr.
      // Divide by 2, since the variables are in the inner scope (loop body).
      const auto DepthStr = std::to_string(S->getDepth() / 2);
      VarDecl *BeginVar = BuildForRangeVarDecl(*this, ColonLoc, AutoType,
                                               std::string("__begin") + DepthStr);
      VarDecl *EndVar = BuildForRangeVarDecl(*this, ColonLoc, AutoType,
                                             std::string("__end") + DepthStr);
  
      // Build begin-expr and end-expr and attach to __begin and __end variables.
      ExprResult BeginExpr, EndExpr;
      if (const ArrayType *UnqAT = RangeType->getAsArrayTypeUnsafe()) {
        // - if _RangeT is an array type, begin-expr and end-expr are __range and
        //   __range + __bound, respectively, where __bound is the array bound. If
        //   _RangeT is an array of unknown size or an array of incomplete type,
        //   the program is ill-formed;
  
        // begin-expr is __range.
        BeginExpr = BeginRangeRef;
        if (!CoawaitLoc.isInvalid()) {
          BeginExpr = ActOnCoawaitExpr(S, ColonLoc, BeginExpr.get());
          if (BeginExpr.isInvalid())
            return StmtError();
        }
        if (FinishForRangeVarDecl(*this, BeginVar, BeginRangeRef.get(), ColonLoc,
                                  diag::err_for_range_iter_deduction_failure)) {
          NoteForRangeBeginEndFunction(*this, BeginExpr.get(), BEF_begin);
          return StmtError();
        }
  
        // Find the array bound.
        ExprResult BoundExpr;
        if (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(UnqAT))
          BoundExpr = IntegerLiteral::Create(
              Context, CAT->getSize(), Context.getPointerDiffType(), RangeLoc);
        else if (const VariableArrayType *VAT =
                 dyn_cast<VariableArrayType>(UnqAT)) {
          // For a variably modified type we can't just use the expression within
          // the array bounds, since we don't want that to be re-evaluated here.
          // Rather, we need to determine what it was when the array was first
          // created - so we resort to using sizeof(vla)/sizeof(element).
          // For e.g.
          //  void f(int b) {
          //    int vla[b];
          //    b = -1;   <-- This should not affect the num of iterations below
          //    for (int &c : vla) { .. }
          //  }
  
          // FIXME: This results in codegen generating IR that recalculates the
          // run-time number of elements (as opposed to just using the IR Value
          // that corresponds to the run-time value of each bound that was
          // generated when the array was created.) If this proves too embarrassing
          // even for unoptimized IR, consider passing a magic-value/cookie to
          // codegen that then knows to simply use that initial llvm::Value (that
          // corresponds to the bound at time of array creation) within
          // getelementptr.  But be prepared to pay the price of increasing a
          // customized form of coupling between the two components - which  could
          // be hard to maintain as the codebase evolves.
  
          ExprResult SizeOfVLAExprR = ActOnUnaryExprOrTypeTraitExpr(
              EndVar->getLocation(), UETT_SizeOf,
              /*IsType=*/true,
              CreateParsedType(VAT->desugar(), Context.getTrivialTypeSourceInfo(
                                                   VAT->desugar(), RangeLoc))
                  .getAsOpaquePtr(),
              EndVar->getSourceRange());
          if (SizeOfVLAExprR.isInvalid())
            return StmtError();
  
          ExprResult SizeOfEachElementExprR = ActOnUnaryExprOrTypeTraitExpr(
              EndVar->getLocation(), UETT_SizeOf,
              /*IsType=*/true,
              CreateParsedType(VAT->desugar(),
                               Context.getTrivialTypeSourceInfo(
                                   VAT->getElementType(), RangeLoc))
                  .getAsOpaquePtr(),
              EndVar->getSourceRange());
          if (SizeOfEachElementExprR.isInvalid())
            return StmtError();
  
          BoundExpr =
              ActOnBinOp(S, EndVar->getLocation(), tok::slash,
                         SizeOfVLAExprR.get(), SizeOfEachElementExprR.get());
          if (BoundExpr.isInvalid())
            return StmtError();
  
        } else {
          // Can't be a DependentSizedArrayType or an IncompleteArrayType since
          // UnqAT is not incomplete and Range is not type-dependent.
          llvm_unreachable("Unexpected array type in for-range");
        }
  
        // end-expr is __range + __bound.
        EndExpr = ActOnBinOp(S, ColonLoc, tok::plus, EndRangeRef.get(),
                             BoundExpr.get());
        if (EndExpr.isInvalid())
          return StmtError();
        if (FinishForRangeVarDecl(*this, EndVar, EndExpr.get(), ColonLoc,
                                  diag::err_for_range_iter_deduction_failure)) {
          NoteForRangeBeginEndFunction(*this, EndExpr.get(), BEF_end);
          return StmtError();
        }
      } else {
        OverloadCandidateSet CandidateSet(RangeLoc,
                                          OverloadCandidateSet::CSK_Normal);
        BeginEndFunction BEFFailure;
        ForRangeStatus RangeStatus = BuildNonArrayForRange(
            *this, BeginRangeRef.get(), EndRangeRef.get(), RangeType, BeginVar,
            EndVar, ColonLoc, CoawaitLoc, &CandidateSet, &BeginExpr, &EndExpr,
            &BEFFailure);
  
        if (Kind == BFRK_Build && RangeStatus == FRS_NoViableFunction &&
            BEFFailure == BEF_begin) {
          // If the range is being built from an array parameter, emit a
          // a diagnostic that it is being treated as a pointer.
          if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Range)) {
            if (ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(DRE->getDecl())) {
              QualType ArrayTy = PVD->getOriginalType();
              QualType PointerTy = PVD->getType();
              if (PointerTy->isPointerType() && ArrayTy->isArrayType()) {
                Diag(Range->getBeginLoc(), diag::err_range_on_array_parameter)
                    << RangeLoc << PVD << ArrayTy << PointerTy;
                Diag(PVD->getLocation(), diag::note_declared_at);
                return StmtError();
              }
            }
          }
  
          // If building the range failed, try dereferencing the range expression
          // unless a diagnostic was issued or the end function is problematic.
          StmtResult SR = RebuildForRangeWithDereference(*this, S, ForLoc,
                                                         CoawaitLoc, InitStmt,
                                                         LoopVarDecl, ColonLoc,
                                                         Range, RangeLoc,
                                                         RParenLoc);
          if (SR.isInvalid() || SR.isUsable())
            return SR;
        }
  
        // Otherwise, emit diagnostics if we haven't already.
        if (RangeStatus == FRS_NoViableFunction) {
          Expr *Range = BEFFailure ? EndRangeRef.get() : BeginRangeRef.get();
          CandidateSet.NoteCandidates(
              PartialDiagnosticAt(Range->getBeginLoc(),
                                  PDiag(diag::err_for_range_invalid)
                                      << RangeLoc << Range->getType()
                                      << BEFFailure),
              *this, OCD_AllCandidates, Range);
        }
        // Return an error if no fix was discovered.
        if (RangeStatus != FRS_Success)
          return StmtError();
      }
  
      assert(!BeginExpr.isInvalid() && !EndExpr.isInvalid() &&
             "invalid range expression in for loop");
  
      // C++11 [dcl.spec.auto]p7: BeginType and EndType must be the same.
      // C++1z removes this restriction.
      QualType BeginType = BeginVar->getType(), EndType = EndVar->getType();
      if (!Context.hasSameType(BeginType, EndType)) {
        Diag(RangeLoc, getLangOpts().CPlusPlus17
                           ? diag::warn_for_range_begin_end_types_differ
                           : diag::ext_for_range_begin_end_types_differ)
            << BeginType << EndType;
        NoteForRangeBeginEndFunction(*this, BeginExpr.get(), BEF_begin);
        NoteForRangeBeginEndFunction(*this, EndExpr.get(), BEF_end);
      }
  
      BeginDeclStmt =
          ActOnDeclStmt(ConvertDeclToDeclGroup(BeginVar), ColonLoc, ColonLoc);
      EndDeclStmt =
          ActOnDeclStmt(ConvertDeclToDeclGroup(EndVar), ColonLoc, ColonLoc);
  
      const QualType BeginRefNonRefType = BeginType.getNonReferenceType();
      ExprResult BeginRef = BuildDeclRefExpr(BeginVar, BeginRefNonRefType,
                                             VK_LValue, ColonLoc);
      if (BeginRef.isInvalid())
        return StmtError();
  
      ExprResult EndRef = BuildDeclRefExpr(EndVar, EndType.getNonReferenceType(),
                                           VK_LValue, ColonLoc);
      if (EndRef.isInvalid())
        return StmtError();
  
      // Build and check __begin != __end expression.
      NotEqExpr = ActOnBinOp(S, ColonLoc, tok::exclaimequal,
                             BeginRef.get(), EndRef.get());
      if (!NotEqExpr.isInvalid())
        NotEqExpr = CheckBooleanCondition(ColonLoc, NotEqExpr.get());
      if (!NotEqExpr.isInvalid())
        NotEqExpr =
            ActOnFinishFullExpr(NotEqExpr.get(), /*DiscardedValue*/ false);
      if (NotEqExpr.isInvalid()) {
        Diag(RangeLoc, diag::note_for_range_invalid_iterator)
          << RangeLoc << 0 << BeginRangeRef.get()->getType();
        NoteForRangeBeginEndFunction(*this, BeginExpr.get(), BEF_begin);
        if (!Context.hasSameType(BeginType, EndType))
          NoteForRangeBeginEndFunction(*this, EndExpr.get(), BEF_end);
        return StmtError();
      }
  
      // Build and check ++__begin expression.
      BeginRef = BuildDeclRefExpr(BeginVar, BeginRefNonRefType,
                                  VK_LValue, ColonLoc);
      if (BeginRef.isInvalid())
        return StmtError();
  
      IncrExpr = ActOnUnaryOp(S, ColonLoc, tok::plusplus, BeginRef.get());
      if (!IncrExpr.isInvalid() && CoawaitLoc.isValid())
        // FIXME: getCurScope() should not be used during template instantiation.
        // We should pick up the set of unqualified lookup results for operator
        // co_await during the initial parse.
        IncrExpr = ActOnCoawaitExpr(S, CoawaitLoc, IncrExpr.get());
      if (!IncrExpr.isInvalid())
        IncrExpr = ActOnFinishFullExpr(IncrExpr.get(), /*DiscardedValue*/ false);
      if (IncrExpr.isInvalid()) {
        Diag(RangeLoc, diag::note_for_range_invalid_iterator)
          << RangeLoc << 2 << BeginRangeRef.get()->getType() ;
        NoteForRangeBeginEndFunction(*this, BeginExpr.get(), BEF_begin);
        return StmtError();
      }
  
      // Build and check *__begin  expression.
      BeginRef = BuildDeclRefExpr(BeginVar, BeginRefNonRefType,
                                  VK_LValue, ColonLoc);
      if (BeginRef.isInvalid())
        return StmtError();
  
      ExprResult DerefExpr = ActOnUnaryOp(S, ColonLoc, tok::star, BeginRef.get());
      if (DerefExpr.isInvalid()) {
        Diag(RangeLoc, diag::note_for_range_invalid_iterator)
          << RangeLoc << 1 << BeginRangeRef.get()->getType();
        NoteForRangeBeginEndFunction(*this, BeginExpr.get(), BEF_begin);
        return StmtError();
      }
  
      // Attach  *__begin  as initializer for VD. Don't touch it if we're just
      // trying to determine whether this would be a valid range.
      if (!LoopVar->isInvalidDecl() && Kind != BFRK_Check) {
        AddInitializerToDecl(LoopVar, DerefExpr.get(), /*DirectInit=*/false);
        if (LoopVar->isInvalidDecl())
          NoteForRangeBeginEndFunction(*this, BeginExpr.get(), BEF_begin);
      }
    }
  
    // Don't bother to actually allocate the result if we're just trying to
    // determine whether it would be valid.
    if (Kind == BFRK_Check)
      return StmtResult();
  
    // In OpenMP loop region loop control variable must be private. Perform
    // analysis of first part (if any).
    if (getLangOpts().OpenMP >= 50 && BeginDeclStmt.isUsable())
      ActOnOpenMPLoopInitialization(ForLoc, BeginDeclStmt.get());
  
    return new (Context) CXXForRangeStmt(
        InitStmt, RangeDS, cast_or_null<DeclStmt>(BeginDeclStmt.get()),
        cast_or_null<DeclStmt>(EndDeclStmt.get()), NotEqExpr.get(),
        IncrExpr.get(), LoopVarDS, /*Body=*/nullptr, ForLoc, CoawaitLoc,
        ColonLoc, RParenLoc);
  }
  
  /// FinishObjCForCollectionStmt - Attach the body to a objective-C foreach
  /// statement.
  StmtResult Sema::FinishObjCForCollectionStmt(Stmt *S, Stmt *B) {
    if (!S || !B)
      return StmtError();
    ObjCForCollectionStmt * ForStmt = cast<ObjCForCollectionStmt>(S);
  
    ForStmt->setBody(B);
    return S;
  }
  
  // Warn when the loop variable is a const reference that creates a copy.
  // Suggest using the non-reference type for copies.  If a copy can be prevented
  // suggest the const reference type that would do so.
  // For instance, given "for (const &Foo : Range)", suggest
  // "for (const Foo : Range)" to denote a copy is made for the loop.  If
  // possible, also suggest "for (const &Bar : Range)" if this type prevents
  // the copy altogether.
  static void DiagnoseForRangeReferenceVariableCopies(Sema &SemaRef,
                                                      const VarDecl *VD,
                                                      QualType RangeInitType) {
    const Expr *InitExpr = VD->getInit();
    if (!InitExpr)
      return;
  
    QualType VariableType = VD->getType();
  
    if (auto Cleanups = dyn_cast<ExprWithCleanups>(InitExpr))
      if (!Cleanups->cleanupsHaveSideEffects())
        InitExpr = Cleanups->getSubExpr();
  
    const MaterializeTemporaryExpr *MTE =
        dyn_cast<MaterializeTemporaryExpr>(InitExpr);
  
    // No copy made.
    if (!MTE)
      return;
  
    const Expr *E = MTE->getSubExpr()->IgnoreImpCasts();
  
    // Searching for either UnaryOperator for dereference of a pointer or
    // CXXOperatorCallExpr for handling iterators.
    while (!isa<CXXOperatorCallExpr>(E) && !isa<UnaryOperator>(E)) {
      if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(E)) {
        E = CCE->getArg(0);
      } else if (const CXXMemberCallExpr *Call = dyn_cast<CXXMemberCallExpr>(E)) {
        const MemberExpr *ME = cast<MemberExpr>(Call->getCallee());
        E = ME->getBase();
      } else {
        const MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(E);
        E = MTE->getSubExpr();
      }
      E = E->IgnoreImpCasts();
    }
  
    bool ReturnsReference = false;
    if (isa<UnaryOperator>(E)) {
      ReturnsReference = true;
    } else {
      const CXXOperatorCallExpr *Call = cast<CXXOperatorCallExpr>(E);
      const FunctionDecl *FD = Call->getDirectCallee();
      QualType ReturnType = FD->getReturnType();
      ReturnsReference = ReturnType->isReferenceType();
    }
  
    if (ReturnsReference) {
      // Loop variable creates a temporary.  Suggest either to go with
      // non-reference loop variable to indicate a copy is made, or
      // the correct time to bind a const reference.
      SemaRef.Diag(VD->getLocation(), diag::warn_for_range_const_reference_copy)
          << VD << VariableType << E->getType();
      QualType NonReferenceType = VariableType.getNonReferenceType();
      NonReferenceType.removeLocalConst();
      QualType NewReferenceType =
          SemaRef.Context.getLValueReferenceType(E->getType().withConst());
      SemaRef.Diag(VD->getBeginLoc(), diag::note_use_type_or_non_reference)
          << NonReferenceType << NewReferenceType << VD->getSourceRange()
          << FixItHint::CreateRemoval(VD->getTypeSpecEndLoc());
    } else if (!VariableType->isRValueReferenceType()) {
      // The range always returns a copy, so a temporary is always created.
      // Suggest removing the reference from the loop variable.
      // If the type is a rvalue reference do not warn since that changes the
      // semantic of the code.
      SemaRef.Diag(VD->getLocation(), diag::warn_for_range_variable_always_copy)
          << VD << RangeInitType;
      QualType NonReferenceType = VariableType.getNonReferenceType();
      NonReferenceType.removeLocalConst();
      SemaRef.Diag(VD->getBeginLoc(), diag::note_use_non_reference_type)
          << NonReferenceType << VD->getSourceRange()
          << FixItHint::CreateRemoval(VD->getTypeSpecEndLoc());
    }
  }
  
  /// Determines whether the @p VariableType's declaration is a record with the
  /// clang::trivial_abi attribute.
  static bool hasTrivialABIAttr(QualType VariableType) {
    if (CXXRecordDecl *RD = VariableType->getAsCXXRecordDecl())
      return RD->hasAttr<TrivialABIAttr>();
  
    return false;
  }
  
  // Warns when the loop variable can be changed to a reference type to
  // prevent a copy.  For instance, if given "for (const Foo x : Range)" suggest
  // "for (const Foo &x : Range)" if this form does not make a copy.
  static void DiagnoseForRangeConstVariableCopies(Sema &SemaRef,
                                                  const VarDecl *VD) {
    const Expr *InitExpr = VD->getInit();
    if (!InitExpr)
      return;
  
    QualType VariableType = VD->getType();
  
    if (const CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(InitExpr)) {
      if (!CE->getConstructor()->isCopyConstructor())
        return;
    } else if (const CastExpr *CE = dyn_cast<CastExpr>(InitExpr)) {
      if (CE->getCastKind() != CK_LValueToRValue)
        return;
    } else {
      return;
    }
  
    // Small trivially copyable types are cheap to copy. Do not emit the
    // diagnostic for these instances. 64 bytes is a common size of a cache line.
    // (The function `getTypeSize` returns the size in bits.)
    ASTContext &Ctx = SemaRef.Context;
    if (Ctx.getTypeSize(VariableType) <= 64 * 8 &&
        (VariableType.isTriviallyCopyableType(Ctx) ||
         hasTrivialABIAttr(VariableType)))
      return;
  
    // Suggest changing from a const variable to a const reference variable
    // if doing so will prevent a copy.
    SemaRef.Diag(VD->getLocation(), diag::warn_for_range_copy)
        << VD << VariableType << InitExpr->getType();
    SemaRef.Diag(VD->getBeginLoc(), diag::note_use_reference_type)
        << SemaRef.Context.getLValueReferenceType(VariableType)
        << VD->getSourceRange()
        << FixItHint::CreateInsertion(VD->getLocation(), "&");
  }
  
  /// DiagnoseForRangeVariableCopies - Diagnose three cases and fixes for them.
  /// 1) for (const foo &x : foos) where foos only returns a copy.  Suggest
  ///    using "const foo x" to show that a copy is made
  /// 2) for (const bar &x : foos) where bar is a temporary initialized by bar.
  ///    Suggest either "const bar x" to keep the copying or "const foo& x" to
  ///    prevent the copy.
  /// 3) for (const foo x : foos) where x is constructed from a reference foo.
  ///    Suggest "const foo &x" to prevent the copy.
  static void DiagnoseForRangeVariableCopies(Sema &SemaRef,
                                             const CXXForRangeStmt *ForStmt) {
    if (SemaRef.inTemplateInstantiation())
      return;
  
    if (SemaRef.Diags.isIgnored(diag::warn_for_range_const_reference_copy,
                                ForStmt->getBeginLoc()) &&
        SemaRef.Diags.isIgnored(diag::warn_for_range_variable_always_copy,
                                ForStmt->getBeginLoc()) &&
        SemaRef.Diags.isIgnored(diag::warn_for_range_copy,
                                ForStmt->getBeginLoc())) {
      return;
    }
  
    const VarDecl *VD = ForStmt->getLoopVariable();
    if (!VD)
      return;
  
    QualType VariableType = VD->getType();
  
    if (VariableType->isIncompleteType())
      return;
  
    const Expr *InitExpr = VD->getInit();
    if (!InitExpr)
      return;
  
    if (InitExpr->getExprLoc().isMacroID())
      return;
  
    if (VariableType->isReferenceType()) {
      DiagnoseForRangeReferenceVariableCopies(SemaRef, VD,
                                              ForStmt->getRangeInit()->getType());
    } else if (VariableType.isConstQualified()) {
      DiagnoseForRangeConstVariableCopies(SemaRef, VD);
    }
  }
  
  /// FinishCXXForRangeStmt - Attach the body to a C++0x for-range statement.
  /// This is a separate step from ActOnCXXForRangeStmt because analysis of the
  /// body cannot be performed until after the type of the range variable is
  /// determined.
  StmtResult Sema::FinishCXXForRangeStmt(Stmt *S, Stmt *B) {
    if (!S || !B)
      return StmtError();
  
    if (isa<ObjCForCollectionStmt>(S))
      return FinishObjCForCollectionStmt(S, B);
  
    CXXForRangeStmt *ForStmt = cast<CXXForRangeStmt>(S);
    ForStmt->setBody(B);
  
    DiagnoseEmptyStmtBody(ForStmt->getRParenLoc(), B,
                          diag::warn_empty_range_based_for_body);
  
    DiagnoseForRangeVariableCopies(*this, ForStmt);
  
    return S;
  }
  
  StmtResult Sema::ActOnGotoStmt(SourceLocation GotoLoc,
                                 SourceLocation LabelLoc,
                                 LabelDecl *TheDecl) {
    setFunctionHasBranchIntoScope();
    TheDecl->markUsed(Context);
    return new (Context) GotoStmt(TheDecl, GotoLoc, LabelLoc);
  }
  
  StmtResult
  Sema::ActOnIndirectGotoStmt(SourceLocation GotoLoc, SourceLocation StarLoc,
                              Expr *E) {
    // Convert operand to void*
    if (!E->isTypeDependent()) {
      QualType ETy = E->getType();
      QualType DestTy = Context.getPointerType(Context.VoidTy.withConst());
      ExprResult ExprRes = E;
      AssignConvertType ConvTy =
        CheckSingleAssignmentConstraints(DestTy, ExprRes);
      if (ExprRes.isInvalid())
        return StmtError();
      E = ExprRes.get();
      if (DiagnoseAssignmentResult(ConvTy, StarLoc, DestTy, ETy, E, AA_Passing))
        return StmtError();
    }
  
    ExprResult ExprRes = ActOnFinishFullExpr(E, /*DiscardedValue*/ false);
    if (ExprRes.isInvalid())
      return StmtError();
    E = ExprRes.get();
  
    setFunctionHasIndirectGoto();
  
    return new (Context) IndirectGotoStmt(GotoLoc, StarLoc, E);
  }
  
  static void CheckJumpOutOfSEHFinally(Sema &S, SourceLocation Loc,
                                       const Scope &DestScope) {
    if (!S.CurrentSEHFinally.empty() &&
        DestScope.Contains(*S.CurrentSEHFinally.back())) {
      S.Diag(Loc, diag::warn_jump_out_of_seh_finally);
    }
  }
  
  StmtResult
  Sema::ActOnContinueStmt(SourceLocation ContinueLoc, Scope *CurScope) {
    Scope *S = CurScope->getContinueParent();
    if (!S) {
      // C99 6.8.6.2p1: A break shall appear only in or as a loop body.
      return StmtError(Diag(ContinueLoc, diag::err_continue_not_in_loop));
    }
    CheckJumpOutOfSEHFinally(*this, ContinueLoc, *S);
  
    return new (Context) ContinueStmt(ContinueLoc);
  }
  
  StmtResult
  Sema::ActOnBreakStmt(SourceLocation BreakLoc, Scope *CurScope) {
    Scope *S = CurScope->getBreakParent();
    if (!S) {
      // C99 6.8.6.3p1: A break shall appear only in or as a switch/loop body.
      return StmtError(Diag(BreakLoc, diag::err_break_not_in_loop_or_switch));
    }
    if (S->isOpenMPLoopScope())
      return StmtError(Diag(BreakLoc, diag::err_omp_loop_cannot_use_stmt)
                       << "break");
    CheckJumpOutOfSEHFinally(*this, BreakLoc, *S);
  
    return new (Context) BreakStmt(BreakLoc);
  }
  
  /// Determine whether the given expression is a candidate for
  /// copy elision in either a return statement or a throw expression.
  ///
  /// \param ReturnType If we're determining the copy elision candidate for
  /// a return statement, this is the return type of the function. If we're
  /// determining the copy elision candidate for a throw expression, this will
  /// be a NULL type.
  ///
  /// \param E The expression being returned from the function or block, or
  /// being thrown.
  ///
  /// \param CESK Whether we allow function parameters or
  /// id-expressions that could be moved out of the function to be considered NRVO
  /// candidates. C++ prohibits these for NRVO itself, but we re-use this logic to
  /// determine whether we should try to move as part of a return or throw (which
  /// does allow function parameters).
  ///
  /// \returns The NRVO candidate variable, if the return statement may use the
  /// NRVO, or NULL if there is no such candidate.
  VarDecl *Sema::getCopyElisionCandidate(QualType ReturnType, Expr *E,
                                         CopyElisionSemanticsKind CESK) {
    // - in a return statement in a function [where] ...
    // ... the expression is the name of a non-volatile automatic object ...
    DeclRefExpr *DR = dyn_cast<DeclRefExpr>(E->IgnoreParens());
    if (!DR || DR->refersToEnclosingVariableOrCapture())
      return nullptr;
    VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl());
    if (!VD)
      return nullptr;
  
    if (isCopyElisionCandidate(ReturnType, VD, CESK))
      return VD;
    return nullptr;
  }
  
  bool Sema::isCopyElisionCandidate(QualType ReturnType, const VarDecl *VD,
                                    CopyElisionSemanticsKind CESK) {
    QualType VDType = VD->getType();
    // - in a return statement in a function with ...
    // ... a class return type ...
    if (!ReturnType.isNull() && !ReturnType->isDependentType()) {
      if (!ReturnType->isRecordType())
        return false;
      // ... the same cv-unqualified type as the function return type ...
      // When considering moving this expression out, allow dissimilar types.
      if (!(CESK & CES_AllowDifferentTypes) && !VDType->isDependentType() &&
          !Context.hasSameUnqualifiedType(ReturnType, VDType))
        return false;
    }
  
    // ...object (other than a function or catch-clause parameter)...
    if (VD->getKind() != Decl::Var &&
        !((CESK & CES_AllowParameters) && VD->getKind() == Decl::ParmVar))
      return false;
    if (!(CESK & CES_AllowExceptionVariables) && VD->isExceptionVariable())
      return false;
  
    // ...automatic...
    if (!VD->hasLocalStorage()) return false;
  
    // Return false if VD is a __block variable. We don't want to implicitly move
    // out of a __block variable during a return because we cannot assume the
    // variable will no longer be used.
    if (VD->hasAttr<BlocksAttr>()) return false;
  
    if (CESK & CES_AllowDifferentTypes)
      return true;
  
    // ...non-volatile...
    if (VD->getType().isVolatileQualified()) return false;
  
    // Variables with higher required alignment than their type's ABI
    // alignment cannot use NRVO.
    if (!VD->getType()->isDependentType() && VD->hasAttr<AlignedAttr>() &&
        Context.getDeclAlign(VD) > Context.getTypeAlignInChars(VD->getType()))
      return false;
  
    return true;
  }
  
  /// Try to perform the initialization of a potentially-movable value,
  /// which is the operand to a return or throw statement.
  ///
  /// This routine implements C++14 [class.copy]p32, which attempts to treat
  /// returned lvalues as rvalues in certain cases (to prefer move construction),
  /// then falls back to treating them as lvalues if that failed.
  ///
  /// \param ConvertingConstructorsOnly If true, follow [class.copy]p32 and reject
  /// resolutions that find non-constructors, such as derived-to-base conversions
  /// or `operator T()&&` member functions. If false, do consider such
  /// conversion sequences.
  ///
  /// \param Res We will fill this in if move-initialization was possible.
  /// If move-initialization is not possible, such that we must fall back to
  /// treating the operand as an lvalue, we will leave Res in its original
  /// invalid state.
  static void TryMoveInitialization(Sema& S,
                                    const InitializedEntity &Entity,
                                    const VarDecl *NRVOCandidate,
                                    QualType ResultType,
                                    Expr *&Value,
                                    bool ConvertingConstructorsOnly,
                                    ExprResult &Res) {
    ImplicitCastExpr AsRvalue(ImplicitCastExpr::OnStack, Value->getType(),
                              CK_NoOp, Value, VK_XValue);
  
    Expr *InitExpr = &AsRvalue;
  
    InitializationKind Kind = InitializationKind::CreateCopy(
        Value->getBeginLoc(), Value->getBeginLoc());
  
    InitializationSequence Seq(S, Entity, Kind, InitExpr);
  
    if (!Seq)
      return;
  
    for (const InitializationSequence::Step &Step : Seq.steps()) {
      if (Step.Kind != InitializationSequence::SK_ConstructorInitialization &&
          Step.Kind != InitializationSequence::SK_UserConversion)
        continue;
  
      FunctionDecl *FD = Step.Function.Function;
      if (ConvertingConstructorsOnly) {
        if (isa<CXXConstructorDecl>(FD)) {
          // C++14 [class.copy]p32:
          // [...] If the first overload resolution fails or was not performed,
          // or if the type of the first parameter of the selected constructor
          // is not an rvalue reference to the object's type (possibly
          // cv-qualified), overload resolution is performed again, considering
          // the object as an lvalue.
          const RValueReferenceType *RRefType =
              FD->getParamDecl(0)->getType()->getAs<RValueReferenceType>();
          if (!RRefType)
            break;
          if (!S.Context.hasSameUnqualifiedType(RRefType->getPointeeType(),
                                                NRVOCandidate->getType()))
            break;
        } else {
          continue;
        }
      } else {
        if (isa<CXXConstructorDecl>(FD)) {
          // Check that overload resolution selected a constructor taking an
          // rvalue reference. If it selected an lvalue reference, then we
          // didn't need to cast this thing to an rvalue in the first place.
          if (!isa<RValueReferenceType>(FD->getParamDecl(0)->getType()))
            break;
        } else if (isa<CXXMethodDecl>(FD)) {
          // Check that overload resolution selected a conversion operator
          // taking an rvalue reference.
          if (cast<CXXMethodDecl>(FD)->getRefQualifier() != RQ_RValue)
            break;
        } else {
          continue;
        }
      }
  
      // Promote "AsRvalue" to the heap, since we now need this
      // expression node to persist.
      Value = ImplicitCastExpr::Create(S.Context, Value->getType(), CK_NoOp,
                                       Value, nullptr, VK_XValue);
  
      // Complete type-checking the initialization of the return type
      // using the constructor we found.
      Res = Seq.Perform(S, Entity, Kind, Value);
    }
  }
  
  /// Perform the initialization of a potentially-movable value, which
  /// is the result of return value.
  ///
  /// This routine implements C++14 [class.copy]p32, which attempts to treat
  /// returned lvalues as rvalues in certain cases (to prefer move construction),
  /// then falls back to treating them as lvalues if that failed.
  ExprResult
  Sema::PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
                                        const VarDecl *NRVOCandidate,
                                        QualType ResultType,
                                        Expr *Value,
                                        bool AllowNRVO) {
    // C++14 [class.copy]p32:
    // When the criteria for elision of a copy/move operation are met, but not for
    // an exception-declaration, and the object to be copied is designated by an
    // lvalue, or when the expression in a return statement is a (possibly
    // parenthesized) id-expression that names an object with automatic storage
    // duration declared in the body or parameter-declaration-clause of the
    // innermost enclosing function or lambda-expression, overload resolution to
    // select the constructor for the copy is first performed as if the object
    // were designated by an rvalue.
    ExprResult Res = ExprError();
  
    if (AllowNRVO) {
      bool AffectedByCWG1579 = false;
  
      if (!NRVOCandidate) {
        NRVOCandidate = getCopyElisionCandidate(ResultType, Value, CES_Default);
        if (NRVOCandidate &&
            !getDiagnostics().isIgnored(diag::warn_return_std_move_in_cxx11,
                                        Value->getExprLoc())) {
          const VarDecl *NRVOCandidateInCXX11 =
              getCopyElisionCandidate(ResultType, Value, CES_FormerDefault);
          AffectedByCWG1579 = (!NRVOCandidateInCXX11);
        }
      }
  
      if (NRVOCandidate) {
        TryMoveInitialization(*this, Entity, NRVOCandidate, ResultType, Value,
                              true, Res);
      }
  
      if (!Res.isInvalid() && AffectedByCWG1579) {
        QualType QT = NRVOCandidate->getType();
        if (QT.getNonReferenceType()
                       .getUnqualifiedType()
                       .isTriviallyCopyableType(Context)) {
          // Adding 'std::move' around a trivially copyable variable is probably
          // pointless. Don't suggest it.
        } else {
          // Common cases for this are returning unique_ptr<Derived> from a
          // function of return type unique_ptr<Base>, or returning T from a
          // function of return type Expected<T>. This is totally fine in a
          // post-CWG1579 world, but was not fine before.
          assert(!ResultType.isNull());
          SmallString<32> Str;
          Str += "std::move(";
          Str += NRVOCandidate->getDeclName().getAsString();
          Str += ")";
          Diag(Value->getExprLoc(), diag::warn_return_std_move_in_cxx11)
              << Value->getSourceRange()
              << NRVOCandidate->getDeclName() << ResultType << QT;
          Diag(Value->getExprLoc(), diag::note_add_std_move_in_cxx11)
              << FixItHint::CreateReplacement(Value->getSourceRange(), Str);
        }
      } else if (Res.isInvalid() &&
                 !getDiagnostics().isIgnored(diag::warn_return_std_move,
                                             Value->getExprLoc())) {
        const VarDecl *FakeNRVOCandidate =
            getCopyElisionCandidate(QualType(), Value, CES_AsIfByStdMove);
        if (FakeNRVOCandidate) {
          QualType QT = FakeNRVOCandidate->getType();
          if (QT->isLValueReferenceType()) {
            // Adding 'std::move' around an lvalue reference variable's name is
            // dangerous. Don't suggest it.
          } else if (QT.getNonReferenceType()
                         .getUnqualifiedType()
                         .isTriviallyCopyableType(Context)) {
            // Adding 'std::move' around a trivially copyable variable is probably
            // pointless. Don't suggest it.
          } else {
            ExprResult FakeRes = ExprError();
            Expr *FakeValue = Value;
            TryMoveInitialization(*this, Entity, FakeNRVOCandidate, ResultType,
                                  FakeValue, false, FakeRes);
            if (!FakeRes.isInvalid()) {
              bool IsThrow =
                  (Entity.getKind() == InitializedEntity::EK_Exception);
              SmallString<32> Str;
              Str += "std::move(";
              Str += FakeNRVOCandidate->getDeclName().getAsString();
              Str += ")";
              Diag(Value->getExprLoc(), diag::warn_return_std_move)
                  << Value->getSourceRange()
                  << FakeNRVOCandidate->getDeclName() << IsThrow;
              Diag(Value->getExprLoc(), diag::note_add_std_move)
                  << FixItHint::CreateReplacement(Value->getSourceRange(), Str);
            }
          }
        }
      }
    }
  
    // Either we didn't meet the criteria for treating an lvalue as an rvalue,
    // above, or overload resolution failed. Either way, we need to try
    // (again) now with the return value expression as written.
    if (Res.isInvalid())
      Res = PerformCopyInitialization(Entity, SourceLocation(), Value);
  
    return Res;
  }
  
  /// Determine whether the declared return type of the specified function
  /// contains 'auto'.
  static bool hasDeducedReturnType(FunctionDecl *FD) {
    const FunctionProtoType *FPT =
        FD->getTypeSourceInfo()->getType()->castAs<FunctionProtoType>();
    return FPT->getReturnType()->isUndeducedType();
  }
  
  /// ActOnCapScopeReturnStmt - Utility routine to type-check return statements
  /// for capturing scopes.
  ///
  StmtResult
  Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
    // If this is the first return we've seen, infer the return type.
    // [expr.prim.lambda]p4 in C++11; block literals follow the same rules.
    CapturingScopeInfo *CurCap = cast<CapturingScopeInfo>(getCurFunction());
    QualType FnRetType = CurCap->ReturnType;
    LambdaScopeInfo *CurLambda = dyn_cast<LambdaScopeInfo>(CurCap);
    bool HasDeducedReturnType =
        CurLambda && hasDeducedReturnType(CurLambda->CallOperator);
  
    if (ExprEvalContexts.back().Context ==
            ExpressionEvaluationContext::DiscardedStatement &&
        (HasDeducedReturnType || CurCap->HasImplicitReturnType)) {
      if (RetValExp) {
        ExprResult ER =
            ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
        if (ER.isInvalid())
          return StmtError();
        RetValExp = ER.get();
      }
      return ReturnStmt::Create(Context, ReturnLoc, RetValExp,
                                /* NRVOCandidate=*/nullptr);
    }
  
    if (HasDeducedReturnType) {
      // In C++1y, the return type may involve 'auto'.
      // FIXME: Blocks might have a return type of 'auto' explicitly specified.
      FunctionDecl *FD = CurLambda->CallOperator;
      if (CurCap->ReturnType.isNull())
        CurCap->ReturnType = FD->getReturnType();
  
      AutoType *AT = CurCap->ReturnType->getContainedAutoType();
      assert(AT && "lost auto type from lambda return type");
      if (DeduceFunctionTypeFromReturnExpr(FD, ReturnLoc, RetValExp, AT)) {
        FD->setInvalidDecl();
        return StmtError();
      }
      CurCap->ReturnType = FnRetType = FD->getReturnType();
    } else if (CurCap->HasImplicitReturnType) {
      // For blocks/lambdas with implicit return types, we check each return
      // statement individually, and deduce the common return type when the block
      // or lambda is completed.
      // FIXME: Fold this into the 'auto' codepath above.
      if (RetValExp && !isa<InitListExpr>(RetValExp)) {
        ExprResult Result = DefaultFunctionArrayLvalueConversion(RetValExp);
        if (Result.isInvalid())
          return StmtError();
        RetValExp = Result.get();
  
        // DR1048: even prior to C++14, we should use the 'auto' deduction rules
        // when deducing a return type for a lambda-expression (or by extension
        // for a block). These rules differ from the stated C++11 rules only in
        // that they remove top-level cv-qualifiers.
        if (!CurContext->isDependentContext())
          FnRetType = RetValExp->getType().getUnqualifiedType();
        else
          FnRetType = CurCap->ReturnType = Context.DependentTy;
      } else {
        if (RetValExp) {
          // C++11 [expr.lambda.prim]p4 bans inferring the result from an
          // initializer list, because it is not an expression (even
          // though we represent it as one). We still deduce 'void'.
          Diag(ReturnLoc, diag::err_lambda_return_init_list)
            << RetValExp->getSourceRange();
        }
  
        FnRetType = Context.VoidTy;
      }
  
      // Although we'll properly infer the type of the block once it's completed,
      // make sure we provide a return type now for better error recovery.
      if (CurCap->ReturnType.isNull())
        CurCap->ReturnType = FnRetType;
    }
    assert(!FnRetType.isNull());
  
    if (auto *CurBlock = dyn_cast<BlockScopeInfo>(CurCap)) {
      if (CurBlock->FunctionType->castAs<FunctionType>()->getNoReturnAttr()) {
        Diag(ReturnLoc, diag::err_noreturn_block_has_return_expr);
        return StmtError();
      }
    } else if (auto *CurRegion = dyn_cast<CapturedRegionScopeInfo>(CurCap)) {
      Diag(ReturnLoc, diag::err_return_in_captured_stmt) << CurRegion->getRegionName();
      return StmtError();
    } else {
      assert(CurLambda && "unknown kind of captured scope");
      if (CurLambda->CallOperator->getType()
              ->castAs<FunctionType>()
              ->getNoReturnAttr()) {
        Diag(ReturnLoc, diag::err_noreturn_lambda_has_return_expr);
        return StmtError();
      }
    }
  
    // Otherwise, verify that this result type matches the previous one.  We are
    // pickier with blocks than for normal functions because we don't have GCC
    // compatibility to worry about here.
    const VarDecl *NRVOCandidate = nullptr;
    if (FnRetType->isDependentType()) {
      // Delay processing for now.  TODO: there are lots of dependent
      // types we can conclusively prove aren't void.
    } else if (FnRetType->isVoidType()) {
      if (RetValExp && !isa<InitListExpr>(RetValExp) &&
          !(getLangOpts().CPlusPlus &&
            (RetValExp->isTypeDependent() ||
             RetValExp->getType()->isVoidType()))) {
        if (!getLangOpts().CPlusPlus &&
            RetValExp->getType()->isVoidType())
          Diag(ReturnLoc, diag::ext_return_has_void_expr) << "literal" << 2;
        else {
          Diag(ReturnLoc, diag::err_return_block_has_expr);
          RetValExp = nullptr;
        }
      }
    } else if (!RetValExp) {
      return StmtError(Diag(ReturnLoc, diag::err_block_return_missing_expr));
    } else if (!RetValExp->isTypeDependent()) {
      // we have a non-void block with an expression, continue checking
  
      // C99 6.8.6.4p3(136): The return statement is not an assignment. The
      // overlap restriction of subclause 6.5.16.1 does not apply to the case of
      // function return.
  
      // In C++ the return statement is handled via a copy initialization.
      // the C version of which boils down to CheckSingleAssignmentConstraints.
      NRVOCandidate = getCopyElisionCandidate(FnRetType, RetValExp, CES_Strict);
      InitializedEntity Entity = InitializedEntity::InitializeResult(ReturnLoc,
                                                                     FnRetType,
                                                        NRVOCandidate != nullptr);
      ExprResult Res = PerformMoveOrCopyInitialization(Entity, NRVOCandidate,
                                                       FnRetType, RetValExp);
      if (Res.isInvalid()) {
        // FIXME: Cleanup temporaries here, anyway?
        return StmtError();
      }
      RetValExp = Res.get();
      CheckReturnValExpr(RetValExp, FnRetType, ReturnLoc);
    } else {
      NRVOCandidate = getCopyElisionCandidate(FnRetType, RetValExp, CES_Strict);
    }
  
    if (RetValExp) {
      ExprResult ER =
          ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
      if (ER.isInvalid())
        return StmtError();
      RetValExp = ER.get();
    }
    auto *Result =
        ReturnStmt::Create(Context, ReturnLoc, RetValExp, NRVOCandidate);
  
    // If we need to check for the named return value optimization,
    // or if we need to infer the return type,
    // save the return statement in our scope for later processing.
    if (CurCap->HasImplicitReturnType || NRVOCandidate)
      FunctionScopes.back()->Returns.push_back(Result);
  
    if (FunctionScopes.back()->FirstReturnLoc.isInvalid())
      FunctionScopes.back()->FirstReturnLoc = ReturnLoc;
  
    return Result;
  }
  
  namespace {
  /// Marks all typedefs in all local classes in a type referenced.
  ///
  /// In a function like
  /// auto f() {
  ///   struct S { typedef int a; };
  ///   return S();
  /// }
  ///
  /// the local type escapes and could be referenced in some TUs but not in
  /// others. Pretend that all local typedefs are always referenced, to not warn
  /// on this. This isn't necessary if f has internal linkage, or the typedef
  /// is private.
  class LocalTypedefNameReferencer
      : public RecursiveASTVisitor<LocalTypedefNameReferencer> {
  public:
    LocalTypedefNameReferencer(Sema &S) : S(S) {}
    bool VisitRecordType(const RecordType *RT);
  private:
    Sema &S;
  };
  bool LocalTypedefNameReferencer::VisitRecordType(const RecordType *RT) {
    auto *R = dyn_cast<CXXRecordDecl>(RT->getDecl());
    if (!R || !R->isLocalClass() || !R->isLocalClass()->isExternallyVisible() ||
        R->isDependentType())
      return true;
    for (auto *TmpD : R->decls())
      if (auto *T = dyn_cast<TypedefNameDecl>(TmpD))
        if (T->getAccess() != AS_private || R->hasFriends())
          S.MarkAnyDeclReferenced(T->getLocation(), T, /*OdrUse=*/false);
    return true;
  }
  }
  
  TypeLoc Sema::getReturnTypeLoc(FunctionDecl *FD) const {
    return FD->getTypeSourceInfo()
        ->getTypeLoc()
        .getAsAdjusted<FunctionProtoTypeLoc>()
        .getReturnLoc();
  }
  
  /// Deduce the return type for a function from a returned expression, per
  /// C++1y [dcl.spec.auto]p6.
  bool Sema::DeduceFunctionTypeFromReturnExpr(FunctionDecl *FD,
                                              SourceLocation ReturnLoc,
                                              Expr *&RetExpr,
                                              AutoType *AT) {
    // If this is the conversion function for a lambda, we choose to deduce it
    // type from the corresponding call operator, not from the synthesized return
    // statement within it. See Sema::DeduceReturnType.
    if (isLambdaConversionOperator(FD))
      return false;
  
    TypeLoc OrigResultType = getReturnTypeLoc(FD);
    QualType Deduced;
  
    if (RetExpr && isa<InitListExpr>(RetExpr)) {
      //  If the deduction is for a return statement and the initializer is
      //  a braced-init-list, the program is ill-formed.
      Diag(RetExpr->getExprLoc(),
           getCurLambda() ? diag::err_lambda_return_init_list
                          : diag::err_auto_fn_return_init_list)
          << RetExpr->getSourceRange();
      return true;
    }
  
    if (FD->isDependentContext()) {
      // C++1y [dcl.spec.auto]p12:
      //   Return type deduction [...] occurs when the definition is
      //   instantiated even if the function body contains a return
      //   statement with a non-type-dependent operand.
      assert(AT->isDeduced() && "should have deduced to dependent type");
      return false;
    }
  
    if (RetExpr) {
      //  Otherwise, [...] deduce a value for U using the rules of template
      //  argument deduction.
      DeduceAutoResult DAR = DeduceAutoType(OrigResultType, RetExpr, Deduced);
  
      if (DAR == DAR_Failed && !FD->isInvalidDecl())
        Diag(RetExpr->getExprLoc(), diag::err_auto_fn_deduction_failure)
          << OrigResultType.getType() << RetExpr->getType();
  
      if (DAR != DAR_Succeeded)
        return true;
  
      // If a local type is part of the returned type, mark its fields as
      // referenced.
      LocalTypedefNameReferencer Referencer(*this);
      Referencer.TraverseType(RetExpr->getType());
    } else {
      //  In the case of a return with no operand, the initializer is considered
      //  to be void().
      //
      // Deduction here can only succeed if the return type is exactly 'cv auto'
      // or 'decltype(auto)', so just check for that case directly.
      if (!OrigResultType.getType()->getAs<AutoType>()) {
        Diag(ReturnLoc, diag::err_auto_fn_return_void_but_not_auto)
          << OrigResultType.getType();
        return true;
      }
      // We always deduce U = void in this case.
      Deduced = SubstAutoType(OrigResultType.getType(), Context.VoidTy);
      if (Deduced.isNull())
        return true;
    }
  
    // CUDA: Kernel function must have 'void' return type.
    if (getLangOpts().CUDA)
      if (FD->hasAttr<CUDAGlobalAttr>() && !Deduced->isVoidType()) {
        Diag(FD->getLocation(), diag::err_kern_type_not_void_return)
            << FD->getType() << FD->getSourceRange();
        return true;
      }
  
    //  If a function with a declared return type that contains a placeholder type
    //  has multiple return statements, the return type is deduced for each return
    //  statement. [...] if the type deduced is not the same in each deduction,
    //  the program is ill-formed.
    QualType DeducedT = AT->getDeducedType();
    if (!DeducedT.isNull() && !FD->isInvalidDecl()) {
      AutoType *NewAT = Deduced->getContainedAutoType();
      // It is possible that NewAT->getDeducedType() is null. When that happens,
      // we should not crash, instead we ignore this deduction.
      if (NewAT->getDeducedType().isNull())
        return false;
  
      CanQualType OldDeducedType = Context.getCanonicalFunctionResultType(
                                     DeducedT);
      CanQualType NewDeducedType = Context.getCanonicalFunctionResultType(
                                     NewAT->getDeducedType());
      if (!FD->isDependentContext() && OldDeducedType != NewDeducedType) {
        const LambdaScopeInfo *LambdaSI = getCurLambda();
        if (LambdaSI && LambdaSI->HasImplicitReturnType) {
          Diag(ReturnLoc, diag::err_typecheck_missing_return_type_incompatible)
            << NewAT->getDeducedType() << DeducedT
            << true /*IsLambda*/;
        } else {
          Diag(ReturnLoc, diag::err_auto_fn_different_deductions)
            << (AT->isDecltypeAuto() ? 1 : 0)
            << NewAT->getDeducedType() << DeducedT;
        }
        return true;
      }
    } else if (!FD->isInvalidDecl()) {
      // Update all declarations of the function to have the deduced return type.
      Context.adjustDeducedFunctionResultType(FD, Deduced);
    }
  
    return false;
  }
  
  StmtResult
  Sema::ActOnReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp,
                        Scope *CurScope) {
    // Correct typos, in case the containing function returns 'auto' and
    // RetValExp should determine the deduced type.
    ExprResult RetVal = CorrectDelayedTyposInExpr(RetValExp);
    if (RetVal.isInvalid())
      return StmtError();
    StmtResult R = BuildReturnStmt(ReturnLoc, RetVal.get());
    if (R.isInvalid() || ExprEvalContexts.back().Context ==
                             ExpressionEvaluationContext::DiscardedStatement)
      return R;
  
    if (VarDecl *VD =
        const_cast<VarDecl*>(cast<ReturnStmt>(R.get())->getNRVOCandidate())) {
      CurScope->addNRVOCandidate(VD);
    } else {
      CurScope->setNoNRVO();
    }
  
    CheckJumpOutOfSEHFinally(*this, ReturnLoc, *CurScope->getFnParent());
  
    return R;
  }
  
  StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
    // Check for unexpanded parameter packs.
    if (RetValExp && DiagnoseUnexpandedParameterPack(RetValExp))
      return StmtError();
  
    if (isa<CapturingScopeInfo>(getCurFunction()))
      return ActOnCapScopeReturnStmt(ReturnLoc, RetValExp);
  
    QualType FnRetType;
    QualType RelatedRetType;
    const AttrVec *Attrs = nullptr;
    bool isObjCMethod = false;
  
    if (const FunctionDecl *FD = getCurFunctionDecl()) {
      FnRetType = FD->getReturnType();
      if (FD->hasAttrs())
        Attrs = &FD->getAttrs();
      if (FD->isNoReturn())
        Diag(ReturnLoc, diag::warn_noreturn_function_has_return_expr)
          << FD->getDeclName();
      if (FD->isMain() && RetValExp)
        if (isa<CXXBoolLiteralExpr>(RetValExp))
          Diag(ReturnLoc, diag::warn_main_returns_bool_literal)
            << RetValExp->getSourceRange();
    } else if (ObjCMethodDecl *MD = getCurMethodDecl()) {
      FnRetType = MD->getReturnType();
      isObjCMethod = true;
      if (MD->hasAttrs())
        Attrs = &MD->getAttrs();
      if (MD->hasRelatedResultType() && MD->getClassInterface()) {
        // In the implementation of a method with a related return type, the
        // type used to type-check the validity of return statements within the
        // method body is a pointer to the type of the class being implemented.
        RelatedRetType = Context.getObjCInterfaceType(MD->getClassInterface());
        RelatedRetType = Context.getObjCObjectPointerType(RelatedRetType);
      }
    } else // If we don't have a function/method context, bail.
      return StmtError();
  
    // C++1z: discarded return statements are not considered when deducing a
    // return type.
    if (ExprEvalContexts.back().Context ==
            ExpressionEvaluationContext::DiscardedStatement &&
        FnRetType->getContainedAutoType()) {
      if (RetValExp) {
        ExprResult ER =
            ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
        if (ER.isInvalid())
          return StmtError();
        RetValExp = ER.get();
      }
      return ReturnStmt::Create(Context, ReturnLoc, RetValExp,
                                /* NRVOCandidate=*/nullptr);
    }
  
    // FIXME: Add a flag to the ScopeInfo to indicate whether we're performing
    // deduction.
    if (getLangOpts().CPlusPlus14) {
      if (AutoType *AT = FnRetType->getContainedAutoType()) {
        FunctionDecl *FD = cast<FunctionDecl>(CurContext);
        if (DeduceFunctionTypeFromReturnExpr(FD, ReturnLoc, RetValExp, AT)) {
          FD->setInvalidDecl();
          return StmtError();
        } else {
          FnRetType = FD->getReturnType();
        }
      }
    }
  
    bool HasDependentReturnType = FnRetType->isDependentType();
  
    ReturnStmt *Result = nullptr;
    if (FnRetType->isVoidType()) {
      if (RetValExp) {
        if (isa<InitListExpr>(RetValExp)) {
          // We simply never allow init lists as the return value of void
          // functions. This is compatible because this was never allowed before,
          // so there's no legacy code to deal with.
          NamedDecl *CurDecl = getCurFunctionOrMethodDecl();
          int FunctionKind = 0;
          if (isa<ObjCMethodDecl>(CurDecl))
            FunctionKind = 1;
          else if (isa<CXXConstructorDecl>(CurDecl))
            FunctionKind = 2;
          else if (isa<CXXDestructorDecl>(CurDecl))
            FunctionKind = 3;
  
          Diag(ReturnLoc, diag::err_return_init_list)
            << CurDecl->getDeclName() << FunctionKind
            << RetValExp->getSourceRange();
  
          // Drop the expression.
          RetValExp = nullptr;
        } else if (!RetValExp->isTypeDependent()) {
          // C99 6.8.6.4p1 (ext_ since GCC warns)
          unsigned D = diag::ext_return_has_expr;
          if (RetValExp->getType()->isVoidType()) {
            NamedDecl *CurDecl = getCurFunctionOrMethodDecl();
            if (isa<CXXConstructorDecl>(CurDecl) ||
                isa<CXXDestructorDecl>(CurDecl))
              D = diag::err_ctor_dtor_returns_void;
            else
              D = diag::ext_return_has_void_expr;
          }
          else {
            ExprResult Result = RetValExp;
            Result = IgnoredValueConversions(Result.get());
            if (Result.isInvalid())
              return StmtError();
            RetValExp = Result.get();
            RetValExp = ImpCastExprToType(RetValExp,
                                          Context.VoidTy, CK_ToVoid).get();
          }
          // return of void in constructor/destructor is illegal in C++.
          if (D == diag::err_ctor_dtor_returns_void) {
            NamedDecl *CurDecl = getCurFunctionOrMethodDecl();
            Diag(ReturnLoc, D)
              << CurDecl->getDeclName() << isa<CXXDestructorDecl>(CurDecl)
              << RetValExp->getSourceRange();
          }
          // return (some void expression); is legal in C++.
          else if (D != diag::ext_return_has_void_expr ||
                   !getLangOpts().CPlusPlus) {
            NamedDecl *CurDecl = getCurFunctionOrMethodDecl();
  
            int FunctionKind = 0;
            if (isa<ObjCMethodDecl>(CurDecl))
              FunctionKind = 1;
            else if (isa<CXXConstructorDecl>(CurDecl))
              FunctionKind = 2;
            else if (isa<CXXDestructorDecl>(CurDecl))
              FunctionKind = 3;
  
            Diag(ReturnLoc, D)
              << CurDecl->getDeclName() << FunctionKind
              << RetValExp->getSourceRange();
          }
        }
  
        if (RetValExp) {
          ExprResult ER =
              ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
          if (ER.isInvalid())
            return StmtError();
          RetValExp = ER.get();
        }
      }
  
      Result = ReturnStmt::Create(Context, ReturnLoc, RetValExp,
                                  /* NRVOCandidate=*/nullptr);
    } else if (!RetValExp && !HasDependentReturnType) {
      FunctionDecl *FD = getCurFunctionDecl();
  
      unsigned DiagID;
      if (getLangOpts().CPlusPlus11 && FD && FD->isConstexpr()) {
        // C++11 [stmt.return]p2
        DiagID = diag::err_constexpr_return_missing_expr;
        FD->setInvalidDecl();
      } else if (getLangOpts().C99) {
        // C99 6.8.6.4p1 (ext_ since GCC warns)
        DiagID = diag::ext_return_missing_expr;
      } else {
        // C90 6.6.6.4p4
        DiagID = diag::warn_return_missing_expr;
      }
  
      if (FD)
        Diag(ReturnLoc, DiagID)
            << FD->getIdentifier() << 0 /*fn*/ << FD->isConsteval();
      else
        Diag(ReturnLoc, DiagID) << getCurMethodDecl()->getDeclName() << 1/*meth*/;
  
      Result = ReturnStmt::Create(Context, ReturnLoc, /* RetExpr=*/nullptr,
                                  /* NRVOCandidate=*/nullptr);
    } else {
      assert(RetValExp || HasDependentReturnType);
      const VarDecl *NRVOCandidate = nullptr;
  
      QualType RetType = RelatedRetType.isNull() ? FnRetType : RelatedRetType;
  
      // C99 6.8.6.4p3(136): The return statement is not an assignment. The
      // overlap restriction of subclause 6.5.16.1 does not apply to the case of
      // function return.
  
      // In C++ the return statement is handled via a copy initialization,
      // the C version of which boils down to CheckSingleAssignmentConstraints.
      if (RetValExp)
        NRVOCandidate = getCopyElisionCandidate(FnRetType, RetValExp, CES_Strict);
      if (!HasDependentReturnType && !RetValExp->isTypeDependent()) {
        // we have a non-void function with an expression, continue checking
        InitializedEntity Entity = InitializedEntity::InitializeResult(ReturnLoc,
                                                                       RetType,
                                                        NRVOCandidate != nullptr);
        ExprResult Res = PerformMoveOrCopyInitialization(Entity, NRVOCandidate,
                                                         RetType, RetValExp);
        if (Res.isInvalid()) {
          // FIXME: Clean up temporaries here anyway?
          return StmtError();
        }
        RetValExp = Res.getAs<Expr>();
  
        // If we have a related result type, we need to implicitly
        // convert back to the formal result type.  We can't pretend to
        // initialize the result again --- we might end double-retaining
        // --- so instead we initialize a notional temporary.
        if (!RelatedRetType.isNull()) {
          Entity = InitializedEntity::InitializeRelatedResult(getCurMethodDecl(),
                                                              FnRetType);
          Res = PerformCopyInitialization(Entity, ReturnLoc, RetValExp);
          if (Res.isInvalid()) {
            // FIXME: Clean up temporaries here anyway?
            return StmtError();
          }
          RetValExp = Res.getAs<Expr>();
        }
  
        CheckReturnValExpr(RetValExp, FnRetType, ReturnLoc, isObjCMethod, Attrs,
                           getCurFunctionDecl());
      }
  
      if (RetValExp) {
        ExprResult ER =
            ActOnFinishFullExpr(RetValExp, ReturnLoc, /*DiscardedValue*/ false);
        if (ER.isInvalid())
          return StmtError();
        RetValExp = ER.get();
      }
      Result = ReturnStmt::Create(Context, ReturnLoc, RetValExp, NRVOCandidate);
    }
  
    // If we need to check for the named return value optimization, save the
    // return statement in our scope for later processing.
    if (Result->getNRVOCandidate())
      FunctionScopes.back()->Returns.push_back(Result);
  
    if (FunctionScopes.back()->FirstReturnLoc.isInvalid())
      FunctionScopes.back()->FirstReturnLoc = ReturnLoc;
  
    return Result;
  }
  
  StmtResult
  Sema::ActOnObjCAtCatchStmt(SourceLocation AtLoc,
                             SourceLocation RParen, Decl *Parm,
                             Stmt *Body) {
    VarDecl *Var = cast_or_null<VarDecl>(Parm);
    if (Var && Var->isInvalidDecl())
      return StmtError();
  
    return new (Context) ObjCAtCatchStmt(AtLoc, RParen, Var, Body);
  }
  
  StmtResult
  Sema::ActOnObjCAtFinallyStmt(SourceLocation AtLoc, Stmt *Body) {
    return new (Context) ObjCAtFinallyStmt(AtLoc, Body);
  }
  
  StmtResult
  Sema::ActOnObjCAtTryStmt(SourceLocation AtLoc, Stmt *Try,
                           MultiStmtArg CatchStmts, Stmt *Finally) {
    if (!getLangOpts().ObjCExceptions)
      Diag(AtLoc, diag::err_objc_exceptions_disabled) << "@try";
  
    setFunctionHasBranchProtectedScope();
    unsigned NumCatchStmts = CatchStmts.size();
    return ObjCAtTryStmt::Create(Context, AtLoc, Try, CatchStmts.data(),
                                 NumCatchStmts, Finally);
  }
  
  StmtResult Sema::BuildObjCAtThrowStmt(SourceLocation AtLoc, Expr *Throw) {
    if (Throw) {
      ExprResult Result = DefaultLvalueConversion(Throw);
      if (Result.isInvalid())
        return StmtError();
  
      Result = ActOnFinishFullExpr(Result.get(), /*DiscardedValue*/ false);
      if (Result.isInvalid())
        return StmtError();
      Throw = Result.get();
  
      QualType ThrowType = Throw->getType();
      // Make sure the expression type is an ObjC pointer or "void *".
      if (!ThrowType->isDependentType() &&
          !ThrowType->isObjCObjectPointerType()) {
        const PointerType *PT = ThrowType->getAs<PointerType>();
        if (!PT || !PT->getPointeeType()->isVoidType())
          return StmtError(Diag(AtLoc, diag::err_objc_throw_expects_object)
                           << Throw->getType() << Throw->getSourceRange());
      }
    }
  
    return new (Context) ObjCAtThrowStmt(AtLoc, Throw);
  }
  
  StmtResult
  Sema::ActOnObjCAtThrowStmt(SourceLocation AtLoc, Expr *Throw,
                             Scope *CurScope) {
    if (!getLangOpts().ObjCExceptions)
      Diag(AtLoc, diag::err_objc_exceptions_disabled) << "@throw";
  
    if (!Throw) {
      // @throw without an expression designates a rethrow (which must occur
      // in the context of an @catch clause).
      Scope *AtCatchParent = CurScope;
      while (AtCatchParent && !AtCatchParent->isAtCatchScope())
        AtCatchParent = AtCatchParent->getParent();
      if (!AtCatchParent)
        return StmtError(Diag(AtLoc, diag::err_rethrow_used_outside_catch));
    }
    return BuildObjCAtThrowStmt(AtLoc, Throw);
  }
  
  ExprResult
  Sema::ActOnObjCAtSynchronizedOperand(SourceLocation atLoc, Expr *operand) {
    ExprResult result = DefaultLvalueConversion(operand);
    if (result.isInvalid())
      return ExprError();
    operand = result.get();
  
    // Make sure the expression type is an ObjC pointer or "void *".
    QualType type = operand->getType();
    if (!type->isDependentType() &&
        !type->isObjCObjectPointerType()) {
      const PointerType *pointerType = type->getAs<PointerType>();
      if (!pointerType || !pointerType->getPointeeType()->isVoidType()) {
        if (getLangOpts().CPlusPlus) {
          if (RequireCompleteType(atLoc, type,
                                  diag::err_incomplete_receiver_type))
            return Diag(atLoc, diag::err_objc_synchronized_expects_object)
                     << type << operand->getSourceRange();
  
          ExprResult result = PerformContextuallyConvertToObjCPointer(operand);
          if (result.isInvalid())
            return ExprError();
          if (!result.isUsable())
            return Diag(atLoc, diag::err_objc_synchronized_expects_object)
                     << type << operand->getSourceRange();
  
          operand = result.get();
        } else {
            return Diag(atLoc, diag::err_objc_synchronized_expects_object)
                     << type << operand->getSourceRange();
        }
      }
    }
  
    // The operand to @synchronized is a full-expression.
    return ActOnFinishFullExpr(operand, /*DiscardedValue*/ false);
  }
  
  StmtResult
  Sema::ActOnObjCAtSynchronizedStmt(SourceLocation AtLoc, Expr *SyncExpr,
                                    Stmt *SyncBody) {
    // We can't jump into or indirect-jump out of a @synchronized block.
    setFunctionHasBranchProtectedScope();
    return new (Context) ObjCAtSynchronizedStmt(AtLoc, SyncExpr, SyncBody);
  }
  
  /// ActOnCXXCatchBlock - Takes an exception declaration and a handler block
  /// and creates a proper catch handler from them.
  StmtResult
  Sema::ActOnCXXCatchBlock(SourceLocation CatchLoc, Decl *ExDecl,
                           Stmt *HandlerBlock) {
    // There's nothing to test that ActOnExceptionDecl didn't already test.
    return new (Context)
        CXXCatchStmt(CatchLoc, cast_or_null<VarDecl>(ExDecl), HandlerBlock);
  }
  
  StmtResult
  Sema::ActOnObjCAutoreleasePoolStmt(SourceLocation AtLoc, Stmt *Body) {
    setFunctionHasBranchProtectedScope();
    return new (Context) ObjCAutoreleasePoolStmt(AtLoc, Body);
  }
  
  namespace {
  class CatchHandlerType {
    QualType QT;
    unsigned IsPointer : 1;
  
    // This is a special constructor to be used only with DenseMapInfo's
    // getEmptyKey() and getTombstoneKey() functions.
    friend struct llvm::DenseMapInfo<CatchHandlerType>;
    enum Unique { ForDenseMap };
    CatchHandlerType(QualType QT, Unique) : QT(QT), IsPointer(false) {}
  
  public:
    /// Used when creating a CatchHandlerType from a handler type; will determine
    /// whether the type is a pointer or reference and will strip off the top
    /// level pointer and cv-qualifiers.
    CatchHandlerType(QualType Q) : QT(Q), IsPointer(false) {
      if (QT->isPointerType())
        IsPointer = true;
  
      if (IsPointer || QT->isReferenceType())
        QT = QT->getPointeeType();
      QT = QT.getUnqualifiedType();
    }
  
    /// Used when creating a CatchHandlerType from a base class type; pretends the
    /// type passed in had the pointer qualifier, does not need to get an
    /// unqualified type.
    CatchHandlerType(QualType QT, bool IsPointer)
        : QT(QT), IsPointer(IsPointer) {}
  
    QualType underlying() const { return QT; }
    bool isPointer() const { return IsPointer; }
  
    friend bool operator==(const CatchHandlerType &LHS,
                           const CatchHandlerType &RHS) {
      // If the pointer qualification does not match, we can return early.
      if (LHS.IsPointer != RHS.IsPointer)
        return false;
      // Otherwise, check the underlying type without cv-qualifiers.
      return LHS.QT == RHS.QT;
    }
  };
  } // namespace
  
  namespace llvm {
  template <> struct DenseMapInfo<CatchHandlerType> {
    static CatchHandlerType getEmptyKey() {
      return CatchHandlerType(DenseMapInfo<QualType>::getEmptyKey(),
                         CatchHandlerType::ForDenseMap);
    }
  
    static CatchHandlerType getTombstoneKey() {
      return CatchHandlerType(DenseMapInfo<QualType>::getTombstoneKey(),
                         CatchHandlerType::ForDenseMap);
    }
  
    static unsigned getHashValue(const CatchHandlerType &Base) {
      return DenseMapInfo<QualType>::getHashValue(Base.underlying());
    }
  
    static bool isEqual(const CatchHandlerType &LHS,
                        const CatchHandlerType &RHS) {
      return LHS == RHS;
    }
  };
  }
  
  namespace {
  class CatchTypePublicBases {
    ASTContext &Ctx;
    const llvm::DenseMap<CatchHandlerType, CXXCatchStmt *> &TypesToCheck;
    const bool CheckAgainstPointer;
  
    CXXCatchStmt *FoundHandler;
    CanQualType FoundHandlerType;
  
  public:
    CatchTypePublicBases(
        ASTContext &Ctx,
        const llvm::DenseMap<CatchHandlerType, CXXCatchStmt *> &T, bool C)
        : Ctx(Ctx), TypesToCheck(T), CheckAgainstPointer(C),
          FoundHandler(nullptr) {}
  
    CXXCatchStmt *getFoundHandler() const { return FoundHandler; }
    CanQualType getFoundHandlerType() const { return FoundHandlerType; }
  
    bool operator()(const CXXBaseSpecifier *S, CXXBasePath &) {
      if (S->getAccessSpecifier() == AccessSpecifier::AS_public) {
        CatchHandlerType Check(S->getType(), CheckAgainstPointer);
        const auto &M = TypesToCheck;
        auto I = M.find(Check);
        if (I != M.end()) {
          FoundHandler = I->second;
          FoundHandlerType = Ctx.getCanonicalType(S->getType());
          return true;
        }
      }
      return false;
    }
  };
  }
  
  /// ActOnCXXTryBlock - Takes a try compound-statement and a number of
  /// handlers and creates a try statement from them.
  StmtResult Sema::ActOnCXXTryBlock(SourceLocation TryLoc, Stmt *TryBlock,
                                    ArrayRef<Stmt *> Handlers) {
    // Don't report an error if 'try' is used in system headers.
    if (!getLangOpts().CXXExceptions &&
        !getSourceManager().isInSystemHeader(TryLoc) && !getLangOpts().CUDA) {
      // Delay error emission for the OpenMP device code.
      targetDiag(TryLoc, diag::err_exceptions_disabled) << "try";
    }
  
    // Exceptions aren't allowed in CUDA device code.
    if (getLangOpts().CUDA)
      CUDADiagIfDeviceCode(TryLoc, diag::err_cuda_device_exceptions)
          << "try" << CurrentCUDATarget();
  
    // Exceptions aren't allowed in SYCL device code.
    if (getLangOpts().SYCLIsDevice)
      SYCLDiagIfDeviceCode(TryLoc, diag::err_sycl_restrict)
          << KernelUseExceptions;
  
    if (getCurScope() && getCurScope()->isOpenMPSimdDirectiveScope())
      Diag(TryLoc, diag::err_omp_simd_region_cannot_use_stmt) << "try";
  
    sema::FunctionScopeInfo *FSI = getCurFunction();
  
    // C++ try is incompatible with SEH __try.
    if (!getLangOpts().Borland && FSI->FirstSEHTryLoc.isValid()) {
      Diag(TryLoc, diag::err_mixing_cxx_try_seh_try);
      Diag(FSI->FirstSEHTryLoc, diag::note_conflicting_try_here) << "'__try'";
    }
  
    const unsigned NumHandlers = Handlers.size();
    assert(!Handlers.empty() &&
           "The parser shouldn't call this if there are no handlers.");
  
    llvm::DenseMap<CatchHandlerType, CXXCatchStmt *> HandledTypes;
    for (unsigned i = 0; i < NumHandlers; ++i) {
      CXXCatchStmt *H = cast<CXXCatchStmt>(Handlers[i]);
  
      // Diagnose when the handler is a catch-all handler, but it isn't the last
      // handler for the try block. [except.handle]p5. Also, skip exception
      // declarations that are invalid, since we can't usefully report on them.
      if (!H->getExceptionDecl()) {
        if (i < NumHandlers - 1)
          return StmtError(Diag(H->getBeginLoc(), diag::err_early_catch_all));
        continue;
      } else if (H->getExceptionDecl()->isInvalidDecl())
        continue;
  
      // Walk the type hierarchy to diagnose when this type has already been
      // handled (duplication), or cannot be handled (derivation inversion). We
      // ignore top-level cv-qualifiers, per [except.handle]p3
      CatchHandlerType HandlerCHT =
          (QualType)Context.getCanonicalType(H->getCaughtType());
  
      // We can ignore whether the type is a reference or a pointer; we need the
      // underlying declaration type in order to get at the underlying record
      // decl, if there is one.
      QualType Underlying = HandlerCHT.underlying();
      if (auto *RD = Underlying->getAsCXXRecordDecl()) {
        if (!RD->hasDefinition())
          continue;
        // Check that none of the public, unambiguous base classes are in the
        // map ([except.handle]p1). Give the base classes the same pointer
        // qualification as the original type we are basing off of. This allows
        // comparison against the handler type using the same top-level pointer
        // as the original type.
        CXXBasePaths Paths;
        Paths.setOrigin(RD);
        CatchTypePublicBases CTPB(Context, HandledTypes, HandlerCHT.isPointer());
        if (RD->lookupInBases(CTPB, Paths)) {
          const CXXCatchStmt *Problem = CTPB.getFoundHandler();
          if (!Paths.isAmbiguous(CTPB.getFoundHandlerType())) {
            Diag(H->getExceptionDecl()->getTypeSpecStartLoc(),
                 diag::warn_exception_caught_by_earlier_handler)
                << H->getCaughtType();
            Diag(Problem->getExceptionDecl()->getTypeSpecStartLoc(),
                  diag::note_previous_exception_handler)
                << Problem->getCaughtType();
          }
        }
      }
  
      // Add the type the list of ones we have handled; diagnose if we've already
      // handled it.
      auto R = HandledTypes.insert(std::make_pair(H->getCaughtType(), H));
      if (!R.second) {
        const CXXCatchStmt *Problem = R.first->second;
        Diag(H->getExceptionDecl()->getTypeSpecStartLoc(),
             diag::warn_exception_caught_by_earlier_handler)
            << H->getCaughtType();
        Diag(Problem->getExceptionDecl()->getTypeSpecStartLoc(),
             diag::note_previous_exception_handler)
            << Problem->getCaughtType();
      }
    }
  
    FSI->setHasCXXTry(TryLoc);
  
    return CXXTryStmt::Create(Context, TryLoc, TryBlock, Handlers);
  }
  
  StmtResult Sema::ActOnSEHTryBlock(bool IsCXXTry, SourceLocation TryLoc,
                                    Stmt *TryBlock, Stmt *Handler) {
    assert(TryBlock && Handler);
  
    sema::FunctionScopeInfo *FSI = getCurFunction();
  
    // SEH __try is incompatible with C++ try. Borland appears to support this,
    // however.
    if (!getLangOpts().Borland) {
      if (FSI->FirstCXXTryLoc.isValid()) {
        Diag(TryLoc, diag::err_mixing_cxx_try_seh_try);
        Diag(FSI->FirstCXXTryLoc, diag::note_conflicting_try_here) << "'try'";
      }
    }
  
    // Exceptions aren't allowed in SYCL device code.
    if (getLangOpts().SYCLIsDevice)
      SYCLDiagIfDeviceCode(TryLoc, diag::err_sycl_restrict)
          << KernelUseExceptions;
  
    FSI->setHasSEHTry(TryLoc);
  
    // Reject __try in Obj-C methods, blocks, and captured decls, since we don't
    // track if they use SEH.
    DeclContext *DC = CurContext;
    while (DC && !DC->isFunctionOrMethod())
      DC = DC->getParent();
    FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(DC);
    if (FD)
      FD->setUsesSEHTry(true);
    else
      Diag(TryLoc, diag::err_seh_try_outside_functions);
  
    // Reject __try on unsupported targets.
    if (!Context.getTargetInfo().isSEHTrySupported())
      Diag(TryLoc, diag::err_seh_try_unsupported);
  
    return SEHTryStmt::Create(Context, IsCXXTry, TryLoc, TryBlock, Handler);
  }
  
  StmtResult Sema::ActOnSEHExceptBlock(SourceLocation Loc, Expr *FilterExpr,
                                       Stmt *Block) {
    assert(FilterExpr && Block);
    QualType FTy = FilterExpr->getType();
    if (!FTy->isIntegerType() && !FTy->isDependentType()) {
      return StmtError(
          Diag(FilterExpr->getExprLoc(), diag::err_filter_expression_integral)
          << FTy);
    }
    return SEHExceptStmt::Create(Context, Loc, FilterExpr, Block);
  }
  
  void Sema::ActOnStartSEHFinallyBlock() {
    CurrentSEHFinally.push_back(CurScope);
  }
  
  void Sema::ActOnAbortSEHFinallyBlock() {
    CurrentSEHFinally.pop_back();
  }
  
  StmtResult Sema::ActOnFinishSEHFinallyBlock(SourceLocation Loc, Stmt *Block) {
    assert(Block);
    CurrentSEHFinally.pop_back();
    return SEHFinallyStmt::Create(Context, Loc, Block);
  }
  
  StmtResult
  Sema::ActOnSEHLeaveStmt(SourceLocation Loc, Scope *CurScope) {
    Scope *SEHTryParent = CurScope;
    while (SEHTryParent && !SEHTryParent->isSEHTryScope())
      SEHTryParent = SEHTryParent->getParent();
    if (!SEHTryParent)
      return StmtError(Diag(Loc, diag::err_ms___leave_not_in___try));
    CheckJumpOutOfSEHFinally(*this, Loc, *SEHTryParent);
  
    return new (Context) SEHLeaveStmt(Loc);
  }
  
  StmtResult Sema::BuildMSDependentExistsStmt(SourceLocation KeywordLoc,
                                              bool IsIfExists,
                                              NestedNameSpecifierLoc QualifierLoc,
                                              DeclarationNameInfo NameInfo,
                                              Stmt *Nested)
  {
    return new (Context) MSDependentExistsStmt(KeywordLoc, IsIfExists,
                                               QualifierLoc, NameInfo,
                                               cast<CompoundStmt>(Nested));
  }
  
  
  StmtResult Sema::ActOnMSDependentExistsStmt(SourceLocation KeywordLoc,
                                              bool IsIfExists,
                                              CXXScopeSpec &SS,
                                              UnqualifiedId &Name,
                                              Stmt *Nested) {
    return BuildMSDependentExistsStmt(KeywordLoc, IsIfExists,
                                      SS.getWithLocInContext(Context),
                                      GetNameFromUnqualifiedId(Name),
                                      Nested);
  }
  
  RecordDecl*
  Sema::CreateCapturedStmtRecordDecl(CapturedDecl *&CD, SourceLocation Loc,
                                     unsigned NumParams) {
    DeclContext *DC = CurContext;
    while (!(DC->isFunctionOrMethod() || DC->isRecord() || DC->isFileContext()))
      DC = DC->getParent();
  
    RecordDecl *RD = nullptr;
    if (getLangOpts().CPlusPlus)
      RD = CXXRecordDecl::Create(Context, TTK_Struct, DC, Loc, Loc,
                                 /*Id=*/nullptr);
    else
      RD = RecordDecl::Create(Context, TTK_Struct, DC, Loc, Loc, /*Id=*/nullptr);
  
    RD->setCapturedRecord();
    DC->addDecl(RD);
    RD->setImplicit();
    RD->startDefinition();
  
    assert(NumParams > 0 && "CapturedStmt requires context parameter");
    CD = CapturedDecl::Create(Context, CurContext, NumParams);
    DC->addDecl(CD);
    return RD;
  }
  
  static bool
  buildCapturedStmtCaptureList(Sema &S, CapturedRegionScopeInfo *RSI,
                               SmallVectorImpl<CapturedStmt::Capture> &Captures,
                               SmallVectorImpl<Expr *> &CaptureInits) {
    for (const sema::Capture &Cap : RSI->Captures) {
      if (Cap.isInvalid())
        continue;
  
      // Form the initializer for the capture.
      ExprResult Init = S.BuildCaptureInit(Cap, Cap.getLocation(),
                                           RSI->CapRegionKind == CR_OpenMP);
  
      // FIXME: Bail out now if the capture is not used and the initializer has
      // no side-effects.
  
      // Create a field for this capture.
      FieldDecl *Field = S.BuildCaptureField(RSI->TheRecordDecl, Cap);
  
      // Add the capture to our list of captures.
      if (Cap.isThisCapture()) {
        Captures.push_back(CapturedStmt::Capture(Cap.getLocation(),
                                                 CapturedStmt::VCK_This));
      } else if (Cap.isVLATypeCapture()) {
        Captures.push_back(
            CapturedStmt::Capture(Cap.getLocation(), CapturedStmt::VCK_VLAType));
      } else {
        assert(Cap.isVariableCapture() && "unknown kind of capture");
  
        if (S.getLangOpts().OpenMP && RSI->CapRegionKind == CR_OpenMP)
          S.setOpenMPCaptureKind(Field, Cap.getVariable(), RSI->OpenMPLevel);
  
        Captures.push_back(CapturedStmt::Capture(Cap.getLocation(),
                                                 Cap.isReferenceCapture()
                                                     ? CapturedStmt::VCK_ByRef
                                                     : CapturedStmt::VCK_ByCopy,
                                                 Cap.getVariable()));
      }
      CaptureInits.push_back(Init.get());
    }
    return false;
  }
  
  void Sema::ActOnCapturedRegionStart(SourceLocation Loc, Scope *CurScope,
                                      CapturedRegionKind Kind,
                                      unsigned NumParams) {
    CapturedDecl *CD = nullptr;
    RecordDecl *RD = CreateCapturedStmtRecordDecl(CD, Loc, NumParams);
  
    // Build the context parameter
    DeclContext *DC = CapturedDecl::castToDeclContext(CD);
    IdentifierInfo *ParamName = &Context.Idents.get("__context");
    QualType ParamType = Context.getPointerType(Context.getTagDeclType(RD));
    auto *Param =
        ImplicitParamDecl::Create(Context, DC, Loc, ParamName, ParamType,
                                  ImplicitParamDecl::CapturedContext);
    DC->addDecl(Param);
  
    CD->setContextParam(0, Param);
  
    // Enter the capturing scope for this captured region.
    PushCapturedRegionScope(CurScope, CD, RD, Kind);
  
    if (CurScope)
      PushDeclContext(CurScope, CD);
    else
      CurContext = CD;
  
    PushExpressionEvaluationContext(
        ExpressionEvaluationContext::PotentiallyEvaluated);
  }
  
  void Sema::ActOnCapturedRegionStart(SourceLocation Loc, Scope *CurScope,
                                      CapturedRegionKind Kind,
                                      ArrayRef<CapturedParamNameType> Params,
                                      unsigned OpenMPCaptureLevel) {
    CapturedDecl *CD = nullptr;
    RecordDecl *RD = CreateCapturedStmtRecordDecl(CD, Loc, Params.size());
  
    // Build the context parameter
    DeclContext *DC = CapturedDecl::castToDeclContext(CD);
    bool ContextIsFound = false;
    unsigned ParamNum = 0;
    for (ArrayRef<CapturedParamNameType>::iterator I = Params.begin(),
                                                   E = Params.end();
         I != E; ++I, ++ParamNum) {
      if (I->second.isNull()) {
        assert(!ContextIsFound &&
               "null type has been found already for '__context' parameter");
        IdentifierInfo *ParamName = &Context.Idents.get("__context");
        QualType ParamType = Context.getPointerType(Context.getTagDeclType(RD))
                                 .withConst()
                                 .withRestrict();
        auto *Param =
            ImplicitParamDecl::Create(Context, DC, Loc, ParamName, ParamType,
                                      ImplicitParamDecl::CapturedContext);
        DC->addDecl(Param);
        CD->setContextParam(ParamNum, Param);
        ContextIsFound = true;
      } else {
        IdentifierInfo *ParamName = &Context.Idents.get(I->first);
        auto *Param =
            ImplicitParamDecl::Create(Context, DC, Loc, ParamName, I->second,
                                      ImplicitParamDecl::CapturedContext);
        DC->addDecl(Param);
        CD->setParam(ParamNum, Param);
      }
    }
    assert(ContextIsFound && "no null type for '__context' parameter");
    if (!ContextIsFound) {
      // Add __context implicitly if it is not specified.
      IdentifierInfo *ParamName = &Context.Idents.get("__context");
      QualType ParamType = Context.getPointerType(Context.getTagDeclType(RD));
      auto *Param =
          ImplicitParamDecl::Create(Context, DC, Loc, ParamName, ParamType,
                                    ImplicitParamDecl::CapturedContext);
      DC->addDecl(Param);
      CD->setContextParam(ParamNum, Param);
    }
    // Enter the capturing scope for this captured region.
    PushCapturedRegionScope(CurScope, CD, RD, Kind, OpenMPCaptureLevel);
  
    if (CurScope)
      PushDeclContext(CurScope, CD);
    else
      CurContext = CD;
  
    PushExpressionEvaluationContext(
        ExpressionEvaluationContext::PotentiallyEvaluated);
  }
  
  void Sema::ActOnCapturedRegionError() {
    DiscardCleanupsInEvaluationContext();
    PopExpressionEvaluationContext();
    PopDeclContext();
    PoppedFunctionScopePtr ScopeRAII = PopFunctionScopeInfo();
    CapturedRegionScopeInfo *RSI = cast<CapturedRegionScopeInfo>(ScopeRAII.get());
  
    RecordDecl *Record = RSI->TheRecordDecl;
    Record->setInvalidDecl();
  
    SmallVector<Decl*, 4> Fields(Record->fields());
    ActOnFields(/*Scope=*/nullptr, Record->getLocation(), Record, Fields,
                SourceLocation(), SourceLocation(), ParsedAttributesView());
  }
  
  StmtResult Sema::ActOnCapturedRegionEnd(Stmt *S) {
    // Leave the captured scope before we start creating captures in the
    // enclosing scope.
    DiscardCleanupsInEvaluationContext();
    PopExpressionEvaluationContext();
    PopDeclContext();
    PoppedFunctionScopePtr ScopeRAII = PopFunctionScopeInfo();
    CapturedRegionScopeInfo *RSI = cast<CapturedRegionScopeInfo>(ScopeRAII.get());
  
    SmallVector<CapturedStmt::Capture, 4> Captures;
    SmallVector<Expr *, 4> CaptureInits;
    if (buildCapturedStmtCaptureList(*this, RSI, Captures, CaptureInits))
      return StmtError();
  
    CapturedDecl *CD = RSI->TheCapturedDecl;
    RecordDecl *RD = RSI->TheRecordDecl;
  
    CapturedStmt *Res = CapturedStmt::Create(
        getASTContext(), S, static_cast<CapturedRegionKind>(RSI->CapRegionKind),
        Captures, CaptureInits, CD, RD);
  
    CD->setBody(Res->getCapturedStmt());
    RD->completeDefinition();
  
    return Res;
  }
  