text: //===--- SemaDecl.cpp - Semantic Analysis for Declarations ----------------===//
  //
  // 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 declarations.
  //
  //===----------------------------------------------------------------------===//
  
  #include "TypeLocBuilder.h"
  #include "clang/AST/ASTConsumer.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/ASTLambda.h"
  #include "clang/AST/CXXInheritance.h"
  #include "clang/AST/CharUnits.h"
  #include "clang/AST/CommentDiagnostic.h"
  #include "clang/AST/DeclCXX.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/DeclTemplate.h"
  #include "clang/AST/EvaluatedExprVisitor.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/AST/StmtCXX.h"
  #include "clang/Basic/Builtins.h"
  #include "clang/Basic/PartialDiagnostic.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/Lex/HeaderSearch.h" // TODO: Sema shouldn't depend on Lex
  #include "clang/Lex/Lexer.h" // TODO: Extract static functions to fix layering.
  #include "clang/Lex/ModuleLoader.h" // TODO: Sema shouldn't depend on Lex
  #include "clang/Lex/Preprocessor.h" // Included for isCodeCompletionEnabled()
  #include "clang/Sema/CXXFieldCollector.h"
  #include "clang/Sema/DeclSpec.h"
  #include "clang/Sema/DelayedDiagnostic.h"
  #include "clang/Sema/Initialization.h"
  #include "clang/Sema/Lookup.h"
  #include "clang/Sema/ParsedTemplate.h"
  #include "clang/Sema/Scope.h"
  #include "clang/Sema/ScopeInfo.h"
  #include "clang/Sema/SemaInternal.h"
  #include "clang/Sema/Template.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/Triple.h"
  #include <algorithm>
  #include <cstring>
  #include <functional>
  
  using namespace clang;
  using namespace sema;
  
  Sema::DeclGroupPtrTy Sema::ConvertDeclToDeclGroup(Decl *Ptr, Decl *OwnedType) {
    if (OwnedType) {
      Decl *Group[2] = { OwnedType, Ptr };
      return DeclGroupPtrTy::make(DeclGroupRef::Create(Context, Group, 2));
    }
  
    return DeclGroupPtrTy::make(DeclGroupRef(Ptr));
  }
  
  namespace {
  
  class TypeNameValidatorCCC final : public CorrectionCandidateCallback {
   public:
     TypeNameValidatorCCC(bool AllowInvalid, bool WantClass = false,
                          bool AllowTemplates = false,
                          bool AllowNonTemplates = true)
         : AllowInvalidDecl(AllowInvalid), WantClassName(WantClass),
           AllowTemplates(AllowTemplates), AllowNonTemplates(AllowNonTemplates) {
       WantExpressionKeywords = false;
       WantCXXNamedCasts = false;
       WantRemainingKeywords = false;
    }
  
    bool ValidateCandidate(const TypoCorrection &candidate) override {
      if (NamedDecl *ND = candidate.getCorrectionDecl()) {
        if (!AllowInvalidDecl && ND->isInvalidDecl())
          return false;
  
        if (getAsTypeTemplateDecl(ND))
          return AllowTemplates;
  
        bool IsType = isa<TypeDecl>(ND) || isa<ObjCInterfaceDecl>(ND);
        if (!IsType)
          return false;
  
        if (AllowNonTemplates)
          return true;
  
        // An injected-class-name of a class template (specialization) is valid
        // as a template or as a non-template.
        if (AllowTemplates) {
          auto *RD = dyn_cast<CXXRecordDecl>(ND);
          if (!RD || !RD->isInjectedClassName())
            return false;
          RD = cast<CXXRecordDecl>(RD->getDeclContext());
          return RD->getDescribedClassTemplate() ||
                 isa<ClassTemplateSpecializationDecl>(RD);
        }
  
        return false;
      }
  
      return !WantClassName && candidate.isKeyword();
    }
  
    std::unique_ptr<CorrectionCandidateCallback> clone() override {
      return llvm::make_unique<TypeNameValidatorCCC>(*this);
    }
  
   private:
    bool AllowInvalidDecl;
    bool WantClassName;
    bool AllowTemplates;
    bool AllowNonTemplates;
  };
  
  } // end anonymous namespace
  
  /// Determine whether the token kind starts a simple-type-specifier.
  bool Sema::isSimpleTypeSpecifier(tok::TokenKind Kind) const {
    switch (Kind) {
    // FIXME: Take into account the current language when deciding whether a
    // token kind is a valid type specifier
    case tok::kw_short:
    case tok::kw_long:
    case tok::kw___int64:
    case tok::kw___int128:
    case tok::kw_signed:
    case tok::kw_unsigned:
    case tok::kw_void:
    case tok::kw_char:
    case tok::kw_int:
    case tok::kw_half:
    case tok::kw_float:
    case tok::kw_double:
    case tok::kw__Float16:
    case tok::kw___float128:
    case tok::kw_wchar_t:
    case tok::kw_bool:
    case tok::kw___underlying_type:
    case tok::kw___auto_type:
      return true;
  
    case tok::annot_typename:
    case tok::kw_char16_t:
    case tok::kw_char32_t:
    case tok::kw_typeof:
    case tok::annot_decltype:
    case tok::kw_decltype:
      return getLangOpts().CPlusPlus;
  
    case tok::kw_char8_t:
      return getLangOpts().Char8;
  
    default:
      break;
    }
  
    return false;
  }
  
  namespace {
  enum class UnqualifiedTypeNameLookupResult {
    NotFound,
    FoundNonType,
    FoundType
  };
  } // end anonymous namespace
  
  /// Tries to perform unqualified lookup of the type decls in bases for
  /// dependent class.
  /// \return \a NotFound if no any decls is found, \a FoundNotType if found not a
  /// type decl, \a FoundType if only type decls are found.
  static UnqualifiedTypeNameLookupResult
  lookupUnqualifiedTypeNameInBase(Sema &S, const IdentifierInfo &II,
                                  SourceLocation NameLoc,
                                  const CXXRecordDecl *RD) {
    if (!RD->hasDefinition())
      return UnqualifiedTypeNameLookupResult::NotFound;
    // Look for type decls in base classes.
    UnqualifiedTypeNameLookupResult FoundTypeDecl =
        UnqualifiedTypeNameLookupResult::NotFound;
    for (const auto &Base : RD->bases()) {
      const CXXRecordDecl *BaseRD = nullptr;
      if (auto *BaseTT = Base.getType()->getAs<TagType>())
        BaseRD = BaseTT->getAsCXXRecordDecl();
      else if (auto *TST = Base.getType()->getAs<TemplateSpecializationType>()) {
        // Look for type decls in dependent base classes that have known primary
        // templates.
        if (!TST || !TST->isDependentType())
          continue;
        auto *TD = TST->getTemplateName().getAsTemplateDecl();
        if (!TD)
          continue;
        if (auto *BasePrimaryTemplate =
            dyn_cast_or_null<CXXRecordDecl>(TD->getTemplatedDecl())) {
          if (BasePrimaryTemplate->getCanonicalDecl() != RD->getCanonicalDecl())
            BaseRD = BasePrimaryTemplate;
          else if (auto *CTD = dyn_cast<ClassTemplateDecl>(TD)) {
            if (const ClassTemplatePartialSpecializationDecl *PS =
                    CTD->findPartialSpecialization(Base.getType()))
              if (PS->getCanonicalDecl() != RD->getCanonicalDecl())
                BaseRD = PS;
          }
        }
      }
      if (BaseRD) {
        for (NamedDecl *ND : BaseRD->lookup(&II)) {
          if (!isa<TypeDecl>(ND))
            return UnqualifiedTypeNameLookupResult::FoundNonType;
          FoundTypeDecl = UnqualifiedTypeNameLookupResult::FoundType;
        }
        if (FoundTypeDecl == UnqualifiedTypeNameLookupResult::NotFound) {
          switch (lookupUnqualifiedTypeNameInBase(S, II, NameLoc, BaseRD)) {
          case UnqualifiedTypeNameLookupResult::FoundNonType:
            return UnqualifiedTypeNameLookupResult::FoundNonType;
          case UnqualifiedTypeNameLookupResult::FoundType:
            FoundTypeDecl = UnqualifiedTypeNameLookupResult::FoundType;
            break;
          case UnqualifiedTypeNameLookupResult::NotFound:
            break;
          }
        }
      }
    }
  
    return FoundTypeDecl;
  }
  
  static ParsedType recoverFromTypeInKnownDependentBase(Sema &S,
                                                        const IdentifierInfo &II,
                                                        SourceLocation NameLoc) {
    // Lookup in the parent class template context, if any.
    const CXXRecordDecl *RD = nullptr;
    UnqualifiedTypeNameLookupResult FoundTypeDecl =
        UnqualifiedTypeNameLookupResult::NotFound;
    for (DeclContext *DC = S.CurContext;
         DC && FoundTypeDecl == UnqualifiedTypeNameLookupResult::NotFound;
         DC = DC->getParent()) {
      // Look for type decls in dependent base classes that have known primary
      // templates.
      RD = dyn_cast<CXXRecordDecl>(DC);
      if (RD && RD->getDescribedClassTemplate())
        FoundTypeDecl = lookupUnqualifiedTypeNameInBase(S, II, NameLoc, RD);
    }
    if (FoundTypeDecl != UnqualifiedTypeNameLookupResult::FoundType)
      return nullptr;
  
    // We found some types in dependent base classes.  Recover as if the user
    // wrote 'typename MyClass::II' instead of 'II'.  We'll fully resolve the
    // lookup during template instantiation.
    S.Diag(NameLoc, diag::ext_found_via_dependent_bases_lookup) << &II;
  
    ASTContext &Context = S.Context;
    auto *NNS = NestedNameSpecifier::Create(Context, nullptr, false,
                                            cast<Type>(Context.getRecordType(RD)));
    QualType T = Context.getDependentNameType(ETK_Typename, NNS, &II);
  
    CXXScopeSpec SS;
    SS.MakeTrivial(Context, NNS, SourceRange(NameLoc));
  
    TypeLocBuilder Builder;
    DependentNameTypeLoc DepTL = Builder.push<DependentNameTypeLoc>(T);
    DepTL.setNameLoc(NameLoc);
    DepTL.setElaboratedKeywordLoc(SourceLocation());
    DepTL.setQualifierLoc(SS.getWithLocInContext(Context));
    return S.CreateParsedType(T, Builder.getTypeSourceInfo(Context, T));
  }
  
  /// If the identifier refers to a type name within this scope,
  /// return the declaration of that type.
  ///
  /// This routine performs ordinary name lookup of the identifier II
  /// within the given scope, with optional C++ scope specifier SS, to
  /// determine whether the name refers to a type. If so, returns an
  /// opaque pointer (actually a QualType) corresponding to that
  /// type. Otherwise, returns NULL.
  ParsedType Sema::getTypeName(const IdentifierInfo &II, SourceLocation NameLoc,
                               Scope *S, CXXScopeSpec *SS,
                               bool isClassName, bool HasTrailingDot,
                               ParsedType ObjectTypePtr,
                               bool IsCtorOrDtorName,
                               bool WantNontrivialTypeSourceInfo,
                               bool IsClassTemplateDeductionContext,
                               IdentifierInfo **CorrectedII) {
    // FIXME: Consider allowing this outside C++1z mode as an extension.
    bool AllowDeducedTemplate = IsClassTemplateDeductionContext &&
                                getLangOpts().CPlusPlus17 && !IsCtorOrDtorName &&
                                !isClassName && !HasTrailingDot;
  
    // Determine where we will perform name lookup.
    DeclContext *LookupCtx = nullptr;
    if (ObjectTypePtr) {
      QualType ObjectType = ObjectTypePtr.get();
      if (ObjectType->isRecordType())
        LookupCtx = computeDeclContext(ObjectType);
    } else if (SS && SS->isNotEmpty()) {
      LookupCtx = computeDeclContext(*SS, false);
  
      if (!LookupCtx) {
        if (isDependentScopeSpecifier(*SS)) {
          // C++ [temp.res]p3:
          //   A qualified-id that refers to a type and in which the
          //   nested-name-specifier depends on a template-parameter (14.6.2)
          //   shall be prefixed by the keyword typename to indicate that the
          //   qualified-id denotes a type, forming an
          //   elaborated-type-specifier (7.1.5.3).
          //
          // We therefore do not perform any name lookup if the result would
          // refer to a member of an unknown specialization.
          if (!isClassName && !IsCtorOrDtorName)
            return nullptr;
  
          // We know from the grammar that this name refers to a type,
          // so build a dependent node to describe the type.
          if (WantNontrivialTypeSourceInfo)
            return ActOnTypenameType(S, SourceLocation(), *SS, II, NameLoc).get();
  
          NestedNameSpecifierLoc QualifierLoc = SS->getWithLocInContext(Context);
          QualType T = CheckTypenameType(ETK_None, SourceLocation(), QualifierLoc,
                                         II, NameLoc);
          return ParsedType::make(T);
        }
  
        return nullptr;
      }
  
      if (!LookupCtx->isDependentContext() &&
          RequireCompleteDeclContext(*SS, LookupCtx))
        return nullptr;
    }
  
    // FIXME: LookupNestedNameSpecifierName isn't the right kind of
    // lookup for class-names.
    LookupNameKind Kind = isClassName ? LookupNestedNameSpecifierName :
                                        LookupOrdinaryName;
    LookupResult Result(*this, &II, NameLoc, Kind);
    if (LookupCtx) {
      // Perform "qualified" name lookup into the declaration context we
      // computed, which is either the type of the base of a member access
      // expression or the declaration context associated with a prior
      // nested-name-specifier.
      LookupQualifiedName(Result, LookupCtx);
  
      if (ObjectTypePtr && Result.empty()) {
        // C++ [basic.lookup.classref]p3:
        //   If the unqualified-id is ~type-name, the type-name is looked up
        //   in the context of the entire postfix-expression. If the type T of
        //   the object expression is of a class type C, the type-name is also
        //   looked up in the scope of class C. At least one of the lookups shall
        //   find a name that refers to (possibly cv-qualified) T.
        LookupName(Result, S);
      }
    } else {
      // Perform unqualified name lookup.
      LookupName(Result, S);
  
      // For unqualified lookup in a class template in MSVC mode, look into
      // dependent base classes where the primary class template is known.
      if (Result.empty() && getLangOpts().MSVCCompat && (!SS || SS->isEmpty())) {
        if (ParsedType TypeInBase =
                recoverFromTypeInKnownDependentBase(*this, II, NameLoc))
          return TypeInBase;
      }
    }
  
    NamedDecl *IIDecl = nullptr;
    switch (Result.getResultKind()) {
    case LookupResult::NotFound:
    case LookupResult::NotFoundInCurrentInstantiation:
      if (CorrectedII) {
        TypeNameValidatorCCC CCC(/*AllowInvalid=*/true, isClassName,
                                 AllowDeducedTemplate);
        TypoCorrection Correction = CorrectTypo(Result.getLookupNameInfo(), Kind,
                                                S, SS, CCC, CTK_ErrorRecovery);
        IdentifierInfo *NewII = Correction.getCorrectionAsIdentifierInfo();
        TemplateTy Template;
        bool MemberOfUnknownSpecialization;
        UnqualifiedId TemplateName;
        TemplateName.setIdentifier(NewII, NameLoc);
        NestedNameSpecifier *NNS = Correction.getCorrectionSpecifier();
        CXXScopeSpec NewSS, *NewSSPtr = SS;
        if (SS && NNS) {
          NewSS.MakeTrivial(Context, NNS, SourceRange(NameLoc));
          NewSSPtr = &NewSS;
        }
        if (Correction && (NNS || NewII != &II) &&
            // Ignore a correction to a template type as the to-be-corrected
            // identifier is not a template (typo correction for template names
            // is handled elsewhere).
            !(getLangOpts().CPlusPlus && NewSSPtr &&
              isTemplateName(S, *NewSSPtr, false, TemplateName, nullptr, false,
                             Template, MemberOfUnknownSpecialization))) {
          ParsedType Ty = getTypeName(*NewII, NameLoc, S, NewSSPtr,
                                      isClassName, HasTrailingDot, ObjectTypePtr,
                                      IsCtorOrDtorName,
                                      WantNontrivialTypeSourceInfo,
                                      IsClassTemplateDeductionContext);
          if (Ty) {
            diagnoseTypo(Correction,
                         PDiag(diag::err_unknown_type_or_class_name_suggest)
                           << Result.getLookupName() << isClassName);
            if (SS && NNS)
              SS->MakeTrivial(Context, NNS, SourceRange(NameLoc));
            *CorrectedII = NewII;
            return Ty;
          }
        }
      }
      // If typo correction failed or was not performed, fall through
      LLVM_FALLTHROUGH;
    case LookupResult::FoundOverloaded:
    case LookupResult::FoundUnresolvedValue:
      Result.suppressDiagnostics();
      return nullptr;
  
    case LookupResult::Ambiguous:
      // Recover from type-hiding ambiguities by hiding the type.  We'll
      // do the lookup again when looking for an object, and we can
      // diagnose the error then.  If we don't do this, then the error
      // about hiding the type will be immediately followed by an error
      // that only makes sense if the identifier was treated like a type.
      if (Result.getAmbiguityKind() == LookupResult::AmbiguousTagHiding) {
        Result.suppressDiagnostics();
        return nullptr;
      }
  
      // Look to see if we have a type anywhere in the list of results.
      for (LookupResult::iterator Res = Result.begin(), ResEnd = Result.end();
           Res != ResEnd; ++Res) {
        if (isa<TypeDecl>(*Res) || isa<ObjCInterfaceDecl>(*Res) ||
            (AllowDeducedTemplate && getAsTypeTemplateDecl(*Res))) {
          if (!IIDecl ||
              (*Res)->getLocation().getRawEncoding() <
                IIDecl->getLocation().getRawEncoding())
            IIDecl = *Res;
        }
      }
  
      if (!IIDecl) {
        // None of the entities we found is a type, so there is no way
        // to even assume that the result is a type. In this case, don't
        // complain about the ambiguity. The parser will either try to
        // perform this lookup again (e.g., as an object name), which
        // will produce the ambiguity, or will complain that it expected
        // a type name.
        Result.suppressDiagnostics();
        return nullptr;
      }
  
      // We found a type within the ambiguous lookup; diagnose the
      // ambiguity and then return that type. This might be the right
      // answer, or it might not be, but it suppresses any attempt to
      // perform the name lookup again.
      break;
  
    case LookupResult::Found:
      IIDecl = Result.getFoundDecl();
      break;
    }
  
    assert(IIDecl && "Didn't find decl");
  
    QualType T;
    if (TypeDecl *TD = dyn_cast<TypeDecl>(IIDecl)) {
      // C++ [class.qual]p2: A lookup that would find the injected-class-name
      // instead names the constructors of the class, except when naming a class.
      // This is ill-formed when we're not actually forming a ctor or dtor name.
      auto *LookupRD = dyn_cast_or_null<CXXRecordDecl>(LookupCtx);
      auto *FoundRD = dyn_cast<CXXRecordDecl>(TD);
      if (!isClassName && !IsCtorOrDtorName && LookupRD && FoundRD &&
          FoundRD->isInjectedClassName() &&
          declaresSameEntity(LookupRD, cast<Decl>(FoundRD->getParent())))
        Diag(NameLoc, diag::err_out_of_line_qualified_id_type_names_constructor)
            << &II << /*Type*/1;
  
      DiagnoseUseOfDecl(IIDecl, NameLoc);
  
      T = Context.getTypeDeclType(TD);
      MarkAnyDeclReferenced(TD->getLocation(), TD, /*OdrUse=*/false);
    } else if (ObjCInterfaceDecl *IDecl = dyn_cast<ObjCInterfaceDecl>(IIDecl)) {
      (void)DiagnoseUseOfDecl(IDecl, NameLoc);
      if (!HasTrailingDot)
        T = Context.getObjCInterfaceType(IDecl);
    } else if (AllowDeducedTemplate) {
      if (auto *TD = getAsTypeTemplateDecl(IIDecl))
        T = Context.getDeducedTemplateSpecializationType(TemplateName(TD),
                                                         QualType(), false);
    }
  
    if (T.isNull()) {
      // If it's not plausibly a type, suppress diagnostics.
      Result.suppressDiagnostics();
      return nullptr;
    }
  
    // NOTE: avoid constructing an ElaboratedType(Loc) if this is a
    // constructor or destructor name (in such a case, the scope specifier
    // will be attached to the enclosing Expr or Decl node).
    if (SS && SS->isNotEmpty() && !IsCtorOrDtorName &&
        !isa<ObjCInterfaceDecl>(IIDecl)) {
      if (WantNontrivialTypeSourceInfo) {
        // Construct a type with type-source information.
        TypeLocBuilder Builder;
        Builder.pushTypeSpec(T).setNameLoc(NameLoc);
  
        T = getElaboratedType(ETK_None, *SS, T);
        ElaboratedTypeLoc ElabTL = Builder.push<ElaboratedTypeLoc>(T);
        ElabTL.setElaboratedKeywordLoc(SourceLocation());
        ElabTL.setQualifierLoc(SS->getWithLocInContext(Context));
        return CreateParsedType(T, Builder.getTypeSourceInfo(Context, T));
      } else {
        T = getElaboratedType(ETK_None, *SS, T);
      }
    }
  
    return ParsedType::make(T);
  }
  
  // Builds a fake NNS for the given decl context.
  static NestedNameSpecifier *
  synthesizeCurrentNestedNameSpecifier(ASTContext &Context, DeclContext *DC) {
    for (;; DC = DC->getLookupParent()) {
      DC = DC->getPrimaryContext();
      auto *ND = dyn_cast<NamespaceDecl>(DC);
      if (ND && !ND->isInline() && !ND->isAnonymousNamespace())
        return NestedNameSpecifier::Create(Context, nullptr, ND);
      else if (auto *RD = dyn_cast<CXXRecordDecl>(DC))
        return NestedNameSpecifier::Create(Context, nullptr, RD->isTemplateDecl(),
                                           RD->getTypeForDecl());
      else if (isa<TranslationUnitDecl>(DC))
        return NestedNameSpecifier::GlobalSpecifier(Context);
    }
    llvm_unreachable("something isn't in TU scope?");
  }
  
  /// Find the parent class with dependent bases of the innermost enclosing method
  /// context. Do not look for enclosing CXXRecordDecls directly, or we will end
  /// up allowing unqualified dependent type names at class-level, which MSVC
  /// correctly rejects.
  static const CXXRecordDecl *
  findRecordWithDependentBasesOfEnclosingMethod(const DeclContext *DC) {
    for (; DC && DC->isDependentContext(); DC = DC->getLookupParent()) {
      DC = DC->getPrimaryContext();
      if (const auto *MD = dyn_cast<CXXMethodDecl>(DC))
        if (MD->getParent()->hasAnyDependentBases())
          return MD->getParent();
    }
    return nullptr;
  }
  
  ParsedType Sema::ActOnMSVCUnknownTypeName(const IdentifierInfo &II,
                                            SourceLocation NameLoc,
                                            bool IsTemplateTypeArg) {
    assert(getLangOpts().MSVCCompat && "shouldn't be called in non-MSVC mode");
  
    NestedNameSpecifier *NNS = nullptr;
    if (IsTemplateTypeArg && getCurScope()->isTemplateParamScope()) {
      // If we weren't able to parse a default template argument, delay lookup
      // until instantiation time by making a non-dependent DependentTypeName. We
      // pretend we saw a NestedNameSpecifier referring to the current scope, and
      // lookup is retried.
      // FIXME: This hurts our diagnostic quality, since we get errors like "no
      // type named 'Foo' in 'current_namespace'" when the user didn't write any
      // name specifiers.
      NNS = synthesizeCurrentNestedNameSpecifier(Context, CurContext);
      Diag(NameLoc, diag::ext_ms_delayed_template_argument) << &II;
    } else if (const CXXRecordDecl *RD =
                   findRecordWithDependentBasesOfEnclosingMethod(CurContext)) {
      // Build a DependentNameType that will perform lookup into RD at
      // instantiation time.
      NNS = NestedNameSpecifier::Create(Context, nullptr, RD->isTemplateDecl(),
                                        RD->getTypeForDecl());
  
      // Diagnose that this identifier was undeclared, and retry the lookup during
      // template instantiation.
      Diag(NameLoc, diag::ext_undeclared_unqual_id_with_dependent_base) << &II
                                                                        << RD;
    } else {
      // This is not a situation that we should recover from.
      return ParsedType();
    }
  
    QualType T = Context.getDependentNameType(ETK_None, NNS, &II);
  
    // Build type location information.  We synthesized the qualifier, so we have
    // to build a fake NestedNameSpecifierLoc.
    NestedNameSpecifierLocBuilder NNSLocBuilder;
    NNSLocBuilder.MakeTrivial(Context, NNS, SourceRange(NameLoc));
    NestedNameSpecifierLoc QualifierLoc = NNSLocBuilder.getWithLocInContext(Context);
  
    TypeLocBuilder Builder;
    DependentNameTypeLoc DepTL = Builder.push<DependentNameTypeLoc>(T);
    DepTL.setNameLoc(NameLoc);
    DepTL.setElaboratedKeywordLoc(SourceLocation());
    DepTL.setQualifierLoc(QualifierLoc);
    return CreateParsedType(T, Builder.getTypeSourceInfo(Context, T));
  }
  
  /// isTagName() - This method is called *for error recovery purposes only*
  /// to determine if the specified name is a valid tag name ("struct foo").  If
  /// so, this returns the TST for the tag corresponding to it (TST_enum,
  /// TST_union, TST_struct, TST_interface, TST_class).  This is used to diagnose
  /// cases in C where the user forgot to specify the tag.
  DeclSpec::TST Sema::isTagName(IdentifierInfo &II, Scope *S) {
    // Do a tag name lookup in this scope.
    LookupResult R(*this, &II, SourceLocation(), LookupTagName);
    LookupName(R, S, false);
    R.suppressDiagnostics();
    if (R.getResultKind() == LookupResult::Found)
      if (const TagDecl *TD = R.getAsSingle<TagDecl>()) {
        switch (TD->getTagKind()) {
        case TTK_Struct: return DeclSpec::TST_struct;
        case TTK_Interface: return DeclSpec::TST_interface;
        case TTK_Union:  return DeclSpec::TST_union;
        case TTK_Class:  return DeclSpec::TST_class;
        case TTK_Enum:   return DeclSpec::TST_enum;
        }
      }
  
    return DeclSpec::TST_unspecified;
  }
  
  /// isMicrosoftMissingTypename - In Microsoft mode, within class scope,
  /// if a CXXScopeSpec's type is equal to the type of one of the base classes
  /// then downgrade the missing typename error to a warning.
  /// This is needed for MSVC compatibility; Example:
  /// @code
  /// template<class T> class A {
  /// public:
  ///   typedef int TYPE;
  /// };
  /// template<class T> class B : public A<T> {
  /// public:
  ///   A<T>::TYPE a; // no typename required because A<T> is a base class.
  /// };
  /// @endcode
  bool Sema::isMicrosoftMissingTypename(const CXXScopeSpec *SS, Scope *S) {
    if (CurContext->isRecord()) {
      if (SS->getScopeRep()->getKind() == NestedNameSpecifier::Super)
        return true;
  
      const Type *Ty = SS->getScopeRep()->getAsType();
  
      CXXRecordDecl *RD = cast<CXXRecordDecl>(CurContext);
      for (const auto &Base : RD->bases())
        if (Ty && Context.hasSameUnqualifiedType(QualType(Ty, 1), Base.getType()))
          return true;
      return S->isFunctionPrototypeScope();
    }
    return CurContext->isFunctionOrMethod() || S->isFunctionPrototypeScope();
  }
  
  void Sema::DiagnoseUnknownTypeName(IdentifierInfo *&II,
                                     SourceLocation IILoc,
                                     Scope *S,
                                     CXXScopeSpec *SS,
                                     ParsedType &SuggestedType,
                                     bool IsTemplateName) {
    // Don't report typename errors for editor placeholders.
    if (II->isEditorPlaceholder())
      return;
    // We don't have anything to suggest (yet).
    SuggestedType = nullptr;
  
    // There may have been a typo in the name of the type. Look up typo
    // results, in case we have something that we can suggest.
    TypeNameValidatorCCC CCC(/*AllowInvalid=*/false, /*WantClass=*/false,
                             /*AllowTemplates=*/IsTemplateName,
                             /*AllowNonTemplates=*/!IsTemplateName);
    if (TypoCorrection Corrected =
            CorrectTypo(DeclarationNameInfo(II, IILoc), LookupOrdinaryName, S, SS,
                        CCC, CTK_ErrorRecovery)) {
      // FIXME: Support error recovery for the template-name case.
      bool CanRecover = !IsTemplateName;
      if (Corrected.isKeyword()) {
        // We corrected to a keyword.
        diagnoseTypo(Corrected,
                     PDiag(IsTemplateName ? diag::err_no_template_suggest
                                          : diag::err_unknown_typename_suggest)
                         << II);
        II = Corrected.getCorrectionAsIdentifierInfo();
      } else {
        // We found a similarly-named type or interface; suggest that.
        if (!SS || !SS->isSet()) {
          diagnoseTypo(Corrected,
                       PDiag(IsTemplateName ? diag::err_no_template_suggest
                                            : diag::err_unknown_typename_suggest)
                           << II, CanRecover);
        } else if (DeclContext *DC = computeDeclContext(*SS, false)) {
          std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
          bool DroppedSpecifier = Corrected.WillReplaceSpecifier() &&
                                  II->getName().equals(CorrectedStr);
          diagnoseTypo(Corrected,
                       PDiag(IsTemplateName
                                 ? diag::err_no_member_template_suggest
                                 : diag::err_unknown_nested_typename_suggest)
                           << II << DC << DroppedSpecifier << SS->getRange(),
                       CanRecover);
        } else {
          llvm_unreachable("could not have corrected a typo here");
        }
  
        if (!CanRecover)
          return;
  
        CXXScopeSpec tmpSS;
        if (Corrected.getCorrectionSpecifier())
          tmpSS.MakeTrivial(Context, Corrected.getCorrectionSpecifier(),
                            SourceRange(IILoc));
        // FIXME: Support class template argument deduction here.
        SuggestedType =
            getTypeName(*Corrected.getCorrectionAsIdentifierInfo(), IILoc, S,
                        tmpSS.isSet() ? &tmpSS : SS, false, false, nullptr,
                        /*IsCtorOrDtorName=*/false,
                        /*NonTrivialTypeSourceInfo=*/true);
      }
      return;
    }
  
    if (getLangOpts().CPlusPlus && !IsTemplateName) {
      // See if II is a class template that the user forgot to pass arguments to.
      UnqualifiedId Name;
      Name.setIdentifier(II, IILoc);
      CXXScopeSpec EmptySS;
      TemplateTy TemplateResult;
      bool MemberOfUnknownSpecialization;
      if (isTemplateName(S, SS ? *SS : EmptySS, /*hasTemplateKeyword=*/false,
                         Name, nullptr, true, TemplateResult,
                         MemberOfUnknownSpecialization) == TNK_Type_template) {
        diagnoseMissingTemplateArguments(TemplateResult.get(), IILoc);
        return;
      }
    }
  
    // FIXME: Should we move the logic that tries to recover from a missing tag
    // (struct, union, enum) from Parser::ParseImplicitInt here, instead?
  
    if (!SS || (!SS->isSet() && !SS->isInvalid()))
      Diag(IILoc, IsTemplateName ? diag::err_no_template
                                 : diag::err_unknown_typename)
          << II;
    else if (DeclContext *DC = computeDeclContext(*SS, false))
      Diag(IILoc, IsTemplateName ? diag::err_no_member_template
                                 : diag::err_typename_nested_not_found)
          << II << DC << SS->getRange();
    else if (isDependentScopeSpecifier(*SS)) {
      unsigned DiagID = diag::err_typename_missing;
      if (getLangOpts().MSVCCompat && isMicrosoftMissingTypename(SS, S))
        DiagID = diag::ext_typename_missing;
  
      Diag(SS->getRange().getBegin(), DiagID)
        << SS->getScopeRep() << II->getName()
        << SourceRange(SS->getRange().getBegin(), IILoc)
        << FixItHint::CreateInsertion(SS->getRange().getBegin(), "typename ");
      SuggestedType = ActOnTypenameType(S, SourceLocation(),
                                        *SS, *II, IILoc).get();
    } else {
      assert(SS && SS->isInvalid() &&
             "Invalid scope specifier has already been diagnosed");
    }
  }
  
  /// Determine whether the given result set contains either a type name
  /// or
  static bool isResultTypeOrTemplate(LookupResult &R, const Token &NextToken) {
    bool CheckTemplate = R.getSema().getLangOpts().CPlusPlus &&
                         NextToken.is(tok::less);
  
    for (LookupResult::iterator I = R.begin(), IEnd = R.end(); I != IEnd; ++I) {
      if (isa<TypeDecl>(*I) || isa<ObjCInterfaceDecl>(*I))
        return true;
  
      if (CheckTemplate && isa<TemplateDecl>(*I))
        return true;
    }
  
    return false;
  }
  
  static bool isTagTypeWithMissingTag(Sema &SemaRef, LookupResult &Result,
                                      Scope *S, CXXScopeSpec &SS,
                                      IdentifierInfo *&Name,
                                      SourceLocation NameLoc) {
    LookupResult R(SemaRef, Name, NameLoc, Sema::LookupTagName);
    SemaRef.LookupParsedName(R, S, &SS);
    if (TagDecl *Tag = R.getAsSingle<TagDecl>()) {
      StringRef FixItTagName;
      switch (Tag->getTagKind()) {
        case TTK_Class:
          FixItTagName = "class ";
          break;
  
        case TTK_Enum:
          FixItTagName = "enum ";
          break;
  
        case TTK_Struct:
          FixItTagName = "struct ";
          break;
  
        case TTK_Interface:
          FixItTagName = "__interface ";
          break;
  
        case TTK_Union:
          FixItTagName = "union ";
          break;
      }
  
      StringRef TagName = FixItTagName.drop_back();
      SemaRef.Diag(NameLoc, diag::err_use_of_tag_name_without_tag)
        << Name << TagName << SemaRef.getLangOpts().CPlusPlus
        << FixItHint::CreateInsertion(NameLoc, FixItTagName);
  
      for (LookupResult::iterator I = Result.begin(), IEnd = Result.end();
           I != IEnd; ++I)
        SemaRef.Diag((*I)->getLocation(), diag::note_decl_hiding_tag_type)
          << Name << TagName;
  
      // Replace lookup results with just the tag decl.
      Result.clear(Sema::LookupTagName);
      SemaRef.LookupParsedName(Result, S, &SS);
      return true;
    }
  
    return false;
  }
  
  /// Build a ParsedType for a simple-type-specifier with a nested-name-specifier.
  static ParsedType buildNestedType(Sema &S, CXXScopeSpec &SS,
                                    QualType T, SourceLocation NameLoc) {
    ASTContext &Context = S.Context;
  
    TypeLocBuilder Builder;
    Builder.pushTypeSpec(T).setNameLoc(NameLoc);
  
    T = S.getElaboratedType(ETK_None, SS, T);
    ElaboratedTypeLoc ElabTL = Builder.push<ElaboratedTypeLoc>(T);
    ElabTL.setElaboratedKeywordLoc(SourceLocation());
    ElabTL.setQualifierLoc(SS.getWithLocInContext(Context));
    return S.CreateParsedType(T, Builder.getTypeSourceInfo(Context, T));
  }
  
  Sema::NameClassification
  Sema::ClassifyName(Scope *S, CXXScopeSpec &SS, IdentifierInfo *&Name,
                     SourceLocation NameLoc, const Token &NextToken,
                     bool IsAddressOfOperand, CorrectionCandidateCallback *CCC) {
    DeclarationNameInfo NameInfo(Name, NameLoc);
    ObjCMethodDecl *CurMethod = getCurMethodDecl();
  
    if (NextToken.is(tok::coloncolon)) {
      NestedNameSpecInfo IdInfo(Name, NameLoc, NextToken.getLocation());
      BuildCXXNestedNameSpecifier(S, IdInfo, false, SS, nullptr, false);
    } else if (getLangOpts().CPlusPlus && SS.isSet() &&
               isCurrentClassName(*Name, S, &SS)) {
      // Per [class.qual]p2, this names the constructors of SS, not the
      // injected-class-name. We don't have a classification for that.
      // There's not much point caching this result, since the parser
      // will reject it later.
      return NameClassification::Unknown();
    }
  
    LookupResult Result(*this, Name, NameLoc, LookupOrdinaryName);
    LookupParsedName(Result, S, &SS, !CurMethod);
  
    // For unqualified lookup in a class template in MSVC mode, look into
    // dependent base classes where the primary class template is known.
    if (Result.empty() && SS.isEmpty() && getLangOpts().MSVCCompat) {
      if (ParsedType TypeInBase =
              recoverFromTypeInKnownDependentBase(*this, *Name, NameLoc))
        return TypeInBase;
    }
  
    // Perform lookup for Objective-C instance variables (including automatically
    // synthesized instance variables), if we're in an Objective-C method.
    // FIXME: This lookup really, really needs to be folded in to the normal
    // unqualified lookup mechanism.
    if (!SS.isSet() && CurMethod && !isResultTypeOrTemplate(Result, NextToken)) {
      ExprResult E = LookupInObjCMethod(Result, S, Name, true);
      if (E.get() || E.isInvalid())
        return E;
    }
  
    bool SecondTry = false;
    bool IsFilteredTemplateName = false;
  
  Corrected:
    switch (Result.getResultKind()) {
    case LookupResult::NotFound:
      // If an unqualified-id is followed by a '(', then we have a function
      // call.
      if (!SS.isSet() && NextToken.is(tok::l_paren)) {
        // In C++, this is an ADL-only call.
        // FIXME: Reference?
        if (getLangOpts().CPlusPlus)
          return BuildDeclarationNameExpr(SS, Result, /*ADL=*/true);
  
        // C90 6.3.2.2:
        //   If the expression that precedes the parenthesized argument list in a
        //   function call consists solely of an identifier, and if no
        //   declaration is visible for this identifier, the identifier is
        //   implicitly declared exactly as if, in the innermost block containing
        //   the function call, the declaration
        //
        //     extern int identifier ();
        //
        //   appeared.
        //
        // We also allow this in C99 as an extension.
        if (NamedDecl *D = ImplicitlyDefineFunction(NameLoc, *Name, S)) {
          Result.addDecl(D);
          Result.resolveKind();
          return BuildDeclarationNameExpr(SS, Result, /*ADL=*/false);
        }
      }
  
      // In C, we first see whether there is a tag type by the same name, in
      // which case it's likely that the user just forgot to write "enum",
      // "struct", or "union".
      if (!getLangOpts().CPlusPlus && !SecondTry &&
          isTagTypeWithMissingTag(*this, Result, S, SS, Name, NameLoc)) {
        break;
      }
  
      // Perform typo correction to determine if there is another name that is
      // close to this name.
      if (!SecondTry && CCC) {
        SecondTry = true;
        if (TypoCorrection Corrected =
                CorrectTypo(Result.getLookupNameInfo(), Result.getLookupKind(), S,
                            &SS, *CCC, CTK_ErrorRecovery)) {
          unsigned UnqualifiedDiag = diag::err_undeclared_var_use_suggest;
          unsigned QualifiedDiag = diag::err_no_member_suggest;
  
          NamedDecl *FirstDecl = Corrected.getFoundDecl();
          NamedDecl *UnderlyingFirstDecl = Corrected.getCorrectionDecl();
          if (getLangOpts().CPlusPlus && NextToken.is(tok::less) &&
              UnderlyingFirstDecl && isa<TemplateDecl>(UnderlyingFirstDecl)) {
            UnqualifiedDiag = diag::err_no_template_suggest;
            QualifiedDiag = diag::err_no_member_template_suggest;
          } else if (UnderlyingFirstDecl &&
                     (isa<TypeDecl>(UnderlyingFirstDecl) ||
                      isa<ObjCInterfaceDecl>(UnderlyingFirstDecl) ||
                      isa<ObjCCompatibleAliasDecl>(UnderlyingFirstDecl))) {
            UnqualifiedDiag = diag::err_unknown_typename_suggest;
            QualifiedDiag = diag::err_unknown_nested_typename_suggest;
          }
  
          if (SS.isEmpty()) {
            diagnoseTypo(Corrected, PDiag(UnqualifiedDiag) << Name);
          } else {// FIXME: is this even reachable? Test it.
            std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
            bool DroppedSpecifier = Corrected.WillReplaceSpecifier() &&
                                    Name->getName().equals(CorrectedStr);
            diagnoseTypo(Corrected, PDiag(QualifiedDiag)
                                      << Name << computeDeclContext(SS, false)
                                      << DroppedSpecifier << SS.getRange());
          }
  
          // Update the name, so that the caller has the new name.
          Name = Corrected.getCorrectionAsIdentifierInfo();
  
          // Typo correction corrected to a keyword.
          if (Corrected.isKeyword())
            return Name;
  
          // Also update the LookupResult...
          // FIXME: This should probably go away at some point
          Result.clear();
          Result.setLookupName(Corrected.getCorrection());
          if (FirstDecl)
            Result.addDecl(FirstDecl);
  
          // If we found an Objective-C instance variable, let
          // LookupInObjCMethod build the appropriate expression to
          // reference the ivar.
          // FIXME: This is a gross hack.
          if (ObjCIvarDecl *Ivar = Result.getAsSingle<ObjCIvarDecl>()) {
            Result.clear();
            ExprResult E(LookupInObjCMethod(Result, S, Ivar->getIdentifier()));
            return E;
          }
  
          goto Corrected;
        }
      }
  
      // We failed to correct; just fall through and let the parser deal with it.
      Result.suppressDiagnostics();
      return NameClassification::Unknown();
  
    case LookupResult::NotFoundInCurrentInstantiation: {
      // We performed name lookup into the current instantiation, and there were
      // dependent bases, so we treat this result the same way as any other
      // dependent nested-name-specifier.
  
      // C++ [temp.res]p2:
      //   A name used in a template declaration or definition and that is
      //   dependent on a template-parameter is assumed not to name a type
      //   unless the applicable name lookup finds a type name or the name is
      //   qualified by the keyword typename.
      //
      // FIXME: If the next token is '<', we might want to ask the parser to
      // perform some heroics to see if we actually have a
      // template-argument-list, which would indicate a missing 'template'
      // keyword here.
      return ActOnDependentIdExpression(SS, /*TemplateKWLoc=*/SourceLocation(),
                                        NameInfo, IsAddressOfOperand,
                                        /*TemplateArgs=*/nullptr);
    }
  
    case LookupResult::Found:
    case LookupResult::FoundOverloaded:
    case LookupResult::FoundUnresolvedValue:
      break;
  
    case LookupResult::Ambiguous:
      if (getLangOpts().CPlusPlus && NextToken.is(tok::less) &&
          hasAnyAcceptableTemplateNames(Result, /*AllowFunctionTemplates=*/true,
                                        /*AllowDependent=*/false)) {
        // C++ [temp.local]p3:
        //   A lookup that finds an injected-class-name (10.2) can result in an
        //   ambiguity in certain cases (for example, if it is found in more than
        //   one base class). If all of the injected-class-names that are found
        //   refer to specializations of the same class template, and if the name
        //   is followed by a template-argument-list, the reference refers to the
        //   class template itself and not a specialization thereof, and is not
        //   ambiguous.
        //
        // This filtering can make an ambiguous result into an unambiguous one,
        // so try again after filtering out template names.
        FilterAcceptableTemplateNames(Result);
        if (!Result.isAmbiguous()) {
          IsFilteredTemplateName = true;
          break;
        }
      }
  
      // Diagnose the ambiguity and return an error.
      return NameClassification::Error();
    }
  
    if (getLangOpts().CPlusPlus && NextToken.is(tok::less) &&
        (IsFilteredTemplateName ||
         hasAnyAcceptableTemplateNames(Result, /*AllowFunctionTemplates=*/true,
                                       /*AllowDependent=*/false))) {
      // C++ [temp.names]p3:
      //   After name lookup (3.4) finds that a name is a template-name or that
      //   an operator-function-id or a literal- operator-id refers to a set of
      //   overloaded functions any member of which is a function template if
      //   this is followed by a <, the < is always taken as the delimiter of a
      //   template-argument-list and never as the less-than operator.
      if (!IsFilteredTemplateName)
        FilterAcceptableTemplateNames(Result);
  
      if (!Result.empty()) {
        bool IsFunctionTemplate;
        bool IsVarTemplate;
        TemplateName Template;
        if (Result.end() - Result.begin() > 1) {
          IsFunctionTemplate = true;
          Template = Context.getOverloadedTemplateName(Result.begin(),
                                                       Result.end());
        } else {
          auto *TD = cast<TemplateDecl>(getAsTemplateNameDecl(
              *Result.begin(), /*AllowFunctionTemplates=*/true,
              /*AllowDependent=*/false));
          IsFunctionTemplate = isa<FunctionTemplateDecl>(TD);
          IsVarTemplate = isa<VarTemplateDecl>(TD);
  
          if (SS.isSet() && !SS.isInvalid())
            Template =
                Context.getQualifiedTemplateName(SS.getScopeRep(),
                                                 /*TemplateKeyword=*/false, TD);
          else
            Template = TemplateName(TD);
        }
  
        if (IsFunctionTemplate) {
          // Function templates always go through overload resolution, at which
          // point we'll perform the various checks (e.g., accessibility) we need
          // to based on which function we selected.
          Result.suppressDiagnostics();
  
          return NameClassification::FunctionTemplate(Template);
        }
  
        return IsVarTemplate ? NameClassification::VarTemplate(Template)
                             : NameClassification::TypeTemplate(Template);
      }
    }
  
    NamedDecl *FirstDecl = (*Result.begin())->getUnderlyingDecl();
    if (TypeDecl *Type = dyn_cast<TypeDecl>(FirstDecl)) {
      DiagnoseUseOfDecl(Type, NameLoc);
      MarkAnyDeclReferenced(Type->getLocation(), Type, /*OdrUse=*/false);
      QualType T = Context.getTypeDeclType(Type);
      if (SS.isNotEmpty())
        return buildNestedType(*this, SS, T, NameLoc);
      return ParsedType::make(T);
    }
  
    ObjCInterfaceDecl *Class = dyn_cast<ObjCInterfaceDecl>(FirstDecl);
    if (!Class) {
      // FIXME: It's unfortunate that we don't have a Type node for handling this.
      if (ObjCCompatibleAliasDecl *Alias =
              dyn_cast<ObjCCompatibleAliasDecl>(FirstDecl))
        Class = Alias->getClassInterface();
    }
  
    if (Class) {
      DiagnoseUseOfDecl(Class, NameLoc);
  
      if (NextToken.is(tok::period)) {
        // Interface. <something> is parsed as a property reference expression.
        // Just return "unknown" as a fall-through for now.
        Result.suppressDiagnostics();
        return NameClassification::Unknown();
      }
  
      QualType T = Context.getObjCInterfaceType(Class);
      return ParsedType::make(T);
    }
  
    // We can have a type template here if we're classifying a template argument.
    if (isa<TemplateDecl>(FirstDecl) && !isa<FunctionTemplateDecl>(FirstDecl) &&
        !isa<VarTemplateDecl>(FirstDecl))
      return NameClassification::TypeTemplate(
          TemplateName(cast<TemplateDecl>(FirstDecl)));
  
    // Check for a tag type hidden by a non-type decl in a few cases where it
    // seems likely a type is wanted instead of the non-type that was found.
    bool NextIsOp = NextToken.isOneOf(tok::amp, tok::star);
    if ((NextToken.is(tok::identifier) ||
         (NextIsOp &&
          FirstDecl->getUnderlyingDecl()->isFunctionOrFunctionTemplate())) &&
        isTagTypeWithMissingTag(*this, Result, S, SS, Name, NameLoc)) {
      TypeDecl *Type = Result.getAsSingle<TypeDecl>();
      DiagnoseUseOfDecl(Type, NameLoc);
      QualType T = Context.getTypeDeclType(Type);
      if (SS.isNotEmpty())
        return buildNestedType(*this, SS, T, NameLoc);
      return ParsedType::make(T);
    }
  
    if (FirstDecl->isCXXClassMember())
      return BuildPossibleImplicitMemberExpr(SS, SourceLocation(), Result,
                                             nullptr, S);
  
    bool ADL = UseArgumentDependentLookup(SS, Result, NextToken.is(tok::l_paren));
    return BuildDeclarationNameExpr(SS, Result, ADL);
  }
  
  Sema::TemplateNameKindForDiagnostics
  Sema::getTemplateNameKindForDiagnostics(TemplateName Name) {
    auto *TD = Name.getAsTemplateDecl();
    if (!TD)
      return TemplateNameKindForDiagnostics::DependentTemplate;
    if (isa<ClassTemplateDecl>(TD))
      return TemplateNameKindForDiagnostics::ClassTemplate;
    if (isa<FunctionTemplateDecl>(TD))
      return TemplateNameKindForDiagnostics::FunctionTemplate;
    if (isa<VarTemplateDecl>(TD))
      return TemplateNameKindForDiagnostics::VarTemplate;
    if (isa<TypeAliasTemplateDecl>(TD))
      return TemplateNameKindForDiagnostics::AliasTemplate;
    if (isa<TemplateTemplateParmDecl>(TD))
      return TemplateNameKindForDiagnostics::TemplateTemplateParam;
    return TemplateNameKindForDiagnostics::DependentTemplate;
  }
  
  // Determines the context to return to after temporarily entering a
  // context.  This depends in an unnecessarily complicated way on the
  // exact ordering of callbacks from the parser.
  DeclContext *Sema::getContainingDC(DeclContext *DC) {
  
    // Functions defined inline within classes aren't parsed until we've
    // finished parsing the top-level class, so the top-level class is
    // the context we'll need to return to.
    // A Lambda call operator whose parent is a class must not be treated
    // as an inline member function.  A Lambda can be used legally
    // either as an in-class member initializer or a default argument.  These
    // are parsed once the class has been marked complete and so the containing
    // context would be the nested class (when the lambda is defined in one);
    // If the class is not complete, then the lambda is being used in an
    // ill-formed fashion (such as to specify the width of a bit-field, or
    // in an array-bound) - in which case we still want to return the
    // lexically containing DC (which could be a nested class).
    if (isa<FunctionDecl>(DC) && !isLambdaCallOperator(DC)) {
      DC = DC->getLexicalParent();
  
      // A function not defined within a class will always return to its
      // lexical context.
      if (!isa<CXXRecordDecl>(DC))
        return DC;
  
      // A C++ inline method/friend is parsed *after* the topmost class
      // it was declared in is fully parsed ("complete");  the topmost
      // class is the context we need to return to.
      while (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(DC->getLexicalParent()))
        DC = RD;
  
      // Return the declaration context of the topmost class the inline method is
      // declared in.
      return DC;
    }
  
    return DC->getLexicalParent();
  }
  
  void Sema::PushDeclContext(Scope *S, DeclContext *DC) {
    assert(getContainingDC(DC) == CurContext &&
        "The next DeclContext should be lexically contained in the current one.");
    CurContext = DC;
    S->setEntity(DC);
  }
  
  void Sema::PopDeclContext() {
    assert(CurContext && "DeclContext imbalance!");
  
    CurContext = getContainingDC(CurContext);
    assert(CurContext && "Popped translation unit!");
  }
  
  Sema::SkippedDefinitionContext Sema::ActOnTagStartSkippedDefinition(Scope *S,
                                                                      Decl *D) {
    // Unlike PushDeclContext, the context to which we return is not necessarily
    // the containing DC of TD, because the new context will be some pre-existing
    // TagDecl definition instead of a fresh one.
    auto Result = static_cast<SkippedDefinitionContext>(CurContext);
    CurContext = cast<TagDecl>(D)->getDefinition();
    assert(CurContext && "skipping definition of undefined tag");
    // Start lookups from the parent of the current context; we don't want to look
    // into the pre-existing complete definition.
    S->setEntity(CurContext->getLookupParent());
    return Result;
  }
  
  void Sema::ActOnTagFinishSkippedDefinition(SkippedDefinitionContext Context) {
    CurContext = static_cast<decltype(CurContext)>(Context);
  }
  
  /// EnterDeclaratorContext - Used when we must lookup names in the context
  /// of a declarator's nested name specifier.
  ///
  void Sema::EnterDeclaratorContext(Scope *S, DeclContext *DC) {
    // C++0x [basic.lookup.unqual]p13:
    //   A name used in the definition of a static data member of class
    //   X (after the qualified-id of the static member) is looked up as
    //   if the name was used in a member function of X.
    // C++0x [basic.lookup.unqual]p14:
    //   If a variable member of a namespace is defined outside of the
    //   scope of its namespace then any name used in the definition of
    //   the variable member (after the declarator-id) is looked up as
    //   if the definition of the variable member occurred in its
    //   namespace.
    // Both of these imply that we should push a scope whose context
    // is the semantic context of the declaration.  We can't use
    // PushDeclContext here because that context is not necessarily
    // lexically contained in the current context.  Fortunately,
    // the containing scope should have the appropriate information.
  
    assert(!S->getEntity() && "scope already has entity");
  
  #ifndef NDEBUG
    Scope *Ancestor = S->getParent();
    while (!Ancestor->getEntity()) Ancestor = Ancestor->getParent();
    assert(Ancestor->getEntity() == CurContext && "ancestor context mismatch");
  #endif
  
    CurContext = DC;
    S->setEntity(DC);
  }
  
  void Sema::ExitDeclaratorContext(Scope *S) {
    assert(S->getEntity() == CurContext && "Context imbalance!");
  
    // Switch back to the lexical context.  The safety of this is
    // enforced by an assert in EnterDeclaratorContext.
    Scope *Ancestor = S->getParent();
    while (!Ancestor->getEntity()) Ancestor = Ancestor->getParent();
    CurContext = Ancestor->getEntity();
  
    // We don't need to do anything with the scope, which is going to
    // disappear.
  }
  
  void Sema::ActOnReenterFunctionContext(Scope* S, Decl *D) {
    // We assume that the caller has already called
    // ActOnReenterTemplateScope so getTemplatedDecl() works.
    FunctionDecl *FD = D->getAsFunction();
    if (!FD)
      return;
  
    // Same implementation as PushDeclContext, but enters the context
    // from the lexical parent, rather than the top-level class.
    assert(CurContext == FD->getLexicalParent() &&
      "The next DeclContext should be lexically contained in the current one.");
    CurContext = FD;
    S->setEntity(CurContext);
  
    for (unsigned P = 0, NumParams = FD->getNumParams(); P < NumParams; ++P) {
      ParmVarDecl *Param = FD->getParamDecl(P);
      // If the parameter has an identifier, then add it to the scope
      if (Param->getIdentifier()) {
        S->AddDecl(Param);
        IdResolver.AddDecl(Param);
      }
    }
  }
  
  void Sema::ActOnExitFunctionContext() {
    // Same implementation as PopDeclContext, but returns to the lexical parent,
    // rather than the top-level class.
    assert(CurContext && "DeclContext imbalance!");
    CurContext = CurContext->getLexicalParent();
    assert(CurContext && "Popped translation unit!");
  }
  
  /// Determine whether we allow overloading of the function
  /// PrevDecl with another declaration.
  ///
  /// This routine determines whether overloading is possible, not
  /// whether some new function is actually an overload. It will return
  /// true in C++ (where we can always provide overloads) or, as an
  /// extension, in C when the previous function is already an
  /// overloaded function declaration or has the "overloadable"
  /// attribute.
  static bool AllowOverloadingOfFunction(LookupResult &Previous,
                                         ASTContext &Context,
                                         const FunctionDecl *New) {
    if (Context.getLangOpts().CPlusPlus)
      return true;
  
    if (Previous.getResultKind() == LookupResult::FoundOverloaded)
      return true;
  
    return Previous.getResultKind() == LookupResult::Found &&
           (Previous.getFoundDecl()->hasAttr<OverloadableAttr>() ||
            New->hasAttr<OverloadableAttr>());
  }
  
  /// Add this decl to the scope shadowed decl chains.
  void Sema::PushOnScopeChains(NamedDecl *D, Scope *S, bool AddToContext) {
    // Move up the scope chain until we find the nearest enclosing
    // non-transparent context. The declaration will be introduced into this
    // scope.
    while (S->getEntity() && S->getEntity()->isTransparentContext())
      S = S->getParent();
  
    // Add scoped declarations into their context, so that they can be
    // found later. Declarations without a context won't be inserted
    // into any context.
    if (AddToContext)
      CurContext->addDecl(D);
  
    // Out-of-line definitions shouldn't be pushed into scope in C++, unless they
    // are function-local declarations.
    if (getLangOpts().CPlusPlus && D->isOutOfLine() &&
        !D->getDeclContext()->getRedeclContext()->Equals(
          D->getLexicalDeclContext()->getRedeclContext()) &&
        !D->getLexicalDeclContext()->isFunctionOrMethod())
      return;
  
    // Template instantiations should also not be pushed into scope.
    if (isa<FunctionDecl>(D) &&
        cast<FunctionDecl>(D)->isFunctionTemplateSpecialization())
      return;
  
    // If this replaces anything in the current scope,
    IdentifierResolver::iterator I = IdResolver.begin(D->getDeclName()),
                                 IEnd = IdResolver.end();
    for (; I != IEnd; ++I) {
      if (S->isDeclScope(*I) && D->declarationReplaces(*I)) {
        S->RemoveDecl(*I);
        IdResolver.RemoveDecl(*I);
  
        // Should only need to replace one decl.
        break;
      }
    }
  
    S->AddDecl(D);
  
    if (isa<LabelDecl>(D) && !cast<LabelDecl>(D)->isGnuLocal()) {
      // Implicitly-generated labels may end up getting generated in an order that
      // isn't strictly lexical, which breaks name lookup. Be careful to insert
      // the label at the appropriate place in the identifier chain.
      for (I = IdResolver.begin(D->getDeclName()); I != IEnd; ++I) {
        DeclContext *IDC = (*I)->getLexicalDeclContext()->getRedeclContext();
        if (IDC == CurContext) {
          if (!S->isDeclScope(*I))
            continue;
        } else if (IDC->Encloses(CurContext))
          break;
      }
  
      IdResolver.InsertDeclAfter(I, D);
    } else {
      IdResolver.AddDecl(D);
    }
  }
  
  void Sema::pushExternalDeclIntoScope(NamedDecl *D, DeclarationName Name) {
    if (IdResolver.tryAddTopLevelDecl(D, Name) && TUScope)
      TUScope->AddDecl(D);
  }
  
  bool Sema::isDeclInScope(NamedDecl *D, DeclContext *Ctx, Scope *S,
                           bool AllowInlineNamespace) {
    return IdResolver.isDeclInScope(D, Ctx, S, AllowInlineNamespace);
  }
  
  Scope *Sema::getScopeForDeclContext(Scope *S, DeclContext *DC) {
    DeclContext *TargetDC = DC->getPrimaryContext();
    do {
      if (DeclContext *ScopeDC = S->getEntity())
        if (ScopeDC->getPrimaryContext() == TargetDC)
          return S;
    } while ((S = S->getParent()));
  
    return nullptr;
  }
  
  static bool isOutOfScopePreviousDeclaration(NamedDecl *,
                                              DeclContext*,
                                              ASTContext&);
  
  /// Filters out lookup results that don't fall within the given scope
  /// as determined by isDeclInScope.
  void Sema::FilterLookupForScope(LookupResult &R, DeclContext *Ctx, Scope *S,
                                  bool ConsiderLinkage,
                                  bool AllowInlineNamespace) {
    LookupResult::Filter F = R.makeFilter();
    while (F.hasNext()) {
      NamedDecl *D = F.next();
  
      if (isDeclInScope(D, Ctx, S, AllowInlineNamespace))
        continue;
  
      if (ConsiderLinkage && isOutOfScopePreviousDeclaration(D, Ctx, Context))
        continue;
  
      F.erase();
    }
  
    F.done();
  }
  
  /// We've determined that \p New is a redeclaration of \p Old. Check that they
  /// have compatible owning modules.
  bool Sema::CheckRedeclarationModuleOwnership(NamedDecl *New, NamedDecl *Old) {
    // FIXME: The Modules TS is not clear about how friend declarations are
    // to be treated. It's not meaningful to have different owning modules for
    // linkage in redeclarations of the same entity, so for now allow the
    // redeclaration and change the owning modules to match.
    if (New->getFriendObjectKind() &&
        Old->getOwningModuleForLinkage() != New->getOwningModuleForLinkage()) {
      New->setLocalOwningModule(Old->getOwningModule());
      makeMergedDefinitionVisible(New);
      return false;
    }
  
    Module *NewM = New->getOwningModule();
    Module *OldM = Old->getOwningModule();
    if (NewM == OldM)
      return false;
  
    // FIXME: Check proclaimed-ownership-declarations here too.
    bool NewIsModuleInterface = NewM && NewM->Kind == Module::ModuleInterfaceUnit;
    bool OldIsModuleInterface = OldM && OldM->Kind == Module::ModuleInterfaceUnit;
    if (NewIsModuleInterface || OldIsModuleInterface) {
      // C++ Modules TS [basic.def.odr] 6.2/6.7 [sic]:
      //   if a declaration of D [...] appears in the purview of a module, all
      //   other such declarations shall appear in the purview of the same module
      Diag(New->getLocation(), diag::err_mismatched_owning_module)
        << New
        << NewIsModuleInterface
        << (NewIsModuleInterface ? NewM->getFullModuleName() : "")
        << OldIsModuleInterface
        << (OldIsModuleInterface ? OldM->getFullModuleName() : "");
      Diag(Old->getLocation(), diag::note_previous_declaration);
      New->setInvalidDecl();
      return true;
    }
  
    return false;
  }
  
  static bool isUsingDecl(NamedDecl *D) {
    return isa<UsingShadowDecl>(D) ||
           isa<UnresolvedUsingTypenameDecl>(D) ||
           isa<UnresolvedUsingValueDecl>(D);
  }
  
  /// Removes using shadow declarations from the lookup results.
  static void RemoveUsingDecls(LookupResult &R) {
    LookupResult::Filter F = R.makeFilter();
    while (F.hasNext())
      if (isUsingDecl(F.next()))
        F.erase();
  
    F.done();
  }
  
  /// Check for this common pattern:
  /// @code
  /// class S {
  ///   S(const S&); // DO NOT IMPLEMENT
  ///   void operator=(const S&); // DO NOT IMPLEMENT
  /// };
  /// @endcode
  static bool IsDisallowedCopyOrAssign(const CXXMethodDecl *D) {
    // FIXME: Should check for private access too but access is set after we get
    // the decl here.
    if (D->doesThisDeclarationHaveABody())
      return false;
  
    if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(D))
      return CD->isCopyConstructor();
    return D->isCopyAssignmentOperator();
  }
  
  // We need this to handle
  //
  // typedef struct {
  //   void *foo() { return 0; }
  // } A;
  //
  // When we see foo we don't know if after the typedef we will get 'A' or '*A'
  // for example. If 'A', foo will have external linkage. If we have '*A',
  // foo will have no linkage. Since we can't know until we get to the end
  // of the typedef, this function finds out if D might have non-external linkage.
  // Callers should verify at the end of the TU if it D has external linkage or
  // not.
  bool Sema::mightHaveNonExternalLinkage(const DeclaratorDecl *D) {
    const DeclContext *DC = D->getDeclContext();
    while (!DC->isTranslationUnit()) {
      if (const RecordDecl *RD = dyn_cast<RecordDecl>(DC)){
        if (!RD->hasNameForLinkage())
          return true;
      }
      DC = DC->getParent();
    }
  
    return !D->isExternallyVisible();
  }
  
  // FIXME: This needs to be refactored; some other isInMainFile users want
  // these semantics.
  static bool isMainFileLoc(const Sema &S, SourceLocation Loc) {
    if (S.TUKind != TU_Complete)
      return false;
    return S.SourceMgr.isInMainFile(Loc);
  }
  
  bool Sema::ShouldWarnIfUnusedFileScopedDecl(const DeclaratorDecl *D) const {
    assert(D);
  
    if (D->isInvalidDecl() || D->isUsed() || D->hasAttr<UnusedAttr>())
      return false;
  
    // Ignore all entities declared within templates, and out-of-line definitions
    // of members of class templates.
    if (D->getDeclContext()->isDependentContext() ||
        D->getLexicalDeclContext()->isDependentContext())
      return false;
  
    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
      if (FD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
        return false;
      // A non-out-of-line declaration of a member specialization was implicitly
      // instantiated; it's the out-of-line declaration that we're interested in.
      if (FD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization &&
          FD->getMemberSpecializationInfo() && !FD->isOutOfLine())
        return false;
  
      if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
        if (MD->isVirtual() || IsDisallowedCopyOrAssign(MD))
          return false;
      } else {
        // 'static inline' functions are defined in headers; don't warn.
        if (FD->isInlined() && !isMainFileLoc(*this, FD->getLocation()))
          return false;
      }
  
      if (FD->doesThisDeclarationHaveABody() &&
          Context.DeclMustBeEmitted(FD))
        return false;
    } else if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
      // Constants and utility variables are defined in headers with internal
      // linkage; don't warn.  (Unlike functions, there isn't a convenient marker
      // like "inline".)
      if (!isMainFileLoc(*this, VD->getLocation()))
        return false;
  
      if (Context.DeclMustBeEmitted(VD))
        return false;
  
      if (VD->isStaticDataMember() &&
          VD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
        return false;
      if (VD->isStaticDataMember() &&
          VD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization &&
          VD->getMemberSpecializationInfo() && !VD->isOutOfLine())
        return false;
  
      if (VD->isInline() && !isMainFileLoc(*this, VD->getLocation()))
        return false;
    } else {
      return false;
    }
  
    // Only warn for unused decls internal to the translation unit.
    // FIXME: This seems like a bogus check; it suppresses -Wunused-function
    // for inline functions defined in the main source file, for instance.
    return mightHaveNonExternalLinkage(D);
  }
  
  void Sema::MarkUnusedFileScopedDecl(const DeclaratorDecl *D) {
    if (!D)
      return;
  
    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
      const FunctionDecl *First = FD->getFirstDecl();
      if (FD != First && ShouldWarnIfUnusedFileScopedDecl(First))
        return; // First should already be in the vector.
    }
  
    if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
      const VarDecl *First = VD->getFirstDecl();
      if (VD != First && ShouldWarnIfUnusedFileScopedDecl(First))
        return; // First should already be in the vector.
    }
  
    if (ShouldWarnIfUnusedFileScopedDecl(D))
      UnusedFileScopedDecls.push_back(D);
  }
  
  static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
    if (D->isInvalidDecl())
      return false;
  
    bool Referenced = false;
    if (auto *DD = dyn_cast<DecompositionDecl>(D)) {
      // For a decomposition declaration, warn if none of the bindings are
      // referenced, instead of if the variable itself is referenced (which
      // it is, by the bindings' expressions).
      for (auto *BD : DD->bindings()) {
        if (BD->isReferenced()) {
          Referenced = true;
          break;
        }
      }
    } else if (!D->getDeclName()) {
      return false;
    } else if (D->isReferenced() || D->isUsed()) {
      Referenced = true;
    }
  
    if (Referenced || D->hasAttr<UnusedAttr>() ||
        D->hasAttr<ObjCPreciseLifetimeAttr>())
      return false;
  
    if (isa<LabelDecl>(D))
      return true;
  
    // Except for labels, we only care about unused decls that are local to
    // functions.
    bool WithinFunction = D->getDeclContext()->isFunctionOrMethod();
    if (const auto *R = dyn_cast<CXXRecordDecl>(D->getDeclContext()))
      // For dependent types, the diagnostic is deferred.
      WithinFunction =
          WithinFunction || (R->isLocalClass() && !R->isDependentType());
    if (!WithinFunction)
      return false;
  
    if (isa<TypedefNameDecl>(D))
      return true;
  
    // White-list anything that isn't a local variable.
    if (!isa<VarDecl>(D) || isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D))
      return false;
  
    // Types of valid local variables should be complete, so this should succeed.
    if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
  
      // White-list anything with an __attribute__((unused)) type.
      const auto *Ty = VD->getType().getTypePtr();
  
      // Only look at the outermost level of typedef.
      if (const TypedefType *TT = Ty->getAs<TypedefType>()) {
        if (TT->getDecl()->hasAttr<UnusedAttr>())
          return false;
      }
  
      // If we failed to complete the type for some reason, or if the type is
      // dependent, don't diagnose the variable.
      if (Ty->isIncompleteType() || Ty->isDependentType())
        return false;
  
      // Look at the element type to ensure that the warning behaviour is
      // consistent for both scalars and arrays.
      Ty = Ty->getBaseElementTypeUnsafe();
  
      if (const TagType *TT = Ty->getAs<TagType>()) {
        const TagDecl *Tag = TT->getDecl();
        if (Tag->hasAttr<UnusedAttr>())
          return false;
  
        if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Tag)) {
          if (!RD->hasTrivialDestructor() && !RD->hasAttr<WarnUnusedAttr>())
            return false;
  
          if (const Expr *Init = VD->getInit()) {
            if (const ExprWithCleanups *Cleanups =
                    dyn_cast<ExprWithCleanups>(Init))
              Init = Cleanups->getSubExpr();
            const CXXConstructExpr *Construct =
              dyn_cast<CXXConstructExpr>(Init);
            if (Construct && !Construct->isElidable()) {
              CXXConstructorDecl *CD = Construct->getConstructor();
              if (!CD->isTrivial() && !RD->hasAttr<WarnUnusedAttr>() &&
                  (VD->getInit()->isValueDependent() || !VD->evaluateValue()))
                return false;
            }
          }
        }
      }
  
      // TODO: __attribute__((unused)) templates?
    }
  
    return true;
  }
  
  static void GenerateFixForUnusedDecl(const NamedDecl *D, ASTContext &Ctx,
                                       FixItHint &Hint) {
    if (isa<LabelDecl>(D)) {
      SourceLocation AfterColon = Lexer::findLocationAfterToken(
          D->getEndLoc(), tok::colon, Ctx.getSourceManager(), Ctx.getLangOpts(),
          true);
      if (AfterColon.isInvalid())
        return;
      Hint = FixItHint::CreateRemoval(
          CharSourceRange::getCharRange(D->getBeginLoc(), AfterColon));
    }
  }
  
  void Sema::DiagnoseUnusedNestedTypedefs(const RecordDecl *D) {
    if (D->getTypeForDecl()->isDependentType())
      return;
  
    for (auto *TmpD : D->decls()) {
      if (const auto *T = dyn_cast<TypedefNameDecl>(TmpD))
        DiagnoseUnusedDecl(T);
      else if(const auto *R = dyn_cast<RecordDecl>(TmpD))
        DiagnoseUnusedNestedTypedefs(R);
    }
  }
  
  /// DiagnoseUnusedDecl - Emit warnings about declarations that are not used
  /// unless they are marked attr(unused).
  void Sema::DiagnoseUnusedDecl(const NamedDecl *D) {
    if (!ShouldDiagnoseUnusedDecl(D))
      return;
  
    if (auto *TD = dyn_cast<TypedefNameDecl>(D)) {
      // typedefs can be referenced later on, so the diagnostics are emitted
      // at end-of-translation-unit.
      UnusedLocalTypedefNameCandidates.insert(TD);
      return;
    }
  
    FixItHint Hint;
    GenerateFixForUnusedDecl(D, Context, Hint);
  
    unsigned DiagID;
    if (isa<VarDecl>(D) && cast<VarDecl>(D)->isExceptionVariable())
      DiagID = diag::warn_unused_exception_param;
    else if (isa<LabelDecl>(D))
      DiagID = diag::warn_unused_label;
    else
      DiagID = diag::warn_unused_variable;
  
    Diag(D->getLocation(), DiagID) << D << Hint;
  }
  
  static void CheckPoppedLabel(LabelDecl *L, Sema &S) {
    // Verify that we have no forward references left.  If so, there was a goto
    // or address of a label taken, but no definition of it.  Label fwd
    // definitions are indicated with a null substmt which is also not a resolved
    // MS inline assembly label name.
    bool Diagnose = false;
    if (L->isMSAsmLabel())
      Diagnose = !L->isResolvedMSAsmLabel();
    else
      Diagnose = L->getStmt() == nullptr;
    if (Diagnose)
      S.Diag(L->getLocation(), diag::err_undeclared_label_use) <<L->getDeclName();
  }
  
  void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
    S->mergeNRVOIntoParent();
  
    if (S->decl_empty()) return;
    assert((S->getFlags() & (Scope::DeclScope | Scope::TemplateParamScope)) &&
           "Scope shouldn't contain decls!");
  
    for (auto *TmpD : S->decls()) {
      assert(TmpD && "This decl didn't get pushed??");
  
      assert(isa<NamedDecl>(TmpD) && "Decl isn't NamedDecl?");
      NamedDecl *D = cast<NamedDecl>(TmpD);
  
      // Diagnose unused variables in this scope.
      if (!S->hasUnrecoverableErrorOccurred()) {
        DiagnoseUnusedDecl(D);
        if (const auto *RD = dyn_cast<RecordDecl>(D))
          DiagnoseUnusedNestedTypedefs(RD);
      }
  
      if (!D->getDeclName()) continue;
  
      // If this was a forward reference to a label, verify it was defined.
      if (LabelDecl *LD = dyn_cast<LabelDecl>(D))
        CheckPoppedLabel(LD, *this);
  
      // Remove this name from our lexical scope, and warn on it if we haven't
      // already.
      IdResolver.RemoveDecl(D);
      auto ShadowI = ShadowingDecls.find(D);
      if (ShadowI != ShadowingDecls.end()) {
        if (const auto *FD = dyn_cast<FieldDecl>(ShadowI->second)) {
          Diag(D->getLocation(), diag::warn_ctor_parm_shadows_field)
              << D << FD << FD->getParent();
          Diag(FD->getLocation(), diag::note_previous_declaration);
        }
        ShadowingDecls.erase(ShadowI);
      }
    }
  }
  
  /// Look for an Objective-C class in the translation unit.
  ///
  /// \param Id The name of the Objective-C class we're looking for. If
  /// typo-correction fixes this name, the Id will be updated
  /// to the fixed name.
  ///
  /// \param IdLoc The location of the name in the translation unit.
  ///
  /// \param DoTypoCorrection If true, this routine will attempt typo correction
  /// if there is no class with the given name.
  ///
  /// \returns The declaration of the named Objective-C class, or NULL if the
  /// class could not be found.
  ObjCInterfaceDecl *Sema::getObjCInterfaceDecl(IdentifierInfo *&Id,
                                                SourceLocation IdLoc,
                                                bool DoTypoCorrection) {
    // The third "scope" argument is 0 since we aren't enabling lazy built-in
    // creation from this context.
    NamedDecl *IDecl = LookupSingleName(TUScope, Id, IdLoc, LookupOrdinaryName);
  
    if (!IDecl && DoTypoCorrection) {
      // Perform typo correction at the given location, but only if we
      // find an Objective-C class name.
      DeclFilterCCC<ObjCInterfaceDecl> CCC{};
      if (TypoCorrection C =
              CorrectTypo(DeclarationNameInfo(Id, IdLoc), LookupOrdinaryName,
                          TUScope, nullptr, CCC, CTK_ErrorRecovery)) {
        diagnoseTypo(C, PDiag(diag::err_undef_interface_suggest) << Id);
        IDecl = C.getCorrectionDeclAs<ObjCInterfaceDecl>();
        Id = IDecl->getIdentifier();
      }
    }
    ObjCInterfaceDecl *Def = dyn_cast_or_null<ObjCInterfaceDecl>(IDecl);
    // This routine must always return a class definition, if any.
    if (Def && Def->getDefinition())
        Def = Def->getDefinition();
    return Def;
  }
  
  /// getNonFieldDeclScope - Retrieves the innermost scope, starting
  /// from S, where a non-field would be declared. This routine copes
  /// with the difference between C and C++ scoping rules in structs and
  /// unions. For example, the following code is well-formed in C but
  /// ill-formed in C++:
  /// @code
  /// struct S6 {
  ///   enum { BAR } e;
  /// };
  ///
  /// void test_S6() {
  ///   struct S6 a;
  ///   a.e = BAR;
  /// }
  /// @endcode
  /// For the declaration of BAR, this routine will return a different
  /// scope. The scope S will be the scope of the unnamed enumeration
  /// within S6. In C++, this routine will return the scope associated
  /// with S6, because the enumeration's scope is a transparent
  /// context but structures can contain non-field names. In C, this
  /// routine will return the translation unit scope, since the
  /// enumeration's scope is a transparent context and structures cannot
  /// contain non-field names.
  Scope *Sema::getNonFieldDeclScope(Scope *S) {
    while (((S->getFlags() & Scope::DeclScope) == 0) ||
           (S->getEntity() && S->getEntity()->isTransparentContext()) ||
           (S->isClassScope() && !getLangOpts().CPlusPlus))
      S = S->getParent();
    return S;
  }
  
  /// Looks up the declaration of "struct objc_super" and
  /// saves it for later use in building builtin declaration of
  /// objc_msgSendSuper and objc_msgSendSuper_stret. If no such
  /// pre-existing declaration exists no action takes place.
  static void LookupPredefedObjCSuperType(Sema &ThisSema, Scope *S,
                                          IdentifierInfo *II) {
    if (!II->isStr("objc_msgSendSuper"))
      return;
    ASTContext &Context = ThisSema.Context;
  
    LookupResult Result(ThisSema, &Context.Idents.get("objc_super"),
                        SourceLocation(), Sema::LookupTagName);
    ThisSema.LookupName(Result, S);
    if (Result.getResultKind() == LookupResult::Found)
      if (const TagDecl *TD = Result.getAsSingle<TagDecl>())
        Context.setObjCSuperType(Context.getTagDeclType(TD));
  }
  
  static StringRef getHeaderName(Builtin::Context &BuiltinInfo, unsigned ID,
                                 ASTContext::GetBuiltinTypeError Error) {
    switch (Error) {
    case ASTContext::GE_None:
      return "";
    case ASTContext::GE_Missing_type:
      return BuiltinInfo.getHeaderName(ID);
    case ASTContext::GE_Missing_stdio:
      return "stdio.h";
    case ASTContext::GE_Missing_setjmp:
      return "setjmp.h";
    case ASTContext::GE_Missing_ucontext:
      return "ucontext.h";
    }
    llvm_unreachable("unhandled error kind");
  }
  
  /// LazilyCreateBuiltin - The specified Builtin-ID was first used at
  /// file scope.  lazily create a decl for it. ForRedeclaration is true
  /// if we're creating this built-in in anticipation of redeclaring the
  /// built-in.
  NamedDecl *Sema::LazilyCreateBuiltin(IdentifierInfo *II, unsigned ID,
                                       Scope *S, bool ForRedeclaration,
                                       SourceLocation Loc) {
    LookupPredefedObjCSuperType(*this, S, II);
  
    ASTContext::GetBuiltinTypeError Error;
    QualType R = Context.GetBuiltinType(ID, Error);
    if (Error) {
      if (ForRedeclaration)
        Diag(Loc, diag::warn_implicit_decl_requires_sysheader)
            << getHeaderName(Context.BuiltinInfo, ID, Error)
            << Context.BuiltinInfo.getName(ID);
      return nullptr;
    }
  
    if (!ForRedeclaration &&
        (Context.BuiltinInfo.isPredefinedLibFunction(ID) ||
         Context.BuiltinInfo.isHeaderDependentFunction(ID))) {
      Diag(Loc, diag::ext_implicit_lib_function_decl)
          << Context.BuiltinInfo.getName(ID) << R;
      if (Context.BuiltinInfo.getHeaderName(ID) &&
          !Diags.isIgnored(diag::ext_implicit_lib_function_decl, Loc))
        Diag(Loc, diag::note_include_header_or_declare)
            << Context.BuiltinInfo.getHeaderName(ID)
            << Context.BuiltinInfo.getName(ID);
    }
  
    if (R.isNull())
      return nullptr;
  
    DeclContext *Parent = Context.getTranslationUnitDecl();
    if (getLangOpts().CPlusPlus) {
      LinkageSpecDecl *CLinkageDecl =
          LinkageSpecDecl::Create(Context, Parent, Loc, Loc,
                                  LinkageSpecDecl::lang_c, false);
      CLinkageDecl->setImplicit();
      Parent->addDecl(CLinkageDecl);
      Parent = CLinkageDecl;
    }
  
    FunctionDecl *New = FunctionDecl::Create(Context,
                                             Parent,
                                             Loc, Loc, II, R, /*TInfo=*/nullptr,
                                             SC_Extern,
                                             false,
                                             R->isFunctionProtoType());
    New->setImplicit();
  
    // Create Decl objects for each parameter, adding them to the
    // FunctionDecl.
    if (const FunctionProtoType *FT = dyn_cast<FunctionProtoType>(R)) {
      SmallVector<ParmVarDecl*, 16> Params;
      for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i) {
        ParmVarDecl *parm =
            ParmVarDecl::Create(Context, New, SourceLocation(), SourceLocation(),
                                nullptr, FT->getParamType(i), /*TInfo=*/nullptr,
                                SC_None, nullptr);
        parm->setScopeInfo(0, i);
        Params.push_back(parm);
      }
      New->setParams(Params);
    }
  
    AddKnownFunctionAttributes(New);
    RegisterLocallyScopedExternCDecl(New, S);
  
    // TUScope is the translation-unit scope to insert this function into.
    // FIXME: This is hideous. We need to teach PushOnScopeChains to
    // relate Scopes to DeclContexts, and probably eliminate CurContext
    // entirely, but we're not there yet.
    DeclContext *SavedContext = CurContext;
    CurContext = Parent;
    PushOnScopeChains(New, TUScope);
    CurContext = SavedContext;
    return New;
  }
  
  /// Typedef declarations don't have linkage, but they still denote the same
  /// entity if their types are the same.
  /// FIXME: This is notionally doing the same thing as ASTReaderDecl's
  /// isSameEntity.
  static void filterNonConflictingPreviousTypedefDecls(Sema &S,
                                                       TypedefNameDecl *Decl,
                                                       LookupResult &Previous) {
    // This is only interesting when modules are enabled.
    if (!S.getLangOpts().Modules && !S.getLangOpts().ModulesLocalVisibility)
      return;
  
    // Empty sets are uninteresting.
    if (Previous.empty())
      return;
  
    LookupResult::Filter Filter = Previous.makeFilter();
    while (Filter.hasNext()) {
      NamedDecl *Old = Filter.next();
  
      // Non-hidden declarations are never ignored.
      if (S.isVisible(Old))
        continue;
  
      // Declarations of the same entity are not ignored, even if they have
      // different linkages.
      if (auto *OldTD = dyn_cast<TypedefNameDecl>(Old)) {
        if (S.Context.hasSameType(OldTD->getUnderlyingType(),
                                  Decl->getUnderlyingType()))
          continue;
  
        // If both declarations give a tag declaration a typedef name for linkage
        // purposes, then they declare the same entity.
        if (OldTD->getAnonDeclWithTypedefName(/*AnyRedecl*/true) &&
            Decl->getAnonDeclWithTypedefName())
          continue;
      }
  
      Filter.erase();
    }
  
    Filter.done();
  }
  
  bool Sema::isIncompatibleTypedef(TypeDecl *Old, TypedefNameDecl *New) {
    QualType OldType;
    if (TypedefNameDecl *OldTypedef = dyn_cast<TypedefNameDecl>(Old))
      OldType = OldTypedef->getUnderlyingType();
    else
      OldType = Context.getTypeDeclType(Old);
    QualType NewType = New->getUnderlyingType();
  
    if (NewType->isVariablyModifiedType()) {
      // Must not redefine a typedef with a variably-modified type.
      int Kind = isa<TypeAliasDecl>(Old) ? 1 : 0;
      Diag(New->getLocation(), diag::err_redefinition_variably_modified_typedef)
        << Kind << NewType;
      if (Old->getLocation().isValid())
        notePreviousDefinition(Old, New->getLocation());
      New->setInvalidDecl();
      return true;
    }
  
    if (OldType != NewType &&
        !OldType->isDependentType() &&
        !NewType->isDependentType() &&
        !Context.hasSameType(OldType, NewType)) {
      int Kind = isa<TypeAliasDecl>(Old) ? 1 : 0;
      Diag(New->getLocation(), diag::err_redefinition_different_typedef)
        << Kind << NewType << OldType;
      if (Old->getLocation().isValid())
        notePreviousDefinition(Old, New->getLocation());
      New->setInvalidDecl();
      return true;
    }
    return false;
  }
  
  /// MergeTypedefNameDecl - We just parsed a typedef 'New' which has the
  /// same name and scope as a previous declaration 'Old'.  Figure out
  /// how to resolve this situation, merging decls or emitting
  /// diagnostics as appropriate. If there was an error, set New to be invalid.
  ///
  void Sema::MergeTypedefNameDecl(Scope *S, TypedefNameDecl *New,
                                  LookupResult &OldDecls) {
    // If the new decl is known invalid already, don't bother doing any
    // merging checks.
    if (New->isInvalidDecl()) return;
  
    // Allow multiple definitions for ObjC built-in typedefs.
    // FIXME: Verify the underlying types are equivalent!
    if (getLangOpts().ObjC) {
      const IdentifierInfo *TypeID = New->getIdentifier();
      switch (TypeID->getLength()) {
      default: break;
      case 2:
        {
          if (!TypeID->isStr("id"))
            break;
          QualType T = New->getUnderlyingType();
          if (!T->isPointerType())
            break;
          if (!T->isVoidPointerType()) {
            QualType PT = T->getAs<PointerType>()->getPointeeType();
            if (!PT->isStructureType())
              break;
          }
          Context.setObjCIdRedefinitionType(T);
          // Install the built-in type for 'id', ignoring the current definition.
          New->setTypeForDecl(Context.getObjCIdType().getTypePtr());
          return;
        }
      case 5:
        if (!TypeID->isStr("Class"))
          break;
        Context.setObjCClassRedefinitionType(New->getUnderlyingType());
        // Install the built-in type for 'Class', ignoring the current definition.
        New->setTypeForDecl(Context.getObjCClassType().getTypePtr());
        return;
      case 3:
        if (!TypeID->isStr("SEL"))
          break;
        Context.setObjCSelRedefinitionType(New->getUnderlyingType());
        // Install the built-in type for 'SEL', ignoring the current definition.
        New->setTypeForDecl(Context.getObjCSelType().getTypePtr());
        return;
      }
      // Fall through - the typedef name was not a builtin type.
    }
  
    // Verify the old decl was also a type.
    TypeDecl *Old = OldDecls.getAsSingle<TypeDecl>();
    if (!Old) {
      Diag(New->getLocation(), diag::err_redefinition_different_kind)
        << New->getDeclName();
  
      NamedDecl *OldD = OldDecls.getRepresentativeDecl();
      if (OldD->getLocation().isValid())
        notePreviousDefinition(OldD, New->getLocation());
  
      return New->setInvalidDecl();
    }
  
    // If the old declaration is invalid, just give up here.
    if (Old->isInvalidDecl())
      return New->setInvalidDecl();
  
    if (auto *OldTD = dyn_cast<TypedefNameDecl>(Old)) {
      auto *OldTag = OldTD->getAnonDeclWithTypedefName(/*AnyRedecl*/true);
      auto *NewTag = New->getAnonDeclWithTypedefName();
      NamedDecl *Hidden = nullptr;
      if (OldTag && NewTag &&
          OldTag->getCanonicalDecl() != NewTag->getCanonicalDecl() &&
          !hasVisibleDefinition(OldTag, &Hidden)) {
        // There is a definition of this tag, but it is not visible. Use it
        // instead of our tag.
        New->setTypeForDecl(OldTD->getTypeForDecl());
        if (OldTD->isModed())
          New->setModedTypeSourceInfo(OldTD->getTypeSourceInfo(),
                                      OldTD->getUnderlyingType());
        else
          New->setTypeSourceInfo(OldTD->getTypeSourceInfo());
  
        // Make the old tag definition visible.
        makeMergedDefinitionVisible(Hidden);
  
        // If this was an unscoped enumeration, yank all of its enumerators
        // out of the scope.
        if (isa<EnumDecl>(NewTag)) {
          Scope *EnumScope = getNonFieldDeclScope(S);
          for (auto *D : NewTag->decls()) {
            auto *ED = cast<EnumConstantDecl>(D);
            assert(EnumScope->isDeclScope(ED));
            EnumScope->RemoveDecl(ED);
            IdResolver.RemoveDecl(ED);
            ED->getLexicalDeclContext()->removeDecl(ED);
          }
        }
      }
    }
  
    // If the typedef types are not identical, reject them in all languages and
    // with any extensions enabled.
    if (isIncompatibleTypedef(Old, New))
      return;
  
    // The types match.  Link up the redeclaration chain and merge attributes if
    // the old declaration was a typedef.
    if (TypedefNameDecl *Typedef = dyn_cast<TypedefNameDecl>(Old)) {
      New->setPreviousDecl(Typedef);
      mergeDeclAttributes(New, Old);
    }
  
    if (getLangOpts().MicrosoftExt)
      return;
  
    if (getLangOpts().CPlusPlus) {
      // C++ [dcl.typedef]p2:
      //   In a given non-class scope, a typedef specifier can be used to
      //   redefine the name of any type declared in that scope to refer
      //   to the type to which it already refers.
      if (!isa<CXXRecordDecl>(CurContext))
        return;
  
      // C++0x [dcl.typedef]p4:
      //   In a given class scope, a typedef specifier can be used to redefine
      //   any class-name declared in that scope that is not also a typedef-name
      //   to refer to the type to which it already refers.
      //
      // This wording came in via DR424, which was a correction to the
      // wording in DR56, which accidentally banned code like:
      //
      //   struct S {
      //     typedef struct A { } A;
      //   };
      //
      // in the C++03 standard. We implement the C++0x semantics, which
      // allow the above but disallow
      //
      //   struct S {
      //     typedef int I;
      //     typedef int I;
      //   };
      //
      // since that was the intent of DR56.
      if (!isa<TypedefNameDecl>(Old))
        return;
  
      Diag(New->getLocation(), diag::err_redefinition)
        << New->getDeclName();
      notePreviousDefinition(Old, New->getLocation());
      return New->setInvalidDecl();
    }
  
    // Modules always permit redefinition of typedefs, as does C11.
    if (getLangOpts().Modules || getLangOpts().C11)
      return;
  
    // If we have a redefinition of a typedef in C, emit a warning.  This warning
    // is normally mapped to an error, but can be controlled with
    // -Wtypedef-redefinition.  If either the original or the redefinition is
    // in a system header, don't emit this for compatibility with GCC.
    if (getDiagnostics().getSuppressSystemWarnings() &&
        // Some standard types are defined implicitly in Clang (e.g. OpenCL).
        (Old->isImplicit() ||
         Context.getSourceManager().isInSystemHeader(Old->getLocation()) ||
         Context.getSourceManager().isInSystemHeader(New->getLocation())))
      return;
  
    Diag(New->getLocation(), diag::ext_redefinition_of_typedef)
      << New->getDeclName();
    notePreviousDefinition(Old, New->getLocation());
  }
  
  /// DeclhasAttr - returns true if decl Declaration already has the target
  /// attribute.
  static bool DeclHasAttr(const Decl *D, const Attr *A) {
    const OwnershipAttr *OA = dyn_cast<OwnershipAttr>(A);
    const AnnotateAttr *Ann = dyn_cast<AnnotateAttr>(A);
    for (const auto *i : D->attrs())
      if (i->getKind() == A->getKind()) {
        if (Ann) {
          if (Ann->getAnnotation() == cast<AnnotateAttr>(i)->getAnnotation())
            return true;
          continue;
        }
        // FIXME: Don't hardcode this check
        if (OA && isa<OwnershipAttr>(i))
          return OA->getOwnKind() == cast<OwnershipAttr>(i)->getOwnKind();
        return true;
      }
  
    return false;
  }
  
  static bool isAttributeTargetADefinition(Decl *D) {
    if (VarDecl *VD = dyn_cast<VarDecl>(D))
      return VD->isThisDeclarationADefinition();
    if (TagDecl *TD = dyn_cast<TagDecl>(D))
      return TD->isCompleteDefinition() || TD->isBeingDefined();
    return true;
  }
  
  /// Merge alignment attributes from \p Old to \p New, taking into account the
  /// special semantics of C11's _Alignas specifier and C++11's alignas attribute.
  ///
  /// \return \c true if any attributes were added to \p New.
  static bool mergeAlignedAttrs(Sema &S, NamedDecl *New, Decl *Old) {
    // Look for alignas attributes on Old, and pick out whichever attribute
    // specifies the strictest alignment requirement.
    AlignedAttr *OldAlignasAttr = nullptr;
    AlignedAttr *OldStrictestAlignAttr = nullptr;
    unsigned OldAlign = 0;
    for (auto *I : Old->specific_attrs<AlignedAttr>()) {
      // FIXME: We have no way of representing inherited dependent alignments
      // in a case like:
      //   template<int A, int B> struct alignas(A) X;
      //   template<int A, int B> struct alignas(B) X {};
      // For now, we just ignore any alignas attributes which are not on the
      // definition in such a case.
      if (I->isAlignmentDependent())
        return false;
  
      if (I->isAlignas())
        OldAlignasAttr = I;
  
      unsigned Align = I->getAlignment(S.Context);
      if (Align > OldAlign) {
        OldAlign = Align;
        OldStrictestAlignAttr = I;
      }
    }
  
    // Look for alignas attributes on New.
    AlignedAttr *NewAlignasAttr = nullptr;
    unsigned NewAlign = 0;
    for (auto *I : New->specific_attrs<AlignedAttr>()) {
      if (I->isAlignmentDependent())
        return false;
  
      if (I->isAlignas())
        NewAlignasAttr = I;
  
      unsigned Align = I->getAlignment(S.Context);
      if (Align > NewAlign)
        NewAlign = Align;
    }
  
    if (OldAlignasAttr && NewAlignasAttr && OldAlign != NewAlign) {
      // Both declarations have 'alignas' attributes. We require them to match.
      // C++11 [dcl.align]p6 and C11 6.7.5/7 both come close to saying this, but
      // fall short. (If two declarations both have alignas, they must both match
      // every definition, and so must match each other if there is a definition.)
  
      // If either declaration only contains 'alignas(0)' specifiers, then it
      // specifies the natural alignment for the type.
      if (OldAlign == 0 || NewAlign == 0) {
        QualType Ty;
        if (ValueDecl *VD = dyn_cast<ValueDecl>(New))
          Ty = VD->getType();
        else
          Ty = S.Context.getTagDeclType(cast<TagDecl>(New));
  
        if (OldAlign == 0)
          OldAlign = S.Context.getTypeAlign(Ty);
        if (NewAlign == 0)
          NewAlign = S.Context.getTypeAlign(Ty);
      }
  
      if (OldAlign != NewAlign) {
        S.Diag(NewAlignasAttr->getLocation(), diag::err_alignas_mismatch)
          << (unsigned)S.Context.toCharUnitsFromBits(OldAlign).getQuantity()
          << (unsigned)S.Context.toCharUnitsFromBits(NewAlign).getQuantity();
        S.Diag(OldAlignasAttr->getLocation(), diag::note_previous_declaration);
      }
    }
  
    if (OldAlignasAttr && !NewAlignasAttr && isAttributeTargetADefinition(New)) {
      // C++11 [dcl.align]p6:
      //   if any declaration of an entity has an alignment-specifier,
      //   every defining declaration of that entity shall specify an
      //   equivalent alignment.
      // C11 6.7.5/7:
      //   If the definition of an object does not have an alignment
      //   specifier, any other declaration of that object shall also
      //   have no alignment specifier.
      S.Diag(New->getLocation(), diag::err_alignas_missing_on_definition)
        << OldAlignasAttr;
      S.Diag(OldAlignasAttr->getLocation(), diag::note_alignas_on_declaration)
        << OldAlignasAttr;
    }
  
    bool AnyAdded = false;
  
    // Ensure we have an attribute representing the strictest alignment.
    if (OldAlign > NewAlign) {
      AlignedAttr *Clone = OldStrictestAlignAttr->clone(S.Context);
      Clone->setInherited(true);
      New->addAttr(Clone);
      AnyAdded = true;
    }
  
    // Ensure we have an alignas attribute if the old declaration had one.
    if (OldAlignasAttr && !NewAlignasAttr &&
        !(AnyAdded && OldStrictestAlignAttr->isAlignas())) {
      AlignedAttr *Clone = OldAlignasAttr->clone(S.Context);
      Clone->setInherited(true);
      New->addAttr(Clone);
      AnyAdded = true;
    }
  
    return AnyAdded;
  }
  
  static bool mergeDeclAttribute(Sema &S, NamedDecl *D,
                                 const InheritableAttr *Attr,
                                 Sema::AvailabilityMergeKind AMK) {
    // This function copies an attribute Attr from a previous declaration to the
    // new declaration D if the new declaration doesn't itself have that attribute
    // yet or if that attribute allows duplicates.
    // If you're adding a new attribute that requires logic different from
    // "use explicit attribute on decl if present, else use attribute from
    // previous decl", for example if the attribute needs to be consistent
    // between redeclarations, you need to call a custom merge function here.
    InheritableAttr *NewAttr = nullptr;
    unsigned AttrSpellingListIndex = Attr->getSpellingListIndex();
    if (const auto *AA = dyn_cast<AvailabilityAttr>(Attr))
      NewAttr = S.mergeAvailabilityAttr(
          D, AA->getRange(), AA->getPlatform(), AA->isImplicit(),
          AA->getIntroduced(), AA->getDeprecated(), AA->getObsoleted(),
          AA->getUnavailable(), AA->getMessage(), AA->getStrict(),
          AA->getReplacement(), AMK, AA->getPriority(), AttrSpellingListIndex);
    else if (const auto *VA = dyn_cast<VisibilityAttr>(Attr))
      NewAttr = S.mergeVisibilityAttr(D, VA->getRange(), VA->getVisibility(),
                                      AttrSpellingListIndex);
    else if (const auto *VA = dyn_cast<TypeVisibilityAttr>(Attr))
      NewAttr = S.mergeTypeVisibilityAttr(D, VA->getRange(), VA->getVisibility(),
                                          AttrSpellingListIndex);
    else if (const auto *ImportA = dyn_cast<DLLImportAttr>(Attr))
      NewAttr = S.mergeDLLImportAttr(D, ImportA->getRange(),
                                     AttrSpellingListIndex);
    else if (const auto *ExportA = dyn_cast<DLLExportAttr>(Attr))
      NewAttr = S.mergeDLLExportAttr(D, ExportA->getRange(),
                                     AttrSpellingListIndex);
    else if (const auto *FA = dyn_cast<FormatAttr>(Attr))
      NewAttr = S.mergeFormatAttr(D, FA->getRange(), FA->getType(),
                                  FA->getFormatIdx(), FA->getFirstArg(),
                                  AttrSpellingListIndex);
    else if (const auto *SA = dyn_cast<SectionAttr>(Attr))
      NewAttr = S.mergeSectionAttr(D, SA->getRange(), SA->getName(),
                                   AttrSpellingListIndex);
    else if (const auto *CSA = dyn_cast<CodeSegAttr>(Attr))
      NewAttr = S.mergeCodeSegAttr(D, CSA->getRange(), CSA->getName(),
                                   AttrSpellingListIndex);
    else if (const auto *IA = dyn_cast<MSInheritanceAttr>(Attr))
      NewAttr = S.mergeMSInheritanceAttr(D, IA->getRange(), IA->getBestCase(),
                                         AttrSpellingListIndex,
                                         IA->getSemanticSpelling());
    else if (const auto *AA = dyn_cast<AlwaysInlineAttr>(Attr))
      NewAttr = S.mergeAlwaysInlineAttr(D, AA->getRange(),
                                        &S.Context.Idents.get(AA->getSpelling()),
                                        AttrSpellingListIndex);
    else if (S.getLangOpts().CUDA && isa<FunctionDecl>(D) &&
             (isa<CUDAHostAttr>(Attr) || isa<CUDADeviceAttr>(Attr) ||
              isa<CUDAGlobalAttr>(Attr))) {
      // CUDA target attributes are part of function signature for
      // overloading purposes and must not be merged.
      return false;
    } else if (const auto *MA = dyn_cast<MinSizeAttr>(Attr))
      NewAttr = S.mergeMinSizeAttr(D, MA->getRange(), AttrSpellingListIndex);
    else if (const auto *OA = dyn_cast<OptimizeNoneAttr>(Attr))
      NewAttr = S.mergeOptimizeNoneAttr(D, OA->getRange(), AttrSpellingListIndex);
    else if (const auto *InternalLinkageA = dyn_cast<InternalLinkageAttr>(Attr))
      NewAttr = S.mergeInternalLinkageAttr(D, *InternalLinkageA);
    else if (const auto *CommonA = dyn_cast<CommonAttr>(Attr))
      NewAttr = S.mergeCommonAttr(D, *CommonA);
    else if (isa<AlignedAttr>(Attr))
      // AlignedAttrs are handled separately, because we need to handle all
      // such attributes on a declaration at the same time.
      NewAttr = nullptr;
    else if ((isa<DeprecatedAttr>(Attr) || isa<UnavailableAttr>(Attr)) &&
             (AMK == Sema::AMK_Override ||
              AMK == Sema::AMK_ProtocolImplementation))
      NewAttr = nullptr;
    else if (const auto *UA = dyn_cast<UuidAttr>(Attr))
      NewAttr = S.mergeUuidAttr(D, UA->getRange(), AttrSpellingListIndex,
                                UA->getGuid());
    else if (const auto *SLHA = dyn_cast<SpeculativeLoadHardeningAttr>(Attr))
      NewAttr = S.mergeSpeculativeLoadHardeningAttr(D, *SLHA);
    else if (const auto *SLHA = dyn_cast<NoSpeculativeLoadHardeningAttr>(Attr))
      NewAttr = S.mergeNoSpeculativeLoadHardeningAttr(D, *SLHA);
    else if (Attr->shouldInheritEvenIfAlreadyPresent() || !DeclHasAttr(D, Attr))
      NewAttr = cast<InheritableAttr>(Attr->clone(S.Context));
  
    if (NewAttr) {
      NewAttr->setInherited(true);
      D->addAttr(NewAttr);
      if (isa<MSInheritanceAttr>(NewAttr))
        S.Consumer.AssignInheritanceModel(cast<CXXRecordDecl>(D));
      return true;
    }
  
    return false;
  }
  
  static const NamedDecl *getDefinition(const Decl *D) {
    if (const TagDecl *TD = dyn_cast<TagDecl>(D))
      return TD->getDefinition();
    if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
      const VarDecl *Def = VD->getDefinition();
      if (Def)
        return Def;
      return VD->getActingDefinition();
    }
    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
      return FD->getDefinition();
    return nullptr;
  }
  
  static bool hasAttribute(const Decl *D, attr::Kind Kind) {
    for (const auto *Attribute : D->attrs())
      if (Attribute->getKind() == Kind)
        return true;
    return false;
  }
  
  /// checkNewAttributesAfterDef - If we already have a definition, check that
  /// there are no new attributes in this declaration.
  static void checkNewAttributesAfterDef(Sema &S, Decl *New, const Decl *Old) {
    if (!New->hasAttrs())
      return;
  
    const NamedDecl *Def = getDefinition(Old);
    if (!Def || Def == New)
      return;
  
    AttrVec &NewAttributes = New->getAttrs();
    for (unsigned I = 0, E = NewAttributes.size(); I != E;) {
      const Attr *NewAttribute = NewAttributes[I];
  
      if (isa<AliasAttr>(NewAttribute) || isa<IFuncAttr>(NewAttribute)) {
        if (FunctionDecl *FD = dyn_cast<FunctionDecl>(New)) {
          Sema::SkipBodyInfo SkipBody;
          S.CheckForFunctionRedefinition(FD, cast<FunctionDecl>(Def), &SkipBody);
  
          // If we're skipping this definition, drop the "alias" attribute.
          if (SkipBody.ShouldSkip) {
            NewAttributes.erase(NewAttributes.begin() + I);
            --E;
            continue;
          }
        } else {
          VarDecl *VD = cast<VarDecl>(New);
          unsigned Diag = cast<VarDecl>(Def)->isThisDeclarationADefinition() ==
                                  VarDecl::TentativeDefinition
                              ? diag::err_alias_after_tentative
                              : diag::err_redefinition;
          S.Diag(VD->getLocation(), Diag) << VD->getDeclName();
          if (Diag == diag::err_redefinition)
            S.notePreviousDefinition(Def, VD->getLocation());
          else
            S.Diag(Def->getLocation(), diag::note_previous_definition);
          VD->setInvalidDecl();
        }
        ++I;
        continue;
      }
  
      if (const VarDecl *VD = dyn_cast<VarDecl>(Def)) {
        // Tentative definitions are only interesting for the alias check above.
        if (VD->isThisDeclarationADefinition() != VarDecl::Definition) {
          ++I;
          continue;
        }
      }
  
      if (hasAttribute(Def, NewAttribute->getKind())) {
        ++I;
        continue; // regular attr merging will take care of validating this.
      }
  
      if (isa<C11NoReturnAttr>(NewAttribute)) {
        // C's _Noreturn is allowed to be added to a function after it is defined.
        ++I;
        continue;
      } else if (const AlignedAttr *AA = dyn_cast<AlignedAttr>(NewAttribute)) {
        if (AA->isAlignas()) {
          // C++11 [dcl.align]p6:
          //   if any declaration of an entity has an alignment-specifier,
          //   every defining declaration of that entity shall specify an
          //   equivalent alignment.
          // C11 6.7.5/7:
          //   If the definition of an object does not have an alignment
          //   specifier, any other declaration of that object shall also
          //   have no alignment specifier.
          S.Diag(Def->getLocation(), diag::err_alignas_missing_on_definition)
            << AA;
          S.Diag(NewAttribute->getLocation(), diag::note_alignas_on_declaration)
            << AA;
          NewAttributes.erase(NewAttributes.begin() + I);
          --E;
          continue;
        }
      }
  
      S.Diag(NewAttribute->getLocation(),
             diag::warn_attribute_precede_definition);
      S.Diag(Def->getLocation(), diag::note_previous_definition);
      NewAttributes.erase(NewAttributes.begin() + I);
      --E;
    }
  }
  
  /// mergeDeclAttributes - Copy attributes from the Old decl to the New one.
  void Sema::mergeDeclAttributes(NamedDecl *New, Decl *Old,
                                 AvailabilityMergeKind AMK) {
    if (UsedAttr *OldAttr = Old->getMostRecentDecl()->getAttr<UsedAttr>()) {
      UsedAttr *NewAttr = OldAttr->clone(Context);
      NewAttr->setInherited(true);
      New->addAttr(NewAttr);
    }
  
    if (!Old->hasAttrs() && !New->hasAttrs())
      return;
  
    // Attributes declared post-definition are currently ignored.
    checkNewAttributesAfterDef(*this, New, Old);
  
    if (AsmLabelAttr *NewA = New->getAttr<AsmLabelAttr>()) {
      if (AsmLabelAttr *OldA = Old->getAttr<AsmLabelAttr>()) {
        if (OldA->getLabel() != NewA->getLabel()) {
          // This redeclaration changes __asm__ label.
          Diag(New->getLocation(), diag::err_different_asm_label);
          Diag(OldA->getLocation(), diag::note_previous_declaration);
        }
      } else if (Old->isUsed()) {
        // This redeclaration adds an __asm__ label to a declaration that has
        // already been ODR-used.
        Diag(New->getLocation(), diag::err_late_asm_label_name)
          << isa<FunctionDecl>(Old) << New->getAttr<AsmLabelAttr>()->getRange();
      }
    }
  
    // Re-declaration cannot add abi_tag's.
    if (const auto *NewAbiTagAttr = New->getAttr<AbiTagAttr>()) {
      if (const auto *OldAbiTagAttr = Old->getAttr<AbiTagAttr>()) {
        for (const auto &NewTag : NewAbiTagAttr->tags()) {
          if (std::find(OldAbiTagAttr->tags_begin(), OldAbiTagAttr->tags_end(),
                        NewTag) == OldAbiTagAttr->tags_end()) {
            Diag(NewAbiTagAttr->getLocation(),
                 diag::err_new_abi_tag_on_redeclaration)
                << NewTag;
            Diag(OldAbiTagAttr->getLocation(), diag::note_previous_declaration);
          }
        }
      } else {
        Diag(NewAbiTagAttr->getLocation(), diag::err_abi_tag_on_redeclaration);
        Diag(Old->getLocation(), diag::note_previous_declaration);
      }
    }
  
    // This redeclaration adds a section attribute.
    if (New->hasAttr<SectionAttr>() && !Old->hasAttr<SectionAttr>()) {
      if (auto *VD = dyn_cast<VarDecl>(New)) {
        if (VD->isThisDeclarationADefinition() == VarDecl::DeclarationOnly) {
          Diag(New->getLocation(), diag::warn_attribute_section_on_redeclaration);
          Diag(Old->getLocation(), diag::note_previous_declaration);
        }
      }
    }
  
    // Redeclaration adds code-seg attribute.
    const auto *NewCSA = New->getAttr<CodeSegAttr>();
    if (NewCSA && !Old->hasAttr<CodeSegAttr>() &&
        !NewCSA->isImplicit() && isa<CXXMethodDecl>(New)) {
      Diag(New->getLocation(), diag::warn_mismatched_section)
           << 0 /*codeseg*/;
      Diag(Old->getLocation(), diag::note_previous_declaration);
    }
  
    if (!Old->hasAttrs())
      return;
  
    bool foundAny = New->hasAttrs();
  
    // Ensure that any moving of objects within the allocated map is done before
    // we process them.
    if (!foundAny) New->setAttrs(AttrVec());
  
    for (auto *I : Old->specific_attrs<InheritableAttr>()) {
      // Ignore deprecated/unavailable/availability attributes if requested.
      AvailabilityMergeKind LocalAMK = AMK_None;
      if (isa<DeprecatedAttr>(I) ||
          isa<UnavailableAttr>(I) ||
          isa<AvailabilityAttr>(I)) {
        switch (AMK) {
        case AMK_None:
          continue;
  
        case AMK_Redeclaration:
        case AMK_Override:
        case AMK_ProtocolImplementation:
          LocalAMK = AMK;
          break;
        }
      }
  
      // Already handled.
      if (isa<UsedAttr>(I))
        continue;
  
      if (mergeDeclAttribute(*this, New, I, LocalAMK))
        foundAny = true;
    }
  
    if (mergeAlignedAttrs(*this, New, Old))
      foundAny = true;
  
    if (!foundAny) New->dropAttrs();
  }
  
  /// mergeParamDeclAttributes - Copy attributes from the old parameter
  /// to the new one.
  static void mergeParamDeclAttributes(ParmVarDecl *newDecl,
                                       const ParmVarDecl *oldDecl,
                                       Sema &S) {
    // C++11 [dcl.attr.depend]p2:
    //   The first declaration of a function shall specify the
    //   carries_dependency attribute for its declarator-id if any declaration
    //   of the function specifies the carries_dependency attribute.
    const CarriesDependencyAttr *CDA = newDecl->getAttr<CarriesDependencyAttr>();
    if (CDA && !oldDecl->hasAttr<CarriesDependencyAttr>()) {
      S.Diag(CDA->getLocation(),
             diag::err_carries_dependency_missing_on_first_decl) << 1/*Param*/;
      // Find the first declaration of the parameter.
      // FIXME: Should we build redeclaration chains for function parameters?
      const FunctionDecl *FirstFD =
        cast<FunctionDecl>(oldDecl->getDeclContext())->getFirstDecl();
      const ParmVarDecl *FirstVD =
        FirstFD->getParamDecl(oldDecl->getFunctionScopeIndex());
      S.Diag(FirstVD->getLocation(),
             diag::note_carries_dependency_missing_first_decl) << 1/*Param*/;
    }
  
    if (!oldDecl->hasAttrs())
      return;
  
    bool foundAny = newDecl->hasAttrs();
  
    // Ensure that any moving of objects within the allocated map is
    // done before we process them.
    if (!foundAny) newDecl->setAttrs(AttrVec());
  
    for (const auto *I : oldDecl->specific_attrs<InheritableParamAttr>()) {
      if (!DeclHasAttr(newDecl, I)) {
        InheritableAttr *newAttr =
          cast<InheritableParamAttr>(I->clone(S.Context));
        newAttr->setInherited(true);
        newDecl->addAttr(newAttr);
        foundAny = true;
      }
    }
  
    if (!foundAny) newDecl->dropAttrs();
  }
  
  static void mergeParamDeclTypes(ParmVarDecl *NewParam,
                                  const ParmVarDecl *OldParam,
                                  Sema &S) {
    if (auto Oldnullability = OldParam->getType()->getNullability(S.Context)) {
      if (auto Newnullability = NewParam->getType()->getNullability(S.Context)) {
        if (*Oldnullability != *Newnullability) {
          S.Diag(NewParam->getLocation(), diag::warn_mismatched_nullability_attr)
            << DiagNullabilityKind(
                 *Newnullability,
                 ((NewParam->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability)
                  != 0))
            << DiagNullabilityKind(
                 *Oldnullability,
                 ((OldParam->getObjCDeclQualifier() & Decl::OBJC_TQ_CSNullability)
                  != 0));
          S.Diag(OldParam->getLocation(), diag::note_previous_declaration);
        }
      } else {
        QualType NewT = NewParam->getType();
        NewT = S.Context.getAttributedType(
                           AttributedType::getNullabilityAttrKind(*Oldnullability),
                           NewT, NewT);
        NewParam->setType(NewT);
      }
    }
  }
  
  namespace {
  
  /// Used in MergeFunctionDecl to keep track of function parameters in
  /// C.
  struct GNUCompatibleParamWarning {
    ParmVarDecl *OldParm;
    ParmVarDecl *NewParm;
    QualType PromotedType;
  };
  
  } // end anonymous namespace
  
  /// getSpecialMember - get the special member enum for a method.
  Sema::CXXSpecialMember Sema::getSpecialMember(const CXXMethodDecl *MD) {
    if (const CXXConstructorDecl *Ctor = dyn_cast<CXXConstructorDecl>(MD)) {
      if (Ctor->isDefaultConstructor())
        return Sema::CXXDefaultConstructor;
  
      if (Ctor->isCopyConstructor())
        return Sema::CXXCopyConstructor;
  
      if (Ctor->isMoveConstructor())
        return Sema::CXXMoveConstructor;
    } else if (isa<CXXDestructorDecl>(MD)) {
      return Sema::CXXDestructor;
    } else if (MD->isCopyAssignmentOperator()) {
      return Sema::CXXCopyAssignment;
    } else if (MD->isMoveAssignmentOperator()) {
      return Sema::CXXMoveAssignment;
    }
  
    return Sema::CXXInvalid;
  }
  
  // Determine whether the previous declaration was a definition, implicit
  // declaration, or a declaration.
  template <typename T>
  static std::pair<diag::kind, SourceLocation>
  getNoteDiagForInvalidRedeclaration(const T *Old, const T *New) {
    diag::kind PrevDiag;
    SourceLocation OldLocation = Old->getLocation();
    if (Old->isThisDeclarationADefinition())
      PrevDiag = diag::note_previous_definition;
    else if (Old->isImplicit()) {
      PrevDiag = diag::note_previous_implicit_declaration;
      if (OldLocation.isInvalid())
        OldLocation = New->getLocation();
    } else
      PrevDiag = diag::note_previous_declaration;
    return std::make_pair(PrevDiag, OldLocation);
  }
  
  /// canRedefineFunction - checks if a function can be redefined. Currently,
  /// only extern inline functions can be redefined, and even then only in
  /// GNU89 mode.
  static bool canRedefineFunction(const FunctionDecl *FD,
                                  const LangOptions& LangOpts) {
    return ((FD->hasAttr<GNUInlineAttr>() || LangOpts.GNUInline) &&
            !LangOpts.CPlusPlus &&
            FD->isInlineSpecified() &&
            FD->getStorageClass() == SC_Extern);
  }
  
  const AttributedType *Sema::getCallingConvAttributedType(QualType T) const {
    const AttributedType *AT = T->getAs<AttributedType>();
    while (AT && !AT->isCallingConv())
      AT = AT->getModifiedType()->getAs<AttributedType>();
    return AT;
  }
  
  template <typename T>
  static bool haveIncompatibleLanguageLinkages(const T *Old, const T *New) {
    const DeclContext *DC = Old->getDeclContext();
    if (DC->isRecord())
      return false;
  
    LanguageLinkage OldLinkage = Old->getLanguageLinkage();
    if (OldLinkage == CXXLanguageLinkage && New->isInExternCContext())
      return true;
    if (OldLinkage == CLanguageLinkage && New->isInExternCXXContext())
      return true;
    return false;
  }
  
  template<typename T> static bool isExternC(T *D) { return D->isExternC(); }
  static bool isExternC(VarTemplateDecl *) { return false; }
  
  /// Check whether a redeclaration of an entity introduced by a
  /// using-declaration is valid, given that we know it's not an overload
  /// (nor a hidden tag declaration).
  template<typename ExpectedDecl>
  static bool checkUsingShadowRedecl(Sema &S, UsingShadowDecl *OldS,
                                     ExpectedDecl *New) {
    // C++11 [basic.scope.declarative]p4:
    //   Given a set of declarations in a single declarative region, each of
    //   which specifies the same unqualified name,
    //   -- they shall all refer to the same entity, or all refer to functions
    //      and function templates; or
    //   -- exactly one declaration shall declare a class name or enumeration
    //      name that is not a typedef name and the other declarations shall all
    //      refer to the same variable or enumerator, or all refer to functions
    //      and function templates; in this case the class name or enumeration
    //      name is hidden (3.3.10).
  
    // C++11 [namespace.udecl]p14:
    //   If a function declaration in namespace scope or block scope has the
    //   same name and the same parameter-type-list as a function introduced
    //   by a using-declaration, and the declarations do not declare the same
    //   function, the program is ill-formed.
  
    auto *Old = dyn_cast<ExpectedDecl>(OldS->getTargetDecl());
    if (Old &&
        !Old->getDeclContext()->getRedeclContext()->Equals(
            New->getDeclContext()->getRedeclContext()) &&
        !(isExternC(Old) && isExternC(New)))
      Old = nullptr;
  
    if (!Old) {
      S.Diag(New->getLocation(), diag::err_using_decl_conflict_reverse);
      S.Diag(OldS->getTargetDecl()->getLocation(), diag::note_using_decl_target);
      S.Diag(OldS->getUsingDecl()->getLocation(), diag::note_using_decl) << 0;
      return true;
    }
    return false;
  }
  
  static bool hasIdenticalPassObjectSizeAttrs(const FunctionDecl *A,
                                              const FunctionDecl *B) {
    assert(A->getNumParams() == B->getNumParams());
  
    auto AttrEq = [](const ParmVarDecl *A, const ParmVarDecl *B) {
      const auto *AttrA = A->getAttr<PassObjectSizeAttr>();
      const auto *AttrB = B->getAttr<PassObjectSizeAttr>();
      if (AttrA == AttrB)
        return true;
      return AttrA && AttrB && AttrA->getType() == AttrB->getType() &&
             AttrA->isDynamic() == AttrB->isDynamic();
    };
  
    return std::equal(A->param_begin(), A->param_end(), B->param_begin(), AttrEq);
  }
  
  /// If necessary, adjust the semantic declaration context for a qualified
  /// declaration to name the correct inline namespace within the qualifier.
  static void adjustDeclContextForDeclaratorDecl(DeclaratorDecl *NewD,
                                                 DeclaratorDecl *OldD) {
    // The only case where we need to update the DeclContext is when
    // redeclaration lookup for a qualified name finds a declaration
    // in an inline namespace within the context named by the qualifier:
    //
    //   inline namespace N { int f(); }
    //   int ::f(); // Sema DC needs adjusting from :: to N::.
    //
    // For unqualified declarations, the semantic context *can* change
    // along the redeclaration chain (for local extern declarations,
    // extern "C" declarations, and friend declarations in particular).
    if (!NewD->getQualifier())
      return;
  
    // NewD is probably already in the right context.
    auto *NamedDC = NewD->getDeclContext()->getRedeclContext();
    auto *SemaDC = OldD->getDeclContext()->getRedeclContext();
    if (NamedDC->Equals(SemaDC))
      return;
  
    assert((NamedDC->InEnclosingNamespaceSetOf(SemaDC) ||
            NewD->isInvalidDecl() || OldD->isInvalidDecl()) &&
           "unexpected context for redeclaration");
  
    auto *LexDC = NewD->getLexicalDeclContext();
    auto FixSemaDC = [=](NamedDecl *D) {
      if (!D)
        return;
      D->setDeclContext(SemaDC);
      D->setLexicalDeclContext(LexDC);
    };
  
    FixSemaDC(NewD);
    if (auto *FD = dyn_cast<FunctionDecl>(NewD))
      FixSemaDC(FD->getDescribedFunctionTemplate());
    else if (auto *VD = dyn_cast<VarDecl>(NewD))
      FixSemaDC(VD->getDescribedVarTemplate());
  }
  
  /// MergeFunctionDecl - We just parsed a function 'New' from
  /// declarator D which has the same name and scope as a previous
  /// declaration 'Old'.  Figure out how to resolve this situation,
  /// merging decls or emitting diagnostics as appropriate.
  ///
  /// In C++, New and Old must be declarations that are not
  /// overloaded. Use IsOverload to determine whether New and Old are
  /// overloaded, and to select the Old declaration that New should be
  /// merged with.
  ///
  /// Returns true if there was an error, false otherwise.
  bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD,
                               Scope *S, bool MergeTypeWithOld) {
    // Verify the old decl was also a function.
    FunctionDecl *Old = OldD->getAsFunction();
    if (!Old) {
      if (UsingShadowDecl *Shadow = dyn_cast<UsingShadowDecl>(OldD)) {
        if (New->getFriendObjectKind()) {
          Diag(New->getLocation(), diag::err_using_decl_friend);
          Diag(Shadow->getTargetDecl()->getLocation(),
               diag::note_using_decl_target);
          Diag(Shadow->getUsingDecl()->getLocation(),
               diag::note_using_decl) << 0;
          return true;
        }
  
        // Check whether the two declarations might declare the same function.
        if (checkUsingShadowRedecl<FunctionDecl>(*this, Shadow, New))
          return true;
        OldD = Old = cast<FunctionDecl>(Shadow->getTargetDecl());
      } else {
        Diag(New->getLocation(), diag::err_redefinition_different_kind)
          << New->getDeclName();
        notePreviousDefinition(OldD, New->getLocation());
        return true;
      }
    }
  
    // If the old declaration is invalid, just give up here.
    if (Old->isInvalidDecl())
      return true;
  
    // Disallow redeclaration of some builtins.
    if (!getASTContext().canBuiltinBeRedeclared(Old)) {
      Diag(New->getLocation(), diag::err_builtin_redeclare) << Old->getDeclName();
      Diag(Old->getLocation(), diag::note_previous_builtin_declaration)
          << Old << Old->getType();
      return true;
    }
  
    diag::kind PrevDiag;
    SourceLocation OldLocation;
    std::tie(PrevDiag, OldLocation) =
        getNoteDiagForInvalidRedeclaration(Old, New);
  
    // Don't complain about this if we're in GNU89 mode and the old function
    // is an extern inline function.
    // Don't complain about specializations. They are not supposed to have
    // storage classes.
    if (!isa<CXXMethodDecl>(New) && !isa<CXXMethodDecl>(Old) &&
        New->getStorageClass() == SC_Static &&
        Old->hasExternalFormalLinkage() &&
        !New->getTemplateSpecializationInfo() &&
        !canRedefineFunction(Old, getLangOpts())) {
      if (getLangOpts().MicrosoftExt) {
        Diag(New->getLocation(), diag::ext_static_non_static) << New;
        Diag(OldLocation, PrevDiag);
      } else {
        Diag(New->getLocation(), diag::err_static_non_static) << New;
        Diag(OldLocation, PrevDiag);
        return true;
      }
    }
  
    if (New->hasAttr<InternalLinkageAttr>() &&
        !Old->hasAttr<InternalLinkageAttr>()) {
      Diag(New->getLocation(), diag::err_internal_linkage_redeclaration)
          << New->getDeclName();
      notePreviousDefinition(Old, New->getLocation());
      New->dropAttr<InternalLinkageAttr>();
    }
  
    if (CheckRedeclarationModuleOwnership(New, Old))
      return true;
  
    if (!getLangOpts().CPlusPlus) {
      bool OldOvl = Old->hasAttr<OverloadableAttr>();
      if (OldOvl != New->hasAttr<OverloadableAttr>() && !Old->isImplicit()) {
        Diag(New->getLocation(), diag::err_attribute_overloadable_mismatch)
          << New << OldOvl;
  
        // Try our best to find a decl that actually has the overloadable
        // attribute for the note. In most cases (e.g. programs with only one
        // broken declaration/definition), this won't matter.
        //
        // FIXME: We could do this if we juggled some extra state in
        // OverloadableAttr, rather than just removing it.
        const Decl *DiagOld = Old;
        if (OldOvl) {
          auto OldIter = llvm::find_if(Old->redecls(), [](const Decl *D) {
            const auto *A = D->getAttr<OverloadableAttr>();
            return A && !A->isImplicit();
          });
          // If we've implicitly added *all* of the overloadable attrs to this
          // chain, emitting a "previous redecl" note is pointless.
          DiagOld = OldIter == Old->redecls_end() ? nullptr : *OldIter;
        }
  
        if (DiagOld)
          Diag(DiagOld->getLocation(),
               diag::note_attribute_overloadable_prev_overload)
            << OldOvl;
  
        if (OldOvl)
          New->addAttr(OverloadableAttr::CreateImplicit(Context));
        else
          New->dropAttr<OverloadableAttr>();
      }
    }
  
    // If a function is first declared with a calling convention, but is later
    // declared or defined without one, all following decls assume the calling
    // convention of the first.
    //
    // It's OK if a function is first declared without a calling convention,
    // but is later declared or defined with the default calling convention.
    //
    // To test if either decl has an explicit calling convention, we look for
    // AttributedType sugar nodes on the type as written.  If they are missing or
    // were canonicalized away, we assume the calling convention was implicit.
    //
    // Note also that we DO NOT return at this point, because we still have
    // other tests to run.
    QualType OldQType = Context.getCanonicalType(Old->getType());
    QualType NewQType = Context.getCanonicalType(New->getType());
    const FunctionType *OldType = cast<FunctionType>(OldQType);
    const FunctionType *NewType = cast<FunctionType>(NewQType);
    FunctionType::ExtInfo OldTypeInfo = OldType->getExtInfo();
    FunctionType::ExtInfo NewTypeInfo = NewType->getExtInfo();
    bool RequiresAdjustment = false;
  
    if (OldTypeInfo.getCC() != NewTypeInfo.getCC()) {
      FunctionDecl *First = Old->getFirstDecl();
      const FunctionType *FT =
          First->getType().getCanonicalType()->castAs<FunctionType>();
      FunctionType::ExtInfo FI = FT->getExtInfo();
      bool NewCCExplicit = getCallingConvAttributedType(New->getType());
      if (!NewCCExplicit) {
        // Inherit the CC from the previous declaration if it was specified
        // there but not here.
        NewTypeInfo = NewTypeInfo.withCallingConv(OldTypeInfo.getCC());
        RequiresAdjustment = true;
      } else if (New->getBuiltinID()) {
        // Calling Conventions on a Builtin aren't really useful and setting a
        // default calling convention and cdecl'ing some builtin redeclarations is
        // common, so warn and ignore the calling convention on the redeclaration.
        Diag(New->getLocation(), diag::warn_cconv_ignored)
            << FunctionType::getNameForCallConv(NewTypeInfo.getCC())
            << (int)CallingConventionIgnoredReason::BuiltinFunction;
        NewTypeInfo = NewTypeInfo.withCallingConv(OldTypeInfo.getCC());
        RequiresAdjustment = true;
      } else {
        // Calling conventions aren't compatible, so complain.
        bool FirstCCExplicit = getCallingConvAttributedType(First->getType());
        Diag(New->getLocation(), diag::err_cconv_change)
          << FunctionType::getNameForCallConv(NewTypeInfo.getCC())
          << !FirstCCExplicit
          << (!FirstCCExplicit ? "" :
              FunctionType::getNameForCallConv(FI.getCC()));
  
        // Put the note on the first decl, since it is the one that matters.
        Diag(First->getLocation(), diag::note_previous_declaration);
        return true;
      }
    }
  
    // FIXME: diagnose the other way around?
    if (OldTypeInfo.getNoReturn() && !NewTypeInfo.getNoReturn()) {
      NewTypeInfo = NewTypeInfo.withNoReturn(true);
      RequiresAdjustment = true;
    }
  
    // Merge regparm attribute.
    if (OldTypeInfo.getHasRegParm() != NewTypeInfo.getHasRegParm() ||
        OldTypeInfo.getRegParm() != NewTypeInfo.getRegParm()) {
      if (NewTypeInfo.getHasRegParm()) {
        Diag(New->getLocation(), diag::err_regparm_mismatch)
          << NewType->getRegParmType()
          << OldType->getRegParmType();
        Diag(OldLocation, diag::note_previous_declaration);
        return true;
      }
  
      NewTypeInfo = NewTypeInfo.withRegParm(OldTypeInfo.getRegParm());
      RequiresAdjustment = true;
    }
  
    // Merge ns_returns_retained attribute.
    if (OldTypeInfo.getProducesResult() != NewTypeInfo.getProducesResult()) {
      if (NewTypeInfo.getProducesResult()) {
        Diag(New->getLocation(), diag::err_function_attribute_mismatch)
            << "'ns_returns_retained'";
        Diag(OldLocation, diag::note_previous_declaration);
        return true;
      }
  
      NewTypeInfo = NewTypeInfo.withProducesResult(true);
      RequiresAdjustment = true;
    }
  
    if (OldTypeInfo.getNoCallerSavedRegs() !=
        NewTypeInfo.getNoCallerSavedRegs()) {
      if (NewTypeInfo.getNoCallerSavedRegs()) {
        AnyX86NoCallerSavedRegistersAttr *Attr =
          New->getAttr<AnyX86NoCallerSavedRegistersAttr>();
        Diag(New->getLocation(), diag::err_function_attribute_mismatch) << Attr;
        Diag(OldLocation, diag::note_previous_declaration);
        return true;
      }
  
      NewTypeInfo = NewTypeInfo.withNoCallerSavedRegs(true);
      RequiresAdjustment = true;
    }
  
    if (RequiresAdjustment) {
      const FunctionType *AdjustedType = New->getType()->getAs<FunctionType>();
      AdjustedType = Context.adjustFunctionType(AdjustedType, NewTypeInfo);
      New->setType(QualType(AdjustedType, 0));
      NewQType = Context.getCanonicalType(New->getType());
      NewType = cast<FunctionType>(NewQType);
    }
  
    // If this redeclaration makes the function inline, we may need to add it to
    // UndefinedButUsed.
    if (!Old->isInlined() && New->isInlined() &&
        !New->hasAttr<GNUInlineAttr>() &&
        !getLangOpts().GNUInline &&
        Old->isUsed(false) &&
        !Old->isDefined() && !New->isThisDeclarationADefinition())
      UndefinedButUsed.insert(std::make_pair(Old->getCanonicalDecl(),
                                             SourceLocation()));
  
    // If this redeclaration makes it newly gnu_inline, we don't want to warn
    // about it.
    if (New->hasAttr<GNUInlineAttr>() &&
        Old->isInlined() && !Old->hasAttr<GNUInlineAttr>()) {
      UndefinedButUsed.erase(Old->getCanonicalDecl());
    }
  
    // If pass_object_size params don't match up perfectly, this isn't a valid
    // redeclaration.
    if (Old->getNumParams() > 0 && Old->getNumParams() == New->getNumParams() &&
        !hasIdenticalPassObjectSizeAttrs(Old, New)) {
      Diag(New->getLocation(), diag::err_different_pass_object_size_params)
          << New->getDeclName();
      Diag(OldLocation, PrevDiag) << Old << Old->getType();
      return true;
    }
  
    if (getLangOpts().CPlusPlus) {
      // C++1z [over.load]p2
      //   Certain function declarations cannot be overloaded:
      //     -- Function declarations that differ only in the return type,
      //        the exception specification, or both cannot be overloaded.
  
      // Check the exception specifications match. This may recompute the type of
      // both Old and New if it resolved exception specifications, so grab the
      // types again after this. Because this updates the type, we do this before
      // any of the other checks below, which may update the "de facto" NewQType
      // but do not necessarily update the type of New.
      if (CheckEquivalentExceptionSpec(Old, New))
        return true;
      OldQType = Context.getCanonicalType(Old->getType());
      NewQType = Context.getCanonicalType(New->getType());
  
      // Go back to the type source info to compare the declared return types,
      // per C++1y [dcl.type.auto]p13:
      //   Redeclarations or specializations of a function or function template
      //   with a declared return type that uses a placeholder type shall also
      //   use that placeholder, not a deduced type.
      QualType OldDeclaredReturnType = Old->getDeclaredReturnType();
      QualType NewDeclaredReturnType = New->getDeclaredReturnType();
      if (!Context.hasSameType(OldDeclaredReturnType, NewDeclaredReturnType) &&
          canFullyTypeCheckRedeclaration(New, Old, NewDeclaredReturnType,
                                         OldDeclaredReturnType)) {
        QualType ResQT;
        if (NewDeclaredReturnType->isObjCObjectPointerType() &&
            OldDeclaredReturnType->isObjCObjectPointerType())
          // FIXME: This does the wrong thing for a deduced return type.
          ResQT = Context.mergeObjCGCQualifiers(NewQType, OldQType);
        if (ResQT.isNull()) {
          if (New->isCXXClassMember() && New->isOutOfLine())
            Diag(New->getLocation(), diag::err_member_def_does_not_match_ret_type)
                << New << New->getReturnTypeSourceRange();
          else
            Diag(New->getLocation(), diag::err_ovl_diff_return_type)
                << New->getReturnTypeSourceRange();
          Diag(OldLocation, PrevDiag) << Old << Old->getType()
                                      << Old->getReturnTypeSourceRange();
          return true;
        }
        else
          NewQType = ResQT;
      }
  
      QualType OldReturnType = OldType->getReturnType();
      QualType NewReturnType = cast<FunctionType>(NewQType)->getReturnType();
      if (OldReturnType != NewReturnType) {
        // If this function has a deduced return type and has already been
        // defined, copy the deduced value from the old declaration.
        AutoType *OldAT = Old->getReturnType()->getContainedAutoType();
        if (OldAT && OldAT->isDeduced()) {
          New->setType(
              SubstAutoType(New->getType(),
                            OldAT->isDependentType() ? Context.DependentTy
                                                     : OldAT->getDeducedType()));
          NewQType = Context.getCanonicalType(
              SubstAutoType(NewQType,
                            OldAT->isDependentType() ? Context.DependentTy
                                                     : OldAT->getDeducedType()));
        }
      }
  
      const CXXMethodDecl *OldMethod = dyn_cast<CXXMethodDecl>(Old);
      CXXMethodDecl *NewMethod = dyn_cast<CXXMethodDecl>(New);
      if (OldMethod && NewMethod) {
        // Preserve triviality.
        NewMethod->setTrivial(OldMethod->isTrivial());
  
        // MSVC allows explicit template specialization at class scope:
        // 2 CXXMethodDecls referring to the same function will be injected.
        // We don't want a redeclaration error.
        bool IsClassScopeExplicitSpecialization =
                                OldMethod->isFunctionTemplateSpecialization() &&
                                NewMethod->isFunctionTemplateSpecialization();
        bool isFriend = NewMethod->getFriendObjectKind();
  
        if (!isFriend && NewMethod->getLexicalDeclContext()->isRecord() &&
            !IsClassScopeExplicitSpecialization) {
          //    -- Member function declarations with the same name and the
          //       same parameter types cannot be overloaded if any of them
          //       is a static member function declaration.
          if (OldMethod->isStatic() != NewMethod->isStatic()) {
            Diag(New->getLocation(), diag::err_ovl_static_nonstatic_member);
            Diag(OldLocation, PrevDiag) << Old << Old->getType();
            return true;
          }
  
          // C++ [class.mem]p1:
          //   [...] A member shall not be declared twice in the
          //   member-specification, except that a nested class or member
          //   class template can be declared and then later defined.
          if (!inTemplateInstantiation()) {
            unsigned NewDiag;
            if (isa<CXXConstructorDecl>(OldMethod))
              NewDiag = diag::err_constructor_redeclared;
            else if (isa<CXXDestructorDecl>(NewMethod))
              NewDiag = diag::err_destructor_redeclared;
            else if (isa<CXXConversionDecl>(NewMethod))
              NewDiag = diag::err_conv_function_redeclared;
            else
              NewDiag = diag::err_member_redeclared;
  
            Diag(New->getLocation(), NewDiag);
          } else {
            Diag(New->getLocation(), diag::err_member_redeclared_in_instantiation)
              << New << New->getType();
          }
          Diag(OldLocation, PrevDiag) << Old << Old->getType();
          return true;
  
        // Complain if this is an explicit declaration of a special
        // member that was initially declared implicitly.
        //
        // As an exception, it's okay to befriend such methods in order
        // to permit the implicit constructor/destructor/operator calls.
        } else if (OldMethod->isImplicit()) {
          if (isFriend) {
            NewMethod->setImplicit();
          } else {
            Diag(NewMethod->getLocation(),
                 diag::err_definition_of_implicitly_declared_member)
              << New << getSpecialMember(OldMethod);
            return true;
          }
        } else if (OldMethod->getFirstDecl()->isExplicitlyDefaulted() && !isFriend) {
          Diag(NewMethod->getLocation(),
               diag::err_definition_of_explicitly_defaulted_member)
            << getSpecialMember(OldMethod);
          return true;
        }
      }
  
      // C++11 [dcl.attr.noreturn]p1:
      //   The first declaration of a function shall specify the noreturn
      //   attribute if any declaration of that function specifies the noreturn
      //   attribute.
      const CXX11NoReturnAttr *NRA = New->getAttr<CXX11NoReturnAttr>();
      if (NRA && !Old->hasAttr<CXX11NoReturnAttr>()) {
        Diag(NRA->getLocation(), diag::err_noreturn_missing_on_first_decl);
        Diag(Old->getFirstDecl()->getLocation(),
             diag::note_noreturn_missing_first_decl);
      }
  
      // C++11 [dcl.attr.depend]p2:
      //   The first declaration of a function shall specify the
      //   carries_dependency attribute for its declarator-id if any declaration
      //   of the function specifies the carries_dependency attribute.
      const CarriesDependencyAttr *CDA = New->getAttr<CarriesDependencyAttr>();
      if (CDA && !Old->hasAttr<CarriesDependencyAttr>()) {
        Diag(CDA->getLocation(),
             diag::err_carries_dependency_missing_on_first_decl) << 0/*Function*/;
        Diag(Old->getFirstDecl()->getLocation(),
             diag::note_carries_dependency_missing_first_decl) << 0/*Function*/;
      }
  
      // (C++98 8.3.5p3):
      //   All declarations for a function shall agree exactly in both the
      //   return type and the parameter-type-list.
      // We also want to respect all the extended bits except noreturn.
  
      // noreturn should now match unless the old type info didn't have it.
      QualType OldQTypeForComparison = OldQType;
      if (!OldTypeInfo.getNoReturn() && NewTypeInfo.getNoReturn()) {
        auto *OldType = OldQType->castAs<FunctionProtoType>();
        const FunctionType *OldTypeForComparison
          = Context.adjustFunctionType(OldType, OldTypeInfo.withNoReturn(true));
        OldQTypeForComparison = QualType(OldTypeForComparison, 0);
        assert(OldQTypeForComparison.isCanonical());
      }
  
      if (haveIncompatibleLanguageLinkages(Old, New)) {
        // As a special case, retain the language linkage from previous
        // declarations of a friend function as an extension.
        //
        // This liberal interpretation of C++ [class.friend]p3 matches GCC/MSVC
        // and is useful because there's otherwise no way to specify language
        // linkage within class scope.
        //
        // Check cautiously as the friend object kind isn't yet complete.
        if (New->getFriendObjectKind() != Decl::FOK_None) {
          Diag(New->getLocation(), diag::ext_retained_language_linkage) << New;
          Diag(OldLocation, PrevDiag);
        } else {
          Diag(New->getLocation(), diag::err_different_language_linkage) << New;
          Diag(OldLocation, PrevDiag);
          return true;
        }
      }
  
      if (OldQTypeForComparison == NewQType)
        return MergeCompatibleFunctionDecls(New, Old, S, MergeTypeWithOld);
  
      // If the types are imprecise (due to dependent constructs in friends or
      // local extern declarations), it's OK if they differ. We'll check again
      // during instantiation.
      if (!canFullyTypeCheckRedeclaration(New, Old, NewQType, OldQType))
        return false;
  
      // Fall through for conflicting redeclarations and redefinitions.
    }
  
    // C: Function types need to be compatible, not identical. This handles
    // duplicate function decls like "void f(int); void f(enum X);" properly.
    if (!getLangOpts().CPlusPlus &&
        Context.typesAreCompatible(OldQType, NewQType)) {
      const FunctionType *OldFuncType = OldQType->getAs<FunctionType>();
      const FunctionType *NewFuncType = NewQType->getAs<FunctionType>();
      const FunctionProtoType *OldProto = nullptr;
      if (MergeTypeWithOld && isa<FunctionNoProtoType>(NewFuncType) &&
          (OldProto = dyn_cast<FunctionProtoType>(OldFuncType))) {
        // The old declaration provided a function prototype, but the
        // new declaration does not. Merge in the prototype.
        assert(!OldProto->hasExceptionSpec() && "Exception spec in C");
        SmallVector<QualType, 16> ParamTypes(OldProto->param_types());
        NewQType =
            Context.getFunctionType(NewFuncType->getReturnType(), ParamTypes,
                                    OldProto->getExtProtoInfo());
        New->setType(NewQType);
        New->setHasInheritedPrototype();
  
        // Synthesize parameters with the same types.
        SmallVector<ParmVarDecl*, 16> Params;
        for (const auto &ParamType : OldProto->param_types()) {
          ParmVarDecl *Param = ParmVarDecl::Create(Context, New, SourceLocation(),
                                                   SourceLocation(), nullptr,
                                                   ParamType, /*TInfo=*/nullptr,
                                                   SC_None, nullptr);
          Param->setScopeInfo(0, Params.size());
          Param->setImplicit();
          Params.push_back(Param);
        }
  
        New->setParams(Params);
      }
  
      return MergeCompatibleFunctionDecls(New, Old, S, MergeTypeWithOld);
    }
  
    // GNU C permits a K&R definition to follow a prototype declaration
    // if the declared types of the parameters in the K&R definition
    // match the types in the prototype declaration, even when the
    // promoted types of the parameters from the K&R definition differ
    // from the types in the prototype. GCC then keeps the types from
    // the prototype.
    //
    // If a variadic prototype is followed by a non-variadic K&R definition,
    // the K&R definition becomes variadic.  This is sort of an edge case, but
    // it's legal per the standard depending on how you read C99 6.7.5.3p15 and
    // C99 6.9.1p8.
    if (!getLangOpts().CPlusPlus &&
        Old->hasPrototype() && !New->hasPrototype() &&
        New->getType()->getAs<FunctionProtoType>() &&
        Old->getNumParams() == New->getNumParams()) {
      SmallVector<QualType, 16> ArgTypes;
      SmallVector<GNUCompatibleParamWarning, 16> Warnings;
      const FunctionProtoType *OldProto
        = Old->getType()->getAs<FunctionProtoType>();
      const FunctionProtoType *NewProto
        = New->getType()->getAs<FunctionProtoType>();
  
      // Determine whether this is the GNU C extension.
      QualType MergedReturn = Context.mergeTypes(OldProto->getReturnType(),
                                                 NewProto->getReturnType());
      bool LooseCompatible = !MergedReturn.isNull();
      for (unsigned Idx = 0, End = Old->getNumParams();
           LooseCompatible && Idx != End; ++Idx) {
        ParmVarDecl *OldParm = Old->getParamDecl(Idx);
        ParmVarDecl *NewParm = New->getParamDecl(Idx);
        if (Context.typesAreCompatible(OldParm->getType(),
                                       NewProto->getParamType(Idx))) {
          ArgTypes.push_back(NewParm->getType());
        } else if (Context.typesAreCompatible(OldParm->getType(),
                                              NewParm->getType(),
                                              /*CompareUnqualified=*/true)) {
          GNUCompatibleParamWarning Warn = { OldParm, NewParm,
                                             NewProto->getParamType(Idx) };
          Warnings.push_back(Warn);
          ArgTypes.push_back(NewParm->getType());
        } else
          LooseCompatible = false;
      }
  
      if (LooseCompatible) {
        for (unsigned Warn = 0; Warn < Warnings.size(); ++Warn) {
          Diag(Warnings[Warn].NewParm->getLocation(),
               diag::ext_param_promoted_not_compatible_with_prototype)
            << Warnings[Warn].PromotedType
            << Warnings[Warn].OldParm->getType();
          if (Warnings[Warn].OldParm->getLocation().isValid())
            Diag(Warnings[Warn].OldParm->getLocation(),
                 diag::note_previous_declaration);
        }
  
        if (MergeTypeWithOld)
          New->setType(Context.getFunctionType(MergedReturn, ArgTypes,
                                               OldProto->getExtProtoInfo()));
        return MergeCompatibleFunctionDecls(New, Old, S, MergeTypeWithOld);
      }
  
      // Fall through to diagnose conflicting types.
    }
  
    // A function that has already been declared has been redeclared or
    // defined with a different type; show an appropriate diagnostic.
  
    // If the previous declaration was an implicitly-generated builtin
    // declaration, then at the very least we should use a specialized note.
    unsigned BuiltinID;
    if (Old->isImplicit() && (BuiltinID = Old->getBuiltinID())) {
      // If it's actually a library-defined builtin function like 'malloc'
      // or 'printf', just warn about the incompatible redeclaration.
      if (Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID)) {
        Diag(New->getLocation(), diag::warn_redecl_library_builtin) << New;
        Diag(OldLocation, diag::note_previous_builtin_declaration)
          << Old << Old->getType();
  
        // If this is a global redeclaration, just forget hereafter
        // about the "builtin-ness" of the function.
        //
        // Doing this for local extern declarations is problematic.  If
        // the builtin declaration remains visible, a second invalid
        // local declaration will produce a hard error; if it doesn't
        // remain visible, a single bogus local redeclaration (which is
        // actually only a warning) could break all the downstream code.
        if (!New->getLexicalDeclContext()->isFunctionOrMethod())
          New->getIdentifier()->revertBuiltin();
  
        return false;
      }
  
      PrevDiag = diag::note_previous_builtin_declaration;
    }
  
    Diag(New->getLocation(), diag::err_conflicting_types) << New->getDeclName();
    Diag(OldLocation, PrevDiag) << Old << Old->getType();
    return true;
  }
  
  /// Completes the merge of two function declarations that are
  /// known to be compatible.
  ///
  /// This routine handles the merging of attributes and other
  /// properties of function declarations from the old declaration to
  /// the new declaration, once we know that New is in fact a
  /// redeclaration of Old.
  ///
  /// \returns false
  bool Sema::MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
                                          Scope *S, bool MergeTypeWithOld) {
    // Merge the attributes
    mergeDeclAttributes(New, Old);
  
    // Merge "pure" flag.
    if (Old->isPure())
      New->setPure();
  
    // Merge "used" flag.
    if (Old->getMostRecentDecl()->isUsed(false))
      New->setIsUsed();
  
    // Merge attributes from the parameters.  These can mismatch with K&R
    // declarations.
    if (New->getNumParams() == Old->getNumParams())
        for (unsigned i = 0, e = New->getNumParams(); i != e; ++i) {
          ParmVarDecl *NewParam = New->getParamDecl(i);
          ParmVarDecl *OldParam = Old->getParamDecl(i);
          mergeParamDeclAttributes(NewParam, OldParam, *this);
          mergeParamDeclTypes(NewParam, OldParam, *this);
        }
  
    if (getLangOpts().CPlusPlus)
      return MergeCXXFunctionDecl(New, Old, S);
  
    // Merge the function types so the we get the composite types for the return
    // and argument types. Per C11 6.2.7/4, only update the type if the old decl
    // was visible.
    QualType Merged = Context.mergeTypes(Old->getType(), New->getType());
    if (!Merged.isNull() && MergeTypeWithOld)
      New->setType(Merged);
  
    return false;
  }
  
  void Sema::mergeObjCMethodDecls(ObjCMethodDecl *newMethod,
                                  ObjCMethodDecl *oldMethod) {
    // Merge the attributes, including deprecated/unavailable
    AvailabilityMergeKind MergeKind =
      isa<ObjCProtocolDecl>(oldMethod->getDeclContext())
        ? AMK_ProtocolImplementation
        : isa<ObjCImplDecl>(newMethod->getDeclContext()) ? AMK_Redeclaration
                                                         : AMK_Override;
  
    mergeDeclAttributes(newMethod, oldMethod, MergeKind);
  
    // Merge attributes from the parameters.
    ObjCMethodDecl::param_const_iterator oi = oldMethod->param_begin(),
                                         oe = oldMethod->param_end();
    for (ObjCMethodDecl::param_iterator
           ni = newMethod->param_begin(), ne = newMethod->param_end();
         ni != ne && oi != oe; ++ni, ++oi)
      mergeParamDeclAttributes(*ni, *oi, *this);
  
    CheckObjCMethodOverride(newMethod, oldMethod);
  }
  
  static void diagnoseVarDeclTypeMismatch(Sema &S, VarDecl *New, VarDecl* Old) {
    assert(!S.Context.hasSameType(New->getType(), Old->getType()));
  
    S.Diag(New->getLocation(), New->isThisDeclarationADefinition()
           ? diag::err_redefinition_different_type
           : diag::err_redeclaration_different_type)
      << New->getDeclName() << New->getType() << Old->getType();
  
    diag::kind PrevDiag;
    SourceLocation OldLocation;
    std::tie(PrevDiag, OldLocation)
      = getNoteDiagForInvalidRedeclaration(Old, New);
    S.Diag(OldLocation, PrevDiag);
    New->setInvalidDecl();
  }
  
  /// MergeVarDeclTypes - We parsed a variable 'New' which has the same name and
  /// scope as a previous declaration 'Old'.  Figure out how to merge their types,
  /// emitting diagnostics as appropriate.
  ///
  /// Declarations using the auto type specifier (C++ [decl.spec.auto]) call back
  /// to here in AddInitializerToDecl. We can't check them before the initializer
  /// is attached.
  void Sema::MergeVarDeclTypes(VarDecl *New, VarDecl *Old,
                               bool MergeTypeWithOld) {
    if (New->isInvalidDecl() || Old->isInvalidDecl())
      return;
  
    QualType MergedT;
    if (getLangOpts().CPlusPlus) {
      if (New->getType()->isUndeducedType()) {
        // We don't know what the new type is until the initializer is attached.
        return;
      } else if (Context.hasSameType(New->getType(), Old->getType())) {
        // These could still be something that needs exception specs checked.
        return MergeVarDeclExceptionSpecs(New, Old);
      }
      // C++ [basic.link]p10:
      //   [...] the types specified by all declarations referring to a given
      //   object or function shall be identical, except that declarations for an
      //   array object can specify array types that differ by the presence or
      //   absence of a major array bound (8.3.4).
      else if (Old->getType()->isArrayType() && New->getType()->isArrayType()) {
        const ArrayType *OldArray = Context.getAsArrayType(Old->getType());
        const ArrayType *NewArray = Context.getAsArrayType(New->getType());
  
        // We are merging a variable declaration New into Old. If it has an array
        // bound, and that bound differs from Old's bound, we should diagnose the
        // mismatch.
        if (!NewArray->isIncompleteArrayType() && !NewArray->isDependentType()) {
          for (VarDecl *PrevVD = Old->getMostRecentDecl(); PrevVD;
               PrevVD = PrevVD->getPreviousDecl()) {
            const ArrayType *PrevVDTy = Context.getAsArrayType(PrevVD->getType());
            if (PrevVDTy->isIncompleteArrayType() || PrevVDTy->isDependentType())
              continue;
  
            if (!Context.hasSameType(NewArray, PrevVDTy))
              return diagnoseVarDeclTypeMismatch(*this, New, PrevVD);
          }
        }
  
        if (OldArray->isIncompleteArrayType() && NewArray->isArrayType()) {
          if (Context.hasSameType(OldArray->getElementType(),
                                  NewArray->getElementType()))
            MergedT = New->getType();
        }
        // FIXME: Check visibility. New is hidden but has a complete type. If New
        // has no array bound, it should not inherit one from Old, if Old is not
        // visible.
        else if (OldArray->isArrayType() && NewArray->isIncompleteArrayType()) {
          if (Context.hasSameType(OldArray->getElementType(),
                                  NewArray->getElementType()))
            MergedT = Old->getType();
        }
      }
      else if (New->getType()->isObjCObjectPointerType() &&
                 Old->getType()->isObjCObjectPointerType()) {
        MergedT = Context.mergeObjCGCQualifiers(New->getType(),
                                                Old->getType());
      }
    } else {
      // C 6.2.7p2:
      //   All declarations that refer to the same object or function shall have
      //   compatible type.
      MergedT = Context.mergeTypes(New->getType(), Old->getType());
    }
    if (MergedT.isNull()) {
      // It's OK if we couldn't merge types if either type is dependent, for a
      // block-scope variable. In other cases (static data members of class
      // templates, variable templates, ...), we require the types to be
      // equivalent.
      // FIXME: The C++ standard doesn't say anything about this.
      if ((New->getType()->isDependentType() ||
           Old->getType()->isDependentType()) && New->isLocalVarDecl()) {
        // If the old type was dependent, we can't merge with it, so the new type
        // becomes dependent for now. We'll reproduce the original type when we
        // instantiate the TypeSourceInfo for the variable.
        if (!New->getType()->isDependentType() && MergeTypeWithOld)
          New->setType(Context.DependentTy);
        return;
      }
      return diagnoseVarDeclTypeMismatch(*this, New, Old);
    }
  
    // Don't actually update the type on the new declaration if the old
    // declaration was an extern declaration in a different scope.
    if (MergeTypeWithOld)
      New->setType(MergedT);
  }
  
  static bool mergeTypeWithPrevious(Sema &S, VarDecl *NewVD, VarDecl *OldVD,
                                    LookupResult &Previous) {
    // C11 6.2.7p4:
    //   For an identifier with internal or external linkage declared
    //   in a scope in which a prior declaration of that identifier is
    //   visible, if the prior declaration specifies internal or
    //   external linkage, the type of the identifier at the later
    //   declaration becomes the composite type.
    //
    // If the variable isn't visible, we do not merge with its type.
    if (Previous.isShadowed())
      return false;
  
    if (S.getLangOpts().CPlusPlus) {
      // C++11 [dcl.array]p3:
      //   If there is a preceding declaration of the entity in the same
      //   scope in which the bound was specified, an omitted array bound
      //   is taken to be the same as in that earlier declaration.
      return NewVD->isPreviousDeclInSameBlockScope() ||
             (!OldVD->getLexicalDeclContext()->isFunctionOrMethod() &&
              !NewVD->getLexicalDeclContext()->isFunctionOrMethod());
    } else {
      // If the old declaration was function-local, don't merge with its
      // type unless we're in the same function.
      return !OldVD->getLexicalDeclContext()->isFunctionOrMethod() ||
             OldVD->getLexicalDeclContext() == NewVD->getLexicalDeclContext();
    }
  }
  
  /// MergeVarDecl - We just parsed a variable 'New' which has the same name
  /// and scope as a previous declaration 'Old'.  Figure out how to resolve this
  /// situation, merging decls or emitting diagnostics as appropriate.
  ///
  /// Tentative definition rules (C99 6.9.2p2) are checked by
  /// FinalizeDeclaratorGroup. Unfortunately, we can't analyze tentative
  /// definitions here, since the initializer hasn't been attached.
  ///
  void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
    // If the new decl is already invalid, don't do any other checking.
    if (New->isInvalidDecl())
      return;
  
    if (!shouldLinkPossiblyHiddenDecl(Previous, New))
      return;
  
    VarTemplateDecl *NewTemplate = New->getDescribedVarTemplate();
  
    // Verify the old decl was also a variable or variable template.
    VarDecl *Old = nullptr;
    VarTemplateDecl *OldTemplate = nullptr;
    if (Previous.isSingleResult()) {
      if (NewTemplate) {
        OldTemplate = dyn_cast<VarTemplateDecl>(Previous.getFoundDecl());
        Old = OldTemplate ? OldTemplate->getTemplatedDecl() : nullptr;
  
        if (auto *Shadow =
                dyn_cast<UsingShadowDecl>(Previous.getRepresentativeDecl()))
          if (checkUsingShadowRedecl<VarTemplateDecl>(*this, Shadow, NewTemplate))
            return New->setInvalidDecl();
      } else {
        Old = dyn_cast<VarDecl>(Previous.getFoundDecl());
  
        if (auto *Shadow =
                dyn_cast<UsingShadowDecl>(Previous.getRepresentativeDecl()))
          if (checkUsingShadowRedecl<VarDecl>(*this, Shadow, New))
            return New->setInvalidDecl();
      }
    }
    if (!Old) {
      Diag(New->getLocation(), diag::err_redefinition_different_kind)
          << New->getDeclName();
      notePreviousDefinition(Previous.getRepresentativeDecl(),
                             New->getLocation());
      return New->setInvalidDecl();
    }
  
    // Ensure the template parameters are compatible.
    if (NewTemplate &&
        !TemplateParameterListsAreEqual(NewTemplate->getTemplateParameters(),
                                        OldTemplate->getTemplateParameters(),
                                        /*Complain=*/true, TPL_TemplateMatch))
      return New->setInvalidDecl();
  
    // C++ [class.mem]p1:
    //   A member shall not be declared twice in the member-specification [...]
    //
    // Here, we need only consider static data members.
    if (Old->isStaticDataMember() && !New->isOutOfLine()) {
      Diag(New->getLocation(), diag::err_duplicate_member)
        << New->getIdentifier();
      Diag(Old->getLocation(), diag::note_previous_declaration);
      New->setInvalidDecl();
    }
  
    mergeDeclAttributes(New, Old);
    // Warn if an already-declared variable is made a weak_import in a subsequent
    // declaration
    if (New->hasAttr<WeakImportAttr>() &&
        Old->getStorageClass() == SC_None &&
        !Old->hasAttr<WeakImportAttr>()) {
      Diag(New->getLocation(), diag::warn_weak_import) << New->getDeclName();
      notePreviousDefinition(Old, New->getLocation());
      // Remove weak_import attribute on new declaration.
      New->dropAttr<WeakImportAttr>();
    }
  
    if (New->hasAttr<InternalLinkageAttr>() &&
        !Old->hasAttr<InternalLinkageAttr>()) {
      Diag(New->getLocation(), diag::err_internal_linkage_redeclaration)
          << New->getDeclName();
      notePreviousDefinition(Old, New->getLocation());
      New->dropAttr<InternalLinkageAttr>();
    }
  
    // Merge the types.
    VarDecl *MostRecent = Old->getMostRecentDecl();
    if (MostRecent != Old) {
      MergeVarDeclTypes(New, MostRecent,
                        mergeTypeWithPrevious(*this, New, MostRecent, Previous));
      if (New->isInvalidDecl())
        return;
    }
  
    MergeVarDeclTypes(New, Old, mergeTypeWithPrevious(*this, New, Old, Previous));
    if (New->isInvalidDecl())
      return;
  
    diag::kind PrevDiag;
    SourceLocation OldLocation;
    std::tie(PrevDiag, OldLocation) =
        getNoteDiagForInvalidRedeclaration(Old, New);
  
    // [dcl.stc]p8: Check if we have a non-static decl followed by a static.
    if (New->getStorageClass() == SC_Static &&
        !New->isStaticDataMember() &&
        Old->hasExternalFormalLinkage()) {
      if (getLangOpts().MicrosoftExt) {
        Diag(New->getLocation(), diag::ext_static_non_static)
            << New->getDeclName();
        Diag(OldLocation, PrevDiag);
      } else {
        Diag(New->getLocation(), diag::err_static_non_static)
            << New->getDeclName();
        Diag(OldLocation, PrevDiag);
        return New->setInvalidDecl();
      }
    }
    // C99 6.2.2p4:
    //   For an identifier declared with the storage-class specifier
    //   extern in a scope in which a prior declaration of that
    //   identifier is visible,23) if the prior declaration specifies
    //   internal or external linkage, the linkage of the identifier at
    //   the later declaration is the same as the linkage specified at
    //   the prior declaration. If no prior declaration is visible, or
    //   if the prior declaration specifies no linkage, then the
    //   identifier has external linkage.
    if (New->hasExternalStorage() && Old->hasLinkage())
      /* Okay */;
    else if (New->getCanonicalDecl()->getStorageClass() != SC_Static &&
             !New->isStaticDataMember() &&
             Old->getCanonicalDecl()->getStorageClass() == SC_Static) {
      Diag(New->getLocation(), diag::err_non_static_static) << New->getDeclName();
      Diag(OldLocation, PrevDiag);
      return New->setInvalidDecl();
    }
  
    // Check if extern is followed by non-extern and vice-versa.
    if (New->hasExternalStorage() &&
        !Old->hasLinkage() && Old->isLocalVarDeclOrParm()) {
      Diag(New->getLocation(), diag::err_extern_non_extern) << New->getDeclName();
      Diag(OldLocation, PrevDiag);
      return New->setInvalidDecl();
    }
    if (Old->hasLinkage() && New->isLocalVarDeclOrParm() &&
        !New->hasExternalStorage()) {
      Diag(New->getLocation(), diag::err_non_extern_extern) << New->getDeclName();
      Diag(OldLocation, PrevDiag);
      return New->setInvalidDecl();
    }
  
    if (CheckRedeclarationModuleOwnership(New, Old))
      return;
  
    // Variables with external linkage are analyzed in FinalizeDeclaratorGroup.
  
    // FIXME: The test for external storage here seems wrong? We still
    // need to check for mismatches.
    if (!New->hasExternalStorage() && !New->isFileVarDecl() &&
        // Don't complain about out-of-line definitions of static members.
        !(Old->getLexicalDeclContext()->isRecord() &&
          !New->getLexicalDeclContext()->isRecord())) {
      Diag(New->getLocation(), diag::err_redefinition) << New->getDeclName();
      Diag(OldLocation, PrevDiag);
      return New->setInvalidDecl();
    }
  
    if (New->isInline() && !Old->getMostRecentDecl()->isInline()) {
      if (VarDecl *Def = Old->getDefinition()) {
        // C++1z [dcl.fcn.spec]p4:
        //   If the definition of a variable appears in a translation unit before
        //   its first declaration as inline, the program is ill-formed.
        Diag(New->getLocation(), diag::err_inline_decl_follows_def) << New;
        Diag(Def->getLocation(), diag::note_previous_definition);
      }
    }
  
    // If this redeclaration makes the variable inline, we may need to add it to
    // UndefinedButUsed.
    if (!Old->isInline() && New->isInline() && Old->isUsed(false) &&
        !Old->getDefinition() && !New->isThisDeclarationADefinition())
      UndefinedButUsed.insert(std::make_pair(Old->getCanonicalDecl(),
                                             SourceLocation()));
  
    if (New->getTLSKind() != Old->getTLSKind()) {
      if (!Old->getTLSKind()) {
        Diag(New->getLocation(), diag::err_thread_non_thread) << New->getDeclName();
        Diag(OldLocation, PrevDiag);
      } else if (!New->getTLSKind()) {
        Diag(New->getLocation(), diag::err_non_thread_thread) << New->getDeclName();
        Diag(OldLocation, PrevDiag);
      } else {
        // Do not allow redeclaration to change the variable between requiring
        // static and dynamic initialization.
        // FIXME: GCC allows this, but uses the TLS keyword on the first
        // declaration to determine the kind. Do we need to be compatible here?
        Diag(New->getLocation(), diag::err_thread_thread_different_kind)
          << New->getDeclName() << (New->getTLSKind() == VarDecl::TLS_Dynamic);
        Diag(OldLocation, PrevDiag);
      }
    }
  
    // C++ doesn't have tentative definitions, so go right ahead and check here.
    if (getLangOpts().CPlusPlus &&
        New->isThisDeclarationADefinition() == VarDecl::Definition) {
      if (Old->isStaticDataMember() && Old->getCanonicalDecl()->isInline() &&
          Old->getCanonicalDecl()->isConstexpr()) {
        // This definition won't be a definition any more once it's been merged.
        Diag(New->getLocation(),
             diag::warn_deprecated_redundant_constexpr_static_def);
      } else if (VarDecl *Def = Old->getDefinition()) {
        if (checkVarDeclRedefinition(Def, New))
          return;
      }
    }
  
    if (haveIncompatibleLanguageLinkages(Old, New)) {
      Diag(New->getLocation(), diag::err_different_language_linkage) << New;
      Diag(OldLocation, PrevDiag);
      New->setInvalidDecl();
      return;
    }
  
    // Merge "used" flag.
    if (Old->getMostRecentDecl()->isUsed(false))
      New->setIsUsed();
  
    // Keep a chain of previous declarations.
    New->setPreviousDecl(Old);
    if (NewTemplate)
      NewTemplate->setPreviousDecl(OldTemplate);
    adjustDeclContextForDeclaratorDecl(New, Old);
  
    // Inherit access appropriately.
    New->setAccess(Old->getAccess());
    if (NewTemplate)
      NewTemplate->setAccess(New->getAccess());
  
    if (Old->isInline())
      New->setImplicitlyInline();
  }
  
  void Sema::notePreviousDefinition(const NamedDecl *Old, SourceLocation New) {
    SourceManager &SrcMgr = getSourceManager();
    auto FNewDecLoc = SrcMgr.getDecomposedLoc(New);
    auto FOldDecLoc = SrcMgr.getDecomposedLoc(Old->getLocation());
    auto *FNew = SrcMgr.getFileEntryForID(FNewDecLoc.first);
    auto *FOld = SrcMgr.getFileEntryForID(FOldDecLoc.first);
    auto &HSI = PP.getHeaderSearchInfo();
    StringRef HdrFilename =
        SrcMgr.getFilename(SrcMgr.getSpellingLoc(Old->getLocation()));
  
    auto noteFromModuleOrInclude = [&](Module *Mod,
                                       SourceLocation IncLoc) -> bool {
      // Redefinition errors with modules are common with non modular mapped
      // headers, example: a non-modular header H in module A that also gets
      // included directly in a TU. Pointing twice to the same header/definition
      // is confusing, try to get better diagnostics when modules is on.
      if (IncLoc.isValid()) {
        if (Mod) {
          Diag(IncLoc, diag::note_redefinition_modules_same_file)
              << HdrFilename.str() << Mod->getFullModuleName();
          if (!Mod->DefinitionLoc.isInvalid())
            Diag(Mod->DefinitionLoc, diag::note_defined_here)
                << Mod->getFullModuleName();
        } else {
          Diag(IncLoc, diag::note_redefinition_include_same_file)
              << HdrFilename.str();
        }
        return true;
      }
  
      return false;
    };
  
    // Is it the same file and same offset? Provide more information on why
    // this leads to a redefinition error.
    bool EmittedDiag = false;
    if (FNew == FOld && FNewDecLoc.second == FOldDecLoc.second) {
      SourceLocation OldIncLoc = SrcMgr.getIncludeLoc(FOldDecLoc.first);
      SourceLocation NewIncLoc = SrcMgr.getIncludeLoc(FNewDecLoc.first);
      EmittedDiag = noteFromModuleOrInclude(Old->getOwningModule(), OldIncLoc);
      EmittedDiag |= noteFromModuleOrInclude(getCurrentModule(), NewIncLoc);
  
      // If the header has no guards, emit a note suggesting one.
      if (FOld && !HSI.isFileMultipleIncludeGuarded(FOld))
        Diag(Old->getLocation(), diag::note_use_ifdef_guards);
  
      if (EmittedDiag)
        return;
    }
  
    // Redefinition coming from different files or couldn't do better above.
    if (Old->getLocation().isValid())
      Diag(Old->getLocation(), diag::note_previous_definition);
  }
  
  /// We've just determined that \p Old and \p New both appear to be definitions
  /// of the same variable. Either diagnose or fix the problem.
  bool Sema::checkVarDeclRedefinition(VarDecl *Old, VarDecl *New) {
    if (!hasVisibleDefinition(Old) &&
        (New->getFormalLinkage() == InternalLinkage ||
         New->isInline() ||
         New->getDescribedVarTemplate() ||
         New->getNumTemplateParameterLists() ||
         New->getDeclContext()->isDependentContext())) {
      // The previous definition is hidden, and multiple definitions are
      // permitted (in separate TUs). Demote this to a declaration.
      New->demoteThisDefinitionToDeclaration();
  
      // Make the canonical definition visible.
      if (auto *OldTD = Old->getDescribedVarTemplate())
        makeMergedDefinitionVisible(OldTD);
      makeMergedDefinitionVisible(Old);
      return false;
    } else {
      Diag(New->getLocation(), diag::err_redefinition) << New;
      notePreviousDefinition(Old, New->getLocation());
      New->setInvalidDecl();
      return true;
    }
  }
  
  /// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
  /// no declarator (e.g. "struct foo;") is parsed.
  Decl *
  Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, DeclSpec &DS,
                                   RecordDecl *&AnonRecord) {
    return ParsedFreeStandingDeclSpec(S, AS, DS, MultiTemplateParamsArg(), false,
                                      AnonRecord);
  }
  
  // The MS ABI changed between VS2013 and VS2015 with regard to numbers used to
  // disambiguate entities defined in different scopes.
  // While the VS2015 ABI fixes potential miscompiles, it is also breaks
  // compatibility.
  // We will pick our mangling number depending on which version of MSVC is being
  // targeted.
  static unsigned getMSManglingNumber(const LangOptions &LO, Scope *S) {
    return LO.isCompatibleWithMSVC(LangOptions::MSVC2015)
               ? S->getMSCurManglingNumber()
               : S->getMSLastManglingNumber();
  }
  
  void Sema::handleTagNumbering(const TagDecl *Tag, Scope *TagScope) {
    if (!Context.getLangOpts().CPlusPlus)
      return;
  
    if (isa<CXXRecordDecl>(Tag->getParent())) {
      // If this tag is the direct child of a class, number it if
      // it is anonymous.
      if (!Tag->getName().empty() || Tag->getTypedefNameForAnonDecl())
        return;
      MangleNumberingContext &MCtx =
          Context.getManglingNumberContext(Tag->getParent());
      Context.setManglingNumber(
          Tag, MCtx.getManglingNumber(
                   Tag, getMSManglingNumber(getLangOpts(), TagScope)));
      return;
    }
  
    // If this tag isn't a direct child of a class, number it if it is local.
    Decl *ManglingContextDecl;
    if (MangleNumberingContext *MCtx = getCurrentMangleNumberContext(
            Tag->getDeclContext(), ManglingContextDecl)) {
      Context.setManglingNumber(
          Tag, MCtx->getManglingNumber(
                   Tag, getMSManglingNumber(getLangOpts(), TagScope)));
    }
  }
  
  void Sema::setTagNameForLinkagePurposes(TagDecl *TagFromDeclSpec,
                                          TypedefNameDecl *NewTD) {
    if (TagFromDeclSpec->isInvalidDecl())
      return;
  
    // Do nothing if the tag already has a name for linkage purposes.
    if (TagFromDeclSpec->hasNameForLinkage())
      return;
  
    // A well-formed anonymous tag must always be a TUK_Definition.
    assert(TagFromDeclSpec->isThisDeclarationADefinition());
  
    // The type must match the tag exactly;  no qualifiers allowed.
    if (!Context.hasSameType(NewTD->getUnderlyingType(),
                             Context.getTagDeclType(TagFromDeclSpec))) {
      if (getLangOpts().CPlusPlus)
        Context.addTypedefNameForUnnamedTagDecl(TagFromDeclSpec, NewTD);
      return;
    }
  
    // If we've already computed linkage for the anonymous tag, then
    // adding a typedef name for the anonymous decl can change that
    // linkage, which might be a serious problem.  Diagnose this as
    // unsupported and ignore the typedef name.  TODO: we should
    // pursue this as a language defect and establish a formal rule
    // for how to handle it.
    if (TagFromDeclSpec->hasLinkageBeenComputed()) {
      Diag(NewTD->getLocation(), diag::err_typedef_changes_linkage);
  
      SourceLocation tagLoc = TagFromDeclSpec->getInnerLocStart();
      tagLoc = getLocForEndOfToken(tagLoc);
  
      llvm::SmallString<40> textToInsert;
      textToInsert += ' ';
      textToInsert += NewTD->getIdentifier()->getName();
      Diag(tagLoc, diag::note_typedef_changes_linkage)
          << FixItHint::CreateInsertion(tagLoc, textToInsert);
      return;
    }
  
    // Otherwise, set this is the anon-decl typedef for the tag.
    TagFromDeclSpec->setTypedefNameForAnonDecl(NewTD);
  }
  
  static unsigned GetDiagnosticTypeSpecifierID(DeclSpec::TST T) {
    switch (T) {
    case DeclSpec::TST_class:
      return 0;
    case DeclSpec::TST_struct:
      return 1;
    case DeclSpec::TST_interface:
      return 2;
    case DeclSpec::TST_union:
      return 3;
    case DeclSpec::TST_enum:
      return 4;
    default:
      llvm_unreachable("unexpected type specifier");
    }
  }
  
  /// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
  /// no declarator (e.g. "struct foo;") is parsed. It also accepts template
  /// parameters to cope with template friend declarations.
  Decl *
  Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, DeclSpec &DS,
                                   MultiTemplateParamsArg TemplateParams,
                                   bool IsExplicitInstantiation,
                                   RecordDecl *&AnonRecord) {
    Decl *TagD = nullptr;
    TagDecl *Tag = nullptr;
    if (DS.getTypeSpecType() == DeclSpec::TST_class ||
        DS.getTypeSpecType() == DeclSpec::TST_struct ||
        DS.getTypeSpecType() == DeclSpec::TST_interface ||
        DS.getTypeSpecType() == DeclSpec::TST_union ||
        DS.getTypeSpecType() == DeclSpec::TST_enum) {
      TagD = DS.getRepAsDecl();
  
      if (!TagD) // We probably had an error
        return nullptr;
  
      // Note that the above type specs guarantee that the
      // type rep is a Decl, whereas in many of the others
      // it's a Type.
      if (isa<TagDecl>(TagD))
        Tag = cast<TagDecl>(TagD);
      else if (ClassTemplateDecl *CTD = dyn_cast<ClassTemplateDecl>(TagD))
        Tag = CTD->getTemplatedDecl();
    }
  
    if (Tag) {
      handleTagNumbering(Tag, S);
      Tag->setFreeStanding();
      if (Tag->isInvalidDecl())
        return Tag;
    }
  
    if (unsigned TypeQuals = DS.getTypeQualifiers()) {
      // Enforce C99 6.7.3p2: "Types other than pointer types derived from object
      // or incomplete types shall not be restrict-qualified."
      if (TypeQuals & DeclSpec::TQ_restrict)
        Diag(DS.getRestrictSpecLoc(),
             diag::err_typecheck_invalid_restrict_not_pointer_noarg)
             << DS.getSourceRange();
    }
  
    if (DS.isInlineSpecified())
      Diag(DS.getInlineSpecLoc(), diag::err_inline_non_function)
          << getLangOpts().CPlusPlus17;
  
    if (DS.isConstexprSpecified()) {
      // C++0x [dcl.constexpr]p1: constexpr can only be applied to declarations
      // and definitions of functions and variables.
      if (Tag)
        Diag(DS.getConstexprSpecLoc(), diag::err_constexpr_tag)
            << GetDiagnosticTypeSpecifierID(DS.getTypeSpecType());
      else
        Diag(DS.getConstexprSpecLoc(), diag::err_constexpr_no_declarators);
      // Don't emit warnings after this error.
      return TagD;
    }
  
    DiagnoseFunctionSpecifiers(DS);
  
    if (DS.isFriendSpecified()) {
      // If we're dealing with a decl but not a TagDecl, assume that
      // whatever routines created it handled the friendship aspect.
      if (TagD && !Tag)
        return nullptr;
      return ActOnFriendTypeDecl(S, DS, TemplateParams);
    }
  
    const CXXScopeSpec &SS = DS.getTypeSpecScope();
    bool IsExplicitSpecialization =
      !TemplateParams.empty() && TemplateParams.back()->size() == 0;
    if (Tag && SS.isNotEmpty() && !Tag->isCompleteDefinition() &&
        !IsExplicitInstantiation && !IsExplicitSpecialization &&
        !isa<ClassTemplatePartialSpecializationDecl>(Tag)) {
      // Per C++ [dcl.type.elab]p1, a class declaration cannot have a
      // nested-name-specifier unless it is an explicit instantiation
      // or an explicit specialization.
      //
      // FIXME: We allow class template partial specializations here too, per the
      // obvious intent of DR1819.
      //
      // Per C++ [dcl.enum]p1, an opaque-enum-declaration can't either.
      Diag(SS.getBeginLoc(), diag::err_standalone_class_nested_name_specifier)
          << GetDiagnosticTypeSpecifierID(DS.getTypeSpecType()) << SS.getRange();
      return nullptr;
    }
  
    // Track whether this decl-specifier declares anything.
    bool DeclaresAnything = true;
  
    // Handle anonymous struct definitions.
    if (RecordDecl *Record = dyn_cast_or_null<RecordDecl>(Tag)) {
      if (!Record->getDeclName() && Record->isCompleteDefinition() &&
          DS.getStorageClassSpec() != DeclSpec::SCS_typedef) {
        if (getLangOpts().CPlusPlus ||
            Record->getDeclContext()->isRecord()) {
          // If CurContext is a DeclContext that can contain statements,
          // RecursiveASTVisitor won't visit the decls that
          // BuildAnonymousStructOrUnion() will put into CurContext.
          // Also store them here so that they can be part of the
          // DeclStmt that gets created in this case.
          // FIXME: Also return the IndirectFieldDecls created by
          // BuildAnonymousStructOr union, for the same reason?
          if (CurContext->isFunctionOrMethod())
            AnonRecord = Record;
          return BuildAnonymousStructOrUnion(S, DS, AS, Record,
                                             Context.getPrintingPolicy());
        }
  
        DeclaresAnything = false;
      }
    }
  
    // C11 6.7.2.1p2:
    //   A struct-declaration that does not declare an anonymous structure or
    //   anonymous union shall contain a struct-declarator-list.
    //
    // This rule also existed in C89 and C99; the grammar for struct-declaration
    // did not permit a struct-declaration without a struct-declarator-list.
    if (!getLangOpts().CPlusPlus && CurContext->isRecord() &&
        DS.getStorageClassSpec() == DeclSpec::SCS_unspecified) {
      // Check for Microsoft C extension: anonymous struct/union member.
      // Handle 2 kinds of anonymous struct/union:
      //   struct STRUCT;
      //   union UNION;
      // and
      //   STRUCT_TYPE;  <- where STRUCT_TYPE is a typedef struct.
      //   UNION_TYPE;   <- where UNION_TYPE is a typedef union.
      if ((Tag && Tag->getDeclName()) ||
          DS.getTypeSpecType() == DeclSpec::TST_typename) {
        RecordDecl *Record = nullptr;
        if (Tag)
          Record = dyn_cast<RecordDecl>(Tag);
        else if (const RecordType *RT =
                     DS.getRepAsType().get()->getAsStructureType())
          Record = RT->getDecl();
        else if (const RecordType *UT = DS.getRepAsType().get()->getAsUnionType())
          Record = UT->getDecl();
  
        if (Record && getLangOpts().MicrosoftExt) {
          Diag(DS.getBeginLoc(), diag::ext_ms_anonymous_record)
              << Record->isUnion() << DS.getSourceRange();
          return BuildMicrosoftCAnonymousStruct(S, DS, Record);
        }
  
        DeclaresAnything = false;
      }
    }
  
    // Skip all the checks below if we have a type error.
    if (DS.getTypeSpecType() == DeclSpec::TST_error ||
        (TagD && TagD->isInvalidDecl()))
      return TagD;
  
    if (getLangOpts().CPlusPlus &&
        DS.getStorageClassSpec() != DeclSpec::SCS_typedef)
      if (EnumDecl *Enum = dyn_cast_or_null<EnumDecl>(Tag))
        if (Enum->enumerator_begin() == Enum->enumerator_end() &&
            !Enum->getIdentifier() && !Enum->isInvalidDecl())
          DeclaresAnything = false;
  
    if (!DS.isMissingDeclaratorOk()) {
      // Customize diagnostic for a typedef missing a name.
      if (DS.getStorageClassSpec() == DeclSpec::SCS_typedef)
        Diag(DS.getBeginLoc(), diag::ext_typedef_without_a_name)
            << DS.getSourceRange();
      else
        DeclaresAnything = false;
    }
  
    if (DS.isModulePrivateSpecified() &&
        Tag && Tag->getDeclContext()->isFunctionOrMethod())
      Diag(DS.getModulePrivateSpecLoc(), diag::err_module_private_local_class)
        << Tag->getTagKind()
        << FixItHint::CreateRemoval(DS.getModulePrivateSpecLoc());
  
    ActOnDocumentableDecl(TagD);
  
    // C 6.7/2:
    //   A declaration [...] shall declare at least a declarator [...], a tag,
    //   or the members of an enumeration.
    // C++ [dcl.dcl]p3:
    //   [If there are no declarators], and except for the declaration of an
    //   unnamed bit-field, the decl-specifier-seq shall introduce one or more
    //   names into the program, or shall redeclare a name introduced by a
    //   previous declaration.
    if (!DeclaresAnything) {
      // In C, we allow this as a (popular) extension / bug. Don't bother
      // producing further diagnostics for redundant qualifiers after this.
      Diag(DS.getBeginLoc(), diag::ext_no_declarators) << DS.getSourceRange();
      return TagD;
    }
  
    // C++ [dcl.stc]p1:
    //   If a storage-class-specifier appears in a decl-specifier-seq, [...] the
    //   init-declarator-list of the declaration shall not be empty.
    // C++ [dcl.fct.spec]p1:
    //   If a cv-qualifier appears in a decl-specifier-seq, the
    //   init-declarator-list of the declaration shall not be empty.
    //
    // Spurious qualifiers here appear to be valid in C.
    unsigned DiagID = diag::warn_standalone_specifier;
    if (getLangOpts().CPlusPlus)
      DiagID = diag::ext_standalone_specifier;
  
    // Note that a linkage-specification sets a storage class, but
    // 'extern "C" struct foo;' is actually valid and not theoretically
    // useless.
    if (DeclSpec::SCS SCS = DS.getStorageClassSpec()) {
      if (SCS == DeclSpec::SCS_mutable)
        // Since mutable is not a viable storage class specifier in C, there is
        // no reason to treat it as an extension. Instead, diagnose as an error.
        Diag(DS.getStorageClassSpecLoc(), diag::err_mutable_nonmember);
      else if (!DS.isExternInLinkageSpec() && SCS != DeclSpec::SCS_typedef)
        Diag(DS.getStorageClassSpecLoc(), DiagID)
          << DeclSpec::getSpecifierName(SCS);
    }
  
    if (DeclSpec::TSCS TSCS = DS.getThreadStorageClassSpec())
      Diag(DS.getThreadStorageClassSpecLoc(), DiagID)
        << DeclSpec::getSpecifierName(TSCS);
    if (DS.getTypeQualifiers()) {
      if (DS.getTypeQualifiers() & DeclSpec::TQ_const)
        Diag(DS.getConstSpecLoc(), DiagID) << "const";
      if (DS.getTypeQualifiers() & DeclSpec::TQ_volatile)
        Diag(DS.getConstSpecLoc(), DiagID) << "volatile";
      // Restrict is covered above.
      if (DS.getTypeQualifiers() & DeclSpec::TQ_atomic)
        Diag(DS.getAtomicSpecLoc(), DiagID) << "_Atomic";
      if (DS.getTypeQualifiers() & DeclSpec::TQ_unaligned)
        Diag(DS.getUnalignedSpecLoc(), DiagID) << "__unaligned";
    }
  
    // Warn about ignored type attributes, for example:
    // __attribute__((aligned)) struct A;
    // Attributes should be placed after tag to apply to type declaration.
    if (!DS.getAttributes().empty()) {
      DeclSpec::TST TypeSpecType = DS.getTypeSpecType();
      if (TypeSpecType == DeclSpec::TST_class ||
          TypeSpecType == DeclSpec::TST_struct ||
          TypeSpecType == DeclSpec::TST_interface ||
          TypeSpecType == DeclSpec::TST_union ||
          TypeSpecType == DeclSpec::TST_enum) {
        for (const ParsedAttr &AL : DS.getAttributes())
          Diag(AL.getLoc(), diag::warn_declspec_attribute_ignored)
              << AL.getName() << GetDiagnosticTypeSpecifierID(TypeSpecType);
      }
    }
  
    return TagD;
  }
  
  /// We are trying to inject an anonymous member into the given scope;
  /// check if there's an existing declaration that can't be overloaded.
  ///
  /// \return true if this is a forbidden redeclaration
  static bool CheckAnonMemberRedeclaration(Sema &SemaRef,
                                           Scope *S,
                                           DeclContext *Owner,
                                           DeclarationName Name,
                                           SourceLocation NameLoc,
                                           bool IsUnion) {
    LookupResult R(SemaRef, Name, NameLoc, Sema::LookupMemberName,
                   Sema::ForVisibleRedeclaration);
    if (!SemaRef.LookupName(R, S)) return false;
  
    // Pick a representative declaration.
    NamedDecl *PrevDecl = R.getRepresentativeDecl()->getUnderlyingDecl();
    assert(PrevDecl && "Expected a non-null Decl");
  
    if (!SemaRef.isDeclInScope(PrevDecl, Owner, S))
      return false;
  
    SemaRef.Diag(NameLoc, diag::err_anonymous_record_member_redecl)
      << IsUnion << Name;
    SemaRef.Diag(PrevDecl->getLocation(), diag::note_previous_declaration);
  
    return true;
  }
  
  /// InjectAnonymousStructOrUnionMembers - Inject the members of the
  /// anonymous struct or union AnonRecord into the owning context Owner
  /// and scope S. This routine will be invoked just after we realize
  /// that an unnamed union or struct is actually an anonymous union or
  /// struct, e.g.,
  ///
  /// @code
  /// union {
  ///   int i;
  ///   float f;
  /// }; // InjectAnonymousStructOrUnionMembers called here to inject i and
  ///    // f into the surrounding scope.x
  /// @endcode
  ///
  /// This routine is recursive, injecting the names of nested anonymous
  /// structs/unions into the owning context and scope as well.
  static bool
  InjectAnonymousStructOrUnionMembers(Sema &SemaRef, Scope *S, DeclContext *Owner,
                                      RecordDecl *AnonRecord, AccessSpecifier AS,
                                      SmallVectorImpl<NamedDecl *> &Chaining) {
    bool Invalid = false;
  
    // Look every FieldDecl and IndirectFieldDecl with a name.
    for (auto *D : AnonRecord->decls()) {
      if ((isa<FieldDecl>(D) || isa<IndirectFieldDecl>(D)) &&
          cast<NamedDecl>(D)->getDeclName()) {
        ValueDecl *VD = cast<ValueDecl>(D);
        if (CheckAnonMemberRedeclaration(SemaRef, S, Owner, VD->getDeclName(),
                                         VD->getLocation(),
                                         AnonRecord->isUnion())) {
          // C++ [class.union]p2:
          //   The names of the members of an anonymous union shall be
          //   distinct from the names of any other entity in the
          //   scope in which the anonymous union is declared.
          Invalid = true;
        } else {
          // C++ [class.union]p2:
          //   For the purpose of name lookup, after the anonymous union
          //   definition, the members of the anonymous union are
          //   considered to have been defined in the scope in which the
          //   anonymous union is declared.
          unsigned OldChainingSize = Chaining.size();
          if (IndirectFieldDecl *IF = dyn_cast<IndirectFieldDecl>(VD))
            Chaining.append(IF->chain_begin(), IF->chain_end());
          else
            Chaining.push_back(VD);
  
          assert(Chaining.size() >= 2);
          NamedDecl **NamedChain =
            new (SemaRef.Context)NamedDecl*[Chaining.size()];
          for (unsigned i = 0; i < Chaining.size(); i++)
            NamedChain[i] = Chaining[i];
  
          IndirectFieldDecl *IndirectField = IndirectFieldDecl::Create(
              SemaRef.Context, Owner, VD->getLocation(), VD->getIdentifier(),
              VD->getType(), {NamedChain, Chaining.size()});
  
          for (const auto *Attr : VD->attrs())
            IndirectField->addAttr(Attr->clone(SemaRef.Context));
  
          IndirectField->setAccess(AS);
          IndirectField->setImplicit();
          SemaRef.PushOnScopeChains(IndirectField, S);
  
          // That includes picking up the appropriate access specifier.
          if (AS != AS_none) IndirectField->setAccess(AS);
  
          Chaining.resize(OldChainingSize);
        }
      }
    }
  
    return Invalid;
  }
  
  /// StorageClassSpecToVarDeclStorageClass - Maps a DeclSpec::SCS to
  /// a VarDecl::StorageClass. Any error reporting is up to the caller:
  /// illegal input values are mapped to SC_None.
  static StorageClass
  StorageClassSpecToVarDeclStorageClass(const DeclSpec &DS) {
    DeclSpec::SCS StorageClassSpec = DS.getStorageClassSpec();
    assert(StorageClassSpec != DeclSpec::SCS_typedef &&
           "Parser allowed 'typedef' as storage class VarDecl.");
    switch (StorageClassSpec) {
    case DeclSpec::SCS_unspecified:    return SC_None;
    case DeclSpec::SCS_extern:
      if (DS.isExternInLinkageSpec())
        return SC_None;
      return SC_Extern;
    case DeclSpec::SCS_static:         return SC_Static;
    case DeclSpec::SCS_auto:           return SC_Auto;
    case DeclSpec::SCS_register:       return SC_Register;
    case DeclSpec::SCS_private_extern: return SC_PrivateExtern;
      // Illegal SCSs map to None: error reporting is up to the caller.
    case DeclSpec::SCS_mutable:        // Fall through.
    case DeclSpec::SCS_typedef:        return SC_None;
    }
    llvm_unreachable("unknown storage class specifier");
  }
  
  static SourceLocation findDefaultInitializer(const CXXRecordDecl *Record) {
    assert(Record->hasInClassInitializer());
  
    for (const auto *I : Record->decls()) {
      const auto *FD = dyn_cast<FieldDecl>(I);
      if (const auto *IFD = dyn_cast<IndirectFieldDecl>(I))
        FD = IFD->getAnonField();
      if (FD && FD->hasInClassInitializer())
        return FD->getLocation();
    }
  
    llvm_unreachable("couldn't find in-class initializer");
  }
  
  static void checkDuplicateDefaultInit(Sema &S, CXXRecordDecl *Parent,
                                        SourceLocation DefaultInitLoc) {
    if (!Parent->isUnion() || !Parent->hasInClassInitializer())
      return;
  
    S.Diag(DefaultInitLoc, diag::err_multiple_mem_union_initialization);
    S.Diag(findDefaultInitializer(Parent), diag::note_previous_initializer) << 0;
  }
  
  static void checkDuplicateDefaultInit(Sema &S, CXXRecordDecl *Parent,
                                        CXXRecordDecl *AnonUnion) {
    if (!Parent->isUnion() || !Parent->hasInClassInitializer())
      return;
  
    checkDuplicateDefaultInit(S, Parent, findDefaultInitializer(AnonUnion));
  }
  
  /// BuildAnonymousStructOrUnion - Handle the declaration of an
  /// anonymous structure or union. Anonymous unions are a C++ feature
  /// (C++ [class.union]) and a C11 feature; anonymous structures
  /// are a C11 feature and GNU C++ extension.
  Decl *Sema::BuildAnonymousStructOrUnion(Scope *S, DeclSpec &DS,
                                          AccessSpecifier AS,
                                          RecordDecl *Record,
                                          const PrintingPolicy &Policy) {
    DeclContext *Owner = Record->getDeclContext();
  
    // Diagnose whether this anonymous struct/union is an extension.
    if (Record->isUnion() && !getLangOpts().CPlusPlus && !getLangOpts().C11)
      Diag(Record->getLocation(), diag::ext_anonymous_union);
    else if (!Record->isUnion() && getLangOpts().CPlusPlus)
      Diag(Record->getLocation(), diag::ext_gnu_anonymous_struct);
    else if (!Record->isUnion() && !getLangOpts().C11)
      Diag(Record->getLocation(), diag::ext_c11_anonymous_struct);
  
    // C and C++ require different kinds of checks for anonymous
    // structs/unions.
    bool Invalid = false;
    if (getLangOpts().CPlusPlus) {
      const char *PrevSpec = nullptr;
      unsigned DiagID;
      if (Record->isUnion()) {
        // C++ [class.union]p6:
        // C++17 [class.union.anon]p2:
        //   Anonymous unions declared in a named namespace or in the
        //   global namespace shall be declared static.
        DeclContext *OwnerScope = Owner->getRedeclContext();
        if (DS.getStorageClassSpec() != DeclSpec::SCS_static &&
            (OwnerScope->isTranslationUnit() ||
             (OwnerScope->isNamespace() &&
              !cast<NamespaceDecl>(OwnerScope)->isAnonymousNamespace()))) {
          Diag(Record->getLocation(), diag::err_anonymous_union_not_static)
            << FixItHint::CreateInsertion(Record->getLocation(), "static ");
  
          // Recover by adding 'static'.
          DS.SetStorageClassSpec(*this, DeclSpec::SCS_static, SourceLocation(),
                                 PrevSpec, DiagID, Policy);
        }
        // C++ [class.union]p6:
        //   A storage class is not allowed in a declaration of an
        //   anonymous union in a class scope.
        else if (DS.getStorageClassSpec() != DeclSpec::SCS_unspecified &&
                 isa<RecordDecl>(Owner)) {
          Diag(DS.getStorageClassSpecLoc(),
               diag::err_anonymous_union_with_storage_spec)
            << FixItHint::CreateRemoval(DS.getStorageClassSpecLoc());
  
          // Recover by removing the storage specifier.
          DS.SetStorageClassSpec(*this, DeclSpec::SCS_unspecified,
                                 SourceLocation(),
                                 PrevSpec, DiagID, Context.getPrintingPolicy());
        }
      }
  
      // Ignore const/volatile/restrict qualifiers.
      if (DS.getTypeQualifiers()) {
        if (DS.getTypeQualifiers() & DeclSpec::TQ_const)
          Diag(DS.getConstSpecLoc(), diag::ext_anonymous_struct_union_qualified)
            << Record->isUnion() << "const"
            << FixItHint::CreateRemoval(DS.getConstSpecLoc());
        if (DS.getTypeQualifiers() & DeclSpec::TQ_volatile)
          Diag(DS.getVolatileSpecLoc(),
               diag::ext_anonymous_struct_union_qualified)
            << Record->isUnion() << "volatile"
            << FixItHint::CreateRemoval(DS.getVolatileSpecLoc());
        if (DS.getTypeQualifiers() & DeclSpec::TQ_restrict)
          Diag(DS.getRestrictSpecLoc(),
               diag::ext_anonymous_struct_union_qualified)
            << Record->isUnion() << "restrict"
            << FixItHint::CreateRemoval(DS.getRestrictSpecLoc());
        if (DS.getTypeQualifiers() & DeclSpec::TQ_atomic)
          Diag(DS.getAtomicSpecLoc(),
               diag::ext_anonymous_struct_union_qualified)
            << Record->isUnion() << "_Atomic"
            << FixItHint::CreateRemoval(DS.getAtomicSpecLoc());
        if (DS.getTypeQualifiers() & DeclSpec::TQ_unaligned)
          Diag(DS.getUnalignedSpecLoc(),
               diag::ext_anonymous_struct_union_qualified)
            << Record->isUnion() << "__unaligned"
            << FixItHint::CreateRemoval(DS.getUnalignedSpecLoc());
  
        DS.ClearTypeQualifiers();
      }
  
      // C++ [class.union]p2:
      //   The member-specification of an anonymous union shall only
      //   define non-static data members. [Note: nested types and
      //   functions cannot be declared within an anonymous union. ]
      for (auto *Mem : Record->decls()) {
        if (auto *FD = dyn_cast<FieldDecl>(Mem)) {
          // C++ [class.union]p3:
          //   An anonymous union shall not have private or protected
          //   members (clause 11).
          assert(FD->getAccess() != AS_none);
          if (FD->getAccess() != AS_public) {
            Diag(FD->getLocation(), diag::err_anonymous_record_nonpublic_member)
              << Record->isUnion() << (FD->getAccess() == AS_protected);
            Invalid = true;
          }
  
          // C++ [class.union]p1
          //   An object of a class with a non-trivial constructor, a non-trivial
          //   copy constructor, a non-trivial destructor, or a non-trivial copy
          //   assignment operator cannot be a member of a union, nor can an
          //   array of such objects.
          if (CheckNontrivialField(FD))
            Invalid = true;
        } else if (Mem->isImplicit()) {
          // Any implicit members are fine.
        } else if (isa<TagDecl>(Mem) && Mem->getDeclContext() != Record) {
          // This is a type that showed up in an
          // elaborated-type-specifier inside the anonymous struct or
          // union, but which actually declares a type outside of the
          // anonymous struct or union. It's okay.
        } else if (auto *MemRecord = dyn_cast<RecordDecl>(Mem)) {
          if (!MemRecord->isAnonymousStructOrUnion() &&
              MemRecord->getDeclName()) {
            // Visual C++ allows type definition in anonymous struct or union.
            if (getLangOpts().MicrosoftExt)
              Diag(MemRecord->getLocation(), diag::ext_anonymous_record_with_type)
                << Record->isUnion();
            else {
              // This is a nested type declaration.
              Diag(MemRecord->getLocation(), diag::err_anonymous_record_with_type)
                << Record->isUnion();
              Invalid = true;
            }
          } else {
            // This is an anonymous type definition within another anonymous type.
            // This is a popular extension, provided by Plan9, MSVC and GCC, but
            // not part of standard C++.
            Diag(MemRecord->getLocation(),
                 diag::ext_anonymous_record_with_anonymous_type)
              << Record->isUnion();
          }
        } else if (isa<AccessSpecDecl>(Mem)) {
          // Any access specifier is fine.
        } else if (isa<StaticAssertDecl>(Mem)) {
          // In C++1z, static_assert declarations are also fine.
        } else {
          // We have something that isn't a non-static data
          // member. Complain about it.
          unsigned DK = diag::err_anonymous_record_bad_member;
          if (isa<TypeDecl>(Mem))
            DK = diag::err_anonymous_record_with_type;
          else if (isa<FunctionDecl>(Mem))
            DK = diag::err_anonymous_record_with_function;
          else if (isa<VarDecl>(Mem))
            DK = diag::err_anonymous_record_with_static;
  
          // Visual C++ allows type definition in anonymous struct or union.
          if (getLangOpts().MicrosoftExt &&
              DK == diag::err_anonymous_record_with_type)
            Diag(Mem->getLocation(), diag::ext_anonymous_record_with_type)
              << Record->isUnion();
          else {
            Diag(Mem->getLocation(), DK) << Record->isUnion();
            Invalid = true;
          }
        }
      }
  
      // C++11 [class.union]p8 (DR1460):
      //   At most one variant member of a union may have a
      //   brace-or-equal-initializer.
      if (cast<CXXRecordDecl>(Record)->hasInClassInitializer() &&
          Owner->isRecord())
        checkDuplicateDefaultInit(*this, cast<CXXRecordDecl>(Owner),
                                  cast<CXXRecordDecl>(Record));
    }
  
    if (!Record->isUnion() && !Owner->isRecord()) {
      Diag(Record->getLocation(), diag::err_anonymous_struct_not_member)
        << getLangOpts().CPlusPlus;
      Invalid = true;
    }
  
    // Mock up a declarator.
    Declarator Dc(DS, DeclaratorContext::MemberContext);
    TypeSourceInfo *TInfo = GetTypeForDeclarator(Dc, S);
    assert(TInfo && "couldn't build declarator info for anonymous struct/union");
  
    // Create a declaration for this anonymous struct/union.
    NamedDecl *Anon = nullptr;
    if (RecordDecl *OwningClass = dyn_cast<RecordDecl>(Owner)) {
      Anon = FieldDecl::Create(
          Context, OwningClass, DS.getBeginLoc(), Record->getLocation(),
          /*IdentifierInfo=*/nullptr, Context.getTypeDeclType(Record), TInfo,
          /*BitWidth=*/nullptr, /*Mutable=*/false,
          /*InitStyle=*/ICIS_NoInit);
      Anon->setAccess(AS);
      if (getLangOpts().CPlusPlus)
        FieldCollector->Add(cast<FieldDecl>(Anon));
    } else {
      DeclSpec::SCS SCSpec = DS.getStorageClassSpec();
      StorageClass SC = StorageClassSpecToVarDeclStorageClass(DS);
      if (SCSpec == DeclSpec::SCS_mutable) {
        // mutable can only appear on non-static class members, so it's always
        // an error here
        Diag(Record->getLocation(), diag::err_mutable_nonmember);
        Invalid = true;
        SC = SC_None;
      }
  
      Anon = VarDecl::Create(Context, Owner, DS.getBeginLoc(),
                             Record->getLocation(), /*IdentifierInfo=*/nullptr,
                             Context.getTypeDeclType(Record), TInfo, SC);
  
      // Default-initialize the implicit variable. This initialization will be
      // trivial in almost all cases, except if a union member has an in-class
      // initializer:
      //   union { int n = 0; };
      ActOnUninitializedDecl(Anon);
    }
    Anon->setImplicit();
  
    // Mark this as an anonymous struct/union type.
    Record->setAnonymousStructOrUnion(true);
  
    // Add the anonymous struct/union object to the current
    // context. We'll be referencing this object when we refer to one of
    // its members.
    Owner->addDecl(Anon);
  
    // Inject the members of the anonymous struct/union into the owning
    // context and into the identifier resolver chain for name lookup
    // purposes.
    SmallVector<NamedDecl*, 2> Chain;
    Chain.push_back(Anon);
  
    if (InjectAnonymousStructOrUnionMembers(*this, S, Owner, Record, AS, Chain))
      Invalid = true;
  
    if (VarDecl *NewVD = dyn_cast<VarDecl>(Anon)) {
      if (getLangOpts().CPlusPlus && NewVD->isStaticLocal()) {
        Decl *ManglingContextDecl;
        if (MangleNumberingContext *MCtx = getCurrentMangleNumberContext(
                NewVD->getDeclContext(), ManglingContextDecl)) {
          Context.setManglingNumber(
              NewVD, MCtx->getManglingNumber(
                         NewVD, getMSManglingNumber(getLangOpts(), S)));
          Context.setStaticLocalNumber(NewVD, MCtx->getStaticLocalNumber(NewVD));
        }
      }
    }
  
    if (Invalid)
      Anon->setInvalidDecl();
  
    return Anon;
  }
  
  /// BuildMicrosoftCAnonymousStruct - Handle the declaration of an
  /// Microsoft C anonymous structure.
  /// Ref: http://msdn.microsoft.com/en-us/library/z2cx9y4f.aspx
  /// Example:
  ///
  /// struct A { int a; };
  /// struct B { struct A; int b; };
  ///
  /// void foo() {
  ///   B var;
  ///   var.a = 3;
  /// }
  ///
  Decl *Sema::BuildMicrosoftCAnonymousStruct(Scope *S, DeclSpec &DS,
                                             RecordDecl *Record) {
    assert(Record && "expected a record!");
  
    // Mock up a declarator.
    Declarator Dc(DS, DeclaratorContext::TypeNameContext);
    TypeSourceInfo *TInfo = GetTypeForDeclarator(Dc, S);
    assert(TInfo && "couldn't build declarator info for anonymous struct");
  
    auto *ParentDecl = cast<RecordDecl>(CurContext);
    QualType RecTy = Context.getTypeDeclType(Record);
  
    // Create a declaration for this anonymous struct.
    NamedDecl *Anon =
        FieldDecl::Create(Context, ParentDecl, DS.getBeginLoc(), DS.getBeginLoc(),
                          /*IdentifierInfo=*/nullptr, RecTy, TInfo,
                          /*BitWidth=*/nullptr, /*Mutable=*/false,
                          /*InitStyle=*/ICIS_NoInit);
    Anon->setImplicit();
  
    // Add the anonymous struct object to the current context.
    CurContext->addDecl(Anon);
  
    // Inject the members of the anonymous struct into the current
    // context and into the identifier resolver chain for name lookup
    // purposes.
    SmallVector<NamedDecl*, 2> Chain;
    Chain.push_back(Anon);
  
    RecordDecl *RecordDef = Record->getDefinition();
    if (RequireCompleteType(Anon->getLocation(), RecTy,
                            diag::err_field_incomplete) ||
        InjectAnonymousStructOrUnionMembers(*this, S, CurContext, RecordDef,
                                            AS_none, Chain)) {
      Anon->setInvalidDecl();
      ParentDecl->setInvalidDecl();
    }
  
    return Anon;
  }
  
  /// GetNameForDeclarator - Determine the full declaration name for the
  /// given Declarator.
  DeclarationNameInfo Sema::GetNameForDeclarator(Declarator &D) {
    return GetNameFromUnqualifiedId(D.getName());
  }
  
  /// Retrieves the declaration name from a parsed unqualified-id.
  DeclarationNameInfo
  Sema::GetNameFromUnqualifiedId(const UnqualifiedId &Name) {
    DeclarationNameInfo NameInfo;
    NameInfo.setLoc(Name.StartLocation);
  
    switch (Name.getKind()) {
  
    case UnqualifiedIdKind::IK_ImplicitSelfParam:
    case UnqualifiedIdKind::IK_Identifier:
      NameInfo.setName(Name.Identifier);
      return NameInfo;
  
    case UnqualifiedIdKind::IK_DeductionGuideName: {
      // C++ [temp.deduct.guide]p3:
      //   The simple-template-id shall name a class template specialization.
      //   The template-name shall be the same identifier as the template-name
      //   of the simple-template-id.
      // These together intend to imply that the template-name shall name a
      // class template.
      // FIXME: template<typename T> struct X {};
      //        template<typename T> using Y = X<T>;
      //        Y(int) -> Y<int>;
      //   satisfies these rules but does not name a class template.
      TemplateName TN = Name.TemplateName.get().get();
      auto *Template = TN.getAsTemplateDecl();
      if (!Template || !isa<ClassTemplateDecl>(Template)) {
        Diag(Name.StartLocation,
             diag::err_deduction_guide_name_not_class_template)
          << (int)getTemplateNameKindForDiagnostics(TN) << TN;
        if (Template)
          Diag(Template->getLocation(), diag::note_template_decl_here);
        return DeclarationNameInfo();
      }
  
      NameInfo.setName(
          Context.DeclarationNames.getCXXDeductionGuideName(Template));
      return NameInfo;
    }
  
    case UnqualifiedIdKind::IK_OperatorFunctionId:
      NameInfo.setName(Context.DeclarationNames.getCXXOperatorName(
                                             Name.OperatorFunctionId.Operator));
      NameInfo.getInfo().CXXOperatorName.BeginOpNameLoc
        = Name.OperatorFunctionId.SymbolLocations[0];
      NameInfo.getInfo().CXXOperatorName.EndOpNameLoc
        = Name.EndLocation.getRawEncoding();
      return NameInfo;
  
    case UnqualifiedIdKind::IK_LiteralOperatorId:
      NameInfo.setName(Context.DeclarationNames.getCXXLiteralOperatorName(
                                                             Name.Identifier));
      NameInfo.setCXXLiteralOperatorNameLoc(Name.EndLocation);
      return NameInfo;
  
    case UnqualifiedIdKind::IK_ConversionFunctionId: {
      TypeSourceInfo *TInfo;
      QualType Ty = GetTypeFromParser(Name.ConversionFunctionId, &TInfo);
      if (Ty.isNull())
        return DeclarationNameInfo();
      NameInfo.setName(Context.DeclarationNames.getCXXConversionFunctionName(
                                                 Context.getCanonicalType(Ty)));
      NameInfo.setNamedTypeInfo(TInfo);
      return NameInfo;
    }
  
    case UnqualifiedIdKind::IK_ConstructorName: {
      TypeSourceInfo *TInfo;
      QualType Ty = GetTypeFromParser(Name.ConstructorName, &TInfo);
      if (Ty.isNull())
        return DeclarationNameInfo();
      NameInfo.setName(Context.DeclarationNames.getCXXConstructorName(
                                                Context.getCanonicalType(Ty)));
      NameInfo.setNamedTypeInfo(TInfo);
      return NameInfo;
    }
  
    case UnqualifiedIdKind::IK_ConstructorTemplateId: {
      // In well-formed code, we can only have a constructor
      // template-id that refers to the current context, so go there
      // to find the actual type being constructed.
      CXXRecordDecl *CurClass = dyn_cast<CXXRecordDecl>(CurContext);
      if (!CurClass || CurClass->getIdentifier() != Name.TemplateId->Name)
        return DeclarationNameInfo();
  
      // Determine the type of the class being constructed.
      QualType CurClassType = Context.getTypeDeclType(CurClass);
  
      // FIXME: Check two things: that the template-id names the same type as
      // CurClassType, and that the template-id does not occur when the name
      // was qualified.
  
      NameInfo.setName(Context.DeclarationNames.getCXXConstructorName(
                                      Context.getCanonicalType(CurClassType)));
      // FIXME: should we retrieve TypeSourceInfo?
      NameInfo.setNamedTypeInfo(nullptr);
      return NameInfo;
    }
  
    case UnqualifiedIdKind::IK_DestructorName: {
      TypeSourceInfo *TInfo;
      QualType Ty = GetTypeFromParser(Name.DestructorName, &TInfo);
      if (Ty.isNull())
        return DeclarationNameInfo();
      NameInfo.setName(Context.DeclarationNames.getCXXDestructorName(
                                                Context.getCanonicalType(Ty)));
      NameInfo.setNamedTypeInfo(TInfo);
      return NameInfo;
    }
  
    case UnqualifiedIdKind::IK_TemplateId: {
      TemplateName TName = Name.TemplateId->Template.get();
      SourceLocation TNameLoc = Name.TemplateId->TemplateNameLoc;
      return Context.getNameForTemplate(TName, TNameLoc);
    }
  
    } // switch (Name.getKind())
  
    llvm_unreachable("Unknown name kind");
  }
  
  static QualType getCoreType(QualType Ty) {
    do {
      if (Ty->isPointerType() || Ty->isReferenceType())
        Ty = Ty->getPointeeType();
      else if (Ty->isArrayType())
        Ty = Ty->castAsArrayTypeUnsafe()->getElementType();
      else
        return Ty.withoutLocalFastQualifiers();
    } while (true);
  }
  
  /// hasSimilarParameters - Determine whether the C++ functions Declaration
  /// and Definition have "nearly" matching parameters. This heuristic is
  /// used to improve diagnostics in the case where an out-of-line function
  /// definition doesn't match any declaration within the class or namespace.
  /// Also sets Params to the list of indices to the parameters that differ
  /// between the declaration and the definition. If hasSimilarParameters
  /// returns true and Params is empty, then all of the parameters match.
  static bool hasSimilarParameters(ASTContext &Context,
                                       FunctionDecl *Declaration,
                                       FunctionDecl *Definition,
                                       SmallVectorImpl<unsigned> &Params) {
    Params.clear();
    if (Declaration->param_size() != Definition->param_size())
      return false;
    for (unsigned Idx = 0; Idx < Declaration->param_size(); ++Idx) {
      QualType DeclParamTy = Declaration->getParamDecl(Idx)->getType();
      QualType DefParamTy = Definition->getParamDecl(Idx)->getType();
  
      // The parameter types are identical
      if (Context.hasSameUnqualifiedType(DefParamTy, DeclParamTy))
        continue;
  
      QualType DeclParamBaseTy = getCoreType(DeclParamTy);
      QualType DefParamBaseTy = getCoreType(DefParamTy);
      const IdentifierInfo *DeclTyName = DeclParamBaseTy.getBaseTypeIdentifier();
      const IdentifierInfo *DefTyName = DefParamBaseTy.getBaseTypeIdentifier();
  
      if (Context.hasSameUnqualifiedType(DeclParamBaseTy, DefParamBaseTy) ||
          (DeclTyName && DeclTyName == DefTyName))
        Params.push_back(Idx);
      else  // The two parameters aren't even close
        return false;
    }
  
    return true;
  }
  
  /// NeedsRebuildingInCurrentInstantiation - Checks whether the given
  /// declarator needs to be rebuilt in the current instantiation.
  /// Any bits of declarator which appear before the name are valid for
  /// consideration here.  That's specifically the type in the decl spec
  /// and the base type in any member-pointer chunks.
  static bool RebuildDeclaratorInCurrentInstantiation(Sema &S, Declarator &D,
                                                      DeclarationName Name) {
    // The types we specifically need to rebuild are:
    //   - typenames, typeofs, and decltypes
    //   - types which will become injected class names
    // Of course, we also need to rebuild any type referencing such a
    // type.  It's safest to just say "dependent", but we call out a
    // few cases here.
  
    DeclSpec &DS = D.getMutableDeclSpec();
    switch (DS.getTypeSpecType()) {
    case DeclSpec::TST_typename:
    case DeclSpec::TST_typeofType:
    case DeclSpec::TST_underlyingType:
    case DeclSpec::TST_atomic: {
      // Grab the type from the parser.
      TypeSourceInfo *TSI = nullptr;
      QualType T = S.GetTypeFromParser(DS.getRepAsType(), &TSI);
      if (T.isNull() || !T->isDependentType()) break;
  
      // Make sure there's a type source info.  This isn't really much
      // of a waste; most dependent types should have type source info
      // attached already.
      if (!TSI)
        TSI = S.Context.getTrivialTypeSourceInfo(T, DS.getTypeSpecTypeLoc());
  
      // Rebuild the type in the current instantiation.
      TSI = S.RebuildTypeInCurrentInstantiation(TSI, D.getIdentifierLoc(), Name);
      if (!TSI) return true;
  
      // Store the new type back in the decl spec.
      ParsedType LocType = S.CreateParsedType(TSI->getType(), TSI);
      DS.UpdateTypeRep(LocType);
      break;
    }
  
    case DeclSpec::TST_decltype:
    case DeclSpec::TST_typeofExpr: {
      Expr *E = DS.getRepAsExpr();
      ExprResult Result = S.RebuildExprInCurrentInstantiation(E);
      if (Result.isInvalid()) return true;
      DS.UpdateExprRep(Result.get());
      break;
    }
  
    default:
      // Nothing to do for these decl specs.
      break;
    }
  
    // It doesn't matter what order we do this in.
    for (unsigned I = 0, E = D.getNumTypeObjects(); I != E; ++I) {
      DeclaratorChunk &Chunk = D.getTypeObject(I);
  
      // The only type information in the declarator which can come
      // before the declaration name is the base type of a member
      // pointer.
      if (Chunk.Kind != DeclaratorChunk::MemberPointer)
        continue;
  
      // Rebuild the scope specifier in-place.
      CXXScopeSpec &SS = Chunk.Mem.Scope();
      if (S.RebuildNestedNameSpecifierInCurrentInstantiation(SS))
        return true;
    }
  
    return false;
  }
  
  Decl *Sema::ActOnDeclarator(Scope *S, Declarator &D) {
    D.setFunctionDefinitionKind(FDK_Declaration);
    Decl *Dcl = HandleDeclarator(S, D, MultiTemplateParamsArg());
  
    if (OriginalLexicalContext && OriginalLexicalContext->isObjCContainer() &&
        Dcl && Dcl->getDeclContext()->isFileContext())
      Dcl->setTopLevelDeclInObjCContainer();
  
    if (getLangOpts().OpenCL)
      setCurrentOpenCLExtensionForDecl(Dcl);
  
    return Dcl;
  }
  
  /// DiagnoseClassNameShadow - Implement C++ [class.mem]p13:
  ///   If T is the name of a class, then each of the following shall have a
  ///   name different from T:
  ///     - every static data member of class T;
  ///     - every member function of class T
  ///     - every member of class T that is itself a type;
  /// \returns true if the declaration name violates these rules.
  bool Sema::DiagnoseClassNameShadow(DeclContext *DC,
                                     DeclarationNameInfo NameInfo) {
    DeclarationName Name = NameInfo.getName();
  
    CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC);
    while (Record && Record->isAnonymousStructOrUnion())
      Record = dyn_cast<CXXRecordDecl>(Record->getParent());
    if (Record && Record->getIdentifier() && Record->getDeclName() == Name) {
      Diag(NameInfo.getLoc(), diag::err_member_name_of_class) << Name;
      return true;
    }
  
    return false;
  }
  
  /// Diagnose a declaration whose declarator-id has the given
  /// nested-name-specifier.
  ///
  /// \param SS The nested-name-specifier of the declarator-id.
  ///
  /// \param DC The declaration context to which the nested-name-specifier
  /// resolves.
  ///
  /// \param Name The name of the entity being declared.
  ///
  /// \param Loc The location of the name of the entity being declared.
  ///
  /// \param IsTemplateId Whether the name is a (simple-)template-id, and thus
  /// we're declaring an explicit / partial specialization / instantiation.
  ///
  /// \returns true if we cannot safely recover from this error, false otherwise.
  bool Sema::diagnoseQualifiedDeclaration(CXXScopeSpec &SS, DeclContext *DC,
                                          DeclarationName Name,
                                          SourceLocation Loc, bool IsTemplateId) {
    DeclContext *Cur = CurContext;
    while (isa<LinkageSpecDecl>(Cur) || isa<CapturedDecl>(Cur))
      Cur = Cur->getParent();
  
    // If the user provided a superfluous scope specifier that refers back to the
    // class in which the entity is already declared, diagnose and ignore it.
    //
    // class X {
    //   void X::f();
    // };
    //
    // Note, it was once ill-formed to give redundant qualification in all
    // contexts, but that rule was removed by DR482.
    if (Cur->Equals(DC)) {
      if (Cur->isRecord()) {
        Diag(Loc, LangOpts.MicrosoftExt ? diag::warn_member_extra_qualification
                                        : diag::err_member_extra_qualification)
          << Name << FixItHint::CreateRemoval(SS.getRange());
        SS.clear();
      } else {
        Diag(Loc, diag::warn_namespace_member_extra_qualification) << Name;
      }
      return false;
    }
  
    // Check whether the qualifying scope encloses the scope of the original
    // declaration. For a template-id, we perform the checks in
    // CheckTemplateSpecializationScope.
    if (!Cur->Encloses(DC) && !IsTemplateId) {
      if (Cur->isRecord())
        Diag(Loc, diag::err_member_qualification)
          << Name << SS.getRange();
      else if (isa<TranslationUnitDecl>(DC))
        Diag(Loc, diag::err_invalid_declarator_global_scope)
          << Name << SS.getRange();
      else if (isa<FunctionDecl>(Cur))
        Diag(Loc, diag::err_invalid_declarator_in_function)
          << Name << SS.getRange();
      else if (isa<BlockDecl>(Cur))
        Diag(Loc, diag::err_invalid_declarator_in_block)
          << Name << SS.getRange();
      else
        Diag(Loc, diag::err_invalid_declarator_scope)
        << Name << cast<NamedDecl>(Cur) << cast<NamedDecl>(DC) << SS.getRange();
  
      return true;
    }
  
    if (Cur->isRecord()) {
      // Cannot qualify members within a class.
      Diag(Loc, diag::err_member_qualification)
        << Name << SS.getRange();
      SS.clear();
  
      // C++ constructors and destructors with incorrect scopes can break
      // our AST invariants by having the wrong underlying types. If
      // that's the case, then drop this declaration entirely.
      if ((Name.getNameKind() == DeclarationName::CXXConstructorName ||
           Name.getNameKind() == DeclarationName::CXXDestructorName) &&
          !Context.hasSameType(Name.getCXXNameType(),
                               Context.getTypeDeclType(cast<CXXRecordDecl>(Cur))))
        return true;
  
      return false;
    }
  
    // C++11 [dcl.meaning]p1:
    //   [...] "The nested-name-specifier of the qualified declarator-id shall
    //   not begin with a decltype-specifer"
    NestedNameSpecifierLoc SpecLoc(SS.getScopeRep(), SS.location_data());
    while (SpecLoc.getPrefix())
      SpecLoc = SpecLoc.getPrefix();
    if (dyn_cast_or_null<DecltypeType>(
          SpecLoc.getNestedNameSpecifier()->getAsType()))
      Diag(Loc, diag::err_decltype_in_declarator)
        << SpecLoc.getTypeLoc().getSourceRange();
  
    return false;
  }
  
  NamedDecl *Sema::HandleDeclarator(Scope *S, Declarator &D,
                                    MultiTemplateParamsArg TemplateParamLists) {
    // TODO: consider using NameInfo for diagnostic.
    DeclarationNameInfo NameInfo = GetNameForDeclarator(D);
    DeclarationName Name = NameInfo.getName();
  
    // All of these full declarators require an identifier.  If it doesn't have
    // one, the ParsedFreeStandingDeclSpec action should be used.
    if (D.isDecompositionDeclarator()) {
      return ActOnDecompositionDeclarator(S, D, TemplateParamLists);
    } else if (!Name) {
      if (!D.isInvalidType())  // Reject this if we think it is valid.
        Diag(D.getDeclSpec().getBeginLoc(), diag::err_declarator_need_ident)
            << D.getDeclSpec().getSourceRange() << D.getSourceRange();
      return nullptr;
    } else if (DiagnoseUnexpandedParameterPack(NameInfo, UPPC_DeclarationType))
      return nullptr;
  
    // The scope passed in may not be a decl scope.  Zip up the scope tree until
    // we find one that is.
    while ((S->getFlags() & Scope::DeclScope) == 0 ||
           (S->getFlags() & Scope::TemplateParamScope) != 0)
      S = S->getParent();
  
    DeclContext *DC = CurContext;
    if (D.getCXXScopeSpec().isInvalid())
      D.setInvalidType();
    else if (D.getCXXScopeSpec().isSet()) {
      if (DiagnoseUnexpandedParameterPack(D.getCXXScopeSpec(),
                                          UPPC_DeclarationQualifier))
        return nullptr;
  
      bool EnteringContext = !D.getDeclSpec().isFriendSpecified();
      DC = computeDeclContext(D.getCXXScopeSpec(), EnteringContext);
      if (!DC || isa<EnumDecl>(DC)) {
        // If we could not compute the declaration context, it's because the
        // declaration context is dependent but does not refer to a class,
        // class template, or class template partial specialization. Complain
        // and return early, to avoid the coming semantic disaster.
        Diag(D.getIdentifierLoc(),
             diag::err_template_qualified_declarator_no_match)
          << D.getCXXScopeSpec().getScopeRep()
          << D.getCXXScopeSpec().getRange();
        return nullptr;
      }
      bool IsDependentContext = DC->isDependentContext();
  
      if (!IsDependentContext &&
          RequireCompleteDeclContext(D.getCXXScopeSpec(), DC))
        return nullptr;
  
      // If a class is incomplete, do not parse entities inside it.
      if (isa<CXXRecordDecl>(DC) && !cast<CXXRecordDecl>(DC)->hasDefinition()) {
        Diag(D.getIdentifierLoc(),
             diag::err_member_def_undefined_record)
          << Name << DC << D.getCXXScopeSpec().getRange();
        return nullptr;
      }
      if (!D.getDeclSpec().isFriendSpecified()) {
        if (diagnoseQualifiedDeclaration(
                D.getCXXScopeSpec(), DC, Name, D.getIdentifierLoc(),
                D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId)) {
          if (DC->isRecord())
            return nullptr;
  
          D.setInvalidType();
        }
      }
  
      // Check whether we need to rebuild the type of the given
      // declaration in the current instantiation.
      if (EnteringContext && IsDependentContext &&
          TemplateParamLists.size() != 0) {
        ContextRAII SavedContext(*this, DC);
        if (RebuildDeclaratorInCurrentInstantiation(*this, D, Name))
          D.setInvalidType();
      }
    }
  
    TypeSourceInfo *TInfo = GetTypeForDeclarator(D, S);
    QualType R = TInfo->getType();
  
    if (DiagnoseUnexpandedParameterPack(D.getIdentifierLoc(), TInfo,
                                        UPPC_DeclarationType))
      D.setInvalidType();
  
    LookupResult Previous(*this, NameInfo, LookupOrdinaryName,
                          forRedeclarationInCurContext());
  
    // See if this is a redefinition of a variable in the same scope.
    if (!D.getCXXScopeSpec().isSet()) {
      bool IsLinkageLookup = false;
      bool CreateBuiltins = false;
  
      // If the declaration we're planning to build will be a function
      // or object with linkage, then look for another declaration with
      // linkage (C99 6.2.2p4-5 and C++ [basic.link]p6).
      //
      // If the declaration we're planning to build will be declared with
      // external linkage in the translation unit, create any builtin with
      // the same name.
      if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef)
        /* Do nothing*/;
      else if (CurContext->isFunctionOrMethod() &&
               (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_extern ||
                R->isFunctionType())) {
        IsLinkageLookup = true;
        CreateBuiltins =
            CurContext->getEnclosingNamespaceContext()->isTranslationUnit();
      } else if (CurContext->getRedeclContext()->isTranslationUnit() &&
                 D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_static)
        CreateBuiltins = true;
  
      if (IsLinkageLookup) {
        Previous.clear(LookupRedeclarationWithLinkage);
        Previous.setRedeclarationKind(ForExternalRedeclaration);
      }
  
      LookupName(Previous, S, CreateBuiltins);
    } else { // Something like "int foo::x;"
      LookupQualifiedName(Previous, DC);
  
      // C++ [dcl.meaning]p1:
      //   When the declarator-id is qualified, the declaration shall refer to a
      //  previously declared member of the class or namespace to which the
      //  qualifier refers (or, in the case of a namespace, of an element of the
      //  inline namespace set of that namespace (7.3.1)) or to a specialization
      //  thereof; [...]
      //
      // Note that we already checked the context above, and that we do not have
      // enough information to make sure that Previous contains the declaration
      // we want to match. For example, given:
      //
      //   class X {
      //     void f();
      //     void f(float);
      //   };
      //
      //   void X::f(int) { } // ill-formed
      //
      // In this case, Previous will point to the overload set
      // containing the two f's declared in X, but neither of them
      // matches.
  
      // C++ [dcl.meaning]p1:
      //   [...] the member shall not merely have been introduced by a
      //   using-declaration in the scope of the class or namespace nominated by
      //   the nested-name-specifier of the declarator-id.
      RemoveUsingDecls(Previous);
    }
  
    if (Previous.isSingleResult() &&
        Previous.getFoundDecl()->isTemplateParameter()) {
      // Maybe we will complain about the shadowed template parameter.
      if (!D.isInvalidType())
        DiagnoseTemplateParameterShadow(D.getIdentifierLoc(),
                                        Previous.getFoundDecl());
  
      // Just pretend that we didn't see the previous declaration.
      Previous.clear();
    }
  
    if (!R->isFunctionType() && DiagnoseClassNameShadow(DC, NameInfo))
      // Forget that the previous declaration is the injected-class-name.
      Previous.clear();
  
    // In C++, the previous declaration we find might be a tag type
    // (class or enum). In this case, the new declaration will hide the
    // tag type. Note that this applies to functions, function templates, and
    // variables, but not to typedefs (C++ [dcl.typedef]p4) or variable templates.
    if (Previous.isSingleTagDecl() &&
        D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_typedef &&
        (TemplateParamLists.size() == 0 || R->isFunctionType()))
      Previous.clear();
  
    // Check that there are no default arguments other than in the parameters
    // of a function declaration (C++ only).
    if (getLangOpts().CPlusPlus)
      CheckExtraCXXDefaultArguments(D);
  
    NamedDecl *New;
  
    bool AddToScope = true;
    if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef) {
      if (TemplateParamLists.size()) {
        Diag(D.getIdentifierLoc(), diag::err_template_typedef);
        return nullptr;
      }
  
      New = ActOnTypedefDeclarator(S, D, DC, TInfo, Previous);
    } else if (R->isFunctionType()) {
      New = ActOnFunctionDeclarator(S, D, DC, TInfo, Previous,
                                    TemplateParamLists,
                                    AddToScope);
    } else {
      New = ActOnVariableDeclarator(S, D, DC, TInfo, Previous, TemplateParamLists,
                                    AddToScope);
    }
  
    if (!New)
      return nullptr;
  
    // If this has an identifier and is not a function template specialization,
    // add it to the scope stack.
    if (New->getDeclName() && AddToScope)
      PushOnScopeChains(New, S);
  
    if (isInOpenMPDeclareTargetContext())
      checkDeclIsAllowedInOpenMPTarget(nullptr, New);
  
    return New;
  }
  
  /// Helper method to turn variable array types into constant array
  /// types in certain situations which would otherwise be errors (for
  /// GCC compatibility).
  static QualType TryToFixInvalidVariablyModifiedType(QualType T,
                                                      ASTContext &Context,
                                                      bool &SizeIsNegative,
                                                      llvm::APSInt &Oversized) {
    // This method tries to turn a variable array into a constant
    // array even when the size isn't an ICE.  This is necessary
    // for compatibility with code that depends on gcc's buggy
    // constant expression folding, like struct {char x[(int)(char*)2];}
    SizeIsNegative = false;
    Oversized = 0;
  
    if (T->isDependentType())
      return QualType();
  
    QualifierCollector Qs;
    const Type *Ty = Qs.strip(T);
  
    if (const PointerType* PTy = dyn_cast<PointerType>(Ty)) {
      QualType Pointee = PTy->getPointeeType();
      QualType FixedType =
          TryToFixInvalidVariablyModifiedType(Pointee, Context, SizeIsNegative,
                                              Oversized);
      if (FixedType.isNull()) return FixedType;
      FixedType = Context.getPointerType(FixedType);
      return Qs.apply(Context, FixedType);
    }
    if (const ParenType* PTy = dyn_cast<ParenType>(Ty)) {
      QualType Inner = PTy->getInnerType();
      QualType FixedType =
          TryToFixInvalidVariablyModifiedType(Inner, Context, SizeIsNegative,
                                              Oversized);
      if (FixedType.isNull()) return FixedType;
      FixedType = Context.getParenType(FixedType);
      return Qs.apply(Context, FixedType);
    }
  
    const VariableArrayType* VLATy = dyn_cast<VariableArrayType>(T);
    if (!VLATy)
      return QualType();
    // FIXME: We should probably handle this case
    if (VLATy->getElementType()->isVariablyModifiedType())
      return QualType();
  
    Expr::EvalResult Result;
    if (!VLATy->getSizeExpr() ||
        !VLATy->getSizeExpr()->EvaluateAsInt(Result, Context))
      return QualType();
  
    llvm::APSInt Res = Result.Val.getInt();
  
    // Check whether the array size is negative.
    if (Res.isSigned() && Res.isNegative()) {
      SizeIsNegative = true;
      return QualType();
    }
  
    // Check whether the array is too large to be addressed.
    unsigned ActiveSizeBits
      = ConstantArrayType::getNumAddressingBits(Context, VLATy->getElementType(),
                                                Res);
    if (ActiveSizeBits > ConstantArrayType::getMaxSizeBits(Context)) {
      Oversized = Res;
      return QualType();
    }
  
    return Context.getConstantArrayType(VLATy->getElementType(),
                                        Res, ArrayType::Normal, 0);
  }
  
  static void
  FixInvalidVariablyModifiedTypeLoc(TypeLoc SrcTL, TypeLoc DstTL) {
    SrcTL = SrcTL.getUnqualifiedLoc();
    DstTL = DstTL.getUnqualifiedLoc();
    if (PointerTypeLoc SrcPTL = SrcTL.getAs<PointerTypeLoc>()) {
      PointerTypeLoc DstPTL = DstTL.castAs<PointerTypeLoc>();
      FixInvalidVariablyModifiedTypeLoc(SrcPTL.getPointeeLoc(),
                                        DstPTL.getPointeeLoc());
      DstPTL.setStarLoc(SrcPTL.getStarLoc());
      return;
    }
    if (ParenTypeLoc SrcPTL = SrcTL.getAs<ParenTypeLoc>()) {
      ParenTypeLoc DstPTL = DstTL.castAs<ParenTypeLoc>();
      FixInvalidVariablyModifiedTypeLoc(SrcPTL.getInnerLoc(),
                                        DstPTL.getInnerLoc());
      DstPTL.setLParenLoc(SrcPTL.getLParenLoc());
      DstPTL.setRParenLoc(SrcPTL.getRParenLoc());
      return;
    }
    ArrayTypeLoc SrcATL = SrcTL.castAs<ArrayTypeLoc>();
    ArrayTypeLoc DstATL = DstTL.castAs<ArrayTypeLoc>();
    TypeLoc SrcElemTL = SrcATL.getElementLoc();
    TypeLoc DstElemTL = DstATL.getElementLoc();
    DstElemTL.initializeFullCopy(SrcElemTL);
    DstATL.setLBracketLoc(SrcATL.getLBracketLoc());
    DstATL.setSizeExpr(SrcATL.getSizeExpr());
    DstATL.setRBracketLoc(SrcATL.getRBracketLoc());
  }
  
  /// Helper method to turn variable array types into constant array
  /// types in certain situations which would otherwise be errors (for
  /// GCC compatibility).
  static TypeSourceInfo*
  TryToFixInvalidVariablyModifiedTypeSourceInfo(TypeSourceInfo *TInfo,
                                                ASTContext &Context,
                                                bool &SizeIsNegative,
                                                llvm::APSInt &Oversized) {
    QualType FixedTy
      = TryToFixInvalidVariablyModifiedType(TInfo->getType(), Context,
                                            SizeIsNegative, Oversized);
    if (FixedTy.isNull())
      return nullptr;
    TypeSourceInfo *FixedTInfo = Context.getTrivialTypeSourceInfo(FixedTy);
    FixInvalidVariablyModifiedTypeLoc(TInfo->getTypeLoc(),
                                      FixedTInfo->getTypeLoc());
    return FixedTInfo;
  }
  
  /// Register the given locally-scoped extern "C" declaration so
  /// that it can be found later for redeclarations. We include any extern "C"
  /// declaration that is not visible in the translation unit here, not just
  /// function-scope declarations.
  void
  Sema::RegisterLocallyScopedExternCDecl(NamedDecl *ND, Scope *S) {
    if (!getLangOpts().CPlusPlus &&
        ND->getLexicalDeclContext()->getRedeclContext()->isTranslationUnit())
      // Don't need to track declarations in the TU in C.
      return;
  
    // Note that we have a locally-scoped external with this name.
    Context.getExternCContextDecl()->makeDeclVisibleInContext(ND);
  }
  
  NamedDecl *Sema::findLocallyScopedExternCDecl(DeclarationName Name) {
    // FIXME: We can have multiple results via __attribute__((overloadable)).
    auto Result = Context.getExternCContextDecl()->lookup(Name);
    return Result.empty() ? nullptr : *Result.begin();
  }
  
  /// Diagnose function specifiers on a declaration of an identifier that
  /// does not identify a function.
  void Sema::DiagnoseFunctionSpecifiers(const DeclSpec &DS) {
    // FIXME: We should probably indicate the identifier in question to avoid
    // confusion for constructs like "virtual int a(), b;"
    if (DS.isVirtualSpecified())
      Diag(DS.getVirtualSpecLoc(),
           diag::err_virtual_non_function);
  
    if (DS.isExplicitSpecified())
      Diag(DS.getExplicitSpecLoc(),
           diag::err_explicit_non_function);
  
    if (DS.isNoreturnSpecified())
      Diag(DS.getNoreturnSpecLoc(),
           diag::err_noreturn_non_function);
  }
  
  NamedDecl*
  Sema::ActOnTypedefDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                               TypeSourceInfo *TInfo, LookupResult &Previous) {
    // Typedef declarators cannot be qualified (C++ [dcl.meaning]p1).
    if (D.getCXXScopeSpec().isSet()) {
      Diag(D.getIdentifierLoc(), diag::err_qualified_typedef_declarator)
        << D.getCXXScopeSpec().getRange();
      D.setInvalidType();
      // Pretend we didn't see the scope specifier.
      DC = CurContext;
      Previous.clear();
    }
  
    DiagnoseFunctionSpecifiers(D.getDeclSpec());
  
    if (D.getDeclSpec().isInlineSpecified())
      Diag(D.getDeclSpec().getInlineSpecLoc(), diag::err_inline_non_function)
          << getLangOpts().CPlusPlus17;
    if (D.getDeclSpec().isConstexprSpecified())
      Diag(D.getDeclSpec().getConstexprSpecLoc(), diag::err_invalid_constexpr)
        << 1;
  
    if (D.getName().Kind != UnqualifiedIdKind::IK_Identifier) {
      if (D.getName().Kind == UnqualifiedIdKind::IK_DeductionGuideName)
        Diag(D.getName().StartLocation,
             diag::err_deduction_guide_invalid_specifier)
            << "typedef";
      else
        Diag(D.getName().StartLocation, diag::err_typedef_not_identifier)
            << D.getName().getSourceRange();
      return nullptr;
    }
  
    TypedefDecl *NewTD = ParseTypedefDecl(S, D, TInfo->getType(), TInfo);
    if (!NewTD) return nullptr;
  
    // Handle attributes prior to checking for duplicates in MergeVarDecl
    ProcessDeclAttributes(S, NewTD, D);
  
    CheckTypedefForVariablyModifiedType(S, NewTD);
  
    bool Redeclaration = D.isRedeclaration();
    NamedDecl *ND = ActOnTypedefNameDecl(S, DC, NewTD, Previous, Redeclaration);
    D.setRedeclaration(Redeclaration);
    return ND;
  }
  
  void
  Sema::CheckTypedefForVariablyModifiedType(Scope *S, TypedefNameDecl *NewTD) {
    // C99 6.7.7p2: If a typedef name specifies a variably modified type
    // then it shall have block scope.
    // Note that variably modified types must be fixed before merging the decl so
    // that redeclarations will match.
    TypeSourceInfo *TInfo = NewTD->getTypeSourceInfo();
    QualType T = TInfo->getType();
    if (T->isVariablyModifiedType()) {
      setFunctionHasBranchProtectedScope();
  
      if (S->getFnParent() == nullptr) {
        bool SizeIsNegative;
        llvm::APSInt Oversized;
        TypeSourceInfo *FixedTInfo =
          TryToFixInvalidVariablyModifiedTypeSourceInfo(TInfo, Context,
                                                        SizeIsNegative,
                                                        Oversized);
        if (FixedTInfo) {
          Diag(NewTD->getLocation(), diag::warn_illegal_constant_array_size);
          NewTD->setTypeSourceInfo(FixedTInfo);
        } else {
          if (SizeIsNegative)
            Diag(NewTD->getLocation(), diag::err_typecheck_negative_array_size);
          else if (T->isVariableArrayType())
            Diag(NewTD->getLocation(), diag::err_vla_decl_in_file_scope);
          else if (Oversized.getBoolValue())
            Diag(NewTD->getLocation(), diag::err_array_too_large)
              << Oversized.toString(10);
          else
            Diag(NewTD->getLocation(), diag::err_vm_decl_in_file_scope);
          NewTD->setInvalidDecl();
        }
      }
    }
  }
  
  /// ActOnTypedefNameDecl - Perform semantic checking for a declaration which
  /// declares a typedef-name, either using the 'typedef' type specifier or via
  /// a C++0x [dcl.typedef]p2 alias-declaration: 'using T = A;'.
  NamedDecl*
  Sema::ActOnTypedefNameDecl(Scope *S, DeclContext *DC, TypedefNameDecl *NewTD,
                             LookupResult &Previous, bool &Redeclaration) {
  
    // Find the shadowed declaration before filtering for scope.
    NamedDecl *ShadowedDecl = getShadowedDeclaration(NewTD, Previous);
  
    // Merge the decl with the existing one if appropriate. If the decl is
    // in an outer scope, it isn't the same thing.
    FilterLookupForScope(Previous, DC, S, /*ConsiderLinkage*/false,
                         /*AllowInlineNamespace*/false);
    filterNonConflictingPreviousTypedefDecls(*this, NewTD, Previous);
    if (!Previous.empty()) {
      Redeclaration = true;
      MergeTypedefNameDecl(S, NewTD, Previous);
    }
  
    if (ShadowedDecl && !Redeclaration)
      CheckShadow(NewTD, ShadowedDecl, Previous);
  
    // If this is the C FILE type, notify the AST context.
    if (IdentifierInfo *II = NewTD->getIdentifier())
      if (!NewTD->isInvalidDecl() &&
          NewTD->getDeclContext()->getRedeclContext()->isTranslationUnit()) {
        if (II->isStr("FILE"))
          Context.setFILEDecl(NewTD);
        else if (II->isStr("jmp_buf"))
          Context.setjmp_bufDecl(NewTD);
        else if (II->isStr("sigjmp_buf"))
          Context.setsigjmp_bufDecl(NewTD);
        else if (II->isStr("ucontext_t"))
          Context.setucontext_tDecl(NewTD);
      }
  
    return NewTD;
  }
  
  /// Determines whether the given declaration is an out-of-scope
  /// previous declaration.
  ///
  /// This routine should be invoked when name lookup has found a
  /// previous declaration (PrevDecl) that is not in the scope where a
  /// new declaration by the same name is being introduced. If the new
  /// declaration occurs in a local scope, previous declarations with
  /// linkage may still be considered previous declarations (C99
  /// 6.2.2p4-5, C++ [basic.link]p6).
  ///
  /// \param PrevDecl the previous declaration found by name
  /// lookup
  ///
  /// \param DC the context in which the new declaration is being
  /// declared.
  ///
  /// \returns true if PrevDecl is an out-of-scope previous declaration
  /// for a new delcaration with the same name.
  static bool
  isOutOfScopePreviousDeclaration(NamedDecl *PrevDecl, DeclContext *DC,
                                  ASTContext &Context) {
    if (!PrevDecl)
      return false;
  
    if (!PrevDecl->hasLinkage())
      return false;
  
    if (Context.getLangOpts().CPlusPlus) {
      // C++ [basic.link]p6:
      //   If there is a visible declaration of an entity with linkage
      //   having the same name and type, ignoring entities declared
      //   outside the innermost enclosing namespace scope, the block
      //   scope declaration declares that same entity and receives the
      //   linkage of the previous declaration.
      DeclContext *OuterContext = DC->getRedeclContext();
      if (!OuterContext->isFunctionOrMethod())
        // This rule only applies to block-scope declarations.
        return false;
  
      DeclContext *PrevOuterContext = PrevDecl->getDeclContext();
      if (PrevOuterContext->isRecord())
        // We found a member function: ignore it.
        return false;
  
      // Find the innermost enclosing namespace for the new and
      // previous declarations.
      OuterContext = OuterContext->getEnclosingNamespaceContext();
      PrevOuterContext = PrevOuterContext->getEnclosingNamespaceContext();
  
      // The previous declaration is in a different namespace, so it
      // isn't the same function.
      if (!OuterContext->Equals(PrevOuterContext))
        return false;
    }
  
    return true;
  }
  
  static void SetNestedNameSpecifier(Sema &S, DeclaratorDecl *DD, Declarator &D) {
    CXXScopeSpec &SS = D.getCXXScopeSpec();
    if (!SS.isSet()) return;
    DD->setQualifierInfo(SS.getWithLocInContext(S.Context));
  }
  
  bool Sema::inferObjCARCLifetime(ValueDecl *decl) {
    QualType type = decl->getType();
    Qualifiers::ObjCLifetime lifetime = type.getObjCLifetime();
    if (lifetime == Qualifiers::OCL_Autoreleasing) {
      // Various kinds of declaration aren't allowed to be __autoreleasing.
      unsigned kind = -1U;
      if (VarDecl *var = dyn_cast<VarDecl>(decl)) {
        if (var->hasAttr<BlocksAttr>())
          kind = 0; // __block
        else if (!var->hasLocalStorage())
          kind = 1; // global
      } else if (isa<ObjCIvarDecl>(decl)) {
        kind = 3; // ivar
      } else if (isa<FieldDecl>(decl)) {
        kind = 2; // field
      }
  
      if (kind != -1U) {
        Diag(decl->getLocation(), diag::err_arc_autoreleasing_var)
          << kind;
      }
    } else if (lifetime == Qualifiers::OCL_None) {
      // Try to infer lifetime.
      if (!type->isObjCLifetimeType())
        return false;
  
      lifetime = type->getObjCARCImplicitLifetime();
      type = Context.getLifetimeQualifiedType(type, lifetime);
      decl->setType(type);
    }
  
    if (VarDecl *var = dyn_cast<VarDecl>(decl)) {
      // Thread-local variables cannot have lifetime.
      if (lifetime && lifetime != Qualifiers::OCL_ExplicitNone &&
          var->getTLSKind()) {
        Diag(var->getLocation(), diag::err_arc_thread_ownership)
          << var->getType();
        return true;
      }
    }
  
    return false;
  }
  
  static void checkAttributesAfterMerging(Sema &S, NamedDecl &ND) {
    // Ensure that an auto decl is deduced otherwise the checks below might cache
    // the wrong linkage.
    assert(S.ParsingInitForAutoVars.count(&ND) == 0);
  
    // 'weak' only applies to declarations with external linkage.
    if (WeakAttr *Attr = ND.getAttr<WeakAttr>()) {
      if (!ND.isExternallyVisible()) {
        S.Diag(Attr->getLocation(), diag::err_attribute_weak_static);
        ND.dropAttr<WeakAttr>();
      }
    }
    if (WeakRefAttr *Attr = ND.getAttr<WeakRefAttr>()) {
      if (ND.isExternallyVisible()) {
        S.Diag(Attr->getLocation(), diag::err_attribute_weakref_not_static);
        ND.dropAttr<WeakRefAttr>();
        ND.dropAttr<AliasAttr>();
      }
    }
  
    if (auto *VD = dyn_cast<VarDecl>(&ND)) {
      if (VD->hasInit()) {
        if (const auto *Attr = VD->getAttr<AliasAttr>()) {
          assert(VD->isThisDeclarationADefinition() &&
                 !VD->isExternallyVisible() && "Broken AliasAttr handled late!");
          S.Diag(Attr->getLocation(), diag::err_alias_is_definition) << VD << 0;
          VD->dropAttr<AliasAttr>();
        }
      }
    }
  
    // 'selectany' only applies to externally visible variable declarations.
    // It does not apply to functions.
    if (SelectAnyAttr *Attr = ND.getAttr<SelectAnyAttr>()) {
      if (isa<FunctionDecl>(ND) || !ND.isExternallyVisible()) {
        S.Diag(Attr->getLocation(),
               diag::err_attribute_selectany_non_extern_data);
        ND.dropAttr<SelectAnyAttr>();
      }
    }
  
    if (const InheritableAttr *Attr = getDLLAttr(&ND)) {
      auto *VD = dyn_cast<VarDecl>(&ND);
      bool IsAnonymousNS = false;
      bool IsMicrosoft = S.Context.getTargetInfo().getCXXABI().isMicrosoft();
      if (VD) {
        const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(VD->getDeclContext());
        while (NS && !IsAnonymousNS) {
          IsAnonymousNS = NS->isAnonymousNamespace();
          NS = dyn_cast<NamespaceDecl>(NS->getParent());
        }
      }
      // dll attributes require external linkage. Static locals may have external
      // linkage but still cannot be explicitly imported or exported.
      // In Microsoft mode, a variable defined in anonymous namespace must have
      // external linkage in order to be exported.
      bool AnonNSInMicrosoftMode = IsAnonymousNS && IsMicrosoft;
      if ((ND.isExternallyVisible() && AnonNSInMicrosoftMode) ||
          (!AnonNSInMicrosoftMode &&
           (!ND.isExternallyVisible() || (VD && VD->isStaticLocal())))) {
        S.Diag(ND.getLocation(), diag::err_attribute_dll_not_extern)
          << &ND << Attr;
        ND.setInvalidDecl();
      }
    }
  
    // Virtual functions cannot be marked as 'notail'.
    if (auto *Attr = ND.getAttr<NotTailCalledAttr>())
      if (auto *MD = dyn_cast<CXXMethodDecl>(&ND))
        if (MD->isVirtual()) {
          S.Diag(ND.getLocation(),
                 diag::err_invalid_attribute_on_virtual_function)
              << Attr;
          ND.dropAttr<NotTailCalledAttr>();
        }
  
    // Check the attributes on the function type, if any.
    if (const auto *FD = dyn_cast<FunctionDecl>(&ND)) {
      // Don't declare this variable in the second operand of the for-statement;
      // GCC miscompiles that by ending its lifetime before evaluating the
      // third operand. See gcc.gnu.org/PR86769.
      AttributedTypeLoc ATL;
      for (TypeLoc TL = FD->getTypeSourceInfo()->getTypeLoc();
           (ATL = TL.getAsAdjusted<AttributedTypeLoc>());
           TL = ATL.getModifiedLoc()) {
        // The [[lifetimebound]] attribute can be applied to the implicit object
        // parameter of a non-static member function (other than a ctor or dtor)
        // by applying it to the function type.
        if (const auto *A = ATL.getAttrAs<LifetimeBoundAttr>()) {
          const auto *MD = dyn_cast<CXXMethodDecl>(FD);
          if (!MD || MD->isStatic()) {
            S.Diag(A->getLocation(), diag::err_lifetimebound_no_object_param)
                << !MD << A->getRange();
          } else if (isa<CXXConstructorDecl>(MD) || isa<CXXDestructorDecl>(MD)) {
            S.Diag(A->getLocation(), diag::err_lifetimebound_ctor_dtor)
                << isa<CXXDestructorDecl>(MD) << A->getRange();
          }
        }
      }
    }
  }
  
  static void checkDLLAttributeRedeclaration(Sema &S, NamedDecl *OldDecl,
                                             NamedDecl *NewDecl,
                                             bool IsSpecialization,
                                             bool IsDefinition) {
    if (OldDecl->isInvalidDecl() || NewDecl->isInvalidDecl())
      return;
  
    bool IsTemplate = false;
    if (TemplateDecl *OldTD = dyn_cast<TemplateDecl>(OldDecl)) {
      OldDecl = OldTD->getTemplatedDecl();
      IsTemplate = true;
      if (!IsSpecialization)
        IsDefinition = false;
    }
    if (TemplateDecl *NewTD = dyn_cast<TemplateDecl>(NewDecl)) {
      NewDecl = NewTD->getTemplatedDecl();
      IsTemplate = true;
    }
  
    if (!OldDecl || !NewDecl)
      return;
  
    const DLLImportAttr *OldImportAttr = OldDecl->getAttr<DLLImportAttr>();
    const DLLExportAttr *OldExportAttr = OldDecl->getAttr<DLLExportAttr>();
    const DLLImportAttr *NewImportAttr = NewDecl->getAttr<DLLImportAttr>();
    const DLLExportAttr *NewExportAttr = NewDecl->getAttr<DLLExportAttr>();
  
    // dllimport and dllexport are inheritable attributes so we have to exclude
    // inherited attribute instances.
    bool HasNewAttr = (NewImportAttr && !NewImportAttr->isInherited()) ||
                      (NewExportAttr && !NewExportAttr->isInherited());
  
    // A redeclaration is not allowed to add a dllimport or dllexport attribute,
    // the only exception being explicit specializations.
    // Implicitly generated declarations are also excluded for now because there
    // is no other way to switch these to use dllimport or dllexport.
    bool AddsAttr = !(OldImportAttr || OldExportAttr) && HasNewAttr;
  
    if (AddsAttr && !IsSpecialization && !OldDecl->isImplicit()) {
      // Allow with a warning for free functions and global variables.
      bool JustWarn = false;
      if (!OldDecl->isCXXClassMember()) {
        auto *VD = dyn_cast<VarDecl>(OldDecl);
        if (VD && !VD->getDescribedVarTemplate())
          JustWarn = true;
        auto *FD = dyn_cast<FunctionDecl>(OldDecl);
        if (FD && FD->getTemplatedKind() == FunctionDecl::TK_NonTemplate)
          JustWarn = true;
      }
  
      // We cannot change a declaration that's been used because IR has already
      // been emitted. Dllimported functions will still work though (modulo
      // address equality) as they can use the thunk.
      if (OldDecl->isUsed())
        if (!isa<FunctionDecl>(OldDecl) || !NewImportAttr)
          JustWarn = false;
  
      unsigned DiagID = JustWarn ? diag::warn_attribute_dll_redeclaration
                                 : diag::err_attribute_dll_redeclaration;
      S.Diag(NewDecl->getLocation(), DiagID)
          << NewDecl
          << (NewImportAttr ? (const Attr *)NewImportAttr : NewExportAttr);
      S.Diag(OldDecl->getLocation(), diag::note_previous_declaration);
      if (!JustWarn) {
        NewDecl->setInvalidDecl();
        return;
      }
    }
  
    // A redeclaration is not allowed to drop a dllimport attribute, the only
    // exceptions being inline function definitions (except for function
    // templates), local extern declarations, qualified friend declarations or
    // special MSVC extension: in the last case, the declaration is treated as if
    // it were marked dllexport.
    bool IsInline = false, IsStaticDataMember = false, IsQualifiedFriend = false;
    bool IsMicrosoft = S.Context.getTargetInfo().getCXXABI().isMicrosoft();
    if (const auto *VD = dyn_cast<VarDecl>(NewDecl)) {
      // Ignore static data because out-of-line definitions are diagnosed
      // separately.
      IsStaticDataMember = VD->isStaticDataMember();
      IsDefinition = VD->isThisDeclarationADefinition(S.Context) !=
                     VarDecl::DeclarationOnly;
    } else if (const auto *FD = dyn_cast<FunctionDecl>(NewDecl)) {
      IsInline = FD->isInlined();
      IsQualifiedFriend = FD->getQualifier() &&
                          FD->getFriendObjectKind() == Decl::FOK_Declared;
    }
  
    if (OldImportAttr && !HasNewAttr &&
        (!IsInline || (IsMicrosoft && IsTemplate)) && !IsStaticDataMember &&
        !NewDecl->isLocalExternDecl() && !IsQualifiedFriend) {
      if (IsMicrosoft && IsDefinition) {
        S.Diag(NewDecl->getLocation(),
               diag::warn_redeclaration_without_import_attribute)
            << NewDecl;
        S.Diag(OldDecl->getLocation(), diag::note_previous_declaration);
        NewDecl->dropAttr<DLLImportAttr>();
        NewDecl->addAttr(::new (S.Context) DLLExportAttr(
            NewImportAttr->getRange(), S.Context,
            NewImportAttr->getSpellingListIndex()));
      } else {
        S.Diag(NewDecl->getLocation(),
               diag::warn_redeclaration_without_attribute_prev_attribute_ignored)
            << NewDecl << OldImportAttr;
        S.Diag(OldDecl->getLocation(), diag::note_previous_declaration);
        S.Diag(OldImportAttr->getLocation(), diag::note_previous_attribute);
        OldDecl->dropAttr<DLLImportAttr>();
        NewDecl->dropAttr<DLLImportAttr>();
      }
    } else if (IsInline && OldImportAttr && !IsMicrosoft) {
      // In MinGW, seeing a function declared inline drops the dllimport
      // attribute.
      OldDecl->dropAttr<DLLImportAttr>();
      NewDecl->dropAttr<DLLImportAttr>();
      S.Diag(NewDecl->getLocation(),
             diag::warn_dllimport_dropped_from_inline_function)
          << NewDecl << OldImportAttr;
    }
  
    // A specialization of a class template member function is processed here
    // since it's a redeclaration. If the parent class is dllexport, the
    // specialization inherits that attribute. This doesn't happen automatically
    // since the parent class isn't instantiated until later.
    if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewDecl)) {
      if (MD->getTemplatedKind() == FunctionDecl::TK_MemberSpecialization &&
          !NewImportAttr && !NewExportAttr) {
        if (const DLLExportAttr *ParentExportAttr =
                MD->getParent()->getAttr<DLLExportAttr>()) {
          DLLExportAttr *NewAttr = ParentExportAttr->clone(S.Context);
          NewAttr->setInherited(true);
          NewDecl->addAttr(NewAttr);
        }
      }
    }
  }
  
  /// Given that we are within the definition of the given function,
  /// will that definition behave like C99's 'inline', where the
  /// definition is discarded except for optimization purposes?
  static bool isFunctionDefinitionDiscarded(Sema &S, FunctionDecl *FD) {
    // Try to avoid calling GetGVALinkageForFunction.
  
    // All cases of this require the 'inline' keyword.
    if (!FD->isInlined()) return false;
  
    // This is only possible in C++ with the gnu_inline attribute.
    if (S.getLangOpts().CPlusPlus && !FD->hasAttr<GNUInlineAttr>())
      return false;
  
    // Okay, go ahead and call the relatively-more-expensive function.
    return S.Context.GetGVALinkageForFunction(FD) == GVA_AvailableExternally;
  }
  
  /// Determine whether a variable is extern "C" prior to attaching
  /// an initializer. We can't just call isExternC() here, because that
  /// will also compute and cache whether the declaration is externally
  /// visible, which might change when we attach the initializer.
  ///
  /// This can only be used if the declaration is known to not be a
  /// redeclaration of an internal linkage declaration.
  ///
  /// For instance:
  ///
  ///   auto x = []{};
  ///
  /// Attaching the initializer here makes this declaration not externally
  /// visible, because its type has internal linkage.
  ///
  /// FIXME: This is a hack.
  template<typename T>
  static bool isIncompleteDeclExternC(Sema &S, const T *D) {
    if (S.getLangOpts().CPlusPlus) {
      // In C++, the overloadable attribute negates the effects of extern "C".
      if (!D->isInExternCContext() || D->template hasAttr<OverloadableAttr>())
        return false;
  
      // So do CUDA's host/device attributes.
      if (S.getLangOpts().CUDA && (D->template hasAttr<CUDADeviceAttr>() ||
                                   D->template hasAttr<CUDAHostAttr>()))
        return false;
    }
    return D->isExternC();
  }
  
  static bool shouldConsiderLinkage(const VarDecl *VD) {
    const DeclContext *DC = VD->getDeclContext()->getRedeclContext();
    if (DC->isFunctionOrMethod() || isa<OMPDeclareReductionDecl>(DC) ||
        isa<OMPDeclareMapperDecl>(DC))
      return VD->hasExternalStorage();
    if (DC->isFileContext())
      return true;
    if (DC->isRecord())
      return false;
    llvm_unreachable("Unexpected context");
  }
  
  static bool shouldConsiderLinkage(const FunctionDecl *FD) {
    const DeclContext *DC = FD->getDeclContext()->getRedeclContext();
    if (DC->isFileContext() || DC->isFunctionOrMethod() ||
        isa<OMPDeclareReductionDecl>(DC) || isa<OMPDeclareMapperDecl>(DC))
      return true;
    if (DC->isRecord())
      return false;
    llvm_unreachable("Unexpected context");
  }
  
  static bool hasParsedAttr(Scope *S, const Declarator &PD,
                            ParsedAttr::Kind Kind) {
    // Check decl attributes on the DeclSpec.
    if (PD.getDeclSpec().getAttributes().hasAttribute(Kind))
      return true;
  
    // Walk the declarator structure, checking decl attributes that were in a type
    // position to the decl itself.
    for (unsigned I = 0, E = PD.getNumTypeObjects(); I != E; ++I) {
      if (PD.getTypeObject(I).getAttrs().hasAttribute(Kind))
        return true;
    }
  
    // Finally, check attributes on the decl itself.
    return PD.getAttributes().hasAttribute(Kind);
  }
  
  /// Adjust the \c DeclContext for a function or variable that might be a
  /// function-local external declaration.
  bool Sema::adjustContextForLocalExternDecl(DeclContext *&DC) {
    if (!DC->isFunctionOrMethod())
      return false;
  
    // If this is a local extern function or variable declared within a function
    // template, don't add it into the enclosing namespace scope until it is
    // instantiated; it might have a dependent type right now.
    if (DC->isDependentContext())
      return true;
  
    // C++11 [basic.link]p7:
    //   When a block scope declaration of an entity with linkage is not found to
    //   refer to some other declaration, then that entity is a member of the
    //   innermost enclosing namespace.
    //
    // Per C++11 [namespace.def]p6, the innermost enclosing namespace is a
    // semantically-enclosing namespace, not a lexically-enclosing one.
    while (!DC->isFileContext() && !isa<LinkageSpecDecl>(DC))
      DC = DC->getParent();
    return true;
  }
  
  /// Returns true if given declaration has external C language linkage.
  static bool isDeclExternC(const Decl *D) {
    if (const auto *FD = dyn_cast<FunctionDecl>(D))
      return FD->isExternC();
    if (const auto *VD = dyn_cast<VarDecl>(D))
      return VD->isExternC();
  
    llvm_unreachable("Unknown type of decl!");
  }
  
  NamedDecl *Sema::ActOnVariableDeclarator(
      Scope *S, Declarator &D, DeclContext *DC, TypeSourceInfo *TInfo,
      LookupResult &Previous, MultiTemplateParamsArg TemplateParamLists,
      bool &AddToScope, ArrayRef<BindingDecl *> Bindings) {
    QualType R = TInfo->getType();
    DeclarationName Name = GetNameForDeclarator(D).getName();
  
    IdentifierInfo *II = Name.getAsIdentifierInfo();
  
    if (D.isDecompositionDeclarator()) {
      // Take the name of the first declarator as our name for diagnostic
      // purposes.
      auto &Decomp = D.getDecompositionDeclarator();
      if (!Decomp.bindings().empty()) {
        II = Decomp.bindings()[0].Name;
        Name = II;
      }
    } else if (!II) {
      Diag(D.getIdentifierLoc(), diag::err_bad_variable_name) << Name;
      return nullptr;
    }
  
    if (getLangOpts().OpenCL) {
      // OpenCL v2.0 s6.9.b - Image type can only be used as a function argument.
      // OpenCL v2.0 s6.13.16.1 - Pipe type can only be used as a function
      // argument.
      if (R->isImageType() || R->isPipeType()) {
        Diag(D.getIdentifierLoc(),
             diag::err_opencl_type_can_only_be_used_as_function_parameter)
            << R;
        D.setInvalidType();
        return nullptr;
      }
  
      // OpenCL v1.2 s6.9.r:
      // The event type cannot be used to declare a program scope variable.
      // OpenCL v2.0 s6.9.q:
      // The clk_event_t and reserve_id_t types cannot be declared in program scope.
      if (NULL == S->getParent()) {
        if (R->isReserveIDT() || R->isClkEventT() || R->isEventT()) {
          Diag(D.getIdentifierLoc(),
               diag::err_invalid_type_for_program_scope_var) << R;
          D.setInvalidType();
          return nullptr;
        }
      }
  
      // OpenCL v1.0 s6.8.a.3: Pointers to functions are not allowed.
      QualType NR = R;
      while (NR->isPointerType()) {
        if (NR->isFunctionPointerType()) {
          Diag(D.getIdentifierLoc(), diag::err_opencl_function_pointer);
          D.setInvalidType();
          break;
        }
        NR = NR->getPointeeType();
      }
  
      if (!getOpenCLOptions().isEnabled("cl_khr_fp16")) {
        // OpenCL v1.2 s6.1.1.1: reject declaring variables of the half and
        // half array type (unless the cl_khr_fp16 extension is enabled).
        if (Context.getBaseElementType(R)->isHalfType()) {
          Diag(D.getIdentifierLoc(), diag::err_opencl_half_declaration) << R;
          D.setInvalidType();
        }
      }
  
      if (R->isSamplerT()) {
        // OpenCL v1.2 s6.9.b p4:
        // The sampler type cannot be used with the __local and __global address
        // space qualifiers.
        if (R.getAddressSpace() == LangAS::opencl_local ||
            R.getAddressSpace() == LangAS::opencl_global) {
          Diag(D.getIdentifierLoc(), diag::err_wrong_sampler_addressspace);
        }
  
        // OpenCL v1.2 s6.12.14.1:
        // A global sampler must be declared with either the constant address
        // space qualifier or with the const qualifier.
        if (DC->isTranslationUnit() &&
            !(R.getAddressSpace() == LangAS::opencl_constant ||
            R.isConstQualified())) {
          Diag(D.getIdentifierLoc(), diag::err_opencl_nonconst_global_sampler);
          D.setInvalidType();
        }
      }
  
      // OpenCL v1.2 s6.9.r:
      // The event type cannot be used with the __local, __constant and __global
      // address space qualifiers.
      if (R->isEventT()) {
        if (R.getAddressSpace() != LangAS::opencl_private) {
          Diag(D.getBeginLoc(), diag::err_event_t_addr_space_qual);
          D.setInvalidType();
        }
      }
  
      // OpenCL C++ 1.0 s2.9: the thread_local storage qualifier is not
      // supported.  OpenCL C does not support thread_local either, and
      // also reject all other thread storage class specifiers.
      DeclSpec::TSCS TSC = D.getDeclSpec().getThreadStorageClassSpec();
      if (TSC != TSCS_unspecified) {
        bool IsCXX = getLangOpts().OpenCLCPlusPlus;
        Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
             diag::err_opencl_unknown_type_specifier)
            << IsCXX << getLangOpts().getOpenCLVersionTuple().getAsString()
            << DeclSpec::getSpecifierName(TSC) << 1;
        D.setInvalidType();
        return nullptr;
      }
    }
  
    DeclSpec::SCS SCSpec = D.getDeclSpec().getStorageClassSpec();
    StorageClass SC = StorageClassSpecToVarDeclStorageClass(D.getDeclSpec());
  
    // dllimport globals without explicit storage class are treated as extern. We
    // have to change the storage class this early to get the right DeclContext.
    if (SC == SC_None && !DC->isRecord() &&
        hasParsedAttr(S, D, ParsedAttr::AT_DLLImport) &&
        !hasParsedAttr(S, D, ParsedAttr::AT_DLLExport))
      SC = SC_Extern;
  
    DeclContext *OriginalDC = DC;
    bool IsLocalExternDecl = SC == SC_Extern &&
                             adjustContextForLocalExternDecl(DC);
  
    if (SCSpec == DeclSpec::SCS_mutable) {
      // mutable can only appear on non-static class members, so it's always
      // an error here
      Diag(D.getIdentifierLoc(), diag::err_mutable_nonmember);
      D.setInvalidType();
      SC = SC_None;
    }
  
    if (getLangOpts().CPlusPlus11 && SCSpec == DeclSpec::SCS_register &&
        !D.getAsmLabel() && !getSourceManager().isInSystemMacro(
                                D.getDeclSpec().getStorageClassSpecLoc())) {
      // In C++11, the 'register' storage class specifier is deprecated.
      // Suppress the warning in system macros, it's used in macros in some
      // popular C system headers, such as in glibc's htonl() macro.
      Diag(D.getDeclSpec().getStorageClassSpecLoc(),
           getLangOpts().CPlusPlus17 ? diag::ext_register_storage_class
                                     : diag::warn_deprecated_register)
        << FixItHint::CreateRemoval(D.getDeclSpec().getStorageClassSpecLoc());
    }
  
    DiagnoseFunctionSpecifiers(D.getDeclSpec());
  
    if (!DC->isRecord() && S->getFnParent() == nullptr) {
      // C99 6.9p2: The storage-class specifiers auto and register shall not
      // appear in the declaration specifiers in an external declaration.
      // Global Register+Asm is a GNU extension we support.
      if (SC == SC_Auto || (SC == SC_Register && !D.getAsmLabel())) {
        Diag(D.getIdentifierLoc(), diag::err_typecheck_sclass_fscope);
        D.setInvalidType();
      }
    }
  
    bool IsMemberSpecialization = false;
    bool IsVariableTemplateSpecialization = false;
    bool IsPartialSpecialization = false;
    bool IsVariableTemplate = false;
    VarDecl *NewVD = nullptr;
    VarTemplateDecl *NewTemplate = nullptr;
    TemplateParameterList *TemplateParams = nullptr;
    if (!getLangOpts().CPlusPlus) {
      NewVD = VarDecl::Create(Context, DC, D.getBeginLoc(), D.getIdentifierLoc(),
                              II, R, TInfo, SC);
  
      if (R->getContainedDeducedType())
        ParsingInitForAutoVars.insert(NewVD);
  
      if (D.isInvalidType())
        NewVD->setInvalidDecl();
    } else {
      bool Invalid = false;
  
      if (DC->isRecord() && !CurContext->isRecord()) {
        // This is an out-of-line definition of a static data member.
        switch (SC) {
        case SC_None:
          break;
        case SC_Static:
          Diag(D.getDeclSpec().getStorageClassSpecLoc(),
               diag::err_static_out_of_line)
            << FixItHint::CreateRemoval(D.getDeclSpec().getStorageClassSpecLoc());
          break;
        case SC_Auto:
        case SC_Register:
        case SC_Extern:
          // [dcl.stc] p2: The auto or register specifiers shall be applied only
          // to names of variables declared in a block or to function parameters.
          // [dcl.stc] p6: The extern specifier cannot be used in the declaration
          // of class members
  
          Diag(D.getDeclSpec().getStorageClassSpecLoc(),
               diag::err_storage_class_for_static_member)
            << FixItHint::CreateRemoval(D.getDeclSpec().getStorageClassSpecLoc());
          break;
        case SC_PrivateExtern:
          llvm_unreachable("C storage class in c++!");
        }
      }
  
      if (SC == SC_Static && CurContext->isRecord()) {
        if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(DC)) {
          if (RD->isLocalClass())
            Diag(D.getIdentifierLoc(),
                 diag::err_static_data_member_not_allowed_in_local_class)
              << Name << RD->getDeclName();
  
          // C++98 [class.union]p1: If a union contains a static data member,
          // the program is ill-formed. C++11 drops this restriction.
          if (RD->isUnion())
            Diag(D.getIdentifierLoc(),
                 getLangOpts().CPlusPlus11
                   ? diag::warn_cxx98_compat_static_data_member_in_union
                   : diag::ext_static_data_member_in_union) << Name;
          // We conservatively disallow static data members in anonymous structs.
          else if (!RD->getDeclName())
            Diag(D.getIdentifierLoc(),
                 diag::err_static_data_member_not_allowed_in_anon_struct)
              << Name << RD->isUnion();
        }
      }
  
      // Match up the template parameter lists with the scope specifier, then
      // determine whether we have a template or a template specialization.
      TemplateParams = MatchTemplateParametersToScopeSpecifier(
          D.getDeclSpec().getBeginLoc(), D.getIdentifierLoc(),
          D.getCXXScopeSpec(),
          D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId
              ? D.getName().TemplateId
              : nullptr,
          TemplateParamLists,
          /*never a friend*/ false, IsMemberSpecialization, Invalid);
  
      if (TemplateParams) {
        if (!TemplateParams->size() &&
            D.getName().getKind() != UnqualifiedIdKind::IK_TemplateId) {
          // There is an extraneous 'template<>' for this variable. Complain
          // about it, but allow the declaration of the variable.
          Diag(TemplateParams->getTemplateLoc(),
               diag::err_template_variable_noparams)
            << II
            << SourceRange(TemplateParams->getTemplateLoc(),
                           TemplateParams->getRAngleLoc());
          TemplateParams = nullptr;
        } else {
          if (D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId) {
            // This is an explicit specialization or a partial specialization.
            // FIXME: Check that we can declare a specialization here.
            IsVariableTemplateSpecialization = true;
            IsPartialSpecialization = TemplateParams->size() > 0;
          } else { // if (TemplateParams->size() > 0)
            // This is a template declaration.
            IsVariableTemplate = true;
  
            // Check that we can declare a template here.
            if (CheckTemplateDeclScope(S, TemplateParams))
              return nullptr;
  
            // Only C++1y supports variable templates (N3651).
            Diag(D.getIdentifierLoc(),
                 getLangOpts().CPlusPlus14
                     ? diag::warn_cxx11_compat_variable_template
                     : diag::ext_variable_template);
          }
        }
      } else {
        assert((Invalid ||
                D.getName().getKind() != UnqualifiedIdKind::IK_TemplateId) &&
               "should have a 'template<>' for this decl");
      }
  
      if (IsVariableTemplateSpecialization) {
        SourceLocation TemplateKWLoc =
            TemplateParamLists.size() > 0
                ? TemplateParamLists[0]->getTemplateLoc()
                : SourceLocation();
        DeclResult Res = ActOnVarTemplateSpecialization(
            S, D, TInfo, TemplateKWLoc, TemplateParams, SC,
            IsPartialSpecialization);
        if (Res.isInvalid())
          return nullptr;
        NewVD = cast<VarDecl>(Res.get());
        AddToScope = false;
      } else if (D.isDecompositionDeclarator()) {
        NewVD = DecompositionDecl::Create(Context, DC, D.getBeginLoc(),
                                          D.getIdentifierLoc(), R, TInfo, SC,
                                          Bindings);
      } else
        NewVD = VarDecl::Create(Context, DC, D.getBeginLoc(),
                                D.getIdentifierLoc(), II, R, TInfo, SC);
  
      // If this is supposed to be a variable template, create it as such.
      if (IsVariableTemplate) {
        NewTemplate =
            VarTemplateDecl::Create(Context, DC, D.getIdentifierLoc(), Name,
                                    TemplateParams, NewVD);
        NewVD->setDescribedVarTemplate(NewTemplate);
      }
  
      // If this decl has an auto type in need of deduction, make a note of the
      // Decl so we can diagnose uses of it in its own initializer.
      if (R->getContainedDeducedType())
        ParsingInitForAutoVars.insert(NewVD);
  
      if (D.isInvalidType() || Invalid) {
        NewVD->setInvalidDecl();
        if (NewTemplate)
          NewTemplate->setInvalidDecl();
      }
  
      SetNestedNameSpecifier(*this, NewVD, D);
  
      // If we have any template parameter lists that don't directly belong to
      // the variable (matching the scope specifier), store them.
      unsigned VDTemplateParamLists = TemplateParams ? 1 : 0;
      if (TemplateParamLists.size() > VDTemplateParamLists)
        NewVD->setTemplateParameterListsInfo(
            Context, TemplateParamLists.drop_back(VDTemplateParamLists));
  
      if (D.getDeclSpec().isConstexprSpecified()) {
        NewVD->setConstexpr(true);
        // C++1z [dcl.spec.constexpr]p1:
        //   A static data member declared with the constexpr specifier is
        //   implicitly an inline variable.
        if (NewVD->isStaticDataMember() && getLangOpts().CPlusPlus17)
          NewVD->setImplicitlyInline();
      }
    }
  
    if (D.getDeclSpec().isInlineSpecified()) {
      if (!getLangOpts().CPlusPlus) {
        Diag(D.getDeclSpec().getInlineSpecLoc(), diag::err_inline_non_function)
            << 0;
      } else if (CurContext->isFunctionOrMethod()) {
        // 'inline' is not allowed on block scope variable declaration.
        Diag(D.getDeclSpec().getInlineSpecLoc(),
             diag::err_inline_declaration_block_scope) << Name
          << FixItHint::CreateRemoval(D.getDeclSpec().getInlineSpecLoc());
      } else {
        Diag(D.getDeclSpec().getInlineSpecLoc(),
             getLangOpts().CPlusPlus17 ? diag::warn_cxx14_compat_inline_variable
                                       : diag::ext_inline_variable);
        NewVD->setInlineSpecified();
      }
    }
  
    // Set the lexical context. If the declarator has a C++ scope specifier, the
    // lexical context will be different from the semantic context.
    NewVD->setLexicalDeclContext(CurContext);
    if (NewTemplate)
      NewTemplate->setLexicalDeclContext(CurContext);
  
    if (IsLocalExternDecl) {
      if (D.isDecompositionDeclarator())
        for (auto *B : Bindings)
          B->setLocalExternDecl();
      else
        NewVD->setLocalExternDecl();
    }
  
    bool EmitTLSUnsupportedError = false;
    if (DeclSpec::TSCS TSCS = D.getDeclSpec().getThreadStorageClassSpec()) {
      // C++11 [dcl.stc]p4:
      //   When thread_local is applied to a variable of block scope the
      //   storage-class-specifier static is implied if it does not appear
      //   explicitly.
      // Core issue: 'static' is not implied if the variable is declared
      //   'extern'.
      if (NewVD->hasLocalStorage() &&
          (SCSpec != DeclSpec::SCS_unspecified ||
           TSCS != DeclSpec::TSCS_thread_local ||
           !DC->isFunctionOrMethod()))
        Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
             diag::err_thread_non_global)
          << DeclSpec::getSpecifierName(TSCS);
      else if (!Context.getTargetInfo().isTLSSupported()) {
        if (getLangOpts().CUDA || getLangOpts().OpenMPIsDevice) {
          // Postpone error emission until we've collected attributes required to
          // figure out whether it's a host or device variable and whether the
          // error should be ignored.
          EmitTLSUnsupportedError = true;
          // We still need to mark the variable as TLS so it shows up in AST with
          // proper storage class for other tools to use even if we're not going
          // to emit any code for it.
          NewVD->setTSCSpec(TSCS);
        } else
          Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
               diag::err_thread_unsupported);
      } else
        NewVD->setTSCSpec(TSCS);
    }
  
    // C99 6.7.4p3
    //   An inline definition of a function with external linkage shall
    //   not contain a definition of a modifiable object with static or
    //   thread storage duration...
    // We only apply this when the function is required to be defined
    // elsewhere, i.e. when the function is not 'extern inline'.  Note
    // that a local variable with thread storage duration still has to
    // be marked 'static'.  Also note that it's possible to get these
    // semantics in C++ using __attribute__((gnu_inline)).
    if (SC == SC_Static && S->getFnParent() != nullptr &&
        !NewVD->getType().isConstQualified()) {
      FunctionDecl *CurFD = getCurFunctionDecl();
      if (CurFD && isFunctionDefinitionDiscarded(*this, CurFD)) {
        Diag(D.getDeclSpec().getStorageClassSpecLoc(),
             diag::warn_static_local_in_extern_inline);
        MaybeSuggestAddingStaticToDecl(CurFD);
      }
    }
  
    if (D.getDeclSpec().isModulePrivateSpecified()) {
      if (IsVariableTemplateSpecialization)
        Diag(NewVD->getLocation(), diag::err_module_private_specialization)
            << (IsPartialSpecialization ? 1 : 0)
            << FixItHint::CreateRemoval(
                   D.getDeclSpec().getModulePrivateSpecLoc());
      else if (IsMemberSpecialization)
        Diag(NewVD->getLocation(), diag::err_module_private_specialization)
          << 2
          << FixItHint::CreateRemoval(D.getDeclSpec().getModulePrivateSpecLoc());
      else if (NewVD->hasLocalStorage())
        Diag(NewVD->getLocation(), diag::err_module_private_local)
          << 0 << NewVD->getDeclName()
          << SourceRange(D.getDeclSpec().getModulePrivateSpecLoc())
          << FixItHint::CreateRemoval(D.getDeclSpec().getModulePrivateSpecLoc());
      else {
        NewVD->setModulePrivate();
        if (NewTemplate)
          NewTemplate->setModulePrivate();
        for (auto *B : Bindings)
          B->setModulePrivate();
      }
    }
  
    // Handle attributes prior to checking for duplicates in MergeVarDecl
    ProcessDeclAttributes(S, NewVD, D);
  
    if (getLangOpts().CUDA || getLangOpts().OpenMPIsDevice) {
      if (EmitTLSUnsupportedError &&
          ((getLangOpts().CUDA && DeclAttrsMatchCUDAMode(getLangOpts(), NewVD)) ||
           (getLangOpts().OpenMPIsDevice &&
            NewVD->hasAttr<OMPDeclareTargetDeclAttr>())))
        Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
             diag::err_thread_unsupported);
      // CUDA B.2.5: "__shared__ and __constant__ variables have implied static
      // storage [duration]."
      if (SC == SC_None && S->getFnParent() != nullptr &&
          (NewVD->hasAttr<CUDASharedAttr>() ||
           NewVD->hasAttr<CUDAConstantAttr>())) {
        NewVD->setStorageClass(SC_Static);
      }
    }
  
    // Ensure that dllimport globals without explicit storage class are treated as
    // extern. The storage class is set above using parsed attributes. Now we can
    // check the VarDecl itself.
    assert(!NewVD->hasAttr<DLLImportAttr>() ||
           NewVD->getAttr<DLLImportAttr>()->isInherited() ||
           NewVD->isStaticDataMember() || NewVD->getStorageClass() != SC_None);
  
    // In auto-retain/release, infer strong retension for variables of
    // retainable type.
    if (getLangOpts().ObjCAutoRefCount && inferObjCARCLifetime(NewVD))
      NewVD->setInvalidDecl();
  
    // Handle GNU asm-label extension (encoded as an attribute).
    if (Expr *E = (Expr*)D.getAsmLabel()) {
      // The parser guarantees this is a string.
      StringLiteral *SE = cast<StringLiteral>(E);
      StringRef Label = SE->getString();
      if (S->getFnParent() != nullptr) {
        switch (SC) {
        case SC_None:
        case SC_Auto:
          Diag(E->getExprLoc(), diag::warn_asm_label_on_auto_decl) << Label;
          break;
        case SC_Register:
          // Local Named register
          if (!Context.getTargetInfo().isValidGCCRegisterName(Label) &&
              DeclAttrsMatchCUDAMode(getLangOpts(), getCurFunctionDecl()))
            Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
          break;
        case SC_Static:
        case SC_Extern:
        case SC_PrivateExtern:
          break;
        }
      } else if (SC == SC_Register) {
        // Global Named register
        if (DeclAttrsMatchCUDAMode(getLangOpts(), NewVD)) {
          const auto &TI = Context.getTargetInfo();
          bool HasSizeMismatch;
  
          if (!TI.isValidGCCRegisterName(Label))
            Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
          else if (!TI.validateGlobalRegisterVariable(Label,
                                                      Context.getTypeSize(R),
                                                      HasSizeMismatch))
            Diag(E->getExprLoc(), diag::err_asm_invalid_global_var_reg) << Label;
          else if (HasSizeMismatch)
            Diag(E->getExprLoc(), diag::err_asm_register_size_mismatch) << Label;
        }
  
        if (!R->isIntegralType(Context) && !R->isPointerType()) {
          Diag(D.getBeginLoc(), diag::err_asm_bad_register_type);
          NewVD->setInvalidDecl(true);
        }
      }
  
      NewVD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0),
                                                  Context, Label, 0));
    } else if (!ExtnameUndeclaredIdentifiers.empty()) {
      llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
        ExtnameUndeclaredIdentifiers.find(NewVD->getIdentifier());
      if (I != ExtnameUndeclaredIdentifiers.end()) {
        if (isDeclExternC(NewVD)) {
          NewVD->addAttr(I->second);
          ExtnameUndeclaredIdentifiers.erase(I);
        } else
          Diag(NewVD->getLocation(), diag::warn_redefine_extname_not_applied)
              << /*Variable*/1 << NewVD;
      }
    }
  
    // Find the shadowed declaration before filtering for scope.
    NamedDecl *ShadowedDecl = D.getCXXScopeSpec().isEmpty()
                                  ? getShadowedDeclaration(NewVD, Previous)
                                  : nullptr;
  
    // Don't consider existing declarations that are in a different
    // scope and are out-of-semantic-context declarations (if the new
    // declaration has linkage).
    FilterLookupForScope(Previous, OriginalDC, S, shouldConsiderLinkage(NewVD),
                         D.getCXXScopeSpec().isNotEmpty() ||
                         IsMemberSpecialization ||
                         IsVariableTemplateSpecialization);
  
    // Check whether the previous declaration is in the same block scope. This
    // affects whether we merge types with it, per C++11 [dcl.array]p3.
    if (getLangOpts().CPlusPlus &&
        NewVD->isLocalVarDecl() && NewVD->hasExternalStorage())
      NewVD->setPreviousDeclInSameBlockScope(
          Previous.isSingleResult() && !Previous.isShadowed() &&
          isDeclInScope(Previous.getFoundDecl(), OriginalDC, S, false));
  
    if (!getLangOpts().CPlusPlus) {
      D.setRedeclaration(CheckVariableDeclaration(NewVD, Previous));
    } else {
      // If this is an explicit specialization of a static data member, check it.
      if (IsMemberSpecialization && !NewVD->isInvalidDecl() &&
          CheckMemberSpecialization(NewVD, Previous))
        NewVD->setInvalidDecl();
  
      // Merge the decl with the existing one if appropriate.
      if (!Previous.empty()) {
        if (Previous.isSingleResult() &&
            isa<FieldDecl>(Previous.getFoundDecl()) &&
            D.getCXXScopeSpec().isSet()) {
          // The user tried to define a non-static data member
          // out-of-line (C++ [dcl.meaning]p1).
          Diag(NewVD->getLocation(), diag::err_nonstatic_member_out_of_line)
            << D.getCXXScopeSpec().getRange();
          Previous.clear();
          NewVD->setInvalidDecl();
        }
      } else if (D.getCXXScopeSpec().isSet()) {
        // No previous declaration in the qualifying scope.
        Diag(D.getIdentifierLoc(), diag::err_no_member)
          << Name << computeDeclContext(D.getCXXScopeSpec(), true)
          << D.getCXXScopeSpec().getRange();
        NewVD->setInvalidDecl();
      }
  
      if (!IsVariableTemplateSpecialization)
        D.setRedeclaration(CheckVariableDeclaration(NewVD, Previous));
  
      if (NewTemplate) {
        VarTemplateDecl *PrevVarTemplate =
            NewVD->getPreviousDecl()
                ? NewVD->getPreviousDecl()->getDescribedVarTemplate()
                : nullptr;
  
        // Check the template parameter list of this declaration, possibly
        // merging in the template parameter list from the previous variable
        // template declaration.
        if (CheckTemplateParameterList(
                TemplateParams,
                PrevVarTemplate ? PrevVarTemplate->getTemplateParameters()
                                : nullptr,
                (D.getCXXScopeSpec().isSet() && DC && DC->isRecord() &&
                 DC->isDependentContext())
                    ? TPC_ClassTemplateMember
                    : TPC_VarTemplate))
          NewVD->setInvalidDecl();
  
        // If we are providing an explicit specialization of a static variable
        // template, make a note of that.
        if (PrevVarTemplate &&
            PrevVarTemplate->getInstantiatedFromMemberTemplate())
          PrevVarTemplate->setMemberSpecialization();
      }
    }
  
    // Diagnose shadowed variables iff this isn't a redeclaration.
    if (ShadowedDecl && !D.isRedeclaration())
      CheckShadow(NewVD, ShadowedDecl, Previous);
  
    ProcessPragmaWeak(S, NewVD);
  
    // If this is the first declaration of an extern C variable, update
    // the map of such variables.
    if (NewVD->isFirstDecl() && !NewVD->isInvalidDecl() &&
        isIncompleteDeclExternC(*this, NewVD))
      RegisterLocallyScopedExternCDecl(NewVD, S);
  
    if (getLangOpts().CPlusPlus && NewVD->isStaticLocal()) {
      Decl *ManglingContextDecl;
      if (MangleNumberingContext *MCtx = getCurrentMangleNumberContext(
              NewVD->getDeclContext(), ManglingContextDecl)) {
        Context.setManglingNumber(
            NewVD, MCtx->getManglingNumber(
                       NewVD, getMSManglingNumber(getLangOpts(), S)));
        Context.setStaticLocalNumber(NewVD, MCtx->getStaticLocalNumber(NewVD));
      }
    }
  
    // Special handling of variable named 'main'.
    if (Name.getAsIdentifierInfo() && Name.getAsIdentifierInfo()->isStr("main") &&
        NewVD->getDeclContext()->getRedeclContext()->isTranslationUnit() &&
        !getLangOpts().Freestanding && !NewVD->getDescribedVarTemplate()) {
  
      // C++ [basic.start.main]p3
      // A program that declares a variable main at global scope is ill-formed.
      if (getLangOpts().CPlusPlus)
        Diag(D.getBeginLoc(), diag::err_main_global_variable);
  
      // In C, and external-linkage variable named main results in undefined
      // behavior.
      else if (NewVD->hasExternalFormalLinkage())
        Diag(D.getBeginLoc(), diag::warn_main_redefined);
    }
  
    if (D.isRedeclaration() && !Previous.empty()) {
      NamedDecl *Prev = Previous.getRepresentativeDecl();
      checkDLLAttributeRedeclaration(*this, Prev, NewVD, IsMemberSpecialization,
                                     D.isFunctionDefinition());
    }
  
    if (NewTemplate) {
      if (NewVD->isInvalidDecl())
        NewTemplate->setInvalidDecl();
      ActOnDocumentableDecl(NewTemplate);
      return NewTemplate;
    }
  
    if (IsMemberSpecialization && !NewVD->isInvalidDecl())
      CompleteMemberSpecialization(NewVD, Previous);
  
    return NewVD;
  }
  
  /// Enum describing the %select options in diag::warn_decl_shadow.
  enum ShadowedDeclKind {
    SDK_Local,
    SDK_Global,
    SDK_StaticMember,
    SDK_Field,
    SDK_Typedef,
    SDK_Using
  };
  
  /// Determine what kind of declaration we're shadowing.
  static ShadowedDeclKind computeShadowedDeclKind(const NamedDecl *ShadowedDecl,
                                                  const DeclContext *OldDC) {
    if (isa<TypeAliasDecl>(ShadowedDecl))
      return SDK_Using;
    else if (isa<TypedefDecl>(ShadowedDecl))
      return SDK_Typedef;
    else if (isa<RecordDecl>(OldDC))
      return isa<FieldDecl>(ShadowedDecl) ? SDK_Field : SDK_StaticMember;
  
    return OldDC->isFileContext() ? SDK_Global : SDK_Local;
  }
  
  /// Return the location of the capture if the given lambda captures the given
  /// variable \p VD, or an invalid source location otherwise.
  static SourceLocation getCaptureLocation(const LambdaScopeInfo *LSI,
                                           const VarDecl *VD) {
    for (const Capture &Capture : LSI->Captures) {
      if (Capture.isVariableCapture() && Capture.getVariable() == VD)
        return Capture.getLocation();
    }
    return SourceLocation();
  }
  
  static bool shouldWarnIfShadowedDecl(const DiagnosticsEngine &Diags,
                                       const LookupResult &R) {
    // Only diagnose if we're shadowing an unambiguous field or variable.
    if (R.getResultKind() != LookupResult::Found)
      return false;
  
    // Return false if warning is ignored.
    return !Diags.isIgnored(diag::warn_decl_shadow, R.getNameLoc());
  }
  
  /// Return the declaration shadowed by the given variable \p D, or null
  /// if it doesn't shadow any declaration or shadowing warnings are disabled.
  NamedDecl *Sema::getShadowedDeclaration(const VarDecl *D,
                                          const LookupResult &R) {
    if (!shouldWarnIfShadowedDecl(Diags, R))
      return nullptr;
  
    // Don't diagnose declarations at file scope.
    if (D->hasGlobalStorage())
      return nullptr;
  
    NamedDecl *ShadowedDecl = R.getFoundDecl();
    return isa<VarDecl>(ShadowedDecl) || isa<FieldDecl>(ShadowedDecl)
               ? ShadowedDecl
               : nullptr;
  }
  
  /// Return the declaration shadowed by the given typedef \p D, or null
  /// if it doesn't shadow any declaration or shadowing warnings are disabled.
  NamedDecl *Sema::getShadowedDeclaration(const TypedefNameDecl *D,
                                          const LookupResult &R) {
    // Don't warn if typedef declaration is part of a class
    if (D->getDeclContext()->isRecord())
      return nullptr;
  
    if (!shouldWarnIfShadowedDecl(Diags, R))
      return nullptr;
  
    NamedDecl *ShadowedDecl = R.getFoundDecl();
    return isa<TypedefNameDecl>(ShadowedDecl) ? ShadowedDecl : nullptr;
  }
  
  /// Diagnose variable or built-in function shadowing.  Implements
  /// -Wshadow.
  ///
  /// This method is called whenever a VarDecl is added to a "useful"
  /// scope.
  ///
  /// \param ShadowedDecl the declaration that is shadowed by the given variable
  /// \param R the lookup of the name
  ///
  void Sema::CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
                         const LookupResult &R) {
    DeclContext *NewDC = D->getDeclContext();
  
    if (FieldDecl *FD = dyn_cast<FieldDecl>(ShadowedDecl)) {
      // Fields are not shadowed by variables in C++ static methods.
      if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewDC))
        if (MD->isStatic())
          return;
  
      // Fields shadowed by constructor parameters are a special case. Usually
      // the constructor initializes the field with the parameter.
      if (isa<CXXConstructorDecl>(NewDC))
        if (const auto PVD = dyn_cast<ParmVarDecl>(D)) {
          // Remember that this was shadowed so we can either warn about its
          // modification or its existence depending on warning settings.
          ShadowingDecls.insert({PVD->getCanonicalDecl(), FD});
          return;
        }
    }
  
    if (VarDecl *shadowedVar = dyn_cast<VarDecl>(ShadowedDecl))
      if (shadowedVar->isExternC()) {
        // For shadowing external vars, make sure that we point to the global
        // declaration, not a locally scoped extern declaration.
        for (auto I : shadowedVar->redecls())
          if (I->isFileVarDecl()) {
            ShadowedDecl = I;
            break;
          }
      }
  
    DeclContext *OldDC = ShadowedDecl->getDeclContext()->getRedeclContext();
  
    unsigned WarningDiag = diag::warn_decl_shadow;
    SourceLocation CaptureLoc;
    if (isa<VarDecl>(D) && isa<VarDecl>(ShadowedDecl) && NewDC &&
        isa<CXXMethodDecl>(NewDC)) {
      if (const auto *RD = dyn_cast<CXXRecordDecl>(NewDC->getParent())) {
        if (RD->isLambda() && OldDC->Encloses(NewDC->getLexicalParent())) {
          if (RD->getLambdaCaptureDefault() == LCD_None) {
            // Try to avoid warnings for lambdas with an explicit capture list.
            const auto *LSI = cast<LambdaScopeInfo>(getCurFunction());
            // Warn only when the lambda captures the shadowed decl explicitly.
            CaptureLoc = getCaptureLocation(LSI, cast<VarDecl>(ShadowedDecl));
            if (CaptureLoc.isInvalid())
              WarningDiag = diag::warn_decl_shadow_uncaptured_local;
          } else {
            // Remember that this was shadowed so we can avoid the warning if the
            // shadowed decl isn't captured and the warning settings allow it.
            cast<LambdaScopeInfo>(getCurFunction())
                ->ShadowingDecls.push_back(
                    {cast<VarDecl>(D), cast<VarDecl>(ShadowedDecl)});
            return;
          }
        }
  
        if (cast<VarDecl>(ShadowedDecl)->hasLocalStorage()) {
          // A variable can't shadow a local variable in an enclosing scope, if
          // they are separated by a non-capturing declaration context.
          for (DeclContext *ParentDC = NewDC;
               ParentDC && !ParentDC->Equals(OldDC);
               ParentDC = getLambdaAwareParentOfDeclContext(ParentDC)) {
            // Only block literals, captured statements, and lambda expressions
            // can capture; other scopes don't.
            if (!isa<BlockDecl>(ParentDC) && !isa<CapturedDecl>(ParentDC) &&
                !isLambdaCallOperator(ParentDC)) {
              return;
            }
          }
        }
      }
    }
  
    // Only warn about certain kinds of shadowing for class members.
    if (NewDC && NewDC->isRecord()) {
      // In particular, don't warn about shadowing non-class members.
      if (!OldDC->isRecord())
        return;
  
      // TODO: should we warn about static data members shadowing
      // static data members from base classes?
  
      // TODO: don't diagnose for inaccessible shadowed members.
      // This is hard to do perfectly because we might friend the
      // shadowing context, but that's just a false negative.
    }
  
  
    DeclarationName Name = R.getLookupName();
  
    // Emit warning and note.
    if (getSourceManager().isInSystemMacro(R.getNameLoc()))
      return;
    ShadowedDeclKind Kind = computeShadowedDeclKind(ShadowedDecl, OldDC);
    Diag(R.getNameLoc(), WarningDiag) << Name << Kind << OldDC;
    if (!CaptureLoc.isInvalid())
      Diag(CaptureLoc, diag::note_var_explicitly_captured_here)
          << Name << /*explicitly*/ 1;
    Diag(ShadowedDecl->getLocation(), diag::note_previous_declaration);
  }
  
  /// Diagnose shadowing for variables shadowed in the lambda record \p LambdaRD
  /// when these variables are captured by the lambda.
  void Sema::DiagnoseShadowingLambdaDecls(const LambdaScopeInfo *LSI) {
    for (const auto &Shadow : LSI->ShadowingDecls) {
      const VarDecl *ShadowedDecl = Shadow.ShadowedDecl;
      // Try to avoid the warning when the shadowed decl isn't captured.
      SourceLocation CaptureLoc = getCaptureLocation(LSI, ShadowedDecl);
      const DeclContext *OldDC = ShadowedDecl->getDeclContext();
      Diag(Shadow.VD->getLocation(), CaptureLoc.isInvalid()
                                         ? diag::warn_decl_shadow_uncaptured_local
                                         : diag::warn_decl_shadow)
          << Shadow.VD->getDeclName()
          << computeShadowedDeclKind(ShadowedDecl, OldDC) << OldDC;
      if (!CaptureLoc.isInvalid())
        Diag(CaptureLoc, diag::note_var_explicitly_captured_here)
            << Shadow.VD->getDeclName() << /*explicitly*/ 0;
      Diag(ShadowedDecl->getLocation(), diag::note_previous_declaration);
    }
  }
  
  /// Check -Wshadow without the advantage of a previous lookup.
  void Sema::CheckShadow(Scope *S, VarDecl *D) {
    if (Diags.isIgnored(diag::warn_decl_shadow, D->getLocation()))
      return;
  
    LookupResult R(*this, D->getDeclName(), D->getLocation(),
                   Sema::LookupOrdinaryName, Sema::ForVisibleRedeclaration);
    LookupName(R, S);
    if (NamedDecl *ShadowedDecl = getShadowedDeclaration(D, R))
      CheckShadow(D, ShadowedDecl, R);
  }
  
  /// Check if 'E', which is an expression that is about to be modified, refers
  /// to a constructor parameter that shadows a field.
  void Sema::CheckShadowingDeclModification(Expr *E, SourceLocation Loc) {
    // Quickly ignore expressions that can't be shadowing ctor parameters.
    if (!getLangOpts().CPlusPlus || ShadowingDecls.empty())
      return;
    E = E->IgnoreParenImpCasts();
    auto *DRE = dyn_cast<DeclRefExpr>(E);
    if (!DRE)
      return;
    const NamedDecl *D = cast<NamedDecl>(DRE->getDecl()->getCanonicalDecl());
    auto I = ShadowingDecls.find(D);
    if (I == ShadowingDecls.end())
      return;
    const NamedDecl *ShadowedDecl = I->second;
    const DeclContext *OldDC = ShadowedDecl->getDeclContext();
    Diag(Loc, diag::warn_modifying_shadowing_decl) << D << OldDC;
    Diag(D->getLocation(), diag::note_var_declared_here) << D;
    Diag(ShadowedDecl->getLocation(), diag::note_previous_declaration);
  
    // Avoid issuing multiple warnings about the same decl.
    ShadowingDecls.erase(I);
  }
  
  /// Check for conflict between this global or extern "C" declaration and
  /// previous global or extern "C" declarations. This is only used in C++.
  template<typename T>
  static bool checkGlobalOrExternCConflict(
      Sema &S, const T *ND, bool IsGlobal, LookupResult &Previous) {
    assert(S.getLangOpts().CPlusPlus && "only C++ has extern \"C\"");
    NamedDecl *Prev = S.findLocallyScopedExternCDecl(ND->getDeclName());
  
    if (!Prev && IsGlobal && !isIncompleteDeclExternC(S, ND)) {
      // The common case: this global doesn't conflict with any extern "C"
      // declaration.
      return false;
    }
  
    if (Prev) {
      if (!IsGlobal || isIncompleteDeclExternC(S, ND)) {
        // Both the old and new declarations have C language linkage. This is a
        // redeclaration.
        Previous.clear();
        Previous.addDecl(Prev);
        return true;
      }
  
      // This is a global, non-extern "C" declaration, and there is a previous
      // non-global extern "C" declaration. Diagnose if this is a variable
      // declaration.
      if (!isa<VarDecl>(ND))
        return false;
    } else {
      // The declaration is extern "C". Check for any declaration in the
      // translation unit which might conflict.
      if (IsGlobal) {
        // We have already performed the lookup into the translation unit.
        IsGlobal = false;
        for (LookupResult::iterator I = Previous.begin(), E = Previous.end();
             I != E; ++I) {
          if (isa<VarDecl>(*I)) {
            Prev = *I;
            break;
          }
        }
      } else {
        DeclContext::lookup_result R =
            S.Context.getTranslationUnitDecl()->lookup(ND->getDeclName());
        for (DeclContext::lookup_result::iterator I = R.begin(), E = R.end();
             I != E; ++I) {
          if (isa<VarDecl>(*I)) {
            Prev = *I;
            break;
          }
          // FIXME: If we have any other entity with this name in global scope,
          // the declaration is ill-formed, but that is a defect: it breaks the
          // 'stat' hack, for instance. Only variables can have mangled name
          // clashes with extern "C" declarations, so only they deserve a
          // diagnostic.
        }
      }
  
      if (!Prev)
        return false;
    }
  
    // Use the first declaration's location to ensure we point at something which
    // is lexically inside an extern "C" linkage-spec.
    assert(Prev && "should have found a previous declaration to diagnose");
    if (FunctionDecl *FD = dyn_cast<FunctionDecl>(Prev))
      Prev = FD->getFirstDecl();
    else
      Prev = cast<VarDecl>(Prev)->getFirstDecl();
  
    S.Diag(ND->getLocation(), diag::err_extern_c_global_conflict)
      << IsGlobal << ND;
    S.Diag(Prev->getLocation(), diag::note_extern_c_global_conflict)
      << IsGlobal;
    return false;
  }
  
  /// Apply special rules for handling extern "C" declarations. Returns \c true
  /// if we have found that this is a redeclaration of some prior entity.
  ///
  /// Per C++ [dcl.link]p6:
  ///   Two declarations [for a function or variable] with C language linkage
  ///   with the same name that appear in different scopes refer to the same
  ///   [entity]. An entity with C language linkage shall not be declared with
  ///   the same name as an entity in global scope.
  template<typename T>
  static bool checkForConflictWithNonVisibleExternC(Sema &S, const T *ND,
                                                    LookupResult &Previous) {
    if (!S.getLangOpts().CPlusPlus) {
      // In C, when declaring a global variable, look for a corresponding 'extern'
      // variable declared in function scope. We don't need this in C++, because
      // we find local extern decls in the surrounding file-scope DeclContext.
      if (ND->getDeclContext()->getRedeclContext()->isTranslationUnit()) {
        if (NamedDecl *Prev = S.findLocallyScopedExternCDecl(ND->getDeclName())) {
          Previous.clear();
          Previous.addDecl(Prev);
          return true;
        }
      }
      return false;
    }
  
    // A declaration in the translation unit can conflict with an extern "C"
    // declaration.
    if (ND->getDeclContext()->getRedeclContext()->isTranslationUnit())
      return checkGlobalOrExternCConflict(S, ND, /*IsGlobal*/true, Previous);
  
    // An extern "C" declaration can conflict with a declaration in the
    // translation unit or can be a redeclaration of an extern "C" declaration
    // in another scope.
    if (isIncompleteDeclExternC(S,ND))
      return checkGlobalOrExternCConflict(S, ND, /*IsGlobal*/false, Previous);
  
    // Neither global nor extern "C": nothing to do.
    return false;
  }
  
  void Sema::CheckVariableDeclarationType(VarDecl *NewVD) {
    // If the decl is already known invalid, don't check it.
    if (NewVD->isInvalidDecl())
      return;
  
    QualType T = NewVD->getType();
  
    // Defer checking an 'auto' type until its initializer is attached.
    if (T->isUndeducedType())
      return;
  
    if (NewVD->hasAttrs())
      CheckAlignasUnderalignment(NewVD);
  
    if (T->isObjCObjectType()) {
      Diag(NewVD->getLocation(), diag::err_statically_allocated_object)
        << FixItHint::CreateInsertion(NewVD->getLocation(), "*");
      T = Context.getObjCObjectPointerType(T);
      NewVD->setType(T);
    }
  
    // Emit an error if an address space was applied to decl with local storage.
    // This includes arrays of objects with address space qualifiers, but not
    // automatic variables that point to other address spaces.
    // ISO/IEC TR 18037 S5.1.2
    if (!getLangOpts().OpenCL && NewVD->hasLocalStorage() &&
        T.getAddressSpace() != LangAS::Default) {
      Diag(NewVD->getLocation(), diag::err_as_qualified_auto_decl) << 0;
      NewVD->setInvalidDecl();
      return;
    }
  
    // OpenCL v1.2 s6.8 - The static qualifier is valid only in program
    // scope.
    if (getLangOpts().OpenCLVersion == 120 &&
        !getOpenCLOptions().isEnabled("cl_clang_storage_class_specifiers") &&
        NewVD->isStaticLocal()) {
      Diag(NewVD->getLocation(), diag::err_static_function_scope);
      NewVD->setInvalidDecl();
      return;
    }
  
    if (getLangOpts().OpenCL) {
      // OpenCL v2.0 s6.12.5 - The __block storage type is not supported.
      if (NewVD->hasAttr<BlocksAttr>()) {
        Diag(NewVD->getLocation(), diag::err_opencl_block_storage_type);
        return;
      }
  
      if (T->isBlockPointerType()) {
        // OpenCL v2.0 s6.12.5 - Any block declaration must be const qualified and
        // can't use 'extern' storage class.
        if (!T.isConstQualified()) {
          Diag(NewVD->getLocation(), diag::err_opencl_invalid_block_declaration)
              << 0 /*const*/;
          NewVD->setInvalidDecl();
          return;
        }
        if (NewVD->hasExternalStorage()) {
          Diag(NewVD->getLocation(), diag::err_opencl_extern_block_declaration);
          NewVD->setInvalidDecl();
          return;
        }
      }
      // OpenCL C v1.2 s6.5 - All program scope variables must be declared in the
      // __constant address space.
      // OpenCL C v2.0 s6.5.1 - Variables defined at program scope and static
      // variables inside a function can also be declared in the global
      // address space.
      // OpenCL C++ v1.0 s2.5 inherits rule from OpenCL C v2.0 and allows local
      // address space additionally.
      // FIXME: Add local AS for OpenCL C++.
      if (NewVD->isFileVarDecl() || NewVD->isStaticLocal() ||
          NewVD->hasExternalStorage()) {
        if (!T->isSamplerT() &&
            !(T.getAddressSpace() == LangAS::opencl_constant ||
              (T.getAddressSpace() == LangAS::opencl_global &&
               (getLangOpts().OpenCLVersion == 200 ||
                getLangOpts().OpenCLCPlusPlus)))) {
          int Scope = NewVD->isStaticLocal() | NewVD->hasExternalStorage() << 1;
          if (getLangOpts().OpenCLVersion == 200 || getLangOpts().OpenCLCPlusPlus)
            Diag(NewVD->getLocation(), diag::err_opencl_global_invalid_addr_space)
                << Scope << "global or constant";
          else
            Diag(NewVD->getLocation(), diag::err_opencl_global_invalid_addr_space)
                << Scope << "constant";
          NewVD->setInvalidDecl();
          return;
        }
      } else {
        if (T.getAddressSpace() == LangAS::opencl_global) {
          Diag(NewVD->getLocation(), diag::err_opencl_function_variable)
              << 1 /*is any function*/ << "global";
          NewVD->setInvalidDecl();
          return;
        }
        if (T.getAddressSpace() == LangAS::opencl_constant ||
            T.getAddressSpace() == LangAS::opencl_local) {
          FunctionDecl *FD = getCurFunctionDecl();
          // OpenCL v1.1 s6.5.2 and s6.5.3: no local or constant variables
          // in functions.
          if (FD && !FD->hasAttr<OpenCLKernelAttr>()) {
            if (T.getAddressSpace() == LangAS::opencl_constant)
              Diag(NewVD->getLocation(), diag::err_opencl_function_variable)
                  << 0 /*non-kernel only*/ << "constant";
            else
              Diag(NewVD->getLocation(), diag::err_opencl_function_variable)
                  << 0 /*non-kernel only*/ << "local";
            NewVD->setInvalidDecl();
            return;
          }
          // OpenCL v2.0 s6.5.2 and s6.5.3: local and constant variables must be
          // in the outermost scope of a kernel function.
          if (FD && FD->hasAttr<OpenCLKernelAttr>()) {
            if (!getCurScope()->isFunctionScope()) {
              if (T.getAddressSpace() == LangAS::opencl_constant)
                Diag(NewVD->getLocation(), diag::err_opencl_addrspace_scope)
                    << "constant";
              else
                Diag(NewVD->getLocation(), diag::err_opencl_addrspace_scope)
                    << "local";
              NewVD->setInvalidDecl();
              return;
            }
          }
        } else if (T.getAddressSpace() != LangAS::opencl_private) {
          // Do not allow other address spaces on automatic variable.
          Diag(NewVD->getLocation(), diag::err_as_qualified_auto_decl) << 1;
          NewVD->setInvalidDecl();
          return;
        }
      }
    }
  
    if (NewVD->hasLocalStorage() && T.isObjCGCWeak()
        && !NewVD->hasAttr<BlocksAttr>()) {
      if (getLangOpts().getGC() != LangOptions::NonGC)
        Diag(NewVD->getLocation(), diag::warn_gc_attribute_weak_on_local);
      else {
        assert(!getLangOpts().ObjCAutoRefCount);
        Diag(NewVD->getLocation(), diag::warn_attribute_weak_on_local);
      }
    }
  
    bool isVM = T->isVariablyModifiedType();
    if (isVM || NewVD->hasAttr<CleanupAttr>() ||
        NewVD->hasAttr<BlocksAttr>())
      setFunctionHasBranchProtectedScope();
  
    if ((isVM && NewVD->hasLinkage()) ||
        (T->isVariableArrayType() && NewVD->hasGlobalStorage())) {
      bool SizeIsNegative;
      llvm::APSInt Oversized;
      TypeSourceInfo *FixedTInfo = TryToFixInvalidVariablyModifiedTypeSourceInfo(
          NewVD->getTypeSourceInfo(), Context, SizeIsNegative, Oversized);
      QualType FixedT;
      if (FixedTInfo &&  T == NewVD->getTypeSourceInfo()->getType())
        FixedT = FixedTInfo->getType();
      else if (FixedTInfo) {
        // Type and type-as-written are canonically different. We need to fix up
        // both types separately.
        FixedT = TryToFixInvalidVariablyModifiedType(T, Context, SizeIsNegative,
                                                     Oversized);
      }
      if ((!FixedTInfo || FixedT.isNull()) && T->isVariableArrayType()) {
        const VariableArrayType *VAT = Context.getAsVariableArrayType(T);
        // FIXME: This won't give the correct result for
        // int a[10][n];
        SourceRange SizeRange = VAT->getSizeExpr()->getSourceRange();
  
        if (NewVD->isFileVarDecl())
          Diag(NewVD->getLocation(), diag::err_vla_decl_in_file_scope)
          << SizeRange;
        else if (NewVD->isStaticLocal())
          Diag(NewVD->getLocation(), diag::err_vla_decl_has_static_storage)
          << SizeRange;
        else
          Diag(NewVD->getLocation(), diag::err_vla_decl_has_extern_linkage)
          << SizeRange;
        NewVD->setInvalidDecl();
        return;
      }
  
      if (!FixedTInfo) {
        if (NewVD->isFileVarDecl())
          Diag(NewVD->getLocation(), diag::err_vm_decl_in_file_scope);
        else
          Diag(NewVD->getLocation(), diag::err_vm_decl_has_extern_linkage);
        NewVD->setInvalidDecl();
        return;
      }
  
      Diag(NewVD->getLocation(), diag::warn_illegal_constant_array_size);
      NewVD->setType(FixedT);
      NewVD->setTypeSourceInfo(FixedTInfo);
    }
  
    if (T->isVoidType()) {
      // C++98 [dcl.stc]p5: The extern specifier can be applied only to the names
      //                    of objects and functions.
      if (NewVD->isThisDeclarationADefinition() || getLangOpts().CPlusPlus) {
        Diag(NewVD->getLocation(), diag::err_typecheck_decl_incomplete_type)
          << T;
        NewVD->setInvalidDecl();
        return;
      }
    }
  
    if (!NewVD->hasLocalStorage() && NewVD->hasAttr<BlocksAttr>()) {
      Diag(NewVD->getLocation(), diag::err_block_on_nonlocal);
      NewVD->setInvalidDecl();
      return;
    }
  
    if (isVM && NewVD->hasAttr<BlocksAttr>()) {
      Diag(NewVD->getLocation(), diag::err_block_on_vm);
      NewVD->setInvalidDecl();
      return;
    }
  
    if (NewVD->isConstexpr() && !T->isDependentType() &&
        RequireLiteralType(NewVD->getLocation(), T,
                           diag::err_constexpr_var_non_literal)) {
      NewVD->setInvalidDecl();
      return;
    }
  }
  
  /// Perform semantic checking on a newly-created variable
  /// declaration.
  ///
  /// This routine performs all of the type-checking required for a
  /// variable declaration once it has been built. It is used both to
  /// check variables after they have been parsed and their declarators
  /// have been translated into a declaration, and to check variables
  /// that have been instantiated from a template.
  ///
  /// Sets NewVD->isInvalidDecl() if an error was encountered.
  ///
  /// Returns true if the variable declaration is a redeclaration.
  bool Sema::CheckVariableDeclaration(VarDecl *NewVD, LookupResult &Previous) {
    CheckVariableDeclarationType(NewVD);
  
    // If the decl is already known invalid, don't check it.
    if (NewVD->isInvalidDecl())
      return false;
  
    // If we did not find anything by this name, look for a non-visible
    // extern "C" declaration with the same name.
    if (Previous.empty() &&
        checkForConflictWithNonVisibleExternC(*this, NewVD, Previous))
      Previous.setShadowed();
  
    if (!Previous.empty()) {
      MergeVarDecl(NewVD, Previous);
      return true;
    }
    return false;
  }
  
  namespace {
  struct FindOverriddenMethod {
    Sema *S;
    CXXMethodDecl *Method;
  
    /// Member lookup function that determines whether a given C++
    /// method overrides a method in a base class, to be used with
    /// CXXRecordDecl::lookupInBases().
    bool operator()(const CXXBaseSpecifier *Specifier, CXXBasePath &Path) {
      RecordDecl *BaseRecord =
          Specifier->getType()->getAs<RecordType>()->getDecl();
  
      DeclarationName Name = Method->getDeclName();
  
      // FIXME: Do we care about other names here too?
      if (Name.getNameKind() == DeclarationName::CXXDestructorName) {
        // We really want to find the base class destructor here.
        QualType T = S->Context.getTypeDeclType(BaseRecord);
        CanQualType CT = S->Context.getCanonicalType(T);
  
        Name = S->Context.DeclarationNames.getCXXDestructorName(CT);
      }
  
      for (Path.Decls = BaseRecord->lookup(Name); !Path.Decls.empty();
           Path.Decls = Path.Decls.slice(1)) {
        NamedDecl *D = Path.Decls.front();
        if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
          if (MD->isVirtual() && !S->IsOverload(Method, MD, false))
            return true;
        }
      }
  
      return false;
    }
  };
  
  enum OverrideErrorKind { OEK_All, OEK_NonDeleted, OEK_Deleted };
  } // end anonymous namespace
  
  /// Report an error regarding overriding, along with any relevant
  /// overridden methods.
  ///
  /// \param DiagID the primary error to report.
  /// \param MD the overriding method.
  /// \param OEK which overrides to include as notes.
  static void ReportOverrides(Sema& S, unsigned DiagID, const CXXMethodDecl *MD,
                              OverrideErrorKind OEK = OEK_All) {
    S.Diag(MD->getLocation(), DiagID) << MD->getDeclName();
    for (const CXXMethodDecl *O : MD->overridden_methods()) {
      // This check (& the OEK parameter) could be replaced by a predicate, but
      // without lambdas that would be overkill. This is still nicer than writing
      // out the diag loop 3 times.
      if ((OEK == OEK_All) ||
          (OEK == OEK_NonDeleted && !O->isDeleted()) ||
          (OEK == OEK_Deleted && O->isDeleted()))
        S.Diag(O->getLocation(), diag::note_overridden_virtual_function);
    }
  }
  
  /// AddOverriddenMethods - See if a method overrides any in the base classes,
  /// and if so, check that it's a valid override and remember it.
  bool Sema::AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD) {
    // Look for methods in base classes that this method might override.
    CXXBasePaths Paths;
    FindOverriddenMethod FOM;
    FOM.Method = MD;
    FOM.S = this;
    bool hasDeletedOverridenMethods = false;
    bool hasNonDeletedOverridenMethods = false;
    bool AddedAny = false;
    if (DC->lookupInBases(FOM, Paths)) {
      for (auto *I : Paths.found_decls()) {
        if (CXXMethodDecl *OldMD = dyn_cast<CXXMethodDecl>(I)) {
          MD->addOverriddenMethod(OldMD->getCanonicalDecl());
          if (!CheckOverridingFunctionReturnType(MD, OldMD) &&
              !CheckOverridingFunctionAttributes(MD, OldMD) &&
              !CheckOverridingFunctionExceptionSpec(MD, OldMD) &&
              !CheckIfOverriddenFunctionIsMarkedFinal(MD, OldMD)) {
            hasDeletedOverridenMethods |= OldMD->isDeleted();
            hasNonDeletedOverridenMethods |= !OldMD->isDeleted();
            AddedAny = true;
          }
        }
      }
    }
  
    if (hasDeletedOverridenMethods && !MD->isDeleted()) {
      ReportOverrides(*this, diag::err_non_deleted_override, MD, OEK_Deleted);
    }
    if (hasNonDeletedOverridenMethods && MD->isDeleted()) {
      ReportOverrides(*this, diag::err_deleted_override, MD, OEK_NonDeleted);
    }
  
    return AddedAny;
  }
  
  namespace {
    // Struct for holding all of the extra arguments needed by
    // DiagnoseInvalidRedeclaration to call Sema::ActOnFunctionDeclarator.
    struct ActOnFDArgs {
      Scope *S;
      Declarator &D;
      MultiTemplateParamsArg TemplateParamLists;
      bool AddToScope;
    };
  } // end anonymous namespace
  
  namespace {
  
  // Callback to only accept typo corrections that have a non-zero edit distance.
  // Also only accept corrections that have the same parent decl.
  class DifferentNameValidatorCCC final : public CorrectionCandidateCallback {
   public:
    DifferentNameValidatorCCC(ASTContext &Context, FunctionDecl *TypoFD,
                              CXXRecordDecl *Parent)
        : Context(Context), OriginalFD(TypoFD),
          ExpectedParent(Parent ? Parent->getCanonicalDecl() : nullptr) {}
  
    bool ValidateCandidate(const TypoCorrection &candidate) override {
      if (candidate.getEditDistance() == 0)
        return false;
  
      SmallVector<unsigned, 1> MismatchedParams;
      for (TypoCorrection::const_decl_iterator CDecl = candidate.begin(),
                                            CDeclEnd = candidate.end();
           CDecl != CDeclEnd; ++CDecl) {
        FunctionDecl *FD = dyn_cast<FunctionDecl>(*CDecl);
  
        if (FD && !FD->hasBody() &&
            hasSimilarParameters(Context, FD, OriginalFD, MismatchedParams)) {
          if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
            CXXRecordDecl *Parent = MD->getParent();
            if (Parent && Parent->getCanonicalDecl() == ExpectedParent)
              return true;
          } else if (!ExpectedParent) {
            return true;
          }
        }
      }
  
      return false;
    }
  
    std::unique_ptr<CorrectionCandidateCallback> clone() override {
      return llvm::make_unique<DifferentNameValidatorCCC>(*this);
    }
  
   private:
    ASTContext &Context;
    FunctionDecl *OriginalFD;
    CXXRecordDecl *ExpectedParent;
  };
  
  } // end anonymous namespace
  
  void Sema::MarkTypoCorrectedFunctionDefinition(const NamedDecl *F) {
    TypoCorrectedFunctionDefinitions.insert(F);
  }
  
  /// Generate diagnostics for an invalid function redeclaration.
  ///
  /// This routine handles generating the diagnostic messages for an invalid
  /// function redeclaration, including finding possible similar declarations
  /// or performing typo correction if there are no previous declarations with
  /// the same name.
  ///
  /// Returns a NamedDecl iff typo correction was performed and substituting in
  /// the new declaration name does not cause new errors.
  static NamedDecl *DiagnoseInvalidRedeclaration(
      Sema &SemaRef, LookupResult &Previous, FunctionDecl *NewFD,
      ActOnFDArgs &ExtraArgs, bool IsLocalFriend, Scope *S) {
    DeclarationName Name = NewFD->getDeclName();
    DeclContext *NewDC = NewFD->getDeclContext();
    SmallVector<unsigned, 1> MismatchedParams;
    SmallVector<std::pair<FunctionDecl *, unsigned>, 1> NearMatches;
    TypoCorrection Correction;
    bool IsDefinition = ExtraArgs.D.isFunctionDefinition();
    unsigned DiagMsg =
      IsLocalFriend ? diag::err_no_matching_local_friend :
      NewFD->getFriendObjectKind() ? diag::err_qualified_friend_no_match :
      diag::err_member_decl_does_not_match;
    LookupResult Prev(SemaRef, Name, NewFD->getLocation(),
                      IsLocalFriend ? Sema::LookupLocalFriendName
                                    : Sema::LookupOrdinaryName,
                      Sema::ForVisibleRedeclaration);
  
    NewFD->setInvalidDecl();
    if (IsLocalFriend)
      SemaRef.LookupName(Prev, S);
    else
      SemaRef.LookupQualifiedName(Prev, NewDC);
    assert(!Prev.isAmbiguous() &&
           "Cannot have an ambiguity in previous-declaration lookup");
    CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewFD);
    DifferentNameValidatorCCC CCC(SemaRef.Context, NewFD,
                                  MD ? MD->getParent() : nullptr);
    if (!Prev.empty()) {
      for (LookupResult::iterator Func = Prev.begin(), FuncEnd = Prev.end();
           Func != FuncEnd; ++Func) {
        FunctionDecl *FD = dyn_cast<FunctionDecl>(*Func);
        if (FD &&
            hasSimilarParameters(SemaRef.Context, FD, NewFD, MismatchedParams)) {
          // Add 1 to the index so that 0 can mean the mismatch didn't
          // involve a parameter
          unsigned ParamNum =
              MismatchedParams.empty() ? 0 : MismatchedParams.front() + 1;
          NearMatches.push_back(std::make_pair(FD, ParamNum));
        }
      }
    // If the qualified name lookup yielded nothing, try typo correction
    } else if ((Correction = SemaRef.CorrectTypo(
                    Prev.getLookupNameInfo(), Prev.getLookupKind(), S,
                    &ExtraArgs.D.getCXXScopeSpec(), CCC, Sema::CTK_ErrorRecovery,
                    IsLocalFriend ? nullptr : NewDC))) {
      // Set up everything for the call to ActOnFunctionDeclarator
      ExtraArgs.D.SetIdentifier(Correction.getCorrectionAsIdentifierInfo(),
                                ExtraArgs.D.getIdentifierLoc());
      Previous.clear();
      Previous.setLookupName(Correction.getCorrection());
      for (TypoCorrection::decl_iterator CDecl = Correction.begin(),
                                      CDeclEnd = Correction.end();
           CDecl != CDeclEnd; ++CDecl) {
        FunctionDecl *FD = dyn_cast<FunctionDecl>(*CDecl);
        if (FD && !FD->hasBody() &&
            hasSimilarParameters(SemaRef.Context, FD, NewFD, MismatchedParams)) {
          Previous.addDecl(FD);
        }
      }
      bool wasRedeclaration = ExtraArgs.D.isRedeclaration();
  
      NamedDecl *Result;
      // Retry building the function declaration with the new previous
      // declarations, and with errors suppressed.
      {
        // Trap errors.
        Sema::SFINAETrap Trap(SemaRef);
  
        // TODO: Refactor ActOnFunctionDeclarator so that we can call only the
        // pieces need to verify the typo-corrected C++ declaration and hopefully
        // eliminate the need for the parameter pack ExtraArgs.
        Result = SemaRef.ActOnFunctionDeclarator(
            ExtraArgs.S, ExtraArgs.D,
            Correction.getCorrectionDecl()->getDeclContext(),
            NewFD->getTypeSourceInfo(), Previous, ExtraArgs.TemplateParamLists,
            ExtraArgs.AddToScope);
  
        if (Trap.hasErrorOccurred())
          Result = nullptr;
      }
  
      if (Result) {
        // Determine which correction we picked.
        Decl *Canonical = Result->getCanonicalDecl();
        for (LookupResult::iterator I = Previous.begin(), E = Previous.end();
             I != E; ++I)
          if ((*I)->getCanonicalDecl() == Canonical)
            Correction.setCorrectionDecl(*I);
  
        // Let Sema know about the correction.
        SemaRef.MarkTypoCorrectedFunctionDefinition(Result);
        SemaRef.diagnoseTypo(
            Correction,
            SemaRef.PDiag(IsLocalFriend
                            ? diag::err_no_matching_local_friend_suggest
                            : diag::err_member_decl_does_not_match_suggest)
              << Name << NewDC << IsDefinition);
        return Result;
      }
  
      // Pretend the typo correction never occurred
      ExtraArgs.D.SetIdentifier(Name.getAsIdentifierInfo(),
                                ExtraArgs.D.getIdentifierLoc());
      ExtraArgs.D.setRedeclaration(wasRedeclaration);
      Previous.clear();
      Previous.setLookupName(Name);
    }
  
    SemaRef.Diag(NewFD->getLocation(), DiagMsg)
        << Name << NewDC << IsDefinition << NewFD->getLocation();
  
    bool NewFDisConst = false;
    if (CXXMethodDecl *NewMD = dyn_cast<CXXMethodDecl>(NewFD))
      NewFDisConst = NewMD->isConst();
  
    for (SmallVectorImpl<std::pair<FunctionDecl *, unsigned> >::iterator
         NearMatch = NearMatches.begin(), NearMatchEnd = NearMatches.end();
         NearMatch != NearMatchEnd; ++NearMatch) {
      FunctionDecl *FD = NearMatch->first;
      CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
      bool FDisConst = MD && MD->isConst();
      bool IsMember = MD || !IsLocalFriend;
  
      // FIXME: These notes are poorly worded for the local friend case.
      if (unsigned Idx = NearMatch->second) {
        ParmVarDecl *FDParam = FD->getParamDecl(Idx-1);
        SourceLocation Loc = FDParam->getTypeSpecStartLoc();
        if (Loc.isInvalid()) Loc = FD->getLocation();
        SemaRef.Diag(Loc, IsMember ? diag::note_member_def_close_param_match
                                   : diag::note_local_decl_close_param_match)
          << Idx << FDParam->getType()
          << NewFD->getParamDecl(Idx - 1)->getType();
      } else if (FDisConst != NewFDisConst) {
        SemaRef.Diag(FD->getLocation(), diag::note_member_def_close_const_match)
            << NewFDisConst << FD->getSourceRange().getEnd();
      } else
        SemaRef.Diag(FD->getLocation(),
                     IsMember ? diag::note_member_def_close_match
                              : diag::note_local_decl_close_match);
    }
    return nullptr;
  }
  
  static StorageClass getFunctionStorageClass(Sema &SemaRef, Declarator &D) {
    switch (D.getDeclSpec().getStorageClassSpec()) {
    default: llvm_unreachable("Unknown storage class!");
    case DeclSpec::SCS_auto:
    case DeclSpec::SCS_register:
    case DeclSpec::SCS_mutable:
      SemaRef.Diag(D.getDeclSpec().getStorageClassSpecLoc(),
                   diag::err_typecheck_sclass_func);
      D.getMutableDeclSpec().ClearStorageClassSpecs();
      D.setInvalidType();
      break;
    case DeclSpec::SCS_unspecified: break;
    case DeclSpec::SCS_extern:
      if (D.getDeclSpec().isExternInLinkageSpec())
        return SC_None;
      return SC_Extern;
    case DeclSpec::SCS_static: {
      if (SemaRef.CurContext->getRedeclContext()->isFunctionOrMethod()) {
        // C99 6.7.1p5:
        //   The declaration of an identifier for a function that has
        //   block scope shall have no explicit storage-class specifier
        //   other than extern
        // See also (C++ [dcl.stc]p4).
        SemaRef.Diag(D.getDeclSpec().getStorageClassSpecLoc(),
                     diag::err_static_block_func);
        break;
      } else
        return SC_Static;
    }
    case DeclSpec::SCS_private_extern: return SC_PrivateExtern;
    }
  
    // No explicit storage class has already been returned
    return SC_None;
  }
  
  static FunctionDecl* CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
                                             DeclContext *DC, QualType &R,
                                             TypeSourceInfo *TInfo,
                                             StorageClass SC,
                                             bool &IsVirtualOkay) {
    DeclarationNameInfo NameInfo = SemaRef.GetNameForDeclarator(D);
    DeclarationName Name = NameInfo.getName();
  
    FunctionDecl *NewFD = nullptr;
    bool isInline = D.getDeclSpec().isInlineSpecified();
  
    if (!SemaRef.getLangOpts().CPlusPlus) {
      // Determine whether the function was written with a
      // prototype. This true when:
      //   - there is a prototype in the declarator, or
      //   - the type R of the function is some kind of typedef or other non-
      //     attributed reference to a type name (which eventually refers to a
      //     function type).
      bool HasPrototype =
        (D.isFunctionDeclarator() && D.getFunctionTypeInfo().hasPrototype) ||
        (!R->getAsAdjusted<FunctionType>() && R->isFunctionProtoType());
  
      NewFD = FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(), NameInfo,
                                   R, TInfo, SC, isInline, HasPrototype, false);
      if (D.isInvalidType())
        NewFD->setInvalidDecl();
  
      return NewFD;
    }
  
    bool isExplicit = D.getDeclSpec().isExplicitSpecified();
    bool isConstexpr = D.getDeclSpec().isConstexprSpecified();
  
    // Check that the return type is not an abstract class type.
    // For record types, this is done by the AbstractClassUsageDiagnoser once
    // the class has been completely parsed.
    if (!DC->isRecord() &&
        SemaRef.RequireNonAbstractType(
            D.getIdentifierLoc(), R->getAs<FunctionType>()->getReturnType(),
            diag::err_abstract_type_in_decl, SemaRef.AbstractReturnType))
      D.setInvalidType();
  
    if (Name.getNameKind() == DeclarationName::CXXConstructorName) {
      // This is a C++ constructor declaration.
      assert(DC->isRecord() &&
             "Constructors can only be declared in a member context");
  
      R = SemaRef.CheckConstructorDeclarator(D, R, SC);
      return CXXConstructorDecl::Create(
          SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
          TInfo, isExplicit, isInline,
          /*isImplicitlyDeclared=*/false, isConstexpr);
  
    } else if (Name.getNameKind() == DeclarationName::CXXDestructorName) {
      // This is a C++ destructor declaration.
      if (DC->isRecord()) {
        R = SemaRef.CheckDestructorDeclarator(D, R, SC);
        CXXRecordDecl *Record = cast<CXXRecordDecl>(DC);
        CXXDestructorDecl *NewDD =
            CXXDestructorDecl::Create(SemaRef.Context, Record, D.getBeginLoc(),
                                      NameInfo, R, TInfo, isInline,
                                      /*isImplicitlyDeclared=*/false);
  
        // If the destructor needs an implicit exception specification, set it
        // now. FIXME: It'd be nice to be able to create the right type to start
        // with, but the type needs to reference the destructor declaration.
        if (SemaRef.getLangOpts().CPlusPlus11)
          SemaRef.AdjustDestructorExceptionSpec(NewDD);
  
        IsVirtualOkay = true;
        return NewDD;
  
      } else {
        SemaRef.Diag(D.getIdentifierLoc(), diag::err_destructor_not_member);
        D.setInvalidType();
  
        // Create a FunctionDecl to satisfy the function definition parsing
        // code path.
        return FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(),
                                    D.getIdentifierLoc(), Name, R, TInfo, SC,
                                    isInline,
                                    /*hasPrototype=*/true, isConstexpr);
      }
  
    } else if (Name.getNameKind() == DeclarationName::CXXConversionFunctionName) {
      if (!DC->isRecord()) {
        SemaRef.Diag(D.getIdentifierLoc(),
             diag::err_conv_function_not_member);
        return nullptr;
      }
  
      SemaRef.CheckConversionDeclarator(D, R, SC);
      IsVirtualOkay = true;
      return CXXConversionDecl::Create(
          SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
          TInfo, isInline, isExplicit, isConstexpr, SourceLocation());
  
    } else if (Name.getNameKind() == DeclarationName::CXXDeductionGuideName) {
      SemaRef.CheckDeductionGuideDeclarator(D, R, SC);
  
      return CXXDeductionGuideDecl::Create(SemaRef.Context, DC, D.getBeginLoc(),
                                           isExplicit, NameInfo, R, TInfo,
                                           D.getEndLoc());
    } else if (DC->isRecord()) {
      // If the name of the function is the same as the name of the record,
      // then this must be an invalid constructor that has a return type.
      // (The parser checks for a return type and makes the declarator a
      // constructor if it has no return type).
      if (Name.getAsIdentifierInfo() &&
          Name.getAsIdentifierInfo() == cast<CXXRecordDecl>(DC)->getIdentifier()){
        SemaRef.Diag(D.getIdentifierLoc(), diag::err_constructor_return_type)
          << SourceRange(D.getDeclSpec().getTypeSpecTypeLoc())
          << SourceRange(D.getIdentifierLoc());
        return nullptr;
      }
  
      // This is a C++ method declaration.
      CXXMethodDecl *Ret = CXXMethodDecl::Create(
          SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
          TInfo, SC, isInline, isConstexpr, SourceLocation());
      IsVirtualOkay = !Ret->isStatic();
      return Ret;
    } else {
      bool isFriend =
          SemaRef.getLangOpts().CPlusPlus && D.getDeclSpec().isFriendSpecified();
      if (!isFriend && SemaRef.CurContext->isRecord())
        return nullptr;
  
      // Determine whether the function was written with a
      // prototype. This true when:
      //   - we're in C++ (where every function has a prototype),
      return FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(), NameInfo,
                                  R, TInfo, SC, isInline, true /*HasPrototype*/,
                                  isConstexpr);
    }
  }
  
  enum OpenCLParamType {
    ValidKernelParam,
    PtrPtrKernelParam,
    PtrKernelParam,
    InvalidAddrSpacePtrKernelParam,
    InvalidKernelParam,
    RecordKernelParam
  };
  
  static bool isOpenCLSizeDependentType(ASTContext &C, QualType Ty) {
    // Size dependent types are just typedefs to normal integer types
    // (e.g. unsigned long), so we cannot distinguish them from other typedefs to
    // integers other than by their names.
    StringRef SizeTypeNames[] = {"size_t", "intptr_t", "uintptr_t", "ptrdiff_t"};
  
    // Remove typedefs one by one until we reach a typedef
    // for a size dependent type.
    QualType DesugaredTy = Ty;
    do {
      ArrayRef<StringRef> Names(SizeTypeNames);
      auto Match = llvm::find(Names, DesugaredTy.getAsString());
      if (Names.end() != Match)
        return true;
  
      Ty = DesugaredTy;
      DesugaredTy = Ty.getSingleStepDesugaredType(C);
    } while (DesugaredTy != Ty);
  
    return false;
  }
  
  static OpenCLParamType getOpenCLKernelParameterType(Sema &S, QualType PT) {
    if (PT->isPointerType()) {
      QualType PointeeType = PT->getPointeeType();
      if (PointeeType->isPointerType())
        return PtrPtrKernelParam;
      if (PointeeType.getAddressSpace() == LangAS::opencl_generic ||
          PointeeType.getAddressSpace() == LangAS::opencl_private ||
          PointeeType.getAddressSpace() == LangAS::Default)
        return InvalidAddrSpacePtrKernelParam;
      return PtrKernelParam;
    }
  
    // OpenCL v1.2 s6.9.k:
    // Arguments to kernel functions in a program cannot be declared with the
    // built-in scalar types bool, half, size_t, ptrdiff_t, intptr_t, and
    // uintptr_t or a struct and/or union that contain fields declared to be one
    // of these built-in scalar types.
    if (isOpenCLSizeDependentType(S.getASTContext(), PT))
      return InvalidKernelParam;
  
    if (PT->isImageType())
      return PtrKernelParam;
  
    if (PT->isBooleanType() || PT->isEventT() || PT->isReserveIDT())
      return InvalidKernelParam;
  
    // OpenCL extension spec v1.2 s9.5:
    // This extension adds support for half scalar and vector types as built-in
    // types that can be used for arithmetic operations, conversions etc.
    if (!S.getOpenCLOptions().isEnabled("cl_khr_fp16") && PT->isHalfType())
      return InvalidKernelParam;
  
    if (PT->isRecordType())
      return RecordKernelParam;
  
    // Look into an array argument to check if it has a forbidden type.
    if (PT->isArrayType()) {
      const Type *UnderlyingTy = PT->getPointeeOrArrayElementType();
      // Call ourself to check an underlying type of an array. Since the
      // getPointeeOrArrayElementType returns an innermost type which is not an
      // array, this recursive call only happens once.
      return getOpenCLKernelParameterType(S, QualType(UnderlyingTy, 0));
    }
  
    return ValidKernelParam;
  }
  
  static void checkIsValidOpenCLKernelParameter(
    Sema &S,
    Declarator &D,
    ParmVarDecl *Param,
    llvm::SmallPtrSetImpl<const Type *> &ValidTypes) {
    QualType PT = Param->getType();
  
    // Cache the valid types we encounter to avoid rechecking structs that are
    // used again
    if (ValidTypes.count(PT.getTypePtr()))
      return;
  
    switch (getOpenCLKernelParameterType(S, PT)) {
    case PtrPtrKernelParam:
      // OpenCL v1.2 s6.9.a:
      // A kernel function argument cannot be declared as a
      // pointer to a pointer type.
      S.Diag(Param->getLocation(), diag::err_opencl_ptrptr_kernel_param);
      D.setInvalidType();
      return;
  
    case InvalidAddrSpacePtrKernelParam:
      // OpenCL v1.0 s6.5:
      // __kernel function arguments declared to be a pointer of a type can point
      // to one of the following address spaces only : __global, __local or
      // __constant.
      S.Diag(Param->getLocation(), diag::err_kernel_arg_address_space);
      D.setInvalidType();
      return;
  
      // OpenCL v1.2 s6.9.k:
      // Arguments to kernel functions in a program cannot be declared with the
      // built-in scalar types bool, half, size_t, ptrdiff_t, intptr_t, and
      // uintptr_t or a struct and/or union that contain fields declared to be
      // one of these built-in scalar types.
  
    case InvalidKernelParam:
      // OpenCL v1.2 s6.8 n:
      // A kernel function argument cannot be declared
      // of event_t type.
      // Do not diagnose half type since it is diagnosed as invalid argument
      // type for any function elsewhere.
      if (!PT->isHalfType()) {
        S.Diag(Param->getLocation(), diag::err_bad_kernel_param_type) << PT;
  
        // Explain what typedefs are involved.
        const TypedefType *Typedef = nullptr;
        while ((Typedef = PT->getAs<TypedefType>())) {
          SourceLocation Loc = Typedef->getDecl()->getLocation();
          // SourceLocation may be invalid for a built-in type.
          if (Loc.isValid())
            S.Diag(Loc, diag::note_entity_declared_at) << PT;
          PT = Typedef->desugar();
        }
      }
  
      D.setInvalidType();
      return;
  
    case PtrKernelParam:
    case ValidKernelParam:
      ValidTypes.insert(PT.getTypePtr());
      return;
  
    case RecordKernelParam:
      break;
    }
  
    // Track nested structs we will inspect
    SmallVector<const Decl *, 4> VisitStack;
  
    // Track where we are in the nested structs. Items will migrate from
    // VisitStack to HistoryStack as we do the DFS for bad field.
    SmallVector<const FieldDecl *, 4> HistoryStack;
    HistoryStack.push_back(nullptr);
  
    // At this point we already handled everything except of a RecordType or
    // an ArrayType of a RecordType.
    assert((PT->isArrayType() || PT->isRecordType()) && "Unexpected type.");
    const RecordType *RecTy =
        PT->getPointeeOrArrayElementType()->getAs<RecordType>();
    const RecordDecl *OrigRecDecl = RecTy->getDecl();
  
    VisitStack.push_back(RecTy->getDecl());
    assert(VisitStack.back() && "First decl null?");
  
    do {
      const Decl *Next = VisitStack.pop_back_val();
      if (!Next) {
        assert(!HistoryStack.empty());
        // Found a marker, we have gone up a level
        if (const FieldDecl *Hist = HistoryStack.pop_back_val())
          ValidTypes.insert(Hist->getType().getTypePtr());
  
        continue;
      }
  
      // Adds everything except the original parameter declaration (which is not a
      // field itself) to the history stack.
      const RecordDecl *RD;
      if (const FieldDecl *Field = dyn_cast<FieldDecl>(Next)) {
        HistoryStack.push_back(Field);
  
        QualType FieldTy = Field->getType();
        // Other field types (known to be valid or invalid) are handled while we
        // walk around RecordDecl::fields().
        assert((FieldTy->isArrayType() || FieldTy->isRecordType()) &&
               "Unexpected type.");
        const Type *FieldRecTy = FieldTy->getPointeeOrArrayElementType();
  
        RD = FieldRecTy->castAs<RecordType>()->getDecl();
      } else {
        RD = cast<RecordDecl>(Next);
      }
  
      // Add a null marker so we know when we've gone back up a level
      VisitStack.push_back(nullptr);
  
      for (const auto *FD : RD->fields()) {
        QualType QT = FD->getType();
  
        if (ValidTypes.count(QT.getTypePtr()))
          continue;
  
        OpenCLParamType ParamType = getOpenCLKernelParameterType(S, QT);
        if (ParamType == ValidKernelParam)
          continue;
  
        if (ParamType == RecordKernelParam) {
          VisitStack.push_back(FD);
          continue;
        }
  
        // OpenCL v1.2 s6.9.p:
        // Arguments to kernel functions that are declared to be a struct or union
        // do not allow OpenCL objects to be passed as elements of the struct or
        // union.
        if (ParamType == PtrKernelParam || ParamType == PtrPtrKernelParam ||
            ParamType == InvalidAddrSpacePtrKernelParam) {
          S.Diag(Param->getLocation(),
                 diag::err_record_with_pointers_kernel_param)
            << PT->isUnionType()
            << PT;
        } else {
          S.Diag(Param->getLocation(), diag::err_bad_kernel_param_type) << PT;
        }
  
        S.Diag(OrigRecDecl->getLocation(), diag::note_within_field_of_type)
            << OrigRecDecl->getDeclName();
  
        // We have an error, now let's go back up through history and show where
        // the offending field came from
        for (ArrayRef<const FieldDecl *>::const_iterator
                 I = HistoryStack.begin() + 1,
                 E = HistoryStack.end();
             I != E; ++I) {
          const FieldDecl *OuterField = *I;
          S.Diag(OuterField->getLocation(), diag::note_within_field_of_type)
            << OuterField->getType();
        }
  
        S.Diag(FD->getLocation(), diag::note_illegal_field_declared_here)
          << QT->isPointerType()
          << QT;
        D.setInvalidType();
        return;
      }
    } while (!VisitStack.empty());
  }
  
  /// Find the DeclContext in which a tag is implicitly declared if we see an
  /// elaborated type specifier in the specified context, and lookup finds
  /// nothing.
  static DeclContext *getTagInjectionContext(DeclContext *DC) {
    while (!DC->isFileContext() && !DC->isFunctionOrMethod())
      DC = DC->getParent();
    return DC;
  }
  
  /// Find the Scope in which a tag is implicitly declared if we see an
  /// elaborated type specifier in the specified context, and lookup finds
  /// nothing.
  static Scope *getTagInjectionScope(Scope *S, const LangOptions &LangOpts) {
    while (S->isClassScope() ||
           (LangOpts.CPlusPlus &&
            S->isFunctionPrototypeScope()) ||
           ((S->getFlags() & Scope::DeclScope) == 0) ||
           (S->getEntity() && S->getEntity()->isTransparentContext()))
      S = S->getParent();
    return S;
  }
  
  NamedDecl*
  Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
                                TypeSourceInfo *TInfo, LookupResult &Previous,
                                MultiTemplateParamsArg TemplateParamLists,
                                bool &AddToScope) {
    QualType R = TInfo->getType();
  
    assert(R->isFunctionType());
  
    // TODO: consider using NameInfo for diagnostic.
    DeclarationNameInfo NameInfo = GetNameForDeclarator(D);
    DeclarationName Name = NameInfo.getName();
    StorageClass SC = getFunctionStorageClass(*this, D);
  
    if (DeclSpec::TSCS TSCS = D.getDeclSpec().getThreadStorageClassSpec())
      Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
           diag::err_invalid_thread)
        << DeclSpec::getSpecifierName(TSCS);
  
    if (D.isFirstDeclarationOfMember())
      adjustMemberFunctionCC(R, D.isStaticMember(), D.isCtorOrDtor(),
                             D.getIdentifierLoc());
  
    bool isFriend = false;
    FunctionTemplateDecl *FunctionTemplate = nullptr;
    bool isMemberSpecialization = false;
    bool isFunctionTemplateSpecialization = false;
  
    bool isDependentClassScopeExplicitSpecialization = false;
    bool HasExplicitTemplateArgs = false;
    TemplateArgumentListInfo TemplateArgs;
  
    bool isVirtualOkay = false;
  
    DeclContext *OriginalDC = DC;
    bool IsLocalExternDecl = adjustContextForLocalExternDecl(DC);
  
    FunctionDecl *NewFD = CreateNewFunctionDecl(*this, D, DC, R, TInfo, SC,
                                                isVirtualOkay);
    if (!NewFD) return nullptr;
  
    if (OriginalLexicalContext && OriginalLexicalContext->isObjCContainer())
      NewFD->setTopLevelDeclInObjCContainer();
  
    // Set the lexical context. If this is a function-scope declaration, or has a
    // C++ scope specifier, or is the object of a friend declaration, the lexical
    // context will be different from the semantic context.
    NewFD->setLexicalDeclContext(CurContext);
  
    if (IsLocalExternDecl)
      NewFD->setLocalExternDecl();
  
    if (getLangOpts().CPlusPlus) {
      bool isInline = D.getDeclSpec().isInlineSpecified();
      bool isVirtual = D.getDeclSpec().isVirtualSpecified();
      bool isExplicit = D.getDeclSpec().isExplicitSpecified();
      bool isConstexpr = D.getDeclSpec().isConstexprSpecified();
      isFriend = D.getDeclSpec().isFriendSpecified();
      if (isFriend && !isInline && D.isFunctionDefinition()) {
        // C++ [class.friend]p5
        //   A function can be defined in a friend declaration of a
        //   class . . . . Such a function is implicitly inline.
        NewFD->setImplicitlyInline();
      }
  
      // If this is a method defined in an __interface, and is not a constructor
      // or an overloaded operator, then set the pure flag (isVirtual will already
      // return true).
      if (const CXXRecordDecl *Parent =
            dyn_cast<CXXRecordDecl>(NewFD->getDeclContext())) {
        if (Parent->isInterface() && cast<CXXMethodDecl>(NewFD)->isUserProvided())
          NewFD->setPure(true);
  
        // C++ [class.union]p2
        //   A union can have member functions, but not virtual functions.
        if (isVirtual && Parent->isUnion())
          Diag(D.getDeclSpec().getVirtualSpecLoc(), diag::err_virtual_in_union);
      }
  
      SetNestedNameSpecifier(*this, NewFD, D);
      isMemberSpecialization = false;
      isFunctionTemplateSpecialization = false;
      if (D.isInvalidType())
        NewFD->setInvalidDecl();
  
      // Match up the template parameter lists with the scope specifier, then
      // determine whether we have a template or a template specialization.
      bool Invalid = false;
      if (TemplateParameterList *TemplateParams =
              MatchTemplateParametersToScopeSpecifier(
                  D.getDeclSpec().getBeginLoc(), D.getIdentifierLoc(),
                  D.getCXXScopeSpec(),
                  D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId
                      ? D.getName().TemplateId
                      : nullptr,
                  TemplateParamLists, isFriend, isMemberSpecialization,
                  Invalid)) {
        if (TemplateParams->size() > 0) {
          // This is a function template
  
          // Check that we can declare a template here.
          if (CheckTemplateDeclScope(S, TemplateParams))
            NewFD->setInvalidDecl();
  
          // A destructor cannot be a template.
          if (Name.getNameKind() == DeclarationName::CXXDestructorName) {
            Diag(NewFD->getLocation(), diag::err_destructor_template);
            NewFD->setInvalidDecl();
          }
  
          // If we're adding a template to a dependent context, we may need to
          // rebuilding some of the types used within the template parameter list,
          // now that we know what the current instantiation is.
          if (DC->isDependentContext()) {
            ContextRAII SavedContext(*this, DC);
            if (RebuildTemplateParamsInCurrentInstantiation(TemplateParams))
              Invalid = true;
          }
  
          FunctionTemplate = FunctionTemplateDecl::Create(Context, DC,
                                                          NewFD->getLocation(),
                                                          Name, TemplateParams,
                                                          NewFD);
          FunctionTemplate->setLexicalDeclContext(CurContext);
          NewFD->setDescribedFunctionTemplate(FunctionTemplate);
  
          // For source fidelity, store the other template param lists.
          if (TemplateParamLists.size() > 1) {
            NewFD->setTemplateParameterListsInfo(Context,
                                                 TemplateParamLists.drop_back(1));
          }
        } else {
          // This is a function template specialization.
          isFunctionTemplateSpecialization = true;
          // For source fidelity, store all the template param lists.
          if (TemplateParamLists.size() > 0)
            NewFD->setTemplateParameterListsInfo(Context, TemplateParamLists);
  
          // C++0x [temp.expl.spec]p20 forbids "template<> friend void foo(int);".
          if (isFriend) {
            // We want to remove the "template<>", found here.
            SourceRange RemoveRange = TemplateParams->getSourceRange();
  
            // If we remove the template<> and the name is not a
            // template-id, we're actually silently creating a problem:
            // the friend declaration will refer to an untemplated decl,
            // and clearly the user wants a template specialization.  So
            // we need to insert '<>' after the name.
            SourceLocation InsertLoc;
            if (D.getName().getKind() != UnqualifiedIdKind::IK_TemplateId) {
              InsertLoc = D.getName().getSourceRange().getEnd();
              InsertLoc = getLocForEndOfToken(InsertLoc);
            }
  
            Diag(D.getIdentifierLoc(), diag::err_template_spec_decl_friend)
              << Name << RemoveRange
              << FixItHint::CreateRemoval(RemoveRange)
              << FixItHint::CreateInsertion(InsertLoc, "<>");
          }
        }
      } else {
        // All template param lists were matched against the scope specifier:
        // this is NOT (an explicit specialization of) a template.
        if (TemplateParamLists.size() > 0)
          // For source fidelity, store all the template param lists.
          NewFD->setTemplateParameterListsInfo(Context, TemplateParamLists);
      }
  
      if (Invalid) {
        NewFD->setInvalidDecl();
        if (FunctionTemplate)
          FunctionTemplate->setInvalidDecl();
      }
  
      // C++ [dcl.fct.spec]p5:
      //   The virtual specifier shall only be used in declarations of
      //   nonstatic class member functions that appear within a
      //   member-specification of a class declaration; see 10.3.
      //
      if (isVirtual && !NewFD->isInvalidDecl()) {
        if (!isVirtualOkay) {
          Diag(D.getDeclSpec().getVirtualSpecLoc(),
               diag::err_virtual_non_function);
        } else if (!CurContext->isRecord()) {
          // 'virtual' was specified outside of the class.
          Diag(D.getDeclSpec().getVirtualSpecLoc(),
               diag::err_virtual_out_of_class)
            << FixItHint::CreateRemoval(D.getDeclSpec().getVirtualSpecLoc());
        } else if (NewFD->getDescribedFunctionTemplate()) {
          // C++ [temp.mem]p3:
          //  A member function template shall not be virtual.
          Diag(D.getDeclSpec().getVirtualSpecLoc(),
               diag::err_virtual_member_function_template)
            << FixItHint::CreateRemoval(D.getDeclSpec().getVirtualSpecLoc());
        } else {
          // Okay: Add virtual to the method.
          NewFD->setVirtualAsWritten(true);
        }
  
        if (getLangOpts().CPlusPlus14 &&
            NewFD->getReturnType()->isUndeducedType())
          Diag(D.getDeclSpec().getVirtualSpecLoc(), diag::err_auto_fn_virtual);
      }
  
      if (getLangOpts().CPlusPlus14 &&
          (NewFD->isDependentContext() ||
           (isFriend && CurContext->isDependentContext())) &&
          NewFD->getReturnType()->isUndeducedType()) {
        // If the function template is referenced directly (for instance, as a
        // member of the current instantiation), pretend it has a dependent type.
        // This is not really justified by the standard, but is the only sane
        // thing to do.
        // FIXME: For a friend function, we have not marked the function as being
        // a friend yet, so 'isDependentContext' on the FD doesn't work.
        const FunctionProtoType *FPT =
            NewFD->getType()->castAs<FunctionProtoType>();
        QualType Result =
            SubstAutoType(FPT->getReturnType(), Context.DependentTy);
        NewFD->setType(Context.getFunctionType(Result, FPT->getParamTypes(),
                                               FPT->getExtProtoInfo()));
      }
  
      // C++ [dcl.fct.spec]p3:
      //  The inline specifier shall not appear on a block scope function
      //  declaration.
      if (isInline && !NewFD->isInvalidDecl()) {
        if (CurContext->isFunctionOrMethod()) {
          // 'inline' is not allowed on block scope function declaration.
          Diag(D.getDeclSpec().getInlineSpecLoc(),
               diag::err_inline_declaration_block_scope) << Name
            << FixItHint::CreateRemoval(D.getDeclSpec().getInlineSpecLoc());
        }
      }
  
      // C++ [dcl.fct.spec]p6:
      //  The explicit specifier shall be used only in the declaration of a
      //  constructor or conversion function within its class definition;
      //  see 12.3.1 and 12.3.2.
      if (isExplicit && !NewFD->isInvalidDecl() &&
          !isa<CXXDeductionGuideDecl>(NewFD)) {
        if (!CurContext->isRecord()) {
          // 'explicit' was specified outside of the class.
          Diag(D.getDeclSpec().getExplicitSpecLoc(),
               diag::err_explicit_out_of_class)
            << FixItHint::CreateRemoval(D.getDeclSpec().getExplicitSpecLoc());
        } else if (!isa<CXXConstructorDecl>(NewFD) &&
                   !isa<CXXConversionDecl>(NewFD)) {
          // 'explicit' was specified on a function that wasn't a constructor
          // or conversion function.
          Diag(D.getDeclSpec().getExplicitSpecLoc(),
               diag::err_explicit_non_ctor_or_conv_function)
            << FixItHint::CreateRemoval(D.getDeclSpec().getExplicitSpecLoc());
        }
      }
  
      if (isConstexpr) {
        // C++11 [dcl.constexpr]p2: constexpr functions and constexpr constructors
        // are implicitly inline.
        NewFD->setImplicitlyInline();
  
        // C++11 [dcl.constexpr]p3: functions declared constexpr are required to
        // be either constructors or to return a literal type. Therefore,
        // destructors cannot be declared constexpr.
        if (isa<CXXDestructorDecl>(NewFD))
          Diag(D.getDeclSpec().getConstexprSpecLoc(), diag::err_constexpr_dtor);
      }
  
      // If __module_private__ was specified, mark the function accordingly.
      if (D.getDeclSpec().isModulePrivateSpecified()) {
        if (isFunctionTemplateSpecialization) {
          SourceLocation ModulePrivateLoc
            = D.getDeclSpec().getModulePrivateSpecLoc();
          Diag(ModulePrivateLoc, diag::err_module_private_specialization)
            << 0
            << FixItHint::CreateRemoval(ModulePrivateLoc);
        } else {
          NewFD->setModulePrivate();
          if (FunctionTemplate)
            FunctionTemplate->setModulePrivate();
        }
      }
  
      if (isFriend) {
        if (FunctionTemplate) {
          FunctionTemplate->setObjectOfFriendDecl();
          FunctionTemplate->setAccess(AS_public);
        }
        NewFD->setObjectOfFriendDecl();
        NewFD->setAccess(AS_public);
      }
  
      // If a function is defined as defaulted or deleted, mark it as such now.
      // FIXME: Does this ever happen? ActOnStartOfFunctionDef forces the function
      // definition kind to FDK_Definition.
      switch (D.getFunctionDefinitionKind()) {
        case FDK_Declaration:
        case FDK_Definition:
          break;
  
        case FDK_Defaulted:
          NewFD->setDefaulted();
          break;
  
        case FDK_Deleted:
          NewFD->setDeletedAsWritten();
          break;
      }
  
      if (isa<CXXMethodDecl>(NewFD) && DC == CurContext &&
          D.isFunctionDefinition()) {
        // C++ [class.mfct]p2:
        //   A member function may be defined (8.4) in its class definition, in
        //   which case it is an inline member function (7.1.2)
        NewFD->setImplicitlyInline();
      }
  
      if (SC == SC_Static && isa<CXXMethodDecl>(NewFD) &&
          !CurContext->isRecord()) {
        // C++ [class.static]p1:
        //   A data or function member of a class may be declared static
        //   in a class definition, in which case it is a static member of
        //   the class.
  
        // Complain about the 'static' specifier if it's on an out-of-line
        // member function definition.
  
        // MSVC permits the use of a 'static' storage specifier on an out-of-line
        // member function template declaration, warn about this.
        Diag(D.getDeclSpec().getStorageClassSpecLoc(),
             NewFD->getDescribedFunctionTemplate() && getLangOpts().MSVCCompat
             ? diag::ext_static_out_of_line : diag::err_static_out_of_line)
          << FixItHint::CreateRemoval(D.getDeclSpec().getStorageClassSpecLoc());
      }
  
      // C++11 [except.spec]p15:
      //   A deallocation function with no exception-specification is treated
      //   as if it were specified with noexcept(true).
      const FunctionProtoType *FPT = R->getAs<FunctionProtoType>();
      if ((Name.getCXXOverloadedOperator() == OO_Delete ||
           Name.getCXXOverloadedOperator() == OO_Array_Delete) &&
          getLangOpts().CPlusPlus11 && FPT && !FPT->hasExceptionSpec())
        NewFD->setType(Context.getFunctionType(
            FPT->getReturnType(), FPT->getParamTypes(),
            FPT->getExtProtoInfo().withExceptionSpec(EST_BasicNoexcept)));
    }
  
    // Filter out previous declarations that don't match the scope.
    FilterLookupForScope(Previous, OriginalDC, S, shouldConsiderLinkage(NewFD),
                         D.getCXXScopeSpec().isNotEmpty() ||
                         isMemberSpecialization ||
                         isFunctionTemplateSpecialization);
  
    // Handle GNU asm-label extension (encoded as an attribute).
    if (Expr *E = (Expr*) D.getAsmLabel()) {
      // The parser guarantees this is a string.
      StringLiteral *SE = cast<StringLiteral>(E);
      NewFD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0), Context,
                                                  SE->getString(), 0));
    } else if (!ExtnameUndeclaredIdentifiers.empty()) {
      llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
        ExtnameUndeclaredIdentifiers.find(NewFD->getIdentifier());
      if (I != ExtnameUndeclaredIdentifiers.end()) {
        if (isDeclExternC(NewFD)) {
          NewFD->addAttr(I->second);
          ExtnameUndeclaredIdentifiers.erase(I);
        } else
          Diag(NewFD->getLocation(), diag::warn_redefine_extname_not_applied)
              << /*Variable*/0 << NewFD;
      }
    }
  
    // Copy the parameter declarations from the declarator D to the function
    // declaration NewFD, if they are available.  First scavenge them into Params.
    SmallVector<ParmVarDecl*, 16> Params;
    unsigned FTIIdx;
    if (D.isFunctionDeclarator(FTIIdx)) {
      DeclaratorChunk::FunctionTypeInfo &FTI = D.getTypeObject(FTIIdx).Fun;
  
      // Check for C99 6.7.5.3p10 - foo(void) is a non-varargs
      // function that takes no arguments, not a function that takes a
      // single void argument.
      // We let through "const void" here because Sema::GetTypeForDeclarator
      // already checks for that case.
      if (FTIHasNonVoidParameters(FTI) && FTI.Params[0].Param) {
        for (unsigned i = 0, e = FTI.NumParams; i != e; ++i) {
          ParmVarDecl *Param = cast<ParmVarDecl>(FTI.Params[i].Param);
          assert(Param->getDeclContext() != NewFD && "Was set before ?");
          Param->setDeclContext(NewFD);
          Params.push_back(Param);
  
          if (Param->isInvalidDecl())
            NewFD->setInvalidDecl();
        }
      }
  
      if (!getLangOpts().CPlusPlus) {
        // In C, find all the tag declarations from the prototype and move them
        // into the function DeclContext. Remove them from the surrounding tag
        // injection context of the function, which is typically but not always
        // the TU.
        DeclContext *PrototypeTagContext =
            getTagInjectionContext(NewFD->getLexicalDeclContext());
        for (NamedDecl *NonParmDecl : FTI.getDeclsInPrototype()) {
          auto *TD = dyn_cast<TagDecl>(NonParmDecl);
  
          // We don't want to reparent enumerators. Look at their parent enum
          // instead.
          if (!TD) {
            if (auto *ECD = dyn_cast<EnumConstantDecl>(NonParmDecl))
              TD = cast<EnumDecl>(ECD->getDeclContext());
          }
          if (!TD)
            continue;
          DeclContext *TagDC = TD->getLexicalDeclContext();
          if (!TagDC->containsDecl(TD))
            continue;
          TagDC->removeDecl(TD);
          TD->setDeclContext(NewFD);
          NewFD->addDecl(TD);
  
          // Preserve the lexical DeclContext if it is not the surrounding tag
          // injection context of the FD. In this example, the semantic context of
          // E will be f and the lexical context will be S, while both the
          // semantic and lexical contexts of S will be f:
          //   void f(struct S { enum E { a } f; } s);
          if (TagDC != PrototypeTagContext)
            TD->setLexicalDeclContext(TagDC);
        }
      }
    } else if (const FunctionProtoType *FT = R->getAs<FunctionProtoType>()) {
      // When we're declaring a function with a typedef, typeof, etc as in the
      // following example, we'll need to synthesize (unnamed)
      // parameters for use in the declaration.
      //
      // @code
      // typedef void fn(int);
      // fn f;
      // @endcode
  
      // Synthesize a parameter for each argument type.
      for (const auto &AI : FT->param_types()) {
        ParmVarDecl *Param =
            BuildParmVarDeclForTypedef(NewFD, D.getIdentifierLoc(), AI);
        Param->setScopeInfo(0, Params.size());
        Params.push_back(Param);
      }
    } else {
      assert(R->isFunctionNoProtoType() && NewFD->getNumParams() == 0 &&
             "Should not need args for typedef of non-prototype fn");
    }
  
    // Finally, we know we have the right number of parameters, install them.
    NewFD->setParams(Params);
  
    if (D.getDeclSpec().isNoreturnSpecified())
      NewFD->addAttr(
          ::new(Context) C11NoReturnAttr(D.getDeclSpec().getNoreturnSpecLoc(),
                                         Context, 0));
  
    // Functions returning a variably modified type violate C99 6.7.5.2p2
    // because all functions have linkage.
    if (!NewFD->isInvalidDecl() &&
        NewFD->getReturnType()->isVariablyModifiedType()) {
      Diag(NewFD->getLocation(), diag::err_vm_func_decl);
      NewFD->setInvalidDecl();
    }
  
    // Apply an implicit SectionAttr if '#pragma clang section text' is active
    if (PragmaClangTextSection.Valid && D.isFunctionDefinition() &&
        !NewFD->hasAttr<SectionAttr>()) {
      NewFD->addAttr(PragmaClangTextSectionAttr::CreateImplicit(Context,
                                                   PragmaClangTextSection.SectionName,
                                                   PragmaClangTextSection.PragmaLocation));
    }
  
    // Apply an implicit SectionAttr if #pragma code_seg is active.
    if (CodeSegStack.CurrentValue && D.isFunctionDefinition() &&
        !NewFD->hasAttr<SectionAttr>()) {
      NewFD->addAttr(
          SectionAttr::CreateImplicit(Context, SectionAttr::Declspec_allocate,
                                      CodeSegStack.CurrentValue->getString(),
                                      CodeSegStack.CurrentPragmaLocation));
      if (UnifySection(CodeSegStack.CurrentValue->getString(),
                       ASTContext::PSF_Implicit | ASTContext::PSF_Execute |
                           ASTContext::PSF_Read,
                       NewFD))
        NewFD->dropAttr<SectionAttr>();
    }
  
    // Apply an implicit CodeSegAttr from class declspec or
    // apply an implicit SectionAttr from #pragma code_seg if active.
    if (!NewFD->hasAttr<CodeSegAttr>()) {
      if (Attr *SAttr = getImplicitCodeSegOrSectionAttrForFunction(NewFD,
                                                                   D.isFunctionDefinition())) {
        NewFD->addAttr(SAttr);
      }
    }
  
    // Handle attributes.
    ProcessDeclAttributes(S, NewFD, D);
  
    if (getLangOpts().OpenCL) {
      // OpenCL v1.1 s6.5: Using an address space qualifier in a function return
      // type declaration will generate a compilation error.
      LangAS AddressSpace = NewFD->getReturnType().getAddressSpace();
      if (AddressSpace != LangAS::Default) {
        Diag(NewFD->getLocation(),
             diag::err_opencl_return_value_with_address_space);
        NewFD->setInvalidDecl();
      }
    }
  
    if (!getLangOpts().CPlusPlus) {
      // Perform semantic checking on the function declaration.
      if (!NewFD->isInvalidDecl() && NewFD->isMain())
        CheckMain(NewFD, D.getDeclSpec());
  
      if (!NewFD->isInvalidDecl() && NewFD->isMSVCRTEntryPoint())
        CheckMSVCRTEntryPoint(NewFD);
  
      if (!NewFD->isInvalidDecl())
        D.setRedeclaration(CheckFunctionDeclaration(S, NewFD, Previous,
                                                    isMemberSpecialization));
      else if (!Previous.empty())
        // Recover gracefully from an invalid redeclaration.
        D.setRedeclaration(true);
      assert((NewFD->isInvalidDecl() || !D.isRedeclaration() ||
              Previous.getResultKind() != LookupResult::FoundOverloaded) &&
             "previous declaration set still overloaded");
  
      // Diagnose no-prototype function declarations with calling conventions that
      // don't support variadic calls. Only do this in C and do it after merging
      // possibly prototyped redeclarations.
      const FunctionType *FT = NewFD->getType()->castAs<FunctionType>();
      if (isa<FunctionNoProtoType>(FT) && !D.isFunctionDefinition()) {
        CallingConv CC = FT->getExtInfo().getCC();
        if (!supportsVariadicCall(CC)) {
          // Windows system headers sometimes accidentally use stdcall without
          // (void) parameters, so we relax this to a warning.
          int DiagID =
              CC == CC_X86StdCall ? diag::warn_cconv_knr : diag::err_cconv_knr;
          Diag(NewFD->getLocation(), DiagID)
              << FunctionType::getNameForCallConv(CC);
        }
      }
    } else {
      // C++11 [replacement.functions]p3:
      //  The program's definitions shall not be specified as inline.
      //
      // N.B. We diagnose declarations instead of definitions per LWG issue 2340.
      //
      // Suppress the diagnostic if the function is __attribute__((used)), since
      // that forces an external definition to be emitted.
      if (D.getDeclSpec().isInlineSpecified() &&
          NewFD->isReplaceableGlobalAllocationFunction() &&
          !NewFD->hasAttr<UsedAttr>())
        Diag(D.getDeclSpec().getInlineSpecLoc(),
             diag::ext_operator_new_delete_declared_inline)
          << NewFD->getDeclName();
  
      // If the declarator is a template-id, translate the parser's template
      // argument list into our AST format.
      if (D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId) {
        TemplateIdAnnotation *TemplateId = D.getName().TemplateId;
        TemplateArgs.setLAngleLoc(TemplateId->LAngleLoc);
        TemplateArgs.setRAngleLoc(TemplateId->RAngleLoc);
        ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
                                           TemplateId->NumArgs);
        translateTemplateArguments(TemplateArgsPtr,
                                   TemplateArgs);
  
        HasExplicitTemplateArgs = true;
  
        if (NewFD->isInvalidDecl()) {
          HasExplicitTemplateArgs = false;
        } else if (FunctionTemplate) {
          // Function template with explicit template arguments.
          Diag(D.getIdentifierLoc(), diag::err_function_template_partial_spec)
            << SourceRange(TemplateId->LAngleLoc, TemplateId->RAngleLoc);
  
          HasExplicitTemplateArgs = false;
        } else {
          assert((isFunctionTemplateSpecialization ||
                  D.getDeclSpec().isFriendSpecified()) &&
                 "should have a 'template<>' for this decl");
          // "friend void foo<>(int);" is an implicit specialization decl.
          isFunctionTemplateSpecialization = true;
        }
      } else if (isFriend && isFunctionTemplateSpecialization) {
        // This combination is only possible in a recovery case;  the user
        // wrote something like:
        //   template <> friend void foo(int);
        // which we're recovering from as if the user had written:
        //   friend void foo<>(int);
        // Go ahead and fake up a template id.
        HasExplicitTemplateArgs = true;
        TemplateArgs.setLAngleLoc(D.getIdentifierLoc());
        TemplateArgs.setRAngleLoc(D.getIdentifierLoc());
      }
  
      // We do not add HD attributes to specializations here because
      // they may have different constexpr-ness compared to their
      // templates and, after maybeAddCUDAHostDeviceAttrs() is applied,
      // may end up with different effective targets. Instead, a
      // specialization inherits its target attributes from its template
      // in the CheckFunctionTemplateSpecialization() call below.
      if (getLangOpts().CUDA & !isFunctionTemplateSpecialization)
        maybeAddCUDAHostDeviceAttrs(NewFD, Previous);
  
      // If it's a friend (and only if it's a friend), it's possible
      // that either the specialized function type or the specialized
      // template is dependent, and therefore matching will fail.  In
      // this case, don't check the specialization yet.
      bool InstantiationDependent = false;
      if (isFunctionTemplateSpecialization && isFriend &&
          (NewFD->getType()->isDependentType() || DC->isDependentContext() ||
           TemplateSpecializationType::anyDependentTemplateArguments(
              TemplateArgs,
              InstantiationDependent))) {
        assert(HasExplicitTemplateArgs &&
               "friend function specialization without template args");
        if (CheckDependentFunctionTemplateSpecialization(NewFD, TemplateArgs,
                                                         Previous))
          NewFD->setInvalidDecl();
      } else if (isFunctionTemplateSpecialization) {
        if (CurContext->isDependentContext() && CurContext->isRecord()
            && !isFriend) {
          isDependentClassScopeExplicitSpecialization = true;
        } else if (!NewFD->isInvalidDecl() &&
                   CheckFunctionTemplateSpecialization(
                       NewFD, (HasExplicitTemplateArgs ? &TemplateArgs : nullptr),
                       Previous))
          NewFD->setInvalidDecl();
  
        // C++ [dcl.stc]p1:
        //   A storage-class-specifier shall not be specified in an explicit
        //   specialization (14.7.3)
        FunctionTemplateSpecializationInfo *Info =
            NewFD->getTemplateSpecializationInfo();
        if (Info && SC != SC_None) {
          if (SC != Info->getTemplate()->getTemplatedDecl()->getStorageClass())
            Diag(NewFD->getLocation(),
                 diag::err_explicit_specialization_inconsistent_storage_class)
              << SC
              << FixItHint::CreateRemoval(
                                        D.getDeclSpec().getStorageClassSpecLoc());
  
          else
            Diag(NewFD->getLocation(),
                 diag::ext_explicit_specialization_storage_class)
              << FixItHint::CreateRemoval(
                                        D.getDeclSpec().getStorageClassSpecLoc());
        }
      } else if (isMemberSpecialization && isa<CXXMethodDecl>(NewFD)) {
        if (CheckMemberSpecialization(NewFD, Previous))
            NewFD->setInvalidDecl();
      }
  
      // Perform semantic checking on the function declaration.
      if (!isDependentClassScopeExplicitSpecialization) {
        if (!NewFD->isInvalidDecl() && NewFD->isMain())
          CheckMain(NewFD, D.getDeclSpec());
  
        if (!NewFD->isInvalidDecl() && NewFD->isMSVCRTEntryPoint())
          CheckMSVCRTEntryPoint(NewFD);
  
        if (!NewFD->isInvalidDecl())
          D.setRedeclaration(CheckFunctionDeclaration(S, NewFD, Previous,
                                                      isMemberSpecialization));
        else if (!Previous.empty())
          // Recover gracefully from an invalid redeclaration.
          D.setRedeclaration(true);
      }
  
      assert((NewFD->isInvalidDecl() || !D.isRedeclaration() ||
              Previous.getResultKind() != LookupResult::FoundOverloaded) &&
             "previous declaration set still overloaded");
  
      NamedDecl *PrincipalDecl = (FunctionTemplate
                                  ? cast<NamedDecl>(FunctionTemplate)
                                  : NewFD);
  
      if (isFriend && NewFD->getPreviousDecl()) {
        AccessSpecifier Access = AS_public;
        if (!NewFD->isInvalidDecl())
          Access = NewFD->getPreviousDecl()->getAccess();
  
        NewFD->setAccess(Access);
        if (FunctionTemplate) FunctionTemplate->setAccess(Access);
      }
  
      if (NewFD->isOverloadedOperator() && !DC->isRecord() &&
          PrincipalDecl->isInIdentifierNamespace(Decl::IDNS_Ordinary))
        PrincipalDecl->setNonMemberOperator();
  
      // If we have a function template, check the template parameter
      // list. This will check and merge default template arguments.
      if (FunctionTemplate) {
        FunctionTemplateDecl *PrevTemplate =
                                       FunctionTemplate->getPreviousDecl();
        CheckTemplateParameterList(FunctionTemplate->getTemplateParameters(),
                         PrevTemplate ? PrevTemplate->getTemplateParameters()
                                      : nullptr,
                              D.getDeclSpec().isFriendSpecified()
                                ? (D.isFunctionDefinition()
                                     ? TPC_FriendFunctionTemplateDefinition
                                     : TPC_FriendFunctionTemplate)
                                : (D.getCXXScopeSpec().isSet() &&
                                   DC && DC->isRecord() &&
                                   DC->isDependentContext())
                                    ? TPC_ClassTemplateMember
                                    : TPC_FunctionTemplate);
      }
  
      if (NewFD->isInvalidDecl()) {
        // Ignore all the rest of this.
      } else if (!D.isRedeclaration()) {
        struct ActOnFDArgs ExtraArgs = { S, D, TemplateParamLists,
                                         AddToScope };
        // Fake up an access specifier if it's supposed to be a class member.
        if (isa<CXXRecordDecl>(NewFD->getDeclContext()))
          NewFD->setAccess(AS_public);
  
        // Qualified decls generally require a previous declaration.
        if (D.getCXXScopeSpec().isSet()) {
          // ...with the major exception of templated-scope or
          // dependent-scope friend declarations.
  
          // TODO: we currently also suppress this check in dependent
          // contexts because (1) the parameter depth will be off when
          // matching friend templates and (2) we might actually be
          // selecting a friend based on a dependent factor.  But there
          // are situations where these conditions don't apply and we
          // can actually do this check immediately.
          //
          // Unless the scope is dependent, it's always an error if qualified
          // redeclaration lookup found nothing at all. Diagnose that now;
          // nothing will diagnose that error later.
          if (isFriend &&
              (D.getCXXScopeSpec().getScopeRep()->isDependent() ||
               (!Previous.empty() && (TemplateParamLists.size() ||
                                      CurContext->isDependentContext())))) {
            // ignore these
          } else {
            // The user tried to provide an out-of-line definition for a
            // function that is a member of a class or namespace, but there
            // was no such member function declared (C++ [class.mfct]p2,
            // C++ [namespace.memdef]p2). For example:
            //
            // class X {
            //   void f() const;
            // };
            //
            // void X::f() { } // ill-formed
            //
            // Complain about this problem, and attempt to suggest close
            // matches (e.g., those that differ only in cv-qualifiers and
            // whether the parameter types are references).
  
            if (NamedDecl *Result = DiagnoseInvalidRedeclaration(
                    *this, Previous, NewFD, ExtraArgs, false, nullptr)) {
              AddToScope = ExtraArgs.AddToScope;
              return Result;
            }
          }
  
          // Unqualified local friend declarations are required to resolve
          // to something.
        } else if (isFriend && cast<CXXRecordDecl>(CurContext)->isLocalClass()) {
          if (NamedDecl *Result = DiagnoseInvalidRedeclaration(
                  *this, Previous, NewFD, ExtraArgs, true, S)) {
            AddToScope = ExtraArgs.AddToScope;
            return Result;
          }
        }
      } else if (!D.isFunctionDefinition() &&
                 isa<CXXMethodDecl>(NewFD) && NewFD->isOutOfLine() &&
                 !isFriend && !isFunctionTemplateSpecialization &&
                 !isMemberSpecialization) {
        // An out-of-line member function declaration must also be a
        // definition (C++ [class.mfct]p2).
        // Note that this is not the case for explicit specializations of
        // function templates or member functions of class templates, per
        // C++ [temp.expl.spec]p2. We also allow these declarations as an
        // extension for compatibility with old SWIG code which likes to
        // generate them.
        Diag(NewFD->getLocation(), diag::ext_out_of_line_declaration)
          << D.getCXXScopeSpec().getRange();
      }
    }
  
    ProcessPragmaWeak(S, NewFD);
    checkAttributesAfterMerging(*this, *NewFD);
  
    AddKnownFunctionAttributes(NewFD);
  
    if (NewFD->hasAttr<OverloadableAttr>() &&
        !NewFD->getType()->getAs<FunctionProtoType>()) {
      Diag(NewFD->getLocation(),
           diag::err_attribute_overloadable_no_prototype)
        << NewFD;
  
      // Turn this into a variadic function with no parameters.
      const FunctionType *FT = NewFD->getType()->getAs<FunctionType>();
      FunctionProtoType::ExtProtoInfo EPI(
          Context.getDefaultCallingConvention(true, false));
      EPI.Variadic = true;
      EPI.ExtInfo = FT->getExtInfo();
  
      QualType R = Context.getFunctionType(FT->getReturnType(), None, EPI);
      NewFD->setType(R);
    }
  
    // If there's a #pragma GCC visibility in scope, and this isn't a class
    // member, set the visibility of this function.
    if (!DC->isRecord() && NewFD->isExternallyVisible())
      AddPushedVisibilityAttribute(NewFD);
  
    // If there's a #pragma clang arc_cf_code_audited in scope, consider
    // marking the function.
    AddCFAuditedAttribute(NewFD);
  
    // If this is a function definition, check if we have to apply optnone due to
    // a pragma.
    if(D.isFunctionDefinition())
      AddRangeBasedOptnone(NewFD);
  
    // If this is the first declaration of an extern C variable, update
    // the map of such variables.
    if (NewFD->isFirstDecl() && !NewFD->isInvalidDecl() &&
        isIncompleteDeclExternC(*this, NewFD))
      RegisterLocallyScopedExternCDecl(NewFD, S);
  
    // Set this FunctionDecl's range up to the right paren.
    NewFD->setRangeEnd(D.getSourceRange().getEnd());
  
    if (D.isRedeclaration() && !Previous.empty()) {
      NamedDecl *Prev = Previous.getRepresentativeDecl();
      checkDLLAttributeRedeclaration(*this, Prev, NewFD,
                                     isMemberSpecialization ||
                                         isFunctionTemplateSpecialization,
                                     D.isFunctionDefinition());
    }
  
    if (getLangOpts().CUDA) {
      IdentifierInfo *II = NewFD->getIdentifier();
      if (II && II->isStr(getCudaConfigureFuncName()) &&
          !NewFD->isInvalidDecl() &&
          NewFD->getDeclContext()->getRedeclContext()->isTranslationUnit()) {
        if (!R->getAs<FunctionType>()->getReturnType()->isScalarType())
          Diag(NewFD->getLocation(), diag::err_config_scalar_return)
              << getCudaConfigureFuncName();
        Context.setcudaConfigureCallDecl(NewFD);
      }
  
      // Variadic functions, other than a *declaration* of printf, are not allowed
      // in device-side CUDA code, unless someone passed
      // -fcuda-allow-variadic-functions.
      if (!getLangOpts().CUDAAllowVariadicFunctions && NewFD->isVariadic() &&
          (NewFD->hasAttr<CUDADeviceAttr>() ||
           NewFD->hasAttr<CUDAGlobalAttr>()) &&
          !(II && II->isStr("printf") && NewFD->isExternC() &&
            !D.isFunctionDefinition())) {
        Diag(NewFD->getLocation(), diag::err_variadic_device_fn);
      }
    }
  
    MarkUnusedFileScopedDecl(NewFD);
  
    if (getLangOpts().CPlusPlus) {
      if (FunctionTemplate) {
        if (NewFD->isInvalidDecl())
          FunctionTemplate->setInvalidDecl();
        return FunctionTemplate;
      }
  
      if (isMemberSpecialization && !NewFD->isInvalidDecl())
        CompleteMemberSpecialization(NewFD, Previous);
    }
  
    if (NewFD->hasAttr<OpenCLKernelAttr>()) {
      // OpenCL v1.2 s6.8 static is invalid for kernel functions.
      if ((getLangOpts().OpenCLVersion >= 120)
          && (SC == SC_Static)) {
        Diag(D.getIdentifierLoc(), diag::err_static_kernel);
        D.setInvalidType();
      }
  
      // OpenCL v1.2, s6.9 -- Kernels can only have return type void.
      if (!NewFD->getReturnType()->isVoidType()) {
        SourceRange RTRange = NewFD->getReturnTypeSourceRange();
        Diag(D.getIdentifierLoc(), diag::err_expected_kernel_void_return_type)
            << (RTRange.isValid() ? FixItHint::CreateReplacement(RTRange, "void")
                                  : FixItHint());
        D.setInvalidType();
      }
  
      llvm::SmallPtrSet<const Type *, 16> ValidTypes;
      for (auto Param : NewFD->parameters())
        checkIsValidOpenCLKernelParameter(*this, D, Param, ValidTypes);
    }
    for (const ParmVarDecl *Param : NewFD->parameters()) {
      QualType PT = Param->getType();
  
      // OpenCL 2.0 pipe restrictions forbids pipe packet types to be non-value
      // types.
      if (getLangOpts().OpenCLVersion >= 200) {
        if(const PipeType *PipeTy = PT->getAs<PipeType>()) {
          QualType ElemTy = PipeTy->getElementType();
            if (ElemTy->isReferenceType() || ElemTy->isPointerType()) {
              Diag(Param->getTypeSpecStartLoc(), diag::err_reference_pipe_type );
              D.setInvalidType();
            }
        }
      }
    }
  
    // Here we have an function template explicit specialization at class scope.
    // The actual specialization will be postponed to template instatiation
    // time via the ClassScopeFunctionSpecializationDecl node.
    if (isDependentClassScopeExplicitSpecialization) {
      ClassScopeFunctionSpecializationDecl *NewSpec =
                           ClassScopeFunctionSpecializationDecl::Create(
                                  Context, CurContext, NewFD->getLocation(),
                                  cast<CXXMethodDecl>(NewFD),
                                  HasExplicitTemplateArgs, TemplateArgs);
      CurContext->addDecl(NewSpec);
      AddToScope = false;
    }
  
    // Diagnose availability attributes. Availability cannot be used on functions
    // that are run during load/unload.
    if (const auto *attr = NewFD->getAttr<AvailabilityAttr>()) {
      if (NewFD->hasAttr<ConstructorAttr>()) {
        Diag(attr->getLocation(), diag::warn_availability_on_static_initializer)
            << 1;
        NewFD->dropAttr<AvailabilityAttr>();
      }
      if (NewFD->hasAttr<DestructorAttr>()) {
        Diag(attr->getLocation(), diag::warn_availability_on_static_initializer)
            << 2;
        NewFD->dropAttr<AvailabilityAttr>();
      }
    }
  
    return NewFD;
  }
  
  /// Return a CodeSegAttr from a containing class.  The Microsoft docs say
  /// when __declspec(code_seg) "is applied to a class, all member functions of
  /// the class and nested classes -- this includes compiler-generated special
  /// member functions -- are put in the specified segment."
  /// The actual behavior is a little more complicated. The Microsoft compiler
  /// won't check outer classes if there is an active value from #pragma code_seg.
  /// The CodeSeg is always applied from the direct parent but only from outer
  /// classes when the #pragma code_seg stack is empty. See:
  /// https://reviews.llvm.org/D22931, the Microsoft feedback page is no longer
  /// available since MS has removed the page.
  static Attr *getImplicitCodeSegAttrFromClass(Sema &S, const FunctionDecl *FD) {
    const auto *Method = dyn_cast<CXXMethodDecl>(FD);
    if (!Method)
      return nullptr;
    const CXXRecordDecl *Parent = Method->getParent();
    if (const auto *SAttr = Parent->getAttr<CodeSegAttr>()) {
      Attr *NewAttr = SAttr->clone(S.getASTContext());
      NewAttr->setImplicit(true);
      return NewAttr;
    }
  
    // The Microsoft compiler won't check outer classes for the CodeSeg
    // when the #pragma code_seg stack is active.
    if (S.CodeSegStack.CurrentValue)
     return nullptr;
  
    while ((Parent = dyn_cast<CXXRecordDecl>(Parent->getParent()))) {
      if (const auto *SAttr = Parent->getAttr<CodeSegAttr>()) {
        Attr *NewAttr = SAttr->clone(S.getASTContext());
        NewAttr->setImplicit(true);
        return NewAttr;
      }
    }
    return nullptr;
  }
  
  /// Returns an implicit CodeSegAttr if a __declspec(code_seg) is found on a
  /// containing class. Otherwise it will return implicit SectionAttr if the
  /// function is a definition and there is an active value on CodeSegStack
  /// (from the current #pragma code-seg value).
  ///
  /// \param FD Function being declared.
  /// \param IsDefinition Whether it is a definition or just a declarartion.
  /// \returns A CodeSegAttr or SectionAttr to apply to the function or
  ///          nullptr if no attribute should be added.
  Attr *Sema::getImplicitCodeSegOrSectionAttrForFunction(const FunctionDecl *FD,
                                                         bool IsDefinition) {
    if (Attr *A = getImplicitCodeSegAttrFromClass(*this, FD))
      return A;
    if (!FD->hasAttr<SectionAttr>() && IsDefinition &&
        CodeSegStack.CurrentValue) {
      return SectionAttr::CreateImplicit(getASTContext(),
                                         SectionAttr::Declspec_allocate,
                                         CodeSegStack.CurrentValue->getString(),
                                         CodeSegStack.CurrentPragmaLocation);
    }
    return nullptr;
  }
  
  /// Determines if we can perform a correct type check for \p D as a
  /// redeclaration of \p PrevDecl. If not, we can generally still perform a
  /// best-effort check.
  ///
  /// \param NewD The new declaration.
  /// \param OldD The old declaration.
  /// \param NewT The portion of the type of the new declaration to check.
  /// \param OldT The portion of the type of the old declaration to check.
  bool Sema::canFullyTypeCheckRedeclaration(ValueDecl *NewD, ValueDecl *OldD,
                                            QualType NewT, QualType OldT) {
    if (!NewD->getLexicalDeclContext()->isDependentContext())
      return true;
  
    // For dependently-typed local extern declarations and friends, we can't
    // perform a correct type check in general until instantiation:
    //
    //   int f();
    //   template<typename T> void g() { T f(); }
    //
    // (valid if g() is only instantiated with T = int).
    if (NewT->isDependentType() &&
        (NewD->isLocalExternDecl() || NewD->getFriendObjectKind()))
      return false;
  
    // Similarly, if the previous declaration was a dependent local extern
    // declaration, we don't really know its type yet.
    if (OldT->isDependentType() && OldD->isLocalExternDecl())
      return false;
  
    return true;
  }
  
  /// Checks if the new declaration declared in dependent context must be
  /// put in the same redeclaration chain as the specified declaration.
  ///
  /// \param D Declaration that is checked.
  /// \param PrevDecl Previous declaration found with proper lookup method for the
  ///                 same declaration name.
  /// \returns True if D must be added to the redeclaration chain which PrevDecl
  ///          belongs to.
  ///
  bool Sema::shouldLinkDependentDeclWithPrevious(Decl *D, Decl *PrevDecl) {
    if (!D->getLexicalDeclContext()->isDependentContext())
      return true;
  
    // Don't chain dependent friend function definitions until instantiation, to
    // permit cases like
    //
    //   void func();
    //   template<typename T> class C1 { friend void func() {} };
    //   template<typename T> class C2 { friend void func() {} };
    //
    // ... which is valid if only one of C1 and C2 is ever instantiated.
    //
    // FIXME: This need only apply to function definitions. For now, we proxy
    // this by checking for a file-scope function. We do not want this to apply
    // to friend declarations nominating member functions, because that gets in
    // the way of access checks.
    if (D->getFriendObjectKind() && D->getDeclContext()->isFileContext())
      return false;
  
    auto *VD = dyn_cast<ValueDecl>(D);
    auto *PrevVD = dyn_cast<ValueDecl>(PrevDecl);
    return !VD || !PrevVD ||
           canFullyTypeCheckRedeclaration(VD, PrevVD, VD->getType(),
                                          PrevVD->getType());
  }
  
  /// Check the target attribute of the function for MultiVersion
  /// validity.
  ///
  /// Returns true if there was an error, false otherwise.
  static bool CheckMultiVersionValue(Sema &S, const FunctionDecl *FD) {
    const auto *TA = FD->getAttr<TargetAttr>();
    assert(TA && "MultiVersion Candidate requires a target attribute");
    TargetAttr::ParsedTargetAttr ParseInfo = TA->parse();
    const TargetInfo &TargetInfo = S.Context.getTargetInfo();
    enum ErrType { Feature = 0, Architecture = 1 };
  
    if (!ParseInfo.Architecture.empty() &&
        !TargetInfo.validateCpuIs(ParseInfo.Architecture)) {
      S.Diag(FD->getLocation(), diag::err_bad_multiversion_option)
          << Architecture << ParseInfo.Architecture;
      return true;
    }
  
    for (const auto &Feat : ParseInfo.Features) {
      auto BareFeat = StringRef{Feat}.substr(1);
      if (Feat[0] == '-') {
        S.Diag(FD->getLocation(), diag::err_bad_multiversion_option)
            << Feature << ("no-" + BareFeat).str();
        return true;
      }
  
      if (!TargetInfo.validateCpuSupports(BareFeat) ||
          !TargetInfo.isValidFeatureName(BareFeat)) {
        S.Diag(FD->getLocation(), diag::err_bad_multiversion_option)
            << Feature << BareFeat;
        return true;
      }
    }
    return false;
  }
  
  static bool HasNonMultiVersionAttributes(const FunctionDecl *FD,
                                           MultiVersionKind MVType) {
    for (const Attr *A : FD->attrs()) {
      switch (A->getKind()) {
      case attr::CPUDispatch:
      case attr::CPUSpecific:
        if (MVType != MultiVersionKind::CPUDispatch &&
            MVType != MultiVersionKind::CPUSpecific)
          return true;
        break;
      case attr::Target:
        if (MVType != MultiVersionKind::Target)
          return true;
        break;
      default:
        return true;
      }
    }
    return false;
  }
  
  static bool CheckMultiVersionAdditionalRules(Sema &S, const FunctionDecl *OldFD,
                                               const FunctionDecl *NewFD,
                                               bool CausesMV,
                                               MultiVersionKind MVType) {
    enum DoesntSupport {
      FuncTemplates = 0,
      VirtFuncs = 1,
      DeducedReturn = 2,
      Constructors = 3,
      Destructors = 4,
      DeletedFuncs = 5,
      DefaultedFuncs = 6,
      ConstexprFuncs = 7,
    };
    enum Different {
      CallingConv = 0,
      ReturnType = 1,
      ConstexprSpec = 2,
      InlineSpec = 3,
      StorageClass = 4,
      Linkage = 5
    };
  
    bool IsCPUSpecificCPUDispatchMVType =
        MVType == MultiVersionKind::CPUDispatch ||
        MVType == MultiVersionKind::CPUSpecific;
  
    if (OldFD && !OldFD->getType()->getAs<FunctionProtoType>()) {
      S.Diag(OldFD->getLocation(), diag::err_multiversion_noproto);
      S.Diag(NewFD->getLocation(), diag::note_multiversioning_caused_here);
      return true;
    }
  
    if (!NewFD->getType()->getAs<FunctionProtoType>())
      return S.Diag(NewFD->getLocation(), diag::err_multiversion_noproto);
  
    if (!S.getASTContext().getTargetInfo().supportsMultiVersioning()) {
      S.Diag(NewFD->getLocation(), diag::err_multiversion_not_supported);
      if (OldFD)
        S.Diag(OldFD->getLocation(), diag::note_previous_declaration);
      return true;
    }
  
    // For now, disallow all other attributes.  These should be opt-in, but
    // an analysis of all of them is a future FIXME.
    if (CausesMV && OldFD && HasNonMultiVersionAttributes(OldFD, MVType)) {
      S.Diag(OldFD->getLocation(), diag::err_multiversion_no_other_attrs)
          << IsCPUSpecificCPUDispatchMVType;
      S.Diag(NewFD->getLocation(), diag::note_multiversioning_caused_here);
      return true;
    }
  
    if (HasNonMultiVersionAttributes(NewFD, MVType))
      return S.Diag(NewFD->getLocation(), diag::err_multiversion_no_other_attrs)
             << IsCPUSpecificCPUDispatchMVType;
  
    if (NewFD->getTemplatedKind() == FunctionDecl::TK_FunctionTemplate)
      return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
             << IsCPUSpecificCPUDispatchMVType << FuncTemplates;
  
    if (const auto *NewCXXFD = dyn_cast<CXXMethodDecl>(NewFD)) {
      if (NewCXXFD->isVirtual())
        return S.Diag(NewCXXFD->getLocation(),
                      diag::err_multiversion_doesnt_support)
               << IsCPUSpecificCPUDispatchMVType << VirtFuncs;
  
      if (const auto *NewCXXCtor = dyn_cast<CXXConstructorDecl>(NewFD))
        return S.Diag(NewCXXCtor->getLocation(),
                      diag::err_multiversion_doesnt_support)
               << IsCPUSpecificCPUDispatchMVType << Constructors;
  
      if (const auto *NewCXXDtor = dyn_cast<CXXDestructorDecl>(NewFD))
        return S.Diag(NewCXXDtor->getLocation(),
                      diag::err_multiversion_doesnt_support)
               << IsCPUSpecificCPUDispatchMVType << Destructors;
    }
  
    if (NewFD->isDeleted())
      return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
             << IsCPUSpecificCPUDispatchMVType << DeletedFuncs;
  
    if (NewFD->isDefaulted())
      return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
             << IsCPUSpecificCPUDispatchMVType << DefaultedFuncs;
  
    if (NewFD->isConstexpr() && (MVType == MultiVersionKind::CPUDispatch ||
                                 MVType == MultiVersionKind::CPUSpecific))
      return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
             << IsCPUSpecificCPUDispatchMVType << ConstexprFuncs;
  
    QualType NewQType = S.getASTContext().getCanonicalType(NewFD->getType());
    const auto *NewType = cast<FunctionType>(NewQType);
    QualType NewReturnType = NewType->getReturnType();
  
    if (NewReturnType->isUndeducedType())
      return S.Diag(NewFD->getLocation(), diag::err_multiversion_doesnt_support)
             << IsCPUSpecificCPUDispatchMVType << DeducedReturn;
  
    // Only allow transition to MultiVersion if it hasn't been used.
    if (OldFD && CausesMV && OldFD->isUsed(false))
      return S.Diag(NewFD->getLocation(), diag::err_multiversion_after_used);
  
    // Ensure the return type is identical.
    if (OldFD) {
      QualType OldQType = S.getASTContext().getCanonicalType(OldFD->getType());
      const auto *OldType = cast<FunctionType>(OldQType);
      FunctionType::ExtInfo OldTypeInfo = OldType->getExtInfo();
      FunctionType::ExtInfo NewTypeInfo = NewType->getExtInfo();
  
      if (OldTypeInfo.getCC() != NewTypeInfo.getCC())
        return S.Diag(NewFD->getLocation(), diag::err_multiversion_diff)
               << CallingConv;
  
      QualType OldReturnType = OldType->getReturnType();
  
      if (OldReturnType != NewReturnType)
        return S.Diag(NewFD->getLocation(), diag::err_multiversion_diff)
               << ReturnType;
  
      if (OldFD->isConstexpr() != NewFD->isConstexpr())
        return S.Diag(NewFD->getLocation(), diag::err_multiversion_diff)
               << ConstexprSpec;
  
      if (OldFD->isInlineSpecified() != NewFD->isInlineSpecified())
        return S.Diag(NewFD->getLocation(), diag::err_multiversion_diff)
               << InlineSpec;
  
      if (OldFD->getStorageClass() != NewFD->getStorageClass())
        return S.Diag(NewFD->getLocation(), diag::err_multiversion_diff)
               << StorageClass;
  
      if (OldFD->isExternC() != NewFD->isExternC())
        return S.Diag(NewFD->getLocation(), diag::err_multiversion_diff)
               << Linkage;
  
      if (S.CheckEquivalentExceptionSpec(
              OldFD->getType()->getAs<FunctionProtoType>(), OldFD->getLocation(),
              NewFD->getType()->getAs<FunctionProtoType>(), NewFD->getLocation()))
        return true;
    }
    return false;
  }
  
  /// Check the validity of a multiversion function declaration that is the
  /// first of its kind. Also sets the multiversion'ness' of the function itself.
  ///
  /// This sets NewFD->isInvalidDecl() to true if there was an error.
  ///
  /// Returns true if there was an error, false otherwise.
  static bool CheckMultiVersionFirstFunction(Sema &S, FunctionDecl *FD,
                                             MultiVersionKind MVType,
                                             const TargetAttr *TA,
                                             const CPUDispatchAttr *CPUDisp,
                                             const CPUSpecificAttr *CPUSpec) {
    assert(MVType != MultiVersionKind::None &&
           "Function lacks multiversion attribute");
  
    // Target only causes MV if it is default, otherwise this is a normal
    // function.
    if (MVType == MultiVersionKind::Target && !TA->isDefaultVersion())
      return false;
  
    if (MVType == MultiVersionKind::Target && CheckMultiVersionValue(S, FD)) {
      FD->setInvalidDecl();
      return true;
    }
  
    if (CheckMultiVersionAdditionalRules(S, nullptr, FD, true, MVType)) {
      FD->setInvalidDecl();
      return true;
    }
  
    FD->setIsMultiVersion();
    return false;
  }
  
  static bool PreviousDeclsHaveMultiVersionAttribute(const FunctionDecl *FD) {
    for (const Decl *D = FD->getPreviousDecl(); D; D = D->getPreviousDecl()) {
      if (D->getAsFunction()->getMultiVersionKind() != MultiVersionKind::None)
        return true;
    }
  
    return false;
  }
  
  static bool CheckTargetCausesMultiVersioning(
      Sema &S, FunctionDecl *OldFD, FunctionDecl *NewFD, const TargetAttr *NewTA,
      bool &Redeclaration, NamedDecl *&OldDecl, bool &MergeTypeWithPrevious,
      LookupResult &Previous) {
    const auto *OldTA = OldFD->getAttr<TargetAttr>();
    TargetAttr::ParsedTargetAttr NewParsed = NewTA->parse();
    // Sort order doesn't matter, it just needs to be consistent.
    llvm::sort(NewParsed.Features);
  
    // If the old decl is NOT MultiVersioned yet, and we don't cause that
    // to change, this is a simple redeclaration.
    if (!NewTA->isDefaultVersion() &&
        (!OldTA || OldTA->getFeaturesStr() == NewTA->getFeaturesStr()))
      return false;
  
    // Otherwise, this decl causes MultiVersioning.
    if (!S.getASTContext().getTargetInfo().supportsMultiVersioning()) {
      S.Diag(NewFD->getLocation(), diag::err_multiversion_not_supported);
      S.Diag(OldFD->getLocation(), diag::note_previous_declaration);
      NewFD->setInvalidDecl();
      return true;
    }
  
    if (CheckMultiVersionAdditionalRules(S, OldFD, NewFD, true,
                                         MultiVersionKind::Target)) {
      NewFD->setInvalidDecl();
      return true;
    }
  
    if (CheckMultiVersionValue(S, NewFD)) {
      NewFD->setInvalidDecl();
      return true;
    }
  
    // If this is 'default', permit the forward declaration.
    if (!OldFD->isMultiVersion() && !OldTA && NewTA->isDefaultVersion()) {
      Redeclaration = true;
      OldDecl = OldFD;
      OldFD->setIsMultiVersion();
      NewFD->setIsMultiVersion();
      return false;
    }
  
    if (CheckMultiVersionValue(S, OldFD)) {
      S.Diag(NewFD->getLocation(), diag::note_multiversioning_caused_here);
      NewFD->setInvalidDecl();
      return true;
    }
  
    TargetAttr::ParsedTargetAttr OldParsed =
        OldTA->parse(std::less<std::string>());
  
    if (OldParsed == NewParsed) {
      S.Diag(NewFD->getLocation(), diag::err_multiversion_duplicate);
      S.Diag(OldFD->getLocation(), diag::note_previous_declaration);
      NewFD->setInvalidDecl();
      return true;
    }
  
    for (const auto *FD : OldFD->redecls()) {
      const auto *CurTA = FD->getAttr<TargetAttr>();
      // We allow forward declarations before ANY multiversioning attributes, but
      // nothing after the fact.
      if (PreviousDeclsHaveMultiVersionAttribute(FD) &&
          (!CurTA || CurTA->isInherited())) {
        S.Diag(FD->getLocation(), diag::err_multiversion_required_in_redecl)
            << 0;
        S.Diag(NewFD->getLocation(), diag::note_multiversioning_caused_here);
        NewFD->setInvalidDecl();
        return true;
      }
    }
  
    OldFD->setIsMultiVersion();
    NewFD->setIsMultiVersion();
    Redeclaration = false;
    MergeTypeWithPrevious = false;
    OldDecl = nullptr;
    Previous.clear();
    return false;
  }
  
  /// Check the validity of a new function declaration being added to an existing
  /// multiversioned declaration collection.
  static bool CheckMultiVersionAdditionalDecl(
      Sema &S, FunctionDecl *OldFD, FunctionDecl *NewFD,
      MultiVersionKind NewMVType, const TargetAttr *NewTA,
      const CPUDispatchAttr *NewCPUDisp, const CPUSpecificAttr *NewCPUSpec,
      bool &Redeclaration, NamedDecl *&OldDecl, bool &MergeTypeWithPrevious,
      LookupResult &Previous) {
  
    MultiVersionKind OldMVType = OldFD->getMultiVersionKind();
    // Disallow mixing of multiversioning types.
    if ((OldMVType == MultiVersionKind::Target &&
         NewMVType != MultiVersionKind::Target) ||
        (NewMVType == MultiVersionKind::Target &&
         OldMVType != MultiVersionKind::Target)) {
      S.Diag(NewFD->getLocation(), diag::err_multiversion_types_mixed);
      S.Diag(OldFD->getLocation(), diag::note_previous_declaration);
      NewFD->setInvalidDecl();
      return true;
    }
  
    TargetAttr::ParsedTargetAttr NewParsed;
    if (NewTA) {
      NewParsed = NewTA->parse();
      llvm::sort(NewParsed.Features);
    }
  
    bool UseMemberUsingDeclRules =
        S.CurContext->isRecord() && !NewFD->getFriendObjectKind();
  
    // Next, check ALL non-overloads to see if this is a redeclaration of a
    // previous member of the MultiVersion set.
    for (NamedDecl *ND : Previous) {
      FunctionDecl *CurFD = ND->getAsFunction();
      if (!CurFD)
        continue;
      if (S.IsOverload(NewFD, CurFD, UseMemberUsingDeclRules))
        continue;
  
      if (NewMVType == MultiVersionKind::Target) {
        const auto *CurTA = CurFD->getAttr<TargetAttr>();
        if (CurTA->getFeaturesStr() == NewTA->getFeaturesStr()) {
          NewFD->setIsMultiVersion();
          Redeclaration = true;
          OldDecl = ND;
          return false;
        }
  
        TargetAttr::ParsedTargetAttr CurParsed =
            CurTA->parse(std::less<std::string>());
        if (CurParsed == NewParsed) {
          S.Diag(NewFD->getLocation(), diag::err_multiversion_duplicate);
          S.Diag(CurFD->getLocation(), diag::note_previous_declaration);
          NewFD->setInvalidDecl();
          return true;
        }
      } else {
        const auto *CurCPUSpec = CurFD->getAttr<CPUSpecificAttr>();
        const auto *CurCPUDisp = CurFD->getAttr<CPUDispatchAttr>();
        // Handle CPUDispatch/CPUSpecific versions.
        // Only 1 CPUDispatch function is allowed, this will make it go through
        // the redeclaration errors.
        if (NewMVType == MultiVersionKind::CPUDispatch &&
            CurFD->hasAttr<CPUDispatchAttr>()) {
          if (CurCPUDisp->cpus_size() == NewCPUDisp->cpus_size() &&
              std::equal(
                  CurCPUDisp->cpus_begin(), CurCPUDisp->cpus_end(),
                  NewCPUDisp->cpus_begin(),
                  [](const IdentifierInfo *Cur, const IdentifierInfo *New) {
                    return Cur->getName() == New->getName();
                  })) {
            NewFD->setIsMultiVersion();
            Redeclaration = true;
            OldDecl = ND;
            return false;
          }
  
          // If the declarations don't match, this is an error condition.
          S.Diag(NewFD->getLocation(), diag::err_cpu_dispatch_mismatch);
          S.Diag(CurFD->getLocation(), diag::note_previous_declaration);
          NewFD->setInvalidDecl();
          return true;
        }
        if (NewMVType == MultiVersionKind::CPUSpecific && CurCPUSpec) {
  
          if (CurCPUSpec->cpus_size() == NewCPUSpec->cpus_size() &&
              std::equal(
                  CurCPUSpec->cpus_begin(), CurCPUSpec->cpus_end(),
                  NewCPUSpec->cpus_begin(),
                  [](const IdentifierInfo *Cur, const IdentifierInfo *New) {
                    return Cur->getName() == New->getName();
                  })) {
            NewFD->setIsMultiVersion();
            Redeclaration = true;
            OldDecl = ND;
            return false;
          }
  
          // Only 1 version of CPUSpecific is allowed for each CPU.
          for (const IdentifierInfo *CurII : CurCPUSpec->cpus()) {
            for (const IdentifierInfo *NewII : NewCPUSpec->cpus()) {
              if (CurII == NewII) {
                S.Diag(NewFD->getLocation(), diag::err_cpu_specific_multiple_defs)
                    << NewII;
                S.Diag(CurFD->getLocation(), diag::note_previous_declaration);
                NewFD->setInvalidDecl();
                return true;
              }
            }
          }
        }
        // If the two decls aren't the same MVType, there is no possible error
        // condition.
      }
    }
  
    // Else, this is simply a non-redecl case.  Checking the 'value' is only
    // necessary in the Target case, since The CPUSpecific/Dispatch cases are
    // handled in the attribute adding step.
    if (NewMVType == MultiVersionKind::Target &&
        CheckMultiVersionValue(S, NewFD)) {
      NewFD->setInvalidDecl();
      return true;
    }
  
    if (CheckMultiVersionAdditionalRules(S, OldFD, NewFD,
                                         !OldFD->isMultiVersion(), NewMVType)) {
      NewFD->setInvalidDecl();
      return true;
    }
  
    // Permit forward declarations in the case where these two are compatible.
    if (!OldFD->isMultiVersion()) {
      OldFD->setIsMultiVersion();
      NewFD->setIsMultiVersion();
      Redeclaration = true;
      OldDecl = OldFD;
      return false;
    }
  
    NewFD->setIsMultiVersion();
    Redeclaration = false;
    MergeTypeWithPrevious = false;
    OldDecl = nullptr;
    Previous.clear();
    return false;
  }
  
  
  /// Check the validity of a mulitversion function declaration.
  /// Also sets the multiversion'ness' of the function itself.
  ///
  /// This sets NewFD->isInvalidDecl() to true if there was an error.
  ///
  /// Returns true if there was an error, false otherwise.
  static bool CheckMultiVersionFunction(Sema &S, FunctionDecl *NewFD,
                                        bool &Redeclaration, NamedDecl *&OldDecl,
                                        bool &MergeTypeWithPrevious,
                                        LookupResult &Previous) {
    const auto *NewTA = NewFD->getAttr<TargetAttr>();
    const auto *NewCPUDisp = NewFD->getAttr<CPUDispatchAttr>();
    const auto *NewCPUSpec = NewFD->getAttr<CPUSpecificAttr>();
  
    // Mixing Multiversioning types is prohibited.
    if ((NewTA && NewCPUDisp) || (NewTA && NewCPUSpec) ||
        (NewCPUDisp && NewCPUSpec)) {
      S.Diag(NewFD->getLocation(), diag::err_multiversion_types_mixed);
      NewFD->setInvalidDecl();
      return true;
    }
  
    MultiVersionKind  MVType = NewFD->getMultiVersionKind();
  
    // Main isn't allowed to become a multiversion function, however it IS
    // permitted to have 'main' be marked with the 'target' optimization hint.
    if (NewFD->isMain()) {
      if ((MVType == MultiVersionKind::Target && NewTA->isDefaultVersion()) ||
          MVType == MultiVersionKind::CPUDispatch ||
          MVType == MultiVersionKind::CPUSpecific) {
        S.Diag(NewFD->getLocation(), diag::err_multiversion_not_allowed_on_main);
        NewFD->setInvalidDecl();
        return true;
      }
      return false;
    }
  
    if (!OldDecl || !OldDecl->getAsFunction() ||
        OldDecl->getDeclContext()->getRedeclContext() !=
            NewFD->getDeclContext()->getRedeclContext()) {
      // If there's no previous declaration, AND this isn't attempting to cause
      // multiversioning, this isn't an error condition.
      if (MVType == MultiVersionKind::None)
        return false;
      return CheckMultiVersionFirstFunction(S, NewFD, MVType, NewTA, NewCPUDisp,
                                            NewCPUSpec);
    }
  
    FunctionDecl *OldFD = OldDecl->getAsFunction();
  
    if (!OldFD->isMultiVersion() && MVType == MultiVersionKind::None)
      return false;
  
    if (OldFD->isMultiVersion() && MVType == MultiVersionKind::None) {
      S.Diag(NewFD->getLocation(), diag::err_multiversion_required_in_redecl)
          << (OldFD->getMultiVersionKind() != MultiVersionKind::Target);
      NewFD->setInvalidDecl();
      return true;
    }
  
    // Handle the target potentially causes multiversioning case.
    if (!OldFD->isMultiVersion() && MVType == MultiVersionKind::Target)
      return CheckTargetCausesMultiVersioning(S, OldFD, NewFD, NewTA,
                                              Redeclaration, OldDecl,
                                              MergeTypeWithPrevious, Previous);
  
    // At this point, we have a multiversion function decl (in OldFD) AND an
    // appropriate attribute in the current function decl.  Resolve that these are
    // still compatible with previous declarations.
    return CheckMultiVersionAdditionalDecl(
        S, OldFD, NewFD, MVType, NewTA, NewCPUDisp, NewCPUSpec, Redeclaration,
        OldDecl, MergeTypeWithPrevious, Previous);
  }
  
  /// Perform semantic checking of a new function declaration.
  ///
  /// Performs semantic analysis of the new function declaration
  /// NewFD. This routine performs all semantic checking that does not
  /// require the actual declarator involved in the declaration, and is
  /// used both for the declaration of functions as they are parsed
  /// (called via ActOnDeclarator) and for the declaration of functions
  /// that have been instantiated via C++ template instantiation (called
  /// via InstantiateDecl).
  ///
  /// \param IsMemberSpecialization whether this new function declaration is
  /// a member specialization (that replaces any definition provided by the
  /// previous declaration).
  ///
  /// This sets NewFD->isInvalidDecl() to true if there was an error.
  ///
  /// \returns true if the function declaration is a redeclaration.
  bool Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
                                      LookupResult &Previous,
                                      bool IsMemberSpecialization) {
    assert(!NewFD->getReturnType()->isVariablyModifiedType() &&
           "Variably modified return types are not handled here");
  
    // Determine whether the type of this function should be merged with
    // a previous visible declaration. This never happens for functions in C++,
    // and always happens in C if the previous declaration was visible.
    bool MergeTypeWithPrevious = !getLangOpts().CPlusPlus &&
                                 !Previous.isShadowed();
  
    bool Redeclaration = false;
    NamedDecl *OldDecl = nullptr;
    bool MayNeedOverloadableChecks = false;
  
    // Merge or overload the declaration with an existing declaration of
    // the same name, if appropriate.
    if (!Previous.empty()) {
      // Determine whether NewFD is an overload of PrevDecl or
      // a declaration that requires merging. If it's an overload,
      // there's no more work to do here; we'll just add the new
      // function to the scope.
      if (!AllowOverloadingOfFunction(Previous, Context, NewFD)) {
        NamedDecl *Candidate = Previous.getRepresentativeDecl();
        if (shouldLinkPossiblyHiddenDecl(Candidate, NewFD)) {
          Redeclaration = true;
          OldDecl = Candidate;
        }
      } else {
        MayNeedOverloadableChecks = true;
        switch (CheckOverload(S, NewFD, Previous, OldDecl,
                              /*NewIsUsingDecl*/ false)) {
        case Ovl_Match:
          Redeclaration = true;
          break;
  
        case Ovl_NonFunction:
          Redeclaration = true;
          break;
  
        case Ovl_Overload:
          Redeclaration = false;
          break;
        }
      }
    }
  
    // Check for a previous extern "C" declaration with this name.
    if (!Redeclaration &&
        checkForConflictWithNonVisibleExternC(*this, NewFD, Previous)) {
      if (!Previous.empty()) {
        // This is an extern "C" declaration with the same name as a previous
        // declaration, and thus redeclares that entity...
        Redeclaration = true;
        OldDecl = Previous.getFoundDecl();
        MergeTypeWithPrevious = false;
  
        // ... except in the presence of __attribute__((overloadable)).
        if (OldDecl->hasAttr<OverloadableAttr>() ||
            NewFD->hasAttr<OverloadableAttr>()) {
          if (IsOverload(NewFD, cast<FunctionDecl>(OldDecl), false)) {
            MayNeedOverloadableChecks = true;
            Redeclaration = false;
            OldDecl = nullptr;
          }
        }
      }
    }
  
    if (CheckMultiVersionFunction(*this, NewFD, Redeclaration, OldDecl,
                                  MergeTypeWithPrevious, Previous))
      return Redeclaration;
  
    // C++11 [dcl.constexpr]p8:
    //   A constexpr specifier for a non-static member function that is not
    //   a constructor declares that member function to be const.
    //
    // This needs to be delayed until we know whether this is an out-of-line
    // definition of a static member function.
    //
    // This rule is not present in C++1y, so we produce a backwards
    // compatibility warning whenever it happens in C++11.
    CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewFD);
    if (!getLangOpts().CPlusPlus14 && MD && MD->isConstexpr() &&
        !MD->isStatic() && !isa<CXXConstructorDecl>(MD) &&
        !MD->getMethodQualifiers().hasConst()) {
      CXXMethodDecl *OldMD = nullptr;
      if (OldDecl)
        OldMD = dyn_cast_or_null<CXXMethodDecl>(OldDecl->getAsFunction());
      if (!OldMD || !OldMD->isStatic()) {
        const FunctionProtoType *FPT =
          MD->getType()->castAs<FunctionProtoType>();
        FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
        EPI.TypeQuals.addConst();
        MD->setType(Context.getFunctionType(FPT->getReturnType(),
                                            FPT->getParamTypes(), EPI));
  
        // Warn that we did this, if we're not performing template instantiation.
        // In that case, we'll have warned already when the template was defined.
        if (!inTemplateInstantiation()) {
          SourceLocation AddConstLoc;
          if (FunctionTypeLoc FTL = MD->getTypeSourceInfo()->getTypeLoc()
                  .IgnoreParens().getAs<FunctionTypeLoc>())
            AddConstLoc = getLocForEndOfToken(FTL.getRParenLoc());
  
          Diag(MD->getLocation(), diag::warn_cxx14_compat_constexpr_not_const)
            << FixItHint::CreateInsertion(AddConstLoc, " const");
        }
      }
    }
  
    if (Redeclaration) {
      // NewFD and OldDecl represent declarations that need to be
      // merged.
      if (MergeFunctionDecl(NewFD, OldDecl, S, MergeTypeWithPrevious)) {
        NewFD->setInvalidDecl();
        return Redeclaration;
      }
  
      Previous.clear();
      Previous.addDecl(OldDecl);
  
      if (FunctionTemplateDecl *OldTemplateDecl =
              dyn_cast<FunctionTemplateDecl>(OldDecl)) {
        auto *OldFD = OldTemplateDecl->getTemplatedDecl();
        FunctionTemplateDecl *NewTemplateDecl
          = NewFD->getDescribedFunctionTemplate();
        assert(NewTemplateDecl && "Template/non-template mismatch");
  
        // The call to MergeFunctionDecl above may have created some state in
        // NewTemplateDecl that needs to be merged with OldTemplateDecl before we
        // can add it as a redeclaration.
        NewTemplateDecl->mergePrevDecl(OldTemplateDecl);
  
        NewFD->setPreviousDeclaration(OldFD);
        adjustDeclContextForDeclaratorDecl(NewFD, OldFD);
        if (NewFD->isCXXClassMember()) {
          NewFD->setAccess(OldTemplateDecl->getAccess());
          NewTemplateDecl->setAccess(OldTemplateDecl->getAccess());
        }
  
        // If this is an explicit specialization of a member that is a function
        // template, mark it as a member specialization.
        if (IsMemberSpecialization &&
            NewTemplateDecl->getInstantiatedFromMemberTemplate()) {
          NewTemplateDecl->setMemberSpecialization();
          assert(OldTemplateDecl->isMemberSpecialization());
          // Explicit specializations of a member template do not inherit deleted
          // status from the parent member template that they are specializing.
          if (OldFD->isDeleted()) {
            // FIXME: This assert will not hold in the presence of modules.
            assert(OldFD->getCanonicalDecl() == OldFD);
            // FIXME: We need an update record for this AST mutation.
            OldFD->setDeletedAsWritten(false);
          }
        }
  
      } else {
        if (shouldLinkDependentDeclWithPrevious(NewFD, OldDecl)) {
          auto *OldFD = cast<FunctionDecl>(OldDecl);
          // This needs to happen first so that 'inline' propagates.
          NewFD->setPreviousDeclaration(OldFD);
          adjustDeclContextForDeclaratorDecl(NewFD, OldFD);
          if (NewFD->isCXXClassMember())
            NewFD->setAccess(OldFD->getAccess());
        }
      }
    } else if (!getLangOpts().CPlusPlus && MayNeedOverloadableChecks &&
               !NewFD->getAttr<OverloadableAttr>()) {
      assert((Previous.empty() ||
              llvm::any_of(Previous,
                           [](const NamedDecl *ND) {
                             return ND->hasAttr<OverloadableAttr>();
                           })) &&
             "Non-redecls shouldn't happen without overloadable present");
  
      auto OtherUnmarkedIter = llvm::find_if(Previous, [](const NamedDecl *ND) {
        const auto *FD = dyn_cast<FunctionDecl>(ND);
        return FD && !FD->hasAttr<OverloadableAttr>();
      });
  
      if (OtherUnmarkedIter != Previous.end()) {
        Diag(NewFD->getLocation(),
             diag::err_attribute_overloadable_multiple_unmarked_overloads);
        Diag((*OtherUnmarkedIter)->getLocation(),
             diag::note_attribute_overloadable_prev_overload)
            << false;
  
        NewFD->addAttr(OverloadableAttr::CreateImplicit(Context));
      }
    }
  
    // Semantic checking for this function declaration (in isolation).
  
    if (getLangOpts().CPlusPlus) {
      // C++-specific checks.
      if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(NewFD)) {
        CheckConstructor(Constructor);
      } else if (CXXDestructorDecl *Destructor =
                  dyn_cast<CXXDestructorDecl>(NewFD)) {
        CXXRecordDecl *Record = Destructor->getParent();
        QualType ClassType = Context.getTypeDeclType(Record);
  
        // FIXME: Shouldn't we be able to perform this check even when the class
        // type is dependent? Both gcc and edg can handle that.
        if (!ClassType->isDependentType()) {
          DeclarationName Name
            = Context.DeclarationNames.getCXXDestructorName(
                                          Context.getCanonicalType(ClassType));
          if (NewFD->getDeclName() != Name) {
            Diag(NewFD->getLocation(), diag::err_destructor_name);
            NewFD->setInvalidDecl();
            return Redeclaration;
          }
        }
      } else if (CXXConversionDecl *Conversion
                 = dyn_cast<CXXConversionDecl>(NewFD)) {
        ActOnConversionDeclarator(Conversion);
      } else if (auto *Guide = dyn_cast<CXXDeductionGuideDecl>(NewFD)) {
        if (auto *TD = Guide->getDescribedFunctionTemplate())
          CheckDeductionGuideTemplate(TD);
  
        // A deduction guide is not on the list of entities that can be
        // explicitly specialized.
        if (Guide->getTemplateSpecializationKind() == TSK_ExplicitSpecialization)
          Diag(Guide->getBeginLoc(), diag::err_deduction_guide_specialized)
              << /*explicit specialization*/ 1;
      }
  
      // Find any virtual functions that this function overrides.
      if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(NewFD)) {
        if (!Method->isFunctionTemplateSpecialization() &&
            !Method->getDescribedFunctionTemplate() &&
            Method->isCanonicalDecl()) {
          if (AddOverriddenMethods(Method->getParent(), Method)) {
            // If the function was marked as "static", we have a problem.
            if (NewFD->getStorageClass() == SC_Static) {
              ReportOverrides(*this, diag::err_static_overrides_virtual, Method);
            }
          }
        }
  
        if (Method->isStatic())
          checkThisInStaticMemberFunctionType(Method);
      }
  
      // Extra checking for C++ overloaded operators (C++ [over.oper]).
      if (NewFD->isOverloadedOperator() &&
          CheckOverloadedOperatorDeclaration(NewFD)) {
        NewFD->setInvalidDecl();
        return Redeclaration;
      }
  
      // Extra checking for C++0x literal operators (C++0x [over.literal]).
      if (NewFD->getLiteralIdentifier() &&
          CheckLiteralOperatorDeclaration(NewFD)) {
        NewFD->setInvalidDecl();
        return Redeclaration;
      }
  
      // In C++, check default arguments now that we have merged decls. Unless
      // the lexical context is the class, because in this case this is done
      // during delayed parsing anyway.
      if (!CurContext->isRecord())
        CheckCXXDefaultArguments(NewFD);
  
      // If this function declares a builtin function, check the type of this
      // declaration against the expected type for the builtin.
      if (unsigned BuiltinID = NewFD->getBuiltinID()) {
        ASTContext::GetBuiltinTypeError Error;
        LookupPredefedObjCSuperType(*this, S, NewFD->getIdentifier());
        QualType T = Context.GetBuiltinType(BuiltinID, Error);
        // If the type of the builtin differs only in its exception
        // specification, that's OK.
        // FIXME: If the types do differ in this way, it would be better to
        // retain the 'noexcept' form of the type.
        if (!T.isNull() &&
            !Context.hasSameFunctionTypeIgnoringExceptionSpec(T,
                                                              NewFD->getType()))
          // The type of this function differs from the type of the builtin,
          // so forget about the builtin entirely.
          Context.BuiltinInfo.forgetBuiltin(BuiltinID, Context.Idents);
      }
  
      // If this function is declared as being extern "C", then check to see if
      // the function returns a UDT (class, struct, or union type) that is not C
      // compatible, and if it does, warn the user.
      // But, issue any diagnostic on the first declaration only.
      if (Previous.empty() && NewFD->isExternC()) {
        QualType R = NewFD->getReturnType();
        if (R->isIncompleteType() && !R->isVoidType())
          Diag(NewFD->getLocation(), diag::warn_return_value_udt_incomplete)
              << NewFD << R;
        else if (!R.isPODType(Context) && !R->isVoidType() &&
                 !R->isObjCObjectPointerType())
          Diag(NewFD->getLocation(), diag::warn_return_value_udt) << NewFD << R;
      }
  
      // C++1z [dcl.fct]p6:
      //   [...] whether the function has a non-throwing exception-specification
      //   [is] part of the function type
      //
      // This results in an ABI break between C++14 and C++17 for functions whose
      // declared type includes an exception-specification in a parameter or
      // return type. (Exception specifications on the function itself are OK in
      // most cases, and exception specifications are not permitted in most other
      // contexts where they could make it into a mangling.)
      if (!getLangOpts().CPlusPlus17 && !NewFD->getPrimaryTemplate()) {
        auto HasNoexcept = [&](QualType T) -> bool {
          // Strip off declarator chunks that could be between us and a function
          // type. We don't need to look far, exception specifications are very
          // restricted prior to C++17.
          if (auto *RT = T->getAs<ReferenceType>())
            T = RT->getPointeeType();
          else if (T->isAnyPointerType())
            T = T->getPointeeType();
          else if (auto *MPT = T->getAs<MemberPointerType>())
            T = MPT->getPointeeType();
          if (auto *FPT = T->getAs<FunctionProtoType>())
            if (FPT->isNothrow())
              return true;
          return false;
        };
  
        auto *FPT = NewFD->getType()->castAs<FunctionProtoType>();
        bool AnyNoexcept = HasNoexcept(FPT->getReturnType());
        for (QualType T : FPT->param_types())
          AnyNoexcept |= HasNoexcept(T);
        if (AnyNoexcept)
          Diag(NewFD->getLocation(),
               diag::warn_cxx17_compat_exception_spec_in_signature)
              << NewFD;
      }
  
      if (!Redeclaration && LangOpts.CUDA)
        checkCUDATargetOverload(NewFD, Previous);
    }
    return Redeclaration;
  }
  
  void Sema::CheckMain(FunctionDecl* FD, const DeclSpec& DS) {
    // C++11 [basic.start.main]p3:
    //   A program that [...] declares main to be inline, static or
    //   constexpr is ill-formed.
    // C11 6.7.4p4:  In a hosted environment, no function specifier(s) shall
    //   appear in a declaration of main.
    // static main is not an error under C99, but we should warn about it.
    // We accept _Noreturn main as an extension.
    if (FD->getStorageClass() == SC_Static)
      Diag(DS.getStorageClassSpecLoc(), getLangOpts().CPlusPlus
           ? diag::err_static_main : diag::warn_static_main)
        << FixItHint::CreateRemoval(DS.getStorageClassSpecLoc());
    if (FD->isInlineSpecified())
      Diag(DS.getInlineSpecLoc(), diag::err_inline_main)
        << FixItHint::CreateRemoval(DS.getInlineSpecLoc());
    if (DS.isNoreturnSpecified()) {
      SourceLocation NoreturnLoc = DS.getNoreturnSpecLoc();
      SourceRange NoreturnRange(NoreturnLoc, getLocForEndOfToken(NoreturnLoc));
      Diag(NoreturnLoc, diag::ext_noreturn_main);
      Diag(NoreturnLoc, diag::note_main_remove_noreturn)
        << FixItHint::CreateRemoval(NoreturnRange);
    }
    if (FD->isConstexpr()) {
      Diag(DS.getConstexprSpecLoc(), diag::err_constexpr_main)
        << FixItHint::CreateRemoval(DS.getConstexprSpecLoc());
      FD->setConstexpr(false);
    }
  
    if (getLangOpts().OpenCL) {
      Diag(FD->getLocation(), diag::err_opencl_no_main)
          << FD->hasAttr<OpenCLKernelAttr>();
      FD->setInvalidDecl();
      return;
    }
  
    QualType T = FD->getType();
    assert(T->isFunctionType() && "function decl is not of function type");
    const FunctionType* FT = T->castAs<FunctionType>();
  
    // Set default calling convention for main()
    if (FT->getCallConv() != CC_C) {
      FT = Context.adjustFunctionType(FT, FT->getExtInfo().withCallingConv(CC_C));
      FD->setType(QualType(FT, 0));
      T = Context.getCanonicalType(FD->getType());
    }
  
    if (getLangOpts().GNUMode && !getLangOpts().CPlusPlus) {
      // In C with GNU extensions we allow main() to have non-integer return
      // type, but we should warn about the extension, and we disable the
      // implicit-return-zero rule.
  
      // GCC in C mode accepts qualified 'int'.
      if (Context.hasSameUnqualifiedType(FT->getReturnType(), Context.IntTy))
        FD->setHasImplicitReturnZero(true);
      else {
        Diag(FD->getTypeSpecStartLoc(), diag::ext_main_returns_nonint);
        SourceRange RTRange = FD->getReturnTypeSourceRange();
        if (RTRange.isValid())
          Diag(RTRange.getBegin(), diag::note_main_change_return_type)
              << FixItHint::CreateReplacement(RTRange, "int");
      }
    } else {
      // In C and C++, main magically returns 0 if you fall off the end;
      // set the flag which tells us that.
      // This is C++ [basic.start.main]p5 and C99 5.1.2.2.3.
  
      // All the standards say that main() should return 'int'.
      if (Context.hasSameType(FT->getReturnType(), Context.IntTy))
        FD->setHasImplicitReturnZero(true);
      else {
        // Otherwise, this is just a flat-out error.
        SourceRange RTRange = FD->getReturnTypeSourceRange();
        Diag(FD->getTypeSpecStartLoc(), diag::err_main_returns_nonint)
            << (RTRange.isValid() ? FixItHint::CreateReplacement(RTRange, "int")
                                  : FixItHint());
        FD->setInvalidDecl(true);
      }
    }
  
    // Treat protoless main() as nullary.
    if (isa<FunctionNoProtoType>(FT)) return;
  
    const FunctionProtoType* FTP = cast<const FunctionProtoType>(FT);
    unsigned nparams = FTP->getNumParams();
    assert(FD->getNumParams() == nparams);
  
    bool HasExtraParameters = (nparams > 3);
  
    if (FTP->isVariadic()) {
      Diag(FD->getLocation(), diag::ext_variadic_main);
      // FIXME: if we had information about the location of the ellipsis, we
      // could add a FixIt hint to remove it as a parameter.
    }
  
    // Darwin passes an undocumented fourth argument of type char**.  If
    // other platforms start sprouting these, the logic below will start
    // getting shifty.
    if (nparams == 4 && Context.getTargetInfo().getTriple().isOSDarwin())
      HasExtraParameters = false;
  
    if (HasExtraParameters) {
      Diag(FD->getLocation(), diag::err_main_surplus_args) << nparams;
      FD->setInvalidDecl(true);
      nparams = 3;
    }
  
    // FIXME: a lot of the following diagnostics would be improved
    // if we had some location information about types.
  
    QualType CharPP =
      Context.getPointerType(Context.getPointerType(Context.CharTy));
    QualType Expected[] = { Context.IntTy, CharPP, CharPP, CharPP };
  
    for (unsigned i = 0; i < nparams; ++i) {
      QualType AT = FTP->getParamType(i);
  
      bool mismatch = true;
  
      if (Context.hasSameUnqualifiedType(AT, Expected[i]))
        mismatch = false;
      else if (Expected[i] == CharPP) {
        // As an extension, the following forms are okay:
        //   char const **
        //   char const * const *
        //   char * const *
  
        QualifierCollector qs;
        const PointerType* PT;
        if ((PT = qs.strip(AT)->getAs<PointerType>()) &&
            (PT = qs.strip(PT->getPointeeType())->getAs<PointerType>()) &&
            Context.hasSameType(QualType(qs.strip(PT->getPointeeType()), 0),
                                Context.CharTy)) {
          qs.removeConst();
          mismatch = !qs.empty();
        }
      }
  
      if (mismatch) {
        Diag(FD->getLocation(), diag::err_main_arg_wrong) << i << Expected[i];
        // TODO: suggest replacing given type with expected type
        FD->setInvalidDecl(true);
      }
    }
  
    if (nparams == 1 && !FD->isInvalidDecl()) {
      Diag(FD->getLocation(), diag::warn_main_one_arg);
    }
  
    if (!FD->isInvalidDecl() && FD->getDescribedFunctionTemplate()) {
      Diag(FD->getLocation(), diag::err_mainlike_template_decl) << FD;
      FD->setInvalidDecl();
    }
  }
  
  void Sema::CheckMSVCRTEntryPoint(FunctionDecl *FD) {
    QualType T = FD->getType();
    assert(T->isFunctionType() && "function decl is not of function type");
    const FunctionType *FT = T->castAs<FunctionType>();
  
    // Set an implicit return of 'zero' if the function can return some integral,
    // enumeration, pointer or nullptr type.
    if (FT->getReturnType()->isIntegralOrEnumerationType() ||
        FT->getReturnType()->isAnyPointerType() ||
        FT->getReturnType()->isNullPtrType())
      // DllMain is exempt because a return value of zero means it failed.
      if (FD->getName() != "DllMain")
        FD->setHasImplicitReturnZero(true);
  
    if (!FD->isInvalidDecl() && FD->getDescribedFunctionTemplate()) {
      Diag(FD->getLocation(), diag::err_mainlike_template_decl) << FD;
      FD->setInvalidDecl();
    }
  }
  
  bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
    // FIXME: Need strict checking.  In C89, we need to check for
    // any assignment, increment, decrement, function-calls, or
    // commas outside of a sizeof.  In C99, it's the same list,
    // except that the aforementioned are allowed in unevaluated
    // expressions.  Everything else falls under the
    // "may accept other forms of constant expressions" exception.
    // (We never end up here for C++, so the constant expression
    // rules there don't matter.)
    const Expr *Culprit;
    if (Init->isConstantInitializer(Context, false, &Culprit))
      return false;
    Diag(Culprit->getExprLoc(), diag::err_init_element_not_constant)
      << Culprit->getSourceRange();
    return true;
  }
  
  namespace {
    // Visits an initialization expression to see if OrigDecl is evaluated in
    // its own initialization and throws a warning if it does.
    class SelfReferenceChecker
        : public EvaluatedExprVisitor<SelfReferenceChecker> {
      Sema &S;
      Decl *OrigDecl;
      bool isRecordType;
      bool isPODType;
      bool isReferenceType;
  
      bool isInitList;
      llvm::SmallVector<unsigned, 4> InitFieldIndex;
  
    public:
      typedef EvaluatedExprVisitor<SelfReferenceChecker> Inherited;
  
      SelfReferenceChecker(Sema &S, Decl *OrigDecl) : Inherited(S.Context),
                                                      S(S), OrigDecl(OrigDecl) {
        isPODType = false;
        isRecordType = false;
        isReferenceType = false;
        isInitList = false;
        if (ValueDecl *VD = dyn_cast<ValueDecl>(OrigDecl)) {
          isPODType = VD->getType().isPODType(S.Context);
          isRecordType = VD->getType()->isRecordType();
          isReferenceType = VD->getType()->isReferenceType();
        }
      }
  
      // For most expressions, just call the visitor.  For initializer lists,
      // track the index of the field being initialized since fields are
      // initialized in order allowing use of previously initialized fields.
      void CheckExpr(Expr *E) {
        InitListExpr *InitList = dyn_cast<InitListExpr>(E);
        if (!InitList) {
          Visit(E);
          return;
        }
  
        // Track and increment the index here.
        isInitList = true;
        InitFieldIndex.push_back(0);
        for (auto Child : InitList->children()) {
          CheckExpr(cast<Expr>(Child));
          ++InitFieldIndex.back();
        }
        InitFieldIndex.pop_back();
      }
  
      // Returns true if MemberExpr is checked and no further checking is needed.
      // Returns false if additional checking is required.
      bool CheckInitListMemberExpr(MemberExpr *E, bool CheckReference) {
        llvm::SmallVector<FieldDecl*, 4> Fields;
        Expr *Base = E;
        bool ReferenceField = false;
  
        // Get the field members used.
        while (MemberExpr *ME = dyn_cast<MemberExpr>(Base)) {
          FieldDecl *FD = dyn_cast<FieldDecl>(ME->getMemberDecl());
          if (!FD)
            return false;
          Fields.push_back(FD);
          if (FD->getType()->isReferenceType())
            ReferenceField = true;
          Base = ME->getBase()->IgnoreParenImpCasts();
        }
  
        // Keep checking only if the base Decl is the same.
        DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base);
        if (!DRE || DRE->getDecl() != OrigDecl)
          return false;
  
        // A reference field can be bound to an unininitialized field.
        if (CheckReference && !ReferenceField)
          return true;
  
        // Convert FieldDecls to their index number.
        llvm::SmallVector<unsigned, 4> UsedFieldIndex;
        for (const FieldDecl *I : llvm::reverse(Fields))
          UsedFieldIndex.push_back(I->getFieldIndex());
  
        // See if a warning is needed by checking the first difference in index
        // numbers.  If field being used has index less than the field being
        // initialized, then the use is safe.
        for (auto UsedIter = UsedFieldIndex.begin(),
                  UsedEnd = UsedFieldIndex.end(),
                  OrigIter = InitFieldIndex.begin(),
                  OrigEnd = InitFieldIndex.end();
             UsedIter != UsedEnd && OrigIter != OrigEnd; ++UsedIter, ++OrigIter) {
          if (*UsedIter < *OrigIter)
            return true;
          if (*UsedIter > *OrigIter)
            break;
        }
  
        // TODO: Add a different warning which will print the field names.
        HandleDeclRefExpr(DRE);
        return true;
      }
  
      // For most expressions, the cast is directly above the DeclRefExpr.
      // For conditional operators, the cast can be outside the conditional
      // operator if both expressions are DeclRefExpr's.
      void HandleValue(Expr *E) {
        E = E->IgnoreParens();
        if (DeclRefExpr* DRE = dyn_cast<DeclRefExpr>(E)) {
          HandleDeclRefExpr(DRE);
          return;
        }
  
        if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
          Visit(CO->getCond());
          HandleValue(CO->getTrueExpr());
          HandleValue(CO->getFalseExpr());
          return;
        }
  
        if (BinaryConditionalOperator *BCO =
                dyn_cast<BinaryConditionalOperator>(E)) {
          Visit(BCO->getCond());
          HandleValue(BCO->getFalseExpr());
          return;
        }
  
        if (OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(E)) {
          HandleValue(OVE->getSourceExpr());
          return;
        }
  
        if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
          if (BO->getOpcode() == BO_Comma) {
            Visit(BO->getLHS());
            HandleValue(BO->getRHS());
            return;
          }
        }
  
        if (isa<MemberExpr>(E)) {
          if (isInitList) {
            if (CheckInitListMemberExpr(cast<MemberExpr>(E),
                                        false /*CheckReference*/))
              return;
          }
  
          Expr *Base = E->IgnoreParenImpCasts();
          while (MemberExpr *ME = dyn_cast<MemberExpr>(Base)) {
            // Check for static member variables and don't warn on them.
            if (!isa<FieldDecl>(ME->getMemberDecl()))
              return;
            Base = ME->getBase()->IgnoreParenImpCasts();
          }
          if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base))
            HandleDeclRefExpr(DRE);
          return;
        }
  
        Visit(E);
      }
  
      // Reference types not handled in HandleValue are handled here since all
      // uses of references are bad, not just r-value uses.
      void VisitDeclRefExpr(DeclRefExpr *E) {
        if (isReferenceType)
          HandleDeclRefExpr(E);
      }
  
      void VisitImplicitCastExpr(ImplicitCastExpr *E) {
        if (E->getCastKind() == CK_LValueToRValue) {
          HandleValue(E->getSubExpr());
          return;
        }
  
        Inherited::VisitImplicitCastExpr(E);
      }
  
      void VisitMemberExpr(MemberExpr *E) {
        if (isInitList) {
          if (CheckInitListMemberExpr(E, true /*CheckReference*/))
            return;
        }
  
        // Don't warn on arrays since they can be treated as pointers.
        if (E->getType()->canDecayToPointerType()) return;
  
        // Warn when a non-static method call is followed by non-static member
        // field accesses, which is followed by a DeclRefExpr.
        CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(E->getMemberDecl());
        bool Warn = (MD && !MD->isStatic());
        Expr *Base = E->getBase()->IgnoreParenImpCasts();
        while (MemberExpr *ME = dyn_cast<MemberExpr>(Base)) {
          if (!isa<FieldDecl>(ME->getMemberDecl()))
            Warn = false;
          Base = ME->getBase()->IgnoreParenImpCasts();
        }
  
        if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base)) {
          if (Warn)
            HandleDeclRefExpr(DRE);
          return;
        }
  
        // The base of a MemberExpr is not a MemberExpr or a DeclRefExpr.
        // Visit that expression.
        Visit(Base);
      }
  
      void VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E) {
        Expr *Callee = E->getCallee();
  
        if (isa<UnresolvedLookupExpr>(Callee))
          return Inherited::VisitCXXOperatorCallExpr(E);
  
        Visit(Callee);
        for (auto Arg: E->arguments())
          HandleValue(Arg->IgnoreParenImpCasts());
      }
  
      void VisitUnaryOperator(UnaryOperator *E) {
        // For POD record types, addresses of its own members are well-defined.
        if (E->getOpcode() == UO_AddrOf && isRecordType &&
            isa<MemberExpr>(E->getSubExpr()->IgnoreParens())) {
          if (!isPODType)
            HandleValue(E->getSubExpr());
          return;
        }
  
        if (E->isIncrementDecrementOp()) {
          HandleValue(E->getSubExpr());
          return;
        }
  
        Inherited::VisitUnaryOperator(E);
      }
  
      void VisitObjCMessageExpr(ObjCMessageExpr *E) {}
  
      void VisitCXXConstructExpr(CXXConstructExpr *E) {
        if (E->getConstructor()->isCopyConstructor()) {
          Expr *ArgExpr = E->getArg(0);
          if (InitListExpr *ILE = dyn_cast<InitListExpr>(ArgExpr))
            if (ILE->getNumInits() == 1)
              ArgExpr = ILE->getInit(0);
          if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(ArgExpr))
            if (ICE->getCastKind() == CK_NoOp)
              ArgExpr = ICE->getSubExpr();
          HandleValue(ArgExpr);
          return;
        }
        Inherited::VisitCXXConstructExpr(E);
      }
  
      void VisitCallExpr(CallExpr *E) {
        // Treat std::move as a use.
        if (E->isCallToStdMove()) {
          HandleValue(E->getArg(0));
          return;
        }
  
        Inherited::VisitCallExpr(E);
      }
  
      void VisitBinaryOperator(BinaryOperator *E) {
        if (E->isCompoundAssignmentOp()) {
          HandleValue(E->getLHS());
          Visit(E->getRHS());
          return;
        }
  
        Inherited::VisitBinaryOperator(E);
      }
  
      // A custom visitor for BinaryConditionalOperator is needed because the
      // regular visitor would check the condition and true expression separately
      // but both point to the same place giving duplicate diagnostics.
      void VisitBinaryConditionalOperator(BinaryConditionalOperator *E) {
        Visit(E->getCond());
        Visit(E->getFalseExpr());
      }
  
      void HandleDeclRefExpr(DeclRefExpr *DRE) {
        Decl* ReferenceDecl = DRE->getDecl();
        if (OrigDecl != ReferenceDecl) return;
        unsigned diag;
        if (isReferenceType) {
          diag = diag::warn_uninit_self_reference_in_reference_init;
        } else if (cast<VarDecl>(OrigDecl)->isStaticLocal()) {
          diag = diag::warn_static_self_reference_in_init;
        } else if (isa<TranslationUnitDecl>(OrigDecl->getDeclContext()) ||
                   isa<NamespaceDecl>(OrigDecl->getDeclContext()) ||
                   DRE->getDecl()->getType()->isRecordType()) {
          diag = diag::warn_uninit_self_reference_in_init;
        } else {
          // Local variables will be handled by the CFG analysis.
          return;
        }
  
        S.DiagRuntimeBehavior(DRE->getBeginLoc(), DRE,
                              S.PDiag(diag)
                                  << DRE->getDecl() << OrigDecl->getLocation()
                                  << DRE->getSourceRange());
      }
    };
  
    /// CheckSelfReference - Warns if OrigDecl is used in expression E.
    static void CheckSelfReference(Sema &S, Decl* OrigDecl, Expr *E,
                                   bool DirectInit) {
      // Parameters arguments are occassionially constructed with itself,
      // for instance, in recursive functions.  Skip them.
      if (isa<ParmVarDecl>(OrigDecl))
        return;
  
      E = E->IgnoreParens();
  
      // Skip checking T a = a where T is not a record or reference type.
      // Doing so is a way to silence uninitialized warnings.
      if (!DirectInit && !cast<VarDecl>(OrigDecl)->getType()->isRecordType())
        if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E))
          if (ICE->getCastKind() == CK_LValueToRValue)
            if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(ICE->getSubExpr()))
              if (DRE->getDecl() == OrigDecl)
                return;
  
      SelfReferenceChecker(S, OrigDecl).CheckExpr(E);
    }
  } // end anonymous namespace
  
  namespace {
    // Simple wrapper to add the name of a variable or (if no variable is
    // available) a DeclarationName into a diagnostic.
    struct VarDeclOrName {
      VarDecl *VDecl;
      DeclarationName Name;
  
      friend const Sema::SemaDiagnosticBuilder &
      operator<<(const Sema::SemaDiagnosticBuilder &Diag, VarDeclOrName VN) {
        return VN.VDecl ? Diag << VN.VDecl : Diag << VN.Name;
      }
    };
  } // end anonymous namespace
  
  QualType Sema::deduceVarTypeFromInitializer(VarDecl *VDecl,
                                              DeclarationName Name, QualType Type,
                                              TypeSourceInfo *TSI,
                                              SourceRange Range, bool DirectInit,
                                              Expr *&Init) {
    bool IsInitCapture = !VDecl;
    assert((!VDecl || !VDecl->isInitCapture()) &&
           "init captures are expected to be deduced prior to initialization");
  
    VarDeclOrName VN{VDecl, Name};
  
    DeducedType *Deduced = Type->getContainedDeducedType();
    assert(Deduced && "deduceVarTypeFromInitializer for non-deduced type");
  
    // C++11 [dcl.spec.auto]p3
    if (!Init) {
      assert(VDecl && "no init for init capture deduction?");
  
      // Except for class argument deduction, and then for an initializing
      // declaration only, i.e. no static at class scope or extern.
      if (!isa<DeducedTemplateSpecializationType>(Deduced) ||
          VDecl->hasExternalStorage() ||
          VDecl->isStaticDataMember()) {
        Diag(VDecl->getLocation(), diag::err_auto_var_requires_init)
          << VDecl->getDeclName() << Type;
        return QualType();
      }
    }
  
    ArrayRef<Expr*> DeduceInits;
    if (Init)
      DeduceInits = Init;
  
    if (DirectInit) {
      if (auto *PL = dyn_cast_or_null<ParenListExpr>(Init))
        DeduceInits = PL->exprs();
    }
  
    if (isa<DeducedTemplateSpecializationType>(Deduced)) {
      assert(VDecl && "non-auto type for init capture deduction?");
      InitializedEntity Entity = InitializedEntity::InitializeVariable(VDecl);
      InitializationKind Kind = InitializationKind::CreateForInit(
          VDecl->getLocation(), DirectInit, Init);
      // FIXME: Initialization should not be taking a mutable list of inits.
      SmallVector<Expr*, 8> InitsCopy(DeduceInits.begin(), DeduceInits.end());
      return DeduceTemplateSpecializationFromInitializer(TSI, Entity, Kind,
                                                         InitsCopy);
    }
  
    if (DirectInit) {
      if (auto *IL = dyn_cast<InitListExpr>(Init))
        DeduceInits = IL->inits();
    }
  
    // Deduction only works if we have exactly one source expression.
    if (DeduceInits.empty()) {
      // It isn't possible to write this directly, but it is possible to
      // end up in this situation with "auto x(some_pack...);"
      Diag(Init->getBeginLoc(), IsInitCapture
                                    ? diag::err_init_capture_no_expression
                                    : diag::err_auto_var_init_no_expression)
          << VN << Type << Range;
      return QualType();
    }
  
    if (DeduceInits.size() > 1) {
      Diag(DeduceInits[1]->getBeginLoc(),
           IsInitCapture ? diag::err_init_capture_multiple_expressions
                         : diag::err_auto_var_init_multiple_expressions)
          << VN << Type << Range;
      return QualType();
    }
  
    Expr *DeduceInit = DeduceInits[0];
    if (DirectInit && isa<InitListExpr>(DeduceInit)) {
      Diag(Init->getBeginLoc(), IsInitCapture
                                    ? diag::err_init_capture_paren_braces
                                    : diag::err_auto_var_init_paren_braces)
          << isa<InitListExpr>(Init) << VN << Type << Range;
      return QualType();
    }
  
    // Expressions default to 'id' when we're in a debugger.
    bool DefaultedAnyToId = false;
    if (getLangOpts().DebuggerCastResultToId &&
        Init->getType() == Context.UnknownAnyTy && !IsInitCapture) {
      ExprResult Result = forceUnknownAnyToType(Init, Context.getObjCIdType());
      if (Result.isInvalid()) {
        return QualType();
      }
      Init = Result.get();
      DefaultedAnyToId = true;
    }
  
    // C++ [dcl.decomp]p1:
    //   If the assignment-expression [...] has array type A and no ref-qualifier
    //   is present, e has type cv A
    if (VDecl && isa<DecompositionDecl>(VDecl) &&
        Context.hasSameUnqualifiedType(Type, Context.getAutoDeductType()) &&
        DeduceInit->getType()->isConstantArrayType())
      return Context.getQualifiedType(DeduceInit->getType(),
                                      Type.getQualifiers());
  
    QualType DeducedType;
    if (DeduceAutoType(TSI, DeduceInit, DeducedType) == DAR_Failed) {
      if (!IsInitCapture)
        DiagnoseAutoDeductionFailure(VDecl, DeduceInit);
      else if (isa<InitListExpr>(Init))
        Diag(Range.getBegin(),
             diag::err_init_capture_deduction_failure_from_init_list)
            << VN
            << (DeduceInit->getType().isNull() ? TSI->getType()
                                               : DeduceInit->getType())
            << DeduceInit->getSourceRange();
      else
        Diag(Range.getBegin(), diag::err_init_capture_deduction_failure)
            << VN << TSI->getType()
            << (DeduceInit->getType().isNull() ? TSI->getType()
                                               : DeduceInit->getType())
            << DeduceInit->getSourceRange();
    } else
      Init = DeduceInit;
  
    // Warn if we deduced 'id'. 'auto' usually implies type-safety, but using
    // 'id' instead of a specific object type prevents most of our usual
    // checks.
    // We only want to warn outside of template instantiations, though:
    // inside a template, the 'id' could have come from a parameter.
    if (!inTemplateInstantiation() && !DefaultedAnyToId && !IsInitCapture &&
        !DeducedType.isNull() && DeducedType->isObjCIdType()) {
      SourceLocation Loc = TSI->getTypeLoc().getBeginLoc();
      Diag(Loc, diag::warn_auto_var_is_id) << VN << Range;
    }
  
    return DeducedType;
  }
  
  bool Sema::DeduceVariableDeclarationType(VarDecl *VDecl, bool DirectInit,
                                           Expr *&Init) {
    QualType DeducedType = deduceVarTypeFromInitializer(
        VDecl, VDecl->getDeclName(), VDecl->getType(), VDecl->getTypeSourceInfo(),
        VDecl->getSourceRange(), DirectInit, Init);
    if (DeducedType.isNull()) {
      VDecl->setInvalidDecl();
      return true;
    }
  
    VDecl->setType(DeducedType);
    assert(VDecl->isLinkageValid());
  
    // In ARC, infer lifetime.
    if (getLangOpts().ObjCAutoRefCount && inferObjCARCLifetime(VDecl))
      VDecl->setInvalidDecl();
  
    // If this is a redeclaration, check that the type we just deduced matches
    // the previously declared type.
    if (VarDecl *Old = VDecl->getPreviousDecl()) {
      // We never need to merge the type, because we cannot form an incomplete
      // array of auto, nor deduce such a type.
      MergeVarDeclTypes(VDecl, Old, /*MergeTypeWithPrevious*/ false);
    }
  
    // Check the deduced type is valid for a variable declaration.
    CheckVariableDeclarationType(VDecl);
    return VDecl->isInvalidDecl();
  }
  
  /// AddInitializerToDecl - Adds the initializer Init to the
  /// declaration dcl. If DirectInit is true, this is C++ direct
  /// initialization rather than copy initialization.
  void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
    // If there is no declaration, there was an error parsing it.  Just ignore
    // the initializer.
    if (!RealDecl || RealDecl->isInvalidDecl()) {
      CorrectDelayedTyposInExpr(Init, dyn_cast_or_null<VarDecl>(RealDecl));
      return;
    }
  
    if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(RealDecl)) {
      // Pure-specifiers are handled in ActOnPureSpecifier.
      Diag(Method->getLocation(), diag::err_member_function_initialization)
        << Method->getDeclName() << Init->getSourceRange();
      Method->setInvalidDecl();
      return;
    }
  
    VarDecl *VDecl = dyn_cast<VarDecl>(RealDecl);
    if (!VDecl) {
      assert(!isa<FieldDecl>(RealDecl) && "field init shouldn't get here");
      Diag(RealDecl->getLocation(), diag::err_illegal_initializer);
      RealDecl->setInvalidDecl();
      return;
    }
  
    // C++11 [decl.spec.auto]p6. Deduce the type which 'auto' stands in for.
    if (VDecl->getType()->isUndeducedType()) {
      // Attempt typo correction early so that the type of the init expression can
      // be deduced based on the chosen correction if the original init contains a
      // TypoExpr.
      ExprResult Res = CorrectDelayedTyposInExpr(Init, VDecl);
      if (!Res.isUsable()) {
        RealDecl->setInvalidDecl();
        return;
      }
      Init = Res.get();
  
      if (DeduceVariableDeclarationType(VDecl, DirectInit, Init))
        return;
    }
  
    // dllimport cannot be used on variable definitions.
    if (VDecl->hasAttr<DLLImportAttr>() && !VDecl->isStaticDataMember()) {
      Diag(VDecl->getLocation(), diag::err_attribute_dllimport_data_definition);
      VDecl->setInvalidDecl();
      return;
    }
  
    if (VDecl->isLocalVarDecl() && VDecl->hasExternalStorage()) {
      // C99 6.7.8p5. C++ has no such restriction, but that is a defect.
      Diag(VDecl->getLocation(), diag::err_block_extern_cant_init);
      VDecl->setInvalidDecl();
      return;
    }
  
    if (!VDecl->getType()->isDependentType()) {
      // A definition must end up with a complete type, which means it must be
      // complete with the restriction that an array type might be completed by
      // the initializer; note that later code assumes this restriction.
      QualType BaseDeclType = VDecl->getType();
      if (const ArrayType *Array = Context.getAsIncompleteArrayType(BaseDeclType))
        BaseDeclType = Array->getElementType();
      if (RequireCompleteType(VDecl->getLocation(), BaseDeclType,
                              diag::err_typecheck_decl_incomplete_type)) {
        RealDecl->setInvalidDecl();
        return;
      }
  
      // The variable can not have an abstract class type.
      if (RequireNonAbstractType(VDecl->getLocation(), VDecl->getType(),
                                 diag::err_abstract_type_in_decl,
                                 AbstractVariableType))
        VDecl->setInvalidDecl();
    }
  
    // If adding the initializer will turn this declaration into a definition,
    // and we already have a definition for this variable, diagnose or otherwise
    // handle the situation.
    VarDecl *Def;
    if ((Def = VDecl->getDefinition()) && Def != VDecl &&
        (!VDecl->isStaticDataMember() || VDecl->isOutOfLine()) &&
        !VDecl->isThisDeclarationADemotedDefinition() &&
        checkVarDeclRedefinition(Def, VDecl))
      return;
  
    if (getLangOpts().CPlusPlus) {
      // C++ [class.static.data]p4
      //   If a static data member is of const integral or const
      //   enumeration type, its declaration in the class definition can
      //   specify a constant-initializer which shall be an integral
      //   constant expression (5.19). In that case, the member can appear
      //   in integral constant expressions. The member shall still be
      //   defined in a namespace scope if it is used in the program and the
      //   namespace scope definition shall not contain an initializer.
      //
      // We already performed a redefinition check above, but for static
      // data members we also need to check whether there was an in-class
      // declaration with an initializer.
      if (VDecl->isStaticDataMember() && VDecl->getCanonicalDecl()->hasInit()) {
        Diag(Init->getExprLoc(), diag::err_static_data_member_reinitialization)
            << VDecl->getDeclName();
        Diag(VDecl->getCanonicalDecl()->getInit()->getExprLoc(),
             diag::note_previous_initializer)
            << 0;
        return;
      }
  
      if (VDecl->hasLocalStorage())
        setFunctionHasBranchProtectedScope();
  
      if (DiagnoseUnexpandedParameterPack(Init, UPPC_Initializer)) {
        VDecl->setInvalidDecl();
        return;
      }
    }
  
    // OpenCL 1.1 6.5.2: "Variables allocated in the __local address space inside
    // a kernel function cannot be initialized."
    if (VDecl->getType().getAddressSpace() == LangAS::opencl_local) {
      Diag(VDecl->getLocation(), diag::err_local_cant_init);
      VDecl->setInvalidDecl();
      return;
    }
  
    // Get the decls type and save a reference for later, since
    // CheckInitializerTypes may change it.
    QualType DclT = VDecl->getType(), SavT = DclT;
  
    // Expressions default to 'id' when we're in a debugger
    // and we are assigning it to a variable of Objective-C pointer type.
    if (getLangOpts().DebuggerCastResultToId && DclT->isObjCObjectPointerType() &&
        Init->getType() == Context.UnknownAnyTy) {
      ExprResult Result = forceUnknownAnyToType(Init, Context.getObjCIdType());
      if (Result.isInvalid()) {
        VDecl->setInvalidDecl();
        return;
      }
      Init = Result.get();
    }
  
    // Perform the initialization.
    ParenListExpr *CXXDirectInit = dyn_cast<ParenListExpr>(Init);
    if (!VDecl->isInvalidDecl()) {
      InitializedEntity Entity = InitializedEntity::InitializeVariable(VDecl);
      InitializationKind Kind = InitializationKind::CreateForInit(
          VDecl->getLocation(), DirectInit, Init);
  
      MultiExprArg Args = Init;
      if (CXXDirectInit)
        Args = MultiExprArg(CXXDirectInit->getExprs(),
                            CXXDirectInit->getNumExprs());
  
      // Try to correct any TypoExprs in the initialization arguments.
      for (size_t Idx = 0; Idx < Args.size(); ++Idx) {
        ExprResult Res = CorrectDelayedTyposInExpr(
            Args[Idx], VDecl, [this, Entity, Kind](Expr *E) {
              InitializationSequence Init(*this, Entity, Kind, MultiExprArg(E));
              return Init.Failed() ? ExprError() : E;
            });
        if (Res.isInvalid()) {
          VDecl->setInvalidDecl();
        } else if (Res.get() != Args[Idx]) {
          Args[Idx] = Res.get();
        }
      }
      if (VDecl->isInvalidDecl())
        return;
  
      InitializationSequence InitSeq(*this, Entity, Kind, Args,
                                     /*TopLevelOfInitList=*/false,
                                     /*TreatUnavailableAsInvalid=*/false);
      ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Args, &DclT);
      if (Result.isInvalid()) {
        VDecl->setInvalidDecl();
        return;
      }
  
      Init = Result.getAs<Expr>();
    }
  
    // Check for self-references within variable initializers.
    // Variables declared within a function/method body (except for references)
    // are handled by a dataflow analysis.
    if (!VDecl->hasLocalStorage() || VDecl->getType()->isRecordType() ||
        VDecl->getType()->isReferenceType()) {
      CheckSelfReference(*this, RealDecl, Init, DirectInit);
    }
  
    // If the type changed, it means we had an incomplete type that was
    // completed by the initializer. For example:
    //   int ary[] = { 1, 3, 5 };
    // "ary" transitions from an IncompleteArrayType to a ConstantArrayType.
    if (!VDecl->isInvalidDecl() && (DclT != SavT))
      VDecl->setType(DclT);
  
    if (!VDecl->isInvalidDecl()) {
      checkUnsafeAssigns(VDecl->getLocation(), VDecl->getType(), Init);
  
      if (VDecl->hasAttr<BlocksAttr>())
        checkRetainCycles(VDecl, Init);
  
      // It is safe to assign a weak reference into a strong variable.
      // Although this code can still have problems:
      //   id x = self.weakProp;
      //   id y = self.weakProp;
      // we do not warn to warn spuriously when 'x' and 'y' are on separate
      // paths through the function. This should be revisited if
      // -Wrepeated-use-of-weak is made flow-sensitive.
      if (FunctionScopeInfo *FSI = getCurFunction())
        if ((VDecl->getType().getObjCLifetime() == Qualifiers::OCL_Strong ||
             VDecl->getType().isNonWeakInMRRWithObjCWeak(Context)) &&
            !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak,
                             Init->getBeginLoc()))
          FSI->markSafeWeakUse(Init);
    }
  
    // The initialization is usually a full-expression.
    //
    // FIXME: If this is a braced initialization of an aggregate, it is not
    // an expression, and each individual field initializer is a separate
    // full-expression. For instance, in:
    //
    //   struct Temp { ~Temp(); };
    //   struct S { S(Temp); };
    //   struct T { S a, b; } t = { Temp(), Temp() }
    //
    // we should destroy the first Temp before constructing the second.
    ExprResult Result =
        ActOnFinishFullExpr(Init, VDecl->getLocation(),
                            /*DiscardedValue*/ false, VDecl->isConstexpr());
    if (Result.isInvalid()) {
      VDecl->setInvalidDecl();
      return;
    }
    Init = Result.get();
  
    // Attach the initializer to the decl.
    VDecl->setInit(Init);
  
    if (VDecl->isLocalVarDecl()) {
      // Don't check the initializer if the declaration is malformed.
      if (VDecl->isInvalidDecl()) {
        // do nothing
  
      // OpenCL v1.2 s6.5.3: __constant locals must be constant-initialized.
      // This is true even in OpenCL C++.
      } else if (VDecl->getType().getAddressSpace() == LangAS::opencl_constant) {
        CheckForConstantInitializer(Init, DclT);
  
      // Otherwise, C++ does not restrict the initializer.
      } else if (getLangOpts().CPlusPlus) {
        // do nothing
  
      // C99 6.7.8p4: All the expressions in an initializer for an object that has
      // static storage duration shall be constant expressions or string literals.
      } else if (VDecl->getStorageClass() == SC_Static) {
        CheckForConstantInitializer(Init, DclT);
  
      // C89 is stricter than C99 for aggregate initializers.
      // C89 6.5.7p3: All the expressions [...] in an initializer list
      // for an object that has aggregate or union type shall be
      // constant expressions.
      } else if (!getLangOpts().C99 && VDecl->getType()->isAggregateType() &&
                 isa<InitListExpr>(Init)) {
        const Expr *Culprit;
        if (!Init->isConstantInitializer(Context, false, &Culprit)) {
          Diag(Culprit->getExprLoc(),
               diag::ext_aggregate_init_not_constant)
            << Culprit->getSourceRange();
        }
      }
  
      if (auto *E = dyn_cast<ExprWithCleanups>(Init))
        if (auto *BE = dyn_cast<BlockExpr>(E->getSubExpr()->IgnoreParens()))
          if (VDecl->hasLocalStorage())
            BE->getBlockDecl()->setCanAvoidCopyToHeap();
    } else if (VDecl->isStaticDataMember() && !VDecl->isInline() &&
               VDecl->getLexicalDeclContext()->isRecord()) {
      // This is an in-class initialization for a static data member, e.g.,
      //
      // struct S {
      //   static const int value = 17;
      // };
  
      // C++ [class.mem]p4:
      //   A member-declarator can contain a constant-initializer only
      //   if it declares a static member (9.4) of const integral or
      //   const enumeration type, see 9.4.2.
      //
      // C++11 [class.static.data]p3:
      //   If a non-volatile non-inline const static data member is of integral
      //   or enumeration type, its declaration in the class definition can
      //   specify a brace-or-equal-initializer in which every initializer-clause
      //   that is an assignment-expression is a constant expression. A static
      //   data member of literal type can be declared in the class definition
      //   with the constexpr specifier; if so, its declaration shall specify a
      //   brace-or-equal-initializer in which every initializer-clause that is
      //   an assignment-expression is a constant expression.
  
      // Do nothing on dependent types.
      if (DclT->isDependentType()) {
  
      // Allow any 'static constexpr' members, whether or not they are of literal
      // type. We separately check that every constexpr variable is of literal
      // type.
      } else if (VDecl->isConstexpr()) {
  
      // Require constness.
      } else if (!DclT.isConstQualified()) {
        Diag(VDecl->getLocation(), diag::err_in_class_initializer_non_const)
          << Init->getSourceRange();
        VDecl->setInvalidDecl();
  
      // We allow integer constant expressions in all cases.
      } else if (DclT->isIntegralOrEnumerationType()) {
        // Check whether the expression is a constant expression.
        SourceLocation Loc;
        if (getLangOpts().CPlusPlus11 && DclT.isVolatileQualified())
          // In C++11, a non-constexpr const static data member with an
          // in-class initializer cannot be volatile.
          Diag(VDecl->getLocation(), diag::err_in_class_initializer_volatile);
        else if (Init->isValueDependent())
          ; // Nothing to check.
        else if (Init->isIntegerConstantExpr(Context, &Loc))
          ; // Ok, it's an ICE!
        else if (Init->getType()->isScopedEnumeralType() &&
                 Init->isCXX11ConstantExpr(Context))
          ; // Ok, it is a scoped-enum constant expression.
        else if (Init->isEvaluatable(Context)) {
          // If we can constant fold the initializer through heroics, accept it,
          // but report this as a use of an extension for -pedantic.
          Diag(Loc, diag::ext_in_class_initializer_non_constant)
            << Init->getSourceRange();
        } else {
          // Otherwise, this is some crazy unknown case.  Report the issue at the
          // location provided by the isIntegerConstantExpr failed check.
          Diag(Loc, diag::err_in_class_initializer_non_constant)
            << Init->getSourceRange();
          VDecl->setInvalidDecl();
        }
  
      // We allow foldable floating-point constants as an extension.
      } else if (DclT->isFloatingType()) { // also permits complex, which is ok
        // In C++98, this is a GNU extension. In C++11, it is not, but we support
        // it anyway and provide a fixit to add the 'constexpr'.
        if (getLangOpts().CPlusPlus11) {
          Diag(VDecl->getLocation(),
               diag::ext_in_class_initializer_float_type_cxx11)
              << DclT << Init->getSourceRange();
          Diag(VDecl->getBeginLoc(),
               diag::note_in_class_initializer_float_type_cxx11)
              << FixItHint::CreateInsertion(VDecl->getBeginLoc(), "constexpr ");
        } else {
          Diag(VDecl->getLocation(), diag::ext_in_class_initializer_float_type)
            << DclT << Init->getSourceRange();
  
          if (!Init->isValueDependent() && !Init->isEvaluatable(Context)) {
            Diag(Init->getExprLoc(), diag::err_in_class_initializer_non_constant)
              << Init->getSourceRange();
            VDecl->setInvalidDecl();
          }
        }
  
      // Suggest adding 'constexpr' in C++11 for literal types.
      } else if (getLangOpts().CPlusPlus11 && DclT->isLiteralType(Context)) {
        Diag(VDecl->getLocation(), diag::err_in_class_initializer_literal_type)
            << DclT << Init->getSourceRange()
            << FixItHint::CreateInsertion(VDecl->getBeginLoc(), "constexpr ");
        VDecl->setConstexpr(true);
  
      } else {
        Diag(VDecl->getLocation(), diag::err_in_class_initializer_bad_type)
          << DclT << Init->getSourceRange();
        VDecl->setInvalidDecl();
      }
    } else if (VDecl->isFileVarDecl()) {
      // In C, extern is typically used to avoid tentative definitions when
      // declaring variables in headers, but adding an intializer makes it a
      // definition. This is somewhat confusing, so GCC and Clang both warn on it.
      // In C++, extern is often used to give implictly static const variables
      // external linkage, so don't warn in that case. If selectany is present,
      // this might be header code intended for C and C++ inclusion, so apply the
      // C++ rules.
      if (VDecl->getStorageClass() == SC_Extern &&
          ((!getLangOpts().CPlusPlus && !VDecl->hasAttr<SelectAnyAttr>()) ||
           !Context.getBaseElementType(VDecl->getType()).isConstQualified()) &&
          !(getLangOpts().CPlusPlus && VDecl->isExternC()) &&
          !isTemplateInstantiation(VDecl->getTemplateSpecializationKind()))
        Diag(VDecl->getLocation(), diag::warn_extern_init);
  
      // In Microsoft C++ mode, a const variable defined in namespace scope has
      // external linkage by default if the variable is declared with
      // __declspec(dllexport).
      if (Context.getTargetInfo().getCXXABI().isMicrosoft() &&
          getLangOpts().CPlusPlus && VDecl->getType().isConstQualified() &&
          VDecl->hasAttr<DLLExportAttr>() && VDecl->getDefinition())
        VDecl->setStorageClass(SC_Extern);
  
      // C99 6.7.8p4. All file scoped initializers need to be constant.
      if (!getLangOpts().CPlusPlus && !VDecl->isInvalidDecl())
        CheckForConstantInitializer(Init, DclT);
    }
  
    // We will represent direct-initialization similarly to copy-initialization:
    //    int x(1);  -as-> int x = 1;
    //    ClassType x(a,b,c); -as-> ClassType x = ClassType(a,b,c);
    //
    // Clients that want to distinguish between the two forms, can check for
    // direct initializer using VarDecl::getInitStyle().
    // A major benefit is that clients that don't particularly care about which
    // exactly form was it (like the CodeGen) can handle both cases without
    // special case code.
  
    // C++ 8.5p11:
    // The form of initialization (using parentheses or '=') is generally
    // insignificant, but does matter when the entity being initialized has a
    // class type.
    if (CXXDirectInit) {
      assert(DirectInit && "Call-style initializer must be direct init.");
      VDecl->setInitStyle(VarDecl::CallInit);
    } else if (DirectInit) {
      // This must be list-initialization. No other way is direct-initialization.
      VDecl->setInitStyle(VarDecl::ListInit);
    }
  
    CheckCompleteVariableDeclaration(VDecl);
  }
  
  /// ActOnInitializerError - Given that there was an error parsing an
  /// initializer for the given declaration, try to return to some form
  /// of sanity.
  void Sema::ActOnInitializerError(Decl *D) {
    // Our main concern here is re-establishing invariants like "a
    // variable's type is either dependent or complete".
    if (!D || D->isInvalidDecl()) return;
  
    VarDecl *VD = dyn_cast<VarDecl>(D);
    if (!VD) return;
  
    // Bindings are not usable if we can't make sense of the initializer.
    if (auto *DD = dyn_cast<DecompositionDecl>(D))
      for (auto *BD : DD->bindings())
        BD->setInvalidDecl();
  
    // Auto types are meaningless if we can't make sense of the initializer.
    if (ParsingInitForAutoVars.count(D)) {
      D->setInvalidDecl();
      return;
    }
  
    QualType Ty = VD->getType();
    if (Ty->isDependentType()) return;
  
    // Require a complete type.
    if (RequireCompleteType(VD->getLocation(),
                            Context.getBaseElementType(Ty),
                            diag::err_typecheck_decl_incomplete_type)) {
      VD->setInvalidDecl();
      return;
    }
  
    // Require a non-abstract type.
    if (RequireNonAbstractType(VD->getLocation(), Ty,
                               diag::err_abstract_type_in_decl,
                               AbstractVariableType)) {
      VD->setInvalidDecl();
      return;
    }
  
    // Don't bother complaining about constructors or destructors,
    // though.
  }
  
  void Sema::ActOnUninitializedDecl(Decl *RealDecl) {
    // If there is no declaration, there was an error parsing it. Just ignore it.
    if (!RealDecl)
      return;
  
    if (VarDecl *Var = dyn_cast<VarDecl>(RealDecl)) {
      QualType Type = Var->getType();
  
      // C++1z [dcl.dcl]p1 grammar implies that an initializer is mandatory.
      if (isa<DecompositionDecl>(RealDecl)) {
        Diag(Var->getLocation(), diag::err_decomp_decl_requires_init) << Var;
        Var->setInvalidDecl();
        return;
      }
  
      Expr *TmpInit = nullptr;
      if (Type->isUndeducedType() &&
          DeduceVariableDeclarationType(Var, false, TmpInit))
        return;
  
      // C++11 [class.static.data]p3: A static data member can be declared with
      // the constexpr specifier; if so, its declaration shall specify
      // a brace-or-equal-initializer.
      // C++11 [dcl.constexpr]p1: The constexpr specifier shall be applied only to
      // the definition of a variable [...] or the declaration of a static data
      // member.
      if (Var->isConstexpr() && !Var->isThisDeclarationADefinition() &&
          !Var->isThisDeclarationADemotedDefinition()) {
        if (Var->isStaticDataMember()) {
          // C++1z removes the relevant rule; the in-class declaration is always
          // a definition there.
          if (!getLangOpts().CPlusPlus17) {
            Diag(Var->getLocation(),
                 diag::err_constexpr_static_mem_var_requires_init)
              << Var->getDeclName();
            Var->setInvalidDecl();
            return;
          }
        } else {
          Diag(Var->getLocation(), diag::err_invalid_constexpr_var_decl);
          Var->setInvalidDecl();
          return;
        }
      }
  
      // OpenCL v1.1 s6.5.3: variables declared in the constant address space must
      // be initialized.
      if (!Var->isInvalidDecl() &&
          Var->getType().getAddressSpace() == LangAS::opencl_constant &&
          Var->getStorageClass() != SC_Extern && !Var->getInit()) {
        Diag(Var->getLocation(), diag::err_opencl_constant_no_init);
        Var->setInvalidDecl();
        return;
      }
  
      switch (Var->isThisDeclarationADefinition()) {
      case VarDecl::Definition:
        if (!Var->isStaticDataMember() || !Var->getAnyInitializer())
          break;
  
        // We have an out-of-line definition of a static data member
        // that has an in-class initializer, so we type-check this like
        // a declaration.
        //
        LLVM_FALLTHROUGH;
  
      case VarDecl::DeclarationOnly:
        // It's only a declaration.
  
        // Block scope. C99 6.7p7: If an identifier for an object is
        // declared with no linkage (C99 6.2.2p6), the type for the
        // object shall be complete.
        if (!Type->isDependentType() && Var->isLocalVarDecl() &&
            !Var->hasLinkage() && !Var->isInvalidDecl() &&
            RequireCompleteType(Var->getLocation(), Type,
                                diag::err_typecheck_decl_incomplete_type))
          Var->setInvalidDecl();
  
        // Make sure that the type is not abstract.
        if (!Type->isDependentType() && !Var->isInvalidDecl() &&
            RequireNonAbstractType(Var->getLocation(), Type,
                                   diag::err_abstract_type_in_decl,
                                   AbstractVariableType))
          Var->setInvalidDecl();
        if (!Type->isDependentType() && !Var->isInvalidDecl() &&
            Var->getStorageClass() == SC_PrivateExtern) {
          Diag(Var->getLocation(), diag::warn_private_extern);
          Diag(Var->getLocation(), diag::note_private_extern);
        }
  
        return;
  
      case VarDecl::TentativeDefinition:
        // File scope. C99 6.9.2p2: A declaration of an identifier for an
        // object that has file scope without an initializer, and without a
        // storage-class specifier or with the storage-class specifier "static",
        // constitutes a tentative definition. Note: A tentative definition with
        // external linkage is valid (C99 6.2.2p5).
        if (!Var->isInvalidDecl()) {
          if (const IncompleteArrayType *ArrayT
                                      = Context.getAsIncompleteArrayType(Type)) {
            if (RequireCompleteType(Var->getLocation(),
                                    ArrayT->getElementType(),
                                    diag::err_illegal_decl_array_incomplete_type))
              Var->setInvalidDecl();
          } else if (Var->getStorageClass() == SC_Static) {
            // C99 6.9.2p3: If the declaration of an identifier for an object is
            // a tentative definition and has internal linkage (C99 6.2.2p3), the
            // declared type shall not be an incomplete type.
            // NOTE: code such as the following
            //     static struct s;
            //     struct s { int a; };
            // is accepted by gcc. Hence here we issue a warning instead of
            // an error and we do not invalidate the static declaration.
            // NOTE: to avoid multiple warnings, only check the first declaration.
            if (Var->isFirstDecl())
              RequireCompleteType(Var->getLocation(), Type,
                                  diag::ext_typecheck_decl_incomplete_type);
          }
        }
  
        // Record the tentative definition; we're done.
        if (!Var->isInvalidDecl())
          TentativeDefinitions.push_back(Var);
        return;
      }
  
      // Provide a specific diagnostic for uninitialized variable
      // definitions with incomplete array type.
      if (Type->isIncompleteArrayType()) {
        Diag(Var->getLocation(),
             diag::err_typecheck_incomplete_array_needs_initializer);
        Var->setInvalidDecl();
        return;
      }
  
      // Provide a specific diagnostic for uninitialized variable
      // definitions with reference type.
      if (Type->isReferenceType()) {
        Diag(Var->getLocation(), diag::err_reference_var_requires_init)
          << Var->getDeclName()
          << SourceRange(Var->getLocation(), Var->getLocation());
        Var->setInvalidDecl();
        return;
      }
  
      // Do not attempt to type-check the default initializer for a
      // variable with dependent type.
      if (Type->isDependentType())
        return;
  
      if (Var->isInvalidDecl())
        return;
  
      if (!Var->hasAttr<AliasAttr>()) {
        if (RequireCompleteType(Var->getLocation(),
                                Context.getBaseElementType(Type),
                                diag::err_typecheck_decl_incomplete_type)) {
          Var->setInvalidDecl();
          return;
        }
      } else {
        return;
      }
  
      // The variable can not have an abstract class type.
      if (RequireNonAbstractType(Var->getLocation(), Type,
                                 diag::err_abstract_type_in_decl,
                                 AbstractVariableType)) {
        Var->setInvalidDecl();
        return;
      }
  
      // Check for jumps past the implicit initializer.  C++0x
      // clarifies that this applies to a "variable with automatic
      // storage duration", not a "local variable".
      // C++11 [stmt.dcl]p3
      //   A program that jumps from a point where a variable with automatic
      //   storage duration is not in scope to a point where it is in scope is
      //   ill-formed unless the variable has scalar type, class type with a
      //   trivial default constructor and a trivial destructor, a cv-qualified
      //   version of one of these types, or an array of one of the preceding
      //   types and is declared without an initializer.
      if (getLangOpts().CPlusPlus && Var->hasLocalStorage()) {
        if (const RecordType *Record
              = Context.getBaseElementType(Type)->getAs<RecordType>()) {
          CXXRecordDecl *CXXRecord = cast<CXXRecordDecl>(Record->getDecl());
          // Mark the function (if we're in one) for further checking even if the
          // looser rules of C++11 do not require such checks, so that we can
          // diagnose incompatibilities with C++98.
          if (!CXXRecord->isPOD())
            setFunctionHasBranchProtectedScope();
        }
      }
  
      // C++03 [dcl.init]p9:
      //   If no initializer is specified for an object, and the
      //   object is of (possibly cv-qualified) non-POD class type (or
      //   array thereof), the object shall be default-initialized; if
      //   the object is of const-qualified type, the underlying class
      //   type shall have a user-declared default
      //   constructor. Otherwise, if no initializer is specified for
      //   a non- static object, the object and its subobjects, if
      //   any, have an indeterminate initial value); if the object
      //   or any of its subobjects are of const-qualified type, the
      //   program is ill-formed.
      // C++0x [dcl.init]p11:
      //   If no initializer is specified for an object, the object is
      //   default-initialized; [...].
      InitializedEntity Entity = InitializedEntity::InitializeVariable(Var);
      InitializationKind Kind
        = InitializationKind::CreateDefault(Var->getLocation());
  
      InitializationSequence InitSeq(*this, Entity, Kind, None);
      ExprResult Init = InitSeq.Perform(*this, Entity, Kind, None);
      if (Init.isInvalid())
        Var->setInvalidDecl();
      else if (Init.get()) {
        Var->setInit(MaybeCreateExprWithCleanups(Init.get()));
        // This is important for template substitution.
        Var->setInitStyle(VarDecl::CallInit);
      }
  
      CheckCompleteVariableDeclaration(Var);
    }
  }
  
  void Sema::ActOnCXXForRangeDecl(Decl *D) {
    // If there is no declaration, there was an error parsing it. Ignore it.
    if (!D)
      return;
  
    VarDecl *VD = dyn_cast<VarDecl>(D);
    if (!VD) {
      Diag(D->getLocation(), diag::err_for_range_decl_must_be_var);
      D->setInvalidDecl();
      return;
    }
  
    VD->setCXXForRangeDecl(true);
  
    // for-range-declaration cannot be given a storage class specifier.
    int Error = -1;
    switch (VD->getStorageClass()) {
    case SC_None:
      break;
    case SC_Extern:
      Error = 0;
      break;
    case SC_Static:
      Error = 1;
      break;
    case SC_PrivateExtern:
      Error = 2;
      break;
    case SC_Auto:
      Error = 3;
      break;
    case SC_Register:
      Error = 4;
      break;
    }
    if (Error != -1) {
      Diag(VD->getOuterLocStart(), diag::err_for_range_storage_class)
        << VD->getDeclName() << Error;
      D->setInvalidDecl();
    }
  }
  
  StmtResult
  Sema::ActOnCXXForRangeIdentifier(Scope *S, SourceLocation IdentLoc,
                                   IdentifierInfo *Ident,
                                   ParsedAttributes &Attrs,
                                   SourceLocation AttrEnd) {
    // C++1y [stmt.iter]p1:
    //   A range-based for statement of the form
    //      for ( for-range-identifier : for-range-initializer ) statement
    //   is equivalent to
    //      for ( auto&& for-range-identifier : for-range-initializer ) statement
    DeclSpec DS(Attrs.getPool().getFactory());
  
    const char *PrevSpec;
    unsigned DiagID;
    DS.SetTypeSpecType(DeclSpec::TST_auto, IdentLoc, PrevSpec, DiagID,
                       getPrintingPolicy());
  
    Declarator D(DS, DeclaratorContext::ForContext);
    D.SetIdentifier(Ident, IdentLoc);
    D.takeAttributes(Attrs, AttrEnd);
  
    ParsedAttributes EmptyAttrs(Attrs.getPool().getFactory());
    D.AddTypeInfo(DeclaratorChunk::getReference(0, IdentLoc, /*lvalue*/ false),
                  IdentLoc);
    Decl *Var = ActOnDeclarator(S, D);
    cast<VarDecl>(Var)->setCXXForRangeDecl(true);
    FinalizeDeclaration(Var);
    return ActOnDeclStmt(FinalizeDeclaratorGroup(S, DS, Var), IdentLoc,
                         AttrEnd.isValid() ? AttrEnd : IdentLoc);
  }
  
  void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
    if (var->isInvalidDecl()) return;
  
    if (getLangOpts().OpenCL) {
      // OpenCL v2.0 s6.12.5 - Every block variable declaration must have an
      // initialiser
      if (var->getTypeSourceInfo()->getType()->isBlockPointerType() &&
          !var->hasInit()) {
        Diag(var->getLocation(), diag::err_opencl_invalid_block_declaration)
            << 1 /*Init*/;
        var->setInvalidDecl();
        return;
      }
    }
  
    // In Objective-C, don't allow jumps past the implicit initialization of a
    // local retaining variable.
    if (getLangOpts().ObjC &&
        var->hasLocalStorage()) {
      switch (var->getType().getObjCLifetime()) {
      case Qualifiers::OCL_None:
      case Qualifiers::OCL_ExplicitNone:
      case Qualifiers::OCL_Autoreleasing:
        break;
  
      case Qualifiers::OCL_Weak:
      case Qualifiers::OCL_Strong:
        setFunctionHasBranchProtectedScope();
        break;
      }
    }
  
    if (var->hasLocalStorage() &&
        var->getType().isDestructedType() == QualType::DK_nontrivial_c_struct)
      setFunctionHasBranchProtectedScope();
  
    // Warn about externally-visible variables being defined without a
    // prior declaration.  We only want to do this for global
    // declarations, but we also specifically need to avoid doing it for
    // class members because the linkage of an anonymous class can
    // change if it's later given a typedef name.
    if (var->isThisDeclarationADefinition() &&
        var->getDeclContext()->getRedeclContext()->isFileContext() &&
        var->isExternallyVisible() && var->hasLinkage() &&
        !var->isInline() && !var->getDescribedVarTemplate() &&
        !isTemplateInstantiation(var->getTemplateSpecializationKind()) &&
        !getDiagnostics().isIgnored(diag::warn_missing_variable_declarations,
                                    var->getLocation())) {
      // Find a previous declaration that's not a definition.
      VarDecl *prev = var->getPreviousDecl();
      while (prev && prev->isThisDeclarationADefinition())
        prev = prev->getPreviousDecl();
  
      if (!prev)
        Diag(var->getLocation(), diag::warn_missing_variable_declarations) << var;
    }
  
    // Cache the result of checking for constant initialization.
    Optional<bool> CacheHasConstInit;
    const Expr *CacheCulprit;
    auto checkConstInit = [&]() mutable {
      if (!CacheHasConstInit)
        CacheHasConstInit = var->getInit()->isConstantInitializer(
              Context, var->getType()->isReferenceType(), &CacheCulprit);
      return *CacheHasConstInit;
    };
  
    if (var->getTLSKind() == VarDecl::TLS_Static) {
      if (var->getType().isDestructedType()) {
        // GNU C++98 edits for __thread, [basic.start.term]p3:
        //   The type of an object with thread storage duration shall not
        //   have a non-trivial destructor.
        Diag(var->getLocation(), diag::err_thread_nontrivial_dtor);
        if (getLangOpts().CPlusPlus11)
          Diag(var->getLocation(), diag::note_use_thread_local);
      } else if (getLangOpts().CPlusPlus && var->hasInit()) {
        if (!checkConstInit()) {
          // GNU C++98 edits for __thread, [basic.start.init]p4:
          //   An object of thread storage duration shall not require dynamic
          //   initialization.
          // FIXME: Need strict checking here.
          Diag(CacheCulprit->getExprLoc(), diag::err_thread_dynamic_init)
            << CacheCulprit->getSourceRange();
          if (getLangOpts().CPlusPlus11)
            Diag(var->getLocation(), diag::note_use_thread_local);
        }
      }
    }
  
    // Apply section attributes and pragmas to global variables.
    bool GlobalStorage = var->hasGlobalStorage();
    if (GlobalStorage && var->isThisDeclarationADefinition() &&
        !inTemplateInstantiation()) {
      PragmaStack<StringLiteral *> *Stack = nullptr;
      int SectionFlags = ASTContext::PSF_Implicit | ASTContext::PSF_Read;
      if (var->getType().isConstQualified())
        Stack = &ConstSegStack;
      else if (!var->getInit()) {
        Stack = &BSSSegStack;
        SectionFlags |= ASTContext::PSF_Write;
      } else {
        Stack = &DataSegStack;
        SectionFlags |= ASTContext::PSF_Write;
      }
      if (Stack->CurrentValue && !var->hasAttr<SectionAttr>()) {
        var->addAttr(SectionAttr::CreateImplicit(
            Context, SectionAttr::Declspec_allocate,
            Stack->CurrentValue->getString(), Stack->CurrentPragmaLocation));
      }
      if (const SectionAttr *SA = var->getAttr<SectionAttr>())
        if (UnifySection(SA->getName(), SectionFlags, var))
          var->dropAttr<SectionAttr>();
  
      // Apply the init_seg attribute if this has an initializer.  If the
      // initializer turns out to not be dynamic, we'll end up ignoring this
      // attribute.
      if (CurInitSeg && var->getInit())
        var->addAttr(InitSegAttr::CreateImplicit(Context, CurInitSeg->getString(),
                                                 CurInitSegLoc));
    }
  
    // All the following checks are C++ only.
    if (!getLangOpts().CPlusPlus) {
        // If this variable must be emitted, add it as an initializer for the
        // current module.
       if (Context.DeclMustBeEmitted(var) && !ModuleScopes.empty())
         Context.addModuleInitializer(ModuleScopes.back().Module, var);
       return;
    }
  
    if (auto *DD = dyn_cast<DecompositionDecl>(var))
      CheckCompleteDecompositionDeclaration(DD);
  
    QualType type = var->getType();
    if (type->isDependentType()) return;
  
    if (var->hasAttr<BlocksAttr>())
      getCurFunction()->addByrefBlockVar(var);
  
    Expr *Init = var->getInit();
    bool IsGlobal = GlobalStorage && !var->isStaticLocal();
    QualType baseType = Context.getBaseElementType(type);
  
    if (Init && !Init->isValueDependent()) {
      if (var->isConstexpr()) {
        SmallVector<PartialDiagnosticAt, 8> Notes;
        if (!var->evaluateValue(Notes) || !var->isInitICE()) {
          SourceLocation DiagLoc = var->getLocation();
          // If the note doesn't add any useful information other than a source
          // location, fold it into the primary diagnostic.
          if (Notes.size() == 1 && Notes[0].second.getDiagID() ==
                diag::note_invalid_subexpr_in_const_expr) {
            DiagLoc = Notes[0].first;
            Notes.clear();
          }
          Diag(DiagLoc, diag::err_constexpr_var_requires_const_init)
            << var << Init->getSourceRange();
          for (unsigned I = 0, N = Notes.size(); I != N; ++I)
            Diag(Notes[I].first, Notes[I].second);
        }
      } else if (var->isUsableInConstantExpressions(Context)) {
        // Check whether the initializer of a const variable of integral or
        // enumeration type is an ICE now, since we can't tell whether it was
        // initialized by a constant expression if we check later.
        var->checkInitIsICE();
      }
  
      // Don't emit further diagnostics about constexpr globals since they
      // were just diagnosed.
      if (!var->isConstexpr() && GlobalStorage &&
              var->hasAttr<RequireConstantInitAttr>()) {
        // FIXME: Need strict checking in C++03 here.
        bool DiagErr = getLangOpts().CPlusPlus11
            ? !var->checkInitIsICE() : !checkConstInit();
        if (DiagErr) {
          auto attr = var->getAttr<RequireConstantInitAttr>();
          Diag(var->getLocation(), diag::err_require_constant_init_failed)
            << Init->getSourceRange();
          Diag(attr->getLocation(), diag::note_declared_required_constant_init_here)
            << attr->getRange();
          if (getLangOpts().CPlusPlus11) {
            APValue Value;
            SmallVector<PartialDiagnosticAt, 8> Notes;
            Init->EvaluateAsInitializer(Value, getASTContext(), var, Notes);
            for (auto &it : Notes)
              Diag(it.first, it.second);
          } else {
            Diag(CacheCulprit->getExprLoc(),
                 diag::note_invalid_subexpr_in_const_expr)
                << CacheCulprit->getSourceRange();
          }
        }
      }
      else if (!var->isConstexpr() && IsGlobal &&
               !getDiagnostics().isIgnored(diag::warn_global_constructor,
                                      var->getLocation())) {
        // Warn about globals which don't have a constant initializer.  Don't
        // warn about globals with a non-trivial destructor because we already
        // warned about them.
        CXXRecordDecl *RD = baseType->getAsCXXRecordDecl();
        if (!(RD && !RD->hasTrivialDestructor())) {
          if (!checkConstInit())
            Diag(var->getLocation(), diag::warn_global_constructor)
              << Init->getSourceRange();
        }
      }
    }
  
    // Require the destructor.
    if (const RecordType *recordType = baseType->getAs<RecordType>())
      FinalizeVarWithDestructor(var, recordType);
  
    // If this variable must be emitted, add it as an initializer for the current
    // module.
    if (Context.DeclMustBeEmitted(var) && !ModuleScopes.empty())
      Context.addModuleInitializer(ModuleScopes.back().Module, var);
  }
  
  /// Determines if a variable's alignment is dependent.
  static bool hasDependentAlignment(VarDecl *VD) {
    if (VD->getType()->isDependentType())
      return true;
    for (auto *I : VD->specific_attrs<AlignedAttr>())
      if (I->isAlignmentDependent())
        return true;
    return false;
  }
  
  /// Check if VD needs to be dllexport/dllimport due to being in a
  /// dllexport/import function.
  void Sema::CheckStaticLocalForDllExport(VarDecl *VD) {
    assert(VD->isStaticLocal());
  
    auto *FD = dyn_cast_or_null<FunctionDecl>(VD->getParentFunctionOrMethod());
  
    // Find outermost function when VD is in lambda function.
    while (FD && !getDLLAttr(FD) &&
           !FD->hasAttr<DLLExportStaticLocalAttr>() &&
           !FD->hasAttr<DLLImportStaticLocalAttr>()) {
      FD = dyn_cast_or_null<FunctionDecl>(FD->getParentFunctionOrMethod());
    }
  
    if (!FD)
      return;
  
    // Static locals inherit dll attributes from their function.
    if (Attr *A = getDLLAttr(FD)) {
      auto *NewAttr = cast<InheritableAttr>(A->clone(getASTContext()));
      NewAttr->setInherited(true);
      VD->addAttr(NewAttr);
    } else if (Attr *A = FD->getAttr<DLLExportStaticLocalAttr>()) {
      auto *NewAttr = ::new (getASTContext()) DLLExportAttr(A->getRange(),
                                                            getASTContext(),
                                                            A->getSpellingListIndex());
      NewAttr->setInherited(true);
      VD->addAttr(NewAttr);
  
      // Export this function to enforce exporting this static variable even
      // if it is not used in this compilation unit.
      if (!FD->hasAttr<DLLExportAttr>())
        FD->addAttr(NewAttr);
  
    } else if (Attr *A = FD->getAttr<DLLImportStaticLocalAttr>()) {
      auto *NewAttr = ::new (getASTContext()) DLLImportAttr(A->getRange(),
                                                            getASTContext(),
                                                            A->getSpellingListIndex());
      NewAttr->setInherited(true);
      VD->addAttr(NewAttr);
    }
  }
  
  /// FinalizeDeclaration - called by ParseDeclarationAfterDeclarator to perform
  /// any semantic actions necessary after any initializer has been attached.
  void Sema::FinalizeDeclaration(Decl *ThisDecl) {
    // Note that we are no longer parsing the initializer for this declaration.
    ParsingInitForAutoVars.erase(ThisDecl);
  
    VarDecl *VD = dyn_cast_or_null<VarDecl>(ThisDecl);
    if (!VD)
      return;
  
    // Apply an implicit SectionAttr if '#pragma clang section bss|data|rodata' is active
    if (VD->hasGlobalStorage() && VD->isThisDeclarationADefinition() &&
        !inTemplateInstantiation() && !VD->hasAttr<SectionAttr>()) {
      if (PragmaClangBSSSection.Valid)
        VD->addAttr(PragmaClangBSSSectionAttr::CreateImplicit(Context,
                                                              PragmaClangBSSSection.SectionName,
                                                              PragmaClangBSSSection.PragmaLocation));
      if (PragmaClangDataSection.Valid)
        VD->addAttr(PragmaClangDataSectionAttr::CreateImplicit(Context,
                                                               PragmaClangDataSection.SectionName,
                                                               PragmaClangDataSection.PragmaLocation));
      if (PragmaClangRodataSection.Valid)
        VD->addAttr(PragmaClangRodataSectionAttr::CreateImplicit(Context,
                                                                 PragmaClangRodataSection.SectionName,
                                                                 PragmaClangRodataSection.PragmaLocation));
    }
  
    if (auto *DD = dyn_cast<DecompositionDecl>(ThisDecl)) {
      for (auto *BD : DD->bindings()) {
        FinalizeDeclaration(BD);
      }
    }
  
    checkAttributesAfterMerging(*this, *VD);
  
    // Perform TLS alignment check here after attributes attached to the variable
    // which may affect the alignment have been processed. Only perform the check
    // if the target has a maximum TLS alignment (zero means no constraints).
    if (unsigned MaxAlign = Context.getTargetInfo().getMaxTLSAlign()) {
      // Protect the check so that it's not performed on dependent types and
      // dependent alignments (we can't determine the alignment in that case).
      if (VD->getTLSKind() && !hasDependentAlignment(VD) &&
          !VD->isInvalidDecl()) {
        CharUnits MaxAlignChars = Context.toCharUnitsFromBits(MaxAlign);
        if (Context.getDeclAlign(VD) > MaxAlignChars) {
          Diag(VD->getLocation(), diag::err_tls_var_aligned_over_maximum)
            << (unsigned)Context.getDeclAlign(VD).getQuantity() << VD
            << (unsigned)MaxAlignChars.getQuantity();
        }
      }
    }
  
    if (VD->isStaticLocal()) {
      CheckStaticLocalForDllExport(VD);
  
      if (dyn_cast_or_null<FunctionDecl>(VD->getParentFunctionOrMethod())) {
        // CUDA 8.0 E.3.9.4: Within the body of a __device__ or __global__
        // function, only __shared__ variables or variables without any device
        // memory qualifiers may be declared with static storage class.
        // Note: It is unclear how a function-scope non-const static variable
        // without device memory qualifier is implemented, therefore only static
        // const variable without device memory qualifier is allowed.
        [&]() {
          if (!getLangOpts().CUDA)
            return;
          if (VD->hasAttr<CUDASharedAttr>())
            return;
          if (VD->getType().isConstQualified() &&
              !(VD->hasAttr<CUDADeviceAttr>() || VD->hasAttr<CUDAConstantAttr>()))
            return;
          if (CUDADiagIfDeviceCode(VD->getLocation(),
                                   diag::err_device_static_local_var)
              << CurrentCUDATarget())
            VD->setInvalidDecl();
        }();
      }
    }
  
    // Perform check for initializers of device-side global variables.
    // CUDA allows empty constructors as initializers (see E.2.3.1, CUDA
    // 7.5). We must also apply the same checks to all __shared__
    // variables whether they are local or not. CUDA also allows
    // constant initializers for __constant__ and __device__ variables.
    if (getLangOpts().CUDA)
      checkAllowedCUDAInitializer(VD);
  
    // Grab the dllimport or dllexport attribute off of the VarDecl.
    const InheritableAttr *DLLAttr = getDLLAttr(VD);
  
    // Imported static data members cannot be defined out-of-line.
    if (const auto *IA = dyn_cast_or_null<DLLImportAttr>(DLLAttr)) {
      if (VD->isStaticDataMember() && VD->isOutOfLine() &&
          VD->isThisDeclarationADefinition()) {
        // We allow definitions of dllimport class template static data members
        // with a warning.
        CXXRecordDecl *Context =
          cast<CXXRecordDecl>(VD->getFirstDecl()->getDeclContext());
        bool IsClassTemplateMember =
            isa<ClassTemplatePartialSpecializationDecl>(Context) ||
            Context->getDescribedClassTemplate();
  
        Diag(VD->getLocation(),
             IsClassTemplateMember
                 ? diag::warn_attribute_dllimport_static_field_definition
                 : diag::err_attribute_dllimport_static_field_definition);
        Diag(IA->getLocation(), diag::note_attribute);
        if (!IsClassTemplateMember)
          VD->setInvalidDecl();
      }
    }
  
    // dllimport/dllexport variables cannot be thread local, their TLS index
    // isn't exported with the variable.
    if (DLLAttr && VD->getTLSKind()) {
      auto *F = dyn_cast_or_null<FunctionDecl>(VD->getParentFunctionOrMethod());
      if (F && getDLLAttr(F)) {
        assert(VD->isStaticLocal());
        // But if this is a static local in a dlimport/dllexport function, the
        // function will never be inlined, which means the var would never be
        // imported, so having it marked import/export is safe.
      } else {
        Diag(VD->getLocation(), diag::err_attribute_dll_thread_local) << VD
                                                                      << DLLAttr;
        VD->setInvalidDecl();
      }
    }
  
    if (UsedAttr *Attr = VD->getAttr<UsedAttr>()) {
      if (!Attr->isInherited() && !VD->isThisDeclarationADefinition()) {
        Diag(Attr->getLocation(), diag::warn_attribute_ignored) << Attr;
        VD->dropAttr<UsedAttr>();
      }
    }
  
    const DeclContext *DC = VD->getDeclContext();
    // If there's a #pragma GCC visibility in scope, and this isn't a class
    // member, set the visibility of this variable.
    if (DC->getRedeclContext()->isFileContext() && VD->isExternallyVisible())
      AddPushedVisibilityAttribute(VD);
  
    // FIXME: Warn on unused var template partial specializations.
    if (VD->isFileVarDecl() && !isa<VarTemplatePartialSpecializationDecl>(VD))
      MarkUnusedFileScopedDecl(VD);
  
    // Now we have parsed the initializer and can update the table of magic
    // tag values.
    if (!VD->hasAttr<TypeTagForDatatypeAttr>() ||
        !VD->getType()->isIntegralOrEnumerationType())
      return;
  
    for (const auto *I : ThisDecl->specific_attrs<TypeTagForDatatypeAttr>()) {
      const Expr *MagicValueExpr = VD->getInit();
      if (!MagicValueExpr) {
        continue;
      }
      llvm::APSInt MagicValueInt;
      if (!MagicValueExpr->isIntegerConstantExpr(MagicValueInt, Context)) {
        Diag(I->getRange().getBegin(),
             diag::err_type_tag_for_datatype_not_ice)
          << LangOpts.CPlusPlus << MagicValueExpr->getSourceRange();
        continue;
      }
      if (MagicValueInt.getActiveBits() > 64) {
        Diag(I->getRange().getBegin(),
             diag::err_type_tag_for_datatype_too_large)
          << LangOpts.CPlusPlus << MagicValueExpr->getSourceRange();
        continue;
      }
      uint64_t MagicValue = MagicValueInt.getZExtValue();
      RegisterTypeTagForDatatype(I->getArgumentKind(),
                                 MagicValue,
                                 I->getMatchingCType(),
                                 I->getLayoutCompatible(),
                                 I->getMustBeNull());
    }
  }
  
  static bool hasDeducedAuto(DeclaratorDecl *DD) {
    auto *VD = dyn_cast<VarDecl>(DD);
    return VD && !VD->getType()->hasAutoForTrailingReturnType();
  }
  
  Sema::DeclGroupPtrTy Sema::FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
                                                     ArrayRef<Decl *> Group) {
    SmallVector<Decl*, 8> Decls;
  
    if (DS.isTypeSpecOwned())
      Decls.push_back(DS.getRepAsDecl());
  
    DeclaratorDecl *FirstDeclaratorInGroup = nullptr;
    DecompositionDecl *FirstDecompDeclaratorInGroup = nullptr;
    bool DiagnosedMultipleDecomps = false;
    DeclaratorDecl *FirstNonDeducedAutoInGroup = nullptr;
    bool DiagnosedNonDeducedAuto = false;
  
    for (unsigned i = 0, e = Group.size(); i != e; ++i) {
      if (Decl *D = Group[i]) {
        // For declarators, there are some additional syntactic-ish checks we need
        // to perform.
        if (auto *DD = dyn_cast<DeclaratorDecl>(D)) {
          if (!FirstDeclaratorInGroup)
            FirstDeclaratorInGroup = DD;
          if (!FirstDecompDeclaratorInGroup)
            FirstDecompDeclaratorInGroup = dyn_cast<DecompositionDecl>(D);
          if (!FirstNonDeducedAutoInGroup && DS.hasAutoTypeSpec() &&
              !hasDeducedAuto(DD))
            FirstNonDeducedAutoInGroup = DD;
  
          if (FirstDeclaratorInGroup != DD) {
            // A decomposition declaration cannot be combined with any other
            // declaration in the same group.
            if (FirstDecompDeclaratorInGroup && !DiagnosedMultipleDecomps) {
              Diag(FirstDecompDeclaratorInGroup->getLocation(),
                   diag::err_decomp_decl_not_alone)
                  << FirstDeclaratorInGroup->getSourceRange()
                  << DD->getSourceRange();
              DiagnosedMultipleDecomps = true;
            }
  
            // A declarator that uses 'auto' in any way other than to declare a
            // variable with a deduced type cannot be combined with any other
            // declarator in the same group.
            if (FirstNonDeducedAutoInGroup && !DiagnosedNonDeducedAuto) {
              Diag(FirstNonDeducedAutoInGroup->getLocation(),
                   diag::err_auto_non_deduced_not_alone)
                  << FirstNonDeducedAutoInGroup->getType()
                         ->hasAutoForTrailingReturnType()
                  << FirstDeclaratorInGroup->getSourceRange()
                  << DD->getSourceRange();
              DiagnosedNonDeducedAuto = true;
            }
          }
        }
  
        Decls.push_back(D);
      }
    }
  
    if (DeclSpec::isDeclRep(DS.getTypeSpecType())) {
      if (TagDecl *Tag = dyn_cast_or_null<TagDecl>(DS.getRepAsDecl())) {
        handleTagNumbering(Tag, S);
        if (FirstDeclaratorInGroup && !Tag->hasNameForLinkage() &&
            getLangOpts().CPlusPlus)
          Context.addDeclaratorForUnnamedTagDecl(Tag, FirstDeclaratorInGroup);
      }
    }
  
    return BuildDeclaratorGroup(Decls);
  }
  
  /// BuildDeclaratorGroup - convert a list of declarations into a declaration
  /// group, performing any necessary semantic checking.
  Sema::DeclGroupPtrTy
  Sema::BuildDeclaratorGroup(MutableArrayRef<Decl *> Group) {
    // C++14 [dcl.spec.auto]p7: (DR1347)
    //   If the type that replaces the placeholder type is not the same in each
    //   deduction, the program is ill-formed.
    if (Group.size() > 1) {
      QualType Deduced;
      VarDecl *DeducedDecl = nullptr;
      for (unsigned i = 0, e = Group.size(); i != e; ++i) {
        VarDecl *D = dyn_cast<VarDecl>(Group[i]);
        if (!D || D->isInvalidDecl())
          break;
        DeducedType *DT = D->getType()->getContainedDeducedType();
        if (!DT || DT->getDeducedType().isNull())
          continue;
        if (Deduced.isNull()) {
          Deduced = DT->getDeducedType();
          DeducedDecl = D;
        } else if (!Context.hasSameType(DT->getDeducedType(), Deduced)) {
          auto *AT = dyn_cast<AutoType>(DT);
          Diag(D->getTypeSourceInfo()->getTypeLoc().getBeginLoc(),
               diag::err_auto_different_deductions)
            << (AT ? (unsigned)AT->getKeyword() : 3)
            << Deduced << DeducedDecl->getDeclName()
            << DT->getDeducedType() << D->getDeclName()
            << DeducedDecl->getInit()->getSourceRange()
            << D->getInit()->getSourceRange();
          D->setInvalidDecl();
          break;
        }
      }
    }
  
    ActOnDocumentableDecls(Group);
  
    return DeclGroupPtrTy::make(
        DeclGroupRef::Create(Context, Group.data(), Group.size()));
  }
  
  void Sema::ActOnDocumentableDecl(Decl *D) {
    ActOnDocumentableDecls(D);
  }
  
  void Sema::ActOnDocumentableDecls(ArrayRef<Decl *> Group) {
    // Don't parse the comment if Doxygen diagnostics are ignored.
    if (Group.empty() || !Group[0])
      return;
  
    if (Diags.isIgnored(diag::warn_doc_param_not_found,
                        Group[0]->getLocation()) &&
        Diags.isIgnored(diag::warn_unknown_comment_command_name,
                        Group[0]->getLocation()))
      return;
  
    if (Group.size() >= 2) {
      // This is a decl group.  Normally it will contain only declarations
      // produced from declarator list.  But in case we have any definitions or
      // additional declaration references:
      //   'typedef struct S {} S;'
      //   'typedef struct S *S;'
      //   'struct S *pS;'
      // FinalizeDeclaratorGroup adds these as separate declarations.
      Decl *MaybeTagDecl = Group[0];
      if (MaybeTagDecl && isa<TagDecl>(MaybeTagDecl)) {
        Group = Group.slice(1);
      }
    }
  
    // See if there are any new comments that are not attached to a decl.
    ArrayRef<RawComment *> Comments = Context.getRawCommentList().getComments();
    if (!Comments.empty() &&
        !Comments.back()->isAttached()) {
      // There is at least one comment that not attached to a decl.
      // Maybe it should be attached to one of these decls?
      //
      // Note that this way we pick up not only comments that precede the
      // declaration, but also comments that *follow* the declaration -- thanks to
      // the lookahead in the lexer: we've consumed the semicolon and looked
      // ahead through comments.
      for (unsigned i = 0, e = Group.size(); i != e; ++i)
        Context.getCommentForDecl(Group[i], &PP);
    }
  }
  
  /// ActOnParamDeclarator - Called from Parser::ParseFunctionDeclarator()
  /// to introduce parameters into function prototype scope.
  Decl *Sema::ActOnParamDeclarator(Scope *S, Declarator &D) {
    const DeclSpec &DS = D.getDeclSpec();
  
    // Verify C99 6.7.5.3p2: The only SCS allowed is 'register'.
  
    // C++03 [dcl.stc]p2 also permits 'auto'.
    StorageClass SC = SC_None;
    if (DS.getStorageClassSpec() == DeclSpec::SCS_register) {
      SC = SC_Register;
      // In C++11, the 'register' storage class specifier is deprecated.
      // In C++17, it is not allowed, but we tolerate it as an extension.
      if (getLangOpts().CPlusPlus11) {
        Diag(DS.getStorageClassSpecLoc(),
             getLangOpts().CPlusPlus17 ? diag::ext_register_storage_class
                                       : diag::warn_deprecated_register)
          << FixItHint::CreateRemoval(DS.getStorageClassSpecLoc());
      }
    } else if (getLangOpts().CPlusPlus &&
               DS.getStorageClassSpec() == DeclSpec::SCS_auto) {
      SC = SC_Auto;
    } else if (DS.getStorageClassSpec() != DeclSpec::SCS_unspecified) {
      Diag(DS.getStorageClassSpecLoc(),
           diag::err_invalid_storage_class_in_func_decl);
      D.getMutableDeclSpec().ClearStorageClassSpecs();
    }
  
    if (DeclSpec::TSCS TSCS = DS.getThreadStorageClassSpec())
      Diag(DS.getThreadStorageClassSpecLoc(), diag::err_invalid_thread)
        << DeclSpec::getSpecifierName(TSCS);
    if (DS.isInlineSpecified())
      Diag(DS.getInlineSpecLoc(), diag::err_inline_non_function)
          << getLangOpts().CPlusPlus17;
    if (DS.isConstexprSpecified())
      Diag(DS.getConstexprSpecLoc(), diag::err_invalid_constexpr)
        << 0;
  
    DiagnoseFunctionSpecifiers(DS);
  
    TypeSourceInfo *TInfo = GetTypeForDeclarator(D, S);
    QualType parmDeclType = TInfo->getType();
  
    if (getLangOpts().CPlusPlus) {
      // Check that there are no default arguments inside the type of this
      // parameter.
      CheckExtraCXXDefaultArguments(D);
  
      // Parameter declarators cannot be qualified (C++ [dcl.meaning]p1).
      if (D.getCXXScopeSpec().isSet()) {
        Diag(D.getIdentifierLoc(), diag::err_qualified_param_declarator)
          << D.getCXXScopeSpec().getRange();
        D.getCXXScopeSpec().clear();
      }
    }
  
    // Ensure we have a valid name
    IdentifierInfo *II = nullptr;
    if (D.hasName()) {
      II = D.getIdentifier();
      if (!II) {
        Diag(D.getIdentifierLoc(), diag::err_bad_parameter_name)
          << GetNameForDeclarator(D).getName();
        D.setInvalidType(true);
      }
    }
  
    // Check for redeclaration of parameters, e.g. int foo(int x, int x);
    if (II) {
      LookupResult R(*this, II, D.getIdentifierLoc(), LookupOrdinaryName,
                     ForVisibleRedeclaration);
      LookupName(R, S);
      if (R.isSingleResult()) {
        NamedDecl *PrevDecl = R.getFoundDecl();
        if (PrevDecl->isTemplateParameter()) {
          // Maybe we will complain about the shadowed template parameter.
          DiagnoseTemplateParameterShadow(D.getIdentifierLoc(), PrevDecl);
          // Just pretend that we didn't see the previous declaration.
          PrevDecl = nullptr;
        } else if (S->isDeclScope(PrevDecl)) {
          Diag(D.getIdentifierLoc(), diag::err_param_redefinition) << II;
          Diag(PrevDecl->getLocation(), diag::note_previous_declaration);
  
          // Recover by removing the name
          II = nullptr;
          D.SetIdentifier(nullptr, D.getIdentifierLoc());
          D.setInvalidType(true);
        }
      }
    }
  
    // Temporarily put parameter variables in the translation unit, not
    // the enclosing context.  This prevents them from accidentally
    // looking like class members in C++.
    ParmVarDecl *New =
        CheckParameter(Context.getTranslationUnitDecl(), D.getBeginLoc(),
                       D.getIdentifierLoc(), II, parmDeclType, TInfo, SC);
  
    if (D.isInvalidType())
      New->setInvalidDecl();
  
    assert(S->isFunctionPrototypeScope());
    assert(S->getFunctionPrototypeDepth() >= 1);
    New->setScopeInfo(S->getFunctionPrototypeDepth() - 1,
                      S->getNextFunctionPrototypeIndex());
  
    // Add the parameter declaration into this scope.
    S->AddDecl(New);
    if (II)
      IdResolver.AddDecl(New);
  
    ProcessDeclAttributes(S, New, D);
  
    if (D.getDeclSpec().isModulePrivateSpecified())
      Diag(New->getLocation(), diag::err_module_private_local)
        << 1 << New->getDeclName()
        << SourceRange(D.getDeclSpec().getModulePrivateSpecLoc())
        << FixItHint::CreateRemoval(D.getDeclSpec().getModulePrivateSpecLoc());
  
    if (New->hasAttr<BlocksAttr>()) {
      Diag(New->getLocation(), diag::err_block_on_nonlocal);
    }
    return New;
  }
  
  /// Synthesizes a variable for a parameter arising from a
  /// typedef.
  ParmVarDecl *Sema::BuildParmVarDeclForTypedef(DeclContext *DC,
                                                SourceLocation Loc,
                                                QualType T) {
    /* FIXME: setting StartLoc == Loc.
       Would it be worth to modify callers so as to provide proper source
       location for the unnamed parameters, embedding the parameter's type? */
    ParmVarDecl *Param = ParmVarDecl::Create(Context, DC, Loc, Loc, nullptr,
                                  T, Context.getTrivialTypeSourceInfo(T, Loc),
                                             SC_None, nullptr);
    Param->setImplicit();
    return Param;
  }
  
  void Sema::DiagnoseUnusedParameters(ArrayRef<ParmVarDecl *> Parameters) {
    // Don't diagnose unused-parameter errors in template instantiations; we
    // will already have done so in the template itself.
    if (inTemplateInstantiation())
      return;
  
    for (const ParmVarDecl *Parameter : Parameters) {
      if (!Parameter->isReferenced() && Parameter->getDeclName() &&
          !Parameter->hasAttr<UnusedAttr>()) {
        Diag(Parameter->getLocation(), diag::warn_unused_parameter)
          << Parameter->getDeclName();
      }
    }
  }
  
  void Sema::DiagnoseSizeOfParametersAndReturnValue(
      ArrayRef<ParmVarDecl *> Parameters, QualType ReturnTy, NamedDecl *D) {
    if (LangOpts.NumLargeByValueCopy == 0) // No check.
      return;
  
    // Warn if the return value is pass-by-value and larger than the specified
    // threshold.
    if (!ReturnTy->isDependentType() && ReturnTy.isPODType(Context)) {
      unsigned Size = Context.getTypeSizeInChars(ReturnTy).getQuantity();
      if (Size > LangOpts.NumLargeByValueCopy)
        Diag(D->getLocation(), diag::warn_return_value_size)
            << D->getDeclName() << Size;
    }
  
    // Warn if any parameter is pass-by-value and larger than the specified
    // threshold.
    for (const ParmVarDecl *Parameter : Parameters) {
      QualType T = Parameter->getType();
      if (T->isDependentType() || !T.isPODType(Context))
        continue;
      unsigned Size = Context.getTypeSizeInChars(T).getQuantity();
      if (Size > LangOpts.NumLargeByValueCopy)
        Diag(Parameter->getLocation(), diag::warn_parameter_size)
            << Parameter->getDeclName() << Size;
    }
  }
  
  ParmVarDecl *Sema::CheckParameter(DeclContext *DC, SourceLocation StartLoc,
                                    SourceLocation NameLoc, IdentifierInfo *Name,
                                    QualType T, TypeSourceInfo *TSInfo,
                                    StorageClass SC) {
    // In ARC, infer a lifetime qualifier for appropriate parameter types.
    if (getLangOpts().ObjCAutoRefCount &&
        T.getObjCLifetime() == Qualifiers::OCL_None &&
        T->isObjCLifetimeType()) {
  
      Qualifiers::ObjCLifetime lifetime;
  
      // Special cases for arrays:
      //   - if it's const, use __unsafe_unretained
      //   - otherwise, it's an error
      if (T->isArrayType()) {
        if (!T.isConstQualified()) {
          if (DelayedDiagnostics.shouldDelayDiagnostics())
            DelayedDiagnostics.add(
                sema::DelayedDiagnostic::makeForbiddenType(
                NameLoc, diag::err_arc_array_param_no_ownership, T, false));
          else
            Diag(NameLoc, diag::err_arc_array_param_no_ownership)
                << TSInfo->getTypeLoc().getSourceRange();
        }
        lifetime = Qualifiers::OCL_ExplicitNone;
      } else {
        lifetime = T->getObjCARCImplicitLifetime();
      }
      T = Context.getLifetimeQualifiedType(T, lifetime);
    }
  
    ParmVarDecl *New = ParmVarDecl::Create(Context, DC, StartLoc, NameLoc, Name,
                                           Context.getAdjustedParameterType(T),
                                           TSInfo, SC, nullptr);
  
    // Parameters can not be abstract class types.
    // For record types, this is done by the AbstractClassUsageDiagnoser once
    // the class has been completely parsed.
    if (!CurContext->isRecord() &&
        RequireNonAbstractType(NameLoc, T, diag::err_abstract_type_in_decl,
                               AbstractParamType))
      New->setInvalidDecl();
  
    // Parameter declarators cannot be interface types. All ObjC objects are
    // passed by reference.
    if (T->isObjCObjectType()) {
      SourceLocation TypeEndLoc =
          getLocForEndOfToken(TSInfo->getTypeLoc().getEndLoc());
      Diag(NameLoc,
           diag::err_object_cannot_be_passed_returned_by_value) << 1 << T
        << FixItHint::CreateInsertion(TypeEndLoc, "*");
      T = Context.getObjCObjectPointerType(T);
      New->setType(T);
    }
  
    // ISO/IEC TR 18037 S6.7.3: "The type of an object with automatic storage
    // duration shall not be qualified by an address-space qualifier."
    // Since all parameters have automatic store duration, they can not have
    // an address space.
    if (T.getAddressSpace() != LangAS::Default &&
        // OpenCL allows function arguments declared to be an array of a type
        // to be qualified with an address space.
        !(getLangOpts().OpenCL &&
          (T->isArrayType() || T.getAddressSpace() == LangAS::opencl_private))) {
      Diag(NameLoc, diag::err_arg_with_address_space);
      New->setInvalidDecl();
    }
  
    return New;
  }
  
  void Sema::ActOnFinishKNRParamDeclarations(Scope *S, Declarator &D,
                                             SourceLocation LocAfterDecls) {
    DeclaratorChunk::FunctionTypeInfo &FTI = D.getFunctionTypeInfo();
  
    // Verify 6.9.1p6: 'every identifier in the identifier list shall be declared'
    // for a K&R function.
    if (!FTI.hasPrototype) {
      for (int i = FTI.NumParams; i != 0; /* decrement in loop */) {
        --i;
        if (FTI.Params[i].Param == nullptr) {
          SmallString<256> Code;
          llvm::raw_svector_ostream(Code)
              << "  int " << FTI.Params[i].Ident->getName() << ";\n";
          Diag(FTI.Params[i].IdentLoc, diag::ext_param_not_declared)
              << FTI.Params[i].Ident
              << FixItHint::CreateInsertion(LocAfterDecls, Code);
  
          // Implicitly declare the argument as type 'int' for lack of a better
          // type.
          AttributeFactory attrs;
          DeclSpec DS(attrs);
          const char* PrevSpec; // unused
          unsigned DiagID; // unused
          DS.SetTypeSpecType(DeclSpec::TST_int, FTI.Params[i].IdentLoc, PrevSpec,
                             DiagID, Context.getPrintingPolicy());
          // Use the identifier location for the type source range.
          DS.SetRangeStart(FTI.Params[i].IdentLoc);
          DS.SetRangeEnd(FTI.Params[i].IdentLoc);
          Declarator ParamD(DS, DeclaratorContext::KNRTypeListContext);
          ParamD.SetIdentifier(FTI.Params[i].Ident, FTI.Params[i].IdentLoc);
          FTI.Params[i].Param = ActOnParamDeclarator(S, ParamD);
        }
      }
    }
  }
  
  Decl *
  Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Declarator &D,
                                MultiTemplateParamsArg TemplateParameterLists,
                                SkipBodyInfo *SkipBody) {
    assert(getCurFunctionDecl() == nullptr && "Function parsing confused");
    assert(D.isFunctionDeclarator() && "Not a function declarator!");
    Scope *ParentScope = FnBodyScope->getParent();
  
    D.setFunctionDefinitionKind(FDK_Definition);
    Decl *DP = HandleDeclarator(ParentScope, D, TemplateParameterLists);
    return ActOnStartOfFunctionDef(FnBodyScope, DP, SkipBody);
  }
  
  void Sema::ActOnFinishInlineFunctionDef(FunctionDecl *D) {
    Consumer.HandleInlineFunctionDefinition(D);
  }
  
  static bool ShouldWarnAboutMissingPrototype(const FunctionDecl *FD,
                               const FunctionDecl*& PossibleZeroParamPrototype) {
    // Don't warn about invalid declarations.
    if (FD->isInvalidDecl())
      return false;
  
    // Or declarations that aren't global.
    if (!FD->isGlobal())
      return false;
  
    // Don't warn about C++ member functions.
    if (isa<CXXMethodDecl>(FD))
      return false;
  
    // Don't warn about 'main'.
    if (FD->isMain())
      return false;
  
    // Don't warn about inline functions.
    if (FD->isInlined())
      return false;
  
    // Don't warn about function templates.
    if (FD->getDescribedFunctionTemplate())
      return false;
  
    // Don't warn about function template specializations.
    if (FD->isFunctionTemplateSpecialization())
      return false;
  
    // Don't warn for OpenCL kernels.
    if (FD->hasAttr<OpenCLKernelAttr>())
      return false;
  
    // Don't warn on explicitly deleted functions.
    if (FD->isDeleted())
      return false;
  
    bool MissingPrototype = true;
    for (const FunctionDecl *Prev = FD->getPreviousDecl();
         Prev; Prev = Prev->getPreviousDecl()) {
      // Ignore any declarations that occur in function or method
      // scope, because they aren't visible from the header.
      if (Prev->getLexicalDeclContext()->isFunctionOrMethod())
        continue;
  
      MissingPrototype = !Prev->getType()->isFunctionProtoType();
      if (FD->getNumParams() == 0)
        PossibleZeroParamPrototype = Prev;
      break;
    }
  
    return MissingPrototype;
  }
  
  void
  Sema::CheckForFunctionRedefinition(FunctionDecl *FD,
                                     const FunctionDecl *EffectiveDefinition,
                                     SkipBodyInfo *SkipBody) {
    const FunctionDecl *Definition = EffectiveDefinition;
    if (!Definition && !FD->isDefined(Definition) && !FD->isCXXClassMember()) {
      // If this is a friend function defined in a class template, it does not
      // have a body until it is used, nevertheless it is a definition, see
      // [temp.inst]p2:
      //
      // ... for the purpose of determining whether an instantiated redeclaration
      // is valid according to [basic.def.odr] and [class.mem], a declaration that
      // corresponds to a definition in the template is considered to be a
      // definition.
      //
      // The following code must produce redefinition error:
      //
      //     template<typename T> struct C20 { friend void func_20() {} };
      //     C20<int> c20i;
      //     void func_20() {}
      //
      for (auto I : FD->redecls()) {
        if (I != FD && !I->isInvalidDecl() &&
            I->getFriendObjectKind() != Decl::FOK_None) {
          if (FunctionDecl *Original = I->getInstantiatedFromMemberFunction()) {
            if (FunctionDecl *OrigFD = FD->getInstantiatedFromMemberFunction()) {
              // A merged copy of the same function, instantiated as a member of
              // the same class, is OK.
              if (declaresSameEntity(OrigFD, Original) &&
                  declaresSameEntity(cast<Decl>(I->getLexicalDeclContext()),
                                     cast<Decl>(FD->getLexicalDeclContext())))
                continue;
            }
  
            if (Original->isThisDeclarationADefinition()) {
              Definition = I;
              break;
            }
          }
        }
      }
    }
  
    if (!Definition)
      // Similar to friend functions a friend function template may be a
      // definition and do not have a body if it is instantiated in a class
      // template.
      if (FunctionTemplateDecl *FTD = FD->getDescribedFunctionTemplate()) {
        for (auto I : FTD->redecls()) {
          auto D = cast<FunctionTemplateDecl>(I);
          if (D != FTD) {
            assert(!D->isThisDeclarationADefinition() &&
                   "More than one definition in redeclaration chain");
            if (D->getFriendObjectKind() != Decl::FOK_None)
              if (FunctionTemplateDecl *FT =
                                         D->getInstantiatedFromMemberTemplate()) {
                if (FT->isThisDeclarationADefinition()) {
                  Definition = D->getTemplatedDecl();
                  break;
                }
              }
          }
        }
      }
  
    if (!Definition)
      return;
  
    if (canRedefineFunction(Definition, getLangOpts()))
      return;
  
    // Don't emit an error when this is redefinition of a typo-corrected
    // definition.
    if (TypoCorrectedFunctionDefinitions.count(Definition))
      return;
  
    // If we don't have a visible definition of the function, and it's inline or
    // a template, skip the new definition.
    if (SkipBody && !hasVisibleDefinition(Definition) &&
        (Definition->getFormalLinkage() == InternalLinkage ||
         Definition->isInlined() ||
         Definition->getDescribedFunctionTemplate() ||
         Definition->getNumTemplateParameterLists())) {
      SkipBody->ShouldSkip = true;
      SkipBody->Previous = const_cast<FunctionDecl*>(Definition);
      if (auto *TD = Definition->getDescribedFunctionTemplate())
        makeMergedDefinitionVisible(TD);
      makeMergedDefinitionVisible(const_cast<FunctionDecl*>(Definition));
      return;
    }
  
    if (getLangOpts().GNUMode && Definition->isInlineSpecified() &&
        Definition->getStorageClass() == SC_Extern)
      Diag(FD->getLocation(), diag::err_redefinition_extern_inline)
          << FD->getDeclName() << getLangOpts().CPlusPlus;
    else
      Diag(FD->getLocation(), diag::err_redefinition) << FD->getDeclName();
  
    Diag(Definition->getLocation(), diag::note_previous_definition);
    FD->setInvalidDecl();
  }
  
  static void RebuildLambdaScopeInfo(CXXMethodDecl *CallOperator,
                                     Sema &S) {
    CXXRecordDecl *const LambdaClass = CallOperator->getParent();
  
    LambdaScopeInfo *LSI = S.PushLambdaScope();
    LSI->CallOperator = CallOperator;
    LSI->Lambda = LambdaClass;
    LSI->ReturnType = CallOperator->getReturnType();
    const LambdaCaptureDefault LCD = LambdaClass->getLambdaCaptureDefault();
  
    if (LCD == LCD_None)
      LSI->ImpCaptureStyle = CapturingScopeInfo::ImpCap_None;
    else if (LCD == LCD_ByCopy)
      LSI->ImpCaptureStyle = CapturingScopeInfo::ImpCap_LambdaByval;
    else if (LCD == LCD_ByRef)
      LSI->ImpCaptureStyle = CapturingScopeInfo::ImpCap_LambdaByref;
    DeclarationNameInfo DNI = CallOperator->getNameInfo();
  
    LSI->IntroducerRange = DNI.getCXXOperatorNameRange();
    LSI->Mutable = !CallOperator->isConst();
  
    // Add the captures to the LSI so they can be noted as already
    // captured within tryCaptureVar.
    auto I = LambdaClass->field_begin();
    for (const auto &C : LambdaClass->captures()) {
      if (C.capturesVariable()) {
        VarDecl *VD = C.getCapturedVar();
        if (VD->isInitCapture())
          S.CurrentInstantiationScope->InstantiatedLocal(VD, VD);
        QualType CaptureType = VD->getType();
        const bool ByRef = C.getCaptureKind() == LCK_ByRef;
        LSI->addCapture(VD, /*IsBlock*/false, ByRef,
            /*RefersToEnclosingVariableOrCapture*/true, C.getLocation(),
            /*EllipsisLoc*/C.isPackExpansion()
                           ? C.getEllipsisLoc() : SourceLocation(),
            CaptureType, /*Expr*/ nullptr);
  
      } else if (C.capturesThis()) {
        LSI->addThisCapture(/*Nested*/ false, C.getLocation(),
                                /*Expr*/ nullptr,
                                C.getCaptureKind() == LCK_StarThis);
      } else {
        LSI->addVLATypeCapture(C.getLocation(), I->getType());
      }
      ++I;
    }
  }
  
  Decl *Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Decl *D,
                                      SkipBodyInfo *SkipBody) {
    if (!D) {
      // Parsing the function declaration failed in some way. Push on a fake scope
      // anyway so we can try to parse the function body.
      PushFunctionScope();
      PushExpressionEvaluationContext(ExprEvalContexts.back().Context);
      return D;
    }
  
    FunctionDecl *FD = nullptr;
  
    if (FunctionTemplateDecl *FunTmpl = dyn_cast<FunctionTemplateDecl>(D))
      FD = FunTmpl->getTemplatedDecl();
    else
      FD = cast<FunctionDecl>(D);
  
    // Do not push if it is a lambda because one is already pushed when building
    // the lambda in ActOnStartOfLambdaDefinition().
    if (!isLambdaCallOperator(FD))
      PushExpressionEvaluationContext(ExprEvalContexts.back().Context);
  
    // Check for defining attributes before the check for redefinition.
    if (const auto *Attr = FD->getAttr<AliasAttr>()) {
      Diag(Attr->getLocation(), diag::err_alias_is_definition) << FD << 0;
      FD->dropAttr<AliasAttr>();
      FD->setInvalidDecl();
    }
    if (const auto *Attr = FD->getAttr<IFuncAttr>()) {
      Diag(Attr->getLocation(), diag::err_alias_is_definition) << FD << 1;
      FD->dropAttr<IFuncAttr>();
      FD->setInvalidDecl();
    }
  
    // See if this is a redefinition. If 'will have body' is already set, then
    // these checks were already performed when it was set.
    if (!FD->willHaveBody() && !FD->isLateTemplateParsed()) {
      CheckForFunctionRedefinition(FD, nullptr, SkipBody);
  
      // If we're skipping the body, we're done. Don't enter the scope.
      if (SkipBody && SkipBody->ShouldSkip)
        return D;
    }
  
    // Mark this function as "will have a body eventually".  This lets users to
    // call e.g. isInlineDefinitionExternallyVisible while we're still parsing
    // this function.
    FD->setWillHaveBody();
  
    // If we are instantiating a generic lambda call operator, push
    // a LambdaScopeInfo onto the function stack.  But use the information
    // that's already been calculated (ActOnLambdaExpr) to prime the current
    // LambdaScopeInfo.
    // When the template operator is being specialized, the LambdaScopeInfo,
    // has to be properly restored so that tryCaptureVariable doesn't try
    // and capture any new variables. In addition when calculating potential
    // captures during transformation of nested lambdas, it is necessary to
    // have the LSI properly restored.
    if (isGenericLambdaCallOperatorSpecialization(FD)) {
      assert(inTemplateInstantiation() &&
             "There should be an active template instantiation on the stack "
             "when instantiating a generic lambda!");
      RebuildLambdaScopeInfo(cast<CXXMethodDecl>(D), *this);
    } else {
      // Enter a new function scope
      PushFunctionScope();
    }
  
    // Builtin functions cannot be defined.
    if (unsigned BuiltinID = FD->getBuiltinID()) {
      if (!Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID) &&
          !Context.BuiltinInfo.isPredefinedRuntimeFunction(BuiltinID)) {
        Diag(FD->getLocation(), diag::err_builtin_definition) << FD;
        FD->setInvalidDecl();
      }
    }
  
    // The return type of a function definition must be complete
    // (C99 6.9.1p3, C++ [dcl.fct]p6).
    QualType ResultType = FD->getReturnType();
    if (!ResultType->isDependentType() && !ResultType->isVoidType() &&
        !FD->isInvalidDecl() &&
        RequireCompleteType(FD->getLocation(), ResultType,
                            diag::err_func_def_incomplete_result))
      FD->setInvalidDecl();
  
    if (FnBodyScope)
      PushDeclContext(FnBodyScope, FD);
  
    // Check the validity of our function parameters
    CheckParmsForFunctionDef(FD->parameters(),
                             /*CheckParameterNames=*/true);
  
    // Add non-parameter declarations already in the function to the current
    // scope.
    if (FnBodyScope) {
      for (Decl *NPD : FD->decls()) {
        auto *NonParmDecl = dyn_cast<NamedDecl>(NPD);
        if (!NonParmDecl)
          continue;
        assert(!isa<ParmVarDecl>(NonParmDecl) &&
               "parameters should not be in newly created FD yet");
  
        // If the decl has a name, make it accessible in the current scope.
        if (NonParmDecl->getDeclName())
          PushOnScopeChains(NonParmDecl, FnBodyScope, /*AddToContext=*/false);
  
        // Similarly, dive into enums and fish their constants out, making them
        // accessible in this scope.
        if (auto *ED = dyn_cast<EnumDecl>(NonParmDecl)) {
          for (auto *EI : ED->enumerators())
            PushOnScopeChains(EI, FnBodyScope, /*AddToContext=*/false);
        }
      }
    }
  
    // Introduce our parameters into the function scope
    for (auto Param : FD->parameters()) {
      Param->setOwningFunction(FD);
  
      // If this has an identifier, add it to the scope stack.
      if (Param->getIdentifier() && FnBodyScope) {
        CheckShadow(FnBodyScope, Param);
  
        PushOnScopeChains(Param, FnBodyScope);
      }
    }
  
    // Ensure that the function's exception specification is instantiated.
    if (const FunctionProtoType *FPT = FD->getType()->getAs<FunctionProtoType>())
      ResolveExceptionSpec(D->getLocation(), FPT);
  
    // dllimport cannot be applied to non-inline function definitions.
    if (FD->hasAttr<DLLImportAttr>() && !FD->isInlined() &&
        !FD->isTemplateInstantiation()) {
      assert(!FD->hasAttr<DLLExportAttr>());
      Diag(FD->getLocation(), diag::err_attribute_dllimport_function_definition);
      FD->setInvalidDecl();
      return D;
    }
    // We want to attach documentation to original Decl (which might be
    // a function template).
    ActOnDocumentableDecl(D);
    if (getCurLexicalContext()->isObjCContainer() &&
        getCurLexicalContext()->getDeclKind() != Decl::ObjCCategoryImpl &&
        getCurLexicalContext()->getDeclKind() != Decl::ObjCImplementation)
      Diag(FD->getLocation(), diag::warn_function_def_in_objc_container);
  
    return D;
  }
  
  /// Given the set of return statements within a function body,
  /// compute the variables that are subject to the named return value
  /// optimization.
  ///
  /// Each of the variables that is subject to the named return value
  /// optimization will be marked as NRVO variables in the AST, and any
  /// return statement that has a marked NRVO variable as its NRVO candidate can
  /// use the named return value optimization.
  ///
  /// This function applies a very simplistic algorithm for NRVO: if every return
  /// statement in the scope of a variable has the same NRVO candidate, that
  /// candidate is an NRVO variable.
  void Sema::computeNRVO(Stmt *Body, FunctionScopeInfo *Scope) {
    ReturnStmt **Returns = Scope->Returns.data();
  
    for (unsigned I = 0, E = Scope->Returns.size(); I != E; ++I) {
      if (const VarDecl *NRVOCandidate = Returns[I]->getNRVOCandidate()) {
        if (!NRVOCandidate->isNRVOVariable())
          Returns[I]->setNRVOCandidate(nullptr);
      }
    }
  }
  
  bool Sema::canDelayFunctionBody(const Declarator &D) {
    // We can't delay parsing the body of a constexpr function template (yet).
    if (D.getDeclSpec().isConstexprSpecified())
      return false;
  
    // We can't delay parsing the body of a function template with a deduced
    // return type (yet).
    if (D.getDeclSpec().hasAutoTypeSpec()) {
      // If the placeholder introduces a non-deduced trailing return type,
      // we can still delay parsing it.
      if (D.getNumTypeObjects()) {
        const auto &Outer = D.getTypeObject(D.getNumTypeObjects() - 1);
        if (Outer.Kind == DeclaratorChunk::Function &&
            Outer.Fun.hasTrailingReturnType()) {
          QualType Ty = GetTypeFromParser(Outer.Fun.getTrailingReturnType());
          return Ty.isNull() || !Ty->isUndeducedType();
        }
      }
      return false;
    }
  
    return true;
  }
  
  bool Sema::canSkipFunctionBody(Decl *D) {
    // We cannot skip the body of a function (or function template) which is
    // constexpr, since we may need to evaluate its body in order to parse the
    // rest of the file.
    // We cannot skip the body of a function with an undeduced return type,
    // because any callers of that function need to know the type.
    if (const FunctionDecl *FD = D->getAsFunction()) {
      if (FD->isConstexpr())
        return false;
      // We can't simply call Type::isUndeducedType here, because inside template
      // auto can be deduced to a dependent type, which is not considered
      // "undeduced".
      if (FD->getReturnType()->getContainedDeducedType())
        return false;
    }
    return Consumer.shouldSkipFunctionBody(D);
  }
  
  Decl *Sema::ActOnSkippedFunctionBody(Decl *Decl) {
    if (!Decl)
      return nullptr;
    if (FunctionDecl *FD = Decl->getAsFunction())
      FD->setHasSkippedBody();
    else if (ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(Decl))
      MD->setHasSkippedBody();
    return Decl;
  }
  
  Decl *Sema::ActOnFinishFunctionBody(Decl *D, Stmt *BodyArg) {
    return ActOnFinishFunctionBody(D, BodyArg, false);
  }
  
  /// RAII object that pops an ExpressionEvaluationContext when exiting a function
  /// body.
  class ExitFunctionBodyRAII {
  public:
    ExitFunctionBodyRAII(Sema &S, bool IsLambda) : S(S), IsLambda(IsLambda) {}
    ~ExitFunctionBodyRAII() {
      if (!IsLambda)
        S.PopExpressionEvaluationContext();
    }
  
  private:
    Sema &S;
    bool IsLambda = false;
  };
  
  Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
                                      bool IsInstantiation) {
    FunctionDecl *FD = dcl ? dcl->getAsFunction() : nullptr;
  
    sema::AnalysisBasedWarnings::Policy WP = AnalysisWarnings.getDefaultPolicy();
    sema::AnalysisBasedWarnings::Policy *ActivePolicy = nullptr;
  
    if (getLangOpts().Coroutines && getCurFunction()->isCoroutine())
      CheckCompletedCoroutineBody(FD, Body);
  
    // Do not call PopExpressionEvaluationContext() if it is a lambda because one
    // is already popped when finishing the lambda in BuildLambdaExpr(). This is
    // meant to pop the context added in ActOnStartOfFunctionDef().
    ExitFunctionBodyRAII ExitRAII(*this, isLambdaCallOperator(FD));
  
    if (FD) {
      FD->setBody(Body);
      FD->setWillHaveBody(false);
  
      if (getLangOpts().CPlusPlus14) {
        if (!FD->isInvalidDecl() && Body && !FD->isDependentContext() &&
            FD->getReturnType()->isUndeducedType()) {
          // If the function has a deduced result type but contains no 'return'
          // statements, the result type as written must be exactly 'auto', and
          // the deduced result type is 'void'.
          if (!FD->getReturnType()->getAs<AutoType>()) {
            Diag(dcl->getLocation(), diag::err_auto_fn_no_return_but_not_auto)
                << FD->getReturnType();
            FD->setInvalidDecl();
          } else {
            // Substitute 'void' for the 'auto' in the type.
            TypeLoc ResultType = getReturnTypeLoc(FD);
            Context.adjustDeducedFunctionResultType(
                FD, SubstAutoType(ResultType.getType(), Context.VoidTy));
          }
        }
      } else if (getLangOpts().CPlusPlus11 && isLambdaCallOperator(FD)) {
        // In C++11, we don't use 'auto' deduction rules for lambda call
        // operators because we don't support return type deduction.
        auto *LSI = getCurLambda();
        if (LSI->HasImplicitReturnType) {
          deduceClosureReturnType(*LSI);
  
          // C++11 [expr.prim.lambda]p4:
          //   [...] if there are no return statements in the compound-statement
          //   [the deduced type is] the type void
          QualType RetType =
              LSI->ReturnType.isNull() ? Context.VoidTy : LSI->ReturnType;
  
          // Update the return type to the deduced type.
          const FunctionProtoType *Proto =
              FD->getType()->getAs<FunctionProtoType>();
          FD->setType(Context.getFunctionType(RetType, Proto->getParamTypes(),
                                              Proto->getExtProtoInfo()));
        }
      }
  
      // If the function implicitly returns zero (like 'main') or is naked,
      // don't complain about missing return statements.
      if (FD->hasImplicitReturnZero() || FD->hasAttr<NakedAttr>())
        WP.disableCheckFallThrough();
  
      // MSVC permits the use of pure specifier (=0) on function definition,
      // defined at class scope, warn about this non-standard construct.
      if (getLangOpts().MicrosoftExt && FD->isPure() && FD->isCanonicalDecl())
        Diag(FD->getLocation(), diag::ext_pure_function_definition);
  
      if (!FD->isInvalidDecl()) {
        // Don't diagnose unused parameters of defaulted or deleted functions.
        if (!FD->isDeleted() && !FD->isDefaulted() && !FD->hasSkippedBody())
          DiagnoseUnusedParameters(FD->parameters());
        DiagnoseSizeOfParametersAndReturnValue(FD->parameters(),
                                               FD->getReturnType(), FD);
  
        // If this is a structor, we need a vtable.
        if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(FD))
          MarkVTableUsed(FD->getLocation(), Constructor->getParent());
        else if (CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(FD))
          MarkVTableUsed(FD->getLocation(), Destructor->getParent());
  
        // Try to apply the named return value optimization. We have to check
        // if we can do this here because lambdas keep return statements around
        // to deduce an implicit return type.
        if (FD->getReturnType()->isRecordType() &&
            (!getLangOpts().CPlusPlus || !FD->isDependentContext()))
          computeNRVO(Body, getCurFunction());
      }
  
      // GNU warning -Wmissing-prototypes:
      //   Warn if a global function is defined without a previous
      //   prototype declaration. This warning is issued even if the
      //   definition itself provides a prototype. The aim is to detect
      //   global functions that fail to be declared in header files.
      const FunctionDecl *PossibleZeroParamPrototype = nullptr;
      if (ShouldWarnAboutMissingPrototype(FD, PossibleZeroParamPrototype)) {
        Diag(FD->getLocation(), diag::warn_missing_prototype) << FD;
  
        if (PossibleZeroParamPrototype) {
          // We found a declaration that is not a prototype,
          // but that could be a zero-parameter prototype
          if (TypeSourceInfo *TI =
                  PossibleZeroParamPrototype->getTypeSourceInfo()) {
            TypeLoc TL = TI->getTypeLoc();
            if (FunctionNoProtoTypeLoc FTL = TL.getAs<FunctionNoProtoTypeLoc>())
              Diag(PossibleZeroParamPrototype->getLocation(),
                   diag::note_declaration_not_a_prototype)
                  << PossibleZeroParamPrototype
                  << FixItHint::CreateInsertion(FTL.getRParenLoc(), "void");
          }
        }
  
        // GNU warning -Wstrict-prototypes
        //   Warn if K&R function is defined without a previous declaration.
        //   This warning is issued only if the definition itself does not provide
        //   a prototype. Only K&R definitions do not provide a prototype.
        //   An empty list in a function declarator that is part of a definition
        //   of that function specifies that the function has no parameters
        //   (C99 6.7.5.3p14)
        if (!FD->hasWrittenPrototype() && FD->getNumParams() > 0 &&
            !LangOpts.CPlusPlus) {
          TypeSourceInfo *TI = FD->getTypeSourceInfo();
          TypeLoc TL = TI->getTypeLoc();
          FunctionTypeLoc FTL = TL.getAsAdjusted<FunctionTypeLoc>();
          Diag(FTL.getLParenLoc(), diag::warn_strict_prototypes) << 2;
        }
      }
  
      // Warn on CPUDispatch with an actual body.
      if (FD->isMultiVersion() && FD->hasAttr<CPUDispatchAttr>() && Body)
        if (const auto *CmpndBody = dyn_cast<CompoundStmt>(Body))
          if (!CmpndBody->body_empty())
            Diag(CmpndBody->body_front()->getBeginLoc(),
                 diag::warn_dispatch_body_ignored);
  
      if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
        const CXXMethodDecl *KeyFunction;
        if (MD->isOutOfLine() && (MD = MD->getCanonicalDecl()) &&
            MD->isVirtual() &&
            (KeyFunction = Context.getCurrentKeyFunction(MD->getParent())) &&
            MD == KeyFunction->getCanonicalDecl()) {
          // Update the key-function state if necessary for this ABI.
          if (FD->isInlined() &&
              !Context.getTargetInfo().getCXXABI().canKeyFunctionBeInline()) {
            Context.setNonKeyFunction(MD);
  
            // If the newly-chosen key function is already defined, then we
            // need to mark the vtable as used retroactively.
            KeyFunction = Context.getCurrentKeyFunction(MD->getParent());
            const FunctionDecl *Definition;
            if (KeyFunction && KeyFunction->isDefined(Definition))
              MarkVTableUsed(Definition->getLocation(), MD->getParent(), true);
          } else {
            // We just defined they key function; mark the vtable as used.
            MarkVTableUsed(FD->getLocation(), MD->getParent(), true);
          }
        }
      }
  
      assert((FD == getCurFunctionDecl() || getCurLambda()->CallOperator == FD) &&
             "Function parsing confused");
    } else if (ObjCMethodDecl *MD = dyn_cast_or_null<ObjCMethodDecl>(dcl)) {
      assert(MD == getCurMethodDecl() && "Method parsing confused");
      MD->setBody(Body);
      if (!MD->isInvalidDecl()) {
        if (!MD->hasSkippedBody())
          DiagnoseUnusedParameters(MD->parameters());
        DiagnoseSizeOfParametersAndReturnValue(MD->parameters(),
                                               MD->getReturnType(), MD);
  
        if (Body)
          computeNRVO(Body, getCurFunction());
      }
      if (getCurFunction()->ObjCShouldCallSuper) {
        Diag(MD->getEndLoc(), diag::warn_objc_missing_super_call)
            << MD->getSelector().getAsString();
        getCurFunction()->ObjCShouldCallSuper = false;
      }
      if (getCurFunction()->ObjCWarnForNoDesignatedInitChain) {
        const ObjCMethodDecl *InitMethod = nullptr;
        bool isDesignated =
            MD->isDesignatedInitializerForTheInterface(&InitMethod);
        assert(isDesignated && InitMethod);
        (void)isDesignated;
  
        auto superIsNSObject = [&](const ObjCMethodDecl *MD) {
          auto IFace = MD->getClassInterface();
          if (!IFace)
            return false;
          auto SuperD = IFace->getSuperClass();
          if (!SuperD)
            return false;
          return SuperD->getIdentifier() ==
              NSAPIObj->getNSClassId(NSAPI::ClassId_NSObject);
        };
        // Don't issue this warning for unavailable inits or direct subclasses
        // of NSObject.
        if (!MD->isUnavailable() && !superIsNSObject(MD)) {
          Diag(MD->getLocation(),
               diag::warn_objc_designated_init_missing_super_call);
          Diag(InitMethod->getLocation(),
               diag::note_objc_designated_init_marked_here);
        }
        getCurFunction()->ObjCWarnForNoDesignatedInitChain = false;
      }
      if (getCurFunction()->ObjCWarnForNoInitDelegation) {
        // Don't issue this warning for unavaialable inits.
        if (!MD->isUnavailable())
          Diag(MD->getLocation(),
               diag::warn_objc_secondary_init_missing_init_call);
        getCurFunction()->ObjCWarnForNoInitDelegation = false;
      }
    } else {
      // Parsing the function declaration failed in some way. Pop the fake scope
      // we pushed on.
      PopFunctionScopeInfo(ActivePolicy, dcl);
      return nullptr;
    }
  
    if (Body && getCurFunction()->HasPotentialAvailabilityViolations)
      DiagnoseUnguardedAvailabilityViolations(dcl);
  
    assert(!getCurFunction()->ObjCShouldCallSuper &&
           "This should only be set for ObjC methods, which should have been "
           "handled in the block above.");
  
    // Verify and clean out per-function state.
    if (Body && (!FD || !FD->isDefaulted())) {
      // C++ constructors that have function-try-blocks can't have return
      // statements in the handlers of that block. (C++ [except.handle]p14)
      // Verify this.
      if (FD && isa<CXXConstructorDecl>(FD) && isa<CXXTryStmt>(Body))
        DiagnoseReturnInConstructorExceptionHandler(cast<CXXTryStmt>(Body));
  
      // Verify that gotos and switch cases don't jump into scopes illegally.
      if (getCurFunction()->NeedsScopeChecking() &&
          !PP.isCodeCompletionEnabled())
        DiagnoseInvalidJumps(Body);
  
      if (CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(dcl)) {
        if (!Destructor->getParent()->isDependentType())
          CheckDestructor(Destructor);
  
        MarkBaseAndMemberDestructorsReferenced(Destructor->getLocation(),
                                               Destructor->getParent());
      }
  
      // If any errors have occurred, clear out any temporaries that may have
      // been leftover. This ensures that these temporaries won't be picked up for
      // deletion in some later function.
      if (getDiagnostics().hasErrorOccurred() ||
          getDiagnostics().getSuppressAllDiagnostics()) {
        DiscardCleanupsInEvaluationContext();
      }
      if (!getDiagnostics().hasUncompilableErrorOccurred() &&
          !isa<FunctionTemplateDecl>(dcl)) {
        // Since the body is valid, issue any analysis-based warnings that are
        // enabled.
        ActivePolicy = &WP;
      }
  
      if (!IsInstantiation && FD && FD->isConstexpr() && !FD->isInvalidDecl() &&
          (!CheckConstexprFunctionDecl(FD) ||
           !CheckConstexprFunctionBody(FD, Body)))
        FD->setInvalidDecl();
  
      if (FD && FD->hasAttr<NakedAttr>()) {
        for (const Stmt *S : Body->children()) {
          // Allow local register variables without initializer as they don't
          // require prologue.
          bool RegisterVariables = false;
          if (auto *DS = dyn_cast<DeclStmt>(S)) {
            for (const auto *Decl : DS->decls()) {
              if (const auto *Var = dyn_cast<VarDecl>(Decl)) {
                RegisterVariables =
                    Var->hasAttr<AsmLabelAttr>() && !Var->hasInit();
                if (!RegisterVariables)
                  break;
              }
            }
          }
          if (RegisterVariables)
            continue;
          if (!isa<AsmStmt>(S) && !isa<NullStmt>(S)) {
            Diag(S->getBeginLoc(), diag::err_non_asm_stmt_in_naked_function);
            Diag(FD->getAttr<NakedAttr>()->getLocation(), diag::note_attribute);
            FD->setInvalidDecl();
            break;
          }
        }
      }
  
      assert(ExprCleanupObjects.size() ==
                 ExprEvalContexts.back().NumCleanupObjects &&
             "Leftover temporaries in function");
      assert(!Cleanup.exprNeedsCleanups() && "Unaccounted cleanups in function");
      assert(MaybeODRUseExprs.empty() &&
             "Leftover expressions for odr-use checking");
    }
  
    if (!IsInstantiation)
      PopDeclContext();
  
    PopFunctionScopeInfo(ActivePolicy, dcl);
    // If any errors have occurred, clear out any temporaries that may have
    // been leftover. This ensures that these temporaries won't be picked up for
    // deletion in some later function.
    if (getDiagnostics().hasErrorOccurred()) {
      DiscardCleanupsInEvaluationContext();
    }
  
    return dcl;
  }
  
  /// When we finish delayed parsing of an attribute, we must attach it to the
  /// relevant Decl.
  void Sema::ActOnFinishDelayedAttribute(Scope *S, Decl *D,
                                         ParsedAttributes &Attrs) {
    // Always attach attributes to the underlying decl.
    if (TemplateDecl *TD = dyn_cast<TemplateDecl>(D))
      D = TD->getTemplatedDecl();
    ProcessDeclAttributeList(S, D, Attrs);
  
    if (CXXMethodDecl *Method = dyn_cast_or_null<CXXMethodDecl>(D))
      if (Method->isStatic())
        checkThisInStaticMemberFunctionAttributes(Method);
  }
  
  /// ImplicitlyDefineFunction - An undeclared identifier was used in a function
  /// call, forming a call to an implicitly defined function (per C99 6.5.1p2).
  NamedDecl *Sema::ImplicitlyDefineFunction(SourceLocation Loc,
                                            IdentifierInfo &II, Scope *S) {
    // Find the scope in which the identifier is injected and the corresponding
    // DeclContext.
    // FIXME: C89 does not say what happens if there is no enclosing block scope.
    // In that case, we inject the declaration into the translation unit scope
    // instead.
    Scope *BlockScope = S;
    while (!BlockScope->isCompoundStmtScope() && BlockScope->getParent())
      BlockScope = BlockScope->getParent();
  
    Scope *ContextScope = BlockScope;
    while (!ContextScope->getEntity())
      ContextScope = ContextScope->getParent();
    ContextRAII SavedContext(*this, ContextScope->getEntity());
  
    // Before we produce a declaration for an implicitly defined
    // function, see whether there was a locally-scoped declaration of
    // this name as a function or variable. If so, use that
    // (non-visible) declaration, and complain about it.
    NamedDecl *ExternCPrev = findLocallyScopedExternCDecl(&II);
    if (ExternCPrev) {
      // We still need to inject the function into the enclosing block scope so
      // that later (non-call) uses can see it.
      PushOnScopeChains(ExternCPrev, BlockScope, /*AddToContext*/false);
  
      // C89 footnote 38:
      //   If in fact it is not defined as having type "function returning int",
      //   the behavior is undefined.
      if (!isa<FunctionDecl>(ExternCPrev) ||
          !Context.typesAreCompatible(
              cast<FunctionDecl>(ExternCPrev)->getType(),
              Context.getFunctionNoProtoType(Context.IntTy))) {
        Diag(Loc, diag::ext_use_out_of_scope_declaration)
            << ExternCPrev << !getLangOpts().C99;
        Diag(ExternCPrev->getLocation(), diag::note_previous_declaration);
        return ExternCPrev;
      }
    }
  
    // Extension in C99.  Legal in C90, but warn about it.
    unsigned diag_id;
    if (II.getName().startswith("__builtin_"))
      diag_id = diag::warn_builtin_unknown;
    // OpenCL v2.0 s6.9.u - Implicit function declaration is not supported.
    else if (getLangOpts().OpenCL)
      diag_id = diag::err_opencl_implicit_function_decl;
    else if (getLangOpts().C99)
      diag_id = diag::ext_implicit_function_decl;
    else
      diag_id = diag::warn_implicit_function_decl;
    Diag(Loc, diag_id) << &II;
  
    // If we found a prior declaration of this function, don't bother building
    // another one. We've already pushed that one into scope, so there's nothing
    // more to do.
    if (ExternCPrev)
      return ExternCPrev;
  
    // Because typo correction is expensive, only do it if the implicit
    // function declaration is going to be treated as an error.
    if (Diags.getDiagnosticLevel(diag_id, Loc) >= DiagnosticsEngine::Error) {
      TypoCorrection Corrected;
      DeclFilterCCC<FunctionDecl> CCC{};
      if (S && (Corrected =
                    CorrectTypo(DeclarationNameInfo(&II, Loc), LookupOrdinaryName,
                                S, nullptr, CCC, CTK_NonError)))
        diagnoseTypo(Corrected, PDiag(diag::note_function_suggestion),
                     /*ErrorRecovery*/false);
    }
  
    // Set a Declarator for the implicit definition: int foo();
    const char *Dummy;
    AttributeFactory attrFactory;
    DeclSpec DS(attrFactory);
    unsigned DiagID;
    bool Error = DS.SetTypeSpecType(DeclSpec::TST_int, Loc, Dummy, DiagID,
                                    Context.getPrintingPolicy());
    (void)Error; // Silence warning.
    assert(!Error && "Error setting up implicit decl!");
    SourceLocation NoLoc;
    Declarator D(DS, DeclaratorContext::BlockContext);
    D.AddTypeInfo(DeclaratorChunk::getFunction(/*HasProto=*/false,
                                               /*IsAmbiguous=*/false,
                                               /*LParenLoc=*/NoLoc,
                                               /*Params=*/nullptr,
                                               /*NumParams=*/0,
                                               /*EllipsisLoc=*/NoLoc,
                                               /*RParenLoc=*/NoLoc,
                                               /*RefQualifierIsLvalueRef=*/true,
                                               /*RefQualifierLoc=*/NoLoc,
                                               /*MutableLoc=*/NoLoc, EST_None,
                                               /*ESpecRange=*/SourceRange(),
                                               /*Exceptions=*/nullptr,
                                               /*ExceptionRanges=*/nullptr,
                                               /*NumExceptions=*/0,
                                               /*NoexceptExpr=*/nullptr,
                                               /*ExceptionSpecTokens=*/nullptr,
                                               /*DeclsInPrototype=*/None, Loc,
                                               Loc, D),
                  std::move(DS.getAttributes()), SourceLocation());
    D.SetIdentifier(&II, Loc);
  
    // Insert this function into the enclosing block scope.
    FunctionDecl *FD = cast<FunctionDecl>(ActOnDeclarator(BlockScope, D));
    FD->setImplicit();
  
    AddKnownFunctionAttributes(FD);
  
    return FD;
  }
  
  /// Adds any function attributes that we know a priori based on
  /// the declaration of this function.
  ///
  /// These attributes can apply both to implicitly-declared builtins
  /// (like __builtin___printf_chk) or to library-declared functions
  /// like NSLog or printf.
  ///
  /// We need to check for duplicate attributes both here and where user-written
  /// attributes are applied to declarations.
  void Sema::AddKnownFunctionAttributes(FunctionDecl *FD) {
    if (FD->isInvalidDecl())
      return;
  
    // If this is a built-in function, map its builtin attributes to
    // actual attributes.
    if (unsigned BuiltinID = FD->getBuiltinID()) {
      // Handle printf-formatting attributes.
      unsigned FormatIdx;
      bool HasVAListArg;
      if (Context.BuiltinInfo.isPrintfLike(BuiltinID, FormatIdx, HasVAListArg)) {
        if (!FD->hasAttr<FormatAttr>()) {
          const char *fmt = "printf";
          unsigned int NumParams = FD->getNumParams();
          if (FormatIdx < NumParams && // NumParams may be 0 (e.g. vfprintf)
              FD->getParamDecl(FormatIdx)->getType()->isObjCObjectPointerType())
            fmt = "NSString";
          FD->addAttr(FormatAttr::CreateImplicit(Context,
                                                 &Context.Idents.get(fmt),
                                                 FormatIdx+1,
                                                 HasVAListArg ? 0 : FormatIdx+2,
                                                 FD->getLocation()));
        }
      }
      if (Context.BuiltinInfo.isScanfLike(BuiltinID, FormatIdx,
                                               HasVAListArg)) {
       if (!FD->hasAttr<FormatAttr>())
         FD->addAttr(FormatAttr::CreateImplicit(Context,
                                                &Context.Idents.get("scanf"),
                                                FormatIdx+1,
                                                HasVAListArg ? 0 : FormatIdx+2,
                                                FD->getLocation()));
      }
  
      // Handle automatically recognized callbacks.
      SmallVector<int, 4> Encoding;
      if (!FD->hasAttr<CallbackAttr>() &&
          Context.BuiltinInfo.performsCallback(BuiltinID, Encoding))
        FD->addAttr(CallbackAttr::CreateImplicit(
            Context, Encoding.data(), Encoding.size(), FD->getLocation()));
  
      // Mark const if we don't care about errno and that is the only thing
      // preventing the function from being const. This allows IRgen to use LLVM
      // intrinsics for such functions.
      if (!getLangOpts().MathErrno && !FD->hasAttr<ConstAttr>() &&
          Context.BuiltinInfo.isConstWithoutErrno(BuiltinID))
        FD->addAttr(ConstAttr::CreateImplicit(Context, FD->getLocation()));
  
      // We make "fma" on some platforms const because we know it does not set
      // errno in those environments even though it could set errno based on the
      // C standard.
      const llvm::Triple &Trip = Context.getTargetInfo().getTriple();
      if ((Trip.isGNUEnvironment() || Trip.isAndroid() || Trip.isOSMSVCRT()) &&
          !FD->hasAttr<ConstAttr>()) {
        switch (BuiltinID) {
        case Builtin::BI__builtin_fma:
        case Builtin::BI__builtin_fmaf:
        case Builtin::BI__builtin_fmal:
        case Builtin::BIfma:
        case Builtin::BIfmaf:
        case Builtin::BIfmal:
          FD->addAttr(ConstAttr::CreateImplicit(Context, FD->getLocation()));
          break;
        default:
          break;
        }
      }
  
      if (Context.BuiltinInfo.isReturnsTwice(BuiltinID) &&
          !FD->hasAttr<ReturnsTwiceAttr>())
        FD->addAttr(ReturnsTwiceAttr::CreateImplicit(Context,
                                           FD->getLocation()));
      if (Context.BuiltinInfo.isNoThrow(BuiltinID) && !FD->hasAttr<NoThrowAttr>())
        FD->addAttr(NoThrowAttr::CreateImplicit(Context, FD->getLocation()));
      if (Context.BuiltinInfo.isPure(BuiltinID) && !FD->hasAttr<PureAttr>())
        FD->addAttr(PureAttr::CreateImplicit(Context, FD->getLocation()));
      if (Context.BuiltinInfo.isConst(BuiltinID) && !FD->hasAttr<ConstAttr>())
        FD->addAttr(ConstAttr::CreateImplicit(Context, FD->getLocation()));
      if (getLangOpts().CUDA && Context.BuiltinInfo.isTSBuiltin(BuiltinID) &&
          !FD->hasAttr<CUDADeviceAttr>() && !FD->hasAttr<CUDAHostAttr>()) {
        // Add the appropriate attribute, depending on the CUDA compilation mode
        // and which target the builtin belongs to. For example, during host
        // compilation, aux builtins are __device__, while the rest are __host__.
        if (getLangOpts().CUDAIsDevice !=
            Context.BuiltinInfo.isAuxBuiltinID(BuiltinID))
          FD->addAttr(CUDADeviceAttr::CreateImplicit(Context, FD->getLocation()));
        else
          FD->addAttr(CUDAHostAttr::CreateImplicit(Context, FD->getLocation()));
      }
    }
  
    // If C++ exceptions are enabled but we are told extern "C" functions cannot
    // throw, add an implicit nothrow attribute to any extern "C" function we come
    // across.
    if (getLangOpts().CXXExceptions && getLangOpts().ExternCNoUnwind &&
        FD->isExternC() && !FD->hasAttr<NoThrowAttr>()) {
      const auto *FPT = FD->getType()->getAs<FunctionProtoType>();
      if (!FPT || FPT->getExceptionSpecType() == EST_None)
        FD->addAttr(NoThrowAttr::CreateImplicit(Context, FD->getLocation()));
    }
  
    IdentifierInfo *Name = FD->getIdentifier();
    if (!Name)
      return;
    if ((!getLangOpts().CPlusPlus &&
         FD->getDeclContext()->isTranslationUnit()) ||
        (isa<LinkageSpecDecl>(FD->getDeclContext()) &&
         cast<LinkageSpecDecl>(FD->getDeclContext())->getLanguage() ==
         LinkageSpecDecl::lang_c)) {
      // Okay: this could be a libc/libm/Objective-C function we know
      // about.
    } else
      return;
  
    if (Name->isStr("asprintf") || Name->isStr("vasprintf")) {
      // FIXME: asprintf and vasprintf aren't C99 functions. Should they be
      // target-specific builtins, perhaps?
      if (!FD->hasAttr<FormatAttr>())
        FD->addAttr(FormatAttr::CreateImplicit(Context,
                                               &Context.Idents.get("printf"), 2,
                                               Name->isStr("vasprintf") ? 0 : 3,
                                               FD->getLocation()));
    }
  
    if (Name->isStr("__CFStringMakeConstantString")) {
      // We already have a __builtin___CFStringMakeConstantString,
      // but builds that use -fno-constant-cfstrings don't go through that.
      if (!FD->hasAttr<FormatArgAttr>())
        FD->addAttr(FormatArgAttr::CreateImplicit(Context, ParamIdx(1, FD),
                                                  FD->getLocation()));
    }
  }
  
  TypedefDecl *Sema::ParseTypedefDecl(Scope *S, Declarator &D, QualType T,
                                      TypeSourceInfo *TInfo) {
    assert(D.getIdentifier() && "Wrong callback for declspec without declarator");
    assert(!T.isNull() && "GetTypeForDeclarator() returned null type");
  
    if (!TInfo) {
      assert(D.isInvalidType() && "no declarator info for valid type");
      TInfo = Context.getTrivialTypeSourceInfo(T);
    }
  
    // Scope manipulation handled by caller.
    TypedefDecl *NewTD =
        TypedefDecl::Create(Context, CurContext, D.getBeginLoc(),
                            D.getIdentifierLoc(), D.getIdentifier(), TInfo);
  
    // Bail out immediately if we have an invalid declaration.
    if (D.isInvalidType()) {
      NewTD->setInvalidDecl();
      return NewTD;
    }
  
    if (D.getDeclSpec().isModulePrivateSpecified()) {
      if (CurContext->isFunctionOrMethod())
        Diag(NewTD->getLocation(), diag::err_module_private_local)
          << 2 << NewTD->getDeclName()
          << SourceRange(D.getDeclSpec().getModulePrivateSpecLoc())
          << FixItHint::CreateRemoval(D.getDeclSpec().getModulePrivateSpecLoc());
      else
        NewTD->setModulePrivate();
    }
  
    // C++ [dcl.typedef]p8:
    //   If the typedef declaration defines an unnamed class (or
    //   enum), the first typedef-name declared by the declaration
    //   to be that class type (or enum type) is used to denote the
    //   class type (or enum type) for linkage purposes only.
    // We need to check whether the type was declared in the declaration.
    switch (D.getDeclSpec().getTypeSpecType()) {
    case TST_enum:
    case TST_struct:
    case TST_interface:
    case TST_union:
    case TST_class: {
      TagDecl *tagFromDeclSpec = cast<TagDecl>(D.getDeclSpec().getRepAsDecl());
      setTagNameForLinkagePurposes(tagFromDeclSpec, NewTD);
      break;
    }
  
    default:
      break;
    }
  
    return NewTD;
  }
  
  /// Check that this is a valid underlying type for an enum declaration.
  bool Sema::CheckEnumUnderlyingType(TypeSourceInfo *TI) {
    SourceLocation UnderlyingLoc = TI->getTypeLoc().getBeginLoc();
    QualType T = TI->getType();
  
    if (T->isDependentType())
      return false;
  
    if (const BuiltinType *BT = T->getAs<BuiltinType>())
      if (BT->isInteger())
        return false;
  
    Diag(UnderlyingLoc, diag::err_enum_invalid_underlying) << T;
    return true;
  }
  
  /// Check whether this is a valid redeclaration of a previous enumeration.
  /// \return true if the redeclaration was invalid.
  bool Sema::CheckEnumRedeclaration(SourceLocation EnumLoc, bool IsScoped,
                                    QualType EnumUnderlyingTy, bool IsFixed,
                                    const EnumDecl *Prev) {
    if (IsScoped != Prev->isScoped()) {
      Diag(EnumLoc, diag::err_enum_redeclare_scoped_mismatch)
        << Prev->isScoped();
      Diag(Prev->getLocation(), diag::note_previous_declaration);
      return true;
    }
  
    if (IsFixed && Prev->isFixed()) {
      if (!EnumUnderlyingTy->isDependentType() &&
          !Prev->getIntegerType()->isDependentType() &&
          !Context.hasSameUnqualifiedType(EnumUnderlyingTy,
                                          Prev->getIntegerType())) {
        // TODO: Highlight the underlying type of the redeclaration.
        Diag(EnumLoc, diag::err_enum_redeclare_type_mismatch)
          << EnumUnderlyingTy << Prev->getIntegerType();
        Diag(Prev->getLocation(), diag::note_previous_declaration)
            << Prev->getIntegerTypeRange();
        return true;
      }
    } else if (IsFixed != Prev->isFixed()) {
      Diag(EnumLoc, diag::err_enum_redeclare_fixed_mismatch)
        << Prev->isFixed();
      Diag(Prev->getLocation(), diag::note_previous_declaration);
      return true;
    }
  
    return false;
  }
  
  /// Get diagnostic %select index for tag kind for
  /// redeclaration diagnostic message.
  /// WARNING: Indexes apply to particular diagnostics only!
  ///
  /// \returns diagnostic %select index.
  static unsigned getRedeclDiagFromTagKind(TagTypeKind Tag) {
    switch (Tag) {
    case TTK_Struct: return 0;
    case TTK_Interface: return 1;
    case TTK_Class:  return 2;
    default: llvm_unreachable("Invalid tag kind for redecl diagnostic!");
    }
  }
  
  /// Determine if tag kind is a class-key compatible with
  /// class for redeclaration (class, struct, or __interface).
  ///
  /// \returns true iff the tag kind is compatible.
  static bool isClassCompatTagKind(TagTypeKind Tag)
  {
    return Tag == TTK_Struct || Tag == TTK_Class || Tag == TTK_Interface;
  }
  
  Sema::NonTagKind Sema::getNonTagTypeDeclKind(const Decl *PrevDecl,
                                               TagTypeKind TTK) {
    if (isa<TypedefDecl>(PrevDecl))
      return NTK_Typedef;
    else if (isa<TypeAliasDecl>(PrevDecl))
      return NTK_TypeAlias;
    else if (isa<ClassTemplateDecl>(PrevDecl))
      return NTK_Template;
    else if (isa<TypeAliasTemplateDecl>(PrevDecl))
      return NTK_TypeAliasTemplate;
    else if (isa<TemplateTemplateParmDecl>(PrevDecl))
      return NTK_TemplateTemplateArgument;
    switch (TTK) {
    case TTK_Struct:
    case TTK_Interface:
    case TTK_Class:
      return getLangOpts().CPlusPlus ? NTK_NonClass : NTK_NonStruct;
    case TTK_Union:
      return NTK_NonUnion;
    case TTK_Enum:
      return NTK_NonEnum;
    }
    llvm_unreachable("invalid TTK");
  }
  
  /// Determine whether a tag with a given kind is acceptable
  /// as a redeclaration of the given tag declaration.
  ///
  /// \returns true if the new tag kind is acceptable, false otherwise.
  bool Sema::isAcceptableTagRedeclaration(const TagDecl *Previous,
                                          TagTypeKind NewTag, bool isDefinition,
                                          SourceLocation NewTagLoc,
                                          const IdentifierInfo *Name) {
    // C++ [dcl.type.elab]p3:
    //   The class-key or enum keyword present in the
    //   elaborated-type-specifier shall agree in kind with the
    //   declaration to which the name in the elaborated-type-specifier
    //   refers. This rule also applies to the form of
    //   elaborated-type-specifier that declares a class-name or
    //   friend class since it can be construed as referring to the
    //   definition of the class. Thus, in any
    //   elaborated-type-specifier, the enum keyword shall be used to
    //   refer to an enumeration (7.2), the union class-key shall be
    //   used to refer to a union (clause 9), and either the class or
    //   struct class-key shall be used to refer to a class (clause 9)
    //   declared using the class or struct class-key.
    TagTypeKind OldTag = Previous->getTagKind();
    if (OldTag != NewTag &&
        !(isClassCompatTagKind(OldTag) && isClassCompatTagKind(NewTag)))
      return false;
  
    // Tags are compatible, but we might still want to warn on mismatched tags.
    // Non-class tags can't be mismatched at this point.
    if (!isClassCompatTagKind(NewTag))
      return true;
  
    // Declarations for which -Wmismatched-tags is disabled are entirely ignored
    // by our warning analysis. We don't want to warn about mismatches with (eg)
    // declarations in system headers that are designed to be specialized, but if
    // a user asks us to warn, we should warn if their code contains mismatched
    // declarations.
    auto IsIgnoredLoc = [&](SourceLocation Loc) {
      return getDiagnostics().isIgnored(diag::warn_struct_class_tag_mismatch,
                                        Loc);
    };
    if (IsIgnoredLoc(NewTagLoc))
      return true;
  
    auto IsIgnored = [&](const TagDecl *Tag) {
      return IsIgnoredLoc(Tag->getLocation());
    };
    while (IsIgnored(Previous)) {
      Previous = Previous->getPreviousDecl();
      if (!Previous)
        return true;
      OldTag = Previous->getTagKind();
    }
  
    bool isTemplate = false;
    if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(Previous))
      isTemplate = Record->getDescribedClassTemplate();
  
    if (inTemplateInstantiation()) {
      if (OldTag != NewTag) {
        // In a template instantiation, do not offer fix-its for tag mismatches
        // since they usually mess up the template instead of fixing the problem.
        Diag(NewTagLoc, diag::warn_struct_class_tag_mismatch)
          << getRedeclDiagFromTagKind(NewTag) << isTemplate << Name
          << getRedeclDiagFromTagKind(OldTag);
        // FIXME: Note previous location?
      }
      return true;
    }
  
    if (isDefinition) {
      // On definitions, check all previous tags and issue a fix-it for each
      // one that doesn't match the current tag.
      if (Previous->getDefinition()) {
        // Don't suggest fix-its for redefinitions.
        return true;
      }
  
      bool previousMismatch = false;
      for (const TagDecl *I : Previous->redecls()) {
        if (I->getTagKind() != NewTag) {
          // Ignore previous declarations for which the warning was disabled.
          if (IsIgnored(I))
            continue;
  
          if (!previousMismatch) {
            previousMismatch = true;
            Diag(NewTagLoc, diag::warn_struct_class_previous_tag_mismatch)
              << getRedeclDiagFromTagKind(NewTag) << isTemplate << Name
              << getRedeclDiagFromTagKind(I->getTagKind());
          }
          Diag(I->getInnerLocStart(), diag::note_struct_class_suggestion)
            << getRedeclDiagFromTagKind(NewTag)
            << FixItHint::CreateReplacement(I->getInnerLocStart(),
                 TypeWithKeyword::getTagTypeKindName(NewTag));
        }
      }
      return true;
    }
  
    // Identify the prevailing tag kind: this is the kind of the definition (if
    // there is a non-ignored definition), or otherwise the kind of the prior
    // (non-ignored) declaration.
    const TagDecl *PrevDef = Previous->getDefinition();
    if (PrevDef && IsIgnored(PrevDef))
      PrevDef = nullptr;
    const TagDecl *Redecl = PrevDef ? PrevDef : Previous;
    if (Redecl->getTagKind() != NewTag) {
      Diag(NewTagLoc, diag::warn_struct_class_tag_mismatch)
        << getRedeclDiagFromTagKind(NewTag) << isTemplate << Name
        << getRedeclDiagFromTagKind(OldTag);
      Diag(Redecl->getLocation(), diag::note_previous_use);
  
      // If there is a previous definition, suggest a fix-it.
      if (PrevDef) {
        Diag(NewTagLoc, diag::note_struct_class_suggestion)
          << getRedeclDiagFromTagKind(Redecl->getTagKind())
          << FixItHint::CreateReplacement(SourceRange(NewTagLoc),
               TypeWithKeyword::getTagTypeKindName(Redecl->getTagKind()));
      }
    }
  
    return true;
  }
  
  /// Add a minimal nested name specifier fixit hint to allow lookup of a tag name
  /// from an outer enclosing namespace or file scope inside a friend declaration.
  /// This should provide the commented out code in the following snippet:
  ///   namespace N {
  ///     struct X;
  ///     namespace M {
  ///       struct Y { friend struct /*N::*/ X; };
  ///     }
  ///   }
  static FixItHint createFriendTagNNSFixIt(Sema &SemaRef, NamedDecl *ND, Scope *S,
                                           SourceLocation NameLoc) {
    // While the decl is in a namespace, do repeated lookup of that name and see
    // if we get the same namespace back.  If we do not, continue until
    // translation unit scope, at which point we have a fully qualified NNS.
    SmallVector<IdentifierInfo *, 4> Namespaces;
    DeclContext *DC = ND->getDeclContext()->getRedeclContext();
    for (; !DC->isTranslationUnit(); DC = DC->getParent()) {
      // This tag should be declared in a namespace, which can only be enclosed by
      // other namespaces.  Bail if there's an anonymous namespace in the chain.
      NamespaceDecl *Namespace = dyn_cast<NamespaceDecl>(DC);
      if (!Namespace || Namespace->isAnonymousNamespace())
        return FixItHint();
      IdentifierInfo *II = Namespace->getIdentifier();
      Namespaces.push_back(II);
      NamedDecl *Lookup = SemaRef.LookupSingleName(
          S, II, NameLoc, Sema::LookupNestedNameSpecifierName);
      if (Lookup == Namespace)
        break;
    }
  
    // Once we have all the namespaces, reverse them to go outermost first, and
    // build an NNS.
    SmallString<64> Insertion;
    llvm::raw_svector_ostream OS(Insertion);
    if (DC->isTranslationUnit())
      OS << "::";
    std::reverse(Namespaces.begin(), Namespaces.end());
    for (auto *II : Namespaces)
      OS << II->getName() << "::";
    return FixItHint::CreateInsertion(NameLoc, Insertion);
  }
  
  /// Determine whether a tag originally declared in context \p OldDC can
  /// be redeclared with an unqualified name in \p NewDC (assuming name lookup
  /// found a declaration in \p OldDC as a previous decl, perhaps through a
  /// using-declaration).
  static bool isAcceptableTagRedeclContext(Sema &S, DeclContext *OldDC,
                                           DeclContext *NewDC) {
    OldDC = OldDC->getRedeclContext();
    NewDC = NewDC->getRedeclContext();
  
    if (OldDC->Equals(NewDC))
      return true;
  
    // In MSVC mode, we allow a redeclaration if the contexts are related (either
    // encloses the other).
    if (S.getLangOpts().MSVCCompat &&
        (OldDC->Encloses(NewDC) || NewDC->Encloses(OldDC)))
      return true;
  
    return false;
  }
  
  /// This is invoked when we see 'struct foo' or 'struct {'.  In the
  /// former case, Name will be non-null.  In the later case, Name will be null.
  /// TagSpec indicates what kind of tag this is. TUK indicates whether this is a
  /// reference/declaration/definition of a tag.
  ///
  /// \param IsTypeSpecifier \c true if this is a type-specifier (or
  /// trailing-type-specifier) other than one in an alias-declaration.
  ///
  /// \param SkipBody If non-null, will be set to indicate if the caller should
  /// skip the definition of this tag and treat it as if it were a declaration.
  Decl *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
                       SourceLocation KWLoc, CXXScopeSpec &SS,
                       IdentifierInfo *Name, SourceLocation NameLoc,
                       const ParsedAttributesView &Attrs, AccessSpecifier AS,
                       SourceLocation ModulePrivateLoc,
                       MultiTemplateParamsArg TemplateParameterLists,
                       bool &OwnedDecl, bool &IsDependent,
                       SourceLocation ScopedEnumKWLoc,
                       bool ScopedEnumUsesClassTag, TypeResult UnderlyingType,
                       bool IsTypeSpecifier, bool IsTemplateParamOrArg,
                       SkipBodyInfo *SkipBody) {
    // If this is not a definition, it must have a name.
    IdentifierInfo *OrigName = Name;
    assert((Name != nullptr || TUK == TUK_Definition) &&
           "Nameless record must be a definition!");
    assert(TemplateParameterLists.size() == 0 || TUK != TUK_Reference);
  
    OwnedDecl = false;
    TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForTypeSpec(TagSpec);
    bool ScopedEnum = ScopedEnumKWLoc.isValid();
  
    // FIXME: Check member specializations more carefully.
    bool isMemberSpecialization = false;
    bool Invalid = false;
  
    // We only need to do this matching if we have template parameters
    // or a scope specifier, which also conveniently avoids this work
    // for non-C++ cases.
    if (TemplateParameterLists.size() > 0 ||
        (SS.isNotEmpty() && TUK != TUK_Reference)) {
      if (TemplateParameterList *TemplateParams =
              MatchTemplateParametersToScopeSpecifier(
                  KWLoc, NameLoc, SS, nullptr, TemplateParameterLists,
                  TUK == TUK_Friend, isMemberSpecialization, Invalid)) {
        if (Kind == TTK_Enum) {
          Diag(KWLoc, diag::err_enum_template);
          return nullptr;
        }
  
        if (TemplateParams->size() > 0) {
          // This is a declaration or definition of a class template (which may
          // be a member of another template).
  
          if (Invalid)
            return nullptr;
  
          OwnedDecl = false;
          DeclResult Result = CheckClassTemplate(
              S, TagSpec, TUK, KWLoc, SS, Name, NameLoc, Attrs, TemplateParams,
              AS, ModulePrivateLoc,
              /*FriendLoc*/ SourceLocation(), TemplateParameterLists.size() - 1,
              TemplateParameterLists.data(), SkipBody);
          return Result.get();
        } else {
          // The "template<>" header is extraneous.
          Diag(TemplateParams->getTemplateLoc(), diag::err_template_tag_noparams)
            << TypeWithKeyword::getTagTypeKindName(Kind) << Name;
          isMemberSpecialization = true;
        }
      }
    }
  
    // Figure out the underlying type if this a enum declaration. We need to do
    // this early, because it's needed to detect if this is an incompatible
    // redeclaration.
    llvm::PointerUnion<const Type*, TypeSourceInfo*> EnumUnderlying;
    bool IsFixed = !UnderlyingType.isUnset() || ScopedEnum;
  
    if (Kind == TTK_Enum) {
      if (UnderlyingType.isInvalid() || (!UnderlyingType.get() && ScopedEnum)) {
        // No underlying type explicitly specified, or we failed to parse the
        // type, default to int.
        EnumUnderlying = Context.IntTy.getTypePtr();
      } else if (UnderlyingType.get()) {
        // C++0x 7.2p2: The type-specifier-seq of an enum-base shall name an
        // integral type; any cv-qualification is ignored.
        TypeSourceInfo *TI = nullptr;
        GetTypeFromParser(UnderlyingType.get(), &TI);
        EnumUnderlying = TI;
  
        if (CheckEnumUnderlyingType(TI))
          // Recover by falling back to int.
          EnumUnderlying = Context.IntTy.getTypePtr();
  
        if (DiagnoseUnexpandedParameterPack(TI->getTypeLoc().getBeginLoc(), TI,
                                            UPPC_FixedUnderlyingType))
          EnumUnderlying = Context.IntTy.getTypePtr();
  
      } else if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
        // For MSVC ABI compatibility, unfixed enums must use an underlying type
        // of 'int'. However, if this is an unfixed forward declaration, don't set
        // the underlying type unless the user enables -fms-compatibility. This
        // makes unfixed forward declared enums incomplete and is more conforming.
        if (TUK == TUK_Definition || getLangOpts().MSVCCompat)
          EnumUnderlying = Context.IntTy.getTypePtr();
      }
    }
  
    DeclContext *SearchDC = CurContext;
    DeclContext *DC = CurContext;
    bool isStdBadAlloc = false;
    bool isStdAlignValT = false;
  
    RedeclarationKind Redecl = forRedeclarationInCurContext();
    if (TUK == TUK_Friend || TUK == TUK_Reference)
      Redecl = NotForRedeclaration;
  
    /// Create a new tag decl in C/ObjC. Since the ODR-like semantics for ObjC/C
    /// implemented asks for structural equivalence checking, the returned decl
    /// here is passed back to the parser, allowing the tag body to be parsed.
    auto createTagFromNewDecl = [&]() -> TagDecl * {
      assert(!getLangOpts().CPlusPlus && "not meant for C++ usage");
      // If there is an identifier, use the location of the identifier as the
      // location of the decl, otherwise use the location of the struct/union
      // keyword.
      SourceLocation Loc = NameLoc.isValid() ? NameLoc : KWLoc;
      TagDecl *New = nullptr;
  
      if (Kind == TTK_Enum) {
        New = EnumDecl::Create(Context, SearchDC, KWLoc, Loc, Name, nullptr,
                               ScopedEnum, ScopedEnumUsesClassTag, IsFixed);
        // If this is an undefined enum, bail.
        if (TUK != TUK_Definition && !Invalid)
          return nullptr;
        if (EnumUnderlying) {
          EnumDecl *ED = cast<EnumDecl>(New);
          if (TypeSourceInfo *TI = EnumUnderlying.dyn_cast<TypeSourceInfo *>())
            ED->setIntegerTypeSourceInfo(TI);
          else
            ED->setIntegerType(QualType(EnumUnderlying.get<const Type *>(), 0));
          ED->setPromotionType(ED->getIntegerType());
        }
      } else { // struct/union
        New = RecordDecl::Create(Context, Kind, SearchDC, KWLoc, Loc, Name,
                                 nullptr);
      }
  
      if (RecordDecl *RD = dyn_cast<RecordDecl>(New)) {
        // Add alignment attributes if necessary; these attributes are checked
        // when the ASTContext lays out the structure.
        //
        // It is important for implementing the correct semantics that this
        // happen here (in ActOnTag). The #pragma pack stack is
        // maintained as a result of parser callbacks which can occur at
        // many points during the parsing of a struct declaration (because
        // the #pragma tokens are effectively skipped over during the
        // parsing of the struct).
        if (TUK == TUK_Definition && (!SkipBody || !SkipBody->ShouldSkip)) {
          AddAlignmentAttributesForRecord(RD);
          AddMsStructLayoutForRecord(RD);
        }
      }
      New->setLexicalDeclContext(CurContext);
      return New;
    };
  
    LookupResult Previous(*this, Name, NameLoc, LookupTagName, Redecl);
    if (Name && SS.isNotEmpty()) {
      // We have a nested-name tag ('struct foo::bar').
  
      // Check for invalid 'foo::'.
      if (SS.isInvalid()) {
        Name = nullptr;
        goto CreateNewDecl;
      }
  
      // If this is a friend or a reference to a class in a dependent
      // context, don't try to make a decl for it.
      if (TUK == TUK_Friend || TUK == TUK_Reference) {
        DC = computeDeclContext(SS, false);
        if (!DC) {
          IsDependent = true;
          return nullptr;
        }
      } else {
        DC = computeDeclContext(SS, true);
        if (!DC) {
          Diag(SS.getRange().getBegin(), diag::err_dependent_nested_name_spec)
            << SS.getRange();
          return nullptr;
        }
      }
  
      if (RequireCompleteDeclContext(SS, DC))
        return nullptr;
  
      SearchDC = DC;
      // Look-up name inside 'foo::'.
      LookupQualifiedName(Previous, DC);
  
      if (Previous.isAmbiguous())
        return nullptr;
  
      if (Previous.empty()) {
        // Name lookup did not find anything. However, if the
        // nested-name-specifier refers to the current instantiation,
        // and that current instantiation has any dependent base
        // classes, we might find something at instantiation time: treat
        // this as a dependent elaborated-type-specifier.
        // But this only makes any sense for reference-like lookups.
        if (Previous.wasNotFoundInCurrentInstantiation() &&
            (TUK == TUK_Reference || TUK == TUK_Friend)) {
          IsDependent = true;
          return nullptr;
        }
  
        // A tag 'foo::bar' must already exist.
        Diag(NameLoc, diag::err_not_tag_in_scope)
          << Kind << Name << DC << SS.getRange();
        Name = nullptr;
        Invalid = true;
        goto CreateNewDecl;
      }
    } else if (Name) {
      // C++14 [class.mem]p14:
      //   If T is the name of a class, then each of the following shall have a
      //   name different from T:
      //    -- every member of class T that is itself a type
      if (TUK != TUK_Reference && TUK != TUK_Friend &&
          DiagnoseClassNameShadow(SearchDC, DeclarationNameInfo(Name, NameLoc)))
        return nullptr;
  
      // If this is a named struct, check to see if there was a previous forward
      // declaration or definition.
      // FIXME: We're looking into outer scopes here, even when we
      // shouldn't be. Doing so can result in ambiguities that we
      // shouldn't be diagnosing.
      LookupName(Previous, S);
  
      // When declaring or defining a tag, ignore ambiguities introduced
      // by types using'ed into this scope.
      if (Previous.isAmbiguous() &&
          (TUK == TUK_Definition || TUK == TUK_Declaration)) {
        LookupResult::Filter F = Previous.makeFilter();
        while (F.hasNext()) {
          NamedDecl *ND = F.next();
          if (!ND->getDeclContext()->getRedeclContext()->Equals(
                  SearchDC->getRedeclContext()))
            F.erase();
        }
        F.done();
      }
  
      // C++11 [namespace.memdef]p3:
      //   If the name in a friend declaration is neither qualified nor
      //   a template-id and the declaration is a function or an
      //   elaborated-type-specifier, the lookup to determine whether
      //   the entity has been previously declared shall not consider
      //   any scopes outside the innermost enclosing namespace.
      //
      // MSVC doesn't implement the above rule for types, so a friend tag
      // declaration may be a redeclaration of a type declared in an enclosing
      // scope.  They do implement this rule for friend functions.
      //
      // Does it matter that this should be by scope instead of by
      // semantic context?
      if (!Previous.empty() && TUK == TUK_Friend) {
        DeclContext *EnclosingNS = SearchDC->getEnclosingNamespaceContext();
        LookupResult::Filter F = Previous.makeFilter();
        bool FriendSawTagOutsideEnclosingNamespace = false;
        while (F.hasNext()) {
          NamedDecl *ND = F.next();
          DeclContext *DC = ND->getDeclContext()->getRedeclContext();
          if (DC->isFileContext() &&
              !EnclosingNS->Encloses(ND->getDeclContext())) {
            if (getLangOpts().MSVCCompat)
              FriendSawTagOutsideEnclosingNamespace = true;
            else
              F.erase();
          }
        }
        F.done();
  
        // Diagnose this MSVC extension in the easy case where lookup would have
        // unambiguously found something outside the enclosing namespace.
        if (Previous.isSingleResult() && FriendSawTagOutsideEnclosingNamespace) {
          NamedDecl *ND = Previous.getFoundDecl();
          Diag(NameLoc, diag::ext_friend_tag_redecl_outside_namespace)
              << createFriendTagNNSFixIt(*this, ND, S, NameLoc);
        }
      }
  
      // Note:  there used to be some attempt at recovery here.
      if (Previous.isAmbiguous())
        return nullptr;
  
      if (!getLangOpts().CPlusPlus && TUK != TUK_Reference) {
        // FIXME: This makes sure that we ignore the contexts associated
        // with C structs, unions, and enums when looking for a matching
        // tag declaration or definition. See the similar lookup tweak
        // in Sema::LookupName; is there a better way to deal with this?
        while (isa<RecordDecl>(SearchDC) || isa<EnumDecl>(SearchDC))
          SearchDC = SearchDC->getParent();
      }
    }
  
    if (Previous.isSingleResult() &&
        Previous.getFoundDecl()->isTemplateParameter()) {
      // Maybe we will complain about the shadowed template parameter.
      DiagnoseTemplateParameterShadow(NameLoc, Previous.getFoundDecl());
      // Just pretend that we didn't see the previous declaration.
      Previous.clear();
    }
  
    if (getLangOpts().CPlusPlus && Name && DC && StdNamespace &&
        DC->Equals(getStdNamespace())) {
      if (Name->isStr("bad_alloc")) {
        // This is a declaration of or a reference to "std::bad_alloc".
        isStdBadAlloc = true;
  
        // If std::bad_alloc has been implicitly declared (but made invisible to
        // name lookup), fill in this implicit declaration as the previous
        // declaration, so that the declarations get chained appropriately.
        if (Previous.empty() && StdBadAlloc)
          Previous.addDecl(getStdBadAlloc());
      } else if (Name->isStr("align_val_t")) {
        isStdAlignValT = true;
        if (Previous.empty() && StdAlignValT)
          Previous.addDecl(getStdAlignValT());
      }
    }
  
    // If we didn't find a previous declaration, and this is a reference
    // (or friend reference), move to the correct scope.  In C++, we
    // also need to do a redeclaration lookup there, just in case
    // there's a shadow friend decl.
    if (Name && Previous.empty() &&
        (TUK == TUK_Reference || TUK == TUK_Friend || IsTemplateParamOrArg)) {
      if (Invalid) goto CreateNewDecl;
      assert(SS.isEmpty());
  
      if (TUK == TUK_Reference || IsTemplateParamOrArg) {
        // C++ [basic.scope.pdecl]p5:
        //   -- for an elaborated-type-specifier of the form
        //
        //          class-key identifier
        //
        //      if the elaborated-type-specifier is used in the
        //      decl-specifier-seq or parameter-declaration-clause of a
        //      function defined in namespace scope, the identifier is
        //      declared as a class-name in the namespace that contains
        //      the declaration; otherwise, except as a friend
        //      declaration, the identifier is declared in the smallest
        //      non-class, non-function-prototype scope that contains the
        //      declaration.
        //
        // C99 6.7.2.3p8 has a similar (but not identical!) provision for
        // C structs and unions.
        //
        // It is an error in C++ to declare (rather than define) an enum
        // type, including via an elaborated type specifier.  We'll
        // diagnose that later; for now, declare the enum in the same
        // scope as we would have picked for any other tag type.
        //
        // GNU C also supports this behavior as part of its incomplete
        // enum types extension, while GNU C++ does not.
        //
        // Find the context where we'll be declaring the tag.
        // FIXME: We would like to maintain the current DeclContext as the
        // lexical context,
        SearchDC = getTagInjectionContext(SearchDC);
  
        // Find the scope where we'll be declaring the tag.
        S = getTagInjectionScope(S, getLangOpts());
      } else {
        assert(TUK == TUK_Friend);
        // C++ [namespace.memdef]p3:
        //   If a friend declaration in a non-local class first declares a
        //   class or function, the friend class or function is a member of
        //   the innermost enclosing namespace.
        SearchDC = SearchDC->getEnclosingNamespaceContext();
      }
  
      // In C++, we need to do a redeclaration lookup to properly
      // diagnose some problems.
      // FIXME: redeclaration lookup is also used (with and without C++) to find a
      // hidden declaration so that we don't get ambiguity errors when using a
      // type declared by an elaborated-type-specifier.  In C that is not correct
      // and we should instead merge compatible types found by lookup.
      if (getLangOpts().CPlusPlus) {
        Previous.setRedeclarationKind(forRedeclarationInCurContext());
        LookupQualifiedName(Previous, SearchDC);
      } else {
        Previous.setRedeclarationKind(forRedeclarationInCurContext());
        LookupName(Previous, S);
      }
    }
  
    // If we have a known previous declaration to use, then use it.
    if (Previous.empty() && SkipBody && SkipBody->Previous)
      Previous.addDecl(SkipBody->Previous);
  
    if (!Previous.empty()) {
      NamedDecl *PrevDecl = Previous.getFoundDecl();
      NamedDecl *DirectPrevDecl = Previous.getRepresentativeDecl();
  
      // It's okay to have a tag decl in the same scope as a typedef
      // which hides a tag decl in the same scope.  Finding this
      // insanity with a redeclaration lookup can only actually happen
      // in C++.
      //
      // This is also okay for elaborated-type-specifiers, which is
      // technically forbidden by the current standard but which is
      // okay according to the likely resolution of an open issue;
      // see http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#407
      if (getLangOpts().CPlusPlus) {
        if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(PrevDecl)) {
          if (const TagType *TT = TD->getUnderlyingType()->getAs<TagType>()) {
            TagDecl *Tag = TT->getDecl();
            if (Tag->getDeclName() == Name &&
                Tag->getDeclContext()->getRedeclContext()
                            ->Equals(TD->getDeclContext()->getRedeclContext())) {
              PrevDecl = Tag;
              Previous.clear();
              Previous.addDecl(Tag);
              Previous.resolveKind();
            }
          }
        }
      }
  
      // If this is a redeclaration of a using shadow declaration, it must
      // declare a tag in the same context. In MSVC mode, we allow a
      // redefinition if either context is within the other.
      if (auto *Shadow = dyn_cast<UsingShadowDecl>(DirectPrevDecl)) {
        auto *OldTag = dyn_cast<TagDecl>(PrevDecl);
        if (SS.isEmpty() && TUK != TUK_Reference && TUK != TUK_Friend &&
            isDeclInScope(Shadow, SearchDC, S, isMemberSpecialization) &&
            !(OldTag && isAcceptableTagRedeclContext(
                            *this, OldTag->getDeclContext(), SearchDC))) {
          Diag(KWLoc, diag::err_using_decl_conflict_reverse);
          Diag(Shadow->getTargetDecl()->getLocation(),
               diag::note_using_decl_target);
          Diag(Shadow->getUsingDecl()->getLocation(), diag::note_using_decl)
              << 0;
          // Recover by ignoring the old declaration.
          Previous.clear();
          goto CreateNewDecl;
        }
      }
  
      if (TagDecl *PrevTagDecl = dyn_cast<TagDecl>(PrevDecl)) {
        // If this is a use of a previous tag, or if the tag is already declared
        // in the same scope (so that the definition/declaration completes or
        // rementions the tag), reuse the decl.
        if (TUK == TUK_Reference || TUK == TUK_Friend ||
            isDeclInScope(DirectPrevDecl, SearchDC, S,
                          SS.isNotEmpty() || isMemberSpecialization)) {
          // Make sure that this wasn't declared as an enum and now used as a
          // struct or something similar.
          if (!isAcceptableTagRedeclaration(PrevTagDecl, Kind,
                                            TUK == TUK_Definition, KWLoc,
                                            Name)) {
            bool SafeToContinue
              = (PrevTagDecl->getTagKind() != TTK_Enum &&
                 Kind != TTK_Enum);
            if (SafeToContinue)
              Diag(KWLoc, diag::err_use_with_wrong_tag)
                << Name
                << FixItHint::CreateReplacement(SourceRange(KWLoc),
                                                PrevTagDecl->getKindName());
            else
              Diag(KWLoc, diag::err_use_with_wrong_tag) << Name;
            Diag(PrevTagDecl->getLocation(), diag::note_previous_use);
  
            if (SafeToContinue)
              Kind = PrevTagDecl->getTagKind();
            else {
              // Recover by making this an anonymous redefinition.
              Name = nullptr;
              Previous.clear();
              Invalid = true;
            }
          }
  
          if (Kind == TTK_Enum && PrevTagDecl->getTagKind() == TTK_Enum) {
            const EnumDecl *PrevEnum = cast<EnumDecl>(PrevTagDecl);
  
            // If this is an elaborated-type-specifier for a scoped enumeration,
            // the 'class' keyword is not necessary and not permitted.
            if (TUK == TUK_Reference || TUK == TUK_Friend) {
              if (ScopedEnum)
                Diag(ScopedEnumKWLoc, diag::err_enum_class_reference)
                  << PrevEnum->isScoped()
                  << FixItHint::CreateRemoval(ScopedEnumKWLoc);
              return PrevTagDecl;
            }
  
            QualType EnumUnderlyingTy;
            if (TypeSourceInfo *TI = EnumUnderlying.dyn_cast<TypeSourceInfo*>())
              EnumUnderlyingTy = TI->getType().getUnqualifiedType();
            else if (const Type *T = EnumUnderlying.dyn_cast<const Type*>())
              EnumUnderlyingTy = QualType(T, 0);
  
            // All conflicts with previous declarations are recovered by
            // returning the previous declaration, unless this is a definition,
            // in which case we want the caller to bail out.
            if (CheckEnumRedeclaration(NameLoc.isValid() ? NameLoc : KWLoc,
                                       ScopedEnum, EnumUnderlyingTy,
                                       IsFixed, PrevEnum))
              return TUK == TUK_Declaration ? PrevTagDecl : nullptr;
          }
  
          // C++11 [class.mem]p1:
          //   A member shall not be declared twice in the member-specification,
          //   except that a nested class or member class template can be declared
          //   and then later defined.
          if (TUK == TUK_Declaration && PrevDecl->isCXXClassMember() &&
              S->isDeclScope(PrevDecl)) {
            Diag(NameLoc, diag::ext_member_redeclared);
            Diag(PrevTagDecl->getLocation(), diag::note_previous_declaration);
          }
  
          if (!Invalid) {
            // If this is a use, just return the declaration we found, unless
            // we have attributes.
            if (TUK == TUK_Reference || TUK == TUK_Friend) {
              if (!Attrs.empty()) {
                // FIXME: Diagnose these attributes. For now, we create a new
                // declaration to hold them.
              } else if (TUK == TUK_Reference &&
                         (PrevTagDecl->getFriendObjectKind() ==
                              Decl::FOK_Undeclared ||
                          PrevDecl->getOwningModule() != getCurrentModule()) &&
                         SS.isEmpty()) {
                // This declaration is a reference to an existing entity, but
                // has different visibility from that entity: it either makes
                // a friend visible or it makes a type visible in a new module.
                // In either case, create a new declaration. We only do this if
                // the declaration would have meant the same thing if no prior
                // declaration were found, that is, if it was found in the same
                // scope where we would have injected a declaration.
                if (!getTagInjectionContext(CurContext)->getRedeclContext()
                         ->Equals(PrevDecl->getDeclContext()->getRedeclContext()))
                  return PrevTagDecl;
                // This is in the injected scope, create a new declaration in
                // that scope.
                S = getTagInjectionScope(S, getLangOpts());
              } else {
                return PrevTagDecl;
              }
            }
  
            // Diagnose attempts to redefine a tag.
            if (TUK == TUK_Definition) {
              if (NamedDecl *Def = PrevTagDecl->getDefinition()) {
                // If we're defining a specialization and the previous definition
                // is from an implicit instantiation, don't emit an error
                // here; we'll catch this in the general case below.
                bool IsExplicitSpecializationAfterInstantiation = false;
                if (isMemberSpecialization) {
                  if (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Def))
                    IsExplicitSpecializationAfterInstantiation =
                      RD->getTemplateSpecializationKind() !=
                      TSK_ExplicitSpecialization;
                  else if (EnumDecl *ED = dyn_cast<EnumDecl>(Def))
                    IsExplicitSpecializationAfterInstantiation =
                      ED->getTemplateSpecializationKind() !=
                      TSK_ExplicitSpecialization;
                }
  
                // Note that clang allows ODR-like semantics for ObjC/C, i.e., do
                // not keep more that one definition around (merge them). However,
                // ensure the decl passes the structural compatibility check in
                // C11 6.2.7/1 (or 6.1.2.6/1 in C89).
                NamedDecl *Hidden = nullptr;
                if (SkipBody && !hasVisibleDefinition(Def, &Hidden)) {
                  // There is a definition of this tag, but it is not visible. We
                  // explicitly make use of C++'s one definition rule here, and
                  // assume that this definition is identical to the hidden one
                  // we already have. Make the existing definition visible and
                  // use it in place of this one.
                  if (!getLangOpts().CPlusPlus) {
                    // Postpone making the old definition visible until after we
                    // complete parsing the new one and do the structural
                    // comparison.
                    SkipBody->CheckSameAsPrevious = true;
                    SkipBody->New = createTagFromNewDecl();
                    SkipBody->Previous = Def;
                    return Def;
                  } else {
                    SkipBody->ShouldSkip = true;
                    SkipBody->Previous = Def;
                    makeMergedDefinitionVisible(Hidden);
                    // Carry on and handle it like a normal definition. We'll
                    // skip starting the definitiion later.
                  }
                } else if (!IsExplicitSpecializationAfterInstantiation) {
                  // A redeclaration in function prototype scope in C isn't
                  // visible elsewhere, so merely issue a warning.
                  if (!getLangOpts().CPlusPlus && S->containedInPrototypeScope())
                    Diag(NameLoc, diag::warn_redefinition_in_param_list) << Name;
                  else
                    Diag(NameLoc, diag::err_redefinition) << Name;
                  notePreviousDefinition(Def,
                                         NameLoc.isValid() ? NameLoc : KWLoc);
                  // If this is a redefinition, recover by making this
                  // struct be anonymous, which will make any later
                  // references get the previous definition.
                  Name = nullptr;
                  Previous.clear();
                  Invalid = true;
                }
              } else {
                // If the type is currently being defined, complain
                // about a nested redefinition.
                auto *TD = Context.getTagDeclType(PrevTagDecl)->getAsTagDecl();
                if (TD->isBeingDefined()) {
                  Diag(NameLoc, diag::err_nested_redefinition) << Name;
                  Diag(PrevTagDecl->getLocation(),
                       diag::note_previous_definition);
                  Name = nullptr;
                  Previous.clear();
                  Invalid = true;
                }
              }
  
              // Okay, this is definition of a previously declared or referenced
              // tag. We're going to create a new Decl for it.
            }
  
            // Okay, we're going to make a redeclaration.  If this is some kind
            // of reference, make sure we build the redeclaration in the same DC
            // as the original, and ignore the current access specifier.
            if (TUK == TUK_Friend || TUK == TUK_Reference) {
              SearchDC = PrevTagDecl->getDeclContext();
              AS = AS_none;
            }
          }
          // If we get here we have (another) forward declaration or we
          // have a definition.  Just create a new decl.
  
        } else {
          // If we get here, this is a definition of a new tag type in a nested
          // scope, e.g. "struct foo; void bar() { struct foo; }", just create a
          // new decl/type.  We set PrevDecl to NULL so that the entities
          // have distinct types.
          Previous.clear();
        }
        // If we get here, we're going to create a new Decl. If PrevDecl
        // is non-NULL, it's a definition of the tag declared by
        // PrevDecl. If it's NULL, we have a new definition.
  
      // Otherwise, PrevDecl is not a tag, but was found with tag
      // lookup.  This is only actually possible in C++, where a few
      // things like templates still live in the tag namespace.
      } else {
        // Use a better diagnostic if an elaborated-type-specifier
        // found the wrong kind of type on the first
        // (non-redeclaration) lookup.
        if ((TUK == TUK_Reference || TUK == TUK_Friend) &&
            !Previous.isForRedeclaration()) {
          NonTagKind NTK = getNonTagTypeDeclKind(PrevDecl, Kind);
          Diag(NameLoc, diag::err_tag_reference_non_tag) << PrevDecl << NTK
                                                         << Kind;
          Diag(PrevDecl->getLocation(), diag::note_declared_at);
          Invalid = true;
  
        // Otherwise, only diagnose if the declaration is in scope.
        } else if (!isDeclInScope(DirectPrevDecl, SearchDC, S,
                                  SS.isNotEmpty() || isMemberSpecialization)) {
          // do nothing
  
        // Diagnose implicit declarations introduced by elaborated types.
        } else if (TUK == TUK_Reference || TUK == TUK_Friend) {
          NonTagKind NTK = getNonTagTypeDeclKind(PrevDecl, Kind);
          Diag(NameLoc, diag::err_tag_reference_conflict) << NTK;
          Diag(PrevDecl->getLocation(), diag::note_previous_decl) << PrevDecl;
          Invalid = true;
  
        // Otherwise it's a declaration.  Call out a particularly common
        // case here.
        } else if (TypedefNameDecl *TND = dyn_cast<TypedefNameDecl>(PrevDecl)) {
          unsigned Kind = 0;
          if (isa<TypeAliasDecl>(PrevDecl)) Kind = 1;
          Diag(NameLoc, diag::err_tag_definition_of_typedef)
            << Name << Kind << TND->getUnderlyingType();
          Diag(PrevDecl->getLocation(), diag::note_previous_decl) << PrevDecl;
          Invalid = true;
  
        // Otherwise, diagnose.
        } else {
          // The tag name clashes with something else in the target scope,
          // issue an error and recover by making this tag be anonymous.
          Diag(NameLoc, diag::err_redefinition_different_kind) << Name;
          notePreviousDefinition(PrevDecl, NameLoc);
          Name = nullptr;
          Invalid = true;
        }
  
        // The existing declaration isn't relevant to us; we're in a
        // new scope, so clear out the previous declaration.
        Previous.clear();
      }
    }
  
  CreateNewDecl:
  
    TagDecl *PrevDecl = nullptr;
    if (Previous.isSingleResult())
      PrevDecl = cast<TagDecl>(Previous.getFoundDecl());
  
    // If there is an identifier, use the location of the identifier as the
    // location of the decl, otherwise use the location of the struct/union
    // keyword.
    SourceLocation Loc = NameLoc.isValid() ? NameLoc : KWLoc;
  
    // Otherwise, create a new declaration. If there is a previous
    // declaration of the same entity, the two will be linked via
    // PrevDecl.
    TagDecl *New;
  
    if (Kind == TTK_Enum) {
      // FIXME: Tag decls should be chained to any simultaneous vardecls, e.g.:
      // enum X { A, B, C } D;    D should chain to X.
      New = EnumDecl::Create(Context, SearchDC, KWLoc, Loc, Name,
                             cast_or_null<EnumDecl>(PrevDecl), ScopedEnum,
                             ScopedEnumUsesClassTag, IsFixed);
  
      if (isStdAlignValT && (!StdAlignValT || getStdAlignValT()->isImplicit()))
        StdAlignValT = cast<EnumDecl>(New);
  
      // If this is an undefined enum, warn.
      if (TUK != TUK_Definition && !Invalid) {
        TagDecl *Def;
        if (IsFixed && cast<EnumDecl>(New)->isFixed()) {
          // C++0x: 7.2p2: opaque-enum-declaration.
          // Conflicts are diagnosed above. Do nothing.
        }
        else if (PrevDecl && (Def = cast<EnumDecl>(PrevDecl)->getDefinition())) {
          Diag(Loc, diag::ext_forward_ref_enum_def)
            << New;
          Diag(Def->getLocation(), diag::note_previous_definition);
        } else {
          unsigned DiagID = diag::ext_forward_ref_enum;
          if (getLangOpts().MSVCCompat)
            DiagID = diag::ext_ms_forward_ref_enum;
          else if (getLangOpts().CPlusPlus)
            DiagID = diag::err_forward_ref_enum;
          Diag(Loc, DiagID);
        }
      }
  
      if (EnumUnderlying) {
        EnumDecl *ED = cast<EnumDecl>(New);
        if (TypeSourceInfo *TI = EnumUnderlying.dyn_cast<TypeSourceInfo*>())
          ED->setIntegerTypeSourceInfo(TI);
        else
          ED->setIntegerType(QualType(EnumUnderlying.get<const Type*>(), 0));
        ED->setPromotionType(ED->getIntegerType());
        assert(ED->isComplete() && "enum with type should be complete");
      }
    } else {
      // struct/union/class
  
      // FIXME: Tag decls should be chained to any simultaneous vardecls, e.g.:
      // struct X { int A; } D;    D should chain to X.
      if (getLangOpts().CPlusPlus) {
        // FIXME: Look for a way to use RecordDecl for simple structs.
        New = CXXRecordDecl::Create(Context, Kind, SearchDC, KWLoc, Loc, Name,
                                    cast_or_null<CXXRecordDecl>(PrevDecl));
  
        if (isStdBadAlloc && (!StdBadAlloc || getStdBadAlloc()->isImplicit()))
          StdBadAlloc = cast<CXXRecordDecl>(New);
      } else
        New = RecordDecl::Create(Context, Kind, SearchDC, KWLoc, Loc, Name,
                                 cast_or_null<RecordDecl>(PrevDecl));
    }
  
    // C++11 [dcl.type]p3:
    //   A type-specifier-seq shall not define a class or enumeration [...].
    if (getLangOpts().CPlusPlus && (IsTypeSpecifier || IsTemplateParamOrArg) &&
        TUK == TUK_Definition) {
      Diag(New->getLocation(), diag::err_type_defined_in_type_specifier)
        << Context.getTagDeclType(New);
      Invalid = true;
    }
  
    if (!Invalid && getLangOpts().CPlusPlus && TUK == TUK_Definition &&
        DC->getDeclKind() == Decl::Enum) {
      Diag(New->getLocation(), diag::err_type_defined_in_enum)
        << Context.getTagDeclType(New);
      Invalid = true;
    }
  
    // Maybe add qualifier info.
    if (SS.isNotEmpty()) {
      if (SS.isSet()) {
        // If this is either a declaration or a definition, check the
        // nested-name-specifier against the current context.
        if ((TUK == TUK_Definition || TUK == TUK_Declaration) &&
            diagnoseQualifiedDeclaration(SS, DC, OrigName, Loc,
                                         isMemberSpecialization))
          Invalid = true;
  
        New->setQualifierInfo(SS.getWithLocInContext(Context));
        if (TemplateParameterLists.size() > 0) {
          New->setTemplateParameterListsInfo(Context, TemplateParameterLists);
        }
      }
      else
        Invalid = true;
    }
  
    if (RecordDecl *RD = dyn_cast<RecordDecl>(New)) {
      // Add alignment attributes if necessary; these attributes are checked when
      // the ASTContext lays out the structure.
      //
      // It is important for implementing the correct semantics that this
      // happen here (in ActOnTag). The #pragma pack stack is
      // maintained as a result of parser callbacks which can occur at
      // many points during the parsing of a struct declaration (because
      // the #pragma tokens are effectively skipped over during the
      // parsing of the struct).
      if (TUK == TUK_Definition && (!SkipBody || !SkipBody->ShouldSkip)) {
        AddAlignmentAttributesForRecord(RD);
        AddMsStructLayoutForRecord(RD);
      }
    }
  
    if (ModulePrivateLoc.isValid()) {
      if (isMemberSpecialization)
        Diag(New->getLocation(), diag::err_module_private_specialization)
          << 2
          << FixItHint::CreateRemoval(ModulePrivateLoc);
      // __module_private__ does not apply to local classes. However, we only
      // diagnose this as an error when the declaration specifiers are
      // freestanding. Here, we just ignore the __module_private__.
      else if (!SearchDC->isFunctionOrMethod())
        New->setModulePrivate();
    }
  
    // If this is a specialization of a member class (of a class template),
    // check the specialization.
    if (isMemberSpecialization && CheckMemberSpecialization(New, Previous))
      Invalid = true;
  
    // If we're declaring or defining a tag in function prototype scope in C,
    // note that this type can only be used within the function and add it to
    // the list of decls to inject into the function definition scope.
    if ((Name || Kind == TTK_Enum) &&
        getNonFieldDeclScope(S)->isFunctionPrototypeScope()) {
      if (getLangOpts().CPlusPlus) {
        // C++ [dcl.fct]p6:
        //   Types shall not be defined in return or parameter types.
        if (TUK == TUK_Definition && !IsTypeSpecifier) {
          Diag(Loc, diag::err_type_defined_in_param_type)
              << Name;
          Invalid = true;
        }
      } else if (!PrevDecl) {
        Diag(Loc, diag::warn_decl_in_param_list) << Context.getTagDeclType(New);
      }
    }
  
    if (Invalid)
      New->setInvalidDecl();
  
    // Set the lexical context. If the tag has a C++ scope specifier, the
    // lexical context will be different from the semantic context.
    New->setLexicalDeclContext(CurContext);
  
    // Mark this as a friend decl if applicable.
    // In Microsoft mode, a friend declaration also acts as a forward
    // declaration so we always pass true to setObjectOfFriendDecl to make
    // the tag name visible.
    if (TUK == TUK_Friend)
      New->setObjectOfFriendDecl(getLangOpts().MSVCCompat);
  
    // Set the access specifier.
    if (!Invalid && SearchDC->isRecord())
      SetMemberAccessSpecifier(New, PrevDecl, AS);
  
    if (PrevDecl)
      CheckRedeclarationModuleOwnership(New, PrevDecl);
  
    if (TUK == TUK_Definition && (!SkipBody || !SkipBody->ShouldSkip))
      New->startDefinition();
  
    ProcessDeclAttributeList(S, New, Attrs);
    AddPragmaAttributes(S, New);
  
    // If this has an identifier, add it to the scope stack.
    if (TUK == TUK_Friend) {
      // We might be replacing an existing declaration in the lookup tables;
      // if so, borrow its access specifier.
      if (PrevDecl)
        New->setAccess(PrevDecl->getAccess());
  
      DeclContext *DC = New->getDeclContext()->getRedeclContext();
      DC->makeDeclVisibleInContext(New);
      if (Name) // can be null along some error paths
        if (Scope *EnclosingScope = getScopeForDeclContext(S, DC))
          PushOnScopeChains(New, EnclosingScope, /* AddToContext = */ false);
    } else if (Name) {
      S = getNonFieldDeclScope(S);
      PushOnScopeChains(New, S, true);
    } else {
      CurContext->addDecl(New);
    }
  
    // If this is the C FILE type, notify the AST context.
    if (IdentifierInfo *II = New->getIdentifier())
      if (!New->isInvalidDecl() &&
          New->getDeclContext()->getRedeclContext()->isTranslationUnit() &&
          II->isStr("FILE"))
        Context.setFILEDecl(New);
  
    if (PrevDecl)
      mergeDeclAttributes(New, PrevDecl);
  
    // If there's a #pragma GCC visibility in scope, set the visibility of this
    // record.
    AddPushedVisibilityAttribute(New);
  
    if (isMemberSpecialization && !New->isInvalidDecl())
      CompleteMemberSpecialization(New, Previous);
  
    OwnedDecl = true;
    // In C++, don't return an invalid declaration. We can't recover well from
    // the cases where we make the type anonymous.
    if (Invalid && getLangOpts().CPlusPlus) {
      if (New->isBeingDefined())
        if (auto RD = dyn_cast<RecordDecl>(New))
          RD->completeDefinition();
      return nullptr;
    } else if (SkipBody && SkipBody->ShouldSkip) {
      return SkipBody->Previous;
    } else {
      return New;
    }
  }
  
  void Sema::ActOnTagStartDefinition(Scope *S, Decl *TagD) {
    AdjustDeclIfTemplate(TagD);
    TagDecl *Tag = cast<TagDecl>(TagD);
  
    // Enter the tag context.
    PushDeclContext(S, Tag);
  
    ActOnDocumentableDecl(TagD);
  
    // If there's a #pragma GCC visibility in scope, set the visibility of this
    // record.
    AddPushedVisibilityAttribute(Tag);
  }
  
  bool Sema::ActOnDuplicateDefinition(DeclSpec &DS, Decl *Prev,
                                      SkipBodyInfo &SkipBody) {
    if (!hasStructuralCompatLayout(Prev, SkipBody.New))
      return false;
  
    // Make the previous decl visible.
    makeMergedDefinitionVisible(SkipBody.Previous);
    return true;
  }
  
  Decl *Sema::ActOnObjCContainerStartDefinition(Decl *IDecl) {
    assert(isa<ObjCContainerDecl>(IDecl) &&
           "ActOnObjCContainerStartDefinition - Not ObjCContainerDecl");
    DeclContext *OCD = cast<DeclContext>(IDecl);
    assert(getContainingDC(OCD) == CurContext &&
        "The next DeclContext should be lexically contained in the current one.");
    CurContext = OCD;
    return IDecl;
  }
  
  void Sema::ActOnStartCXXMemberDeclarations(Scope *S, Decl *TagD,
                                             SourceLocation FinalLoc,
                                             bool IsFinalSpelledSealed,
                                             SourceLocation LBraceLoc) {
    AdjustDeclIfTemplate(TagD);
    CXXRecordDecl *Record = cast<CXXRecordDecl>(TagD);
  
    FieldCollector->StartClass();
  
    if (!Record->getIdentifier())
      return;
  
    if (FinalLoc.isValid())
      Record->addAttr(new (Context)
                      FinalAttr(FinalLoc, Context, IsFinalSpelledSealed));
  
    // C++ [class]p2:
    //   [...] The class-name is also inserted into the scope of the
    //   class itself; this is known as the injected-class-name. For
    //   purposes of access checking, the injected-class-name is treated
    //   as if it were a public member name.
    CXXRecordDecl *InjectedClassName = CXXRecordDecl::Create(
        Context, Record->getTagKind(), CurContext, Record->getBeginLoc(),
        Record->getLocation(), Record->getIdentifier(),
        /*PrevDecl=*/nullptr,
        /*DelayTypeCreation=*/true);
    Context.getTypeDeclType(InjectedClassName, Record);
    InjectedClassName->setImplicit();
    InjectedClassName->setAccess(AS_public);
    if (ClassTemplateDecl *Template = Record->getDescribedClassTemplate())
        InjectedClassName->setDescribedClassTemplate(Template);
    PushOnScopeChains(InjectedClassName, S);
    assert(InjectedClassName->isInjectedClassName() &&
           "Broken injected-class-name");
  }
  
  void Sema::ActOnTagFinishDefinition(Scope *S, Decl *TagD,
                                      SourceRange BraceRange) {
    AdjustDeclIfTemplate(TagD);
    TagDecl *Tag = cast<TagDecl>(TagD);
    Tag->setBraceRange(BraceRange);
  
    // Make sure we "complete" the definition even it is invalid.
    if (Tag->isBeingDefined()) {
      assert(Tag->isInvalidDecl() && "We should already have completed it");
      if (RecordDecl *RD = dyn_cast<RecordDecl>(Tag))
        RD->completeDefinition();
    }
  
    if (isa<CXXRecordDecl>(Tag)) {
      FieldCollector->FinishClass();
    }
  
    // Exit this scope of this tag's definition.
    PopDeclContext();
  
    if (getCurLexicalContext()->isObjCContainer() &&
        Tag->getDeclContext()->isFileContext())
      Tag->setTopLevelDeclInObjCContainer();
  
    // Notify the consumer that we've defined a tag.
    if (!Tag->isInvalidDecl())
      Consumer.HandleTagDeclDefinition(Tag);
  }
  
  void Sema::ActOnObjCContainerFinishDefinition() {
    // Exit this scope of this interface definition.
    PopDeclContext();
  }
  
  void Sema::ActOnObjCTemporaryExitContainerContext(DeclContext *DC) {
    assert(DC == CurContext && "Mismatch of container contexts");
    OriginalLexicalContext = DC;
    ActOnObjCContainerFinishDefinition();
  }
  
  void Sema::ActOnObjCReenterContainerContext(DeclContext *DC) {
    ActOnObjCContainerStartDefinition(cast<Decl>(DC));
    OriginalLexicalContext = nullptr;
  }
  
  void Sema::ActOnTagDefinitionError(Scope *S, Decl *TagD) {
    AdjustDeclIfTemplate(TagD);
    TagDecl *Tag = cast<TagDecl>(TagD);
    Tag->setInvalidDecl();
  
    // Make sure we "complete" the definition even it is invalid.
    if (Tag->isBeingDefined()) {
      if (RecordDecl *RD = dyn_cast<RecordDecl>(Tag))
        RD->completeDefinition();
    }
  
    // We're undoing ActOnTagStartDefinition here, not
    // ActOnStartCXXMemberDeclarations, so we don't have to mess with
    // the FieldCollector.
  
    PopDeclContext();
  }
  
  // Note that FieldName may be null for anonymous bitfields.
  ExprResult Sema::VerifyBitField(SourceLocation FieldLoc,
                                  IdentifierInfo *FieldName,
                                  QualType FieldTy, bool IsMsStruct,
                                  Expr *BitWidth, bool *ZeroWidth) {
    // Default to true; that shouldn't confuse checks for emptiness
    if (ZeroWidth)
      *ZeroWidth = true;
  
    // C99 6.7.2.1p4 - verify the field type.
    // C++ 9.6p3: A bit-field shall have integral or enumeration type.
    if (!FieldTy->isDependentType() && !FieldTy->isIntegralOrEnumerationType()) {
      // Handle incomplete types with specific error.
      if (RequireCompleteType(FieldLoc, FieldTy, diag::err_field_incomplete))
        return ExprError();
      if (FieldName)
        return Diag(FieldLoc, diag::err_not_integral_type_bitfield)
          << FieldName << FieldTy << BitWidth->getSourceRange();
      return Diag(FieldLoc, diag::err_not_integral_type_anon_bitfield)
        << FieldTy << BitWidth->getSourceRange();
    } else if (DiagnoseUnexpandedParameterPack(const_cast<Expr *>(BitWidth),
                                               UPPC_BitFieldWidth))
      return ExprError();
  
    // If the bit-width is type- or value-dependent, don't try to check
    // it now.
    if (BitWidth->isValueDependent() || BitWidth->isTypeDependent())
      return BitWidth;
  
    llvm::APSInt Value;
    ExprResult ICE = VerifyIntegerConstantExpression(BitWidth, &Value);
    if (ICE.isInvalid())
      return ICE;
    BitWidth = ICE.get();
  
    if (Value != 0 && ZeroWidth)
      *ZeroWidth = false;
  
    // Zero-width bitfield is ok for anonymous field.
    if (Value == 0 && FieldName)
      return Diag(FieldLoc, diag::err_bitfield_has_zero_width) << FieldName;
  
    if (Value.isSigned() && Value.isNegative()) {
      if (FieldName)
        return Diag(FieldLoc, diag::err_bitfield_has_negative_width)
                 << FieldName << Value.toString(10);
      return Diag(FieldLoc, diag::err_anon_bitfield_has_negative_width)
        << Value.toString(10);
    }
  
    if (!FieldTy->isDependentType()) {
      uint64_t TypeStorageSize = Context.getTypeSize(FieldTy);
      uint64_t TypeWidth = Context.getIntWidth(FieldTy);
      bool BitfieldIsOverwide = Value.ugt(TypeWidth);
  
      // Over-wide bitfields are an error in C or when using the MSVC bitfield
      // ABI.
      bool CStdConstraintViolation =
          BitfieldIsOverwide && !getLangOpts().CPlusPlus;
      bool MSBitfieldViolation =
          Value.ugt(TypeStorageSize) &&
          (IsMsStruct || Context.getTargetInfo().getCXXABI().isMicrosoft());
      if (CStdConstraintViolation || MSBitfieldViolation) {
        unsigned DiagWidth =
            CStdConstraintViolation ? TypeWidth : TypeStorageSize;
        if (FieldName)
          return Diag(FieldLoc, diag::err_bitfield_width_exceeds_type_width)
                 << FieldName << (unsigned)Value.getZExtValue()
                 << !CStdConstraintViolation << DiagWidth;
  
        return Diag(FieldLoc, diag::err_anon_bitfield_width_exceeds_type_width)
               << (unsigned)Value.getZExtValue() << !CStdConstraintViolation
               << DiagWidth;
      }
  
      // Warn on types where the user might conceivably expect to get all
      // specified bits as value bits: that's all integral types other than
      // 'bool'.
      if (BitfieldIsOverwide && !FieldTy->isBooleanType()) {
        if (FieldName)
          Diag(FieldLoc, diag::warn_bitfield_width_exceeds_type_width)
              << FieldName << (unsigned)Value.getZExtValue()
              << (unsigned)TypeWidth;
        else
          Diag(FieldLoc, diag::warn_anon_bitfield_width_exceeds_type_width)
              << (unsigned)Value.getZExtValue() << (unsigned)TypeWidth;
      }
    }
  
    return BitWidth;
  }
  
  /// ActOnField - Each field of a C struct/union is passed into this in order
  /// to create a FieldDecl object for it.
  Decl *Sema::ActOnField(Scope *S, Decl *TagD, SourceLocation DeclStart,
                         Declarator &D, Expr *BitfieldWidth) {
    FieldDecl *Res = HandleField(S, cast_or_null<RecordDecl>(TagD),
                                 DeclStart, D, static_cast<Expr*>(BitfieldWidth),
                                 /*InitStyle=*/ICIS_NoInit, AS_public);
    return Res;
  }
  
  /// HandleField - Analyze a field of a C struct or a C++ data member.
  ///
  FieldDecl *Sema::HandleField(Scope *S, RecordDecl *Record,
                               SourceLocation DeclStart,
                               Declarator &D, Expr *BitWidth,
                               InClassInitStyle InitStyle,
                               AccessSpecifier AS) {
    if (D.isDecompositionDeclarator()) {
      const DecompositionDeclarator &Decomp = D.getDecompositionDeclarator();
      Diag(Decomp.getLSquareLoc(), diag::err_decomp_decl_context)
        << Decomp.getSourceRange();
      return nullptr;
    }
  
    IdentifierInfo *II = D.getIdentifier();
    SourceLocation Loc = DeclStart;
    if (II) Loc = D.getIdentifierLoc();
  
    TypeSourceInfo *TInfo = GetTypeForDeclarator(D, S);
    QualType T = TInfo->getType();
    if (getLangOpts().CPlusPlus) {
      CheckExtraCXXDefaultArguments(D);
  
      if (DiagnoseUnexpandedParameterPack(D.getIdentifierLoc(), TInfo,
                                          UPPC_DataMemberType)) {
        D.setInvalidType();
        T = Context.IntTy;
        TInfo = Context.getTrivialTypeSourceInfo(T, Loc);
      }
    }
  
    DiagnoseFunctionSpecifiers(D.getDeclSpec());
  
    if (D.getDeclSpec().isInlineSpecified())
      Diag(D.getDeclSpec().getInlineSpecLoc(), diag::err_inline_non_function)
          << getLangOpts().CPlusPlus17;
    if (DeclSpec::TSCS TSCS = D.getDeclSpec().getThreadStorageClassSpec())
      Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
           diag::err_invalid_thread)
        << DeclSpec::getSpecifierName(TSCS);
  
    // Check to see if this name was declared as a member previously
    NamedDecl *PrevDecl = nullptr;
    LookupResult Previous(*this, II, Loc, LookupMemberName,
                          ForVisibleRedeclaration);
    LookupName(Previous, S);
    switch (Previous.getResultKind()) {
      case LookupResult::Found:
      case LookupResult::FoundUnresolvedValue:
        PrevDecl = Previous.getAsSingle<NamedDecl>();
        break;
  
      case LookupResult::FoundOverloaded:
        PrevDecl = Previous.getRepresentativeDecl();
        break;
  
      case LookupResult::NotFound:
      case LookupResult::NotFoundInCurrentInstantiation:
      case LookupResult::Ambiguous:
        break;
    }
    Previous.suppressDiagnostics();
  
    if (PrevDecl && PrevDecl->isTemplateParameter()) {
      // Maybe we will complain about the shadowed template parameter.
      DiagnoseTemplateParameterShadow(D.getIdentifierLoc(), PrevDecl);
      // Just pretend that we didn't see the previous declaration.
      PrevDecl = nullptr;
    }
  
    if (PrevDecl && !isDeclInScope(PrevDecl, Record, S))
      PrevDecl = nullptr;
  
    bool Mutable
      = (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_mutable);
    SourceLocation TSSL = D.getBeginLoc();
    FieldDecl *NewFD
      = CheckFieldDecl(II, T, TInfo, Record, Loc, Mutable, BitWidth, InitStyle,
                       TSSL, AS, PrevDecl, &D);
  
    if (NewFD->isInvalidDecl())
      Record->setInvalidDecl();
  
    if (D.getDeclSpec().isModulePrivateSpecified())
      NewFD->setModulePrivate();
  
    if (NewFD->isInvalidDecl() && PrevDecl) {
      // Don't introduce NewFD into scope; there's already something
      // with the same name in the same scope.
    } else if (II) {
      PushOnScopeChains(NewFD, S);
    } else
      Record->addDecl(NewFD);
  
    return NewFD;
  }
  
  /// Build a new FieldDecl and check its well-formedness.
  ///
  /// This routine builds a new FieldDecl given the fields name, type,
  /// record, etc. \p PrevDecl should refer to any previous declaration
  /// with the same name and in the same scope as the field to be
  /// created.
  ///
  /// \returns a new FieldDecl.
  ///
  /// \todo The Declarator argument is a hack. It will be removed once
  FieldDecl *Sema::CheckFieldDecl(DeclarationName Name, QualType T,
                                  TypeSourceInfo *TInfo,
                                  RecordDecl *Record, SourceLocation Loc,
                                  bool Mutable, Expr *BitWidth,
                                  InClassInitStyle InitStyle,
                                  SourceLocation TSSL,
                                  AccessSpecifier AS, NamedDecl *PrevDecl,
                                  Declarator *D) {
    IdentifierInfo *II = Name.getAsIdentifierInfo();
    bool InvalidDecl = false;
    if (D) InvalidDecl = D->isInvalidType();
  
    // If we receive a broken type, recover by assuming 'int' and
    // marking this declaration as invalid.
    if (T.isNull()) {
      InvalidDecl = true;
      T = Context.IntTy;
    }
  
    QualType EltTy = Context.getBaseElementType(T);
    if (!EltTy->isDependentType()) {
      if (RequireCompleteType(Loc, EltTy, diag::err_field_incomplete)) {
        // Fields of incomplete type force their record to be invalid.
        Record->setInvalidDecl();
        InvalidDecl = true;
      } else {
        NamedDecl *Def;
        EltTy->isIncompleteType(&Def);
        if (Def && Def->isInvalidDecl()) {
          Record->setInvalidDecl();
          InvalidDecl = true;
        }
      }
    }
  
    // TR 18037 does not allow fields to be declared with address space
    if (T.getQualifiers().hasAddressSpace() || T->isDependentAddressSpaceType() ||
        T->getBaseElementTypeUnsafe()->isDependentAddressSpaceType()) {
      Diag(Loc, diag::err_field_with_address_space);
      Record->setInvalidDecl();
      InvalidDecl = true;
    }
  
    if (LangOpts.OpenCL) {
      // OpenCL v1.2 s6.9b,r & OpenCL v2.0 s6.12.5 - The following types cannot be
      // used as structure or union field: image, sampler, event or block types.
      if (T->isEventT() || T->isImageType() || T->isSamplerT() ||
          T->isBlockPointerType()) {
        Diag(Loc, diag::err_opencl_type_struct_or_union_field) << T;
        Record->setInvalidDecl();
        InvalidDecl = true;
      }
      // OpenCL v1.2 s6.9.c: bitfields are not supported.
      if (BitWidth) {
        Diag(Loc, diag::err_opencl_bitfields);
        InvalidDecl = true;
      }
    }
  
    // Anonymous bit-fields cannot be cv-qualified (CWG 2229).
    if (!InvalidDecl && getLangOpts().CPlusPlus && !II && BitWidth &&
        T.hasQualifiers()) {
      InvalidDecl = true;
      Diag(Loc, diag::err_anon_bitfield_qualifiers);
    }
  
    // C99 6.7.2.1p8: A member of a structure or union may have any type other
    // than a variably modified type.
    if (!InvalidDecl && T->isVariablyModifiedType()) {
      bool SizeIsNegative;
      llvm::APSInt Oversized;
  
      TypeSourceInfo *FixedTInfo =
        TryToFixInvalidVariablyModifiedTypeSourceInfo(TInfo, Context,
                                                      SizeIsNegative,
                                                      Oversized);
      if (FixedTInfo) {
        Diag(Loc, diag::warn_illegal_constant_array_size);
        TInfo = FixedTInfo;
        T = FixedTInfo->getType();
      } else {
        if (SizeIsNegative)
          Diag(Loc, diag::err_typecheck_negative_array_size);
        else if (Oversized.getBoolValue())
          Diag(Loc, diag::err_array_too_large)
            << Oversized.toString(10);
        else
          Diag(Loc, diag::err_typecheck_field_variable_size);
        InvalidDecl = true;
      }
    }
  
    // Fields can not have abstract class types
    if (!InvalidDecl && RequireNonAbstractType(Loc, T,
                                               diag::err_abstract_type_in_decl,
                                               AbstractFieldType))
      InvalidDecl = true;
  
    bool ZeroWidth = false;
    if (InvalidDecl)
      BitWidth = nullptr;
    // If this is declared as a bit-field, check the bit-field.
    if (BitWidth) {
      BitWidth = VerifyBitField(Loc, II, T, Record->isMsStruct(Context), BitWidth,
                                &ZeroWidth).get();
      if (!BitWidth) {
        InvalidDecl = true;
        BitWidth = nullptr;
        ZeroWidth = false;
      }
    }
  
    // Check that 'mutable' is consistent with the type of the declaration.
    if (!InvalidDecl && Mutable) {
      unsigned DiagID = 0;
      if (T->isReferenceType())
        DiagID = getLangOpts().MSVCCompat ? diag::ext_mutable_reference
                                          : diag::err_mutable_reference;
      else if (T.isConstQualified())
        DiagID = diag::err_mutable_const;
  
      if (DiagID) {
        SourceLocation ErrLoc = Loc;
        if (D && D->getDeclSpec().getStorageClassSpecLoc().isValid())
          ErrLoc = D->getDeclSpec().getStorageClassSpecLoc();
        Diag(ErrLoc, DiagID);
        if (DiagID != diag::ext_mutable_reference) {
          Mutable = false;
          InvalidDecl = true;
        }
      }
    }
  
    // C++11 [class.union]p8 (DR1460):
    //   At most one variant member of a union may have a
    //   brace-or-equal-initializer.
    if (InitStyle != ICIS_NoInit)
      checkDuplicateDefaultInit(*this, cast<CXXRecordDecl>(Record), Loc);
  
    FieldDecl *NewFD = FieldDecl::Create(Context, Record, TSSL, Loc, II, T, TInfo,
                                         BitWidth, Mutable, InitStyle);
    if (InvalidDecl)
      NewFD->setInvalidDecl();
  
    if (PrevDecl && !isa<TagDecl>(PrevDecl)) {
      Diag(Loc, diag::err_duplicate_member) << II;
      Diag(PrevDecl->getLocation(), diag::note_previous_declaration);
      NewFD->setInvalidDecl();
    }
  
    if (!InvalidDecl && getLangOpts().CPlusPlus) {
      if (Record->isUnion()) {
        if (const RecordType *RT = EltTy->getAs<RecordType>()) {
          CXXRecordDecl* RDecl = cast<CXXRecordDecl>(RT->getDecl());
          if (RDecl->getDefinition()) {
            // C++ [class.union]p1: An object of a class with a non-trivial
            // constructor, a non-trivial copy constructor, a non-trivial
            // destructor, or a non-trivial copy assignment operator
            // cannot be a member of a union, nor can an array of such
            // objects.
            if (CheckNontrivialField(NewFD))
              NewFD->setInvalidDecl();
          }
        }
  
        // C++ [class.union]p1: If a union contains a member of reference type,
        // the program is ill-formed, except when compiling with MSVC extensions
        // enabled.
        if (EltTy->isReferenceType()) {
          Diag(NewFD->getLocation(), getLangOpts().MicrosoftExt ?
                                      diag::ext_union_member_of_reference_type :
                                      diag::err_union_member_of_reference_type)
            << NewFD->getDeclName() << EltTy;
          if (!getLangOpts().MicrosoftExt)
            NewFD->setInvalidDecl();
        }
      }
    }
  
    // FIXME: We need to pass in the attributes given an AST
    // representation, not a parser representation.
    if (D) {
      // FIXME: The current scope is almost... but not entirely... correct here.
      ProcessDeclAttributes(getCurScope(), NewFD, *D);
  
      if (NewFD->hasAttrs())
        CheckAlignasUnderalignment(NewFD);
    }
  
    // In auto-retain/release, infer strong retension for fields of
    // retainable type.
    if (getLangOpts().ObjCAutoRefCount && inferObjCARCLifetime(NewFD))
      NewFD->setInvalidDecl();
  
    if (T.isObjCGCWeak())
      Diag(Loc, diag::warn_attribute_weak_on_field);
  
    NewFD->setAccess(AS);
    return NewFD;
  }
  
  bool Sema::CheckNontrivialField(FieldDecl *FD) {
    assert(FD);
    assert(getLangOpts().CPlusPlus && "valid check only for C++");
  
    if (FD->isInvalidDecl() || FD->getType()->isDependentType())
      return false;
  
    QualType EltTy = Context.getBaseElementType(FD->getType());
    if (const RecordType *RT = EltTy->getAs<RecordType>()) {
      CXXRecordDecl *RDecl = cast<CXXRecordDecl>(RT->getDecl());
      if (RDecl->getDefinition()) {
        // We check for copy constructors before constructors
        // because otherwise we'll never get complaints about
        // copy constructors.
  
        CXXSpecialMember member = CXXInvalid;
        // We're required to check for any non-trivial constructors. Since the
        // implicit default constructor is suppressed if there are any
        // user-declared constructors, we just need to check that there is a
        // trivial default constructor and a trivial copy constructor. (We don't
        // worry about move constructors here, since this is a C++98 check.)
        if (RDecl->hasNonTrivialCopyConstructor())
          member = CXXCopyConstructor;
        else if (!RDecl->hasTrivialDefaultConstructor())
          member = CXXDefaultConstructor;
        else if (RDecl->hasNonTrivialCopyAssignment())
          member = CXXCopyAssignment;
        else if (RDecl->hasNonTrivialDestructor())
          member = CXXDestructor;
  
        if (member != CXXInvalid) {
          if (!getLangOpts().CPlusPlus11 &&
              getLangOpts().ObjCAutoRefCount && RDecl->hasObjectMember()) {
            // Objective-C++ ARC: it is an error to have a non-trivial field of
            // a union. However, system headers in Objective-C programs
            // occasionally have Objective-C lifetime objects within unions,
            // and rather than cause the program to fail, we make those
            // members unavailable.
            SourceLocation Loc = FD->getLocation();
            if (getSourceManager().isInSystemHeader(Loc)) {
              if (!FD->hasAttr<UnavailableAttr>())
                FD->addAttr(UnavailableAttr::CreateImplicit(Context, "",
                              UnavailableAttr::IR_ARCFieldWithOwnership, Loc));
              return false;
            }
          }
  
          Diag(FD->getLocation(), getLangOpts().CPlusPlus11 ?
                 diag::warn_cxx98_compat_nontrivial_union_or_anon_struct_member :
                 diag::err_illegal_union_or_anon_struct_member)
            << FD->getParent()->isUnion() << FD->getDeclName() << member;
          DiagnoseNontrivial(RDecl, member);
          return !getLangOpts().CPlusPlus11;
        }
      }
    }
  
    return false;
  }
  
  /// TranslateIvarVisibility - Translate visibility from a token ID to an
  ///  AST enum value.
  static ObjCIvarDecl::AccessControl
  TranslateIvarVisibility(tok::ObjCKeywordKind ivarVisibility) {
    switch (ivarVisibility) {
    default: llvm_unreachable("Unknown visitibility kind");
    case tok::objc_private: return ObjCIvarDecl::Private;
    case tok::objc_public: return ObjCIvarDecl::Public;
    case tok::objc_protected: return ObjCIvarDecl::Protected;
    case tok::objc_package: return ObjCIvarDecl::Package;
    }
  }
  
  /// ActOnIvar - Each ivar field of an objective-c class is passed into this
  /// in order to create an IvarDecl object for it.
  Decl *Sema::ActOnIvar(Scope *S,
                                  SourceLocation DeclStart,
                                  Declarator &D, Expr *BitfieldWidth,
                                  tok::ObjCKeywordKind Visibility) {
  
    IdentifierInfo *II = D.getIdentifier();
    Expr *BitWidth = (Expr*)BitfieldWidth;
    SourceLocation Loc = DeclStart;
    if (II) Loc = D.getIdentifierLoc();
  
    // FIXME: Unnamed fields can be handled in various different ways, for
    // example, unnamed unions inject all members into the struct namespace!
  
    TypeSourceInfo *TInfo = GetTypeForDeclarator(D, S);
    QualType T = TInfo->getType();
  
    if (BitWidth) {
      // 6.7.2.1p3, 6.7.2.1p4
      BitWidth = VerifyBitField(Loc, II, T, /*IsMsStruct*/false, BitWidth).get();
      if (!BitWidth)
        D.setInvalidType();
    } else {
      // Not a bitfield.
  
      // validate II.
  
    }
    if (T->isReferenceType()) {
      Diag(Loc, diag::err_ivar_reference_type);
      D.setInvalidType();
    }
    // C99 6.7.2.1p8: A member of a structure or union may have any type other
    // than a variably modified type.
    else if (T->isVariablyModifiedType()) {
      Diag(Loc, diag::err_typecheck_ivar_variable_size);
      D.setInvalidType();
    }
  
    // Get the visibility (access control) for this ivar.
    ObjCIvarDecl::AccessControl ac =
      Visibility != tok::objc_not_keyword ? TranslateIvarVisibility(Visibility)
                                          : ObjCIvarDecl::None;
    // Must set ivar's DeclContext to its enclosing interface.
    ObjCContainerDecl *EnclosingDecl = cast<ObjCContainerDecl>(CurContext);
    if (!EnclosingDecl || EnclosingDecl->isInvalidDecl())
      return nullptr;
    ObjCContainerDecl *EnclosingContext;
    if (ObjCImplementationDecl *IMPDecl =
        dyn_cast<ObjCImplementationDecl>(EnclosingDecl)) {
      if (LangOpts.ObjCRuntime.isFragile()) {
      // Case of ivar declared in an implementation. Context is that of its class.
        EnclosingContext = IMPDecl->getClassInterface();
        assert(EnclosingContext && "Implementation has no class interface!");
      }
      else
        EnclosingContext = EnclosingDecl;
    } else {
      if (ObjCCategoryDecl *CDecl =
          dyn_cast<ObjCCategoryDecl>(EnclosingDecl)) {
        if (LangOpts.ObjCRuntime.isFragile() || !CDecl->IsClassExtension()) {
          Diag(Loc, diag::err_misplaced_ivar) << CDecl->IsClassExtension();
          return nullptr;
        }
      }
      EnclosingContext = EnclosingDecl;
    }
  
    // Construct the decl.
    ObjCIvarDecl *NewID = ObjCIvarDecl::Create(Context, EnclosingContext,
                                               DeclStart, Loc, II, T,
                                               TInfo, ac, (Expr *)BitfieldWidth);
  
    if (II) {
      NamedDecl *PrevDecl = LookupSingleName(S, II, Loc, LookupMemberName,
                                             ForVisibleRedeclaration);
      if (PrevDecl && isDeclInScope(PrevDecl, EnclosingContext, S)
          && !isa<TagDecl>(PrevDecl)) {
        Diag(Loc, diag::err_duplicate_member) << II;
        Diag(PrevDecl->getLocation(), diag::note_previous_declaration);
        NewID->setInvalidDecl();
      }
    }
  
    // Process attributes attached to the ivar.
    ProcessDeclAttributes(S, NewID, D);
  
    if (D.isInvalidType())
      NewID->setInvalidDecl();
  
    // In ARC, infer 'retaining' for ivars of retainable type.
    if (getLangOpts().ObjCAutoRefCount && inferObjCARCLifetime(NewID))
      NewID->setInvalidDecl();
  
    if (D.getDeclSpec().isModulePrivateSpecified())
      NewID->setModulePrivate();
  
    if (II) {
      // FIXME: When interfaces are DeclContexts, we'll need to add
      // these to the interface.
      S->AddDecl(NewID);
      IdResolver.AddDecl(NewID);
    }
  
    if (LangOpts.ObjCRuntime.isNonFragile() &&
        !NewID->isInvalidDecl() && isa<ObjCInterfaceDecl>(EnclosingDecl))
      Diag(Loc, diag::warn_ivars_in_interface);
  
    return NewID;
  }
  
  /// ActOnLastBitfield - This routine handles synthesized bitfields rules for
  /// class and class extensions. For every class \@interface and class
  /// extension \@interface, if the last ivar is a bitfield of any type,
  /// then add an implicit `char :0` ivar to the end of that interface.
  void Sema::ActOnLastBitfield(SourceLocation DeclLoc,
                               SmallVectorImpl<Decl *> &AllIvarDecls) {
    if (LangOpts.ObjCRuntime.isFragile() || AllIvarDecls.empty())
      return;
  
    Decl *ivarDecl = AllIvarDecls[AllIvarDecls.size()-1];
    ObjCIvarDecl *Ivar = cast<ObjCIvarDecl>(ivarDecl);
  
    if (!Ivar->isBitField() || Ivar->isZeroLengthBitField(Context))
      return;
    ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(CurContext);
    if (!ID) {
      if (ObjCCategoryDecl *CD = dyn_cast<ObjCCategoryDecl>(CurContext)) {
        if (!CD->IsClassExtension())
          return;
      }
      // No need to add this to end of @implementation.
      else
        return;
    }
    // All conditions are met. Add a new bitfield to the tail end of ivars.
    llvm::APInt Zero(Context.getTypeSize(Context.IntTy), 0);
    Expr * BW = IntegerLiteral::Create(Context, Zero, Context.IntTy, DeclLoc);
  
    Ivar = ObjCIvarDecl::Create(Context, cast<ObjCContainerDecl>(CurContext),
                                DeclLoc, DeclLoc, nullptr,
                                Context.CharTy,
                                Context.getTrivialTypeSourceInfo(Context.CharTy,
                                                                 DeclLoc),
                                ObjCIvarDecl::Private, BW,
                                true);
    AllIvarDecls.push_back(Ivar);
  }
  
  void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
                         ArrayRef<Decl *> Fields, SourceLocation LBrac,
                         SourceLocation RBrac,
                         const ParsedAttributesView &Attrs) {
    assert(EnclosingDecl && "missing record or interface decl");
  
    // If this is an Objective-C @implementation or category and we have
    // new fields here we should reset the layout of the interface since
    // it will now change.
    if (!Fields.empty() && isa<ObjCContainerDecl>(EnclosingDecl)) {
      ObjCContainerDecl *DC = cast<ObjCContainerDecl>(EnclosingDecl);
      switch (DC->getKind()) {
      default: break;
      case Decl::ObjCCategory:
        Context.ResetObjCLayout(cast<ObjCCategoryDecl>(DC)->getClassInterface());
        break;
      case Decl::ObjCImplementation:
        Context.
          ResetObjCLayout(cast<ObjCImplementationDecl>(DC)->getClassInterface());
        break;
      }
    }
  
    RecordDecl *Record = dyn_cast<RecordDecl>(EnclosingDecl);
    CXXRecordDecl *CXXRecord = dyn_cast<CXXRecordDecl>(EnclosingDecl);
  
    // Start counting up the number of named members; make sure to include
    // members of anonymous structs and unions in the total.
    unsigned NumNamedMembers = 0;
    if (Record) {
      for (const auto *I : Record->decls()) {
        if (const auto *IFD = dyn_cast<IndirectFieldDecl>(I))
          if (IFD->getDeclName())
            ++NumNamedMembers;
      }
    }
  
    // Verify that all the fields are okay.
    SmallVector<FieldDecl*, 32> RecFields;
  
    bool ObjCFieldLifetimeErrReported = false;
    for (ArrayRef<Decl *>::iterator i = Fields.begin(), end = Fields.end();
         i != end; ++i) {
      FieldDecl *FD = cast<FieldDecl>(*i);
  
      // Get the type for the field.
      const Type *FDTy = FD->getType().getTypePtr();
  
      if (!FD->isAnonymousStructOrUnion()) {
        // Remember all fields written by the user.
        RecFields.push_back(FD);
      }
  
      // If the field is already invalid for some reason, don't emit more
      // diagnostics about it.
      if (FD->isInvalidDecl()) {
        EnclosingDecl->setInvalidDecl();
        continue;
      }
  
      // C99 6.7.2.1p2:
      //   A structure or union shall not contain a member with
      //   incomplete or function type (hence, a structure shall not
      //   contain an instance of itself, but may contain a pointer to
      //   an instance of itself), except that the last member of a
      //   structure with more than one named member may have incomplete
      //   array type; such a structure (and any union containing,
      //   possibly recursively, a member that is such a structure)
      //   shall not be a member of a structure or an element of an
      //   array.
      bool IsLastField = (i + 1 == Fields.end());
      if (FDTy->isFunctionType()) {
        // Field declared as a function.
        Diag(FD->getLocation(), diag::err_field_declared_as_function)
          << FD->getDeclName();
        FD->setInvalidDecl();
        EnclosingDecl->setInvalidDecl();
        continue;
      } else if (FDTy->isIncompleteArrayType() &&
                 (Record || isa<ObjCContainerDecl>(EnclosingDecl))) {
        if (Record) {
          // Flexible array member.
          // Microsoft and g++ is more permissive regarding flexible array.
          // It will accept flexible array in union and also
          // as the sole element of a struct/class.
          unsigned DiagID = 0;
          if (!Record->isUnion() && !IsLastField) {
            Diag(FD->getLocation(), diag::err_flexible_array_not_at_end)
              << FD->getDeclName() << FD->getType() << Record->getTagKind();
            Diag((*(i + 1))->getLocation(), diag::note_next_field_declaration);
            FD->setInvalidDecl();
            EnclosingDecl->setInvalidDecl();
            continue;
          } else if (Record->isUnion())
            DiagID = getLangOpts().MicrosoftExt
                         ? diag::ext_flexible_array_union_ms
                         : getLangOpts().CPlusPlus
                               ? diag::ext_flexible_array_union_gnu
                               : diag::err_flexible_array_union;
          else if (NumNamedMembers < 1)
            DiagID = getLangOpts().MicrosoftExt
                         ? diag::ext_flexible_array_empty_aggregate_ms
                         : getLangOpts().CPlusPlus
                               ? diag::ext_flexible_array_empty_aggregate_gnu
                               : diag::err_flexible_array_empty_aggregate;
  
          if (DiagID)
            Diag(FD->getLocation(), DiagID) << FD->getDeclName()
                                            << Record->getTagKind();
          // While the layout of types that contain virtual bases is not specified
          // by the C++ standard, both the Itanium and Microsoft C++ ABIs place
          // virtual bases after the derived members.  This would make a flexible
          // array member declared at the end of an object not adjacent to the end
          // of the type.
          if (CXXRecord && CXXRecord->getNumVBases() != 0)
            Diag(FD->getLocation(), diag::err_flexible_array_virtual_base)
                << FD->getDeclName() << Record->getTagKind();
          if (!getLangOpts().C99)
            Diag(FD->getLocation(), diag::ext_c99_flexible_array_member)
              << FD->getDeclName() << Record->getTagKind();
  
          // If the element type has a non-trivial destructor, we would not
          // implicitly destroy the elements, so disallow it for now.
          //
          // FIXME: GCC allows this. We should probably either implicitly delete
          // the destructor of the containing class, or just allow this.
          QualType BaseElem = Context.getBaseElementType(FD->getType());
          if (!BaseElem->isDependentType() && BaseElem.isDestructedType()) {
            Diag(FD->getLocation(), diag::err_flexible_array_has_nontrivial_dtor)
              << FD->getDeclName() << FD->getType();
            FD->setInvalidDecl();
            EnclosingDecl->setInvalidDecl();
            continue;
          }
          // Okay, we have a legal flexible array member at the end of the struct.
          Record->setHasFlexibleArrayMember(true);
        } else {
          // In ObjCContainerDecl ivars with incomplete array type are accepted,
          // unless they are followed by another ivar. That check is done
          // elsewhere, after synthesized ivars are known.
        }
      } else if (!FDTy->isDependentType() &&
                 RequireCompleteType(FD->getLocation(), FD->getType(),
                                     diag::err_field_incomplete)) {
        // Incomplete type
        FD->setInvalidDecl();
        EnclosingDecl->setInvalidDecl();
        continue;
      } else if (const RecordType *FDTTy = FDTy->getAs<RecordType>()) {
        if (Record && FDTTy->getDecl()->hasFlexibleArrayMember()) {
          // A type which contains a flexible array member is considered to be a
          // flexible array member.
          Record->setHasFlexibleArrayMember(true);
          if (!Record->isUnion()) {
            // If this is a struct/class and this is not the last element, reject
            // it.  Note that GCC supports variable sized arrays in the middle of
            // structures.
            if (!IsLastField)
              Diag(FD->getLocation(), diag::ext_variable_sized_type_in_struct)
                << FD->getDeclName() << FD->getType();
            else {
              // We support flexible arrays at the end of structs in
              // other structs as an extension.
              Diag(FD->getLocation(), diag::ext_flexible_array_in_struct)
                << FD->getDeclName();
            }
          }
        }
        if (isa<ObjCContainerDecl>(EnclosingDecl) &&
            RequireNonAbstractType(FD->getLocation(), FD->getType(),
                                   diag::err_abstract_type_in_decl,
                                   AbstractIvarType)) {
          // Ivars can not have abstract class types
          FD->setInvalidDecl();
        }
        if (Record && FDTTy->getDecl()->hasObjectMember())
          Record->setHasObjectMember(true);
        if (Record && FDTTy->getDecl()->hasVolatileMember())
          Record->setHasVolatileMember(true);
        if (Record && Record->isUnion() &&
            FD->getType().isNonTrivialPrimitiveCType(Context))
          Diag(FD->getLocation(),
               diag::err_nontrivial_primitive_type_in_union);
      } else if (FDTy->isObjCObjectType()) {
        /// A field cannot be an Objective-c object
        Diag(FD->getLocation(), diag::err_statically_allocated_object)
          << FixItHint::CreateInsertion(FD->getLocation(), "*");
        QualType T = Context.getObjCObjectPointerType(FD->getType());
        FD->setType(T);
      } else if (getLangOpts().allowsNonTrivialObjCLifetimeQualifiers() &&
                 Record && !ObjCFieldLifetimeErrReported && Record->isUnion() &&
                 !getLangOpts().CPlusPlus) {
        // It's an error in ARC or Weak if a field has lifetime.
        // We don't want to report this in a system header, though,
        // so we just make the field unavailable.
        // FIXME: that's really not sufficient; we need to make the type
        // itself invalid to, say, initialize or copy.
        QualType T = FD->getType();
        if (T.hasNonTrivialObjCLifetime()) {
          SourceLocation loc = FD->getLocation();
          if (getSourceManager().isInSystemHeader(loc)) {
            if (!FD->hasAttr<UnavailableAttr>()) {
              FD->addAttr(UnavailableAttr::CreateImplicit(Context, "",
                            UnavailableAttr::IR_ARCFieldWithOwnership, loc));
            }
          } else {
            Diag(FD->getLocation(), diag::err_arc_objc_object_in_tag)
              << T->isBlockPointerType() << Record->getTagKind();
          }
          ObjCFieldLifetimeErrReported = true;
        }
      } else if (getLangOpts().ObjC &&
                 getLangOpts().getGC() != LangOptions::NonGC &&
                 Record && !Record->hasObjectMember()) {
        if (FD->getType()->isObjCObjectPointerType() ||
            FD->getType().isObjCGCStrong())
          Record->setHasObjectMember(true);
        else if (Context.getAsArrayType(FD->getType())) {
          QualType BaseType = Context.getBaseElementType(FD->getType());
          if (BaseType->isRecordType() &&
              BaseType->getAs<RecordType>()->getDecl()->hasObjectMember())
            Record->setHasObjectMember(true);
          else if (BaseType->isObjCObjectPointerType() ||
                   BaseType.isObjCGCStrong())
                 Record->setHasObjectMember(true);
        }
      }
  
      if (Record && !getLangOpts().CPlusPlus && !FD->hasAttr<UnavailableAttr>()) {
        QualType FT = FD->getType();
        if (FT.isNonTrivialToPrimitiveDefaultInitialize())
          Record->setNonTrivialToPrimitiveDefaultInitialize(true);
        QualType::PrimitiveCopyKind PCK = FT.isNonTrivialToPrimitiveCopy();
        if (PCK != QualType::PCK_Trivial && PCK != QualType::PCK_VolatileTrivial)
          Record->setNonTrivialToPrimitiveCopy(true);
        if (FT.isDestructedType()) {
          Record->setNonTrivialToPrimitiveDestroy(true);
          Record->setParamDestroyedInCallee(true);
        }
  
        if (const auto *RT = FT->getAs<RecordType>()) {
          if (RT->getDecl()->getArgPassingRestrictions() ==
              RecordDecl::APK_CanNeverPassInRegs)
            Record->setArgPassingRestrictions(RecordDecl::APK_CanNeverPassInRegs);
        } else if (FT.getQualifiers().getObjCLifetime() == Qualifiers::OCL_Weak)
          Record->setArgPassingRestrictions(RecordDecl::APK_CanNeverPassInRegs);
      }
  
      if (Record && FD->getType().isVolatileQualified())
        Record->setHasVolatileMember(true);
      // Keep track of the number of named members.
      if (FD->getIdentifier())
        ++NumNamedMembers;
    }
  
    // Okay, we successfully defined 'Record'.
    if (Record) {
      bool Completed = false;
      if (CXXRecord) {
        if (!CXXRecord->isInvalidDecl()) {
          // Set access bits correctly on the directly-declared conversions.
          for (CXXRecordDecl::conversion_iterator
                 I = CXXRecord->conversion_begin(),
                 E = CXXRecord->conversion_end(); I != E; ++I)
            I.setAccess((*I)->getAccess());
        }
  
        if (!CXXRecord->isDependentType()) {
          // Add any implicitly-declared members to this class.
          AddImplicitlyDeclaredMembersToClass(CXXRecord);
  
          if (!CXXRecord->isInvalidDecl()) {
            // If we have virtual base classes, we may end up finding multiple
            // final overriders for a given virtual function. Check for this
            // problem now.
            if (CXXRecord->getNumVBases()) {
              CXXFinalOverriderMap FinalOverriders;
              CXXRecord->getFinalOverriders(FinalOverriders);
  
              for (CXXFinalOverriderMap::iterator M = FinalOverriders.begin(),
                                               MEnd = FinalOverriders.end();
                   M != MEnd; ++M) {
                for (OverridingMethods::iterator SO = M->second.begin(),
                                              SOEnd = M->second.end();
                     SO != SOEnd; ++SO) {
                  assert(SO->second.size() > 0 &&
                         "Virtual function without overriding functions?");
                  if (SO->second.size() == 1)
                    continue;
  
                  // C++ [class.virtual]p2:
                  //   In a derived class, if a virtual member function of a base
                  //   class subobject has more than one final overrider the
                  //   program is ill-formed.
                  Diag(Record->getLocation(), diag::err_multiple_final_overriders)
                    << (const NamedDecl *)M->first << Record;
                  Diag(M->first->getLocation(),
                       diag::note_overridden_virtual_function);
                  for (OverridingMethods::overriding_iterator
                            OM = SO->second.begin(),
                         OMEnd = SO->second.end();
                       OM != OMEnd; ++OM)
                    Diag(OM->Method->getLocation(), diag::note_final_overrider)
                      << (const NamedDecl *)M->first << OM->Method->getParent();
  
                  Record->setInvalidDecl();
                }
              }
              CXXRecord->completeDefinition(&FinalOverriders);
              Completed = true;
            }
          }
        }
      }
  
      if (!Completed)
        Record->completeDefinition();
  
      // Handle attributes before checking the layout.
      ProcessDeclAttributeList(S, Record, Attrs);
  
      // We may have deferred checking for a deleted destructor. Check now.
      if (CXXRecord) {
        auto *Dtor = CXXRecord->getDestructor();
        if (Dtor && Dtor->isImplicit() &&
            ShouldDeleteSpecialMember(Dtor, CXXDestructor)) {
          CXXRecord->setImplicitDestructorIsDeleted();
          SetDeclDeleted(Dtor, CXXRecord->getLocation());
        }
      }
  
      if (Record->hasAttrs()) {
        CheckAlignasUnderalignment(Record);
  
        if (const MSInheritanceAttr *IA = Record->getAttr<MSInheritanceAttr>())
          checkMSInheritanceAttrOnDefinition(cast<CXXRecordDecl>(Record),
                                             IA->getRange(), IA->getBestCase(),
                                             IA->getSemanticSpelling());
      }
  
      // Check if the structure/union declaration is a type that can have zero
      // size in C. For C this is a language extension, for C++ it may cause
      // compatibility problems.
      bool CheckForZeroSize;
      if (!getLangOpts().CPlusPlus) {
        CheckForZeroSize = true;
      } else {
        // For C++ filter out types that cannot be referenced in C code.
        CXXRecordDecl *CXXRecord = cast<CXXRecordDecl>(Record);
        CheckForZeroSize =
            CXXRecord->getLexicalDeclContext()->isExternCContext() &&
            !CXXRecord->isDependentType() &&
            CXXRecord->isCLike();
      }
      if (CheckForZeroSize) {
        bool ZeroSize = true;
        bool IsEmpty = true;
        unsigned NonBitFields = 0;
        for (RecordDecl::field_iterator I = Record->field_begin(),
                                        E = Record->field_end();
             (NonBitFields == 0 || ZeroSize) && I != E; ++I) {
          IsEmpty = false;
          if (I->isUnnamedBitfield()) {
            if (!I->isZeroLengthBitField(Context))
              ZeroSize = false;
          } else {
            ++NonBitFields;
            QualType FieldType = I->getType();
            if (FieldType->isIncompleteType() ||
                !Context.getTypeSizeInChars(FieldType).isZero())
              ZeroSize = false;
          }
        }
  
        // Empty structs are an extension in C (C99 6.7.2.1p7). They are
        // allowed in C++, but warn if its declaration is inside
        // extern "C" block.
        if (ZeroSize) {
          Diag(RecLoc, getLangOpts().CPlusPlus ?
                           diag::warn_zero_size_struct_union_in_extern_c :
                           diag::warn_zero_size_struct_union_compat)
            << IsEmpty << Record->isUnion() << (NonBitFields > 1);
        }
  
        // Structs without named members are extension in C (C99 6.7.2.1p7),
        // but are accepted by GCC.
        if (NonBitFields == 0 && !getLangOpts().CPlusPlus) {
          Diag(RecLoc, IsEmpty ? diag::ext_empty_struct_union :
                                 diag::ext_no_named_members_in_struct_union)
            << Record->isUnion();
        }
      }
    } else {
      ObjCIvarDecl **ClsFields =
        reinterpret_cast<ObjCIvarDecl**>(RecFields.data());
      if (ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(EnclosingDecl)) {
        ID->setEndOfDefinitionLoc(RBrac);
        // Add ivar's to class's DeclContext.
        for (unsigned i = 0, e = RecFields.size(); i != e; ++i) {
          ClsFields[i]->setLexicalDeclContext(ID);
          ID->addDecl(ClsFields[i]);
        }
        // Must enforce the rule that ivars in the base classes may not be
        // duplicates.
        if (ID->getSuperClass())
          DiagnoseDuplicateIvars(ID, ID->getSuperClass());
      } else if (ObjCImplementationDecl *IMPDecl =
                    dyn_cast<ObjCImplementationDecl>(EnclosingDecl)) {
        assert(IMPDecl && "ActOnFields - missing ObjCImplementationDecl");
        for (unsigned I = 0, N = RecFields.size(); I != N; ++I)
          // Ivar declared in @implementation never belongs to the implementation.
          // Only it is in implementation's lexical context.
          ClsFields[I]->setLexicalDeclContext(IMPDecl);
        CheckImplementationIvars(IMPDecl, ClsFields, RecFields.size(), RBrac);
        IMPDecl->setIvarLBraceLoc(LBrac);
        IMPDecl->setIvarRBraceLoc(RBrac);
      } else if (ObjCCategoryDecl *CDecl =
                  dyn_cast<ObjCCategoryDecl>(EnclosingDecl)) {
        // case of ivars in class extension; all other cases have been
        // reported as errors elsewhere.
        // FIXME. Class extension does not have a LocEnd field.
        // CDecl->setLocEnd(RBrac);
        // Add ivar's to class extension's DeclContext.
        // Diagnose redeclaration of private ivars.
        ObjCInterfaceDecl *IDecl = CDecl->getClassInterface();
        for (unsigned i = 0, e = RecFields.size(); i != e; ++i) {
          if (IDecl) {
            if (const ObjCIvarDecl *ClsIvar =
                IDecl->getIvarDecl(ClsFields[i]->getIdentifier())) {
              Diag(ClsFields[i]->getLocation(),
                   diag::err_duplicate_ivar_declaration);
              Diag(ClsIvar->getLocation(), diag::note_previous_definition);
              continue;
            }
            for (const auto *Ext : IDecl->known_extensions()) {
              if (const ObjCIvarDecl *ClsExtIvar
                    = Ext->getIvarDecl(ClsFields[i]->getIdentifier())) {
                Diag(ClsFields[i]->getLocation(),
                     diag::err_duplicate_ivar_declaration);
                Diag(ClsExtIvar->getLocation(), diag::note_previous_definition);
                continue;
              }
            }
          }
          ClsFields[i]->setLexicalDeclContext(CDecl);
          CDecl->addDecl(ClsFields[i]);
        }
        CDecl->setIvarLBraceLoc(LBrac);
        CDecl->setIvarRBraceLoc(RBrac);
      }
    }
  }
  
  /// Determine whether the given integral value is representable within
  /// the given type T.
  static bool isRepresentableIntegerValue(ASTContext &Context,
                                          llvm::APSInt &Value,
                                          QualType T) {
    assert((T->isIntegralType(Context) || T->isEnumeralType()) &&
           "Integral type required!");
    unsigned BitWidth = Context.getIntWidth(T);
  
    if (Value.isUnsigned() || Value.isNonNegative()) {
      if (T->isSignedIntegerOrEnumerationType())
        --BitWidth;
      return Value.getActiveBits() <= BitWidth;
    }
    return Value.getMinSignedBits() <= BitWidth;
  }
  
  // Given an integral type, return the next larger integral type
  // (or a NULL type of no such type exists).
  static QualType getNextLargerIntegralType(ASTContext &Context, QualType T) {
    // FIXME: Int128/UInt128 support, which also needs to be introduced into
    // enum checking below.
    assert((T->isIntegralType(Context) ||
           T->isEnumeralType()) && "Integral type required!");
    const unsigned NumTypes = 4;
    QualType SignedIntegralTypes[NumTypes] = {
      Context.ShortTy, Context.IntTy, Context.LongTy, Context.LongLongTy
    };
    QualType UnsignedIntegralTypes[NumTypes] = {
      Context.UnsignedShortTy, Context.UnsignedIntTy, Context.UnsignedLongTy,
      Context.UnsignedLongLongTy
    };
  
    unsigned BitWidth = Context.getTypeSize(T);
    QualType *Types = T->isSignedIntegerOrEnumerationType()? SignedIntegralTypes
                                                          : UnsignedIntegralTypes;
    for (unsigned I = 0; I != NumTypes; ++I)
      if (Context.getTypeSize(Types[I]) > BitWidth)
        return Types[I];
  
    return QualType();
  }
  
  EnumConstantDecl *Sema::CheckEnumConstant(EnumDecl *Enum,
                                            EnumConstantDecl *LastEnumConst,
                                            SourceLocation IdLoc,
                                            IdentifierInfo *Id,
                                            Expr *Val) {
    unsigned IntWidth = Context.getTargetInfo().getIntWidth();
    llvm::APSInt EnumVal(IntWidth);
    QualType EltTy;
  
    if (Val && DiagnoseUnexpandedParameterPack(Val, UPPC_EnumeratorValue))
      Val = nullptr;
  
    if (Val)
      Val = DefaultLvalueConversion(Val).get();
  
    if (Val) {
      if (Enum->isDependentType() || Val->isTypeDependent())
        EltTy = Context.DependentTy;
      else {
        if (getLangOpts().CPlusPlus11 && Enum->isFixed() &&
            !getLangOpts().MSVCCompat) {
          // C++11 [dcl.enum]p5: If the underlying type is fixed, [...] the
          // constant-expression in the enumerator-definition shall be a converted
          // constant expression of the underlying type.
          EltTy = Enum->getIntegerType();
          ExprResult Converted =
            CheckConvertedConstantExpression(Val, EltTy, EnumVal,
                                             CCEK_Enumerator);
          if (Converted.isInvalid())
            Val = nullptr;
          else
            Val = Converted.get();
        } else if (!Val->isValueDependent() &&
                   !(Val = VerifyIntegerConstantExpression(Val,
                                                           &EnumVal).get())) {
          // C99 6.7.2.2p2: Make sure we have an integer constant expression.
        } else {
          if (Enum->isComplete()) {
            EltTy = Enum->getIntegerType();
  
            // In Obj-C and Microsoft mode, require the enumeration value to be
            // representable in the underlying type of the enumeration. In C++11,
            // we perform a non-narrowing conversion as part of converted constant
            // expression checking.
            if (!isRepresentableIntegerValue(Context, EnumVal, EltTy)) {
              if (getLangOpts().MSVCCompat) {
                Diag(IdLoc, diag::ext_enumerator_too_large) << EltTy;
                Val = ImpCastExprToType(Val, EltTy, CK_IntegralCast).get();
              } else
                Diag(IdLoc, diag::err_enumerator_too_large) << EltTy;
            } else
              Val = ImpCastExprToType(Val, EltTy,
                                      EltTy->isBooleanType() ?
                                      CK_IntegralToBoolean : CK_IntegralCast)
                      .get();
          } else if (getLangOpts().CPlusPlus) {
            // C++11 [dcl.enum]p5:
            //   If the underlying type is not fixed, the type of each enumerator
            //   is the type of its initializing value:
            //     - If an initializer is specified for an enumerator, the
            //       initializing value has the same type as the expression.
            EltTy = Val->getType();
          } else {
            // C99 6.7.2.2p2:
            //   The expression that defines the value of an enumeration constant
            //   shall be an integer constant expression that has a value
            //   representable as an int.
  
            // Complain if the value is not representable in an int.
            if (!isRepresentableIntegerValue(Context, EnumVal, Context.IntTy))
              Diag(IdLoc, diag::ext_enum_value_not_int)
                << EnumVal.toString(10) << Val->getSourceRange()
                << (EnumVal.isUnsigned() || EnumVal.isNonNegative());
            else if (!Context.hasSameType(Val->getType(), Context.IntTy)) {
              // Force the type of the expression to 'int'.
              Val = ImpCastExprToType(Val, Context.IntTy, CK_IntegralCast).get();
            }
            EltTy = Val->getType();
          }
        }
      }
    }
  
    if (!Val) {
      if (Enum->isDependentType())
        EltTy = Context.DependentTy;
      else if (!LastEnumConst) {
        // C++0x [dcl.enum]p5:
        //   If the underlying type is not fixed, the type of each enumerator
        //   is the type of its initializing value:
        //     - If no initializer is specified for the first enumerator, the
        //       initializing value has an unspecified integral type.
        //
        // GCC uses 'int' for its unspecified integral type, as does
        // C99 6.7.2.2p3.
        if (Enum->isFixed()) {
          EltTy = Enum->getIntegerType();
        }
        else {
          EltTy = Context.IntTy;
        }
      } else {
        // Assign the last value + 1.
        EnumVal = LastEnumConst->getInitVal();
        ++EnumVal;
        EltTy = LastEnumConst->getType();
  
        // Check for overflow on increment.
        if (EnumVal < LastEnumConst->getInitVal()) {
          // C++0x [dcl.enum]p5:
          //   If the underlying type is not fixed, the type of each enumerator
          //   is the type of its initializing value:
          //
          //     - Otherwise the type of the initializing value is the same as
          //       the type of the initializing value of the preceding enumerator
          //       unless the incremented value is not representable in that type,
          //       in which case the type is an unspecified integral type
          //       sufficient to contain the incremented value. If no such type
          //       exists, the program is ill-formed.
          QualType T = getNextLargerIntegralType(Context, EltTy);
          if (T.isNull() || Enum->isFixed()) {
            // There is no integral type larger enough to represent this
            // value. Complain, then allow the value to wrap around.
            EnumVal = LastEnumConst->getInitVal();
            EnumVal = EnumVal.zext(EnumVal.getBitWidth() * 2);
            ++EnumVal;
            if (Enum->isFixed())
              // When the underlying type is fixed, this is ill-formed.
              Diag(IdLoc, diag::err_enumerator_wrapped)
                << EnumVal.toString(10)
                << EltTy;
            else
              Diag(IdLoc, diag::ext_enumerator_increment_too_large)
                << EnumVal.toString(10);
          } else {
            EltTy = T;
          }
  
          // Retrieve the last enumerator's value, extent that type to the
          // type that is supposed to be large enough to represent the incremented
          // value, then increment.
          EnumVal = LastEnumConst->getInitVal();
          EnumVal.setIsSigned(EltTy->isSignedIntegerOrEnumerationType());
          EnumVal = EnumVal.zextOrTrunc(Context.getIntWidth(EltTy));
          ++EnumVal;
  
          // If we're not in C++, diagnose the overflow of enumerator values,
          // which in C99 means that the enumerator value is not representable in
          // an int (C99 6.7.2.2p2). However, we support GCC's extension that
          // permits enumerator values that are representable in some larger
          // integral type.
          if (!getLangOpts().CPlusPlus && !T.isNull())
            Diag(IdLoc, diag::warn_enum_value_overflow);
        } else if (!getLangOpts().CPlusPlus &&
                   !isRepresentableIntegerValue(Context, EnumVal, EltTy)) {
          // Enforce C99 6.7.2.2p2 even when we compute the next value.
          Diag(IdLoc, diag::ext_enum_value_not_int)
            << EnumVal.toString(10) << 1;
        }
      }
    }
  
    if (!EltTy->isDependentType()) {
      // Make the enumerator value match the signedness and size of the
      // enumerator's type.
      EnumVal = EnumVal.extOrTrunc(Context.getIntWidth(EltTy));
      EnumVal.setIsSigned(EltTy->isSignedIntegerOrEnumerationType());
    }
  
    return EnumConstantDecl::Create(Context, Enum, IdLoc, Id, EltTy,
                                    Val, EnumVal);
  }
  
  Sema::SkipBodyInfo Sema::shouldSkipAnonEnumBody(Scope *S, IdentifierInfo *II,
                                                  SourceLocation IILoc) {
    if (!(getLangOpts().Modules || getLangOpts().ModulesLocalVisibility) ||
        !getLangOpts().CPlusPlus)
      return SkipBodyInfo();
  
    // We have an anonymous enum definition. Look up the first enumerator to
    // determine if we should merge the definition with an existing one and
    // skip the body.
    NamedDecl *PrevDecl = LookupSingleName(S, II, IILoc, LookupOrdinaryName,
                                           forRedeclarationInCurContext());
    auto *PrevECD = dyn_cast_or_null<EnumConstantDecl>(PrevDecl);
    if (!PrevECD)
      return SkipBodyInfo();
  
    EnumDecl *PrevED = cast<EnumDecl>(PrevECD->getDeclContext());
    NamedDecl *Hidden;
    if (!PrevED->getDeclName() && !hasVisibleDefinition(PrevED, &Hidden)) {
      SkipBodyInfo Skip;
      Skip.Previous = Hidden;
      return Skip;
    }
  
    return SkipBodyInfo();
  }
  
  Decl *Sema::ActOnEnumConstant(Scope *S, Decl *theEnumDecl, Decl *lastEnumConst,
                                SourceLocation IdLoc, IdentifierInfo *Id,
                                const ParsedAttributesView &Attrs,
                                SourceLocation EqualLoc, Expr *Val) {
    EnumDecl *TheEnumDecl = cast<EnumDecl>(theEnumDecl);
    EnumConstantDecl *LastEnumConst =
      cast_or_null<EnumConstantDecl>(lastEnumConst);
  
    // The scope passed in may not be a decl scope.  Zip up the scope tree until
    // we find one that is.
    S = getNonFieldDeclScope(S);
  
    // Verify that there isn't already something declared with this name in this
    // scope.
    LookupResult R(*this, Id, IdLoc, LookupOrdinaryName, ForVisibleRedeclaration);
    LookupName(R, S);
    NamedDecl *PrevDecl = R.getAsSingle<NamedDecl>();
  
    if (PrevDecl && PrevDecl->isTemplateParameter()) {
      // Maybe we will complain about the shadowed template parameter.
      DiagnoseTemplateParameterShadow(IdLoc, PrevDecl);
      // Just pretend that we didn't see the previous declaration.
      PrevDecl = nullptr;
    }
  
    // C++ [class.mem]p15:
    // If T is the name of a class, then each of the following shall have a name
    // different from T:
    // - every enumerator of every member of class T that is an unscoped
    // enumerated type
    if (getLangOpts().CPlusPlus && !TheEnumDecl->isScoped())
      DiagnoseClassNameShadow(TheEnumDecl->getDeclContext(),
                              DeclarationNameInfo(Id, IdLoc));
  
    EnumConstantDecl *New =
      CheckEnumConstant(TheEnumDecl, LastEnumConst, IdLoc, Id, Val);
    if (!New)
      return nullptr;
  
    if (PrevDecl) {
      if (!TheEnumDecl->isScoped() && isa<ValueDecl>(PrevDecl)) {
        // Check for other kinds of shadowing not already handled.
        CheckShadow(New, PrevDecl, R);
      }
  
      // When in C++, we may get a TagDecl with the same name; in this case the
      // enum constant will 'hide' the tag.
      assert((getLangOpts().CPlusPlus || !isa<TagDecl>(PrevDecl)) &&
             "Received TagDecl when not in C++!");
      if (!isa<TagDecl>(PrevDecl) && isDeclInScope(PrevDecl, CurContext, S)) {
        if (isa<EnumConstantDecl>(PrevDecl))
          Diag(IdLoc, diag::err_redefinition_of_enumerator) << Id;
        else
          Diag(IdLoc, diag::err_redefinition) << Id;
        notePreviousDefinition(PrevDecl, IdLoc);
        return nullptr;
      }
    }
  
    // Process attributes.
    ProcessDeclAttributeList(S, New, Attrs);
    AddPragmaAttributes(S, New);
  
    // Register this decl in the current scope stack.
    New->setAccess(TheEnumDecl->getAccess());
    PushOnScopeChains(New, S);
  
    ActOnDocumentableDecl(New);
  
    return New;
  }
  
  // Returns true when the enum initial expression does not trigger the
  // duplicate enum warning.  A few common cases are exempted as follows:
  // Element2 = Element1
  // Element2 = Element1 + 1
  // Element2 = Element1 - 1
  // Where Element2 and Element1 are from the same enum.
  static bool ValidDuplicateEnum(EnumConstantDecl *ECD, EnumDecl *Enum) {
    Expr *InitExpr = ECD->getInitExpr();
    if (!InitExpr)
      return true;
    InitExpr = InitExpr->IgnoreImpCasts();
  
    if (BinaryOperator *BO = dyn_cast<BinaryOperator>(InitExpr)) {
      if (!BO->isAdditiveOp())
        return true;
      IntegerLiteral *IL = dyn_cast<IntegerLiteral>(BO->getRHS());
      if (!IL)
        return true;
      if (IL->getValue() != 1)
        return true;
  
      InitExpr = BO->getLHS();
    }
  
    // This checks if the elements are from the same enum.
    DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(InitExpr);
    if (!DRE)
      return true;
  
    EnumConstantDecl *EnumConstant = dyn_cast<EnumConstantDecl>(DRE->getDecl());
    if (!EnumConstant)
      return true;
  
    if (cast<EnumDecl>(TagDecl::castFromDeclContext(ECD->getDeclContext())) !=
        Enum)
      return true;
  
    return false;
  }
  
  // Emits a warning when an element is implicitly set a value that
  // a previous element has already been set to.
  static void CheckForDuplicateEnumValues(Sema &S, ArrayRef<Decl *> Elements,
                                          EnumDecl *Enum, QualType EnumType) {
    // Avoid anonymous enums
    if (!Enum->getIdentifier())
      return;
  
    // Only check for small enums.
    if (Enum->getNumPositiveBits() > 63 || Enum->getNumNegativeBits() > 64)
      return;
  
    if (S.Diags.isIgnored(diag::warn_duplicate_enum_values, Enum->getLocation()))
      return;
  
    typedef SmallVector<EnumConstantDecl *, 3> ECDVector;
    typedef SmallVector<std::unique_ptr<ECDVector>, 3> DuplicatesVector;
  
    typedef llvm::PointerUnion<EnumConstantDecl*, ECDVector*> DeclOrVector;
    typedef std::unordered_map<int64_t, DeclOrVector> ValueToVectorMap;
  
    // Use int64_t as a key to avoid needing special handling for DenseMap keys.
    auto EnumConstantToKey = [](const EnumConstantDecl *D) {
      llvm::APSInt Val = D->getInitVal();
      return Val.isSigned() ? Val.getSExtValue() : Val.getZExtValue();
    };
  
    DuplicatesVector DupVector;
    ValueToVectorMap EnumMap;
  
    // Populate the EnumMap with all values represented by enum constants without
    // an initializer.
    for (auto *Element : Elements) {
      EnumConstantDecl *ECD = cast_or_null<EnumConstantDecl>(Element);
  
      // Null EnumConstantDecl means a previous diagnostic has been emitted for
      // this constant.  Skip this enum since it may be ill-formed.
      if (!ECD) {
        return;
      }
  
      // Constants with initalizers are handled in the next loop.
      if (ECD->getInitExpr())
        continue;
  
      // Duplicate values are handled in the next loop.
      EnumMap.insert({EnumConstantToKey(ECD), ECD});
    }
  
    if (EnumMap.size() == 0)
      return;
  
    // Create vectors for any values that has duplicates.
    for (auto *Element : Elements) {
      // The last loop returned if any constant was null.
      EnumConstantDecl *ECD = cast<EnumConstantDecl>(Element);
      if (!ValidDuplicateEnum(ECD, Enum))
        continue;
  
      auto Iter = EnumMap.find(EnumConstantToKey(ECD));
      if (Iter == EnumMap.end())
        continue;
  
      DeclOrVector& Entry = Iter->second;
      if (EnumConstantDecl *D = Entry.dyn_cast<EnumConstantDecl*>()) {
        // Ensure constants are different.
        if (D == ECD)
          continue;
  
        // Create new vector and push values onto it.
        auto Vec = llvm::make_unique<ECDVector>();
        Vec->push_back(D);
        Vec->push_back(ECD);
  
        // Update entry to point to the duplicates vector.
        Entry = Vec.get();
  
        // Store the vector somewhere we can consult later for quick emission of
        // diagnostics.
        DupVector.emplace_back(std::move(Vec));
        continue;
      }
  
      ECDVector *Vec = Entry.get<ECDVector*>();
      // Make sure constants are not added more than once.
      if (*Vec->begin() == ECD)
        continue;
  
      Vec->push_back(ECD);
    }
  
    // Emit diagnostics.
    for (const auto &Vec : DupVector) {
      assert(Vec->size() > 1 && "ECDVector should have at least 2 elements.");
  
      // Emit warning for one enum constant.
      auto *FirstECD = Vec->front();
      S.Diag(FirstECD->getLocation(), diag::warn_duplicate_enum_values)
        << FirstECD << FirstECD->getInitVal().toString(10)
        << FirstECD->getSourceRange();
  
      // Emit one note for each of the remaining enum constants with
      // the same value.
      for (auto *ECD : llvm::make_range(Vec->begin() + 1, Vec->end()))
        S.Diag(ECD->getLocation(), diag::note_duplicate_element)
          << ECD << ECD->getInitVal().toString(10)
          << ECD->getSourceRange();
    }
  }
  
  bool Sema::IsValueInFlagEnum(const EnumDecl *ED, const llvm::APInt &Val,
                               bool AllowMask) const {
    assert(ED->isClosedFlag() && "looking for value in non-flag or open enum");
    assert(ED->isCompleteDefinition() && "expected enum definition");
  
    auto R = FlagBitsCache.insert(std::make_pair(ED, llvm::APInt()));
    llvm::APInt &FlagBits = R.first->second;
  
    if (R.second) {
      for (auto *E : ED->enumerators()) {
        const auto &EVal = E->getInitVal();
        // Only single-bit enumerators introduce new flag values.
        if (EVal.isPowerOf2())
          FlagBits = FlagBits.zextOrSelf(EVal.getBitWidth()) | EVal;
      }
    }
  
    // A value is in a flag enum if either its bits are a subset of the enum's
    // flag bits (the first condition) or we are allowing masks and the same is
    // true of its complement (the second condition). When masks are allowed, we
    // allow the common idiom of ~(enum1 | enum2) to be a valid enum value.
    //
    // While it's true that any value could be used as a mask, the assumption is
    // that a mask will have all of the insignificant bits set. Anything else is
    // likely a logic error.
    llvm::APInt FlagMask = ~FlagBits.zextOrTrunc(Val.getBitWidth());
    return !(FlagMask & Val) || (AllowMask && !(FlagMask & ~Val));
  }
  
  void Sema::ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
                           Decl *EnumDeclX, ArrayRef<Decl *> Elements, Scope *S,
                           const ParsedAttributesView &Attrs) {
    EnumDecl *Enum = cast<EnumDecl>(EnumDeclX);
    QualType EnumType = Context.getTypeDeclType(Enum);
  
    ProcessDeclAttributeList(S, Enum, Attrs);
  
    if (Enum->isDependentType()) {
      for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
        EnumConstantDecl *ECD =
          cast_or_null<EnumConstantDecl>(Elements[i]);
        if (!ECD) continue;
  
        ECD->setType(EnumType);
      }
  
      Enum->completeDefinition(Context.DependentTy, Context.DependentTy, 0, 0);
      return;
    }
  
    // TODO: If the result value doesn't fit in an int, it must be a long or long
    // long value.  ISO C does not support this, but GCC does as an extension,
    // emit a warning.
    unsigned IntWidth = Context.getTargetInfo().getIntWidth();
    unsigned CharWidth = Context.getTargetInfo().getCharWidth();
    unsigned ShortWidth = Context.getTargetInfo().getShortWidth();
  
    // Verify that all the values are okay, compute the size of the values, and
    // reverse the list.
    unsigned NumNegativeBits = 0;
    unsigned NumPositiveBits = 0;
  
    // Keep track of whether all elements have type int.
    bool AllElementsInt = true;
  
    for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
      EnumConstantDecl *ECD =
        cast_or_null<EnumConstantDecl>(Elements[i]);
      if (!ECD) continue;  // Already issued a diagnostic.
  
      const llvm::APSInt &InitVal = ECD->getInitVal();
  
      // Keep track of the size of positive and negative values.
      if (InitVal.isUnsigned() || InitVal.isNonNegative())
        NumPositiveBits = std::max(NumPositiveBits,
                                   (unsigned)InitVal.getActiveBits());
      else
        NumNegativeBits = std::max(NumNegativeBits,
                                   (unsigned)InitVal.getMinSignedBits());
  
      // Keep track of whether every enum element has type int (very common).
      if (AllElementsInt)
        AllElementsInt = ECD->getType() == Context.IntTy;
    }
  
    // Figure out the type that should be used for this enum.
    QualType BestType;
    unsigned BestWidth;
  
    // C++0x N3000 [conv.prom]p3:
    //   An rvalue of an unscoped enumeration type whose underlying
    //   type is not fixed can be converted to an rvalue of the first
    //   of the following types that can represent all the values of
    //   the enumeration: int, unsigned int, long int, unsigned long
    //   int, long long int, or unsigned long long int.
    // C99 6.4.4.3p2:
    //   An identifier declared as an enumeration constant has type int.
    // The C99 rule is modified by a gcc extension
    QualType BestPromotionType;
  
    bool Packed = Enum->hasAttr<PackedAttr>();
    // -fshort-enums is the equivalent to specifying the packed attribute on all
    // enum definitions.
    if (LangOpts.ShortEnums)
      Packed = true;
  
    // If the enum already has a type because it is fixed or dictated by the
    // target, promote that type instead of analyzing the enumerators.
    if (Enum->isComplete()) {
      BestType = Enum->getIntegerType();
      if (BestType->isPromotableIntegerType())
        BestPromotionType = Context.getPromotedIntegerType(BestType);
      else
        BestPromotionType = BestType;
  
      BestWidth = Context.getIntWidth(BestType);
    }
    else if (NumNegativeBits) {
      // If there is a negative value, figure out the smallest integer type (of
      // int/long/longlong) that fits.
      // If it's packed, check also if it fits a char or a short.
      if (Packed && NumNegativeBits <= CharWidth && NumPositiveBits < CharWidth) {
        BestType = Context.SignedCharTy;
        BestWidth = CharWidth;
      } else if (Packed && NumNegativeBits <= ShortWidth &&
                 NumPositiveBits < ShortWidth) {
        BestType = Context.ShortTy;
        BestWidth = ShortWidth;
      } else if (NumNegativeBits <= IntWidth && NumPositiveBits < IntWidth) {
        BestType = Context.IntTy;
        BestWidth = IntWidth;
      } else {
        BestWidth = Context.getTargetInfo().getLongWidth();
  
        if (NumNegativeBits <= BestWidth && NumPositiveBits < BestWidth) {
          BestType = Context.LongTy;
        } else {
          BestWidth = Context.getTargetInfo().getLongLongWidth();
  
          if (NumNegativeBits > BestWidth || NumPositiveBits >= BestWidth)
            Diag(Enum->getLocation(), diag::ext_enum_too_large);
          BestType = Context.LongLongTy;
        }
      }
      BestPromotionType = (BestWidth <= IntWidth ? Context.IntTy : BestType);
    } else {
      // If there is no negative value, figure out the smallest type that fits
      // all of the enumerator values.
      // If it's packed, check also if it fits a char or a short.
      if (Packed && NumPositiveBits <= CharWidth) {
        BestType = Context.UnsignedCharTy;
        BestPromotionType = Context.IntTy;
        BestWidth = CharWidth;
      } else if (Packed && NumPositiveBits <= ShortWidth) {
        BestType = Context.UnsignedShortTy;
        BestPromotionType = Context.IntTy;
        BestWidth = ShortWidth;
      } else if (NumPositiveBits <= IntWidth) {
        BestType = Context.UnsignedIntTy;
        BestWidth = IntWidth;
        BestPromotionType
          = (NumPositiveBits == BestWidth || !getLangOpts().CPlusPlus)
                             ? Context.UnsignedIntTy : Context.IntTy;
      } else if (NumPositiveBits <=
                 (BestWidth = Context.getTargetInfo().getLongWidth())) {
        BestType = Context.UnsignedLongTy;
        BestPromotionType
          = (NumPositiveBits == BestWidth || !getLangOpts().CPlusPlus)
                             ? Context.UnsignedLongTy : Context.LongTy;
      } else {
        BestWidth = Context.getTargetInfo().getLongLongWidth();
        assert(NumPositiveBits <= BestWidth &&
               "How could an initializer get larger than ULL?");
        BestType = Context.UnsignedLongLongTy;
        BestPromotionType
          = (NumPositiveBits == BestWidth || !getLangOpts().CPlusPlus)
                             ? Context.UnsignedLongLongTy : Context.LongLongTy;
      }
    }
  
    // Loop over all of the enumerator constants, changing their types to match
    // the type of the enum if needed.
    for (auto *D : Elements) {
      auto *ECD = cast_or_null<EnumConstantDecl>(D);
      if (!ECD) continue;  // Already issued a diagnostic.
  
      // Standard C says the enumerators have int type, but we allow, as an
      // extension, the enumerators to be larger than int size.  If each
      // enumerator value fits in an int, type it as an int, otherwise type it the
      // same as the enumerator decl itself.  This means that in "enum { X = 1U }"
      // that X has type 'int', not 'unsigned'.
  
      // Determine whether the value fits into an int.
      llvm::APSInt InitVal = ECD->getInitVal();
  
      // If it fits into an integer type, force it.  Otherwise force it to match
      // the enum decl type.
      QualType NewTy;
      unsigned NewWidth;
      bool NewSign;
      if (!getLangOpts().CPlusPlus &&
          !Enum->isFixed() &&
          isRepresentableIntegerValue(Context, InitVal, Context.IntTy)) {
        NewTy = Context.IntTy;
        NewWidth = IntWidth;
        NewSign = true;
      } else if (ECD->getType() == BestType) {
        // Already the right type!
        if (getLangOpts().CPlusPlus)
          // C++ [dcl.enum]p4: Following the closing brace of an
          // enum-specifier, each enumerator has the type of its
          // enumeration.
          ECD->setType(EnumType);
        continue;
      } else {
        NewTy = BestType;
        NewWidth = BestWidth;
        NewSign = BestType->isSignedIntegerOrEnumerationType();
      }
  
      // Adjust the APSInt value.
      InitVal = InitVal.extOrTrunc(NewWidth);
      InitVal.setIsSigned(NewSign);
      ECD->setInitVal(InitVal);
  
      // Adjust the Expr initializer and type.
      if (ECD->getInitExpr() &&
          !Context.hasSameType(NewTy, ECD->getInitExpr()->getType()))
        ECD->setInitExpr(ImplicitCastExpr::Create(Context, NewTy,
                                                  CK_IntegralCast,
                                                  ECD->getInitExpr(),
                                                  /*base paths*/ nullptr,
                                                  VK_RValue));
      if (getLangOpts().CPlusPlus)
        // C++ [dcl.enum]p4: Following the closing brace of an
        // enum-specifier, each enumerator has the type of its
        // enumeration.
        ECD->setType(EnumType);
      else
        ECD->setType(NewTy);
    }
  
    Enum->completeDefinition(BestType, BestPromotionType,
                             NumPositiveBits, NumNegativeBits);
  
    CheckForDuplicateEnumValues(*this, Elements, Enum, EnumType);
  
    if (Enum->isClosedFlag()) {
      for (Decl *D : Elements) {
        EnumConstantDecl *ECD = cast_or_null<EnumConstantDecl>(D);
        if (!ECD) continue;  // Already issued a diagnostic.
  
        llvm::APSInt InitVal = ECD->getInitVal();
        if (InitVal != 0 && !InitVal.isPowerOf2() &&
            !IsValueInFlagEnum(Enum, InitVal, true))
          Diag(ECD->getLocation(), diag::warn_flag_enum_constant_out_of_range)
            << ECD << Enum;
      }
    }
  
    // Now that the enum type is defined, ensure it's not been underaligned.
    if (Enum->hasAttrs())
      CheckAlignasUnderalignment(Enum);
  }
  
  Decl *Sema::ActOnFileScopeAsmDecl(Expr *expr,
                                    SourceLocation StartLoc,
                                    SourceLocation EndLoc) {
    StringLiteral *AsmString = cast<StringLiteral>(expr);
  
    FileScopeAsmDecl *New = FileScopeAsmDecl::Create(Context, CurContext,
                                                     AsmString, StartLoc,
                                                     EndLoc);
    CurContext->addDecl(New);
    return New;
  }
  
  static void checkModuleImportContext(Sema &S, Module *M,
                                       SourceLocation ImportLoc, DeclContext *DC,
                                       bool FromInclude = false) {
    SourceLocation ExternCLoc;
  
    if (auto *LSD = dyn_cast<LinkageSpecDecl>(DC)) {
      switch (LSD->getLanguage()) {
      case LinkageSpecDecl::lang_c:
        if (ExternCLoc.isInvalid())
          ExternCLoc = LSD->getBeginLoc();
        break;
      case LinkageSpecDecl::lang_cxx:
        break;
      }
      DC = LSD->getParent();
    }
  
    while (isa<LinkageSpecDecl>(DC) || isa<ExportDecl>(DC))
      DC = DC->getParent();
  
    if (!isa<TranslationUnitDecl>(DC)) {
      S.Diag(ImportLoc, (FromInclude && S.isModuleVisible(M))
                            ? diag::ext_module_import_not_at_top_level_noop
                            : diag::err_module_import_not_at_top_level_fatal)
          << M->getFullModuleName() << DC;
      S.Diag(cast<Decl>(DC)->getBeginLoc(),
             diag::note_module_import_not_at_top_level)
          << DC;
    } else if (!M->IsExternC && ExternCLoc.isValid()) {
      S.Diag(ImportLoc, diag::ext_module_import_in_extern_c)
        << M->getFullModuleName();
      S.Diag(ExternCLoc, diag::note_extern_c_begins_here);
    }
  }
  
  Sema::DeclGroupPtrTy Sema::ActOnModuleDecl(SourceLocation StartLoc,
                                             SourceLocation ModuleLoc,
                                             ModuleDeclKind MDK,
                                             ModuleIdPath Path) {
    assert(getLangOpts().ModulesTS &&
           "should only have module decl in modules TS");
  
    // A module implementation unit requires that we are not compiling a module
    // of any kind. A module interface unit requires that we are not compiling a
    // module map.
    switch (getLangOpts().getCompilingModule()) {
    case LangOptions::CMK_None:
      // It's OK to compile a module interface as a normal translation unit.
      break;
  
    case LangOptions::CMK_ModuleInterface:
      if (MDK != ModuleDeclKind::Implementation)
        break;
  
      // We were asked to compile a module interface unit but this is a module
      // implementation unit. That indicates the 'export' is missing.
      Diag(ModuleLoc, diag::err_module_interface_implementation_mismatch)
        << FixItHint::CreateInsertion(ModuleLoc, "export ");
      MDK = ModuleDeclKind::Interface;
      break;
  
    case LangOptions::CMK_ModuleMap:
      Diag(ModuleLoc, diag::err_module_decl_in_module_map_module);
      return nullptr;
  
    case LangOptions::CMK_HeaderModule:
      Diag(ModuleLoc, diag::err_module_decl_in_header_module);
      return nullptr;
    }
  
    assert(ModuleScopes.size() == 1 && "expected to be at global module scope");
  
    // FIXME: Most of this work should be done by the preprocessor rather than
    // here, in order to support macro import.
  
    // Only one module-declaration is permitted per source file.
    if (ModuleScopes.back().Module->Kind == Module::ModuleInterfaceUnit) {
      Diag(ModuleLoc, diag::err_module_redeclaration);
      Diag(VisibleModules.getImportLoc(ModuleScopes.back().Module),
           diag::note_prev_module_declaration);
      return nullptr;
    }
  
    // Flatten the dots in a module name. Unlike Clang's hierarchical module map
    // modules, the dots here are just another character that can appear in a
    // module name.
    std::string ModuleName;
    for (auto &Piece : Path) {
      if (!ModuleName.empty())
        ModuleName += ".";
      ModuleName += Piece.first->getName();
    }
  
    // If a module name was explicitly specified on the command line, it must be
    // correct.
    if (!getLangOpts().CurrentModule.empty() &&
        getLangOpts().CurrentModule != ModuleName) {
      Diag(Path.front().second, diag::err_current_module_name_mismatch)
          << SourceRange(Path.front().second, Path.back().second)
          << getLangOpts().CurrentModule;
      return nullptr;
    }
    const_cast<LangOptions&>(getLangOpts()).CurrentModule = ModuleName;
  
    auto &Map = PP.getHeaderSearchInfo().getModuleMap();
    Module *Mod;
  
    switch (MDK) {
    case ModuleDeclKind::Interface: {
      // We can't have parsed or imported a definition of this module or parsed a
      // module map defining it already.
      if (auto *M = Map.findModule(ModuleName)) {
        Diag(Path[0].second, diag::err_module_redefinition) << ModuleName;
        if (M->DefinitionLoc.isValid())
          Diag(M->DefinitionLoc, diag::note_prev_module_definition);
        else if (const auto *FE = M->getASTFile())
          Diag(M->DefinitionLoc, diag::note_prev_module_definition_from_ast_file)
              << FE->getName();
        Mod = M;
        break;
      }
  
      // Create a Module for the module that we're defining.
      Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
                                             ModuleScopes.front().Module);
      assert(Mod && "module creation should not fail");
      break;
    }
  
    case ModuleDeclKind::Partition:
      // FIXME: Check we are in a submodule of the named module.
      return nullptr;
  
    case ModuleDeclKind::Implementation:
      std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc(
          PP.getIdentifierInfo(ModuleName), Path[0].second);
      Mod = getModuleLoader().loadModule(ModuleLoc, {ModuleNameLoc},
                                         Module::AllVisible,
                                         /*IsIncludeDirective=*/false);
      if (!Mod) {
        Diag(ModuleLoc, diag::err_module_not_defined) << ModuleName;
        // Create an empty module interface unit for error recovery.
        Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
                                               ModuleScopes.front().Module);
      }
      break;
    }
  
    // Switch from the global module to the named module.
    ModuleScopes.back().Module = Mod;
    ModuleScopes.back().ModuleInterface = MDK != ModuleDeclKind::Implementation;
    VisibleModules.setVisible(Mod, ModuleLoc);
  
    // From now on, we have an owning module for all declarations we see.
    // However, those declarations are module-private unless explicitly
    // exported.
    auto *TU = Context.getTranslationUnitDecl();
    TU->setModuleOwnershipKind(Decl::ModuleOwnershipKind::ModulePrivate);
    TU->setLocalOwningModule(Mod);
  
    // FIXME: Create a ModuleDecl.
    return nullptr;
  }
  
  DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
                                     SourceLocation ImportLoc,
                                     ModuleIdPath Path) {
    // Flatten the module path for a Modules TS module name.
    std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc;
    if (getLangOpts().ModulesTS) {
      std::string ModuleName;
      for (auto &Piece : Path) {
        if (!ModuleName.empty())
          ModuleName += ".";
        ModuleName += Piece.first->getName();
      }
      ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Path[0].second};
      Path = ModuleIdPath(ModuleNameLoc);
    }
  
    Module *Mod =
        getModuleLoader().loadModule(ImportLoc, Path, Module::AllVisible,
                                     /*IsIncludeDirective=*/false);
    if (!Mod)
      return true;
  
    VisibleModules.setVisible(Mod, ImportLoc);
  
    checkModuleImportContext(*this, Mod, ImportLoc, CurContext);
  
    // FIXME: we should support importing a submodule within a different submodule
    // of the same top-level module. Until we do, make it an error rather than
    // silently ignoring the import.
    // Import-from-implementation is valid in the Modules TS. FIXME: Should we
    // warn on a redundant import of the current module?
    if (Mod->getTopLevelModuleName() == getLangOpts().CurrentModule &&
        (getLangOpts().isCompilingModule() || !getLangOpts().ModulesTS))
      Diag(ImportLoc, getLangOpts().isCompilingModule()
                          ? diag::err_module_self_import
                          : diag::err_module_import_in_implementation)
          << Mod->getFullModuleName() << getLangOpts().CurrentModule;
  
    SmallVector<SourceLocation, 2> IdentifierLocs;
    Module *ModCheck = Mod;
    for (unsigned I = 0, N = Path.size(); I != N; ++I) {
      // If we've run out of module parents, just drop the remaining identifiers.
      // We need the length to be consistent.
      if (!ModCheck)
        break;
      ModCheck = ModCheck->Parent;
  
      IdentifierLocs.push_back(Path[I].second);
    }
  
    ImportDecl *Import = ImportDecl::Create(Context, CurContext, StartLoc,
                                            Mod, IdentifierLocs);
    if (!ModuleScopes.empty())
      Context.addModuleInitializer(ModuleScopes.back().Module, Import);
    CurContext->addDecl(Import);
  
    // Re-export the module if needed.
    if (Import->isExported() &&
        !ModuleScopes.empty() && ModuleScopes.back().ModuleInterface)
      getCurrentModule()->Exports.emplace_back(Mod, false);
  
    return Import;
  }
  
  void Sema::ActOnModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
    checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
    BuildModuleInclude(DirectiveLoc, Mod);
  }
  
  void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
    // Determine whether we're in the #include buffer for a module. The #includes
    // in that buffer do not qualify as module imports; they're just an
    // implementation detail of us building the module.
    //
    // FIXME: Should we even get ActOnModuleInclude calls for those?
    bool IsInModuleIncludes =
        TUKind == TU_Module &&
        getSourceManager().isWrittenInMainFile(DirectiveLoc);
  
    bool ShouldAddImport = !IsInModuleIncludes;
  
    // If this module import was due to an inclusion directive, create an
    // implicit import declaration to capture it in the AST.
    if (ShouldAddImport) {
      TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
      ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
                                                       DirectiveLoc, Mod,
                                                       DirectiveLoc);
      if (!ModuleScopes.empty())
        Context.addModuleInitializer(ModuleScopes.back().Module, ImportD);
      TU->addDecl(ImportD);
      Consumer.HandleImplicitImportDecl(ImportD);
    }
  
    getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, DirectiveLoc);
    VisibleModules.setVisible(Mod, DirectiveLoc);
  }
  
  void Sema::ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
    checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
  
    ModuleScopes.push_back({});
    ModuleScopes.back().Module = Mod;
    if (getLangOpts().ModulesLocalVisibility)
      ModuleScopes.back().OuterVisibleModules = std::move(VisibleModules);
  
    VisibleModules.setVisible(Mod, DirectiveLoc);
  
    // The enclosing context is now part of this module.
    // FIXME: Consider creating a child DeclContext to hold the entities
    // lexically within the module.
    if (getLangOpts().trackLocalOwningModule()) {
      for (auto *DC = CurContext; DC; DC = DC->getLexicalParent()) {
        cast<Decl>(DC)->setModuleOwnershipKind(
            getLangOpts().ModulesLocalVisibility
                ? Decl::ModuleOwnershipKind::VisibleWhenImported
                : Decl::ModuleOwnershipKind::Visible);
        cast<Decl>(DC)->setLocalOwningModule(Mod);
      }
    }
  }
  
  void Sema::ActOnModuleEnd(SourceLocation EomLoc, Module *Mod) {
    if (getLangOpts().ModulesLocalVisibility) {
      VisibleModules = std::move(ModuleScopes.back().OuterVisibleModules);
      // Leaving a module hides namespace names, so our visible namespace cache
      // is now out of date.
      VisibleNamespaceCache.clear();
    }
  
    assert(!ModuleScopes.empty() && ModuleScopes.back().Module == Mod &&
           "left the wrong module scope");
    ModuleScopes.pop_back();
  
    // We got to the end of processing a local module. Create an
    // ImportDecl as we would for an imported module.
    FileID File = getSourceManager().getFileID(EomLoc);
    SourceLocation DirectiveLoc;
    if (EomLoc == getSourceManager().getLocForEndOfFile(File)) {
      // We reached the end of a #included module header. Use the #include loc.
      assert(File != getSourceManager().getMainFileID() &&
             "end of submodule in main source file");
      DirectiveLoc = getSourceManager().getIncludeLoc(File);
    } else {
      // We reached an EOM pragma. Use the pragma location.
      DirectiveLoc = EomLoc;
    }
    BuildModuleInclude(DirectiveLoc, Mod);
  
    // Any further declarations are in whatever module we returned to.
    if (getLangOpts().trackLocalOwningModule()) {
      // The parser guarantees that this is the same context that we entered
      // the module within.
      for (auto *DC = CurContext; DC; DC = DC->getLexicalParent()) {
        cast<Decl>(DC)->setLocalOwningModule(getCurrentModule());
        if (!getCurrentModule())
          cast<Decl>(DC)->setModuleOwnershipKind(
              Decl::ModuleOwnershipKind::Unowned);
      }
    }
  }
  
  void Sema::createImplicitModuleImportForErrorRecovery(SourceLocation Loc,
                                                        Module *Mod) {
    // Bail if we're not allowed to implicitly import a module here.
    if (isSFINAEContext() || !getLangOpts().ModulesErrorRecovery ||
        VisibleModules.isVisible(Mod))
      return;
  
    // Create the implicit import declaration.
    TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
    ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
                                                     Loc, Mod, Loc);
    TU->addDecl(ImportD);
    Consumer.HandleImplicitImportDecl(ImportD);
  
    // Make the module visible.
    getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, Loc);
    VisibleModules.setVisible(Mod, Loc);
  }
  
  /// We have parsed the start of an export declaration, including the '{'
  /// (if present).
  Decl *Sema::ActOnStartExportDecl(Scope *S, SourceLocation ExportLoc,
                                   SourceLocation LBraceLoc) {
    ExportDecl *D = ExportDecl::Create(Context, CurContext, ExportLoc);
  
    // C++ Modules TS draft:
    //   An export-declaration shall appear in the purview of a module other than
    //   the global module.
    if (ModuleScopes.empty() || !ModuleScopes.back().ModuleInterface)
      Diag(ExportLoc, diag::err_export_not_in_module_interface);
  
    //   An export-declaration [...] shall not contain more than one
    //   export keyword.
    //
    // The intent here is that an export-declaration cannot appear within another
    // export-declaration.
    if (D->isExported())
      Diag(ExportLoc, diag::err_export_within_export);
  
    CurContext->addDecl(D);
    PushDeclContext(S, D);
    D->setModuleOwnershipKind(Decl::ModuleOwnershipKind::VisibleWhenImported);
    return D;
  }
  
  /// Complete the definition of an export declaration.
  Decl *Sema::ActOnFinishExportDecl(Scope *S, Decl *D, SourceLocation RBraceLoc) {
    auto *ED = cast<ExportDecl>(D);
    if (RBraceLoc.isValid())
      ED->setRBraceLoc(RBraceLoc);
  
    // FIXME: Diagnose export of internal-linkage declaration (including
    // anonymous namespace).
  
    PopDeclContext();
    return D;
  }
  
  void Sema::ActOnPragmaRedefineExtname(IdentifierInfo* Name,
                                        IdentifierInfo* AliasName,
                                        SourceLocation PragmaLoc,
                                        SourceLocation NameLoc,
                                        SourceLocation AliasNameLoc) {
    NamedDecl *PrevDecl = LookupSingleName(TUScope, Name, NameLoc,
                                           LookupOrdinaryName);
    AsmLabelAttr *Attr =
        AsmLabelAttr::CreateImplicit(Context, AliasName->getName(), AliasNameLoc);
  
    // If a declaration that:
    // 1) declares a function or a variable
    // 2) has external linkage
    // already exists, add a label attribute to it.
    if (PrevDecl && (isa<FunctionDecl>(PrevDecl) || isa<VarDecl>(PrevDecl))) {
      if (isDeclExternC(PrevDecl))
        PrevDecl->addAttr(Attr);
      else
        Diag(PrevDecl->getLocation(), diag::warn_redefine_extname_not_applied)
            << /*Variable*/(isa<FunctionDecl>(PrevDecl) ? 0 : 1) << PrevDecl;
    // Otherwise, add a label atttibute to ExtnameUndeclaredIdentifiers.
    } else
      (void)ExtnameUndeclaredIdentifiers.insert(std::make_pair(Name, Attr));
  }
  
  void Sema::ActOnPragmaWeakID(IdentifierInfo* Name,
                               SourceLocation PragmaLoc,
                               SourceLocation NameLoc) {
    Decl *PrevDecl = LookupSingleName(TUScope, Name, NameLoc, LookupOrdinaryName);
  
    if (PrevDecl) {
      PrevDecl->addAttr(WeakAttr::CreateImplicit(Context, PragmaLoc));
    } else {
      (void)WeakUndeclaredIdentifiers.insert(
        std::pair<IdentifierInfo*,WeakInfo>
          (Name, WeakInfo((IdentifierInfo*)nullptr, NameLoc)));
    }
  }
  
  void Sema::ActOnPragmaWeakAlias(IdentifierInfo* Name,
                                  IdentifierInfo* AliasName,
                                  SourceLocation PragmaLoc,
                                  SourceLocation NameLoc,
                                  SourceLocation AliasNameLoc) {
    Decl *PrevDecl = LookupSingleName(TUScope, AliasName, AliasNameLoc,
                                      LookupOrdinaryName);
    WeakInfo W = WeakInfo(Name, NameLoc);
  
    if (PrevDecl && (isa<FunctionDecl>(PrevDecl) || isa<VarDecl>(PrevDecl))) {
      if (!PrevDecl->hasAttr<AliasAttr>())
        if (NamedDecl *ND = dyn_cast<NamedDecl>(PrevDecl))
          DeclApplyPragmaWeak(TUScope, ND, W);
    } else {
      (void)WeakUndeclaredIdentifiers.insert(
        std::pair<IdentifierInfo*,WeakInfo>(AliasName, W));
    }
  }
  
  Decl *Sema::getObjCDeclContext() const {
    return (dyn_cast_or_null<ObjCContainerDecl>(CurContext));
  }
  