text: //===--- Sema.cpp - AST Builder and Semantic Analysis Implementation ------===//
  //
  // 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 the actions class which performs semantic analysis and
  // builds an AST out of a parse stream.
  //
  //===----------------------------------------------------------------------===//
  
  #include "UsedDeclVisitor.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/ASTDiagnostic.h"
  #include "clang/AST/Decl.h"
  #include "clang/AST/DeclCXX.h"
  #include "clang/AST/DeclFriend.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/Expr.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/AST/PrettyDeclStackTrace.h"
  #include "clang/AST/StmtCXX.h"
  #include "clang/Basic/DarwinSDKInfo.h"
  #include "clang/Basic/DiagnosticOptions.h"
  #include "clang/Basic/PartialDiagnostic.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/Stack.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/Lex/HeaderSearch.h"
  #include "clang/Lex/HeaderSearchOptions.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Sema/CXXFieldCollector.h"
  #include "clang/Sema/DelayedDiagnostic.h"
  #include "clang/Sema/ExternalSemaSource.h"
  #include "clang/Sema/Initialization.h"
  #include "clang/Sema/MultiplexExternalSemaSource.h"
  #include "clang/Sema/ObjCMethodList.h"
  #include "clang/Sema/Scope.h"
  #include "clang/Sema/ScopeInfo.h"
  #include "clang/Sema/SemaConsumer.h"
  #include "clang/Sema/SemaInternal.h"
  #include "clang/Sema/TemplateDeduction.h"
  #include "clang/Sema/TemplateInstCallback.h"
  #include "clang/Sema/TypoCorrection.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/SmallPtrSet.h"
  #include "llvm/Support/TimeProfiler.h"
  
  using namespace clang;
  using namespace sema;
  
  SourceLocation Sema::getLocForEndOfToken(SourceLocation Loc, unsigned Offset) {
    return Lexer::getLocForEndOfToken(Loc, Offset, SourceMgr, LangOpts);
  }
  
  ModuleLoader &Sema::getModuleLoader() const { return PP.getModuleLoader(); }
  
  DarwinSDKInfo *
  Sema::getDarwinSDKInfoForAvailabilityChecking(SourceLocation Loc,
                                                StringRef Platform) {
    if (CachedDarwinSDKInfo)
      return CachedDarwinSDKInfo->get();
    auto SDKInfo = parseDarwinSDKInfo(
        PP.getFileManager().getVirtualFileSystem(),
        PP.getHeaderSearchInfo().getHeaderSearchOpts().Sysroot);
    if (SDKInfo && *SDKInfo) {
      CachedDarwinSDKInfo = std::make_unique<DarwinSDKInfo>(std::move(**SDKInfo));
      return CachedDarwinSDKInfo->get();
    }
    if (!SDKInfo)
      llvm::consumeError(SDKInfo.takeError());
    Diag(Loc, diag::warn_missing_sdksettings_for_availability_checking)
        << Platform;
    CachedDarwinSDKInfo = std::unique_ptr<DarwinSDKInfo>();
    return nullptr;
  }
  
  IdentifierInfo *
  Sema::InventAbbreviatedTemplateParameterTypeName(IdentifierInfo *ParamName,
                                                   unsigned int Index) {
    std::string InventedName;
    llvm::raw_string_ostream OS(InventedName);
  
    if (!ParamName)
      OS << "auto:" << Index + 1;
    else
      OS << ParamName->getName() << ":auto";
  
    OS.flush();
    return &Context.Idents.get(OS.str());
  }
  
  PrintingPolicy Sema::getPrintingPolicy(const ASTContext &Context,
                                         const Preprocessor &PP) {
    PrintingPolicy Policy = Context.getPrintingPolicy();
    // In diagnostics, we print _Bool as bool if the latter is defined as the
    // former.
    Policy.Bool = Context.getLangOpts().Bool;
    if (!Policy.Bool) {
      if (const MacroInfo *BoolMacro = PP.getMacroInfo(Context.getBoolName())) {
        Policy.Bool = BoolMacro->isObjectLike() &&
                      BoolMacro->getNumTokens() == 1 &&
                      BoolMacro->getReplacementToken(0).is(tok::kw__Bool);
      }
    }
  
    return Policy;
  }
  
  void Sema::ActOnTranslationUnitScope(Scope *S) {
    TUScope = S;
    PushDeclContext(S, Context.getTranslationUnitDecl());
  }
  
  namespace clang {
  namespace sema {
  
  class SemaPPCallbacks : public PPCallbacks {
    Sema *S = nullptr;
    llvm::SmallVector<SourceLocation, 8> IncludeStack;
  
  public:
    void set(Sema &S) { this->S = &S; }
  
    void reset() { S = nullptr; }
  
    virtual void FileChanged(SourceLocation Loc, FileChangeReason Reason,
                             SrcMgr::CharacteristicKind FileType,
                             FileID PrevFID) override {
      if (!S)
        return;
      switch (Reason) {
      case EnterFile: {
        SourceManager &SM = S->getSourceManager();
        SourceLocation IncludeLoc = SM.getIncludeLoc(SM.getFileID(Loc));
        if (IncludeLoc.isValid()) {
          if (llvm::timeTraceProfilerEnabled()) {
            const FileEntry *FE = SM.getFileEntryForID(SM.getFileID(Loc));
            llvm::timeTraceProfilerBegin(
                "Source", FE != nullptr ? FE->getName() : StringRef("<unknown>"));
          }
  
          IncludeStack.push_back(IncludeLoc);
          S->DiagnoseNonDefaultPragmaAlignPack(
              Sema::PragmaAlignPackDiagnoseKind::NonDefaultStateAtInclude,
              IncludeLoc);
        }
        break;
      }
      case ExitFile:
        if (!IncludeStack.empty()) {
          if (llvm::timeTraceProfilerEnabled())
            llvm::timeTraceProfilerEnd();
  
          S->DiagnoseNonDefaultPragmaAlignPack(
              Sema::PragmaAlignPackDiagnoseKind::ChangedStateAtExit,
              IncludeStack.pop_back_val());
        }
        break;
      default:
        break;
      }
    }
  };
  
  } // end namespace sema
  } // end namespace clang
  
  const unsigned Sema::MaxAlignmentExponent;
  const unsigned Sema::MaximumAlignment;
  
  Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
             TranslationUnitKind TUKind, CodeCompleteConsumer *CodeCompleter)
      : ExternalSource(nullptr), isMultiplexExternalSource(false),
        CurFPFeatures(pp.getLangOpts()), LangOpts(pp.getLangOpts()), PP(pp),
        Context(ctxt), Consumer(consumer), Diags(PP.getDiagnostics()),
        SourceMgr(PP.getSourceManager()), CollectStats(false),
        CodeCompleter(CodeCompleter), CurContext(nullptr),
        OriginalLexicalContext(nullptr), MSStructPragmaOn(false),
        MSPointerToMemberRepresentationMethod(
            LangOpts.getMSPointerToMemberRepresentationMethod()),
        VtorDispStack(LangOpts.getVtorDispMode()),
        AlignPackStack(AlignPackInfo(getLangOpts().XLPragmaPack)),
        DataSegStack(nullptr), BSSSegStack(nullptr), ConstSegStack(nullptr),
        CodeSegStack(nullptr), FpPragmaStack(FPOptionsOverride()),
        CurInitSeg(nullptr), VisContext(nullptr),
        PragmaAttributeCurrentTargetDecl(nullptr),
        IsBuildingRecoveryCallExpr(false), Cleanup{}, LateTemplateParser(nullptr),
        LateTemplateParserCleanup(nullptr), OpaqueParser(nullptr), IdResolver(pp),
        StdExperimentalNamespaceCache(nullptr), StdInitializerList(nullptr),
        StdCoroutineTraitsCache(nullptr), CXXTypeInfoDecl(nullptr),
        MSVCGuidDecl(nullptr), NSNumberDecl(nullptr), NSValueDecl(nullptr),
        NSStringDecl(nullptr), StringWithUTF8StringMethod(nullptr),
        ValueWithBytesObjCTypeMethod(nullptr), NSArrayDecl(nullptr),
        ArrayWithObjectsMethod(nullptr), NSDictionaryDecl(nullptr),
        DictionaryWithObjectsMethod(nullptr), GlobalNewDeleteDeclared(false),
        TUKind(TUKind), NumSFINAEErrors(0),
        FullyCheckedComparisonCategories(
            static_cast<unsigned>(ComparisonCategoryType::Last) + 1),
        SatisfactionCache(Context), AccessCheckingSFINAE(false),
        InNonInstantiationSFINAEContext(false), NonInstantiationEntries(0),
        ArgumentPackSubstitutionIndex(-1), CurrentInstantiationScope(nullptr),
        DisableTypoCorrection(false), TyposCorrected(0), AnalysisWarnings(*this),
        ThreadSafetyDeclCache(nullptr), VarDataSharingAttributesStack(nullptr),
        CurScope(nullptr), Ident_super(nullptr), Ident___float128(nullptr) {
    assert(pp.TUKind == TUKind);
    TUScope = nullptr;
    isConstantEvaluatedOverride = false;
  
    LoadedExternalKnownNamespaces = false;
    for (unsigned I = 0; I != NSAPI::NumNSNumberLiteralMethods; ++I)
      NSNumberLiteralMethods[I] = nullptr;
  
    if (getLangOpts().ObjC)
      NSAPIObj.reset(new NSAPI(Context));
  
    if (getLangOpts().CPlusPlus)
      FieldCollector.reset(new CXXFieldCollector());
  
    // Tell diagnostics how to render things from the AST library.
    Diags.SetArgToStringFn(&FormatASTNodeDiagnosticArgument, &Context);
  
    ExprEvalContexts.emplace_back(
        ExpressionEvaluationContext::PotentiallyEvaluated, 0, CleanupInfo{},
        nullptr, ExpressionEvaluationContextRecord::EK_Other);
  
    // Initialization of data sharing attributes stack for OpenMP
    InitDataSharingAttributesStack();
  
    std::unique_ptr<sema::SemaPPCallbacks> Callbacks =
        std::make_unique<sema::SemaPPCallbacks>();
    SemaPPCallbackHandler = Callbacks.get();
    PP.addPPCallbacks(std::move(Callbacks));
    SemaPPCallbackHandler->set(*this);
  }
  
  // Anchor Sema's type info to this TU.
  void Sema::anchor() {}
  
  void Sema::addImplicitTypedef(StringRef Name, QualType T) {
    DeclarationName DN = &Context.Idents.get(Name);
    if (IdResolver.begin(DN) == IdResolver.end())
      PushOnScopeChains(Context.buildImplicitTypedef(T, Name), TUScope);
  }
  
  void Sema::Initialize() {
    if (SemaConsumer *SC = dyn_cast<SemaConsumer>(&Consumer))
      SC->InitializeSema(*this);
  
    // Tell the external Sema source about this Sema object.
    if (ExternalSemaSource *ExternalSema
        = dyn_cast_or_null<ExternalSemaSource>(Context.getExternalSource()))
      ExternalSema->InitializeSema(*this);
  
    // This needs to happen after ExternalSemaSource::InitializeSema(this) or we
    // will not be able to merge any duplicate __va_list_tag decls correctly.
    VAListTagName = PP.getIdentifierInfo("__va_list_tag");
  
    if (!TUScope)
      return;
  
    // Initialize predefined 128-bit integer types, if needed.
    if (Context.getTargetInfo().hasInt128Type() ||
        (Context.getAuxTargetInfo() &&
         Context.getAuxTargetInfo()->hasInt128Type())) {
      // If either of the 128-bit integer types are unavailable to name lookup,
      // define them now.
      DeclarationName Int128 = &Context.Idents.get("__int128_t");
      if (IdResolver.begin(Int128) == IdResolver.end())
        PushOnScopeChains(Context.getInt128Decl(), TUScope);
  
      DeclarationName UInt128 = &Context.Idents.get("__uint128_t");
      if (IdResolver.begin(UInt128) == IdResolver.end())
        PushOnScopeChains(Context.getUInt128Decl(), TUScope);
    }
  
  
    // Initialize predefined Objective-C types:
    if (getLangOpts().ObjC) {
      // If 'SEL' does not yet refer to any declarations, make it refer to the
      // predefined 'SEL'.
      DeclarationName SEL = &Context.Idents.get("SEL");
      if (IdResolver.begin(SEL) == IdResolver.end())
        PushOnScopeChains(Context.getObjCSelDecl(), TUScope);
  
      // If 'id' does not yet refer to any declarations, make it refer to the
      // predefined 'id'.
      DeclarationName Id = &Context.Idents.get("id");
      if (IdResolver.begin(Id) == IdResolver.end())
        PushOnScopeChains(Context.getObjCIdDecl(), TUScope);
  
      // Create the built-in typedef for 'Class'.
      DeclarationName Class = &Context.Idents.get("Class");
      if (IdResolver.begin(Class) == IdResolver.end())
        PushOnScopeChains(Context.getObjCClassDecl(), TUScope);
  
      // Create the built-in forward declaratino for 'Protocol'.
      DeclarationName Protocol = &Context.Idents.get("Protocol");
      if (IdResolver.begin(Protocol) == IdResolver.end())
        PushOnScopeChains(Context.getObjCProtocolDecl(), TUScope);
    }
  
    // Create the internal type for the *StringMakeConstantString builtins.
    DeclarationName ConstantString = &Context.Idents.get("__NSConstantString");
    if (IdResolver.begin(ConstantString) == IdResolver.end())
      PushOnScopeChains(Context.getCFConstantStringDecl(), TUScope);
  
    // Initialize Microsoft "predefined C++ types".
    if (getLangOpts().MSVCCompat) {
      if (getLangOpts().CPlusPlus &&
          IdResolver.begin(&Context.Idents.get("type_info")) == IdResolver.end())
        PushOnScopeChains(Context.buildImplicitRecord("type_info", TTK_Class),
                          TUScope);
  
      addImplicitTypedef("size_t", Context.getSizeType());
    }
  
    // Initialize predefined OpenCL types and supported extensions and (optional)
    // core features.
    if (getLangOpts().OpenCL) {
      getOpenCLOptions().addSupport(
          Context.getTargetInfo().getSupportedOpenCLOpts(), getLangOpts());
      addImplicitTypedef("sampler_t", Context.OCLSamplerTy);
      addImplicitTypedef("event_t", Context.OCLEventTy);
      if (getLangOpts().getOpenCLCompatibleVersion() >= 200) {
        addImplicitTypedef("clk_event_t", Context.OCLClkEventTy);
        addImplicitTypedef("queue_t", Context.OCLQueueTy);
        if (getLangOpts().OpenCLPipes)
          addImplicitTypedef("reserve_id_t", Context.OCLReserveIDTy);
        addImplicitTypedef("atomic_int", Context.getAtomicType(Context.IntTy));
        addImplicitTypedef("atomic_uint",
                           Context.getAtomicType(Context.UnsignedIntTy));
        addImplicitTypedef("atomic_float",
                           Context.getAtomicType(Context.FloatTy));
        // OpenCLC v2.0, s6.13.11.6 requires that atomic_flag is implemented as
        // 32-bit integer and OpenCLC v2.0, s6.1.1 int is always 32-bit wide.
        addImplicitTypedef("atomic_flag", Context.getAtomicType(Context.IntTy));
  
  
        // OpenCL v2.0 s6.13.11.6:
        // - The atomic_long and atomic_ulong types are supported if the
        //   cl_khr_int64_base_atomics and cl_khr_int64_extended_atomics
        //   extensions are supported.
        // - The atomic_double type is only supported if double precision
        //   is supported and the cl_khr_int64_base_atomics and
        //   cl_khr_int64_extended_atomics extensions are supported.
        // - If the device address space is 64-bits, the data types
        //   atomic_intptr_t, atomic_uintptr_t, atomic_size_t and
        //   atomic_ptrdiff_t are supported if the cl_khr_int64_base_atomics and
        //   cl_khr_int64_extended_atomics extensions are supported.
  
        auto AddPointerSizeDependentTypes = [&]() {
          auto AtomicSizeT = Context.getAtomicType(Context.getSizeType());
          auto AtomicIntPtrT = Context.getAtomicType(Context.getIntPtrType());
          auto AtomicUIntPtrT = Context.getAtomicType(Context.getUIntPtrType());
          auto AtomicPtrDiffT =
              Context.getAtomicType(Context.getPointerDiffType());
          addImplicitTypedef("atomic_size_t", AtomicSizeT);
          addImplicitTypedef("atomic_intptr_t", AtomicIntPtrT);
          addImplicitTypedef("atomic_uintptr_t", AtomicUIntPtrT);
          addImplicitTypedef("atomic_ptrdiff_t", AtomicPtrDiffT);
        };
  
        if (Context.getTypeSize(Context.getSizeType()) == 32) {
          AddPointerSizeDependentTypes();
        }
  
        std::vector<QualType> Atomic64BitTypes;
        if (getOpenCLOptions().isSupported("cl_khr_int64_base_atomics",
                                           getLangOpts()) &&
            getOpenCLOptions().isSupported("cl_khr_int64_extended_atomics",
                                           getLangOpts())) {
          if (getOpenCLOptions().isSupported("cl_khr_fp64", getLangOpts())) {
            auto AtomicDoubleT = Context.getAtomicType(Context.DoubleTy);
            addImplicitTypedef("atomic_double", AtomicDoubleT);
            Atomic64BitTypes.push_back(AtomicDoubleT);
          }
          auto AtomicLongT = Context.getAtomicType(Context.LongTy);
          auto AtomicULongT = Context.getAtomicType(Context.UnsignedLongTy);
          addImplicitTypedef("atomic_long", AtomicLongT);
          addImplicitTypedef("atomic_ulong", AtomicULongT);
  
  
          if (Context.getTypeSize(Context.getSizeType()) == 64) {
            AddPointerSizeDependentTypes();
          }
        }
      }
  
  
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext)                                      \
    if (getOpenCLOptions().isSupported(#Ext, getLangOpts())) {                   \
      addImplicitTypedef(#ExtType, Context.Id##Ty);                              \
    }
  #include "clang/Basic/OpenCLExtensionTypes.def"
    }
  
    if (Context.getTargetInfo().hasAArch64SVETypes()) {
  #define SVE_TYPE(Name, Id, SingletonId) \
      addImplicitTypedef(Name, Context.SingletonId);
  #include "clang/Basic/AArch64SVEACLETypes.def"
    }
  
    if (Context.getTargetInfo().getTriple().isPPC64() &&
        Context.getTargetInfo().hasFeature("paired-vector-memops")) {
      if (Context.getTargetInfo().hasFeature("mma")) {
  #define PPC_VECTOR_MMA_TYPE(Name, Id, Size) \
        addImplicitTypedef(#Name, Context.Id##Ty);
  #include "clang/Basic/PPCTypes.def"
      }
  #define PPC_VECTOR_VSX_TYPE(Name, Id, Size) \
      addImplicitTypedef(#Name, Context.Id##Ty);
  #include "clang/Basic/PPCTypes.def"
    }
  
    if (Context.getTargetInfo().hasRISCVVTypes()) {
  #define RVV_TYPE(Name, Id, SingletonId)                                        \
    addImplicitTypedef(Name, Context.SingletonId);
  #include "clang/Basic/RISCVVTypes.def"
    }
  
    if (Context.getTargetInfo().hasBuiltinMSVaList()) {
      DeclarationName MSVaList = &Context.Idents.get("__builtin_ms_va_list");
      if (IdResolver.begin(MSVaList) == IdResolver.end())
        PushOnScopeChains(Context.getBuiltinMSVaListDecl(), TUScope);
    }
  
    DeclarationName BuiltinVaList = &Context.Idents.get("__builtin_va_list");
    if (IdResolver.begin(BuiltinVaList) == IdResolver.end())
      PushOnScopeChains(Context.getBuiltinVaListDecl(), TUScope);
  }
  
  Sema::~Sema() {
    assert(InstantiatingSpecializations.empty() &&
           "failed to clean up an InstantiatingTemplate?");
  
    if (VisContext) FreeVisContext();
  
    // Kill all the active scopes.
    for (sema::FunctionScopeInfo *FSI : FunctionScopes)
      delete FSI;
  
    // Tell the SemaConsumer to forget about us; we're going out of scope.
    if (SemaConsumer *SC = dyn_cast<SemaConsumer>(&Consumer))
      SC->ForgetSema();
  
    // Detach from the external Sema source.
    if (ExternalSemaSource *ExternalSema
          = dyn_cast_or_null<ExternalSemaSource>(Context.getExternalSource()))
      ExternalSema->ForgetSema();
  
    // If Sema's ExternalSource is the multiplexer - we own it.
    if (isMultiplexExternalSource)
      delete ExternalSource;
  
    // Delete cached satisfactions.
    std::vector<ConstraintSatisfaction *> Satisfactions;
    Satisfactions.reserve(Satisfactions.size());
    for (auto &Node : SatisfactionCache)
      Satisfactions.push_back(&Node);
    for (auto *Node : Satisfactions)
      delete Node;
  
    threadSafety::threadSafetyCleanup(ThreadSafetyDeclCache);
  
    // Destroys data sharing attributes stack for OpenMP
    DestroyDataSharingAttributesStack();
  
    // Detach from the PP callback handler which outlives Sema since it's owned
    // by the preprocessor.
    SemaPPCallbackHandler->reset();
  }
  
  void Sema::warnStackExhausted(SourceLocation Loc) {
    // Only warn about this once.
    if (!WarnedStackExhausted) {
      Diag(Loc, diag::warn_stack_exhausted);
      WarnedStackExhausted = true;
    }
  }
  
  void Sema::runWithSufficientStackSpace(SourceLocation Loc,
                                         llvm::function_ref<void()> Fn) {
    clang::runWithSufficientStackSpace([&] { warnStackExhausted(Loc); }, Fn);
  }
  
  /// makeUnavailableInSystemHeader - There is an error in the current
  /// context.  If we're still in a system header, and we can plausibly
  /// make the relevant declaration unavailable instead of erroring, do
  /// so and return true.
  bool Sema::makeUnavailableInSystemHeader(SourceLocation loc,
                                        UnavailableAttr::ImplicitReason reason) {
    // If we're not in a function, it's an error.
    FunctionDecl *fn = dyn_cast<FunctionDecl>(CurContext);
    if (!fn) return false;
  
    // If we're in template instantiation, it's an error.
    if (inTemplateInstantiation())
      return false;
  
    // If that function's not in a system header, it's an error.
    if (!Context.getSourceManager().isInSystemHeader(loc))
      return false;
  
    // If the function is already unavailable, it's not an error.
    if (fn->hasAttr<UnavailableAttr>()) return true;
  
    fn->addAttr(UnavailableAttr::CreateImplicit(Context, "", reason, loc));
    return true;
  }
  
  ASTMutationListener *Sema::getASTMutationListener() const {
    return getASTConsumer().GetASTMutationListener();
  }
  
  ///Registers an external source. If an external source already exists,
  /// creates a multiplex external source and appends to it.
  ///
  ///\param[in] E - A non-null external sema source.
  ///
  void Sema::addExternalSource(ExternalSemaSource *E) {
    assert(E && "Cannot use with NULL ptr");
  
    if (!ExternalSource) {
      ExternalSource = E;
      return;
    }
  
    if (isMultiplexExternalSource)
      static_cast<MultiplexExternalSemaSource*>(ExternalSource)->addSource(*E);
    else {
      ExternalSource = new MultiplexExternalSemaSource(*ExternalSource, *E);
      isMultiplexExternalSource = true;
    }
  }
  
  /// Print out statistics about the semantic analysis.
  void Sema::PrintStats() const {
    llvm::errs() << "\n*** Semantic Analysis Stats:\n";
    llvm::errs() << NumSFINAEErrors << " SFINAE diagnostics trapped.\n";
  
    BumpAlloc.PrintStats();
    AnalysisWarnings.PrintStats();
  }
  
  void Sema::diagnoseNullableToNonnullConversion(QualType DstType,
                                                 QualType SrcType,
                                                 SourceLocation Loc) {
    Optional<NullabilityKind> ExprNullability = SrcType->getNullability(Context);
    if (!ExprNullability || (*ExprNullability != NullabilityKind::Nullable &&
                             *ExprNullability != NullabilityKind::NullableResult))
      return;
  
    Optional<NullabilityKind> TypeNullability = DstType->getNullability(Context);
    if (!TypeNullability || *TypeNullability != NullabilityKind::NonNull)
      return;
  
    Diag(Loc, diag::warn_nullability_lost) << SrcType << DstType;
  }
  
  void Sema::diagnoseZeroToNullptrConversion(CastKind Kind, const Expr* E) {
    if (Diags.isIgnored(diag::warn_zero_as_null_pointer_constant,
                        E->getBeginLoc()))
      return;
    // nullptr only exists from C++11 on, so don't warn on its absence earlier.
    if (!getLangOpts().CPlusPlus11)
      return;
  
    if (Kind != CK_NullToPointer && Kind != CK_NullToMemberPointer)
      return;
    if (E->IgnoreParenImpCasts()->getType()->isNullPtrType())
      return;
  
    // Don't diagnose the conversion from a 0 literal to a null pointer argument
    // in a synthesized call to operator<=>.
    if (!CodeSynthesisContexts.empty() &&
        CodeSynthesisContexts.back().Kind ==
            CodeSynthesisContext::RewritingOperatorAsSpaceship)
      return;
  
    // If it is a macro from system header, and if the macro name is not "NULL",
    // do not warn.
    SourceLocation MaybeMacroLoc = E->getBeginLoc();
    if (Diags.getSuppressSystemWarnings() &&
        SourceMgr.isInSystemMacro(MaybeMacroLoc) &&
        !findMacroSpelling(MaybeMacroLoc, "NULL"))
      return;
  
    Diag(E->getBeginLoc(), diag::warn_zero_as_null_pointer_constant)
        << FixItHint::CreateReplacement(E->getSourceRange(), "nullptr");
  }
  
  /// ImpCastExprToType - If Expr is not of type 'Type', insert an implicit cast.
  /// If there is already an implicit cast, merge into the existing one.
  /// The result is of the given category.
  ExprResult Sema::ImpCastExprToType(Expr *E, QualType Ty,
                                     CastKind Kind, ExprValueKind VK,
                                     const CXXCastPath *BasePath,
                                     CheckedConversionKind CCK) {
  #ifndef NDEBUG
    if (VK == VK_PRValue && !E->isPRValue()) {
      switch (Kind) {
      default:
        llvm_unreachable(
            ("can't implicitly cast glvalue to prvalue with this cast "
             "kind: " +
             std::string(CastExpr::getCastKindName(Kind)))
                .c_str());
      case CK_Dependent:
      case CK_LValueToRValue:
      case CK_ArrayToPointerDecay:
      case CK_FunctionToPointerDecay:
      case CK_ToVoid:
      case CK_NonAtomicToAtomic:
        break;
      }
    }
    assert((VK == VK_PRValue || Kind == CK_Dependent || !E->isPRValue()) &&
           "can't cast prvalue to glvalue");
  #endif
  
    diagnoseNullableToNonnullConversion(Ty, E->getType(), E->getBeginLoc());
    diagnoseZeroToNullptrConversion(Kind, E);
  
    QualType ExprTy = Context.getCanonicalType(E->getType());
    QualType TypeTy = Context.getCanonicalType(Ty);
  
    if (ExprTy == TypeTy)
      return E;
  
    if (Kind == CK_ArrayToPointerDecay) {
      // C++1z [conv.array]: The temporary materialization conversion is applied.
      // We also use this to fuel C++ DR1213, which applies to C++11 onwards.
      if (getLangOpts().CPlusPlus && E->isPRValue()) {
        // The temporary is an lvalue in C++98 and an xvalue otherwise.
        ExprResult Materialized = CreateMaterializeTemporaryExpr(
            E->getType(), E, !getLangOpts().CPlusPlus11);
        if (Materialized.isInvalid())
          return ExprError();
        E = Materialized.get();
      }
      // C17 6.7.1p6 footnote 124: The implementation can treat any register
      // declaration simply as an auto declaration. However, whether or not
      // addressable storage is actually used, the address of any part of an
      // object declared with storage-class specifier register cannot be
      // computed, either explicitly(by use of the unary & operator as discussed
      // in 6.5.3.2) or implicitly(by converting an array name to a pointer as
      // discussed in 6.3.2.1).Thus, the only operator that can be applied to an
      // array declared with storage-class specifier register is sizeof.
      if (VK == VK_PRValue && !getLangOpts().CPlusPlus && !E->isPRValue()) {
        if (const auto *DRE = dyn_cast<DeclRefExpr>(E)) {
          if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
            if (VD->getStorageClass() == SC_Register) {
              Diag(E->getExprLoc(), diag::err_typecheck_address_of)
                  << /*register variable*/ 3 << E->getSourceRange();
              return ExprError();
            }
          }
        }
      }
    }
  
    if (ImplicitCastExpr *ImpCast = dyn_cast<ImplicitCastExpr>(E)) {
      if (ImpCast->getCastKind() == Kind && (!BasePath || BasePath->empty())) {
        ImpCast->setType(Ty);
        ImpCast->setValueKind(VK);
        return E;
      }
    }
  
    return ImplicitCastExpr::Create(Context, Ty, Kind, E, BasePath, VK,
                                    CurFPFeatureOverrides());
  }
  
  /// ScalarTypeToBooleanCastKind - Returns the cast kind corresponding
  /// to the conversion from scalar type ScalarTy to the Boolean type.
  CastKind Sema::ScalarTypeToBooleanCastKind(QualType ScalarTy) {
    switch (ScalarTy->getScalarTypeKind()) {
    case Type::STK_Bool: return CK_NoOp;
    case Type::STK_CPointer: return CK_PointerToBoolean;
    case Type::STK_BlockPointer: return CK_PointerToBoolean;
    case Type::STK_ObjCObjectPointer: return CK_PointerToBoolean;
    case Type::STK_MemberPointer: return CK_MemberPointerToBoolean;
    case Type::STK_Integral: return CK_IntegralToBoolean;
    case Type::STK_Floating: return CK_FloatingToBoolean;
    case Type::STK_IntegralComplex: return CK_IntegralComplexToBoolean;
    case Type::STK_FloatingComplex: return CK_FloatingComplexToBoolean;
    case Type::STK_FixedPoint: return CK_FixedPointToBoolean;
    }
    llvm_unreachable("unknown scalar type kind");
  }
  
  /// Used to prune the decls of Sema's UnusedFileScopedDecls vector.
  static bool ShouldRemoveFromUnused(Sema *SemaRef, const DeclaratorDecl *D) {
    if (D->getMostRecentDecl()->isUsed())
      return true;
  
    if (D->isExternallyVisible())
      return true;
  
    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
      // If this is a function template and none of its specializations is used,
      // we should warn.
      if (FunctionTemplateDecl *Template = FD->getDescribedFunctionTemplate())
        for (const auto *Spec : Template->specializations())
          if (ShouldRemoveFromUnused(SemaRef, Spec))
            return true;
  
      // UnusedFileScopedDecls stores the first declaration.
      // The declaration may have become definition so check again.
      const FunctionDecl *DeclToCheck;
      if (FD->hasBody(DeclToCheck))
        return !SemaRef->ShouldWarnIfUnusedFileScopedDecl(DeclToCheck);
  
      // Later redecls may add new information resulting in not having to warn,
      // so check again.
      DeclToCheck = FD->getMostRecentDecl();
      if (DeclToCheck != FD)
        return !SemaRef->ShouldWarnIfUnusedFileScopedDecl(DeclToCheck);
    }
  
    if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
      // If a variable usable in constant expressions is referenced,
      // don't warn if it isn't used: if the value of a variable is required
      // for the computation of a constant expression, it doesn't make sense to
      // warn even if the variable isn't odr-used.  (isReferenced doesn't
      // precisely reflect that, but it's a decent approximation.)
      if (VD->isReferenced() &&
          VD->mightBeUsableInConstantExpressions(SemaRef->Context))
        return true;
  
      if (VarTemplateDecl *Template = VD->getDescribedVarTemplate())
        // If this is a variable template and none of its specializations is used,
        // we should warn.
        for (const auto *Spec : Template->specializations())
          if (ShouldRemoveFromUnused(SemaRef, Spec))
            return true;
  
      // UnusedFileScopedDecls stores the first declaration.
      // The declaration may have become definition so check again.
      const VarDecl *DeclToCheck = VD->getDefinition();
      if (DeclToCheck)
        return !SemaRef->ShouldWarnIfUnusedFileScopedDecl(DeclToCheck);
  
      // Later redecls may add new information resulting in not having to warn,
      // so check again.
      DeclToCheck = VD->getMostRecentDecl();
      if (DeclToCheck != VD)
        return !SemaRef->ShouldWarnIfUnusedFileScopedDecl(DeclToCheck);
    }
  
    return false;
  }
  
  static bool isFunctionOrVarDeclExternC(NamedDecl *ND) {
    if (auto *FD = dyn_cast<FunctionDecl>(ND))
      return FD->isExternC();
    return cast<VarDecl>(ND)->isExternC();
  }
  
  /// Determine whether ND is an external-linkage function or variable whose
  /// type has no linkage.
  bool Sema::isExternalWithNoLinkageType(ValueDecl *VD) {
    // Note: it's not quite enough to check whether VD has UniqueExternalLinkage,
    // because we also want to catch the case where its type has VisibleNoLinkage,
    // which does not affect the linkage of VD.
    return getLangOpts().CPlusPlus && VD->hasExternalFormalLinkage() &&
           !isExternalFormalLinkage(VD->getType()->getLinkage()) &&
           !isFunctionOrVarDeclExternC(VD);
  }
  
  /// Obtains a sorted list of functions and variables that are undefined but
  /// ODR-used.
  void Sema::getUndefinedButUsed(
      SmallVectorImpl<std::pair<NamedDecl *, SourceLocation> > &Undefined) {
    for (const auto &UndefinedUse : UndefinedButUsed) {
      NamedDecl *ND = UndefinedUse.first;
  
      // Ignore attributes that have become invalid.
      if (ND->isInvalidDecl()) continue;
  
      // __attribute__((weakref)) is basically a definition.
      if (ND->hasAttr<WeakRefAttr>()) continue;
  
      if (isa<CXXDeductionGuideDecl>(ND))
        continue;
  
      if (ND->hasAttr<DLLImportAttr>() || ND->hasAttr<DLLExportAttr>()) {
        // An exported function will always be emitted when defined, so even if
        // the function is inline, it doesn't have to be emitted in this TU. An
        // imported function implies that it has been exported somewhere else.
        continue;
      }
  
      if (FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
        if (FD->isDefined())
          continue;
        if (FD->isExternallyVisible() &&
            !isExternalWithNoLinkageType(FD) &&
            !FD->getMostRecentDecl()->isInlined() &&
            !FD->hasAttr<ExcludeFromExplicitInstantiationAttr>())
          continue;
        if (FD->getBuiltinID())
          continue;
      } else {
        auto *VD = cast<VarDecl>(ND);
        if (VD->hasDefinition() != VarDecl::DeclarationOnly)
          continue;
        if (VD->isExternallyVisible() &&
            !isExternalWithNoLinkageType(VD) &&
            !VD->getMostRecentDecl()->isInline() &&
            !VD->hasAttr<ExcludeFromExplicitInstantiationAttr>())
          continue;
  
        // Skip VarDecls that lack formal definitions but which we know are in
        // fact defined somewhere.
        if (VD->isKnownToBeDefined())
          continue;
      }
  
      Undefined.push_back(std::make_pair(ND, UndefinedUse.second));
    }
  }
  
  /// checkUndefinedButUsed - Check for undefined objects with internal linkage
  /// or that are inline.
  static void checkUndefinedButUsed(Sema &S) {
    if (S.UndefinedButUsed.empty()) return;
  
    // Collect all the still-undefined entities with internal linkage.
    SmallVector<std::pair<NamedDecl *, SourceLocation>, 16> Undefined;
    S.getUndefinedButUsed(Undefined);
    if (Undefined.empty()) return;
  
    for (auto Undef : Undefined) {
      ValueDecl *VD = cast<ValueDecl>(Undef.first);
      SourceLocation UseLoc = Undef.second;
  
      if (S.isExternalWithNoLinkageType(VD)) {
        // C++ [basic.link]p8:
        //   A type without linkage shall not be used as the type of a variable
        //   or function with external linkage unless
        //    -- the entity has C language linkage
        //    -- the entity is not odr-used or is defined in the same TU
        //
        // As an extension, accept this in cases where the type is externally
        // visible, since the function or variable actually can be defined in
        // another translation unit in that case.
        S.Diag(VD->getLocation(), isExternallyVisible(VD->getType()->getLinkage())
                                      ? diag::ext_undefined_internal_type
                                      : diag::err_undefined_internal_type)
          << isa<VarDecl>(VD) << VD;
      } else if (!VD->isExternallyVisible()) {
        // FIXME: We can promote this to an error. The function or variable can't
        // be defined anywhere else, so the program must necessarily violate the
        // one definition rule.
        bool IsImplicitBase = false;
        if (const auto *BaseD = dyn_cast<FunctionDecl>(VD)) {
          auto *DVAttr = BaseD->getAttr<OMPDeclareVariantAttr>();
          if (DVAttr && !DVAttr->getTraitInfo().isExtensionActive(
                            llvm::omp::TraitProperty::
                                implementation_extension_disable_implicit_base)) {
            const auto *Func = cast<FunctionDecl>(
                cast<DeclRefExpr>(DVAttr->getVariantFuncRef())->getDecl());
            IsImplicitBase = BaseD->isImplicit() &&
                             Func->getIdentifier()->isMangledOpenMPVariantName();
          }
        }
        if (!S.getLangOpts().OpenMP || !IsImplicitBase)
          S.Diag(VD->getLocation(), diag::warn_undefined_internal)
              << isa<VarDecl>(VD) << VD;
      } else if (auto *FD = dyn_cast<FunctionDecl>(VD)) {
        (void)FD;
        assert(FD->getMostRecentDecl()->isInlined() &&
               "used object requires definition but isn't inline or internal?");
        // FIXME: This is ill-formed; we should reject.
        S.Diag(VD->getLocation(), diag::warn_undefined_inline) << VD;
      } else {
        assert(cast<VarDecl>(VD)->getMostRecentDecl()->isInline() &&
               "used var requires definition but isn't inline or internal?");
        S.Diag(VD->getLocation(), diag::err_undefined_inline_var) << VD;
      }
      if (UseLoc.isValid())
        S.Diag(UseLoc, diag::note_used_here);
    }
  
    S.UndefinedButUsed.clear();
  }
  
  void Sema::LoadExternalWeakUndeclaredIdentifiers() {
    if (!ExternalSource)
      return;
  
    SmallVector<std::pair<IdentifierInfo *, WeakInfo>, 4> WeakIDs;
    ExternalSource->ReadWeakUndeclaredIdentifiers(WeakIDs);
    for (auto &WeakID : WeakIDs)
      WeakUndeclaredIdentifiers.insert(WeakID);
  }
  
  
  typedef llvm::DenseMap<const CXXRecordDecl*, bool> RecordCompleteMap;
  
  /// Returns true, if all methods and nested classes of the given
  /// CXXRecordDecl are defined in this translation unit.
  ///
  /// Should only be called from ActOnEndOfTranslationUnit so that all
  /// definitions are actually read.
  static bool MethodsAndNestedClassesComplete(const CXXRecordDecl *RD,
                                              RecordCompleteMap &MNCComplete) {
    RecordCompleteMap::iterator Cache = MNCComplete.find(RD);
    if (Cache != MNCComplete.end())
      return Cache->second;
    if (!RD->isCompleteDefinition())
      return false;
    bool Complete = true;
    for (DeclContext::decl_iterator I = RD->decls_begin(),
                                    E = RD->decls_end();
         I != E && Complete; ++I) {
      if (const CXXMethodDecl *M = dyn_cast<CXXMethodDecl>(*I))
        Complete = M->isDefined() || M->isDefaulted() ||
                   (M->isPure() && !isa<CXXDestructorDecl>(M));
      else if (const FunctionTemplateDecl *F = dyn_cast<FunctionTemplateDecl>(*I))
        // If the template function is marked as late template parsed at this
        // point, it has not been instantiated and therefore we have not
        // performed semantic analysis on it yet, so we cannot know if the type
        // can be considered complete.
        Complete = !F->getTemplatedDecl()->isLateTemplateParsed() &&
                    F->getTemplatedDecl()->isDefined();
      else if (const CXXRecordDecl *R = dyn_cast<CXXRecordDecl>(*I)) {
        if (R->isInjectedClassName())
          continue;
        if (R->hasDefinition())
          Complete = MethodsAndNestedClassesComplete(R->getDefinition(),
                                                     MNCComplete);
        else
          Complete = false;
      }
    }
    MNCComplete[RD] = Complete;
    return Complete;
  }
  
  /// Returns true, if the given CXXRecordDecl is fully defined in this
  /// translation unit, i.e. all methods are defined or pure virtual and all
  /// friends, friend functions and nested classes are fully defined in this
  /// translation unit.
  ///
  /// Should only be called from ActOnEndOfTranslationUnit so that all
  /// definitions are actually read.
  static bool IsRecordFullyDefined(const CXXRecordDecl *RD,
                                   RecordCompleteMap &RecordsComplete,
                                   RecordCompleteMap &MNCComplete) {
    RecordCompleteMap::iterator Cache = RecordsComplete.find(RD);
    if (Cache != RecordsComplete.end())
      return Cache->second;
    bool Complete = MethodsAndNestedClassesComplete(RD, MNCComplete);
    for (CXXRecordDecl::friend_iterator I = RD->friend_begin(),
                                        E = RD->friend_end();
         I != E && Complete; ++I) {
      // Check if friend classes and methods are complete.
      if (TypeSourceInfo *TSI = (*I)->getFriendType()) {
        // Friend classes are available as the TypeSourceInfo of the FriendDecl.
        if (CXXRecordDecl *FriendD = TSI->getType()->getAsCXXRecordDecl())
          Complete = MethodsAndNestedClassesComplete(FriendD, MNCComplete);
        else
          Complete = false;
      } else {
        // Friend functions are available through the NamedDecl of FriendDecl.
        if (const FunctionDecl *FD =
            dyn_cast<FunctionDecl>((*I)->getFriendDecl()))
          Complete = FD->isDefined();
        else
          // This is a template friend, give up.
          Complete = false;
      }
    }
    RecordsComplete[RD] = Complete;
    return Complete;
  }
  
  void Sema::emitAndClearUnusedLocalTypedefWarnings() {
    if (ExternalSource)
      ExternalSource->ReadUnusedLocalTypedefNameCandidates(
          UnusedLocalTypedefNameCandidates);
    for (const TypedefNameDecl *TD : UnusedLocalTypedefNameCandidates) {
      if (TD->isReferenced())
        continue;
      Diag(TD->getLocation(), diag::warn_unused_local_typedef)
          << isa<TypeAliasDecl>(TD) << TD->getDeclName();
    }
    UnusedLocalTypedefNameCandidates.clear();
  }
  
  /// This is called before the very first declaration in the translation unit
  /// is parsed. Note that the ASTContext may have already injected some
  /// declarations.
  void Sema::ActOnStartOfTranslationUnit() {
    if (getLangOpts().ModulesTS &&
        (getLangOpts().getCompilingModule() == LangOptions::CMK_ModuleInterface ||
         getLangOpts().getCompilingModule() == LangOptions::CMK_None)) {
      // We start in an implied global module fragment.
      SourceLocation StartOfTU =
          SourceMgr.getLocForStartOfFile(SourceMgr.getMainFileID());
      ActOnGlobalModuleFragmentDecl(StartOfTU);
      ModuleScopes.back().ImplicitGlobalModuleFragment = true;
    }
  }
  
  void Sema::ActOnEndOfTranslationUnitFragment(TUFragmentKind Kind) {
    // No explicit actions are required at the end of the global module fragment.
    if (Kind == TUFragmentKind::Global)
      return;
  
    // Transfer late parsed template instantiations over to the pending template
    // instantiation list. During normal compilation, the late template parser
    // will be installed and instantiating these templates will succeed.
    //
    // If we are building a TU prefix for serialization, it is also safe to
    // transfer these over, even though they are not parsed. The end of the TU
    // should be outside of any eager template instantiation scope, so when this
    // AST is deserialized, these templates will not be parsed until the end of
    // the combined TU.
    PendingInstantiations.insert(PendingInstantiations.end(),
                                 LateParsedInstantiations.begin(),
                                 LateParsedInstantiations.end());
    LateParsedInstantiations.clear();
  
    // If DefinedUsedVTables ends up marking any virtual member functions it
    // might lead to more pending template instantiations, which we then need
    // to instantiate.
    DefineUsedVTables();
  
    // C++: Perform implicit template instantiations.
    //
    // FIXME: When we perform these implicit instantiations, we do not
    // carefully keep track of the point of instantiation (C++ [temp.point]).
    // This means that name lookup that occurs within the template
    // instantiation will always happen at the end of the translation unit,
    // so it will find some names that are not required to be found. This is
    // valid, but we could do better by diagnosing if an instantiation uses a
    // name that was not visible at its first point of instantiation.
    if (ExternalSource) {
      // Load pending instantiations from the external source.
      SmallVector<PendingImplicitInstantiation, 4> Pending;
      ExternalSource->ReadPendingInstantiations(Pending);
      for (auto PII : Pending)
        if (auto Func = dyn_cast<FunctionDecl>(PII.first))
          Func->setInstantiationIsPending(true);
      PendingInstantiations.insert(PendingInstantiations.begin(),
                                   Pending.begin(), Pending.end());
    }
  
    {
      llvm::TimeTraceScope TimeScope("PerformPendingInstantiations");
      PerformPendingInstantiations();
    }
  
    emitDeferredDiags();
  
    assert(LateParsedInstantiations.empty() &&
           "end of TU template instantiation should not create more "
           "late-parsed templates");
  
    // Report diagnostics for uncorrected delayed typos. Ideally all of them
    // should have been corrected by that time, but it is very hard to cover all
    // cases in practice.
    for (const auto &Typo : DelayedTypos) {
      // We pass an empty TypoCorrection to indicate no correction was performed.
      Typo.second.DiagHandler(TypoCorrection());
    }
    DelayedTypos.clear();
  }
  
  /// ActOnEndOfTranslationUnit - This is called at the very end of the
  /// translation unit when EOF is reached and all but the top-level scope is
  /// popped.
  void Sema::ActOnEndOfTranslationUnit() {
    assert(DelayedDiagnostics.getCurrentPool() == nullptr
           && "reached end of translation unit with a pool attached?");
  
    // If code completion is enabled, don't perform any end-of-translation-unit
    // work.
    if (PP.isCodeCompletionEnabled())
      return;
  
    // Complete translation units and modules define vtables and perform implicit
    // instantiations. PCH files do not.
    if (TUKind != TU_Prefix) {
      DiagnoseUseOfUnimplementedSelectors();
  
      ActOnEndOfTranslationUnitFragment(
          !ModuleScopes.empty() && ModuleScopes.back().Module->Kind ==
                                       Module::PrivateModuleFragment
              ? TUFragmentKind::Private
              : TUFragmentKind::Normal);
  
      if (LateTemplateParserCleanup)
        LateTemplateParserCleanup(OpaqueParser);
  
      CheckDelayedMemberExceptionSpecs();
    } else {
      // If we are building a TU prefix for serialization, it is safe to transfer
      // these over, even though they are not parsed. The end of the TU should be
      // outside of any eager template instantiation scope, so when this AST is
      // deserialized, these templates will not be parsed until the end of the
      // combined TU.
      PendingInstantiations.insert(PendingInstantiations.end(),
                                   LateParsedInstantiations.begin(),
                                   LateParsedInstantiations.end());
      LateParsedInstantiations.clear();
  
      if (LangOpts.PCHInstantiateTemplates) {
        llvm::TimeTraceScope TimeScope("PerformPendingInstantiations");
        PerformPendingInstantiations();
      }
    }
  
    DiagnoseUnterminatedPragmaAlignPack();
    DiagnoseUnterminatedPragmaAttribute();
  
    // All delayed member exception specs should be checked or we end up accepting
    // incompatible declarations.
    assert(DelayedOverridingExceptionSpecChecks.empty());
    assert(DelayedEquivalentExceptionSpecChecks.empty());
  
    // All dllexport classes should have been processed already.
    assert(DelayedDllExportClasses.empty());
    assert(DelayedDllExportMemberFunctions.empty());
  
    // Remove file scoped decls that turned out to be used.
    UnusedFileScopedDecls.erase(
        std::remove_if(UnusedFileScopedDecls.begin(nullptr, true),
                       UnusedFileScopedDecls.end(),
                       [this](const DeclaratorDecl *DD) {
                         return ShouldRemoveFromUnused(this, DD);
                       }),
        UnusedFileScopedDecls.end());
  
    if (TUKind == TU_Prefix) {
      // Translation unit prefixes don't need any of the checking below.
      if (!PP.isIncrementalProcessingEnabled())
        TUScope = nullptr;
      return;
    }
  
    // Check for #pragma weak identifiers that were never declared
    LoadExternalWeakUndeclaredIdentifiers();
    for (auto WeakID : WeakUndeclaredIdentifiers) {
      if (WeakID.second.getUsed())
        continue;
  
      Decl *PrevDecl = LookupSingleName(TUScope, WeakID.first, SourceLocation(),
                                        LookupOrdinaryName);
      if (PrevDecl != nullptr &&
          !(isa<FunctionDecl>(PrevDecl) || isa<VarDecl>(PrevDecl)))
        Diag(WeakID.second.getLocation(), diag::warn_attribute_wrong_decl_type)
            << "'weak'" << ExpectedVariableOrFunction;
      else
        Diag(WeakID.second.getLocation(), diag::warn_weak_identifier_undeclared)
            << WeakID.first;
    }
  
    if (LangOpts.CPlusPlus11 &&
        !Diags.isIgnored(diag::warn_delegating_ctor_cycle, SourceLocation()))
      CheckDelegatingCtorCycles();
  
    if (!Diags.hasErrorOccurred()) {
      if (ExternalSource)
        ExternalSource->ReadUndefinedButUsed(UndefinedButUsed);
      checkUndefinedButUsed(*this);
    }
  
    // A global-module-fragment is only permitted within a module unit.
    bool DiagnosedMissingModuleDeclaration = false;
    if (!ModuleScopes.empty() &&
        ModuleScopes.back().Module->Kind == Module::GlobalModuleFragment &&
        !ModuleScopes.back().ImplicitGlobalModuleFragment) {
      Diag(ModuleScopes.back().BeginLoc,
           diag::err_module_declaration_missing_after_global_module_introducer);
      DiagnosedMissingModuleDeclaration = true;
    }
  
    if (TUKind == TU_Module) {
      // If we are building a module interface unit, we need to have seen the
      // module declaration by now.
      if (getLangOpts().getCompilingModule() ==
              LangOptions::CMK_ModuleInterface &&
          (ModuleScopes.empty() ||
           !ModuleScopes.back().Module->isModulePurview()) &&
          !DiagnosedMissingModuleDeclaration) {
        // FIXME: Make a better guess as to where to put the module declaration.
        Diag(getSourceManager().getLocForStartOfFile(
                 getSourceManager().getMainFileID()),
             diag::err_module_declaration_missing);
      }
  
      // If we are building a module, resolve all of the exported declarations
      // now.
      if (Module *CurrentModule = PP.getCurrentModule()) {
        ModuleMap &ModMap = PP.getHeaderSearchInfo().getModuleMap();
  
        SmallVector<Module *, 2> Stack;
        Stack.push_back(CurrentModule);
        while (!Stack.empty()) {
          Module *Mod = Stack.pop_back_val();
  
          // Resolve the exported declarations and conflicts.
          // FIXME: Actually complain, once we figure out how to teach the
          // diagnostic client to deal with complaints in the module map at this
          // point.
          ModMap.resolveExports(Mod, /*Complain=*/false);
          ModMap.resolveUses(Mod, /*Complain=*/false);
          ModMap.resolveConflicts(Mod, /*Complain=*/false);
  
          // Queue the submodules, so their exports will also be resolved.
          Stack.append(Mod->submodule_begin(), Mod->submodule_end());
        }
      }
  
      // Warnings emitted in ActOnEndOfTranslationUnit() should be emitted for
      // modules when they are built, not every time they are used.
      emitAndClearUnusedLocalTypedefWarnings();
    }
  
    // 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. If a translation unit
    //   contains one or more tentative definitions for an identifier,
    //   and the translation unit contains no external definition for
    //   that identifier, then the behavior is exactly as if the
    //   translation unit contains a file scope declaration of that
    //   identifier, with the composite type as of the end of the
    //   translation unit, with an initializer equal to 0.
    llvm::SmallSet<VarDecl *, 32> Seen;
    for (TentativeDefinitionsType::iterator
              T = TentativeDefinitions.begin(ExternalSource),
           TEnd = TentativeDefinitions.end();
         T != TEnd; ++T) {
      VarDecl *VD = (*T)->getActingDefinition();
  
      // If the tentative definition was completed, getActingDefinition() returns
      // null. If we've already seen this variable before, insert()'s second
      // return value is false.
      if (!VD || VD->isInvalidDecl() || !Seen.insert(VD).second)
        continue;
  
      if (const IncompleteArrayType *ArrayT
          = Context.getAsIncompleteArrayType(VD->getType())) {
        // Set the length of the array to 1 (C99 6.9.2p5).
        Diag(VD->getLocation(), diag::warn_tentative_incomplete_array);
        llvm::APInt One(Context.getTypeSize(Context.getSizeType()), true);
        QualType T = Context.getConstantArrayType(ArrayT->getElementType(), One,
                                                  nullptr, ArrayType::Normal, 0);
        VD->setType(T);
      } else if (RequireCompleteType(VD->getLocation(), VD->getType(),
                                     diag::err_tentative_def_incomplete_type))
        VD->setInvalidDecl();
  
      // No initialization is performed for a tentative definition.
      CheckCompleteVariableDeclaration(VD);
  
      // Notify the consumer that we've completed a tentative definition.
      if (!VD->isInvalidDecl())
        Consumer.CompleteTentativeDefinition(VD);
    }
  
    for (auto D : ExternalDeclarations) {
      if (!D || D->isInvalidDecl() || D->getPreviousDecl() || !D->isUsed())
        continue;
  
      Consumer.CompleteExternalDeclaration(D);
    }
  
    // If there were errors, disable 'unused' warnings since they will mostly be
    // noise. Don't warn for a use from a module: either we should warn on all
    // file-scope declarations in modules or not at all, but whether the
    // declaration is used is immaterial.
    if (!Diags.hasErrorOccurred() && TUKind != TU_Module) {
      // Output warning for unused file scoped decls.
      for (UnusedFileScopedDeclsType::iterator
             I = UnusedFileScopedDecls.begin(ExternalSource),
             E = UnusedFileScopedDecls.end(); I != E; ++I) {
        if (ShouldRemoveFromUnused(this, *I))
          continue;
  
        if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(*I)) {
          const FunctionDecl *DiagD;
          if (!FD->hasBody(DiagD))
            DiagD = FD;
          if (DiagD->isDeleted())
            continue; // Deleted functions are supposed to be unused.
          if (DiagD->isReferenced()) {
            if (isa<CXXMethodDecl>(DiagD))
              Diag(DiagD->getLocation(), diag::warn_unneeded_member_function)
                  << DiagD;
            else {
              if (FD->getStorageClass() == SC_Static &&
                  !FD->isInlineSpecified() &&
                  !SourceMgr.isInMainFile(
                     SourceMgr.getExpansionLoc(FD->getLocation())))
                Diag(DiagD->getLocation(),
                     diag::warn_unneeded_static_internal_decl)
                    << DiagD;
              else
                Diag(DiagD->getLocation(), diag::warn_unneeded_internal_decl)
                    << /*function*/ 0 << DiagD;
            }
          } else {
            if (FD->getDescribedFunctionTemplate())
              Diag(DiagD->getLocation(), diag::warn_unused_template)
                  << /*function*/ 0 << DiagD;
            else
              Diag(DiagD->getLocation(), isa<CXXMethodDecl>(DiagD)
                                             ? diag::warn_unused_member_function
                                             : diag::warn_unused_function)
                  << DiagD;
          }
        } else {
          const VarDecl *DiagD = cast<VarDecl>(*I)->getDefinition();
          if (!DiagD)
            DiagD = cast<VarDecl>(*I);
          if (DiagD->isReferenced()) {
            Diag(DiagD->getLocation(), diag::warn_unneeded_internal_decl)
                << /*variable*/ 1 << DiagD;
          } else if (DiagD->getType().isConstQualified()) {
            const SourceManager &SM = SourceMgr;
            if (SM.getMainFileID() != SM.getFileID(DiagD->getLocation()) ||
                !PP.getLangOpts().IsHeaderFile)
              Diag(DiagD->getLocation(), diag::warn_unused_const_variable)
                  << DiagD;
          } else {
            if (DiagD->getDescribedVarTemplate())
              Diag(DiagD->getLocation(), diag::warn_unused_template)
                  << /*variable*/ 1 << DiagD;
            else
              Diag(DiagD->getLocation(), diag::warn_unused_variable) << DiagD;
          }
        }
      }
  
      emitAndClearUnusedLocalTypedefWarnings();
    }
  
    if (!Diags.isIgnored(diag::warn_unused_private_field, SourceLocation())) {
      // FIXME: Load additional unused private field candidates from the external
      // source.
      RecordCompleteMap RecordsComplete;
      RecordCompleteMap MNCComplete;
      for (NamedDeclSetType::iterator I = UnusedPrivateFields.begin(),
           E = UnusedPrivateFields.end(); I != E; ++I) {
        const NamedDecl *D = *I;
        const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D->getDeclContext());
        if (RD && !RD->isUnion() &&
            IsRecordFullyDefined(RD, RecordsComplete, MNCComplete)) {
          Diag(D->getLocation(), diag::warn_unused_private_field)
                << D->getDeclName();
        }
      }
    }
  
    if (!Diags.isIgnored(diag::warn_mismatched_delete_new, SourceLocation())) {
      if (ExternalSource)
        ExternalSource->ReadMismatchingDeleteExpressions(DeleteExprs);
      for (const auto &DeletedFieldInfo : DeleteExprs) {
        for (const auto &DeleteExprLoc : DeletedFieldInfo.second) {
          AnalyzeDeleteExprMismatch(DeletedFieldInfo.first, DeleteExprLoc.first,
                                    DeleteExprLoc.second);
        }
      }
    }
  
    // Check we've noticed that we're no longer parsing the initializer for every
    // variable. If we miss cases, then at best we have a performance issue and
    // at worst a rejects-valid bug.
    assert(ParsingInitForAutoVars.empty() &&
           "Didn't unmark var as having its initializer parsed");
  
    if (!PP.isIncrementalProcessingEnabled())
      TUScope = nullptr;
  }
  
  
  //===----------------------------------------------------------------------===//
  // Helper functions.
  //===----------------------------------------------------------------------===//
  
  DeclContext *Sema::getFunctionLevelDeclContext() {
    DeclContext *DC = CurContext;
  
    while (true) {
      if (isa<BlockDecl>(DC) || isa<EnumDecl>(DC) || isa<CapturedDecl>(DC) ||
          isa<RequiresExprBodyDecl>(DC)) {
        DC = DC->getParent();
      } else if (isa<CXXMethodDecl>(DC) &&
                 cast<CXXMethodDecl>(DC)->getOverloadedOperator() == OO_Call &&
                 cast<CXXRecordDecl>(DC->getParent())->isLambda()) {
        DC = DC->getParent()->getParent();
      }
      else break;
    }
  
    return DC;
  }
  
  /// getCurFunctionDecl - If inside of a function body, this returns a pointer
  /// to the function decl for the function being parsed.  If we're currently
  /// in a 'block', this returns the containing context.
  FunctionDecl *Sema::getCurFunctionDecl() {
    DeclContext *DC = getFunctionLevelDeclContext();
    return dyn_cast<FunctionDecl>(DC);
  }
  
  ObjCMethodDecl *Sema::getCurMethodDecl() {
    DeclContext *DC = getFunctionLevelDeclContext();
    while (isa<RecordDecl>(DC))
      DC = DC->getParent();
    return dyn_cast<ObjCMethodDecl>(DC);
  }
  
  NamedDecl *Sema::getCurFunctionOrMethodDecl() {
    DeclContext *DC = getFunctionLevelDeclContext();
    if (isa<ObjCMethodDecl>(DC) || isa<FunctionDecl>(DC))
      return cast<NamedDecl>(DC);
    return nullptr;
  }
  
  LangAS Sema::getDefaultCXXMethodAddrSpace() const {
    if (getLangOpts().OpenCL)
      return getASTContext().getDefaultOpenCLPointeeAddrSpace();
    return LangAS::Default;
  }
  
  void Sema::EmitCurrentDiagnostic(unsigned DiagID) {
    // FIXME: It doesn't make sense to me that DiagID is an incoming argument here
    // and yet we also use the current diag ID on the DiagnosticsEngine. This has
    // been made more painfully obvious by the refactor that introduced this
    // function, but it is possible that the incoming argument can be
    // eliminated. If it truly cannot be (for example, there is some reentrancy
    // issue I am not seeing yet), then there should at least be a clarifying
    // comment somewhere.
    if (Optional<TemplateDeductionInfo*> Info = isSFINAEContext()) {
      switch (DiagnosticIDs::getDiagnosticSFINAEResponse(
                Diags.getCurrentDiagID())) {
      case DiagnosticIDs::SFINAE_Report:
        // We'll report the diagnostic below.
        break;
  
      case DiagnosticIDs::SFINAE_SubstitutionFailure:
        // Count this failure so that we know that template argument deduction
        // has failed.
        ++NumSFINAEErrors;
  
        // Make a copy of this suppressed diagnostic and store it with the
        // template-deduction information.
        if (*Info && !(*Info)->hasSFINAEDiagnostic()) {
          Diagnostic DiagInfo(&Diags);
          (*Info)->addSFINAEDiagnostic(DiagInfo.getLocation(),
                         PartialDiagnostic(DiagInfo, Context.getDiagAllocator()));
        }
  
        Diags.setLastDiagnosticIgnored(true);
        Diags.Clear();
        return;
  
      case DiagnosticIDs::SFINAE_AccessControl: {
        // Per C++ Core Issue 1170, access control is part of SFINAE.
        // Additionally, the AccessCheckingSFINAE flag can be used to temporarily
        // make access control a part of SFINAE for the purposes of checking
        // type traits.
        if (!AccessCheckingSFINAE && !getLangOpts().CPlusPlus11)
          break;
  
        SourceLocation Loc = Diags.getCurrentDiagLoc();
  
        // Suppress this diagnostic.
        ++NumSFINAEErrors;
  
        // Make a copy of this suppressed diagnostic and store it with the
        // template-deduction information.
        if (*Info && !(*Info)->hasSFINAEDiagnostic()) {
          Diagnostic DiagInfo(&Diags);
          (*Info)->addSFINAEDiagnostic(DiagInfo.getLocation(),
                         PartialDiagnostic(DiagInfo, Context.getDiagAllocator()));
        }
  
        Diags.setLastDiagnosticIgnored(true);
        Diags.Clear();
  
        // Now the diagnostic state is clear, produce a C++98 compatibility
        // warning.
        Diag(Loc, diag::warn_cxx98_compat_sfinae_access_control);
  
        // The last diagnostic which Sema produced was ignored. Suppress any
        // notes attached to it.
        Diags.setLastDiagnosticIgnored(true);
        return;
      }
  
      case DiagnosticIDs::SFINAE_Suppress:
        // Make a copy of this suppressed diagnostic and store it with the
        // template-deduction information;
        if (*Info) {
          Diagnostic DiagInfo(&Diags);
          (*Info)->addSuppressedDiagnostic(DiagInfo.getLocation(),
                         PartialDiagnostic(DiagInfo, Context.getDiagAllocator()));
        }
  
        // Suppress this diagnostic.
        Diags.setLastDiagnosticIgnored(true);
        Diags.Clear();
        return;
      }
    }
  
    // Copy the diagnostic printing policy over the ASTContext printing policy.
    // TODO: Stop doing that.  See: https://reviews.llvm.org/D45093#1090292
    Context.setPrintingPolicy(getPrintingPolicy());
  
    // Emit the diagnostic.
    if (!Diags.EmitCurrentDiagnostic())
      return;
  
    // If this is not a note, and we're in a template instantiation
    // that is different from the last template instantiation where
    // we emitted an error, print a template instantiation
    // backtrace.
    if (!DiagnosticIDs::isBuiltinNote(DiagID))
      PrintContextStack();
  }
  
  Sema::SemaDiagnosticBuilder
  Sema::Diag(SourceLocation Loc, const PartialDiagnostic &PD, bool DeferHint) {
    return Diag(Loc, PD.getDiagID(), DeferHint) << PD;
  }
  
  bool Sema::hasUncompilableErrorOccurred() const {
    if (getDiagnostics().hasUncompilableErrorOccurred())
      return true;
    auto *FD = dyn_cast<FunctionDecl>(CurContext);
    if (!FD)
      return false;
    auto Loc = DeviceDeferredDiags.find(FD);
    if (Loc == DeviceDeferredDiags.end())
      return false;
    for (auto PDAt : Loc->second) {
      if (DiagnosticIDs::isDefaultMappingAsError(PDAt.second.getDiagID()))
        return true;
    }
    return false;
  }
  
  // Print notes showing how we can reach FD starting from an a priori
  // known-callable function.
  static void emitCallStackNotes(Sema &S, FunctionDecl *FD) {
    auto FnIt = S.DeviceKnownEmittedFns.find(FD);
    while (FnIt != S.DeviceKnownEmittedFns.end()) {
      // Respect error limit.
      if (S.Diags.hasFatalErrorOccurred())
        return;
      DiagnosticBuilder Builder(
          S.Diags.Report(FnIt->second.Loc, diag::note_called_by));
      Builder << FnIt->second.FD;
      FnIt = S.DeviceKnownEmittedFns.find(FnIt->second.FD);
    }
  }
  
  namespace {
  
  /// Helper class that emits deferred diagnostic messages if an entity directly
  /// or indirectly using the function that causes the deferred diagnostic
  /// messages is known to be emitted.
  ///
  /// During parsing of AST, certain diagnostic messages are recorded as deferred
  /// diagnostics since it is unknown whether the functions containing such
  /// diagnostics will be emitted. A list of potentially emitted functions and
  /// variables that may potentially trigger emission of functions are also
  /// recorded. DeferredDiagnosticsEmitter recursively visits used functions
  /// by each function to emit deferred diagnostics.
  ///
  /// During the visit, certain OpenMP directives or initializer of variables
  /// with certain OpenMP attributes will cause subsequent visiting of any
  /// functions enter a state which is called OpenMP device context in this
  /// implementation. The state is exited when the directive or initializer is
  /// exited. This state can change the emission states of subsequent uses
  /// of functions.
  ///
  /// Conceptually the functions or variables to be visited form a use graph
  /// where the parent node uses the child node. At any point of the visit,
  /// the tree nodes traversed from the tree root to the current node form a use
  /// stack. The emission state of the current node depends on two factors:
  ///    1. the emission state of the root node
  ///    2. whether the current node is in OpenMP device context
  /// If the function is decided to be emitted, its contained deferred diagnostics
  /// are emitted, together with the information about the use stack.
  ///
  class DeferredDiagnosticsEmitter
      : public UsedDeclVisitor<DeferredDiagnosticsEmitter> {
  public:
    typedef UsedDeclVisitor<DeferredDiagnosticsEmitter> Inherited;
  
    // Whether the function is already in the current use-path.
    llvm::SmallPtrSet<CanonicalDeclPtr<Decl>, 4> InUsePath;
  
    // The current use-path.
    llvm::SmallVector<CanonicalDeclPtr<FunctionDecl>, 4> UsePath;
  
    // Whether the visiting of the function has been done. Done[0] is for the
    // case not in OpenMP device context. Done[1] is for the case in OpenMP
    // device context. We need two sets because diagnostics emission may be
    // different depending on whether it is in OpenMP device context.
    llvm::SmallPtrSet<CanonicalDeclPtr<Decl>, 4> DoneMap[2];
  
    // Emission state of the root node of the current use graph.
    bool ShouldEmitRootNode;
  
    // Current OpenMP device context level. It is initialized to 0 and each
    // entering of device context increases it by 1 and each exit decreases
    // it by 1. Non-zero value indicates it is currently in device context.
    unsigned InOMPDeviceContext;
  
    DeferredDiagnosticsEmitter(Sema &S)
        : Inherited(S), ShouldEmitRootNode(false), InOMPDeviceContext(0) {}
  
    bool shouldVisitDiscardedStmt() const { return false; }
  
    void VisitOMPTargetDirective(OMPTargetDirective *Node) {
      ++InOMPDeviceContext;
      Inherited::VisitOMPTargetDirective(Node);
      --InOMPDeviceContext;
    }
  
    void visitUsedDecl(SourceLocation Loc, Decl *D) {
      if (isa<VarDecl>(D))
        return;
      if (auto *FD = dyn_cast<FunctionDecl>(D))
        checkFunc(Loc, FD);
      else
        Inherited::visitUsedDecl(Loc, D);
    }
  
    void checkVar(VarDecl *VD) {
      assert(VD->isFileVarDecl() &&
             "Should only check file-scope variables");
      if (auto *Init = VD->getInit()) {
        auto DevTy = OMPDeclareTargetDeclAttr::getDeviceType(VD);
        bool IsDev = DevTy && (*DevTy == OMPDeclareTargetDeclAttr::DT_NoHost ||
                               *DevTy == OMPDeclareTargetDeclAttr::DT_Any);
        if (IsDev)
          ++InOMPDeviceContext;
        this->Visit(Init);
        if (IsDev)
          --InOMPDeviceContext;
      }
    }
  
    void checkFunc(SourceLocation Loc, FunctionDecl *FD) {
      auto &Done = DoneMap[InOMPDeviceContext > 0 ? 1 : 0];
      FunctionDecl *Caller = UsePath.empty() ? nullptr : UsePath.back();
      if ((!ShouldEmitRootNode && !S.getLangOpts().OpenMP && !Caller) ||
          S.shouldIgnoreInHostDeviceCheck(FD) || InUsePath.count(FD))
        return;
      // Finalize analysis of OpenMP-specific constructs.
      if (Caller && S.LangOpts.OpenMP && UsePath.size() == 1 &&
          (ShouldEmitRootNode || InOMPDeviceContext))
        S.finalizeOpenMPDelayedAnalysis(Caller, FD, Loc);
      if (Caller)
        S.DeviceKnownEmittedFns[FD] = {Caller, Loc};
      // Always emit deferred diagnostics for the direct users. This does not
      // lead to explosion of diagnostics since each user is visited at most
      // twice.
      if (ShouldEmitRootNode || InOMPDeviceContext)
        emitDeferredDiags(FD, Caller);
      // Do not revisit a function if the function body has been completely
      // visited before.
      if (!Done.insert(FD).second)
        return;
      InUsePath.insert(FD);
      UsePath.push_back(FD);
      if (auto *S = FD->getBody()) {
        this->Visit(S);
      }
      UsePath.pop_back();
      InUsePath.erase(FD);
    }
  
    void checkRecordedDecl(Decl *D) {
      if (auto *FD = dyn_cast<FunctionDecl>(D)) {
        ShouldEmitRootNode = S.getEmissionStatus(FD, /*Final=*/true) ==
                             Sema::FunctionEmissionStatus::Emitted;
        checkFunc(SourceLocation(), FD);
      } else
        checkVar(cast<VarDecl>(D));
    }
  
    // Emit any deferred diagnostics for FD
    void emitDeferredDiags(FunctionDecl *FD, bool ShowCallStack) {
      auto It = S.DeviceDeferredDiags.find(FD);
      if (It == S.DeviceDeferredDiags.end())
        return;
      bool HasWarningOrError = false;
      bool FirstDiag = true;
      for (PartialDiagnosticAt &PDAt : It->second) {
        // Respect error limit.
        if (S.Diags.hasFatalErrorOccurred())
          return;
        const SourceLocation &Loc = PDAt.first;
        const PartialDiagnostic &PD = PDAt.second;
        HasWarningOrError |=
            S.getDiagnostics().getDiagnosticLevel(PD.getDiagID(), Loc) >=
            DiagnosticsEngine::Warning;
        {
          DiagnosticBuilder Builder(S.Diags.Report(Loc, PD.getDiagID()));
          PD.Emit(Builder);
        }
        // Emit the note on the first diagnostic in case too many diagnostics
        // cause the note not emitted.
        if (FirstDiag && HasWarningOrError && ShowCallStack) {
          emitCallStackNotes(S, FD);
          FirstDiag = false;
        }
      }
    }
  };
  } // namespace
  
  void Sema::emitDeferredDiags() {
    if (ExternalSource)
      ExternalSource->ReadDeclsToCheckForDeferredDiags(
          DeclsToCheckForDeferredDiags);
  
    if ((DeviceDeferredDiags.empty() && !LangOpts.OpenMP) ||
        DeclsToCheckForDeferredDiags.empty())
      return;
  
    DeferredDiagnosticsEmitter DDE(*this);
    for (auto D : DeclsToCheckForDeferredDiags)
      DDE.checkRecordedDecl(D);
  }
  
  // In CUDA, there are some constructs which may appear in semantically-valid
  // code, but trigger errors if we ever generate code for the function in which
  // they appear.  Essentially every construct you're not allowed to use on the
  // device falls into this category, because you are allowed to use these
  // constructs in a __host__ __device__ function, but only if that function is
  // never codegen'ed on the device.
  //
  // To handle semantic checking for these constructs, we keep track of the set of
  // functions we know will be emitted, either because we could tell a priori that
  // they would be emitted, or because they were transitively called by a
  // known-emitted function.
  //
  // We also keep a partial call graph of which not-known-emitted functions call
  // which other not-known-emitted functions.
  //
  // When we see something which is illegal if the current function is emitted
  // (usually by way of CUDADiagIfDeviceCode, CUDADiagIfHostCode, or
  // CheckCUDACall), we first check if the current function is known-emitted.  If
  // so, we immediately output the diagnostic.
  //
  // Otherwise, we "defer" the diagnostic.  It sits in Sema::DeviceDeferredDiags
  // until we discover that the function is known-emitted, at which point we take
  // it out of this map and emit the diagnostic.
  
  Sema::SemaDiagnosticBuilder::SemaDiagnosticBuilder(Kind K, SourceLocation Loc,
                                                     unsigned DiagID,
                                                     FunctionDecl *Fn, Sema &S)
      : S(S), Loc(Loc), DiagID(DiagID), Fn(Fn),
        ShowCallStack(K == K_ImmediateWithCallStack || K == K_Deferred) {
    switch (K) {
    case K_Nop:
      break;
    case K_Immediate:
    case K_ImmediateWithCallStack:
      ImmediateDiag.emplace(
          ImmediateDiagBuilder(S.Diags.Report(Loc, DiagID), S, DiagID));
      break;
    case K_Deferred:
      assert(Fn && "Must have a function to attach the deferred diag to.");
      auto &Diags = S.DeviceDeferredDiags[Fn];
      PartialDiagId.emplace(Diags.size());
      Diags.emplace_back(Loc, S.PDiag(DiagID));
      break;
    }
  }
  
  Sema::SemaDiagnosticBuilder::SemaDiagnosticBuilder(SemaDiagnosticBuilder &&D)
      : S(D.S), Loc(D.Loc), DiagID(D.DiagID), Fn(D.Fn),
        ShowCallStack(D.ShowCallStack), ImmediateDiag(D.ImmediateDiag),
        PartialDiagId(D.PartialDiagId) {
    // Clean the previous diagnostics.
    D.ShowCallStack = false;
    D.ImmediateDiag.reset();
    D.PartialDiagId.reset();
  }
  
  Sema::SemaDiagnosticBuilder::~SemaDiagnosticBuilder() {
    if (ImmediateDiag) {
      // Emit our diagnostic and, if it was a warning or error, output a callstack
      // if Fn isn't a priori known-emitted.
      bool IsWarningOrError = S.getDiagnostics().getDiagnosticLevel(
                                  DiagID, Loc) >= DiagnosticsEngine::Warning;
      ImmediateDiag.reset(); // Emit the immediate diag.
      if (IsWarningOrError && ShowCallStack)
        emitCallStackNotes(S, Fn);
    } else {
      assert((!PartialDiagId || ShowCallStack) &&
             "Must always show call stack for deferred diags.");
    }
  }
  
  Sema::SemaDiagnosticBuilder
  Sema::targetDiag(SourceLocation Loc, unsigned DiagID, FunctionDecl *FD) {
    FD = FD ? FD : getCurFunctionDecl();
    if (LangOpts.OpenMP)
      return LangOpts.OpenMPIsDevice ? diagIfOpenMPDeviceCode(Loc, DiagID, FD)
                                     : diagIfOpenMPHostCode(Loc, DiagID, FD);
    if (getLangOpts().CUDA)
      return getLangOpts().CUDAIsDevice ? CUDADiagIfDeviceCode(Loc, DiagID)
                                        : CUDADiagIfHostCode(Loc, DiagID);
  
    if (getLangOpts().SYCLIsDevice)
      return SYCLDiagIfDeviceCode(Loc, DiagID);
  
    return SemaDiagnosticBuilder(SemaDiagnosticBuilder::K_Immediate, Loc, DiagID,
                                 FD, *this);
  }
  
  Sema::SemaDiagnosticBuilder Sema::Diag(SourceLocation Loc, unsigned DiagID,
                                         bool DeferHint) {
    bool IsError = Diags.getDiagnosticIDs()->isDefaultMappingAsError(DiagID);
    bool ShouldDefer = getLangOpts().CUDA && LangOpts.GPUDeferDiag &&
                       DiagnosticIDs::isDeferrable(DiagID) &&
                       (DeferHint || DeferDiags || !IsError);
    auto SetIsLastErrorImmediate = [&](bool Flag) {
      if (IsError)
        IsLastErrorImmediate = Flag;
    };
    if (!ShouldDefer) {
      SetIsLastErrorImmediate(true);
      return SemaDiagnosticBuilder(SemaDiagnosticBuilder::K_Immediate, Loc,
                                   DiagID, getCurFunctionDecl(), *this);
    }
  
    SemaDiagnosticBuilder DB = getLangOpts().CUDAIsDevice
                                   ? CUDADiagIfDeviceCode(Loc, DiagID)
                                   : CUDADiagIfHostCode(Loc, DiagID);
    SetIsLastErrorImmediate(DB.isImmediate());
    return DB;
  }
  
  void Sema::checkDeviceDecl(ValueDecl *D, SourceLocation Loc) {
    if (isUnevaluatedContext())
      return;
  
    Decl *C = cast<Decl>(getCurLexicalContext());
  
    // Memcpy operations for structs containing a member with unsupported type
    // are ok, though.
    if (const auto *MD = dyn_cast<CXXMethodDecl>(C)) {
      if ((MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()) &&
          MD->isTrivial())
        return;
  
      if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(MD))
        if (Ctor->isCopyOrMoveConstructor() && Ctor->isTrivial())
          return;
    }
  
    // Try to associate errors with the lexical context, if that is a function, or
    // the value declaration otherwise.
    FunctionDecl *FD =
        isa<FunctionDecl>(C) ? cast<FunctionDecl>(C) : dyn_cast<FunctionDecl>(D);
    auto CheckType = [&](QualType Ty) {
      if (Ty->isDependentType())
        return;
  
      if (Ty->isExtIntType()) {
        if (!Context.getTargetInfo().hasExtIntType()) {
          targetDiag(Loc, diag::err_device_unsupported_type, FD)
              << D << false /*show bit size*/ << 0 /*bitsize*/
              << Ty << Context.getTargetInfo().getTriple().str();
        }
        return;
      }
  
      // Check if we are dealing with two 'long double' but with different
      // semantics.
      bool LongDoubleMismatched = false;
      if (Ty->isRealFloatingType() && Context.getTypeSize(Ty) == 128) {
        const llvm::fltSemantics &Sem = Context.getFloatTypeSemantics(Ty);
        if ((&Sem != &llvm::APFloat::PPCDoubleDouble() &&
             !Context.getTargetInfo().hasFloat128Type()) ||
            (&Sem == &llvm::APFloat::PPCDoubleDouble() &&
             !Context.getTargetInfo().hasIbm128Type()))
          LongDoubleMismatched = true;
      }
  
      if ((Ty->isFloat16Type() && !Context.getTargetInfo().hasFloat16Type()) ||
          (Ty->isFloat128Type() && !Context.getTargetInfo().hasFloat128Type()) ||
          (Ty->isIbm128Type() && !Context.getTargetInfo().hasIbm128Type()) ||
          (Ty->isIntegerType() && Context.getTypeSize(Ty) == 128 &&
           !Context.getTargetInfo().hasInt128Type()) ||
          LongDoubleMismatched) {
        if (targetDiag(Loc, diag::err_device_unsupported_type, FD)
            << D << true /*show bit size*/
            << static_cast<unsigned>(Context.getTypeSize(Ty)) << Ty
            << Context.getTargetInfo().getTriple().str())
          D->setInvalidDecl();
        targetDiag(D->getLocation(), diag::note_defined_here, FD) << D;
      }
    };
  
    QualType Ty = D->getType();
    CheckType(Ty);
  
    if (const auto *FPTy = dyn_cast<FunctionProtoType>(Ty)) {
      for (const auto &ParamTy : FPTy->param_types())
        CheckType(ParamTy);
      CheckType(FPTy->getReturnType());
    }
    if (const auto *FNPTy = dyn_cast<FunctionNoProtoType>(Ty))
      CheckType(FNPTy->getReturnType());
  }
  
  /// Looks through the macro-expansion chain for the given
  /// location, looking for a macro expansion with the given name.
  /// If one is found, returns true and sets the location to that
  /// expansion loc.
  bool Sema::findMacroSpelling(SourceLocation &locref, StringRef name) {
    SourceLocation loc = locref;
    if (!loc.isMacroID()) return false;
  
    // There's no good way right now to look at the intermediate
    // expansions, so just jump to the expansion location.
    loc = getSourceManager().getExpansionLoc(loc);
  
    // If that's written with the name, stop here.
    SmallString<16> buffer;
    if (getPreprocessor().getSpelling(loc, buffer) == name) {
      locref = loc;
      return true;
    }
    return false;
  }
  
  /// Determines the active Scope associated with the given declaration
  /// context.
  ///
  /// This routine maps a declaration context to the active Scope object that
  /// represents that declaration context in the parser. It is typically used
  /// from "scope-less" code (e.g., template instantiation, lazy creation of
  /// declarations) that injects a name for name-lookup purposes and, therefore,
  /// must update the Scope.
  ///
  /// \returns The scope corresponding to the given declaraion context, or NULL
  /// if no such scope is open.
  Scope *Sema::getScopeForContext(DeclContext *Ctx) {
  
    if (!Ctx)
      return nullptr;
  
    Ctx = Ctx->getPrimaryContext();
    for (Scope *S = getCurScope(); S; S = S->getParent()) {
      // Ignore scopes that cannot have declarations. This is important for
      // out-of-line definitions of static class members.
      if (S->getFlags() & (Scope::DeclScope | Scope::TemplateParamScope))
        if (DeclContext *Entity = S->getEntity())
          if (Ctx == Entity->getPrimaryContext())
            return S;
    }
  
    return nullptr;
  }
  
  /// Enter a new function scope
  void Sema::PushFunctionScope() {
    if (FunctionScopes.empty() && CachedFunctionScope) {
      // Use CachedFunctionScope to avoid allocating memory when possible.
      CachedFunctionScope->Clear();
      FunctionScopes.push_back(CachedFunctionScope.release());
    } else {
      FunctionScopes.push_back(new FunctionScopeInfo(getDiagnostics()));
    }
    if (LangOpts.OpenMP)
      pushOpenMPFunctionRegion();
  }
  
  void Sema::PushBlockScope(Scope *BlockScope, BlockDecl *Block) {
    FunctionScopes.push_back(new BlockScopeInfo(getDiagnostics(),
                                                BlockScope, Block));
  }
  
  LambdaScopeInfo *Sema::PushLambdaScope() {
    LambdaScopeInfo *const LSI = new LambdaScopeInfo(getDiagnostics());
    FunctionScopes.push_back(LSI);
    return LSI;
  }
  
  void Sema::RecordParsingTemplateParameterDepth(unsigned Depth) {
    if (LambdaScopeInfo *const LSI = getCurLambda()) {
      LSI->AutoTemplateParameterDepth = Depth;
      return;
    }
    llvm_unreachable(
        "Remove assertion if intentionally called in a non-lambda context.");
  }
  
  // Check that the type of the VarDecl has an accessible copy constructor and
  // resolve its destructor's exception specification.
  // This also performs initialization of block variables when they are moved
  // to the heap. It uses the same rules as applicable for implicit moves
  // according to the C++ standard in effect ([class.copy.elision]p3).
  static void checkEscapingByref(VarDecl *VD, Sema &S) {
    QualType T = VD->getType();
    EnterExpressionEvaluationContext scope(
        S, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
    SourceLocation Loc = VD->getLocation();
    Expr *VarRef =
        new (S.Context) DeclRefExpr(S.Context, VD, false, T, VK_LValue, Loc);
    ExprResult Result;
    auto IE = InitializedEntity::InitializeBlock(Loc, T);
    if (S.getLangOpts().CPlusPlus2b) {
      auto *E = ImplicitCastExpr::Create(S.Context, T, CK_NoOp, VarRef, nullptr,
                                         VK_XValue, FPOptionsOverride());
      Result = S.PerformCopyInitialization(IE, SourceLocation(), E);
    } else {
      Result = S.PerformMoveOrCopyInitialization(
          IE, Sema::NamedReturnInfo{VD, Sema::NamedReturnInfo::MoveEligible},
          VarRef);
    }
  
    if (!Result.isInvalid()) {
      Result = S.MaybeCreateExprWithCleanups(Result);
      Expr *Init = Result.getAs<Expr>();
      S.Context.setBlockVarCopyInit(VD, Init, S.canThrow(Init));
    }
  
    // The destructor's exception specification is needed when IRGen generates
    // block copy/destroy functions. Resolve it here.
    if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      if (CXXDestructorDecl *DD = RD->getDestructor()) {
        auto *FPT = DD->getType()->getAs<FunctionProtoType>();
        S.ResolveExceptionSpec(Loc, FPT);
      }
  }
  
  static void markEscapingByrefs(const FunctionScopeInfo &FSI, Sema &S) {
    // Set the EscapingByref flag of __block variables captured by
    // escaping blocks.
    for (const BlockDecl *BD : FSI.Blocks) {
      for (const BlockDecl::Capture &BC : BD->captures()) {
        VarDecl *VD = BC.getVariable();
        if (VD->hasAttr<BlocksAttr>()) {
          // Nothing to do if this is a __block variable captured by a
          // non-escaping block.
          if (BD->doesNotEscape())
            continue;
          VD->setEscapingByref();
        }
        // Check whether the captured variable is or contains an object of
        // non-trivial C union type.
        QualType CapType = BC.getVariable()->getType();
        if (CapType.hasNonTrivialToPrimitiveDestructCUnion() ||
            CapType.hasNonTrivialToPrimitiveCopyCUnion())
          S.checkNonTrivialCUnion(BC.getVariable()->getType(),
                                  BD->getCaretLocation(),
                                  Sema::NTCUC_BlockCapture,
                                  Sema::NTCUK_Destruct|Sema::NTCUK_Copy);
      }
    }
  
    for (VarDecl *VD : FSI.ByrefBlockVars) {
      // __block variables might require us to capture a copy-initializer.
      if (!VD->isEscapingByref())
        continue;
      // It's currently invalid to ever have a __block variable with an
      // array type; should we diagnose that here?
      // Regardless, we don't want to ignore array nesting when
      // constructing this copy.
      if (VD->getType()->isStructureOrClassType())
        checkEscapingByref(VD, S);
    }
  }
  
  /// Pop a function (or block or lambda or captured region) scope from the stack.
  ///
  /// \param WP The warning policy to use for CFG-based warnings, or null if such
  ///        warnings should not be produced.
  /// \param D The declaration corresponding to this function scope, if producing
  ///        CFG-based warnings.
  /// \param BlockType The type of the block expression, if D is a BlockDecl.
  Sema::PoppedFunctionScopePtr
  Sema::PopFunctionScopeInfo(const AnalysisBasedWarnings::Policy *WP,
                             const Decl *D, QualType BlockType) {
    assert(!FunctionScopes.empty() && "mismatched push/pop!");
  
    markEscapingByrefs(*FunctionScopes.back(), *this);
  
    PoppedFunctionScopePtr Scope(FunctionScopes.pop_back_val(),
                                 PoppedFunctionScopeDeleter(this));
  
    if (LangOpts.OpenMP)
      popOpenMPFunctionRegion(Scope.get());
  
    // Issue any analysis-based warnings.
    if (WP && D)
      AnalysisWarnings.IssueWarnings(*WP, Scope.get(), D, BlockType);
    else
      for (const auto &PUD : Scope->PossiblyUnreachableDiags)
        Diag(PUD.Loc, PUD.PD);
  
    return Scope;
  }
  
  void Sema::PoppedFunctionScopeDeleter::
  operator()(sema::FunctionScopeInfo *Scope) const {
    // Stash the function scope for later reuse if it's for a normal function.
    if (Scope->isPlainFunction() && !Self->CachedFunctionScope)
      Self->CachedFunctionScope.reset(Scope);
    else
      delete Scope;
  }
  
  void Sema::PushCompoundScope(bool IsStmtExpr) {
    getCurFunction()->CompoundScopes.push_back(CompoundScopeInfo(IsStmtExpr));
  }
  
  void Sema::PopCompoundScope() {
    FunctionScopeInfo *CurFunction = getCurFunction();
    assert(!CurFunction->CompoundScopes.empty() && "mismatched push/pop");
  
    CurFunction->CompoundScopes.pop_back();
  }
  
  /// Determine whether any errors occurred within this function/method/
  /// block.
  bool Sema::hasAnyUnrecoverableErrorsInThisFunction() const {
    return getCurFunction()->hasUnrecoverableErrorOccurred();
  }
  
  void Sema::setFunctionHasBranchIntoScope() {
    if (!FunctionScopes.empty())
      FunctionScopes.back()->setHasBranchIntoScope();
  }
  
  void Sema::setFunctionHasBranchProtectedScope() {
    if (!FunctionScopes.empty())
      FunctionScopes.back()->setHasBranchProtectedScope();
  }
  
  void Sema::setFunctionHasIndirectGoto() {
    if (!FunctionScopes.empty())
      FunctionScopes.back()->setHasIndirectGoto();
  }
  
  void Sema::setFunctionHasMustTail() {
    if (!FunctionScopes.empty())
      FunctionScopes.back()->setHasMustTail();
  }
  
  BlockScopeInfo *Sema::getCurBlock() {
    if (FunctionScopes.empty())
      return nullptr;
  
    auto CurBSI = dyn_cast<BlockScopeInfo>(FunctionScopes.back());
    if (CurBSI && CurBSI->TheDecl &&
        !CurBSI->TheDecl->Encloses(CurContext)) {
      // We have switched contexts due to template instantiation.
      assert(!CodeSynthesisContexts.empty());
      return nullptr;
    }
  
    return CurBSI;
  }
  
  FunctionScopeInfo *Sema::getEnclosingFunction() const {
    if (FunctionScopes.empty())
      return nullptr;
  
    for (int e = FunctionScopes.size() - 1; e >= 0; --e) {
      if (isa<sema::BlockScopeInfo>(FunctionScopes[e]))
        continue;
      return FunctionScopes[e];
    }
    return nullptr;
  }
  
  LambdaScopeInfo *Sema::getEnclosingLambda() const {
    for (auto *Scope : llvm::reverse(FunctionScopes)) {
      if (auto *LSI = dyn_cast<sema::LambdaScopeInfo>(Scope)) {
        if (LSI->Lambda && !LSI->Lambda->Encloses(CurContext)) {
          // We have switched contexts due to template instantiation.
          // FIXME: We should swap out the FunctionScopes during code synthesis
          // so that we don't need to check for this.
          assert(!CodeSynthesisContexts.empty());
          return nullptr;
        }
        return LSI;
      }
    }
    return nullptr;
  }
  
  LambdaScopeInfo *Sema::getCurLambda(bool IgnoreNonLambdaCapturingScope) {
    if (FunctionScopes.empty())
      return nullptr;
  
    auto I = FunctionScopes.rbegin();
    if (IgnoreNonLambdaCapturingScope) {
      auto E = FunctionScopes.rend();
      while (I != E && isa<CapturingScopeInfo>(*I) && !isa<LambdaScopeInfo>(*I))
        ++I;
      if (I == E)
        return nullptr;
    }
    auto *CurLSI = dyn_cast<LambdaScopeInfo>(*I);
    if (CurLSI && CurLSI->Lambda &&
        !CurLSI->Lambda->Encloses(CurContext)) {
      // We have switched contexts due to template instantiation.
      assert(!CodeSynthesisContexts.empty());
      return nullptr;
    }
  
    return CurLSI;
  }
  
  // We have a generic lambda if we parsed auto parameters, or we have
  // an associated template parameter list.
  LambdaScopeInfo *Sema::getCurGenericLambda() {
    if (LambdaScopeInfo *LSI =  getCurLambda()) {
      return (LSI->TemplateParams.size() ||
                      LSI->GLTemplateParameterList) ? LSI : nullptr;
    }
    return nullptr;
  }
  
  
  void Sema::ActOnComment(SourceRange Comment) {
    if (!LangOpts.RetainCommentsFromSystemHeaders &&
        SourceMgr.isInSystemHeader(Comment.getBegin()))
      return;
    RawComment RC(SourceMgr, Comment, LangOpts.CommentOpts, false);
    if (RC.isAlmostTrailingComment()) {
      SourceRange MagicMarkerRange(Comment.getBegin(),
                                   Comment.getBegin().getLocWithOffset(3));
      StringRef MagicMarkerText;
      switch (RC.getKind()) {
      case RawComment::RCK_OrdinaryBCPL:
        MagicMarkerText = "///<";
        break;
      case RawComment::RCK_OrdinaryC:
        MagicMarkerText = "/**<";
        break;
      default:
        llvm_unreachable("if this is an almost Doxygen comment, "
                         "it should be ordinary");
      }
      Diag(Comment.getBegin(), diag::warn_not_a_doxygen_trailing_member_comment) <<
        FixItHint::CreateReplacement(MagicMarkerRange, MagicMarkerText);
    }
    Context.addComment(RC);
  }
  
  // Pin this vtable to this file.
  ExternalSemaSource::~ExternalSemaSource() {}
  char ExternalSemaSource::ID;
  
  void ExternalSemaSource::ReadMethodPool(Selector Sel) { }
  void ExternalSemaSource::updateOutOfDateSelector(Selector Sel) { }
  
  void ExternalSemaSource::ReadKnownNamespaces(
                             SmallVectorImpl<NamespaceDecl *> &Namespaces) {
  }
  
  void ExternalSemaSource::ReadUndefinedButUsed(
      llvm::MapVector<NamedDecl *, SourceLocation> &Undefined) {}
  
  void ExternalSemaSource::ReadMismatchingDeleteExpressions(llvm::MapVector<
      FieldDecl *, llvm::SmallVector<std::pair<SourceLocation, bool>, 4>> &) {}
  
  /// Figure out if an expression could be turned into a call.
  ///
  /// Use this when trying to recover from an error where the programmer may have
  /// written just the name of a function instead of actually calling it.
  ///
  /// \param E - The expression to examine.
  /// \param ZeroArgCallReturnTy - If the expression can be turned into a call
  ///  with no arguments, this parameter is set to the type returned by such a
  ///  call; otherwise, it is set to an empty QualType.
  /// \param OverloadSet - If the expression is an overloaded function
  ///  name, this parameter is populated with the decls of the various overloads.
  bool Sema::tryExprAsCall(Expr &E, QualType &ZeroArgCallReturnTy,
                           UnresolvedSetImpl &OverloadSet) {
    ZeroArgCallReturnTy = QualType();
    OverloadSet.clear();
  
    const OverloadExpr *Overloads = nullptr;
    bool IsMemExpr = false;
    if (E.getType() == Context.OverloadTy) {
      OverloadExpr::FindResult FR = OverloadExpr::find(const_cast<Expr*>(&E));
  
      // Ignore overloads that are pointer-to-member constants.
      if (FR.HasFormOfMemberPointer)
        return false;
  
      Overloads = FR.Expression;
    } else if (E.getType() == Context.BoundMemberTy) {
      Overloads = dyn_cast<UnresolvedMemberExpr>(E.IgnoreParens());
      IsMemExpr = true;
    }
  
    bool Ambiguous = false;
    bool IsMV = false;
  
    if (Overloads) {
      for (OverloadExpr::decls_iterator it = Overloads->decls_begin(),
           DeclsEnd = Overloads->decls_end(); it != DeclsEnd; ++it) {
        OverloadSet.addDecl(*it);
  
        // Check whether the function is a non-template, non-member which takes no
        // arguments.
        if (IsMemExpr)
          continue;
        if (const FunctionDecl *OverloadDecl
              = dyn_cast<FunctionDecl>((*it)->getUnderlyingDecl())) {
          if (OverloadDecl->getMinRequiredArguments() == 0) {
            if (!ZeroArgCallReturnTy.isNull() && !Ambiguous &&
                (!IsMV || !(OverloadDecl->isCPUDispatchMultiVersion() ||
                            OverloadDecl->isCPUSpecificMultiVersion()))) {
              ZeroArgCallReturnTy = QualType();
              Ambiguous = true;
            } else {
              ZeroArgCallReturnTy = OverloadDecl->getReturnType();
              IsMV = OverloadDecl->isCPUDispatchMultiVersion() ||
                     OverloadDecl->isCPUSpecificMultiVersion();
            }
          }
        }
      }
  
      // If it's not a member, use better machinery to try to resolve the call
      if (!IsMemExpr)
        return !ZeroArgCallReturnTy.isNull();
    }
  
    // Attempt to call the member with no arguments - this will correctly handle
    // member templates with defaults/deduction of template arguments, overloads
    // with default arguments, etc.
    if (IsMemExpr && !E.isTypeDependent()) {
      Sema::TentativeAnalysisScope Trap(*this);
      ExprResult R = BuildCallToMemberFunction(nullptr, &E, SourceLocation(),
                                               None, SourceLocation());
      if (R.isUsable()) {
        ZeroArgCallReturnTy = R.get()->getType();
        return true;
      }
      return false;
    }
  
    if (const DeclRefExpr *DeclRef = dyn_cast<DeclRefExpr>(E.IgnoreParens())) {
      if (const FunctionDecl *Fun = dyn_cast<FunctionDecl>(DeclRef->getDecl())) {
        if (Fun->getMinRequiredArguments() == 0)
          ZeroArgCallReturnTy = Fun->getReturnType();
        return true;
      }
    }
  
    // We don't have an expression that's convenient to get a FunctionDecl from,
    // but we can at least check if the type is "function of 0 arguments".
    QualType ExprTy = E.getType();
    const FunctionType *FunTy = nullptr;
    QualType PointeeTy = ExprTy->getPointeeType();
    if (!PointeeTy.isNull())
      FunTy = PointeeTy->getAs<FunctionType>();
    if (!FunTy)
      FunTy = ExprTy->getAs<FunctionType>();
  
    if (const FunctionProtoType *FPT =
        dyn_cast_or_null<FunctionProtoType>(FunTy)) {
      if (FPT->getNumParams() == 0)
        ZeroArgCallReturnTy = FunTy->getReturnType();
      return true;
    }
    return false;
  }
  
  /// Give notes for a set of overloads.
  ///
  /// A companion to tryExprAsCall. In cases when the name that the programmer
  /// wrote was an overloaded function, we may be able to make some guesses about
  /// plausible overloads based on their return types; such guesses can be handed
  /// off to this method to be emitted as notes.
  ///
  /// \param Overloads - The overloads to note.
  /// \param FinalNoteLoc - If we've suppressed printing some overloads due to
  ///  -fshow-overloads=best, this is the location to attach to the note about too
  ///  many candidates. Typically this will be the location of the original
  ///  ill-formed expression.
  static void noteOverloads(Sema &S, const UnresolvedSetImpl &Overloads,
                            const SourceLocation FinalNoteLoc) {
    unsigned ShownOverloads = 0;
    unsigned SuppressedOverloads = 0;
    for (UnresolvedSetImpl::iterator It = Overloads.begin(),
         DeclsEnd = Overloads.end(); It != DeclsEnd; ++It) {
      if (ShownOverloads >= S.Diags.getNumOverloadCandidatesToShow()) {
        ++SuppressedOverloads;
        continue;
      }
  
      NamedDecl *Fn = (*It)->getUnderlyingDecl();
      // Don't print overloads for non-default multiversioned functions.
      if (const auto *FD = Fn->getAsFunction()) {
        if (FD->isMultiVersion() && FD->hasAttr<TargetAttr>() &&
            !FD->getAttr<TargetAttr>()->isDefaultVersion())
          continue;
      }
      S.Diag(Fn->getLocation(), diag::note_possible_target_of_call);
      ++ShownOverloads;
    }
  
    S.Diags.overloadCandidatesShown(ShownOverloads);
  
    if (SuppressedOverloads)
      S.Diag(FinalNoteLoc, diag::note_ovl_too_many_candidates)
        << SuppressedOverloads;
  }
  
  static void notePlausibleOverloads(Sema &S, SourceLocation Loc,
                                     const UnresolvedSetImpl &Overloads,
                                     bool (*IsPlausibleResult)(QualType)) {
    if (!IsPlausibleResult)
      return noteOverloads(S, Overloads, Loc);
  
    UnresolvedSet<2> PlausibleOverloads;
    for (OverloadExpr::decls_iterator It = Overloads.begin(),
           DeclsEnd = Overloads.end(); It != DeclsEnd; ++It) {
      const FunctionDecl *OverloadDecl = cast<FunctionDecl>(*It);
      QualType OverloadResultTy = OverloadDecl->getReturnType();
      if (IsPlausibleResult(OverloadResultTy))
        PlausibleOverloads.addDecl(It.getDecl());
    }
    noteOverloads(S, PlausibleOverloads, Loc);
  }
  
  /// Determine whether the given expression can be called by just
  /// putting parentheses after it.  Notably, expressions with unary
  /// operators can't be because the unary operator will start parsing
  /// outside the call.
  static bool IsCallableWithAppend(Expr *E) {
    E = E->IgnoreImplicit();
    return (!isa<CStyleCastExpr>(E) &&
            !isa<UnaryOperator>(E) &&
            !isa<BinaryOperator>(E) &&
            !isa<CXXOperatorCallExpr>(E));
  }
  
  static bool IsCPUDispatchCPUSpecificMultiVersion(const Expr *E) {
    if (const auto *UO = dyn_cast<UnaryOperator>(E))
      E = UO->getSubExpr();
  
    if (const auto *ULE = dyn_cast<UnresolvedLookupExpr>(E)) {
      if (ULE->getNumDecls() == 0)
        return false;
  
      const NamedDecl *ND = *ULE->decls_begin();
      if (const auto *FD = dyn_cast<FunctionDecl>(ND))
        return FD->isCPUDispatchMultiVersion() || FD->isCPUSpecificMultiVersion();
    }
    return false;
  }
  
  bool Sema::tryToRecoverWithCall(ExprResult &E, const PartialDiagnostic &PD,
                                  bool ForceComplain,
                                  bool (*IsPlausibleResult)(QualType)) {
    SourceLocation Loc = E.get()->getExprLoc();
    SourceRange Range = E.get()->getSourceRange();
  
    QualType ZeroArgCallTy;
    UnresolvedSet<4> Overloads;
    if (tryExprAsCall(*E.get(), ZeroArgCallTy, Overloads) &&
        !ZeroArgCallTy.isNull() &&
        (!IsPlausibleResult || IsPlausibleResult(ZeroArgCallTy))) {
      // At this point, we know E is potentially callable with 0
      // arguments and that it returns something of a reasonable type,
      // so we can emit a fixit and carry on pretending that E was
      // actually a CallExpr.
      SourceLocation ParenInsertionLoc = getLocForEndOfToken(Range.getEnd());
      bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
      Diag(Loc, PD) << /*zero-arg*/ 1 << IsMV << Range
                    << (IsCallableWithAppend(E.get())
                            ? FixItHint::CreateInsertion(ParenInsertionLoc, "()")
                            : FixItHint());
      if (!IsMV)
        notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
  
      // FIXME: Try this before emitting the fixit, and suppress diagnostics
      // while doing so.
      E = BuildCallExpr(nullptr, E.get(), Range.getEnd(), None,
                        Range.getEnd().getLocWithOffset(1));
      return true;
    }
  
    if (!ForceComplain) return false;
  
    bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
    Diag(Loc, PD) << /*not zero-arg*/ 0 << IsMV << Range;
    if (!IsMV)
      notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
    E = ExprError();
    return true;
  }
  
  IdentifierInfo *Sema::getSuperIdentifier() const {
    if (!Ident_super)
      Ident_super = &Context.Idents.get("super");
    return Ident_super;
  }
  
  IdentifierInfo *Sema::getFloat128Identifier() const {
    if (!Ident___float128)
      Ident___float128 = &Context.Idents.get("__float128");
    return Ident___float128;
  }
  
  void Sema::PushCapturedRegionScope(Scope *S, CapturedDecl *CD, RecordDecl *RD,
                                     CapturedRegionKind K,
                                     unsigned OpenMPCaptureLevel) {
    auto *CSI = new CapturedRegionScopeInfo(
        getDiagnostics(), S, CD, RD, CD->getContextParam(), K,
        (getLangOpts().OpenMP && K == CR_OpenMP) ? getOpenMPNestingLevel() : 0,
        OpenMPCaptureLevel);
    CSI->ReturnType = Context.VoidTy;
    FunctionScopes.push_back(CSI);
  }
  
  CapturedRegionScopeInfo *Sema::getCurCapturedRegion() {
    if (FunctionScopes.empty())
      return nullptr;
  
    return dyn_cast<CapturedRegionScopeInfo>(FunctionScopes.back());
  }
  
  const llvm::MapVector<FieldDecl *, Sema::DeleteLocs> &
  Sema::getMismatchingDeleteExpressions() const {
    return DeleteExprs;
  }
  