text: //===--- Sema.h - Semantic Analysis & AST Building --------------*- C++ -*-===//
  //
  // 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 defines the Sema class, which performs semantic analysis and
  // builds ASTs.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CLANG_SEMA_SEMA_H
  #define LLVM_CLANG_SEMA_SEMA_H
  
  #include "clang/AST/ASTConcept.h"
  #include "clang/AST/ASTFwd.h"
  #include "clang/AST/Attr.h"
  #include "clang/AST/Availability.h"
  #include "clang/AST/ComparisonCategories.h"
  #include "clang/AST/DeclTemplate.h"
  #include "clang/AST/DeclarationName.h"
  #include "clang/AST/Expr.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/AST/ExprConcepts.h"
  #include "clang/AST/ExprObjC.h"
  #include "clang/AST/ExternalASTSource.h"
  #include "clang/AST/LocInfoType.h"
  #include "clang/AST/MangleNumberingContext.h"
  #include "clang/AST/NSAPI.h"
  #include "clang/AST/PrettyPrinter.h"
  #include "clang/AST/StmtCXX.h"
  #include "clang/AST/TypeLoc.h"
  #include "clang/APINotes/APINotesManager.h"
  #include "clang/AST/TypeOrdering.h"
  #include "clang/Basic/BitmaskEnum.h"
  #include "clang/Basic/ExpressionTraits.h"
  #include "clang/Basic/Module.h"
  #include "clang/Basic/OpenCLOptions.h"
  #include "clang/Basic/OpenMPKinds.h"
  #include "clang/Basic/PragmaKinds.h"
  #include "clang/Basic/Specifiers.h"
  #include "clang/Basic/TemplateKinds.h"
  #include "clang/Basic/TypeTraits.h"
  #include "clang/Sema/AnalysisBasedWarnings.h"
  #include "clang/Sema/CleanupInfo.h"
  #include "clang/Sema/DeclSpec.h"
  #include "clang/Sema/ExternalSemaSource.h"
  #include "clang/Sema/IdentifierResolver.h"
  #include "clang/Sema/ObjCMethodList.h"
  #include "clang/Sema/Ownership.h"
  #include "clang/Sema/Scope.h"
  #include "clang/Sema/SemaConcept.h"
  #include "clang/Sema/TypoCorrection.h"
  #include "clang/Sema/Weak.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/Optional.h"
  #include "llvm/ADT/SetVector.h"
  #include "llvm/ADT/SmallBitVector.h"
  #include "llvm/ADT/SmallPtrSet.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/TinyPtrVector.h"
  #include "llvm/Frontend/OpenMP/OMPConstants.h"
  #include <deque>
  #include <functional>
  #include <memory>
  #include <string>
  #include <tuple>
  #include <vector>
  
  namespace llvm {
    class APSInt;
    template <typename ValueT> struct DenseMapInfo;
    template <typename ValueT, typename ValueInfoT> class DenseSet;
    class SmallBitVector;
    struct InlineAsmIdentifierInfo;
  }
  
  namespace clang {
    class ADLResult;
    class ASTConsumer;
    class ASTContext;
    class ASTMutationListener;
    class ASTReader;
    class ASTWriter;
    class ArrayType;
    class ParsedAttr;
    class BindingDecl;
    class BlockDecl;
    class CapturedDecl;
    class CXXBasePath;
    class CXXBasePaths;
    class CXXBindTemporaryExpr;
    typedef SmallVector<CXXBaseSpecifier*, 4> CXXCastPath;
    class CXXConstructorDecl;
    class CXXConversionDecl;
    class CXXDeleteExpr;
    class CXXDestructorDecl;
    class CXXFieldCollector;
    class CXXMemberCallExpr;
    class CXXMethodDecl;
    class CXXScopeSpec;
    class CXXTemporary;
    class CXXTryStmt;
    class CallExpr;
    class ClassTemplateDecl;
    class ClassTemplatePartialSpecializationDecl;
    class ClassTemplateSpecializationDecl;
    class VarTemplatePartialSpecializationDecl;
    class CodeCompleteConsumer;
    class CodeCompletionAllocator;
    class CodeCompletionTUInfo;
    class CodeCompletionResult;
    class CoroutineBodyStmt;
    class Decl;
    class DeclAccessPair;
    class DeclContext;
    class DeclRefExpr;
    class DeclaratorDecl;
    class DeducedTemplateArgument;
    class DependentDiagnostic;
    class DesignatedInitExpr;
    class Designation;
    class EnableIfAttr;
    class EnumConstantDecl;
    class Expr;
    class ExtVectorType;
    class FormatAttr;
    class FriendDecl;
    class FunctionDecl;
    class FunctionProtoType;
    class FunctionTemplateDecl;
    class ImplicitConversionSequence;
    typedef MutableArrayRef<ImplicitConversionSequence> ConversionSequenceList;
    class InitListExpr;
    class InitializationKind;
    class InitializationSequence;
    class InitializedEntity;
    class IntegerLiteral;
    class LabelStmt;
    class LambdaExpr;
    class LangOptions;
    class LocalInstantiationScope;
    class LookupResult;
    class MacroInfo;
    typedef ArrayRef<std::pair<IdentifierInfo *, SourceLocation>> ModuleIdPath;
    class ModuleLoader;
    class MultiLevelTemplateArgumentList;
    class NamedDecl;
    class ObjCCategoryDecl;
    class ObjCCategoryImplDecl;
    class ObjCCompatibleAliasDecl;
    class ObjCContainerDecl;
    class ObjCImplDecl;
    class ObjCImplementationDecl;
    class ObjCInterfaceDecl;
    class ObjCIvarDecl;
    template <class T> class ObjCList;
    class ObjCMessageExpr;
    class ObjCMethodDecl;
    class ObjCPropertyDecl;
    class ObjCProtocolDecl;
    class OMPThreadPrivateDecl;
    class OMPRequiresDecl;
    class OMPDeclareReductionDecl;
    class OMPDeclareSimdDecl;
    class OMPClause;
    struct OMPVarListLocTy;
    struct OverloadCandidate;
    enum class OverloadCandidateParamOrder : char;
    enum OverloadCandidateRewriteKind : unsigned;
    class OverloadCandidateSet;
    class OverloadExpr;
    class ParenListExpr;
    class ParmVarDecl;
    class Preprocessor;
    class PseudoDestructorTypeStorage;
    class PseudoObjectExpr;
    class QualType;
    class StandardConversionSequence;
    class Stmt;
    class StringLiteral;
    class SwitchStmt;
    class TemplateArgument;
    class TemplateArgumentList;
    class TemplateArgumentLoc;
    class TemplateDecl;
    class TemplateInstantiationCallback;
    class TemplateParameterList;
    class TemplatePartialOrderingContext;
    class TemplateTemplateParmDecl;
    class Token;
    class TypeAliasDecl;
    class TypedefDecl;
    class TypedefNameDecl;
    class TypeLoc;
    class TypoCorrectionConsumer;
    class UnqualifiedId;
    class UnresolvedLookupExpr;
    class UnresolvedMemberExpr;
    class UnresolvedSetImpl;
    class UnresolvedSetIterator;
    class UsingDecl;
    class UsingShadowDecl;
    class ValueDecl;
    class VarDecl;
    class VarTemplateSpecializationDecl;
    class VisibilityAttr;
    class VisibleDeclConsumer;
    class IndirectFieldDecl;
    struct DeductionFailureInfo;
    class TemplateSpecCandidateSet;
  
  namespace sema {
    class AccessedEntity;
    class BlockScopeInfo;
    class Capture;
    class CapturedRegionScopeInfo;
    class CapturingScopeInfo;
    class CompoundScopeInfo;
    class DelayedDiagnostic;
    class DelayedDiagnosticPool;
    class FunctionScopeInfo;
    class LambdaScopeInfo;
    class PossiblyUnreachableDiag;
    class SemaPPCallbacks;
    class TemplateDeductionInfo;
  }
  
  namespace threadSafety {
    class BeforeSet;
    void threadSafetyCleanup(BeforeSet* Cache);
  }
  
  // FIXME: No way to easily map from TemplateTypeParmTypes to
  // TemplateTypeParmDecls, so we have this horrible PointerUnion.
  typedef std::pair<llvm::PointerUnion<const TemplateTypeParmType*, NamedDecl*>,
                    SourceLocation> UnexpandedParameterPack;
  
  /// Describes whether we've seen any nullability information for the given
  /// file.
  struct FileNullability {
    /// The first pointer declarator (of any pointer kind) in the file that does
    /// not have a corresponding nullability annotation.
    SourceLocation PointerLoc;
  
    /// The end location for the first pointer declarator in the file. Used for
    /// placing fix-its.
    SourceLocation PointerEndLoc;
  
    /// Which kind of pointer declarator we saw.
    uint8_t PointerKind;
  
    /// Whether we saw any type nullability annotations in the given file.
    bool SawTypeNullability = false;
  };
  
  /// A mapping from file IDs to a record of whether we've seen nullability
  /// information in that file.
  class FileNullabilityMap {
    /// A mapping from file IDs to the nullability information for each file ID.
    llvm::DenseMap<FileID, FileNullability> Map;
  
    /// A single-element cache based on the file ID.
    struct {
      FileID File;
      FileNullability Nullability;
    } Cache;
  
  public:
    FileNullability &operator[](FileID file) {
      // Check the single-element cache.
      if (file == Cache.File)
        return Cache.Nullability;
  
      // It's not in the single-element cache; flush the cache if we have one.
      if (!Cache.File.isInvalid()) {
        Map[Cache.File] = Cache.Nullability;
      }
  
      // Pull this entry into the cache.
      Cache.File = file;
      Cache.Nullability = Map[file];
      return Cache.Nullability;
    }
  };
  
  /// Keeps track of expected type during expression parsing. The type is tied to
  /// a particular token, all functions that update or consume the type take a
  /// start location of the token they are looking at as a parameter. This allows
  /// to avoid updating the type on hot paths in the parser.
  class PreferredTypeBuilder {
  public:
    PreferredTypeBuilder() = default;
    explicit PreferredTypeBuilder(QualType Type) : Type(Type) {}
  
    void enterCondition(Sema &S, SourceLocation Tok);
    void enterReturn(Sema &S, SourceLocation Tok);
    void enterVariableInit(SourceLocation Tok, Decl *D);
    /// Computing a type for the function argument may require running
    /// overloading, so we postpone its computation until it is actually needed.
    ///
    /// Clients should be very careful when using this funciton, as it stores a
    /// function_ref, clients should make sure all calls to get() with the same
    /// location happen while function_ref is alive.
    void enterFunctionArgument(SourceLocation Tok,
                               llvm::function_ref<QualType()> ComputeType);
  
    void enterParenExpr(SourceLocation Tok, SourceLocation LParLoc);
    void enterUnary(Sema &S, SourceLocation Tok, tok::TokenKind OpKind,
                    SourceLocation OpLoc);
    void enterBinary(Sema &S, SourceLocation Tok, Expr *LHS, tok::TokenKind Op);
    void enterMemAccess(Sema &S, SourceLocation Tok, Expr *Base);
    void enterSubscript(Sema &S, SourceLocation Tok, Expr *LHS);
    /// Handles all type casts, including C-style cast, C++ casts, etc.
    void enterTypeCast(SourceLocation Tok, QualType CastType);
  
    QualType get(SourceLocation Tok) const {
      if (Tok != ExpectedLoc)
        return QualType();
      if (!Type.isNull())
        return Type;
      if (ComputeType)
        return ComputeType();
      return QualType();
    }
  
  private:
    /// Start position of a token for which we store expected type.
    SourceLocation ExpectedLoc;
    /// Expected type for a token starting at ExpectedLoc.
    QualType Type;
    /// A function to compute expected type at ExpectedLoc. It is only considered
    /// if Type is null.
    llvm::function_ref<QualType()> ComputeType;
  };
  
  /// Sema - This implements semantic analysis and AST building for C.
  class Sema final {
    Sema(const Sema &) = delete;
    void operator=(const Sema &) = delete;
  
    /// A key method to reduce duplicate debug info from Sema.
    virtual void anchor();
  
    ///Source of additional semantic information.
    ExternalSemaSource *ExternalSource;
  
    ///Whether Sema has generated a multiplexer and has to delete it.
    bool isMultiplexExternalSource;
  
    static bool mightHaveNonExternalLinkage(const DeclaratorDecl *FD);
  
    bool isVisibleSlow(const NamedDecl *D);
  
    /// Determine whether two declarations should be linked together, given that
    /// the old declaration might not be visible and the new declaration might
    /// not have external linkage.
    bool shouldLinkPossiblyHiddenDecl(const NamedDecl *Old,
                                      const NamedDecl *New) {
      if (isVisible(Old))
       return true;
      // See comment in below overload for why it's safe to compute the linkage
      // of the new declaration here.
      if (New->isExternallyDeclarable()) {
        assert(Old->isExternallyDeclarable() &&
               "should not have found a non-externally-declarable previous decl");
        return true;
      }
      return false;
    }
    bool shouldLinkPossiblyHiddenDecl(LookupResult &Old, const NamedDecl *New);
  
    void setupImplicitSpecialMemberType(CXXMethodDecl *SpecialMem,
                                        QualType ResultTy,
                                        ArrayRef<QualType> Args);
  
  public:
    /// The maximum alignment, same as in llvm::Value. We duplicate them here
    /// because that allows us not to duplicate the constants in clang code,
    /// which we must to since we can't directly use the llvm constants.
    /// The value is verified against llvm here: lib/CodeGen/CGDecl.cpp
    ///
    /// This is the greatest alignment value supported by load, store, and alloca
    /// instructions, and global values.
    static const unsigned MaxAlignmentExponent = 29;
    static const unsigned MaximumAlignment = 1u << MaxAlignmentExponent;
  
    typedef OpaquePtr<DeclGroupRef> DeclGroupPtrTy;
    typedef OpaquePtr<TemplateName> TemplateTy;
    typedef OpaquePtr<QualType> TypeTy;
  
    OpenCLOptions OpenCLFeatures;
    FPOptions FPFeatures;
  
    const LangOptions &LangOpts;
    Preprocessor &PP;
    ASTContext &Context;
    ASTConsumer &Consumer;
    DiagnosticsEngine &Diags;
    SourceManager &SourceMgr;
    api_notes::APINotesManager APINotes;
  
    /// Flag indicating whether or not to collect detailed statistics.
    bool CollectStats;
  
    /// Code-completion consumer.
    CodeCompleteConsumer *CodeCompleter;
  
    /// CurContext - This is the current declaration context of parsing.
    DeclContext *CurContext;
  
    /// Generally null except when we temporarily switch decl contexts,
    /// like in \see ActOnObjCTemporaryExitContainerContext.
    DeclContext *OriginalLexicalContext;
  
    /// VAListTagName - The declaration name corresponding to __va_list_tag.
    /// This is used as part of a hack to omit that class from ADL results.
    DeclarationName VAListTagName;
  
    bool MSStructPragmaOn; // True when \#pragma ms_struct on
  
    /// Controls member pointer representation format under the MS ABI.
    LangOptions::PragmaMSPointersToMembersKind
        MSPointerToMemberRepresentationMethod;
  
    /// Stack of active SEH __finally scopes.  Can be empty.
    SmallVector<Scope*, 2> CurrentSEHFinally;
  
    /// Source location for newly created implicit MSInheritanceAttrs
    SourceLocation ImplicitMSInheritanceAttrLoc;
  
    /// Holds TypoExprs that are created from `createDelayedTypo`. This is used by
    /// `TransformTypos` in order to keep track of any TypoExprs that are created
    /// recursively during typo correction and wipe them away if the correction
    /// fails.
    llvm::SmallVector<TypoExpr *, 2> TypoExprs;
  
    /// pragma clang section kind
    enum PragmaClangSectionKind {
      PCSK_Invalid      = 0,
      PCSK_BSS          = 1,
      PCSK_Data         = 2,
      PCSK_Rodata       = 3,
      PCSK_Text         = 4,
      PCSK_Relro        = 5
     };
  
    enum PragmaClangSectionAction {
      PCSA_Set     = 0,
      PCSA_Clear   = 1
    };
  
    struct PragmaClangSection {
      std::string SectionName;
      bool Valid = false;
      SourceLocation PragmaLocation;
  
      void Act(SourceLocation PragmaLocation,
               PragmaClangSectionAction Action,
               StringLiteral* Name);
     };
  
     PragmaClangSection PragmaClangBSSSection;
     PragmaClangSection PragmaClangDataSection;
     PragmaClangSection PragmaClangRodataSection;
     PragmaClangSection PragmaClangRelroSection;
     PragmaClangSection PragmaClangTextSection;
  
    enum PragmaMsStackAction {
      PSK_Reset     = 0x0,                // #pragma ()
      PSK_Set       = 0x1,                // #pragma (value)
      PSK_Push      = 0x2,                // #pragma (push[, id])
      PSK_Pop       = 0x4,                // #pragma (pop[, id])
      PSK_Show      = 0x8,                // #pragma (show) -- only for "pack"!
      PSK_Push_Set  = PSK_Push | PSK_Set, // #pragma (push[, id], value)
      PSK_Pop_Set   = PSK_Pop | PSK_Set,  // #pragma (pop[, id], value)
    };
  
    template<typename ValueType>
    struct PragmaStack {
      struct Slot {
        llvm::StringRef StackSlotLabel;
        ValueType Value;
        SourceLocation PragmaLocation;
        SourceLocation PragmaPushLocation;
        Slot(llvm::StringRef StackSlotLabel, ValueType Value,
             SourceLocation PragmaLocation, SourceLocation PragmaPushLocation)
            : StackSlotLabel(StackSlotLabel), Value(Value),
              PragmaLocation(PragmaLocation),
              PragmaPushLocation(PragmaPushLocation) {}
      };
      void Act(SourceLocation PragmaLocation,
               PragmaMsStackAction Action,
               llvm::StringRef StackSlotLabel,
               ValueType Value);
  
      // MSVC seems to add artificial slots to #pragma stacks on entering a C++
      // method body to restore the stacks on exit, so it works like this:
      //
      //   struct S {
      //     #pragma <name>(push, InternalPragmaSlot, <current_pragma_value>)
      //     void Method {}
      //     #pragma <name>(pop, InternalPragmaSlot)
      //   };
      //
      // It works even with #pragma vtordisp, although MSVC doesn't support
      //   #pragma vtordisp(push [, id], n)
      // syntax.
      //
      // Push / pop a named sentinel slot.
      void SentinelAction(PragmaMsStackAction Action, StringRef Label) {
        assert((Action == PSK_Push || Action == PSK_Pop) &&
               "Can only push / pop #pragma stack sentinels!");
        Act(CurrentPragmaLocation, Action, Label, CurrentValue);
      }
  
      // Constructors.
      explicit PragmaStack(const ValueType &Default)
          : DefaultValue(Default), CurrentValue(Default) {}
  
      bool hasValue() const { return CurrentValue != DefaultValue; }
  
      SmallVector<Slot, 2> Stack;
      ValueType DefaultValue; // Value used for PSK_Reset action.
      ValueType CurrentValue;
      SourceLocation CurrentPragmaLocation;
    };
    // FIXME: We should serialize / deserialize these if they occur in a PCH (but
    // we shouldn't do so if they're in a module).
  
    /// Whether to insert vtordisps prior to virtual bases in the Microsoft
    /// C++ ABI.  Possible values are 0, 1, and 2, which mean:
    ///
    /// 0: Suppress all vtordisps
    /// 1: Insert vtordisps in the presence of vbase overrides and non-trivial
    ///    structors
    /// 2: Always insert vtordisps to support RTTI on partially constructed
    ///    objects
    PragmaStack<MSVtorDispMode> VtorDispStack;
    // #pragma pack.
    // Sentinel to represent when the stack is set to mac68k alignment.
    static const unsigned kMac68kAlignmentSentinel = ~0U;
    PragmaStack<unsigned> PackStack;
    // The current #pragma pack values and locations at each #include.
    struct PackIncludeState {
      unsigned CurrentValue;
      SourceLocation CurrentPragmaLocation;
      bool HasNonDefaultValue, ShouldWarnOnInclude;
    };
    SmallVector<PackIncludeState, 8> PackIncludeStack;
    // Segment #pragmas.
    PragmaStack<StringLiteral *> DataSegStack;
    PragmaStack<StringLiteral *> BSSSegStack;
    PragmaStack<StringLiteral *> ConstSegStack;
    PragmaStack<StringLiteral *> CodeSegStack;
  
    // RAII object to push / pop sentinel slots for all MS #pragma stacks.
    // Actions should be performed only if we enter / exit a C++ method body.
    class PragmaStackSentinelRAII {
    public:
      PragmaStackSentinelRAII(Sema &S, StringRef SlotLabel, bool ShouldAct);
      ~PragmaStackSentinelRAII();
  
    private:
      Sema &S;
      StringRef SlotLabel;
      bool ShouldAct;
    };
  
    /// A mapping that describes the nullability we've seen in each header file.
    FileNullabilityMap NullabilityMap;
  
    /// Last section used with #pragma init_seg.
    StringLiteral *CurInitSeg;
    SourceLocation CurInitSegLoc;
  
    /// VisContext - Manages the stack for \#pragma GCC visibility.
    void *VisContext; // Really a "PragmaVisStack*"
  
    /// This an attribute introduced by \#pragma clang attribute.
    struct PragmaAttributeEntry {
      SourceLocation Loc;
      ParsedAttr *Attribute;
      SmallVector<attr::SubjectMatchRule, 4> MatchRules;
      bool IsUsed;
    };
  
    /// A push'd group of PragmaAttributeEntries.
    struct PragmaAttributeGroup {
      /// The location of the push attribute.
      SourceLocation Loc;
      /// The namespace of this push group.
      const IdentifierInfo *Namespace;
      SmallVector<PragmaAttributeEntry, 2> Entries;
    };
  
    SmallVector<PragmaAttributeGroup, 2> PragmaAttributeStack;
  
    /// The declaration that is currently receiving an attribute from the
    /// #pragma attribute stack.
    const Decl *PragmaAttributeCurrentTargetDecl;
  
    /// This represents the last location of a "#pragma clang optimize off"
    /// directive if such a directive has not been closed by an "on" yet. If
    /// optimizations are currently "on", this is set to an invalid location.
    SourceLocation OptimizeOffPragmaLocation;
  
    /// Flag indicating if Sema is building a recovery call expression.
    ///
    /// This flag is used to avoid building recovery call expressions
    /// if Sema is already doing so, which would cause infinite recursions.
    bool IsBuildingRecoveryCallExpr;
  
    /// Used to control the generation of ExprWithCleanups.
    CleanupInfo Cleanup;
  
    /// ExprCleanupObjects - This is the stack of objects requiring
    /// cleanup that are created by the current full expression.
    SmallVector<ExprWithCleanups::CleanupObject, 8> ExprCleanupObjects;
  
    /// Store a set of either DeclRefExprs or MemberExprs that contain a reference
    /// to a variable (constant) that may or may not be odr-used in this Expr, and
    /// we won't know until all lvalue-to-rvalue and discarded value conversions
    /// have been applied to all subexpressions of the enclosing full expression.
    /// This is cleared at the end of each full expression.
    using MaybeODRUseExprSet = llvm::SmallPtrSet<Expr *, 2>;
    MaybeODRUseExprSet MaybeODRUseExprs;
  
    std::unique_ptr<sema::FunctionScopeInfo> CachedFunctionScope;
  
    /// Stack containing information about each of the nested
    /// function, block, and method scopes that are currently active.
    SmallVector<sema::FunctionScopeInfo *, 4> FunctionScopes;
  
    /// The index of the first FunctionScope that corresponds to the current
    /// context.
    unsigned FunctionScopesStart = 0;
  
    ArrayRef<sema::FunctionScopeInfo*> getFunctionScopes() const {
      return llvm::makeArrayRef(FunctionScopes.begin() + FunctionScopesStart,
                                FunctionScopes.end());
    }
  
    /// Stack containing information needed when in C++2a an 'auto' is encountered
    /// in a function declaration parameter type specifier in order to invent a
    /// corresponding template parameter in the enclosing abbreviated function
    /// template. This information is also present in LambdaScopeInfo, stored in
    /// the FunctionScopes stack.
    SmallVector<InventedTemplateParameterInfo, 4> InventedParameterInfos;
  
    /// The index of the first InventedParameterInfo that refers to the current
    /// context.
    unsigned InventedParameterInfosStart = 0;
  
    ArrayRef<InventedTemplateParameterInfo> getInventedParameterInfos() const {
      return llvm::makeArrayRef(InventedParameterInfos.begin() +
                                    InventedParameterInfosStart,
                                InventedParameterInfos.end());
    }
  
    typedef LazyVector<TypedefNameDecl *, ExternalSemaSource,
                       &ExternalSemaSource::ReadExtVectorDecls, 2, 2>
      ExtVectorDeclsType;
  
    /// ExtVectorDecls - This is a list all the extended vector types. This allows
    /// us to associate a raw vector type with one of the ext_vector type names.
    /// This is only necessary for issuing pretty diagnostics.
    ExtVectorDeclsType ExtVectorDecls;
  
    /// FieldCollector - Collects CXXFieldDecls during parsing of C++ classes.
    std::unique_ptr<CXXFieldCollector> FieldCollector;
  
    typedef llvm::SmallSetVector<NamedDecl *, 16> NamedDeclSetType;
  
    /// Set containing all declared private fields that are not used.
    NamedDeclSetType UnusedPrivateFields;
  
    /// Set containing all typedefs that are likely unused.
    llvm::SmallSetVector<const TypedefNameDecl *, 4>
        UnusedLocalTypedefNameCandidates;
  
    /// Delete-expressions to be analyzed at the end of translation unit
    ///
    /// This list contains class members, and locations of delete-expressions
    /// that could not be proven as to whether they mismatch with new-expression
    /// used in initializer of the field.
    typedef std::pair<SourceLocation, bool> DeleteExprLoc;
    typedef llvm::SmallVector<DeleteExprLoc, 4> DeleteLocs;
    llvm::MapVector<FieldDecl *, DeleteLocs> DeleteExprs;
  
    typedef llvm::SmallPtrSet<const CXXRecordDecl*, 8> RecordDeclSetTy;
  
    /// PureVirtualClassDiagSet - a set of class declarations which we have
    /// emitted a list of pure virtual functions. Used to prevent emitting the
    /// same list more than once.
    std::unique_ptr<RecordDeclSetTy> PureVirtualClassDiagSet;
  
    /// ParsingInitForAutoVars - a set of declarations with auto types for which
    /// we are currently parsing the initializer.
    llvm::SmallPtrSet<const Decl*, 4> ParsingInitForAutoVars;
  
    /// Look for a locally scoped extern "C" declaration by the given name.
    NamedDecl *findLocallyScopedExternCDecl(DeclarationName Name);
  
    typedef LazyVector<VarDecl *, ExternalSemaSource,
                       &ExternalSemaSource::ReadTentativeDefinitions, 2, 2>
      TentativeDefinitionsType;
  
    /// All the tentative definitions encountered in the TU.
    TentativeDefinitionsType TentativeDefinitions;
  
    /// All the external declarations encoutered and used in the TU.
    SmallVector<VarDecl *, 4> ExternalDeclarations;
  
    typedef LazyVector<const DeclaratorDecl *, ExternalSemaSource,
                       &ExternalSemaSource::ReadUnusedFileScopedDecls, 2, 2>
      UnusedFileScopedDeclsType;
  
    /// The set of file scoped decls seen so far that have not been used
    /// and must warn if not used. Only contains the first declaration.
    UnusedFileScopedDeclsType UnusedFileScopedDecls;
  
    typedef LazyVector<CXXConstructorDecl *, ExternalSemaSource,
                       &ExternalSemaSource::ReadDelegatingConstructors, 2, 2>
      DelegatingCtorDeclsType;
  
    /// All the delegating constructors seen so far in the file, used for
    /// cycle detection at the end of the TU.
    DelegatingCtorDeclsType DelegatingCtorDecls;
  
    /// All the overriding functions seen during a class definition
    /// that had their exception spec checks delayed, plus the overridden
    /// function.
    SmallVector<std::pair<const CXXMethodDecl*, const CXXMethodDecl*>, 2>
      DelayedOverridingExceptionSpecChecks;
  
    /// All the function redeclarations seen during a class definition that had
    /// their exception spec checks delayed, plus the prior declaration they
    /// should be checked against. Except during error recovery, the new decl
    /// should always be a friend declaration, as that's the only valid way to
    /// redeclare a special member before its class is complete.
    SmallVector<std::pair<FunctionDecl*, FunctionDecl*>, 2>
      DelayedEquivalentExceptionSpecChecks;
  
    typedef llvm::MapVector<const FunctionDecl *,
                            std::unique_ptr<LateParsedTemplate>>
        LateParsedTemplateMapT;
    LateParsedTemplateMapT LateParsedTemplateMap;
  
    /// Callback to the parser to parse templated functions when needed.
    typedef void LateTemplateParserCB(void *P, LateParsedTemplate &LPT);
    typedef void LateTemplateParserCleanupCB(void *P);
    LateTemplateParserCB *LateTemplateParser;
    LateTemplateParserCleanupCB *LateTemplateParserCleanup;
    void *OpaqueParser;
  
    void SetLateTemplateParser(LateTemplateParserCB *LTP,
                               LateTemplateParserCleanupCB *LTPCleanup,
                               void *P) {
      LateTemplateParser = LTP;
      LateTemplateParserCleanup = LTPCleanup;
      OpaqueParser = P;
    }
  
    /// \brief Callback to the parser to parse a type expressed as a string.
    std::function<TypeResult(StringRef, StringRef, SourceLocation)>
      ParseTypeFromStringCallback;
  
    class DelayedDiagnostics;
  
    class DelayedDiagnosticsState {
      sema::DelayedDiagnosticPool *SavedPool;
      friend class Sema::DelayedDiagnostics;
    };
    typedef DelayedDiagnosticsState ParsingDeclState;
    typedef DelayedDiagnosticsState ProcessingContextState;
  
    /// A class which encapsulates the logic for delaying diagnostics
    /// during parsing and other processing.
    class DelayedDiagnostics {
      /// The current pool of diagnostics into which delayed
      /// diagnostics should go.
      sema::DelayedDiagnosticPool *CurPool;
  
    public:
      DelayedDiagnostics() : CurPool(nullptr) {}
  
      /// Adds a delayed diagnostic.
      void add(const sema::DelayedDiagnostic &diag); // in DelayedDiagnostic.h
  
      /// Determines whether diagnostics should be delayed.
      bool shouldDelayDiagnostics() { return CurPool != nullptr; }
  
      /// Returns the current delayed-diagnostics pool.
      sema::DelayedDiagnosticPool *getCurrentPool() const {
        return CurPool;
      }
  
      /// Enter a new scope.  Access and deprecation diagnostics will be
      /// collected in this pool.
      DelayedDiagnosticsState push(sema::DelayedDiagnosticPool &pool) {
        DelayedDiagnosticsState state;
        state.SavedPool = CurPool;
        CurPool = &pool;
        return state;
      }
  
      /// Leave a delayed-diagnostic state that was previously pushed.
      /// Do not emit any of the diagnostics.  This is performed as part
      /// of the bookkeeping of popping a pool "properly".
      void popWithoutEmitting(DelayedDiagnosticsState state) {
        CurPool = state.SavedPool;
      }
  
      /// Enter a new scope where access and deprecation diagnostics are
      /// not delayed.
      DelayedDiagnosticsState pushUndelayed() {
        DelayedDiagnosticsState state;
        state.SavedPool = CurPool;
        CurPool = nullptr;
        return state;
      }
  
      /// Undo a previous pushUndelayed().
      void popUndelayed(DelayedDiagnosticsState state) {
        assert(CurPool == nullptr);
        CurPool = state.SavedPool;
      }
    } DelayedDiagnostics;
  
    /// A RAII object to temporarily push a declaration context.
    class ContextRAII {
    private:
      Sema &S;
      DeclContext *SavedContext;
      ProcessingContextState SavedContextState;
      QualType SavedCXXThisTypeOverride;
      unsigned SavedFunctionScopesStart;
      unsigned SavedInventedParameterInfosStart;
  
    public:
      ContextRAII(Sema &S, DeclContext *ContextToPush, bool NewThisContext = true)
        : S(S), SavedContext(S.CurContext),
          SavedContextState(S.DelayedDiagnostics.pushUndelayed()),
          SavedCXXThisTypeOverride(S.CXXThisTypeOverride),
          SavedFunctionScopesStart(S.FunctionScopesStart),
          SavedInventedParameterInfosStart(S.InventedParameterInfosStart)
      {
        assert(ContextToPush && "pushing null context");
        S.CurContext = ContextToPush;
        if (NewThisContext)
          S.CXXThisTypeOverride = QualType();
        // Any saved FunctionScopes do not refer to this context.
        S.FunctionScopesStart = S.FunctionScopes.size();
        S.InventedParameterInfosStart = S.InventedParameterInfos.size();
      }
  
      void pop() {
        if (!SavedContext) return;
        S.CurContext = SavedContext;
        S.DelayedDiagnostics.popUndelayed(SavedContextState);
        S.CXXThisTypeOverride = SavedCXXThisTypeOverride;
        S.FunctionScopesStart = SavedFunctionScopesStart;
        S.InventedParameterInfosStart = SavedInventedParameterInfosStart;
        SavedContext = nullptr;
      }
  
      ~ContextRAII() {
        pop();
      }
    };
  
    /// Whether the AST is currently being rebuilt to correct immediate
    /// invocations. Immediate invocation candidates and references to consteval
    /// functions aren't tracked when this is set.
    bool RebuildingImmediateInvocation = false;
  
    /// Used to change context to isConstantEvaluated without pushing a heavy
    /// ExpressionEvaluationContextRecord object.
    bool isConstantEvaluatedOverride;
  
    bool isConstantEvaluated() {
      return ExprEvalContexts.back().isConstantEvaluated() ||
             isConstantEvaluatedOverride;
    }
  
    /// RAII object to handle the state changes required to synthesize
    /// a function body.
    class SynthesizedFunctionScope {
      Sema &S;
      Sema::ContextRAII SavedContext;
      bool PushedCodeSynthesisContext = false;
  
    public:
      SynthesizedFunctionScope(Sema &S, DeclContext *DC)
          : S(S), SavedContext(S, DC) {
        S.PushFunctionScope();
        S.PushExpressionEvaluationContext(
            Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
        if (auto *FD = dyn_cast<FunctionDecl>(DC))
          FD->setWillHaveBody(true);
        else
          assert(isa<ObjCMethodDecl>(DC));
      }
  
      void addContextNote(SourceLocation UseLoc) {
        assert(!PushedCodeSynthesisContext);
  
        Sema::CodeSynthesisContext Ctx;
        Ctx.Kind = Sema::CodeSynthesisContext::DefiningSynthesizedFunction;
        Ctx.PointOfInstantiation = UseLoc;
        Ctx.Entity = cast<Decl>(S.CurContext);
        S.pushCodeSynthesisContext(Ctx);
  
        PushedCodeSynthesisContext = true;
      }
  
      ~SynthesizedFunctionScope() {
        if (PushedCodeSynthesisContext)
          S.popCodeSynthesisContext();
        if (auto *FD = dyn_cast<FunctionDecl>(S.CurContext))
          FD->setWillHaveBody(false);
        S.PopExpressionEvaluationContext();
        S.PopFunctionScopeInfo();
      }
    };
  
    /// WeakUndeclaredIdentifiers - Identifiers contained in
    /// \#pragma weak before declared. rare. may alias another
    /// identifier, declared or undeclared
    llvm::MapVector<IdentifierInfo *, WeakInfo> WeakUndeclaredIdentifiers;
  
    /// ExtnameUndeclaredIdentifiers - Identifiers contained in
    /// \#pragma redefine_extname before declared.  Used in Solaris system headers
    /// to define functions that occur in multiple standards to call the version
    /// in the currently selected standard.
    llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*> ExtnameUndeclaredIdentifiers;
  
  
    /// Load weak undeclared identifiers from the external source.
    void LoadExternalWeakUndeclaredIdentifiers();
  
    /// WeakTopLevelDecl - Translation-unit scoped declarations generated by
    /// \#pragma weak during processing of other Decls.
    /// I couldn't figure out a clean way to generate these in-line, so
    /// we store them here and handle separately -- which is a hack.
    /// It would be best to refactor this.
    SmallVector<Decl*,2> WeakTopLevelDecl;
  
    IdentifierResolver IdResolver;
  
    /// Translation Unit Scope - useful to Objective-C actions that need
    /// to lookup file scope declarations in the "ordinary" C decl namespace.
    /// For example, user-defined classes, built-in "id" type, etc.
    Scope *TUScope;
  
    /// The C++ "std" namespace, where the standard library resides.
    LazyDeclPtr StdNamespace;
  
    /// The C++ "std::bad_alloc" class, which is defined by the C++
    /// standard library.
    LazyDeclPtr StdBadAlloc;
  
    /// The C++ "std::align_val_t" enum class, which is defined by the C++
    /// standard library.
    LazyDeclPtr StdAlignValT;
  
    /// The C++ "std::experimental" namespace, where the experimental parts
    /// of the standard library resides.
    NamespaceDecl *StdExperimentalNamespaceCache;
  
    /// The C++ "std::initializer_list" template, which is defined in
    /// \<initializer_list>.
    ClassTemplateDecl *StdInitializerList;
  
    /// The C++ "std::coroutine_traits" template, which is defined in
    /// \<coroutine_traits>
    ClassTemplateDecl *StdCoroutineTraitsCache;
  
    /// The C++ "type_info" declaration, which is defined in \<typeinfo>.
    RecordDecl *CXXTypeInfoDecl;
  
    /// The MSVC "_GUID" struct, which is defined in MSVC header files.
    RecordDecl *MSVCGuidDecl;
  
    /// Caches identifiers/selectors for NSFoundation APIs.
    std::unique_ptr<NSAPI> NSAPIObj;
  
    /// The declaration of the Objective-C NSNumber class.
    ObjCInterfaceDecl *NSNumberDecl;
  
    /// The declaration of the Objective-C NSValue class.
    ObjCInterfaceDecl *NSValueDecl;
  
    /// Pointer to NSNumber type (NSNumber *).
    QualType NSNumberPointer;
  
    /// Pointer to NSValue type (NSValue *).
    QualType NSValuePointer;
  
    /// The Objective-C NSNumber methods used to create NSNumber literals.
    ObjCMethodDecl *NSNumberLiteralMethods[NSAPI::NumNSNumberLiteralMethods];
  
    /// The declaration of the Objective-C NSString class.
    ObjCInterfaceDecl *NSStringDecl;
  
    /// Pointer to NSString type (NSString *).
    QualType NSStringPointer;
  
    /// The declaration of the stringWithUTF8String: method.
    ObjCMethodDecl *StringWithUTF8StringMethod;
  
    /// The declaration of the valueWithBytes:objCType: method.
    ObjCMethodDecl *ValueWithBytesObjCTypeMethod;
  
    /// The declaration of the Objective-C NSArray class.
    ObjCInterfaceDecl *NSArrayDecl;
  
    /// The declaration of the arrayWithObjects:count: method.
    ObjCMethodDecl *ArrayWithObjectsMethod;
  
    /// The declaration of the Objective-C NSDictionary class.
    ObjCInterfaceDecl *NSDictionaryDecl;
  
    /// The declaration of the dictionaryWithObjects:forKeys:count: method.
    ObjCMethodDecl *DictionaryWithObjectsMethod;
  
    /// id<NSCopying> type.
    QualType QIDNSCopying;
  
    /// will hold 'respondsToSelector:'
    Selector RespondsToSelectorSel;
  
    /// A flag to remember whether the implicit forms of operator new and delete
    /// have been declared.
    bool GlobalNewDeleteDeclared;
  
    /// A flag to indicate that we're in a context that permits abstract
    /// references to fields.  This is really a
    bool AllowAbstractFieldReference;
  
    /// Describes how the expressions currently being parsed are
    /// evaluated at run-time, if at all.
    enum class ExpressionEvaluationContext {
      /// The current expression and its subexpressions occur within an
      /// unevaluated operand (C++11 [expr]p7), such as the subexpression of
      /// \c sizeof, where the type of the expression may be significant but
      /// no code will be generated to evaluate the value of the expression at
      /// run time.
      Unevaluated,
  
      /// The current expression occurs within a braced-init-list within
      /// an unevaluated operand. This is mostly like a regular unevaluated
      /// context, except that we still instantiate constexpr functions that are
      /// referenced here so that we can perform narrowing checks correctly.
      UnevaluatedList,
  
      /// The current expression occurs within a discarded statement.
      /// This behaves largely similarly to an unevaluated operand in preventing
      /// definitions from being required, but not in other ways.
      DiscardedStatement,
  
      /// The current expression occurs within an unevaluated
      /// operand that unconditionally permits abstract references to
      /// fields, such as a SIZE operator in MS-style inline assembly.
      UnevaluatedAbstract,
  
      /// The current context is "potentially evaluated" in C++11 terms,
      /// but the expression is evaluated at compile-time (like the values of
      /// cases in a switch statement).
      ConstantEvaluated,
  
      /// The current expression is potentially evaluated at run time,
      /// which means that code may be generated to evaluate the value of the
      /// expression at run time.
      PotentiallyEvaluated,
  
      /// The current expression is potentially evaluated, but any
      /// declarations referenced inside that expression are only used if
      /// in fact the current expression is used.
      ///
      /// This value is used when parsing default function arguments, for which
      /// we would like to provide diagnostics (e.g., passing non-POD arguments
      /// through varargs) but do not want to mark declarations as "referenced"
      /// until the default argument is used.
      PotentiallyEvaluatedIfUsed
    };
  
    using ImmediateInvocationCandidate = llvm::PointerIntPair<ConstantExpr *, 1>;
  
    /// Data structure used to record current or nested
    /// expression evaluation contexts.
    struct ExpressionEvaluationContextRecord {
      /// The expression evaluation context.
      ExpressionEvaluationContext Context;
  
      /// Whether the enclosing context needed a cleanup.
      CleanupInfo ParentCleanup;
  
      /// Whether we are in a decltype expression.
      bool IsDecltype;
  
      /// The number of active cleanup objects when we entered
      /// this expression evaluation context.
      unsigned NumCleanupObjects;
  
      /// The number of typos encountered during this expression evaluation
      /// context (i.e. the number of TypoExprs created).
      unsigned NumTypos;
  
      MaybeODRUseExprSet SavedMaybeODRUseExprs;
  
      /// The lambdas that are present within this context, if it
      /// is indeed an unevaluated context.
      SmallVector<LambdaExpr *, 2> Lambdas;
  
      /// The declaration that provides context for lambda expressions
      /// and block literals if the normal declaration context does not
      /// suffice, e.g., in a default function argument.
      Decl *ManglingContextDecl;
  
      /// If we are processing a decltype type, a set of call expressions
      /// for which we have deferred checking the completeness of the return type.
      SmallVector<CallExpr *, 8> DelayedDecltypeCalls;
  
      /// If we are processing a decltype type, a set of temporary binding
      /// expressions for which we have deferred checking the destructor.
      SmallVector<CXXBindTemporaryExpr *, 8> DelayedDecltypeBinds;
  
      llvm::SmallPtrSet<const Expr *, 8> PossibleDerefs;
  
      /// Expressions appearing as the LHS of a volatile assignment in this
      /// context. We produce a warning for these when popping the context if
      /// they are not discarded-value expressions nor unevaluated operands.
      SmallVector<Expr*, 2> VolatileAssignmentLHSs;
  
      /// Set of candidates for starting an immediate invocation.
      llvm::SmallVector<ImmediateInvocationCandidate, 4> ImmediateInvocationCandidates;
  
      /// Set of DeclRefExprs referencing a consteval function when used in a
      /// context not already known to be immediately invoked.
      llvm::SmallPtrSet<DeclRefExpr *, 4> ReferenceToConsteval;
  
      /// \brief Describes whether we are in an expression constext which we have
      /// to handle differently.
      enum ExpressionKind {
        EK_Decltype, EK_TemplateArgument, EK_Other
      } ExprContext;
  
      ExpressionEvaluationContextRecord(ExpressionEvaluationContext Context,
                                        unsigned NumCleanupObjects,
                                        CleanupInfo ParentCleanup,
                                        Decl *ManglingContextDecl,
                                        ExpressionKind ExprContext)
          : Context(Context), ParentCleanup(ParentCleanup),
            NumCleanupObjects(NumCleanupObjects), NumTypos(0),
            ManglingContextDecl(ManglingContextDecl), ExprContext(ExprContext) {}
  
      bool isUnevaluated() const {
        return Context == ExpressionEvaluationContext::Unevaluated ||
               Context == ExpressionEvaluationContext::UnevaluatedAbstract ||
               Context == ExpressionEvaluationContext::UnevaluatedList;
      }
      bool isConstantEvaluated() const {
        return Context == ExpressionEvaluationContext::ConstantEvaluated;
      }
    };
  
    /// A stack of expression evaluation contexts.
    SmallVector<ExpressionEvaluationContextRecord, 8> ExprEvalContexts;
  
    /// Emit a warning for all pending noderef expressions that we recorded.
    void WarnOnPendingNoDerefs(ExpressionEvaluationContextRecord &Rec);
  
    /// Compute the mangling number context for a lambda expression or
    /// block literal. Also return the extra mangling decl if any.
    ///
    /// \param DC - The DeclContext containing the lambda expression or
    /// block literal.
    std::tuple<MangleNumberingContext *, Decl *>
    getCurrentMangleNumberContext(const DeclContext *DC);
  
  
    /// SpecialMemberOverloadResult - The overloading result for a special member
    /// function.
    ///
    /// This is basically a wrapper around PointerIntPair. The lowest bits of the
    /// integer are used to determine whether overload resolution succeeded.
    class SpecialMemberOverloadResult {
    public:
      enum Kind {
        NoMemberOrDeleted,
        Ambiguous,
        Success
      };
  
    private:
      llvm::PointerIntPair<CXXMethodDecl*, 2> Pair;
  
    public:
      SpecialMemberOverloadResult() : Pair() {}
      SpecialMemberOverloadResult(CXXMethodDecl *MD)
          : Pair(MD, MD->isDeleted() ? NoMemberOrDeleted : Success) {}
  
      CXXMethodDecl *getMethod() const { return Pair.getPointer(); }
      void setMethod(CXXMethodDecl *MD) { Pair.setPointer(MD); }
  
      Kind getKind() const { return static_cast<Kind>(Pair.getInt()); }
      void setKind(Kind K) { Pair.setInt(K); }
    };
  
    class SpecialMemberOverloadResultEntry
        : public llvm::FastFoldingSetNode,
          public SpecialMemberOverloadResult {
    public:
      SpecialMemberOverloadResultEntry(const llvm::FoldingSetNodeID &ID)
        : FastFoldingSetNode(ID)
      {}
    };
  
    /// A cache of special member function overload resolution results
    /// for C++ records.
    llvm::FoldingSet<SpecialMemberOverloadResultEntry> SpecialMemberCache;
  
    /// A cache of the flags available in enumerations with the flag_bits
    /// attribute.
    mutable llvm::DenseMap<const EnumDecl*, llvm::APInt> FlagBitsCache;
  
    /// The kind of translation unit we are processing.
    ///
    /// When we're processing a complete translation unit, Sema will perform
    /// end-of-translation-unit semantic tasks (such as creating
    /// initializers for tentative definitions in C) once parsing has
    /// completed. Modules and precompiled headers perform different kinds of
    /// checks.
    TranslationUnitKind TUKind;
  
    llvm::BumpPtrAllocator BumpAlloc;
  
    /// The number of SFINAE diagnostics that have been trapped.
    unsigned NumSFINAEErrors;
  
    typedef llvm::DenseMap<ParmVarDecl *, llvm::TinyPtrVector<ParmVarDecl *>>
      UnparsedDefaultArgInstantiationsMap;
  
    /// A mapping from parameters with unparsed default arguments to the
    /// set of instantiations of each parameter.
    ///
    /// This mapping is a temporary data structure used when parsing
    /// nested class templates or nested classes of class templates,
    /// where we might end up instantiating an inner class before the
    /// default arguments of its methods have been parsed.
    UnparsedDefaultArgInstantiationsMap UnparsedDefaultArgInstantiations;
  
    // Contains the locations of the beginning of unparsed default
    // argument locations.
    llvm::DenseMap<ParmVarDecl *, SourceLocation> UnparsedDefaultArgLocs;
  
    /// UndefinedInternals - all the used, undefined objects which require a
    /// definition in this translation unit.
    llvm::MapVector<NamedDecl *, SourceLocation> UndefinedButUsed;
  
    /// Determine if VD, which must be a variable or function, is an external
    /// symbol that nonetheless can't be referenced from outside this translation
    /// unit because its type has no linkage and it's not extern "C".
    bool isExternalWithNoLinkageType(ValueDecl *VD);
  
    /// Obtain a sorted list of functions that are undefined but ODR-used.
    void getUndefinedButUsed(
        SmallVectorImpl<std::pair<NamedDecl *, SourceLocation> > &Undefined);
  
    /// Retrieves list of suspicious delete-expressions that will be checked at
    /// the end of translation unit.
    const llvm::MapVector<FieldDecl *, DeleteLocs> &
    getMismatchingDeleteExpressions() const;
  
    typedef std::pair<ObjCMethodList, ObjCMethodList> GlobalMethods;
    typedef llvm::DenseMap<Selector, GlobalMethods> GlobalMethodPool;
  
    /// Method Pool - allows efficient lookup when typechecking messages to "id".
    /// We need to maintain a list, since selectors can have differing signatures
    /// across classes. In Cocoa, this happens to be extremely uncommon (only 1%
    /// of selectors are "overloaded").
    /// At the head of the list it is recorded whether there were 0, 1, or >= 2
    /// methods inside categories with a particular selector.
    GlobalMethodPool MethodPool;
  
    /// Method selectors used in a \@selector expression. Used for implementation
    /// of -Wselector.
    llvm::MapVector<Selector, SourceLocation> ReferencedSelectors;
  
    /// List of SourceLocations where 'self' is implicitly retained inside a
    /// block.
    llvm::SmallVector<std::pair<SourceLocation, const BlockDecl *>, 1>
        ImplicitlyRetainedSelfLocs;
  
    /// Kinds of C++ special members.
    enum CXXSpecialMember {
      CXXDefaultConstructor,
      CXXCopyConstructor,
      CXXMoveConstructor,
      CXXCopyAssignment,
      CXXMoveAssignment,
      CXXDestructor,
      CXXInvalid
    };
  
    typedef llvm::PointerIntPair<CXXRecordDecl *, 3, CXXSpecialMember>
        SpecialMemberDecl;
  
    /// The C++ special members which we are currently in the process of
    /// declaring. If this process recursively triggers the declaration of the
    /// same special member, we should act as if it is not yet declared.
    llvm::SmallPtrSet<SpecialMemberDecl, 4> SpecialMembersBeingDeclared;
  
    /// Kinds of defaulted comparison operator functions.
    enum class DefaultedComparisonKind : unsigned char {
      /// This is not a defaultable comparison operator.
      None,
      /// This is an operator== that should be implemented as a series of
      /// subobject comparisons.
      Equal,
      /// This is an operator<=> that should be implemented as a series of
      /// subobject comparisons.
      ThreeWay,
      /// This is an operator!= that should be implemented as a rewrite in terms
      /// of a == comparison.
      NotEqual,
      /// This is an <, <=, >, or >= that should be implemented as a rewrite in
      /// terms of a <=> comparison.
      Relational,
    };
  
    /// The function definitions which were renamed as part of typo-correction
    /// to match their respective declarations. We want to keep track of them
    /// to ensure that we don't emit a "redefinition" error if we encounter a
    /// correctly named definition after the renamed definition.
    llvm::SmallPtrSet<const NamedDecl *, 4> TypoCorrectedFunctionDefinitions;
  
    /// Stack of types that correspond to the parameter entities that are
    /// currently being copy-initialized. Can be empty.
    llvm::SmallVector<QualType, 4> CurrentParameterCopyTypes;
  
    void ReadMethodPool(Selector Sel);
    void updateOutOfDateSelector(Selector Sel);
  
    /// Private Helper predicate to check for 'self'.
    bool isSelfExpr(Expr *RExpr);
    bool isSelfExpr(Expr *RExpr, const ObjCMethodDecl *Method);
  
    /// Cause the active diagnostic on the DiagosticsEngine to be
    /// emitted. This is closely coupled to the SemaDiagnosticBuilder class and
    /// should not be used elsewhere.
    void EmitCurrentDiagnostic(unsigned DiagID);
  
    /// Records and restores the FPFeatures state on entry/exit of compound
    /// statements.
    class FPFeaturesStateRAII {
    public:
      FPFeaturesStateRAII(Sema &S) : S(S), OldFPFeaturesState(S.FPFeatures) {}
      ~FPFeaturesStateRAII() { S.FPFeatures = OldFPFeaturesState; }
  
    private:
      Sema& S;
      FPOptions OldFPFeaturesState;
    };
  
    void addImplicitTypedef(StringRef Name, QualType T);
  
    bool WarnedStackExhausted = false;
  
  public:
    Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
         TranslationUnitKind TUKind = TU_Complete,
         CodeCompleteConsumer *CompletionConsumer = nullptr);
    ~Sema();
  
    /// Perform initialization that occurs after the parser has been
    /// initialized but before it parses anything.
    void Initialize();
  
    const LangOptions &getLangOpts() const { return LangOpts; }
    OpenCLOptions &getOpenCLOptions() { return OpenCLFeatures; }
    FPOptions     &getFPOptions() { return FPFeatures; }
  
    DiagnosticsEngine &getDiagnostics() const { return Diags; }
    SourceManager &getSourceManager() const { return SourceMgr; }
    Preprocessor &getPreprocessor() const { return PP; }
    ASTContext &getASTContext() const { return Context; }
    ASTConsumer &getASTConsumer() const { return Consumer; }
    ASTMutationListener *getASTMutationListener() const;
    ExternalSemaSource* getExternalSource() const { return ExternalSource; }
  
    ///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 addExternalSource(ExternalSemaSource *E);
  
    void PrintStats() const;
  
    /// Warn that the stack is nearly exhausted.
    void warnStackExhausted(SourceLocation Loc);
  
    /// Run some code with "sufficient" stack space. (Currently, at least 256K is
    /// guaranteed). Produces a warning if we're low on stack space and allocates
    /// more in that case. Use this in code that may recurse deeply (for example,
    /// in template instantiation) to avoid stack overflow.
    void runWithSufficientStackSpace(SourceLocation Loc,
                                     llvm::function_ref<void()> Fn);
  
    /// Helper class that creates diagnostics with optional
    /// template instantiation stacks.
    ///
    /// This class provides a wrapper around the basic DiagnosticBuilder
    /// class that emits diagnostics. SemaDiagnosticBuilder is
    /// responsible for emitting the diagnostic (as DiagnosticBuilder
    /// does) and, if the diagnostic comes from inside a template
    /// instantiation, printing the template instantiation stack as
    /// well.
    class SemaDiagnosticBuilder : public DiagnosticBuilder {
      Sema &SemaRef;
      unsigned DiagID;
  
    public:
      SemaDiagnosticBuilder(DiagnosticBuilder &DB, Sema &SemaRef, unsigned DiagID)
        : DiagnosticBuilder(DB), SemaRef(SemaRef), DiagID(DiagID) { }
  
      // This is a cunning lie. DiagnosticBuilder actually performs move
      // construction in its copy constructor (but due to varied uses, it's not
      // possible to conveniently express this as actual move construction). So
      // the default copy ctor here is fine, because the base class disables the
      // source anyway, so the user-defined ~SemaDiagnosticBuilder is a safe no-op
      // in that case anwyay.
      SemaDiagnosticBuilder(const SemaDiagnosticBuilder&) = default;
  
      ~SemaDiagnosticBuilder() {
        // If we aren't active, there is nothing to do.
        if (!isActive()) return;
  
        // Otherwise, we need to emit the diagnostic. First flush the underlying
        // DiagnosticBuilder data, and clear the diagnostic builder itself so it
        // won't emit the diagnostic in its own destructor.
        //
        // This seems wasteful, in that as written the DiagnosticBuilder dtor will
        // do its own needless checks to see if the diagnostic needs to be
        // emitted. However, because we take care to ensure that the builder
        // objects never escape, a sufficiently smart compiler will be able to
        // eliminate that code.
        FlushCounts();
        Clear();
  
        // Dispatch to Sema to emit the diagnostic.
        SemaRef.EmitCurrentDiagnostic(DiagID);
      }
  
      /// Teach operator<< to produce an object of the correct type.
      template<typename T>
      friend const SemaDiagnosticBuilder &operator<<(
          const SemaDiagnosticBuilder &Diag, const T &Value) {
        const DiagnosticBuilder &BaseDiag = Diag;
        BaseDiag << Value;
        return Diag;
      }
    };
  
    /// Emit a diagnostic.
    SemaDiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID) {
      DiagnosticBuilder DB = Diags.Report(Loc, DiagID);
      return SemaDiagnosticBuilder(DB, *this, DiagID);
    }
  
    /// Emit a partial diagnostic.
    SemaDiagnosticBuilder Diag(SourceLocation Loc, const PartialDiagnostic& PD);
  
    /// Build a partial diagnostic.
    PartialDiagnostic PDiag(unsigned DiagID = 0); // in SemaInternal.h
  
    bool findMacroSpelling(SourceLocation &loc, StringRef name);
  
    /// Get a string to suggest for zero-initialization of a type.
    std::string
    getFixItZeroInitializerForType(QualType T, SourceLocation Loc) const;
    std::string getFixItZeroLiteralForType(QualType T, SourceLocation Loc) const;
  
    /// Calls \c Lexer::getLocForEndOfToken()
    SourceLocation getLocForEndOfToken(SourceLocation Loc, unsigned Offset = 0);
  
    /// Retrieve the module loader associated with the preprocessor.
    ModuleLoader &getModuleLoader() const;
  
    /// Invent a new identifier for parameters of abbreviated templates.
    IdentifierInfo *
    InventAbbreviatedTemplateParameterTypeName(IdentifierInfo *ParamName,
                                               unsigned Index);
  
    void emitAndClearUnusedLocalTypedefWarnings();
  
    enum TUFragmentKind {
      /// The global module fragment, between 'module;' and a module-declaration.
      Global,
      /// A normal translation unit fragment. For a non-module unit, this is the
      /// entire translation unit. Otherwise, it runs from the module-declaration
      /// to the private-module-fragment (if any) or the end of the TU (if not).
      Normal,
      /// The private module fragment, between 'module :private;' and the end of
      /// the translation unit.
      Private
    };
  
    void ActOnStartOfTranslationUnit();
    void ActOnEndOfTranslationUnit();
    void ActOnEndOfTranslationUnitFragment(TUFragmentKind Kind);
  
    void CheckDelegatingCtorCycles();
  
    Scope *getScopeForContext(DeclContext *Ctx);
  
    void PushFunctionScope();
    void PushBlockScope(Scope *BlockScope, BlockDecl *Block);
    sema::LambdaScopeInfo *PushLambdaScope();
  
    /// This is used to inform Sema what the current TemplateParameterDepth
    /// is during Parsing.  Currently it is used to pass on the depth
    /// when parsing generic lambda 'auto' parameters.
    void RecordParsingTemplateParameterDepth(unsigned Depth);
  
    void PushCapturedRegionScope(Scope *RegionScope, CapturedDecl *CD,
                                 RecordDecl *RD, CapturedRegionKind K,
                                 unsigned OpenMPCaptureLevel = 0);
  
    /// Custom deleter to allow FunctionScopeInfos to be kept alive for a short
    /// time after they've been popped.
    class PoppedFunctionScopeDeleter {
      Sema *Self;
  
    public:
      explicit PoppedFunctionScopeDeleter(Sema *Self) : Self(Self) {}
      void operator()(sema::FunctionScopeInfo *Scope) const;
    };
  
    using PoppedFunctionScopePtr =
        std::unique_ptr<sema::FunctionScopeInfo, PoppedFunctionScopeDeleter>;
  
    PoppedFunctionScopePtr
    PopFunctionScopeInfo(const sema::AnalysisBasedWarnings::Policy *WP = nullptr,
                         const Decl *D = nullptr,
                         QualType BlockType = QualType());
  
    sema::FunctionScopeInfo *getCurFunction() const {
      return FunctionScopes.empty() ? nullptr : FunctionScopes.back();
    }
  
    sema::FunctionScopeInfo *getEnclosingFunction() const;
  
    void setFunctionHasBranchIntoScope();
    void setFunctionHasBranchProtectedScope();
    void setFunctionHasIndirectGoto();
  
    void PushCompoundScope(bool IsStmtExpr);
    void PopCompoundScope();
  
    sema::CompoundScopeInfo &getCurCompoundScope() const;
  
    bool hasAnyUnrecoverableErrorsInThisFunction() const;
  
    /// Retrieve the current block, if any.
    sema::BlockScopeInfo *getCurBlock();
  
    /// Get the innermost lambda enclosing the current location, if any. This
    /// looks through intervening non-lambda scopes such as local functions and
    /// blocks.
    sema::LambdaScopeInfo *getEnclosingLambda() const;
  
    /// Retrieve the current lambda scope info, if any.
    /// \param IgnoreNonLambdaCapturingScope true if should find the top-most
    /// lambda scope info ignoring all inner capturing scopes that are not
    /// lambda scopes.
    sema::LambdaScopeInfo *
    getCurLambda(bool IgnoreNonLambdaCapturingScope = false);
  
    /// Retrieve the current generic lambda info, if any.
    sema::LambdaScopeInfo *getCurGenericLambda();
  
    /// Retrieve the current captured region, if any.
    sema::CapturedRegionScopeInfo *getCurCapturedRegion();
  
    /// WeakTopLevelDeclDecls - access to \#pragma weak-generated Decls
    SmallVectorImpl<Decl *> &WeakTopLevelDecls() { return WeakTopLevelDecl; }
  
    /// Called before parsing a function declarator belonging to a function
    /// declaration.
    void ActOnStartFunctionDeclarationDeclarator(Declarator &D,
                                                 unsigned TemplateParameterDepth);
  
    /// Called after parsing a function declarator belonging to a function
    /// declaration.
    void ActOnFinishFunctionDeclarationDeclarator(Declarator &D);
  
    void ActOnComment(SourceRange Comment);
  
    //===--------------------------------------------------------------------===//
    // Type Analysis / Processing: SemaType.cpp.
    //
  
    QualType BuildQualifiedType(QualType T, SourceLocation Loc, Qualifiers Qs,
                                const DeclSpec *DS = nullptr);
    QualType BuildQualifiedType(QualType T, SourceLocation Loc, unsigned CVRA,
                                const DeclSpec *DS = nullptr);
    QualType BuildPointerType(QualType T,
                              SourceLocation Loc, DeclarationName Entity);
    QualType BuildReferenceType(QualType T, bool LValueRef,
                                SourceLocation Loc, DeclarationName Entity);
    QualType BuildArrayType(QualType T, ArrayType::ArraySizeModifier ASM,
                            Expr *ArraySize, unsigned Quals,
                            SourceRange Brackets, DeclarationName Entity);
    QualType BuildVectorType(QualType T, Expr *VecSize, SourceLocation AttrLoc);
    QualType BuildExtVectorType(QualType T, Expr *ArraySize,
                                SourceLocation AttrLoc);
    QualType BuildAddressSpaceAttr(QualType &T, LangAS ASIdx, Expr *AddrSpace,
                                   SourceLocation AttrLoc);
  
    /// Same as above, but constructs the AddressSpace index if not provided.
    QualType BuildAddressSpaceAttr(QualType &T, Expr *AddrSpace,
                                   SourceLocation AttrLoc);
  
    bool CheckQualifiedFunctionForTypeId(QualType T, SourceLocation Loc);
  
    bool CheckFunctionReturnType(QualType T, SourceLocation Loc);
  
    /// Build a function type.
    ///
    /// This routine checks the function type according to C++ rules and
    /// under the assumption that the result type and parameter types have
    /// just been instantiated from a template. It therefore duplicates
    /// some of the behavior of GetTypeForDeclarator, but in a much
    /// simpler form that is only suitable for this narrow use case.
    ///
    /// \param T The return type of the function.
    ///
    /// \param ParamTypes The parameter types of the function. This array
    /// will be modified to account for adjustments to the types of the
    /// function parameters.
    ///
    /// \param Loc The location of the entity whose type involves this
    /// function type or, if there is no such entity, the location of the
    /// type that will have function type.
    ///
    /// \param Entity The name of the entity that involves the function
    /// type, if known.
    ///
    /// \param EPI Extra information about the function type. Usually this will
    /// be taken from an existing function with the same prototype.
    ///
    /// \returns A suitable function type, if there are no errors. The
    /// unqualified type will always be a FunctionProtoType.
    /// Otherwise, returns a NULL type.
    QualType BuildFunctionType(QualType T,
                               MutableArrayRef<QualType> ParamTypes,
                               SourceLocation Loc, DeclarationName Entity,
                               const FunctionProtoType::ExtProtoInfo &EPI);
  
    QualType BuildMemberPointerType(QualType T, QualType Class,
                                    SourceLocation Loc,
                                    DeclarationName Entity);
    QualType BuildBlockPointerType(QualType T,
                                   SourceLocation Loc, DeclarationName Entity);
    QualType BuildParenType(QualType T);
    QualType BuildAtomicType(QualType T, SourceLocation Loc);
    QualType BuildReadPipeType(QualType T,
                           SourceLocation Loc);
    QualType BuildWritePipeType(QualType T,
                           SourceLocation Loc);
  
    TypeSourceInfo *GetTypeForDeclarator(Declarator &D, Scope *S);
    TypeSourceInfo *GetTypeForDeclaratorCast(Declarator &D, QualType FromTy);
  
    /// Package the given type and TSI into a ParsedType.
    ParsedType CreateParsedType(QualType T, TypeSourceInfo *TInfo);
    DeclarationNameInfo GetNameForDeclarator(Declarator &D);
    DeclarationNameInfo GetNameFromUnqualifiedId(const UnqualifiedId &Name);
    static QualType GetTypeFromParser(ParsedType Ty,
                                      TypeSourceInfo **TInfo = nullptr);
    CanThrowResult canThrow(const Stmt *E);
    const FunctionProtoType *ResolveExceptionSpec(SourceLocation Loc,
                                                  const FunctionProtoType *FPT);
    void UpdateExceptionSpec(FunctionDecl *FD,
                             const FunctionProtoType::ExceptionSpecInfo &ESI);
    bool CheckSpecifiedExceptionType(QualType &T, SourceRange Range);
    bool CheckDistantExceptionSpec(QualType T);
    bool CheckEquivalentExceptionSpec(FunctionDecl *Old, FunctionDecl *New);
    bool CheckEquivalentExceptionSpec(
        const FunctionProtoType *Old, SourceLocation OldLoc,
        const FunctionProtoType *New, SourceLocation NewLoc);
    bool CheckEquivalentExceptionSpec(
        const PartialDiagnostic &DiagID, const PartialDiagnostic & NoteID,
        const FunctionProtoType *Old, SourceLocation OldLoc,
        const FunctionProtoType *New, SourceLocation NewLoc);
    bool handlerCanCatch(QualType HandlerType, QualType ExceptionType);
    bool CheckExceptionSpecSubset(const PartialDiagnostic &DiagID,
                                  const PartialDiagnostic &NestedDiagID,
                                  const PartialDiagnostic &NoteID,
                                  const PartialDiagnostic &NoThrowDiagID,
                                  const FunctionProtoType *Superset,
                                  SourceLocation SuperLoc,
                                  const FunctionProtoType *Subset,
                                  SourceLocation SubLoc);
    bool CheckParamExceptionSpec(const PartialDiagnostic &NestedDiagID,
                                 const PartialDiagnostic &NoteID,
                                 const FunctionProtoType *Target,
                                 SourceLocation TargetLoc,
                                 const FunctionProtoType *Source,
                                 SourceLocation SourceLoc);
  
    TypeResult ActOnTypeName(Scope *S, Declarator &D);
  
    /// The parser has parsed the context-sensitive type 'instancetype'
    /// in an Objective-C message declaration. Return the appropriate type.
    ParsedType ActOnObjCInstanceType(SourceLocation Loc);
  
    /// Abstract class used to diagnose incomplete types.
    struct TypeDiagnoser {
      TypeDiagnoser() {}
  
      virtual void diagnose(Sema &S, SourceLocation Loc, QualType T) = 0;
      virtual ~TypeDiagnoser() {}
    };
  
    static int getPrintable(int I) { return I; }
    static unsigned getPrintable(unsigned I) { return I; }
    static bool getPrintable(bool B) { return B; }
    static const char * getPrintable(const char *S) { return S; }
    static StringRef getPrintable(StringRef S) { return S; }
    static const std::string &getPrintable(const std::string &S) { return S; }
    static const IdentifierInfo *getPrintable(const IdentifierInfo *II) {
      return II;
    }
    static DeclarationName getPrintable(DeclarationName N) { return N; }
    static QualType getPrintable(QualType T) { return T; }
    static SourceRange getPrintable(SourceRange R) { return R; }
    static SourceRange getPrintable(SourceLocation L) { return L; }
    static SourceRange getPrintable(const Expr *E) { return E->getSourceRange(); }
    static SourceRange getPrintable(TypeLoc TL) { return TL.getSourceRange();}
  
    template <typename... Ts> class BoundTypeDiagnoser : public TypeDiagnoser {
    protected:
      unsigned DiagID;
      std::tuple<const Ts &...> Args;
  
      template <std::size_t... Is>
      void emit(const SemaDiagnosticBuilder &DB,
                std::index_sequence<Is...>) const {
        // Apply all tuple elements to the builder in order.
        bool Dummy[] = {false, (DB << getPrintable(std::get<Is>(Args)))...};
        (void)Dummy;
      }
  
    public:
      BoundTypeDiagnoser(unsigned DiagID, const Ts &...Args)
          : TypeDiagnoser(), DiagID(DiagID), Args(Args...) {
        assert(DiagID != 0 && "no diagnostic for type diagnoser");
      }
  
      void diagnose(Sema &S, SourceLocation Loc, QualType T) override {
        const SemaDiagnosticBuilder &DB = S.Diag(Loc, DiagID);
        emit(DB, std::index_sequence_for<Ts...>());
        DB << T;
      }
    };
  
    /// Do a check to make sure \p Name looks like a legal swift_name
    /// attribute for the decl \p D. Raise a diagnostic if the name is invalid
    /// for the given declaration.
    ///
    /// For a function, this will validate a compound Swift name,
    /// e.g. <code>init(foo:bar:baz:)</code> or <code>controllerForName(_:)</code>,
    /// and the function will output the number of parameter names, and whether
    /// this is a single-arg initializer.
    ///
    /// For a type, enum constant, property, or variable declaration, this will
    /// validate either a simple identifier, or a qualified
    /// <code>context.identifier</code> name.
    ///
    /// \returns true if the name is a valid swift name for \p D, false otherwise.
    bool DiagnoseSwiftName(Decl *D, StringRef Name,
                           SourceLocation ArgLoc,
                           const IdentifierInfo *AttrName);
  
    /// A derivative of BoundTypeDiagnoser for which the diagnostic's type
    /// parameter is preceded by a 0/1 enum that is 1 if the type is sizeless.
    /// For example, a diagnostic with no other parameters would generally have
    /// the form "...%select{incomplete|sizeless}0 type %1...".
    template <typename... Ts>
    class SizelessTypeDiagnoser : public BoundTypeDiagnoser<Ts...> {
    public:
      SizelessTypeDiagnoser(unsigned DiagID, const Ts &... Args)
          : BoundTypeDiagnoser<Ts...>(DiagID, Args...) {}
  
      void diagnose(Sema &S, SourceLocation Loc, QualType T) override {
        const SemaDiagnosticBuilder &DB = S.Diag(Loc, this->DiagID);
        this->emit(DB, std::index_sequence_for<Ts...>());
        DB << T->isSizelessType() << T;
      }
    };
  
    enum class CompleteTypeKind {
      /// Apply the normal rules for complete types.  In particular,
      /// treat all sizeless types as incomplete.
      Normal,
  
      /// Relax the normal rules for complete types so that they include
      /// sizeless built-in types.
      AcceptSizeless,
  
      // FIXME: Eventually we should flip the default to Normal and opt in
      // to AcceptSizeless rather than opt out of it.
      Default = AcceptSizeless
    };
  
  private:
    /// Methods for marking which expressions involve dereferencing a pointer
    /// marked with the 'noderef' attribute. Expressions are checked bottom up as
    /// they are parsed, meaning that a noderef pointer may not be accessed. For
    /// example, in `&*p` where `p` is a noderef pointer, we will first parse the
    /// `*p`, but need to check that `address of` is called on it. This requires
    /// keeping a container of all pending expressions and checking if the address
    /// of them are eventually taken.
    void CheckSubscriptAccessOfNoDeref(const ArraySubscriptExpr *E);
    void CheckAddressOfNoDeref(const Expr *E);
    void CheckMemberAccessOfNoDeref(const MemberExpr *E);
  
    bool RequireCompleteTypeImpl(SourceLocation Loc, QualType T,
                                 CompleteTypeKind Kind, TypeDiagnoser *Diagnoser);
  
    struct ModuleScope {
      SourceLocation BeginLoc;
      clang::Module *Module = nullptr;
      bool ModuleInterface = false;
      bool ImplicitGlobalModuleFragment = false;
      VisibleModuleSet OuterVisibleModules;
    };
    /// The modules we're currently parsing.
    llvm::SmallVector<ModuleScope, 16> ModuleScopes;
  
    /// Namespace definitions that we will export when they finish.
    llvm::SmallPtrSet<const NamespaceDecl*, 8> DeferredExportedNamespaces;
  
    /// Get the module whose scope we are currently within.
    Module *getCurrentModule() const {
      return ModuleScopes.empty() ? nullptr : ModuleScopes.back().Module;
    }
  
    VisibleModuleSet VisibleModules;
  
  public:
    /// Get the module owning an entity.
    Module *getOwningModule(const Decl *Entity) {
      return Entity->getOwningModule();
    }
  
    /// Make a merged definition of an existing hidden definition \p ND
    /// visible at the specified location.
    void makeMergedDefinitionVisible(NamedDecl *ND);
  
    bool isModuleVisible(const Module *M, bool ModulePrivate = false);
  
    /// Determine whether a declaration is visible to name lookup.
    bool isVisible(const NamedDecl *D) {
      return !D->isHidden() || isVisibleSlow(D);
    }
  
    /// Determine whether any declaration of an entity is visible.
    bool
    hasVisibleDeclaration(const NamedDecl *D,
                          llvm::SmallVectorImpl<Module *> *Modules = nullptr) {
      return isVisible(D) || hasVisibleDeclarationSlow(D, Modules);
    }
    bool hasVisibleDeclarationSlow(const NamedDecl *D,
                                   llvm::SmallVectorImpl<Module *> *Modules);
  
    bool hasVisibleMergedDefinition(NamedDecl *Def);
    bool hasMergedDefinitionInCurrentModule(NamedDecl *Def);
  
    /// Determine if \p D and \p Suggested have a structurally compatible
    /// layout as described in C11 6.2.7/1.
    bool hasStructuralCompatLayout(Decl *D, Decl *Suggested);
  
    /// Determine if \p D has a visible definition. If not, suggest a declaration
    /// that should be made visible to expose the definition.
    bool hasVisibleDefinition(NamedDecl *D, NamedDecl **Suggested,
                              bool OnlyNeedComplete = false);
    bool hasVisibleDefinition(const NamedDecl *D) {
      NamedDecl *Hidden;
      return hasVisibleDefinition(const_cast<NamedDecl*>(D), &Hidden);
    }
  
    /// Determine if the template parameter \p D has a visible default argument.
    bool
    hasVisibleDefaultArgument(const NamedDecl *D,
                              llvm::SmallVectorImpl<Module *> *Modules = nullptr);
  
    /// Determine if there is a visible declaration of \p D that is an explicit
    /// specialization declaration for a specialization of a template. (For a
    /// member specialization, use hasVisibleMemberSpecialization.)
    bool hasVisibleExplicitSpecialization(
        const NamedDecl *D, llvm::SmallVectorImpl<Module *> *Modules = nullptr);
  
    /// Determine if there is a visible declaration of \p D that is a member
    /// specialization declaration (as opposed to an instantiated declaration).
    bool hasVisibleMemberSpecialization(
        const NamedDecl *D, llvm::SmallVectorImpl<Module *> *Modules = nullptr);
  
    /// Determine if \p A and \p B are equivalent internal linkage declarations
    /// from different modules, and thus an ambiguity error can be downgraded to
    /// an extension warning.
    bool isEquivalentInternalLinkageDeclaration(const NamedDecl *A,
                                                const NamedDecl *B);
    void diagnoseEquivalentInternalLinkageDeclarations(
        SourceLocation Loc, const NamedDecl *D,
        ArrayRef<const NamedDecl *> Equiv);
  
    bool isUsualDeallocationFunction(const CXXMethodDecl *FD);
  
    bool isCompleteType(SourceLocation Loc, QualType T,
                        CompleteTypeKind Kind = CompleteTypeKind::Default) {
      return !RequireCompleteTypeImpl(Loc, T, Kind, nullptr);
    }
    bool RequireCompleteType(SourceLocation Loc, QualType T,
                             CompleteTypeKind Kind, TypeDiagnoser &Diagnoser);
    bool RequireCompleteType(SourceLocation Loc, QualType T,
                             CompleteTypeKind Kind, unsigned DiagID);
  
    bool RequireCompleteType(SourceLocation Loc, QualType T,
                             TypeDiagnoser &Diagnoser) {
      return RequireCompleteType(Loc, T, CompleteTypeKind::Default, Diagnoser);
    }
    bool RequireCompleteType(SourceLocation Loc, QualType T, unsigned DiagID) {
      return RequireCompleteType(Loc, T, CompleteTypeKind::Default, DiagID);
    }
  
    template <typename... Ts>
    bool RequireCompleteType(SourceLocation Loc, QualType T, unsigned DiagID,
                             const Ts &...Args) {
      BoundTypeDiagnoser<Ts...> Diagnoser(DiagID, Args...);
      return RequireCompleteType(Loc, T, Diagnoser);
    }
  
    template <typename... Ts>
    bool RequireCompleteSizedType(SourceLocation Loc, QualType T, unsigned DiagID,
                                  const Ts &... Args) {
      SizelessTypeDiagnoser<Ts...> Diagnoser(DiagID, Args...);
      return RequireCompleteType(Loc, T, CompleteTypeKind::Normal, Diagnoser);
    }
  
    void completeExprArrayBound(Expr *E);
    bool RequireCompleteExprType(Expr *E, CompleteTypeKind Kind,
                                 TypeDiagnoser &Diagnoser);
    bool RequireCompleteExprType(Expr *E, unsigned DiagID);
  
    template <typename... Ts>
    bool RequireCompleteExprType(Expr *E, unsigned DiagID, const Ts &...Args) {
      BoundTypeDiagnoser<Ts...> Diagnoser(DiagID, Args...);
      return RequireCompleteExprType(E, CompleteTypeKind::Default, Diagnoser);
    }
  
    template <typename... Ts>
    bool RequireCompleteSizedExprType(Expr *E, unsigned DiagID,
                                      const Ts &... Args) {
      SizelessTypeDiagnoser<Ts...> Diagnoser(DiagID, Args...);
      return RequireCompleteExprType(E, CompleteTypeKind::Normal, Diagnoser);
    }
  
    bool RequireLiteralType(SourceLocation Loc, QualType T,
                            TypeDiagnoser &Diagnoser);
    bool RequireLiteralType(SourceLocation Loc, QualType T, unsigned DiagID);
  
    template <typename... Ts>
    bool RequireLiteralType(SourceLocation Loc, QualType T, unsigned DiagID,
                            const Ts &...Args) {
      BoundTypeDiagnoser<Ts...> Diagnoser(DiagID, Args...);
      return RequireLiteralType(Loc, T, Diagnoser);
    }
  
    QualType getElaboratedType(ElaboratedTypeKeyword Keyword,
                               const CXXScopeSpec &SS, QualType T,
                               TagDecl *OwnedTagDecl = nullptr);
  
    QualType BuildTypeofExprType(Expr *E, SourceLocation Loc);
    /// If AsUnevaluated is false, E is treated as though it were an evaluated
    /// context, such as when building a type for decltype(auto).
    QualType BuildDecltypeType(Expr *E, SourceLocation Loc,
                               bool AsUnevaluated = true);
    QualType BuildUnaryTransformType(QualType BaseType,
                                     UnaryTransformType::UTTKind UKind,
                                     SourceLocation Loc);
  
    //===--------------------------------------------------------------------===//
    // Symbol table / Decl tracking callbacks: SemaDecl.cpp.
    //
  
    struct SkipBodyInfo {
      SkipBodyInfo()
          : ShouldSkip(false), CheckSameAsPrevious(false), Previous(nullptr),
            New(nullptr) {}
      bool ShouldSkip;
      bool CheckSameAsPrevious;
      NamedDecl *Previous;
      NamedDecl *New;
    };
  
    DeclGroupPtrTy ConvertDeclToDeclGroup(Decl *Ptr, Decl *OwnedType = nullptr);
  
    void DiagnoseUseOfUnimplementedSelectors();
  
    bool isSimpleTypeSpecifier(tok::TokenKind Kind) const;
  
    ParsedType getTypeName(const IdentifierInfo &II, SourceLocation NameLoc,
                           Scope *S, CXXScopeSpec *SS = nullptr,
                           bool isClassName = false, bool HasTrailingDot = false,
                           ParsedType ObjectType = nullptr,
                           bool IsCtorOrDtorName = false,
                           bool WantNontrivialTypeSourceInfo = false,
                           bool IsClassTemplateDeductionContext = true,
                           IdentifierInfo **CorrectedII = nullptr);
    TypeSpecifierType isTagName(IdentifierInfo &II, Scope *S);
    bool isMicrosoftMissingTypename(const CXXScopeSpec *SS, Scope *S);
    void DiagnoseUnknownTypeName(IdentifierInfo *&II,
                                 SourceLocation IILoc,
                                 Scope *S,
                                 CXXScopeSpec *SS,
                                 ParsedType &SuggestedType,
                                 bool IsTemplateName = false);
  
    /// Attempt to behave like MSVC in situations where lookup of an unqualified
    /// type name has failed in a dependent context. In these situations, we
    /// automatically form a DependentTypeName that will retry lookup in a related
    /// scope during instantiation.
    ParsedType ActOnMSVCUnknownTypeName(const IdentifierInfo &II,
                                        SourceLocation NameLoc,
                                        bool IsTemplateTypeArg);
  
    /// Describes the result of the name lookup and resolution performed
    /// by \c ClassifyName().
    enum NameClassificationKind {
      /// This name is not a type or template in this context, but might be
      /// something else.
      NC_Unknown,
      /// Classification failed; an error has been produced.
      NC_Error,
      /// The name has been typo-corrected to a keyword.
      NC_Keyword,
      /// The name was classified as a type.
      NC_Type,
      /// The name was classified as a specific non-type, non-template
      /// declaration. ActOnNameClassifiedAsNonType should be called to
      /// convert the declaration to an expression.
      NC_NonType,
      /// The name was classified as an ADL-only function name.
      /// ActOnNameClassifiedAsUndeclaredNonType should be called to convert the
      /// result to an expression.
      NC_UndeclaredNonType,
      /// The name denotes a member of a dependent type that could not be
      /// resolved. ActOnNameClassifiedAsDependentNonType should be called to
      /// convert the result to an expression.
      NC_DependentNonType,
      /// The name was classified as a non-type, and an expression representing
      /// that name has been formed.
      NC_ContextIndependentExpr,
      /// The name was classified as a template whose specializations are types.
      NC_TypeTemplate,
      /// The name was classified as a variable template name.
      NC_VarTemplate,
      /// The name was classified as a function template name.
      NC_FunctionTemplate,
      /// The name was classified as an ADL-only function template name.
      NC_UndeclaredTemplate,
      /// The name was classified as a concept name.
      NC_Concept,
    };
  
    class NameClassification {
      NameClassificationKind Kind;
      union {
        ExprResult Expr;
        NamedDecl *NonTypeDecl;
        TemplateName Template;
        ParsedType Type;
      };
  
      explicit NameClassification(NameClassificationKind Kind) : Kind(Kind) {}
  
    public:
      NameClassification(ParsedType Type) : Kind(NC_Type), Type(Type) {}
  
      NameClassification(const IdentifierInfo *Keyword) : Kind(NC_Keyword) {}
  
      static NameClassification Error() {
        return NameClassification(NC_Error);
      }
  
      static NameClassification Unknown() {
        return NameClassification(NC_Unknown);
      }
  
      static NameClassification ContextIndependentExpr(ExprResult E) {
        NameClassification Result(NC_ContextIndependentExpr);
        Result.Expr = E;
        return Result;
      }
  
      static NameClassification NonType(NamedDecl *D) {
        NameClassification Result(NC_NonType);
        Result.NonTypeDecl = D;
        return Result;
      }
  
      static NameClassification UndeclaredNonType() {
        return NameClassification(NC_UndeclaredNonType);
      }
  
      static NameClassification DependentNonType() {
        return NameClassification(NC_DependentNonType);
      }
  
      static NameClassification TypeTemplate(TemplateName Name) {
        NameClassification Result(NC_TypeTemplate);
        Result.Template = Name;
        return Result;
      }
  
      static NameClassification VarTemplate(TemplateName Name) {
        NameClassification Result(NC_VarTemplate);
        Result.Template = Name;
        return Result;
      }
  
      static NameClassification FunctionTemplate(TemplateName Name) {
        NameClassification Result(NC_FunctionTemplate);
        Result.Template = Name;
        return Result;
      }
  
      static NameClassification Concept(TemplateName Name) {
        NameClassification Result(NC_Concept);
        Result.Template = Name;
        return Result;
      }
  
      static NameClassification UndeclaredTemplate(TemplateName Name) {
        NameClassification Result(NC_UndeclaredTemplate);
        Result.Template = Name;
        return Result;
      }
  
      NameClassificationKind getKind() const { return Kind; }
  
      ExprResult getExpression() const {
        assert(Kind == NC_ContextIndependentExpr);
        return Expr;
      }
  
      ParsedType getType() const {
        assert(Kind == NC_Type);
        return Type;
      }
  
      NamedDecl *getNonTypeDecl() const {
        assert(Kind == NC_NonType);
        return NonTypeDecl;
      }
  
      TemplateName getTemplateName() const {
        assert(Kind == NC_TypeTemplate || Kind == NC_FunctionTemplate ||
               Kind == NC_VarTemplate || Kind == NC_Concept ||
               Kind == NC_UndeclaredTemplate);
        return Template;
      }
  
      TemplateNameKind getTemplateNameKind() const {
        switch (Kind) {
        case NC_TypeTemplate:
          return TNK_Type_template;
        case NC_FunctionTemplate:
          return TNK_Function_template;
        case NC_VarTemplate:
          return TNK_Var_template;
        case NC_Concept:
          return TNK_Concept_template;
        case NC_UndeclaredTemplate:
          return TNK_Undeclared_template;
        default:
          llvm_unreachable("unsupported name classification.");
        }
      }
    };
  
    /// Perform name lookup on the given name, classifying it based on
    /// the results of name lookup and the following token.
    ///
    /// This routine is used by the parser to resolve identifiers and help direct
    /// parsing. When the identifier cannot be found, this routine will attempt
    /// to correct the typo and classify based on the resulting name.
    ///
    /// \param S The scope in which we're performing name lookup.
    ///
    /// \param SS The nested-name-specifier that precedes the name.
    ///
    /// \param Name The identifier. If typo correction finds an alternative name,
    /// this pointer parameter will be updated accordingly.
    ///
    /// \param NameLoc The location of the identifier.
    ///
    /// \param NextToken The token following the identifier. Used to help
    /// disambiguate the name.
    ///
    /// \param CCC The correction callback, if typo correction is desired.
    NameClassification ClassifyName(Scope *S, CXXScopeSpec &SS,
                                    IdentifierInfo *&Name, SourceLocation NameLoc,
                                    const Token &NextToken,
                                    CorrectionCandidateCallback *CCC = nullptr);
  
    /// Act on the result of classifying a name as an undeclared (ADL-only)
    /// non-type declaration.
    ExprResult ActOnNameClassifiedAsUndeclaredNonType(IdentifierInfo *Name,
                                                      SourceLocation NameLoc);
    /// Act on the result of classifying a name as an undeclared member of a
    /// dependent base class.
    ExprResult ActOnNameClassifiedAsDependentNonType(const CXXScopeSpec &SS,
                                                     IdentifierInfo *Name,
                                                     SourceLocation NameLoc,
                                                     bool IsAddressOfOperand);
    /// Act on the result of classifying a name as a specific non-type
    /// declaration.
    ExprResult ActOnNameClassifiedAsNonType(Scope *S, const CXXScopeSpec &SS,
                                            NamedDecl *Found,
                                            SourceLocation NameLoc,
                                            const Token &NextToken);
  
    /// Describes the detailed kind of a template name. Used in diagnostics.
    enum class TemplateNameKindForDiagnostics {
      ClassTemplate,
      FunctionTemplate,
      VarTemplate,
      AliasTemplate,
      TemplateTemplateParam,
      Concept,
      DependentTemplate
    };
    TemplateNameKindForDiagnostics
    getTemplateNameKindForDiagnostics(TemplateName Name);
  
    /// Determine whether it's plausible that E was intended to be a
    /// template-name.
    bool mightBeIntendedToBeTemplateName(ExprResult E, bool &Dependent) {
      if (!getLangOpts().CPlusPlus || E.isInvalid())
        return false;
      Dependent = false;
      if (auto *DRE = dyn_cast<DeclRefExpr>(E.get()))
        return !DRE->hasExplicitTemplateArgs();
      if (auto *ME = dyn_cast<MemberExpr>(E.get()))
        return !ME->hasExplicitTemplateArgs();
      Dependent = true;
      if (auto *DSDRE = dyn_cast<DependentScopeDeclRefExpr>(E.get()))
        return !DSDRE->hasExplicitTemplateArgs();
      if (auto *DSME = dyn_cast<CXXDependentScopeMemberExpr>(E.get()))
        return !DSME->hasExplicitTemplateArgs();
      // Any additional cases recognized here should also be handled by
      // diagnoseExprIntendedAsTemplateName.
      return false;
    }
    void diagnoseExprIntendedAsTemplateName(Scope *S, ExprResult TemplateName,
                                            SourceLocation Less,
                                            SourceLocation Greater);
  
    Decl *ActOnDeclarator(Scope *S, Declarator &D);
  
    NamedDecl *HandleDeclarator(Scope *S, Declarator &D,
                                MultiTemplateParamsArg TemplateParameterLists);
    void RegisterLocallyScopedExternCDecl(NamedDecl *ND, Scope *S);
    bool DiagnoseClassNameShadow(DeclContext *DC, DeclarationNameInfo Info);
    bool diagnoseQualifiedDeclaration(CXXScopeSpec &SS, DeclContext *DC,
                                      DeclarationName Name, SourceLocation Loc,
                                      bool IsTemplateId);
    void
    diagnoseIgnoredQualifiers(unsigned DiagID, unsigned Quals,
                              SourceLocation FallbackLoc,
                              SourceLocation ConstQualLoc = SourceLocation(),
                              SourceLocation VolatileQualLoc = SourceLocation(),
                              SourceLocation RestrictQualLoc = SourceLocation(),
                              SourceLocation AtomicQualLoc = SourceLocation(),
                              SourceLocation UnalignedQualLoc = SourceLocation());
  
    void diagnosePointerAuthDisabled(SourceLocation loc, SourceRange range);
    bool checkConstantPointerAuthKey(Expr *keyExpr, unsigned &key);
  
    static bool adjustContextForLocalExternDecl(DeclContext *&DC);
    void DiagnoseFunctionSpecifiers(const DeclSpec &DS);
    NamedDecl *getShadowedDeclaration(const TypedefNameDecl *D,
                                      const LookupResult &R);
    NamedDecl *getShadowedDeclaration(const VarDecl *D, const LookupResult &R);
    void CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
                     const LookupResult &R);
    void CheckShadow(Scope *S, VarDecl *D);
  
    /// Warn if 'E', which is an expression that is about to be modified, refers
    /// to a shadowing declaration.
    void CheckShadowingDeclModification(Expr *E, SourceLocation Loc);
  
    void DiagnoseShadowingLambdaDecls(const sema::LambdaScopeInfo *LSI);
  
  private:
    /// Map of current shadowing declarations to shadowed declarations. Warn if
    /// it looks like the user is trying to modify the shadowing declaration.
    llvm::DenseMap<const NamedDecl *, const NamedDecl *> ShadowingDecls;
  
  public:
    void CheckCastAlign(Expr *Op, QualType T, SourceRange TRange);
    void handleTagNumbering(const TagDecl *Tag, Scope *TagScope);
    void setTagNameForLinkagePurposes(TagDecl *TagFromDeclSpec,
                                      TypedefNameDecl *NewTD);
    void CheckTypedefForVariablyModifiedType(Scope *S, TypedefNameDecl *D);
    NamedDecl* ActOnTypedefDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                                      TypeSourceInfo *TInfo,
                                      LookupResult &Previous);
    NamedDecl* ActOnTypedefNameDecl(Scope* S, DeclContext* DC, TypedefNameDecl *D,
                                    LookupResult &Previous, bool &Redeclaration);
    NamedDecl *ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
                                       TypeSourceInfo *TInfo,
                                       LookupResult &Previous,
                                       MultiTemplateParamsArg TemplateParamLists,
                                       bool &AddToScope,
                                       ArrayRef<BindingDecl *> Bindings = None);
    NamedDecl *
    ActOnDecompositionDeclarator(Scope *S, Declarator &D,
                                 MultiTemplateParamsArg TemplateParamLists);
    // Returns true if the variable declaration is a redeclaration
    bool CheckVariableDeclaration(VarDecl *NewVD, LookupResult &Previous);
    void CheckVariableDeclarationType(VarDecl *NewVD);
    bool DeduceVariableDeclarationType(VarDecl *VDecl, bool DirectInit,
                                       Expr *Init);
    void CheckCompleteVariableDeclaration(VarDecl *VD);
    void CheckCompleteDecompositionDeclaration(DecompositionDecl *DD);
    void MaybeSuggestAddingStaticToDecl(const FunctionDecl *D);
  
    NamedDecl* ActOnFunctionDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                                       TypeSourceInfo *TInfo,
                                       LookupResult &Previous,
                                       MultiTemplateParamsArg TemplateParamLists,
                                       bool &AddToScope);
    bool AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD);
  
    enum class CheckConstexprKind {
      /// Diagnose issues that are non-constant or that are extensions.
      Diagnose,
      /// Identify whether this function satisfies the formal rules for constexpr
      /// functions in the current lanugage mode (with no extensions).
      CheckValid
    };
  
    bool CheckConstexprFunctionDefinition(const FunctionDecl *FD,
                                          CheckConstexprKind Kind);
  
    void DiagnoseHiddenVirtualMethods(CXXMethodDecl *MD);
    void FindHiddenVirtualMethods(CXXMethodDecl *MD,
                            SmallVectorImpl<CXXMethodDecl*> &OverloadedMethods);
    void NoteHiddenVirtualMethods(CXXMethodDecl *MD,
                            SmallVectorImpl<CXXMethodDecl*> &OverloadedMethods);
    // Returns true if the function declaration is a redeclaration
    bool CheckFunctionDeclaration(Scope *S,
                                  FunctionDecl *NewFD, LookupResult &Previous,
                                  bool IsMemberSpecialization);
    bool shouldLinkDependentDeclWithPrevious(Decl *D, Decl *OldDecl);
    bool canFullyTypeCheckRedeclaration(ValueDecl *NewD, ValueDecl *OldD,
                                        QualType NewT, QualType OldT);
    void CheckMain(FunctionDecl *FD, const DeclSpec &D);
    void CheckMSVCRTEntryPoint(FunctionDecl *FD);
    Attr *getImplicitCodeSegOrSectionAttrForFunction(const FunctionDecl *FD,
                                                     bool IsDefinition);
    void CheckFunctionOrTemplateParamDeclarator(Scope *S, Declarator &D);
    Decl *ActOnParamDeclarator(Scope *S, Declarator &D);
    ParmVarDecl *BuildParmVarDeclForTypedef(DeclContext *DC,
                                            SourceLocation Loc,
                                            QualType T);
    QualType adjustParameterTypeForObjCAutoRefCount(QualType T,
                                                    SourceLocation NameLoc,
                                                    TypeSourceInfo *TSInfo);
    ParmVarDecl *CheckParameter(DeclContext *DC, SourceLocation StartLoc,
                                SourceLocation NameLoc, IdentifierInfo *Name,
                                QualType T, TypeSourceInfo *TSInfo,
                                StorageClass SC);
    void ActOnParamDefaultArgument(Decl *param,
                                   SourceLocation EqualLoc,
                                   Expr *defarg);
    void ActOnParamUnparsedDefaultArgument(Decl *param,
                                           SourceLocation EqualLoc,
                                           SourceLocation ArgLoc);
    void ActOnParamDefaultArgumentError(Decl *param, SourceLocation EqualLoc);
    bool SetParamDefaultArgument(ParmVarDecl *Param, Expr *DefaultArg,
                                 SourceLocation EqualLoc);
  
    // Contexts where using non-trivial C union types can be disallowed. This is
    // passed to err_non_trivial_c_union_in_invalid_context.
    enum NonTrivialCUnionContext {
      // Function parameter.
      NTCUC_FunctionParam,
      // Function return.
      NTCUC_FunctionReturn,
      // Default-initialized object.
      NTCUC_DefaultInitializedObject,
      // Variable with automatic storage duration.
      NTCUC_AutoVar,
      // Initializer expression that might copy from another object.
      NTCUC_CopyInit,
      // Assignment.
      NTCUC_Assignment,
      // Compound literal.
      NTCUC_CompoundLiteral,
      // Block capture.
      NTCUC_BlockCapture,
      // lvalue-to-rvalue conversion of volatile type.
      NTCUC_LValueToRValueVolatile,
    };
  
    /// Emit diagnostics if the initializer or any of its explicit or
    /// implicitly-generated subexpressions require copying or
    /// default-initializing a type that is or contains a C union type that is
    /// non-trivial to copy or default-initialize.
    void checkNonTrivialCUnionInInitializer(const Expr *Init, SourceLocation Loc);
  
    // These flags are passed to checkNonTrivialCUnion.
    enum NonTrivialCUnionKind {
      NTCUK_Init = 0x1,
      NTCUK_Destruct = 0x2,
      NTCUK_Copy = 0x4,
    };
  
    /// Emit diagnostics if a non-trivial C union type or a struct that contains
    /// a non-trivial C union is used in an invalid context.
    void checkNonTrivialCUnion(QualType QT, SourceLocation Loc,
                               NonTrivialCUnionContext UseContext,
                               unsigned NonTrivialKind);
  
    void AddInitializerToDecl(Decl *dcl, Expr *init, bool DirectInit);
    void ActOnUninitializedDecl(Decl *dcl);
    void ActOnInitializerError(Decl *Dcl);
  
    void ActOnPureSpecifier(Decl *D, SourceLocation PureSpecLoc);
    void ActOnCXXForRangeDecl(Decl *D);
    StmtResult ActOnCXXForRangeIdentifier(Scope *S, SourceLocation IdentLoc,
                                          IdentifierInfo *Ident,
                                          ParsedAttributes &Attrs,
                                          SourceLocation AttrEnd);
    void SetDeclDeleted(Decl *dcl, SourceLocation DelLoc);
    void SetDeclDefaulted(Decl *dcl, SourceLocation DefaultLoc);
    void CheckStaticLocalForDllExport(VarDecl *VD);
    void FinalizeDeclaration(Decl *D);
    DeclGroupPtrTy FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
                                           ArrayRef<Decl *> Group);
    DeclGroupPtrTy BuildDeclaratorGroup(MutableArrayRef<Decl *> Group);
  
    /// Should be called on all declarations that might have attached
    /// documentation comments.
    void ActOnDocumentableDecl(Decl *D);
    void ActOnDocumentableDecls(ArrayRef<Decl *> Group);
  
    void ActOnFinishKNRParamDeclarations(Scope *S, Declarator &D,
                                         SourceLocation LocAfterDecls);
    void CheckForFunctionRedefinition(
        FunctionDecl *FD, const FunctionDecl *EffectiveDefinition = nullptr,
        SkipBodyInfo *SkipBody = nullptr);
    Decl *ActOnStartOfFunctionDef(Scope *S, Declarator &D,
                                  MultiTemplateParamsArg TemplateParamLists,
                                  SkipBodyInfo *SkipBody = nullptr);
    Decl *ActOnStartOfFunctionDef(Scope *S, Decl *D,
                                  SkipBodyInfo *SkipBody = nullptr);
    void ActOnStartTrailingRequiresClause(Scope *S, Declarator &D);
    ExprResult ActOnFinishTrailingRequiresClause(ExprResult ConstraintExpr);
    void ActOnStartOfObjCMethodDef(Scope *S, Decl *D);
    bool isObjCMethodDecl(Decl *D) {
      return D && isa<ObjCMethodDecl>(D);
    }
  
    /// Determine whether we can delay parsing the body of a function or
    /// function template until it is used, assuming we don't care about emitting
    /// code for that function.
    ///
    /// This will be \c false if we may need the body of the function in the
    /// middle of parsing an expression (where it's impractical to switch to
    /// parsing a different function), for instance, if it's constexpr in C++11
    /// or has an 'auto' return type in C++14. These cases are essentially bugs.
    bool canDelayFunctionBody(const Declarator &D);
  
    /// Determine whether we can skip parsing the body of a function
    /// definition, assuming we don't care about analyzing its body or emitting
    /// code for that function.
    ///
    /// This will be \c false only if we may need the body of the function in
    /// order to parse the rest of the program (for instance, if it is
    /// \c constexpr in C++11 or has an 'auto' return type in C++14).
    bool canSkipFunctionBody(Decl *D);
  
    void computeNRVO(Stmt *Body, sema::FunctionScopeInfo *Scope);
    Decl *ActOnFinishFunctionBody(Decl *Decl, Stmt *Body);
    Decl *ActOnFinishFunctionBody(Decl *Decl, Stmt *Body, bool IsInstantiation);
    Decl *ActOnSkippedFunctionBody(Decl *Decl);
    void ActOnFinishInlineFunctionDef(FunctionDecl *D);
  
    /// ActOnFinishDelayedAttribute - Invoked when we have finished parsing an
    /// attribute for which parsing is delayed.
    void ActOnFinishDelayedAttribute(Scope *S, Decl *D, ParsedAttributes &Attrs);
  
    /// Diagnose any unused parameters in the given sequence of
    /// ParmVarDecl pointers.
    void DiagnoseUnusedParameters(ArrayRef<ParmVarDecl *> Parameters);
  
    /// Diagnose whether the size of parameters or return value of a
    /// function or obj-c method definition is pass-by-value and larger than a
    /// specified threshold.
    void
    DiagnoseSizeOfParametersAndReturnValue(ArrayRef<ParmVarDecl *> Parameters,
                                           QualType ReturnTy, NamedDecl *D);
  
    void DiagnoseInvalidJumps(Stmt *Body);
    Decl *ActOnFileScopeAsmDecl(Expr *expr,
                                SourceLocation AsmLoc,
                                SourceLocation RParenLoc);
  
    /// Handle a C++11 empty-declaration and attribute-declaration.
    Decl *ActOnEmptyDeclaration(Scope *S, const ParsedAttributesView &AttrList,
                                SourceLocation SemiLoc);
  
    enum class ModuleDeclKind {
      Interface,      ///< 'export module X;'
      Implementation, ///< 'module X;'
    };
  
    /// The parser has processed a module-declaration that begins the definition
    /// of a module interface or implementation.
    DeclGroupPtrTy ActOnModuleDecl(SourceLocation StartLoc,
                                   SourceLocation ModuleLoc, ModuleDeclKind MDK,
                                   ModuleIdPath Path, bool IsFirstDecl);
  
    /// The parser has processed a global-module-fragment declaration that begins
    /// the definition of the global module fragment of the current module unit.
    /// \param ModuleLoc The location of the 'module' keyword.
    DeclGroupPtrTy ActOnGlobalModuleFragmentDecl(SourceLocation ModuleLoc);
  
    /// The parser has processed a private-module-fragment declaration that begins
    /// the definition of the private module fragment of the current module unit.
    /// \param ModuleLoc The location of the 'module' keyword.
    /// \param PrivateLoc The location of the 'private' keyword.
    DeclGroupPtrTy ActOnPrivateModuleFragmentDecl(SourceLocation ModuleLoc,
                                                  SourceLocation PrivateLoc);
  
    /// The parser has processed a module import declaration.
    ///
    /// \param StartLoc The location of the first token in the declaration. This
    ///        could be the location of an '@', 'export', or 'import'.
    /// \param ExportLoc The location of the 'export' keyword, if any.
    /// \param ImportLoc The location of the 'import' keyword.
    /// \param Path The module access path.
    DeclResult ActOnModuleImport(SourceLocation StartLoc,
                                 SourceLocation ExportLoc,
                                 SourceLocation ImportLoc, ModuleIdPath Path);
    DeclResult ActOnModuleImport(SourceLocation StartLoc,
                                 SourceLocation ExportLoc,
                                 SourceLocation ImportLoc, Module *M,
                                 ModuleIdPath Path = {});
  
    /// The parser has processed a module import translated from a
    /// #include or similar preprocessing directive.
    void ActOnModuleInclude(SourceLocation DirectiveLoc, Module *Mod);
    void BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod);
  
    /// The parsed has entered a submodule.
    void ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod);
    /// The parser has left a submodule.
    void ActOnModuleEnd(SourceLocation DirectiveLoc, Module *Mod);
  
    /// Create an implicit import of the given module at the given
    /// source location, for error recovery, if possible.
    ///
    /// This routine is typically used when an entity found by name lookup
    /// is actually hidden within a module that we know about but the user
    /// has forgotten to import.
    void createImplicitModuleImportForErrorRecovery(SourceLocation Loc,
                                                    Module *Mod);
  
    /// Kinds of missing import. Note, the values of these enumerators correspond
    /// to %select values in diagnostics.
    enum class MissingImportKind {
      Declaration,
      Definition,
      DefaultArgument,
      ExplicitSpecialization,
      PartialSpecialization
    };
  
    /// Diagnose that the specified declaration needs to be visible but
    /// isn't, and suggest a module import that would resolve the problem.
    void diagnoseMissingImport(SourceLocation Loc, NamedDecl *Decl,
                               MissingImportKind MIK, bool Recover = true);
    void diagnoseMissingImport(SourceLocation Loc, NamedDecl *Decl,
                               SourceLocation DeclLoc, ArrayRef<Module *> Modules,
                               MissingImportKind MIK, bool Recover);
  
    Decl *ActOnStartExportDecl(Scope *S, SourceLocation ExportLoc,
                               SourceLocation LBraceLoc);
    Decl *ActOnFinishExportDecl(Scope *S, Decl *ExportDecl,
                                SourceLocation RBraceLoc);
  
    /// We've found a use of a templated declaration that would trigger an
    /// implicit instantiation. Check that any relevant explicit specializations
    /// and partial specializations are visible, and diagnose if not.
    void checkSpecializationVisibility(SourceLocation Loc, NamedDecl *Spec);
  
    /// We've found a use of a template specialization that would select a
    /// partial specialization. Check that the partial specialization is visible,
    /// and diagnose if not.
    void checkPartialSpecializationVisibility(SourceLocation Loc,
                                              NamedDecl *Spec);
  
    /// Retrieve a suitable printing policy for diagnostics.
    PrintingPolicy getPrintingPolicy() const {
      return getPrintingPolicy(Context, PP);
    }
  
    /// Retrieve a suitable printing policy for diagnostics.
    static PrintingPolicy getPrintingPolicy(const ASTContext &Ctx,
                                            const Preprocessor &PP);
  
    /// Scope actions.
    void ActOnPopScope(SourceLocation Loc, Scope *S);
    void ActOnTranslationUnitScope(Scope *S);
  
    Decl *ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, DeclSpec &DS,
                                     RecordDecl *&AnonRecord);
    Decl *ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, DeclSpec &DS,
                                     MultiTemplateParamsArg TemplateParams,
                                     bool IsExplicitInstantiation,
                                     RecordDecl *&AnonRecord);
  
    Decl *BuildAnonymousStructOrUnion(Scope *S, DeclSpec &DS,
                                      AccessSpecifier AS,
                                      RecordDecl *Record,
                                      const PrintingPolicy &Policy);
  
    Decl *BuildMicrosoftCAnonymousStruct(Scope *S, DeclSpec &DS,
                                         RecordDecl *Record);
  
    /// Common ways to introduce type names without a tag for use in diagnostics.
    /// Keep in sync with err_tag_reference_non_tag.
    enum NonTagKind {
      NTK_NonStruct,
      NTK_NonClass,
      NTK_NonUnion,
      NTK_NonEnum,
      NTK_Typedef,
      NTK_TypeAlias,
      NTK_Template,
      NTK_TypeAliasTemplate,
      NTK_TemplateTemplateArgument,
    };
  
    /// Given a non-tag type declaration, returns an enum useful for indicating
    /// what kind of non-tag type this is.
    NonTagKind getNonTagTypeDeclKind(const Decl *D, TagTypeKind TTK);
  
    bool isAcceptableTagRedeclaration(const TagDecl *Previous,
                                      TagTypeKind NewTag, bool isDefinition,
                                      SourceLocation NewTagLoc,
                                      const IdentifierInfo *Name);
  
    enum TagUseKind {
      TUK_Reference,   // Reference to a tag:  'struct foo *X;'
      TUK_Declaration, // Fwd decl of a tag:   'struct foo;'
      TUK_Definition,  // Definition of a tag: 'struct foo { int X; } Y;'
      TUK_Friend       // Friend declaration:  'friend struct foo;'
    };
  
    Decl *ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
                   SourceLocation KWLoc, CXXScopeSpec &SS, IdentifierInfo *Name,
                   SourceLocation NameLoc, const ParsedAttributesView &Attr,
                   AccessSpecifier AS, SourceLocation ModulePrivateLoc,
                   MultiTemplateParamsArg TemplateParameterLists, bool &OwnedDecl,
                   bool &IsDependent, SourceLocation ScopedEnumKWLoc,
                   bool ScopedEnumUsesClassTag, TypeResult UnderlyingType,
                   bool IsTypeSpecifier, bool IsTemplateParamOrArg,
                   SkipBodyInfo *SkipBody = nullptr);
  
    Decl *ActOnTemplatedFriendTag(Scope *S, SourceLocation FriendLoc,
                                  unsigned TagSpec, SourceLocation TagLoc,
                                  CXXScopeSpec &SS, IdentifierInfo *Name,
                                  SourceLocation NameLoc,
                                  const ParsedAttributesView &Attr,
                                  MultiTemplateParamsArg TempParamLists);
  
    TypeResult ActOnDependentTag(Scope *S,
                                 unsigned TagSpec,
                                 TagUseKind TUK,
                                 const CXXScopeSpec &SS,
                                 IdentifierInfo *Name,
                                 SourceLocation TagLoc,
                                 SourceLocation NameLoc);
  
    void ActOnDefs(Scope *S, Decl *TagD, SourceLocation DeclStart,
                   IdentifierInfo *ClassName,
                   SmallVectorImpl<Decl *> &Decls);
    Decl *ActOnField(Scope *S, Decl *TagD, SourceLocation DeclStart,
                     Declarator &D, Expr *BitfieldWidth);
  
    FieldDecl *HandleField(Scope *S, RecordDecl *TagD, SourceLocation DeclStart,
                           Declarator &D, Expr *BitfieldWidth,
                           InClassInitStyle InitStyle,
                           AccessSpecifier AS);
    MSPropertyDecl *HandleMSProperty(Scope *S, RecordDecl *TagD,
                                     SourceLocation DeclStart, Declarator &D,
                                     Expr *BitfieldWidth,
                                     InClassInitStyle InitStyle,
                                     AccessSpecifier AS,
                                     const ParsedAttr &MSPropertyAttr);
  
    FieldDecl *CheckFieldDecl(DeclarationName Name, QualType T,
                              TypeSourceInfo *TInfo,
                              RecordDecl *Record, SourceLocation Loc,
                              bool Mutable, Expr *BitfieldWidth,
                              InClassInitStyle InitStyle,
                              SourceLocation TSSL,
                              AccessSpecifier AS, NamedDecl *PrevDecl,
                              Declarator *D = nullptr);
  
    bool CheckNontrivialField(FieldDecl *FD);
    void DiagnoseNontrivial(const CXXRecordDecl *Record, CXXSpecialMember CSM);
  
    enum TrivialABIHandling {
      /// The triviality of a method unaffected by "trivial_abi".
      TAH_IgnoreTrivialABI,
  
      /// The triviality of a method affected by "trivial_abi".
      TAH_ConsiderTrivialABI
    };
  
    bool SpecialMemberIsTrivial(CXXMethodDecl *MD, CXXSpecialMember CSM,
                                TrivialABIHandling TAH = TAH_IgnoreTrivialABI,
                                bool Diagnose = false);
  
    /// For a defaulted function, the kind of defaulted function that it is.
    class DefaultedFunctionKind {
      CXXSpecialMember SpecialMember : 8;
      DefaultedComparisonKind Comparison : 8;
  
    public:
      DefaultedFunctionKind()
          : SpecialMember(CXXInvalid), Comparison(DefaultedComparisonKind::None) {
      }
      DefaultedFunctionKind(CXXSpecialMember CSM)
          : SpecialMember(CSM), Comparison(DefaultedComparisonKind::None) {}
      DefaultedFunctionKind(DefaultedComparisonKind Comp)
          : SpecialMember(CXXInvalid), Comparison(Comp) {}
  
      bool isSpecialMember() const { return SpecialMember != CXXInvalid; }
      bool isComparison() const {
        return Comparison != DefaultedComparisonKind::None;
      }
  
      explicit operator bool() const {
        return isSpecialMember() || isComparison();
      }
  
      CXXSpecialMember asSpecialMember() const { return SpecialMember; }
      DefaultedComparisonKind asComparison() const { return Comparison; }
  
      /// Get the index of this function kind for use in diagnostics.
      unsigned getDiagnosticIndex() const {
        static_assert(CXXInvalid > CXXDestructor,
                      "invalid should have highest index");
        static_assert((unsigned)DefaultedComparisonKind::None == 0,
                      "none should be equal to zero");
        return SpecialMember + (unsigned)Comparison;
      }
    };
  
    DefaultedFunctionKind getDefaultedFunctionKind(const FunctionDecl *FD);
  
    CXXSpecialMember getSpecialMember(const CXXMethodDecl *MD) {
      return getDefaultedFunctionKind(MD).asSpecialMember();
    }
    DefaultedComparisonKind getDefaultedComparisonKind(const FunctionDecl *FD) {
      return getDefaultedFunctionKind(FD).asComparison();
    }
  
    void ActOnLastBitfield(SourceLocation DeclStart,
                           SmallVectorImpl<Decl *> &AllIvarDecls);
    Decl *ActOnIvar(Scope *S, SourceLocation DeclStart,
                    Declarator &D, Expr *BitfieldWidth,
                    tok::ObjCKeywordKind visibility);
  
    // This is used for both record definitions and ObjC interface declarations.
    void ActOnFields(Scope *S, SourceLocation RecLoc, Decl *TagDecl,
                     ArrayRef<Decl *> Fields, SourceLocation LBrac,
                     SourceLocation RBrac, const ParsedAttributesView &AttrList);
  
    /// ActOnTagStartDefinition - Invoked when we have entered the
    /// scope of a tag's definition (e.g., for an enumeration, class,
    /// struct, or union).
    void ActOnTagStartDefinition(Scope *S, Decl *TagDecl);
  
    /// Perform ODR-like check for C/ObjC when merging tag types from modules.
    /// Differently from C++, actually parse the body and reject / error out
    /// in case of a structural mismatch.
    bool ActOnDuplicateDefinition(DeclSpec &DS, Decl *Prev,
                                  SkipBodyInfo &SkipBody);
  
    typedef void *SkippedDefinitionContext;
  
    /// Invoked when we enter a tag definition that we're skipping.
    SkippedDefinitionContext ActOnTagStartSkippedDefinition(Scope *S, Decl *TD);
  
    Decl *ActOnObjCContainerStartDefinition(Decl *IDecl);
  
    /// ActOnStartCXXMemberDeclarations - Invoked when we have parsed a
    /// C++ record definition's base-specifiers clause and are starting its
    /// member declarations.
    void ActOnStartCXXMemberDeclarations(Scope *S, Decl *TagDecl,
                                         SourceLocation FinalLoc,
                                         bool IsFinalSpelledSealed,
                                         SourceLocation LBraceLoc);
  
    /// ActOnTagFinishDefinition - Invoked once we have finished parsing
    /// the definition of a tag (enumeration, class, struct, or union).
    void ActOnTagFinishDefinition(Scope *S, Decl *TagDecl,
                                  SourceRange BraceRange);
  
    void ActOnTagFinishSkippedDefinition(SkippedDefinitionContext Context);
  
    void ActOnObjCContainerFinishDefinition();
  
    /// Invoked when we must temporarily exit the objective-c container
    /// scope for parsing/looking-up C constructs.
    ///
    /// Must be followed by a call to \see ActOnObjCReenterContainerContext
    void ActOnObjCTemporaryExitContainerContext(DeclContext *DC);
    void ActOnObjCReenterContainerContext(DeclContext *DC);
  
    /// ActOnTagDefinitionError - Invoked when there was an unrecoverable
    /// error parsing the definition of a tag.
    void ActOnTagDefinitionError(Scope *S, Decl *TagDecl);
  
    EnumConstantDecl *CheckEnumConstant(EnumDecl *Enum,
                                        EnumConstantDecl *LastEnumConst,
                                        SourceLocation IdLoc,
                                        IdentifierInfo *Id,
                                        Expr *val);
    bool CheckEnumUnderlyingType(TypeSourceInfo *TI);
    bool CheckEnumRedeclaration(SourceLocation EnumLoc, bool IsScoped,
                                QualType EnumUnderlyingTy, bool IsFixed,
                                const EnumDecl *Prev);
  
    /// Determine whether the body of an anonymous enumeration should be skipped.
    /// \param II The name of the first enumerator.
    SkipBodyInfo shouldSkipAnonEnumBody(Scope *S, IdentifierInfo *II,
                                        SourceLocation IILoc);
  
    Decl *ActOnEnumConstant(Scope *S, Decl *EnumDecl, Decl *LastEnumConstant,
                            SourceLocation IdLoc, IdentifierInfo *Id,
                            const ParsedAttributesView &Attrs,
                            SourceLocation EqualLoc, Expr *Val);
    void ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
                       Decl *EnumDecl, ArrayRef<Decl *> Elements, Scope *S,
                       const ParsedAttributesView &Attr);
  
    DeclContext *getContainingDC(DeclContext *DC);
  
    /// Set the current declaration context until it gets popped.
    void PushDeclContext(Scope *S, DeclContext *DC);
    void PopDeclContext();
  
    /// EnterDeclaratorContext - Used when we must lookup names in the context
    /// of a declarator's nested name specifier.
    void EnterDeclaratorContext(Scope *S, DeclContext *DC);
    void ExitDeclaratorContext(Scope *S);
  
    /// Push the parameters of D, which must be a function, into scope.
    void ActOnReenterFunctionContext(Scope* S, Decl* D);
    void ActOnExitFunctionContext();
  
    DeclContext *getFunctionLevelDeclContext();
  
    /// 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 *getCurFunctionDecl();
  
    /// getCurMethodDecl - If inside of a method body, this returns a pointer to
    /// the method decl for the method being parsed.  If we're currently
    /// in a 'block', this returns the containing context.
    ObjCMethodDecl *getCurMethodDecl();
  
    /// getCurFunctionOrMethodDecl - Return the Decl for the current ObjC method
    /// or C function we're in, otherwise return null.  If we're currently
    /// in a 'block', this returns the containing context.
    NamedDecl *getCurFunctionOrMethodDecl();
  
    /// Add this decl to the scope shadowed decl chains.
    void PushOnScopeChains(NamedDecl *D, Scope *S, bool AddToContext = true);
  
    /// isDeclInScope - If 'Ctx' is a function/method, isDeclInScope returns true
    /// if 'D' is in Scope 'S', otherwise 'S' is ignored and isDeclInScope returns
    /// true if 'D' belongs to the given declaration context.
    ///
    /// \param AllowInlineNamespace If \c true, allow the declaration to be in the
    ///        enclosing namespace set of the context, rather than contained
    ///        directly within it.
    bool isDeclInScope(NamedDecl *D, DeclContext *Ctx, Scope *S = nullptr,
                       bool AllowInlineNamespace = false);
  
    /// Finds the scope corresponding to the given decl context, if it
    /// happens to be an enclosing scope.  Otherwise return NULL.
    static Scope *getScopeForDeclContext(Scope *S, DeclContext *DC);
  
    /// Subroutines of ActOnDeclarator().
    TypedefDecl *ParseTypedefDecl(Scope *S, Declarator &D, QualType T,
                                  TypeSourceInfo *TInfo);
    bool isIncompatibleTypedef(TypeDecl *Old, TypedefNameDecl *New);
  
    /// Describes the kind of merge to perform for availability
    /// attributes (including "deprecated", "unavailable", and "availability").
    enum AvailabilityMergeKind {
      /// Don't merge availability attributes at all.
      AMK_None,
      /// Merge availability attributes for a redeclaration, which requires
      /// an exact match.
      AMK_Redeclaration,
      /// Merge availability attributes for an override, which requires
      /// an exact match or a weakening of constraints.
      AMK_Override,
      /// Merge availability attributes for an implementation of
      /// a protocol requirement.
      AMK_ProtocolImplementation,
    };
  
    /// Describes the kind of priority given to an availability attribute.
    ///
    /// The sum of priorities deteremines the final priority of the attribute.
    /// The final priority determines how the attribute will be merged.
    /// An attribute with a lower priority will always remove higher priority
    /// attributes for the specified platform when it is being applied. An
    /// attribute with a higher priority will not be applied if the declaration
    /// already has an availability attribute with a lower priority for the
    /// specified platform. The final prirority values are not expected to match
    /// the values in this enumeration, but instead should be treated as a plain
    /// integer value. This enumeration just names the priority weights that are
    /// used to calculate that final vaue.
    enum AvailabilityPriority : int {
      /// The availability attribute was specified explicitly next to the
      /// declaration.
      AP_Explicit = 0,
  
      /// The availability attribute was applied using '#pragma clang attribute'.
      AP_PragmaClangAttribute = 1,
  
      /// The availability attribute for a specific platform was inferred from
      /// an availability attribute for another platform.
      AP_InferredFromOtherPlatform = 2
    };
  
    /// Attribute merging methods. Return true if a new attribute was added.
    AvailabilityAttr *
    mergeAvailabilityAttr(NamedDecl *D, const AttributeCommonInfo &CI,
                          IdentifierInfo *Platform, bool Implicit,
                          VersionTuple Introduced, VersionTuple Deprecated,
                          VersionTuple Obsoleted, bool IsUnavailable,
                          StringRef Message, bool IsStrict, StringRef Replacement,
                          AvailabilityMergeKind AMK, int Priority);
    TypeVisibilityAttr *
    mergeTypeVisibilityAttr(Decl *D, const AttributeCommonInfo &CI,
                            TypeVisibilityAttr::VisibilityType Vis);
    VisibilityAttr *mergeVisibilityAttr(Decl *D, const AttributeCommonInfo &CI,
                                        VisibilityAttr::VisibilityType Vis);
    UuidAttr *mergeUuidAttr(Decl *D, const AttributeCommonInfo &CI,
                            StringRef Uuid);
    DLLImportAttr *mergeDLLImportAttr(Decl *D, const AttributeCommonInfo &CI);
    DLLExportAttr *mergeDLLExportAttr(Decl *D, const AttributeCommonInfo &CI);
    MSInheritanceAttr *mergeMSInheritanceAttr(Decl *D,
                                              const AttributeCommonInfo &CI,
                                              bool BestCase,
                                              MSInheritanceModel Model);
    FormatAttr *mergeFormatAttr(Decl *D, const AttributeCommonInfo &CI,
                                IdentifierInfo *Format, int FormatIdx,
                                int FirstArg);
    SectionAttr *mergeSectionAttr(Decl *D, const AttributeCommonInfo &CI,
                                  StringRef Name);
    CodeSegAttr *mergeCodeSegAttr(Decl *D, const AttributeCommonInfo &CI,
                                  StringRef Name);
    AlwaysInlineAttr *mergeAlwaysInlineAttr(Decl *D,
                                            const AttributeCommonInfo &CI,
                                            const IdentifierInfo *Ident);
    MinSizeAttr *mergeMinSizeAttr(Decl *D, const AttributeCommonInfo &CI);
    NoSpeculativeLoadHardeningAttr *
    mergeNoSpeculativeLoadHardeningAttr(Decl *D,
                                        const NoSpeculativeLoadHardeningAttr &AL);
    SpeculativeLoadHardeningAttr *
    mergeSpeculativeLoadHardeningAttr(Decl *D,
                                      const SpeculativeLoadHardeningAttr &AL);
    OptimizeNoneAttr *mergeOptimizeNoneAttr(Decl *D,
                                            const AttributeCommonInfo &CI);
    SwiftNameAttr *mergeSwiftNameAttr(Decl *D, const AttributeCommonInfo &CI,
                                      StringRef Name, bool Override);
    InternalLinkageAttr *mergeInternalLinkageAttr(Decl *D, const ParsedAttr &AL);
    InternalLinkageAttr *mergeInternalLinkageAttr(Decl *D,
                                                  const InternalLinkageAttr &AL);
    CommonAttr *mergeCommonAttr(Decl *D, const ParsedAttr &AL);
    CommonAttr *mergeCommonAttr(Decl *D, const CommonAttr &AL);
  
    void mergeDeclAttributes(NamedDecl *New, Decl *Old,
                             AvailabilityMergeKind AMK = AMK_Redeclaration);
    void MergeTypedefNameDecl(Scope *S, TypedefNameDecl *New,
                              LookupResult &OldDecls);
    bool MergeFunctionDecl(FunctionDecl *New, NamedDecl *&Old, Scope *S,
                           bool MergeTypeWithOld);
    bool MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
                                      Scope *S, bool MergeTypeWithOld);
    void mergeObjCMethodDecls(ObjCMethodDecl *New, ObjCMethodDecl *Old);
    void MergeVarDecl(VarDecl *New, LookupResult &Previous);
    void MergeVarDeclTypes(VarDecl *New, VarDecl *Old, bool MergeTypeWithOld);
    void MergeVarDeclExceptionSpecs(VarDecl *New, VarDecl *Old);
    bool checkVarDeclRedefinition(VarDecl *OldDefn, VarDecl *NewDefn);
    void notePreviousDefinition(const NamedDecl *Old, SourceLocation New);
    bool MergeCXXFunctionDecl(FunctionDecl *New, FunctionDecl *Old, Scope *S);
  
    // AssignmentAction - This is used by all the assignment diagnostic functions
    // to represent what is actually causing the operation
    enum AssignmentAction {
      AA_Assigning,
      AA_Passing,
      AA_Returning,
      AA_Converting,
      AA_Initializing,
      AA_Sending,
      AA_Casting,
      AA_Passing_CFAudited
    };
  
    /// C++ Overloading.
    enum OverloadKind {
      /// This is a legitimate overload: the existing declarations are
      /// functions or function templates with different signatures.
      Ovl_Overload,
  
      /// This is not an overload because the signature exactly matches
      /// an existing declaration.
      Ovl_Match,
  
      /// This is not an overload because the lookup results contain a
      /// non-function.
      Ovl_NonFunction
    };
    OverloadKind CheckOverload(Scope *S,
                               FunctionDecl *New,
                               const LookupResult &OldDecls,
                               NamedDecl *&OldDecl,
                               bool IsForUsingDecl);
    bool IsOverload(FunctionDecl *New, FunctionDecl *Old, bool IsForUsingDecl,
                    bool ConsiderCudaAttrs = true,
                    bool ConsiderRequiresClauses = true);
  
    enum class AllowedExplicit {
      /// Allow no explicit functions to be used.
      None,
      /// Allow explicit conversion functions but not explicit constructors.
      Conversions,
      /// Allow both explicit conversion functions and explicit constructors.
      All
    };
  
    ImplicitConversionSequence
    TryImplicitConversion(Expr *From, QualType ToType,
                          bool SuppressUserConversions,
                          AllowedExplicit AllowExplicit,
                          bool InOverloadResolution,
                          bool CStyle,
                          bool AllowObjCWritebackConversion);
  
    bool IsIntegralPromotion(Expr *From, QualType FromType, QualType ToType);
    bool IsFloatingPointPromotion(QualType FromType, QualType ToType);
    bool IsComplexPromotion(QualType FromType, QualType ToType);
    bool IsPointerConversion(Expr *From, QualType FromType, QualType ToType,
                             bool InOverloadResolution,
                             QualType& ConvertedType, bool &IncompatibleObjC);
    bool isObjCPointerConversion(QualType FromType, QualType ToType,
                                 QualType& ConvertedType, bool &IncompatibleObjC);
    bool isObjCWritebackConversion(QualType FromType, QualType ToType,
                                   QualType &ConvertedType);
    bool IsBlockPointerConversion(QualType FromType, QualType ToType,
                                  QualType& ConvertedType);
    bool FunctionParamTypesAreEqual(const FunctionProtoType *OldType,
                                    const FunctionProtoType *NewType,
                                    unsigned *ArgPos = nullptr);
    void HandleFunctionTypeMismatch(PartialDiagnostic &PDiag,
                                    QualType FromType, QualType ToType);
  
    void maybeExtendBlockObject(ExprResult &E);
    CastKind PrepareCastToObjCObjectPointer(ExprResult &E);
    bool CheckPointerConversion(Expr *From, QualType ToType,
                                CastKind &Kind,
                                CXXCastPath& BasePath,
                                bool IgnoreBaseAccess,
                                bool Diagnose = true);
    bool IsMemberPointerConversion(Expr *From, QualType FromType, QualType ToType,
                                   bool InOverloadResolution,
                                   QualType &ConvertedType);
    bool CheckMemberPointerConversion(Expr *From, QualType ToType,
                                      CastKind &Kind,
                                      CXXCastPath &BasePath,
                                      bool IgnoreBaseAccess);
    bool IsQualificationConversion(QualType FromType, QualType ToType,
                                   bool CStyle, bool &ObjCLifetimeConversion);
    bool IsFunctionConversion(QualType FromType, QualType ToType,
                              QualType &ResultTy);
    bool DiagnoseMultipleUserDefinedConversion(Expr *From, QualType ToType);
    bool isSameOrCompatibleFunctionType(CanQualType Param, CanQualType Arg);
  
    ExprResult PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
                                               const VarDecl *NRVOCandidate,
                                               QualType ResultType,
                                               Expr *Value,
                                               bool AllowNRVO = true);
  
    bool CanPerformAggregateInitializationForOverloadResolution(
        const InitializedEntity &Entity, InitListExpr *From);
  
    bool CanPerformCopyInitialization(const InitializedEntity &Entity,
                                      ExprResult Init);
    ExprResult PerformCopyInitialization(const InitializedEntity &Entity,
                                         SourceLocation EqualLoc,
                                         ExprResult Init,
                                         bool TopLevelOfInitList = false,
                                         bool AllowExplicit = false);
    ExprResult PerformObjectArgumentInitialization(Expr *From,
                                                   NestedNameSpecifier *Qualifier,
                                                   NamedDecl *FoundDecl,
                                                   CXXMethodDecl *Method);
  
    /// Check that the lifetime of the initializer (and its subobjects) is
    /// sufficient for initializing the entity, and perform lifetime extension
    /// (when permitted) if not.
    void checkInitializerLifetime(const InitializedEntity &Entity, Expr *Init);
  
    ExprResult PerformContextuallyConvertToBool(Expr *From);
    ExprResult PerformContextuallyConvertToObjCPointer(Expr *From);
  
    /// Contexts in which a converted constant expression is required.
    enum CCEKind {
      CCEK_CaseValue,   ///< Expression in a case label.
      CCEK_Enumerator,  ///< Enumerator value with fixed underlying type.
      CCEK_TemplateArg, ///< Value of a non-type template parameter.
      CCEK_NewExpr,     ///< Constant expression in a noptr-new-declarator.
      CCEK_ConstexprIf, ///< Condition in a constexpr if statement.
      CCEK_ExplicitBool ///< Condition in an explicit(bool) specifier.
    };
    ExprResult CheckConvertedConstantExpression(Expr *From, QualType T,
                                                llvm::APSInt &Value, CCEKind CCE);
    ExprResult CheckConvertedConstantExpression(Expr *From, QualType T,
                                                APValue &Value, CCEKind CCE);
  
    /// Abstract base class used to perform a contextual implicit
    /// conversion from an expression to any type passing a filter.
    class ContextualImplicitConverter {
    public:
      bool Suppress;
      bool SuppressConversion;
  
      ContextualImplicitConverter(bool Suppress = false,
                                  bool SuppressConversion = false)
          : Suppress(Suppress), SuppressConversion(SuppressConversion) {}
  
      /// Determine whether the specified type is a valid destination type
      /// for this conversion.
      virtual bool match(QualType T) = 0;
  
      /// Emits a diagnostic complaining that the expression does not have
      /// integral or enumeration type.
      virtual SemaDiagnosticBuilder
      diagnoseNoMatch(Sema &S, SourceLocation Loc, QualType T) = 0;
  
      /// Emits a diagnostic when the expression has incomplete class type.
      virtual SemaDiagnosticBuilder
      diagnoseIncomplete(Sema &S, SourceLocation Loc, QualType T) = 0;
  
      /// Emits a diagnostic when the only matching conversion function
      /// is explicit.
      virtual SemaDiagnosticBuilder diagnoseExplicitConv(
          Sema &S, SourceLocation Loc, QualType T, QualType ConvTy) = 0;
  
      /// Emits a note for the explicit conversion function.
      virtual SemaDiagnosticBuilder
      noteExplicitConv(Sema &S, CXXConversionDecl *Conv, QualType ConvTy) = 0;
  
      /// Emits a diagnostic when there are multiple possible conversion
      /// functions.
      virtual SemaDiagnosticBuilder
      diagnoseAmbiguous(Sema &S, SourceLocation Loc, QualType T) = 0;
  
      /// Emits a note for one of the candidate conversions.
      virtual SemaDiagnosticBuilder
      noteAmbiguous(Sema &S, CXXConversionDecl *Conv, QualType ConvTy) = 0;
  
      /// Emits a diagnostic when we picked a conversion function
      /// (for cases when we are not allowed to pick a conversion function).
      virtual SemaDiagnosticBuilder diagnoseConversion(
          Sema &S, SourceLocation Loc, QualType T, QualType ConvTy) = 0;
  
      virtual ~ContextualImplicitConverter() {}
    };
  
    class ICEConvertDiagnoser : public ContextualImplicitConverter {
      bool AllowScopedEnumerations;
  
    public:
      ICEConvertDiagnoser(bool AllowScopedEnumerations,
                          bool Suppress, bool SuppressConversion)
          : ContextualImplicitConverter(Suppress, SuppressConversion),
            AllowScopedEnumerations(AllowScopedEnumerations) {}
  
      /// Match an integral or (possibly scoped) enumeration type.
      bool match(QualType T) override;
  
      SemaDiagnosticBuilder
      diagnoseNoMatch(Sema &S, SourceLocation Loc, QualType T) override {
        return diagnoseNotInt(S, Loc, T);
      }
  
      /// Emits a diagnostic complaining that the expression does not have
      /// integral or enumeration type.
      virtual SemaDiagnosticBuilder
      diagnoseNotInt(Sema &S, SourceLocation Loc, QualType T) = 0;
    };
  
    /// Perform a contextual implicit conversion.
    ExprResult PerformContextualImplicitConversion(
        SourceLocation Loc, Expr *FromE, ContextualImplicitConverter &Converter);
  
  
    enum ObjCSubscriptKind {
      OS_Array,
      OS_Dictionary,
      OS_Error
    };
    ObjCSubscriptKind CheckSubscriptingKind(Expr *FromE);
  
    // Note that LK_String is intentionally after the other literals, as
    // this is used for diagnostics logic.
    enum ObjCLiteralKind {
      LK_Array,
      LK_Dictionary,
      LK_Numeric,
      LK_Boxed,
      LK_String,
      LK_Block,
      LK_None
    };
    ObjCLiteralKind CheckLiteralKind(Expr *FromE);
  
    ExprResult PerformObjectMemberConversion(Expr *From,
                                             NestedNameSpecifier *Qualifier,
                                             NamedDecl *FoundDecl,
                                             NamedDecl *Member);
  
    // Members have to be NamespaceDecl* or TranslationUnitDecl*.
    // TODO: make this is a typesafe union.
    typedef llvm::SmallSetVector<DeclContext   *, 16> AssociatedNamespaceSet;
    typedef llvm::SmallSetVector<CXXRecordDecl *, 16> AssociatedClassSet;
  
    using ADLCallKind = CallExpr::ADLCallKind;
  
    void AddOverloadCandidate(FunctionDecl *Function, DeclAccessPair FoundDecl,
                              ArrayRef<Expr *> Args,
                              OverloadCandidateSet &CandidateSet,
                              bool SuppressUserConversions = false,
                              bool PartialOverloading = false,
                              bool AllowExplicit = true,
                              bool AllowExplicitConversion = false,
                              ADLCallKind IsADLCandidate = ADLCallKind::NotADL,
                              ConversionSequenceList EarlyConversions = None,
                              OverloadCandidateParamOrder PO = {});
    void AddFunctionCandidates(const UnresolvedSetImpl &Functions,
                        ArrayRef<Expr *> Args,
                        OverloadCandidateSet &CandidateSet,
                        TemplateArgumentListInfo *ExplicitTemplateArgs = nullptr,
                        bool SuppressUserConversions = false,
                        bool PartialOverloading = false,
                        bool FirstArgumentIsBase = false);
    void AddMethodCandidate(DeclAccessPair FoundDecl,
                            QualType ObjectType,
                            Expr::Classification ObjectClassification,
                            ArrayRef<Expr *> Args,
                            OverloadCandidateSet& CandidateSet,
                            bool SuppressUserConversion = false,
                            OverloadCandidateParamOrder PO = {});
    void AddMethodCandidate(CXXMethodDecl *Method,
                            DeclAccessPair FoundDecl,
                            CXXRecordDecl *ActingContext, QualType ObjectType,
                            Expr::Classification ObjectClassification,
                            ArrayRef<Expr *> Args,
                            OverloadCandidateSet& CandidateSet,
                            bool SuppressUserConversions = false,
                            bool PartialOverloading = false,
                            ConversionSequenceList EarlyConversions = None,
                            OverloadCandidateParamOrder PO = {});
    void AddMethodTemplateCandidate(FunctionTemplateDecl *MethodTmpl,
                                    DeclAccessPair FoundDecl,
                                    CXXRecordDecl *ActingContext,
                                   TemplateArgumentListInfo *ExplicitTemplateArgs,
                                    QualType ObjectType,
                                    Expr::Classification ObjectClassification,
                                    ArrayRef<Expr *> Args,
                                    OverloadCandidateSet& CandidateSet,
                                    bool SuppressUserConversions = false,
                                    bool PartialOverloading = false,
                                    OverloadCandidateParamOrder PO = {});
    void AddTemplateOverloadCandidate(
        FunctionTemplateDecl *FunctionTemplate, DeclAccessPair FoundDecl,
        TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
        OverloadCandidateSet &CandidateSet, bool SuppressUserConversions = false,
        bool PartialOverloading = false, bool AllowExplicit = true,
        ADLCallKind IsADLCandidate = ADLCallKind::NotADL,
        OverloadCandidateParamOrder PO = {});
    bool CheckNonDependentConversions(
        FunctionTemplateDecl *FunctionTemplate, ArrayRef<QualType> ParamTypes,
        ArrayRef<Expr *> Args, OverloadCandidateSet &CandidateSet,
        ConversionSequenceList &Conversions, bool SuppressUserConversions,
        CXXRecordDecl *ActingContext = nullptr, QualType ObjectType = QualType(),
        Expr::Classification ObjectClassification = {},
        OverloadCandidateParamOrder PO = {});
    void AddConversionCandidate(
        CXXConversionDecl *Conversion, DeclAccessPair FoundDecl,
        CXXRecordDecl *ActingContext, Expr *From, QualType ToType,
        OverloadCandidateSet &CandidateSet, bool AllowObjCConversionOnExplicit,
        bool AllowExplicit, bool AllowResultConversion = true);
    void AddTemplateConversionCandidate(
        FunctionTemplateDecl *FunctionTemplate, DeclAccessPair FoundDecl,
        CXXRecordDecl *ActingContext, Expr *From, QualType ToType,
        OverloadCandidateSet &CandidateSet, bool AllowObjCConversionOnExplicit,
        bool AllowExplicit, bool AllowResultConversion = true);
    void AddSurrogateCandidate(CXXConversionDecl *Conversion,
                               DeclAccessPair FoundDecl,
                               CXXRecordDecl *ActingContext,
                               const FunctionProtoType *Proto,
                               Expr *Object, ArrayRef<Expr *> Args,
                               OverloadCandidateSet& CandidateSet);
    void AddNonMemberOperatorCandidates(
        const UnresolvedSetImpl &Functions, ArrayRef<Expr *> Args,
        OverloadCandidateSet &CandidateSet,
        TemplateArgumentListInfo *ExplicitTemplateArgs = nullptr);
    void AddMemberOperatorCandidates(OverloadedOperatorKind Op,
                                     SourceLocation OpLoc, ArrayRef<Expr *> Args,
                                     OverloadCandidateSet &CandidateSet,
                                     OverloadCandidateParamOrder PO = {});
    void AddBuiltinCandidate(QualType *ParamTys, ArrayRef<Expr *> Args,
                             OverloadCandidateSet& CandidateSet,
                             bool IsAssignmentOperator = false,
                             unsigned NumContextualBoolArguments = 0);
    void AddBuiltinOperatorCandidates(OverloadedOperatorKind Op,
                                      SourceLocation OpLoc, ArrayRef<Expr *> Args,
                                      OverloadCandidateSet& CandidateSet);
    void AddArgumentDependentLookupCandidates(DeclarationName Name,
                                              SourceLocation Loc,
                                              ArrayRef<Expr *> Args,
                                  TemplateArgumentListInfo *ExplicitTemplateArgs,
                                              OverloadCandidateSet& CandidateSet,
                                              bool PartialOverloading = false);
  
    // Emit as a 'note' the specific overload candidate
    void NoteOverloadCandidate(
        NamedDecl *Found, FunctionDecl *Fn,
        OverloadCandidateRewriteKind RewriteKind = OverloadCandidateRewriteKind(),
        QualType DestType = QualType(), bool TakingAddress = false);
  
    // Emit as a series of 'note's all template and non-templates identified by
    // the expression Expr
    void NoteAllOverloadCandidates(Expr *E, QualType DestType = QualType(),
                                   bool TakingAddress = false);
  
    /// Check the enable_if expressions on the given function. Returns the first
    /// failing attribute, or NULL if they were all successful.
    EnableIfAttr *CheckEnableIf(FunctionDecl *Function, ArrayRef<Expr *> Args,
                                bool MissingImplicitThis = false);
  
    /// Find the failed Boolean condition within a given Boolean
    /// constant expression, and describe it with a string.
    std::pair<Expr *, std::string> findFailedBooleanCondition(Expr *Cond);
  
    /// Emit diagnostics for the diagnose_if attributes on Function, ignoring any
    /// non-ArgDependent DiagnoseIfAttrs.
    ///
    /// Argument-dependent diagnose_if attributes should be checked each time a
    /// function is used as a direct callee of a function call.
    ///
    /// Returns true if any errors were emitted.
    bool diagnoseArgDependentDiagnoseIfAttrs(const FunctionDecl *Function,
                                             const Expr *ThisArg,
                                             ArrayRef<const Expr *> Args,
                                             SourceLocation Loc);
  
    /// Emit diagnostics for the diagnose_if attributes on Function, ignoring any
    /// ArgDependent DiagnoseIfAttrs.
    ///
    /// Argument-independent diagnose_if attributes should be checked on every use
    /// of a function.
    ///
    /// Returns true if any errors were emitted.
    bool diagnoseArgIndependentDiagnoseIfAttrs(const NamedDecl *ND,
                                               SourceLocation Loc);
  
    /// Returns whether the given function's address can be taken or not,
    /// optionally emitting a diagnostic if the address can't be taken.
    ///
    /// Returns false if taking the address of the function is illegal.
    bool checkAddressOfFunctionIsAvailable(const FunctionDecl *Function,
                                           bool Complain = false,
                                           SourceLocation Loc = SourceLocation());
  
    // [PossiblyAFunctionType]  -->   [Return]
    // NonFunctionType --> NonFunctionType
    // R (A) --> R(A)
    // R (*)(A) --> R (A)
    // R (&)(A) --> R (A)
    // R (S::*)(A) --> R (A)
    QualType ExtractUnqualifiedFunctionType(QualType PossiblyAFunctionType);
  
    FunctionDecl *
    ResolveAddressOfOverloadedFunction(Expr *AddressOfExpr,
                                       QualType TargetType,
                                       bool Complain,
                                       DeclAccessPair &Found,
                                       bool *pHadMultipleCandidates = nullptr);
  
    FunctionDecl *
    resolveAddressOfSingleOverloadCandidate(Expr *E, DeclAccessPair &FoundResult);
  
    bool resolveAndFixAddressOfSingleOverloadCandidate(
        ExprResult &SrcExpr, bool DoFunctionPointerConversion = false);
  
    FunctionDecl *
    ResolveSingleFunctionTemplateSpecialization(OverloadExpr *ovl,
                                                bool Complain = false,
                                                DeclAccessPair *Found = nullptr);
  
    bool ResolveAndFixSingleFunctionTemplateSpecialization(
                        ExprResult &SrcExpr,
                        bool DoFunctionPointerConverion = false,
                        bool Complain = false,
                        SourceRange OpRangeForComplaining = SourceRange(),
                        QualType DestTypeForComplaining = QualType(),
                        unsigned DiagIDForComplaining = 0);
  
  
    Expr *FixOverloadedFunctionReference(Expr *E,
                                         DeclAccessPair FoundDecl,
                                         FunctionDecl *Fn);
    ExprResult FixOverloadedFunctionReference(ExprResult,
                                              DeclAccessPair FoundDecl,
                                              FunctionDecl *Fn);
  
    void AddOverloadedCallCandidates(UnresolvedLookupExpr *ULE,
                                     ArrayRef<Expr *> Args,
                                     OverloadCandidateSet &CandidateSet,
                                     bool PartialOverloading = false);
  
    // An enum used to represent the different possible results of building a
    // range-based for loop.
    enum ForRangeStatus {
      FRS_Success,
      FRS_NoViableFunction,
      FRS_DiagnosticIssued
    };
  
    ForRangeStatus BuildForRangeBeginEndCall(SourceLocation Loc,
                                             SourceLocation RangeLoc,
                                             const DeclarationNameInfo &NameInfo,
                                             LookupResult &MemberLookup,
                                             OverloadCandidateSet *CandidateSet,
                                             Expr *Range, ExprResult *CallExpr);
  
    ExprResult BuildOverloadedCallExpr(Scope *S, Expr *Fn,
                                       UnresolvedLookupExpr *ULE,
                                       SourceLocation LParenLoc,
                                       MultiExprArg Args,
                                       SourceLocation RParenLoc,
                                       Expr *ExecConfig,
                                       bool AllowTypoCorrection=true,
                                       bool CalleesAddressIsTaken=false);
  
    bool buildOverloadedCallSet(Scope *S, Expr *Fn, UnresolvedLookupExpr *ULE,
                                MultiExprArg Args, SourceLocation RParenLoc,
                                OverloadCandidateSet *CandidateSet,
                                ExprResult *Result);
  
    ExprResult CreateOverloadedUnaryOp(SourceLocation OpLoc,
                                       UnaryOperatorKind Opc,
                                       const UnresolvedSetImpl &Fns,
                                       Expr *input, bool RequiresADL = true);
  
    void LookupOverloadedBinOp(OverloadCandidateSet &CandidateSet,
                               OverloadedOperatorKind Op,
                               const UnresolvedSetImpl &Fns,
                               ArrayRef<Expr *> Args, bool RequiresADL = true);
    ExprResult CreateOverloadedBinOp(SourceLocation OpLoc,
                                     BinaryOperatorKind Opc,
                                     const UnresolvedSetImpl &Fns,
                                     Expr *LHS, Expr *RHS,
                                     bool RequiresADL = true,
                                     bool AllowRewrittenCandidates = true,
                                     FunctionDecl *DefaultedFn = nullptr);
    ExprResult BuildSynthesizedThreeWayComparison(SourceLocation OpLoc,
                                                  const UnresolvedSetImpl &Fns,
                                                  Expr *LHS, Expr *RHS,
                                                  FunctionDecl *DefaultedFn);
  
    ExprResult CreateOverloadedArraySubscriptExpr(SourceLocation LLoc,
                                                  SourceLocation RLoc,
                                                  Expr *Base,Expr *Idx);
  
    ExprResult
    BuildCallToMemberFunction(Scope *S, Expr *MemExpr,
                              SourceLocation LParenLoc,
                              MultiExprArg Args,
                              SourceLocation RParenLoc);
    ExprResult
    BuildCallToObjectOfClassType(Scope *S, Expr *Object, SourceLocation LParenLoc,
                                 MultiExprArg Args,
                                 SourceLocation RParenLoc);
  
    ExprResult BuildOverloadedArrowExpr(Scope *S, Expr *Base,
                                        SourceLocation OpLoc,
                                        bool *NoArrowOperatorFound = nullptr);
  
    /// CheckCallReturnType - Checks that a call expression's return type is
    /// complete. Returns true on failure. The location passed in is the location
    /// that best represents the call.
    bool CheckCallReturnType(QualType ReturnType, SourceLocation Loc,
                             CallExpr *CE, FunctionDecl *FD);
  
    /// Helpers for dealing with blocks and functions.
    bool CheckParmsForFunctionDef(ArrayRef<ParmVarDecl *> Parameters,
                                  bool CheckParameterNames);
    void CheckCXXDefaultArguments(FunctionDecl *FD);
    void CheckExtraCXXDefaultArguments(Declarator &D);
    Scope *getNonFieldDeclScope(Scope *S);
  
    /// \name Name lookup
    ///
    /// These routines provide name lookup that is used during semantic
    /// analysis to resolve the various kinds of names (identifiers,
    /// overloaded operator names, constructor names, etc.) into zero or
    /// more declarations within a particular scope. The major entry
    /// points are LookupName, which performs unqualified name lookup,
    /// and LookupQualifiedName, which performs qualified name lookup.
    ///
    /// All name lookup is performed based on some specific criteria,
    /// which specify what names will be visible to name lookup and how
    /// far name lookup should work. These criteria are important both
    /// for capturing language semantics (certain lookups will ignore
    /// certain names, for example) and for performance, since name
    /// lookup is often a bottleneck in the compilation of C++. Name
    /// lookup criteria is specified via the LookupCriteria enumeration.
    ///
    /// The results of name lookup can vary based on the kind of name
    /// lookup performed, the current language, and the translation
    /// unit. In C, for example, name lookup will either return nothing
    /// (no entity found) or a single declaration. In C++, name lookup
    /// can additionally refer to a set of overloaded functions or
    /// result in an ambiguity. All of the possible results of name
    /// lookup are captured by the LookupResult class, which provides
    /// the ability to distinguish among them.
    //@{
  
    /// Describes the kind of name lookup to perform.
    enum LookupNameKind {
      /// Ordinary name lookup, which finds ordinary names (functions,
      /// variables, typedefs, etc.) in C and most kinds of names
      /// (functions, variables, members, types, etc.) in C++.
      LookupOrdinaryName = 0,
      /// Tag name lookup, which finds the names of enums, classes,
      /// structs, and unions.
      LookupTagName,
      /// Label name lookup.
      LookupLabel,
      /// Member name lookup, which finds the names of
      /// class/struct/union members.
      LookupMemberName,
      /// Look up of an operator name (e.g., operator+) for use with
      /// operator overloading. This lookup is similar to ordinary name
      /// lookup, but will ignore any declarations that are class members.
      LookupOperatorName,
      /// Look up a name following ~ in a destructor name. This is an ordinary
      /// lookup, but prefers tags to typedefs.
      LookupDestructorName,
      /// Look up of a name that precedes the '::' scope resolution
      /// operator in C++. This lookup completely ignores operator, object,
      /// function, and enumerator names (C++ [basic.lookup.qual]p1).
      LookupNestedNameSpecifierName,
      /// Look up a namespace name within a C++ using directive or
      /// namespace alias definition, ignoring non-namespace names (C++
      /// [basic.lookup.udir]p1).
      LookupNamespaceName,
      /// Look up all declarations in a scope with the given name,
      /// including resolved using declarations.  This is appropriate
      /// for checking redeclarations for a using declaration.
      LookupUsingDeclName,
      /// Look up an ordinary name that is going to be redeclared as a
      /// name with linkage. This lookup ignores any declarations that
      /// are outside of the current scope unless they have linkage. See
      /// C99 6.2.2p4-5 and C++ [basic.link]p6.
      LookupRedeclarationWithLinkage,
      /// Look up a friend of a local class. This lookup does not look
      /// outside the innermost non-class scope. See C++11 [class.friend]p11.
      LookupLocalFriendName,
      /// Look up the name of an Objective-C protocol.
      LookupObjCProtocolName,
      /// Look up implicit 'self' parameter of an objective-c method.
      LookupObjCImplicitSelfParam,
      /// Look up the name of an OpenMP user-defined reduction operation.
      LookupOMPReductionName,
      /// Look up the name of an OpenMP user-defined mapper.
      LookupOMPMapperName,
      /// Look up any declaration with any name.
      LookupAnyName
    };
  
    /// Specifies whether (or how) name lookup is being performed for a
    /// redeclaration (vs. a reference).
    enum RedeclarationKind {
      /// The lookup is a reference to this name that is not for the
      /// purpose of redeclaring the name.
      NotForRedeclaration = 0,
      /// The lookup results will be used for redeclaration of a name,
      /// if an entity by that name already exists and is visible.
      ForVisibleRedeclaration,
      /// The lookup results will be used for redeclaration of a name
      /// with external linkage; non-visible lookup results with external linkage
      /// may also be found.
      ForExternalRedeclaration
    };
  
    RedeclarationKind forRedeclarationInCurContext() {
      // A declaration with an owning module for linkage can never link against
      // anything that is not visible. We don't need to check linkage here; if
      // the context has internal linkage, redeclaration lookup won't find things
      // from other TUs, and we can't safely compute linkage yet in general.
      if (cast<Decl>(CurContext)
              ->getOwningModuleForLinkage(/*IgnoreLinkage*/true))
        return ForVisibleRedeclaration;
      return ForExternalRedeclaration;
    }
  
    /// The possible outcomes of name lookup for a literal operator.
    enum LiteralOperatorLookupResult {
      /// The lookup resulted in an error.
      LOLR_Error,
      /// The lookup found no match but no diagnostic was issued.
      LOLR_ErrorNoDiagnostic,
      /// The lookup found a single 'cooked' literal operator, which
      /// expects a normal literal to be built and passed to it.
      LOLR_Cooked,
      /// The lookup found a single 'raw' literal operator, which expects
      /// a string literal containing the spelling of the literal token.
      LOLR_Raw,
      /// The lookup found an overload set of literal operator templates,
      /// which expect the characters of the spelling of the literal token to be
      /// passed as a non-type template argument pack.
      LOLR_Template,
      /// The lookup found an overload set of literal operator templates,
      /// which expect the character type and characters of the spelling of the
      /// string literal token to be passed as template arguments.
      LOLR_StringTemplate
    };
  
    SpecialMemberOverloadResult LookupSpecialMember(CXXRecordDecl *D,
                                                    CXXSpecialMember SM,
                                                    bool ConstArg,
                                                    bool VolatileArg,
                                                    bool RValueThis,
                                                    bool ConstThis,
                                                    bool VolatileThis);
  
    typedef std::function<void(const TypoCorrection &)> TypoDiagnosticGenerator;
    typedef std::function<ExprResult(Sema &, TypoExpr *, TypoCorrection)>
        TypoRecoveryCallback;
  
  private:
    bool CppLookupName(LookupResult &R, Scope *S);
  
    struct TypoExprState {
      std::unique_ptr<TypoCorrectionConsumer> Consumer;
      TypoDiagnosticGenerator DiagHandler;
      TypoRecoveryCallback RecoveryHandler;
      TypoExprState();
      TypoExprState(TypoExprState &&other) noexcept;
      TypoExprState &operator=(TypoExprState &&other) noexcept;
    };
  
    /// The set of unhandled TypoExprs and their associated state.
    llvm::MapVector<TypoExpr *, TypoExprState> DelayedTypos;
  
    /// Creates a new TypoExpr AST node.
    TypoExpr *createDelayedTypo(std::unique_ptr<TypoCorrectionConsumer> TCC,
                                TypoDiagnosticGenerator TDG,
                                TypoRecoveryCallback TRC);
  
    // The set of known/encountered (unique, canonicalized) NamespaceDecls.
    //
    // The boolean value will be true to indicate that the namespace was loaded
    // from an AST/PCH file, or false otherwise.
    llvm::MapVector<NamespaceDecl*, bool> KnownNamespaces;
  
    /// Whether we have already loaded known namespaces from an extenal
    /// source.
    bool LoadedExternalKnownNamespaces;
  
    /// Helper for CorrectTypo and CorrectTypoDelayed used to create and
    /// populate a new TypoCorrectionConsumer. Returns nullptr if typo correction
    /// should be skipped entirely.
    std::unique_ptr<TypoCorrectionConsumer>
    makeTypoCorrectionConsumer(const DeclarationNameInfo &Typo,
                               Sema::LookupNameKind LookupKind, Scope *S,
                               CXXScopeSpec *SS,
                               CorrectionCandidateCallback &CCC,
                               DeclContext *MemberContext, bool EnteringContext,
                               const ObjCObjectPointerType *OPT,
                               bool ErrorRecovery);
  
  public:
    const TypoExprState &getTypoExprState(TypoExpr *TE) const;
  
    /// Clears the state of the given TypoExpr.
    void clearDelayedTypo(TypoExpr *TE);
  
    /// Look up a name, looking for a single declaration.  Return
    /// null if the results were absent, ambiguous, or overloaded.
    ///
    /// It is preferable to use the elaborated form and explicitly handle
    /// ambiguity and overloaded.
    NamedDecl *LookupSingleName(Scope *S, DeclarationName Name,
                                SourceLocation Loc,
                                LookupNameKind NameKind,
                                RedeclarationKind Redecl
                                  = NotForRedeclaration);
    bool LookupBuiltin(LookupResult &R);
    bool LookupName(LookupResult &R, Scope *S,
                    bool AllowBuiltinCreation = false);
    bool LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
                             bool InUnqualifiedLookup = false);
    bool LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
                             CXXScopeSpec &SS);
    bool LookupParsedName(LookupResult &R, Scope *S, CXXScopeSpec *SS,
                          bool AllowBuiltinCreation = false,
                          bool EnteringContext = false);
    ObjCProtocolDecl *LookupProtocol(IdentifierInfo *II, SourceLocation IdLoc,
                                     RedeclarationKind Redecl
                                       = NotForRedeclaration);
    bool LookupInSuper(LookupResult &R, CXXRecordDecl *Class);
  
    void LookupOverloadedOperatorName(OverloadedOperatorKind Op, Scope *S,
                                      QualType T1, QualType T2,
                                      UnresolvedSetImpl &Functions);
  
    LabelDecl *LookupOrCreateLabel(IdentifierInfo *II, SourceLocation IdentLoc,
                                   SourceLocation GnuLabelLoc = SourceLocation());
  
    DeclContextLookupResult LookupConstructors(CXXRecordDecl *Class);
    CXXConstructorDecl *LookupDefaultConstructor(CXXRecordDecl *Class);
    CXXConstructorDecl *LookupCopyingConstructor(CXXRecordDecl *Class,
                                                 unsigned Quals);
    CXXMethodDecl *LookupCopyingAssignment(CXXRecordDecl *Class, unsigned Quals,
                                           bool RValueThis, unsigned ThisQuals);
    CXXConstructorDecl *LookupMovingConstructor(CXXRecordDecl *Class,
                                                unsigned Quals);
    CXXMethodDecl *LookupMovingAssignment(CXXRecordDecl *Class, unsigned Quals,
                                          bool RValueThis, unsigned ThisQuals);
    CXXDestructorDecl *LookupDestructor(CXXRecordDecl *Class);
  
    bool checkLiteralOperatorId(const CXXScopeSpec &SS, const UnqualifiedId &Id);
    LiteralOperatorLookupResult LookupLiteralOperator(Scope *S, LookupResult &R,
                                                      ArrayRef<QualType> ArgTys,
                                                      bool AllowRaw,
                                                      bool AllowTemplate,
                                                      bool AllowStringTemplate,
                                                      bool DiagnoseMissing);
    bool isKnownName(StringRef name);
  
    /// Status of the function emission on the CUDA/HIP/OpenMP host/device attrs.
    enum class FunctionEmissionStatus {
      Emitted,
      CUDADiscarded,     // Discarded due to CUDA/HIP hostness
      OMPDiscarded,      // Discarded due to OpenMP hostness
      TemplateDiscarded, // Discarded due to uninstantiated templates
      Unknown,
    };
    FunctionEmissionStatus getEmissionStatus(FunctionDecl *Decl);
  
    // Whether the callee should be ignored in CUDA/HIP/OpenMP host/device check.
    bool shouldIgnoreInHostDeviceCheck(FunctionDecl *Callee);
  
    void ArgumentDependentLookup(DeclarationName Name, SourceLocation Loc,
                                 ArrayRef<Expr *> Args, ADLResult &Functions);
  
    void LookupVisibleDecls(Scope *S, LookupNameKind Kind,
                            VisibleDeclConsumer &Consumer,
                            bool IncludeGlobalScope = true,
                            bool LoadExternal = true);
    void LookupVisibleDecls(DeclContext *Ctx, LookupNameKind Kind,
                            VisibleDeclConsumer &Consumer,
                            bool IncludeGlobalScope = true,
                            bool IncludeDependentBases = false,
                            bool LoadExternal = true);
  
    enum CorrectTypoKind {
      CTK_NonError,     // CorrectTypo used in a non error recovery situation.
      CTK_ErrorRecovery // CorrectTypo used in normal error recovery.
    };
  
    TypoCorrection CorrectTypo(const DeclarationNameInfo &Typo,
                               Sema::LookupNameKind LookupKind,
                               Scope *S, CXXScopeSpec *SS,
                               CorrectionCandidateCallback &CCC,
                               CorrectTypoKind Mode,
                               DeclContext *MemberContext = nullptr,
                               bool EnteringContext = false,
                               const ObjCObjectPointerType *OPT = nullptr,
                               bool RecordFailure = true);
  
    TypoExpr *CorrectTypoDelayed(const DeclarationNameInfo &Typo,
                                 Sema::LookupNameKind LookupKind, Scope *S,
                                 CXXScopeSpec *SS,
                                 CorrectionCandidateCallback &CCC,
                                 TypoDiagnosticGenerator TDG,
                                 TypoRecoveryCallback TRC, CorrectTypoKind Mode,
                                 DeclContext *MemberContext = nullptr,
                                 bool EnteringContext = false,
                                 const ObjCObjectPointerType *OPT = nullptr);
  
    /// Process any TypoExprs in the given Expr and its children,
    /// generating diagnostics as appropriate and returning a new Expr if there
    /// were typos that were all successfully corrected and ExprError if one or
    /// more typos could not be corrected.
    ///
    /// \param E The Expr to check for TypoExprs.
    ///
    /// \param InitDecl A VarDecl to avoid because the Expr being corrected is its
    /// initializer.
    ///
    /// \param Filter A function applied to a newly rebuilt Expr to determine if
    /// it is an acceptable/usable result from a single combination of typo
    /// corrections. As long as the filter returns ExprError, different
    /// combinations of corrections will be tried until all are exhausted.
    ExprResult
    CorrectDelayedTyposInExpr(Expr *E, VarDecl *InitDecl = nullptr,
                              llvm::function_ref<ExprResult(Expr *)> Filter =
                                  [](Expr *E) -> ExprResult { return E; });
  
    ExprResult
    CorrectDelayedTyposInExpr(Expr *E,
                              llvm::function_ref<ExprResult(Expr *)> Filter) {
      return CorrectDelayedTyposInExpr(E, nullptr, Filter);
    }
  
    ExprResult
    CorrectDelayedTyposInExpr(ExprResult ER, VarDecl *InitDecl = nullptr,
                              llvm::function_ref<ExprResult(Expr *)> Filter =
                                  [](Expr *E) -> ExprResult { return E; }) {
      return ER.isInvalid() ? ER : CorrectDelayedTyposInExpr(ER.get(), Filter);
    }
  
    ExprResult
    CorrectDelayedTyposInExpr(ExprResult ER,
                              llvm::function_ref<ExprResult(Expr *)> Filter) {
      return CorrectDelayedTyposInExpr(ER, nullptr, Filter);
    }
  
    void diagnoseTypo(const TypoCorrection &Correction,
                      const PartialDiagnostic &TypoDiag,
                      bool ErrorRecovery = true);
  
    void diagnoseTypo(const TypoCorrection &Correction,
                      const PartialDiagnostic &TypoDiag,
                      const PartialDiagnostic &PrevNote,
                      bool ErrorRecovery = true);
  
    void MarkTypoCorrectedFunctionDefinition(const NamedDecl *F);
  
    void FindAssociatedClassesAndNamespaces(SourceLocation InstantiationLoc,
                                            ArrayRef<Expr *> Args,
                                     AssociatedNamespaceSet &AssociatedNamespaces,
                                     AssociatedClassSet &AssociatedClasses);
  
    void FilterLookupForScope(LookupResult &R, DeclContext *Ctx, Scope *S,
                              bool ConsiderLinkage, bool AllowInlineNamespace);
  
    bool CheckRedeclarationModuleOwnership(NamedDecl *New, NamedDecl *Old);
  
    void DiagnoseAmbiguousLookup(LookupResult &Result);
    //@}
  
    ObjCInterfaceDecl *getObjCInterfaceDecl(IdentifierInfo *&Id,
                                            SourceLocation IdLoc,
                                            bool TypoCorrection = false);
    NamedDecl *LazilyCreateBuiltin(IdentifierInfo *II, unsigned ID,
                                   Scope *S, bool ForRedeclaration,
                                   SourceLocation Loc);
    NamedDecl *ImplicitlyDefineFunction(SourceLocation Loc, IdentifierInfo &II,
                                        Scope *S);
    void AddKnownFunctionAttributesForReplaceableGlobalAllocationFunction(
        FunctionDecl *FD);
    void AddKnownFunctionAttributes(FunctionDecl *FD);
  
    // More parsing and symbol table subroutines.
  
    void ProcessPragmaWeak(Scope *S, Decl *D);
    // Decl attributes - this routine is the top level dispatcher.
    void ProcessDeclAttributes(Scope *S, Decl *D, const Declarator &PD);
    // Helper for delayed processing of attributes.
    void ProcessDeclAttributeDelayed(Decl *D,
                                     const ParsedAttributesView &AttrList);
    void ProcessDeclAttributeList(Scope *S, Decl *D, const ParsedAttributesView &AL,
                               bool IncludeCXX11Attributes = true);
    bool ProcessAccessDeclAttributeList(AccessSpecDecl *ASDecl,
                                     const ParsedAttributesView &AttrList);
  
    void checkUnusedDeclAttributes(Declarator &D);
  
    /// Map any API notes provided for this declaration to attributes on the
    /// declaration.
    ///
    /// Triggered by declaration-attribute processing.
    void ProcessAPINotes(Decl *D);
  
    /// Determine if type T is a valid subject for a nonnull and similar
    /// attributes. By default, we look through references (the behavior used by
    /// nonnull), but if the second parameter is true, then we treat a reference
    /// type as valid.
    bool isValidPointerAttrType(QualType T, bool RefOkay = false);
  
    bool CheckRegparmAttr(const ParsedAttr &attr, unsigned &value);
    bool CheckCallingConvAttr(const ParsedAttr &attr, CallingConv &CC,
                              const FunctionDecl *FD = nullptr);
    bool CheckAttrTarget(const ParsedAttr &CurrAttr);
    bool CheckAttrNoArgs(const ParsedAttr &CurrAttr);
    bool checkStringLiteralArgumentAttr(const ParsedAttr &Attr, unsigned ArgNum,
                                        StringRef &Str,
                                        SourceLocation *ArgLocation = nullptr);
    bool checkSectionName(SourceLocation LiteralLoc, StringRef Str);
    bool checkTargetAttr(SourceLocation LiteralLoc, StringRef Str);
    bool checkMSInheritanceAttrOnDefinition(
        CXXRecordDecl *RD, SourceRange Range, bool BestCase,
        MSInheritanceModel SemanticSpelling);
  
    void CheckAlignasUnderalignment(Decl *D);
  
    /// Adjust the calling convention of a method to be the ABI default if it
    /// wasn't specified explicitly.  This handles method types formed from
    /// function type typedefs and typename template arguments.
    void adjustMemberFunctionCC(QualType &T, bool IsStatic, bool IsCtorOrDtor,
                                SourceLocation Loc);
  
    // Check if there is an explicit attribute, but only look through parens.
    // The intent is to look for an attribute on the current declarator, but not
    // one that came from a typedef.
    bool hasExplicitCallingConv(QualType T);
  
    /// Get the outermost AttributedType node that sets a calling convention.
    /// Valid types should not have multiple attributes with different CCs.
    const AttributedType *getCallingConvAttributedType(QualType T) const;
  
    /// Check whether a nullability type specifier can be added to the given
    /// type through some means not written in source (e.g. API notes).
    ///
    /// \param type The type to which the nullability specifier will be
    /// added. On success, this type will be updated appropriately.
    ///
    /// \param nullability The nullability specifier to add.
    ///
    /// \param diagLoc The location to use for diagnostics.
    ///
    /// \param allowArrayTypes Whether to accept nullability specifiers on an
    /// array type (e.g., because it will decay to a pointer).
    ///
    /// \param overrideExisting Whether to override an existing, locally-specified
    /// nullability specifier rather than complaining about the conflict.
    ///
    /// \returns true if nullability cannot be applied, false otherwise.
    bool checkImplicitNullabilityTypeSpecifier(QualType &type,
                                               NullabilityKind nullability,
                                               SourceLocation diagLoc,
                                               bool allowArrayTypes,
                                               bool overrideExisting);
  
    /// Stmt attributes - this routine is the top level dispatcher.
    StmtResult ProcessStmtAttributes(Stmt *Stmt,
                                     const ParsedAttributesView &Attrs,
                                     SourceRange Range);
  
    void WarnConflictingTypedMethods(ObjCMethodDecl *Method,
                                     ObjCMethodDecl *MethodDecl,
                                     bool IsProtocolMethodDecl);
  
    void CheckConflictingOverridingMethod(ObjCMethodDecl *Method,
                                     ObjCMethodDecl *Overridden,
                                     bool IsProtocolMethodDecl);
  
    /// WarnExactTypedMethods - This routine issues a warning if method
    /// implementation declaration matches exactly that of its declaration.
    void WarnExactTypedMethods(ObjCMethodDecl *Method,
                               ObjCMethodDecl *MethodDecl,
                               bool IsProtocolMethodDecl);
  
    typedef llvm::SmallPtrSet<Selector, 8> SelectorSet;
  
    /// CheckImplementationIvars - This routine checks if the instance variables
    /// listed in the implelementation match those listed in the interface.
    void CheckImplementationIvars(ObjCImplementationDecl *ImpDecl,
                                  ObjCIvarDecl **Fields, unsigned nIvars,
                                  SourceLocation Loc);
  
    /// ImplMethodsVsClassMethods - This is main routine to warn if any method
    /// remains unimplemented in the class or category \@implementation.
    void ImplMethodsVsClassMethods(Scope *S, ObjCImplDecl* IMPDecl,
                                   ObjCContainerDecl* IDecl,
                                   bool IncompleteImpl = false);
  
    /// DiagnoseUnimplementedProperties - This routine warns on those properties
    /// which must be implemented by this implementation.
    void DiagnoseUnimplementedProperties(Scope *S, ObjCImplDecl* IMPDecl,
                                         ObjCContainerDecl *CDecl,
                                         bool SynthesizeProperties);
  
    /// Diagnose any null-resettable synthesized setters.
    void diagnoseNullResettableSynthesizedSetters(const ObjCImplDecl *impDecl);
  
    /// DefaultSynthesizeProperties - This routine default synthesizes all
    /// properties which must be synthesized in the class's \@implementation.
    void DefaultSynthesizeProperties(Scope *S, ObjCImplDecl *IMPDecl,
                                     ObjCInterfaceDecl *IDecl,
                                     SourceLocation AtEnd);
    void DefaultSynthesizeProperties(Scope *S, Decl *D, SourceLocation AtEnd);
  
    /// IvarBacksCurrentMethodAccessor - This routine returns 'true' if 'IV' is
    /// an ivar synthesized for 'Method' and 'Method' is a property accessor
    /// declared in class 'IFace'.
    bool IvarBacksCurrentMethodAccessor(ObjCInterfaceDecl *IFace,
                                        ObjCMethodDecl *Method, ObjCIvarDecl *IV);
  
    /// DiagnoseUnusedBackingIvarInAccessor - Issue an 'unused' warning if ivar which
    /// backs the property is not used in the property's accessor.
    void DiagnoseUnusedBackingIvarInAccessor(Scope *S,
                                             const ObjCImplementationDecl *ImplD);
  
    /// GetIvarBackingPropertyAccessor - If method is a property setter/getter and
    /// it property has a backing ivar, returns this ivar; otherwise, returns NULL.
    /// It also returns ivar's property on success.
    ObjCIvarDecl *GetIvarBackingPropertyAccessor(const ObjCMethodDecl *Method,
                                                 const ObjCPropertyDecl *&PDecl) const;
  
    /// Called by ActOnProperty to handle \@property declarations in
    /// class extensions.
    ObjCPropertyDecl *HandlePropertyInClassExtension(Scope *S,
                        SourceLocation AtLoc,
                        SourceLocation LParenLoc,
                        FieldDeclarator &FD,
                        Selector GetterSel,
                        SourceLocation GetterNameLoc,
                        Selector SetterSel,
                        SourceLocation SetterNameLoc,
                        const bool isReadWrite,
                        unsigned &Attributes,
                        const unsigned AttributesAsWritten,
                        QualType T,
                        TypeSourceInfo *TSI,
                        tok::ObjCKeywordKind MethodImplKind);
  
    /// Called by ActOnProperty and HandlePropertyInClassExtension to
    /// handle creating the ObjcPropertyDecl for a category or \@interface.
    ObjCPropertyDecl *CreatePropertyDecl(Scope *S,
                                         ObjCContainerDecl *CDecl,
                                         SourceLocation AtLoc,
                                         SourceLocation LParenLoc,
                                         FieldDeclarator &FD,
                                         Selector GetterSel,
                                         SourceLocation GetterNameLoc,
                                         Selector SetterSel,
                                         SourceLocation SetterNameLoc,
                                         const bool isReadWrite,
                                         const unsigned Attributes,
                                         const unsigned AttributesAsWritten,
                                         QualType T,
                                         TypeSourceInfo *TSI,
                                         tok::ObjCKeywordKind MethodImplKind,
                                         DeclContext *lexicalDC = nullptr);
  
    /// AtomicPropertySetterGetterRules - This routine enforces the rule (via
    /// warning) when atomic property has one but not the other user-declared
    /// setter or getter.
    void AtomicPropertySetterGetterRules(ObjCImplDecl* IMPDecl,
                                         ObjCInterfaceDecl* IDecl);
  
    void DiagnoseOwningPropertyGetterSynthesis(const ObjCImplementationDecl *D);
  
    void DiagnoseMissingDesignatedInitOverrides(
                                            const ObjCImplementationDecl *ImplD,
                                            const ObjCInterfaceDecl *IFD);
  
    void DiagnoseDuplicateIvars(ObjCInterfaceDecl *ID, ObjCInterfaceDecl *SID);
  
    enum MethodMatchStrategy {
      MMS_loose,
      MMS_strict
    };
  
    /// MatchTwoMethodDeclarations - Checks if two methods' type match and returns
    /// true, or false, accordingly.
    bool MatchTwoMethodDeclarations(const ObjCMethodDecl *Method,
                                    const ObjCMethodDecl *PrevMethod,
                                    MethodMatchStrategy strategy = MMS_strict);
  
    /// MatchAllMethodDeclarations - Check methods declaraed in interface or
    /// or protocol against those declared in their implementations.
    void MatchAllMethodDeclarations(const SelectorSet &InsMap,
                                    const SelectorSet &ClsMap,
                                    SelectorSet &InsMapSeen,
                                    SelectorSet &ClsMapSeen,
                                    ObjCImplDecl* IMPDecl,
                                    ObjCContainerDecl* IDecl,
                                    bool &IncompleteImpl,
                                    bool ImmediateClass,
                                    bool WarnCategoryMethodImpl=false);
  
    /// CheckCategoryVsClassMethodMatches - Checks that methods implemented in
    /// category matches with those implemented in its primary class and
    /// warns each time an exact match is found.
    void CheckCategoryVsClassMethodMatches(ObjCCategoryImplDecl *CatIMP);
  
    /// Add the given method to the list of globally-known methods.
    void addMethodToGlobalList(ObjCMethodList *List, ObjCMethodDecl *Method);
  
    /// Returns default addr space for method qualifiers.
    LangAS getDefaultCXXMethodAddrSpace() const;
  
  private:
    /// AddMethodToGlobalPool - Add an instance or factory method to the global
    /// pool. See descriptoin of AddInstanceMethodToGlobalPool.
    void AddMethodToGlobalPool(ObjCMethodDecl *Method, bool impl, bool instance);
  
    /// LookupMethodInGlobalPool - Returns the instance or factory method and
    /// optionally warns if there are multiple signatures.
    ObjCMethodDecl *LookupMethodInGlobalPool(Selector Sel, SourceRange R,
                                             bool receiverIdOrClass,
                                             bool instance);
  
  public:
    /// - Returns instance or factory methods in global method pool for
    /// given selector. It checks the desired kind first, if none is found, and
    /// parameter checkTheOther is set, it then checks the other kind. If no such
    /// method or only one method is found, function returns false; otherwise, it
    /// returns true.
    bool
    CollectMultipleMethodsInGlobalPool(Selector Sel,
                                       SmallVectorImpl<ObjCMethodDecl*>& Methods,
                                       bool InstanceFirst, bool CheckTheOther,
                                       const ObjCObjectType *TypeBound = nullptr);
  
    bool
    AreMultipleMethodsInGlobalPool(Selector Sel, ObjCMethodDecl *BestMethod,
                                   SourceRange R, bool receiverIdOrClass,
                                   SmallVectorImpl<ObjCMethodDecl*>& Methods);
  
    void
    DiagnoseMultipleMethodInGlobalPool(SmallVectorImpl<ObjCMethodDecl*> &Methods,
                                       Selector Sel, SourceRange R,
                                       bool receiverIdOrClass);
  
  private:
    /// - Returns a selector which best matches given argument list or
    /// nullptr if none could be found
    ObjCMethodDecl *SelectBestMethod(Selector Sel, MultiExprArg Args,
                                     bool IsInstance,
                                     SmallVectorImpl<ObjCMethodDecl*>& Methods);
  
  
    /// Record the typo correction failure and return an empty correction.
    TypoCorrection FailedCorrection(IdentifierInfo *Typo, SourceLocation TypoLoc,
                                    bool RecordFailure = true) {
      if (RecordFailure)
        TypoCorrectionFailures[Typo].insert(TypoLoc);
      return TypoCorrection();
    }
  
  public:
    /// AddInstanceMethodToGlobalPool - All instance methods in a translation
    /// unit are added to a global pool. This allows us to efficiently associate
    /// a selector with a method declaraation for purposes of typechecking
    /// messages sent to "id" (where the class of the object is unknown).
    void AddInstanceMethodToGlobalPool(ObjCMethodDecl *Method, bool impl=false) {
      AddMethodToGlobalPool(Method, impl, /*instance*/true);
    }
  
    /// AddFactoryMethodToGlobalPool - Same as above, but for factory methods.
    void AddFactoryMethodToGlobalPool(ObjCMethodDecl *Method, bool impl=false) {
      AddMethodToGlobalPool(Method, impl, /*instance*/false);
    }
  
    /// AddAnyMethodToGlobalPool - Add any method, instance or factory to global
    /// pool.
    void AddAnyMethodToGlobalPool(Decl *D);
  
    /// LookupInstanceMethodInGlobalPool - Returns the method and warns if
    /// there are multiple signatures.
    ObjCMethodDecl *LookupInstanceMethodInGlobalPool(Selector Sel, SourceRange R,
                                                     bool receiverIdOrClass=false) {
      return LookupMethodInGlobalPool(Sel, R, receiverIdOrClass,
                                      /*instance*/true);
    }
  
    /// LookupFactoryMethodInGlobalPool - Returns the method and warns if
    /// there are multiple signatures.
    ObjCMethodDecl *LookupFactoryMethodInGlobalPool(Selector Sel, SourceRange R,
                                                    bool receiverIdOrClass=false) {
      return LookupMethodInGlobalPool(Sel, R, receiverIdOrClass,
                                      /*instance*/false);
    }
  
    const ObjCMethodDecl *SelectorsForTypoCorrection(Selector Sel,
                                QualType ObjectType=QualType());
    /// LookupImplementedMethodInGlobalPool - Returns the method which has an
    /// implementation.
    ObjCMethodDecl *LookupImplementedMethodInGlobalPool(Selector Sel);
  
    /// CollectIvarsToConstructOrDestruct - Collect those ivars which require
    /// initialization.
    void CollectIvarsToConstructOrDestruct(ObjCInterfaceDecl *OI,
                                    SmallVectorImpl<ObjCIvarDecl*> &Ivars);
  
    //===--------------------------------------------------------------------===//
    // Statement Parsing Callbacks: SemaStmt.cpp.
  public:
    class FullExprArg {
    public:
      FullExprArg() : E(nullptr) { }
      FullExprArg(Sema &actions) : E(nullptr) { }
  
      ExprResult release() {
        return E;
      }
  
      Expr *get() const { return E; }
  
      Expr *operator->() {
        return E;
      }
  
    private:
      // FIXME: No need to make the entire Sema class a friend when it's just
      // Sema::MakeFullExpr that needs access to the constructor below.
      friend class Sema;
  
      explicit FullExprArg(Expr *expr) : E(expr) {}
  
      Expr *E;
    };
  
    FullExprArg MakeFullExpr(Expr *Arg) {
      return MakeFullExpr(Arg, Arg ? Arg->getExprLoc() : SourceLocation());
    }
    FullExprArg MakeFullExpr(Expr *Arg, SourceLocation CC) {
      return FullExprArg(
          ActOnFinishFullExpr(Arg, CC, /*DiscardedValue*/ false).get());
    }
    FullExprArg MakeFullDiscardedValueExpr(Expr *Arg) {
      ExprResult FE =
          ActOnFinishFullExpr(Arg, Arg ? Arg->getExprLoc() : SourceLocation(),
                              /*DiscardedValue*/ true);
      return FullExprArg(FE.get());
    }
  
    StmtResult ActOnExprStmt(ExprResult Arg, bool DiscardedValue = true);
    StmtResult ActOnExprStmtError();
  
    StmtResult ActOnNullStmt(SourceLocation SemiLoc,
                             bool HasLeadingEmptyMacro = false);
  
    void ActOnStartOfCompoundStmt(bool IsStmtExpr);
    void ActOnFinishOfCompoundStmt();
    StmtResult ActOnCompoundStmt(SourceLocation L, SourceLocation R,
                                 ArrayRef<Stmt *> Elts, bool isStmtExpr);
  
    /// A RAII object to enter scope of a compound statement.
    class CompoundScopeRAII {
    public:
      CompoundScopeRAII(Sema &S, bool IsStmtExpr = false) : S(S) {
        S.ActOnStartOfCompoundStmt(IsStmtExpr);
      }
  
      ~CompoundScopeRAII() {
        S.ActOnFinishOfCompoundStmt();
      }
  
    private:
      Sema &S;
    };
  
    /// An RAII helper that pops function a function scope on exit.
    struct FunctionScopeRAII {
      Sema &S;
      bool Active;
      FunctionScopeRAII(Sema &S) : S(S), Active(true) {}
      ~FunctionScopeRAII() {
        if (Active)
          S.PopFunctionScopeInfo();
      }
      void disable() { Active = false; }
    };
  
    StmtResult ActOnDeclStmt(DeclGroupPtrTy Decl,
                                     SourceLocation StartLoc,
                                     SourceLocation EndLoc);
    void ActOnForEachDeclStmt(DeclGroupPtrTy Decl);
    StmtResult ActOnForEachLValueExpr(Expr *E);
    ExprResult ActOnCaseExpr(SourceLocation CaseLoc, ExprResult Val);
    StmtResult ActOnCaseStmt(SourceLocation CaseLoc, ExprResult LHS,
                             SourceLocation DotDotDotLoc, ExprResult RHS,
                             SourceLocation ColonLoc);
    void ActOnCaseStmtBody(Stmt *CaseStmt, Stmt *SubStmt);
  
    StmtResult ActOnDefaultStmt(SourceLocation DefaultLoc,
                                        SourceLocation ColonLoc,
                                        Stmt *SubStmt, Scope *CurScope);
    StmtResult ActOnLabelStmt(SourceLocation IdentLoc, LabelDecl *TheDecl,
                              SourceLocation ColonLoc, Stmt *SubStmt);
  
    StmtResult ActOnAttributedStmt(SourceLocation AttrLoc,
                                   ArrayRef<const Attr*> Attrs,
                                   Stmt *SubStmt);
  
    class ConditionResult;
    StmtResult ActOnIfStmt(SourceLocation IfLoc, bool IsConstexpr,
                           Stmt *InitStmt,
                           ConditionResult Cond, Stmt *ThenVal,
                           SourceLocation ElseLoc, Stmt *ElseVal);
    StmtResult BuildIfStmt(SourceLocation IfLoc, bool IsConstexpr,
                           Stmt *InitStmt,
                           ConditionResult Cond, Stmt *ThenVal,
                           SourceLocation ElseLoc, Stmt *ElseVal);
    StmtResult ActOnStartOfSwitchStmt(SourceLocation SwitchLoc,
                                      Stmt *InitStmt,
                                      ConditionResult Cond);
    StmtResult ActOnFinishSwitchStmt(SourceLocation SwitchLoc,
                                             Stmt *Switch, Stmt *Body);
    StmtResult ActOnWhileStmt(SourceLocation WhileLoc, ConditionResult Cond,
                              Stmt *Body);
    StmtResult ActOnDoStmt(SourceLocation DoLoc, Stmt *Body,
                           SourceLocation WhileLoc, SourceLocation CondLParen,
                           Expr *Cond, SourceLocation CondRParen);
  
    StmtResult ActOnForStmt(SourceLocation ForLoc,
                            SourceLocation LParenLoc,
                            Stmt *First,
                            ConditionResult Second,
                            FullExprArg Third,
                            SourceLocation RParenLoc,
                            Stmt *Body);
    ExprResult CheckObjCForCollectionOperand(SourceLocation forLoc,
                                             Expr *collection);
    StmtResult ActOnObjCForCollectionStmt(SourceLocation ForColLoc,
                                          Stmt *First, Expr *collection,
                                          SourceLocation RParenLoc);
    StmtResult FinishObjCForCollectionStmt(Stmt *ForCollection, Stmt *Body);
  
    enum BuildForRangeKind {
      /// Initial building of a for-range statement.
      BFRK_Build,
      /// Instantiation or recovery rebuild of a for-range statement. Don't
      /// attempt any typo-correction.
      BFRK_Rebuild,
      /// Determining whether a for-range statement could be built. Avoid any
      /// unnecessary or irreversible actions.
      BFRK_Check
    };
  
    StmtResult ActOnCXXForRangeStmt(Scope *S, SourceLocation ForLoc,
                                    SourceLocation CoawaitLoc,
                                    Stmt *InitStmt,
                                    Stmt *LoopVar,
                                    SourceLocation ColonLoc, Expr *Collection,
                                    SourceLocation RParenLoc,
                                    BuildForRangeKind Kind);
    StmtResult BuildCXXForRangeStmt(SourceLocation ForLoc,
                                    SourceLocation CoawaitLoc,
                                    Stmt *InitStmt,
                                    SourceLocation ColonLoc,
                                    Stmt *RangeDecl, Stmt *Begin, Stmt *End,
                                    Expr *Cond, Expr *Inc,
                                    Stmt *LoopVarDecl,
                                    SourceLocation RParenLoc,
                                    BuildForRangeKind Kind);
    StmtResult FinishCXXForRangeStmt(Stmt *ForRange, Stmt *Body);
  
    StmtResult ActOnGotoStmt(SourceLocation GotoLoc,
                             SourceLocation LabelLoc,
                             LabelDecl *TheDecl);
    StmtResult ActOnIndirectGotoStmt(SourceLocation GotoLoc,
                                     SourceLocation StarLoc,
                                     Expr *DestExp);
    StmtResult ActOnContinueStmt(SourceLocation ContinueLoc, Scope *CurScope);
    StmtResult ActOnBreakStmt(SourceLocation BreakLoc, Scope *CurScope);
  
    void ActOnCapturedRegionStart(SourceLocation Loc, Scope *CurScope,
                                  CapturedRegionKind Kind, unsigned NumParams);
    typedef std::pair<StringRef, QualType> CapturedParamNameType;
    void ActOnCapturedRegionStart(SourceLocation Loc, Scope *CurScope,
                                  CapturedRegionKind Kind,
                                  ArrayRef<CapturedParamNameType> Params,
                                  unsigned OpenMPCaptureLevel = 0);
    StmtResult ActOnCapturedRegionEnd(Stmt *S);
    void ActOnCapturedRegionError();
    RecordDecl *CreateCapturedStmtRecordDecl(CapturedDecl *&CD,
                                             SourceLocation Loc,
                                             unsigned NumParams);
  
    enum CopyElisionSemanticsKind {
      CES_Strict = 0,
      CES_AllowParameters = 1,
      CES_AllowDifferentTypes = 2,
      CES_AllowExceptionVariables = 4,
      CES_FormerDefault = (CES_AllowParameters),
      CES_Default = (CES_AllowParameters | CES_AllowDifferentTypes),
      CES_AsIfByStdMove = (CES_AllowParameters | CES_AllowDifferentTypes |
                           CES_AllowExceptionVariables),
    };
  
    VarDecl *getCopyElisionCandidate(QualType ReturnType, Expr *E,
                                     CopyElisionSemanticsKind CESK);
    bool isCopyElisionCandidate(QualType ReturnType, const VarDecl *VD,
                                CopyElisionSemanticsKind CESK);
  
    StmtResult ActOnReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp,
                               Scope *CurScope);
    StmtResult BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp);
    StmtResult ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp);
  
    StmtResult ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
                               bool IsVolatile, unsigned NumOutputs,
                               unsigned NumInputs, IdentifierInfo **Names,
                               MultiExprArg Constraints, MultiExprArg Exprs,
                               Expr *AsmString, MultiExprArg Clobbers,
                               unsigned NumLabels,
                               SourceLocation RParenLoc);
  
    void FillInlineAsmIdentifierInfo(Expr *Res,
                                     llvm::InlineAsmIdentifierInfo &Info);
    ExprResult LookupInlineAsmIdentifier(CXXScopeSpec &SS,
                                         SourceLocation TemplateKWLoc,
                                         UnqualifiedId &Id,
                                         bool IsUnevaluatedContext);
    bool LookupInlineAsmField(StringRef Base, StringRef Member,
                              unsigned &Offset, SourceLocation AsmLoc);
    ExprResult LookupInlineAsmVarDeclField(Expr *RefExpr, StringRef Member,
                                           SourceLocation AsmLoc);
    StmtResult ActOnMSAsmStmt(SourceLocation AsmLoc, SourceLocation LBraceLoc,
                              ArrayRef<Token> AsmToks,
                              StringRef AsmString,
                              unsigned NumOutputs, unsigned NumInputs,
                              ArrayRef<StringRef> Constraints,
                              ArrayRef<StringRef> Clobbers,
                              ArrayRef<Expr*> Exprs,
                              SourceLocation EndLoc);
    LabelDecl *GetOrCreateMSAsmLabel(StringRef ExternalLabelName,
                                     SourceLocation Location,
                                     bool AlwaysCreate);
  
    VarDecl *BuildObjCExceptionDecl(TypeSourceInfo *TInfo, QualType ExceptionType,
                                    SourceLocation StartLoc,
                                    SourceLocation IdLoc, IdentifierInfo *Id,
                                    bool Invalid = false);
  
    Decl *ActOnObjCExceptionDecl(Scope *S, Declarator &D);
  
    StmtResult ActOnObjCAtCatchStmt(SourceLocation AtLoc, SourceLocation RParen,
                                    Decl *Parm, Stmt *Body);
  
    StmtResult ActOnObjCAtFinallyStmt(SourceLocation AtLoc, Stmt *Body);
  
    StmtResult ActOnObjCAtTryStmt(SourceLocation AtLoc, Stmt *Try,
                                  MultiStmtArg Catch, Stmt *Finally);
  
    StmtResult BuildObjCAtThrowStmt(SourceLocation AtLoc, Expr *Throw);
    StmtResult ActOnObjCAtThrowStmt(SourceLocation AtLoc, Expr *Throw,
                                    Scope *CurScope);
    ExprResult ActOnObjCAtSynchronizedOperand(SourceLocation atLoc,
                                              Expr *operand);
    StmtResult ActOnObjCAtSynchronizedStmt(SourceLocation AtLoc,
                                           Expr *SynchExpr,
                                           Stmt *SynchBody);
  
    StmtResult ActOnObjCAutoreleasePoolStmt(SourceLocation AtLoc, Stmt *Body);
  
    VarDecl *BuildExceptionDeclaration(Scope *S, TypeSourceInfo *TInfo,
                                       SourceLocation StartLoc,
                                       SourceLocation IdLoc,
                                       IdentifierInfo *Id);
  
    Decl *ActOnExceptionDeclarator(Scope *S, Declarator &D);
  
    StmtResult ActOnCXXCatchBlock(SourceLocation CatchLoc,
                                  Decl *ExDecl, Stmt *HandlerBlock);
    StmtResult ActOnCXXTryBlock(SourceLocation TryLoc, Stmt *TryBlock,
                                ArrayRef<Stmt *> Handlers);
  
    StmtResult ActOnSEHTryBlock(bool IsCXXTry, // try (true) or __try (false) ?
                                SourceLocation TryLoc, Stmt *TryBlock,
                                Stmt *Handler);
    StmtResult ActOnSEHExceptBlock(SourceLocation Loc,
                                   Expr *FilterExpr,
                                   Stmt *Block);
    void ActOnStartSEHFinallyBlock();
    void ActOnAbortSEHFinallyBlock();
    StmtResult ActOnFinishSEHFinallyBlock(SourceLocation Loc, Stmt *Block);
    StmtResult ActOnSEHLeaveStmt(SourceLocation Loc, Scope *CurScope);
  
    void DiagnoseReturnInConstructorExceptionHandler(CXXTryStmt *TryBlock);
  
    bool ShouldWarnIfUnusedFileScopedDecl(const DeclaratorDecl *D) const;
  
    /// If it's a file scoped decl that must warn if not used, keep track
    /// of it.
    void MarkUnusedFileScopedDecl(const DeclaratorDecl *D);
  
    /// DiagnoseUnusedExprResult - If the statement passed in is an expression
    /// whose result is unused, warn.
    void DiagnoseUnusedExprResult(const Stmt *S);
    void DiagnoseUnusedNestedTypedefs(const RecordDecl *D);
    void DiagnoseUnusedDecl(const NamedDecl *ND);
  
    /// Emit \p DiagID if statement located on \p StmtLoc has a suspicious null
    /// statement as a \p Body, and it is located on the same line.
    ///
    /// This helps prevent bugs due to typos, such as:
    ///     if (condition);
    ///       do_stuff();
    void DiagnoseEmptyStmtBody(SourceLocation StmtLoc,
                               const Stmt *Body,
                               unsigned DiagID);
  
    /// Warn if a for/while loop statement \p S, which is followed by
    /// \p PossibleBody, has a suspicious null statement as a body.
    void DiagnoseEmptyLoopBody(const Stmt *S,
                               const Stmt *PossibleBody);
  
    /// Warn if a value is moved to itself.
    void DiagnoseSelfMove(const Expr *LHSExpr, const Expr *RHSExpr,
                          SourceLocation OpLoc);
  
    /// Warn if we're implicitly casting from a _Nullable pointer type to a
    /// _Nonnull one.
    void diagnoseNullableToNonnullConversion(QualType DstType, QualType SrcType,
                                             SourceLocation Loc);
  
    /// Warn when implicitly casting 0 to nullptr.
    void diagnoseZeroToNullptrConversion(CastKind Kind, const Expr *E);
  
    ParsingDeclState PushParsingDeclaration(sema::DelayedDiagnosticPool &pool) {
      return DelayedDiagnostics.push(pool);
    }
    void PopParsingDeclaration(ParsingDeclState state, Decl *decl);
  
    typedef ProcessingContextState ParsingClassState;
    ParsingClassState PushParsingClass() {
      ParsingClassDepth++;
      return DelayedDiagnostics.pushUndelayed();
    }
    void PopParsingClass(ParsingClassState state) {
      ParsingClassDepth--;
      DelayedDiagnostics.popUndelayed(state);
    }
  
    void redelayDiagnostics(sema::DelayedDiagnosticPool &pool);
  
    void DiagnoseAvailabilityOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
                                    const ObjCInterfaceDecl *UnknownObjCClass,
                                    bool ObjCPropertyAccess,
                                    bool AvoidPartialAvailabilityChecks = false,
                                    ObjCInterfaceDecl *ClassReceiver = nullptr);
  
    bool makeUnavailableInSystemHeader(SourceLocation loc,
                                       UnavailableAttr::ImplicitReason reason);
  
    /// Issue any -Wunguarded-availability warnings in \c FD
    void DiagnoseUnguardedAvailabilityViolations(Decl *FD);
  
    void handleDelayedAvailabilityCheck(sema::DelayedDiagnostic &DD, Decl *Ctx);
  
    //===--------------------------------------------------------------------===//
    // Expression Parsing Callbacks: SemaExpr.cpp.
  
    bool CanUseDecl(NamedDecl *D, bool TreatUnavailableAsInvalid);
    bool DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
                           const ObjCInterfaceDecl *UnknownObjCClass = nullptr,
                           bool ObjCPropertyAccess = false,
                           bool AvoidPartialAvailabilityChecks = false,
                           ObjCInterfaceDecl *ClassReciever = nullptr);
    void NoteDeletedFunction(FunctionDecl *FD);
    void NoteDeletedInheritingConstructor(CXXConstructorDecl *CD);
    bool DiagnosePropertyAccessorMismatch(ObjCPropertyDecl *PD,
                                          ObjCMethodDecl *Getter,
                                          SourceLocation Loc);
    void DiagnoseSentinelCalls(NamedDecl *D, SourceLocation Loc,
                               ArrayRef<Expr *> Args);
  
    void PushExpressionEvaluationContext(
        ExpressionEvaluationContext NewContext, Decl *LambdaContextDecl = nullptr,
        ExpressionEvaluationContextRecord::ExpressionKind Type =
            ExpressionEvaluationContextRecord::EK_Other);
    enum ReuseLambdaContextDecl_t { ReuseLambdaContextDecl };
    void PushExpressionEvaluationContext(
        ExpressionEvaluationContext NewContext, ReuseLambdaContextDecl_t,
        ExpressionEvaluationContextRecord::ExpressionKind Type =
            ExpressionEvaluationContextRecord::EK_Other);
    void PopExpressionEvaluationContext();
  
    void DiscardCleanupsInEvaluationContext();
  
    ExprResult TransformToPotentiallyEvaluated(Expr *E);
    ExprResult HandleExprEvaluationContextForTypeof(Expr *E);
  
    ExprResult CheckUnevaluatedOperand(Expr *E);
    void CheckUnusedVolatileAssignment(Expr *E);
  
    ExprResult ActOnConstantExpression(ExprResult Res);
  
    // Functions for marking a declaration referenced.  These functions also
    // contain the relevant logic for marking if a reference to a function or
    // variable is an odr-use (in the C++11 sense).  There are separate variants
    // for expressions referring to a decl; these exist because odr-use marking
    // needs to be delayed for some constant variables when we build one of the
    // named expressions.
    //
    // MightBeOdrUse indicates whether the use could possibly be an odr-use, and
    // should usually be true. This only needs to be set to false if the lack of
    // odr-use cannot be determined from the current context (for instance,
    // because the name denotes a virtual function and was written without an
    // explicit nested-name-specifier).
    void MarkAnyDeclReferenced(SourceLocation Loc, Decl *D, bool MightBeOdrUse);
    void MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
                                bool MightBeOdrUse = true);
    void MarkVariableReferenced(SourceLocation Loc, VarDecl *Var);
    void MarkDeclRefReferenced(DeclRefExpr *E, const Expr *Base = nullptr);
    void MarkMemberReferenced(MemberExpr *E);
    void MarkFunctionParmPackReferenced(FunctionParmPackExpr *E);
    void MarkCaptureUsedInEnclosingContext(VarDecl *Capture, SourceLocation Loc,
                                           unsigned CapturingScopeIndex);
  
    ExprResult CheckLValueToRValueConversionOperand(Expr *E);
    void CleanupVarDeclMarking();
  
    enum TryCaptureKind {
      TryCapture_Implicit, TryCapture_ExplicitByVal, TryCapture_ExplicitByRef
    };
  
    /// Try to capture the given variable.
    ///
    /// \param Var The variable to capture.
    ///
    /// \param Loc The location at which the capture occurs.
    ///
    /// \param Kind The kind of capture, which may be implicit (for either a
    /// block or a lambda), or explicit by-value or by-reference (for a lambda).
    ///
    /// \param EllipsisLoc The location of the ellipsis, if one is provided in
    /// an explicit lambda capture.
    ///
    /// \param BuildAndDiagnose Whether we are actually supposed to add the
    /// captures or diagnose errors. If false, this routine merely check whether
    /// the capture can occur without performing the capture itself or complaining
    /// if the variable cannot be captured.
    ///
    /// \param CaptureType Will be set to the type of the field used to capture
    /// this variable in the innermost block or lambda. Only valid when the
    /// variable can be captured.
    ///
    /// \param DeclRefType Will be set to the type of a reference to the capture
    /// from within the current scope. Only valid when the variable can be
    /// captured.
    ///
    /// \param FunctionScopeIndexToStopAt If non-null, it points to the index
    /// of the FunctionScopeInfo stack beyond which we do not attempt to capture.
    /// This is useful when enclosing lambdas must speculatively capture
    /// variables that may or may not be used in certain specializations of
    /// a nested generic lambda.
    ///
    /// \returns true if an error occurred (i.e., the variable cannot be
    /// captured) and false if the capture succeeded.
    bool tryCaptureVariable(VarDecl *Var, SourceLocation Loc, TryCaptureKind Kind,
                            SourceLocation EllipsisLoc, bool BuildAndDiagnose,
                            QualType &CaptureType,
                            QualType &DeclRefType,
                            const unsigned *const FunctionScopeIndexToStopAt);
  
    /// Try to capture the given variable.
    bool tryCaptureVariable(VarDecl *Var, SourceLocation Loc,
                            TryCaptureKind Kind = TryCapture_Implicit,
                            SourceLocation EllipsisLoc = SourceLocation());
  
    /// Checks if the variable must be captured.
    bool NeedToCaptureVariable(VarDecl *Var, SourceLocation Loc);
  
    /// Given a variable, determine the type that a reference to that
    /// variable will have in the given scope.
    QualType getCapturedDeclRefType(VarDecl *Var, SourceLocation Loc);
  
    /// Mark all of the declarations referenced within a particular AST node as
    /// referenced. Used when template instantiation instantiates a non-dependent
    /// type -- entities referenced by the type are now referenced.
    void MarkDeclarationsReferencedInType(SourceLocation Loc, QualType T);
    void MarkDeclarationsReferencedInExpr(Expr *E,
                                          bool SkipLocalVariables = false);
  
    /// Try to recover by turning the given expression into a
    /// call.  Returns true if recovery was attempted or an error was
    /// emitted; this may also leave the ExprResult invalid.
    bool tryToRecoverWithCall(ExprResult &E, const PartialDiagnostic &PD,
                              bool ForceComplain = false,
                              bool (*IsPlausibleResult)(QualType) = nullptr);
  
    /// Figure out if an expression could be turned into a call.
    bool tryExprAsCall(Expr &E, QualType &ZeroArgCallReturnTy,
                       UnresolvedSetImpl &NonTemplateOverloads);
  
    /// Conditionally issue a diagnostic based on the current
    /// evaluation context.
    ///
    /// \param Statement If Statement is non-null, delay reporting the
    /// diagnostic until the function body is parsed, and then do a basic
    /// reachability analysis to determine if the statement is reachable.
    /// If it is unreachable, the diagnostic will not be emitted.
    bool DiagRuntimeBehavior(SourceLocation Loc, const Stmt *Statement,
                             const PartialDiagnostic &PD);
    /// Similar, but diagnostic is only produced if all the specified statements
    /// are reachable.
    bool DiagRuntimeBehavior(SourceLocation Loc, ArrayRef<const Stmt*> Stmts,
                             const PartialDiagnostic &PD);
  
    // Primary Expressions.
    SourceRange getExprRange(Expr *E) const;
  
    ExprResult ActOnIdExpression(
        Scope *S, CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
        UnqualifiedId &Id, bool HasTrailingLParen, bool IsAddressOfOperand,
        CorrectionCandidateCallback *CCC = nullptr,
        bool IsInlineAsmIdentifier = false, Token *KeywordReplacement = nullptr);
  
    void DecomposeUnqualifiedId(const UnqualifiedId &Id,
                                TemplateArgumentListInfo &Buffer,
                                DeclarationNameInfo &NameInfo,
                                const TemplateArgumentListInfo *&TemplateArgs);
  
    bool
    DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
                        CorrectionCandidateCallback &CCC,
                        TemplateArgumentListInfo *ExplicitTemplateArgs = nullptr,
                        ArrayRef<Expr *> Args = None, TypoExpr **Out = nullptr);
  
    DeclResult LookupIvarInObjCMethod(LookupResult &Lookup, Scope *S,
                                      IdentifierInfo *II);
    ExprResult BuildIvarRefExpr(Scope *S, SourceLocation Loc, ObjCIvarDecl *IV);
  
    ExprResult LookupInObjCMethod(LookupResult &LookUp, Scope *S,
                                  IdentifierInfo *II,
                                  bool AllowBuiltinCreation=false);
  
    ExprResult ActOnDependentIdExpression(const CXXScopeSpec &SS,
                                          SourceLocation TemplateKWLoc,
                                          const DeclarationNameInfo &NameInfo,
                                          bool isAddressOfOperand,
                                  const TemplateArgumentListInfo *TemplateArgs);
  
    /// If \p D cannot be odr-used in the current expression evaluation context,
    /// return a reason explaining why. Otherwise, return NOUR_None.
    NonOdrUseReason getNonOdrUseReasonInCurrentContext(ValueDecl *D);
  
    DeclRefExpr *BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
                                  SourceLocation Loc,
                                  const CXXScopeSpec *SS = nullptr);
    DeclRefExpr *
    BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
                     const DeclarationNameInfo &NameInfo,
                     const CXXScopeSpec *SS = nullptr,
                     NamedDecl *FoundD = nullptr,
                     SourceLocation TemplateKWLoc = SourceLocation(),
                     const TemplateArgumentListInfo *TemplateArgs = nullptr);
    DeclRefExpr *
    BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
                     const DeclarationNameInfo &NameInfo,
                     NestedNameSpecifierLoc NNS,
                     NamedDecl *FoundD = nullptr,
                     SourceLocation TemplateKWLoc = SourceLocation(),
                     const TemplateArgumentListInfo *TemplateArgs = nullptr);
  
    ExprResult
    BuildAnonymousStructUnionMemberReference(
        const CXXScopeSpec &SS,
        SourceLocation nameLoc,
        IndirectFieldDecl *indirectField,
        DeclAccessPair FoundDecl = DeclAccessPair::make(nullptr, AS_none),
        Expr *baseObjectExpr = nullptr,
        SourceLocation opLoc = SourceLocation());
  
    ExprResult BuildPossibleImplicitMemberExpr(const CXXScopeSpec &SS,
                                               SourceLocation TemplateKWLoc,
                                               LookupResult &R,
                                  const TemplateArgumentListInfo *TemplateArgs,
                                               const Scope *S);
    ExprResult BuildImplicitMemberExpr(const CXXScopeSpec &SS,
                                       SourceLocation TemplateKWLoc,
                                       LookupResult &R,
                                  const TemplateArgumentListInfo *TemplateArgs,
                                       bool IsDefiniteInstance,
                                       const Scope *S);
    bool UseArgumentDependentLookup(const CXXScopeSpec &SS,
                                    const LookupResult &R,
                                    bool HasTrailingLParen);
  
    ExprResult
    BuildQualifiedDeclarationNameExpr(CXXScopeSpec &SS,
                                      const DeclarationNameInfo &NameInfo,
                                      bool IsAddressOfOperand, const Scope *S,
                                      TypeSourceInfo **RecoveryTSI = nullptr);
  
    ExprResult BuildDependentDeclRefExpr(const CXXScopeSpec &SS,
                                         SourceLocation TemplateKWLoc,
                                  const DeclarationNameInfo &NameInfo,
                                  const TemplateArgumentListInfo *TemplateArgs);
  
    ExprResult BuildDeclarationNameExpr(const CXXScopeSpec &SS,
                                        LookupResult &R,
                                        bool NeedsADL,
                                        bool AcceptInvalidDecl = false);
    ExprResult BuildDeclarationNameExpr(
        const CXXScopeSpec &SS, const DeclarationNameInfo &NameInfo, NamedDecl *D,
        NamedDecl *FoundD = nullptr,
        const TemplateArgumentListInfo *TemplateArgs = nullptr,
        bool AcceptInvalidDecl = false);
  
    ExprResult BuildLiteralOperatorCall(LookupResult &R,
                        DeclarationNameInfo &SuffixInfo,
                        ArrayRef<Expr *> Args,
                        SourceLocation LitEndLoc,
                        TemplateArgumentListInfo *ExplicitTemplateArgs = nullptr);
  
    ExprResult BuildPredefinedExpr(SourceLocation Loc,
                                   PredefinedExpr::IdentKind IK);
    ExprResult ActOnPredefinedExpr(SourceLocation Loc, tok::TokenKind Kind);
    ExprResult ActOnIntegerConstant(SourceLocation Loc, uint64_t Val);
  
    bool CheckLoopHintExpr(Expr *E, SourceLocation Loc);
  
    ExprResult ActOnNumericConstant(const Token &Tok, Scope *UDLScope = nullptr);
    ExprResult ActOnCharacterConstant(const Token &Tok,
                                      Scope *UDLScope = nullptr);
    ExprResult ActOnParenExpr(SourceLocation L, SourceLocation R, Expr *E);
    ExprResult ActOnParenListExpr(SourceLocation L,
                                  SourceLocation R,
                                  MultiExprArg Val);
  
    /// ActOnStringLiteral - The specified tokens were lexed as pasted string
    /// fragments (e.g. "foo" "bar" L"baz").
    ExprResult ActOnStringLiteral(ArrayRef<Token> StringToks,
                                  Scope *UDLScope = nullptr);
  
    ExprResult ActOnGenericSelectionExpr(SourceLocation KeyLoc,
                                         SourceLocation DefaultLoc,
                                         SourceLocation RParenLoc,
                                         Expr *ControllingExpr,
                                         ArrayRef<ParsedType> ArgTypes,
                                         ArrayRef<Expr *> ArgExprs);
    ExprResult CreateGenericSelectionExpr(SourceLocation KeyLoc,
                                          SourceLocation DefaultLoc,
                                          SourceLocation RParenLoc,
                                          Expr *ControllingExpr,
                                          ArrayRef<TypeSourceInfo *> Types,
                                          ArrayRef<Expr *> Exprs);
  
    // Binary/Unary Operators.  'Tok' is the token for the operator.
    ExprResult CreateBuiltinUnaryOp(SourceLocation OpLoc, UnaryOperatorKind Opc,
                                    Expr *InputExpr);
    ExprResult BuildUnaryOp(Scope *S, SourceLocation OpLoc,
                            UnaryOperatorKind Opc, Expr *Input);
    ExprResult ActOnUnaryOp(Scope *S, SourceLocation OpLoc,
                            tok::TokenKind Op, Expr *Input);
  
    bool isQualifiedMemberAccess(Expr *E);
    QualType CheckAddressOfOperand(ExprResult &Operand, SourceLocation OpLoc);
  
    ExprResult CreateUnaryExprOrTypeTraitExpr(TypeSourceInfo *TInfo,
                                              SourceLocation OpLoc,
                                              UnaryExprOrTypeTrait ExprKind,
                                              SourceRange R);
    ExprResult CreateUnaryExprOrTypeTraitExpr(Expr *E, SourceLocation OpLoc,
                                              UnaryExprOrTypeTrait ExprKind);
    ExprResult
      ActOnUnaryExprOrTypeTraitExpr(SourceLocation OpLoc,
                                    UnaryExprOrTypeTrait ExprKind,
                                    bool IsType, void *TyOrEx,
                                    SourceRange ArgRange);
  
    ExprResult CheckPlaceholderExpr(Expr *E);
    bool CheckVecStepExpr(Expr *E);
  
    bool CheckUnaryExprOrTypeTraitOperand(Expr *E, UnaryExprOrTypeTrait ExprKind);
    bool CheckUnaryExprOrTypeTraitOperand(QualType ExprType, SourceLocation OpLoc,
                                          SourceRange ExprRange,
                                          UnaryExprOrTypeTrait ExprKind);
    ExprResult ActOnSizeofParameterPackExpr(Scope *S,
                                            SourceLocation OpLoc,
                                            IdentifierInfo &Name,
                                            SourceLocation NameLoc,
                                            SourceLocation RParenLoc);
    ExprResult ActOnPostfixUnaryOp(Scope *S, SourceLocation OpLoc,
                                   tok::TokenKind Kind, Expr *Input);
  
    ExprResult ActOnArraySubscriptExpr(Scope *S, Expr *Base, SourceLocation LLoc,
                                       Expr *Idx, SourceLocation RLoc);
    ExprResult CreateBuiltinArraySubscriptExpr(Expr *Base, SourceLocation LLoc,
                                               Expr *Idx, SourceLocation RLoc);
    ExprResult ActOnOMPArraySectionExpr(Expr *Base, SourceLocation LBLoc,
                                        Expr *LowerBound, SourceLocation ColonLoc,
                                        Expr *Length, SourceLocation RBLoc);
  
    // This struct is for use by ActOnMemberAccess to allow
    // BuildMemberReferenceExpr to be able to reinvoke ActOnMemberAccess after
    // changing the access operator from a '.' to a '->' (to see if that is the
    // change needed to fix an error about an unknown member, e.g. when the class
    // defines a custom operator->).
    struct ActOnMemberAccessExtraArgs {
      Scope *S;
      UnqualifiedId &Id;
      Decl *ObjCImpDecl;
    };
  
    ExprResult BuildMemberReferenceExpr(
        Expr *Base, QualType BaseType, SourceLocation OpLoc, bool IsArrow,
        CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
        NamedDecl *FirstQualifierInScope, const DeclarationNameInfo &NameInfo,
        const TemplateArgumentListInfo *TemplateArgs,
        const Scope *S,
        ActOnMemberAccessExtraArgs *ExtraArgs = nullptr);
  
    ExprResult
    BuildMemberReferenceExpr(Expr *Base, QualType BaseType, SourceLocation OpLoc,
                             bool IsArrow, const CXXScopeSpec &SS,
                             SourceLocation TemplateKWLoc,
                             NamedDecl *FirstQualifierInScope, LookupResult &R,
                             const TemplateArgumentListInfo *TemplateArgs,
                             const Scope *S,
                             bool SuppressQualifierCheck = false,
                             ActOnMemberAccessExtraArgs *ExtraArgs = nullptr);
  
    ExprResult BuildFieldReferenceExpr(Expr *BaseExpr, bool IsArrow,
                                       SourceLocation OpLoc,
                                       const CXXScopeSpec &SS, FieldDecl *Field,
                                       DeclAccessPair FoundDecl,
                                       const DeclarationNameInfo &MemberNameInfo);
  
    ExprResult PerformMemberExprBaseConversion(Expr *Base, bool IsArrow);
  
    bool CheckQualifiedMemberReference(Expr *BaseExpr, QualType BaseType,
                                       const CXXScopeSpec &SS,
                                       const LookupResult &R);
  
    ExprResult ActOnDependentMemberExpr(Expr *Base, QualType BaseType,
                                        bool IsArrow, SourceLocation OpLoc,
                                        const CXXScopeSpec &SS,
                                        SourceLocation TemplateKWLoc,
                                        NamedDecl *FirstQualifierInScope,
                                 const DeclarationNameInfo &NameInfo,
                                 const TemplateArgumentListInfo *TemplateArgs);
  
    ExprResult ActOnMemberAccessExpr(Scope *S, Expr *Base,
                                     SourceLocation OpLoc,
                                     tok::TokenKind OpKind,
                                     CXXScopeSpec &SS,
                                     SourceLocation TemplateKWLoc,
                                     UnqualifiedId &Member,
                                     Decl *ObjCImpDecl);
  
    MemberExpr *
    BuildMemberExpr(Expr *Base, bool IsArrow, SourceLocation OpLoc,
                    const CXXScopeSpec *SS, SourceLocation TemplateKWLoc,
                    ValueDecl *Member, DeclAccessPair FoundDecl,
                    bool HadMultipleCandidates,
                    const DeclarationNameInfo &MemberNameInfo, QualType Ty,
                    ExprValueKind VK, ExprObjectKind OK,
                    const TemplateArgumentListInfo *TemplateArgs = nullptr);
    MemberExpr *
    BuildMemberExpr(Expr *Base, bool IsArrow, SourceLocation OpLoc,
                    NestedNameSpecifierLoc NNS, SourceLocation TemplateKWLoc,
                    ValueDecl *Member, DeclAccessPair FoundDecl,
                    bool HadMultipleCandidates,
                    const DeclarationNameInfo &MemberNameInfo, QualType Ty,
                    ExprValueKind VK, ExprObjectKind OK,
                    const TemplateArgumentListInfo *TemplateArgs = nullptr);
  
    void ActOnDefaultCtorInitializers(Decl *CDtorDecl);
    bool ConvertArgumentsForCall(CallExpr *Call, Expr *Fn,
                                 FunctionDecl *FDecl,
                                 const FunctionProtoType *Proto,
                                 ArrayRef<Expr *> Args,
                                 SourceLocation RParenLoc,
                                 bool ExecConfig = false);
    void CheckStaticArrayArgument(SourceLocation CallLoc,
                                  ParmVarDecl *Param,
                                  const Expr *ArgExpr);
  
    /// ActOnCallExpr - Handle a call to Fn with the specified array of arguments.
    /// This provides the location of the left/right parens and a list of comma
    /// locations.
    ExprResult ActOnCallExpr(Scope *S, Expr *Fn, SourceLocation LParenLoc,
                             MultiExprArg ArgExprs, SourceLocation RParenLoc,
                             Expr *ExecConfig = nullptr);
    ExprResult BuildCallExpr(Scope *S, Expr *Fn, SourceLocation LParenLoc,
                             MultiExprArg ArgExprs, SourceLocation RParenLoc,
                             Expr *ExecConfig = nullptr,
                             bool IsExecConfig = false);
    enum class AtomicArgumentOrder { API, AST };
    ExprResult
    BuildAtomicExpr(SourceRange CallRange, SourceRange ExprRange,
                    SourceLocation RParenLoc, MultiExprArg Args,
                    AtomicExpr::AtomicOp Op,
                    AtomicArgumentOrder ArgOrder = AtomicArgumentOrder::API);
    ExprResult
    BuildResolvedCallExpr(Expr *Fn, NamedDecl *NDecl, SourceLocation LParenLoc,
                          ArrayRef<Expr *> Arg, SourceLocation RParenLoc,
                          Expr *Config = nullptr, bool IsExecConfig = false,
                          ADLCallKind UsesADL = ADLCallKind::NotADL);
  
    ExprResult ActOnCUDAExecConfigExpr(Scope *S, SourceLocation LLLLoc,
                                       MultiExprArg ExecConfig,
                                       SourceLocation GGGLoc);
  
    ExprResult ActOnCastExpr(Scope *S, SourceLocation LParenLoc,
                             Declarator &D, ParsedType &Ty,
                             SourceLocation RParenLoc, Expr *CastExpr);
    ExprResult BuildCStyleCastExpr(SourceLocation LParenLoc,
                                   TypeSourceInfo *Ty,
                                   SourceLocation RParenLoc,
                                   Expr *Op);
    CastKind PrepareScalarCast(ExprResult &src, QualType destType);
  
    /// Build an altivec or OpenCL literal.
    ExprResult BuildVectorLiteral(SourceLocation LParenLoc,
                                  SourceLocation RParenLoc, Expr *E,
                                  TypeSourceInfo *TInfo);
  
    ExprResult MaybeConvertParenListExprToParenExpr(Scope *S, Expr *ME);
  
    ExprResult ActOnCompoundLiteral(SourceLocation LParenLoc,
                                    ParsedType Ty,
                                    SourceLocation RParenLoc,
                                    Expr *InitExpr);
  
    ExprResult BuildCompoundLiteralExpr(SourceLocation LParenLoc,
                                        TypeSourceInfo *TInfo,
                                        SourceLocation RParenLoc,
                                        Expr *LiteralExpr);
  
    ExprResult ActOnInitList(SourceLocation LBraceLoc,
                             MultiExprArg InitArgList,
                             SourceLocation RBraceLoc);
  
    ExprResult BuildInitList(SourceLocation LBraceLoc,
                             MultiExprArg InitArgList,
                             SourceLocation RBraceLoc);
  
    ExprResult ActOnDesignatedInitializer(Designation &Desig,
                                          SourceLocation EqualOrColonLoc,
                                          bool GNUSyntax,
                                          ExprResult Init);
  
  private:
    static BinaryOperatorKind ConvertTokenKindToBinaryOpcode(tok::TokenKind Kind);
  
  public:
    ExprResult ActOnBinOp(Scope *S, SourceLocation TokLoc,
                          tok::TokenKind Kind, Expr *LHSExpr, Expr *RHSExpr);
    ExprResult BuildBinOp(Scope *S, SourceLocation OpLoc,
                          BinaryOperatorKind Opc, Expr *LHSExpr, Expr *RHSExpr);
    ExprResult CreateBuiltinBinOp(SourceLocation OpLoc, BinaryOperatorKind Opc,
                                  Expr *LHSExpr, Expr *RHSExpr);
  
    void DiagnoseCommaOperator(const Expr *LHS, SourceLocation Loc);
  
    /// ActOnConditionalOp - Parse a ?: operation.  Note that 'LHS' may be null
    /// in the case of a the GNU conditional expr extension.
    ExprResult ActOnConditionalOp(SourceLocation QuestionLoc,
                                  SourceLocation ColonLoc,
                                  Expr *CondExpr, Expr *LHSExpr, Expr *RHSExpr);
  
    /// ActOnAddrLabel - Parse the GNU address of label extension: "&&foo".
    ExprResult ActOnAddrLabel(SourceLocation OpLoc, SourceLocation LabLoc,
                              LabelDecl *TheDecl);
  
    void ActOnStartStmtExpr();
    ExprResult ActOnStmtExpr(Scope *S, SourceLocation LPLoc, Stmt *SubStmt,
                             SourceLocation RPLoc);
    ExprResult BuildStmtExpr(SourceLocation LPLoc, Stmt *SubStmt,
                             SourceLocation RPLoc, unsigned TemplateDepth);
    // Handle the final expression in a statement expression.
    ExprResult ActOnStmtExprResult(ExprResult E);
    void ActOnStmtExprError();
  
    // __builtin_offsetof(type, identifier(.identifier|[expr])*)
    struct OffsetOfComponent {
      SourceLocation LocStart, LocEnd;
      bool isBrackets;  // true if [expr], false if .ident
      union {
        IdentifierInfo *IdentInfo;
        Expr *E;
      } U;
    };
  
    /// __builtin_offsetof(type, a.b[123][456].c)
    ExprResult BuildBuiltinOffsetOf(SourceLocation BuiltinLoc,
                                    TypeSourceInfo *TInfo,
                                    ArrayRef<OffsetOfComponent> Components,
                                    SourceLocation RParenLoc);
    ExprResult ActOnBuiltinOffsetOf(Scope *S,
                                    SourceLocation BuiltinLoc,
                                    SourceLocation TypeLoc,
                                    ParsedType ParsedArgTy,
                                    ArrayRef<OffsetOfComponent> Components,
                                    SourceLocation RParenLoc);
  
    // __builtin_choose_expr(constExpr, expr1, expr2)
    ExprResult ActOnChooseExpr(SourceLocation BuiltinLoc,
                               Expr *CondExpr, Expr *LHSExpr,
                               Expr *RHSExpr, SourceLocation RPLoc);
  
    // __builtin_va_arg(expr, type)
    ExprResult ActOnVAArg(SourceLocation BuiltinLoc, Expr *E, ParsedType Ty,
                          SourceLocation RPLoc);
    ExprResult BuildVAArgExpr(SourceLocation BuiltinLoc, Expr *E,
                              TypeSourceInfo *TInfo, SourceLocation RPLoc);
  
    // __builtin_LINE(), __builtin_FUNCTION(), __builtin_FILE(),
    // __builtin_COLUMN()
    ExprResult ActOnSourceLocExpr(SourceLocExpr::IdentKind Kind,
                                  SourceLocation BuiltinLoc,
                                  SourceLocation RPLoc);
  
    // Build a potentially resolved SourceLocExpr.
    ExprResult BuildSourceLocExpr(SourceLocExpr::IdentKind Kind,
                                  SourceLocation BuiltinLoc, SourceLocation RPLoc,
                                  DeclContext *ParentContext);
  
    // __null
    ExprResult ActOnGNUNullExpr(SourceLocation TokenLoc);
  
    bool CheckCaseExpression(Expr *E);
  
    /// Describes the result of an "if-exists" condition check.
    enum IfExistsResult {
      /// The symbol exists.
      IER_Exists,
  
      /// The symbol does not exist.
      IER_DoesNotExist,
  
      /// The name is a dependent name, so the results will differ
      /// from one instantiation to the next.
      IER_Dependent,
  
      /// An error occurred.
      IER_Error
    };
  
    IfExistsResult
    CheckMicrosoftIfExistsSymbol(Scope *S, CXXScopeSpec &SS,
                                 const DeclarationNameInfo &TargetNameInfo);
  
    IfExistsResult
    CheckMicrosoftIfExistsSymbol(Scope *S, SourceLocation KeywordLoc,
                                 bool IsIfExists, CXXScopeSpec &SS,
                                 UnqualifiedId &Name);
  
    StmtResult BuildMSDependentExistsStmt(SourceLocation KeywordLoc,
                                          bool IsIfExists,
                                          NestedNameSpecifierLoc QualifierLoc,
                                          DeclarationNameInfo NameInfo,
                                          Stmt *Nested);
    StmtResult ActOnMSDependentExistsStmt(SourceLocation KeywordLoc,
                                          bool IsIfExists,
                                          CXXScopeSpec &SS, UnqualifiedId &Name,
                                          Stmt *Nested);
  
    //===------------------------- "Block" Extension ------------------------===//
  
    /// ActOnBlockStart - This callback is invoked when a block literal is
    /// started.
    void ActOnBlockStart(SourceLocation CaretLoc, Scope *CurScope);
  
    /// ActOnBlockArguments - This callback allows processing of block arguments.
    /// If there are no arguments, this is still invoked.
    void ActOnBlockArguments(SourceLocation CaretLoc, Declarator &ParamInfo,
                             Scope *CurScope);
  
    /// ActOnBlockError - If there is an error parsing a block, this callback
    /// is invoked to pop the information about the block from the action impl.
    void ActOnBlockError(SourceLocation CaretLoc, Scope *CurScope);
  
    /// ActOnBlockStmtExpr - This is called when the body of a block statement
    /// literal was successfully completed.  ^(int x){...}
    ExprResult ActOnBlockStmtExpr(SourceLocation CaretLoc, Stmt *Body,
                                  Scope *CurScope);
  
    //===---------------------------- Clang Extensions ----------------------===//
  
    /// __builtin_convertvector(...)
    ExprResult ActOnConvertVectorExpr(Expr *E, ParsedType ParsedDestTy,
                                      SourceLocation BuiltinLoc,
                                      SourceLocation RParenLoc);
  
    //===---------------------------- OpenCL Features -----------------------===//
  
    /// __builtin_astype(...)
    ExprResult ActOnAsTypeExpr(Expr *E, ParsedType ParsedDestTy,
                               SourceLocation BuiltinLoc,
                               SourceLocation RParenLoc);
  
    //===---------------------------- C++ Features --------------------------===//
  
    // Act on C++ namespaces
    Decl *ActOnStartNamespaceDef(Scope *S, SourceLocation InlineLoc,
                                 SourceLocation NamespaceLoc,
                                 SourceLocation IdentLoc, IdentifierInfo *Ident,
                                 SourceLocation LBrace,
                                 const ParsedAttributesView &AttrList,
                                 UsingDirectiveDecl *&UsingDecl);
    void ActOnFinishNamespaceDef(Decl *Dcl, SourceLocation RBrace);
  
    NamespaceDecl *getStdNamespace() const;
    NamespaceDecl *getOrCreateStdNamespace();
  
    NamespaceDecl *lookupStdExperimentalNamespace();
  
    CXXRecordDecl *getStdBadAlloc() const;
    EnumDecl *getStdAlignValT() const;
  
  private:
    // A cache representing if we've fully checked the various comparison category
    // types stored in ASTContext. The bit-index corresponds to the integer value
    // of a ComparisonCategoryType enumerator.
    llvm::SmallBitVector FullyCheckedComparisonCategories;
  
    ValueDecl *tryLookupCtorInitMemberDecl(CXXRecordDecl *ClassDecl,
                                           CXXScopeSpec &SS,
                                           ParsedType TemplateTypeTy,
                                           IdentifierInfo *MemberOrBase);
  
  public:
    enum class ComparisonCategoryUsage {
      /// The '<=>' operator was used in an expression and a builtin operator
      /// was selected.
      OperatorInExpression,
      /// A defaulted 'operator<=>' needed the comparison category. This
      /// typically only applies to 'std::strong_ordering', due to the implicit
      /// fallback return value.
      DefaultedOperator,
    };
  
    /// Lookup the specified comparison category types in the standard
    ///   library, an check the VarDecls possibly returned by the operator<=>
    ///   builtins for that type.
    ///
    /// \return The type of the comparison category type corresponding to the
    ///   specified Kind, or a null type if an error occurs
    QualType CheckComparisonCategoryType(ComparisonCategoryType Kind,
                                         SourceLocation Loc,
                                         ComparisonCategoryUsage Usage);
  
    /// Tests whether Ty is an instance of std::initializer_list and, if
    /// it is and Element is not NULL, assigns the element type to Element.
    bool isStdInitializerList(QualType Ty, QualType *Element);
  
    /// Looks for the std::initializer_list template and instantiates it
    /// with Element, or emits an error if it's not found.
    ///
    /// \returns The instantiated template, or null on error.
    QualType BuildStdInitializerList(QualType Element, SourceLocation Loc);
  
    /// Determine whether Ctor is an initializer-list constructor, as
    /// defined in [dcl.init.list]p2.
    bool isInitListConstructor(const FunctionDecl *Ctor);
  
    Decl *ActOnUsingDirective(Scope *CurScope, SourceLocation UsingLoc,
                              SourceLocation NamespcLoc, CXXScopeSpec &SS,
                              SourceLocation IdentLoc,
                              IdentifierInfo *NamespcName,
                              const ParsedAttributesView &AttrList);
  
    void PushUsingDirective(Scope *S, UsingDirectiveDecl *UDir);
  
    Decl *ActOnNamespaceAliasDef(Scope *CurScope,
                                 SourceLocation NamespaceLoc,
                                 SourceLocation AliasLoc,
                                 IdentifierInfo *Alias,
                                 CXXScopeSpec &SS,
                                 SourceLocation IdentLoc,
                                 IdentifierInfo *Ident);
  
    void HideUsingShadowDecl(Scope *S, UsingShadowDecl *Shadow);
    bool CheckUsingShadowDecl(UsingDecl *UD, NamedDecl *Target,
                              const LookupResult &PreviousDecls,
                              UsingShadowDecl *&PrevShadow);
    UsingShadowDecl *BuildUsingShadowDecl(Scope *S, UsingDecl *UD,
                                          NamedDecl *Target,
                                          UsingShadowDecl *PrevDecl);
  
    bool CheckUsingDeclRedeclaration(SourceLocation UsingLoc,
                                     bool HasTypenameKeyword,
                                     const CXXScopeSpec &SS,
                                     SourceLocation NameLoc,
                                     const LookupResult &Previous);
    bool CheckUsingDeclQualifier(SourceLocation UsingLoc,
                                 bool HasTypename,
                                 const CXXScopeSpec &SS,
                                 const DeclarationNameInfo &NameInfo,
                                 SourceLocation NameLoc);
  
    NamedDecl *BuildUsingDeclaration(
        Scope *S, AccessSpecifier AS, SourceLocation UsingLoc,
        bool HasTypenameKeyword, SourceLocation TypenameLoc, CXXScopeSpec &SS,
        DeclarationNameInfo NameInfo, SourceLocation EllipsisLoc,
        const ParsedAttributesView &AttrList, bool IsInstantiation);
    NamedDecl *BuildUsingPackDecl(NamedDecl *InstantiatedFrom,
                                  ArrayRef<NamedDecl *> Expansions);
  
    bool CheckInheritingConstructorUsingDecl(UsingDecl *UD);
  
    /// Given a derived-class using shadow declaration for a constructor and the
    /// correspnding base class constructor, find or create the implicit
    /// synthesized derived class constructor to use for this initialization.
    CXXConstructorDecl *
    findInheritingConstructor(SourceLocation Loc, CXXConstructorDecl *BaseCtor,
                              ConstructorUsingShadowDecl *DerivedShadow);
  
    Decl *ActOnUsingDeclaration(Scope *CurScope, AccessSpecifier AS,
                                SourceLocation UsingLoc,
                                SourceLocation TypenameLoc, CXXScopeSpec &SS,
                                UnqualifiedId &Name, SourceLocation EllipsisLoc,
                                const ParsedAttributesView &AttrList);
    Decl *ActOnAliasDeclaration(Scope *CurScope, AccessSpecifier AS,
                                MultiTemplateParamsArg TemplateParams,
                                SourceLocation UsingLoc, UnqualifiedId &Name,
                                const ParsedAttributesView &AttrList,
                                TypeResult Type, Decl *DeclFromDeclSpec);
  
    /// BuildCXXConstructExpr - Creates a complete call to a constructor,
    /// including handling of its default argument expressions.
    ///
    /// \param ConstructKind - a CXXConstructExpr::ConstructionKind
    ExprResult
    BuildCXXConstructExpr(SourceLocation ConstructLoc, QualType DeclInitType,
                          NamedDecl *FoundDecl,
                          CXXConstructorDecl *Constructor, MultiExprArg Exprs,
                          bool HadMultipleCandidates, bool IsListInitialization,
                          bool IsStdInitListInitialization,
                          bool RequiresZeroInit, unsigned ConstructKind,
                          SourceRange ParenRange);
  
    /// Build a CXXConstructExpr whose constructor has already been resolved if
    /// it denotes an inherited constructor.
    ExprResult
    BuildCXXConstructExpr(SourceLocation ConstructLoc, QualType DeclInitType,
                          CXXConstructorDecl *Constructor, bool Elidable,
                          MultiExprArg Exprs,
                          bool HadMultipleCandidates, bool IsListInitialization,
                          bool IsStdInitListInitialization,
                          bool RequiresZeroInit, unsigned ConstructKind,
                          SourceRange ParenRange);
  
    // FIXME: Can we remove this and have the above BuildCXXConstructExpr check if
    // the constructor can be elidable?
    ExprResult
    BuildCXXConstructExpr(SourceLocation ConstructLoc, QualType DeclInitType,
                          NamedDecl *FoundDecl,
                          CXXConstructorDecl *Constructor, bool Elidable,
                          MultiExprArg Exprs, bool HadMultipleCandidates,
                          bool IsListInitialization,
                          bool IsStdInitListInitialization, bool RequiresZeroInit,
                          unsigned ConstructKind, SourceRange ParenRange);
  
    ExprResult BuildCXXDefaultInitExpr(SourceLocation Loc, FieldDecl *Field);
  
  
    /// Instantiate or parse a C++ default argument expression as necessary.
    /// Return true on error.
    bool CheckCXXDefaultArgExpr(SourceLocation CallLoc, FunctionDecl *FD,
                                ParmVarDecl *Param);
  
    /// BuildCXXDefaultArgExpr - Creates a CXXDefaultArgExpr, instantiating
    /// the default expr if needed.
    ExprResult BuildCXXDefaultArgExpr(SourceLocation CallLoc,
                                      FunctionDecl *FD,
                                      ParmVarDecl *Param);
  
    /// FinalizeVarWithDestructor - Prepare for calling destructor on the
    /// constructed variable.
    void FinalizeVarWithDestructor(VarDecl *VD, const RecordType *DeclInitType);
  
    /// Helper class that collects exception specifications for
    /// implicitly-declared special member functions.
    class ImplicitExceptionSpecification {
      // Pointer to allow copying
      Sema *Self;
      // We order exception specifications thus:
      // noexcept is the most restrictive, but is only used in C++11.
      // throw() comes next.
      // Then a throw(collected exceptions)
      // Finally no specification, which is expressed as noexcept(false).
      // throw(...) is used instead if any called function uses it.
      ExceptionSpecificationType ComputedEST;
      llvm::SmallPtrSet<CanQualType, 4> ExceptionsSeen;
      SmallVector<QualType, 4> Exceptions;
  
      void ClearExceptions() {
        ExceptionsSeen.clear();
        Exceptions.clear();
      }
  
    public:
      explicit ImplicitExceptionSpecification(Sema &Self)
        : Self(&Self), ComputedEST(EST_BasicNoexcept) {
        if (!Self.getLangOpts().CPlusPlus11)
          ComputedEST = EST_DynamicNone;
      }
  
      /// Get the computed exception specification type.
      ExceptionSpecificationType getExceptionSpecType() const {
        assert(!isComputedNoexcept(ComputedEST) &&
               "noexcept(expr) should not be a possible result");
        return ComputedEST;
      }
  
      /// The number of exceptions in the exception specification.
      unsigned size() const { return Exceptions.size(); }
  
      /// The set of exceptions in the exception specification.
      const QualType *data() const { return Exceptions.data(); }
  
      /// Integrate another called method into the collected data.
      void CalledDecl(SourceLocation CallLoc, const CXXMethodDecl *Method);
  
      /// Integrate an invoked expression into the collected data.
      void CalledExpr(Expr *E) { CalledStmt(E); }
  
      /// Integrate an invoked statement into the collected data.
      void CalledStmt(Stmt *S);
  
      /// Overwrite an EPI's exception specification with this
      /// computed exception specification.
      FunctionProtoType::ExceptionSpecInfo getExceptionSpec() const {
        FunctionProtoType::ExceptionSpecInfo ESI;
        ESI.Type = getExceptionSpecType();
        if (ESI.Type == EST_Dynamic) {
          ESI.Exceptions = Exceptions;
        } else if (ESI.Type == EST_None) {
          /// C++11 [except.spec]p14:
          ///   The exception-specification is noexcept(false) if the set of
          ///   potential exceptions of the special member function contains "any"
          ESI.Type = EST_NoexceptFalse;
          ESI.NoexceptExpr = Self->ActOnCXXBoolLiteral(SourceLocation(),
                                                       tok::kw_false).get();
        }
        return ESI;
      }
    };
  
    /// Determine what sort of exception specification a defaulted
    /// copy constructor of a class will have.
    ImplicitExceptionSpecification
    ComputeDefaultedDefaultCtorExceptionSpec(SourceLocation Loc,
                                             CXXMethodDecl *MD);
  
    /// Determine what sort of exception specification a defaulted
    /// default constructor of a class will have, and whether the parameter
    /// will be const.
    ImplicitExceptionSpecification
    ComputeDefaultedCopyCtorExceptionSpec(CXXMethodDecl *MD);
  
    /// Determine what sort of exception specification a defaulted
    /// copy assignment operator of a class will have, and whether the
    /// parameter will be const.
    ImplicitExceptionSpecification
    ComputeDefaultedCopyAssignmentExceptionSpec(CXXMethodDecl *MD);
  
    /// Determine what sort of exception specification a defaulted move
    /// constructor of a class will have.
    ImplicitExceptionSpecification
    ComputeDefaultedMoveCtorExceptionSpec(CXXMethodDecl *MD);
  
    /// Determine what sort of exception specification a defaulted move
    /// assignment operator of a class will have.
    ImplicitExceptionSpecification
    ComputeDefaultedMoveAssignmentExceptionSpec(CXXMethodDecl *MD);
  
    /// Determine what sort of exception specification a defaulted
    /// destructor of a class will have.
    ImplicitExceptionSpecification
    ComputeDefaultedDtorExceptionSpec(CXXMethodDecl *MD);
  
    /// Determine what sort of exception specification an inheriting
    /// constructor of a class will have.
    ImplicitExceptionSpecification
    ComputeInheritingCtorExceptionSpec(SourceLocation Loc,
                                       CXXConstructorDecl *CD);
  
    /// Evaluate the implicit exception specification for a defaulted
    /// special member function.
    void EvaluateImplicitExceptionSpec(SourceLocation Loc, FunctionDecl *FD);
  
    /// Check the given noexcept-specifier, convert its expression, and compute
    /// the appropriate ExceptionSpecificationType.
    ExprResult ActOnNoexceptSpec(SourceLocation NoexceptLoc, Expr *NoexceptExpr,
                                 ExceptionSpecificationType &EST);
  
    /// Check the given exception-specification and update the
    /// exception specification information with the results.
    void checkExceptionSpecification(bool IsTopLevel,
                                     ExceptionSpecificationType EST,
                                     ArrayRef<ParsedType> DynamicExceptions,
                                     ArrayRef<SourceRange> DynamicExceptionRanges,
                                     Expr *NoexceptExpr,
                                     SmallVectorImpl<QualType> &Exceptions,
                                     FunctionProtoType::ExceptionSpecInfo &ESI);
  
    /// Determine if we're in a case where we need to (incorrectly) eagerly
    /// parse an exception specification to work around a libstdc++ bug.
    bool isLibstdcxxEagerExceptionSpecHack(const Declarator &D);
  
    /// Add an exception-specification to the given member function
    /// (or member function template). The exception-specification was parsed
    /// after the method itself was declared.
    void actOnDelayedExceptionSpecification(Decl *Method,
           ExceptionSpecificationType EST,
           SourceRange SpecificationRange,
           ArrayRef<ParsedType> DynamicExceptions,
           ArrayRef<SourceRange> DynamicExceptionRanges,
           Expr *NoexceptExpr);
  
    class InheritedConstructorInfo;
  
    /// Determine if a special member function should have a deleted
    /// definition when it is defaulted.
    bool ShouldDeleteSpecialMember(CXXMethodDecl *MD, CXXSpecialMember CSM,
                                   InheritedConstructorInfo *ICI = nullptr,
                                   bool Diagnose = false);
  
    /// Produce notes explaining why a defaulted function was defined as deleted.
    void DiagnoseDeletedDefaultedFunction(FunctionDecl *FD);
  
    /// Declare the implicit default constructor for the given class.
    ///
    /// \param ClassDecl The class declaration into which the implicit
    /// default constructor will be added.
    ///
    /// \returns The implicitly-declared default constructor.
    CXXConstructorDecl *DeclareImplicitDefaultConstructor(
                                                       CXXRecordDecl *ClassDecl);
  
    /// DefineImplicitDefaultConstructor - Checks for feasibility of
    /// defining this constructor as the default constructor.
    void DefineImplicitDefaultConstructor(SourceLocation CurrentLocation,
                                          CXXConstructorDecl *Constructor);
  
    /// Declare the implicit destructor for the given class.
    ///
    /// \param ClassDecl The class declaration into which the implicit
    /// destructor will be added.
    ///
    /// \returns The implicitly-declared destructor.
    CXXDestructorDecl *DeclareImplicitDestructor(CXXRecordDecl *ClassDecl);
  
    /// DefineImplicitDestructor - Checks for feasibility of
    /// defining this destructor as the default destructor.
    void DefineImplicitDestructor(SourceLocation CurrentLocation,
                                  CXXDestructorDecl *Destructor);
  
    /// Build an exception spec for destructors that don't have one.
    ///
    /// C++11 says that user-defined destructors with no exception spec get one
    /// that looks as if the destructor was implicitly declared.
    void AdjustDestructorExceptionSpec(CXXDestructorDecl *Destructor);
  
    /// Define the specified inheriting constructor.
    void DefineInheritingConstructor(SourceLocation UseLoc,
                                     CXXConstructorDecl *Constructor);
  
    /// Declare the implicit copy constructor for the given class.
    ///
    /// \param ClassDecl The class declaration into which the implicit
    /// copy constructor will be added.
    ///
    /// \returns The implicitly-declared copy constructor.
    CXXConstructorDecl *DeclareImplicitCopyConstructor(CXXRecordDecl *ClassDecl);
  
    /// DefineImplicitCopyConstructor - Checks for feasibility of
    /// defining this constructor as the copy constructor.
    void DefineImplicitCopyConstructor(SourceLocation CurrentLocation,
                                       CXXConstructorDecl *Constructor);
  
    /// Declare the implicit move constructor for the given class.
    ///
    /// \param ClassDecl The Class declaration into which the implicit
    /// move constructor will be added.
    ///
    /// \returns The implicitly-declared move constructor, or NULL if it wasn't
    /// declared.
    CXXConstructorDecl *DeclareImplicitMoveConstructor(CXXRecordDecl *ClassDecl);
  
    /// DefineImplicitMoveConstructor - Checks for feasibility of
    /// defining this constructor as the move constructor.
    void DefineImplicitMoveConstructor(SourceLocation CurrentLocation,
                                       CXXConstructorDecl *Constructor);
  
    /// Declare the implicit copy assignment operator for the given class.
    ///
    /// \param ClassDecl The class declaration into which the implicit
    /// copy assignment operator will be added.
    ///
    /// \returns The implicitly-declared copy assignment operator.
    CXXMethodDecl *DeclareImplicitCopyAssignment(CXXRecordDecl *ClassDecl);
  
    /// Defines an implicitly-declared copy assignment operator.
    void DefineImplicitCopyAssignment(SourceLocation CurrentLocation,
                                      CXXMethodDecl *MethodDecl);
  
    /// Declare the implicit move assignment operator for the given class.
    ///
    /// \param ClassDecl The Class declaration into which the implicit
    /// move assignment operator will be added.
    ///
    /// \returns The implicitly-declared move assignment operator, or NULL if it
    /// wasn't declared.
    CXXMethodDecl *DeclareImplicitMoveAssignment(CXXRecordDecl *ClassDecl);
  
    /// Defines an implicitly-declared move assignment operator.
    void DefineImplicitMoveAssignment(SourceLocation CurrentLocation,
                                      CXXMethodDecl *MethodDecl);
  
    /// Force the declaration of any implicitly-declared members of this
    /// class.
    void ForceDeclarationOfImplicitMembers(CXXRecordDecl *Class);
  
    /// Check a completed declaration of an implicit special member.
    void CheckImplicitSpecialMemberDeclaration(Scope *S, FunctionDecl *FD);
  
    /// Determine whether the given function is an implicitly-deleted
    /// special member function.
    bool isImplicitlyDeleted(FunctionDecl *FD);
  
    /// Check whether 'this' shows up in the type of a static member
    /// function after the (naturally empty) cv-qualifier-seq would be.
    ///
    /// \returns true if an error occurred.
    bool checkThisInStaticMemberFunctionType(CXXMethodDecl *Method);
  
    /// Whether this' shows up in the exception specification of a static
    /// member function.
    bool checkThisInStaticMemberFunctionExceptionSpec(CXXMethodDecl *Method);
  
    /// Check whether 'this' shows up in the attributes of the given
    /// static member function.
    ///
    /// \returns true if an error occurred.
    bool checkThisInStaticMemberFunctionAttributes(CXXMethodDecl *Method);
  
    /// MaybeBindToTemporary - If the passed in expression has a record type with
    /// a non-trivial destructor, this will return CXXBindTemporaryExpr. Otherwise
    /// it simply returns the passed in expression.
    ExprResult MaybeBindToTemporary(Expr *E);
  
    /// Wrap the expression in a ConstantExpr if it is a potential immediate
    /// invocation.
    ExprResult CheckForImmediateInvocation(ExprResult E, FunctionDecl *Decl);
  
    bool CompleteConstructorCall(CXXConstructorDecl *Constructor,
                                 MultiExprArg ArgsPtr,
                                 SourceLocation Loc,
                                 SmallVectorImpl<Expr*> &ConvertedArgs,
                                 bool AllowExplicit = false,
                                 bool IsListInitialization = false);
  
    ParsedType getInheritingConstructorName(CXXScopeSpec &SS,
                                            SourceLocation NameLoc,
                                            IdentifierInfo &Name);
  
    ParsedType getConstructorName(IdentifierInfo &II, SourceLocation NameLoc,
                                  Scope *S, CXXScopeSpec &SS,
                                  bool EnteringContext);
    ParsedType getDestructorName(SourceLocation TildeLoc,
                                 IdentifierInfo &II, SourceLocation NameLoc,
                                 Scope *S, CXXScopeSpec &SS,
                                 ParsedType ObjectType,
                                 bool EnteringContext);
  
    ParsedType getDestructorTypeForDecltype(const DeclSpec &DS,
                                            ParsedType ObjectType);
  
    // Checks that reinterpret casts don't have undefined behavior.
    void CheckCompatibleReinterpretCast(QualType SrcType, QualType DestType,
                                        bool IsDereference, SourceRange Range);
  
    /// ActOnCXXNamedCast - Parse {dynamic,static,reinterpret,const}_cast's.
    ExprResult ActOnCXXNamedCast(SourceLocation OpLoc,
                                 tok::TokenKind Kind,
                                 SourceLocation LAngleBracketLoc,
                                 Declarator &D,
                                 SourceLocation RAngleBracketLoc,
                                 SourceLocation LParenLoc,
                                 Expr *E,
                                 SourceLocation RParenLoc);
  
    ExprResult BuildCXXNamedCast(SourceLocation OpLoc,
                                 tok::TokenKind Kind,
                                 TypeSourceInfo *Ty,
                                 Expr *E,
                                 SourceRange AngleBrackets,
                                 SourceRange Parens);
  
    ExprResult ActOnBuiltinBitCastExpr(SourceLocation KWLoc, Declarator &Dcl,
                                       ExprResult Operand,
                                       SourceLocation RParenLoc);
  
    ExprResult BuildBuiltinBitCastExpr(SourceLocation KWLoc, TypeSourceInfo *TSI,
                                       Expr *Operand, SourceLocation RParenLoc);
  
    ExprResult BuildCXXTypeId(QualType TypeInfoType,
                              SourceLocation TypeidLoc,
                              TypeSourceInfo *Operand,
                              SourceLocation RParenLoc);
    ExprResult BuildCXXTypeId(QualType TypeInfoType,
                              SourceLocation TypeidLoc,
                              Expr *Operand,
                              SourceLocation RParenLoc);
  
    /// ActOnCXXTypeid - Parse typeid( something ).
    ExprResult ActOnCXXTypeid(SourceLocation OpLoc,
                              SourceLocation LParenLoc, bool isType,
                              void *TyOrExpr,
                              SourceLocation RParenLoc);
  
    ExprResult BuildCXXUuidof(QualType TypeInfoType,
                              SourceLocation TypeidLoc,
                              TypeSourceInfo *Operand,
                              SourceLocation RParenLoc);
    ExprResult BuildCXXUuidof(QualType TypeInfoType,
                              SourceLocation TypeidLoc,
                              Expr *Operand,
                              SourceLocation RParenLoc);
  
    /// ActOnCXXUuidof - Parse __uuidof( something ).
    ExprResult ActOnCXXUuidof(SourceLocation OpLoc,
                              SourceLocation LParenLoc, bool isType,
                              void *TyOrExpr,
                              SourceLocation RParenLoc);
  
    /// Handle a C++1z fold-expression: ( expr op ... op expr ).
    ExprResult ActOnCXXFoldExpr(SourceLocation LParenLoc, Expr *LHS,
                                tok::TokenKind Operator,
                                SourceLocation EllipsisLoc, Expr *RHS,
                                SourceLocation RParenLoc);
    ExprResult BuildCXXFoldExpr(SourceLocation LParenLoc, Expr *LHS,
                                BinaryOperatorKind Operator,
                                SourceLocation EllipsisLoc, Expr *RHS,
                                SourceLocation RParenLoc,
                                Optional<unsigned> NumExpansions);
    ExprResult BuildEmptyCXXFoldExpr(SourceLocation EllipsisLoc,
                                     BinaryOperatorKind Operator);
  
    //// ActOnCXXThis -  Parse 'this' pointer.
    ExprResult ActOnCXXThis(SourceLocation loc);
  
    /// Build a CXXThisExpr and mark it referenced in the current context.
    Expr *BuildCXXThisExpr(SourceLocation Loc, QualType Type, bool IsImplicit);
    void MarkThisReferenced(CXXThisExpr *This);
  
    /// Try to retrieve the type of the 'this' pointer.
    ///
    /// \returns The type of 'this', if possible. Otherwise, returns a NULL type.
    QualType getCurrentThisType();
  
    /// When non-NULL, the C++ 'this' expression is allowed despite the
    /// current context not being a non-static member function. In such cases,
    /// this provides the type used for 'this'.
    QualType CXXThisTypeOverride;
  
    /// RAII object used to temporarily allow the C++ 'this' expression
    /// to be used, with the given qualifiers on the current class type.
    class CXXThisScopeRAII {
      Sema &S;
      QualType OldCXXThisTypeOverride;
      bool Enabled;
  
    public:
      /// Introduce a new scope where 'this' may be allowed (when enabled),
      /// using the given declaration (which is either a class template or a
      /// class) along with the given qualifiers.
      /// along with the qualifiers placed on '*this'.
      CXXThisScopeRAII(Sema &S, Decl *ContextDecl, Qualifiers CXXThisTypeQuals,
                       bool Enabled = true);
  
      ~CXXThisScopeRAII();
    };
  
    /// Make sure the value of 'this' is actually available in the current
    /// context, if it is a potentially evaluated context.
    ///
    /// \param Loc The location at which the capture of 'this' occurs.
    ///
    /// \param Explicit Whether 'this' is explicitly captured in a lambda
    /// capture list.
    ///
    /// \param FunctionScopeIndexToStopAt If non-null, it points to the index
    /// of the FunctionScopeInfo stack beyond which we do not attempt to capture.
    /// This is useful when enclosing lambdas must speculatively capture
    /// 'this' that may or may not be used in certain specializations of
    /// a nested generic lambda (depending on whether the name resolves to
    /// a non-static member function or a static function).
    /// \return returns 'true' if failed, 'false' if success.
    bool CheckCXXThisCapture(SourceLocation Loc, bool Explicit = false,
        bool BuildAndDiagnose = true,
        const unsigned *const FunctionScopeIndexToStopAt = nullptr,
        bool ByCopy = false);
  
    /// Determine whether the given type is the type of *this that is used
    /// outside of the body of a member function for a type that is currently
    /// being defined.
    bool isThisOutsideMemberFunctionBody(QualType BaseType);
  
    /// ActOnCXXBoolLiteral - Parse {true,false} literals.
    ExprResult ActOnCXXBoolLiteral(SourceLocation OpLoc, tok::TokenKind Kind);
  
  
    /// ActOnObjCBoolLiteral - Parse {__objc_yes,__objc_no} literals.
    ExprResult ActOnObjCBoolLiteral(SourceLocation OpLoc, tok::TokenKind Kind);
  
    ExprResult
    ActOnObjCAvailabilityCheckExpr(llvm::ArrayRef<AvailabilitySpec> AvailSpecs,
                                   SourceLocation AtLoc, SourceLocation RParen);
  
    /// ActOnCXXNullPtrLiteral - Parse 'nullptr'.
    ExprResult ActOnCXXNullPtrLiteral(SourceLocation Loc);
  
    //// ActOnCXXThrow -  Parse throw expressions.
    ExprResult ActOnCXXThrow(Scope *S, SourceLocation OpLoc, Expr *expr);
    ExprResult BuildCXXThrow(SourceLocation OpLoc, Expr *Ex,
                             bool IsThrownVarInScope);
    bool CheckCXXThrowOperand(SourceLocation ThrowLoc, QualType ThrowTy, Expr *E);
  
    /// ActOnCXXTypeConstructExpr - Parse construction of a specified type.
    /// Can be interpreted either as function-style casting ("int(x)")
    /// or class type construction ("ClassType(x,y,z)")
    /// or creation of a value-initialized type ("int()").
    ExprResult ActOnCXXTypeConstructExpr(ParsedType TypeRep,
                                         SourceLocation LParenOrBraceLoc,
                                         MultiExprArg Exprs,
                                         SourceLocation RParenOrBraceLoc,
                                         bool ListInitialization);
  
    ExprResult BuildCXXTypeConstructExpr(TypeSourceInfo *Type,
                                         SourceLocation LParenLoc,
                                         MultiExprArg Exprs,
                                         SourceLocation RParenLoc,
                                         bool ListInitialization);
  
    /// ActOnCXXNew - Parsed a C++ 'new' expression.
    ExprResult ActOnCXXNew(SourceLocation StartLoc, bool UseGlobal,
                           SourceLocation PlacementLParen,
                           MultiExprArg PlacementArgs,
                           SourceLocation PlacementRParen,
                           SourceRange TypeIdParens, Declarator &D,
                           Expr *Initializer);
    ExprResult BuildCXXNew(SourceRange Range, bool UseGlobal,
                           SourceLocation PlacementLParen,
                           MultiExprArg PlacementArgs,
                           SourceLocation PlacementRParen,
                           SourceRange TypeIdParens,
                           QualType AllocType,
                           TypeSourceInfo *AllocTypeInfo,
                           Optional<Expr *> ArraySize,
                           SourceRange DirectInitRange,
                           Expr *Initializer);
  
    /// Determine whether \p FD is an aligned allocation or deallocation
    /// function that is unavailable.
    bool isUnavailableAlignedAllocationFunction(const FunctionDecl &FD) const;
  
    /// Produce diagnostics if \p FD is an aligned allocation or deallocation
    /// function that is unavailable.
    void diagnoseUnavailableAlignedAllocation(const FunctionDecl &FD,
                                              SourceLocation Loc);
  
    bool CheckAllocatedType(QualType AllocType, SourceLocation Loc,
                            SourceRange R);
  
    /// The scope in which to find allocation functions.
    enum AllocationFunctionScope {
      /// Only look for allocation functions in the global scope.
      AFS_Global,
      /// Only look for allocation functions in the scope of the
      /// allocated class.
      AFS_Class,
      /// Look for allocation functions in both the global scope
      /// and in the scope of the allocated class.
      AFS_Both
    };
  
    /// Finds the overloads of operator new and delete that are appropriate
    /// for the allocation.
    bool FindAllocationFunctions(SourceLocation StartLoc, SourceRange Range,
                                 AllocationFunctionScope NewScope,
                                 AllocationFunctionScope DeleteScope,
                                 QualType AllocType, bool IsArray,
                                 bool &PassAlignment, MultiExprArg PlaceArgs,
                                 FunctionDecl *&OperatorNew,
                                 FunctionDecl *&OperatorDelete,
                                 bool Diagnose = true);
    void DeclareGlobalNewDelete();
    void DeclareGlobalAllocationFunction(DeclarationName Name, QualType Return,
                                         ArrayRef<QualType> Params);
  
    bool FindDeallocationFunction(SourceLocation StartLoc, CXXRecordDecl *RD,
                                  DeclarationName Name, FunctionDecl* &Operator,
                                  bool Diagnose = true);
    FunctionDecl *FindUsualDeallocationFunction(SourceLocation StartLoc,
                                                bool CanProvideSize,
                                                bool Overaligned,
                                                DeclarationName Name);
    FunctionDecl *FindDeallocationFunctionForDestructor(SourceLocation StartLoc,
                                                        CXXRecordDecl *RD);
  
    /// ActOnCXXDelete - Parsed a C++ 'delete' expression
    ExprResult ActOnCXXDelete(SourceLocation StartLoc,
                              bool UseGlobal, bool ArrayForm,
                              Expr *Operand);
    void CheckVirtualDtorCall(CXXDestructorDecl *dtor, SourceLocation Loc,
                              bool IsDelete, bool CallCanBeVirtual,
                              bool WarnOnNonAbstractTypes,
                              SourceLocation DtorLoc);
  
    ExprResult ActOnNoexceptExpr(SourceLocation KeyLoc, SourceLocation LParen,
                                 Expr *Operand, SourceLocation RParen);
    ExprResult BuildCXXNoexceptExpr(SourceLocation KeyLoc, Expr *Operand,
                                    SourceLocation RParen);
  
    /// Parsed one of the type trait support pseudo-functions.
    ExprResult ActOnTypeTrait(TypeTrait Kind, SourceLocation KWLoc,
                              ArrayRef<ParsedType> Args,
                              SourceLocation RParenLoc);
    ExprResult BuildTypeTrait(TypeTrait Kind, SourceLocation KWLoc,
                              ArrayRef<TypeSourceInfo *> Args,
                              SourceLocation RParenLoc);
  
    /// ActOnArrayTypeTrait - Parsed one of the binary type trait support
    /// pseudo-functions.
    ExprResult ActOnArrayTypeTrait(ArrayTypeTrait ATT,
                                   SourceLocation KWLoc,
                                   ParsedType LhsTy,
                                   Expr *DimExpr,
                                   SourceLocation RParen);
  
    ExprResult BuildArrayTypeTrait(ArrayTypeTrait ATT,
                                   SourceLocation KWLoc,
                                   TypeSourceInfo *TSInfo,
                                   Expr *DimExpr,
                                   SourceLocation RParen);
  
    /// ActOnExpressionTrait - Parsed one of the unary type trait support
    /// pseudo-functions.
    ExprResult ActOnExpressionTrait(ExpressionTrait OET,
                                    SourceLocation KWLoc,
                                    Expr *Queried,
                                    SourceLocation RParen);
  
    ExprResult BuildExpressionTrait(ExpressionTrait OET,
                                    SourceLocation KWLoc,
                                    Expr *Queried,
                                    SourceLocation RParen);
  
    ExprResult ActOnStartCXXMemberReference(Scope *S,
                                            Expr *Base,
                                            SourceLocation OpLoc,
                                            tok::TokenKind OpKind,
                                            ParsedType &ObjectType,
                                            bool &MayBePseudoDestructor);
  
    ExprResult BuildPseudoDestructorExpr(Expr *Base,
                                         SourceLocation OpLoc,
                                         tok::TokenKind OpKind,
                                         const CXXScopeSpec &SS,
                                         TypeSourceInfo *ScopeType,
                                         SourceLocation CCLoc,
                                         SourceLocation TildeLoc,
                                       PseudoDestructorTypeStorage DestroyedType);
  
    ExprResult ActOnPseudoDestructorExpr(Scope *S, Expr *Base,
                                         SourceLocation OpLoc,
                                         tok::TokenKind OpKind,
                                         CXXScopeSpec &SS,
                                         UnqualifiedId &FirstTypeName,
                                         SourceLocation CCLoc,
                                         SourceLocation TildeLoc,
                                         UnqualifiedId &SecondTypeName);
  
    ExprResult ActOnPseudoDestructorExpr(Scope *S, Expr *Base,
                                         SourceLocation OpLoc,
                                         tok::TokenKind OpKind,
                                         SourceLocation TildeLoc,
                                         const DeclSpec& DS);
  
    /// MaybeCreateExprWithCleanups - If the current full-expression
    /// requires any cleanups, surround it with a ExprWithCleanups node.
    /// Otherwise, just returns the passed-in expression.
    Expr *MaybeCreateExprWithCleanups(Expr *SubExpr);
    Stmt *MaybeCreateStmtWithCleanups(Stmt *SubStmt);
    ExprResult MaybeCreateExprWithCleanups(ExprResult SubExpr);
  
    MaterializeTemporaryExpr *
    CreateMaterializeTemporaryExpr(QualType T, Expr *Temporary,
                                   bool BoundToLvalueReference);
  
    ExprResult ActOnFinishFullExpr(Expr *Expr, bool DiscardedValue) {
      return ActOnFinishFullExpr(
          Expr, Expr ? Expr->getExprLoc() : SourceLocation(), DiscardedValue);
    }
    ExprResult ActOnFinishFullExpr(Expr *Expr, SourceLocation CC,
                                   bool DiscardedValue, bool IsConstexpr = false);
    StmtResult ActOnFinishFullStmt(Stmt *Stmt);
  
    // Marks SS invalid if it represents an incomplete type.
    bool RequireCompleteDeclContext(CXXScopeSpec &SS, DeclContext *DC);
  
    DeclContext *computeDeclContext(QualType T);
    DeclContext *computeDeclContext(const CXXScopeSpec &SS,
                                    bool EnteringContext = false);
    bool isDependentScopeSpecifier(const CXXScopeSpec &SS);
    CXXRecordDecl *getCurrentInstantiationOf(NestedNameSpecifier *NNS);
  
    /// The parser has parsed a global nested-name-specifier '::'.
    ///
    /// \param CCLoc The location of the '::'.
    ///
    /// \param SS The nested-name-specifier, which will be updated in-place
    /// to reflect the parsed nested-name-specifier.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool ActOnCXXGlobalScopeSpecifier(SourceLocation CCLoc, CXXScopeSpec &SS);
  
    /// The parser has parsed a '__super' nested-name-specifier.
    ///
    /// \param SuperLoc The location of the '__super' keyword.
    ///
    /// \param ColonColonLoc The location of the '::'.
    ///
    /// \param SS The nested-name-specifier, which will be updated in-place
    /// to reflect the parsed nested-name-specifier.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool ActOnSuperScopeSpecifier(SourceLocation SuperLoc,
                                  SourceLocation ColonColonLoc, CXXScopeSpec &SS);
  
    bool isAcceptableNestedNameSpecifier(const NamedDecl *SD,
                                         bool *CanCorrect = nullptr);
    NamedDecl *FindFirstQualifierInScope(Scope *S, NestedNameSpecifier *NNS);
  
    /// Keeps information about an identifier in a nested-name-spec.
    ///
    struct NestedNameSpecInfo {
      /// The type of the object, if we're parsing nested-name-specifier in
      /// a member access expression.
      ParsedType ObjectType;
  
      /// The identifier preceding the '::'.
      IdentifierInfo *Identifier;
  
      /// The location of the identifier.
      SourceLocation IdentifierLoc;
  
      /// The location of the '::'.
      SourceLocation CCLoc;
  
      /// Creates info object for the most typical case.
      NestedNameSpecInfo(IdentifierInfo *II, SourceLocation IdLoc,
               SourceLocation ColonColonLoc, ParsedType ObjectType = ParsedType())
        : ObjectType(ObjectType), Identifier(II), IdentifierLoc(IdLoc),
          CCLoc(ColonColonLoc) {
      }
  
      NestedNameSpecInfo(IdentifierInfo *II, SourceLocation IdLoc,
                         SourceLocation ColonColonLoc, QualType ObjectType)
        : ObjectType(ParsedType::make(ObjectType)), Identifier(II),
          IdentifierLoc(IdLoc), CCLoc(ColonColonLoc) {
      }
    };
  
    bool isNonTypeNestedNameSpecifier(Scope *S, CXXScopeSpec &SS,
                                      NestedNameSpecInfo &IdInfo);
  
    bool BuildCXXNestedNameSpecifier(Scope *S,
                                     NestedNameSpecInfo &IdInfo,
                                     bool EnteringContext,
                                     CXXScopeSpec &SS,
                                     NamedDecl *ScopeLookupResult,
                                     bool ErrorRecoveryLookup,
                                     bool *IsCorrectedToColon = nullptr,
                                     bool OnlyNamespace = false);
  
    /// The parser has parsed a nested-name-specifier 'identifier::'.
    ///
    /// \param S The scope in which this nested-name-specifier occurs.
    ///
    /// \param IdInfo Parser information about an identifier in the
    /// nested-name-spec.
    ///
    /// \param EnteringContext Whether we're entering the context nominated by
    /// this nested-name-specifier.
    ///
    /// \param SS The nested-name-specifier, which is both an input
    /// parameter (the nested-name-specifier before this type) and an
    /// output parameter (containing the full nested-name-specifier,
    /// including this new type).
    ///
    /// \param ErrorRecoveryLookup If true, then this method is called to improve
    /// error recovery. In this case do not emit error message.
    ///
    /// \param IsCorrectedToColon If not null, suggestions to replace '::' -> ':'
    /// are allowed.  The bool value pointed by this parameter is set to 'true'
    /// if the identifier is treated as if it was followed by ':', not '::'.
    ///
    /// \param OnlyNamespace If true, only considers namespaces in lookup.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool ActOnCXXNestedNameSpecifier(Scope *S,
                                     NestedNameSpecInfo &IdInfo,
                                     bool EnteringContext,
                                     CXXScopeSpec &SS,
                                     bool ErrorRecoveryLookup = false,
                                     bool *IsCorrectedToColon = nullptr,
                                     bool OnlyNamespace = false);
  
    ExprResult ActOnDecltypeExpression(Expr *E);
  
    bool ActOnCXXNestedNameSpecifierDecltype(CXXScopeSpec &SS,
                                             const DeclSpec &DS,
                                             SourceLocation ColonColonLoc);
  
    bool IsInvalidUnlessNestedName(Scope *S, CXXScopeSpec &SS,
                                   NestedNameSpecInfo &IdInfo,
                                   bool EnteringContext);
  
    /// The parser has parsed a nested-name-specifier
    /// 'template[opt] template-name < template-args >::'.
    ///
    /// \param S The scope in which this nested-name-specifier occurs.
    ///
    /// \param SS The nested-name-specifier, which is both an input
    /// parameter (the nested-name-specifier before this type) and an
    /// output parameter (containing the full nested-name-specifier,
    /// including this new type).
    ///
    /// \param TemplateKWLoc the location of the 'template' keyword, if any.
    /// \param TemplateName the template name.
    /// \param TemplateNameLoc The location of the template name.
    /// \param LAngleLoc The location of the opening angle bracket  ('<').
    /// \param TemplateArgs The template arguments.
    /// \param RAngleLoc The location of the closing angle bracket  ('>').
    /// \param CCLoc The location of the '::'.
    ///
    /// \param EnteringContext Whether we're entering the context of the
    /// nested-name-specifier.
    ///
    ///
    /// \returns true if an error occurred, false otherwise.
    bool ActOnCXXNestedNameSpecifier(Scope *S,
                                     CXXScopeSpec &SS,
                                     SourceLocation TemplateKWLoc,
                                     TemplateTy TemplateName,
                                     SourceLocation TemplateNameLoc,
                                     SourceLocation LAngleLoc,
                                     ASTTemplateArgsPtr TemplateArgs,
                                     SourceLocation RAngleLoc,
                                     SourceLocation CCLoc,
                                     bool EnteringContext);
  
    /// Given a C++ nested-name-specifier, produce an annotation value
    /// that the parser can use later to reconstruct the given
    /// nested-name-specifier.
    ///
    /// \param SS A nested-name-specifier.
    ///
    /// \returns A pointer containing all of the information in the
    /// nested-name-specifier \p SS.
    void *SaveNestedNameSpecifierAnnotation(CXXScopeSpec &SS);
  
    /// Given an annotation pointer for a nested-name-specifier, restore
    /// the nested-name-specifier structure.
    ///
    /// \param Annotation The annotation pointer, produced by
    /// \c SaveNestedNameSpecifierAnnotation().
    ///
    /// \param AnnotationRange The source range corresponding to the annotation.
    ///
    /// \param SS The nested-name-specifier that will be updated with the contents
    /// of the annotation pointer.
    void RestoreNestedNameSpecifierAnnotation(void *Annotation,
                                              SourceRange AnnotationRange,
                                              CXXScopeSpec &SS);
  
    bool ShouldEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS);
  
    /// ActOnCXXEnterDeclaratorScope - Called when a C++ scope specifier (global
    /// scope or nested-name-specifier) is parsed, part of a declarator-id.
    /// After this method is called, according to [C++ 3.4.3p3], names should be
    /// looked up in the declarator-id's scope, until the declarator is parsed and
    /// ActOnCXXExitDeclaratorScope is called.
    /// The 'SS' should be a non-empty valid CXXScopeSpec.
    bool ActOnCXXEnterDeclaratorScope(Scope *S, CXXScopeSpec &SS);
  
    /// ActOnCXXExitDeclaratorScope - Called when a declarator that previously
    /// invoked ActOnCXXEnterDeclaratorScope(), is finished. 'SS' is the same
    /// CXXScopeSpec that was passed to ActOnCXXEnterDeclaratorScope as well.
    /// Used to indicate that names should revert to being looked up in the
    /// defining scope.
    void ActOnCXXExitDeclaratorScope(Scope *S, const CXXScopeSpec &SS);
  
    /// ActOnCXXEnterDeclInitializer - Invoked when we are about to parse an
    /// initializer for the declaration 'Dcl'.
    /// After this method is called, according to [C++ 3.4.1p13], if 'Dcl' is a
    /// static data member of class X, names should be looked up in the scope of
    /// class X.
    void ActOnCXXEnterDeclInitializer(Scope *S, Decl *Dcl);
  
    /// ActOnCXXExitDeclInitializer - Invoked after we are finished parsing an
    /// initializer for the declaration 'Dcl'.
    void ActOnCXXExitDeclInitializer(Scope *S, Decl *Dcl);
  
    /// Create a new lambda closure type.
    CXXRecordDecl *createLambdaClosureType(SourceRange IntroducerRange,
                                           TypeSourceInfo *Info,
                                           bool KnownDependent,
                                           LambdaCaptureDefault CaptureDefault);
  
    /// Start the definition of a lambda expression.
    CXXMethodDecl *startLambdaDefinition(CXXRecordDecl *Class,
                                         SourceRange IntroducerRange,
                                         TypeSourceInfo *MethodType,
                                         SourceLocation EndLoc,
                                         ArrayRef<ParmVarDecl *> Params,
                                         ConstexprSpecKind ConstexprKind,
                                         Expr *TrailingRequiresClause);
  
    /// Number lambda for linkage purposes if necessary.
    void handleLambdaNumbering(
        CXXRecordDecl *Class, CXXMethodDecl *Method,
        Optional<std::tuple<unsigned, bool, Decl *>> Mangling = None);
  
    /// Endow the lambda scope info with the relevant properties.
    void buildLambdaScope(sema::LambdaScopeInfo *LSI,
                          CXXMethodDecl *CallOperator,
                          SourceRange IntroducerRange,
                          LambdaCaptureDefault CaptureDefault,
                          SourceLocation CaptureDefaultLoc,
                          bool ExplicitParams,
                          bool ExplicitResultType,
                          bool Mutable);
  
    /// Perform initialization analysis of the init-capture and perform
    /// any implicit conversions such as an lvalue-to-rvalue conversion if
    /// not being used to initialize a reference.
    ParsedType actOnLambdaInitCaptureInitialization(
        SourceLocation Loc, bool ByRef, SourceLocation EllipsisLoc,
        IdentifierInfo *Id, LambdaCaptureInitKind InitKind, Expr *&Init) {
      return ParsedType::make(buildLambdaInitCaptureInitialization(
          Loc, ByRef, EllipsisLoc, None, Id,
          InitKind != LambdaCaptureInitKind::CopyInit, Init));
    }
    QualType buildLambdaInitCaptureInitialization(
        SourceLocation Loc, bool ByRef, SourceLocation EllipsisLoc,
        Optional<unsigned> NumExpansions, IdentifierInfo *Id, bool DirectInit,
        Expr *&Init);
  
    /// Create a dummy variable within the declcontext of the lambda's
    ///  call operator, for name lookup purposes for a lambda init capture.
    ///
    ///  CodeGen handles emission of lambda captures, ignoring these dummy
    ///  variables appropriately.
    VarDecl *createLambdaInitCaptureVarDecl(SourceLocation Loc,
                                            QualType InitCaptureType,
                                            SourceLocation EllipsisLoc,
                                            IdentifierInfo *Id,
                                            unsigned InitStyle, Expr *Init);
  
    /// Add an init-capture to a lambda scope.
    void addInitCapture(sema::LambdaScopeInfo *LSI, VarDecl *Var);
  
    /// Note that we have finished the explicit captures for the
    /// given lambda.
    void finishLambdaExplicitCaptures(sema::LambdaScopeInfo *LSI);
  
    /// \brief This is called after parsing the explicit template parameter list
    /// on a lambda (if it exists) in C++2a.
    void ActOnLambdaExplicitTemplateParameterList(SourceLocation LAngleLoc,
                                                  ArrayRef<NamedDecl *> TParams,
                                                  SourceLocation RAngleLoc);
  
    /// Introduce the lambda parameters into scope.
    void addLambdaParameters(
        ArrayRef<LambdaIntroducer::LambdaCapture> Captures,
        CXXMethodDecl *CallOperator, Scope *CurScope);
  
    /// Deduce a block or lambda's return type based on the return
    /// statements present in the body.
    void deduceClosureReturnType(sema::CapturingScopeInfo &CSI);
  
    /// ActOnStartOfLambdaDefinition - This is called just before we start
    /// parsing the body of a lambda; it analyzes the explicit captures and
    /// arguments, and sets up various data-structures for the body of the
    /// lambda.
    void ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
                                      Declarator &ParamInfo, Scope *CurScope);
  
    /// ActOnLambdaError - If there is an error parsing a lambda, this callback
    /// is invoked to pop the information about the lambda.
    void ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
                          bool IsInstantiation = false);
  
    /// ActOnLambdaExpr - This is called when the body of a lambda expression
    /// was successfully completed.
    ExprResult ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
                               Scope *CurScope);
  
    /// Does copying/destroying the captured variable have side effects?
    bool CaptureHasSideEffects(const sema::Capture &From);
  
    /// Diagnose if an explicit lambda capture is unused. Returns true if a
    /// diagnostic is emitted.
    bool DiagnoseUnusedLambdaCapture(SourceRange CaptureRange,
                                     const sema::Capture &From);
  
    /// Build a FieldDecl suitable to hold the given capture.
    FieldDecl *BuildCaptureField(RecordDecl *RD, const sema::Capture &Capture);
  
    /// Initialize the given capture with a suitable expression.
    ExprResult BuildCaptureInit(const sema::Capture &Capture,
                                SourceLocation ImplicitCaptureLoc,
                                bool IsOpenMPMapping = false);
  
    /// Complete a lambda-expression having processed and attached the
    /// lambda body.
    ExprResult BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
                               sema::LambdaScopeInfo *LSI);
  
    /// Get the return type to use for a lambda's conversion function(s) to
    /// function pointer type, given the type of the call operator.
    QualType
    getLambdaConversionFunctionResultType(const FunctionProtoType *CallOpType);
  
    /// Define the "body" of the conversion from a lambda object to a
    /// function pointer.
    ///
    /// This routine doesn't actually define a sensible body; rather, it fills
    /// in the initialization expression needed to copy the lambda object into
    /// the block, and IR generation actually generates the real body of the
    /// block pointer conversion.
    void DefineImplicitLambdaToFunctionPointerConversion(
           SourceLocation CurrentLoc, CXXConversionDecl *Conv);
  
    /// Define the "body" of the conversion from a lambda object to a
    /// block pointer.
    ///
    /// This routine doesn't actually define a sensible body; rather, it fills
    /// in the initialization expression needed to copy the lambda object into
    /// the block, and IR generation actually generates the real body of the
    /// block pointer conversion.
    void DefineImplicitLambdaToBlockPointerConversion(SourceLocation CurrentLoc,
                                                      CXXConversionDecl *Conv);
  
    ExprResult BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
                                             SourceLocation ConvLocation,
                                             CXXConversionDecl *Conv,
                                             Expr *Src);
  
    /// Check whether the given expression is a valid constraint expression.
    /// A diagnostic is emitted if it is not, false is returned, and
    /// PossibleNonPrimary will be set to true if the failure might be due to a
    /// non-primary expression being used as an atomic constraint.
    bool CheckConstraintExpression(Expr *CE, Token NextToken = Token(),
                                   bool *PossibleNonPrimary = nullptr,
                                   bool IsTrailingRequiresClause = false);
  
    /// Check whether the given type-dependent expression will be the name of a
    /// function or another callable function-like entity (e.g. a function
    // template or overload set) for any substitution.
    bool IsDependentFunctionNameExpr(Expr *E);
  
  private:
    /// Caches pairs of template-like decls whose associated constraints were
    /// checked for subsumption and whether or not the first's constraints did in
    /// fact subsume the second's.
    llvm::DenseMap<std::pair<NamedDecl *, NamedDecl *>, bool> SubsumptionCache;
    /// Caches the normalized associated constraints of declarations (concepts or
    /// constrained declarations). If an error occurred while normalizing the
    /// associated constraints of the template or concept, nullptr will be cached
    /// here.
    llvm::DenseMap<NamedDecl *, NormalizedConstraint *>
        NormalizationCache;
  
    llvm::ContextualFoldingSet<ConstraintSatisfaction, const ASTContext &>
        SatisfactionCache;
  
  public:
    const NormalizedConstraint *
    getNormalizedAssociatedConstraints(
        NamedDecl *ConstrainedDecl, ArrayRef<const Expr *> AssociatedConstraints);
  
    /// \brief Check whether the given declaration's associated constraints are
    /// at least as constrained than another declaration's according to the
    /// partial ordering of constraints.
    ///
    /// \param Result If no error occurred, receives the result of true if D1 is
    /// at least constrained than D2, and false otherwise.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool IsAtLeastAsConstrained(NamedDecl *D1, ArrayRef<const Expr *> AC1,
                                NamedDecl *D2, ArrayRef<const Expr *> AC2,
                                bool &Result);
  
    /// If D1 was not at least as constrained as D2, but would've been if a pair
    /// of atomic constraints involved had been declared in a concept and not
    /// repeated in two separate places in code.
    /// \returns true if such a diagnostic was emitted, false otherwise.
    bool MaybeEmitAmbiguousAtomicConstraintsDiagnostic(NamedDecl *D1,
        ArrayRef<const Expr *> AC1, NamedDecl *D2, ArrayRef<const Expr *> AC2);
  
    /// \brief Check whether the given list of constraint expressions are
    /// satisfied (as if in a 'conjunction') given template arguments.
    /// \param Template the template-like entity that triggered the constraints
    /// check (either a concept or a constrained entity).
    /// \param ConstraintExprs a list of constraint expressions, treated as if
    /// they were 'AND'ed together.
    /// \param TemplateArgs the list of template arguments to substitute into the
    /// constraint expression.
    /// \param TemplateIDRange The source range of the template id that
    /// caused the constraints check.
    /// \param Satisfaction if true is returned, will contain details of the
    /// satisfaction, with enough information to diagnose an unsatisfied
    /// expression.
    /// \returns true if an error occurred and satisfaction could not be checked,
    /// false otherwise.
    bool CheckConstraintSatisfaction(
        const NamedDecl *Template, ArrayRef<const Expr *> ConstraintExprs,
        ArrayRef<TemplateArgument> TemplateArgs,
        SourceRange TemplateIDRange, ConstraintSatisfaction &Satisfaction);
  
    /// \brief Check whether the given non-dependent constraint expression is
    /// satisfied. Returns false and updates Satisfaction with the satisfaction
    /// verdict if successful, emits a diagnostic and returns true if an error
    /// occured and satisfaction could not be determined.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool CheckConstraintSatisfaction(const Expr *ConstraintExpr,
                                     ConstraintSatisfaction &Satisfaction);
  
    /// Check whether the given function decl's trailing requires clause is
    /// satisfied, if any. Returns false and updates Satisfaction with the
    /// satisfaction verdict if successful, emits a diagnostic and returns true if
    /// an error occured and satisfaction could not be determined.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool CheckFunctionConstraints(const FunctionDecl *FD,
                                  ConstraintSatisfaction &Satisfaction,
                                  SourceLocation UsageLoc = SourceLocation());
  
  
    /// \brief Ensure that the given template arguments satisfy the constraints
    /// associated with the given template, emitting a diagnostic if they do not.
    ///
    /// \param Template The template to which the template arguments are being
    /// provided.
    ///
    /// \param TemplateArgs The converted, canonicalized template arguments.
    ///
    /// \param TemplateIDRange The source range of the template id that
    /// caused the constraints check.
    ///
    /// \returns true if the constrains are not satisfied or could not be checked
    /// for satisfaction, false if the constraints are satisfied.
    bool EnsureTemplateArgumentListConstraints(TemplateDecl *Template,
                                         ArrayRef<TemplateArgument> TemplateArgs,
                                               SourceRange TemplateIDRange);
  
    /// \brief Emit diagnostics explaining why a constraint expression was deemed
    /// unsatisfied.
    /// \param First whether this is the first time an unsatisfied constraint is
    /// diagnosed for this error.
    void
    DiagnoseUnsatisfiedConstraint(const ConstraintSatisfaction &Satisfaction,
                                  bool First = true);
  
    /// \brief Emit diagnostics explaining why a constraint expression was deemed
    /// unsatisfied.
    void
    DiagnoseUnsatisfiedConstraint(const ASTConstraintSatisfaction &Satisfaction,
                                  bool First = true);
  
    /// \brief Emit diagnostics explaining why a constraint expression was deemed
    /// unsatisfied because it was ill-formed.
    void DiagnoseUnsatisfiedIllFormedConstraint(SourceLocation DiagnosticLocation,
                                                StringRef Diagnostic);
  
    void DiagnoseRedeclarationConstraintMismatch(SourceLocation Old,
                                                 SourceLocation New);
  
    // ParseObjCStringLiteral - Parse Objective-C string literals.
    ExprResult ParseObjCStringLiteral(SourceLocation *AtLocs,
                                      ArrayRef<Expr *> Strings);
  
    ExprResult BuildObjCStringLiteral(SourceLocation AtLoc, StringLiteral *S);
  
    /// BuildObjCNumericLiteral - builds an ObjCBoxedExpr AST node for the
    /// numeric literal expression. Type of the expression will be "NSNumber *"
    /// or "id" if NSNumber is unavailable.
    ExprResult BuildObjCNumericLiteral(SourceLocation AtLoc, Expr *Number);
    ExprResult ActOnObjCBoolLiteral(SourceLocation AtLoc, SourceLocation ValueLoc,
                                    bool Value);
    ExprResult BuildObjCArrayLiteral(SourceRange SR, MultiExprArg Elements);
  
    /// BuildObjCBoxedExpr - builds an ObjCBoxedExpr AST node for the
    /// '@' prefixed parenthesized expression. The type of the expression will
    /// either be "NSNumber *", "NSString *" or "NSValue *" depending on the type
    /// of ValueType, which is allowed to be a built-in numeric type, "char *",
    /// "const char *" or C structure with attribute 'objc_boxable'.
    ExprResult BuildObjCBoxedExpr(SourceRange SR, Expr *ValueExpr);
  
    ExprResult BuildObjCSubscriptExpression(SourceLocation RB, Expr *BaseExpr,
                                            Expr *IndexExpr,
                                            ObjCMethodDecl *getterMethod,
                                            ObjCMethodDecl *setterMethod);
  
    ExprResult BuildObjCDictionaryLiteral(SourceRange SR,
                                 MutableArrayRef<ObjCDictionaryElement> Elements);
  
    ExprResult BuildObjCEncodeExpression(SourceLocation AtLoc,
                                    TypeSourceInfo *EncodedTypeInfo,
                                    SourceLocation RParenLoc);
    ExprResult BuildCXXMemberCallExpr(Expr *Exp, NamedDecl *FoundDecl,
                                      CXXConversionDecl *Method,
                                      bool HadMultipleCandidates);
  
    ExprResult ParseObjCEncodeExpression(SourceLocation AtLoc,
                                         SourceLocation EncodeLoc,
                                         SourceLocation LParenLoc,
                                         ParsedType Ty,
                                         SourceLocation RParenLoc);
  
    /// ParseObjCSelectorExpression - Build selector expression for \@selector
    ExprResult ParseObjCSelectorExpression(Selector Sel,
                                           SourceLocation AtLoc,
                                           SourceLocation SelLoc,
                                           SourceLocation LParenLoc,
                                           SourceLocation RParenLoc,
                                           bool WarnMultipleSelectors);
  
    /// ParseObjCProtocolExpression - Build protocol expression for \@protocol
    ExprResult ParseObjCProtocolExpression(IdentifierInfo * ProtocolName,
                                           SourceLocation AtLoc,
                                           SourceLocation ProtoLoc,
                                           SourceLocation LParenLoc,
                                           SourceLocation ProtoIdLoc,
                                           SourceLocation RParenLoc);
  
    //===--------------------------------------------------------------------===//
    // C++ Declarations
    //
    Decl *ActOnStartLinkageSpecification(Scope *S,
                                         SourceLocation ExternLoc,
                                         Expr *LangStr,
                                         SourceLocation LBraceLoc);
    Decl *ActOnFinishLinkageSpecification(Scope *S,
                                          Decl *LinkageSpec,
                                          SourceLocation RBraceLoc);
  
  
    //===--------------------------------------------------------------------===//
    // C++ Classes
    //
    CXXRecordDecl *getCurrentClass(Scope *S, const CXXScopeSpec *SS);
    bool isCurrentClassName(const IdentifierInfo &II, Scope *S,
                            const CXXScopeSpec *SS = nullptr);
    bool isCurrentClassNameTypo(IdentifierInfo *&II, const CXXScopeSpec *SS);
  
    bool ActOnAccessSpecifier(AccessSpecifier Access, SourceLocation ASLoc,
                              SourceLocation ColonLoc,
                              const ParsedAttributesView &Attrs);
  
    NamedDecl *ActOnCXXMemberDeclarator(Scope *S, AccessSpecifier AS,
                                   Declarator &D,
                                   MultiTemplateParamsArg TemplateParameterLists,
                                   Expr *BitfieldWidth, const VirtSpecifiers &VS,
                                   InClassInitStyle InitStyle);
  
    void ActOnStartCXXInClassMemberInitializer();
    void ActOnFinishCXXInClassMemberInitializer(Decl *VarDecl,
                                                SourceLocation EqualLoc,
                                                Expr *Init);
  
    MemInitResult ActOnMemInitializer(Decl *ConstructorD,
                                      Scope *S,
                                      CXXScopeSpec &SS,
                                      IdentifierInfo *MemberOrBase,
                                      ParsedType TemplateTypeTy,
                                      const DeclSpec &DS,
                                      SourceLocation IdLoc,
                                      SourceLocation LParenLoc,
                                      ArrayRef<Expr *> Args,
                                      SourceLocation RParenLoc,
                                      SourceLocation EllipsisLoc);
  
    MemInitResult ActOnMemInitializer(Decl *ConstructorD,
                                      Scope *S,
                                      CXXScopeSpec &SS,
                                      IdentifierInfo *MemberOrBase,
                                      ParsedType TemplateTypeTy,
                                      const DeclSpec &DS,
                                      SourceLocation IdLoc,
                                      Expr *InitList,
                                      SourceLocation EllipsisLoc);
  
    MemInitResult BuildMemInitializer(Decl *ConstructorD,
                                      Scope *S,
                                      CXXScopeSpec &SS,
                                      IdentifierInfo *MemberOrBase,
                                      ParsedType TemplateTypeTy,
                                      const DeclSpec &DS,
                                      SourceLocation IdLoc,
                                      Expr *Init,
                                      SourceLocation EllipsisLoc);
  
    MemInitResult BuildMemberInitializer(ValueDecl *Member,
                                         Expr *Init,
                                         SourceLocation IdLoc);
  
    MemInitResult BuildBaseInitializer(QualType BaseType,
                                       TypeSourceInfo *BaseTInfo,
                                       Expr *Init,
                                       CXXRecordDecl *ClassDecl,
                                       SourceLocation EllipsisLoc);
  
    MemInitResult BuildDelegatingInitializer(TypeSourceInfo *TInfo,
                                             Expr *Init,
                                             CXXRecordDecl *ClassDecl);
  
    bool SetDelegatingInitializer(CXXConstructorDecl *Constructor,
                                  CXXCtorInitializer *Initializer);
  
    bool SetCtorInitializers(CXXConstructorDecl *Constructor, bool AnyErrors,
                             ArrayRef<CXXCtorInitializer *> Initializers = None);
  
    void SetIvarInitializers(ObjCImplementationDecl *ObjCImplementation);
  
  
    /// MarkBaseAndMemberDestructorsReferenced - Given a record decl,
    /// mark all the non-trivial destructors of its members and bases as
    /// referenced.
    void MarkBaseAndMemberDestructorsReferenced(SourceLocation Loc,
                                                CXXRecordDecl *Record);
  
    /// The list of classes whose vtables have been used within
    /// this translation unit, and the source locations at which the
    /// first use occurred.
    typedef std::pair<CXXRecordDecl*, SourceLocation> VTableUse;
  
    /// The list of vtables that are required but have not yet been
    /// materialized.
    SmallVector<VTableUse, 16> VTableUses;
  
    /// The set of classes whose vtables have been used within
    /// this translation unit, and a bit that will be true if the vtable is
    /// required to be emitted (otherwise, it should be emitted only if needed
    /// by code generation).
    llvm::DenseMap<CXXRecordDecl *, bool> VTablesUsed;
  
    /// Load any externally-stored vtable uses.
    void LoadExternalVTableUses();
  
    /// Note that the vtable for the given class was used at the
    /// given location.
    void MarkVTableUsed(SourceLocation Loc, CXXRecordDecl *Class,
                        bool DefinitionRequired = false);
  
    /// Mark the exception specifications of all virtual member functions
    /// in the given class as needed.
    void MarkVirtualMemberExceptionSpecsNeeded(SourceLocation Loc,
                                               const CXXRecordDecl *RD);
  
    /// MarkVirtualMembersReferenced - Will mark all members of the given
    /// CXXRecordDecl referenced.
    void MarkVirtualMembersReferenced(SourceLocation Loc, const CXXRecordDecl *RD,
                                      bool ConstexprOnly = false);
  
    /// Define all of the vtables that have been used in this
    /// translation unit and reference any virtual members used by those
    /// vtables.
    ///
    /// \returns true if any work was done, false otherwise.
    bool DefineUsedVTables();
  
    void AddImplicitlyDeclaredMembersToClass(CXXRecordDecl *ClassDecl);
  
    void ActOnMemInitializers(Decl *ConstructorDecl,
                              SourceLocation ColonLoc,
                              ArrayRef<CXXCtorInitializer*> MemInits,
                              bool AnyErrors);
  
    /// Check class-level dllimport/dllexport attribute. The caller must
    /// ensure that referenceDLLExportedClassMethods is called some point later
    /// when all outer classes of Class are complete.
    void checkClassLevelDLLAttribute(CXXRecordDecl *Class);
    void checkClassLevelCodeSegAttribute(CXXRecordDecl *Class);
  
    void referenceDLLExportedClassMethods();
  
    void propagateDLLAttrToBaseClassTemplate(
        CXXRecordDecl *Class, Attr *ClassAttr,
        ClassTemplateSpecializationDecl *BaseTemplateSpec,
        SourceLocation BaseLoc);
  
    /// Add gsl::Pointer attribute to std::container::iterator
    /// \param ND The declaration that introduces the name
    /// std::container::iterator. \param UnderlyingRecord The record named by ND.
    void inferGslPointerAttribute(NamedDecl *ND, CXXRecordDecl *UnderlyingRecord);
  
    /// Add [[gsl::Owner]] and [[gsl::Pointer]] attributes for std:: types.
    void inferGslOwnerPointerAttribute(CXXRecordDecl *Record);
  
    /// Add [[gsl::Pointer]] attributes for std:: types.
    void inferGslPointerAttribute(TypedefNameDecl *TD);
  
    void CheckCompletedCXXClass(Scope *S, CXXRecordDecl *Record);
  
    /// Check that the C++ class annoated with "trivial_abi" satisfies all the
    /// conditions that are needed for the attribute to have an effect.
    void checkIllFormedTrivialABIStruct(CXXRecordDecl &RD);
  
    void ActOnFinishCXXMemberSpecification(Scope *S, SourceLocation RLoc,
                                           Decl *TagDecl, SourceLocation LBrac,
                                           SourceLocation RBrac,
                                           const ParsedAttributesView &AttrList);
    void ActOnFinishCXXMemberDecls();
    void ActOnFinishCXXNonNestedClass();
  
    void ActOnReenterCXXMethodParameter(Scope *S, ParmVarDecl *Param);
    unsigned ActOnReenterTemplateScope(Scope *S, Decl *Template);
    void ActOnStartDelayedMemberDeclarations(Scope *S, Decl *Record);
    void ActOnStartDelayedCXXMethodDeclaration(Scope *S, Decl *Method);
    void ActOnDelayedCXXMethodParameter(Scope *S, Decl *Param);
    void ActOnFinishDelayedMemberDeclarations(Scope *S, Decl *Record);
    void ActOnFinishDelayedCXXMethodDeclaration(Scope *S, Decl *Method);
    void ActOnFinishDelayedMemberInitializers(Decl *Record);
    void MarkAsLateParsedTemplate(FunctionDecl *FD, Decl *FnD,
                                  CachedTokens &Toks);
    void UnmarkAsLateParsedTemplate(FunctionDecl *FD);
    bool IsInsideALocalClassWithinATemplateFunction();
  
    Decl *ActOnStaticAssertDeclaration(SourceLocation StaticAssertLoc,
                                       Expr *AssertExpr,
                                       Expr *AssertMessageExpr,
                                       SourceLocation RParenLoc);
    Decl *BuildStaticAssertDeclaration(SourceLocation StaticAssertLoc,
                                       Expr *AssertExpr,
                                       StringLiteral *AssertMessageExpr,
                                       SourceLocation RParenLoc,
                                       bool Failed);
  
    FriendDecl *CheckFriendTypeDecl(SourceLocation LocStart,
                                    SourceLocation FriendLoc,
                                    TypeSourceInfo *TSInfo);
    Decl *ActOnFriendTypeDecl(Scope *S, const DeclSpec &DS,
                              MultiTemplateParamsArg TemplateParams);
    NamedDecl *ActOnFriendFunctionDecl(Scope *S, Declarator &D,
                                       MultiTemplateParamsArg TemplateParams);
  
    QualType CheckConstructorDeclarator(Declarator &D, QualType R,
                                        StorageClass& SC);
    void CheckConstructor(CXXConstructorDecl *Constructor);
    QualType CheckDestructorDeclarator(Declarator &D, QualType R,
                                       StorageClass& SC);
    bool CheckDestructor(CXXDestructorDecl *Destructor);
    void CheckConversionDeclarator(Declarator &D, QualType &R,
                                   StorageClass& SC);
    Decl *ActOnConversionDeclarator(CXXConversionDecl *Conversion);
    void CheckDeductionGuideDeclarator(Declarator &D, QualType &R,
                                       StorageClass &SC);
    void CheckDeductionGuideTemplate(FunctionTemplateDecl *TD);
  
    void CheckExplicitlyDefaultedFunction(Scope *S, FunctionDecl *MD);
  
    bool CheckExplicitlyDefaultedSpecialMember(CXXMethodDecl *MD,
                                               CXXSpecialMember CSM);
    void CheckDelayedMemberExceptionSpecs();
  
    bool CheckExplicitlyDefaultedComparison(Scope *S, FunctionDecl *MD,
                                            DefaultedComparisonKind DCK);
    void DeclareImplicitEqualityComparison(CXXRecordDecl *RD,
                                           FunctionDecl *Spaceship);
    void DefineDefaultedComparison(SourceLocation Loc, FunctionDecl *FD,
                                   DefaultedComparisonKind DCK);
  
    //===--------------------------------------------------------------------===//
    // C++ Derived Classes
    //
  
    /// ActOnBaseSpecifier - Parsed a base specifier
    CXXBaseSpecifier *CheckBaseSpecifier(CXXRecordDecl *Class,
                                         SourceRange SpecifierRange,
                                         bool Virtual, AccessSpecifier Access,
                                         TypeSourceInfo *TInfo,
                                         SourceLocation EllipsisLoc);
  
    BaseResult ActOnBaseSpecifier(Decl *classdecl,
                                  SourceRange SpecifierRange,
                                  ParsedAttributes &Attrs,
                                  bool Virtual, AccessSpecifier Access,
                                  ParsedType basetype,
                                  SourceLocation BaseLoc,
                                  SourceLocation EllipsisLoc);
  
    bool AttachBaseSpecifiers(CXXRecordDecl *Class,
                              MutableArrayRef<CXXBaseSpecifier *> Bases);
    void ActOnBaseSpecifiers(Decl *ClassDecl,
                             MutableArrayRef<CXXBaseSpecifier *> Bases);
  
    bool IsDerivedFrom(SourceLocation Loc, QualType Derived, QualType Base);
    bool IsDerivedFrom(SourceLocation Loc, QualType Derived, QualType Base,
                       CXXBasePaths &Paths);
  
    // FIXME: I don't like this name.
    void BuildBasePathArray(const CXXBasePaths &Paths, CXXCastPath &BasePath);
  
    bool CheckDerivedToBaseConversion(QualType Derived, QualType Base,
                                      SourceLocation Loc, SourceRange Range,
                                      CXXCastPath *BasePath = nullptr,
                                      bool IgnoreAccess = false);
    bool CheckDerivedToBaseConversion(QualType Derived, QualType Base,
                                      unsigned InaccessibleBaseID,
                                      unsigned AmbigiousBaseConvID,
                                      SourceLocation Loc, SourceRange Range,
                                      DeclarationName Name,
                                      CXXCastPath *BasePath,
                                      bool IgnoreAccess = false);
  
    std::string getAmbiguousPathsDisplayString(CXXBasePaths &Paths);
  
    bool CheckOverridingFunctionAttributes(const CXXMethodDecl *New,
                                           const CXXMethodDecl *Old);
  
    /// CheckOverridingFunctionReturnType - Checks whether the return types are
    /// covariant, according to C++ [class.virtual]p5.
    bool CheckOverridingFunctionReturnType(const CXXMethodDecl *New,
                                           const CXXMethodDecl *Old);
  
    /// CheckOverridingFunctionExceptionSpec - Checks whether the exception
    /// spec is a subset of base spec.
    bool CheckOverridingFunctionExceptionSpec(const CXXMethodDecl *New,
                                              const CXXMethodDecl *Old);
  
    bool CheckPureMethod(CXXMethodDecl *Method, SourceRange InitRange);
  
    /// CheckOverrideControl - Check C++11 override control semantics.
    void CheckOverrideControl(NamedDecl *D);
  
    /// DiagnoseAbsenceOfOverrideControl - Diagnose if 'override' keyword was
    /// not used in the declaration of an overriding method.
    void DiagnoseAbsenceOfOverrideControl(NamedDecl *D);
  
    /// CheckForFunctionMarkedFinal - Checks whether a virtual member function
    /// overrides a virtual member function marked 'final', according to
    /// C++11 [class.virtual]p4.
    bool CheckIfOverriddenFunctionIsMarkedFinal(const CXXMethodDecl *New,
                                                const CXXMethodDecl *Old);
  
  
    //===--------------------------------------------------------------------===//
    // C++ Access Control
    //
  
    enum AccessResult {
      AR_accessible,
      AR_inaccessible,
      AR_dependent,
      AR_delayed
    };
  
    bool SetMemberAccessSpecifier(NamedDecl *MemberDecl,
                                  NamedDecl *PrevMemberDecl,
                                  AccessSpecifier LexicalAS);
  
    AccessResult CheckUnresolvedMemberAccess(UnresolvedMemberExpr *E,
                                             DeclAccessPair FoundDecl);
    AccessResult CheckUnresolvedLookupAccess(UnresolvedLookupExpr *E,
                                             DeclAccessPair FoundDecl);
    AccessResult CheckAllocationAccess(SourceLocation OperatorLoc,
                                       SourceRange PlacementRange,
                                       CXXRecordDecl *NamingClass,
                                       DeclAccessPair FoundDecl,
                                       bool Diagnose = true);
    AccessResult CheckConstructorAccess(SourceLocation Loc,
                                        CXXConstructorDecl *D,
                                        DeclAccessPair FoundDecl,
                                        const InitializedEntity &Entity,
                                        bool IsCopyBindingRefToTemp = false);
    AccessResult CheckConstructorAccess(SourceLocation Loc,
                                        CXXConstructorDecl *D,
                                        DeclAccessPair FoundDecl,
                                        const InitializedEntity &Entity,
                                        const PartialDiagnostic &PDiag);
    AccessResult CheckDestructorAccess(SourceLocation Loc,
                                       CXXDestructorDecl *Dtor,
                                       const PartialDiagnostic &PDiag,
                                       QualType objectType = QualType());
    AccessResult CheckFriendAccess(NamedDecl *D);
    AccessResult CheckMemberAccess(SourceLocation UseLoc,
                                   CXXRecordDecl *NamingClass,
                                   DeclAccessPair Found);
    AccessResult
    CheckStructuredBindingMemberAccess(SourceLocation UseLoc,
                                       CXXRecordDecl *DecomposedClass,
                                       DeclAccessPair Field);
    AccessResult CheckMemberOperatorAccess(SourceLocation Loc,
                                           Expr *ObjectExpr,
                                           Expr *ArgExpr,
                                           DeclAccessPair FoundDecl);
    AccessResult CheckAddressOfMemberAccess(Expr *OvlExpr,
                                            DeclAccessPair FoundDecl);
    AccessResult CheckBaseClassAccess(SourceLocation AccessLoc,
                                      QualType Base, QualType Derived,
                                      const CXXBasePath &Path,
                                      unsigned DiagID,
                                      bool ForceCheck = false,
                                      bool ForceUnprivileged = false);
    void CheckLookupAccess(const LookupResult &R);
    bool IsSimplyAccessible(NamedDecl *Decl, CXXRecordDecl *NamingClass,
                            QualType BaseType);
    bool isMemberAccessibleForDeletion(CXXRecordDecl *NamingClass,
                                       DeclAccessPair Found, QualType ObjectType,
                                       SourceLocation Loc,
                                       const PartialDiagnostic &Diag);
    bool isMemberAccessibleForDeletion(CXXRecordDecl *NamingClass,
                                       DeclAccessPair Found,
                                       QualType ObjectType) {
      return isMemberAccessibleForDeletion(NamingClass, Found, ObjectType,
                                           SourceLocation(), PDiag());
    }
  
    void HandleDependentAccessCheck(const DependentDiagnostic &DD,
                           const MultiLevelTemplateArgumentList &TemplateArgs);
    void PerformDependentDiagnostics(const DeclContext *Pattern,
                          const MultiLevelTemplateArgumentList &TemplateArgs);
  
    void HandleDelayedAccessCheck(sema::DelayedDiagnostic &DD, Decl *Ctx);
  
    /// When true, access checking violations are treated as SFINAE
    /// failures rather than hard errors.
    bool AccessCheckingSFINAE;
  
    enum AbstractDiagSelID {
      AbstractNone = -1,
      AbstractReturnType,
      AbstractParamType,
      AbstractVariableType,
      AbstractFieldType,
      AbstractIvarType,
      AbstractSynthesizedIvarType,
      AbstractArrayType
    };
  
    bool isAbstractType(SourceLocation Loc, QualType T);
    bool RequireNonAbstractType(SourceLocation Loc, QualType T,
                                TypeDiagnoser &Diagnoser);
    template <typename... Ts>
    bool RequireNonAbstractType(SourceLocation Loc, QualType T, unsigned DiagID,
                                const Ts &...Args) {
      BoundTypeDiagnoser<Ts...> Diagnoser(DiagID, Args...);
      return RequireNonAbstractType(Loc, T, Diagnoser);
    }
  
    void DiagnoseAbstractType(const CXXRecordDecl *RD);
  
    //===--------------------------------------------------------------------===//
    // C++ Overloaded Operators [C++ 13.5]
    //
  
    bool CheckOverloadedOperatorDeclaration(FunctionDecl *FnDecl);
  
    bool CheckLiteralOperatorDeclaration(FunctionDecl *FnDecl);
  
    //===--------------------------------------------------------------------===//
    // C++ Templates [C++ 14]
    //
    void FilterAcceptableTemplateNames(LookupResult &R,
                                       bool AllowFunctionTemplates = true,
                                       bool AllowDependent = true);
    bool hasAnyAcceptableTemplateNames(LookupResult &R,
                                       bool AllowFunctionTemplates = true,
                                       bool AllowDependent = true,
                                       bool AllowNonTemplateFunctions = false);
    /// Try to interpret the lookup result D as a template-name.
    ///
    /// \param D A declaration found by name lookup.
    /// \param AllowFunctionTemplates Whether function templates should be
    ///        considered valid results.
    /// \param AllowDependent Whether unresolved using declarations (that might
    ///        name templates) should be considered valid results.
    NamedDecl *getAsTemplateNameDecl(NamedDecl *D,
                                     bool AllowFunctionTemplates = true,
                                     bool AllowDependent = true);
  
    enum class AssumedTemplateKind {
      /// This is not assumed to be a template name.
      None,
      /// This is assumed to be a template name because lookup found nothing.
      FoundNothing,
      /// This is assumed to be a template name because lookup found one or more
      /// functions (but no function templates).
      FoundFunctions,
    };
    bool LookupTemplateName(LookupResult &R, Scope *S, CXXScopeSpec &SS,
                            QualType ObjectType, bool EnteringContext,
                            bool &MemberOfUnknownSpecialization,
                            SourceLocation TemplateKWLoc = SourceLocation(),
                            AssumedTemplateKind *ATK = nullptr);
  
    TemplateNameKind isTemplateName(Scope *S,
                                    CXXScopeSpec &SS,
                                    bool hasTemplateKeyword,
                                    const UnqualifiedId &Name,
                                    ParsedType ObjectType,
                                    bool EnteringContext,
                                    TemplateTy &Template,
                                    bool &MemberOfUnknownSpecialization);
  
    /// Try to resolve an undeclared template name as a type template.
    ///
    /// Sets II to the identifier corresponding to the template name, and updates
    /// Name to a corresponding (typo-corrected) type template name and TNK to
    /// the corresponding kind, if possible.
    void ActOnUndeclaredTypeTemplateName(Scope *S, TemplateTy &Name,
                                         TemplateNameKind &TNK,
                                         SourceLocation NameLoc,
                                         IdentifierInfo *&II);
  
    bool resolveAssumedTemplateNameAsType(Scope *S, TemplateName &Name,
                                          SourceLocation NameLoc,
                                          bool Diagnose = true);
  
    /// Determine whether a particular identifier might be the name in a C++1z
    /// deduction-guide declaration.
    bool isDeductionGuideName(Scope *S, const IdentifierInfo &Name,
                              SourceLocation NameLoc,
                              ParsedTemplateTy *Template = nullptr);
  
    bool DiagnoseUnknownTemplateName(const IdentifierInfo &II,
                                     SourceLocation IILoc,
                                     Scope *S,
                                     const CXXScopeSpec *SS,
                                     TemplateTy &SuggestedTemplate,
                                     TemplateNameKind &SuggestedKind);
  
    bool DiagnoseUninstantiableTemplate(SourceLocation PointOfInstantiation,
                                        NamedDecl *Instantiation,
                                        bool InstantiatedFromMember,
                                        const NamedDecl *Pattern,
                                        const NamedDecl *PatternDef,
                                        TemplateSpecializationKind TSK,
                                        bool Complain = true);
  
    void DiagnoseTemplateParameterShadow(SourceLocation Loc, Decl *PrevDecl);
    TemplateDecl *AdjustDeclIfTemplate(Decl *&Decl);
  
    NamedDecl *ActOnTypeParameter(Scope *S, bool Typename,
                                  SourceLocation EllipsisLoc,
                                  SourceLocation KeyLoc,
                                  IdentifierInfo *ParamName,
                                  SourceLocation ParamNameLoc,
                                  unsigned Depth, unsigned Position,
                                  SourceLocation EqualLoc,
                                  ParsedType DefaultArg, bool HasTypeConstraint);
  
    bool ActOnTypeConstraint(const CXXScopeSpec &SS,
                             TemplateIdAnnotation *TypeConstraint,
                             TemplateTypeParmDecl *ConstrainedParameter,
                             SourceLocation EllipsisLoc);
  
    bool AttachTypeConstraint(NestedNameSpecifierLoc NS,
                              DeclarationNameInfo NameInfo,
                              ConceptDecl *NamedConcept,
                              const TemplateArgumentListInfo *TemplateArgs,
                              TemplateTypeParmDecl *ConstrainedParameter,
                              SourceLocation EllipsisLoc);
  
    bool AttachTypeConstraint(AutoTypeLoc TL,
                              NonTypeTemplateParmDecl *ConstrainedParameter,
                              SourceLocation EllipsisLoc);
  
    QualType CheckNonTypeTemplateParameterType(TypeSourceInfo *&TSI,
                                               SourceLocation Loc);
    QualType CheckNonTypeTemplateParameterType(QualType T, SourceLocation Loc);
  
    NamedDecl *ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
                                        unsigned Depth,
                                        unsigned Position,
                                        SourceLocation EqualLoc,
                                        Expr *DefaultArg);
    NamedDecl *ActOnTemplateTemplateParameter(Scope *S,
                                         SourceLocation TmpLoc,
                                         TemplateParameterList *Params,
                                         SourceLocation EllipsisLoc,
                                         IdentifierInfo *ParamName,
                                         SourceLocation ParamNameLoc,
                                         unsigned Depth,
                                         unsigned Position,
                                         SourceLocation EqualLoc,
                                         ParsedTemplateArgument DefaultArg);
  
    TemplateParameterList *
    ActOnTemplateParameterList(unsigned Depth,
                               SourceLocation ExportLoc,
                               SourceLocation TemplateLoc,
                               SourceLocation LAngleLoc,
                               ArrayRef<NamedDecl *> Params,
                               SourceLocation RAngleLoc,
                               Expr *RequiresClause);
  
    /// The context in which we are checking a template parameter list.
    enum TemplateParamListContext {
      TPC_ClassTemplate,
      TPC_VarTemplate,
      TPC_FunctionTemplate,
      TPC_ClassTemplateMember,
      TPC_FriendClassTemplate,
      TPC_FriendFunctionTemplate,
      TPC_FriendFunctionTemplateDefinition,
      TPC_TypeAliasTemplate
    };
  
    bool CheckTemplateParameterList(TemplateParameterList *NewParams,
                                    TemplateParameterList *OldParams,
                                    TemplateParamListContext TPC,
                                    SkipBodyInfo *SkipBody = nullptr);
    TemplateParameterList *MatchTemplateParametersToScopeSpecifier(
        SourceLocation DeclStartLoc, SourceLocation DeclLoc,
        const CXXScopeSpec &SS, TemplateIdAnnotation *TemplateId,
        ArrayRef<TemplateParameterList *> ParamLists,
        bool IsFriend, bool &IsMemberSpecialization, bool &Invalid,
        bool SuppressDiagnostic = false);
  
    DeclResult CheckClassTemplate(
        Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc,
        CXXScopeSpec &SS, IdentifierInfo *Name, SourceLocation NameLoc,
        const ParsedAttributesView &Attr, TemplateParameterList *TemplateParams,
        AccessSpecifier AS, SourceLocation ModulePrivateLoc,
        SourceLocation FriendLoc, unsigned NumOuterTemplateParamLists,
        TemplateParameterList **OuterTemplateParamLists,
        SkipBodyInfo *SkipBody = nullptr);
  
    TemplateArgumentLoc getTrivialTemplateArgumentLoc(const TemplateArgument &Arg,
                                                      QualType NTTPType,
                                                      SourceLocation Loc);
  
    /// Get a template argument mapping the given template parameter to itself,
    /// e.g. for X in \c template<int X>, this would return an expression template
    /// argument referencing X.
    TemplateArgumentLoc getIdentityTemplateArgumentLoc(NamedDecl *Param,
                                                       SourceLocation Location);
  
    void translateTemplateArguments(const ASTTemplateArgsPtr &In,
                                    TemplateArgumentListInfo &Out);
  
    ParsedTemplateArgument ActOnTemplateTypeArgument(TypeResult ParsedType);
  
    void NoteAllFoundTemplates(TemplateName Name);
  
    QualType CheckTemplateIdType(TemplateName Template,
                                 SourceLocation TemplateLoc,
                                TemplateArgumentListInfo &TemplateArgs);
  
    TypeResult
    ActOnTemplateIdType(Scope *S, CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
                        TemplateTy Template, IdentifierInfo *TemplateII,
                        SourceLocation TemplateIILoc, SourceLocation LAngleLoc,
                        ASTTemplateArgsPtr TemplateArgs, SourceLocation RAngleLoc,
                        bool IsCtorOrDtorName = false, bool IsClassName = false);
  
    /// Parsed an elaborated-type-specifier that refers to a template-id,
    /// such as \c class T::template apply<U>.
    TypeResult ActOnTagTemplateIdType(TagUseKind TUK,
                                      TypeSpecifierType TagSpec,
                                      SourceLocation TagLoc,
                                      CXXScopeSpec &SS,
                                      SourceLocation TemplateKWLoc,
                                      TemplateTy TemplateD,
                                      SourceLocation TemplateLoc,
                                      SourceLocation LAngleLoc,
                                      ASTTemplateArgsPtr TemplateArgsIn,
                                      SourceLocation RAngleLoc);
  
    DeclResult ActOnVarTemplateSpecialization(
        Scope *S, Declarator &D, TypeSourceInfo *DI,
        SourceLocation TemplateKWLoc, TemplateParameterList *TemplateParams,
        StorageClass SC, bool IsPartialSpecialization);
  
    DeclResult CheckVarTemplateId(VarTemplateDecl *Template,
                                  SourceLocation TemplateLoc,
                                  SourceLocation TemplateNameLoc,
                                  const TemplateArgumentListInfo &TemplateArgs);
  
    ExprResult CheckVarTemplateId(const CXXScopeSpec &SS,
                                  const DeclarationNameInfo &NameInfo,
                                  VarTemplateDecl *Template,
                                  SourceLocation TemplateLoc,
                                  const TemplateArgumentListInfo *TemplateArgs);
  
    ExprResult
    CheckConceptTemplateId(const CXXScopeSpec &SS,
                           SourceLocation TemplateKWLoc,
                           const DeclarationNameInfo &ConceptNameInfo,
                           NamedDecl *FoundDecl, ConceptDecl *NamedConcept,
                           const TemplateArgumentListInfo *TemplateArgs);
  
    void diagnoseMissingTemplateArguments(TemplateName Name, SourceLocation Loc);
  
    ExprResult BuildTemplateIdExpr(const CXXScopeSpec &SS,
                                   SourceLocation TemplateKWLoc,
                                   LookupResult &R,
                                   bool RequiresADL,
                                 const TemplateArgumentListInfo *TemplateArgs);
  
    ExprResult BuildQualifiedTemplateIdExpr(CXXScopeSpec &SS,
                                            SourceLocation TemplateKWLoc,
                                 const DeclarationNameInfo &NameInfo,
                                 const TemplateArgumentListInfo *TemplateArgs);
  
    TemplateNameKind ActOnDependentTemplateName(
        Scope *S, CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
        const UnqualifiedId &Name, ParsedType ObjectType, bool EnteringContext,
        TemplateTy &Template, bool AllowInjectedClassName = false);
  
    DeclResult ActOnClassTemplateSpecialization(
        Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc,
        SourceLocation ModulePrivateLoc, CXXScopeSpec &SS,
        TemplateIdAnnotation &TemplateId, const ParsedAttributesView &Attr,
        MultiTemplateParamsArg TemplateParameterLists,
        SkipBodyInfo *SkipBody = nullptr);
  
    bool CheckTemplatePartialSpecializationArgs(SourceLocation Loc,
                                                TemplateDecl *PrimaryTemplate,
                                                unsigned NumExplicitArgs,
                                                ArrayRef<TemplateArgument> Args);
    void CheckTemplatePartialSpecialization(
        ClassTemplatePartialSpecializationDecl *Partial);
    void CheckTemplatePartialSpecialization(
        VarTemplatePartialSpecializationDecl *Partial);
  
    Decl *ActOnTemplateDeclarator(Scope *S,
                                  MultiTemplateParamsArg TemplateParameterLists,
                                  Declarator &D);
  
    bool
    CheckSpecializationInstantiationRedecl(SourceLocation NewLoc,
                                           TemplateSpecializationKind NewTSK,
                                           NamedDecl *PrevDecl,
                                           TemplateSpecializationKind PrevTSK,
                                           SourceLocation PrevPtOfInstantiation,
                                           bool &SuppressNew);
  
    bool CheckDependentFunctionTemplateSpecialization(FunctionDecl *FD,
                      const TemplateArgumentListInfo &ExplicitTemplateArgs,
                                                      LookupResult &Previous);
  
    bool CheckFunctionTemplateSpecialization(
        FunctionDecl *FD, TemplateArgumentListInfo *ExplicitTemplateArgs,
        LookupResult &Previous, bool QualifiedFriend = false);
    bool CheckMemberSpecialization(NamedDecl *Member, LookupResult &Previous);
    void CompleteMemberSpecialization(NamedDecl *Member, LookupResult &Previous);
  
    DeclResult ActOnExplicitInstantiation(
        Scope *S, SourceLocation ExternLoc, SourceLocation TemplateLoc,
        unsigned TagSpec, SourceLocation KWLoc, const CXXScopeSpec &SS,
        TemplateTy Template, SourceLocation TemplateNameLoc,
        SourceLocation LAngleLoc, ASTTemplateArgsPtr TemplateArgs,
        SourceLocation RAngleLoc, const ParsedAttributesView &Attr);
  
    DeclResult ActOnExplicitInstantiation(Scope *S, SourceLocation ExternLoc,
                                          SourceLocation TemplateLoc,
                                          unsigned TagSpec, SourceLocation KWLoc,
                                          CXXScopeSpec &SS, IdentifierInfo *Name,
                                          SourceLocation NameLoc,
                                          const ParsedAttributesView &Attr);
  
    DeclResult ActOnExplicitInstantiation(Scope *S,
                                          SourceLocation ExternLoc,
                                          SourceLocation TemplateLoc,
                                          Declarator &D);
  
    TemplateArgumentLoc
    SubstDefaultTemplateArgumentIfAvailable(TemplateDecl *Template,
                                            SourceLocation TemplateLoc,
                                            SourceLocation RAngleLoc,
                                            Decl *Param,
                                            SmallVectorImpl<TemplateArgument>
                                              &Converted,
                                            bool &HasDefaultArg);
  
    /// Specifies the context in which a particular template
    /// argument is being checked.
    enum CheckTemplateArgumentKind {
      /// The template argument was specified in the code or was
      /// instantiated with some deduced template arguments.
      CTAK_Specified,
  
      /// The template argument was deduced via template argument
      /// deduction.
      CTAK_Deduced,
  
      /// The template argument was deduced from an array bound
      /// via template argument deduction.
      CTAK_DeducedFromArrayBound
    };
  
    bool CheckTemplateArgument(NamedDecl *Param,
                               TemplateArgumentLoc &Arg,
                               NamedDecl *Template,
                               SourceLocation TemplateLoc,
                               SourceLocation RAngleLoc,
                               unsigned ArgumentPackIndex,
                             SmallVectorImpl<TemplateArgument> &Converted,
                               CheckTemplateArgumentKind CTAK = CTAK_Specified);
  
    /// Check that the given template arguments can be be provided to
    /// the given template, converting the arguments along the way.
    ///
    /// \param Template The template to which the template arguments are being
    /// provided.
    ///
    /// \param TemplateLoc The location of the template name in the source.
    ///
    /// \param TemplateArgs The list of template arguments. If the template is
    /// a template template parameter, this function may extend the set of
    /// template arguments to also include substituted, defaulted template
    /// arguments.
    ///
    /// \param PartialTemplateArgs True if the list of template arguments is
    /// intentionally partial, e.g., because we're checking just the initial
    /// set of template arguments.
    ///
    /// \param Converted Will receive the converted, canonicalized template
    /// arguments.
    ///
    /// \param UpdateArgsWithConversions If \c true, update \p TemplateArgs to
    /// contain the converted forms of the template arguments as written.
    /// Otherwise, \p TemplateArgs will not be modified.
    ///
    /// \param ConstraintsNotSatisfied If provided, and an error occured, will
    /// receive true if the cause for the error is the associated constraints of
    /// the template not being satisfied by the template arguments.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool CheckTemplateArgumentList(TemplateDecl *Template,
                                   SourceLocation TemplateLoc,
                                   TemplateArgumentListInfo &TemplateArgs,
                                   bool PartialTemplateArgs,
                                   SmallVectorImpl<TemplateArgument> &Converted,
                                   bool UpdateArgsWithConversions = true,
                                   bool *ConstraintsNotSatisfied = nullptr);
  
    bool CheckTemplateTypeArgument(TemplateTypeParmDecl *Param,
                                   TemplateArgumentLoc &Arg,
                             SmallVectorImpl<TemplateArgument> &Converted);
  
    bool CheckTemplateArgument(TemplateTypeParmDecl *Param,
                               TypeSourceInfo *Arg);
    ExprResult CheckTemplateArgument(NonTypeTemplateParmDecl *Param,
                                     QualType InstantiatedParamType, Expr *Arg,
                                     TemplateArgument &Converted,
                                 CheckTemplateArgumentKind CTAK = CTAK_Specified);
    bool CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
                                       TemplateParameterList *Params,
                                       TemplateArgumentLoc &Arg);
  
    ExprResult
    BuildExpressionFromDeclTemplateArgument(const TemplateArgument &Arg,
                                            QualType ParamType,
                                            SourceLocation Loc);
    ExprResult
    BuildExpressionFromIntegralTemplateArgument(const TemplateArgument &Arg,
                                                SourceLocation Loc);
  
    /// Enumeration describing how template parameter lists are compared
    /// for equality.
    enum TemplateParameterListEqualKind {
      /// We are matching the template parameter lists of two templates
      /// that might be redeclarations.
      ///
      /// \code
      /// template<typename T> struct X;
      /// template<typename T> struct X;
      /// \endcode
      TPL_TemplateMatch,
  
      /// We are matching the template parameter lists of two template
      /// template parameters as part of matching the template parameter lists
      /// of two templates that might be redeclarations.
      ///
      /// \code
      /// template<template<int I> class TT> struct X;
      /// template<template<int Value> class Other> struct X;
      /// \endcode
      TPL_TemplateTemplateParmMatch,
  
      /// We are matching the template parameter lists of a template
      /// template argument against the template parameter lists of a template
      /// template parameter.
      ///
      /// \code
      /// template<template<int Value> class Metafun> struct X;
      /// template<int Value> struct integer_c;
      /// X<integer_c> xic;
      /// \endcode
      TPL_TemplateTemplateArgumentMatch
    };
  
    bool TemplateParameterListsAreEqual(TemplateParameterList *New,
                                        TemplateParameterList *Old,
                                        bool Complain,
                                        TemplateParameterListEqualKind Kind,
                                        SourceLocation TemplateArgLoc
                                          = SourceLocation());
  
    bool CheckTemplateDeclScope(Scope *S, TemplateParameterList *TemplateParams);
  
    /// Called when the parser has parsed a C++ typename
    /// specifier, e.g., "typename T::type".
    ///
    /// \param S The scope in which this typename type occurs.
    /// \param TypenameLoc the location of the 'typename' keyword
    /// \param SS the nested-name-specifier following the typename (e.g., 'T::').
    /// \param II the identifier we're retrieving (e.g., 'type' in the example).
    /// \param IdLoc the location of the identifier.
    TypeResult
    ActOnTypenameType(Scope *S, SourceLocation TypenameLoc,
                      const CXXScopeSpec &SS, const IdentifierInfo &II,
                      SourceLocation IdLoc);
  
    /// Called when the parser has parsed a C++ typename
    /// specifier that ends in a template-id, e.g.,
    /// "typename MetaFun::template apply<T1, T2>".
    ///
    /// \param S The scope in which this typename type occurs.
    /// \param TypenameLoc the location of the 'typename' keyword
    /// \param SS the nested-name-specifier following the typename (e.g., 'T::').
    /// \param TemplateLoc the location of the 'template' keyword, if any.
    /// \param TemplateName The template name.
    /// \param TemplateII The identifier used to name the template.
    /// \param TemplateIILoc The location of the template name.
    /// \param LAngleLoc The location of the opening angle bracket  ('<').
    /// \param TemplateArgs The template arguments.
    /// \param RAngleLoc The location of the closing angle bracket  ('>').
    TypeResult
    ActOnTypenameType(Scope *S, SourceLocation TypenameLoc,
                      const CXXScopeSpec &SS,
                      SourceLocation TemplateLoc,
                      TemplateTy TemplateName,
                      IdentifierInfo *TemplateII,
                      SourceLocation TemplateIILoc,
                      SourceLocation LAngleLoc,
                      ASTTemplateArgsPtr TemplateArgs,
                      SourceLocation RAngleLoc);
  
    QualType CheckTypenameType(ElaboratedTypeKeyword Keyword,
                               SourceLocation KeywordLoc,
                               NestedNameSpecifierLoc QualifierLoc,
                               const IdentifierInfo &II,
                               SourceLocation IILoc,
                               TypeSourceInfo **TSI,
                               bool DeducedTSTContext);
  
    QualType CheckTypenameType(ElaboratedTypeKeyword Keyword,
                               SourceLocation KeywordLoc,
                               NestedNameSpecifierLoc QualifierLoc,
                               const IdentifierInfo &II,
                               SourceLocation IILoc,
                               bool DeducedTSTContext = true);
  
  
    TypeSourceInfo *RebuildTypeInCurrentInstantiation(TypeSourceInfo *T,
                                                      SourceLocation Loc,
                                                      DeclarationName Name);
    bool RebuildNestedNameSpecifierInCurrentInstantiation(CXXScopeSpec &SS);
  
    ExprResult RebuildExprInCurrentInstantiation(Expr *E);
    bool RebuildTemplateParamsInCurrentInstantiation(
                                                  TemplateParameterList *Params);
  
    std::string
    getTemplateArgumentBindingsText(const TemplateParameterList *Params,
                                    const TemplateArgumentList &Args);
  
    std::string
    getTemplateArgumentBindingsText(const TemplateParameterList *Params,
                                    const TemplateArgument *Args,
                                    unsigned NumArgs);
  
    //===--------------------------------------------------------------------===//
    // C++ Concepts
    //===--------------------------------------------------------------------===//
    Decl *ActOnConceptDefinition(
        Scope *S, MultiTemplateParamsArg TemplateParameterLists,
        IdentifierInfo *Name, SourceLocation NameLoc, Expr *ConstraintExpr);
  
    RequiresExprBodyDecl *
    ActOnStartRequiresExpr(SourceLocation RequiresKWLoc,
                           ArrayRef<ParmVarDecl *> LocalParameters,
                           Scope *BodyScope);
    void ActOnFinishRequiresExpr();
    concepts::Requirement *ActOnSimpleRequirement(Expr *E);
    concepts::Requirement *ActOnTypeRequirement(
        SourceLocation TypenameKWLoc, CXXScopeSpec &SS, SourceLocation NameLoc,
        IdentifierInfo *TypeName, TemplateIdAnnotation *TemplateId);
    concepts::Requirement *ActOnCompoundRequirement(Expr *E,
                                                    SourceLocation NoexceptLoc);
    concepts::Requirement *
    ActOnCompoundRequirement(
        Expr *E, SourceLocation NoexceptLoc, CXXScopeSpec &SS,
        TemplateIdAnnotation *TypeConstraint, unsigned Depth);
    concepts::Requirement *ActOnNestedRequirement(Expr *Constraint);
    concepts::ExprRequirement *
    BuildExprRequirement(
        Expr *E, bool IsSatisfied, SourceLocation NoexceptLoc,
        concepts::ExprRequirement::ReturnTypeRequirement ReturnTypeRequirement);
    concepts::ExprRequirement *
    BuildExprRequirement(
        concepts::Requirement::SubstitutionDiagnostic *ExprSubstDiag,
        bool IsSatisfied, SourceLocation NoexceptLoc,
        concepts::ExprRequirement::ReturnTypeRequirement ReturnTypeRequirement);
    concepts::TypeRequirement *BuildTypeRequirement(TypeSourceInfo *Type);
    concepts::TypeRequirement *
    BuildTypeRequirement(
        concepts::Requirement::SubstitutionDiagnostic *SubstDiag);
    concepts::NestedRequirement *BuildNestedRequirement(Expr *E);
    concepts::NestedRequirement *
    BuildNestedRequirement(
        concepts::Requirement::SubstitutionDiagnostic *SubstDiag);
    ExprResult ActOnRequiresExpr(SourceLocation RequiresKWLoc,
                                 RequiresExprBodyDecl *Body,
                                 ArrayRef<ParmVarDecl *> LocalParameters,
                                 ArrayRef<concepts::Requirement *> Requirements,
                                 SourceLocation ClosingBraceLoc);
  
    //===--------------------------------------------------------------------===//
    // C++ Variadic Templates (C++0x [temp.variadic])
    //===--------------------------------------------------------------------===//
  
    /// Determine whether an unexpanded parameter pack might be permitted in this
    /// location. Useful for error recovery.
    bool isUnexpandedParameterPackPermitted();
  
    /// The context in which an unexpanded parameter pack is
    /// being diagnosed.
    ///
    /// Note that the values of this enumeration line up with the first
    /// argument to the \c err_unexpanded_parameter_pack diagnostic.
    enum UnexpandedParameterPackContext {
      /// An arbitrary expression.
      UPPC_Expression = 0,
  
      /// The base type of a class type.
      UPPC_BaseType,
  
      /// The type of an arbitrary declaration.
      UPPC_DeclarationType,
  
      /// The type of a data member.
      UPPC_DataMemberType,
  
      /// The size of a bit-field.
      UPPC_BitFieldWidth,
  
      /// The expression in a static assertion.
      UPPC_StaticAssertExpression,
  
      /// The fixed underlying type of an enumeration.
      UPPC_FixedUnderlyingType,
  
      /// The enumerator value.
      UPPC_EnumeratorValue,
  
      /// A using declaration.
      UPPC_UsingDeclaration,
  
      /// A friend declaration.
      UPPC_FriendDeclaration,
  
      /// A declaration qualifier.
      UPPC_DeclarationQualifier,
  
      /// An initializer.
      UPPC_Initializer,
  
      /// A default argument.
      UPPC_DefaultArgument,
  
      /// The type of a non-type template parameter.
      UPPC_NonTypeTemplateParameterType,
  
      /// The type of an exception.
      UPPC_ExceptionType,
  
      /// Partial specialization.
      UPPC_PartialSpecialization,
  
      /// Microsoft __if_exists.
      UPPC_IfExists,
  
      /// Microsoft __if_not_exists.
      UPPC_IfNotExists,
  
      /// Lambda expression.
      UPPC_Lambda,
  
      /// Block expression,
      UPPC_Block,
  
      /// A type constraint,
      UPPC_TypeConstraint
    };
  
    /// Diagnose unexpanded parameter packs.
    ///
    /// \param Loc The location at which we should emit the diagnostic.
    ///
    /// \param UPPC The context in which we are diagnosing unexpanded
    /// parameter packs.
    ///
    /// \param Unexpanded the set of unexpanded parameter packs.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool DiagnoseUnexpandedParameterPacks(SourceLocation Loc,
                                          UnexpandedParameterPackContext UPPC,
                                    ArrayRef<UnexpandedParameterPack> Unexpanded);
  
    /// If the given type contains an unexpanded parameter pack,
    /// diagnose the error.
    ///
    /// \param Loc The source location where a diagnostc should be emitted.
    ///
    /// \param T The type that is being checked for unexpanded parameter
    /// packs.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool DiagnoseUnexpandedParameterPack(SourceLocation Loc, TypeSourceInfo *T,
                                         UnexpandedParameterPackContext UPPC);
  
    /// If the given expression contains an unexpanded parameter
    /// pack, diagnose the error.
    ///
    /// \param E The expression that is being checked for unexpanded
    /// parameter packs.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool DiagnoseUnexpandedParameterPack(Expr *E,
                         UnexpandedParameterPackContext UPPC = UPPC_Expression);
  
    /// If the given nested-name-specifier contains an unexpanded
    /// parameter pack, diagnose the error.
    ///
    /// \param SS The nested-name-specifier that is being checked for
    /// unexpanded parameter packs.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool DiagnoseUnexpandedParameterPack(const CXXScopeSpec &SS,
                                         UnexpandedParameterPackContext UPPC);
  
    /// If the given name contains an unexpanded parameter pack,
    /// diagnose the error.
    ///
    /// \param NameInfo The name (with source location information) that
    /// is being checked for unexpanded parameter packs.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool DiagnoseUnexpandedParameterPack(const DeclarationNameInfo &NameInfo,
                                         UnexpandedParameterPackContext UPPC);
  
    /// If the given template name contains an unexpanded parameter pack,
    /// diagnose the error.
    ///
    /// \param Loc The location of the template name.
    ///
    /// \param Template The template name that is being checked for unexpanded
    /// parameter packs.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool DiagnoseUnexpandedParameterPack(SourceLocation Loc,
                                         TemplateName Template,
                                         UnexpandedParameterPackContext UPPC);
  
    /// If the given template argument contains an unexpanded parameter
    /// pack, diagnose the error.
    ///
    /// \param Arg The template argument that is being checked for unexpanded
    /// parameter packs.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool DiagnoseUnexpandedParameterPack(TemplateArgumentLoc Arg,
                                         UnexpandedParameterPackContext UPPC);
  
    /// Collect the set of unexpanded parameter packs within the given
    /// template argument.
    ///
    /// \param Arg The template argument that will be traversed to find
    /// unexpanded parameter packs.
    void collectUnexpandedParameterPacks(TemplateArgument Arg,
                     SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
  
    /// Collect the set of unexpanded parameter packs within the given
    /// template argument.
    ///
    /// \param Arg The template argument that will be traversed to find
    /// unexpanded parameter packs.
    void collectUnexpandedParameterPacks(TemplateArgumentLoc Arg,
                      SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
  
    /// Collect the set of unexpanded parameter packs within the given
    /// type.
    ///
    /// \param T The type that will be traversed to find
    /// unexpanded parameter packs.
    void collectUnexpandedParameterPacks(QualType T,
                     SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
  
    /// Collect the set of unexpanded parameter packs within the given
    /// type.
    ///
    /// \param TL The type that will be traversed to find
    /// unexpanded parameter packs.
    void collectUnexpandedParameterPacks(TypeLoc TL,
                     SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
  
    /// Collect the set of unexpanded parameter packs within the given
    /// nested-name-specifier.
    ///
    /// \param NNS The nested-name-specifier that will be traversed to find
    /// unexpanded parameter packs.
    void collectUnexpandedParameterPacks(NestedNameSpecifierLoc NNS,
                           SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
  
    /// Collect the set of unexpanded parameter packs within the given
    /// name.
    ///
    /// \param NameInfo The name that will be traversed to find
    /// unexpanded parameter packs.
    void collectUnexpandedParameterPacks(const DeclarationNameInfo &NameInfo,
                           SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
  
    /// Invoked when parsing a template argument followed by an
    /// ellipsis, which creates a pack expansion.
    ///
    /// \param Arg The template argument preceding the ellipsis, which
    /// may already be invalid.
    ///
    /// \param EllipsisLoc The location of the ellipsis.
    ParsedTemplateArgument ActOnPackExpansion(const ParsedTemplateArgument &Arg,
                                              SourceLocation EllipsisLoc);
  
    /// Invoked when parsing a type followed by an ellipsis, which
    /// creates a pack expansion.
    ///
    /// \param Type The type preceding the ellipsis, which will become
    /// the pattern of the pack expansion.
    ///
    /// \param EllipsisLoc The location of the ellipsis.
    TypeResult ActOnPackExpansion(ParsedType Type, SourceLocation EllipsisLoc);
  
    /// Construct a pack expansion type from the pattern of the pack
    /// expansion.
    TypeSourceInfo *CheckPackExpansion(TypeSourceInfo *Pattern,
                                       SourceLocation EllipsisLoc,
                                       Optional<unsigned> NumExpansions);
  
    /// Construct a pack expansion type from the pattern of the pack
    /// expansion.
    QualType CheckPackExpansion(QualType Pattern,
                                SourceRange PatternRange,
                                SourceLocation EllipsisLoc,
                                Optional<unsigned> NumExpansions);
  
    /// Invoked when parsing an expression followed by an ellipsis, which
    /// creates a pack expansion.
    ///
    /// \param Pattern The expression preceding the ellipsis, which will become
    /// the pattern of the pack expansion.
    ///
    /// \param EllipsisLoc The location of the ellipsis.
    ExprResult ActOnPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc);
  
    /// Invoked when parsing an expression followed by an ellipsis, which
    /// creates a pack expansion.
    ///
    /// \param Pattern The expression preceding the ellipsis, which will become
    /// the pattern of the pack expansion.
    ///
    /// \param EllipsisLoc The location of the ellipsis.
    ExprResult CheckPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc,
                                  Optional<unsigned> NumExpansions);
  
    /// Determine whether we could expand a pack expansion with the
    /// given set of parameter packs into separate arguments by repeatedly
    /// transforming the pattern.
    ///
    /// \param EllipsisLoc The location of the ellipsis that identifies the
    /// pack expansion.
    ///
    /// \param PatternRange The source range that covers the entire pattern of
    /// the pack expansion.
    ///
    /// \param Unexpanded The set of unexpanded parameter packs within the
    /// pattern.
    ///
    /// \param ShouldExpand Will be set to \c true if the transformer should
    /// expand the corresponding pack expansions into separate arguments. When
    /// set, \c NumExpansions must also be set.
    ///
    /// \param RetainExpansion Whether the caller should add an unexpanded
    /// pack expansion after all of the expanded arguments. This is used
    /// when extending explicitly-specified template argument packs per
    /// C++0x [temp.arg.explicit]p9.
    ///
    /// \param NumExpansions The number of separate arguments that will be in
    /// the expanded form of the corresponding pack expansion. This is both an
    /// input and an output parameter, which can be set by the caller if the
    /// number of expansions is known a priori (e.g., due to a prior substitution)
    /// and will be set by the callee when the number of expansions is known.
    /// The callee must set this value when \c ShouldExpand is \c true; it may
    /// set this value in other cases.
    ///
    /// \returns true if an error occurred (e.g., because the parameter packs
    /// are to be instantiated with arguments of different lengths), false
    /// otherwise. If false, \c ShouldExpand (and possibly \c NumExpansions)
    /// must be set.
    bool CheckParameterPacksForExpansion(SourceLocation EllipsisLoc,
                                         SourceRange PatternRange,
                               ArrayRef<UnexpandedParameterPack> Unexpanded,
                               const MultiLevelTemplateArgumentList &TemplateArgs,
                                         bool &ShouldExpand,
                                         bool &RetainExpansion,
                                         Optional<unsigned> &NumExpansions);
  
    /// Determine the number of arguments in the given pack expansion
    /// type.
    ///
    /// This routine assumes that the number of arguments in the expansion is
    /// consistent across all of the unexpanded parameter packs in its pattern.
    ///
    /// Returns an empty Optional if the type can't be expanded.
    Optional<unsigned> getNumArgumentsInExpansion(QualType T,
        const MultiLevelTemplateArgumentList &TemplateArgs);
  
    /// Determine whether the given declarator contains any unexpanded
    /// parameter packs.
    ///
    /// This routine is used by the parser to disambiguate function declarators
    /// with an ellipsis prior to the ')', e.g.,
    ///
    /// \code
    ///   void f(T...);
    /// \endcode
    ///
    /// To determine whether we have an (unnamed) function parameter pack or
    /// a variadic function.
    ///
    /// \returns true if the declarator contains any unexpanded parameter packs,
    /// false otherwise.
    bool containsUnexpandedParameterPacks(Declarator &D);
  
    /// Returns the pattern of the pack expansion for a template argument.
    ///
    /// \param OrigLoc The template argument to expand.
    ///
    /// \param Ellipsis Will be set to the location of the ellipsis.
    ///
    /// \param NumExpansions Will be set to the number of expansions that will
    /// be generated from this pack expansion, if known a priori.
    TemplateArgumentLoc getTemplateArgumentPackExpansionPattern(
        TemplateArgumentLoc OrigLoc,
        SourceLocation &Ellipsis,
        Optional<unsigned> &NumExpansions) const;
  
    /// Given a template argument that contains an unexpanded parameter pack, but
    /// which has already been substituted, attempt to determine the number of
    /// elements that will be produced once this argument is fully-expanded.
    ///
    /// This is intended for use when transforming 'sizeof...(Arg)' in order to
    /// avoid actually expanding the pack where possible.
    Optional<unsigned> getFullyPackExpandedSize(TemplateArgument Arg);
  
    //===--------------------------------------------------------------------===//
    // C++ Template Argument Deduction (C++ [temp.deduct])
    //===--------------------------------------------------------------------===//
  
    /// Adjust the type \p ArgFunctionType to match the calling convention,
    /// noreturn, and optionally the exception specification of \p FunctionType.
    /// Deduction often wants to ignore these properties when matching function
    /// types.
    QualType adjustCCAndNoReturn(QualType ArgFunctionType, QualType FunctionType,
                                 bool AdjustExceptionSpec = false);
  
    /// Describes the result of template argument deduction.
    ///
    /// The TemplateDeductionResult enumeration describes the result of
    /// template argument deduction, as returned from
    /// DeduceTemplateArguments(). The separate TemplateDeductionInfo
    /// structure provides additional information about the results of
    /// template argument deduction, e.g., the deduced template argument
    /// list (if successful) or the specific template parameters or
    /// deduced arguments that were involved in the failure.
    enum TemplateDeductionResult {
      /// Template argument deduction was successful.
      TDK_Success = 0,
      /// The declaration was invalid; do nothing.
      TDK_Invalid,
      /// Template argument deduction exceeded the maximum template
      /// instantiation depth (which has already been diagnosed).
      TDK_InstantiationDepth,
      /// Template argument deduction did not deduce a value
      /// for every template parameter.
      TDK_Incomplete,
      /// Template argument deduction did not deduce a value for every
      /// expansion of an expanded template parameter pack.
      TDK_IncompletePack,
      /// Template argument deduction produced inconsistent
      /// deduced values for the given template parameter.
      TDK_Inconsistent,
      /// Template argument deduction failed due to inconsistent
      /// cv-qualifiers on a template parameter type that would
      /// otherwise be deduced, e.g., we tried to deduce T in "const T"
      /// but were given a non-const "X".
      TDK_Underqualified,
      /// Substitution of the deduced template argument values
      /// resulted in an error.
      TDK_SubstitutionFailure,
      /// After substituting deduced template arguments, a dependent
      /// parameter type did not match the corresponding argument.
      TDK_DeducedMismatch,
      /// After substituting deduced template arguments, an element of
      /// a dependent parameter type did not match the corresponding element
      /// of the corresponding argument (when deducing from an initializer list).
      TDK_DeducedMismatchNested,
      /// A non-depnedent component of the parameter did not match the
      /// corresponding component of the argument.
      TDK_NonDeducedMismatch,
      /// When performing template argument deduction for a function
      /// template, there were too many call arguments.
      TDK_TooManyArguments,
      /// When performing template argument deduction for a function
      /// template, there were too few call arguments.
      TDK_TooFewArguments,
      /// The explicitly-specified template arguments were not valid
      /// template arguments for the given template.
      TDK_InvalidExplicitArguments,
      /// Checking non-dependent argument conversions failed.
      TDK_NonDependentConversionFailure,
      /// The deduced arguments did not satisfy the constraints associated
      /// with the template.
      TDK_ConstraintsNotSatisfied,
      /// Deduction failed; that's all we know.
      TDK_MiscellaneousDeductionFailure,
      /// CUDA Target attributes do not match.
      TDK_CUDATargetMismatch
    };
  
    TemplateDeductionResult
    DeduceTemplateArguments(ClassTemplatePartialSpecializationDecl *Partial,
                            const TemplateArgumentList &TemplateArgs,
                            sema::TemplateDeductionInfo &Info);
  
    TemplateDeductionResult
    DeduceTemplateArguments(VarTemplatePartialSpecializationDecl *Partial,
                            const TemplateArgumentList &TemplateArgs,
                            sema::TemplateDeductionInfo &Info);
  
    TemplateDeductionResult SubstituteExplicitTemplateArguments(
        FunctionTemplateDecl *FunctionTemplate,
        TemplateArgumentListInfo &ExplicitTemplateArgs,
        SmallVectorImpl<DeducedTemplateArgument> &Deduced,
        SmallVectorImpl<QualType> &ParamTypes, QualType *FunctionType,
        sema::TemplateDeductionInfo &Info);
  
    /// brief A function argument from which we performed template argument
    // deduction for a call.
    struct OriginalCallArg {
      OriginalCallArg(QualType OriginalParamType, bool DecomposedParam,
                      unsigned ArgIdx, QualType OriginalArgType)
          : OriginalParamType(OriginalParamType),
            DecomposedParam(DecomposedParam), ArgIdx(ArgIdx),
            OriginalArgType(OriginalArgType) {}
  
      QualType OriginalParamType;
      bool DecomposedParam;
      unsigned ArgIdx;
      QualType OriginalArgType;
    };
  
    TemplateDeductionResult FinishTemplateArgumentDeduction(
        FunctionTemplateDecl *FunctionTemplate,
        SmallVectorImpl<DeducedTemplateArgument> &Deduced,
        unsigned NumExplicitlySpecified, FunctionDecl *&Specialization,
        sema::TemplateDeductionInfo &Info,
        SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs = nullptr,
        bool PartialOverloading = false,
        llvm::function_ref<bool()> CheckNonDependent = []{ return false; });
  
    TemplateDeductionResult DeduceTemplateArguments(
        FunctionTemplateDecl *FunctionTemplate,
        TemplateArgumentListInfo *ExplicitTemplateArgs, ArrayRef<Expr *> Args,
        FunctionDecl *&Specialization, sema::TemplateDeductionInfo &Info,
        bool PartialOverloading,
        llvm::function_ref<bool(ArrayRef<QualType>)> CheckNonDependent);
  
    TemplateDeductionResult
    DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
                            TemplateArgumentListInfo *ExplicitTemplateArgs,
                            QualType ArgFunctionType,
                            FunctionDecl *&Specialization,
                            sema::TemplateDeductionInfo &Info,
                            bool IsAddressOfFunction = false);
  
    TemplateDeductionResult
    DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
                            QualType ToType,
                            CXXConversionDecl *&Specialization,
                            sema::TemplateDeductionInfo &Info);
  
    TemplateDeductionResult
    DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
                            TemplateArgumentListInfo *ExplicitTemplateArgs,
                            FunctionDecl *&Specialization,
                            sema::TemplateDeductionInfo &Info,
                            bool IsAddressOfFunction = false);
  
    /// Substitute Replacement for \p auto in \p TypeWithAuto
    QualType SubstAutoType(QualType TypeWithAuto, QualType Replacement);
    /// Substitute Replacement for auto in TypeWithAuto
    TypeSourceInfo* SubstAutoTypeSourceInfo(TypeSourceInfo *TypeWithAuto,
                                            QualType Replacement);
    /// Completely replace the \c auto in \p TypeWithAuto by
    /// \p Replacement. This does not retain any \c auto type sugar.
    QualType ReplaceAutoType(QualType TypeWithAuto, QualType Replacement);
  
    /// Result type of DeduceAutoType.
    enum DeduceAutoResult {
      DAR_Succeeded,
      DAR_Failed,
      DAR_FailedAlreadyDiagnosed
    };
  
    DeduceAutoResult
    DeduceAutoType(TypeSourceInfo *AutoType, Expr *&Initializer, QualType &Result,
                   Optional<unsigned> DependentDeductionDepth = None,
                   bool IgnoreConstraints = false);
    DeduceAutoResult
    DeduceAutoType(TypeLoc AutoTypeLoc, Expr *&Initializer, QualType &Result,
                   Optional<unsigned> DependentDeductionDepth = None,
                   bool IgnoreConstraints = false);
    void DiagnoseAutoDeductionFailure(VarDecl *VDecl, Expr *Init);
    bool DeduceReturnType(FunctionDecl *FD, SourceLocation Loc,
                          bool Diagnose = true);
  
    /// Declare implicit deduction guides for a class template if we've
    /// not already done so.
    void DeclareImplicitDeductionGuides(TemplateDecl *Template,
                                        SourceLocation Loc);
  
    QualType DeduceTemplateSpecializationFromInitializer(
        TypeSourceInfo *TInfo, const InitializedEntity &Entity,
        const InitializationKind &Kind, MultiExprArg Init);
  
    QualType deduceVarTypeFromInitializer(VarDecl *VDecl, DeclarationName Name,
                                          QualType Type, TypeSourceInfo *TSI,
                                          SourceRange Range, bool DirectInit,
                                          Expr *Init);
  
    TypeLoc getReturnTypeLoc(FunctionDecl *FD) const;
  
    bool DeduceFunctionTypeFromReturnExpr(FunctionDecl *FD,
                                          SourceLocation ReturnLoc,
                                          Expr *&RetExpr, AutoType *AT);
  
    FunctionTemplateDecl *getMoreSpecializedTemplate(
        FunctionTemplateDecl *FT1, FunctionTemplateDecl *FT2, SourceLocation Loc,
        TemplatePartialOrderingContext TPOC, unsigned NumCallArguments1,
        unsigned NumCallArguments2, bool Reversed = false);
    UnresolvedSetIterator
    getMostSpecialized(UnresolvedSetIterator SBegin, UnresolvedSetIterator SEnd,
                       TemplateSpecCandidateSet &FailedCandidates,
                       SourceLocation Loc,
                       const PartialDiagnostic &NoneDiag,
                       const PartialDiagnostic &AmbigDiag,
                       const PartialDiagnostic &CandidateDiag,
                       bool Complain = true, QualType TargetType = QualType());
  
    ClassTemplatePartialSpecializationDecl *
    getMoreSpecializedPartialSpecialization(
                                    ClassTemplatePartialSpecializationDecl *PS1,
                                    ClassTemplatePartialSpecializationDecl *PS2,
                                    SourceLocation Loc);
  
    bool isMoreSpecializedThanPrimary(ClassTemplatePartialSpecializationDecl *T,
                                      sema::TemplateDeductionInfo &Info);
  
    VarTemplatePartialSpecializationDecl *getMoreSpecializedPartialSpecialization(
        VarTemplatePartialSpecializationDecl *PS1,
        VarTemplatePartialSpecializationDecl *PS2, SourceLocation Loc);
  
    bool isMoreSpecializedThanPrimary(VarTemplatePartialSpecializationDecl *T,
                                      sema::TemplateDeductionInfo &Info);
  
    bool isTemplateTemplateParameterAtLeastAsSpecializedAs(
        TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc);
  
    void MarkUsedTemplateParameters(const Expr *E, bool OnlyDeduced,
                                    unsigned Depth, llvm::SmallBitVector &Used);
  
    void MarkUsedTemplateParameters(const TemplateArgumentList &TemplateArgs,
                                    bool OnlyDeduced,
                                    unsigned Depth,
                                    llvm::SmallBitVector &Used);
    void MarkDeducedTemplateParameters(
                                    const FunctionTemplateDecl *FunctionTemplate,
                                    llvm::SmallBitVector &Deduced) {
      return MarkDeducedTemplateParameters(Context, FunctionTemplate, Deduced);
    }
    static void MarkDeducedTemplateParameters(ASTContext &Ctx,
                                    const FunctionTemplateDecl *FunctionTemplate,
                                    llvm::SmallBitVector &Deduced);
  
    //===--------------------------------------------------------------------===//
    // C++ Template Instantiation
    //
  
    MultiLevelTemplateArgumentList
    getTemplateInstantiationArgs(NamedDecl *D,
                                 const TemplateArgumentList *Innermost = nullptr,
                                 bool RelativeToPrimary = false,
                                 const FunctionDecl *Pattern = nullptr);
  
    /// A context in which code is being synthesized (where a source location
    /// alone is not sufficient to identify the context). This covers template
    /// instantiation and various forms of implicitly-generated functions.
    struct CodeSynthesisContext {
      /// The kind of template instantiation we are performing
      enum SynthesisKind {
        /// We are instantiating a template declaration. The entity is
        /// the declaration we're instantiating (e.g., a CXXRecordDecl).
        TemplateInstantiation,
  
        /// We are instantiating a default argument for a template
        /// parameter. The Entity is the template parameter whose argument is
        /// being instantiated, the Template is the template, and the
        /// TemplateArgs/NumTemplateArguments provide the template arguments as
        /// specified.
        DefaultTemplateArgumentInstantiation,
  
        /// We are instantiating a default argument for a function.
        /// The Entity is the ParmVarDecl, and TemplateArgs/NumTemplateArgs
        /// provides the template arguments as specified.
        DefaultFunctionArgumentInstantiation,
  
        /// We are substituting explicit template arguments provided for
        /// a function template. The entity is a FunctionTemplateDecl.
        ExplicitTemplateArgumentSubstitution,
  
        /// We are substituting template argument determined as part of
        /// template argument deduction for either a class template
        /// partial specialization or a function template. The
        /// Entity is either a {Class|Var}TemplatePartialSpecializationDecl or
        /// a TemplateDecl.
        DeducedTemplateArgumentSubstitution,
  
        /// We are substituting prior template arguments into a new
        /// template parameter. The template parameter itself is either a
        /// NonTypeTemplateParmDecl or a TemplateTemplateParmDecl.
        PriorTemplateArgumentSubstitution,
  
        /// We are checking the validity of a default template argument that
        /// has been used when naming a template-id.
        DefaultTemplateArgumentChecking,
  
        /// We are computing the exception specification for a defaulted special
        /// member function.
        ExceptionSpecEvaluation,
  
        /// We are instantiating the exception specification for a function
        /// template which was deferred until it was needed.
        ExceptionSpecInstantiation,
  
        /// We are instantiating a requirement of a requires expression.
        RequirementInstantiation,
  
        /// We are checking the satisfaction of a nested requirement of a requires
        /// expression.
        NestedRequirementConstraintsCheck,
  
        /// We are declaring an implicit special member function.
        DeclaringSpecialMember,
  
        /// We are declaring an implicit 'operator==' for a defaulted
        /// 'operator<=>'.
        DeclaringImplicitEqualityComparison,
  
        /// We are defining a synthesized function (such as a defaulted special
        /// member).
        DefiningSynthesizedFunction,
  
        // We are checking the constraints associated with a constrained entity or
        // the constraint expression of a concept. This includes the checks that
        // atomic constraints have the type 'bool' and that they can be constant
        // evaluated.
        ConstraintsCheck,
  
        // We are substituting template arguments into a constraint expression.
        ConstraintSubstitution,
  
        // We are normalizing a constraint expression.
        ConstraintNormalization,
  
        // We are substituting into the parameter mapping of an atomic constraint
        // during normalization.
        ParameterMappingSubstitution,
  
        /// We are rewriting a comparison operator in terms of an operator<=>.
        RewritingOperatorAsSpaceship,
  
        /// Added for Template instantiation observation.
        /// Memoization means we are _not_ instantiating a template because
        /// it is already instantiated (but we entered a context where we
        /// would have had to if it was not already instantiated).
        Memoization
      } Kind;
  
      /// Was the enclosing context a non-instantiation SFINAE context?
      bool SavedInNonInstantiationSFINAEContext;
  
      /// The point of instantiation or synthesis within the source code.
      SourceLocation PointOfInstantiation;
  
      /// The entity that is being synthesized.
      Decl *Entity;
  
      /// The template (or partial specialization) in which we are
      /// performing the instantiation, for substitutions of prior template
      /// arguments.
      NamedDecl *Template;
  
      /// The list of template arguments we are substituting, if they
      /// are not part of the entity.
      const TemplateArgument *TemplateArgs;
  
      // FIXME: Wrap this union around more members, or perhaps store the
      // kind-specific members in the RAII object owning the context.
      union {
        /// The number of template arguments in TemplateArgs.
        unsigned NumTemplateArgs;
  
        /// The special member being declared or defined.
        CXXSpecialMember SpecialMember;
      };
  
      ArrayRef<TemplateArgument> template_arguments() const {
        assert(Kind != DeclaringSpecialMember);
        return {TemplateArgs, NumTemplateArgs};
      }
  
      /// The template deduction info object associated with the
      /// substitution or checking of explicit or deduced template arguments.
      sema::TemplateDeductionInfo *DeductionInfo;
  
      /// The source range that covers the construct that cause
      /// the instantiation, e.g., the template-id that causes a class
      /// template instantiation.
      SourceRange InstantiationRange;
  
      CodeSynthesisContext()
          : Kind(TemplateInstantiation),
            SavedInNonInstantiationSFINAEContext(false), Entity(nullptr),
            Template(nullptr), TemplateArgs(nullptr), NumTemplateArgs(0),
            DeductionInfo(nullptr) {}
  
      /// Determines whether this template is an actual instantiation
      /// that should be counted toward the maximum instantiation depth.
      bool isInstantiationRecord() const;
    };
  
    /// List of active code synthesis contexts.
    ///
    /// This vector is treated as a stack. As synthesis of one entity requires
    /// synthesis of another, additional contexts are pushed onto the stack.
    SmallVector<CodeSynthesisContext, 16> CodeSynthesisContexts;
  
    /// Specializations whose definitions are currently being instantiated.
    llvm::DenseSet<std::pair<Decl *, unsigned>> InstantiatingSpecializations;
  
    /// Non-dependent types used in templates that have already been instantiated
    /// by some template instantiation.
    llvm::DenseSet<QualType> InstantiatedNonDependentTypes;
  
    /// Extra modules inspected when performing a lookup during a template
    /// instantiation. Computed lazily.
    SmallVector<Module*, 16> CodeSynthesisContextLookupModules;
  
    /// Cache of additional modules that should be used for name lookup
    /// within the current template instantiation. Computed lazily; use
    /// getLookupModules() to get a complete set.
    llvm::DenseSet<Module*> LookupModulesCache;
  
    /// Get the set of additional modules that should be checked during
    /// name lookup. A module and its imports become visible when instanting a
    /// template defined within it.
    llvm::DenseSet<Module*> &getLookupModules();
  
    /// Map from the most recent declaration of a namespace to the most
    /// recent visible declaration of that namespace.
    llvm::DenseMap<NamedDecl*, NamedDecl*> VisibleNamespaceCache;
  
    /// Whether we are in a SFINAE context that is not associated with
    /// template instantiation.
    ///
    /// This is used when setting up a SFINAE trap (\c see SFINAETrap) outside
    /// of a template instantiation or template argument deduction.
    bool InNonInstantiationSFINAEContext;
  
    /// The number of \p CodeSynthesisContexts that are not template
    /// instantiations and, therefore, should not be counted as part of the
    /// instantiation depth.
    ///
    /// When the instantiation depth reaches the user-configurable limit
    /// \p LangOptions::InstantiationDepth we will abort instantiation.
    // FIXME: Should we have a similar limit for other forms of synthesis?
    unsigned NonInstantiationEntries;
  
    /// The depth of the context stack at the point when the most recent
    /// error or warning was produced.
    ///
    /// This value is used to suppress printing of redundant context stacks
    /// when there are multiple errors or warnings in the same instantiation.
    // FIXME: Does this belong in Sema? It's tough to implement it anywhere else.
    unsigned LastEmittedCodeSynthesisContextDepth = 0;
  
    /// The template instantiation callbacks to trace or track
    /// instantiations (objects can be chained).
    ///
    /// This callbacks is used to print, trace or track template
    /// instantiations as they are being constructed.
    std::vector<std::unique_ptr<TemplateInstantiationCallback>>
        TemplateInstCallbacks;
  
    /// The current index into pack expansion arguments that will be
    /// used for substitution of parameter packs.
    ///
    /// The pack expansion index will be -1 to indicate that parameter packs
    /// should be instantiated as themselves. Otherwise, the index specifies
    /// which argument within the parameter pack will be used for substitution.
    int ArgumentPackSubstitutionIndex;
  
    /// RAII object used to change the argument pack substitution index
    /// within a \c Sema object.
    ///
    /// See \c ArgumentPackSubstitutionIndex for more information.
    class ArgumentPackSubstitutionIndexRAII {
      Sema &Self;
      int OldSubstitutionIndex;
  
    public:
      ArgumentPackSubstitutionIndexRAII(Sema &Self, int NewSubstitutionIndex)
        : Self(Self), OldSubstitutionIndex(Self.ArgumentPackSubstitutionIndex) {
        Self.ArgumentPackSubstitutionIndex = NewSubstitutionIndex;
      }
  
      ~ArgumentPackSubstitutionIndexRAII() {
        Self.ArgumentPackSubstitutionIndex = OldSubstitutionIndex;
      }
    };
  
    friend class ArgumentPackSubstitutionRAII;
  
    /// For each declaration that involved template argument deduction, the
    /// set of diagnostics that were suppressed during that template argument
    /// deduction.
    ///
    /// FIXME: Serialize this structure to the AST file.
    typedef llvm::DenseMap<Decl *, SmallVector<PartialDiagnosticAt, 1> >
      SuppressedDiagnosticsMap;
    SuppressedDiagnosticsMap SuppressedDiagnostics;
  
    /// A stack object to be created when performing template
    /// instantiation.
    ///
    /// Construction of an object of type \c InstantiatingTemplate
    /// pushes the current instantiation onto the stack of active
    /// instantiations. If the size of this stack exceeds the maximum
    /// number of recursive template instantiations, construction
    /// produces an error and evaluates true.
    ///
    /// Destruction of this object will pop the named instantiation off
    /// the stack.
    struct InstantiatingTemplate {
      /// Note that we are instantiating a class template,
      /// function template, variable template, alias template,
      /// or a member thereof.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            Decl *Entity,
                            SourceRange InstantiationRange = SourceRange());
  
      struct ExceptionSpecification {};
      /// Note that we are instantiating an exception specification
      /// of a function template.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            FunctionDecl *Entity, ExceptionSpecification,
                            SourceRange InstantiationRange = SourceRange());
  
      /// Note that we are instantiating a default argument in a
      /// template-id.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            TemplateParameter Param, TemplateDecl *Template,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            SourceRange InstantiationRange = SourceRange());
  
      /// Note that we are substituting either explicitly-specified or
      /// deduced template arguments during function template argument deduction.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            FunctionTemplateDecl *FunctionTemplate,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            CodeSynthesisContext::SynthesisKind Kind,
                            sema::TemplateDeductionInfo &DeductionInfo,
                            SourceRange InstantiationRange = SourceRange());
  
      /// Note that we are instantiating as part of template
      /// argument deduction for a class template declaration.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            TemplateDecl *Template,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            sema::TemplateDeductionInfo &DeductionInfo,
                            SourceRange InstantiationRange = SourceRange());
  
      /// Note that we are instantiating as part of template
      /// argument deduction for a class template partial
      /// specialization.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            ClassTemplatePartialSpecializationDecl *PartialSpec,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            sema::TemplateDeductionInfo &DeductionInfo,
                            SourceRange InstantiationRange = SourceRange());
  
      /// Note that we are instantiating as part of template
      /// argument deduction for a variable template partial
      /// specialization.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            VarTemplatePartialSpecializationDecl *PartialSpec,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            sema::TemplateDeductionInfo &DeductionInfo,
                            SourceRange InstantiationRange = SourceRange());
  
      /// Note that we are instantiating a default argument for a function
      /// parameter.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            ParmVarDecl *Param,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            SourceRange InstantiationRange = SourceRange());
  
      /// Note that we are substituting prior template arguments into a
      /// non-type parameter.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            NamedDecl *Template,
                            NonTypeTemplateParmDecl *Param,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            SourceRange InstantiationRange);
  
      /// Note that we are substituting prior template arguments into a
      /// template template parameter.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            NamedDecl *Template,
                            TemplateTemplateParmDecl *Param,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            SourceRange InstantiationRange);
  
      /// Note that we are checking the default template argument
      /// against the template parameter for a given template-id.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            TemplateDecl *Template,
                            NamedDecl *Param,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            SourceRange InstantiationRange);
  
      struct ConstraintsCheck {};
      /// \brief Note that we are checking the constraints associated with some
      /// constrained entity (a concept declaration or a template with associated
      /// constraints).
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            ConstraintsCheck, NamedDecl *Template,
                            ArrayRef<TemplateArgument> TemplateArgs,
                            SourceRange InstantiationRange);
  
      struct ConstraintSubstitution {};
      /// \brief Note that we are checking a constraint expression associated
      /// with a template declaration or as part of the satisfaction check of a
      /// concept.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            ConstraintSubstitution, NamedDecl *Template,
                            sema::TemplateDeductionInfo &DeductionInfo,
                            SourceRange InstantiationRange);
  
      struct ConstraintNormalization {};
      /// \brief Note that we are normalizing a constraint expression.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            ConstraintNormalization, NamedDecl *Template,
                            SourceRange InstantiationRange);
  
      struct ParameterMappingSubstitution {};
      /// \brief Note that we are subtituting into the parameter mapping of an
      /// atomic constraint during constraint normalization.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            ParameterMappingSubstitution, NamedDecl *Template,
                            SourceRange InstantiationRange);
  
      /// \brief Note that we are substituting template arguments into a part of
      /// a requirement of a requires expression.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            concepts::Requirement *Req,
                            sema::TemplateDeductionInfo &DeductionInfo,
                            SourceRange InstantiationRange = SourceRange());
  
      /// \brief Note that we are checking the satisfaction of the constraint
      /// expression inside of a nested requirement.
      InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
                            concepts::NestedRequirement *Req, ConstraintsCheck,
                            SourceRange InstantiationRange = SourceRange());
  
      /// Note that we have finished instantiating this template.
      void Clear();
  
      ~InstantiatingTemplate() { Clear(); }
  
      /// Determines whether we have exceeded the maximum
      /// recursive template instantiations.
      bool isInvalid() const { return Invalid; }
  
      /// Determine whether we are already instantiating this
      /// specialization in some surrounding active instantiation.
      bool isAlreadyInstantiating() const { return AlreadyInstantiating; }
  
    private:
      Sema &SemaRef;
      bool Invalid;
      bool AlreadyInstantiating;
      bool CheckInstantiationDepth(SourceLocation PointOfInstantiation,
                                   SourceRange InstantiationRange);
  
      InstantiatingTemplate(
          Sema &SemaRef, CodeSynthesisContext::SynthesisKind Kind,
          SourceLocation PointOfInstantiation, SourceRange InstantiationRange,
          Decl *Entity, NamedDecl *Template = nullptr,
          ArrayRef<TemplateArgument> TemplateArgs = None,
          sema::TemplateDeductionInfo *DeductionInfo = nullptr);
  
      InstantiatingTemplate(const InstantiatingTemplate&) = delete;
  
      InstantiatingTemplate&
      operator=(const InstantiatingTemplate&) = delete;
    };
  
    void pushCodeSynthesisContext(CodeSynthesisContext Ctx);
    void popCodeSynthesisContext();
  
    /// Determine whether we are currently performing template instantiation.
    bool inTemplateInstantiation() const {
      return CodeSynthesisContexts.size() > NonInstantiationEntries;
    }
  
    void PrintContextStack() {
      if (!CodeSynthesisContexts.empty() &&
          CodeSynthesisContexts.size() != LastEmittedCodeSynthesisContextDepth) {
        PrintInstantiationStack();
        LastEmittedCodeSynthesisContextDepth = CodeSynthesisContexts.size();
      }
      if (PragmaAttributeCurrentTargetDecl)
        PrintPragmaAttributeInstantiationPoint();
    }
    void PrintInstantiationStack();
  
    void PrintPragmaAttributeInstantiationPoint();
  
    /// Determines whether we are currently in a context where
    /// template argument substitution failures are not considered
    /// errors.
    ///
    /// \returns An empty \c Optional if we're not in a SFINAE context.
    /// Otherwise, contains a pointer that, if non-NULL, contains the nearest
    /// template-deduction context object, which can be used to capture
    /// diagnostics that will be suppressed.
    Optional<sema::TemplateDeductionInfo *> isSFINAEContext() const;
  
    /// Determines whether we are currently in a context that
    /// is not evaluated as per C++ [expr] p5.
    bool isUnevaluatedContext() const {
      assert(!ExprEvalContexts.empty() &&
             "Must be in an expression evaluation context");
      return ExprEvalContexts.back().isUnevaluated();
    }
  
    /// RAII class used to determine whether SFINAE has
    /// trapped any errors that occur during template argument
    /// deduction.
    class SFINAETrap {
      Sema &SemaRef;
      unsigned PrevSFINAEErrors;
      bool PrevInNonInstantiationSFINAEContext;
      bool PrevAccessCheckingSFINAE;
      bool PrevLastDiagnosticIgnored;
  
    public:
      explicit SFINAETrap(Sema &SemaRef, bool AccessCheckingSFINAE = false)
        : SemaRef(SemaRef), PrevSFINAEErrors(SemaRef.NumSFINAEErrors),
          PrevInNonInstantiationSFINAEContext(
                                        SemaRef.InNonInstantiationSFINAEContext),
          PrevAccessCheckingSFINAE(SemaRef.AccessCheckingSFINAE),
          PrevLastDiagnosticIgnored(
              SemaRef.getDiagnostics().isLastDiagnosticIgnored())
      {
        if (!SemaRef.isSFINAEContext())
          SemaRef.InNonInstantiationSFINAEContext = true;
        SemaRef.AccessCheckingSFINAE = AccessCheckingSFINAE;
      }
  
      ~SFINAETrap() {
        SemaRef.NumSFINAEErrors = PrevSFINAEErrors;
        SemaRef.InNonInstantiationSFINAEContext
          = PrevInNonInstantiationSFINAEContext;
        SemaRef.AccessCheckingSFINAE = PrevAccessCheckingSFINAE;
        SemaRef.getDiagnostics().setLastDiagnosticIgnored(
            PrevLastDiagnosticIgnored);
      }
  
      /// Determine whether any SFINAE errors have been trapped.
      bool hasErrorOccurred() const {
        return SemaRef.NumSFINAEErrors > PrevSFINAEErrors;
      }
    };
  
    /// RAII class used to indicate that we are performing provisional
    /// semantic analysis to determine the validity of a construct, so
    /// typo-correction and diagnostics in the immediate context (not within
    /// implicitly-instantiated templates) should be suppressed.
    class TentativeAnalysisScope {
      Sema &SemaRef;
      // FIXME: Using a SFINAETrap for this is a hack.
      SFINAETrap Trap;
      bool PrevDisableTypoCorrection;
    public:
      explicit TentativeAnalysisScope(Sema &SemaRef)
          : SemaRef(SemaRef), Trap(SemaRef, true),
            PrevDisableTypoCorrection(SemaRef.DisableTypoCorrection) {
        SemaRef.DisableTypoCorrection = true;
      }
      ~TentativeAnalysisScope() {
        SemaRef.DisableTypoCorrection = PrevDisableTypoCorrection;
      }
    };
  
    /// The current instantiation scope used to store local
    /// variables.
    LocalInstantiationScope *CurrentInstantiationScope;
  
    /// Tracks whether we are in a context where typo correction is
    /// disabled.
    bool DisableTypoCorrection;
  
    /// The number of typos corrected by CorrectTypo.
    unsigned TyposCorrected;
  
    typedef llvm::SmallSet<SourceLocation, 2> SrcLocSet;
    typedef llvm::DenseMap<IdentifierInfo *, SrcLocSet> IdentifierSourceLocations;
  
    /// A cache containing identifiers for which typo correction failed and
    /// their locations, so that repeated attempts to correct an identifier in a
    /// given location are ignored if typo correction already failed for it.
    IdentifierSourceLocations TypoCorrectionFailures;
  
    /// Worker object for performing CFG-based warnings.
    sema::AnalysisBasedWarnings AnalysisWarnings;
    threadSafety::BeforeSet *ThreadSafetyDeclCache;
  
    /// An entity for which implicit template instantiation is required.
    ///
    /// The source location associated with the declaration is the first place in
    /// the source code where the declaration was "used". It is not necessarily
    /// the point of instantiation (which will be either before or after the
    /// namespace-scope declaration that triggered this implicit instantiation),
    /// However, it is the location that diagnostics should generally refer to,
    /// because users will need to know what code triggered the instantiation.
    typedef std::pair<ValueDecl *, SourceLocation> PendingImplicitInstantiation;
  
    /// The queue of implicit template instantiations that are required
    /// but have not yet been performed.
    std::deque<PendingImplicitInstantiation> PendingInstantiations;
  
    /// Queue of implicit template instantiations that cannot be performed
    /// eagerly.
    SmallVector<PendingImplicitInstantiation, 1> LateParsedInstantiations;
  
    class GlobalEagerInstantiationScope {
    public:
      GlobalEagerInstantiationScope(Sema &S, bool Enabled)
          : S(S), Enabled(Enabled) {
        if (!Enabled) return;
  
        SavedPendingInstantiations.swap(S.PendingInstantiations);
        SavedVTableUses.swap(S.VTableUses);
      }
  
      void perform() {
        if (Enabled) {
          S.DefineUsedVTables();
          S.PerformPendingInstantiations();
        }
      }
  
      ~GlobalEagerInstantiationScope() {
        if (!Enabled) return;
  
        // Restore the set of pending vtables.
        assert(S.VTableUses.empty() &&
               "VTableUses should be empty before it is discarded.");
        S.VTableUses.swap(SavedVTableUses);
  
        // Restore the set of pending implicit instantiations.
        assert(S.PendingInstantiations.empty() &&
               "PendingInstantiations should be empty before it is discarded.");
        S.PendingInstantiations.swap(SavedPendingInstantiations);
      }
  
    private:
      Sema &S;
      SmallVector<VTableUse, 16> SavedVTableUses;
      std::deque<PendingImplicitInstantiation> SavedPendingInstantiations;
      bool Enabled;
    };
  
    /// The queue of implicit template instantiations that are required
    /// and must be performed within the current local scope.
    ///
    /// This queue is only used for member functions of local classes in
    /// templates, which must be instantiated in the same scope as their
    /// enclosing function, so that they can reference function-local
    /// types, static variables, enumerators, etc.
    std::deque<PendingImplicitInstantiation> PendingLocalImplicitInstantiations;
  
    class LocalEagerInstantiationScope {
    public:
      LocalEagerInstantiationScope(Sema &S) : S(S) {
        SavedPendingLocalImplicitInstantiations.swap(
            S.PendingLocalImplicitInstantiations);
      }
  
      void perform() { S.PerformPendingInstantiations(/*LocalOnly=*/true); }
  
      ~LocalEagerInstantiationScope() {
        assert(S.PendingLocalImplicitInstantiations.empty() &&
               "there shouldn't be any pending local implicit instantiations");
        SavedPendingLocalImplicitInstantiations.swap(
            S.PendingLocalImplicitInstantiations);
      }
  
    private:
      Sema &S;
      std::deque<PendingImplicitInstantiation>
          SavedPendingLocalImplicitInstantiations;
    };
  
    /// A helper class for building up ExtParameterInfos.
    class ExtParameterInfoBuilder {
      SmallVector<FunctionProtoType::ExtParameterInfo, 16> Infos;
      bool HasInteresting = false;
  
    public:
      /// Set the ExtParameterInfo for the parameter at the given index,
      ///
      void set(unsigned index, FunctionProtoType::ExtParameterInfo info) {
        assert(Infos.size() <= index);
        Infos.resize(index);
        Infos.push_back(info);
  
        if (!HasInteresting)
          HasInteresting = (info != FunctionProtoType::ExtParameterInfo());
      }
  
      /// Return a pointer (suitable for setting in an ExtProtoInfo) to the
      /// ExtParameterInfo array we've built up.
      const FunctionProtoType::ExtParameterInfo *
      getPointerOrNull(unsigned numParams) {
        if (!HasInteresting) return nullptr;
        Infos.resize(numParams);
        return Infos.data();
      }
    };
  
    void PerformPendingInstantiations(bool LocalOnly = false);
  
    TypeSourceInfo *SubstType(TypeSourceInfo *T,
                              const MultiLevelTemplateArgumentList &TemplateArgs,
                              SourceLocation Loc, DeclarationName Entity,
                              bool AllowDeducedTST = false);
  
    QualType SubstType(QualType T,
                       const MultiLevelTemplateArgumentList &TemplateArgs,
                       SourceLocation Loc, DeclarationName Entity);
  
    TypeSourceInfo *SubstType(TypeLoc TL,
                              const MultiLevelTemplateArgumentList &TemplateArgs,
                              SourceLocation Loc, DeclarationName Entity);
  
    TypeSourceInfo *SubstFunctionDeclType(TypeSourceInfo *T,
                              const MultiLevelTemplateArgumentList &TemplateArgs,
                                          SourceLocation Loc,
                                          DeclarationName Entity,
                                          CXXRecordDecl *ThisContext,
                                          Qualifiers ThisTypeQuals);
    void SubstExceptionSpec(FunctionDecl *New, const FunctionProtoType *Proto,
                            const MultiLevelTemplateArgumentList &Args);
    bool SubstExceptionSpec(SourceLocation Loc,
                            FunctionProtoType::ExceptionSpecInfo &ESI,
                            SmallVectorImpl<QualType> &ExceptionStorage,
                            const MultiLevelTemplateArgumentList &Args);
    ParmVarDecl *SubstParmVarDecl(ParmVarDecl *D,
                              const MultiLevelTemplateArgumentList &TemplateArgs,
                                  int indexAdjustment,
                                  Optional<unsigned> NumExpansions,
                                  bool ExpectParameterPack);
    bool SubstParmTypes(SourceLocation Loc, ArrayRef<ParmVarDecl *> Params,
                        const FunctionProtoType::ExtParameterInfo *ExtParamInfos,
                        const MultiLevelTemplateArgumentList &TemplateArgs,
                        SmallVectorImpl<QualType> &ParamTypes,
                        SmallVectorImpl<ParmVarDecl *> *OutParams,
                        ExtParameterInfoBuilder &ParamInfos);
    ExprResult SubstExpr(Expr *E,
                         const MultiLevelTemplateArgumentList &TemplateArgs);
  
    /// Substitute the given template arguments into a list of
    /// expressions, expanding pack expansions if required.
    ///
    /// \param Exprs The list of expressions to substitute into.
    ///
    /// \param IsCall Whether this is some form of call, in which case
    /// default arguments will be dropped.
    ///
    /// \param TemplateArgs The set of template arguments to substitute.
    ///
    /// \param Outputs Will receive all of the substituted arguments.
    ///
    /// \returns true if an error occurred, false otherwise.
    bool SubstExprs(ArrayRef<Expr *> Exprs, bool IsCall,
                    const MultiLevelTemplateArgumentList &TemplateArgs,
                    SmallVectorImpl<Expr *> &Outputs);
  
    StmtResult SubstStmt(Stmt *S,
                         const MultiLevelTemplateArgumentList &TemplateArgs);
  
    TemplateParameterList *
    SubstTemplateParams(TemplateParameterList *Params, DeclContext *Owner,
                        const MultiLevelTemplateArgumentList &TemplateArgs);
  
    bool
    SubstTemplateArguments(ArrayRef<TemplateArgumentLoc> Args,
                           const MultiLevelTemplateArgumentList &TemplateArgs,
                           TemplateArgumentListInfo &Outputs);
  
  
    Decl *SubstDecl(Decl *D, DeclContext *Owner,
                    const MultiLevelTemplateArgumentList &TemplateArgs);
  
    /// Substitute the name and return type of a defaulted 'operator<=>' to form
    /// an implicit 'operator=='.
    FunctionDecl *SubstSpaceshipAsEqualEqual(CXXRecordDecl *RD,
                                             FunctionDecl *Spaceship);
  
    ExprResult SubstInitializer(Expr *E,
                         const MultiLevelTemplateArgumentList &TemplateArgs,
                         bool CXXDirectInit);
  
    bool
    SubstBaseSpecifiers(CXXRecordDecl *Instantiation,
                        CXXRecordDecl *Pattern,
                        const MultiLevelTemplateArgumentList &TemplateArgs);
  
    bool
    InstantiateClass(SourceLocation PointOfInstantiation,
                     CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
                     const MultiLevelTemplateArgumentList &TemplateArgs,
                     TemplateSpecializationKind TSK,
                     bool Complain = true);
  
    bool InstantiateEnum(SourceLocation PointOfInstantiation,
                         EnumDecl *Instantiation, EnumDecl *Pattern,
                         const MultiLevelTemplateArgumentList &TemplateArgs,
                         TemplateSpecializationKind TSK);
  
    bool InstantiateInClassInitializer(
        SourceLocation PointOfInstantiation, FieldDecl *Instantiation,
        FieldDecl *Pattern, const MultiLevelTemplateArgumentList &TemplateArgs);
  
    struct LateInstantiatedAttribute {
      const Attr *TmplAttr;
      LocalInstantiationScope *Scope;
      Decl *NewDecl;
  
      LateInstantiatedAttribute(const Attr *A, LocalInstantiationScope *S,
                                Decl *D)
        : TmplAttr(A), Scope(S), NewDecl(D)
      { }
    };
    typedef SmallVector<LateInstantiatedAttribute, 16> LateInstantiatedAttrVec;
  
    void InstantiateAttrs(const MultiLevelTemplateArgumentList &TemplateArgs,
                          const Decl *Pattern, Decl *Inst,
                          LateInstantiatedAttrVec *LateAttrs = nullptr,
                          LocalInstantiationScope *OuterMostScope = nullptr);
  
    void
    InstantiateAttrsForDecl(const MultiLevelTemplateArgumentList &TemplateArgs,
                            const Decl *Pattern, Decl *Inst,
                            LateInstantiatedAttrVec *LateAttrs = nullptr,
                            LocalInstantiationScope *OuterMostScope = nullptr);
  
    bool usesPartialOrExplicitSpecialization(
        SourceLocation Loc, ClassTemplateSpecializationDecl *ClassTemplateSpec);
  
    bool
    InstantiateClassTemplateSpecialization(SourceLocation PointOfInstantiation,
                             ClassTemplateSpecializationDecl *ClassTemplateSpec,
                             TemplateSpecializationKind TSK,
                             bool Complain = true);
  
    void InstantiateClassMembers(SourceLocation PointOfInstantiation,
                                 CXXRecordDecl *Instantiation,
                              const MultiLevelTemplateArgumentList &TemplateArgs,
                                 TemplateSpecializationKind TSK);
  
    void InstantiateClassTemplateSpecializationMembers(
                                            SourceLocation PointOfInstantiation,
                             ClassTemplateSpecializationDecl *ClassTemplateSpec,
                                                  TemplateSpecializationKind TSK);
  
    NestedNameSpecifierLoc
    SubstNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS,
                             const MultiLevelTemplateArgumentList &TemplateArgs);
  
    DeclarationNameInfo
    SubstDeclarationNameInfo(const DeclarationNameInfo &NameInfo,
                             const MultiLevelTemplateArgumentList &TemplateArgs);
    TemplateName
    SubstTemplateName(NestedNameSpecifierLoc QualifierLoc, TemplateName Name,
                      SourceLocation Loc,
                      const MultiLevelTemplateArgumentList &TemplateArgs);
    bool Subst(const TemplateArgumentLoc *Args, unsigned NumArgs,
               TemplateArgumentListInfo &Result,
               const MultiLevelTemplateArgumentList &TemplateArgs);
  
    void InstantiateExceptionSpec(SourceLocation PointOfInstantiation,
                                  FunctionDecl *Function);
    bool CheckInstantiatedFunctionTemplateConstraints(
        SourceLocation PointOfInstantiation, FunctionDecl *Decl,
        ArrayRef<TemplateArgument> TemplateArgs,
        ConstraintSatisfaction &Satisfaction);
    FunctionDecl *InstantiateFunctionDeclaration(FunctionTemplateDecl *FTD,
                                                 const TemplateArgumentList *Args,
                                                 SourceLocation Loc);
    void InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
                                       FunctionDecl *Function,
                                       bool Recursive = false,
                                       bool DefinitionRequired = false,
                                       bool AtEndOfTU = false);
    VarTemplateSpecializationDecl *BuildVarTemplateInstantiation(
        VarTemplateDecl *VarTemplate, VarDecl *FromVar,
        const TemplateArgumentList &TemplateArgList,
        const TemplateArgumentListInfo &TemplateArgsInfo,
        SmallVectorImpl<TemplateArgument> &Converted,
        SourceLocation PointOfInstantiation, void *InsertPos,
        LateInstantiatedAttrVec *LateAttrs = nullptr,
        LocalInstantiationScope *StartingScope = nullptr);
    VarTemplateSpecializationDecl *CompleteVarTemplateSpecializationDecl(
        VarTemplateSpecializationDecl *VarSpec, VarDecl *PatternDecl,
        const MultiLevelTemplateArgumentList &TemplateArgs);
    void
    BuildVariableInstantiation(VarDecl *NewVar, VarDecl *OldVar,
                               const MultiLevelTemplateArgumentList &TemplateArgs,
                               LateInstantiatedAttrVec *LateAttrs,
                               DeclContext *Owner,
                               LocalInstantiationScope *StartingScope,
                               bool InstantiatingVarTemplate = false,
                               VarTemplateSpecializationDecl *PrevVTSD = nullptr);
  
    VarDecl *getVarTemplateSpecialization(
        VarTemplateDecl *VarTempl, const TemplateArgumentListInfo *TemplateArgs,
        const DeclarationNameInfo &MemberNameInfo, SourceLocation TemplateKWLoc);
  
    void InstantiateVariableInitializer(
        VarDecl *Var, VarDecl *OldVar,
        const MultiLevelTemplateArgumentList &TemplateArgs);
    void InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
                                       VarDecl *Var, bool Recursive = false,
                                       bool DefinitionRequired = false,
                                       bool AtEndOfTU = false);
  
    void InstantiateMemInitializers(CXXConstructorDecl *New,
                                    const CXXConstructorDecl *Tmpl,
                              const MultiLevelTemplateArgumentList &TemplateArgs);
  
    NamedDecl *FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
                            const MultiLevelTemplateArgumentList &TemplateArgs,
                            bool FindingInstantiatedContext = false);
    DeclContext *FindInstantiatedContext(SourceLocation Loc, DeclContext *DC,
                            const MultiLevelTemplateArgumentList &TemplateArgs);
  
    // Objective-C declarations.
    enum ObjCContainerKind {
      OCK_None = -1,
      OCK_Interface = 0,
      OCK_Protocol,
      OCK_Category,
      OCK_ClassExtension,
      OCK_Implementation,
      OCK_CategoryImplementation
    };
    ObjCContainerKind getObjCContainerKind() const;
  
    DeclResult actOnObjCTypeParam(Scope *S,
                                  ObjCTypeParamVariance variance,
                                  SourceLocation varianceLoc,
                                  unsigned index,
                                  IdentifierInfo *paramName,
                                  SourceLocation paramLoc,
                                  SourceLocation colonLoc,
                                  ParsedType typeBound);
  
    ObjCTypeParamList *actOnObjCTypeParamList(Scope *S, SourceLocation lAngleLoc,
                                              ArrayRef<Decl *> typeParams,
                                              SourceLocation rAngleLoc);
    void popObjCTypeParamList(Scope *S, ObjCTypeParamList *typeParamList);
  
    Decl *ActOnStartClassInterface(
        Scope *S, SourceLocation AtInterfaceLoc, IdentifierInfo *ClassName,
        SourceLocation ClassLoc, ObjCTypeParamList *typeParamList,
        IdentifierInfo *SuperName, SourceLocation SuperLoc,
        ArrayRef<ParsedType> SuperTypeArgs, SourceRange SuperTypeArgsRange,
        Decl *const *ProtoRefs, unsigned NumProtoRefs,
        const SourceLocation *ProtoLocs, SourceLocation EndProtoLoc,
        const ParsedAttributesView &AttrList);
  
    void ActOnSuperClassOfClassInterface(Scope *S,
                                         SourceLocation AtInterfaceLoc,
                                         ObjCInterfaceDecl *IDecl,
                                         IdentifierInfo *ClassName,
                                         SourceLocation ClassLoc,
                                         IdentifierInfo *SuperName,
                                         SourceLocation SuperLoc,
                                         ArrayRef<ParsedType> SuperTypeArgs,
                                         SourceRange SuperTypeArgsRange);
  
    void ActOnTypedefedProtocols(SmallVectorImpl<Decl *> &ProtocolRefs,
                                 SmallVectorImpl<SourceLocation> &ProtocolLocs,
                                 IdentifierInfo *SuperName,
                                 SourceLocation SuperLoc);
  
    Decl *ActOnCompatibilityAlias(
                      SourceLocation AtCompatibilityAliasLoc,
                      IdentifierInfo *AliasName,  SourceLocation AliasLocation,
                      IdentifierInfo *ClassName, SourceLocation ClassLocation);
  
    bool CheckForwardProtocolDeclarationForCircularDependency(
      IdentifierInfo *PName,
      SourceLocation &PLoc, SourceLocation PrevLoc,
      const ObjCList<ObjCProtocolDecl> &PList);
  
    Decl *ActOnStartProtocolInterface(
        SourceLocation AtProtoInterfaceLoc, IdentifierInfo *ProtocolName,
        SourceLocation ProtocolLoc, Decl *const *ProtoRefNames,
        unsigned NumProtoRefs, const SourceLocation *ProtoLocs,
        SourceLocation EndProtoLoc, const ParsedAttributesView &AttrList);
  
    Decl *ActOnStartCategoryInterface(
        SourceLocation AtInterfaceLoc, IdentifierInfo *ClassName,
        SourceLocation ClassLoc, ObjCTypeParamList *typeParamList,
        IdentifierInfo *CategoryName, SourceLocation CategoryLoc,
        Decl *const *ProtoRefs, unsigned NumProtoRefs,
        const SourceLocation *ProtoLocs, SourceLocation EndProtoLoc,
        const ParsedAttributesView &AttrList);
  
    Decl *ActOnStartClassImplementation(SourceLocation AtClassImplLoc,
                                        IdentifierInfo *ClassName,
                                        SourceLocation ClassLoc,
                                        IdentifierInfo *SuperClassname,
                                        SourceLocation SuperClassLoc,
                                        const ParsedAttributesView &AttrList);
  
    Decl *ActOnStartCategoryImplementation(SourceLocation AtCatImplLoc,
                                           IdentifierInfo *ClassName,
                                           SourceLocation ClassLoc,
                                           IdentifierInfo *CatName,
                                           SourceLocation CatLoc,
                                           const ParsedAttributesView &AttrList);
  
    DeclGroupPtrTy ActOnFinishObjCImplementation(Decl *ObjCImpDecl,
                                                 ArrayRef<Decl *> Decls);
  
    DeclGroupPtrTy ActOnForwardClassDeclaration(SourceLocation Loc,
                     IdentifierInfo **IdentList,
                     SourceLocation *IdentLocs,
                     ArrayRef<ObjCTypeParamList *> TypeParamLists,
                     unsigned NumElts);
  
    DeclGroupPtrTy
    ActOnForwardProtocolDeclaration(SourceLocation AtProtoclLoc,
                                    ArrayRef<IdentifierLocPair> IdentList,
                                    const ParsedAttributesView &attrList);
  
    void FindProtocolDeclaration(bool WarnOnDeclarations, bool ForObjCContainer,
                                 ArrayRef<IdentifierLocPair> ProtocolId,
                                 SmallVectorImpl<Decl *> &Protocols);
  
    void DiagnoseTypeArgsAndProtocols(IdentifierInfo *ProtocolId,
                                      SourceLocation ProtocolLoc,
                                      IdentifierInfo *TypeArgId,
                                      SourceLocation TypeArgLoc,
                                      bool SelectProtocolFirst = false);
  
    /// Given a list of identifiers (and their locations), resolve the
    /// names to either Objective-C protocol qualifiers or type
    /// arguments, as appropriate.
    void actOnObjCTypeArgsOrProtocolQualifiers(
           Scope *S,
           ParsedType baseType,
           SourceLocation lAngleLoc,
           ArrayRef<IdentifierInfo *> identifiers,
           ArrayRef<SourceLocation> identifierLocs,
           SourceLocation rAngleLoc,
           SourceLocation &typeArgsLAngleLoc,
           SmallVectorImpl<ParsedType> &typeArgs,
           SourceLocation &typeArgsRAngleLoc,
           SourceLocation &protocolLAngleLoc,
           SmallVectorImpl<Decl *> &protocols,
           SourceLocation &protocolRAngleLoc,
           bool warnOnIncompleteProtocols);
  
    /// Build a an Objective-C protocol-qualified 'id' type where no
    /// base type was specified.
    TypeResult actOnObjCProtocolQualifierType(
                 SourceLocation lAngleLoc,
                 ArrayRef<Decl *> protocols,
                 ArrayRef<SourceLocation> protocolLocs,
                 SourceLocation rAngleLoc);
  
    /// Build a specialized and/or protocol-qualified Objective-C type.
    TypeResult actOnObjCTypeArgsAndProtocolQualifiers(
                 Scope *S,
                 SourceLocation Loc,
                 ParsedType BaseType,
                 SourceLocation TypeArgsLAngleLoc,
                 ArrayRef<ParsedType> TypeArgs,
                 SourceLocation TypeArgsRAngleLoc,
                 SourceLocation ProtocolLAngleLoc,
                 ArrayRef<Decl *> Protocols,
                 ArrayRef<SourceLocation> ProtocolLocs,
                 SourceLocation ProtocolRAngleLoc);
  
    /// Build an Objective-C type parameter type.
    QualType BuildObjCTypeParamType(const ObjCTypeParamDecl *Decl,
                                    SourceLocation ProtocolLAngleLoc,
                                    ArrayRef<ObjCProtocolDecl *> Protocols,
                                    ArrayRef<SourceLocation> ProtocolLocs,
                                    SourceLocation ProtocolRAngleLoc,
                                    bool FailOnError = false);
  
    /// Build an Objective-C object pointer type.
    QualType BuildObjCObjectType(QualType BaseType,
                                 SourceLocation Loc,
                                 SourceLocation TypeArgsLAngleLoc,
                                 ArrayRef<TypeSourceInfo *> TypeArgs,
                                 SourceLocation TypeArgsRAngleLoc,
                                 SourceLocation ProtocolLAngleLoc,
                                 ArrayRef<ObjCProtocolDecl *> Protocols,
                                 ArrayRef<SourceLocation> ProtocolLocs,
                                 SourceLocation ProtocolRAngleLoc,
                                 bool FailOnError = false);
  
    /// Ensure attributes are consistent with type.
    /// \param [in, out] Attributes The attributes to check; they will
    /// be modified to be consistent with \p PropertyTy.
    void CheckObjCPropertyAttributes(Decl *PropertyPtrTy,
                                     SourceLocation Loc,
                                     unsigned &Attributes,
                                     bool propertyInPrimaryClass);
  
    /// Process the specified property declaration and create decls for the
    /// setters and getters as needed.
    /// \param property The property declaration being processed
    void ProcessPropertyDecl(ObjCPropertyDecl *property);
  
  
    void DiagnosePropertyMismatch(ObjCPropertyDecl *Property,
                                  ObjCPropertyDecl *SuperProperty,
                                  const IdentifierInfo *Name,
                                  bool OverridingProtocolProperty);
  
    void DiagnoseClassExtensionDupMethods(ObjCCategoryDecl *CAT,
                                          ObjCInterfaceDecl *ID);
  
    Decl *ActOnAtEnd(Scope *S, SourceRange AtEnd,
                     ArrayRef<Decl *> allMethods = None,
                     ArrayRef<DeclGroupPtrTy> allTUVars = None);
  
    Decl *ActOnProperty(Scope *S, SourceLocation AtLoc,
                        SourceLocation LParenLoc,
                        FieldDeclarator &FD, ObjCDeclSpec &ODS,
                        Selector GetterSel, Selector SetterSel,
                        tok::ObjCKeywordKind MethodImplKind,
                        DeclContext *lexicalDC = nullptr);
  
    Decl *ActOnPropertyImplDecl(Scope *S,
                                SourceLocation AtLoc,
                                SourceLocation PropertyLoc,
                                bool ImplKind,
                                IdentifierInfo *PropertyId,
                                IdentifierInfo *PropertyIvar,
                                SourceLocation PropertyIvarLoc,
                                ObjCPropertyQueryKind QueryKind);
  
    enum ObjCSpecialMethodKind {
      OSMK_None,
      OSMK_Alloc,
      OSMK_New,
      OSMK_Copy,
      OSMK_RetainingInit,
      OSMK_NonRetainingInit
    };
  
    struct ObjCArgInfo {
      IdentifierInfo *Name;
      SourceLocation NameLoc;
      // The Type is null if no type was specified, and the DeclSpec is invalid
      // in this case.
      ParsedType Type;
      ObjCDeclSpec DeclSpec;
  
      /// ArgAttrs - Attribute list for this argument.
      ParsedAttributesView ArgAttrs;
    };
  
    Decl *ActOnMethodDeclaration(
        Scope *S,
        SourceLocation BeginLoc, // location of the + or -.
        SourceLocation EndLoc,   // location of the ; or {.
        tok::TokenKind MethodType, ObjCDeclSpec &ReturnQT, ParsedType ReturnType,
        ArrayRef<SourceLocation> SelectorLocs, Selector Sel,
        // optional arguments. The number of types/arguments is obtained
        // from the Sel.getNumArgs().
        ObjCArgInfo *ArgInfo, DeclaratorChunk::ParamInfo *CParamInfo,
        unsigned CNumArgs, // c-style args
        const ParsedAttributesView &AttrList, tok::ObjCKeywordKind MethodImplKind,
        bool isVariadic, bool MethodDefinition);
  
    ObjCMethodDecl *LookupMethodInQualifiedType(Selector Sel,
                                                const ObjCObjectPointerType *OPT,
                                                bool IsInstance);
    ObjCMethodDecl *LookupMethodInObjectType(Selector Sel, QualType Ty,
                                             bool IsInstance);
  
    bool CheckARCMethodDecl(ObjCMethodDecl *method);
    bool inferObjCARCLifetime(ValueDecl *decl);
  
    void deduceOpenCLAddressSpace(ValueDecl *decl);
  
    ExprResult
    HandleExprPropertyRefExpr(const ObjCObjectPointerType *OPT,
                              Expr *BaseExpr,
                              SourceLocation OpLoc,
                              DeclarationName MemberName,
                              SourceLocation MemberLoc,
                              SourceLocation SuperLoc, QualType SuperType,
                              bool Super);
  
    ExprResult
    ActOnClassPropertyRefExpr(IdentifierInfo &receiverName,
                              IdentifierInfo &propertyName,
                              SourceLocation receiverNameLoc,
                              SourceLocation propertyNameLoc);
  
    ObjCMethodDecl *tryCaptureObjCSelf(SourceLocation Loc);
  
    /// Describes the kind of message expression indicated by a message
    /// send that starts with an identifier.
    enum ObjCMessageKind {
      /// The message is sent to 'super'.
      ObjCSuperMessage,
      /// The message is an instance message.
      ObjCInstanceMessage,
      /// The message is a class message, and the identifier is a type
      /// name.
      ObjCClassMessage
    };
  
    ObjCMessageKind getObjCMessageKind(Scope *S,
                                       IdentifierInfo *Name,
                                       SourceLocation NameLoc,
                                       bool IsSuper,
                                       bool HasTrailingDot,
                                       ParsedType &ReceiverType);
  
    ExprResult ActOnSuperMessage(Scope *S, SourceLocation SuperLoc,
                                 Selector Sel,
                                 SourceLocation LBracLoc,
                                 ArrayRef<SourceLocation> SelectorLocs,
                                 SourceLocation RBracLoc,
                                 MultiExprArg Args);
  
    ExprResult BuildClassMessage(TypeSourceInfo *ReceiverTypeInfo,
                                 QualType ReceiverType,
                                 SourceLocation SuperLoc,
                                 Selector Sel,
                                 ObjCMethodDecl *Method,
                                 SourceLocation LBracLoc,
                                 ArrayRef<SourceLocation> SelectorLocs,
                                 SourceLocation RBracLoc,
                                 MultiExprArg Args,
                                 bool isImplicit = false);
  
    ExprResult BuildClassMessageImplicit(QualType ReceiverType,
                                         bool isSuperReceiver,
                                         SourceLocation Loc,
                                         Selector Sel,
                                         ObjCMethodDecl *Method,
                                         MultiExprArg Args);
  
    ExprResult ActOnClassMessage(Scope *S,
                                 ParsedType Receiver,
                                 Selector Sel,
                                 SourceLocation LBracLoc,
                                 ArrayRef<SourceLocation> SelectorLocs,
                                 SourceLocation RBracLoc,
                                 MultiExprArg Args);
  
    ExprResult BuildInstanceMessage(Expr *Receiver,
                                    QualType ReceiverType,
                                    SourceLocation SuperLoc,
                                    Selector Sel,
                                    ObjCMethodDecl *Method,
                                    SourceLocation LBracLoc,
                                    ArrayRef<SourceLocation> SelectorLocs,
                                    SourceLocation RBracLoc,
                                    MultiExprArg Args,
                                    bool isImplicit = false);
  
    ExprResult BuildInstanceMessageImplicit(Expr *Receiver,
                                            QualType ReceiverType,
                                            SourceLocation Loc,
                                            Selector Sel,
                                            ObjCMethodDecl *Method,
                                            MultiExprArg Args);
  
    ExprResult ActOnInstanceMessage(Scope *S,
                                    Expr *Receiver,
                                    Selector Sel,
                                    SourceLocation LBracLoc,
                                    ArrayRef<SourceLocation> SelectorLocs,
                                    SourceLocation RBracLoc,
                                    MultiExprArg Args);
  
    ExprResult BuildObjCBridgedCast(SourceLocation LParenLoc,
                                    ObjCBridgeCastKind Kind,
                                    SourceLocation BridgeKeywordLoc,
                                    TypeSourceInfo *TSInfo,
                                    Expr *SubExpr);
  
    ExprResult ActOnObjCBridgedCast(Scope *S,
                                    SourceLocation LParenLoc,
                                    ObjCBridgeCastKind Kind,
                                    SourceLocation BridgeKeywordLoc,
                                    ParsedType Type,
                                    SourceLocation RParenLoc,
                                    Expr *SubExpr);
  
    void CheckTollFreeBridgeCast(QualType castType, Expr *castExpr);
  
    void CheckObjCBridgeRelatedCast(QualType castType, Expr *castExpr);
  
    bool CheckTollFreeBridgeStaticCast(QualType castType, Expr *castExpr,
                                       CastKind &Kind);
  
    bool checkObjCBridgeRelatedComponents(SourceLocation Loc,
                                          QualType DestType, QualType SrcType,
                                          ObjCInterfaceDecl *&RelatedClass,
                                          ObjCMethodDecl *&ClassMethod,
                                          ObjCMethodDecl *&InstanceMethod,
                                          TypedefNameDecl *&TDNDecl,
                                          bool CfToNs, bool Diagnose = true);
  
    bool CheckObjCBridgeRelatedConversions(SourceLocation Loc,
                                           QualType DestType, QualType SrcType,
                                           Expr *&SrcExpr, bool Diagnose = true);
  
    bool ConversionToObjCStringLiteralCheck(QualType DstType, Expr *&SrcExpr,
                                            bool Diagnose = true);
  
    bool checkInitMethod(ObjCMethodDecl *method, QualType receiverTypeIfCall);
  
    /// Check whether the given new method is a valid override of the
    /// given overridden method, and set any properties that should be inherited.
    void CheckObjCMethodOverride(ObjCMethodDecl *NewMethod,
                                 const ObjCMethodDecl *Overridden);
  
    /// Describes the compatibility of a result type with its method.
    enum ResultTypeCompatibilityKind {
      RTC_Compatible,
      RTC_Incompatible,
      RTC_Unknown
    };
  
    /// Check whether the declared result type of the given Objective-C
    /// method declaration is compatible with the method's class.
    ResultTypeCompatibilityKind
    checkRelatedResultTypeCompatibility(const ObjCMethodDecl *Method,
                                        const ObjCInterfaceDecl *CurrentClass);
  
    void CheckObjCMethodDirectOverrides(ObjCMethodDecl *method,
                                        ObjCMethodDecl *overridden);
  
    void CheckObjCMethodOverrides(ObjCMethodDecl *ObjCMethod,
                                  ObjCInterfaceDecl *CurrentClass,
                                  ResultTypeCompatibilityKind RTC);
  
    enum PragmaOptionsAlignKind {
      POAK_Native,  // #pragma options align=native
      POAK_Natural, // #pragma options align=natural
      POAK_Packed,  // #pragma options align=packed
      POAK_Power,   // #pragma options align=power
      POAK_Mac68k,  // #pragma options align=mac68k
      POAK_Reset    // #pragma options align=reset
    };
  
    /// ActOnPragmaClangSection - Called on well formed \#pragma clang section
    void ActOnPragmaClangSection(SourceLocation PragmaLoc,
                                 PragmaClangSectionAction Action,
                                 PragmaClangSectionKind SecKind, StringRef SecName);
  
    /// ActOnPragmaOptionsAlign - Called on well formed \#pragma options align.
    void ActOnPragmaOptionsAlign(PragmaOptionsAlignKind Kind,
                                 SourceLocation PragmaLoc);
  
    /// ActOnPragmaPack - Called on well formed \#pragma pack(...).
    void ActOnPragmaPack(SourceLocation PragmaLoc, PragmaMsStackAction Action,
                         StringRef SlotLabel, Expr *Alignment);
  
    enum class PragmaPackDiagnoseKind {
      NonDefaultStateAtInclude,
      ChangedStateAtExit
    };
  
    void DiagnoseNonDefaultPragmaPack(PragmaPackDiagnoseKind Kind,
                                      SourceLocation IncludeLoc);
    void DiagnoseUnterminatedPragmaPack();
  
    /// ActOnPragmaMSStruct - Called on well formed \#pragma ms_struct [on|off].
    void ActOnPragmaMSStruct(PragmaMSStructKind Kind);
  
    /// ActOnPragmaMSComment - Called on well formed
    /// \#pragma comment(kind, "arg").
    void ActOnPragmaMSComment(SourceLocation CommentLoc, PragmaMSCommentKind Kind,
                              StringRef Arg);
  
    /// ActOnPragmaMSPointersToMembers - called on well formed \#pragma
    /// pointers_to_members(representation method[, general purpose
    /// representation]).
    void ActOnPragmaMSPointersToMembers(
        LangOptions::PragmaMSPointersToMembersKind Kind,
        SourceLocation PragmaLoc);
  
    /// Called on well formed \#pragma vtordisp().
    void ActOnPragmaMSVtorDisp(PragmaMsStackAction Action,
                               SourceLocation PragmaLoc,
                               MSVtorDispMode Value);
  
    enum PragmaSectionKind {
      PSK_DataSeg,
      PSK_BSSSeg,
      PSK_ConstSeg,
      PSK_CodeSeg,
    };
  
    bool UnifySection(StringRef SectionName,
                      int SectionFlags,
                      DeclaratorDecl *TheDecl);
    bool UnifySection(StringRef SectionName,
                      int SectionFlags,
                      SourceLocation PragmaSectionLocation);
  
    /// Called on well formed \#pragma bss_seg/data_seg/const_seg/code_seg.
    void ActOnPragmaMSSeg(SourceLocation PragmaLocation,
                          PragmaMsStackAction Action,
                          llvm::StringRef StackSlotLabel,
                          StringLiteral *SegmentName,
                          llvm::StringRef PragmaName);
  
    /// Called on well formed \#pragma section().
    void ActOnPragmaMSSection(SourceLocation PragmaLocation,
                              int SectionFlags, StringLiteral *SegmentName);
  
    /// Called on well-formed \#pragma init_seg().
    void ActOnPragmaMSInitSeg(SourceLocation PragmaLocation,
                              StringLiteral *SegmentName);
  
    /// Called on #pragma clang __debug dump II
    void ActOnPragmaDump(Scope *S, SourceLocation Loc, IdentifierInfo *II);
  
    /// ActOnPragmaDetectMismatch - Call on well-formed \#pragma detect_mismatch
    void ActOnPragmaDetectMismatch(SourceLocation Loc, StringRef Name,
                                   StringRef Value);
  
    /// ActOnPragmaUnused - Called on well-formed '\#pragma unused'.
    void ActOnPragmaUnused(const Token &Identifier,
                           Scope *curScope,
                           SourceLocation PragmaLoc);
  
    /// ActOnPragmaVisibility - Called on well formed \#pragma GCC visibility... .
    void ActOnPragmaVisibility(const IdentifierInfo* VisType,
                               SourceLocation PragmaLoc);
  
    NamedDecl *DeclClonePragmaWeak(NamedDecl *ND, IdentifierInfo *II,
                                   SourceLocation Loc);
    void DeclApplyPragmaWeak(Scope *S, NamedDecl *ND, WeakInfo &W);
  
    /// ActOnPragmaWeakID - Called on well formed \#pragma weak ident.
    void ActOnPragmaWeakID(IdentifierInfo* WeakName,
                           SourceLocation PragmaLoc,
                           SourceLocation WeakNameLoc);
  
    /// ActOnPragmaRedefineExtname - Called on well formed
    /// \#pragma redefine_extname oldname newname.
    void ActOnPragmaRedefineExtname(IdentifierInfo* WeakName,
                                    IdentifierInfo* AliasName,
                                    SourceLocation PragmaLoc,
                                    SourceLocation WeakNameLoc,
                                    SourceLocation AliasNameLoc);
  
    /// ActOnPragmaWeakAlias - Called on well formed \#pragma weak ident = ident.
    void ActOnPragmaWeakAlias(IdentifierInfo* WeakName,
                              IdentifierInfo* AliasName,
                              SourceLocation PragmaLoc,
                              SourceLocation WeakNameLoc,
                              SourceLocation AliasNameLoc);
  
    /// ActOnPragmaFPContract - Called on well formed
    /// \#pragma {STDC,OPENCL} FP_CONTRACT and
    /// \#pragma clang fp contract
    void ActOnPragmaFPContract(LangOptions::FPContractModeKind FPC);
  
    /// ActOnPragmaFenvAccess - Called on well formed
    /// \#pragma STDC FENV_ACCESS
    void ActOnPragmaFEnvAccess(LangOptions::FEnvAccessModeKind FPC);
  
    /// Called to set rounding mode for floating point operations.
    void setRoundingMode(LangOptions::FPRoundingModeKind);
  
    /// Called to set exception behavior for floating point operations.
    void setExceptionMode(LangOptions::FPExceptionModeKind);
  
    /// AddAlignmentAttributesForRecord - Adds any needed alignment attributes to
    /// a the record decl, to handle '\#pragma pack' and '\#pragma options align'.
    void AddAlignmentAttributesForRecord(RecordDecl *RD);
  
    /// AddMsStructLayoutForRecord - Adds ms_struct layout attribute to record.
    void AddMsStructLayoutForRecord(RecordDecl *RD);
  
    /// FreePackedContext - Deallocate and null out PackContext.
    void FreePackedContext();
  
    /// PushNamespaceVisibilityAttr - Note that we've entered a
    /// namespace with a visibility attribute.
    void PushNamespaceVisibilityAttr(const VisibilityAttr *Attr,
                                     SourceLocation Loc);
  
    /// AddPushedVisibilityAttribute - If '\#pragma GCC visibility' was used,
    /// add an appropriate visibility attribute.
    void AddPushedVisibilityAttribute(Decl *RD);
  
    /// PopPragmaVisibility - Pop the top element of the visibility stack; used
    /// for '\#pragma GCC visibility' and visibility attributes on namespaces.
    void PopPragmaVisibility(bool IsNamespaceEnd, SourceLocation EndLoc);
  
    /// FreeVisContext - Deallocate and null out VisContext.
    void FreeVisContext();
  
    /// AddCFAuditedAttribute - Check whether we're currently within
    /// '\#pragma clang arc_cf_code_audited' and, if so, consider adding
    /// the appropriate attribute.
    void AddCFAuditedAttribute(Decl *D);
  
    void ActOnPragmaAttributeAttribute(ParsedAttr &Attribute,
                                       SourceLocation PragmaLoc,
                                       attr::ParsedSubjectMatchRuleSet Rules);
    void ActOnPragmaAttributeEmptyPush(SourceLocation PragmaLoc,
                                       const IdentifierInfo *Namespace);
  
    /// Called on well-formed '\#pragma clang attribute pop'.
    void ActOnPragmaAttributePop(SourceLocation PragmaLoc,
                                 const IdentifierInfo *Namespace);
  
    /// Adds the attributes that have been specified using the
    /// '\#pragma clang attribute push' directives to the given declaration.
    void AddPragmaAttributes(Scope *S, Decl *D);
  
    void DiagnoseUnterminatedPragmaAttribute();
  
    /// Called on well formed \#pragma clang optimize.
    void ActOnPragmaOptimize(bool On, SourceLocation PragmaLoc);
  
    /// Get the location for the currently active "\#pragma clang optimize
    /// off". If this location is invalid, then the state of the pragma is "on".
    SourceLocation getOptimizeOffPragmaLocation() const {
      return OptimizeOffPragmaLocation;
    }
  
    /// Only called on function definitions; if there is a pragma in scope
    /// with the effect of a range-based optnone, consider marking the function
    /// with attribute optnone.
    void AddRangeBasedOptnone(FunctionDecl *FD);
  
    /// Adds the 'optnone' attribute to the function declaration if there
    /// are no conflicts; Loc represents the location causing the 'optnone'
    /// attribute to be added (usually because of a pragma).
    void AddOptnoneAttributeIfNoConflicts(FunctionDecl *FD, SourceLocation Loc);
  
    /// AddAlignedAttr - Adds an aligned attribute to a particular declaration.
    void AddAlignedAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E,
                        bool IsPackExpansion);
    void AddAlignedAttr(Decl *D, const AttributeCommonInfo &CI, TypeSourceInfo *T,
                        bool IsPackExpansion);
  
    /// AddAssumeAlignedAttr - Adds an assume_aligned attribute to a particular
    /// declaration.
    void AddAssumeAlignedAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E,
                              Expr *OE);
  
    /// AddAllocAlignAttr - Adds an alloc_align attribute to a particular
    /// declaration.
    void AddAllocAlignAttr(Decl *D, const AttributeCommonInfo &CI,
                           Expr *ParamExpr);
  
    /// AddAlignValueAttr - Adds an align_value attribute to a particular
    /// declaration.
    void AddAlignValueAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E);
  
    /// AddLaunchBoundsAttr - Adds a launch_bounds attribute to a particular
    /// declaration.
    void AddLaunchBoundsAttr(Decl *D, const AttributeCommonInfo &CI,
                             Expr *MaxThreads, Expr *MinBlocks);
  
    /// AddModeAttr - Adds a mode attribute to a particular declaration.
    void AddModeAttr(Decl *D, const AttributeCommonInfo &CI, IdentifierInfo *Name,
                     bool InInstantiation = false);
  
    void AddParameterABIAttr(Decl *D, const AttributeCommonInfo &CI,
                             ParameterABI ABI);
  
    enum class RetainOwnershipKind {NS, CF, OS};
    void AddXConsumedAttr(Decl *D, const AttributeCommonInfo &CI,
                          RetainOwnershipKind K, bool IsTemplateInstantiation);
  
    /// addAMDGPUFlatWorkGroupSizeAttr - Adds an amdgpu_flat_work_group_size
    /// attribute to a particular declaration.
    void addAMDGPUFlatWorkGroupSizeAttr(Decl *D, const AttributeCommonInfo &CI,
                                        Expr *Min, Expr *Max);
  
    /// addAMDGPUWavePersEUAttr - Adds an amdgpu_waves_per_eu attribute to a
    /// particular declaration.
    void addAMDGPUWavesPerEUAttr(Decl *D, const AttributeCommonInfo &CI,
                                 Expr *Min, Expr *Max);
  
    bool checkNSReturnsRetainedReturnType(SourceLocation loc, QualType type);
  
    //===--------------------------------------------------------------------===//
    // C++ Coroutines TS
    //
    bool ActOnCoroutineBodyStart(Scope *S, SourceLocation KwLoc,
                                 StringRef Keyword);
    ExprResult ActOnCoawaitExpr(Scope *S, SourceLocation KwLoc, Expr *E);
    ExprResult ActOnCoyieldExpr(Scope *S, SourceLocation KwLoc, Expr *E);
    StmtResult ActOnCoreturnStmt(Scope *S, SourceLocation KwLoc, Expr *E);
  
    ExprResult BuildResolvedCoawaitExpr(SourceLocation KwLoc, Expr *E,
                                        bool IsImplicit = false);
    ExprResult BuildUnresolvedCoawaitExpr(SourceLocation KwLoc, Expr *E,
                                          UnresolvedLookupExpr* Lookup);
    ExprResult BuildCoyieldExpr(SourceLocation KwLoc, Expr *E);
    StmtResult BuildCoreturnStmt(SourceLocation KwLoc, Expr *E,
                                 bool IsImplicit = false);
    StmtResult BuildCoroutineBodyStmt(CoroutineBodyStmt::CtorArgs);
    bool buildCoroutineParameterMoves(SourceLocation Loc);
    VarDecl *buildCoroutinePromise(SourceLocation Loc);
    void CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body);
    ClassTemplateDecl *lookupCoroutineTraits(SourceLocation KwLoc,
                                             SourceLocation FuncLoc);
  
    //===--------------------------------------------------------------------===//
    // OpenCL extensions.
    //
  private:
    std::string CurrOpenCLExtension;
    /// Extensions required by an OpenCL type.
    llvm::DenseMap<const Type*, std::set<std::string>> OpenCLTypeExtMap;
    /// Extensions required by an OpenCL declaration.
    llvm::DenseMap<const Decl*, std::set<std::string>> OpenCLDeclExtMap;
  public:
    llvm::StringRef getCurrentOpenCLExtension() const {
      return CurrOpenCLExtension;
    }
  
    /// Check if a function declaration \p FD associates with any
    /// extensions present in OpenCLDeclExtMap and if so return the
    /// extension(s) name(s).
    std::string getOpenCLExtensionsFromDeclExtMap(FunctionDecl *FD);
  
    /// Check if a function type \p FT associates with any
    /// extensions present in OpenCLTypeExtMap and if so return the
    /// extension(s) name(s).
    std::string getOpenCLExtensionsFromTypeExtMap(FunctionType *FT);
  
    /// Find an extension in an appropriate extension map and return its name
    template<typename T, typename MapT>
    std::string getOpenCLExtensionsFromExtMap(T* FT, MapT &Map);
  
    void setCurrentOpenCLExtension(llvm::StringRef Ext) {
      CurrOpenCLExtension = std::string(Ext);
    }
  
    /// Set OpenCL extensions for a type which can only be used when these
    /// OpenCL extensions are enabled. If \p Exts is empty, do nothing.
    /// \param Exts A space separated list of OpenCL extensions.
    void setOpenCLExtensionForType(QualType T, llvm::StringRef Exts);
  
    /// Set OpenCL extensions for a declaration which can only be
    /// used when these OpenCL extensions are enabled. If \p Exts is empty, do
    /// nothing.
    /// \param Exts A space separated list of OpenCL extensions.
    void setOpenCLExtensionForDecl(Decl *FD, llvm::StringRef Exts);
  
    /// Set current OpenCL extensions for a type which can only be used
    /// when these OpenCL extensions are enabled. If current OpenCL extension is
    /// empty, do nothing.
    void setCurrentOpenCLExtensionForType(QualType T);
  
    /// Set current OpenCL extensions for a declaration which
    /// can only be used when these OpenCL extensions are enabled. If current
    /// OpenCL extension is empty, do nothing.
    void setCurrentOpenCLExtensionForDecl(Decl *FD);
  
    bool isOpenCLDisabledDecl(Decl *FD);
  
    /// Check if type \p T corresponding to declaration specifier \p DS
    /// is disabled due to required OpenCL extensions being disabled. If so,
    /// emit diagnostics.
    /// \return true if type is disabled.
    bool checkOpenCLDisabledTypeDeclSpec(const DeclSpec &DS, QualType T);
  
    /// Check if declaration \p D used by expression \p E
    /// is disabled due to required OpenCL extensions being disabled. If so,
    /// emit diagnostics.
    /// \return true if type is disabled.
    bool checkOpenCLDisabledDecl(const NamedDecl &D, const Expr &E);
  
    //===--------------------------------------------------------------------===//
    // OpenMP directives and clauses.
    //
  private:
    void *VarDataSharingAttributesStack;
    /// Number of nested '#pragma omp declare target' directives.
    unsigned DeclareTargetNestingLevel = 0;
    /// Initialization of data-sharing attributes stack.
    void InitDataSharingAttributesStack();
    void DestroyDataSharingAttributesStack();
    ExprResult
    VerifyPositiveIntegerConstantInClause(Expr *Op, OpenMPClauseKind CKind,
                                          bool StrictlyPositive = true);
    /// Returns OpenMP nesting level for current directive.
    unsigned getOpenMPNestingLevel() const;
  
    /// Adjusts the function scopes index for the target-based regions.
    void adjustOpenMPTargetScopeIndex(unsigned &FunctionScopesIndex,
                                      unsigned Level) const;
  
    /// Returns the number of scopes associated with the construct on the given
    /// OpenMP level.
    int getNumberOfConstructScopes(unsigned Level) const;
  
    /// Push new OpenMP function region for non-capturing function.
    void pushOpenMPFunctionRegion();
  
    /// Pop OpenMP function region for non-capturing function.
    void popOpenMPFunctionRegion(const sema::FunctionScopeInfo *OldFSI);
  
    /// Check whether we're allowed to call Callee from the current function.
    void checkOpenMPDeviceFunction(SourceLocation Loc, FunctionDecl *Callee,
                                   bool CheckForDelayedContext = true);
  
    /// Check whether we're allowed to call Callee from the current function.
    void checkOpenMPHostFunction(SourceLocation Loc, FunctionDecl *Callee,
                                 bool CheckCaller = true);
  
    /// Check if the expression is allowed to be used in expressions for the
    /// OpenMP devices.
    void checkOpenMPDeviceExpr(const Expr *E);
  
    /// Finishes analysis of the deferred functions calls that may be declared as
    /// host/nohost during device/host compilation.
    void finalizeOpenMPDelayedAnalysis();
  
    /// Checks if a type or a declaration is disabled due to the owning extension
    /// being disabled, and emits diagnostic messages if it is disabled.
    /// \param D type or declaration to be checked.
    /// \param DiagLoc source location for the diagnostic message.
    /// \param DiagInfo information to be emitted for the diagnostic message.
    /// \param SrcRange source range of the declaration.
    /// \param Map maps type or declaration to the extensions.
    /// \param Selector selects diagnostic message: 0 for type and 1 for
    ///        declaration.
    /// \return true if the type or declaration is disabled.
    template <typename T, typename DiagLocT, typename DiagInfoT, typename MapT>
    bool checkOpenCLDisabledTypeOrDecl(T D, DiagLocT DiagLoc, DiagInfoT DiagInfo,
                                       MapT &Map, unsigned Selector = 0,
                                       SourceRange SrcRange = SourceRange());
  
    /// Marks all the functions that might be required for the currently active
    /// OpenMP context.
    void markOpenMPDeclareVariantFuncsReferenced(SourceLocation Loc,
                                                 FunctionDecl *Func,
                                                 bool MightBeOdrUse);
  
  public:
    /// Struct to store the context selectors info for declare variant directive.
  
    /// Checks if the variant/multiversion functions are compatible.
    bool areMultiversionVariantFunctionsCompatible(
        const FunctionDecl *OldFD, const FunctionDecl *NewFD,
        const PartialDiagnostic &NoProtoDiagID,
        const PartialDiagnosticAt &NoteCausedDiagIDAt,
        const PartialDiagnosticAt &NoSupportDiagIDAt,
        const PartialDiagnosticAt &DiffDiagIDAt, bool TemplatesSupported,
        bool ConstexprSupported, bool CLinkageMayDiffer);
  
    /// Function tries to capture lambda's captured variables in the OpenMP region
    /// before the original lambda is captured.
    void tryCaptureOpenMPLambdas(ValueDecl *V);
  
    /// Return true if the provided declaration \a VD should be captured by
    /// reference.
    /// \param Level Relative level of nested OpenMP construct for that the check
    /// is performed.
    /// \param OpenMPCaptureLevel Capture level within an OpenMP construct.
    bool isOpenMPCapturedByRef(const ValueDecl *D, unsigned Level,
                               unsigned OpenMPCaptureLevel) const;
  
    /// Check if the specified variable is used in one of the private
    /// clauses (private, firstprivate, lastprivate, reduction etc.) in OpenMP
    /// constructs.
    VarDecl *isOpenMPCapturedDecl(ValueDecl *D, bool CheckScopeInfo = false,
                                  unsigned StopAt = 0);
    ExprResult getOpenMPCapturedExpr(VarDecl *Capture, ExprValueKind VK,
                                     ExprObjectKind OK, SourceLocation Loc);
  
    /// If the current region is a loop-based region, mark the start of the loop
    /// construct.
    void startOpenMPLoop();
  
    /// If the current region is a range loop-based region, mark the start of the
    /// loop construct.
    void startOpenMPCXXRangeFor();
  
    /// Check if the specified variable is used in 'private' clause.
    /// \param Level Relative level of nested OpenMP construct for that the check
    /// is performed.
    OpenMPClauseKind isOpenMPPrivateDecl(ValueDecl *D, unsigned Level,
                                         unsigned CapLevel) const;
  
    /// Sets OpenMP capture kind (OMPC_private, OMPC_firstprivate, OMPC_map etc.)
    /// for \p FD based on DSA for the provided corresponding captured declaration
    /// \p D.
    void setOpenMPCaptureKind(FieldDecl *FD, const ValueDecl *D, unsigned Level);
  
    /// Check if the specified variable is captured  by 'target' directive.
    /// \param Level Relative level of nested OpenMP construct for that the check
    /// is performed.
    bool isOpenMPTargetCapturedDecl(const ValueDecl *D, unsigned Level,
                                    unsigned CaptureLevel) const;
  
    /// Check if the specified global variable must be captured  by outer capture
    /// regions.
    /// \param Level Relative level of nested OpenMP construct for that
    /// the check is performed.
    bool isOpenMPGlobalCapturedDecl(ValueDecl *D, unsigned Level,
                                    unsigned CaptureLevel) const;
  
    ExprResult PerformOpenMPImplicitIntegerConversion(SourceLocation OpLoc,
                                                      Expr *Op);
    /// Called on start of new data sharing attribute block.
    void StartOpenMPDSABlock(OpenMPDirectiveKind K,
                             const DeclarationNameInfo &DirName, Scope *CurScope,
                             SourceLocation Loc);
    /// Start analysis of clauses.
    void StartOpenMPClause(OpenMPClauseKind K);
    /// End analysis of clauses.
    void EndOpenMPClause();
    /// Called on end of data sharing attribute block.
    void EndOpenMPDSABlock(Stmt *CurDirective);
  
    /// Check if the current region is an OpenMP loop region and if it is,
    /// mark loop control variable, used in \p Init for loop initialization, as
    /// private by default.
    /// \param Init First part of the for loop.
    void ActOnOpenMPLoopInitialization(SourceLocation ForLoc, Stmt *Init);
  
    // OpenMP directives and clauses.
    /// Called on correct id-expression from the '#pragma omp
    /// threadprivate'.
    ExprResult ActOnOpenMPIdExpression(Scope *CurScope, CXXScopeSpec &ScopeSpec,
                                       const DeclarationNameInfo &Id,
                                       OpenMPDirectiveKind Kind);
    /// Called on well-formed '#pragma omp threadprivate'.
    DeclGroupPtrTy ActOnOpenMPThreadprivateDirective(
                                       SourceLocation Loc,
                                       ArrayRef<Expr *> VarList);
    /// Builds a new OpenMPThreadPrivateDecl and checks its correctness.
    OMPThreadPrivateDecl *CheckOMPThreadPrivateDecl(SourceLocation Loc,
                                                    ArrayRef<Expr *> VarList);
    /// Called on well-formed '#pragma omp allocate'.
    DeclGroupPtrTy ActOnOpenMPAllocateDirective(SourceLocation Loc,
                                                ArrayRef<Expr *> VarList,
                                                ArrayRef<OMPClause *> Clauses,
                                                DeclContext *Owner = nullptr);
    /// Called on well-formed '#pragma omp requires'.
    DeclGroupPtrTy ActOnOpenMPRequiresDirective(SourceLocation Loc,
                                                ArrayRef<OMPClause *> ClauseList);
    /// Check restrictions on Requires directive
    OMPRequiresDecl *CheckOMPRequiresDecl(SourceLocation Loc,
                                          ArrayRef<OMPClause *> Clauses);
    /// Check if the specified type is allowed to be used in 'omp declare
    /// reduction' construct.
    QualType ActOnOpenMPDeclareReductionType(SourceLocation TyLoc,
                                             TypeResult ParsedType);
    /// Called on start of '#pragma omp declare reduction'.
    DeclGroupPtrTy ActOnOpenMPDeclareReductionDirectiveStart(
        Scope *S, DeclContext *DC, DeclarationName Name,
        ArrayRef<std::pair<QualType, SourceLocation>> ReductionTypes,
        AccessSpecifier AS, Decl *PrevDeclInScope = nullptr);
    /// Initialize declare reduction construct initializer.
    void ActOnOpenMPDeclareReductionCombinerStart(Scope *S, Decl *D);
    /// Finish current declare reduction construct initializer.
    void ActOnOpenMPDeclareReductionCombinerEnd(Decl *D, Expr *Combiner);
    /// Initialize declare reduction construct initializer.
    /// \return omp_priv variable.
    VarDecl *ActOnOpenMPDeclareReductionInitializerStart(Scope *S, Decl *D);
    /// Finish current declare reduction construct initializer.
    void ActOnOpenMPDeclareReductionInitializerEnd(Decl *D, Expr *Initializer,
                                                   VarDecl *OmpPrivParm);
    /// Called at the end of '#pragma omp declare reduction'.
    DeclGroupPtrTy ActOnOpenMPDeclareReductionDirectiveEnd(
        Scope *S, DeclGroupPtrTy DeclReductions, bool IsValid);
  
    /// Check variable declaration in 'omp declare mapper' construct.
    TypeResult ActOnOpenMPDeclareMapperVarDecl(Scope *S, Declarator &D);
    /// Check if the specified type is allowed to be used in 'omp declare
    /// mapper' construct.
    QualType ActOnOpenMPDeclareMapperType(SourceLocation TyLoc,
                                          TypeResult ParsedType);
    /// Called on start of '#pragma omp declare mapper'.
    OMPDeclareMapperDecl *ActOnOpenMPDeclareMapperDirectiveStart(
        Scope *S, DeclContext *DC, DeclarationName Name, QualType MapperType,
        SourceLocation StartLoc, DeclarationName VN, AccessSpecifier AS,
        Decl *PrevDeclInScope = nullptr);
    /// Build the mapper variable of '#pragma omp declare mapper'.
    void ActOnOpenMPDeclareMapperDirectiveVarDecl(OMPDeclareMapperDecl *DMD,
                                                  Scope *S, QualType MapperType,
                                                  SourceLocation StartLoc,
                                                  DeclarationName VN);
    /// Called at the end of '#pragma omp declare mapper'.
    DeclGroupPtrTy
    ActOnOpenMPDeclareMapperDirectiveEnd(OMPDeclareMapperDecl *D, Scope *S,
                                         ArrayRef<OMPClause *> ClauseList);
  
    /// Called on the start of target region i.e. '#pragma omp declare target'.
    bool ActOnStartOpenMPDeclareTargetDirective(SourceLocation Loc);
    /// Called at the end of target region i.e. '#pragme omp end declare target'.
    void ActOnFinishOpenMPDeclareTargetDirective();
    /// Searches for the provided declaration name for OpenMP declare target
    /// directive.
    NamedDecl *
    lookupOpenMPDeclareTargetName(Scope *CurScope, CXXScopeSpec &ScopeSpec,
                                  const DeclarationNameInfo &Id,
                                  NamedDeclSetType &SameDirectiveDecls);
    /// Called on correct id-expression from the '#pragma omp declare target'.
    void ActOnOpenMPDeclareTargetName(NamedDecl *ND, SourceLocation Loc,
                                      OMPDeclareTargetDeclAttr::MapTypeTy MT,
                                      OMPDeclareTargetDeclAttr::DevTypeTy DT);
    /// Check declaration inside target region.
    void
    checkDeclIsAllowedInOpenMPTarget(Expr *E, Decl *D,
                                     SourceLocation IdLoc = SourceLocation());
    /// Return true inside OpenMP declare target region.
    bool isInOpenMPDeclareTargetContext() const {
      return DeclareTargetNestingLevel > 0;
    }
    /// Return true inside OpenMP target region.
    bool isInOpenMPTargetExecutionDirective() const;
  
    /// Return the number of captured regions created for an OpenMP directive.
    static int getOpenMPCaptureLevels(OpenMPDirectiveKind Kind);
  
    /// Initialization of captured region for OpenMP region.
    void ActOnOpenMPRegionStart(OpenMPDirectiveKind DKind, Scope *CurScope);
    /// End of OpenMP region.
    ///
    /// \param S Statement associated with the current OpenMP region.
    /// \param Clauses List of clauses for the current OpenMP region.
    ///
    /// \returns Statement for finished OpenMP region.
    StmtResult ActOnOpenMPRegionEnd(StmtResult S, ArrayRef<OMPClause *> Clauses);
    StmtResult ActOnOpenMPExecutableDirective(
        OpenMPDirectiveKind Kind, const DeclarationNameInfo &DirName,
        OpenMPDirectiveKind CancelRegion, ArrayRef<OMPClause *> Clauses,
        Stmt *AStmt, SourceLocation StartLoc, SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp parallel' after parsing
    /// of the  associated statement.
    StmtResult ActOnOpenMPParallelDirective(ArrayRef<OMPClause *> Clauses,
                                            Stmt *AStmt,
                                            SourceLocation StartLoc,
                                            SourceLocation EndLoc);
    using VarsWithInheritedDSAType =
        llvm::SmallDenseMap<const ValueDecl *, const Expr *, 4>;
    /// Called on well-formed '\#pragma omp simd' after parsing
    /// of the associated statement.
    StmtResult
    ActOnOpenMPSimdDirective(ArrayRef<OMPClause *> Clauses, Stmt *AStmt,
                             SourceLocation StartLoc, SourceLocation EndLoc,
                             VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp for' after parsing
    /// of the associated statement.
    StmtResult
    ActOnOpenMPForDirective(ArrayRef<OMPClause *> Clauses, Stmt *AStmt,
                            SourceLocation StartLoc, SourceLocation EndLoc,
                            VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp for simd' after parsing
    /// of the associated statement.
    StmtResult
    ActOnOpenMPForSimdDirective(ArrayRef<OMPClause *> Clauses, Stmt *AStmt,
                                SourceLocation StartLoc, SourceLocation EndLoc,
                                VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp sections' after parsing
    /// of the associated statement.
    StmtResult ActOnOpenMPSectionsDirective(ArrayRef<OMPClause *> Clauses,
                                            Stmt *AStmt, SourceLocation StartLoc,
                                            SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp section' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPSectionDirective(Stmt *AStmt, SourceLocation StartLoc,
                                           SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp single' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPSingleDirective(ArrayRef<OMPClause *> Clauses,
                                          Stmt *AStmt, SourceLocation StartLoc,
                                          SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp master' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPMasterDirective(Stmt *AStmt, SourceLocation StartLoc,
                                          SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp critical' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPCriticalDirective(const DeclarationNameInfo &DirName,
                                            ArrayRef<OMPClause *> Clauses,
                                            Stmt *AStmt, SourceLocation StartLoc,
                                            SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp parallel for' after parsing
    /// of the  associated statement.
    StmtResult ActOnOpenMPParallelForDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp parallel for simd' after
    /// parsing of the  associated statement.
    StmtResult ActOnOpenMPParallelForSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp parallel master' after
    /// parsing of the  associated statement.
    StmtResult ActOnOpenMPParallelMasterDirective(ArrayRef<OMPClause *> Clauses,
                                                  Stmt *AStmt,
                                                  SourceLocation StartLoc,
                                                  SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp parallel sections' after
    /// parsing of the  associated statement.
    StmtResult ActOnOpenMPParallelSectionsDirective(ArrayRef<OMPClause *> Clauses,
                                                    Stmt *AStmt,
                                                    SourceLocation StartLoc,
                                                    SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp task' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPTaskDirective(ArrayRef<OMPClause *> Clauses,
                                        Stmt *AStmt, SourceLocation StartLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp taskyield'.
    StmtResult ActOnOpenMPTaskyieldDirective(SourceLocation StartLoc,
                                             SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp barrier'.
    StmtResult ActOnOpenMPBarrierDirective(SourceLocation StartLoc,
                                           SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp taskwait'.
    StmtResult ActOnOpenMPTaskwaitDirective(SourceLocation StartLoc,
                                            SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp taskgroup'.
    StmtResult ActOnOpenMPTaskgroupDirective(ArrayRef<OMPClause *> Clauses,
                                             Stmt *AStmt, SourceLocation StartLoc,
                                             SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp flush'.
    StmtResult ActOnOpenMPFlushDirective(ArrayRef<OMPClause *> Clauses,
                                         SourceLocation StartLoc,
                                         SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp depobj'.
    StmtResult ActOnOpenMPDepobjDirective(ArrayRef<OMPClause *> Clauses,
                                          SourceLocation StartLoc,
                                          SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp ordered' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPOrderedDirective(ArrayRef<OMPClause *> Clauses,
                                           Stmt *AStmt, SourceLocation StartLoc,
                                           SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp atomic' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPAtomicDirective(ArrayRef<OMPClause *> Clauses,
                                          Stmt *AStmt, SourceLocation StartLoc,
                                          SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp target' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPTargetDirective(ArrayRef<OMPClause *> Clauses,
                                          Stmt *AStmt, SourceLocation StartLoc,
                                          SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp target data' after parsing of
    /// the associated statement.
    StmtResult ActOnOpenMPTargetDataDirective(ArrayRef<OMPClause *> Clauses,
                                              Stmt *AStmt, SourceLocation StartLoc,
                                              SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp target enter data' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPTargetEnterDataDirective(ArrayRef<OMPClause *> Clauses,
                                                   SourceLocation StartLoc,
                                                   SourceLocation EndLoc,
                                                   Stmt *AStmt);
    /// Called on well-formed '\#pragma omp target exit data' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPTargetExitDataDirective(ArrayRef<OMPClause *> Clauses,
                                                  SourceLocation StartLoc,
                                                  SourceLocation EndLoc,
                                                  Stmt *AStmt);
    /// Called on well-formed '\#pragma omp target parallel' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPTargetParallelDirective(ArrayRef<OMPClause *> Clauses,
                                                  Stmt *AStmt,
                                                  SourceLocation StartLoc,
                                                  SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp target parallel for' after
    /// parsing of the  associated statement.
    StmtResult ActOnOpenMPTargetParallelForDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp teams' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPTeamsDirective(ArrayRef<OMPClause *> Clauses,
                                         Stmt *AStmt, SourceLocation StartLoc,
                                         SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp cancellation point'.
    StmtResult
    ActOnOpenMPCancellationPointDirective(SourceLocation StartLoc,
                                          SourceLocation EndLoc,
                                          OpenMPDirectiveKind CancelRegion);
    /// Called on well-formed '\#pragma omp cancel'.
    StmtResult ActOnOpenMPCancelDirective(ArrayRef<OMPClause *> Clauses,
                                          SourceLocation StartLoc,
                                          SourceLocation EndLoc,
                                          OpenMPDirectiveKind CancelRegion);
    /// Called on well-formed '\#pragma omp taskloop' after parsing of the
    /// associated statement.
    StmtResult
    ActOnOpenMPTaskLoopDirective(ArrayRef<OMPClause *> Clauses, Stmt *AStmt,
                                 SourceLocation StartLoc, SourceLocation EndLoc,
                                 VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp taskloop simd' after parsing of
    /// the associated statement.
    StmtResult ActOnOpenMPTaskLoopSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp master taskloop' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPMasterTaskLoopDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp master taskloop simd' after parsing of
    /// the associated statement.
    StmtResult ActOnOpenMPMasterTaskLoopSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp parallel master taskloop' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPParallelMasterTaskLoopDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp parallel master taskloop simd' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPParallelMasterTaskLoopSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp distribute' after parsing
    /// of the associated statement.
    StmtResult
    ActOnOpenMPDistributeDirective(ArrayRef<OMPClause *> Clauses, Stmt *AStmt,
                                   SourceLocation StartLoc, SourceLocation EndLoc,
                                   VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp target update'.
    StmtResult ActOnOpenMPTargetUpdateDirective(ArrayRef<OMPClause *> Clauses,
                                                SourceLocation StartLoc,
                                                SourceLocation EndLoc,
                                                Stmt *AStmt);
    /// Called on well-formed '\#pragma omp distribute parallel for' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPDistributeParallelForDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp distribute parallel for simd'
    /// after parsing of the associated statement.
    StmtResult ActOnOpenMPDistributeParallelForSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp distribute simd' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPDistributeSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp target parallel for simd' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPTargetParallelForSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp target simd' after parsing of
    /// the associated statement.
    StmtResult
    ActOnOpenMPTargetSimdDirective(ArrayRef<OMPClause *> Clauses, Stmt *AStmt,
                                   SourceLocation StartLoc, SourceLocation EndLoc,
                                   VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp teams distribute' after parsing of
    /// the associated statement.
    StmtResult ActOnOpenMPTeamsDistributeDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp teams distribute simd' after parsing
    /// of the associated statement.
    StmtResult ActOnOpenMPTeamsDistributeSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp teams distribute parallel for simd'
    /// after parsing of the associated statement.
    StmtResult ActOnOpenMPTeamsDistributeParallelForSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp teams distribute parallel for'
    /// after parsing of the associated statement.
    StmtResult ActOnOpenMPTeamsDistributeParallelForDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp target teams' after parsing of the
    /// associated statement.
    StmtResult ActOnOpenMPTargetTeamsDirective(ArrayRef<OMPClause *> Clauses,
                                               Stmt *AStmt,
                                               SourceLocation StartLoc,
                                               SourceLocation EndLoc);
    /// Called on well-formed '\#pragma omp target teams distribute' after parsing
    /// of the associated statement.
    StmtResult ActOnOpenMPTargetTeamsDistributeDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp target teams distribute parallel for'
    /// after parsing of the associated statement.
    StmtResult ActOnOpenMPTargetTeamsDistributeParallelForDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp target teams distribute parallel for
    /// simd' after parsing of the associated statement.
    StmtResult ActOnOpenMPTargetTeamsDistributeParallelForSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
    /// Called on well-formed '\#pragma omp target teams distribute simd' after
    /// parsing of the associated statement.
    StmtResult ActOnOpenMPTargetTeamsDistributeSimdDirective(
        ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
        SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA);
  
    /// Checks correctness of linear modifiers.
    bool CheckOpenMPLinearModifier(OpenMPLinearClauseKind LinKind,
                                   SourceLocation LinLoc);
    /// Checks that the specified declaration matches requirements for the linear
    /// decls.
    bool CheckOpenMPLinearDecl(const ValueDecl *D, SourceLocation ELoc,
                               OpenMPLinearClauseKind LinKind, QualType Type,
                               bool IsDeclareSimd = false);
  
    /// Called on well-formed '\#pragma omp declare simd' after parsing of
    /// the associated method/function.
    DeclGroupPtrTy ActOnOpenMPDeclareSimdDirective(
        DeclGroupPtrTy DG, OMPDeclareSimdDeclAttr::BranchStateTy BS,
        Expr *Simdlen, ArrayRef<Expr *> Uniforms, ArrayRef<Expr *> Aligneds,
        ArrayRef<Expr *> Alignments, ArrayRef<Expr *> Linears,
        ArrayRef<unsigned> LinModifiers, ArrayRef<Expr *> Steps, SourceRange SR);
  
    /// Checks '\#pragma omp declare variant' variant function and original
    /// functions after parsing of the associated method/function.
    /// \param DG Function declaration to which declare variant directive is
    /// applied to.
    /// \param VariantRef Expression that references the variant function, which
    /// must be used instead of the original one, specified in \p DG.
    /// \param TI The trait info object representing the match clause.
    /// \returns None, if the function/variant function are not compatible with
    /// the pragma, pair of original function/variant ref expression otherwise.
    Optional<std::pair<FunctionDecl *, Expr *>>
    checkOpenMPDeclareVariantFunction(DeclGroupPtrTy DG, Expr *VariantRef,
                                      OMPTraitInfo &TI, SourceRange SR);
  
    /// Called on well-formed '\#pragma omp declare variant' after parsing of
    /// the associated method/function.
    /// \param FD Function declaration to which declare variant directive is
    /// applied to.
    /// \param VariantRef Expression that references the variant function, which
    /// must be used instead of the original one, specified in \p DG.
    /// \param TI The context traits associated with the function variant.
    void ActOnOpenMPDeclareVariantDirective(FunctionDecl *FD, Expr *VariantRef,
                                            OMPTraitInfo &TI, SourceRange SR);
  
    OMPClause *ActOnOpenMPSingleExprClause(OpenMPClauseKind Kind,
                                           Expr *Expr,
                                           SourceLocation StartLoc,
                                           SourceLocation LParenLoc,
                                           SourceLocation EndLoc);
    /// Called on well-formed 'allocator' clause.
    OMPClause *ActOnOpenMPAllocatorClause(Expr *Allocator,
                                          SourceLocation StartLoc,
                                          SourceLocation LParenLoc,
                                          SourceLocation EndLoc);
    /// Called on well-formed 'if' clause.
    OMPClause *ActOnOpenMPIfClause(OpenMPDirectiveKind NameModifier,
                                   Expr *Condition, SourceLocation StartLoc,
                                   SourceLocation LParenLoc,
                                   SourceLocation NameModifierLoc,
                                   SourceLocation ColonLoc,
                                   SourceLocation EndLoc);
    /// Called on well-formed 'final' clause.
    OMPClause *ActOnOpenMPFinalClause(Expr *Condition, SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc);
    /// Called on well-formed 'num_threads' clause.
    OMPClause *ActOnOpenMPNumThreadsClause(Expr *NumThreads,
                                           SourceLocation StartLoc,
                                           SourceLocation LParenLoc,
                                           SourceLocation EndLoc);
    /// Called on well-formed 'safelen' clause.
    OMPClause *ActOnOpenMPSafelenClause(Expr *Length,
                                        SourceLocation StartLoc,
                                        SourceLocation LParenLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'simdlen' clause.
    OMPClause *ActOnOpenMPSimdlenClause(Expr *Length, SourceLocation StartLoc,
                                        SourceLocation LParenLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'collapse' clause.
    OMPClause *ActOnOpenMPCollapseClause(Expr *NumForLoops,
                                         SourceLocation StartLoc,
                                         SourceLocation LParenLoc,
                                         SourceLocation EndLoc);
    /// Called on well-formed 'ordered' clause.
    OMPClause *
    ActOnOpenMPOrderedClause(SourceLocation StartLoc, SourceLocation EndLoc,
                             SourceLocation LParenLoc = SourceLocation(),
                             Expr *NumForLoops = nullptr);
    /// Called on well-formed 'grainsize' clause.
    OMPClause *ActOnOpenMPGrainsizeClause(Expr *Size, SourceLocation StartLoc,
                                          SourceLocation LParenLoc,
                                          SourceLocation EndLoc);
    /// Called on well-formed 'num_tasks' clause.
    OMPClause *ActOnOpenMPNumTasksClause(Expr *NumTasks, SourceLocation StartLoc,
                                         SourceLocation LParenLoc,
                                         SourceLocation EndLoc);
    /// Called on well-formed 'hint' clause.
    OMPClause *ActOnOpenMPHintClause(Expr *Hint, SourceLocation StartLoc,
                                     SourceLocation LParenLoc,
                                     SourceLocation EndLoc);
  
    OMPClause *ActOnOpenMPSimpleClause(OpenMPClauseKind Kind,
                                       unsigned Argument,
                                       SourceLocation ArgumentLoc,
                                       SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'default' clause.
    OMPClause *ActOnOpenMPDefaultClause(llvm::omp::DefaultKind Kind,
                                        SourceLocation KindLoc,
                                        SourceLocation StartLoc,
                                        SourceLocation LParenLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'proc_bind' clause.
    OMPClause *ActOnOpenMPProcBindClause(llvm::omp::ProcBindKind Kind,
                                         SourceLocation KindLoc,
                                         SourceLocation StartLoc,
                                         SourceLocation LParenLoc,
                                         SourceLocation EndLoc);
    /// Called on well-formed 'order' clause.
    OMPClause *ActOnOpenMPOrderClause(OpenMPOrderClauseKind Kind,
                                      SourceLocation KindLoc,
                                      SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc);
    /// Called on well-formed 'update' clause.
    OMPClause *ActOnOpenMPUpdateClause(OpenMPDependClauseKind Kind,
                                       SourceLocation KindLoc,
                                       SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation EndLoc);
  
    OMPClause *ActOnOpenMPSingleExprWithArgClause(
        OpenMPClauseKind Kind, ArrayRef<unsigned> Arguments, Expr *Expr,
        SourceLocation StartLoc, SourceLocation LParenLoc,
        ArrayRef<SourceLocation> ArgumentsLoc, SourceLocation DelimLoc,
        SourceLocation EndLoc);
    /// Called on well-formed 'schedule' clause.
    OMPClause *ActOnOpenMPScheduleClause(
        OpenMPScheduleClauseModifier M1, OpenMPScheduleClauseModifier M2,
        OpenMPScheduleClauseKind Kind, Expr *ChunkSize, SourceLocation StartLoc,
        SourceLocation LParenLoc, SourceLocation M1Loc, SourceLocation M2Loc,
        SourceLocation KindLoc, SourceLocation CommaLoc, SourceLocation EndLoc);
  
    OMPClause *ActOnOpenMPClause(OpenMPClauseKind Kind, SourceLocation StartLoc,
                                 SourceLocation EndLoc);
    /// Called on well-formed 'nowait' clause.
    OMPClause *ActOnOpenMPNowaitClause(SourceLocation StartLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'untied' clause.
    OMPClause *ActOnOpenMPUntiedClause(SourceLocation StartLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'mergeable' clause.
    OMPClause *ActOnOpenMPMergeableClause(SourceLocation StartLoc,
                                          SourceLocation EndLoc);
    /// Called on well-formed 'read' clause.
    OMPClause *ActOnOpenMPReadClause(SourceLocation StartLoc,
                                     SourceLocation EndLoc);
    /// Called on well-formed 'write' clause.
    OMPClause *ActOnOpenMPWriteClause(SourceLocation StartLoc,
                                      SourceLocation EndLoc);
    /// Called on well-formed 'update' clause.
    OMPClause *ActOnOpenMPUpdateClause(SourceLocation StartLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'capture' clause.
    OMPClause *ActOnOpenMPCaptureClause(SourceLocation StartLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'seq_cst' clause.
    OMPClause *ActOnOpenMPSeqCstClause(SourceLocation StartLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'acq_rel' clause.
    OMPClause *ActOnOpenMPAcqRelClause(SourceLocation StartLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'acquire' clause.
    OMPClause *ActOnOpenMPAcquireClause(SourceLocation StartLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'release' clause.
    OMPClause *ActOnOpenMPReleaseClause(SourceLocation StartLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'relaxed' clause.
    OMPClause *ActOnOpenMPRelaxedClause(SourceLocation StartLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'destroy' clause.
    OMPClause *ActOnOpenMPDestroyClause(SourceLocation StartLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'threads' clause.
    OMPClause *ActOnOpenMPThreadsClause(SourceLocation StartLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'simd' clause.
    OMPClause *ActOnOpenMPSIMDClause(SourceLocation StartLoc,
                                     SourceLocation EndLoc);
    /// Called on well-formed 'nogroup' clause.
    OMPClause *ActOnOpenMPNogroupClause(SourceLocation StartLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'unified_address' clause.
    OMPClause *ActOnOpenMPUnifiedAddressClause(SourceLocation StartLoc,
                                               SourceLocation EndLoc);
  
    /// Called on well-formed 'unified_address' clause.
    OMPClause *ActOnOpenMPUnifiedSharedMemoryClause(SourceLocation StartLoc,
                                                    SourceLocation EndLoc);
  
    /// Called on well-formed 'reverse_offload' clause.
    OMPClause *ActOnOpenMPReverseOffloadClause(SourceLocation StartLoc,
                                               SourceLocation EndLoc);
  
    /// Called on well-formed 'dynamic_allocators' clause.
    OMPClause *ActOnOpenMPDynamicAllocatorsClause(SourceLocation StartLoc,
                                                  SourceLocation EndLoc);
  
    /// Called on well-formed 'atomic_default_mem_order' clause.
    OMPClause *ActOnOpenMPAtomicDefaultMemOrderClause(
        OpenMPAtomicDefaultMemOrderClauseKind Kind, SourceLocation KindLoc,
        SourceLocation StartLoc, SourceLocation LParenLoc, SourceLocation EndLoc);
  
    OMPClause *ActOnOpenMPVarListClause(
        OpenMPClauseKind Kind, ArrayRef<Expr *> Vars, Expr *TailExpr,
        const OMPVarListLocTy &Locs, SourceLocation ColonLoc,
        CXXScopeSpec &ReductionOrMapperIdScopeSpec,
        DeclarationNameInfo &ReductionOrMapperId, int ExtraModifier,
        ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
        ArrayRef<SourceLocation> MapTypeModifiersLoc, bool IsMapTypeImplicit,
        SourceLocation DepLinMapLastLoc);
    /// Called on well-formed 'allocate' clause.
    OMPClause *
    ActOnOpenMPAllocateClause(Expr *Allocator, ArrayRef<Expr *> VarList,
                              SourceLocation StartLoc, SourceLocation ColonLoc,
                              SourceLocation LParenLoc, SourceLocation EndLoc);
    /// Called on well-formed 'private' clause.
    OMPClause *ActOnOpenMPPrivateClause(ArrayRef<Expr *> VarList,
                                        SourceLocation StartLoc,
                                        SourceLocation LParenLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'firstprivate' clause.
    OMPClause *ActOnOpenMPFirstprivateClause(ArrayRef<Expr *> VarList,
                                             SourceLocation StartLoc,
                                             SourceLocation LParenLoc,
                                             SourceLocation EndLoc);
    /// Called on well-formed 'lastprivate' clause.
    OMPClause *ActOnOpenMPLastprivateClause(
        ArrayRef<Expr *> VarList, OpenMPLastprivateModifier LPKind,
        SourceLocation LPKindLoc, SourceLocation ColonLoc,
        SourceLocation StartLoc, SourceLocation LParenLoc, SourceLocation EndLoc);
    /// Called on well-formed 'shared' clause.
    OMPClause *ActOnOpenMPSharedClause(ArrayRef<Expr *> VarList,
                                       SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'reduction' clause.
    OMPClause *ActOnOpenMPReductionClause(
        ArrayRef<Expr *> VarList, SourceLocation StartLoc,
        SourceLocation LParenLoc, SourceLocation ColonLoc, SourceLocation EndLoc,
        CXXScopeSpec &ReductionIdScopeSpec,
        const DeclarationNameInfo &ReductionId,
        ArrayRef<Expr *> UnresolvedReductions = llvm::None);
    /// Called on well-formed 'task_reduction' clause.
    OMPClause *ActOnOpenMPTaskReductionClause(
        ArrayRef<Expr *> VarList, SourceLocation StartLoc,
        SourceLocation LParenLoc, SourceLocation ColonLoc, SourceLocation EndLoc,
        CXXScopeSpec &ReductionIdScopeSpec,
        const DeclarationNameInfo &ReductionId,
        ArrayRef<Expr *> UnresolvedReductions = llvm::None);
    /// Called on well-formed 'in_reduction' clause.
    OMPClause *ActOnOpenMPInReductionClause(
        ArrayRef<Expr *> VarList, SourceLocation StartLoc,
        SourceLocation LParenLoc, SourceLocation ColonLoc, SourceLocation EndLoc,
        CXXScopeSpec &ReductionIdScopeSpec,
        const DeclarationNameInfo &ReductionId,
        ArrayRef<Expr *> UnresolvedReductions = llvm::None);
    /// Called on well-formed 'linear' clause.
    OMPClause *
    ActOnOpenMPLinearClause(ArrayRef<Expr *> VarList, Expr *Step,
                            SourceLocation StartLoc, SourceLocation LParenLoc,
                            OpenMPLinearClauseKind LinKind, SourceLocation LinLoc,
                            SourceLocation ColonLoc, SourceLocation EndLoc);
    /// Called on well-formed 'aligned' clause.
    OMPClause *ActOnOpenMPAlignedClause(ArrayRef<Expr *> VarList,
                                        Expr *Alignment,
                                        SourceLocation StartLoc,
                                        SourceLocation LParenLoc,
                                        SourceLocation ColonLoc,
                                        SourceLocation EndLoc);
    /// Called on well-formed 'copyin' clause.
    OMPClause *ActOnOpenMPCopyinClause(ArrayRef<Expr *> VarList,
                                       SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'copyprivate' clause.
    OMPClause *ActOnOpenMPCopyprivateClause(ArrayRef<Expr *> VarList,
                                            SourceLocation StartLoc,
                                            SourceLocation LParenLoc,
                                            SourceLocation EndLoc);
    /// Called on well-formed 'flush' pseudo clause.
    OMPClause *ActOnOpenMPFlushClause(ArrayRef<Expr *> VarList,
                                      SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc);
    /// Called on well-formed 'depobj' pseudo clause.
    OMPClause *ActOnOpenMPDepobjClause(Expr *Depobj, SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'depend' clause.
    OMPClause *
    ActOnOpenMPDependClause(OpenMPDependClauseKind DepKind, SourceLocation DepLoc,
                            SourceLocation ColonLoc, ArrayRef<Expr *> VarList,
                            SourceLocation StartLoc, SourceLocation LParenLoc,
                            SourceLocation EndLoc);
    /// Called on well-formed 'device' clause.
    OMPClause *ActOnOpenMPDeviceClause(Expr *Device, SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
                                       SourceLocation EndLoc);
    /// Called on well-formed 'map' clause.
    OMPClause *
    ActOnOpenMPMapClause(ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
                         ArrayRef<SourceLocation> MapTypeModifiersLoc,
                         CXXScopeSpec &MapperIdScopeSpec,
                         DeclarationNameInfo &MapperId,
                         OpenMPMapClauseKind MapType, bool IsMapTypeImplicit,
                         SourceLocation MapLoc, SourceLocation ColonLoc,
                         ArrayRef<Expr *> VarList, const OMPVarListLocTy &Locs,
                         ArrayRef<Expr *> UnresolvedMappers = llvm::None);
    /// Called on well-formed 'num_teams' clause.
    OMPClause *ActOnOpenMPNumTeamsClause(Expr *NumTeams, SourceLocation StartLoc,
                                         SourceLocation LParenLoc,
                                         SourceLocation EndLoc);
    /// Called on well-formed 'thread_limit' clause.
    OMPClause *ActOnOpenMPThreadLimitClause(Expr *ThreadLimit,
                                            SourceLocation StartLoc,
                                            SourceLocation LParenLoc,
                                            SourceLocation EndLoc);
    /// Called on well-formed 'priority' clause.
    OMPClause *ActOnOpenMPPriorityClause(Expr *Priority, SourceLocation StartLoc,
                                         SourceLocation LParenLoc,
                                         SourceLocation EndLoc);
    /// Called on well-formed 'dist_schedule' clause.
    OMPClause *ActOnOpenMPDistScheduleClause(
        OpenMPDistScheduleClauseKind Kind, Expr *ChunkSize,
        SourceLocation StartLoc, SourceLocation LParenLoc, SourceLocation KindLoc,
        SourceLocation CommaLoc, SourceLocation EndLoc);
    /// Called on well-formed 'defaultmap' clause.
    OMPClause *ActOnOpenMPDefaultmapClause(
        OpenMPDefaultmapClauseModifier M, OpenMPDefaultmapClauseKind Kind,
        SourceLocation StartLoc, SourceLocation LParenLoc, SourceLocation MLoc,
        SourceLocation KindLoc, SourceLocation EndLoc);
    /// Called on well-formed 'to' clause.
    OMPClause *
    ActOnOpenMPToClause(ArrayRef<Expr *> VarList, CXXScopeSpec &MapperIdScopeSpec,
                        DeclarationNameInfo &MapperId,
                        const OMPVarListLocTy &Locs,
                        ArrayRef<Expr *> UnresolvedMappers = llvm::None);
    /// Called on well-formed 'from' clause.
    OMPClause *ActOnOpenMPFromClause(
        ArrayRef<Expr *> VarList, CXXScopeSpec &MapperIdScopeSpec,
        DeclarationNameInfo &MapperId, const OMPVarListLocTy &Locs,
        ArrayRef<Expr *> UnresolvedMappers = llvm::None);
    /// Called on well-formed 'use_device_ptr' clause.
    OMPClause *ActOnOpenMPUseDevicePtrClause(ArrayRef<Expr *> VarList,
                                             const OMPVarListLocTy &Locs);
    /// Called on well-formed 'is_device_ptr' clause.
    OMPClause *ActOnOpenMPIsDevicePtrClause(ArrayRef<Expr *> VarList,
                                            const OMPVarListLocTy &Locs);
    /// Called on well-formed 'nontemporal' clause.
    OMPClause *ActOnOpenMPNontemporalClause(ArrayRef<Expr *> VarList,
                                            SourceLocation StartLoc,
                                            SourceLocation LParenLoc,
                                            SourceLocation EndLoc);
  
    /// The kind of conversion being performed.
    enum CheckedConversionKind {
      /// An implicit conversion.
      CCK_ImplicitConversion,
      /// A C-style cast.
      CCK_CStyleCast,
      /// A functional-style cast.
      CCK_FunctionalCast,
      /// A cast other than a C-style cast.
      CCK_OtherCast,
      /// A conversion for an operand of a builtin overloaded operator.
      CCK_ForBuiltinOverloadedOp
    };
  
    static bool isCast(CheckedConversionKind CCK) {
      return CCK == CCK_CStyleCast || CCK == CCK_FunctionalCast ||
             CCK == CCK_OtherCast;
    }
  
    /// ImpCastExprToType - If Expr is not of type 'Type', insert an implicit
    /// cast.  If there is already an implicit cast, merge into the existing one.
    /// If isLvalue, the result of the cast is an lvalue.
    ExprResult ImpCastExprToType(Expr *E, QualType Type, CastKind CK,
                                 ExprValueKind VK = VK_RValue,
                                 const CXXCastPath *BasePath = nullptr,
                                 CheckedConversionKind CCK
                                    = CCK_ImplicitConversion);
  
    /// ScalarTypeToBooleanCastKind - Returns the cast kind corresponding
    /// to the conversion from scalar type ScalarTy to the Boolean type.
    static CastKind ScalarTypeToBooleanCastKind(QualType ScalarTy);
  
    /// IgnoredValueConversions - Given that an expression's result is
    /// syntactically ignored, perform any conversions that are
    /// required.
    ExprResult IgnoredValueConversions(Expr *E);
  
    // UsualUnaryConversions - promotes integers (C99 6.3.1.1p2) and converts
    // functions and arrays to their respective pointers (C99 6.3.2.1).
    ExprResult UsualUnaryConversions(Expr *E);
  
    /// CallExprUnaryConversions - a special case of an unary conversion
    /// performed on a function designator of a call expression.
    ExprResult CallExprUnaryConversions(Expr *E);
  
    // DefaultFunctionArrayConversion - converts functions and arrays
    // to their respective pointers (C99 6.3.2.1).
    ExprResult DefaultFunctionArrayConversion(Expr *E, bool Diagnose = true);
  
    // DefaultFunctionArrayLvalueConversion - converts functions and
    // arrays to their respective pointers and performs the
    // lvalue-to-rvalue conversion.
    ExprResult DefaultFunctionArrayLvalueConversion(Expr *E,
                                                    bool Diagnose = true);
  
    // DefaultLvalueConversion - performs lvalue-to-rvalue conversion on
    // the operand.  This is DefaultFunctionArrayLvalueConversion,
    // except that it assumes the operand isn't of function or array
    // type.
    ExprResult DefaultLvalueConversion(Expr *E);
  
    // DefaultArgumentPromotion (C99 6.5.2.2p6). Used for function calls that
    // do not have a prototype. Integer promotions are performed on each
    // argument, and arguments that have type float are promoted to double.
    ExprResult DefaultArgumentPromotion(Expr *E);
  
    /// If \p E is a prvalue denoting an unmaterialized temporary, materialize
    /// it as an xvalue. In C++98, the result will still be a prvalue, because
    /// we don't have xvalues there.
    ExprResult TemporaryMaterializationConversion(Expr *E);
  
    // Used for emitting the right warning by DefaultVariadicArgumentPromotion
    enum VariadicCallType {
      VariadicFunction,
      VariadicBlock,
      VariadicMethod,
      VariadicConstructor,
      VariadicDoesNotApply
    };
  
    VariadicCallType getVariadicCallType(FunctionDecl *FDecl,
                                         const FunctionProtoType *Proto,
                                         Expr *Fn);
  
    // Used for determining in which context a type is allowed to be passed to a
    // vararg function.
    enum VarArgKind {
      VAK_Valid,
      VAK_ValidInCXX11,
      VAK_Undefined,
      VAK_MSVCUndefined,
      VAK_Invalid
    };
  
    // Determines which VarArgKind fits an expression.
    VarArgKind isValidVarArgType(const QualType &Ty);
  
    /// Check to see if the given expression is a valid argument to a variadic
    /// function, issuing a diagnostic if not.
    void checkVariadicArgument(const Expr *E, VariadicCallType CT);
  
    /// Check to see if a given expression could have '.c_str()' called on it.
    bool hasCStrMethod(const Expr *E);
  
    /// GatherArgumentsForCall - Collector argument expressions for various
    /// form of call prototypes.
    bool GatherArgumentsForCall(SourceLocation CallLoc, FunctionDecl *FDecl,
                                const FunctionProtoType *Proto,
                                unsigned FirstParam, ArrayRef<Expr *> Args,
                                SmallVectorImpl<Expr *> &AllArgs,
                                VariadicCallType CallType = VariadicDoesNotApply,
                                bool AllowExplicit = false,
                                bool IsListInitialization = false);
  
    // DefaultVariadicArgumentPromotion - Like DefaultArgumentPromotion, but
    // will create a runtime trap if the resulting type is not a POD type.
    ExprResult DefaultVariadicArgumentPromotion(Expr *E, VariadicCallType CT,
                                                FunctionDecl *FDecl);
  
    /// Context in which we're performing a usual arithmetic conversion.
    enum ArithConvKind {
      /// An arithmetic operation.
      ACK_Arithmetic,
      /// A bitwise operation.
      ACK_BitwiseOp,
      /// A comparison.
      ACK_Comparison,
      /// A conditional (?:) operator.
      ACK_Conditional,
      /// A compound assignment expression.
      ACK_CompAssign,
    };
  
    // UsualArithmeticConversions - performs the UsualUnaryConversions on it's
    // operands and then handles various conversions that are common to binary
    // operators (C99 6.3.1.8). If both operands aren't arithmetic, this
    // routine returns the first non-arithmetic type found. The client is
    // responsible for emitting appropriate error diagnostics.
    QualType UsualArithmeticConversions(ExprResult &LHS, ExprResult &RHS,
                                        SourceLocation Loc, ArithConvKind ACK);
  
    /// AssignConvertType - All of the 'assignment' semantic checks return this
    /// enum to indicate whether the assignment was allowed.  These checks are
    /// done for simple assignments, as well as initialization, return from
    /// function, argument passing, etc.  The query is phrased in terms of a
    /// source and destination type.
    enum AssignConvertType {
      /// Compatible - the types are compatible according to the standard.
      Compatible,
  
      /// PointerToInt - The assignment converts a pointer to an int, which we
      /// accept as an extension.
      PointerToInt,
  
      /// IntToPointer - The assignment converts an int to a pointer, which we
      /// accept as an extension.
      IntToPointer,
  
      /// FunctionVoidPointer - The assignment is between a function pointer and
      /// void*, which the standard doesn't allow, but we accept as an extension.
      FunctionVoidPointer,
  
      /// IncompatiblePointer - The assignment is between two pointers types that
      /// are not compatible, but we accept them as an extension.
      IncompatiblePointer,
  
      /// IncompatibleFunctionPointer - The assignment is between two function
      /// pointers types that are not compatible, but we accept them as an
      /// extension.
      IncompatibleFunctionPointer,
  
      /// IncompatiblePointerSign - The assignment is between two pointers types
      /// which point to integers which have a different sign, but are otherwise
      /// identical. This is a subset of the above, but broken out because it's by
      /// far the most common case of incompatible pointers.
      IncompatiblePointerSign,
  
      /// CompatiblePointerDiscardsQualifiers - The assignment discards
      /// c/v/r qualifiers, which we accept as an extension.
      CompatiblePointerDiscardsQualifiers,
  
      /// IncompatiblePointerDiscardsQualifiers - The assignment
      /// discards qualifiers that we don't permit to be discarded,
      /// like address spaces.
      IncompatiblePointerDiscardsQualifiers,
  
      /// IncompatibleNestedPointerAddressSpaceMismatch - The assignment
      /// changes address spaces in nested pointer types which is not allowed.
      /// For instance, converting __private int ** to __generic int ** is
      /// illegal even though __private could be converted to __generic.
      IncompatibleNestedPointerAddressSpaceMismatch,
  
      /// IncompatibleNestedPointerQualifiers - The assignment is between two
      /// nested pointer types, and the qualifiers other than the first two
      /// levels differ e.g. char ** -> const char **, but we accept them as an
      /// extension.
      IncompatibleNestedPointerQualifiers,
  
      /// IncompatibleVectors - The assignment is between two vector types that
      /// have the same size, which we accept as an extension.
      IncompatibleVectors,
  
      /// IntToBlockPointer - The assignment converts an int to a block
      /// pointer. We disallow this.
      IntToBlockPointer,
  
      /// IncompatibleBlockPointer - The assignment is between two block
      /// pointers types that are not compatible.
      IncompatibleBlockPointer,
  
      /// IncompatibleObjCQualifiedId - The assignment is between a qualified
      /// id type and something else (that is incompatible with it). For example,
      /// "id <XXX>" = "Foo *", where "Foo *" doesn't implement the XXX protocol.
      IncompatibleObjCQualifiedId,
  
      /// IncompatibleObjCWeakRef - Assigning a weak-unavailable object to an
      /// object with __weak qualifier.
      IncompatibleObjCWeakRef,
  
      /// Incompatible - We reject this conversion outright, it is invalid to
      /// represent it in the AST.
      Incompatible
    };
  
    /// DiagnoseAssignmentResult - Emit a diagnostic, if required, for the
    /// assignment conversion type specified by ConvTy.  This returns true if the
    /// conversion was invalid or false if the conversion was accepted.
    bool DiagnoseAssignmentResult(AssignConvertType ConvTy,
                                  SourceLocation Loc,
                                  QualType DstType, QualType SrcType,
                                  Expr *SrcExpr, AssignmentAction Action,
                                  bool *Complained = nullptr);
  
    /// IsValueInFlagEnum - Determine if a value is allowed as part of a flag
    /// enum. If AllowMask is true, then we also allow the complement of a valid
    /// value, to be used as a mask.
    bool IsValueInFlagEnum(const EnumDecl *ED, const llvm::APInt &Val,
                           bool AllowMask) const;
  
    /// DiagnoseAssignmentEnum - Warn if assignment to enum is a constant
    /// integer not in the range of enum values.
    void DiagnoseAssignmentEnum(QualType DstType, QualType SrcType,
                                Expr *SrcExpr);
  
    /// CheckAssignmentConstraints - Perform type checking for assignment,
    /// argument passing, variable initialization, and function return values.
    /// C99 6.5.16.
    AssignConvertType CheckAssignmentConstraints(SourceLocation Loc,
                                                 QualType LHSType,
                                                 QualType RHSType);
  
    /// Check assignment constraints and optionally prepare for a conversion of
    /// the RHS to the LHS type. The conversion is prepared for if ConvertRHS
    /// is true.
    AssignConvertType CheckAssignmentConstraints(QualType LHSType,
                                                 ExprResult &RHS,
                                                 CastKind &Kind,
                                                 bool ConvertRHS = true);
  
    /// Check assignment constraints for an assignment of RHS to LHSType.
    ///
    /// \param LHSType The destination type for the assignment.
    /// \param RHS The source expression for the assignment.
    /// \param Diagnose If \c true, diagnostics may be produced when checking
    ///        for assignability. If a diagnostic is produced, \p RHS will be
    ///        set to ExprError(). Note that this function may still return
    ///        without producing a diagnostic, even for an invalid assignment.
    /// \param DiagnoseCFAudited If \c true, the target is a function parameter
    ///        in an audited Core Foundation API and does not need to be checked
    ///        for ARC retain issues.
    /// \param ConvertRHS If \c true, \p RHS will be updated to model the
    ///        conversions necessary to perform the assignment. If \c false,
    ///        \p Diagnose must also be \c false.
    AssignConvertType CheckSingleAssignmentConstraints(
        QualType LHSType, ExprResult &RHS, bool Diagnose = true,
        bool DiagnoseCFAudited = false, bool ConvertRHS = true);
  
    // If the lhs type is a transparent union, check whether we
    // can initialize the transparent union with the given expression.
    AssignConvertType CheckTransparentUnionArgumentConstraints(QualType ArgType,
                                                               ExprResult &RHS);
  
    bool IsStringLiteralToNonConstPointerConversion(Expr *From, QualType ToType);
  
    bool CheckExceptionSpecCompatibility(Expr *From, QualType ToType);
  
    ExprResult PerformImplicitConversion(Expr *From, QualType ToType,
                                         AssignmentAction Action,
                                         bool AllowExplicit = false);
    ExprResult PerformImplicitConversion(Expr *From, QualType ToType,
                                         AssignmentAction Action,
                                         bool AllowExplicit,
                                         ImplicitConversionSequence& ICS);
    ExprResult PerformImplicitConversion(Expr *From, QualType ToType,
                                         const ImplicitConversionSequence& ICS,
                                         AssignmentAction Action,
                                         CheckedConversionKind CCK
                                            = CCK_ImplicitConversion);
    ExprResult PerformImplicitConversion(Expr *From, QualType ToType,
                                         const StandardConversionSequence& SCS,
                                         AssignmentAction Action,
                                         CheckedConversionKind CCK);
  
    ExprResult PerformQualificationConversion(
        Expr *E, QualType Ty, ExprValueKind VK = VK_RValue,
        CheckedConversionKind CCK = CCK_ImplicitConversion);
  
    /// the following "Check" methods will return a valid/converted QualType
    /// or a null QualType (indicating an error diagnostic was issued).
  
    /// type checking binary operators (subroutines of CreateBuiltinBinOp).
    QualType InvalidOperands(SourceLocation Loc, ExprResult &LHS,
                             ExprResult &RHS);
    QualType InvalidLogicalVectorOperands(SourceLocation Loc, ExprResult &LHS,
                                   ExprResult &RHS);
    QualType CheckPointerToMemberOperands( // C++ 5.5
      ExprResult &LHS, ExprResult &RHS, ExprValueKind &VK,
      SourceLocation OpLoc, bool isIndirect);
    QualType CheckMultiplyDivideOperands( // C99 6.5.5
      ExprResult &LHS, ExprResult &RHS, SourceLocation Loc, bool IsCompAssign,
      bool IsDivide);
    QualType CheckRemainderOperands( // C99 6.5.5
      ExprResult &LHS, ExprResult &RHS, SourceLocation Loc,
      bool IsCompAssign = false);
    QualType CheckAdditionOperands( // C99 6.5.6
      ExprResult &LHS, ExprResult &RHS, SourceLocation Loc,
      BinaryOperatorKind Opc, QualType* CompLHSTy = nullptr);
    QualType CheckSubtractionOperands( // C99 6.5.6
      ExprResult &LHS, ExprResult &RHS, SourceLocation Loc,
      QualType* CompLHSTy = nullptr);
    QualType CheckShiftOperands( // C99 6.5.7
      ExprResult &LHS, ExprResult &RHS, SourceLocation Loc,
      BinaryOperatorKind Opc, bool IsCompAssign = false);
    void CheckPtrComparisonWithNullChar(ExprResult &E, ExprResult &NullE);
    QualType CheckCompareOperands( // C99 6.5.8/9
        ExprResult &LHS, ExprResult &RHS, SourceLocation Loc,
        BinaryOperatorKind Opc);
    QualType CheckBitwiseOperands( // C99 6.5.[10...12]
        ExprResult &LHS, ExprResult &RHS, SourceLocation Loc,
        BinaryOperatorKind Opc);
    QualType CheckLogicalOperands( // C99 6.5.[13,14]
      ExprResult &LHS, ExprResult &RHS, SourceLocation Loc,
      BinaryOperatorKind Opc);
    // CheckAssignmentOperands is used for both simple and compound assignment.
    // For simple assignment, pass both expressions and a null converted type.
    // For compound assignment, pass both expressions and the converted type.
    QualType CheckAssignmentOperands( // C99 6.5.16.[1,2]
      Expr *LHSExpr, ExprResult &RHS, SourceLocation Loc, QualType CompoundType);
  
    ExprResult checkPseudoObjectIncDec(Scope *S, SourceLocation OpLoc,
                                       UnaryOperatorKind Opcode, Expr *Op);
    ExprResult checkPseudoObjectAssignment(Scope *S, SourceLocation OpLoc,
                                           BinaryOperatorKind Opcode,
                                           Expr *LHS, Expr *RHS);
    ExprResult checkPseudoObjectRValue(Expr *E);
    Expr *recreateSyntacticForm(PseudoObjectExpr *E);
  
    QualType CheckConditionalOperands( // C99 6.5.15
      ExprResult &Cond, ExprResult &LHS, ExprResult &RHS,
      ExprValueKind &VK, ExprObjectKind &OK, SourceLocation QuestionLoc);
    QualType CXXCheckConditionalOperands( // C++ 5.16
      ExprResult &cond, ExprResult &lhs, ExprResult &rhs,
      ExprValueKind &VK, ExprObjectKind &OK, SourceLocation questionLoc);
    QualType CheckGNUVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
                                            ExprResult &RHS,
                                            SourceLocation QuestionLoc);
    QualType FindCompositePointerType(SourceLocation Loc, Expr *&E1, Expr *&E2,
                                      bool ConvertArgs = true);
    QualType FindCompositePointerType(SourceLocation Loc,
                                      ExprResult &E1, ExprResult &E2,
                                      bool ConvertArgs = true) {
      Expr *E1Tmp = E1.get(), *E2Tmp = E2.get();
      QualType Composite =
          FindCompositePointerType(Loc, E1Tmp, E2Tmp, ConvertArgs);
      E1 = E1Tmp;
      E2 = E2Tmp;
      return Composite;
    }
  
    QualType FindCompositeObjCPointerType(ExprResult &LHS, ExprResult &RHS,
                                          SourceLocation QuestionLoc);
  
    bool DiagnoseConditionalForNull(Expr *LHSExpr, Expr *RHSExpr,
                                    SourceLocation QuestionLoc);
  
    void DiagnoseAlwaysNonNullPointer(Expr *E,
                                      Expr::NullPointerConstantKind NullType,
                                      bool IsEqual, SourceRange Range);
  
    /// type checking for vector binary operators.
    QualType CheckVectorOperands(ExprResult &LHS, ExprResult &RHS,
                                 SourceLocation Loc, bool IsCompAssign,
                                 bool AllowBothBool, bool AllowBoolConversion);
    QualType GetSignedVectorType(QualType V);
    QualType CheckVectorCompareOperands(ExprResult &LHS, ExprResult &RHS,
                                        SourceLocation Loc,
                                        BinaryOperatorKind Opc);
    QualType CheckVectorLogicalOperands(ExprResult &LHS, ExprResult &RHS,
                                        SourceLocation Loc);
  
    bool areLaxCompatibleVectorTypes(QualType srcType, QualType destType);
    bool isLaxVectorConversion(QualType srcType, QualType destType);
  
    /// type checking declaration initializers (C99 6.7.8)
    bool CheckForConstantInitializer(Expr *e, QualType t);
  
    // type checking C++ declaration initializers (C++ [dcl.init]).
  
    /// ReferenceCompareResult - Expresses the result of comparing two
    /// types (cv1 T1 and cv2 T2) to determine their compatibility for the
    /// purposes of initialization by reference (C++ [dcl.init.ref]p4).
    enum ReferenceCompareResult {
      /// Ref_Incompatible - The two types are incompatible, so direct
      /// reference binding is not possible.
      Ref_Incompatible = 0,
      /// Ref_Related - The two types are reference-related, which means
      /// that their unqualified forms (T1 and T2) are either the same
      /// or T1 is a base class of T2.
      Ref_Related,
      /// Ref_Compatible - The two types are reference-compatible.
      Ref_Compatible
    };
  
    // Fake up a scoped enumeration that still contextually converts to bool.
    struct ReferenceConversionsScope {
      /// The conversions that would be performed on an lvalue of type T2 when
      /// binding a reference of type T1 to it, as determined when evaluating
      /// whether T1 is reference-compatible with T2.
      enum ReferenceConversions {
        Qualification = 0x1,
        NestedQualification = 0x2,
        Function = 0x4,
        DerivedToBase = 0x8,
        ObjC = 0x10,
        ObjCLifetime = 0x20,
  
        LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue=*/ObjCLifetime)
      };
    };
    using ReferenceConversions = ReferenceConversionsScope::ReferenceConversions;
  
    ReferenceCompareResult
    CompareReferenceRelationship(SourceLocation Loc, QualType T1, QualType T2,
                                 ReferenceConversions *Conv = nullptr);
  
    ExprResult checkUnknownAnyCast(SourceRange TypeRange, QualType CastType,
                                   Expr *CastExpr, CastKind &CastKind,
                                   ExprValueKind &VK, CXXCastPath &Path);
  
    /// Force an expression with unknown-type to an expression of the
    /// given type.
    ExprResult forceUnknownAnyToType(Expr *E, QualType ToType);
  
    /// Type-check an expression that's being passed to an
    /// __unknown_anytype parameter.
    ExprResult checkUnknownAnyArg(SourceLocation callLoc,
                                  Expr *result, QualType &paramType);
  
    // CheckVectorCast - check type constraints for vectors.
    // Since vectors are an extension, there are no C standard reference for this.
    // We allow casting between vectors and integer datatypes of the same size.
    // returns true if the cast is invalid
    bool CheckVectorCast(SourceRange R, QualType VectorTy, QualType Ty,
                         CastKind &Kind);
  
    /// Prepare `SplattedExpr` for a vector splat operation, adding
    /// implicit casts if necessary.
    ExprResult prepareVectorSplat(QualType VectorTy, Expr *SplattedExpr);
  
    // CheckExtVectorCast - check type constraints for extended vectors.
    // Since vectors are an extension, there are no C standard reference for this.
    // We allow casting between vectors and integer datatypes of the same size,
    // or vectors and the element type of that vector.
    // returns the cast expr
    ExprResult CheckExtVectorCast(SourceRange R, QualType DestTy, Expr *CastExpr,
                                  CastKind &Kind);
  
    ExprResult BuildCXXFunctionalCastExpr(TypeSourceInfo *TInfo, QualType Type,
                                          SourceLocation LParenLoc,
                                          Expr *CastExpr,
                                          SourceLocation RParenLoc);
  
    enum ARCConversionResult { ACR_okay, ACR_unbridged, ACR_error };
  
    /// Checks for invalid conversions and casts between
    /// retainable pointers and other pointer kinds for ARC and Weak.
    ARCConversionResult CheckObjCConversion(SourceRange castRange,
                                            QualType castType, Expr *&op,
                                            CheckedConversionKind CCK,
                                            bool Diagnose = true,
                                            bool DiagnoseCFAudited = false,
                                            BinaryOperatorKind Opc = BO_PtrMemD
                                            );
  
    Expr *stripARCUnbridgedCast(Expr *e);
    void diagnoseARCUnbridgedCast(Expr *e);
  
    bool CheckObjCARCUnavailableWeakConversion(QualType castType,
                                               QualType ExprType);
  
    /// checkRetainCycles - Check whether an Objective-C message send
    /// might create an obvious retain cycle.
    void checkRetainCycles(ObjCMessageExpr *msg);
    void checkRetainCycles(Expr *receiver, Expr *argument);
    void checkRetainCycles(VarDecl *Var, Expr *Init);
  
    /// checkUnsafeAssigns - Check whether +1 expr is being assigned
    /// to weak/__unsafe_unretained type.
    bool checkUnsafeAssigns(SourceLocation Loc, QualType LHS, Expr *RHS);
  
    /// checkUnsafeExprAssigns - Check whether +1 expr is being assigned
    /// to weak/__unsafe_unretained expression.
    void checkUnsafeExprAssigns(SourceLocation Loc, Expr *LHS, Expr *RHS);
  
    /// CheckMessageArgumentTypes - Check types in an Obj-C message send.
    /// \param Method - May be null.
    /// \param [out] ReturnType - The return type of the send.
    /// \return true iff there were any incompatible types.
    bool CheckMessageArgumentTypes(const Expr *Receiver, QualType ReceiverType,
                                   MultiExprArg Args, Selector Sel,
                                   ArrayRef<SourceLocation> SelectorLocs,
                                   ObjCMethodDecl *Method, bool isClassMessage,
                                   bool isSuperMessage, SourceLocation lbrac,
                                   SourceLocation rbrac, SourceRange RecRange,
                                   QualType &ReturnType, ExprValueKind &VK);
  
    /// Determine the result of a message send expression based on
    /// the type of the receiver, the method expected to receive the message,
    /// and the form of the message send.
    QualType getMessageSendResultType(const Expr *Receiver, QualType ReceiverType,
                                      ObjCMethodDecl *Method, bool isClassMessage,
                                      bool isSuperMessage);
  
    /// If the given expression involves a message send to a method
    /// with a related result type, emit a note describing what happened.
    void EmitRelatedResultTypeNote(const Expr *E);
  
    /// Given that we had incompatible pointer types in a return
    /// statement, check whether we're in a method with a related result
    /// type, and if so, emit a note describing what happened.
    void EmitRelatedResultTypeNoteForReturn(QualType destType);
  
    class ConditionResult {
      Decl *ConditionVar;
      FullExprArg Condition;
      bool Invalid;
      bool HasKnownValue;
      bool KnownValue;
  
      friend class Sema;
      ConditionResult(Sema &S, Decl *ConditionVar, FullExprArg Condition,
                      bool IsConstexpr)
          : ConditionVar(ConditionVar), Condition(Condition), Invalid(false),
            HasKnownValue(IsConstexpr && Condition.get() &&
                          !Condition.get()->isValueDependent()),
            KnownValue(HasKnownValue &&
                       !!Condition.get()->EvaluateKnownConstInt(S.Context)) {}
      explicit ConditionResult(bool Invalid)
          : ConditionVar(nullptr), Condition(nullptr), Invalid(Invalid),
            HasKnownValue(false), KnownValue(false) {}
  
    public:
      ConditionResult() : ConditionResult(false) {}
      bool isInvalid() const { return Invalid; }
      std::pair<VarDecl *, Expr *> get() const {
        return std::make_pair(cast_or_null<VarDecl>(ConditionVar),
                              Condition.get());
      }
      llvm::Optional<bool> getKnownValue() const {
        if (!HasKnownValue)
          return None;
        return KnownValue;
      }
    };
    static ConditionResult ConditionError() { return ConditionResult(true); }
  
    enum class ConditionKind {
      Boolean,     ///< A boolean condition, from 'if', 'while', 'for', or 'do'.
      ConstexprIf, ///< A constant boolean condition from 'if constexpr'.
      Switch       ///< An integral condition for a 'switch' statement.
    };
  
    ConditionResult ActOnCondition(Scope *S, SourceLocation Loc,
                                   Expr *SubExpr, ConditionKind CK);
  
    ConditionResult ActOnConditionVariable(Decl *ConditionVar,
                                           SourceLocation StmtLoc,
                                           ConditionKind CK);
  
    DeclResult ActOnCXXConditionDeclaration(Scope *S, Declarator &D);
  
    ExprResult CheckConditionVariable(VarDecl *ConditionVar,
                                      SourceLocation StmtLoc,
                                      ConditionKind CK);
    ExprResult CheckSwitchCondition(SourceLocation SwitchLoc, Expr *Cond);
  
    /// CheckBooleanCondition - Diagnose problems involving the use of
    /// the given expression as a boolean condition (e.g. in an if
    /// statement).  Also performs the standard function and array
    /// decays, possibly changing the input variable.
    ///
    /// \param Loc - A location associated with the condition, e.g. the
    /// 'if' keyword.
    /// \return true iff there were any errors
    ExprResult CheckBooleanCondition(SourceLocation Loc, Expr *E,
                                     bool IsConstexpr = false);
  
    /// ActOnExplicitBoolSpecifier - Build an ExplicitSpecifier from an expression
    /// found in an explicit(bool) specifier.
    ExplicitSpecifier ActOnExplicitBoolSpecifier(Expr *E);
  
    /// tryResolveExplicitSpecifier - Attempt to resolve the explict specifier.
    /// Returns true if the explicit specifier is now resolved.
    bool tryResolveExplicitSpecifier(ExplicitSpecifier &ExplicitSpec);
  
    /// DiagnoseAssignmentAsCondition - Given that an expression is
    /// being used as a boolean condition, warn if it's an assignment.
    void DiagnoseAssignmentAsCondition(Expr *E);
  
    /// Redundant parentheses over an equality comparison can indicate
    /// that the user intended an assignment used as condition.
    void DiagnoseEqualityWithExtraParens(ParenExpr *ParenE);
  
    /// CheckCXXBooleanCondition - Returns true if conversion to bool is invalid.
    ExprResult CheckCXXBooleanCondition(Expr *CondExpr, bool IsConstexpr = false);
  
    /// ConvertIntegerToTypeWarnOnOverflow - Convert the specified APInt to have
    /// the specified width and sign.  If an overflow occurs, detect it and emit
    /// the specified diagnostic.
    void ConvertIntegerToTypeWarnOnOverflow(llvm::APSInt &OldVal,
                                            unsigned NewWidth, bool NewSign,
                                            SourceLocation Loc, unsigned DiagID);
  
    /// Checks that the Objective-C declaration is declared in the global scope.
    /// Emits an error and marks the declaration as invalid if it's not declared
    /// in the global scope.
    bool CheckObjCDeclScope(Decl *D);
  
    /// Abstract base class used for diagnosing integer constant
    /// expression violations.
    class VerifyICEDiagnoser {
    public:
      bool Suppress;
  
      VerifyICEDiagnoser(bool Suppress = false) : Suppress(Suppress) { }
  
      virtual void diagnoseNotICE(Sema &S, SourceLocation Loc, SourceRange SR) =0;
      virtual void diagnoseFold(Sema &S, SourceLocation Loc, SourceRange SR);
      virtual ~VerifyICEDiagnoser() { }
    };
  
    /// VerifyIntegerConstantExpression - Verifies that an expression is an ICE,
    /// and reports the appropriate diagnostics. Returns false on success.
    /// Can optionally return the value of the expression.
    ExprResult VerifyIntegerConstantExpression(Expr *E, llvm::APSInt *Result,
                                               VerifyICEDiagnoser &Diagnoser,
                                               bool AllowFold = true);
    ExprResult VerifyIntegerConstantExpression(Expr *E, llvm::APSInt *Result,
                                               unsigned DiagID,
                                               bool AllowFold = true);
    ExprResult VerifyIntegerConstantExpression(Expr *E,
                                               llvm::APSInt *Result = nullptr);
  
    /// VerifyBitField - verifies that a bit field expression is an ICE and has
    /// the correct width, and that the field type is valid.
    /// Returns false on success.
    /// Can optionally return whether the bit-field is of width 0
    ExprResult VerifyBitField(SourceLocation FieldLoc, IdentifierInfo *FieldName,
                              QualType FieldTy, bool IsMsStruct,
                              Expr *BitWidth, bool *ZeroWidth = nullptr);
  
  private:
    unsigned ForceCUDAHostDeviceDepth = 0;
  
  public:
    /// Increments our count of the number of times we've seen a pragma forcing
    /// functions to be __host__ __device__.  So long as this count is greater
    /// than zero, all functions encountered will be __host__ __device__.
    void PushForceCUDAHostDevice();
  
    /// Decrements our count of the number of times we've seen a pragma forcing
    /// functions to be __host__ __device__.  Returns false if the count is 0
    /// before incrementing, so you can emit an error.
    bool PopForceCUDAHostDevice();
  
    /// Diagnostics that are emitted only if we discover that the given function
    /// must be codegen'ed.  Because handling these correctly adds overhead to
    /// compilation, this is currently only enabled for CUDA compilations.
    llvm::DenseMap<CanonicalDeclPtr<FunctionDecl>,
                   std::vector<PartialDiagnosticAt>>
        DeviceDeferredDiags;
  
    /// A pair of a canonical FunctionDecl and a SourceLocation.  When used as the
    /// key in a hashtable, both the FD and location are hashed.
    struct FunctionDeclAndLoc {
      CanonicalDeclPtr<FunctionDecl> FD;
      SourceLocation Loc;
    };
  
    /// FunctionDecls and SourceLocations for which CheckCUDACall has emitted a
    /// (maybe deferred) "bad call" diagnostic.  We use this to avoid emitting the
    /// same deferred diag twice.
    llvm::DenseSet<FunctionDeclAndLoc> LocsWithCUDACallDiags;
  
    /// An inverse call graph, mapping known-emitted functions to one of their
    /// known-emitted callers (plus the location of the call).
    ///
    /// Functions that we can tell a priori must be emitted aren't added to this
    /// map.
    llvm::DenseMap</* Callee = */ CanonicalDeclPtr<FunctionDecl>,
                   /* Caller = */ FunctionDeclAndLoc>
        DeviceKnownEmittedFns;
  
    /// A partial call graph maintained during CUDA/OpenMP device code compilation
    /// to support deferred diagnostics.
    ///
    /// Functions are only added here if, at the time they're considered, they are
    /// not known-emitted.  As soon as we discover that a function is
    /// known-emitted, we remove it and everything it transitively calls from this
    /// set and add those functions to DeviceKnownEmittedFns.
    llvm::DenseMap</* Caller = */ CanonicalDeclPtr<FunctionDecl>,
                   /* Callees = */ llvm::MapVector<CanonicalDeclPtr<FunctionDecl>,
                                                   SourceLocation>>
        DeviceCallGraph;
  
    /// Diagnostic builder for CUDA/OpenMP devices errors which may or may not be
    /// deferred.
    ///
    /// In CUDA, there exist constructs (e.g. variable-length arrays, try/catch)
    /// which are not allowed to appear inside __device__ functions and are
    /// allowed to appear in __host__ __device__ functions only if the host+device
    /// function is never codegen'ed.
    ///
    /// To handle this, we use the notion of "deferred diagnostics", where we
    /// attach a diagnostic to a FunctionDecl that's emitted iff it's codegen'ed.
    ///
    /// This class lets you emit either a regular diagnostic, a deferred
    /// diagnostic, or no diagnostic at all, according to an argument you pass to
    /// its constructor, thus simplifying the process of creating these "maybe
    /// deferred" diagnostics.
    class DeviceDiagBuilder {
    public:
      enum Kind {
        /// Emit no diagnostics.
        K_Nop,
        /// Emit the diagnostic immediately (i.e., behave like Sema::Diag()).
        K_Immediate,
        /// Emit the diagnostic immediately, and, if it's a warning or error, also
        /// emit a call stack showing how this function can be reached by an a
        /// priori known-emitted function.
        K_ImmediateWithCallStack,
        /// Create a deferred diagnostic, which is emitted only if the function
        /// it's attached to is codegen'ed.  Also emit a call stack as with
        /// K_ImmediateWithCallStack.
        K_Deferred
      };
  
      DeviceDiagBuilder(Kind K, SourceLocation Loc, unsigned DiagID,
                        FunctionDecl *Fn, Sema &S);
      DeviceDiagBuilder(DeviceDiagBuilder &&D);
      DeviceDiagBuilder(const DeviceDiagBuilder &) = default;
      ~DeviceDiagBuilder();
  
      /// Convertible to bool: True if we immediately emitted an error, false if
      /// we didn't emit an error or we created a deferred error.
      ///
      /// Example usage:
      ///
      ///   if (DeviceDiagBuilder(...) << foo << bar)
      ///     return ExprError();
      ///
      /// But see CUDADiagIfDeviceCode() and CUDADiagIfHostCode() -- you probably
      /// want to use these instead of creating a DeviceDiagBuilder yourself.
      operator bool() const { return ImmediateDiag.hasValue(); }
  
      template <typename T>
      friend const DeviceDiagBuilder &operator<<(const DeviceDiagBuilder &Diag,
                                                 const T &Value) {
        if (Diag.ImmediateDiag.hasValue())
          *Diag.ImmediateDiag << Value;
        else if (Diag.PartialDiagId.hasValue())
          Diag.S.DeviceDeferredDiags[Diag.Fn][*Diag.PartialDiagId].second
              << Value;
        return Diag;
      }
  
    private:
      Sema &S;
      SourceLocation Loc;
      unsigned DiagID;
      FunctionDecl *Fn;
      bool ShowCallStack;
  
      // Invariant: At most one of these Optionals has a value.
      // FIXME: Switch these to a Variant once that exists.
      llvm::Optional<SemaDiagnosticBuilder> ImmediateDiag;
      llvm::Optional<unsigned> PartialDiagId;
    };
  
    /// Indicate that this function (and thus everything it transtively calls)
    /// will be codegen'ed, and emit any deferred diagnostics on this function and
    /// its (transitive) callees.
    void markKnownEmitted(
        Sema &S, FunctionDecl *OrigCaller, FunctionDecl *OrigCallee,
        SourceLocation OrigLoc,
        const llvm::function_ref<bool(Sema &, FunctionDecl *)> IsKnownEmitted);
  
    /// Creates a DeviceDiagBuilder that emits the diagnostic if the current context
    /// is "used as device code".
    ///
    /// - If CurContext is a __host__ function, does not emit any diagnostics.
    /// - If CurContext is a __device__ or __global__ function, emits the
    ///   diagnostics immediately.
    /// - If CurContext is a __host__ __device__ function and we are compiling for
    ///   the device, creates a diagnostic which is emitted if and when we realize
    ///   that the function will be codegen'ed.
    ///
    /// Example usage:
    ///
    ///  // Variable-length arrays are not allowed in CUDA device code.
    ///  if (CUDADiagIfDeviceCode(Loc, diag::err_cuda_vla) << CurrentCUDATarget())
    ///    return ExprError();
    ///  // Otherwise, continue parsing as normal.
    DeviceDiagBuilder CUDADiagIfDeviceCode(SourceLocation Loc, unsigned DiagID);
  
    /// Creates a DeviceDiagBuilder that emits the diagnostic if the current context
    /// is "used as host code".
    ///
    /// Same as CUDADiagIfDeviceCode, with "host" and "device" switched.
    DeviceDiagBuilder CUDADiagIfHostCode(SourceLocation Loc, unsigned DiagID);
  
    /// Creates a DeviceDiagBuilder that emits the diagnostic if the current
    /// context is "used as device code".
    ///
    /// - If CurContext is a `declare target` function or it is known that the
    /// function is emitted for the device, emits the diagnostics immediately.
    /// - If CurContext is a non-`declare target` function and we are compiling
    ///   for the device, creates a diagnostic which is emitted if and when we
    ///   realize that the function will be codegen'ed.
    ///
    /// Example usage:
    ///
    ///  // Variable-length arrays are not allowed in NVPTX device code.
    ///  if (diagIfOpenMPDeviceCode(Loc, diag::err_vla_unsupported))
    ///    return ExprError();
    ///  // Otherwise, continue parsing as normal.
    DeviceDiagBuilder diagIfOpenMPDeviceCode(SourceLocation Loc, unsigned DiagID);
  
    /// Creates a DeviceDiagBuilder that emits the diagnostic if the current
    /// context is "used as host code".
    ///
    /// - If CurContext is a `declare target` function or it is known that the
    /// function is emitted for the host, emits the diagnostics immediately.
    /// - If CurContext is a non-host function, just ignore it.
    ///
    /// Example usage:
    ///
    ///  // Variable-length arrays are not allowed in NVPTX device code.
    ///  if (diagIfOpenMPHostode(Loc, diag::err_vla_unsupported))
    ///    return ExprError();
    ///  // Otherwise, continue parsing as normal.
    DeviceDiagBuilder diagIfOpenMPHostCode(SourceLocation Loc, unsigned DiagID);
  
    DeviceDiagBuilder targetDiag(SourceLocation Loc, unsigned DiagID);
  
    enum CUDAFunctionTarget {
      CFT_Device,
      CFT_Global,
      CFT_Host,
      CFT_HostDevice,
      CFT_InvalidTarget
    };
  
    /// Determines whether the given function is a CUDA device/host/kernel/etc.
    /// function.
    ///
    /// Use this rather than examining the function's attributes yourself -- you
    /// will get it wrong.  Returns CFT_Host if D is null.
    CUDAFunctionTarget IdentifyCUDATarget(const FunctionDecl *D,
                                          bool IgnoreImplicitHDAttr = false);
    CUDAFunctionTarget IdentifyCUDATarget(const ParsedAttributesView &Attrs);
  
    /// Gets the CUDA target for the current context.
    CUDAFunctionTarget CurrentCUDATarget() {
      return IdentifyCUDATarget(dyn_cast<FunctionDecl>(CurContext));
    }
  
    // CUDA function call preference. Must be ordered numerically from
    // worst to best.
    enum CUDAFunctionPreference {
      CFP_Never,      // Invalid caller/callee combination.
      CFP_WrongSide,  // Calls from host-device to host or device
                      // function that do not match current compilation
                      // mode.
      CFP_HostDevice, // Any calls to host/device functions.
      CFP_SameSide,   // Calls from host-device to host or device
                      // function matching current compilation mode.
      CFP_Native,     // host-to-host or device-to-device calls.
    };
  
    /// Identifies relative preference of a given Caller/Callee
    /// combination, based on their host/device attributes.
    /// \param Caller function which needs address of \p Callee.
    ///               nullptr in case of global context.
    /// \param Callee target function
    ///
    /// \returns preference value for particular Caller/Callee combination.
    CUDAFunctionPreference IdentifyCUDAPreference(const FunctionDecl *Caller,
                                                  const FunctionDecl *Callee);
  
    /// Determines whether Caller may invoke Callee, based on their CUDA
    /// host/device attributes.  Returns false if the call is not allowed.
    ///
    /// Note: Will return true for CFP_WrongSide calls.  These may appear in
    /// semantically correct CUDA programs, but only if they're never codegen'ed.
    bool IsAllowedCUDACall(const FunctionDecl *Caller,
                           const FunctionDecl *Callee) {
      return IdentifyCUDAPreference(Caller, Callee) != CFP_Never;
    }
  
    /// May add implicit CUDAHostAttr and CUDADeviceAttr attributes to FD,
    /// depending on FD and the current compilation settings.
    void maybeAddCUDAHostDeviceAttrs(FunctionDecl *FD,
                                     const LookupResult &Previous);
  
  public:
    /// Check whether we're allowed to call Callee from the current context.
    ///
    /// - If the call is never allowed in a semantically-correct program
    ///   (CFP_Never), emits an error and returns false.
    ///
    /// - If the call is allowed in semantically-correct programs, but only if
    ///   it's never codegen'ed (CFP_WrongSide), creates a deferred diagnostic to
    ///   be emitted if and when the caller is codegen'ed, and returns true.
    ///
    ///   Will only create deferred diagnostics for a given SourceLocation once,
    ///   so you can safely call this multiple times without generating duplicate
    ///   deferred errors.
    ///
    /// - Otherwise, returns true without emitting any diagnostics.
    bool CheckCUDACall(SourceLocation Loc, FunctionDecl *Callee);
  
    /// Set __device__ or __host__ __device__ attributes on the given lambda
    /// operator() method.
    ///
    /// CUDA lambdas declared inside __device__ or __global__ functions inherit
    /// the __device__ attribute.  Similarly, lambdas inside __host__ __device__
    /// functions become __host__ __device__ themselves.
    void CUDASetLambdaAttrs(CXXMethodDecl *Method);
  
    /// Finds a function in \p Matches with highest calling priority
    /// from \p Caller context and erases all functions with lower
    /// calling priority.
    void EraseUnwantedCUDAMatches(
        const FunctionDecl *Caller,
        SmallVectorImpl<std::pair<DeclAccessPair, FunctionDecl *>> &Matches);
  
    /// Given a implicit special member, infer its CUDA target from the
    /// calls it needs to make to underlying base/field special members.
    /// \param ClassDecl the class for which the member is being created.
    /// \param CSM the kind of special member.
    /// \param MemberDecl the special member itself.
    /// \param ConstRHS true if this is a copy operation with a const object on
    ///        its RHS.
    /// \param Diagnose true if this call should emit diagnostics.
    /// \return true if there was an error inferring.
    /// The result of this call is implicit CUDA target attribute(s) attached to
    /// the member declaration.
    bool inferCUDATargetForImplicitSpecialMember(CXXRecordDecl *ClassDecl,
                                                 CXXSpecialMember CSM,
                                                 CXXMethodDecl *MemberDecl,
                                                 bool ConstRHS,
                                                 bool Diagnose);
  
    /// \return true if \p CD can be considered empty according to CUDA
    /// (E.2.3.1 in CUDA 7.5 Programming guide).
    bool isEmptyCudaConstructor(SourceLocation Loc, CXXConstructorDecl *CD);
    bool isEmptyCudaDestructor(SourceLocation Loc, CXXDestructorDecl *CD);
  
    // \brief Checks that initializers of \p Var satisfy CUDA restrictions. In
    // case of error emits appropriate diagnostic and invalidates \p Var.
    //
    // \details CUDA allows only empty constructors as initializers for global
    // variables (see E.2.3.1, CUDA 7.5). The same restriction also applies to all
    // __shared__ variables whether they are local or not (they all are implicitly
    // static in CUDA). One exception is that CUDA allows constant initializers
    // for __constant__ and __device__ variables.
    void checkAllowedCUDAInitializer(VarDecl *VD);
  
    /// Check whether NewFD is a valid overload for CUDA. Emits
    /// diagnostics and invalidates NewFD if not.
    void checkCUDATargetOverload(FunctionDecl *NewFD,
                                 const LookupResult &Previous);
    /// Copies target attributes from the template TD to the function FD.
    void inheritCUDATargetAttrs(FunctionDecl *FD, const FunctionTemplateDecl &TD);
  
    /// Returns the name of the launch configuration function.  This is the name
    /// of the function that will be called to configure kernel call, with the
    /// parameters specified via <<<>>>.
    std::string getCudaConfigureFuncName() const;
  
    /// \name Code completion
    //@{
    /// Describes the context in which code completion occurs.
    enum ParserCompletionContext {
      /// Code completion occurs at top-level or namespace context.
      PCC_Namespace,
      /// Code completion occurs within a class, struct, or union.
      PCC_Class,
      /// Code completion occurs within an Objective-C interface, protocol,
      /// or category.
      PCC_ObjCInterface,
      /// Code completion occurs within an Objective-C implementation or
      /// category implementation
      PCC_ObjCImplementation,
      /// Code completion occurs within the list of instance variables
      /// in an Objective-C interface, protocol, category, or implementation.
      PCC_ObjCInstanceVariableList,
      /// Code completion occurs following one or more template
      /// headers.
      PCC_Template,
      /// Code completion occurs following one or more template
      /// headers within a class.
      PCC_MemberTemplate,
      /// Code completion occurs within an expression.
      PCC_Expression,
      /// Code completion occurs within a statement, which may
      /// also be an expression or a declaration.
      PCC_Statement,
      /// Code completion occurs at the beginning of the
      /// initialization statement (or expression) in a for loop.
      PCC_ForInit,
      /// Code completion occurs within the condition of an if,
      /// while, switch, or for statement.
      PCC_Condition,
      /// Code completion occurs within the body of a function on a
      /// recovery path, where we do not have a specific handle on our position
      /// in the grammar.
      PCC_RecoveryInFunction,
      /// Code completion occurs where only a type is permitted.
      PCC_Type,
      /// Code completion occurs in a parenthesized expression, which
      /// might also be a type cast.
      PCC_ParenthesizedExpression,
      /// Code completion occurs within a sequence of declaration
      /// specifiers within a function, method, or block.
      PCC_LocalDeclarationSpecifiers
    };
  
    void CodeCompleteModuleImport(SourceLocation ImportLoc, ModuleIdPath Path);
    void CodeCompleteOrdinaryName(Scope *S,
                                  ParserCompletionContext CompletionContext);
    void CodeCompleteDeclSpec(Scope *S, DeclSpec &DS,
                              bool AllowNonIdentifiers,
                              bool AllowNestedNameSpecifiers);
  
    struct CodeCompleteExpressionData;
    void CodeCompleteExpression(Scope *S,
                                const CodeCompleteExpressionData &Data);
    void CodeCompleteExpression(Scope *S, QualType PreferredType,
                                bool IsParenthesized = false);
    void CodeCompleteMemberReferenceExpr(Scope *S, Expr *Base, Expr *OtherOpBase,
                                         SourceLocation OpLoc, bool IsArrow,
                                         bool IsBaseExprStatement,
                                         QualType PreferredType);
    void CodeCompletePostfixExpression(Scope *S, ExprResult LHS,
                                       QualType PreferredType);
    void CodeCompleteTag(Scope *S, unsigned TagSpec);
    void CodeCompleteTypeQualifiers(DeclSpec &DS);
    void CodeCompleteFunctionQualifiers(DeclSpec &DS, Declarator &D,
                                        const VirtSpecifiers *VS = nullptr);
    void CodeCompleteBracketDeclarator(Scope *S);
    void CodeCompleteCase(Scope *S);
    /// Reports signatures for a call to CodeCompleteConsumer and returns the
    /// preferred type for the current argument. Returned type can be null.
    QualType ProduceCallSignatureHelp(Scope *S, Expr *Fn, ArrayRef<Expr *> Args,
                                      SourceLocation OpenParLoc);
    QualType ProduceConstructorSignatureHelp(Scope *S, QualType Type,
                                             SourceLocation Loc,
                                             ArrayRef<Expr *> Args,
                                             SourceLocation OpenParLoc);
    QualType ProduceCtorInitMemberSignatureHelp(Scope *S, Decl *ConstructorDecl,
                                                CXXScopeSpec SS,
                                                ParsedType TemplateTypeTy,
                                                ArrayRef<Expr *> ArgExprs,
                                                IdentifierInfo *II,
                                                SourceLocation OpenParLoc);
    void CodeCompleteInitializer(Scope *S, Decl *D);
    /// Trigger code completion for a record of \p BaseType. \p InitExprs are
    /// expressions in the initializer list seen so far and \p D is the current
    /// Designation being parsed.
    void CodeCompleteDesignator(const QualType BaseType,
                                llvm::ArrayRef<Expr *> InitExprs,
                                const Designation &D);
    void CodeCompleteAfterIf(Scope *S);
  
    void CodeCompleteQualifiedId(Scope *S, CXXScopeSpec &SS, bool EnteringContext,
                                 bool IsUsingDeclaration, QualType BaseType,
                                 QualType PreferredType);
    void CodeCompleteUsing(Scope *S);
    void CodeCompleteUsingDirective(Scope *S);
    void CodeCompleteNamespaceDecl(Scope *S);
    void CodeCompleteNamespaceAliasDecl(Scope *S);
    void CodeCompleteOperatorName(Scope *S);
    void CodeCompleteConstructorInitializer(
                                  Decl *Constructor,
                                  ArrayRef<CXXCtorInitializer *> Initializers);
  
    void CodeCompleteLambdaIntroducer(Scope *S, LambdaIntroducer &Intro,
                                      bool AfterAmpersand);
  
    void CodeCompleteObjCAtDirective(Scope *S);
    void CodeCompleteObjCAtVisibility(Scope *S);
    void CodeCompleteObjCAtStatement(Scope *S);
    void CodeCompleteObjCAtExpression(Scope *S);
    void CodeCompleteObjCPropertyFlags(Scope *S, ObjCDeclSpec &ODS);
    void CodeCompleteObjCPropertyGetter(Scope *S);
    void CodeCompleteObjCPropertySetter(Scope *S);
    void CodeCompleteObjCPassingType(Scope *S, ObjCDeclSpec &DS,
                                     bool IsParameter);
    void CodeCompleteObjCMessageReceiver(Scope *S);
    void CodeCompleteObjCSuperMessage(Scope *S, SourceLocation SuperLoc,
                                      ArrayRef<IdentifierInfo *> SelIdents,
                                      bool AtArgumentExpression);
    void CodeCompleteObjCClassMessage(Scope *S, ParsedType Receiver,
                                      ArrayRef<IdentifierInfo *> SelIdents,
                                      bool AtArgumentExpression,
                                      bool IsSuper = false);
    void CodeCompleteObjCInstanceMessage(Scope *S, Expr *Receiver,
                                         ArrayRef<IdentifierInfo *> SelIdents,
                                         bool AtArgumentExpression,
                                         ObjCInterfaceDecl *Super = nullptr);
    void CodeCompleteObjCForCollection(Scope *S,
                                       DeclGroupPtrTy IterationVar);
    void CodeCompleteObjCSelector(Scope *S,
                                  ArrayRef<IdentifierInfo *> SelIdents);
    void CodeCompleteObjCProtocolReferences(
                                           ArrayRef<IdentifierLocPair> Protocols);
    void CodeCompleteObjCProtocolDecl(Scope *S);
    void CodeCompleteObjCInterfaceDecl(Scope *S);
    void CodeCompleteObjCSuperclass(Scope *S,
                                    IdentifierInfo *ClassName,
                                    SourceLocation ClassNameLoc);
    void CodeCompleteObjCImplementationDecl(Scope *S);
    void CodeCompleteObjCInterfaceCategory(Scope *S,
                                           IdentifierInfo *ClassName,
                                           SourceLocation ClassNameLoc);
    void CodeCompleteObjCImplementationCategory(Scope *S,
                                                IdentifierInfo *ClassName,
                                                SourceLocation ClassNameLoc);
    void CodeCompleteObjCPropertyDefinition(Scope *S);
    void CodeCompleteObjCPropertySynthesizeIvar(Scope *S,
                                                IdentifierInfo *PropertyName);
    void CodeCompleteObjCMethodDecl(Scope *S, Optional<bool> IsInstanceMethod,
                                    ParsedType ReturnType);
    void CodeCompleteObjCMethodDeclSelector(Scope *S,
                                            bool IsInstanceMethod,
                                            bool AtParameterName,
                                            ParsedType ReturnType,
                                            ArrayRef<IdentifierInfo *> SelIdents);
    void CodeCompleteObjCClassPropertyRefExpr(Scope *S, IdentifierInfo &ClassName,
                                              SourceLocation ClassNameLoc,
                                              bool IsBaseExprStatement);
    void CodeCompletePreprocessorDirective(bool InConditional);
    void CodeCompleteInPreprocessorConditionalExclusion(Scope *S);
    void CodeCompletePreprocessorMacroName(bool IsDefinition);
    void CodeCompletePreprocessorExpression();
    void CodeCompletePreprocessorMacroArgument(Scope *S,
                                               IdentifierInfo *Macro,
                                               MacroInfo *MacroInfo,
                                               unsigned Argument);
    void CodeCompleteIncludedFile(llvm::StringRef Dir, bool IsAngled);
    void CodeCompleteNaturalLanguage();
    void CodeCompleteAvailabilityPlatformName();
    void GatherGlobalCodeCompletions(CodeCompletionAllocator &Allocator,
                                     CodeCompletionTUInfo &CCTUInfo,
                    SmallVectorImpl<CodeCompletionResult> &Results);
    //@}
  
    //===--------------------------------------------------------------------===//
    // Extra semantic analysis beyond the C type system
  
  public:
    SourceLocation getLocationOfStringLiteralByte(const StringLiteral *SL,
                                                  unsigned ByteNo) const;
  
  private:
    void CheckArrayAccess(const Expr *BaseExpr, const Expr *IndexExpr,
                          const ArraySubscriptExpr *ASE=nullptr,
                          bool AllowOnePastEnd=true, bool IndexNegated=false);
    void CheckArrayAccess(const Expr *E);
    // Used to grab the relevant information from a FormatAttr and a
    // FunctionDeclaration.
    struct FormatStringInfo {
      unsigned FormatIdx;
      unsigned FirstDataArg;
      bool HasVAListArg;
    };
  
    static bool getFormatStringInfo(const FormatAttr *Format, bool IsCXXMember,
                                    FormatStringInfo *FSI);
    bool CheckFunctionCall(FunctionDecl *FDecl, CallExpr *TheCall,
                           const FunctionProtoType *Proto);
    bool CheckObjCMethodCall(ObjCMethodDecl *Method, SourceLocation loc,
                             ArrayRef<const Expr *> Args);
    bool CheckPointerCall(NamedDecl *NDecl, CallExpr *TheCall,
                          const FunctionProtoType *Proto);
    bool CheckOtherCall(CallExpr *TheCall, const FunctionProtoType *Proto);
    void CheckConstructorCall(FunctionDecl *FDecl,
                              ArrayRef<const Expr *> Args,
                              const FunctionProtoType *Proto,
                              SourceLocation Loc);
  
    void checkCall(NamedDecl *FDecl, const FunctionProtoType *Proto,
                   const Expr *ThisArg, ArrayRef<const Expr *> Args,
                   bool IsMemberFunction, SourceLocation Loc, SourceRange Range,
                   VariadicCallType CallType);
  
    bool CheckObjCString(Expr *Arg);
    ExprResult CheckOSLogFormatStringArg(Expr *Arg);
  
    ExprResult CheckBuiltinFunctionCall(FunctionDecl *FDecl,
                                        unsigned BuiltinID, CallExpr *TheCall);
    void checkFortifiedBuiltinMemoryFunction(FunctionDecl *FD, CallExpr *TheCall);
  
    bool CheckARMBuiltinExclusiveCall(unsigned BuiltinID, CallExpr *TheCall,
                                      unsigned MaxWidth);
    bool CheckNeonBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckMVEBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckCDEBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckARMCoprocessorImmediate(const Expr *CoprocArg, bool WantCDE);
    bool CheckARMBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
  
    bool CheckAArch64BuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckBPFBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckHexagonBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckHexagonBuiltinArgument(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckMipsBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckMipsBuiltinCpu(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckMipsBuiltinArgument(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckSystemZBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckX86BuiltinRoundingOrSAE(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckX86BuiltinGatherScatterScale(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckX86BuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
    bool CheckPPCBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall);
  
    bool SemaBuiltinVAStart(unsigned BuiltinID, CallExpr *TheCall);
    bool SemaBuiltinVAStartARMMicrosoft(CallExpr *Call);
    bool SemaBuiltinUnorderedCompare(CallExpr *TheCall);
    bool SemaBuiltinFPClassification(CallExpr *TheCall, unsigned NumArgs);
    bool SemaBuiltinVSX(CallExpr *TheCall);
    bool SemaBuiltinOSLogFormat(CallExpr *TheCall);
  
  public:
    // Used by C++ template instantiation.
    ExprResult SemaBuiltinShuffleVector(CallExpr *TheCall);
    ExprResult SemaConvertVectorExpr(Expr *E, TypeSourceInfo *TInfo,
                                     SourceLocation BuiltinLoc,
                                     SourceLocation RParenLoc);
  
  private:
    bool SemaBuiltinPrefetch(CallExpr *TheCall);
    bool SemaBuiltinAllocaWithAlign(CallExpr *TheCall);
    bool SemaBuiltinAssume(CallExpr *TheCall);
    bool SemaBuiltinAssumeAligned(CallExpr *TheCall);
    bool SemaBuiltinLongjmp(CallExpr *TheCall);
    bool SemaBuiltinSetjmp(CallExpr *TheCall);
    ExprResult SemaBuiltinAtomicOverloaded(ExprResult TheCallResult);
    ExprResult SemaBuiltinNontemporalOverloaded(ExprResult TheCallResult);
    ExprResult SemaAtomicOpsOverloaded(ExprResult TheCallResult,
                                       AtomicExpr::AtomicOp Op);
    ExprResult SemaBuiltinOperatorNewDeleteOverloaded(ExprResult TheCallResult,
                                                      bool IsDelete);
    bool SemaBuiltinConstantArg(CallExpr *TheCall, int ArgNum,
                                llvm::APSInt &Result);
    bool SemaBuiltinConstantArgRange(CallExpr *TheCall, int ArgNum, int Low,
                                     int High, bool RangeIsError = true);
    bool SemaBuiltinConstantArgMultiple(CallExpr *TheCall, int ArgNum,
                                        unsigned Multiple);
    bool SemaBuiltinConstantArgPower2(CallExpr *TheCall, int ArgNum);
    bool SemaBuiltinConstantArgShiftedByte(CallExpr *TheCall, int ArgNum,
                                           unsigned ArgBits);
    bool SemaBuiltinConstantArgShiftedByteOrXXFF(CallExpr *TheCall, int ArgNum,
                                                 unsigned ArgBits);
    bool SemaBuiltinARMSpecialReg(unsigned BuiltinID, CallExpr *TheCall,
                                  int ArgNum, unsigned ExpectedFieldNum,
                                  bool AllowName);
    bool SemaBuiltinARMMemoryTaggingCall(unsigned BuiltinID, CallExpr *TheCall);
  public:
    enum FormatStringType {
      FST_Scanf,
      FST_Printf,
      FST_NSString,
      FST_Strftime,
      FST_Strfmon,
      FST_Kprintf,
      FST_FreeBSDKPrintf,
      FST_OSTrace,
      FST_OSLog,
      FST_Unknown
    };
    static FormatStringType GetFormatStringType(const FormatAttr *Format);
  
    bool FormatStringHasSArg(const StringLiteral *FExpr);
  
    static bool GetFormatNSStringIdx(const FormatAttr *Format, unsigned &Idx);
  
  private:
    bool CheckFormatArguments(const FormatAttr *Format,
                              ArrayRef<const Expr *> Args,
                              bool IsCXXMember,
                              VariadicCallType CallType,
                              SourceLocation Loc, SourceRange Range,
                              llvm::SmallBitVector &CheckedVarArgs);
    bool CheckFormatArguments(ArrayRef<const Expr *> Args,
                              bool HasVAListArg, unsigned format_idx,
                              unsigned firstDataArg, FormatStringType Type,
                              VariadicCallType CallType,
                              SourceLocation Loc, SourceRange range,
                              llvm::SmallBitVector &CheckedVarArgs);
  
    void CheckAbsoluteValueFunction(const CallExpr *Call,
                                    const FunctionDecl *FDecl);
  
    void CheckMaxUnsignedZero(const CallExpr *Call, const FunctionDecl *FDecl);
  
    void CheckMemaccessArguments(const CallExpr *Call,
                                 unsigned BId,
                                 IdentifierInfo *FnName);
  
    void CheckStrlcpycatArguments(const CallExpr *Call,
                                  IdentifierInfo *FnName);
  
    void CheckStrncatArguments(const CallExpr *Call,
                               IdentifierInfo *FnName);
  
    void CheckReturnValExpr(Expr *RetValExp, QualType lhsType,
                            SourceLocation ReturnLoc,
                            bool isObjCMethod = false,
                            const AttrVec *Attrs = nullptr,
                            const FunctionDecl *FD = nullptr);
  
  public:
    void CheckFloatComparison(SourceLocation Loc, Expr *LHS, Expr *RHS);
  
  private:
    void CheckImplicitConversions(Expr *E, SourceLocation CC = SourceLocation());
    void CheckBoolLikeConversion(Expr *E, SourceLocation CC);
    void CheckForIntOverflow(Expr *E);
    void CheckUnsequencedOperations(const Expr *E);
  
    /// Perform semantic checks on a completed expression. This will either
    /// be a full-expression or a default argument expression.
    void CheckCompletedExpr(Expr *E, SourceLocation CheckLoc = SourceLocation(),
                            bool IsConstexpr = false);
  
    void CheckBitFieldInitialization(SourceLocation InitLoc, FieldDecl *Field,
                                     Expr *Init);
  
    /// Check if there is a field shadowing.
    void CheckShadowInheritedFields(const SourceLocation &Loc,
                                    DeclarationName FieldName,
                                    const CXXRecordDecl *RD,
                                    bool DeclIsField = true);
  
    /// Check if the given expression contains 'break' or 'continue'
    /// statement that produces control flow different from GCC.
    void CheckBreakContinueBinding(Expr *E);
  
    /// Check whether receiver is mutable ObjC container which
    /// attempts to add itself into the container
    void CheckObjCCircularContainer(ObjCMessageExpr *Message);
  
    void AnalyzeDeleteExprMismatch(const CXXDeleteExpr *DE);
    void AnalyzeDeleteExprMismatch(FieldDecl *Field, SourceLocation DeleteLoc,
                                   bool DeleteWasArrayForm);
  public:
    /// Register a magic integral constant to be used as a type tag.
    void RegisterTypeTagForDatatype(const IdentifierInfo *ArgumentKind,
                                    uint64_t MagicValue, QualType Type,
                                    bool LayoutCompatible, bool MustBeNull);
  
    struct TypeTagData {
      TypeTagData() {}
  
      TypeTagData(QualType Type, bool LayoutCompatible, bool MustBeNull) :
          Type(Type), LayoutCompatible(LayoutCompatible),
          MustBeNull(MustBeNull)
      {}
  
      QualType Type;
  
      /// If true, \c Type should be compared with other expression's types for
      /// layout-compatibility.
      unsigned LayoutCompatible : 1;
      unsigned MustBeNull : 1;
    };
  
    /// A pair of ArgumentKind identifier and magic value.  This uniquely
    /// identifies the magic value.
    typedef std::pair<const IdentifierInfo *, uint64_t> TypeTagMagicValue;
  
  private:
    /// A map from magic value to type information.
    std::unique_ptr<llvm::DenseMap<TypeTagMagicValue, TypeTagData>>
        TypeTagForDatatypeMagicValues;
  
    /// Peform checks on a call of a function with argument_with_type_tag
    /// or pointer_with_type_tag attributes.
    void CheckArgumentWithTypeTag(const ArgumentWithTypeTagAttr *Attr,
                                  const ArrayRef<const Expr *> ExprArgs,
                                  SourceLocation CallSiteLoc);
  
    /// Check if we are taking the address of a packed field
    /// as this may be a problem if the pointer value is dereferenced.
    void CheckAddressOfPackedMember(Expr *rhs);
  
    /// The parser's current scope.
    ///
    /// The parser maintains this state here.
    Scope *CurScope;
  
    mutable IdentifierInfo *Ident_super;
    mutable IdentifierInfo *Ident___float128;
  
    /// Nullability type specifiers.
    IdentifierInfo *Ident__Nonnull = nullptr;
    IdentifierInfo *Ident__Nullable = nullptr;
    IdentifierInfo *Ident__Null_unspecified = nullptr;
  
    IdentifierInfo *Ident_NSError = nullptr;
  
    /// The handler for the FileChanged preprocessor events.
    ///
    /// Used for diagnostics that implement custom semantic analysis for #include
    /// directives, like -Wpragma-pack.
    sema::SemaPPCallbacks *SemaPPCallbackHandler;
  
  protected:
    friend class Parser;
    friend class InitializationSequence;
    friend class ASTReader;
    friend class ASTDeclReader;
    friend class ASTWriter;
  
  public:
    /// Retrieve the keyword associated
    IdentifierInfo *getNullabilityKeyword(NullabilityKind nullability);
  
    /// The struct behind the CFErrorRef pointer.
    RecordDecl *CFError = nullptr;
    bool isCFError(RecordDecl *D);
  
    /// Retrieve the identifier "NSError".
    IdentifierInfo *getNSErrorIdent();
  
    /// Retrieve the parser's current scope.
    ///
    /// This routine must only be used when it is certain that semantic analysis
    /// and the parser are in precisely the same context, which is not the case
    /// when, e.g., we are performing any kind of template instantiation.
    /// Therefore, the only safe places to use this scope are in the parser
    /// itself and in routines directly invoked from the parser and *never* from
    /// template substitution or instantiation.
    Scope *getCurScope() const { return CurScope; }
  
    void incrementMSManglingNumber() const {
      return CurScope->incrementMSManglingNumber();
    }
  
    IdentifierInfo *getSuperIdentifier() const;
    IdentifierInfo *getFloat128Identifier() const;
  
    Decl *getObjCDeclContext() const;
  
    DeclContext *getCurLexicalContext() const {
      return OriginalLexicalContext ? OriginalLexicalContext : CurContext;
    }
  
    const DeclContext *getCurObjCLexicalContext() const {
      const DeclContext *DC = getCurLexicalContext();
      // A category implicitly has the attribute of the interface.
      if (const ObjCCategoryDecl *CatD = dyn_cast<ObjCCategoryDecl>(DC))
        DC = CatD->getClassInterface();
      return DC;
    }
  
    /// Determine the number of levels of enclosing template parameters. This is
    /// only usable while parsing. Note that this does not include dependent
    /// contexts in which no template parameters have yet been declared, such as
    /// in a terse function template or generic lambda before the first 'auto' is
    /// encountered.
    unsigned getTemplateDepth(Scope *S) const;
  
    /// To be used for checking whether the arguments being passed to
    /// function exceeds the number of parameters expected for it.
    static bool TooManyArguments(size_t NumParams, size_t NumArgs,
                                 bool PartialOverloading = false) {
      // We check whether we're just after a comma in code-completion.
      if (NumArgs > 0 && PartialOverloading)
        return NumArgs + 1 > NumParams; // If so, we view as an extra argument.
      return NumArgs > NumParams;
    }
  
    // Emitting members of dllexported classes is delayed until the class
    // (including field initializers) is fully parsed.
    SmallVector<CXXRecordDecl*, 4> DelayedDllExportClasses;
    SmallVector<CXXMethodDecl*, 4> DelayedDllExportMemberFunctions;
  
  private:
    int ParsingClassDepth = 0;
  
    class SavePendingParsedClassStateRAII {
    public:
      SavePendingParsedClassStateRAII(Sema &S) : S(S) { swapSavedState(); }
  
      ~SavePendingParsedClassStateRAII() {
        assert(S.DelayedOverridingExceptionSpecChecks.empty() &&
               "there shouldn't be any pending delayed exception spec checks");
        assert(S.DelayedEquivalentExceptionSpecChecks.empty() &&
               "there shouldn't be any pending delayed exception spec checks");
        swapSavedState();
      }
  
    private:
      Sema &S;
      decltype(DelayedOverridingExceptionSpecChecks)
          SavedOverridingExceptionSpecChecks;
      decltype(DelayedEquivalentExceptionSpecChecks)
          SavedEquivalentExceptionSpecChecks;
  
      void swapSavedState() {
        SavedOverridingExceptionSpecChecks.swap(
            S.DelayedOverridingExceptionSpecChecks);
        SavedEquivalentExceptionSpecChecks.swap(
            S.DelayedEquivalentExceptionSpecChecks);
      }
    };
  
    /// Helper class that collects misaligned member designations and
    /// their location info for delayed diagnostics.
    struct MisalignedMember {
      Expr *E;
      RecordDecl *RD;
      ValueDecl *MD;
      CharUnits Alignment;
  
      MisalignedMember() : E(), RD(), MD(), Alignment() {}
      MisalignedMember(Expr *E, RecordDecl *RD, ValueDecl *MD,
                       CharUnits Alignment)
          : E(E), RD(RD), MD(MD), Alignment(Alignment) {}
      explicit MisalignedMember(Expr *E)
          : MisalignedMember(E, nullptr, nullptr, CharUnits()) {}
  
      bool operator==(const MisalignedMember &m) { return this->E == m.E; }
    };
    /// Small set of gathered accesses to potentially misaligned members
    /// due to the packed attribute.
    SmallVector<MisalignedMember, 4> MisalignedMembers;
  
    /// Adds an expression to the set of gathered misaligned members.
    void AddPotentialMisalignedMembers(Expr *E, RecordDecl *RD, ValueDecl *MD,
                                       CharUnits Alignment);
  
  public:
    /// Diagnoses the current set of gathered accesses. This typically
    /// happens at full expression level. The set is cleared after emitting the
    /// diagnostics.
    void DiagnoseMisalignedMembers();
  
    /// This function checks if the expression is in the sef of potentially
    /// misaligned members and it is converted to some pointer type T with lower
    /// or equal alignment requirements. If so it removes it. This is used when
    /// we do not want to diagnose such misaligned access (e.g. in conversions to
    /// void*).
    void DiscardMisalignedMemberAddress(const Type *T, Expr *E);
  
    /// This function calls Action when it determines that E designates a
    /// misaligned member due to the packed attribute. This is used to emit
    /// local diagnostics like in reference binding.
    void RefersToMemberWithReducedAlignment(
        Expr *E,
        llvm::function_ref<void(Expr *, RecordDecl *, FieldDecl *, CharUnits)>
            Action);
  
    /// Describes the reason a calling convention specification was ignored, used
    /// for diagnostics.
    enum class CallingConventionIgnoredReason {
      ForThisTarget = 0,
      VariadicFunction,
      ConstructorDestructor,
      BuiltinFunction
    };
  };
  
  /// RAII object that enters a new expression evaluation context.
  class EnterExpressionEvaluationContext {
    Sema &Actions;
    bool Entered = true;
  
  public:
    EnterExpressionEvaluationContext(
        Sema &Actions, Sema::ExpressionEvaluationContext NewContext,
        Decl *LambdaContextDecl = nullptr,
        Sema::ExpressionEvaluationContextRecord::ExpressionKind ExprContext =
            Sema::ExpressionEvaluationContextRecord::EK_Other,
        bool ShouldEnter = true)
        : Actions(Actions), Entered(ShouldEnter) {
      if (Entered)
        Actions.PushExpressionEvaluationContext(NewContext, LambdaContextDecl,
                                                ExprContext);
    }
    EnterExpressionEvaluationContext(
        Sema &Actions, Sema::ExpressionEvaluationContext NewContext,
        Sema::ReuseLambdaContextDecl_t,
        Sema::ExpressionEvaluationContextRecord::ExpressionKind ExprContext =
            Sema::ExpressionEvaluationContextRecord::EK_Other)
        : Actions(Actions) {
      Actions.PushExpressionEvaluationContext(
          NewContext, Sema::ReuseLambdaContextDecl, ExprContext);
    }
  
    enum InitListTag { InitList };
    EnterExpressionEvaluationContext(Sema &Actions, InitListTag,
                                     bool ShouldEnter = true)
        : Actions(Actions), Entered(false) {
      // In C++11 onwards, narrowing checks are performed on the contents of
      // braced-init-lists, even when they occur within unevaluated operands.
      // Therefore we still need to instantiate constexpr functions used in such
      // a context.
      if (ShouldEnter && Actions.isUnevaluatedContext() &&
          Actions.getLangOpts().CPlusPlus11) {
        Actions.PushExpressionEvaluationContext(
            Sema::ExpressionEvaluationContext::UnevaluatedList);
        Entered = true;
      }
    }
  
    ~EnterExpressionEvaluationContext() {
      if (Entered)
        Actions.PopExpressionEvaluationContext();
    }
  };
  
  DeductionFailureInfo
  MakeDeductionFailureInfo(ASTContext &Context, Sema::TemplateDeductionResult TDK,
                           sema::TemplateDeductionInfo &Info);
  
  /// Contains a late templated function.
  /// Will be parsed at the end of the translation unit, used by Sema & Parser.
  struct LateParsedTemplate {
    CachedTokens Toks;
    /// The template function declaration to be late parsed.
    Decl *D;
  };
  } // end namespace clang
  
  namespace llvm {
  // Hash a FunctionDeclAndLoc by looking at both its FunctionDecl and its
  // SourceLocation.
  template <> struct DenseMapInfo<clang::Sema::FunctionDeclAndLoc> {
    using FunctionDeclAndLoc = clang::Sema::FunctionDeclAndLoc;
    using FDBaseInfo = DenseMapInfo<clang::CanonicalDeclPtr<clang::FunctionDecl>>;
  
    static FunctionDeclAndLoc getEmptyKey() {
      return {FDBaseInfo::getEmptyKey(), clang::SourceLocation()};
    }
  
    static FunctionDeclAndLoc getTombstoneKey() {
      return {FDBaseInfo::getTombstoneKey(), clang::SourceLocation()};
    }
  
    static unsigned getHashValue(const FunctionDeclAndLoc &FDL) {
      return hash_combine(FDBaseInfo::getHashValue(FDL.FD),
                          FDL.Loc.getRawEncoding());
    }
  
    static bool isEqual(const FunctionDeclAndLoc &LHS,
                        const FunctionDeclAndLoc &RHS) {
      return LHS.FD == RHS.FD && LHS.Loc == RHS.Loc;
    }
  };
  } // namespace llvm
  
  #endif
  