Sema.h

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//===--- 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/APINotes/APINotesManager.h"
#include "clang/AST/ASTFwd.h"
#include "clang/AST/Attr.h"
#include "clang/AST/AttrIterator.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/DeclCXX.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/ExternalASTSource.h"
#include "clang/AST/NestedNameSpecifier.h"
#include "clang/AST/OperationKinds.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/Type.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Basic/AttrSubjectMatchRules.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/CapturedStmt.h"
#include "clang/Basic/Cuda.h"
#include "clang/Basic/DiagnosticSema.h"
#include "clang/Basic/ExceptionSpecificationType.h"
#include "clang/Basic/ExpressionTraits.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/Lambda.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/Module.h"
#include "clang/Basic/OpenCLOptions.h"
#include "clang/Basic/OperatorKinds.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "clang/Basic/PragmaKinds.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/Specifiers.h"
#include "clang/Basic/StackExhaustionHandler.h"
#include "clang/Basic/TemplateKinds.h"
#include "clang/Basic/TokenKinds.h"
#include "clang/Basic/TypeTraits.h"
#include "clang/Sema/AnalysisBasedWarnings.h"
#include "clang/Sema/Attr.h"
#include "clang/Sema/CleanupInfo.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/ExternalSemaSource.h"
#include "clang/Sema/IdentifierResolver.h"
#include "clang/Sema/Ownership.h"
#include "clang/Sema/ParsedAttr.h"
#include "clang/Sema/Redeclaration.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/SemaBase.h"
#include "clang/Sema/TypoCorrection.h"
#include "clang/Sema/Weak.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/BitmaskEnum.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/FloatingPointMode.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/STLForwardCompat.h"
#include "llvm/ADT/STLFunctionalExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>
#include <climits>
#include <cstddef>
#include <cstdint>
#include <deque>
#include <functional>
#include <iterator>
#include <memory>
#include <optional>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>
 
namespace llvm {
struct InlineAsmIdentifierInfo;
} // namespace llvm
 
namespace clang {
class ADLResult;
class APValue;
struct ASTConstraintSatisfaction;
class ASTConsumer;
class ASTContext;
class ASTDeclReader;
class ASTMutationListener;
class ASTReader;
class ASTWriter;
class CXXBasePath;
class CXXBasePaths;
class CXXFieldCollector;
class CodeCompleteConsumer;
enum class ComparisonCategoryType : unsigned char;
class ConstraintSatisfaction;
class DarwinSDKInfo;
class DeclGroupRef;
class DeducedTemplateArgument;
struct DeductionFailureInfo;
class DependentDiagnostic;
class Designation;
class IdentifierInfo;
class ImplicitConversionSequence;
typedef MutableArrayRef<ImplicitConversionSequence> ConversionSequenceList;
class InitializationKind;
class InitializationSequence;
class InitializedEntity;
enum class LangAS : unsigned int;
class LocalInstantiationScope;
class LookupResult;
class MangleNumberingContext;
typedef ArrayRef<std::pair<IdentifierInfo *, SourceLocation>> ModuleIdPath;
class ModuleLoader;
class MultiLevelTemplateArgumentList;
struct NormalizedConstraint;
class ObjCInterfaceDecl;
class ObjCMethodDecl;
struct OverloadCandidate;
enum class OverloadCandidateParamOrder : char;
enum OverloadCandidateRewriteKind : unsigned;
class OverloadCandidateSet;
class Preprocessor;
class SemaAMDGPU;
class SemaARM;
class SemaAVR;
class SemaBPF;
class SemaCodeCompletion;
class SemaCUDA;
class SemaHLSL;
class SemaHexagon;
class SemaLoongArch;
class SemaM68k;
class SemaMIPS;
class SemaMSP430;
class SemaNVPTX;
class SemaObjC;
class SemaOpenACC;
class SemaOpenCL;
class SemaOpenMP;
class SemaPPC;
class SemaPseudoObject;
class SemaRISCV;
class SemaSYCL;
class SemaSwift;
class SemaSystemZ;
class SemaWasm;
class SemaX86;
class StandardConversionSequence;
class TemplateArgument;
class TemplateArgumentLoc;
class TemplateInstantiationCallback;
class TemplatePartialOrderingContext;
class TemplateSpecCandidateSet;
class Token;
class TypeConstraint;
class TypoCorrectionConsumer;
class UnresolvedSetImpl;
class UnresolvedSetIterator;
class VisibleDeclConsumer;
 
namespace sema {
class BlockScopeInfo;
class Capture;
class CapturedRegionScopeInfo;
class CapturingScopeInfo;
class CompoundScopeInfo;
class DelayedDiagnostic;
class DelayedDiagnosticPool;
class FunctionScopeInfo;
class LambdaScopeInfo;
class SemaPPCallbacks;
class TemplateDeductionInfo;
} // namespace sema
 
// AssignmentAction - This is used by all the assignment diagnostic functions
// to represent what is actually causing the operation
enum class AssignmentAction {
  Assigning,
  Passing,
  Returning,
  Converting,
  Initializing,
  Sending,
  Casting,
  Passing_CFAudited
};
inline const StreamingDiagnostic &operator<<(const StreamingDiagnostic &DB,
                                             const AssignmentAction &AA) {
  DB << llvm::to_underlying(AA);
  return DB;
}
 
namespace threadSafety {
class BeforeSet;
void threadSafetyCleanup(BeforeSet *Cache);
} // namespace threadSafety
 
// 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;
  }
};
 
/// Tracks expected type during expression parsing, for use in code completion.
/// 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 avoids updating the type on hot paths in the parser.
class PreferredTypeBuilder {
public:
  PreferredTypeBuilder(bool Enabled) : Enabled(Enabled) {}
 
  void enterCondition(Sema &S, SourceLocation Tok);
  void enterReturn(Sema &S, SourceLocation Tok);
  void enterVariableInit(SourceLocation Tok, Decl *D);
  /// Handles e.g. BaseType{ .D = Tok...
  void enterDesignatedInitializer(SourceLocation Tok, QualType BaseType,
                                  const Designation &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 function, as it stores a
  /// function_ref, clients should make sure all calls to get() with the same
  /// location happen while function_ref is alive.
  ///
  /// The callback should also emit signature help as a side-effect, but only
  /// if the completion point has been reached.
  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);
 
  /// Get the expected type associated with this location, if any.
  ///
  /// If the location is a function argument, determining the expected type
  /// involves considering all function overloads and the arguments so far.
  /// In this case, signature help for these function overloads will be reported
  /// as a side-effect (only if the completion point has been reached).
  QualType get(SourceLocation Tok) const {
    if (!Enabled || Tok != ExpectedLoc)
      return QualType();
    if (!Type.isNull())
      return Type;
    if (ComputeType)
      return ComputeType();
    return QualType();
  }
 
private:
  bool Enabled;
  /// 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;
};
 
struct SkipBodyInfo {
  SkipBodyInfo() = default;
  bool ShouldSkip = false;
  bool CheckSameAsPrevious = false;
  NamedDecl *Previous = nullptr;
  NamedDecl *New = nullptr;
};
 
/// 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 class TemplateDeductionResult {
  /// Template argument deduction was successful.
  Success = 0,
  /// The declaration was invalid; do nothing.
  Invalid,
  /// Template argument deduction exceeded the maximum template
  /// instantiation depth (which has already been diagnosed).
  InstantiationDepth,
  /// Template argument deduction did not deduce a value
  /// for every template parameter.
  Incomplete,
  /// Template argument deduction did not deduce a value for every
  /// expansion of an expanded template parameter pack.
  IncompletePack,
  /// Template argument deduction produced inconsistent
  /// deduced values for the given template parameter.
  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".
  Underqualified,
  /// Substitution of the deduced template argument values
  /// resulted in an error.
  SubstitutionFailure,
  /// After substituting deduced template arguments, a dependent
  /// parameter type did not match the corresponding argument.
  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).
  DeducedMismatchNested,
  /// A non-depnedent component of the parameter did not match the
  /// corresponding component of the argument.
  NonDeducedMismatch,
  /// When performing template argument deduction for a function
  /// template, there were too many call arguments.
  TooManyArguments,
  /// When performing template argument deduction for a function
  /// template, there were too few call arguments.
  TooFewArguments,
  /// The explicitly-specified template arguments were not valid
  /// template arguments for the given template.
  InvalidExplicitArguments,
  /// Checking non-dependent argument conversions failed.
  NonDependentConversionFailure,
  /// The deduced arguments did not satisfy the constraints associated
  /// with the template.
  ConstraintsNotSatisfied,
  /// Deduction failed; that's all we know.
  MiscellaneousDeductionFailure,
  /// CUDA Target attributes do not match.
  CUDATargetMismatch,
  /// Some error which was already diagnosed.
  AlreadyDiagnosed
};
 
/// Kinds of C++ special members.
enum class CXXSpecialMemberKind {
  DefaultConstructor,
  CopyConstructor,
  MoveConstructor,
  CopyAssignment,
  MoveAssignment,
  Destructor,
  Invalid
};
 
/// The kind of conversion being performed.
enum class CheckedConversionKind {
  /// An implicit conversion.
  Implicit,
  /// A C-style cast.
  CStyleCast,
  /// A functional-style cast.
  FunctionalCast,
  /// A cast other than a C-style cast.
  OtherCast,
  /// A conversion for an operand of a builtin overloaded operator.
  ForBuiltinOverloadedOp
};
 
enum class TagUseKind {
  Reference,   // Reference to a tag:  'struct foo *X;'
  Declaration, // Fwd decl of a tag:   'struct foo;'
  Definition,  // Definition of a tag: 'struct foo { int X; } Y;'
  Friend       // Friend declaration:  'friend struct foo;'
};
 
/// Used with attributes/effects with a boolean condition, e.g. `nonblocking`.
enum class FunctionEffectMode : uint8_t {
  None,     // effect is not present.
  False,    // effect(false).
  True,     // effect(true).
  Dependent // effect(expr) where expr is dependent.
};
 
/// Sema - This implements semantic analysis and AST building for C.
/// \nosubgrouping
class Sema final : public SemaBase {
  // Table of Contents
  // -----------------
  // 1. Semantic Analysis (Sema.cpp)
  // 2. API Notes (SemaAPINotes.cpp)
  // 3. C++ Access Control (SemaAccess.cpp)
  // 4. Attributes (SemaAttr.cpp)
  // 5. Availability Attribute Handling (SemaAvailability.cpp)
  // 6. Bounds Safety (SemaBoundsSafety.cpp)
  // 7. Casts (SemaCast.cpp)
  // 8. Extra Semantic Checking (SemaChecking.cpp)
  // 9. C++ Coroutines (SemaCoroutine.cpp)
  // 10. C++ Scope Specifiers (SemaCXXScopeSpec.cpp)
  // 11. Declarations (SemaDecl.cpp)
  // 12. Declaration Attribute Handling (SemaDeclAttr.cpp)
  // 13. C++ Declarations (SemaDeclCXX.cpp)
  // 14. C++ Exception Specifications (SemaExceptionSpec.cpp)
  // 15. Expressions (SemaExpr.cpp)
  // 16. C++ Expressions (SemaExprCXX.cpp)
  // 17. Member Access Expressions (SemaExprMember.cpp)
  // 18. Initializers (SemaInit.cpp)
  // 19. C++ Lambda Expressions (SemaLambda.cpp)
  // 20. Name Lookup (SemaLookup.cpp)
  // 21. Modules (SemaModule.cpp)
  // 22. C++ Overloading (SemaOverload.cpp)
  // 23. Statements (SemaStmt.cpp)
  // 24. `inline asm` Statement (SemaStmtAsm.cpp)
  // 25. Statement Attribute Handling (SemaStmtAttr.cpp)
  // 26. C++ Templates (SemaTemplate.cpp)
  // 27. C++ Template Argument Deduction (SemaTemplateDeduction.cpp)
  // 28. C++ Template Deduction Guide (SemaTemplateDeductionGuide.cpp)
  // 29. C++ Template Instantiation (SemaTemplateInstantiate.cpp)
  // 30. C++ Template Declaration Instantiation
  //     (SemaTemplateInstantiateDecl.cpp)
  // 31. C++ Variadic Templates (SemaTemplateVariadic.cpp)
  // 32. Constraints and Concepts (SemaConcept.cpp)
  // 33. Types (SemaType.cpp)
  // 34. FixIt Helpers (SemaFixItUtils.cpp)
  // 35. Function Effects (SemaFunctionEffects.cpp)
 
  /// \name Semantic Analysis
  /// Implementations are in Sema.cpp
  ///@{
 
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();
 
  /// This virtual key function only exists to limit the emission of debug info
  /// describing the Sema class. GCC and Clang only emit debug info for a class
  /// with a vtable when the vtable is emitted. Sema is final and not
  /// polymorphic, but the debug info size savings are so significant that it is
  /// worth adding a vtable just to take advantage of this optimization.
  virtual void anchor();
 
  const LangOptions &getLangOpts() const { return LangOpts; }
  OpenCLOptions &getOpenCLOptions() { return OpenCLFeatures; }
  FPOptions &getCurFPFeatures() { return CurFPFeatures; }
 
  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.get(); }
 
  DarwinSDKInfo *getDarwinSDKInfoForAvailabilityChecking(SourceLocation Loc,
                                                         StringRef Platform);
  DarwinSDKInfo *getDarwinSDKInfoForAvailabilityChecking();
 
  /// 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);
 
  /// Print out statistics about the semantic analysis.
  void PrintStats() const;
 
  /// 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);
 
  /// Returns default addr space for method qualifiers.
  LangAS getDefaultCXXMethodAddrSpace() const;
 
  /// Load weak undeclared identifiers from the external source.
  void LoadExternalWeakUndeclaredIdentifiers();
 
  /// 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(const ValueDecl *VD) const;
 
  /// Obtain a sorted list of functions that are undefined but ODR-used.
  void getUndefinedButUsed(
      SmallVectorImpl<std::pair<NamedDecl *, SourceLocation>> &Undefined);
 
  typedef std::pair<SourceLocation, bool> DeleteExprLoc;
  typedef llvm::SmallVector<DeleteExprLoc, 4> DeleteLocs;
  /// Retrieves list of suspicious delete-expressions that will be checked at
  /// the end of translation unit.
  const llvm::MapVector<FieldDecl *, DeleteLocs> &
  getMismatchingDeleteExpressions() const;
 
  /// Cause the built diagnostic to be emitted on the DiagosticsEngine.
  /// This is closely coupled to the SemaDiagnosticBuilder class and
  /// should not be used elsewhere.
  void EmitDiagnostic(unsigned DiagID, const DiagnosticBuilder &DB);
 
  void addImplicitTypedef(StringRef Name, QualType T);
 
  /// Whether uncompilable error has occurred. This includes error happens
  /// in deferred diagnostics.
  bool hasUncompilableErrorOccurred() const;
 
  /// Looks through the macro-expansion chain for the given
  /// location, looking for a macro expansion with the given name.
  /// If one is found, returns true and sets the location to that
  /// expansion loc.
  bool findMacroSpelling(SourceLocation &loc, StringRef name);
 
  /// 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(const IdentifierInfo *ParamName,
                                             unsigned Index);
 
  void emitAndClearUnusedLocalTypedefWarnings();
 
  // Emit all deferred diagnostics.
  void emitDeferredDiags();
 
  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
  };
 
  /// This is called before the very first declaration in the translation unit
  /// is parsed. Note that the ASTContext may have already injected some
  /// declarations.
  void ActOnStartOfTranslationUnit();
  /// ActOnEndOfTranslationUnit - This is called at the very end of the
  /// translation unit when EOF is reached and all but the top-level scope is
  /// popped.
  void ActOnEndOfTranslationUnit();
  void ActOnEndOfTranslationUnitFragment(TUFragmentKind Kind);
 
  /// Determines the active Scope associated with the given declaration
  /// context.
  ///
  /// This routine maps a declaration context to the active Scope object that
  /// represents that declaration context in the parser. It is typically used
  /// from "scope-less" code (e.g., template instantiation, lazy creation of
  /// declarations) that injects a name for name-lookup purposes and, therefore,
  /// must update the Scope.
  ///
  /// \returns The scope corresponding to the given declaraion context, or NULL
  /// if no such scope is open.
  Scope *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>;
 
  /// Pop a function (or block or lambda or captured region) scope from the
  /// stack.
  ///
  /// \param WP The warning policy to use for CFG-based warnings, or null if
  ///        such warnings should not be produced.
  /// \param D The declaration corresponding to this function scope, if
  ///        producing CFG-based warnings.
  /// \param BlockType The type of the block expression, if D is a BlockDecl.
  PoppedFunctionScopePtr
  PopFunctionScopeInfo(const sema::AnalysisBasedWarnings::Policy *WP = nullptr,
                       const Decl *D = nullptr,
                       QualType BlockType = QualType());
 
  sema::FunctionScopeInfo *getEnclosingFunction() const;
 
  void setFunctionHasBranchIntoScope();
  void setFunctionHasBranchProtectedScope();
  void setFunctionHasIndirectGoto();
  void setFunctionHasMustTail();
 
  void PushCompoundScope(bool IsStmtExpr);
  void PopCompoundScope();
 
  /// Determine whether any errors occurred within this function/method/
  /// block.
  bool hasAnyUnrecoverableErrorsInThisFunction() const;
 
  /// Retrieve the current block, if any.
  sema::BlockScopeInfo *getCurBlock();
 
  /// Get the innermost lambda or block enclosing the current location, if any.
  /// This looks through intervening non-lambda, non-block scopes such as local
  /// functions.
  sema::CapturingScopeInfo *getEnclosingLambdaOrBlock() 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();
 
  void ActOnComment(SourceRange Comment);
 
  /// 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; }
 
  IdentifierInfo *getSuperIdentifier() const;
 
  DeclContext *getCurLexicalContext() const {
    return OriginalLexicalContext ? OriginalLexicalContext : CurContext;
  }
 
  SemaDiagnosticBuilder targetDiag(SourceLocation Loc, unsigned DiagID,
                                   const FunctionDecl *FD = nullptr);
  SemaDiagnosticBuilder targetDiag(SourceLocation Loc,
                                   const PartialDiagnostic &PD,
                                   const FunctionDecl *FD = nullptr) {
    return targetDiag(Loc, PD.getDiagID(), FD) << PD;
  }
 
  /// Check if the type is allowed to be used for the current target.
  void checkTypeSupport(QualType Ty, SourceLocation Loc,
                        ValueDecl *D = nullptr);
 
  // /// 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
  // };
 
  /// 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_PRValue,
      const CXXCastPath *BasePath = nullptr,
      CheckedConversionKind CCK = CheckedConversionKind::Implicit);
 
  /// ScalarTypeToBooleanCastKind - Returns the cast kind corresponding
  /// to the conversion from scalar type ScalarTy to the Boolean type.
  static CastKind ScalarTypeToBooleanCastKind(QualType ScalarTy);
 
  /// If \p AllowLambda is true, treat lambda as function.
  DeclContext *getFunctionLevelDeclContext(bool AllowLambda = false) const;
 
  /// Returns a pointer to the innermost enclosing function, or nullptr if the
  /// current context is not inside a function. If \p AllowLambda is true,
  /// this can return the call operator of an enclosing lambda, otherwise
  /// lambdas are skipped when looking for an enclosing function.
  FunctionDecl *getCurFunctionDecl(bool AllowLambda = false) const;
 
  /// 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() const;
 
  /// 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);
 
  /// Warn when implicitly changing function effects.
  void diagnoseFunctionEffectConversion(QualType DstType, QualType SrcType,
                                        SourceLocation Loc);
 
  /// makeUnavailableInSystemHeader - There is an error in the current
  /// context.  If we're still in a system header, and we can plausibly
  /// make the relevant declaration unavailable instead of erroring, do
  /// so and return true.
  bool makeUnavailableInSystemHeader(SourceLocation loc,
                                     UnavailableAttr::ImplicitReason reason);
 
  /// 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 ActOnTranslationUnitScope(Scope *S);
 
  /// Determine whether \param D is function like (function or function
  /// template) for parsing.
  bool isDeclaratorFunctionLike(Declarator &D);
 
  /// 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 = 32;
  static const uint64_t MaximumAlignment = 1ull << MaxAlignmentExponent;
 
  /// Flag indicating whether or not to collect detailed statistics.
  bool CollectStats;
 
  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;
 
  /// Track the number of currently active capturing scopes.
  unsigned CapturingFunctionScopes = 0;
 
  llvm::BumpPtrAllocator BumpAlloc;
 
  /// 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.
  const TranslationUnitKind TUKind;
 
  /// 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;
 
  void incrementMSManglingNumber() const {
    return CurScope->incrementMSManglingNumber();
  }
 
  /// 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.
  ///
  /// Use this when trying to recover from an error where the programmer may
  /// have written just the name of a function instead of actually calling it.
  ///
  /// \param E - The expression to examine.
  /// \param ZeroArgCallReturnTy - If the expression can be turned into a call
  ///  with no arguments, this parameter is set to the type returned by such a
  ///  call; otherwise, it is set to an empty QualType.
  /// \param OverloadSet - If the expression is an overloaded function
  ///  name, this parameter is populated with the decls of the various
  ///  overloads.
  bool tryExprAsCall(Expr &E, QualType &ZeroArgCallReturnTy,
                     UnresolvedSetImpl &NonTemplateOverloads);
 
  typedef OpaquePtr<DeclGroupRef> DeclGroupPtrTy;
  typedef OpaquePtr<TemplateName> TemplateTy;
  typedef OpaquePtr<QualType> TypeTy;
 
  OpenCLOptions OpenCLFeatures;
  FPOptions CurFPFeatures;
 
  const LangOptions &LangOpts;
  Preprocessor &PP;
  ASTContext &Context;
  ASTConsumer &Consumer;
  DiagnosticsEngine &Diags;
  SourceManager &SourceMgr;
  api_notes::APINotesManager APINotes;
 
  /// 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; }
  };
 
  sema::FunctionScopeInfo *getCurFunction() const {
    return FunctionScopes.empty() ? nullptr : FunctionScopes.back();
  }
 
  /// Worker object for performing CFG-based warnings.
  sema::AnalysisBasedWarnings AnalysisWarnings;
  threadSafety::BeforeSet *ThreadSafetyDeclCache;
 
  /// 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;
  }
 
  /// Callback to the parser to parse a type expressed as a string.
  std::function<TypeResult(StringRef, StringRef, SourceLocation)>
      ParseTypeFromStringCallback;
 
  /// 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;
 
  /// Is the last error level diagnostic immediate. This is used to determined
  /// whether the next info diagnostic should be immediate.
  bool IsLastErrorImmediate = true;
 
  class DelayedDiagnostics;
 
  class DelayedDiagnosticsState {
    sema::DelayedDiagnosticPool *SavedPool = nullptr;
    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 = nullptr;
 
  public:
    DelayedDiagnostics() = default;
 
    /// 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;
 
  ParsingDeclState PushParsingDeclaration(sema::DelayedDiagnosticPool &pool) {
    return DelayedDiagnostics.push(pool);
  }
 
  /// 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.
  SemaDiagnosticBuilder::DeferredDiagnosticsType DeviceDeferredDiags;
 
  /// CurContext - This is the current declaration context of parsing.
  DeclContext *CurContext;
 
  SemaAMDGPU &AMDGPU() {
    assert(AMDGPUPtr);
    return *AMDGPUPtr;
  }
 
  SemaARM &ARM() {
    assert(ARMPtr);
    return *ARMPtr;
  }
 
  SemaAVR &AVR() {
    assert(AVRPtr);
    return *AVRPtr;
  }
 
  SemaBPF &BPF() {
    assert(BPFPtr);
    return *BPFPtr;
  }
 
  SemaCodeCompletion &CodeCompletion() {
    assert(CodeCompletionPtr);
    return *CodeCompletionPtr;
  }
 
  SemaCUDA &CUDA() {
    assert(CUDAPtr);
    return *CUDAPtr;
  }
 
  SemaHLSL &HLSL() {
    assert(HLSLPtr);
    return *HLSLPtr;
  }
 
  SemaHexagon &Hexagon() {
    assert(HexagonPtr);
    return *HexagonPtr;
  }
 
  SemaLoongArch &LoongArch() {
    assert(LoongArchPtr);
    return *LoongArchPtr;
  }
 
  SemaM68k &M68k() {
    assert(M68kPtr);
    return *M68kPtr;
  }
 
  SemaMIPS &MIPS() {
    assert(MIPSPtr);
    return *MIPSPtr;
  }
 
  SemaMSP430 &MSP430() {
    assert(MSP430Ptr);
    return *MSP430Ptr;
  }
 
  SemaNVPTX &NVPTX() {
    assert(NVPTXPtr);
    return *NVPTXPtr;
  }
 
  SemaObjC &ObjC() {
    assert(ObjCPtr);
    return *ObjCPtr;
  }
 
  SemaOpenACC &OpenACC() {
    assert(OpenACCPtr);
    return *OpenACCPtr;
  }
 
  SemaOpenCL &OpenCL() {
    assert(OpenCLPtr);
    return *OpenCLPtr;
  }
 
  SemaOpenMP &OpenMP() {
    assert(OpenMPPtr && "SemaOpenMP is dead");
    return *OpenMPPtr;
  }
 
  SemaPPC &PPC() {
    assert(PPCPtr);
    return *PPCPtr;
  }
 
  SemaPseudoObject &PseudoObject() {
    assert(PseudoObjectPtr);
    return *PseudoObjectPtr;
  }
 
  SemaRISCV &RISCV() {
    assert(RISCVPtr);
    return *RISCVPtr;
  }
 
  SemaSYCL &SYCL() {
    assert(SYCLPtr);
    return *SYCLPtr;
  }
 
  SemaSwift &Swift() {
    assert(SwiftPtr);
    return *SwiftPtr;
  }
 
  SemaSystemZ &SystemZ() {
    assert(SystemZPtr);
    return *SystemZPtr;
  }
 
  SemaWasm &Wasm() {
    assert(WasmPtr);
    return *WasmPtr;
  }
 
  SemaX86 &X86() {
    assert(X86Ptr);
    return *X86Ptr;
  }
 
  /// Source of additional semantic information.
  IntrusiveRefCntPtr<ExternalSemaSource> ExternalSource;
 
protected:
  friend class Parser;
  friend class InitializationSequence;
  friend class ASTReader;
  friend class ASTDeclReader;
  friend class ASTWriter;
 
private:
  std::optional<std::unique_ptr<DarwinSDKInfo>> CachedDarwinSDKInfo;
  bool WarnedDarwinSDKInfoMissing = false;
 
  StackExhaustionHandler StackHandler;
 
  Sema(const Sema &) = delete;
  void operator=(const Sema &) = delete;
 
  /// The handler for the FileChanged preprocessor events.
  ///
  /// Used for diagnostics that implement custom semantic analysis for #include
  /// directives, like -Wpragma-pack.
  sema::SemaPPCallbacks *SemaPPCallbackHandler;
 
  /// The parser's current scope.
  ///
  /// The parser maintains this state here.
  Scope *CurScope;
 
  mutable IdentifierInfo *Ident_super;
 
  std::unique_ptr<SemaAMDGPU> AMDGPUPtr;
  std::unique_ptr<SemaARM> ARMPtr;
  std::unique_ptr<SemaAVR> AVRPtr;
  std::unique_ptr<SemaBPF> BPFPtr;
  std::unique_ptr<SemaCodeCompletion> CodeCompletionPtr;
  std::unique_ptr<SemaCUDA> CUDAPtr;
  std::unique_ptr<SemaHLSL> HLSLPtr;
  std::unique_ptr<SemaHexagon> HexagonPtr;
  std::unique_ptr<SemaLoongArch> LoongArchPtr;
  std::unique_ptr<SemaM68k> M68kPtr;
  std::unique_ptr<SemaMIPS> MIPSPtr;
  std::unique_ptr<SemaMSP430> MSP430Ptr;
  std::unique_ptr<SemaNVPTX> NVPTXPtr;
  std::unique_ptr<SemaObjC> ObjCPtr;
  std::unique_ptr<SemaOpenACC> OpenACCPtr;
  std::unique_ptr<SemaOpenCL> OpenCLPtr;
  std::unique_ptr<SemaOpenMP> OpenMPPtr;
  std::unique_ptr<SemaPPC> PPCPtr;
  std::unique_ptr<SemaPseudoObject> PseudoObjectPtr;
  std::unique_ptr<SemaRISCV> RISCVPtr;
  std::unique_ptr<SemaSYCL> SYCLPtr;
  std::unique_ptr<SemaSwift> SwiftPtr;
  std::unique_ptr<SemaSystemZ> SystemZPtr;
  std::unique_ptr<SemaWasm> WasmPtr;
  std::unique_ptr<SemaX86> X86Ptr;
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name API Notes
  /// Implementations are in SemaAPINotes.cpp
  ///@{
 
public:
  /// Map any API notes provided for this declaration to attributes on the
  /// declaration.
  ///
  /// Triggered by declaration-attribute processing.
  void ProcessAPINotes(Decl *D);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name C++ Access Control
  /// Implementations are in SemaAccess.cpp
  ///@{
 
public:
  enum AccessResult {
    AR_accessible,
    AR_inaccessible,
    AR_dependent,
    AR_delayed
  };
 
  /// SetMemberAccessSpecifier - Set the access specifier of a member.
  /// Returns true on error (when the previous member decl access specifier
  /// is different from the new member decl access specifier).
  bool SetMemberAccessSpecifier(NamedDecl *MemberDecl,
                                NamedDecl *PrevMemberDecl,
                                AccessSpecifier LexicalAS);
 
  /// Perform access-control checking on a previously-unresolved member
  /// access which has now been resolved to a member.
  AccessResult CheckUnresolvedMemberAccess(UnresolvedMemberExpr *E,
                                           DeclAccessPair FoundDecl);
  AccessResult CheckUnresolvedLookupAccess(UnresolvedLookupExpr *E,
                                           DeclAccessPair FoundDecl);
 
  /// Checks access to an overloaded operator new or delete.
  AccessResult CheckAllocationAccess(SourceLocation OperatorLoc,
                                     SourceRange PlacementRange,
                                     CXXRecordDecl *NamingClass,
                                     DeclAccessPair FoundDecl,
                                     bool Diagnose = true);
 
  /// Checks access to a constructor.
  AccessResult CheckConstructorAccess(SourceLocation Loc, CXXConstructorDecl *D,
                                      DeclAccessPair FoundDecl,
                                      const InitializedEntity &Entity,
                                      bool IsCopyBindingRefToTemp = false);
 
  /// Checks access to a constructor.
  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());
 
  /// Checks access to the target of a friend declaration.
  AccessResult CheckFriendAccess(NamedDecl *D);
 
  /// Checks access to a member.
  AccessResult CheckMemberAccess(SourceLocation UseLoc,
                                 CXXRecordDecl *NamingClass,
                                 DeclAccessPair Found);
 
  /// Checks implicit access to a member in a structured binding.
  AccessResult
  CheckStructuredBindingMemberAccess(SourceLocation UseLoc,
                                     CXXRecordDecl *DecomposedClass,
                                     DeclAccessPair Field);
  AccessResult CheckMemberOperatorAccess(SourceLocation Loc, Expr *ObjectExpr,
                                         const SourceRange &,
                                         DeclAccessPair FoundDecl);
 
  /// Checks access to an overloaded member operator, including
  /// conversion operators.
  AccessResult CheckMemberOperatorAccess(SourceLocation Loc, Expr *ObjectExpr,
                                         Expr *ArgExpr,
                                         DeclAccessPair FoundDecl);
  AccessResult CheckMemberOperatorAccess(SourceLocation Loc, Expr *ObjectExpr,
                                         ArrayRef<Expr *> ArgExprs,
                                         DeclAccessPair FoundDecl);
  AccessResult CheckAddressOfMemberAccess(Expr *OvlExpr,
                                          DeclAccessPair FoundDecl);
 
  /// Checks access for a hierarchy conversion.
  ///
  /// \param ForceCheck true if this check should be performed even if access
  ///     control is disabled;  some things rely on this for semantics
  /// \param ForceUnprivileged true if this check should proceed as if the
  ///     context had no special privileges
  AccessResult CheckBaseClassAccess(SourceLocation AccessLoc, QualType Base,
                                    QualType Derived, const CXXBasePath &Path,
                                    unsigned DiagID, bool ForceCheck = false,
                                    bool ForceUnprivileged = false);
 
  /// Checks access to all the declarations in the given result set.
  void CheckLookupAccess(const LookupResult &R);
 
  /// Checks access to Target from the given class. The check will take access
  /// specifiers into account, but no member access expressions and such.
  ///
  /// \param Target the declaration to check if it can be accessed
  /// \param NamingClass the class in which the lookup was started.
  /// \param BaseType type of the left side of member access expression.
  ///        \p BaseType and \p NamingClass are used for C++ access control.
  ///        Depending on the lookup case, they should be set to the following:
  ///        - lhs.target (member access without a qualifier):
  ///          \p BaseType and \p NamingClass are both the type of 'lhs'.
  ///        - lhs.X::target (member access with a qualifier):
  ///          BaseType is the type of 'lhs', NamingClass is 'X'
  ///        - X::target (qualified lookup without member access):
  ///          BaseType is null, NamingClass is 'X'.
  ///        - target (unqualified lookup).
  ///          BaseType is null, NamingClass is the parent class of 'target'.
  /// \return true if the Target is accessible from the Class, false otherwise.
  bool IsSimplyAccessible(NamedDecl *Decl, CXXRecordDecl *NamingClass,
                          QualType BaseType);
 
  /// Is the given member accessible for the purposes of deciding whether to
  /// define a special member function as deleted?
  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 HandleDelayedAccessCheck(sema::DelayedDiagnostic &DD, Decl *Ctx);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name Attributes
  /// Implementations are in SemaAttr.cpp
  ///@{
 
public:
  /// Controls member pointer representation format under the MS ABI.
  LangOptions::PragmaMSPointersToMembersKind
      MSPointerToMemberRepresentationMethod;
 
  bool MSStructPragmaOn; // True when \#pragma ms_struct on
 
  /// Source location for newly created implicit MSInheritanceAttrs
  SourceLocation ImplicitMSInheritanceAttrLoc;
 
  /// 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;
  };
 
  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)
  };
 
  struct PragmaPackInfo {
    PragmaMsStackAction Action;
    StringRef SlotLabel;
    Token Alignment;
  };
 
  // #pragma pack and align.
  class AlignPackInfo {
  public:
    // `Native` represents default align mode, which may vary based on the
    // platform.
    enum Mode : unsigned char { Native, Natural, Packed, Mac68k };
 
    // #pragma pack info constructor
    AlignPackInfo(AlignPackInfo::Mode M, unsigned Num, bool IsXL)
        : PackAttr(true), AlignMode(M), PackNumber(Num), XLStack(IsXL) {
      assert(Num == PackNumber && "The pack number has been truncated.");
    }
 
    // #pragma align info constructor
    AlignPackInfo(AlignPackInfo::Mode M, bool IsXL)
        : PackAttr(false), AlignMode(M),
          PackNumber(M == Packed ? 1 : UninitPackVal), XLStack(IsXL) {}
 
    explicit AlignPackInfo(bool IsXL) : AlignPackInfo(Native, IsXL) {}
 
    AlignPackInfo() : AlignPackInfo(Native, false) {}
 
    // When a AlignPackInfo itself cannot be used, this returns an 32-bit
    // integer encoding for it. This should only be passed to
    // AlignPackInfo::getFromRawEncoding, it should not be inspected directly.
    static uint32_t getRawEncoding(const AlignPackInfo &Info) {
      std::uint32_t Encoding{};
      if (Info.IsXLStack())
        Encoding |= IsXLMask;
 
      Encoding |= static_cast<uint32_t>(Info.getAlignMode()) << 1;
 
      if (Info.IsPackAttr())
        Encoding |= PackAttrMask;
 
      Encoding |= static_cast<uint32_t>(Info.getPackNumber()) << 4;
 
      return Encoding;
    }
 
    static AlignPackInfo getFromRawEncoding(unsigned Encoding) {
      bool IsXL = static_cast<bool>(Encoding & IsXLMask);
      AlignPackInfo::Mode M =
          static_cast<AlignPackInfo::Mode>((Encoding & AlignModeMask) >> 1);
      int PackNumber = (Encoding & PackNumMask) >> 4;
 
      if (Encoding & PackAttrMask)
        return AlignPackInfo(M, PackNumber, IsXL);
 
      return AlignPackInfo(M, IsXL);
    }
 
    bool IsPackAttr() const { return PackAttr; }
 
    bool IsAlignAttr() const { return !PackAttr; }
 
    Mode getAlignMode() const { return AlignMode; }
 
    unsigned getPackNumber() const { return PackNumber; }
 
    bool IsPackSet() const {
      // #pragma align, #pragma pack(), and #pragma pack(0) do not set the pack
      // attriute on a decl.
      return PackNumber != UninitPackVal && PackNumber != 0;
    }
 
    bool IsXLStack() const { return XLStack; }
 
    bool operator==(const AlignPackInfo &Info) const {
      return std::tie(AlignMode, PackNumber, PackAttr, XLStack) ==
             std::tie(Info.AlignMode, Info.PackNumber, Info.PackAttr,
                      Info.XLStack);
    }
 
    bool operator!=(const AlignPackInfo &Info) const {
      return !(*this == Info);
    }
 
  private:
    /// \brief True if this is a pragma pack attribute,
    ///         not a pragma align attribute.
    bool PackAttr;
 
    /// \brief The alignment mode that is in effect.
    Mode AlignMode;
 
    /// \brief The pack number of the stack.
    unsigned char PackNumber;
 
    /// \brief True if it is a XL #pragma align/pack stack.
    bool XLStack;
 
    /// \brief Uninitialized pack value.
    static constexpr unsigned char UninitPackVal = -1;
 
    // Masks to encode and decode an AlignPackInfo.
    static constexpr uint32_t IsXLMask{0x0000'0001};
    static constexpr uint32_t AlignModeMask{0x0000'0006};
    static constexpr uint32_t PackAttrMask{0x00000'0008};
    static constexpr uint32_t PackNumMask{0x0000'01F0};
  };
 
  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) {
      if (Action == PSK_Reset) {
        CurrentValue = DefaultValue;
        CurrentPragmaLocation = PragmaLocation;
        return;
      }
      if (Action & PSK_Push)
        Stack.emplace_back(StackSlotLabel, CurrentValue, CurrentPragmaLocation,
                           PragmaLocation);
      else if (Action & PSK_Pop) {
        if (!StackSlotLabel.empty()) {
          // If we've got a label, try to find it and jump there.
          auto I = llvm::find_if(llvm::reverse(Stack), [&](const Slot &x) {
            return x.StackSlotLabel == StackSlotLabel;
          });
          // If we found the label so pop from there.
          if (I != Stack.rend()) {
            CurrentValue = I->Value;
            CurrentPragmaLocation = I->PragmaLocation;
            Stack.erase(std::prev(I.base()), Stack.end());
          }
        } else if (!Stack.empty()) {
          // We do not have a label, just pop the last entry.
          CurrentValue = Stack.back().Value;
          CurrentPragmaLocation = Stack.back().PragmaLocation;
          Stack.pop_back();
        }
      }
      if (Action & PSK_Set) {
        CurrentValue = Value;
        CurrentPragmaLocation = PragmaLocation;
      }
    }
 
    // 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;
  PragmaStack<AlignPackInfo> AlignPackStack;
  // The current #pragma align/pack values and locations at each #include.
  struct AlignPackIncludeState {
    AlignPackInfo CurrentValue;
    SourceLocation CurrentPragmaLocation;
    bool HasNonDefaultValue, ShouldWarnOnInclude;
  };
  SmallVector<AlignPackIncludeState, 8> AlignPackIncludeStack;
  // Segment #pragmas.
  PragmaStack<StringLiteral *> DataSegStack;
  PragmaStack<StringLiteral *> BSSSegStack;
  PragmaStack<StringLiteral *> ConstSegStack;
  PragmaStack<StringLiteral *> CodeSegStack;
 
  // #pragma strict_gs_check.
  PragmaStack<bool> StrictGuardStackCheckStack;
 
  // This stack tracks the current state of Sema.CurFPFeatures.
  PragmaStack<FPOptionsOverride> FpPragmaStack;
  FPOptionsOverride CurFPFeatureOverrides() {
    FPOptionsOverride result;
    if (!FpPragmaStack.hasValue()) {
      result = FPOptionsOverride();
    } else {
      result = FpPragmaStack.CurrentValue;
    }
    return result;
  }
 
  enum PragmaSectionKind {
    PSK_DataSeg,
    PSK_BSSSeg,
    PSK_ConstSeg,
    PSK_CodeSeg,
  };
 
  // 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;
  };
 
  /// Last section used with #pragma init_seg.
  StringLiteral *CurInitSeg;
  SourceLocation CurInitSegLoc;
 
  /// Sections used with #pragma alloc_text.
  llvm::StringMap<std::tuple<StringRef, SourceLocation>> FunctionToSectionMap;
 
  /// 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;
 
  /// 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;
  }
 
  /// The "on" or "off" argument passed by \#pragma optimize, that denotes
  /// whether the optimizations in the list passed to the pragma should be
  /// turned off or on. This boolean is true by default because command line
  /// options are honored when `#pragma optimize("", on)`.
  /// (i.e. `ModifyFnAttributeMSPragmaOptimze()` does nothing)
  bool MSPragmaOptimizeIsOn = true;
 
  /// Set of no-builtin functions listed by \#pragma function.
  llvm::SmallSetVector<StringRef, 4> MSFunctionNoBuiltins;
 
  /// 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);
 
  /// 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 [[clang:::lifetimebound]] attr for std:: functions and methods.
  void inferLifetimeBoundAttribute(FunctionDecl *FD);
 
  /// Add [[clang:::lifetime_capture_by(this)]] to STL container methods.
  void inferLifetimeCaptureByAttribute(FunctionDecl *FD);
 
  /// Add [[gsl::Pointer]] attributes for std:: types.
  void inferGslPointerAttribute(TypedefNameDecl *TD);
 
  LifetimeCaptureByAttr *ParseLifetimeCaptureByAttr(const ParsedAttr &AL,
                                                    StringRef ParamName);
  // Processes the argument 'X' in [[clang::lifetime_capture_by(X)]]. Since 'X'
  // can be the name of a function parameter, we need to parse the function
  // declaration and rest of the parameters before processesing 'X'. Therefore
  // do this lazily instead of processing while parsing the annotation itself.
  void LazyProcessLifetimeCaptureByParams(FunctionDecl *FD);
 
  /// Add _Nullable attributes for std:: types.
  void inferNullableClassAttribute(CXXRecordDecl *CRD);
 
  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);
 
  /// ConstantFoldAttrArgs - Folds attribute arguments into ConstantExprs
  /// (unless they are value dependent or type dependent). Returns false
  /// and emits a diagnostic if one or more of the arguments could not be
  /// folded into a constant.
  bool ConstantFoldAttrArgs(const AttributeCommonInfo &CI,
                            MutableArrayRef<Expr *> Args);
 
  enum class PragmaAlignPackDiagnoseKind {
    NonDefaultStateAtInclude,
    ChangedStateAtExit
  };
 
  void DiagnoseNonDefaultPragmaAlignPack(PragmaAlignPackDiagnoseKind Kind,
                                         SourceLocation IncludeLoc);
  void DiagnoseUnterminatedPragmaAlignPack();
 
  /// 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);
 
  /// ActOnPragmaDetectMismatch - Call on well-formed \#pragma detect_mismatch
  void ActOnPragmaDetectMismatch(SourceLocation Loc, StringRef Name,
                                 StringRef Value);
 
  /// Are precise floating point semantics currently enabled?
  bool isPreciseFPEnabled() {
    return !CurFPFeatures.getAllowFPReassociate() &&
           !CurFPFeatures.getNoSignedZero() &&
           !CurFPFeatures.getAllowReciprocal() &&
           !CurFPFeatures.getAllowApproxFunc();
  }
 
  void ActOnPragmaFPEvalMethod(SourceLocation Loc,
                               LangOptions::FPEvalMethodKind Value);
 
  /// ActOnPragmaFloatControl - Call on well-formed \#pragma float_control
  void ActOnPragmaFloatControl(SourceLocation Loc, PragmaMsStackAction Action,
                               PragmaFloatControlKind Value);
 
  /// 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);
 
  bool UnifySection(StringRef SectionName, int SectionFlags,
                    NamedDecl *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 well-formed \#pragma alloc_text().
  void ActOnPragmaMSAllocText(
      SourceLocation PragmaLocation, StringRef Section,
      const SmallVector<std::tuple<IdentifierInfo *, SourceLocation>>
          &Functions);
 
  /// ActOnPragmaMSStrictGuardStackCheck - Called on well formed \#pragma
  /// strict_gs_check.
  void ActOnPragmaMSStrictGuardStackCheck(SourceLocation PragmaLocation,
                                          PragmaMsStackAction Action,
                                          bool Value);
 
  /// ActOnPragmaUnused - Called on well-formed '\#pragma unused'.
  void ActOnPragmaUnused(const Token &Identifier, Scope *curScope,
                         SourceLocation PragmaLoc);
 
  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 PrintPragmaAttributeInstantiationPoint();
 
  void DiagnoseUnterminatedPragmaAttribute();
 
  /// Called on well formed \#pragma clang optimize.
  void ActOnPragmaOptimize(bool On, SourceLocation PragmaLoc);
 
  /// #pragma optimize("[optimization-list]", on | off).
  void ActOnPragmaMSOptimize(SourceLocation Loc, bool IsOn);
 
  /// Call on well formed \#pragma function.
  void
  ActOnPragmaMSFunction(SourceLocation Loc,
                        const llvm::SmallVectorImpl<StringRef> &NoBuiltins);
 
  /// 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);
 
  /// Only called on function definitions; if there is a `#pragma alloc_text`
  /// that decides which code section the function should be in, add
  /// attribute section to the function.
  void AddSectionMSAllocText(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);
 
  /// Only called on function definitions; if there is a MSVC #pragma optimize
  /// in scope, consider changing the function's attributes based on the
  /// optimization list passed to the pragma.
  void ModifyFnAttributesMSPragmaOptimize(FunctionDecl *FD);
 
  /// Only called on function definitions; if there is a pragma in scope
  /// with the effect of a range-based no_builtin, consider marking the function
  /// with attribute no_builtin.
  void AddImplicitMSFunctionNoBuiltinAttr(FunctionDecl *FD);
 
  /// AddPushedVisibilityAttribute - If '\#pragma GCC visibility' was used,
  /// add an appropriate visibility attribute.
  void AddPushedVisibilityAttribute(Decl *RD);
 
  /// FreeVisContext - Deallocate and null out VisContext.
  void FreeVisContext();
 
  /// ActOnPragmaVisibility - Called on well formed \#pragma GCC visibility... .
  void ActOnPragmaVisibility(const IdentifierInfo *VisType,
                             SourceLocation PragmaLoc);
 
  /// ActOnPragmaFPContract - Called on well formed
  /// \#pragma {STDC,OPENCL} FP_CONTRACT and
  /// \#pragma clang fp contract
  void ActOnPragmaFPContract(SourceLocation Loc, LangOptions::FPModeKind FPC);
 
  /// Called on well formed
  /// \#pragma clang fp reassociate
  /// or
  /// \#pragma clang fp reciprocal
  void ActOnPragmaFPValueChangingOption(SourceLocation Loc, PragmaFPKind Kind,
                                        bool IsEnabled);
 
  /// ActOnPragmaFenvAccess - Called on well formed
  /// \#pragma STDC FENV_ACCESS
  void ActOnPragmaFEnvAccess(SourceLocation Loc, bool IsEnabled);
 
  /// ActOnPragmaCXLimitedRange - Called on well formed
  /// \#pragma STDC CX_LIMITED_RANGE
  void ActOnPragmaCXLimitedRange(SourceLocation Loc,
                                 LangOptions::ComplexRangeKind Range);
 
  /// Called on well formed '\#pragma clang fp' that has option 'exceptions'.
  void ActOnPragmaFPExceptions(SourceLocation Loc,
                               LangOptions::FPExceptionModeKind);
 
  /// Called to set constant rounding mode for floating point operations.
  void ActOnPragmaFEnvRound(SourceLocation Loc, llvm::RoundingMode);
 
  /// Called to set exception behavior for floating point operations.
  void setExceptionMode(SourceLocation Loc, LangOptions::FPExceptionModeKind);
 
  /// PushNamespaceVisibilityAttr - Note that we've entered a
  /// namespace with a visibility attribute.
  void PushNamespaceVisibilityAttr(const VisibilityAttr *Attr,
                                   SourceLocation Loc);
 
  /// 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);
 
  /// Handles semantic checking for features that are common to all attributes,
  /// such as checking whether a parameter was properly specified, or the
  /// correct number of arguments were passed, etc. Returns true if the
  /// attribute has been diagnosed.
  bool checkCommonAttributeFeatures(const Decl *D, const ParsedAttr &A,
                                    bool SkipArgCountCheck = false);
  bool checkCommonAttributeFeatures(const Stmt *S, const ParsedAttr &A,
                                    bool SkipArgCountCheck = false);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name Availability Attribute Handling
  /// Implementations are in SemaAvailability.cpp
  ///@{
 
public:
  /// Issue any -Wunguarded-availability warnings in \c FD
  void DiagnoseUnguardedAvailabilityViolations(Decl *FD);
 
  void handleDelayedAvailabilityCheck(sema::DelayedDiagnostic &DD, Decl *Ctx);
 
  /// Retrieve the current function, if any, that should be analyzed for
  /// potential availability violations.
  sema::FunctionScopeInfo *getCurFunctionAvailabilityContext();
 
  void DiagnoseAvailabilityOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
                                  const ObjCInterfaceDecl *UnknownObjCClass,
                                  bool ObjCPropertyAccess,
                                  bool AvoidPartialAvailabilityChecks = false,
                                  ObjCInterfaceDecl *ClassReceiver = nullptr);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name Bounds Safety
  /// Implementations are in SemaBoundsSafety.cpp
  ///@{
public:
  /// Check if applying the specified attribute variant from the "counted by"
  /// family of attributes to FieldDecl \p FD is semantically valid. If
  /// semantically invalid diagnostics will be emitted explaining the problems.
  ///
  /// \param FD The FieldDecl to apply the attribute to
  /// \param E The count expression on the attribute
  /// \param CountInBytes If true the attribute is from the "sized_by" family of
  ///                     attributes. If the false the attribute is from
  ///                     "counted_by" family of attributes.
  /// \param OrNull If true the attribute is from the "_or_null" suffixed family
  ///               of attributes. If false the attribute does not have the
  ///               suffix.
  ///
  /// Together \p CountInBytes and \p OrNull decide the attribute variant. E.g.
  /// \p CountInBytes and \p OrNull both being true indicates the
  /// `counted_by_or_null` attribute.
  ///
  /// \returns false iff semantically valid.
  bool CheckCountedByAttrOnField(FieldDecl *FD, Expr *E, bool CountInBytes,
                                 bool OrNull);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name Casts
  /// Implementations are in SemaCast.cpp
  ///@{
 
public:
  static bool isCast(CheckedConversionKind CCK) {
    return CCK == CheckedConversionKind::CStyleCast ||
           CCK == CheckedConversionKind::FunctionalCast ||
           CCK == CheckedConversionKind::OtherCast;
  }
 
  /// ActOnCXXNamedCast - Parse
  /// {dynamic,static,reinterpret,const,addrspace}_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);
 
  // Checks that reinterpret casts don't have undefined behavior.
  void CheckCompatibleReinterpretCast(QualType SrcType, QualType DestType,
                                      bool IsDereference, SourceRange Range);
 
  // Checks that the vector type should be initialized from a scalar
  // by splatting the value rather than populating a single element.
  // This is the case for AltiVecVector types as well as with
  // AltiVecPixel and AltiVecBool when -faltivec-src-compat=xl is specified.
  bool ShouldSplatAltivecScalarInCast(const VectorType *VecTy);
 
  // Checks if the -faltivec-src-compat=gcc option is specified.
  // If so, AltiVecVector, AltiVecBool and AltiVecPixel types are
  // treated the same way as they are when trying to initialize
  // these vectors on gcc (an error is emitted).
  bool CheckAltivecInitFromScalar(SourceRange R, QualType VecTy,
                                  QualType SrcTy);
 
  ExprResult BuildCStyleCastExpr(SourceLocation LParenLoc, TypeSourceInfo *Ty,
                                 SourceLocation RParenLoc, Expr *Op);
 
  ExprResult BuildCXXFunctionalCastExpr(TypeSourceInfo *TInfo, QualType Type,
                                        SourceLocation LParenLoc,
                                        Expr *CastExpr,
                                        SourceLocation RParenLoc);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name Extra Semantic Checking
  /// Implementations are in SemaChecking.cpp
  ///@{
 
public:
  /// Used to change context to isConstantEvaluated without pushing a heavy
  /// ExpressionEvaluationContextRecord object.
  bool isConstantEvaluatedOverride = false;
 
  bool isConstantEvaluatedContext() const {
    return currentEvaluationContext().isConstantEvaluated() ||
           isConstantEvaluatedOverride;
  }
 
  SourceLocation getLocationOfStringLiteralByte(const StringLiteral *SL,
                                                unsigned ByteNo) const;
 
  enum FormatArgumentPassingKind {
    FAPK_Fixed,    // values to format are fixed (no C-style variadic arguments)
    FAPK_Variadic, // values to format are passed as variadic arguments
    FAPK_VAList,   // values to format are passed in a va_list
  };
 
  // Used to grab the relevant information from a FormatAttr and a
  // FunctionDeclaration.
  struct FormatStringInfo {
    unsigned FormatIdx;
    unsigned FirstDataArg;
    FormatArgumentPassingKind ArgPassingKind;
  };
 
  /// Given a FunctionDecl's FormatAttr, attempts to populate the
  /// FomatStringInfo parameter with the FormatAttr's correct format_idx and
  /// firstDataArg. Returns true when the format fits the function and the
  /// FormatStringInfo has been populated.
  static bool getFormatStringInfo(const FormatAttr *Format, bool IsCXXMember,
                                  bool IsVariadic, FormatStringInfo *FSI);
 
  // Used by C++ template instantiation.
  ExprResult BuiltinShuffleVector(CallExpr *TheCall);
 
  /// ConvertVectorExpr - Handle __builtin_convertvector
  ExprResult ConvertVectorExpr(Expr *E, TypeSourceInfo *TInfo,
                               SourceLocation BuiltinLoc,
                               SourceLocation RParenLoc);
 
  enum FormatStringType {
    FST_Scanf,
    FST_Printf,
    FST_NSString,
    FST_Strftime,
    FST_Strfmon,
    FST_Kprintf,
    FST_FreeBSDKPrintf,
    FST_OSTrace,
    FST_OSLog,
    FST_Syslog,
    FST_Unknown
  };
  static FormatStringType GetFormatStringType(const FormatAttr *Format);
 
  bool FormatStringHasSArg(const StringLiteral *FExpr);
 
  /// Check for comparisons of floating-point values using == and !=. Issue a
  /// warning if the comparison is not likely to do what the programmer
  /// intended.
  void CheckFloatComparison(SourceLocation Loc, Expr *LHS, Expr *RHS,
                            BinaryOperatorKind Opcode);
 
  /// 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.
    LLVM_PREFERRED_TYPE(bool)
    unsigned LayoutCompatible : 1;
    LLVM_PREFERRED_TYPE(bool)
    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;
 
  /// 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);
 
  enum class AtomicArgumentOrder { API, AST };
  ExprResult
  BuildAtomicExpr(SourceRange CallRange, SourceRange ExprRange,
                  SourceLocation RParenLoc, MultiExprArg Args,
                  AtomicExpr::AtomicOp Op,
                  AtomicArgumentOrder ArgOrder = AtomicArgumentOrder::API);
 
  /// Check to see if a given expression could have '.c_str()' called on it.
  bool hasCStrMethod(const Expr *E);
 
  /// Diagnose pointers that are always non-null.
  /// \param E the expression containing the pointer
  /// \param NullKind NPCK_NotNull if E is a cast to bool, otherwise, E is
  /// compared to a null pointer
  /// \param IsEqual True when the comparison is equal to a null pointer
  /// \param Range Extra SourceRange to highlight in the diagnostic
  void DiagnoseAlwaysNonNullPointer(Expr *E,
                                    Expr::NullPointerConstantKind NullType,
                                    bool IsEqual, SourceRange Range);
 
  /// CheckParmsForFunctionDef - Check that the parameters of the given
  /// function are appropriate for the definition of a function. This
  /// takes care of any checks that cannot be performed on the
  /// declaration itself, e.g., that the types of each of the function
  /// parameters are complete.
  bool CheckParmsForFunctionDef(ArrayRef<ParmVarDecl *> Parameters,
                                bool CheckParameterNames);
 
  /// CheckCastAlign - Implements -Wcast-align, which warns when a
  /// pointer cast increases the alignment requirements.
  void CheckCastAlign(Expr *Op, QualType T, SourceRange TRange);
 
  /// 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);
 
  /// 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);
 
  /// DiagnoseSelfMove - Emits a warning if a value is moved to itself.
  void DiagnoseSelfMove(const Expr *LHSExpr, const Expr *RHSExpr,
                        SourceLocation OpLoc);
 
  // Used for emitting the right warning by DefaultVariadicArgumentPromotion
  enum VariadicCallType {
    VariadicFunction,
    VariadicBlock,
    VariadicMethod,
    VariadicConstructor,
    VariadicDoesNotApply
  };
 
  bool IsLayoutCompatible(QualType T1, QualType T2) const;
  bool IsPointerInterconvertibleBaseOf(const TypeSourceInfo *Base,
                                       const TypeSourceInfo *Derived);
 
  /// CheckFunctionCall - Check a direct function call for various correctness
  /// and safety properties not strictly enforced by the C type system.
  bool CheckFunctionCall(FunctionDecl *FDecl, CallExpr *TheCall,
                         const FunctionProtoType *Proto);
 
  /// \param FPOnly restricts the arguments to floating-point types.
  bool BuiltinVectorMath(CallExpr *TheCall, QualType &Res, bool FPOnly = false);
  bool BuiltinVectorToScalarMath(CallExpr *TheCall);
 
  void checkLifetimeCaptureBy(FunctionDecl *FDecl, bool IsMemberFunction,
                              const Expr *ThisArg, ArrayRef<const Expr *> Args);
 
  /// Handles the checks for format strings, non-POD arguments to vararg
  /// functions, NULL arguments passed to non-NULL parameters, diagnose_if
  /// attributes and AArch64 SME attributes.
  void checkCall(NamedDecl *FDecl, const FunctionProtoType *Proto,
                 const Expr *ThisArg, ArrayRef<const Expr *> Args,
                 bool IsMemberFunction, SourceLocation Loc, SourceRange Range,
                 VariadicCallType CallType);
 
  /// \brief Enforce the bounds of a TCB
  /// CheckTCBEnforcement - Enforces that every function in a named TCB only
  /// directly calls other functions in the same TCB as marked by the
  /// enforce_tcb and enforce_tcb_leaf attributes.
  void CheckTCBEnforcement(const SourceLocation CallExprLoc,
                           const NamedDecl *Callee);
 
  void CheckConstrainedAuto(const AutoType *AutoT, SourceLocation Loc);
 
  /// BuiltinConstantArg - Handle a check if argument ArgNum of CallExpr
  /// TheCall is a constant expression.
  bool BuiltinConstantArg(CallExpr *TheCall, int ArgNum, llvm::APSInt &Result);
 
  /// BuiltinConstantArgRange - Handle a check if argument ArgNum of CallExpr
  /// TheCall is a constant expression in the range [Low, High].
  bool BuiltinConstantArgRange(CallExpr *TheCall, int ArgNum, int Low, int High,
                               bool RangeIsError = true);
 
  /// BuiltinConstantArgMultiple - Handle a check if argument ArgNum of CallExpr
  /// TheCall is a constant expression is a multiple of Num..
  bool BuiltinConstantArgMultiple(CallExpr *TheCall, int ArgNum,
                                  unsigned Multiple);
 
  /// BuiltinConstantArgPower2 - Check if argument ArgNum of TheCall is a
  /// constant expression representing a power of 2.
  bool BuiltinConstantArgPower2(CallExpr *TheCall, int ArgNum);
 
  /// BuiltinConstantArgShiftedByte - Check if argument ArgNum of TheCall is
  /// a constant expression representing an arbitrary byte value shifted left by
  /// a multiple of 8 bits.
  bool BuiltinConstantArgShiftedByte(CallExpr *TheCall, int ArgNum,
                                     unsigned ArgBits);
 
  /// BuiltinConstantArgShiftedByteOr0xFF - Check if argument ArgNum of
  /// TheCall is a constant expression representing either a shifted byte value,
  /// or a value of the form 0x??FF (i.e. a member of the arithmetic progression
  /// 0x00FF, 0x01FF, ..., 0xFFFF). This strange range check is needed for some
  /// Arm MVE intrinsics.
  bool BuiltinConstantArgShiftedByteOrXXFF(CallExpr *TheCall, int ArgNum,
                                           unsigned ArgBits);
 
  /// Checks that a call expression's argument count is at least the desired
  /// number. This is useful when doing custom type-checking on a variadic
  /// function. Returns true on error.
  bool checkArgCountAtLeast(CallExpr *Call, unsigned MinArgCount);
 
  /// Checks that a call expression's argument count is at most the desired
  /// number. This is useful when doing custom type-checking on a variadic
  /// function. Returns true on error.
  bool checkArgCountAtMost(CallExpr *Call, unsigned MaxArgCount);
 
  /// Checks that a call expression's argument count is in the desired range.
  /// This is useful when doing custom type-checking on a variadic function.
  /// Returns true on error.
  bool checkArgCountRange(CallExpr *Call, unsigned MinArgCount,
                          unsigned MaxArgCount);
 
  /// Checks that a call expression's argument count is the desired number.
  /// This is useful when doing custom type-checking.  Returns true on error.
  bool checkArgCount(CallExpr *Call, unsigned DesiredArgCount);
 
  /// Returns true if the argument consists of one contiguous run of 1s with any
  /// number of 0s on either side. The 1s are allowed to wrap from LSB to MSB,
  /// so 0x000FFF0, 0x0000FFFF, 0xFF0000FF, 0x0 are all runs. 0x0F0F0000 is not,
  /// since all 1s are not contiguous.
  bool ValueIsRunOfOnes(CallExpr *TheCall, unsigned ArgNum);
 
  void CheckImplicitConversion(Expr *E, QualType T, SourceLocation CC,
                               bool *ICContext = nullptr,
                               bool IsListInit = false);
 
  bool BuiltinElementwiseTernaryMath(CallExpr *TheCall,
                                     bool CheckForFloatArgs = true);
  bool PrepareBuiltinElementwiseMathOneArgCall(CallExpr *TheCall);
 
private:
  void CheckArrayAccess(const Expr *BaseExpr, const Expr *IndexExpr,
                        const ArraySubscriptExpr *ASE = nullptr,
                        bool AllowOnePastEnd = true, bool IndexNegated = false);
  void CheckArrayAccess(const Expr *E);
 
  bool CheckPointerCall(NamedDecl *NDecl, CallExpr *TheCall,
                        const FunctionProtoType *Proto);
 
  /// Checks function calls when a FunctionDecl or a NamedDecl is not available,
  /// such as function pointers returned from functions.
  bool CheckOtherCall(CallExpr *TheCall, const FunctionProtoType *Proto);
 
  /// CheckConstructorCall - Check a constructor call for correctness and safety
  /// properties not enforced by the C type system.
  void CheckConstructorCall(FunctionDecl *FDecl, QualType ThisType,
                            ArrayRef<const Expr *> Args,
                            const FunctionProtoType *Proto, SourceLocation Loc);
 
  /// Warn if a pointer or reference argument passed to a function points to an
  /// object that is less aligned than the parameter. This can happen when
  /// creating a typedef with a lower alignment than the original type and then
  /// calling functions defined in terms of the original type.
  void CheckArgAlignment(SourceLocation Loc, NamedDecl *FDecl,
                         StringRef ParamName, QualType ArgTy, QualType ParamTy);
 
  ExprResult CheckOSLogFormatStringArg(Expr *Arg);
 
  ExprResult CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
                                      CallExpr *TheCall);
 
  bool CheckTSBuiltinFunctionCall(const TargetInfo &TI, unsigned BuiltinID,
                                  CallExpr *TheCall);
 
  void checkFortifiedBuiltinMemoryFunction(FunctionDecl *FD, CallExpr *TheCall);
 
  /// Check the arguments to '__builtin_va_start' or '__builtin_ms_va_start'
  /// for validity.  Emit an error and return true on failure; return false
  /// on success.
  bool BuiltinVAStart(unsigned BuiltinID, CallExpr *TheCall);
  bool BuiltinVAStartARMMicrosoft(CallExpr *Call);
 
  /// BuiltinUnorderedCompare - Handle functions like __builtin_isgreater and
  /// friends.  This is declared to take (...), so we have to check everything.
  bool BuiltinUnorderedCompare(CallExpr *TheCall, unsigned BuiltinID);
 
  /// BuiltinSemaBuiltinFPClassification - Handle functions like
  /// __builtin_isnan and friends.  This is declared to take (...), so we have
  /// to check everything.
  bool BuiltinFPClassification(CallExpr *TheCall, unsigned NumArgs,
                               unsigned BuiltinID);
 
  /// Perform semantic analysis for a call to __builtin_complex.
  bool BuiltinComplex(CallExpr *TheCall);
  bool BuiltinOSLogFormat(CallExpr *TheCall);
 
  /// BuiltinPrefetch - Handle __builtin_prefetch.
  /// This is declared to take (const void*, ...) and can take two
  /// optional constant int args.
  bool BuiltinPrefetch(CallExpr *TheCall);
 
  /// Handle __builtin_alloca_with_align. This is declared
  /// as (size_t, size_t) where the second size_t must be a power of 2 greater
  /// than 8.
  bool BuiltinAllocaWithAlign(CallExpr *TheCall);
 
  /// BuiltinArithmeticFence - Handle __arithmetic_fence.
  bool BuiltinArithmeticFence(CallExpr *TheCall);
 
  /// BuiltinAssume - Handle __assume (MS Extension).
  /// __assume does not evaluate its arguments, and should warn if its argument
  /// has side effects.
  bool BuiltinAssume(CallExpr *TheCall);
 
  /// Handle __builtin_assume_aligned. This is declared
  /// as (const void*, size_t, ...) and can take one optional constant int arg.
  bool BuiltinAssumeAligned(CallExpr *TheCall);
 
  /// BuiltinLongjmp - Handle __builtin_longjmp(void *env[5], int val).
  /// This checks that the target supports __builtin_longjmp and
  /// that val is a constant 1.
  bool BuiltinLongjmp(CallExpr *TheCall);
 
  /// BuiltinSetjmp - Handle __builtin_setjmp(void *env[5]).
  /// This checks that the target supports __builtin_setjmp.
  bool BuiltinSetjmp(CallExpr *TheCall);
 
  /// We have a call to a function like __sync_fetch_and_add, which is an
  /// overloaded function based on the pointer type of its first argument.
  /// The main BuildCallExpr routines have already promoted the types of
  /// arguments because all of these calls are prototyped as void(...).
  ///
  /// This function goes through and does final semantic checking for these
  /// builtins, as well as generating any warnings.
  ExprResult BuiltinAtomicOverloaded(ExprResult TheCallResult);
 
  /// BuiltinNontemporalOverloaded - We have a call to
  /// __builtin_nontemporal_store or __builtin_nontemporal_load, which is an
  /// overloaded function based on the pointer type of its last argument.
  ///
  /// This function goes through and does final semantic checking for these
  /// builtins.
  ExprResult BuiltinNontemporalOverloaded(ExprResult TheCallResult);
  ExprResult AtomicOpsOverloaded(ExprResult TheCallResult,
                                 AtomicExpr::AtomicOp Op);
 
  /// \param FPOnly restricts the arguments to floating-point types.
  bool BuiltinElementwiseMath(CallExpr *TheCall, bool FPOnly = false);
  bool PrepareBuiltinReduceMathOneArgCall(CallExpr *TheCall);
 
  bool BuiltinNonDeterministicValue(CallExpr *TheCall);
 
  enum BuiltinCountedByRefKind {
    AssignmentKind,
    InitializerKind,
    FunctionArgKind,
    ReturnArgKind,
    ArraySubscriptKind,
    BinaryExprKind,
  };
 
  bool CheckInvalidBuiltinCountedByRef(const Expr *E,
                                       BuiltinCountedByRefKind K);
  bool BuiltinCountedByRef(CallExpr *TheCall);
 
  // Matrix builtin handling.
  ExprResult BuiltinMatrixTranspose(CallExpr *TheCall, ExprResult CallResult);
  ExprResult BuiltinMatrixColumnMajorLoad(CallExpr *TheCall,
                                          ExprResult CallResult);
  ExprResult BuiltinMatrixColumnMajorStore(CallExpr *TheCall,
                                           ExprResult CallResult);
 
  /// CheckFormatArguments - Check calls to printf and scanf (and similar
  /// functions) for correct use of format strings.
  /// Returns true if a format string has been fully checked.
  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,
                            FormatArgumentPassingKind FAPK, unsigned format_idx,
                            unsigned firstDataArg, FormatStringType Type,
                            VariadicCallType CallType, SourceLocation Loc,
                            SourceRange range,
                            llvm::SmallBitVector &CheckedVarArgs);
 
  void CheckInfNaNFunction(const CallExpr *Call, const FunctionDecl *FDecl);
 
  /// Warn when using the wrong abs() function.
  void CheckAbsoluteValueFunction(const CallExpr *Call,
                                  const FunctionDecl *FDecl);
 
  void CheckMaxUnsignedZero(const CallExpr *Call, const FunctionDecl *FDecl);
 
  /// Check for dangerous or invalid arguments to memset().
  ///
  /// This issues warnings on known problematic, dangerous or unspecified
  /// arguments to the standard 'memset', 'memcpy', 'memmove', and 'memcmp'
  /// function calls.
  ///
  /// \param Call The call expression to diagnose.
  void CheckMemaccessArguments(const CallExpr *Call, unsigned BId,
                               IdentifierInfo *FnName);
 
  // Warn if the user has made the 'size' argument to strlcpy or strlcat
  // be the size of the source, instead of the destination.
  void CheckStrlcpycatArguments(const CallExpr *Call, IdentifierInfo *FnName);
 
  // Warn on anti-patterns as the 'size' argument to strncat.
  // The correct size argument should look like following:
  //   strncat(dst, src, sizeof(dst) - strlen(dest) - 1);
  void CheckStrncatArguments(const CallExpr *Call, IdentifierInfo *FnName);
 
  /// Alerts the user that they are attempting to free a non-malloc'd object.
  void CheckFreeArguments(const CallExpr *E);
 
  void CheckReturnValExpr(Expr *RetValExp, QualType lhsType,
                          SourceLocation ReturnLoc, bool isObjCMethod = false,
                          const AttrVec *Attrs = nullptr,
                          const FunctionDecl *FD = nullptr);
 
  /// Diagnoses "dangerous" implicit conversions within the given
  /// expression (which is a full expression).  Implements -Wconversion
  /// and -Wsign-compare.
  ///
  /// \param CC the "context" location of the implicit conversion, i.e.
  ///   the most location of the syntactic entity requiring the implicit
  ///   conversion
  void CheckImplicitConversions(Expr *E, SourceLocation CC = SourceLocation());
 
  /// CheckBoolLikeConversion - Check conversion of given expression to boolean.
  /// Input argument E is a logical expression.
  void CheckBoolLikeConversion(Expr *E, SourceLocation CC);
 
  /// Diagnose when expression is an integer constant expression and its
  /// evaluation results in integer overflow
  void CheckForIntOverflow(const 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);
 
  /// 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);
 
  /// 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() {}
    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);
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name C++ Coroutines
  /// Implementations are in SemaCoroutine.cpp
  ///@{
 
public:
  /// The C++ "std::coroutine_traits" template, which is defined in
  /// <coroutine_traits>
  ClassTemplateDecl *StdCoroutineTraitsCache;
 
  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 BuildOperatorCoawaitLookupExpr(Scope *S, SourceLocation Loc);
  ExprResult BuildOperatorCoawaitCall(SourceLocation Loc, Expr *E,
                                      UnresolvedLookupExpr *Lookup);
  ExprResult BuildResolvedCoawaitExpr(SourceLocation KwLoc, Expr *Operand,
                                      Expr *Awaiter, bool IsImplicit = false);
  ExprResult BuildUnresolvedCoawaitExpr(SourceLocation KwLoc, Expr *Operand,
                                        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);
 
  // As a clang extension, enforces that a non-coroutine function must be marked
  // with [[clang::coro_wrapper]] if it returns a type marked with
  // [[clang::coro_return_type]].
  // Expects that FD is not a coroutine.
  void CheckCoroutineWrapper(FunctionDecl *FD);
  /// Lookup 'coroutine_traits' in std namespace and std::experimental
  /// namespace. The namespace found is recorded in Namespace.
  ClassTemplateDecl *lookupCoroutineTraits(SourceLocation KwLoc,
                                           SourceLocation FuncLoc);
  /// Check that the expression co_await promise.final_suspend() shall not be
  /// potentially-throwing.
  bool checkFinalSuspendNoThrow(const Stmt *FinalSuspend);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name C++ Scope Specifiers
  /// Implementations are in SemaCXXScopeSpec.cpp
  ///@{
 
public:
  // Marks SS invalid if it represents an incomplete type.
  bool RequireCompleteDeclContext(CXXScopeSpec &SS, DeclContext *DC);
  // Complete an enum decl, maybe without a scope spec.
  bool RequireCompleteEnumDecl(EnumDecl *D, SourceLocation L,
                               CXXScopeSpec *SS = nullptr);
 
  /// Compute the DeclContext that is associated with the given type.
  ///
  /// \param T the type for which we are attempting to find a DeclContext.
  ///
  /// \returns the declaration context represented by the type T,
  /// or NULL if the declaration context cannot be computed (e.g., because it is
  /// dependent and not the current instantiation).
  DeclContext *computeDeclContext(QualType T);
 
  /// Compute the DeclContext that is associated with the given
  /// scope specifier.
  ///
  /// \param SS the C++ scope specifier as it appears in the source
  ///
  /// \param EnteringContext when true, we will be entering the context of
  /// this scope specifier, so we can retrieve the declaration context of a
  /// class template or class template partial specialization even if it is
  /// not the current instantiation.
  ///
  /// \returns the declaration context represented by the scope specifier @p SS,
  /// or NULL if the declaration context cannot be computed (e.g., because it is
  /// dependent and not the current instantiation).
  DeclContext *computeDeclContext(const CXXScopeSpec &SS,
                                  bool EnteringContext = false);
  bool isDependentScopeSpecifier(const CXXScopeSpec &SS);
 
  /// If the given nested name specifier refers to the current
  /// instantiation, return the declaration that corresponds to that
  /// current instantiation (C++0x [temp.dep.type]p1).
  ///
  /// \param NNS a dependent nested name specifier.
  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);
 
  /// Determines whether the given declaration is an valid acceptable
  /// result for name lookup of a nested-name-specifier.
  /// \param SD Declaration checked for nested-name-specifier.
  /// \param IsExtension If not null and the declaration is accepted as an
  /// extension, the pointed variable is assigned true.
  bool isAcceptableNestedNameSpecifier(const NamedDecl *SD,
                                       bool *CanCorrect = nullptr);
 
  /// If the given nested-name-specifier begins with a bare identifier
  /// (e.g., Base::), perform name lookup for that identifier as a
  /// nested-name-specifier within the given scope, and return the result of
  /// that name lookup.
  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) {}
  };
 
  /// Build a new nested-name-specifier for "identifier::", as described
  /// by ActOnCXXNestedNameSpecifier.
  ///
  /// \param S Scope in which the nested-name-specifier occurs.
  /// \param IdInfo Parser information about an identifier in the
  ///        nested-name-spec.
  /// \param EnteringContext If true, enter the context specified by the
  ///        nested-name-specifier.
  /// \param SS Optional nested name specifier preceding the identifier.
  /// \param ScopeLookupResult Provides the result of name lookup within the
  ///        scope of the nested-name-specifier that was computed at template
  ///        definition time.
  /// \param ErrorRecoveryLookup Specifies if the method is called to improve
  ///        error recovery and what kind of recovery is performed.
  /// \param IsCorrectedToColon If not null, suggestion of 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.
  ///
  /// This routine differs only slightly from ActOnCXXNestedNameSpecifier, in
  /// that it contains an extra parameter \p ScopeLookupResult, which provides
  /// the result of name lookup within the scope of the nested-name-specifier
  /// that was computed at template definition time.
  ///
  /// If ErrorRecoveryLookup is true, then this call is used to improve error
  /// recovery.  This means that it should not emit diagnostics, it should
  /// just return true on failure.  It also means it should only return a valid
  /// scope if it *knows* that the result is correct.  It should not return in a
  /// dependent context, for example. Nor will it extend \p SS with the scope
  /// specifier.
  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 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 *IsCorrectedToColon = nullptr,
                                   bool OnlyNamespace = false);
 
  /// 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);
 
  bool ActOnCXXNestedNameSpecifierDecltype(CXXScopeSpec &SS, const DeclSpec &DS,
                                           SourceLocation ColonColonLoc);
 
  bool ActOnCXXNestedNameSpecifierIndexedPack(CXXScopeSpec &SS,
                                              const DeclSpec &DS,
                                              SourceLocation ColonColonLoc,
                                              QualType Type);
 
  /// IsInvalidUnlessNestedName - This method is used for error recovery
  /// purposes to determine whether the specified identifier is only valid as
  /// a nested name specifier, for example a namespace name.  It is
  /// conservatively correct to always return false from this method.
  ///
  /// The arguments are the same as those passed to ActOnCXXNestedNameSpecifier.
  bool IsInvalidUnlessNestedName(Scope *S, CXXScopeSpec &SS,
                                 NestedNameSpecInfo &IdInfo,
                                 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);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name Declarations
  /// Implementations are in SemaDecl.cpp
  ///@{
 
public:
  IdentifierResolver IdResolver;
 
  /// The index of the first InventedParameterInfo that refers to the current
  /// context.
  unsigned InventedParameterInfosStart = 0;
 
  /// 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(); }
  };
 
  void DiagnoseInvalidJumps(Stmt *Body);
 
  /// 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;
 
  /// A cache of the flags available in enumerations with the flag_bits
  /// attribute.
  mutable llvm::DenseMap<const EnumDecl *, llvm::APInt> FlagBitsCache;
 
  /// WeakUndeclaredIdentifiers - Identifiers contained in \#pragma weak before
  /// declared. Rare. May alias another identifier, declared or undeclared.
  ///
  /// For aliases, the target identifier is used as a key for eventual
  /// processing when the target is declared. For the single-identifier form,
  /// the sole identifier is used as the key. Each entry is a `SetVector`
  /// (ordered by parse order) of aliases (identified by the alias name) in case
  /// of multiple aliases to the same undeclared identifier.
  llvm::MapVector<
      IdentifierInfo *,
      llvm::SetVector<
          WeakInfo, llvm::SmallVector<WeakInfo, 1u>,
          llvm::SmallDenseSet<WeakInfo, 2u, WeakInfo::DenseMapInfoByAliasOnly>>>
      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;
 
  /// Set containing all typedefs that are likely unused.
  llvm::SmallSetVector<const TypedefNameDecl *, 4>
      UnusedLocalTypedefNameCandidates;
 
  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<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<DeclaratorDecl *, 4> ExternalDeclarations;
 
  /// Generally null except when we temporarily switch decl contexts,
  /// like in \see SemaObjC::ActOnObjCTemporaryExitContainerContext.
  DeclContext *OriginalLexicalContext;
 
  /// Is the module scope we are in a C++ Header Unit?
  bool currentModuleIsHeaderUnit() const {
    return ModuleScopes.empty() ? false
                                : ModuleScopes.back().Module->isHeaderUnit();
  }
 
  /// Get the module owning an entity.
  Module *getOwningModule(const Decl *Entity) {
    return Entity->getOwningModule();
  }
 
  DeclGroupPtrTy ConvertDeclToDeclGroup(Decl *Ptr, Decl *OwnedType = nullptr);
 
  /// If the identifier refers to a type name within this scope,
  /// return the declaration of that type.
  ///
  /// This routine performs ordinary name lookup of the identifier II
  /// within the given scope, with optional C++ scope specifier SS, to
  /// determine whether the name refers to a type. If so, returns an
  /// opaque pointer (actually a QualType) corresponding to that
  /// type. Otherwise, returns NULL.
  ParsedType 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,
                         ImplicitTypenameContext AllowImplicitTypename =
                             ImplicitTypenameContext::No,
                         IdentifierInfo **CorrectedII = nullptr);
 
  /// isTagName() - This method is called *for error recovery purposes only*
  /// to determine if the specified name is a valid tag name ("struct foo").  If
  /// so, this returns the TST for the tag corresponding to it (TST_enum,
  /// TST_union, TST_struct, TST_interface, TST_class).  This is used to
  /// diagnose cases in C where the user forgot to specify the tag.
  TypeSpecifierType isTagName(IdentifierInfo &II, Scope *S);
 
  /// isMicrosoftMissingTypename - In Microsoft mode, within class scope,
  /// if a CXXScopeSpec's type is equal to the type of one of the base classes
  /// then downgrade the missing typename error to a warning.
  /// This is needed for MSVC compatibility; Example:
  /// @code
  /// template<class T> class A {
  /// public:
  ///   typedef int TYPE;
  /// };
  /// template<class T> class B : public A<T> {
  /// public:
  ///   A<T>::TYPE a; // no typename required because A<T> is a base class.
  /// };
  /// @endcode
  bool 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 an overload set, and an expression
    /// representing that overload set has been formed.
    /// ActOnNameClassifiedAsOverloadSet should be called to form a suitable
    /// expression referencing the overload set.
    NC_OverloadSet,
    /// 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 OverloadSet(ExprResult E) {
      NameClassification Result(NC_OverloadSet);
      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_OverloadSet);
      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);
  /// Act on the result of classifying a name as an overload set.
  ExprResult ActOnNameClassifiedAsOverloadSet(Scope *S, Expr *OverloadSet);
 
  /// 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 warnOnReservedIdentifier(const NamedDecl *D);
 
  Decl *ActOnDeclarator(Scope *S, Declarator &D);
 
  NamedDecl *HandleDeclarator(Scope *S, Declarator &D,
                              MultiTemplateParamsArg TemplateParameterLists);
 
  /// Attempt to fold a variable-sized type to a constant-sized type, returning
  /// true if we were successful.
  bool tryToFixVariablyModifiedVarType(TypeSourceInfo *&TInfo, QualType &T,
                                       SourceLocation Loc,
                                       unsigned FailedFoldDiagID);
 
  /// Register the given locally-scoped extern "C" declaration so
  /// that it can be found later for redeclarations. We include any extern "C"
  /// declaration that is not visible in the translation unit here, not just
  /// function-scope declarations.
  void RegisterLocallyScopedExternCDecl(NamedDecl *ND, Scope *S);
 
  /// DiagnoseClassNameShadow - Implement C++ [class.mem]p13:
  ///   If T is the name of a class, then each of the following shall have a
  ///   name different from T:
  ///     - every static data member of class T;
  ///     - every member function of class T
  ///     - every member of class T that is itself a type;
  /// \returns true if the declaration name violates these rules.
  bool DiagnoseClassNameShadow(DeclContext *DC, DeclarationNameInfo Info);
 
  /// Diagnose a declaration whose declarator-id has the given
  /// nested-name-specifier.
  ///
  /// \param SS The nested-name-specifier of the declarator-id.
  ///
  /// \param DC The declaration context to which the nested-name-specifier
  /// resolves.
  ///
  /// \param Name The name of the entity being declared.
  ///
  /// \param Loc The location of the name of the entity being declared.
  ///
  /// \param IsMemberSpecialization Whether we are declaring a member
  /// specialization.
  ///
  /// \param TemplateId The template-id, if any.
  ///
  /// \returns true if we cannot safely recover from this error, false
  /// otherwise.
  bool diagnoseQualifiedDeclaration(CXXScopeSpec &SS, DeclContext *DC,
                                    DeclarationName Name, SourceLocation Loc,
                                    TemplateIdAnnotation *TemplateId,
                                    bool IsMemberSpecialization);
 
  bool checkPointerAuthEnabled(SourceLocation Loc, SourceRange Range);
 
  bool checkConstantPointerAuthKey(Expr *keyExpr, unsigned &key);
 
  /// Diagnose function specifiers on a declaration of an identifier that
  /// does not identify a function.
  void DiagnoseFunctionSpecifiers(const DeclSpec &DS);
 
  /// Return the declaration shadowed by the given typedef \p D, or null
  /// if it doesn't shadow any declaration or shadowing warnings are disabled.
  NamedDecl *getShadowedDeclaration(const TypedefNameDecl *D,
                                    const LookupResult &R);
 
  /// Return the declaration shadowed by the given variable \p D, or null
  /// if it doesn't shadow any declaration or shadowing warnings are disabled.
  NamedDecl *getShadowedDeclaration(const VarDecl *D, const LookupResult &R);
 
  /// Return the declaration shadowed by the given variable \p D, or null
  /// if it doesn't shadow any declaration or shadowing warnings are disabled.
  NamedDecl *getShadowedDeclaration(const BindingDecl *D,
                                    const LookupResult &R);
  /// Diagnose variable or built-in function shadowing.  Implements
  /// -Wshadow.
  ///
  /// This method is called whenever a VarDecl is added to a "useful"
  /// scope.
  ///
  /// \param ShadowedDecl the declaration that is shadowed by the given variable
  /// \param R the lookup of the name
  void CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
                   const LookupResult &R);
 
  /// Check -Wshadow without the advantage of a previous lookup.
  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);
 
  /// Diagnose shadowing for variables shadowed in the lambda record \p LambdaRD
  /// when these variables are captured by the lambda.
  void DiagnoseShadowingLambdaDecls(const sema::LambdaScopeInfo *LSI);
 
  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);
 
  /// ActOnTypedefNameDecl - Perform semantic checking for a declaration which
  /// declares a typedef-name, either using the 'typedef' type specifier or via
  /// a C++0x [dcl.typedef]p2 alias-declaration: 'using T = A;'.
  NamedDecl *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 = {});
 
  /// Perform semantic checking on a newly-created variable
  /// declaration.
  ///
  /// This routine performs all of the type-checking required for a
  /// variable declaration once it has been built. It is used both to
  /// check variables after they have been parsed and their declarators
  /// have been translated into a declaration, and to check variables
  /// that have been instantiated from a template.
  ///
  /// Sets NewVD->isInvalidDecl() if an error was encountered.
  ///
  /// Returns true if the variable declaration is a redeclaration.
  bool CheckVariableDeclaration(VarDecl *NewVD, LookupResult &Previous);
  void CheckVariableDeclarationType(VarDecl *NewVD);
  void CheckCompleteVariableDeclaration(VarDecl *VD);
 
  NamedDecl *ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
                                     TypeSourceInfo *TInfo,
                                     LookupResult &Previous,
                                     MultiTemplateParamsArg TemplateParamLists,
                                     bool &AddToScope);
 
  /// AddOverriddenMethods - See if a method overrides any in the base classes,
  /// and if so, check that it's a valid override and remember it.
  bool AddOverriddenMethods(CXXRecordDecl *DC, CXXMethodDecl *MD);
 
  /// Perform semantic checking of a new function declaration.
  ///
  /// Performs semantic analysis of the new function declaration
  /// NewFD. This routine performs all semantic checking that does not
  /// require the actual declarator involved in the declaration, and is
  /// used both for the declaration of functions as they are parsed
  /// (called via ActOnDeclarator) and for the declaration of functions
  /// that have been instantiated via C++ template instantiation (called
  /// via InstantiateDecl).
  ///
  /// \param IsMemberSpecialization whether this new function declaration is
  /// a member specialization (that replaces any definition provided by the
  /// previous declaration).
  ///
  /// This sets NewFD->isInvalidDecl() to true if there was an error.
  ///
  /// \returns true if the function declaration is a redeclaration.
  bool CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
                                LookupResult &Previous,
                                bool IsMemberSpecialization, bool DeclIsDefn);
 
  /// Checks if the new declaration declared in dependent context must be
  /// put in the same redeclaration chain as the specified declaration.
  ///
  /// \param D Declaration that is checked.
  /// \param PrevDecl Previous declaration found with proper lookup method for
  ///                 the same declaration name.
  /// \returns True if D must be added to the redeclaration chain which PrevDecl
  ///          belongs to.
  bool shouldLinkDependentDeclWithPrevious(Decl *D, Decl *OldDecl);
 
  /// Determines if we can perform a correct type check for \p D as a
  /// redeclaration of \p PrevDecl. If not, we can generally still perform a
  /// best-effort check.
  ///
  /// \param NewD The new declaration.
  /// \param OldD The old declaration.
  /// \param NewT The portion of the type of the new declaration to check.
  /// \param OldT The portion of the type of the old declaration to check.
  bool canFullyTypeCheckRedeclaration(ValueDecl *NewD, ValueDecl *OldD,
                                      QualType NewT, QualType OldT);
  void CheckMain(FunctionDecl *FD, const DeclSpec &D);
  void CheckMSVCRTEntryPoint(FunctionDecl *FD);
 
  /// Returns an implicit CodeSegAttr if a __declspec(code_seg) is found on a
  /// containing class. Otherwise it will return implicit SectionAttr if the
  /// function is a definition and there is an active value on CodeSegStack
  /// (from the current #pragma code-seg value).
  ///
  /// \param FD Function being declared.
  /// \param IsDefinition Whether it is a definition or just a declaration.
  /// \returns A CodeSegAttr or SectionAttr to apply to the function or
  ///          nullptr if no attribute should be added.
  Attr *getImplicitCodeSegOrSectionAttrForFunction(const FunctionDecl *FD,
                                                   bool IsDefinition);
 
  /// Common checks for a parameter-declaration that should apply to both
  /// function parameters and non-type template parameters.
  void CheckFunctionOrTemplateParamDeclarator(Scope *S, Declarator &D);
 
  /// ActOnParamDeclarator - Called from Parser::ParseFunctionDeclarator()
  /// to introduce parameters into function prototype scope.
  Decl *ActOnParamDeclarator(Scope *S, Declarator &D,
                             SourceLocation ExplicitThisLoc = {});
 
  /// Synthesizes a variable for a parameter arising from a
  /// typedef.
  ParmVarDecl *BuildParmVarDeclForTypedef(DeclContext *DC, SourceLocation Loc,
                                          QualType T);
  ParmVarDecl *CheckParameter(DeclContext *DC, SourceLocation StartLoc,
                              SourceLocation NameLoc,
                              const IdentifierInfo *Name, QualType T,
                              TypeSourceInfo *TSInfo, StorageClass SC);
 
  // 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);
 
  /// AddInitializerToDecl - Adds the initializer Init to the
  /// declaration dcl. If DirectInit is true, this is C++ direct
  /// initialization rather than copy initialization.
  void AddInitializerToDecl(Decl *dcl, Expr *init, bool DirectInit);
  void ActOnUninitializedDecl(Decl *dcl);
 
  /// ActOnInitializerError - Given that there was an error parsing an
  /// initializer for the given declaration, try to at least re-establish
  /// invariants such as whether a variable's type is either dependent or
  /// complete.
  void ActOnInitializerError(Decl *Dcl);
 
  void ActOnCXXForRangeDecl(Decl *D);
  StmtResult ActOnCXXForRangeIdentifier(Scope *S, SourceLocation IdentLoc,
                                        IdentifierInfo *Ident,
                                        ParsedAttributes &Attrs);
 
  /// Check if VD needs to be dllexport/dllimport due to being in a
  /// dllexport/import function.
  void CheckStaticLocalForDllExport(VarDecl *VD);
  void CheckThreadLocalForLargeAlignment(VarDecl *VD);
 
  /// FinalizeDeclaration - called by ParseDeclarationAfterDeclarator to perform
  /// any semantic actions necessary after any initializer has been attached.
  void FinalizeDeclaration(Decl *D);
  DeclGroupPtrTy FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
                                         ArrayRef<Decl *> Group);
 
  /// BuildDeclaratorGroup - convert a list of declarations into a declaration
  /// group, performing any necessary semantic checking.
  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);
 
  enum class FnBodyKind {
    /// C++26 [dcl.fct.def.general]p1
    /// function-body:
    ///   ctor-initializer[opt] compound-statement
    ///   function-try-block
    Other,
    ///   = default ;
    Default,
    ///   deleted-function-body
    ///
    /// deleted-function-body:
    ///   = delete ;
    ///   = delete ( unevaluated-string ) ;
    Delete
  };
 
  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,
                                FnBodyKind BodyKind = FnBodyKind::Other);
  Decl *ActOnStartOfFunctionDef(Scope *S, Decl *D,
                                SkipBodyInfo *SkipBody = nullptr,
                                FnBodyKind BodyKind = FnBodyKind::Other);
  void applyFunctionAttributesBeforeParsingBody(Decl *FD);
 
  /// 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);
 
  /// Given the set of return statements within a function body,
  /// compute the variables that are subject to the named return value
  /// optimization.
  ///
  /// Each of the variables that is subject to the named return value
  /// optimization will be marked as NRVO variables in the AST, and any
  /// return statement that has a marked NRVO variable as its NRVO candidate can
  /// use the named return value optimization.
  ///
  /// This function applies a very simplistic algorithm for NRVO: if every
  /// return statement in the scope of a variable has the same NRVO candidate,
  /// that candidate is an NRVO variable.
  void 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);
 
  Decl *ActOnFileScopeAsmDecl(Expr *expr, SourceLocation AsmLoc,
                              SourceLocation RParenLoc);
 
  TopLevelStmtDecl *ActOnStartTopLevelStmtDecl(Scope *S);
  void ActOnFinishTopLevelStmtDecl(TopLevelStmtDecl *D, Stmt *Statement);
 
  void ActOnPopScope(SourceLocation Loc, Scope *S);
 
  /// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
  /// no declarator (e.g. "struct foo;") is parsed.
  Decl *ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, DeclSpec &DS,
                                   const ParsedAttributesView &DeclAttrs,
                                   RecordDecl *&AnonRecord);
 
  /// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
  /// no declarator (e.g. "struct foo;") is parsed. It also accepts template
  /// parameters to cope with template friend declarations.
  Decl *ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS, DeclSpec &DS,
                                   const ParsedAttributesView &DeclAttrs,
                                   MultiTemplateParamsArg TemplateParams,
                                   bool IsExplicitInstantiation,
                                   RecordDecl *&AnonRecord,
                                   SourceLocation EllipsisLoc = {});
 
  /// BuildAnonymousStructOrUnion - Handle the declaration of an
  /// anonymous structure or union. Anonymous unions are a C++ feature
  /// (C++ [class.union]) and a C11 feature; anonymous structures
  /// are a C11 feature and GNU C++ extension.
  Decl *BuildAnonymousStructOrUnion(Scope *S, DeclSpec &DS, AccessSpecifier AS,
                                    RecordDecl *Record,
                                    const PrintingPolicy &Policy);
 
  /// Called once it is known whether
  /// a tag declaration is an anonymous union or struct.
  void ActOnDefinedDeclarationSpecifier(Decl *D);
 
  /// Emit diagnostic warnings for placeholder members.
  /// We can only do that after the class is fully constructed,
  /// as anonymous union/structs can insert placeholders
  /// in their parent scope (which might be a Record).
  void DiagPlaceholderFieldDeclDefinitions(RecordDecl *Record);
 
  /// BuildMicrosoftCAnonymousStruct - Handle the declaration of an
  /// Microsoft C anonymous structure.
  /// Ref: http://msdn.microsoft.com/en-us/library/z2cx9y4f.aspx
  /// Example:
  ///
  /// struct A { int a; };
  /// struct B { struct A; int b; };
  ///
  /// void foo() {
  ///   B var;
  ///   var.a = 3;
  /// }
  Decl *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);
 
  /// Determine whether a tag with a given kind is acceptable
  /// as a redeclaration of the given tag declaration.
  ///
  /// \returns true if the new tag kind is acceptable, false otherwise.
  bool isAcceptableTagRedeclaration(const TagDecl *Previous, TagTypeKind NewTag,
                                    bool isDefinition, SourceLocation NewTagLoc,
                                    const IdentifierInfo *Name);
 
  enum OffsetOfKind {
    // Not parsing a type within __builtin_offsetof.
    OOK_Outside,
    // Parsing a type within __builtin_offsetof.
    OOK_Builtin,
    // Parsing a type within macro "offsetof", defined in __buitin_offsetof
    // To improve our diagnostic message.
    OOK_Macro,
  };
 
  /// This is invoked when we see 'struct foo' or 'struct {'.  In the
  /// former case, Name will be non-null.  In the later case, Name will be null.
  /// TagSpec indicates what kind of tag this is. TUK indicates whether this is
  /// a reference/declaration/definition of a tag.
  ///
  /// \param IsTypeSpecifier \c true if this is a type-specifier (or
  /// trailing-type-specifier) other than one in an alias-declaration.
  ///
  /// \param SkipBody If non-null, will be set to indicate if the caller should
  /// skip the definition of this tag and treat it as if it were a declaration.
  DeclResult 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,
                      OffsetOfKind OOK, SkipBodyInfo *SkipBody = nullptr);
 
  /// ActOnField - Each field of a C struct/union is passed into this in order
  /// to create a FieldDecl object for it.
  Decl *ActOnField(Scope *S, Decl *TagD, SourceLocation DeclStart,
                   Declarator &D, Expr *BitfieldWidth);
 
  /// HandleField - Analyze a field of a C struct or a C++ data member.
  FieldDecl *HandleField(Scope *S, RecordDecl *TagD, SourceLocation DeclStart,
                         Declarator &D, Expr *BitfieldWidth,
                         InClassInitStyle InitStyle, AccessSpecifier AS);
 
  /// Build a new FieldDecl and check its well-formedness.
  ///
  /// This routine builds a new FieldDecl given the fields name, type,
  /// record, etc. \p PrevDecl should refer to any previous declaration
  /// with the same name and in the same scope as the field to be
  /// created.
  ///
  /// \returns a new FieldDecl.
  ///
  /// \todo The Declarator argument is a hack. It will be removed once
  FieldDecl *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);
 
  /// ActOnLastBitfield - This routine handles synthesized bitfields rules for
  /// class and class extensions. For every class \@interface and class
  /// extension \@interface, if the last ivar is a bitfield of any type,
  /// then add an implicit `char :0` ivar to the end of that interface.
  void ActOnLastBitfield(SourceLocation DeclStart,
                         SmallVectorImpl<Decl *> &AllIvarDecls);
 
  // 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(Decl *Prev, SkipBodyInfo &SkipBody);
 
  typedef void *SkippedDefinitionContext;
 
  /// Invoked when we enter a tag definition that we're skipping.
  SkippedDefinitionContext ActOnTagStartSkippedDefinition(Scope *S, Decl *TD);
 
  /// 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,
                                       bool IsAbstract,
                                       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);
 
  /// 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);
 
  /// Check that this is a valid underlying type for an enum declaration.
  bool CheckEnumUnderlyingType(TypeSourceInfo *TI);
 
  /// Check whether this is a valid redeclaration of a previous enumeration.
  /// \return true if the redeclaration was invalid.
  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);
 
  /// 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);
 
  /// Enter a template parameter scope, after it's been associated with a
  /// particular DeclContext. Causes lookup within the scope to chain through
  /// enclosing contexts in the correct order.
  void EnterTemplatedContext(Scope *S, DeclContext *DC);
 
  /// Push the parameters of D, which must be a function, into scope.
  void ActOnReenterFunctionContext(Scope *S, Decl *D);
  void ActOnExitFunctionContext();
 
  /// 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) const;
 
  /// 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(const 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,
    /// Merge availability attributes for an implementation of
    /// an optional protocol requirement.
    AMK_OptionalProtocolImplementation
  };
 
  /// mergeDeclAttributes - Copy attributes from the Old decl to the New one.
  void mergeDeclAttributes(NamedDecl *New, Decl *Old,
                           AvailabilityMergeKind AMK = AMK_Redeclaration);
 
  /// MergeTypedefNameDecl - We just parsed a typedef 'New' which has the
  /// same name and scope as a previous declaration 'Old'.  Figure out
  /// how to resolve this situation, merging decls or emitting
  /// diagnostics as appropriate. If there was an error, set New to be invalid.
  void MergeTypedefNameDecl(Scope *S, TypedefNameDecl *New,
                            LookupResult &OldDecls);
 
  /// MergeFunctionDecl - We just parsed a function 'New' from
  /// declarator D which has the same name and scope as a previous
  /// declaration 'Old'.  Figure out how to resolve this situation,
  /// merging decls or emitting diagnostics as appropriate.
  ///
  /// In C++, New and Old must be declarations that are not
  /// overloaded. Use IsOverload to determine whether New and Old are
  /// overloaded, and to select the Old declaration that New should be
  /// merged with.
  ///
  /// Returns true if there was an error, false otherwise.
  bool MergeFunctionDecl(FunctionDecl *New, NamedDecl *&Old, Scope *S,
                         bool MergeTypeWithOld, bool NewDeclIsDefn);
 
  /// Completes the merge of two function declarations that are
  /// known to be compatible.
  ///
  /// This routine handles the merging of attributes and other
  /// properties of function declarations from the old declaration to
  /// the new declaration, once we know that New is in fact a
  /// redeclaration of Old.
  ///
  /// \returns false
  bool MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
                                    Scope *S, bool MergeTypeWithOld);
  void mergeObjCMethodDecls(ObjCMethodDecl *New, ObjCMethodDecl *Old);
 
  /// MergeVarDecl - We just parsed a variable 'New' which has the same name
  /// and scope as a previous declaration 'Old'.  Figure out how to resolve this
  /// situation, merging decls or emitting diagnostics as appropriate.
  ///
  /// Tentative definition rules (C99 6.9.2p2) are checked by
  /// FinalizeDeclaratorGroup. Unfortunately, we can't analyze tentative
  /// definitions here, since the initializer hasn't been attached.
  void MergeVarDecl(VarDecl *New, LookupResult &Previous);
 
  /// MergeVarDeclTypes - We parsed a variable 'New' which has the same name and
  /// scope as a previous declaration 'Old'.  Figure out how to merge their
  /// types, emitting diagnostics as appropriate.
  ///
  /// Declarations using the auto type specifier (C++ [decl.spec.auto]) call
  /// back to here in AddInitializerToDecl. We can't check them before the
  /// initializer is attached.
  void MergeVarDeclTypes(VarDecl *New, VarDecl *Old, bool MergeTypeWithOld);
 
  /// We've just determined that \p Old and \p New both appear to be definitions
  /// of the same variable. Either diagnose or fix the problem.
  bool checkVarDeclRedefinition(VarDecl *OldDefn, VarDecl *NewDefn);
  void notePreviousDefinition(const NamedDecl *Old, SourceLocation New);
 
  /// Filters out lookup results that don't fall within the given scope
  /// as determined by isDeclInScope.
  void FilterLookupForScope(LookupResult &R, DeclContext *Ctx, Scope *S,
                            bool ConsiderLinkage, bool AllowInlineNamespace);
 
  /// We've determined that \p New is a redeclaration of \p Old. Check that they
  /// have compatible owning modules.
  bool CheckRedeclarationModuleOwnership(NamedDecl *New, NamedDecl *Old);
 
  /// [module.interface]p6:
  /// A redeclaration of an entity X is implicitly exported if X was introduced
  /// by an exported declaration; otherwise it shall not be exported.
  bool CheckRedeclarationExported(NamedDecl *New, NamedDecl *Old);
 
  /// A wrapper function for checking the semantic restrictions of
  /// a redeclaration within a module.
  bool CheckRedeclarationInModule(NamedDecl *New, NamedDecl *Old);
 
  /// Check the redefinition in C++20 Modules.
  ///
  /// [basic.def.odr]p14:
  /// For any definable item D with definitions in multiple translation units,
  /// - if D is a non-inline non-templated function or variable, or
  /// - if the definitions in different translation units do not satisfy the
  /// following requirements,
  ///   the program is ill-formed; a diagnostic is required only if the
  ///   definable item is attached to a named module and a prior definition is
  ///   reachable at the point where a later definition occurs.
  /// - Each such definition shall not be attached to a named module
  /// ([module.unit]).
  /// - Each such definition shall consist of the same sequence of tokens, ...
  /// ...
  ///
  /// Return true if the redefinition is not allowed. Return false otherwise.
  bool IsRedefinitionInModule(const NamedDecl *New, const NamedDecl *Old) const;
 
  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);
 
  typedef llvm::function_ref<void(SourceLocation Loc, PartialDiagnostic PD)>
      DiagReceiverTy;
 
  void DiagnoseUnusedNestedTypedefs(const RecordDecl *D);
  void DiagnoseUnusedNestedTypedefs(const RecordDecl *D,
                                    DiagReceiverTy DiagReceiver);
  void DiagnoseUnusedDecl(const NamedDecl *ND);
 
  /// DiagnoseUnusedDecl - Emit warnings about declarations that are not used
  /// unless they are marked attr(unused).
  void DiagnoseUnusedDecl(const NamedDecl *ND, DiagReceiverTy DiagReceiver);
 
  /// If VD is set but not otherwise used, diagnose, for a parameter or a
  /// variable.
  void DiagnoseUnusedButSetDecl(const VarDecl *VD, DiagReceiverTy DiagReceiver);
 
  /// getNonFieldDeclScope - Retrieves the innermost scope, starting
  /// from S, where a non-field would be declared. This routine copes
  /// with the difference between C and C++ scoping rules in structs and
  /// unions. For example, the following code is well-formed in C but
  /// ill-formed in C++:
  /// @code
  /// struct S6 {
  ///   enum { BAR } e;
  /// };
  ///
  /// void test_S6() {
  ///   struct S6 a;
  ///   a.e = BAR;
  /// }
  /// @endcode
  /// For the declaration of BAR, this routine will return a different
  /// scope. The scope S will be the scope of the unnamed enumeration
  /// within S6. In C++, this routine will return the scope associated
  /// with S6, because the enumeration's scope is a transparent
  /// context but structures can contain non-field names. In C, this
  /// routine will return the translation unit scope, since the
  /// enumeration's scope is a transparent context and structures cannot
  /// contain non-field names.
  Scope *getNonFieldDeclScope(Scope *S);
 
  FunctionDecl *CreateBuiltin(IdentifierInfo *II, QualType Type, unsigned ID,
                              SourceLocation Loc);
 
  /// LazilyCreateBuiltin - The specified Builtin-ID was first used at
  /// file scope.  lazily create a decl for it. ForRedeclaration is true
  /// if we're creating this built-in in anticipation of redeclaring the
  /// built-in.
  NamedDecl *LazilyCreateBuiltin(IdentifierInfo *II, unsigned ID, Scope *S,
                                 bool ForRedeclaration, SourceLocation Loc);
 
  /// 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;
 
  /// GetNameForDeclarator - Determine the full declaration name for the
  /// given Declarator.
  DeclarationNameInfo GetNameForDeclarator(Declarator &D);
 
  /// Retrieves the declaration name from a parsed unqualified-id.
  DeclarationNameInfo GetNameFromUnqualifiedId(const UnqualifiedId &Name);
 
  /// 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);
 
  void deduceOpenCLAddressSpace(ValueDecl *decl);
 
  /// Adjust the \c DeclContext for a function or variable that might be a
  /// function-local external declaration.
  static bool adjustContextForLocalExternDecl(DeclContext *&DC);
 
  void MarkTypoCorrectedFunctionDefinition(const NamedDecl *F);
 
  /// 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);
 
  /// type checking declaration initializers (C99 6.7.8)
  bool CheckForConstantInitializer(
      Expr *Init, unsigned DiagID = diag::err_init_element_not_constant);
 
  QualType deduceVarTypeFromInitializer(VarDecl *VDecl, DeclarationName Name,
                                        QualType Type, TypeSourceInfo *TSI,
                                        SourceRange Range, bool DirectInit,
                                        Expr *Init);
 
  bool DeduceVariableDeclarationType(VarDecl *VDecl, bool DirectInit,
                                     Expr *Init);
 
  sema::LambdaScopeInfo *RebuildLambdaScopeInfo(CXXMethodDecl *CallOperator);
 
  // Heuristically tells if the function is `get_return_object` member of a
  // coroutine promise_type by matching the function name.
  static bool CanBeGetReturnObject(const FunctionDecl *FD);
  static bool CanBeGetReturnTypeOnAllocFailure(const FunctionDecl *FD);
 
  /// ImplicitlyDefineFunction - An undeclared identifier was used in a function
  /// call, forming a call to an implicitly defined function (per C99 6.5.1p2).
  NamedDecl *ImplicitlyDefineFunction(SourceLocation Loc, IdentifierInfo &II,
                                      Scope *S);
 
  /// If this function is a C++ replaceable global allocation function
  /// (C++2a [basic.stc.dynamic.allocation], C++2a [new.delete]),
  /// adds any function attributes that we know a priori based on the standard.
  ///
  /// We need to check for duplicate attributes both here and where user-written
  /// attributes are applied to declarations.
  void AddKnownFunctionAttributesForReplaceableGlobalAllocationFunction(
      FunctionDecl *FD);
 
  /// Adds any function attributes that we know a priori based on
  /// the declaration of this function.
  ///
  /// These attributes can apply both to implicitly-declared builtins
  /// (like __builtin___printf_chk) or to library-declared functions
  /// like NSLog or printf.
  ///
  /// We need to check for duplicate attributes both here and where user-written
  /// attributes are applied to declarations.
  void AddKnownFunctionAttributes(FunctionDecl *FD);
 
  /// 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.
  ExprResult VerifyBitField(SourceLocation FieldLoc,
                            const IdentifierInfo *FieldName, QualType FieldTy,
                            bool IsMsStruct, Expr *BitWidth);
 
  /// 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;
 
  /// 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);
 
  /// 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(const FunctionDecl *Decl,
                                           bool Final = false);
 
  // Whether the callee should be ignored in CUDA/HIP/OpenMP host/device check.
  bool shouldIgnoreInHostDeviceCheck(FunctionDecl *Callee);
 
private:
  /// Function or variable declarations to be checked for whether the deferred
  /// diagnostics should be emitted.
  llvm::SmallSetVector<Decl *, 4> DeclsToCheckForDeferredDiags;
 
  /// 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;
 
  // We need this to handle
  //
  // typedef struct {
  //   void *foo() { return 0; }
  // } A;
  //
  // When we see foo we don't know if after the typedef we will get 'A' or '*A'
  // for example. If 'A', foo will have external linkage. If we have '*A',
  // foo will have no linkage. Since we can't know until we get to the end
  // of the typedef, this function finds out if D might have non-external
  // linkage. Callers should verify at the end of the TU if it D has external
  // linkage or not.
  static bool mightHaveNonExternalLinkage(const DeclaratorDecl *FD);
 
  ///@}
 
  //
  //
  // -------------------------------------------------------------------------
  //
  //
 
  /// \name Declaration Attribute Handling
  /// Implementations are in SemaDeclAttr.cpp
  ///@{
 
public:
  /// 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
  };
 
  /// Describes the reason a calling convention specification was ignored, used
  /// for diagnostics.
  enum class CallingConventionIgnoredReason {
    ForThisTarget = 0,
    VariadicFunction,
    ConstructorDestructor,
    BuiltinFunction
  };
 
  /// A helper function to provide Attribute Location for the Attr types
  /// AND the ParsedAttr.
  template <typename AttrInfo>
  static std::enable_if_t<std::is_base_of_v<Attr, AttrInfo>, SourceLocation>
  getAttrLoc(const AttrInfo &AL) {
    return AL.getLocation();
  }
  SourceLocation getAttrLoc(const ParsedAttr &AL);
 
  /// If Expr is a valid integer constant, get the value of the integer
  /// expression and return success or failure. May output an error.
  ///
  /// Negative argument is implicitly converted to unsigned, unless
  /// \p StrictlyUnsigned is true.
  template <typename AttrInfo>
  bool checkUInt32Argument(const AttrInfo &AI, const Expr *Expr, uint32_t &Val,
                           unsigned Idx = UINT_MAX,
                           bool StrictlyUnsigned = false) {
    std::optional<llvm::APSInt> I = llvm::APSInt(32);
    if (Expr->isTypeDependent() ||
        !(I = Expr->getIntegerConstantExpr(Context))) {
      if (Idx != UINT_MAX)
        Diag(getAttrLoc(AI), diag::err_attribute_argument_n_type)
            << &AI << Idx << AANT_ArgumentIntegerConstant
            << Expr->getSourceRange();
      else
        Diag(getAttrLoc(AI), diag::err_attribute_argument_type)
            << &AI << AANT_ArgumentIntegerConstant << Expr->getSourceRange();
      return false;
    }
 
    if (!I->isIntN(32)) {
      Diag(Expr->getExprLoc(), diag::err_ice_too_large)
          << toString(*I, 10, false) << 32 << /* Unsigned */ 1;
      return false;
    }
 
    if (StrictlyUnsigned && I->isSigned() && I->isNegative()) {
      Diag(getAttrLoc(AI), diag::err_attribute_requires_positive_integer)
          << &AI << /*non-negative*/ 1;
      return false;
    }
 
    Val = (uint32_t)I->getZExtValue();
    return true;
  }
 
  /// 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;
 
  /// WeakTopLevelDeclDecls - access to \#pragma weak-generated Decls
  SmallVectorImpl<Decl *> &WeakTopLevelDecls() { return WeakTopLevelDecl; }
 
  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;
 
  /// Check if the argument \p E is a ASCII string literal. If not emit an error
  /// and return false, otherwise set \p Str to the value of the string literal
  /// and return true.
  bool checkStringLiteralArgumentAttr(const AttributeCommonInfo &CI,
                                      const Expr *E, StringRef &Str,
                                      SourceLocation *ArgLocation = nullptr);
 
  /// Check if the argument \p ArgNum of \p Attr is a ASCII string literal.
  /// If not emit an error and return false. If the argument is an identifier it
  /// will emit an error with a fixit hint and treat it as if it was a string
  /// literal.
  bool checkStringLiteralArgumentAttr(const ParsedAttr &Attr, unsigned ArgNum,
                                      StringRef &Str,
                                      SourceLocation *ArgLocation = nullptr);
 
  /// Determine if type T is a valid subject for a nonnull and similar
  /// attributes. Dependent types are considered valid so they can be checked
  /// during instantiation time. 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);
 
  /// 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);
 
  bool CheckAttrTarget(const ParsedAttr &CurrAttr);
  bool CheckAttrNoArgs(const ParsedAttr &CurrAttr);
 
  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, IdentifierInfo *IIEnvironment);
 
  TypeVisibilityAttr *
  mergeTypeVisibilityAttr(Decl *D, const AttributeCommonInfo &CI,
                          TypeVisibilityAttr::VisibilityType Vis);
  VisibilityAttr *mergeVisibilityAttr(Decl *D, const AttributeCommonInfo &CI,
                                      VisibilityAttr::VisibilityType Vis);
  SectionAttr *mergeSectionAttr(Decl *D, const AttributeCommonInfo &CI,
                                StringRef Name);
 
  /// Used to implement to perform semantic checking on
  /// attribute((section("foo"))) specifiers.
  ///
  /// In this case, "foo" is passed in to be checked.  If the section
  /// specifier is invalid, return an Error that indicates the problem.
  ///
  /// This is a simple quality of implementation feature to catch errors
  /// and give good diagnostics in cases when the assembler or code generator
  /// would otherwise reject the section specifier.
  llvm::Error isValidSectionSpecifier(StringRef Str);
  bool checkSectionName(SourceLocation LiteralLoc, StringRef Str);
  CodeSegAttr *mergeCodeSegAttr(Decl *D, const AttributeCommonInfo &CI,
                                StringRef Name);
 
  // Check for things we'd like to warn about. Multiversioning issues are
  // handled later in the process, once we know how many exist.
  bool checkTargetAttr(SourceLocation LiteralLoc, StringRef Str);
 
  /// Check Target Version attrs
  bool checkTargetVersionAttr(SourceLocation Loc, Decl *D, StringRef Str);
  bool checkTargetClonesAttrString(
      SourceLocation LiteralLoc, StringRef Str, const StringLiteral *Literal,
      Decl *D, bool &HasDefault, bool &HasCommas, bool &HasNotDefault,
      SmallVectorImpl<SmallString<64>> &StringsBuffer);
 
  ErrorAttr *mergeErrorAttr(Decl *D, const AttributeCommonInfo &CI,
                            StringRef NewUserDiagnostic);
  FormatAttr *mergeFormatAttr(Decl *D, const AttributeCommonInfo &CI,
                              IdentifierInfo *Format, int FormatIdx,
                              int FirstArg);
 
  /// 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);
 
  /// AddAlignValueAttr - Adds an align_value attribute to a particular
  /// declaration.
  void AddAlignValueAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E);
 
  /// CreateAnnotationAttr - Creates an annotation Annot with Args arguments.
  Attr *CreateAnnotationAttr(const AttributeCommonInfo &CI, StringRef Annot,
                             MutableArrayRef<Expr *> Args);
  Attr *CreateAnnotationAttr(const ParsedAttr &AL);
 
  bool checkMSInheritanceAttrOnDefinition(CXXRecordDecl *RD, SourceRange Range,
                                          bool BestCase,
                                          MSInheritanceModel SemanticSpelling);
 
  void CheckAlignasUnderalignment(Decl *D);
 
  /// AddModeAttr - Adds a mode attribute to a particular declaration.
  void AddModeAttr(Decl *D, const AttributeCommonInfo &CI, IdentifierInfo *Name,
                   bool InInstantiation = false);
  AlwaysInlineAttr *mergeAlwaysInlineAttr(Decl *D,
                                          const AttributeCommonInfo &CI,
                                          const IdentifierInfo *Ident);
  MinSizeAttr *mergeMinSizeAttr(Decl *D, const AttributeCommonInfo &CI);
  OptimizeNoneAttr *mergeOptimizeNoneAttr(Decl *D,
                                          const AttributeCommonInfo &CI);
  InternalLinkageAttr *mergeInternalLinkageAttr(Decl *D, const ParsedAttr &AL);
  InternalLinkageAttr *mergeInternalLinkageAttr(Decl *D,
                                                const InternalLinkageAttr &AL);
 
  /// Check validaty of calling convention attribute \p attr. If \p FD
  /// is not null pointer, use \p FD to determine the CUDA/HIP host/device
  /// target. Otherwise, it is specified by \p CFT.
  bool CheckCallingConvAttr(
      const ParsedAttr &attr, CallingConv &CC, const FunctionDecl *FD = nullptr,
      CUDAFunctionTarget CFT = CUDAFunctionTarget::InvalidTarget);
 
  /// Checks a regparm attribute, returning true if it is ill-formed and
  /// otherwise setting numParams to the appropriate value.
  bool CheckRegparmAttr(const ParsedAttr &attr, unsigned &value);
 
  /// Create an CUDALaunchBoundsAttr attribute.
  CUDALaunchBoundsAttr *CreateLaunchBoundsAttr(const AttributeCommonInfo &CI,
                                               Expr *MaxThreads,
                                               Expr *MinBlocks,
                                               Expr *MaxBlocks);
 
  /// AddLaunchBoundsAttr - Adds a launch_bounds attribute to a particular
  /// declaration.
  void AddLaunchBoundsAttr(Decl *D, const AttributeCommonInfo &CI,
                           Expr *MaxThreads, Expr *MinBlocks, Expr *MaxBlocks);
 
  enum class RetainOwnershipKind { NS, CF, OS };
 
  UuidAttr *mergeUuidAttr(Decl *D, const AttributeCommonInfo &CI,
                          StringRef UuidAsWritten, MSGuidDecl *GuidDecl);
 
  BTFDeclTagAttr *mergeBTFDeclTagAttr(Decl *D, const BTFDeclTagAttr &AL);
 
  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);
 
  EnforceTCBAttr *mergeEnforceTCBAttr(Decl *D, const EnforceTCBAttr &AL);
  EnforceTCBLeafAttr *mergeEnforceTCBLeafAttr(Decl *D,
                                              const EnforceTCBLeafAttr &AL);
 
  /// Helper for delayed processing TransparentUnion or
  /// BPFPreserveAccessIndexAttr attribute.
  void ProcessDeclAttributeDelayed(Decl *D,
                                   const ParsedAttributesView &AttrList);
 
  // Options for ProcessDeclAttributeList().
  struct ProcessDeclAttributeOptions {
    ProcessDeclAttributeOptions()
        : IncludeCXX11Attributes(true), IgnoreTypeAttributes(false) {}
 
    ProcessDeclAttributeOptions WithIncludeCXX11Attributes(bool Val) {
      ProcessDeclAttributeOptions Result = *this;
      Result.IncludeCXX11Attributes = Val;
      return Result;
    }
 
    ProcessDeclAttributeOptions WithIgnoreTypeAttributes(bool Val) {
      ProcessDeclAttributeOptions Result = *this;
      Result.IgnoreTypeAttributes = Val;
      return Result;
    }
 
    // Should C++11 attributes be processed?
    bool IncludeCXX11Attributes;