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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/AST/ASTConcept.h"
#include "clang/AST/ASTFwd.h"
#include "clang/AST/Attr.h"
#include "clang/AST/Availability.h"
#include "clang/AST/ComparisonCategories.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/DeclarationName.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprConcepts.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ExprOpenMP.h"
#include "clang/AST/ExternalASTSource.h"
#include "clang/AST/LocInfoType.h"
#include "clang/AST/MangleNumberingContext.h"
#include "clang/AST/NSAPI.h"
#include "clang/AST/PrettyPrinter.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/StmtOpenMP.h"
#include "clang/AST/TypeLoc.h"
#include "clang/AST/TypeOrdering.h"
#include "clang/Basic/BitmaskEnum.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/DarwinSDKInfo.h"
#include "clang/Basic/ExpressionTraits.h"
#include "clang/Basic/Module.h"
#include "clang/Basic/OpenCLOptions.h"
#include "clang/Basic/OpenMPKinds.h"
#include "clang/Basic/PragmaKinds.h"
#include "clang/Basic/Specifiers.h"
#include "clang/Basic/TemplateKinds.h"
#include "clang/Basic/TypeTraits.h"
#include "clang/Sema/AnalysisBasedWarnings.h"
#include "clang/Sema/CleanupInfo.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/ExternalSemaSource.h"
#include "clang/Sema/IdentifierResolver.h"
#include "clang/Sema/ObjCMethodList.h"
#include "clang/Sema/Ownership.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/SemaConcept.h"
#include "clang/Sema/TypoCorrection.h"
#include "clang/Sema/Weak.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Frontend/OpenMP/OMPConstants.h"
#include <deque>
#include <memory>
#include <string>
#include <tuple>
#include <vector>

namespace llvm {
  class APSInt;
  template <typename ValueT, typename ValueInfoT> class DenseSet;
  class SmallBitVector;
  struct InlineAsmIdentifierInfo;
}

namespace clang {
  class ADLResult;
  class ASTConsumer;
  class ASTContext;
  class ASTMutationListener;
  class ASTReader;
  class ASTWriter;
  class ArrayType;
  class ParsedAttr;
  class BindingDecl;
  class BlockDecl;
  class CapturedDecl;
  class CXXBasePath;
  class CXXBasePaths;
  class CXXBindTemporaryExpr;
  typedef SmallVector<CXXBaseSpecifier*, 4> CXXCastPath;
  class CXXConstructorDecl;
  class CXXConversionDecl;
  class CXXDeleteExpr;
  class CXXDestructorDecl;
  class CXXFieldCollector;
  class CXXMemberCallExpr;
  class CXXMethodDecl;
  class CXXScopeSpec;
  class CXXTemporary;
  class CXXTryStmt;
  class CallExpr;
  class ClassTemplateDecl;
  class ClassTemplatePartialSpecializationDecl;
  class ClassTemplateSpecializationDecl;
  class VarTemplatePartialSpecializationDecl;
  class CodeCompleteConsumer;
  class CodeCompletionAllocator;
  class CodeCompletionTUInfo;
  class CodeCompletionResult;
  class CoroutineBodyStmt;
  class Decl;
  class DeclAccessPair;
  class DeclContext;
  class DeclRefExpr;
  class DeclaratorDecl;
  class DeducedTemplateArgument;
  class DependentDiagnostic;
  class DesignatedInitExpr;
  class Designation;
  class EnableIfAttr;
  class EnumConstantDecl;
  class Expr;
  class ExtVectorType;
  class FormatAttr;
  class FriendDecl;
  class FunctionDecl;
  class FunctionProtoType;
  class FunctionTemplateDecl;
  class ImplicitConversionSequence;
  typedef MutableArrayRef<ImplicitConversionSequence> ConversionSequenceList;
  class InitListExpr;
  class InitializationKind;
  class InitializationSequence;
  class InitializedEntity;
  class IntegerLiteral;
  class LabelStmt;
  class LambdaExpr;
  class LangOptions;
  class LocalInstantiationScope;
  class LookupResult;
  class MacroInfo;
  typedef ArrayRef<std::pair<IdentifierInfo *, SourceLocation>> ModuleIdPath;
  class ModuleLoader;
  class MultiLevelTemplateArgumentList;
  class NamedDecl;
  class ObjCCategoryDecl;
  class ObjCCategoryImplDecl;
  class ObjCCompatibleAliasDecl;
  class ObjCContainerDecl;
  class ObjCImplDecl;
  class ObjCImplementationDecl;
  class ObjCInterfaceDecl;
  class ObjCIvarDecl;
  template <class T> class ObjCList;
  class ObjCMessageExpr;
  class ObjCMethodDecl;
  class ObjCPropertyDecl;
  class ObjCProtocolDecl;
  class OMPThreadPrivateDecl;
  class OMPRequiresDecl;
  class OMPDeclareReductionDecl;
  class OMPDeclareSimdDecl;
  class OMPClause;
  struct OMPVarListLocTy;
  struct OverloadCandidate;
  enum class OverloadCandidateParamOrder : char;
  enum OverloadCandidateRewriteKind : unsigned;
  class OverloadCandidateSet;
  class OverloadExpr;
  class ParenListExpr;
  class ParmVarDecl;
  class Preprocessor;
  class PseudoDestructorTypeStorage;
  class PseudoObjectExpr;
  class QualType;
  class StandardConversionSequence;
  class Stmt;
  class StringLiteral;
  class SwitchStmt;
  class TemplateArgument;
  class TemplateArgumentList;
  class TemplateArgumentLoc;
  class TemplateDecl;
  class TemplateInstantiationCallback;
  class TemplateParameterList;
  class TemplatePartialOrderingContext;
  class TemplateTemplateParmDecl;
  class Token;
  class TypeAliasDecl;
  class TypedefDecl;
  class TypedefNameDecl;
  class TypeLoc;
  class TypoCorrectionConsumer;
  class UnqualifiedId;
  class UnresolvedLookupExpr;
  class UnresolvedMemberExpr;
  class UnresolvedSetImpl;
  class UnresolvedSetIterator;
  class UsingDecl;
  class UsingShadowDecl;
  class ValueDecl;
  class VarDecl;
  class VarTemplateSpecializationDecl;
  class VisibilityAttr;
  class VisibleDeclConsumer;
  class IndirectFieldDecl;
  struct DeductionFailureInfo;
  class TemplateSpecCandidateSet;

namespace sema {
  class AccessedEntity;
  class BlockScopeInfo;
  class Capture;
  class CapturedRegionScopeInfo;
  class CapturingScopeInfo;
  class CompoundScopeInfo;
  class DelayedDiagnostic;
  class DelayedDiagnosticPool;
  class FunctionScopeInfo;
  class LambdaScopeInfo;
  class PossiblyUnreachableDiag;
  class SemaPPCallbacks;
  class TemplateDeductionInfo;
}

namespace threadSafety {
  class BeforeSet;
  void threadSafetyCleanup(BeforeSet* Cache);
}

// FIXME: No way to easily map from TemplateTypeParmTypes to
// TemplateTypeParmDecls, so we have this horrible PointerUnion.
typedef std::pair<llvm::PointerUnion<const TemplateTypeParmType*, NamedDecl*>,
                  SourceLocation> UnexpandedParameterPack;

/// Describes whether we've seen any nullability information for the given
/// file.
struct FileNullability {
  /// The first pointer declarator (of any pointer kind) in the file that does
  /// not have a corresponding nullability annotation.
  SourceLocation PointerLoc;

  /// The end location for the first pointer declarator in the file. Used for
  /// placing fix-its.
  SourceLocation PointerEndLoc;

  /// Which kind of pointer declarator we saw.
  uint8_t PointerKind;

  /// Whether we saw any type nullability annotations in the given file.
  bool SawTypeNullability = false;
};

/// A mapping from file IDs to a record of whether we've seen nullability
/// information in that file.
class FileNullabilityMap {
  /// A mapping from file IDs to the nullability information for each file ID.
  llvm::DenseMap<FileID, FileNullability> Map;

  /// A single-element cache based on the file ID.
  struct {
    FileID File;
    FileNullability Nullability;
  } Cache;

public:
  FileNullability &operator[](FileID file) {
    // Check the single-element cache.
    if (file == Cache.File)
      return Cache.Nullability;

    // It's not in the single-element cache; flush the cache if we have one.
    if (!Cache.File.isInvalid()) {
      Map[Cache.File] = Cache.Nullability;
    }

    // Pull this entry into the cache.
    Cache.File = file;
    Cache.Nullability = Map[file];
    return Cache.Nullability;
  }
};

/// 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 funciton, as it stores a
  /// function_ref, clients should make sure all calls to get() with the same
  /// location happen while function_ref is alive.
  ///
  /// 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 != ExpectedLoc747)
      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;
};

/// Sema - This implements semantic analysis and AST building for C.
class Sema final {
  Sema(const Sema &) = delete;
  void operator=(const Sema &) = delete;

  ///Source of additional semantic information.
  ExternalSemaSource *ExternalSource;

  ///Whether Sema has generated a multiplexer and has to delete it.
  bool isMultiplexExternalSource;

  static bool mightHaveNonExternalLinkage(const DeclaratorDecl *FD);

  /// Determine whether two declarations should be linked together, given that
  /// the old declaration might not be visible and the new declaration might
  /// not have external linkage.
  bool shouldLinkPossiblyHiddenDecl(const NamedDecl *Old,
                                    const NamedDecl *New) {
    if (isVisible(Old))
     return true;
    // See comment in below overload for why it's safe to compute the linkage
    // of the new declaration here.
    if (New->isExternallyDeclarable()) {
      assert(Old->isExternallyDeclarable() &&
             "should not have found a non-externally-declarable previous decl");
      return true;
    }
    return false;
  }
  bool shouldLinkPossiblyHiddenDecl(LookupResult &Old, const NamedDecl *New);

  void setupImplicitSpecialMemberType(CXXMethodDecl *SpecialMem,
                                      QualType ResultTy,
                                      ArrayRef<QualType> Args);

public:
  /// The maximum alignment, same as in llvm::Value. We duplicate them here
  /// because that allows us not to duplicate the constants in clang code,
  /// which we must to since we can't directly use the llvm constants.
  /// The value is verified against llvm here: lib/CodeGen/CGDecl.cpp
  ///
  /// This is the greatest alignment value supported by load, store, and alloca
  /// instructions, and global values.
  static const unsigned MaxAlignmentExponent = 32;
  static const uint64_t MaximumAlignment = 1ull << MaxAlignmentExponent;

  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;

  /// Flag indicating whether or not to collect detailed statistics.
  bool CollectStats;

  /// Code-completion consumer.
  CodeCompleteConsumer *CodeCompleter;

  /// CurContext - This is the current declaration context of parsing.
  DeclContext *CurContext;

  /// Generally null except when we temporarily switch decl contexts,
  /// like in \see ActOnObjCTemporaryExitContainerContext.
  DeclContext *OriginalLexicalContext;

  /// VAListTagName - The declaration name corresponding to __va_list_tag.
  /// This is used as part of a hack to omit that class from ADL results.
  DeclarationName VAListTagName;

  bool MSStructPragmaOn; // True when \#pragma ms_struct on

  /// Controls member pointer representation format under the MS ABI.
  LangOptions::PragmaMSPointersToMembersKind
      MSPointerToMemberRepresentationMethod;

  /// Stack of active SEH __finally scopes.  Can be empty.
  SmallVector<Scope*, 2> CurrentSEHFinally;

  /// Source location for newly created implicit MSInheritanceAttrs
  SourceLocation ImplicitMSInheritanceAttrLoc;

  /// Holds TypoExprs that are created from `createDelayedTypo`. This is used by
  /// `TransformTypos` in order to keep track of any TypoExprs that are created
  /// recursively during typo correction and wipe them away if the correction
  /// fails.
  llvm::SmallVector<TypoExpr *, 2> TypoExprs;

  /// pragma clang section kind
  enum PragmaClangSectionKind {
    PCSK_Invalid      = 0,
    PCSK_BSS          = 1,
    PCSK_Data         = 2,
    PCSK_Rodata       = 3,
    PCSK_Text         = 4,
    PCSK_Relro        = 5
   };

  enum PragmaClangSectionAction {
    PCSA_Set     = 0,
    PCSA_Clear   = 1
  };

  struct PragmaClangSection {
    std::string SectionName;
    bool Valid = false;
    SourceLocation PragmaLocation;
  };

   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)
  };

  // #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 != 0239k;
    }

    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 (96!Stack.empty()96) {
          // 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;

  // 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;
  }

  // RAII object to push / pop sentinel slots for all MS #pragma stacks.
  // Actions should be performed only if we enter / exit a C++ method body.
  class PragmaStackSentinelRAII {
  public:
    PragmaStackSentinelRAII(Sema &S, StringRef SlotLabel, bool ShouldAct);
    ~PragmaStackSentinelRAII();

  private:
    Sema &S;
    StringRef SlotLabel;
    bool ShouldAct;
  };

  /// A mapping that describes the nullability we've seen in each header file.
  FileNullabilityMap NullabilityMap;

  /// Last section used with #pragma init_seg.
  StringLiteral *CurInitSeg;
  SourceLocation CurInitSegLoc;

  /// 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;

  /// 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;

  /// Flag indicating if Sema is building a recovery call expression.
  ///
  /// This flag is used to avoid building recovery call expressions
  /// if Sema is already doing so, which would cause infinite recursions.
  bool IsBuildingRecoveryCallExpr;

  /// Used to control the generation of ExprWithCleanups.
  CleanupInfo Cleanup;

  /// ExprCleanupObjects - This is the stack of objects requiring
  /// cleanup that are created by the current full expression.
  SmallVector<ExprWithCleanups::CleanupObject, 8> ExprCleanupObjects;

  /// Store a set of either DeclRefExprs or MemberExprs that contain a reference
  /// to a variable (constant) that may or may not be odr-used in this Expr, and
  /// we won't know until all lvalue-to-rvalue and discarded value conversions
  /// have been applied to all subexpressions of the enclosing full expression.
  /// This is cleared at the end of each full expression.
  using MaybeODRUseExprSet = llvm::SetVector<Expr *, SmallVector<Expr *, 4>,
                                             llvm::SmallPtrSet<Expr *, 4>>;
  MaybeODRUseExprSet MaybeODRUseExprs;

  std::unique_ptr<sema::FunctionScopeInfo> CachedFunctionScope;

  /// Stack containing information about each of the nested
  /// function, block, and method scopes that are currently active.
  SmallVector<sema::FunctionScopeInfo *, 4> FunctionScopes;

  /// The index of the first FunctionScope that corresponds to the current
  /// context.
  unsigned FunctionScopesStart = 0;

  ArrayRef<sema::FunctionScopeInfo*> getFunctionScopes() const {
    return llvm::makeArrayRef(FunctionScopes.begin() + FunctionScopesStart,
                              FunctionScopes.end());
  }

  /// Stack containing information needed when in C++2a an 'auto' is encountered
  /// in a function declaration parameter type specifier in order to invent a
  /// corresponding template parameter in the enclosing abbreviated function
  /// template. This information is also present in LambdaScopeInfo, stored in
  /// the FunctionScopes stack.
  SmallVector<InventedTemplateParameterInfo, 4> InventedParameterInfos;

  /// The index of the first InventedParameterInfo that refers to the current
  /// context.
  unsigned InventedParameterInfosStart = 0;

  ArrayRef<InventedTemplateParameterInfo> getInventedParameterInfos() const {
    return llvm::makeArrayRef(InventedParameterInfos.begin() +
                                  InventedParameterInfosStart,
                              InventedParameterInfos.end());
  }

  typedef LazyVector<TypedefNameDecl *, ExternalSemaSource,
                     &ExternalSemaSource::ReadExtVectorDecls, 2, 2>
    ExtVectorDeclsType;

  /// ExtVectorDecls - This is a list all the extended vector types. This allows
  /// us to associate a raw vector type with one of the ext_vector type names.
  /// This is only necessary for issuing pretty diagnostics.
  ExtVectorDeclsType ExtVectorDecls;

  /// FieldCollector - Collects CXXFieldDecls during parsing of C++ classes.
  std::unique_ptr<CXXFieldCollector> FieldCollector;

  typedef llvm::SmallSetVector<NamedDecl *, 16> NamedDeclSetType;

  /// Set containing all declared private fields that are not used.
  NamedDeclSetType UnusedPrivateFields;

  /// Set containing all typedefs that are likely unused.
  llvm::SmallSetVector<const TypedefNameDecl *, 4>
      UnusedLocalTypedefNameCandidates;

  /// Delete-expressions to be analyzed at the end of translation unit
  ///
  /// This list contains class members, and locations of delete-expressions
  /// that could not be proven as to whether they mismatch with new-expression
  /// used in initializer of the field.
  typedef std::pair<SourceLocation, bool> DeleteExprLoc;
  typedef llvm::SmallVector<DeleteExprLoc, 4> DeleteLocs;
  llvm::MapVector<FieldDecl *, DeleteLocs> DeleteExprs;

  typedef llvm::SmallPtrSet<const CXXRecordDecl*, 8> RecordDeclSetTy;

  /// PureVirtualClassDiagSet - a set of class declarations which we have
  /// emitted a list of pure virtual functions. Used to prevent emitting the
  /// same list more than once.
  std::unique_ptr<RecordDeclSetTy> PureVirtualClassDiagSet;

  /// ParsingInitForAutoVars - a set of declarations with auto types for which
  /// we are currently parsing the initializer.
  llvm::SmallPtrSet<const Decl*, 4> ParsingInitForAutoVars;

  /// Look for a locally scoped extern "C" declaration by the given name.
  NamedDecl *findLocallyScopedExternCDecl(DeclarationName Name);

  typedef LazyVector<VarDecl *, ExternalSemaSource,
                     &ExternalSemaSource::ReadTentativeDefinitions, 2, 2>
    TentativeDefinitionsType;

  /// All the tentative definitions encountered in the TU.
  TentativeDefinitionsType TentativeDefinitions;

  /// All the external declarations encoutered and used in the TU.
  SmallVector<VarDecl *, 4> ExternalDeclarations;

  typedef LazyVector<const DeclaratorDecl *, ExternalSemaSource,
                     &ExternalSemaSource::ReadUnusedFileScopedDecls, 2, 2>
    UnusedFileScopedDeclsType;

  /// The set of file scoped decls seen so far that have not been used
  /// and must warn if not used. Only contains the first declaration.
  UnusedFileScopedDeclsType UnusedFileScopedDecls;

  typedef LazyVector<CXXConstructorDecl *, ExternalSemaSource,
                     &ExternalSemaSource::ReadDelegatingConstructors, 2, 2>
    DelegatingCtorDeclsType;

  /// All the delegating constructors seen so far in the file, used for
  /// cycle detection at the end of the TU.
  DelegatingCtorDeclsType DelegatingCtorDecls;

  /// All the overriding functions seen during a class definition
  /// that had their exception spec checks delayed, plus the overridden
  /// function.
  SmallVector<std::pair<const CXXMethodDecl*, const CXXMethodDecl*>, 2>
    DelayedOverridingExceptionSpecChecks;

  /// All the function redeclarations seen during a class definition that had
  /// their exception spec checks delayed, plus the prior declaration they
  /// should be checked against. Except during error recovery, the new decl
  /// should always be a friend declaration, as that's the only valid way to
  /// redeclare a special member before its class is complete.
  SmallVector<std::pair<FunctionDecl*, FunctionDecl*>, 2>
    DelayedEquivalentExceptionSpecChecks;

  typedef llvm::MapVector<const FunctionDecl *,
                          std::unique_ptr<LateParsedTemplate>>
      LateParsedTemplateMapT;
  LateParsedTemplateMapT LateParsedTemplateMap;

  /// Callback to the parser to parse templated functions when needed.
  typedef void LateTemplateParserCB(void *P, LateParsedTemplate &LPT);
  typedef void LateTemplateParserCleanupCB(void *P);
  LateTemplateParserCB *LateTemplateParser;
  LateTemplateParserCleanupCB *LateTemplateParserCleanup;
  void *OpaqueParser;

  void SetLateTemplateParser(LateTemplateParserCB *LTP,
                             LateTemplateParserCleanupCB *LTPCleanup,
                             void *P) {
    LateTemplateParser = LTP;
    LateTemplateParserCleanup = LTPCleanup;
    OpaqueParser = P;
  }

  class DelayedDiagnostics;

  class DelayedDiagnosticsState {
    sema::DelayedDiagnosticPool *SavedPool;
    friend class Sema::DelayedDiagnostics;
  };
  typedef DelayedDiagnosticsState ParsingDeclState;
  typedef DelayedDiagnosticsState ProcessingContextState;

  /// A class which encapsulates the logic for delaying diagnostics
  /// during parsing and other processing.
  class DelayedDiagnostics {
    /// The current pool of diagnostics into which delayed
    /// diagnostics should go.
    sema::DelayedDiagnosticPool *CurPool;

  public:
    DelayedDiagnostics() : CurPool(nullptr) {}

    /// Adds a delayed diagnostic.
    void add(const sema::DelayedDiagnostic &diag); // in DelayedDiagnostic.h

    /// Determines whether diagnostics should be delayed.
    bool shouldDelayDiagnostics() { return CurPool != nullptr; }

    /// Returns the current delayed-diagnostics pool.
    sema::DelayedDiagnosticPool *getCurrentPool() const {
      return CurPool;
    }

    /// Enter a new scope.  Access and deprecation diagnostics will be
    /// collected in this pool.
    DelayedDiagnosticsState push(sema::DelayedDiagnosticPool &pool) {
      DelayedDiagnosticsState state;
      state.SavedPool = CurPool;
      CurPool = &pool;
      return state;
    }

    /// Leave a delayed-diagnostic state that was previously pushed.
    /// Do not emit any of the diagnostics.  This is performed as part
    /// of the bookkeeping of popping a pool "properly".
    void popWithoutEmitting(DelayedDiagnosticsState state) {
      CurPool = state.SavedPool;
    }

    /// Enter a new scope where access and deprecation diagnostics are
    /// not delayed.
    DelayedDiagnosticsState pushUndelayed() {
      DelayedDiagnosticsState state;
      state.SavedPool = CurPool;
      CurPool = nullptr;
      return state;
    }

    /// Undo a previous pushUndelayed().
    void popUndelayed(DelayedDiagnosticsState state) {
      assert(CurPool == nullptr);
      CurPool = state.SavedPool;
    }
  } DelayedDiagnostics;

  /// A RAII object to temporarily push a declaration context.
  class ContextRAII {
  private:
    Sema &S;
    DeclContext *SavedContext;
    ProcessingContextState SavedContextState;
    QualType SavedCXXThisTypeOverride;
    unsigned SavedFunctionScopesStart;
    unsigned SavedInventedParameterInfosStart;

  public:
    ContextRAII(Sema &S, DeclContext *ContextToPush, bool NewThisContext = true)
      : S(S), SavedContext(S.CurContext),
        SavedContextState(S.DelayedDiagnostics.pushUndelayed()),
        SavedCXXThisTypeOverride(S.CXXThisTypeOverride),
        SavedFunctionScopesStart(S.FunctionScopesStart),
        SavedInventedParameterInfosStart(S.InventedParameterInfosStart)
    {
      assert(ContextToPush && "pushing null context");
      S.CurContext = ContextToPush;
      if (NewThisContext)
        S.CXXThisTypeOverride = QualType();
      // Any saved FunctionScopes do not refer to this context.
      S.FunctionScopesStart = S.FunctionScopes.size();
      S.InventedParameterInfosStart = S.InventedParameterInfos.size();
    }

    void pop() {
      if (!SavedContext) return1.16M;
      S.CurContext = SavedContext;
      S.DelayedDiagnostics.popUndelayed(SavedContextState);
      S.CXXThisTypeOverride = SavedCXXThisTypeOverride;
      S.FunctionScopesStart = SavedFunctionScopesStart;
      S.InventedParameterInfosStart = SavedInventedParameterInfosStart;
      SavedContext = nullptr;
    }

    ~ContextRAII() {
      pop();
    }
  };

  /// Whether the AST is currently being rebuilt to correct immediate
  /// invocations. Immediate invocation candidates and references to consteval
  /// functions aren't tracked when this is set.
  bool RebuildingImmediateInvocation = false;

  /// Used to change context to isConstantEvaluated without pushing a heavy
  /// ExpressionEvaluationContextRecord object.
  bool isConstantEvaluatedOverride;

  bool isConstantEvaluated() {
    return ExprEvalContexts.back().isConstantEvaluated() ||
           isConstantEvaluatedOverride12.5M;
  }

  /// RAII object to handle the state changes required to synthesize
  /// a function body.
  class SynthesizedFunctionScope {
    Sema &S;
    Sema::ContextRAII SavedContext;
    bool PushedCodeSynthesisContext = false;

  public:
    SynthesizedFunctionScope(Sema &S, DeclContext *DC)
        : S(S), SavedContext(S, DC) {
      S.PushFunctionScope();
      S.PushExpressionEvaluationContext(
          Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
      if (auto *FD = dyn_cast<FunctionDecl>(DC))
        FD->setWillHaveBody(true);
      else
        assert(isa<ObjCMethodDecl>(DC));
    }

    void addContextNote(SourceLocation UseLoc) {
      assert(!PushedCodeSynthesisContext);

      Sema::CodeSynthesisContext Ctx;
      Ctx.Kind = Sema::CodeSynthesisContext::DefiningSynthesizedFunction;
      Ctx.PointOfInstantiation = UseLoc;
      Ctx.Entity = cast<Decl>(S.CurContext);
      S.pushCodeSynthesisContext(Ctx);

      PushedCodeSynthesisContext = true;
    }

    ~SynthesizedFunctionScope() {
      if (PushedCodeSynthesisContext)
        S.popCodeSynthesisContext();
      if (auto *FD = dyn_cast<FunctionDecl>(S.CurContext))
        FD->setWillHaveBody(false);
      S.PopExpressionEvaluationContext();
      S.PopFunctionScopeInfo();
    }
  };

  /// WeakUndeclaredIdentifiers - Identifiers contained in \#pragma weak before
  /// declared. Rare. May alias another identifier, declared or undeclared.
  ///
  /// 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;


  /// Load weak undeclared identifiers from the external source.
  void LoadExternalWeakUndeclaredIdentifiers();

  /// WeakTopLevelDecl - Translation-unit scoped declarations generated by
  /// \#pragma weak during processing of other Decls.
  /// I couldn't figure out a clean way to generate these in-line, so
  /// we store them here and handle separately -- which is a hack.
  /// It would be best to refactor this.
  SmallVector<Decl*,2> WeakTopLevelDecl;

  IdentifierResolver IdResolver;

  /// Translation Unit Scope - useful to Objective-C actions that need
  /// to lookup file scope declarations in the "ordinary" C decl namespace.
  /// For example, user-defined classes, built-in "id" type, etc.
  Scope *TUScope;

  /// The C++ "std" namespace, where the standard library resides.
  LazyDeclPtr StdNamespace;

  /// The C++ "std::bad_alloc" class, which is defined by the C++
  /// standard library.
  LazyDeclPtr StdBadAlloc;

  /// The C++ "std::align_val_t" enum class, which is defined by the C++
  /// standard library.
  LazyDeclPtr StdAlignValT;

  /// The C++ "std::experimental" namespace, where the experimental parts
  /// of the standard library resides.
  NamespaceDecl *StdExperimentalNamespaceCache;

  /// The C++ "std::initializer_list" template, which is defined in
  /// \<initializer_list>.
  ClassTemplateDecl *StdInitializerList;

  /// The C++ "std::coroutine_traits" template, which is defined in
  /// \<coroutine_traits>
  ClassTemplateDecl *StdCoroutineTraitsCache;
  /// The namespace where coroutine components are defined. In standard,
  /// they are defined in std namespace. And in the previous implementation,
  /// they are defined in std::experimental namespace.
  NamespaceDecl *CoroTraitsNamespaceCache;

  /// The C++ "type_info" declaration, which is defined in \<typeinfo>.
  RecordDecl *CXXTypeInfoDecl;

  /// The MSVC "_GUID" struct, which is defined in MSVC header files.
  RecordDecl *MSVCGuidDecl;

  /// The C++ "std::source_location::__impl" struct, defined in
  /// \<source_location>.
  RecordDecl *StdSourceLocationImplDecl;

  /// Caches identifiers/selectors for NSFoundation APIs.
  std::unique_ptr<NSAPI> NSAPIObj;

  /// The declaration of the Objective-C NSNumber class.
  ObjCInterfaceDecl *NSNumberDecl;

  /// The declaration of the Objective-C NSValue class.
  ObjCInterfaceDecl *NSValueDecl;

  /// Pointer to NSNumber type (NSNumber *).
  QualType NSNumberPointer;

  /// Pointer to NSValue type (NSValue *).
  QualType NSValuePointer;

  /// The Objective-C NSNumber methods used to create NSNumber literals.
  ObjCMethodDecl *NSNumberLiteralMethods[NSAPI::NumNSNumberLiteralMethods];

  /// The declaration of the Objective-C NSString class.
  ObjCInterfaceDecl *NSStringDecl;

  /// Pointer to NSString type (NSString *).
  QualType NSStringPointer;

  /// The declaration of the stringWithUTF8String: method.
  ObjCMethodDecl *StringWithUTF8StringMethod;

  /// The declaration of the valueWithBytes:objCType: method.
  ObjCMethodDecl *ValueWithBytesObjCTypeMethod;

  /// The declaration of the Objective-C NSArray class.
  ObjCInterfaceDecl *NSArrayDecl;

  /// The declaration of the arrayWithObjects:count: method.
  ObjCMethodDecl *ArrayWithObjectsMethod;

  /// The declaration of the Objective-C NSDictionary class.
  ObjCInterfaceDecl *NSDictionaryDecl;

  /// The declaration of the dictionaryWithObjects:forKeys:count: method.
  ObjCMethodDecl *DictionaryWithObjectsMethod;

  /// id<NSCopying> type.
  QualType QIDNSCopying;

  /// will hold 'respondsToSelector:'
  Selector RespondsToSelectorSel;

  /// A flag to remember whether the implicit forms of operator new and delete
  /// have been declared.
  bool GlobalNewDeleteDeclared;

  /// Describes how the expressions currently being parsed are
  /// evaluated at run-time, if at all.
  enum class ExpressionEvaluationContext {
    /// The current expression and its subexpressions occur within an
    /// unevaluated operand (C++11 [expr]p7), such as the subexpression of
    /// \c sizeof, where the type of the expression may be significant but
    /// no code will be generated to evaluate the value of the expression at
    /// run time.
    Unevaluated,

    /// The current expression occurs within a braced-init-list within
    /// an unevaluated operand. This is mostly like a regular unevaluated
    /// context, except that we still instantiate constexpr functions that are
    /// referenced here so that we can perform narrowing checks correctly.
    UnevaluatedList,

    /// The current expression occurs within a discarded statement.
    /// This behaves largely similarly to an unevaluated operand in preventing
    /// definitions from being required, but not in other ways.
    DiscardedStatement,

    /// The current expression occurs within an unevaluated
    /// operand that unconditionally permits abstract references to
    /// fields, such as a SIZE operator in MS-style inline assembly.
    UnevaluatedAbstract,

    /// The current context is "potentially evaluated" in C++11 terms,
    /// but the expression is evaluated at compile-time (like the values of
    /// cases in a switch statement).
    ConstantEvaluated,

    /// In addition of being constant evaluated, the current expression
    /// occurs in an immediate function context - either a consteval function
    /// or a consteval if function.
    ImmediateFunctionContext,

    /// The current expression is potentially evaluated at run time,
    /// which means that code may be generated to evaluate the value of the
    /// expression at run time.
    PotentiallyEvaluated,

    /// The current expression is potentially evaluated, but any
    /// declarations referenced inside that expression are only used if
    /// in fact the current expression is used.
    ///
    /// This value is used when parsing default function arguments, for which
    /// we would like to provide diagnostics (e.g., passing non-POD arguments
    /// through varargs) but do not want to mark declarations as "referenced"
    /// until the default argument is used.
    PotentiallyEvaluatedIfUsed
  };

  using ImmediateInvocationCandidate = llvm::PointerIntPair<ConstantExpr *, 1>;

  /// Data structure used to record current or nested
  /// expression evaluation contexts.
  struct ExpressionEvaluationContextRecord {
    /// The expression evaluation context.
    ExpressionEvaluationContext Context;

    /// Whether the enclosing context needed a cleanup.
    CleanupInfo ParentCleanup;

    /// The number of active cleanup objects when we entered
    /// this expression evaluation context.
    unsigned NumCleanupObjects;

    /// The number of typos encountered during this expression evaluation
    /// context (i.e. the number of TypoExprs created).
    unsigned NumTypos;

    MaybeODRUseExprSet SavedMaybeODRUseExprs;

    /// The lambdas that are present within this context, if it
    /// is indeed an unevaluated context.
    SmallVector<LambdaExpr *, 2> Lambdas;

    /// The declaration that provides context for lambda expressions
    /// and block literals if the normal declaration context does not
    /// suffice, e.g., in a default function argument.
    Decl *ManglingContextDecl;

    /// If we are processing a decltype type, a set of call expressions
    /// for which we have deferred checking the completeness of the return type.
    SmallVector<CallExpr *, 8> DelayedDecltypeCalls;

    /// If we are processing a decltype type, a set of temporary binding
    /// expressions for which we have deferred checking the destructor.
    SmallVector<CXXBindTemporaryExpr *, 8> DelayedDecltypeBinds;

    llvm::SmallPtrSet<const Expr *, 8> PossibleDerefs;

    /// Expressions appearing as the LHS of a volatile assignment in this
    /// context. We produce a warning for these when popping the context if
    /// they are not discarded-value expressions nor unevaluated operands.
    SmallVector<Expr*, 2> VolatileAssignmentLHSs;

    /// Set of candidates for starting an immediate invocation.
    llvm::SmallVector<ImmediateInvocationCandidate, 4> ImmediateInvocationCandidates;

    /// Set of DeclRefExprs referencing a consteval function when used in a
    /// context not already known to be immediately invoked.
    llvm::SmallPtrSet<DeclRefExpr *, 4> ReferenceToConsteval;

    /// \brief Describes whether we are in an expression constext which we have
    /// to handle differently.
    enum ExpressionKind {
      EK_Decltype, EK_TemplateArgument, EK_Other
    } ExprContext;

    // A context can be nested in both a discarded statement context and
    // an immediate function context, so they need to be tracked independently.
    bool InDiscardedStatement;
    bool InImmediateFunctionContext;

    ExpressionEvaluationContextRecord(ExpressionEvaluationContext Context,
                                      unsigned NumCleanupObjects,
                                      CleanupInfo ParentCleanup,
                                      Decl *ManglingContextDecl,
                                      ExpressionKind ExprContext)
        : Context(Context), ParentCleanup(ParentCleanup),
          NumCleanupObjects(NumCleanupObjects), NumTypos(0),
          ManglingContextDecl(ManglingContextDecl), ExprContext(ExprContext),
          InDiscardedStatement(false), InImmediateFunctionContext(false) {}

    bool isUnevaluated() const {
      return Context == ExpressionEvaluationContext::Unevaluated ||
             Context == ExpressionEvaluationContext::UnevaluatedAbstract134M ||
             Context == ExpressionEvaluationContext::UnevaluatedList134M;
    }

    bool isConstantEvaluated() const {
      return Context == ExpressionEvaluationContext::ConstantEvaluated ||
             Context == ExpressionEvaluationContext::ImmediateFunctionContext19.6M;
    }

    bool isImmediateFunctionContext() const {
      return Context == ExpressionEvaluationContext::ImmediateFunctionContext ||
             (47.7MContext == ExpressionEvaluationContext::DiscardedStatement47.7M &&
              InImmediateFunctionContext60);
    }

    bool isDiscardedStatementContext() const {
      return Context == ExpressionEvaluationContext::DiscardedStatement ||
             (54.6MContext ==
                  ExpressionEvaluationContext::ImmediateFunctionContext &&
              InDiscardedStatement38);
    }
  };

  /// A stack of expression evaluation contexts.
  SmallVector<ExpressionEvaluationContextRecord, 8> ExprEvalContexts;

  /// Emit a warning for all pending noderef expressions that we recorded.
  void WarnOnPendingNoDerefs(ExpressionEvaluationContextRecord &Rec);

  /// Compute the mangling number context for a lambda expression or
  /// block literal. Also return the extra mangling decl if any.
  ///
  /// \param DC - The DeclContext containing the lambda expression or
  /// block literal.
  std::tuple<MangleNumberingContext *, Decl *>
  getCurrentMangleNumberContext(const DeclContext *DC);


  /// SpecialMemberOverloadResult - The overloading result for a special member
  /// function.
  ///
  /// This is basically a wrapper around PointerIntPair. The lowest bits of the
  /// integer are used to determine whether overload resolution succeeded.
  class SpecialMemberOverloadResult {
  public:
    enum Kind {
      NoMemberOrDeleted,
      Ambiguous,
      Success
    };

  private:
    llvm::PointerIntPair<CXXMethodDecl *, 2> Pair;

  public:
    SpecialMemberOverloadResult() {}
    SpecialMemberOverloadResult(CXXMethodDecl *MD)
        : Pair(MD, MD->isDeleted() ? NoMemberOrDeleted : Success) {}

    CXXMethodDecl *getMethod() const { return Pair.getPointer(); }
    void setMethod(CXXMethodDecl *MD) { Pair.setPointer(MD); }

    Kind getKind() const { return static_cast<Kind>(Pair.getInt()); }
    void setKind(Kind K) { Pair.setInt(K); }
  };

  class SpecialMemberOverloadResultEntry
      : public llvm::FastFoldingSetNode,
        public SpecialMemberOverloadResult {
  public:
    SpecialMemberOverloadResultEntry(const llvm::FoldingSetNodeID &ID)
      : FastFoldingSetNode(ID)
    {}
  };

  /// A cache of special member function overload resolution results
  /// for C++ records.
  llvm::FoldingSet<SpecialMemberOverloadResultEntry> SpecialMemberCache;

  /// A cache of the flags available in enumerations with the flag_bits
  /// attribute.
  mutable llvm::DenseMap<const EnumDecl*, llvm::APInt> FlagBitsCache;

  /// The kind of translation unit we are processing.
  ///
  /// When we're processing a complete translation unit, Sema will perform
  /// end-of-translation-unit semantic tasks (such as creating
  /// initializers for tentative definitions in C) once parsing has
  /// completed. Modules and precompiled headers perform different kinds of
  /// checks.
  const TranslationUnitKind TUKind;

  llvm::BumpPtrAllocator BumpAlloc;

  /// The number of SFINAE diagnostics that have been trapped.
  unsigned NumSFINAEErrors;

  typedef llvm::DenseMap<ParmVarDecl *, llvm::TinyPtrVector<ParmVarDecl *>>
    UnparsedDefaultArgInstantiationsMap;

  /// A mapping from parameters with unparsed default arguments to the
  /// set of instantiations of each parameter.
  ///
  /// This mapping is a temporary data structure used when parsing
  /// nested class templates or nested classes of class templates,
  /// where we might end up instantiating an inner class before the
  /// default arguments of its methods have been parsed.
  UnparsedDefaultArgInstantiationsMap UnparsedDefaultArgInstantiations;

  // Contains the locations of the beginning of unparsed default
  // argument locations.
  llvm::DenseMap<ParmVarDecl *, SourceLocation> UnparsedDefaultArgLocs;

  /// UndefinedInternals - all the used, undefined objects which require a
  /// definition in this translation unit.
  llvm::MapVector<NamedDecl *, SourceLocation> UndefinedButUsed;

  /// Determine if VD, which must be a variable or function, is an external
  /// symbol that nonetheless can't be referenced from outside this translation
  /// unit because its type has no linkage and it's not extern "C".
  bool isExternalWithNoLinkageType(ValueDecl *VD);

  /// Obtain a sorted list of functions that are undefined but ODR-used.
  void getUndefinedButUsed(
      SmallVectorImpl<std::pair<NamedDecl *, SourceLocation> > &Undefined);

  /// Retrieves list of suspicious delete-expressions that will be checked at
  /// the end of translation unit.
  const llvm::MapVector<FieldDecl *, DeleteLocs> &
  getMismatchingDeleteExpressions() const;

  class GlobalMethodPool {
  public:
    using Lists = std::pair<ObjCMethodList, ObjCMethodList>;
    using iterator = llvm::DenseMap<Selector, Lists>::iterator;
    iterator begin() { return Methods.begin(); }
    iterator end() { return Methods.end(); }
    iterator find(Selector Sel) { return Methods.find(Sel); }
    std::pair<iterator, bool> insert(std::pair<Selector, Lists> &&Val) {
      return Methods.insert(Val);
    }
    int count(Selector Sel) const { return Methods.count(Sel); }
    bool empty() const { return Methods.empty(); }

  private:
    llvm::DenseMap<Selector, Lists> Methods;
  };

  /// Method Pool - allows efficient lookup when typechecking messages to "id".
  /// We need to maintain a list, since selectors can have differing signatures
  /// across classes. In Cocoa, this happens to be extremely uncommon (only 1%
  /// of selectors are "overloaded").
  /// At the head of the list it is recorded whether there were 0, 1, or >= 2
  /// methods inside categories with a particular selector.
  GlobalMethodPool MethodPool;

  /// Method selectors used in a \@selector expression. Used for implementation
  /// of -Wselector.
  llvm::MapVector<Selector, SourceLocation> ReferencedSelectors;

  /// List of SourceLocations where 'self' is implicitly retained inside a
  /// block.
  llvm::SmallVector<std::pair<SourceLocation, const BlockDecl *>, 1>
      ImplicitlyRetainedSelfLocs;

  /// Kinds of C++ special members.
  enum CXXSpecialMember {
    CXXDefaultConstructor,
    CXXCopyConstructor,
    CXXMoveConstructor,
    CXXCopyAssignment,
    CXXMoveAssignment,
    CXXDestructor,
    CXXInvalid
  };

  typedef llvm::PointerIntPair<CXXRecordDecl *, 3, CXXSpecialMember>
      SpecialMemberDecl;

  /// The C++ special members which we are currently in the process of
  /// declaring. If this process recursively triggers the declaration of the
  /// same special member, we should act as if it is not yet declared.
  llvm::SmallPtrSet<SpecialMemberDecl, 4> SpecialMembersBeingDeclared;

  /// Kinds of defaulted comparison operator functions.
  enum class DefaultedComparisonKind : unsigned char {
    /// This is not a defaultable comparison operator.
    None,
    /// This is an operator== that should be implemented as a series of
    /// subobject comparisons.
    Equal,
    /// This is an operator<=> that should be implemented as a series of
    /// subobject comparisons.
    ThreeWay,
    /// This is an operator!= that should be implemented as a rewrite in terms
    /// of a == comparison.
    NotEqual,
    /// This is an <, <=, >, or >= that should be implemented as a rewrite in
    /// terms of a <=> comparison.
    Relational,
  };

  /// The function definitions which were renamed as part of typo-correction
  /// to match their respective declarations. We want to keep track of them
  /// to ensure that we don't emit a "redefinition" error if we encounter a
  /// correctly named definition after the renamed definition.
  llvm::SmallPtrSet<const NamedDecl *, 4> TypoCorrectedFunctionDefinitions;

  /// Stack of types that correspond to the parameter entities that are
  /// currently being copy-initialized. Can be empty.
  llvm::SmallVector<QualType, 4> CurrentParameterCopyTypes;

  void ReadMethodPool(Selector Sel);
  void updateOutOfDateSelector(Selector Sel);

  /// Private Helper predicate to check for 'self'.
  bool isSelfExpr(Expr *RExpr);
  bool isSelfExpr(Expr *RExpr, const ObjCMethodDecl *Method);

  /// Cause the active diagnostic on the DiagosticsEngine to be
  /// emitted. This is closely coupled to the SemaDiagnosticBuilder class and
  /// should not be used elsewhere.
  void EmitCurrentDiagnostic(unsigned DiagID);

  /// Records and restores the CurFPFeatures state on entry/exit of compound
  /// statements.
  class FPFeaturesStateRAII {
  public:
    FPFeaturesStateRAII(Sema &S);
    ~FPFeaturesStateRAII();
    FPOptionsOverride getOverrides() { return OldOverrides; }

  private:
    Sema& S;
    FPOptions OldFPFeaturesState;
    FPOptionsOverride OldOverrides;
    LangOptions::FPEvalMethodKind OldEvalMethod;
    SourceLocation OldFPPragmaLocation;
  };

  void addImplicitTypedef(StringRef Name, QualType T);

  bool WarnedStackExhausted = false;

  /// Increment when we find a reference; decrement when we find an ignored
  /// assignment.  Ultimately the value is 0 if every reference is an ignored
  /// assignment.
  llvm::DenseMap<const VarDecl *, int> RefsMinusAssignments;

private:
  Optional<std::unique_ptr<DarwinSDKInfo>> CachedDarwinSDKInfo;

  bool WarnedDarwinSDKInfoMissing = false;

public:
  Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
       TranslationUnitKind TUKind = TU_Complete,
       CodeCompleteConsumer *CompletionConsumer = nullptr);
  ~Sema();

  /// Perform initialization that occurs after the parser has been
  /// initialized but before it parses anything.
  void Initialize();

  /// 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; }

  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);

  void PrintStats() const;

  /// Warn that the stack is nearly exhausted.
  void warnStackExhausted(SourceLocation Loc);

  /// Run some code with "sufficient" stack space. (Currently, at least 256K is
  /// guaranteed). Produces a warning if we're low on stack space and allocates
  /// more in that case. Use this in code that may recurse deeply (for example,
  /// in template instantiation) to avoid stack overflow.
  void runWithSufficientStackSpace(SourceLocation Loc,
                                   llvm::function_ref<void()> Fn);

  /// Helper class that creates diagnostics with optional
  /// template instantiation stacks.
  ///
  /// This class provides a wrapper around the basic DiagnosticBuilder
  /// class that emits diagnostics. ImmediateDiagBuilder is
  /// responsible for emitting the diagnostic (as DiagnosticBuilder
  /// does) and, if the diagnostic comes from inside a template
  /// instantiation, printing the template instantiation stack as
  /// well.
  class ImmediateDiagBuilder : public DiagnosticBuilder {
    Sema &SemaRef;
    unsigned DiagID;

  public:
    ImmediateDiagBuilder(DiagnosticBuilder &DB, Sema &SemaRef, unsigned DiagID)
        : DiagnosticBuilder(DB), SemaRef(SemaRef), DiagID(DiagID) {}
    ImmediateDiagBuilder(DiagnosticBuilder &&DB, Sema &SemaRef, unsigned DiagID)
        : DiagnosticBuilder(DB), SemaRef(SemaRef), DiagID(DiagID) {}

    // This is a cunning lie. DiagnosticBuilder actually performs move
    // construction in its copy constructor (but due to varied uses, it's not
    // possible to conveniently express this as actual move construction). So
    // the default copy ctor here is fine, because the base class disables the
    // source anyway, so the user-defined ~ImmediateDiagBuilder is a safe no-op
    // in that case anwyay.
    ImmediateDiagBuilder(const ImmediateDiagBuilder &) = default;

    ~ImmediateDiagBuilder() {
      // If we aren't active, there is nothing to do.
      if (!isActive()) return3.36M;

      // Otherwise, we need to emit the diagnostic. First clear the diagnostic
      // builder itself so it won't emit the diagnostic in its own destructor.
      //
      // This seems wasteful, in that as written the DiagnosticBuilder dtor will
      // do its own needless checks to see if the diagnostic needs to be
      // emitted. However, because we take care to ensure that the builder
      // objects never escape, a sufficiently smart compiler will be able to
      // eliminate that code.
      Clear();

      // Dispatch to Sema to emit the diagnostic.
      SemaRef.EmitCurrentDiagnostic(DiagID);
    }

    /// Teach operator<< to produce an object of the correct type.
    template <typename T>
    friend const ImmediateDiagBuilder &
    operator<<(const ImmediateDiagBuilder &Diag, const T &Value) {
      const DiagnosticBuilder &BaseDiag = Diag;
      BaseDiag << Value;
      return Diag;
    }

    // It is necessary to limit this to rvalue reference to avoid calling this
    // function with a bitfield lvalue argument since non-const reference to
    // bitfield is not allowed.
    template <typename T, typename = typename std::enable_if<
                              !std::is_lvalue_reference<T>::value>::type>
    const ImmediateDiagBuilder &operator<<(T &&V) const {
      const DiagnosticBuilder &BaseDiag = *this;
      BaseDiag << std::move(V);
      return *this;
    }
  };

  /// A generic diagnostic builder for errors which may or may not be deferred.
  ///
  /// In CUDA, there exist constructs (e.g. variable-length arrays, try/catch)
  /// which are not allowed to appear inside __device__ functions and are
  /// allowed to appear in __host__ __device__ functions only if the host+device
  /// function is never codegen'ed.
  ///
  /// To handle this, we use the notion of "deferred diagnostics", where we
  /// attach a diagnostic to a FunctionDecl that's emitted iff it's codegen'ed.
  ///
  /// This class lets you emit either a regular diagnostic, a deferred
  /// diagnostic, or no diagnostic at all, according to an argument you pass to
  /// its constructor, thus simplifying the process of creating these "maybe
  /// deferred" diagnostics.
  class SemaDiagnosticBuilder {
  public:
    enum Kind {
      /// Emit no diagnostics.
      K_Nop,
      /// Emit the diagnostic immediately (i.e., behave like Sema::Diag()).
      K_Immediate,
      /// Emit the diagnostic immediately, and, if it's a warning or error, also
      /// emit a call stack showing how this function can be reached by an a
      /// priori known-emitted function.
      K_ImmediateWithCallStack,
      /// Create a deferred diagnostic, which is emitted only if the function
      /// it's attached to is codegen'ed.  Also emit a call stack as with
      /// K_ImmediateWithCallStack.
      K_Deferred
    };

    SemaDiagnosticBuilder(Kind K, SourceLocation Loc, unsigned DiagID,
                          FunctionDecl *Fn, Sema &S);
    SemaDiagnosticBuilder(SemaDiagnosticBuilder &&D);
    SemaDiagnosticBuilder(const SemaDiagnosticBuilder &) = default;
    ~SemaDiagnosticBuilder();

    bool isImmediate() const { return ImmediateDiag.has_value(); }

    /// Convertible to bool: True if we immediately emitted an error, false if
    /// we didn't emit an error or we created a deferred error.
    ///
    /// Example usage:
    ///
    ///   if (SemaDiagnosticBuilder(...) << foo << bar)
    ///     return ExprError();
    ///
    /// But see CUDADiagIfDeviceCode() and CUDADiagIfHostCode() -- you probably
    /// want to use these instead of creating a SemaDiagnosticBuilder yourself.
    operator bool() const { return isImmediate(); }

    template <typename T>
    friend const SemaDiagnosticBuilder &
    operator<<(const SemaDiagnosticBuilder &Diag, const T &Value) {
      if (Diag.ImmediateDiag)
        *Diag.ImmediateDiag << Value;
      else if (Diag.PartialDiagId)
        Diag.S.DeviceDeferredDiags[Diag.Fn][*Diag.PartialDiagId].second
            << Value;
      return Diag;
      

Coverage Report

Created: 2022-07-16 07:03