clang/lib/Serialization/ASTReaderDecl.cpp

//===- ASTReaderDecl.cpp - Decl Deserialization ---------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the ASTReader::readDeclRecord method, which is the
// entrypoint for loading a decl.
//
//===----------------------------------------------------------------------===//

#include "ASTCommon.h"
#include "ASTReaderInternals.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/AttrIterator.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclFriend.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclOpenMP.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/DeclVisitor.h"
#include "clang/AST/DeclarationName.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExternalASTSource.h"
#include "clang/AST/LambdaCapture.h"
#include "clang/AST/NestedNameSpecifier.h"
#include "clang/AST/OpenMPClause.h"
#include "clang/AST/Redeclarable.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/TemplateBase.h"
#include "clang/AST/Type.h"
#include "clang/AST/UnresolvedSet.h"
#include "clang/Basic/AttrKinds.h"
#include "clang/Basic/ExceptionSpecificationType.h"
#include "clang/Basic/IdentifierTable.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/Lambda.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/Linkage.h"
#include "clang/Basic/Module.h"
#include "clang/Basic/PragmaKinds.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/Specifiers.h"
#include "clang/Sema/IdentifierResolver.h"
#include "clang/Serialization/ASTBitCodes.h"
#include "clang/Serialization/ASTRecordReader.h"
#include "clang/Serialization/ContinuousRangeMap.h"
#include "clang/Serialization/ModuleFile.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Bitstream/BitstreamReader.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/SaveAndRestore.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstring>
#include <string>
#include <utility>

using namespace clang;
using namespace serialization;

//===----------------------------------------------------------------------===//
// Declaration deserialization
//===----------------------------------------------------------------------===//

namespace clang {

  class ASTDeclReader : public DeclVisitor<ASTDeclReader, void> {
    ASTReader &Reader;
    ASTRecordReader &Record;
    ASTReader::RecordLocation Loc;
    const DeclID ThisDeclID;
    const SourceLocation ThisDeclLoc;

    using RecordData = ASTReader::RecordData;

    TypeID DeferredTypeID = 0;
    unsigned AnonymousDeclNumber;
    GlobalDeclID NamedDeclForTagDecl = 0;
    IdentifierInfo *TypedefNameForLinkage = nullptr;

    bool HasPendingBody = false;

    ///A flag to carry the information for a decl from the entity is
    /// used. We use it to delay the marking of the canonical decl as used until
    /// the entire declaration is deserialized and merged.
    bool IsDeclMarkedUsed = false;

    uint64_t GetCurrentCursorOffset();

    uint64_t ReadLocalOffset() {
      uint64_t LocalOffset = Record.readInt();
      assert(LocalOffset < Loc.Offset && "offset point after current record");
      return LocalOffset ? Loc.Offset - LocalOffset : 0;
    }

    uint64_t ReadGlobalOffset() {
      uint64_t Local = ReadLocalOffset();
      return Local ? Record.getGlobalBitOffset(Local) : 0;
    }

    SourceLocation readSourceLocation() {
      return Record.readSourceLocation();
    }

    SourceRange readSourceRange() {
      return Record.readSourceRange();
    }

    TypeSourceInfo *readTypeSourceInfo() {
      return Record.readTypeSourceInfo();
    }

    serialization::DeclID readDeclID() {
      return Record.readDeclID();
    }

    std::string readString() {
      return Record.readString();
    }

    void readDeclIDList(SmallVectorImpl<DeclID> &IDs) {
      for (unsigned I = 0, Size = Record.readInt(); I != Size; ++I)
        IDs.push_back(readDeclID());
    }

    Decl *readDecl() {
      return Record.readDecl();
    }

    template<typename T>
    T *readDeclAs() {
      return Record.readDeclAs<T>();
    }

    serialization::SubmoduleID readSubmoduleID() {
      if (Record.getIdx() == Record.size())
        return 0;

      return Record.getGlobalSubmoduleID(Record.readInt());
    }

    Module *readModule() {
      return Record.getSubmodule(readSubmoduleID());
    }

    void ReadCXXRecordDefinition(CXXRecordDecl *D, bool Update);
    void ReadCXXDefinitionData(struct CXXRecordDecl::DefinitionData &Data,
                               const CXXRecordDecl *D);
    void MergeDefinitionData(CXXRecordDecl *D,
                             struct CXXRecordDecl::DefinitionData &&NewDD);
    void ReadObjCDefinitionData(struct ObjCInterfaceDecl::DefinitionData &Data);
    void MergeDefinitionData(ObjCInterfaceDecl *D,
                             struct ObjCInterfaceDecl::DefinitionData &&NewDD);
    void ReadObjCDefinitionData(struct ObjCProtocolDecl::DefinitionData &Data);
    void MergeDefinitionData(ObjCProtocolDecl *D,
                             struct ObjCProtocolDecl::DefinitionData &&NewDD);

    static DeclContext *getPrimaryDCForAnonymousDecl(DeclContext *LexicalDC);

    static NamedDecl *getAnonymousDeclForMerging(ASTReader &Reader,
                                                 DeclContext *DC,
                                                 unsigned Index);
    static void setAnonymousDeclForMerging(ASTReader &Reader, DeclContext *DC,
                                           unsigned Index, NamedDecl *D);

    /// Results from loading a RedeclarableDecl.
    class RedeclarableResult {
      Decl *MergeWith;
      GlobalDeclID FirstID;
      bool IsKeyDecl;

    public:
      RedeclarableResult(Decl *MergeWith, GlobalDeclID FirstID, bool IsKeyDecl)
          : MergeWith(MergeWith), FirstID(FirstID), IsKeyDecl(IsKeyDecl) {}

      /// Retrieve the first ID.
      GlobalDeclID getFirstID() const { return FirstID; }

      /// Is this declaration a key declaration?
      bool isKeyDecl() const { return IsKeyDecl; }

      /// Get a known declaration that this should be merged with, if
      /// any.
      Decl *getKnownMergeTarget() const { return MergeWith; }
    };

    /// Class used to capture the result of searching for an existing
    /// declaration of a specific kind and name, along with the ability
    /// to update the place where this result was found (the declaration
    /// chain hanging off an identifier or the DeclContext we searched in)
    /// if requested.
    class FindExistingResult {
      ASTReader &Reader;
      NamedDecl *New = nullptr;
      NamedDecl *Existing = nullptr;
      bool AddResult = false;
      unsigned AnonymousDeclNumber = 0;
      IdentifierInfo *TypedefNameForLinkage = nullptr;

    public:
      FindExistingResult(ASTReader &Reader) : Reader(Reader) {}

      FindExistingResult(ASTReader &Reader, NamedDecl *New, NamedDecl *Existing,
                         unsigned AnonymousDeclNumber,
                         IdentifierInfo *TypedefNameForLinkage)
          : Reader(Reader), New(New), Existing(Existing), AddResult(true),
            AnonymousDeclNumber(AnonymousDeclNumber),
            TypedefNameForLinkage(TypedefNameForLinkage) {}

      FindExistingResult(FindExistingResult &&Other)
          : Reader(Other.Reader), New(Other.New), Existing(Other.Existing),
            AddResult(Other.AddResult),
            AnonymousDeclNumber(Other.AnonymousDeclNumber),
            TypedefNameForLinkage(Other.TypedefNameForLinkage) {
        Other.AddResult = false;
      }

      FindExistingResult &operator=(FindExistingResult &&) = delete;
      ~FindExistingResult();

      /// Suppress the addition of this result into the known set of
      /// names.
      void suppress() { AddResult = false; }

      operator NamedDecl*() const { return Existing; }

      template<typename T>
      operator T*() const { return dyn_cast_or_null<T>(Existing); }
    };

    static DeclContext *getPrimaryContextForMerging(ASTReader &Reader,
                                                    DeclContext *DC);
    FindExistingResult findExisting(NamedDecl *D);

  public:
    ASTDeclReader(ASTReader &Reader, ASTRecordReader &Record,
                  ASTReader::RecordLocation Loc,
                  DeclID thisDeclID, SourceLocation ThisDeclLoc)
        : Reader(Reader), Record(Record), Loc(Loc), ThisDeclID(thisDeclID),
          ThisDeclLoc(ThisDeclLoc) {}

    template <typename T> static
    void AddLazySpecializations(T *D,
                                SmallVectorImpl<serialization::DeclID>& IDs) {
      if (IDs.empty())
        return;

      // FIXME: We should avoid this pattern of getting the ASTContext.
      ASTContext &C = D->getASTContext();

      auto *&LazySpecializations = D->getCommonPtr()->LazySpecializations;

      if (auto &Old = LazySpecializations) {
        IDs.insert(IDs.end(), Old + 1, Old + 1 + Old[0]);
        llvm::sort(IDs);
        IDs.erase(std::unique(IDs.begin(), IDs.end()), IDs.end());
      }

      auto *Result = new (C) serialization::DeclID[1 + IDs.size()];
      *Result = IDs.size();
      std::copy(IDs.begin(), IDs.end(), Result + 1);

      LazySpecializations = Result;
    }

    template <typename DeclT>
    static Decl *getMostRecentDeclImpl(Redeclarable<DeclT> *D);
    static Decl *getMostRecentDeclImpl(...);
    static Decl *getMostRecentDecl(Decl *D);

    static void mergeInheritableAttributes(ASTReader &Reader, Decl *D,
                                           Decl *Previous);

    template <typename DeclT>
    static void attachPreviousDeclImpl(ASTReader &Reader,
                                       Redeclarable<DeclT> *D, Decl *Previous,
                                       Decl *Canon);
    static void attachPreviousDeclImpl(ASTReader &Reader, ...);
    static void attachPreviousDecl(ASTReader &Reader, Decl *D, Decl *Previous,
                                   Decl *Canon);

    template <typename DeclT>
    static void attachLatestDeclImpl(Redeclarable<DeclT> *D, Decl *Latest);
    static void attachLatestDeclImpl(...);
    static void attachLatestDecl(Decl *D, Decl *latest);

    template <typename DeclT>
    static void markIncompleteDeclChainImpl(Redeclarable<DeclT> *D);
    static void markIncompleteDeclChainImpl(...);

    /// Determine whether this declaration has a pending body.
    bool hasPendingBody() const { return HasPendingBody; }

    void ReadFunctionDefinition(FunctionDecl *FD);
    void Visit(Decl *D);

    void UpdateDecl(Decl *D, SmallVectorImpl<serialization::DeclID> &);

    static void setNextObjCCategory(ObjCCategoryDecl *Cat,
                                    ObjCCategoryDecl *Next) {
      Cat->NextClassCategory = Next;
    }

    void VisitDecl(Decl *D);
    void VisitPragmaCommentDecl(PragmaCommentDecl *D);
    void VisitPragmaDetectMismatchDecl(PragmaDetectMismatchDecl *D);
    void VisitTranslationUnitDecl(TranslationUnitDecl *TU);
    void VisitNamedDecl(NamedDecl *ND);
    void VisitLabelDecl(LabelDecl *LD);
    void VisitNamespaceDecl(NamespaceDecl *D);
    void VisitUsingDirectiveDecl(UsingDirectiveDecl *D);
    void VisitNamespaceAliasDecl(NamespaceAliasDecl *D);
    void VisitTypeDecl(TypeDecl *TD);
    RedeclarableResult VisitTypedefNameDecl(TypedefNameDecl *TD);
    void VisitTypedefDecl(TypedefDecl *TD);
    void VisitTypeAliasDecl(TypeAliasDecl *TD);
    void VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D);
    void VisitUnresolvedUsingIfExistsDecl(UnresolvedUsingIfExistsDecl *D);
    RedeclarableResult VisitTagDecl(TagDecl *TD);
    void VisitEnumDecl(EnumDecl *ED);
    RedeclarableResult VisitRecordDeclImpl(RecordDecl *RD);
    void VisitRecordDecl(RecordDecl *RD);
    RedeclarableResult VisitCXXRecordDeclImpl(CXXRecordDecl *D);
    void VisitCXXRecordDecl(CXXRecordDecl *D) { VisitCXXRecordDeclImpl(D); }
    RedeclarableResult VisitClassTemplateSpecializationDeclImpl(
                                            ClassTemplateSpecializationDecl *D);

    void VisitClassTemplateSpecializationDecl(
        ClassTemplateSpecializationDecl *D) {
      VisitClassTemplateSpecializationDeclImpl(D);
    }

    void VisitClassTemplatePartialSpecializationDecl(
                                     ClassTemplatePartialSpecializationDecl *D);
    void VisitClassScopeFunctionSpecializationDecl(
                                       ClassScopeFunctionSpecializationDecl *D);
    RedeclarableResult
    VisitVarTemplateSpecializationDeclImpl(VarTemplateSpecializationDecl *D);

    void VisitVarTemplateSpecializationDecl(VarTemplateSpecializationDecl *D) {
      VisitVarTemplateSpecializationDeclImpl(D);
    }

    void VisitVarTemplatePartialSpecializationDecl(
        VarTemplatePartialSpecializationDecl *D);
    void VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D);
    void VisitValueDecl(ValueDecl *VD);
    void VisitEnumConstantDecl(EnumConstantDecl *ECD);
    void VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
    void VisitDeclaratorDecl(DeclaratorDecl *DD);
    void VisitFunctionDecl(FunctionDecl *FD);
    void VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *GD);
    void VisitCXXMethodDecl(CXXMethodDecl *D);
    void VisitCXXConstructorDecl(CXXConstructorDecl *D);
    void VisitCXXDestructorDecl(CXXDestructorDecl *D);
    void VisitCXXConversionDecl(CXXConversionDecl *D);
    void VisitFieldDecl(FieldDecl *FD);
    void VisitMSPropertyDecl(MSPropertyDecl *FD);
    void VisitMSGuidDecl(MSGuidDecl *D);
    void VisitTemplateParamObjectDecl(TemplateParamObjectDecl *D);
    void VisitIndirectFieldDecl(IndirectFieldDecl *FD);
    RedeclarableResult VisitVarDeclImpl(VarDecl *D);
    void VisitVarDecl(VarDecl *VD) { VisitVarDeclImpl(VD); }
    void VisitImplicitParamDecl(ImplicitParamDecl *PD);
    void VisitParmVarDecl(ParmVarDecl *PD);
    void VisitDecompositionDecl(DecompositionDecl *DD);
    void VisitBindingDecl(BindingDecl *BD);
    void VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D);
    DeclID VisitTemplateDecl(TemplateDecl *D);
    void VisitConceptDecl(ConceptDecl *D);
    void VisitRequiresExprBodyDecl(RequiresExprBodyDecl *D);
    RedeclarableResult VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D);
    void VisitClassTemplateDecl(ClassTemplateDecl *D);
    void VisitBuiltinTemplateDecl(BuiltinTemplateDecl *D);
    void VisitVarTemplateDecl(VarTemplateDecl *D);
    void VisitFunctionTemplateDecl(FunctionTemplateDecl *D);
    void VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D);
    void VisitTypeAliasTemplateDecl(TypeAliasTemplateDecl *D);
    void VisitUsingDecl(UsingDecl *D);
    void VisitUsingEnumDecl(UsingEnumDecl *D);
    void VisitUsingPackDecl(UsingPackDecl *D);
    void VisitUsingShadowDecl(UsingShadowDecl *D);
    void VisitConstructorUsingShadowDecl(ConstructorUsingShadowDecl *D);
    void VisitLinkageSpecDecl(LinkageSpecDecl *D);
    void VisitExportDecl(ExportDecl *D);
    void VisitFileScopeAsmDecl(FileScopeAsmDecl *AD);
    void VisitImportDecl(ImportDecl *D);
    void VisitAccessSpecDecl(AccessSpecDecl *D);
    void VisitFriendDecl(FriendDecl *D);
    void VisitFriendTemplateDecl(FriendTemplateDecl *D);
    void VisitStaticAssertDecl(StaticAssertDecl *D);
    void VisitBlockDecl(BlockDecl *BD);
    void VisitCapturedDecl(CapturedDecl *CD);
    void VisitEmptyDecl(EmptyDecl *D);
    void VisitLifetimeExtendedTemporaryDecl(LifetimeExtendedTemporaryDecl *D);

    std::pair<uint64_t, uint64_t> VisitDeclContext(DeclContext *DC);

    template<typename T>
    RedeclarableResult VisitRedeclarable(Redeclarable<T> *D);

    template<typename T>
    void mergeRedeclarable(Redeclarable<T> *D, RedeclarableResult &Redecl,
                           DeclID TemplatePatternID = 0);

    template<typename T>
    void mergeRedeclarable(Redeclarable<T> *D, T *Existing,
                           RedeclarableResult &Redecl,
                           DeclID TemplatePatternID = 0);

    template<typename T>
    void mergeMergeable(Mergeable<T> *D);

    void mergeMergeable(LifetimeExtendedTemporaryDecl *D);

    void mergeTemplatePattern(RedeclarableTemplateDecl *D,
                              RedeclarableTemplateDecl *Existing,
                              DeclID DsID, bool IsKeyDecl);

    ObjCTypeParamList *ReadObjCTypeParamList();

    // FIXME: Reorder according to DeclNodes.td?
    void VisitObjCMethodDecl(ObjCMethodDecl *D);
    void VisitObjCTypeParamDecl(ObjCTypeParamDecl *D);
    void VisitObjCContainerDecl(ObjCContainerDecl *D);
    void VisitObjCInterfaceDecl(ObjCInterfaceDecl *D);
    void VisitObjCIvarDecl(ObjCIvarDecl *D);
    void VisitObjCProtocolDecl(ObjCProtocolDecl *D);
    void VisitObjCAtDefsFieldDecl(ObjCAtDefsFieldDecl *D);
    void VisitObjCCategoryDecl(ObjCCategoryDecl *D);
    void VisitObjCImplDecl(ObjCImplDecl *D);
    void VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D);
    void VisitObjCImplementationDecl(ObjCImplementationDecl *D);
    void VisitObjCCompatibleAliasDecl(ObjCCompatibleAliasDecl *D);
    void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
    void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
    void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
    void VisitOMPAllocateDecl(OMPAllocateDecl *D);
    void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
    void VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D);
    void VisitOMPRequiresDecl(OMPRequiresDecl *D);
    void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
  };

} // namespace clang

namespace {

/// Iterator over the redeclarations of a declaration that have already
/// been merged into the same redeclaration chain.
template<typename DeclT>
class MergedRedeclIterator {
  DeclT *Start;
  DeclT *Canonical = nullptr;
  DeclT *Current = nullptr;

public:
  MergedRedeclIterator() = default;
  MergedRedeclIterator(DeclT *Start) : Start(Start), Current(Start) {}

  DeclT *operator*() { return Current; }

  MergedRedeclIterator &operator++() {
    if (Current->isFirstDecl()) {
      Canonical = Current;
      Current = Current->getMostRecentDecl();
    } else
      Current = Current->getPreviousDecl();

    // If we started in the merged portion, we'll reach our start position
    // eventually. Otherwise, we'll never reach it, but the second declaration
    // we reached was the canonical declaration, so stop when we see that one
    // again.
    if (Current == Start || Current == Canonical)
      Current = nullptr;
    return *this;
  }

  friend bool operator!=(const MergedRedeclIterator &A,
                         const MergedRedeclIterator &B) {
    return A.Current != B.Current;
  }
};

} // namespace

template <typename DeclT>
static llvm::iterator_range<MergedRedeclIterator<DeclT>>
merged_redecls(DeclT *D) {
  return llvm::make_range(MergedRedeclIterator<DeclT>(D),
                          MergedRedeclIterator<DeclT>());
}

uint64_t ASTDeclReader::GetCurrentCursorOffset() {
  return Loc.F->DeclsCursor.GetCurrentBitNo() + Loc.F->GlobalBitOffset;
}

void ASTDeclReader::ReadFunctionDefinition(FunctionDecl *FD) {
  if (Record.readInt()) {
    Reader.DefinitionSource[FD] =
        Loc.F->Kind == ModuleKind::MK_MainFile ||
        Reader.getContext().getLangOpts().BuildingPCHWithObjectFile;
  }
  if (auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
    CD->setNumCtorInitializers(Record.readInt());
    if (CD->getNumCtorInitializers())
      CD->CtorInitializers = ReadGlobalOffset();
  }
  // Store the offset of the body so we can lazily load it later.
  Reader.PendingBodies[FD] = GetCurrentCursorOffset();
  HasPendingBody = true;
}

void ASTDeclReader::Visit(Decl *D) {
  DeclVisitor<ASTDeclReader, void>::Visit(D);

  // At this point we have deserialized and merged the decl and it is safe to
  // update its canonical decl to signal that the entire entity is used.
  D->getCanonicalDecl()->Used |= IsDeclMarkedUsed;
  IsDeclMarkedUsed = false;

  if (auto *DD = dyn_cast<DeclaratorDecl>(D)) {
    if (auto *TInfo = DD->getTypeSourceInfo())
      Record.readTypeLoc(TInfo->getTypeLoc());
  }

  if (auto *TD = dyn_cast<TypeDecl>(D)) {
    // We have a fully initialized TypeDecl. Read its type now.
    TD->setTypeForDecl(Reader.GetType(DeferredTypeID).getTypePtrOrNull());

    // If this is a tag declaration with a typedef name for linkage, it's safe
    // to load that typedef now.
    if (NamedDeclForTagDecl)
      cast<TagDecl>(D)->TypedefNameDeclOrQualifier =
          cast<TypedefNameDecl>(Reader.GetDecl(NamedDeclForTagDecl));
  } else if (auto *ID = dyn_cast<ObjCInterfaceDecl>(D)) {
    // if we have a fully initialized TypeDecl, we can safely read its type now.
    ID->TypeForDecl = Reader.GetType(DeferredTypeID).getTypePtrOrNull();
  } else if (auto *FD = dyn_cast<FunctionDecl>(D)) {
    // FunctionDecl's body was written last after all other Stmts/Exprs.
    // We only read it if FD doesn't already have a body (e.g., from another
    // module).
    // FIXME: Can we diagnose ODR violations somehow?
    if (Record.readInt())
      ReadFunctionDefinition(FD);
  }
}

void ASTDeclReader::VisitDecl(Decl *D) {
  if (D->isTemplateParameter() || D->isTemplateParameterPack() ||
      isa<ParmVarDecl>(D) || isa<ObjCTypeParamDecl>(D)) {
    // We don't want to deserialize the DeclContext of a template
    // parameter or of a parameter of a function template immediately.   These
    // entities might be used in the formulation of its DeclContext (for
    // example, a function parameter can be used in decltype() in trailing
    // return type of the function).  Use the translation unit DeclContext as a
    // placeholder.
    GlobalDeclID SemaDCIDForTemplateParmDecl = readDeclID();
    GlobalDeclID LexicalDCIDForTemplateParmDecl = readDeclID();
    if (!LexicalDCIDForTemplateParmDecl)
      LexicalDCIDForTemplateParmDecl = SemaDCIDForTemplateParmDecl;
    Reader.addPendingDeclContextInfo(D,
                                     SemaDCIDForTemplateParmDecl,
                                     LexicalDCIDForTemplateParmDecl);
    D->setDeclContext(Reader.getContext().getTranslationUnitDecl());
  } else {
    auto *SemaDC = readDeclAs<DeclContext>();
    auto *LexicalDC = readDeclAs<DeclContext>();
    if (!LexicalDC)
      LexicalDC = SemaDC;
    DeclContext *MergedSemaDC = Reader.MergedDeclContexts.lookup(SemaDC);
    // Avoid calling setLexicalDeclContext() directly because it uses
    // Decl::getASTContext() internally which is unsafe during derialization.
    D->setDeclContextsImpl(MergedSemaDC ? MergedSemaDC : SemaDC, LexicalDC,
                           Reader.getContext());
  }
  D->setLocation(ThisDeclLoc);
  D->InvalidDecl = Record.readInt();
  if (Record.readInt()) { // hasAttrs
    AttrVec Attrs;
    Record.readAttributes(Attrs);
    // Avoid calling setAttrs() directly because it uses Decl::getASTContext()
    // internally which is unsafe during derialization.
    D->setAttrsImpl(Attrs, Reader.getContext());
  }
  D->setImplicit(Record.readInt());
  D->Used = Record.readInt();
  IsDeclMarkedUsed |= D->Used;
  D->setReferenced(Record.readInt());
  D->setTopLevelDeclInObjCContainer(Record.readInt());
  D->setAccess((AccessSpecifier)Record.readInt());
  D->FromASTFile = true;
  bool ModulePrivate = Record.readInt();

  // Determine whether this declaration is part of a (sub)module. If so, it
  // may not yet be visible.
  if (unsigned SubmoduleID = readSubmoduleID()) {
    // Store the owning submodule ID in the declaration.
    D->setModuleOwnershipKind(
        ModulePrivate ? Decl::ModuleOwnershipKind::ModulePrivate
                      : Decl::ModuleOwnershipKind::VisibleWhenImported);
    D->setOwningModuleID(SubmoduleID);

    if (ModulePrivate) {
      // Module-private declarations are never visible, so there is no work to
      // do.
    } else if (Reader.getContext().getLangOpts().ModulesLocalVisibility) {
      // If local visibility is being tracked, this declaration will become
      // hidden and visible as the owning module does.
    } else if (Module *Owner = Reader.getSubmodule(SubmoduleID)) {
      // Mark the declaration as visible when its owning module becomes visible.
      if (Owner->NameVisibility == Module::AllVisible)
        D->setVisibleDespiteOwningModule();
      else
        Reader.HiddenNamesMap[Owner].push_back(D);
    }
  } else if (ModulePrivate) {
    D->setModuleOwnershipKind(Decl::ModuleOwnershipKind::ModulePrivate);
  }
}

void ASTDeclReader::VisitPragmaCommentDecl(PragmaCommentDecl *D) {
  VisitDecl(D);
  D->setLocation(readSourceLocation());
  D->CommentKind = (PragmaMSCommentKind)Record.readInt();
  std::string Arg = readString();
  memcpy(D->getTrailingObjects<char>(), Arg.data(), Arg.size());
  D->getTrailingObjects<char>()[Arg.size()] = '\0';
}

void ASTDeclReader::VisitPragmaDetectMismatchDecl(PragmaDetectMismatchDecl *D) {
  VisitDecl(D);
  D->setLocation(readSourceLocation());
  std::string Name = readString();
  memcpy(D->getTrailingObjects<char>(), Name.data(), Name.size());
  D->getTrailingObjects<char>()[Name.size()] = '\0';

  D->ValueStart = Name.size() + 1;
  std::string Value = readString();
  memcpy(D->getTrailingObjects<char>() + D->ValueStart, Value.data(),
         Value.size());
  D->getTrailingObjects<char>()[D->ValueStart + Value.size()] = '\0';
}

void ASTDeclReader::VisitTranslationUnitDecl(TranslationUnitDecl *TU) {
  llvm_unreachable("Translation units are not serialized");
}

void ASTDeclReader::VisitNamedDecl(NamedDecl *ND) {
  VisitDecl(ND);
  ND->setDeclName(Record.readDeclarationName());
  AnonymousDeclNumber = Record.readInt();
}

void ASTDeclReader::VisitTypeDecl(TypeDecl *TD) {
  VisitNamedDecl(TD);
  TD->setLocStart(readSourceLocation());
  // Delay type reading until after we have fully initialized the decl.
  DeferredTypeID = Record.getGlobalTypeID(Record.readInt());
}

ASTDeclReader::RedeclarableResult
ASTDeclReader::VisitTypedefNameDecl(TypedefNameDecl *TD) {
  RedeclarableResult Redecl = VisitRedeclarable(TD);
  VisitTypeDecl(TD);
  TypeSourceInfo *TInfo = readTypeSourceInfo();
  if (Record.readInt()) { // isModed
    QualType modedT = Record.readType();
    TD->setModedTypeSourceInfo(TInfo, modedT);
  } else
    TD->setTypeSourceInfo(TInfo);
  // Read and discard the declaration for which this is a typedef name for
  // linkage, if it exists. We cannot rely on our type to pull in this decl,
  // because it might have been merged with a type from another module and
  // thus might not refer to our version of the declaration.
  readDecl();
  return Redecl;
}

void ASTDeclReader::VisitTypedefDecl(TypedefDecl *TD) {
  RedeclarableResult Redecl = VisitTypedefNameDecl(TD);
  mergeRedeclarable(TD, Redecl);
}

void ASTDeclReader::VisitTypeAliasDecl(TypeAliasDecl *TD) {
  RedeclarableResult Redecl = VisitTypedefNameDecl(TD);
  if (auto *Template = readDeclAs<TypeAliasTemplateDecl>())
    // Merged when we merge the template.
    TD->setDescribedAliasTemplate(Template);
  else
    mergeRedeclarable(TD, Redecl);
}

ASTDeclReader::RedeclarableResult ASTDeclReader::VisitTagDecl(TagDecl *TD) {
  RedeclarableResult Redecl = VisitRedeclarable(TD);
  VisitTypeDecl(TD);

  TD->IdentifierNamespace = Record.readInt();
  TD->setTagKind((TagDecl::TagKind)Record.readInt());
  if (!isa<CXXRecordDecl>(TD))
    TD->setCompleteDefinition(Record.readInt());
  TD->setEmbeddedInDeclarator(Record.readInt());
  TD->setFreeStanding(Record.readInt());
  TD->setCompleteDefinitionRequired(Record.readInt());
  TD->setBraceRange(readSourceRange());

  switch (Record.readInt()) {
  case 0:
    break;
  case 1: { // ExtInfo
    auto *Info = new (Reader.getContext()) TagDecl::ExtInfo();
    Record.readQualifierInfo(*Info);
    TD->TypedefNameDeclOrQualifier = Info;
    break;
  }
  case 2: // TypedefNameForAnonDecl
    NamedDeclForTagDecl = readDeclID();
    TypedefNameForLinkage = Record.readIdentifier();
    break;
  default:
    llvm_unreachable("unexpected tag info kind");
  }

  if (!isa<CXXRecordDecl>(TD))
    mergeRedeclarable(TD, Redecl);
  return Redecl;
}

void ASTDeclReader::VisitEnumDecl(EnumDecl *ED) {
  VisitTagDecl(ED);
  if (TypeSourceInfo *TI = readTypeSourceInfo())
    ED->setIntegerTypeSourceInfo(TI);
  else
    ED->setIntegerType(Record.readType());
  ED->setPromotionType(Record.readType());
  ED->setNumPositiveBits(Record.readInt());
  ED->setNumNegativeBits(Record.readInt());
  ED->setScoped(Record.readInt());
  ED->setScopedUsingClassTag(Record.readInt());
  ED->setFixed(Record.readInt());

  ED->setHasODRHash(true);
  ED->ODRHash = Record.readInt();

  // If this is a definition subject to the ODR, and we already have a
  // definition, merge this one into it.
  if (ED->isCompleteDefinition() &&
      Reader.getContext().getLangOpts().Modules &&
      Reader.getContext().getLangOpts().CPlusPlus) {
    EnumDecl *&OldDef = Reader.EnumDefinitions[ED->getCanonicalDecl()];
    if (!OldDef) {
      // This is the first time we've seen an imported definition. Look for a
      // local definition before deciding that we are the first definition.
      for (auto *D : merged_redecls(ED->getCanonicalDecl())) {
        if (!D->isFromASTFile() && D->isCompleteDefinition()) {
          OldDef = D;
          break;
        }
      }
    }
    if (OldDef) {
      Reader.MergedDeclContexts.insert(std::make_pair(ED, OldDef));
      ED->setCompleteDefinition(false);
      Reader.mergeDefinitionVisibility(OldDef, ED);
      if (OldDef->getODRHash() != ED->getODRHash())
        Reader.PendingEnumOdrMergeFailures[OldDef].push_back(ED);
    } else {
      OldDef = ED;
    }
  }

  if (auto *InstED = readDeclAs<EnumDecl>()) {
    auto TSK = (TemplateSpecializationKind)Record.readInt();
    SourceLocation POI = readSourceLocation();
    ED->setInstantiationOfMemberEnum(Reader.getContext(), InstED, TSK);
    ED->getMemberSpecializationInfo()->setPointOfInstantiation(POI);
  }
}

ASTDeclReader::RedeclarableResult
ASTDeclReader::VisitRecordDeclImpl(RecordDecl *RD) {
  RedeclarableResult Redecl = VisitTagDecl(RD);
  RD->setHasFlexibleArrayMember(Record.readInt());
  RD->setAnonymousStructOrUnion(Record.readInt());
  RD->setHasObjectMember(Record.readInt());
  RD->setHasVolatileMember(Record.readInt());
  RD->setNonTrivialToPrimitiveDefaultInitialize(Record.readInt());
  RD->setNonTrivialToPrimitiveCopy(Record.readInt());
  RD->setNonTrivialToPrimitiveDestroy(Record.readInt());
  RD->setHasNonTrivialToPrimitiveDefaultInitializeCUnion(Record.readInt());
  RD->setHasNonTrivialToPrimitiveDestructCUnion(Record.readInt());
  RD->setHasNonTrivialToPrimitiveCopyCUnion(Record.readInt());
  RD->setParamDestroyedInCallee(Record.readInt());
  RD->setArgPassingRestrictions((RecordDecl::ArgPassingKind)Record.readInt());
  return Redecl;
}

void ASTDeclReader::VisitRecordDecl(RecordDecl *RD) {
  VisitRecordDeclImpl(RD);

  // Maintain the invariant of a redeclaration chain containing only
  // a single definition.
  if (RD->isCompleteDefinition()) {
    RecordDecl *Canon = static_cast<RecordDecl *>(RD->getCanonicalDecl());
    RecordDecl *&OldDef = Reader.RecordDefinitions[Canon];
    if (!OldDef) {
      // This is the first time we've seen an imported definition. Look for a
      // local definition before deciding that we are the first definition.
      for (auto *D : merged_redecls(Canon)) {
        if (!D->isFromASTFile() && D->isCompleteDefinition()) {
          OldDef = D;
          break;
        }
      }
    }
    if (OldDef) {
      Reader.MergedDeclContexts.insert(std::make_pair(RD, OldDef));
      RD->setCompleteDefinition(false);
      Reader.mergeDefinitionVisibility(OldDef, RD);
    } else {
      OldDef = RD;
    }
  }
}

void ASTDeclReader::VisitValueDecl(ValueDecl *VD) {
  VisitNamedDecl(VD);
  // For function declarations, defer reading the type in case the function has
  // a deduced return type that references an entity declared within the
  // function.
  if (isa<FunctionDecl>(VD))
    DeferredTypeID = Record.getGlobalTypeID(Record.readInt());
  else
    VD->setType(Record.readType());
}

void ASTDeclReader::VisitEnumConstantDecl(EnumConstantDecl *ECD) {
  VisitValueDecl(ECD);
  if (Record.readInt())
    ECD->setInitExpr(Record.readExpr());
  ECD->setInitVal(Record.readAPSInt());
  mergeMergeable(ECD);
}

void ASTDeclReader::VisitDeclaratorDecl(DeclaratorDecl *DD) {
  VisitValueDecl(DD);
  DD->setInnerLocStart(readSourceLocation());
  if (Record.readInt()) { // hasExtInfo
    auto *Info = new (Reader.getContext()) DeclaratorDecl::ExtInfo();
    Record.readQualifierInfo(*Info);
    Info->TrailingRequiresClause = Record.readExpr();
    DD->DeclInfo = Info;
  }
  QualType TSIType = Record.readType();
  DD->setTypeSourceInfo(
      TSIType.isNull() ? nullptr
                       : Reader.getContext().CreateTypeSourceInfo(TSIType));
}

void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
  RedeclarableResult Redecl = VisitRedeclarable(FD);
  VisitDeclaratorDecl(FD);

  // Attach a type to this function. Use the real type if possible, but fall
  // back to the type as written if it involves a deduced return type.
  if (FD->getTypeSourceInfo() &&
      FD->getTypeSourceInfo()->getType()->castAs<FunctionType>()
                             ->getReturnType()->getContainedAutoType()) {
    // We'll set up the real type in Visit, once we've finished loading the
    // function.
    FD->setType(FD->getTypeSourceInfo()->getType());
    Reader.PendingFunctionTypes.push_back({FD, DeferredTypeID});
  } else {
    FD->setType(Reader.GetType(DeferredTypeID));
  }
  DeferredTypeID = 0;

  FD->DNLoc = Record.readDeclarationNameLoc(FD->getDeclName());
  FD->IdentifierNamespace = Record.readInt();

  // FunctionDecl's body is handled last at ASTDeclReader::Visit,
  // after everything else is read.

  FD->setStorageClass(static_cast<StorageClass>(Record.readInt()));
  FD->setInlineSpecified(Record.readInt());
  FD->setImplicitlyInline(Record.readInt());
  FD->setVirtualAsWritten(Record.readInt());
  // We defer calling `FunctionDecl::setPure()` here as for methods of
  // `CXXTemplateSpecializationDecl`s, we may not have connected up the
  // definition (which is required for `setPure`).
  const bool Pure = Record.readInt();
  FD->setHasInheritedPrototype(Record.readInt());
  FD->setHasWrittenPrototype(Record.readInt());
  FD->setDeletedAsWritten(Record.readInt());
  FD->setTrivial(Record.readInt());
  FD->setTrivialForCall(Record.readInt());
  FD->setDefaulted(Record.readInt());
  FD->setExplicitlyDefaulted(Record.readInt());
  FD->setHasImplicitReturnZero(Record.readInt());
  FD->setConstexprKind(static_cast<ConstexprSpecKind>(Record.readInt()));
  FD->setUsesSEHTry(Record.readInt());
  FD->setHasSkippedBody(Record.readInt());
  FD->setIsMultiVersion(Record.readInt());
  FD->setLateTemplateParsed(Record.readInt());

  FD->setCachedLinkage(static_cast<Linkage>(Record.readInt()));
  FD->EndRangeLoc = readSourceLocation();

  FD->ODRHash = Record.readInt();
  FD->setHasODRHash(true);

  if (FD->isDefaulted()) {
    if (unsigned NumLookups = Record.readInt()) {
      SmallVector<DeclAccessPair, 8> Lookups;
      for (unsigned I = 0; I != NumLookups; ++I) {
        NamedDecl *ND = Record.readDeclAs<NamedDecl>();
        AccessSpecifier AS = (AccessSpecifier)Record.readInt();
        Lookups.push_back(DeclAccessPair::make(ND, AS));
      }
      FD->setDefaultedFunctionInfo(FunctionDecl::DefaultedFunctionInfo::Create(
          Reader.getContext(), Lookups));
    }
  }

  switch ((FunctionDecl::TemplatedKind)Record.readInt()) {
  case FunctionDecl::TK_NonTemplate:
    mergeRedeclarable(FD, Redecl);
    break;
  case FunctionDecl::TK_FunctionTemplate:
    // Merged when we merge the template.
    FD->setDescribedFunctionTemplate(readDeclAs<FunctionTemplateDecl>());
    break;
  case FunctionDecl::TK_MemberSpecialization: {
    auto *InstFD = readDeclAs<FunctionDecl>();
    auto TSK = (TemplateSpecializationKind)Record.readInt();
    SourceLocation POI = readSourceLocation();
    FD->setInstantiationOfMemberFunction(Reader.getContext(), InstFD, TSK);
    FD->getMemberSpecializationInfo()->setPointOfInstantiation(POI);
    mergeRedeclarable(FD, Redecl);
    break;
  }
  case FunctionDecl::TK_FunctionTemplateSpecialization: {
    auto *Template = readDeclAs<FunctionTemplateDecl>();
    auto TSK = (TemplateSpecializationKind)Record.readInt();

    // Template arguments.
    SmallVector<TemplateArgument, 8> TemplArgs;
    Record.readTemplateArgumentList(TemplArgs, /*Canonicalize*/ true);

    // Template args as written.
    SmallVector<TemplateArgumentLoc, 8> TemplArgLocs;
    SourceLocation LAngleLoc, RAngleLoc;
    bool HasTemplateArgumentsAsWritten = Record.readInt();
    if (HasTemplateArgumentsAsWritten) {
      unsigned NumTemplateArgLocs = Record.readInt();
      TemplArgLocs.reserve(NumTemplateArgLocs);
      for (unsigned i = 0; i != NumTemplateArgLocs; ++i)
        TemplArgLocs.push_back(Record.readTemplateArgumentLoc());

      LAngleLoc = readSourceLocation();
      RAngleLoc = readSourceLocation();
    }

    SourceLocation POI = readSourceLocation();

    ASTContext &C = Reader.getContext();
    TemplateArgumentList *TemplArgList
      = TemplateArgumentList::CreateCopy(C, TemplArgs);
    TemplateArgumentListInfo TemplArgsInfo(LAngleLoc, RAngleLoc);
    for (unsigned i = 0, e = TemplArgLocs.size(); i != e; ++i)
      TemplArgsInfo.addArgument(TemplArgLocs[i]);

    MemberSpecializationInfo *MSInfo = nullptr;
    if (Record.readInt()) {
      auto *FD = readDeclAs<FunctionDecl>();
      auto TSK = (TemplateSpecializationKind)Record.readInt();
      SourceLocation POI = readSourceLocation();

      MSInfo = new (C) MemberSpecializationInfo(FD, TSK);
      MSInfo->setPointOfInstantiation(POI);
    }

    FunctionTemplateSpecializationInfo *FTInfo =
        FunctionTemplateSpecializationInfo::Create(
            C, FD, Template, TSK, TemplArgList,
            HasTemplateArgumentsAsWritten ? &TemplArgsInfo : nullptr, POI,
            MSInfo);
    FD->TemplateOrSpecialization = FTInfo;

    if (FD->isCanonicalDecl()) { // if canonical add to template's set.
      // The template that contains the specializations set. It's not safe to
      // use getCanonicalDecl on Template since it may still be initializing.
      auto *CanonTemplate = readDeclAs<FunctionTemplateDecl>();
      // Get the InsertPos by FindNodeOrInsertPos() instead of calling
      // InsertNode(FTInfo) directly to avoid the getASTContext() call in
      // FunctionTemplateSpecializationInfo's Profile().
      // We avoid getASTContext because a decl in the parent hierarchy may
      // be initializing.
      llvm::FoldingSetNodeID ID;
      FunctionTemplateSpecializationInfo::Profile(ID, TemplArgs, C);
      void *InsertPos = nullptr;
      FunctionTemplateDecl::Common *CommonPtr = CanonTemplate->getCommonPtr();
      FunctionTemplateSpecializationInfo *ExistingInfo =
          CommonPtr->Specializations.FindNodeOrInsertPos(ID, InsertPos);
      if (InsertPos)
        CommonPtr->Specializations.InsertNode(FTInfo, InsertPos);
      else {
        assert(Reader.getContext().getLangOpts().Modules &&
               "already deserialized this template specialization");
        mergeRedeclarable(FD, ExistingInfo->getFunction(), Redecl);
      }
    }
    break;
  }
  case FunctionDecl::TK_DependentFunctionTemplateSpecialization: {
    // Templates.
    UnresolvedSet<8> TemplDecls;
    unsigned NumTemplates = Record.readInt();
    while (NumTemplates--)
      TemplDecls.addDecl(readDeclAs<NamedDecl>());

    // Templates args.
    TemplateArgumentListInfo TemplArgs;
    unsigned NumArgs = Record.readInt();
    while (NumArgs--)
      TemplArgs.addArgument(Record.readTemplateArgumentLoc());
    TemplArgs.setLAngleLoc(readSourceLocation());
    TemplArgs.setRAngleLoc(readSourceLocation());

    FD->setDependentTemplateSpecialization(Reader.getContext(),
                                           TemplDecls, TemplArgs);
    // These are not merged; we don't need to merge redeclarations of dependent
    // template friends.
    break;
  }
  }

  // Defer calling `setPure` until merging above has guaranteed we've set
  // `DefinitionData` (as this will need to access it).
  FD->setPure(Pure);

  // Read in the parameters.
  unsigned NumParams = Record.readInt();
  SmallVector<ParmVarDecl *, 16> Params;
  Params.reserve(NumParams);
  for (unsigned I = 0; I != NumParams; ++I)
    Params.push_back(readDeclAs<ParmVarDecl>());
  FD->setParams(Reader.getContext(), Params);
}

void ASTDeclReader::VisitObjCMethodDecl(ObjCMethodDecl *MD) {
  VisitNamedDecl(MD);
  if (Record.readInt()) {
    // Load the body on-demand. Most clients won't care, because method
    // definitions rarely show up in headers.
    Reader.PendingBodies[MD] = GetCurrentCursorOffset();
    HasPendingBody = true;
  }
  MD->setSelfDecl(readDeclAs<ImplicitParamDecl>());
  MD->setCmdDecl(readDeclAs<ImplicitParamDecl>());
  MD->setInstanceMethod(Record.readInt());
  MD->setVariadic(Record.readInt());
  MD->setPropertyAccessor(Record.readInt());
  MD->setSynthesizedAccessorStub(Record.readInt());
  MD->setDefined(Record.readInt());
  MD->setOverriding(Record.readInt());
  MD->setHasSkippedBody(Record.readInt());

  MD->setIsRedeclaration(Record.readInt());
  MD->setHasRedeclaration(Record.readInt());
  if (MD->hasRedeclaration())
    Reader.getContext().setObjCMethodRedeclaration(MD,
                                       readDeclAs<ObjCMethodDecl>());

  MD->setDeclImplementation((ObjCMethodDecl::ImplementationControl)Record.readInt());
  MD->setObjCDeclQualifier((Decl::ObjCDeclQualifier)Record.readInt());
  MD->setRelatedResultType(Record.readInt());
  MD->setReturnType(Record.readType());
  MD->setReturnTypeSourceInfo(readTypeSourceInfo());
  MD->DeclEndLoc = readSourceLocation();
  unsigned NumParams = Record.readInt();
  SmallVector<ParmVarDecl *, 16> Params;
  Params.reserve(NumParams);
  for (unsigned I = 0; I != NumParams; ++I)
    Params.push_back(readDeclAs<ParmVarDecl>());

  MD->setSelLocsKind((SelectorLocationsKind)Record.readInt());
  unsigned NumStoredSelLocs = Record.readInt();
  SmallVector<SourceLocation, 16> SelLocs;
  SelLocs.reserve(NumStoredSelLocs);
  for (unsigned i = 0; i != NumStoredSelLocs; ++i)
    SelLocs.push_back(readSourceLocation());

  MD->setParamsAndSelLocs(Reader.getContext(), Params, SelLocs);
}

void ASTDeclReader::VisitObjCTypeParamDecl(ObjCTypeParamDecl *D) {
  VisitTypedefNameDecl(D);

  D->Variance = Record.readInt();
  D->Index = Record.readInt();
  D->VarianceLoc = readSourceLocation();
  D->ColonLoc = readSourceLocation();
}

void ASTDeclReader::VisitObjCContainerDecl(ObjCContainerDecl *CD) {
  VisitNamedDecl(CD);
  CD->setAtStartLoc(readSourceLocation());
  CD->setAtEndRange(readSourceRange());
}

ObjCTypeParamList *ASTDeclReader::ReadObjCTypeParamList() {
  unsigned numParams = Record.readInt();
  if (numParams == 0)
    return nullptr;

  SmallVector<ObjCTypeParamDecl *, 4> typeParams;
  typeParams.reserve(numParams);
  for (unsigned i = 0; i != numParams; ++i) {
    auto *typeParam = readDeclAs<ObjCTypeParamDecl>();
    if (!typeParam)
      return nullptr;

    typeParams.push_back(typeParam);
  }

  SourceLocation lAngleLoc = readSourceLocation();
  SourceLocation rAngleLoc = readSourceLocation();

  return ObjCTypeParamList::create(Reader.getContext(), lAngleLoc,
                                   typeParams, rAngleLoc);
}

void ASTDeclReader::ReadObjCDefinitionData(
         struct ObjCInterfaceDecl::DefinitionData &Data) {
  // Read the superclass.
  Data.SuperClassTInfo = readTypeSourceInfo();

  Data.EndLoc = readSourceLocation();
  Data.HasDesignatedInitializers = Record.readInt();

  // Read the directly referenced protocols and their SourceLocations.
  unsigned NumProtocols = Record.readInt();
  SmallVector<ObjCProtocolDecl *, 16> Protocols;
  Protocols.reserve(NumProtocols);
  for (unsigned I = 0; I != NumProtocols; ++I)
    Protocols.push_back(readDeclAs<ObjCProtocolDecl>());
  SmallVector<SourceLocation, 16> ProtoLocs;
  ProtoLocs.reserve(NumProtocols);
  for (unsigned I = 0; I != NumProtocols; ++I)
    ProtoLocs.push_back(readSourceLocation());
  Data.ReferencedProtocols.set(Protocols.data(), NumProtocols, ProtoLocs.data(),
                               Reader.getContext());

  // Read the transitive closure of protocols referenced by this class.
  NumProtocols = Record.readInt();
  Protocols.clear();
  Protocols.reserve(NumProtocols);
  for (unsigned I = 0; I != NumProtocols; ++I)
    Protocols.push_back(readDeclAs<ObjCProtocolDecl>());
  Data.AllReferencedProtocols.set(Protocols.data(), NumProtocols,
                                  Reader.getContext());
}

void ASTDeclReader::MergeDefinitionData(ObjCInterfaceDecl *D,
         struct ObjCInterfaceDecl::DefinitionData &&NewDD) {
  struct ObjCInterfaceDecl::DefinitionData &DD = D->data();
  if (DD.Definition != NewDD.Definition) {
    Reader.MergedDeclContexts.insert(
        std::make_pair(NewDD.Definition, DD.Definition));
    Reader.mergeDefinitionVisibility(DD.Definition, NewDD.Definition);
  }

  // FIXME: odr checking?
}

void ASTDeclReader::VisitObjCInterfaceDecl(ObjCInterfaceDecl *ID) {
  RedeclarableResult Redecl = VisitRedeclarable(ID);
  VisitObjCContainerDecl(ID);
  DeferredTypeID = Record.getGlobalTypeID(Record.readInt());
  mergeRedeclarable(ID, Redecl);

  ID->TypeParamList = ReadObjCTypeParamList();
  if (Record.readInt()) {
    // Read the definition.
    ID->allocateDefinitionData();

    ReadObjCDefinitionData(ID->data());
    ObjCInterfaceDecl *Canon = ID->getCanonicalDecl();
    if (Canon->Data.getPointer()) {
      // If we already have a definition, keep the definition invariant and
      // merge the data.
      MergeDefinitionData(Canon, std::move(ID->data()));
      ID->Data = Canon->Data;
    } else {
      // Set the definition data of the canonical declaration, so other
      // redeclarations will see it.
      ID->getCanonicalDecl()->Data = ID->Data;

      // We will rebuild this list lazily.
      ID->setIvarList(nullptr);
    }

    // Note that we have deserialized a definition.
    Reader.PendingDefinitions.insert(ID);

    // Note that we've loaded this Objective-C class.
    Reader.ObjCClassesLoaded.push_back(ID);
  } else {
    ID->Data = ID->getCanonicalDecl()->Data;
  }
}

void ASTDeclReader::VisitObjCIvarDecl(ObjCIvarDecl *IVD) {
  VisitFieldDecl(IVD);
  IVD->setAccessControl((ObjCIvarDecl::AccessControl)Record.readInt());
  // This field will be built lazily.
  IVD->setNextIvar(nullptr);
  bool synth = Record.readInt();
  IVD->setSynthesize(synth);
}

void ASTDeclReader::ReadObjCDefinitionData(
         struct ObjCProtocolDecl::DefinitionData &Data) {
    unsigned NumProtoRefs = Record.readInt();
    SmallVector<ObjCProtocolDecl *, 16> ProtoRefs;
    ProtoRefs.reserve(NumProtoRefs);
    for (unsigned I = 0; I != NumProtoRefs; ++I)
      ProtoRefs.push_back(readDeclAs<ObjCProtocolDecl>());
    SmallVector<SourceLocation, 16> ProtoLocs;
    ProtoLocs.reserve(NumProtoRefs);
    for (unsigned I = 0; I != NumProtoRefs; ++I)
      ProtoLocs.push_back(readSourceLocation());
    Data.ReferencedProtocols.set(ProtoRefs.data(), NumProtoRefs,
                                 ProtoLocs.data(), Reader.getContext());
}

void ASTDeclReader::MergeDefinitionData(ObjCProtocolDecl *D,
         struct ObjCProtocolDecl::DefinitionData &&NewDD) {
  struct ObjCProtocolDecl::DefinitionData &DD = D->data();
  if (DD.Definition != NewDD.Definition) {
    Reader.MergedDeclContexts.insert(
        std::make_pair(NewDD.Definition, DD.Definition));
    Reader.mergeDefinitionVisibility(DD.Definition, NewDD.Definition);
  }

  // FIXME: odr checking?
}

void ASTDeclReader::VisitObjCProtocolDecl(ObjCProtocolDecl *PD) {
  RedeclarableResult Redecl = VisitRedeclarable(PD);
  VisitObjCContainerDecl(PD);
  mergeRedeclarable(PD, Redecl);

  if (Record.readInt()) {
    // Read the definition.
    PD->allocateDefinitionData();

    ReadObjCDefinitionData(PD->data());

    ObjCProtocolDecl *Canon = PD->getCanonicalDecl();
    if (Canon->Data.getPointer()) {
      // If we already have a definition, keep the definition invariant and
      // merge the data.
      MergeDefinitionData(Canon, std::move(PD->data()));
      PD->Data = Canon->Data;
    } else {
      // Set the definition data of the canonical declaration, so other
      // redeclarations will see it.
      PD->getCanonicalDecl()->Data = PD->Data;
    }
    // Note that we have deserialized a definition.
    Reader.PendingDefinitions.insert(PD);
  } else {
    PD->Data = PD->getCanonicalDecl()->Data;
  }
}

void ASTDeclReader::VisitObjCAtDefsFieldDecl(ObjCAtDefsFieldDecl *FD) {
  VisitFieldDecl(FD);
}

void ASTDeclReader::VisitObjCCategoryDecl(ObjCCategoryDecl *CD) {
  VisitObjCContainerDecl(CD);
  CD->setCategoryNameLoc(readSourceLocation());
  CD->setIvarLBraceLoc(readSourceLocation());
  CD->setIvarRBraceLoc(readSourceLocation());

  // Note that this category has been deserialized. We do this before
  // deserializing the interface declaration, so that it will consider this
  /// category.
  Reader.CategoriesDeserialized.insert(CD);

  CD->ClassInterface = readDeclAs<ObjCInterfaceDecl>();
  CD->TypeParamList = ReadObjCTypeParamList();
  unsigned NumProtoRefs = Record.readInt();
  SmallVector<ObjCProtocolDecl *, 16> ProtoRefs;
  ProtoRefs.reserve(NumProtoRefs);
  for (unsigned I = 0; I != NumProtoRefs; ++I)
    ProtoRefs.push_back(readDeclAs<ObjCProtocolDecl>());
  SmallVector<SourceLocation, 16> ProtoLocs;
  ProtoLocs.reserve(NumProtoRefs);
  for (unsigned I = 0; I != NumProtoRefs; ++I)
    ProtoLocs.push_back(readSourceLocation());
  CD->setProtocolList(ProtoRefs.data(), NumProtoRefs, ProtoLocs.data(),
                      Reader.getContext());

  // Protocols in the class extension belong to the class.
  if (NumProtoRefs > 0 && CD->ClassInterface && CD->IsClassExtension())
    CD->ClassInterface->mergeClassExtensionProtocolList(
        (ObjCProtocolDecl *const *)ProtoRefs.data(), NumProtoRefs,
        Reader.getContext());
}

void ASTDeclReader::VisitObjCCompatibleAliasDecl(ObjCCompatibleAliasDecl *CAD) {
  VisitNamedDecl(CAD);
  CAD->setClassInterface(readDeclAs<ObjCInterfaceDecl>());
}

void ASTDeclReader::VisitObjCPropertyDecl(ObjCPropertyDecl *D) {
  VisitNamedDecl(D);
  D->setAtLoc(readSourceLocation());
  D->setLParenLoc(readSourceLocation());
  QualType T = Record.readType();
  TypeSourceInfo *TSI = readTypeSourceInfo();
  D->setType(T, TSI);
  D->setPropertyAttributes((ObjCPropertyAttribute::Kind)Record.readInt());
  D->setPropertyAttributesAsWritten(
      (ObjCPropertyAttribute::Kind)Record.readInt());
  D->setPropertyImplementation(
      (ObjCPropertyDecl::PropertyControl)Record.readInt());
  DeclarationName GetterName = Record.readDeclarationName();
  SourceLocation GetterLoc = readSourceLocation();
  D->setGetterName(GetterName.getObjCSelector(), GetterLoc);
  DeclarationName SetterName = Record.readDeclarationName();
  SourceLocation SetterLoc = readSourceLocation();
  D->setSetterName(SetterName.getObjCSelector(), SetterLoc);
  D->setGetterMethodDecl(readDeclAs<ObjCMethodDecl>());
  D->setSetterMethodDecl(readDeclAs<ObjCMethodDecl>());
  D->setPropertyIvarDecl(readDeclAs<ObjCIvarDecl>());
}

void ASTDeclReader::VisitObjCImplDecl(ObjCImplDecl *D) {
  VisitObjCContainerDecl(D);
  D->setClassInterface(readDeclAs<ObjCInterfaceDecl>());
}

void ASTDeclReader::VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D) {
  VisitObjCImplDecl(D);
  D->CategoryNameLoc = readSourceLocation();
}

void ASTDeclReader::VisitObjCImplementationDecl(ObjCImplementationDecl *D) {
  VisitObjCImplDecl(D);
  D->setSuperClass(readDeclAs<ObjCInterfaceDecl>());
  D->SuperLoc = readSourceLocation();
  D->setIvarLBraceLoc(readSourceLocation());
  D->setIvarRBraceLoc(readSourceLocation());
  D->setHasNonZeroConstructors(Record.readInt());
  D->setHasDestructors(Record.readInt());
  D->NumIvarInitializers = Record.readInt();
  if (D->NumIvarInitializers)
    D->IvarInitializers = ReadGlobalOffset();
}

void ASTDeclReader::VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D) {
  VisitDecl(D);
  D->setAtLoc(readSourceLocation());
  D->setPropertyDecl(readDeclAs<ObjCPropertyDecl>());
  D->PropertyIvarDecl = readDeclAs<ObjCIvarDecl>();
  D->IvarLoc = readSourceLocation();
  D->setGetterMethodDecl(readDeclAs<ObjCMethodDecl>());
  D->setSetterMethodDecl(readDeclAs<ObjCMethodDecl>());
  D->setGetterCXXConstructor(Record.readExpr());
  D->setSetterCXXAssignment(Record.readExpr());
}

void ASTDeclReader::VisitFieldDecl(FieldDecl *FD) {
  VisitDeclaratorDecl(FD);
  FD->Mutable = Record.readInt();

  if (auto ISK = static_cast<FieldDecl::InitStorageKind>(Record.readInt())) {
    FD->InitStorage.setInt(ISK);
    FD->InitStorage.setPointer(ISK == FieldDecl::ISK_CapturedVLAType
                                   ? Record.readType().getAsOpaquePtr()
                                   : Record.readExpr());
  }

  if (auto *BW = Record.readExpr())
    FD->setBitWidth(BW);

  if (!FD->getDeclName()) {
    if (auto *Tmpl = readDeclAs<FieldDecl>())
      Reader.getContext().setInstantiatedFromUnnamedFieldDecl(FD, Tmpl);
  }
  mergeMergeable(FD);
}

void ASTDeclReader::VisitMSPropertyDecl(MSPropertyDecl *PD) {
  VisitDeclaratorDecl(PD);
  PD->GetterId = Record.readIdentifier();
  PD->SetterId = Record.readIdentifier();
}

void ASTDeclReader::VisitMSGuidDecl(MSGuidDecl *D) {
  VisitValueDecl(D);
  D->PartVal.Part1 = Record.readInt();
  D->PartVal.Part2 = Record.readInt();
  D->PartVal.Part3 = Record.readInt();
  for (auto &C : D->PartVal.Part4And5)
    C = Record.readInt();

  // Add this GUID to the AST context's lookup structure, and merge if needed.
  if (MSGuidDecl *Existing = Reader.getContext().MSGuidDecls.GetOrInsertNode(D))
    Reader.getContext().setPrimaryMergedDecl(D, Existing->getCanonicalDecl());
}

void ASTDeclReader::VisitTemplateParamObjectDecl(TemplateParamObjectDecl *D) {
  VisitValueDecl(D);
  D->Value = Record.readAPValue();

  // Add this template parameter object to the AST context's lookup structure,
  // and merge if needed.
  if (TemplateParamObjectDecl *Existing =
          Reader.getContext().TemplateParamObjectDecls.GetOrInsertNode(D))
    Reader.getContext().setPrimaryMergedDecl(D, Existing->getCanonicalDecl());
}

void ASTDeclReader::VisitIndirectFieldDecl(IndirectFieldDecl *FD) {
  VisitValueDecl(FD);

  FD->ChainingSize = Record.readInt();
  assert(FD->ChainingSize >= 2 && "Anonymous chaining must be >= 2");
  FD->Chaining = new (Reader.getContext())NamedDecl*[FD->ChainingSize];

  for (unsigned I = 0; I != FD->ChainingSize; ++I)
    FD->Chaining[I] = readDeclAs<NamedDecl>();

  mergeMergeable(FD);
}

ASTDeclReader::RedeclarableResult ASTDeclReader::VisitVarDeclImpl(VarDecl *VD) {
  RedeclarableResult Redecl = VisitRedeclarable(VD);
  VisitDeclaratorDecl(VD);

  VD->VarDeclBits.SClass = (StorageClass)Record.readInt();
  VD->VarDeclBits.TSCSpec = Record.readInt();
  VD->VarDeclBits.InitStyle = Record.readInt();
  VD->VarDeclBits.ARCPseudoStrong = Record.readInt();
  if (!isa<ParmVarDecl>(VD)) {
    VD->NonParmVarDeclBits.IsThisDeclarationADemotedDefinition =
        Record.readInt();
    VD->NonParmVarDeclBits.ExceptionVar = Record.readInt();
    VD->NonParmVarDeclBits.NRVOVariable = Record.readInt();
    VD->NonParmVarDeclBits.CXXForRangeDecl = Record.readInt();
    VD->NonParmVarDeclBits.ObjCForDecl = Record.readInt();
    VD->NonParmVarDeclBits.IsInline = Record.readInt();
    VD->NonParmVarDeclBits.IsInlineSpecified = Record.readInt();
    VD->NonParmVarDeclBits.IsConstexpr = Record.readInt();
    VD->NonParmVarDeclBits.IsInitCapture = Record.readInt();
    VD->NonParmVarDeclBits.PreviousDeclInSameBlockScope = Record.readInt();
    VD->NonParmVarDeclBits.ImplicitParamKind = Record.readInt();
    VD->NonParmVarDeclBits.EscapingByref = Record.readInt();
  }
  auto VarLinkage = Linkage(Record.readInt());
  VD->setCachedLinkage(VarLinkage);

  // Reconstruct the one piece of the IdentifierNamespace that we need.
  if (VD->getStorageClass() == SC_Extern && VarLinkage != NoLinkage &&
      VD->getLexicalDeclContext()->isFunctionOrMethod())
    VD->setLocalExternDecl();

  if (uint64_t Val = Record.readInt()) {
    VD->setInit(Record.readExpr());
    if (Val != 1) {
      EvaluatedStmt *Eval = VD->ensureEvaluatedStmt();
      Eval->HasConstantInitialization = (Val & 2) != 0;
      Eval->HasConstantDestruction = (Val & 4) != 0;
    }
  }

  if (VD->hasAttr<BlocksAttr>() && VD->getType()->getAsCXXRecordDecl()) {
    Expr *CopyExpr = Record.readExpr();
    if (CopyExpr)
      Reader.getContext().setBlockVarCopyInit(VD, CopyExpr, Record.readInt());
  }

  if (VD->getStorageDuration() == SD_Static && Record.readInt()) {
    Reader.DefinitionSource[VD] =
        Loc.F->Kind == ModuleKind::MK_MainFile ||
        Reader.getContext().getLangOpts().BuildingPCHWithObjectFile;
  }

  enum VarKind {
    VarNotTemplate = 0, VarTemplate, StaticDataMemberSpecialization
  };
  switch ((VarKind)Record.readInt()) {
  case VarNotTemplate:
    // Only true variables (not parameters or implicit parameters) can be
    // merged; the other kinds are not really redeclarable at all.
    if (!isa<ParmVarDecl>(VD) && !isa<ImplicitParamDecl>(VD) &&
        !isa<VarTemplateSpecializationDecl>(VD))
      mergeRedeclarable(VD, Redecl);
    break;
  case VarTemplate:
    // Merged when we merge the template.
    VD->setDescribedVarTemplate(readDeclAs<VarTemplateDecl>());
    break;
  case StaticDataMemberSpecialization: { // HasMemberSpecializationInfo.
    auto *Tmpl = readDeclAs<VarDecl>();
    auto TSK = (TemplateSpecializationKind)Record.readInt();
    SourceLocation POI = readSourceLocation();
    Reader.getContext().setInstantiatedFromStaticDataMember(VD, Tmpl, TSK,POI);
    mergeRedeclarable(VD, Redecl);
    break;
  }
  }

  return Redecl;
}

void ASTDeclReader::VisitImplicitParamDecl(ImplicitParamDecl *PD) {
  VisitVarDecl(PD);
}

void ASTDeclReader::VisitParmVarDecl(ParmVarDecl *PD) {
  VisitVarDecl(PD);
  unsigned isObjCMethodParam = Record.readInt();
  unsigned scopeDepth = Record.readInt();
  unsigned scopeIndex = Record.readInt();
  unsigned declQualifier = Record.readInt();
  if (isObjCMethodParam) {
    assert(scopeDepth == 0);
    PD->setObjCMethodScopeInfo(scopeIndex);
    PD->ParmVarDeclBits.ScopeDepthOrObjCQuals = declQualifier;
  } else {
    PD->setScopeInfo(scopeDepth, scopeIndex);
  }
  PD->ParmVarDeclBits.IsKNRPromoted = Record.readInt();
  PD->ParmVarDeclBits.HasInheritedDefaultArg = Record.readInt();
  if (Record.readInt()) // hasUninstantiatedDefaultArg.
    PD->setUninstantiatedDefaultArg(Record.readExpr());

  // FIXME: If this is a redeclaration of a function from another module, handle
  // inheritance of default arguments.
}

void ASTDeclReader::VisitDecompositionDecl(DecompositionDecl *DD) {
  VisitVarDecl(DD);
  auto **BDs = DD->getTrailingObjects<BindingDecl *>();
  for (unsigned I = 0; I != DD->NumBindings; ++I) {
    BDs[I] = readDeclAs<BindingDecl>();
    BDs[I]->setDecomposedDecl(DD);
  }
}

void ASTDeclReader::VisitBindingDecl(BindingDecl *BD) {
  VisitValueDecl(BD);
  BD->Binding = Record.readExpr();
}

void ASTDeclReader::VisitFileScopeAsmDecl(FileScopeAsmDecl *AD) {
  VisitDecl(AD);
  AD->setAsmString(cast<StringLiteral>(Record.readExpr()));
  AD->setRParenLoc(readSourceLocation());
}

void ASTDeclReader::VisitBlockDecl(BlockDecl *BD) {
  VisitDecl(BD);
  BD->setBody(cast_or_null<CompoundStmt>(Record.readStmt()));
  BD->setSignatureAsWritten(readTypeSourceInfo());
  unsigned NumParams = Record.readInt();
  SmallVector<ParmVarDecl *, 16> Params;
  Params.reserve(NumParams);
  for (unsigned I = 0; I != NumParams; ++I)
    Params.push_back(readDeclAs<ParmVarDecl>());
  BD->setParams(Params);

  BD->setIsVariadic(Record.readInt());
  BD->setBlockMissingReturnType(Record.readInt());
  BD->setIsConversionFromLambda(Record.readInt());
  BD->setDoesNotEscape(Record.readInt());
  BD->setCanAvoidCopyToHeap(Record.readInt());

  bool capturesCXXThis = Record.readInt();
  unsigned numCaptures = Record.readInt();
  SmallVector<BlockDecl::Capture, 16> captures;
  captures.reserve(numCaptures);
  for (unsigned i = 0; i != numCaptures; ++i) {
    auto *decl = readDeclAs<VarDecl>();
    unsigned flags = Record.readInt();
    bool byRef = (flags & 1);
    bool nested = (flags & 2);
    Expr *copyExpr = ((flags & 4) ? Record.readExpr() : nullptr);

    captures.push_back(BlockDecl::Capture(decl, byRef, nested, copyExpr));
  }
  BD->setCaptures(Reader.getContext(), captures, capturesCXXThis);
}

void ASTDeclReader::VisitCapturedDecl(CapturedDecl *CD) {
  VisitDecl(CD);
  unsigned ContextParamPos = Record.readInt();
  CD->setNothrow(Record.readInt() != 0);
  // Body is set by VisitCapturedStmt.
  for (unsigned I = 0; I < CD->NumParams; ++I) {
    if (I != ContextParamPos)
      CD->setParam(I, readDeclAs<ImplicitParamDecl>());
    else
      CD->setContextParam(I, readDeclAs<ImplicitParamDecl>());
  }
}

void ASTDeclReader::VisitLinkageSpecDecl(LinkageSpecDecl *D) {
  VisitDecl(D);
  D->setLanguage((LinkageSpecDecl::LanguageIDs)Record.readInt());
  D->setExternLoc(readSourceLocation());
  D->setRBraceLoc(readSourceLocation());
}

void ASTDeclReader::VisitExportDecl(ExportDecl *D) {
  VisitDecl(D);
  D->RBraceLoc = readSourceLocation();
}

void ASTDeclReader::VisitLabelDecl(LabelDecl *D) {
  VisitNamedDecl(D);
  D->setLocStart(readSourceLocation());
}

void ASTDeclReader::VisitNamespaceDecl(NamespaceDecl *D) {
  RedeclarableResult Redecl = VisitRedeclarable(D);
  VisitNamedDecl(D);
  D->setInline(Record.readInt());
  D->LocStart = readSourceLocation();
  D->RBraceLoc = readSourceLocation();

  // Defer loading the anonymous namespace until we've finished merging
  // this namespace; loading it might load a later declaration of the
  // same namespace, and we have an invariant that older declarations
  // get merged before newer ones try to merge.
  GlobalDeclID AnonNamespace = 0;
  if (Redecl.getFirstID() == ThisDeclID) {
    AnonNamespace = readDeclID();
  } else {
    // Link this namespace back to the first declaration, which has already
    // been deserialized.
    D->AnonOrFirstNamespaceAndInline.setPointer(D->getFirstDecl());
  }

  mergeRedeclarable(D, Redecl);

  if (AnonNamespace) {
    // Each module has its own anonymous namespace, which is disjoint from
    // any other module's anonymous namespaces, so don't attach the anonymous
    // namespace at all.
    auto *Anon = cast<NamespaceDecl>(Reader.GetDecl(AnonNamespace));
    if (!Record.isModule())
      D->setAnonymousNamespace(Anon);
  }
}

void ASTDeclReader::VisitNamespaceAliasDecl(NamespaceAliasDecl *D) {
  RedeclarableResult Redecl = VisitRedeclarable(D);
  VisitNamedDecl(D);
  D->NamespaceLoc = readSourceLocation();
  D->IdentLoc = readSourceLocation();
  D->QualifierLoc = Record.readNestedNameSpecifierLoc();
  D->Namespace = readDeclAs<NamedDecl>();
  mergeRedeclarable(D, Redecl);
}

void ASTDeclReader::VisitUsingDecl(UsingDecl *D) {
  VisitNamedDecl(D);
  D->setUsingLoc(readSourceLocation());
  D->QualifierLoc = Record.readNestedNameSpecifierLoc();
  D->DNLoc = Record.readDeclarationNameLoc(D->getDeclName());
  D->FirstUsingShadow.setPointer(readDeclAs<UsingShadowDecl>());
  D->setTypename(Record.readInt());
  if (auto *Pattern = readDeclAs<NamedDecl>())
    Reader.getContext().setInstantiatedFromUsingDecl(D, Pattern);
  mergeMergeable(D);
}

void ASTDeclReader::VisitUsingEnumDecl(UsingEnumDecl *D) {
  VisitNamedDecl(D);
  D->setUsingLoc(readSourceLocation());
  D->setEnumLoc(readSourceLocation());
  D->Enum = readDeclAs<EnumDecl>();
  D->FirstUsingShadow.setPointer(readDeclAs<UsingShadowDecl>());
  if (auto *Pattern = readDeclAs<UsingEnumDecl>())
    Reader.getContext().setInstantiatedFromUsingEnumDecl(D, Pattern);
  mergeMergeable(D);
}

void ASTDeclReader::VisitUsingPackDecl(UsingPackDecl *D) {
  VisitNamedDecl(D);
  D->InstantiatedFrom = readDeclAs<NamedDecl>();
  auto **Expansions = D->getTrailingObjects<NamedDecl *>();
  for (unsigned I = 0; I != D->NumExpansions; ++I)
    Expansions[I] = readDeclAs<NamedDecl>();
  mergeMergeable(D);
}

void ASTDeclReader::VisitUsingShadowDecl(UsingShadowDecl *D) {
  RedeclarableResult Redecl = VisitRedeclarable(D);
  VisitNamedDecl(D);
  D->Underlying = readDeclAs<NamedDecl>();
  D->IdentifierNamespace = Record.readInt();
  D->UsingOrNextShadow = readDeclAs<NamedDecl>();
  auto *Pattern = readDeclAs<UsingShadowDecl>();
  if (Pattern)
    Reader.getContext().setInstantiatedFromUsingShadowDecl(D, Pattern);
  mergeRedeclarable(D, Redecl);
}

void ASTDeclReader::VisitConstructorUsingShadowDecl(
    ConstructorUsingShadowDecl *D) {
  VisitUsingShadowDecl(D);
  D->NominatedBaseClassShadowDecl = readDeclAs<ConstructorUsingShadowDecl>();
  D->ConstructedBaseClassShadowDecl = readDeclAs<ConstructorUsingShadowDecl>();
  D->IsVirtual = Record.readInt();
}

void ASTDeclReader::VisitUsingDirectiveDecl(UsingDirectiveDecl *D) {
  VisitNamedDecl(D);
  D->UsingLoc = readSourceLocation();
  D->NamespaceLoc = readSourceLocation();
  D->QualifierLoc = Record.readNestedNameSpecifierLoc();
  D->NominatedNamespace = readDeclAs<NamedDecl>();
  D->CommonAncestor = readDeclAs<DeclContext>();
}

void ASTDeclReader::VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D) {
  VisitValueDecl(D);
  D->setUsingLoc(readSourceLocation());
  D->QualifierLoc = Record.readNestedNameSpecifierLoc();
  D->DNLoc = Record.readDeclarationNameLoc(D->getDeclName());
  D->EllipsisLoc = readSourceLocation();
  mergeMergeable(D);
}

void ASTDeclReader::VisitUnresolvedUsingTypenameDecl(
                                               UnresolvedUsingTypenameDecl *D) {
  VisitTypeDecl(D);
  D->TypenameLocation = readSourceLocation();
  D->QualifierLoc = Record.readNestedNameSpecifierLoc();
  D->EllipsisLoc = readSourceLocation();
  mergeMergeable(D);
}

void ASTDeclReader::VisitUnresolvedUsingIfExistsDecl(
    UnresolvedUsingIfExistsDecl *D) {
  VisitNamedDecl(D);
}

void ASTDeclReader::ReadCXXDefinitionData(
    struct CXXRecordDecl::DefinitionData &Data, const CXXRecordDecl *D) {
  #define FIELD(Name, Width, Merge) \
  Data.Name = Record.readInt();
  #include "clang/AST/CXXRecordDeclDefinitionBits.def"

  // Note: the caller has deserialized the IsLambda bit already.
  Data.ODRHash = Record.readInt();
  Data.HasODRHash = true;

  if (Record.readInt()) {
    Reader.DefinitionSource[D] =
        Loc.F->Kind == ModuleKind::MK_MainFile ||
        Reader.getContext().getLangOpts().BuildingPCHWithObjectFile;
  }

  Data.NumBases = Record.readInt();
  if (Data.NumBases)
    Data.Bases = ReadGlobalOffset();
  Data.NumVBases = Record.readInt();
  if (Data.NumVBases)
    Data.VBases = ReadGlobalOffset();

  Record.readUnresolvedSet(Data.Conversions);
  Data.ComputedVisibleConversions = Record.readInt();
  if (Data.ComputedVisibleConversions)
    Record.readUnresolvedSet(Data.VisibleConversions);
  assert(Data.Definition && "Data.Definition should be already set!");
  Data.FirstFriend = readDeclID();

  if (Data.IsLambda) {
    using Capture = LambdaCapture;

    auto &Lambda = static_cast<CXXRecordDecl::LambdaDefinitionData &>(Data);
    Lambda.Dependent = Record.readInt();
    Lambda.IsGenericLambda = Record.readInt();
    Lambda.CaptureDefault = Record.readInt();
    Lambda.NumCaptures = Record.readInt();
    Lambda.NumExplicitCaptures = Record.readInt();
    Lambda.HasKnownInternalLinkage = Record.readInt();
    Lambda.ManglingNumber = Record.readInt();
    D->setDeviceLambdaManglingNumber(Record.readInt());
    Lambda.ContextDecl = readDeclID();
    Lambda.Captures = (Capture *)Reader.getContext().Allocate(
        sizeof(Capture) * Lambda.NumCaptures);
    Capture *ToCapture = Lambda.Captures;
    Lambda.MethodTyInfo = readTypeSourceInfo();
    for (unsigned I = 0, N = Lambda.NumCaptures; I != N; ++I) {
      SourceLocation Loc = readSourceLocation();
      bool IsImplicit = Record.readInt();
      auto Kind = static_cast<LambdaCaptureKind>(Record.readInt());
      switch (Kind) {
      case LCK_StarThis:
      case LCK_This:
      case LCK_VLAType:
        *ToCapture++ = Capture(Loc, IsImplicit, Kind, nullptr,SourceLocation());
        break;
      case LCK_ByCopy:
      case LCK_ByRef:
        auto *Var = readDeclAs<VarDecl>();
        SourceLocation EllipsisLoc = readSourceLocation();
        *ToCapture++ = Capture(Loc, IsImplicit, Kind, Var, EllipsisLoc);
        break;
      }
    }
  }
}

void ASTDeclReader::MergeDefinitionData(
    CXXRecordDecl *D, struct CXXRecordDecl::DefinitionData &&MergeDD) {
  assert(D->DefinitionData &&
         "merging class definition into non-definition");
  auto &DD = *D->DefinitionData;

  if (DD.Definition != MergeDD.Definition) {
    // Track that we merged the definitions.
    Reader.MergedDeclContexts.insert(std::make_pair(MergeDD.Definition,
                                                    DD.Definition));
    Reader.PendingDefinitions.erase(MergeDD.Definition);
    MergeDD.Definition->setCompleteDefinition(false);
    Reader.mergeDefinitionVisibility(DD.Definition, MergeDD.Definition);
    assert(Reader.Lookups.find(MergeDD.Definition) == Reader.Lookups.end() &&
           "already loaded pending lookups for merged definition");
  }

  auto PFDI = Reader.PendingFakeDefinitionData.find(&DD);
  if (PFDI != Reader.PendingFakeDefinitionData.end() &&
      PFDI->second == ASTReader::PendingFakeDefinitionKind::Fake) {
    // We faked up this definition data because we found a class for which we'd
    // not yet loaded the definition. Replace it with the real thing now.
    assert(!DD.IsLambda && !MergeDD.IsLambda && "faked up lambda definition?");
    PFDI->second = ASTReader::PendingFakeDefinitionKind::FakeLoaded;

    // Don't change which declaration is the definition; that is required
    // to be invariant once we select it.
    auto *Def = DD.Definition;
    DD = std::move(MergeDD);
    DD.Definition = Def;
    return;
  }

  bool DetectedOdrViolation = false;

  #define FIELD(Name, Width, Merge) Merge(Name)
  #define MERGE_OR(Field) DD.Field |= MergeDD.Field;
  #define NO_MERGE(Field) \
    DetectedOdrViolation |= DD.Field != MergeDD.Field; \
    MERGE_OR(Field)
  #include "clang/AST/CXXRecordDeclDefinitionBits.def"
  NO_MERGE(IsLambda)
  #undef NO_MERGE
  #undef MERGE_OR

  if (DD.NumBases != MergeDD.NumBases || DD.NumVBases != MergeDD.NumVBases)
    DetectedOdrViolation = true;
  // FIXME: Issue a diagnostic if the base classes don't match when we come
  // to lazily load them.

  // FIXME: Issue a diagnostic if the list of conversion functions doesn't
  // match when we come to lazily load them.
  if (MergeDD.ComputedVisibleConversions && !DD.ComputedVisibleConversions) {
    DD.VisibleConversions = std::move(MergeDD.VisibleConversions);
    DD.ComputedVisibleConversions = true;
  }

  // FIXME: Issue a diagnostic if FirstFriend doesn't match when we come to
  // lazily load it.

  if (DD.IsLambda) {
    // FIXME: ODR-checking for merging lambdas (this happens, for instance,
    // when they occur within the body of a function template specialization).
  }

  if (D->getODRHash() != MergeDD.ODRHash) {
    DetectedOdrViolation = true;
  }

  if (DetectedOdrViolation)
    Reader.PendingOdrMergeFailures[DD.Definition].push_back(
        {MergeDD.Definition, &MergeDD});
}

void ASTDeclReader::ReadCXXRecordDefinition(CXXRecordDecl *D, bool Update) {
  struct CXXRecordDecl::DefinitionData *DD;
  ASTContext &C = Reader.getContext();

  // Determine whether this is a lambda closure type, so that we can
  // allocate the appropriate DefinitionData structure.
  bool IsLambda = Record.readInt();
  if (IsLambda)
    DD = new (C) CXXRecordDecl::LambdaDefinitionData(D, nullptr, false, false,
                                                     LCD_None);
  else
    DD = new (C) struct CXXRecordDecl::DefinitionData(D);

  CXXRecordDecl *Canon = D->getCanonicalDecl();
  // Set decl definition data before reading it, so that during deserialization
  // when we read CXXRecordDecl, it already has definition data and we don't
  // set fake one.
  if (!Canon->DefinitionData)
    Canon->DefinitionData = DD;
  D->DefinitionData = Canon->DefinitionData;
  ReadCXXDefinitionData(*DD, D);

  // We might already have a different definition for this record. This can
  // happen either because we're reading an update record, or because we've
  // already done some merging. Either way, just merge into it.
  if (Canon->DefinitionData != DD) {
    MergeDefinitionData(Canon, std::move(*DD));
    return;
  }

  // Mark this declaration as being a definition.
  D->setCompleteDefinition(true);

  // If this is not the first declaration or is an update record, we can have
  // other redeclarations already. Make a note that we need to propagate the
  // DefinitionData pointer onto them.
  if (Update || Canon != D)
    Reader.PendingDefinitions.insert(D);
}

ASTDeclReader::RedeclarableResult
ASTDeclReader::VisitCXXRecordDeclImpl(CXXRecordDecl *D) {
  RedeclarableResult Redecl = VisitRecordDeclImpl(D);

  ASTContext &C = Reader.getContext();

  enum CXXRecKind {
    CXXRecNotTemplate = 0, CXXRecTemplate, CXXRecMemberSpecialization
  };
  switch ((CXXRecKind)Record.readInt()) {
  case CXXRecNotTemplate:
    // Merged when we merge the folding set entry in the primary template.
    if (!isa<ClassTemplateSpecializationDecl>(D))
      mergeRedeclarable(D, Redecl);
    break;
  case CXXRecTemplate: {
    // Merged when we merge the template.
    auto *Template = readDeclAs<ClassTemplateDecl>();
    D->TemplateOrInstantiation = Template;
    if (!Template->getTemplatedDecl()) {
      // We've not actually loaded the ClassTemplateDecl yet, because we're
      // currently being loaded as its pattern. Rely on it to set up our
      // TypeForDecl (see VisitClassTemplateDecl).
      //
      // Beware: we do not yet know our canonical declaration, and may still
      // get merged once the surrounding class template has got off the ground.
      DeferredTypeID = 0;
    }
    break;
  }
  case CXXRecMemberSpecialization: {
    auto *RD = readDeclAs<CXXRecordDecl>();
    auto TSK = (TemplateSpecializationKind)Record.readInt();
    SourceLocation POI = readSourceLocation();
    MemberSpecializationInfo *MSI = new (C) MemberSpecializationInfo(RD, TSK);
    MSI->setPointOfInstantiation(POI);
    D->TemplateOrInstantiation = MSI;
    mergeRedeclarable(D, Redecl);
    break;
  }
  }

  bool WasDefinition = Record.readInt();
  if (WasDefinition)
    ReadCXXRecordDefinition(D, /*Update*/false);
  else
    // Propagate DefinitionData pointer from the canonical declaration.
    D->DefinitionData = D->getCanonicalDecl()->DefinitionData;

  // Lazily load the key function to avoid deserializing every method so we can
  // compute it.
  if (WasDefinition) {
    DeclID KeyFn = readDeclID();
    if (KeyFn && D->isCompleteDefinition())
      // FIXME: This is wrong for the ARM ABI, where some other module may have
      // made this function no longer be a key function. We need an update
      // record or similar for that case.
      C.KeyFunctions[D] = KeyFn;
  }

  return Redecl;
}

void ASTDeclReader::VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *D) {
  D->setExplicitSpecifier(Record.readExplicitSpec());
  D->Ctor = readDeclAs<CXXConstructorDecl>();
  VisitFunctionDecl(D);
  D->setIsCopyDeductionCandidate(Record.readInt());
}

void ASTDeclReader::VisitCXXMethodDecl(CXXMethodDecl *D) {
  VisitFunctionDecl(D);

  unsigned NumOverridenMethods = Record.readInt();
  if (D->isCanonicalDecl()) {
    while (NumOverridenMethods--) {
      // Avoid invariant checking of CXXMethodDecl::addOverriddenMethod,
      // MD may be initializing.
      if (auto *MD = readDeclAs<CXXMethodDecl>())
        Reader.getContext().addOverriddenMethod(D, MD->getCanonicalDecl());
    }
  } else {
    // We don't care about which declarations this used to override; we get
    // the relevant information from the canonical declaration.
    Record.skipInts(NumOverridenMethods);
  }
}

void ASTDeclReader::VisitCXXConstructorDecl(CXXConstructorDecl *D) {
  // We need the inherited constructor information to merge the declaration,
  // so we have to read it before we call VisitCXXMethodDecl.
  D->setExplicitSpecifier(Record.readExplicitSpec());
  if (D->isInheritingConstructor()) {
    auto *Shadow = readDeclAs<ConstructorUsingShadowDecl>();
    auto *Ctor = readDeclAs<CXXConstructorDecl>();
    *D->getTrailingObjects<InheritedConstructor>() =
        InheritedConstructor(Shadow, Ctor);
  }

  VisitCXXMethodDecl(D);
}

void ASTDeclReader::VisitCXXDestructorDecl(CXXDestructorDecl *D) {
  VisitCXXMethodDecl(D);

  if (auto *OperatorDelete = readDeclAs<FunctionDecl>()) {
    CXXDestructorDecl *Canon = D->getCanonicalDecl();
    auto *ThisArg = Record.readExpr();
    // FIXME: Check consistency if we have an old and new operator delete.
    if (!Canon->OperatorDelete) {
      Canon->OperatorDelete = OperatorDelete;
      Canon->OperatorDeleteThisArg = ThisArg;
    }
  }
}

void ASTDeclReader::VisitCXXConversionDecl(CXXConversionDecl *D) {
  D->setExplicitSpecifier(Record.readExplicitSpec());
  VisitCXXMethodDecl(D);
}

void ASTDeclReader::VisitImportDecl(ImportDecl *D) {
  VisitDecl(D);
  D->ImportedModule = readModule();
  D->setImportComplete(Record.readInt());
  auto *StoredLocs = D->getTrailingObjects<SourceLocation>();
  for (unsigned I = 0, N = Record.back(); I != N; ++I)
    StoredLocs[I] = readSourceLocation();
  Record.skipInts(1); // The number of stored source locations.
}

void ASTDeclReader::VisitAccessSpecDecl(AccessSpecDecl *D) {
  VisitDecl(D);
  D->setColonLoc(readSourceLocation());
}

void ASTDeclReader::VisitFriendDecl(FriendDecl *D) {
  VisitDecl(D);
  if (Record.readInt()) // hasFriendDecl
    D->Friend = readDeclAs<NamedDecl>();
  else
    D->Friend = readTypeSourceInfo();
  for (unsigned i = 0; i != D->NumTPLists; ++i)
    D->getTrailingObjects<TemplateParameterList *>()[i] =
        Record.readTemplateParameterList();
  D->NextFriend = readDeclID();
  D->UnsupportedFriend = (Record.readInt() != 0);
  D->FriendLoc = readSourceLocation();
}

void ASTDeclReader::VisitFriendTemplateDecl(FriendTemplateDecl *D) {
  VisitDecl(D);
  unsigned NumParams = Record.readInt();
  D->NumParams = NumParams;
  D->Params = new TemplateParameterList*[NumParams];
  for (unsigned i = 0; i != NumParams; ++i)
    D->Params[i] = Record.readTemplateParameterList();
  if (Record.readInt()) // HasFriendDecl
    D->Friend = readDeclAs<NamedDecl>();
  else
    D->Friend = readTypeSourceInfo();
  D->FriendLoc = readSourceLocation();
}

DeclID ASTDeclReader::VisitTemplateDecl(TemplateDecl *D) {
  VisitNamedDecl(D);

  DeclID PatternID = readDeclID();
  auto *TemplatedDecl = cast_or_null<NamedDecl>(Reader.GetDecl(PatternID));
  TemplateParameterList *TemplateParams = Record.readTemplateParameterList();
  D->init(TemplatedDecl, TemplateParams);

  return PatternID;
}

void ASTDeclReader::VisitConceptDecl(ConceptDecl *D) {
  VisitTemplateDecl(D);
  D->ConstraintExpr = Record.readExpr();
  mergeMergeable(D);
}

void ASTDeclReader::VisitRequiresExprBodyDecl(RequiresExprBodyDecl *D) {
}

ASTDeclReader::RedeclarableResult
ASTDeclReader::VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D) {
  RedeclarableResult Redecl = VisitRedeclarable(D);

  // Make sure we've allocated the Common pointer first. We do this before
  // VisitTemplateDecl so that getCommonPtr() can be used during initialization.
  RedeclarableTemplateDecl *CanonD = D->getCanonicalDecl();
  if (!CanonD->Common) {
    CanonD->Common = CanonD->newCommon(Reader.getContext());
    Reader.PendingDefinitions.insert(CanonD);
  }
  D->Common = CanonD->Common;

  // If this is the first declaration of the template, fill in the information
  // for the 'common' pointer.
  if (ThisDeclID == Redecl.getFirstID()) {
    if (auto *RTD = readDeclAs<RedeclarableTemplateDecl>()) {
      assert(RTD->getKind() == D->getKind() &&
             "InstantiatedFromMemberTemplate kind mismatch");
      D->setInstantiatedFromMemberTemplate(RTD);
      if (Record.readInt())
        D->setMemberSpecialization();
    }
  }

  DeclID PatternID = VisitTemplateDecl(D);
  D->IdentifierNamespace = Record.readInt();

  mergeRedeclarable(D, Redecl, PatternID);

  // If we merged the template with a prior declaration chain, merge the common
  // pointer.
  // FIXME: Actually merge here, don't just overwrite.
  D->Common = D->getCanonicalDecl()->Common;

  return Redecl;
}

void ASTDeclReader::VisitClassTemplateDecl(ClassTemplateDecl *D) {
  RedeclarableResult Redecl = VisitRedeclarableTemplateDecl(D);

  if (ThisDeclID == Redecl.getFirstID()) {
    // This ClassTemplateDecl owns a CommonPtr; read it to keep track of all of
    // the specializations.
    SmallVector<serialization::DeclID, 32> SpecIDs;
    readDeclIDList(SpecIDs);
    ASTDeclReader::AddLazySpecializations(D, SpecIDs);
  }

  if (D->getTemplatedDecl()->TemplateOrInstantiation) {
    // We were loaded before our templated declaration was. We've not set up
    // its corresponding type yet (see VisitCXXRecordDeclImpl), so reconstruct
    // it now.
    Reader.getContext().getInjectedClassNameType(
        D->getTemplatedDecl(), D->getInjectedClassNameSpecialization());
  }
}

void ASTDeclReader::VisitBuiltinTemplateDecl(BuiltinTemplateDecl *D) {
  llvm_unreachable("BuiltinTemplates are not serialized");
}

/// TODO: Unify with ClassTemplateDecl version?
///       May require unifying ClassTemplateDecl and
///        VarTemplateDecl beyond TemplateDecl...
void ASTDeclReader::VisitVarTemplateDecl(VarTemplateDecl *D) {
  RedeclarableResult Redecl = VisitRedeclarableTemplateDecl(D);

  if (ThisDeclID == Redecl.getFirstID()) {
    // This VarTemplateDecl owns a CommonPtr; read it to keep track of all of
    // the specializations.
    SmallVector<serialization::DeclID, 32> SpecIDs;
    readDeclIDList(SpecIDs);
    ASTDeclReader::AddLazySpecializations(D, SpecIDs);
  }
}

ASTDeclReader::RedeclarableResult
ASTDeclReader::VisitClassTemplateSpecializationDeclImpl(
    ClassTemplateSpecializationDecl *D) {
  RedeclarableResult Redecl = VisitCXXRecordDeclImpl(D);

  ASTContext &C = Reader.getContext();
  if (Decl *InstD = readDecl()) {
    if (auto *CTD = dyn_cast<ClassTemplateDecl>(InstD)) {
      D->SpecializedTemplate = CTD;
    } else {
      SmallVector<TemplateArgument, 8> TemplArgs;
      Record.readTemplateArgumentList(TemplArgs);
      TemplateArgumentList *ArgList
        = TemplateArgumentList::CreateCopy(C, TemplArgs);
      auto *PS =
          new (C) ClassTemplateSpecializationDecl::
                                             SpecializedPartialSpecialization();
      PS->PartialSpecialization
          = cast<ClassTemplatePartialSpecializationDecl>(InstD);
      PS->TemplateArgs = ArgList;
      D->SpecializedTemplate = PS;
    }
  }

  SmallVector<TemplateArgument, 8> TemplArgs;
  Record.readTemplateArgumentList(TemplArgs, /*Canonicalize*/ true);
  D->TemplateArgs = TemplateArgumentList::CreateCopy(C, TemplArgs);
  D->PointOfInstantiation = readSourceLocation();
  D->SpecializationKind = (TemplateSpecializationKind)Record.readInt();

  bool writtenAsCanonicalDecl = Record.readInt();
  if (writtenAsCanonicalDecl) {
    auto *CanonPattern = readDeclAs<ClassTemplateDecl>();
    if (D->isCanonicalDecl()) { // It's kept in the folding set.
      // Set this as, or find, the canonical declaration for this specialization
      ClassTemplateSpecializationDecl *CanonSpec;
      if (auto *Partial = dyn_cast<ClassTemplatePartialSpecializationDecl>(D)) {
        CanonSpec = CanonPattern->getCommonPtr()->PartialSpecializations
            .GetOrInsertNode(Partial);
      } else {
        CanonSpec =
            CanonPattern->getCommonPtr()->Specializations.GetOrInsertNode(D);
      }
      // If there was already a canonical specialization, merge into it.
      if (CanonSpec != D) {
        mergeRedeclarable<TagDecl>(D, CanonSpec, Redecl);

        // This declaration might be a definition. Merge with any existing
        // definition.
        if (auto *DDD = D->DefinitionData) {
          if (CanonSpec->DefinitionData)
            MergeDefinitionData(CanonSpec, std::move(*DDD));
          else
            CanonSpec->DefinitionData = D->DefinitionData;
        }
        D->DefinitionData = CanonSpec->DefinitionData;
      }
    }
  }

  // Explicit info.
  if (TypeSourceInfo *TyInfo = readTypeSourceInfo()) {
    auto *ExplicitInfo =
        new (C) ClassTemplateSpecializationDecl::ExplicitSpecializationInfo;
    ExplicitInfo->TypeAsWritten = TyInfo;
    ExplicitInfo->ExternLoc = readSourceLocation();
    ExplicitInfo->TemplateKeywordLoc = readSourceLocation();
    D->ExplicitInfo = ExplicitInfo;
  }

  return Redecl;
}

void ASTDeclReader::VisitClassTemplatePartialSpecializationDecl(
                                    ClassTemplatePartialSpecializationDecl *D) {
  // We need to read the template params first because redeclarable is going to
  // need them for profiling
  TemplateParameterList *Params = Record.readTemplateParameterList();
  D->TemplateParams = Params;
  D->ArgsAsWritten = Record.readASTTemplateArgumentListInfo();

  RedeclarableResult Redecl = VisitClassTemplateSpecializationDeclImpl(D);

  // These are read/set from/to the first declaration.
  if (ThisDeclID == Redecl.getFirstID()) {
    D->InstantiatedFromMember.setPointer(
      readDeclAs<ClassTemplatePartialSpecializationDecl>());
    D->InstantiatedFromMember.setInt(Record.readInt());
  }
}

void ASTDeclReader::VisitClassScopeFunctionSpecializationDecl(
                                    ClassScopeFunctionSpecializationDecl *D) {
  VisitDecl(D);
  D->Specialization = readDeclAs<CXXMethodDecl>();
  if (Record.readInt())
    D->TemplateArgs = Record.readASTTemplateArgumentListInfo();
}

void ASTDeclReader::VisitFunctionTemplateDecl(FunctionTemplateDecl *D) {
  RedeclarableResult Redecl = VisitRedeclarableTemplateDecl(D);

  if (ThisDeclID == Redecl.getFirstID()) {
    // This FunctionTemplateDecl owns a CommonPtr; read it.
    SmallVector<serialization::DeclID, 32> SpecIDs;
    readDeclIDList(SpecIDs);
    ASTDeclReader::AddLazySpecializations(D, SpecIDs);
  }
}

/// TODO: Unify with ClassTemplateSpecializationDecl version?
///       May require unifying ClassTemplate(Partial)SpecializationDecl and
///        VarTemplate(Partial)SpecializationDecl with a new data
///        structure Template(Partial)SpecializationDecl, and
///        using Template(Partial)SpecializationDecl as input type.
ASTDeclReader::RedeclarableResult
ASTDeclReader::VisitVarTemplateSpecializationDeclImpl(
    VarTemplateSpecializationDecl *D) {
  RedeclarableResult Redecl = VisitVarDeclImpl(D);

  ASTContext &C = Reader.getContext();
  if (Decl *InstD = readDecl()) {
    if (auto *VTD = dyn_cast<VarTemplateDecl>(InstD)) {
      D->SpecializedTemplate = VTD;
    } else {
      SmallVector<TemplateArgument, 8> TemplArgs;
      Record.readTemplateArgumentList(TemplArgs);
      TemplateArgumentList *ArgList = TemplateArgumentList::CreateCopy(
          C, TemplArgs);
      auto *PS =
          new (C)
          VarTemplateSpecializationDecl::SpecializedPartialSpecialization();
      PS->PartialSpecialization =
          cast<VarTemplatePartialSpecializationDecl>(InstD);
      PS->TemplateArgs = ArgList;
      D->SpecializedTemplate = PS;
    }
  }

  // Explicit info.
  if (TypeSourceInfo *TyInfo = readTypeSourceInfo()) {
    auto *ExplicitInfo =
        new (C) VarTemplateSpecializationDecl::ExplicitSpecializationInfo;
    ExplicitInfo->TypeAsWritten = TyInfo;
    ExplicitInfo->ExternLoc = readSourceLocation();
    ExplicitInfo->TemplateKeywordLoc = readSourceLocation();
    D->ExplicitInfo = ExplicitInfo;
  }

  SmallVector<TemplateArgument, 8> TemplArgs;
  Record.readTemplateArgumentList(TemplArgs, /*Canonicalize*/ true);
  D->TemplateArgs = TemplateArgumentList::CreateCopy(C, TemplArgs);
  D->PointOfInstantiation = readSourceLocation();
  D->SpecializationKind = (TemplateSpecializationKind)Record.readInt();
  D->IsCompleteDefinition = Record.readInt();

  bool writtenAsCanonicalDecl = Record.readInt();
  if (writtenAsCanonicalDecl) {
    auto *CanonPattern = readDeclAs<VarTemplateDecl>();
    if (D->isCanonicalDecl()) { // It's kept in the folding set.
      // FIXME: If it's already present, merge it.
      if (auto *Partial = dyn_cast<VarTemplatePartialSpecializationDecl>(D)) {
        CanonPattern->getCommonPtr()->PartialSpecializations
            .GetOrInsertNode(Partial);
      } else {
        CanonPattern->getCommonPtr()->Specializations.GetOrInsertNode(D);
      }
    }
  }

  return Redecl;
}

/// TODO: Unify with ClassTemplatePartialSpecializationDecl version?
///       May require unifying ClassTemplate(Partial)SpecializationDecl and
///        VarTemplate(Partial)SpecializationDecl with a new data
///        structure Template(Partial)SpecializationDecl, and
///        using Template(Partial)SpecializationDecl as input type.
void ASTDeclReader::VisitVarTemplatePartialSpecializationDecl(
    VarTemplatePartialSpecializationDecl *D) {
  TemplateParameterList *Params = Record.readTemplateParameterList();
  D->TemplateParams = Params;
  D->ArgsAsWritten = Record.readASTTemplateArgumentListInfo();

  RedeclarableResult Redecl = VisitVarTemplateSpecializationDeclImpl(D);

  // These are read/set from/to the first declaration.
  if (ThisDeclID == Redecl.getFirstID()) {
    D->InstantiatedFromMember.setPointer(
        readDeclAs<VarTemplatePartialSpecializationDecl>());
    D->InstantiatedFromMember.setInt(Record.readInt());
  }
}

void ASTDeclReader::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
  VisitTypeDecl(D);

  D->setDeclaredWithTypename(Record.readInt());

  if (Record.readBool()) {
    NestedNameSpecifierLoc NNS = Record.readNestedNameSpecifierLoc();
    DeclarationNameInfo DN = Record.readDeclarationNameInfo();
    ConceptDecl *NamedConcept = Record.readDeclAs<ConceptDecl>();
    const ASTTemplateArgumentListInfo *ArgsAsWritten = nullptr;
    if (Record.readBool())
        ArgsAsWritten = Record.readASTTemplateArgumentListInfo();
    Expr *ImmediatelyDeclaredConstraint = Record.readExpr();
    D->setTypeConstraint(NNS, DN, /*FoundDecl=*/nullptr, NamedConcept,
                         ArgsAsWritten, ImmediatelyDeclaredConstraint);
    if ((D->ExpandedParameterPack = Record.readInt()))
      D->NumExpanded = Record.readInt();
  }

  if (Record.readInt())
    D->setDefaultArgument(readTypeSourceInfo());
}

void ASTDeclReader::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
  VisitDeclaratorDecl(D);
  // TemplateParmPosition.
  D->setDepth(Record.readInt());
  D->setPosition(Record.readInt());
  if (D->hasPlaceholderTypeConstraint())
    D->setPlaceholderTypeConstraint(Record.readExpr());
  if (D->isExpandedParameterPack()) {
    auto TypesAndInfos =
        D->getTrailingObjects<std::pair<QualType, TypeSourceInfo *>>();
    for (unsigned I = 0, N = D->getNumExpansionTypes(); I != N; ++I) {
      new (&TypesAndInfos[I].first) QualType(Record.readType());
      TypesAndInfos[I].second = readTypeSourceInfo();
    }
  } else {
    // Rest of NonTypeTemplateParmDecl.
    D->ParameterPack = Record.readInt();
    if (Record.readInt())
      D->setDefaultArgument(Record.readExpr());
  }
}

void ASTDeclReader::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
  VisitTemplateDecl(D);
  // TemplateParmPosition.
  D->setDepth(Record.readInt());
  D->setPosition(Record.readInt());
  if (D->isExpandedParameterPack()) {
    auto **Data = D->getTrailingObjects<TemplateParameterList *>();
    for (unsigned I = 0, N = D->getNumExpansionTemplateParameters();
         I != N; ++I)
      Data[I] = Record.readTemplateParameterList();
  } else {
    // Rest of TemplateTemplateParmDecl.
    D->ParameterPack = Record.readInt();
    if (Record.readInt())
      D->setDefaultArgument(Reader.getContext(),
                            Record.readTemplateArgumentLoc());
  }
}

void ASTDeclReader::VisitTypeAliasTemplateDecl(TypeAliasTemplateDecl *D) {
  VisitRedeclarableTemplateDecl(D);
}

void ASTDeclReader::VisitStaticAssertDecl(StaticAssertDecl *D) {
  VisitDecl(D);
  D->AssertExprAndFailed.setPointer(Record.readExpr());
  D->AssertExprAndFailed.setInt(Record.readInt());
  D->Message = cast_or_null<StringLiteral>(Record.readExpr());
  D->RParenLoc = readSourceLocation();
}

void ASTDeclReader::VisitEmptyDecl(EmptyDecl *D) {
  VisitDecl(D);
}

void ASTDeclReader::VisitLifetimeExtendedTemporaryDecl(
    LifetimeExtendedTemporaryDecl *D) {
  VisitDecl(D);
  D->ExtendingDecl = readDeclAs<ValueDecl>();
  D->ExprWithTemporary = Record.readStmt();
  if (Record.readInt()) {
    D->Value = new (D->getASTContext()) APValue(Record.readAPValue());
    D->getASTContext().addDestruction(D->Value);
  }
  D->ManglingNumber = Record.readInt();
  mergeMergeable(D);
}

std::pair<uint64_t, uint64_t>
ASTDeclReader::VisitDeclContext(DeclContext *DC) {
  uint64_t LexicalOffset = ReadLocalOffset();
  uint64_t VisibleOffset = ReadLocalOffset();
  return std::make_pair(LexicalOffset, VisibleOffset);
}

template <typename T>
ASTDeclReader::RedeclarableResult
ASTDeclReader::VisitRedeclarable(Redeclarable<T> *D) {
  DeclID FirstDeclID = readDeclID();
  Decl *MergeWith = nullptr;

  bool IsKeyDecl = ThisDeclID == FirstDeclID;
  bool IsFirstLocalDecl = false;

  uint64_t RedeclOffset = 0;

  // 0 indicates that this declaration was the only declaration of its entity,
  // and is used for space optimization.
  if (FirstDeclID == 0) {
    FirstDeclID = ThisDeclID;
    IsKeyDecl = true;
    IsFirstLocalDecl = true;
  } else if (unsigned N = Record.readInt()) {
    // This declaration was the first local declaration, but may have imported
    // other declarations.
    IsKeyDecl = N == 1;
    IsFirstLocalDecl = true;

    // We have some declarations that must be before us in our redeclaration
    // chain. Read them now, and remember that we ought to merge with one of
    // them.
    // FIXME: Provide a known merge target to the second and subsequent such
    // declaration.
    for (unsigned I = 0; I != N - 1; ++I)
      MergeWith = readDecl();

    RedeclOffset = ReadLocalOffset();
  } else {
    // This declaration was not the first local declaration. Read the first
    // local declaration now, to trigger the import of other redeclarations.
    (void)readDecl();
  }

  auto *FirstDecl = cast_or_null<T>(Reader.GetDecl(FirstDeclID));
  if (FirstDecl != D) {
    // We delay loading of the redeclaration chain to avoid deeply nested calls.
    // We temporarily set the first (canonical) declaration as the previous one
    // which is the one that matters and mark the real previous DeclID to be
    // loaded & attached later on.
    D->RedeclLink = Redeclarable<T>::PreviousDeclLink(FirstDecl);
    D->First = FirstDecl->getCanonicalDecl();
  }

  auto *DAsT = static_cast<T *>(D);

  // Note that we need to load local redeclarations of this decl and build a
  // decl chain for them. This must happen *after* we perform the preloading
  // above; this ensures that the redeclaration chain is built in the correct
  // order.
  if (IsFirstLocalDecl)
    Reader.PendingDeclChains.push_back(std::make_pair(DAsT, RedeclOffset));

  return RedeclarableResult(MergeWith, FirstDeclID, IsKeyDecl);
}

/// Attempts to merge the given declaration (D) with another declaration
/// of the same entity.
template<typename T>
void ASTDeclReader::mergeRedeclarable(Redeclarable<T> *DBase,
                                      RedeclarableResult &Redecl,
                                      DeclID TemplatePatternID) {
  // If modules are not available, there is no reason to perform this merge.
  if (!Reader.getContext().getLangOpts().Modules)
    return;

  // If we're not the canonical declaration, we don't need to merge.
  if (!DBase->isFirstDecl())
    return;

  auto *D = static_cast<T *>(DBase);

  if (auto *Existing = Redecl.getKnownMergeTarget())
    // We already know of an existing declaration we should merge with.
    mergeRedeclarable(D, cast<T>(Existing), Redecl, TemplatePatternID);
  else if (FindExistingResult ExistingRes = findExisting(D))
    if (T *Existing = ExistingRes)
      mergeRedeclarable(D, Existing, Redecl, TemplatePatternID);
}

/// "Cast" to type T, asserting if we don't have an implicit conversion.
/// We use this to put code in a template that will only be valid for certain
/// instantiations.
template<typename T> static T assert_cast(T t) { return t; }
template<typename T> static T assert_cast(...) {
  llvm_unreachable("bad assert_cast");
}

/// Merge together the pattern declarations from two template
/// declarations.
void ASTDeclReader::mergeTemplatePattern(RedeclarableTemplateDecl *D,
                                         RedeclarableTemplateDecl *Existing,
                                         DeclID DsID, bool IsKeyDecl) {
  auto *DPattern = D->getTemplatedDecl();
  auto *ExistingPattern = Existing->getTemplatedDecl();
  RedeclarableResult Result(/*MergeWith*/ ExistingPattern,
                            DPattern->getCanonicalDecl()->getGlobalID(),
                            IsKeyDecl);

  if (auto *DClass = dyn_cast<CXXRecordDecl>(DPattern)) {
    // Merge with any existing definition.
    // FIXME: This is duplicated in several places. Refactor.
    auto *ExistingClass =
        cast<CXXRecordDecl>(ExistingPattern)->getCanonicalDecl();
    if (auto *DDD = DClass->DefinitionData) {
      if (ExistingClass->DefinitionData) {
        MergeDefinitionData(ExistingClass, std::move(*DDD));
      } else {
        ExistingClass->DefinitionData = DClass->DefinitionData;
        // We may have skipped this before because we thought that DClass
        // was the canonical declaration.
        Reader.PendingDefinitions.insert(DClass);
      }
    }
    DClass->DefinitionData = ExistingClass->DefinitionData;

    return mergeRedeclarable(DClass, cast<TagDecl>(ExistingPattern),
                             Result);
  }
  if (auto *DFunction = dyn_cast<FunctionDecl>(DPattern))
    return mergeRedeclarable(DFunction, cast<FunctionDecl>(ExistingPattern),
                             Result);
  if (auto *DVar = dyn_cast<VarDecl>(DPattern))
    return mergeRedeclarable(DVar, cast<VarDecl>(ExistingPattern), Result);
  if (auto *DAlias = dyn_cast<TypeAliasDecl>(DPattern))
    return mergeRedeclarable(DAlias, cast<TypedefNameDecl>(ExistingPattern),
                             Result);
  llvm_unreachable("merged an unknown kind of redeclarable template");
}

/// Attempts to merge the given declaration (D) with another declaration
/// of the same entity.
template<typename T>
void ASTDeclReader::mergeRedeclarable(Redeclarable<T> *DBase, T *Existing,
                                      RedeclarableResult &Redecl,
                                      DeclID TemplatePatternID) {
  auto *D = static_cast<T *>(DBase);
  T *ExistingCanon = Existing->getCanonicalDecl();
  T *DCanon = D->getCanonicalDecl();
  if (ExistingCanon != DCanon) {
    assert(DCanon->getGlobalID() == Redecl.getFirstID() &&
           "already merged this declaration");

    // Have our redeclaration link point back at the canonical declaration
    // of the existing declaration, so that this declaration has the
    // appropriate canonical declaration.
    D->RedeclLink </