clang/lib/AST/ASTImporter.cpp

//===- ASTImporter.cpp - Importing ASTs from other Contexts ---------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//  This file defines the ASTImporter class which imports AST nodes from one
//  context into another context.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/ASTImporter.h"
#include "clang/AST/ASTImporterSharedState.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTDiagnostic.h"
#include "clang/AST/ASTStructuralEquivalence.h"
#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclAccessPair.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclFriend.h"
#include "clang/AST/DeclGroup.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/DeclVisitor.h"
#include "clang/AST/DeclarationName.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ExternalASTSource.h"
#include "clang/AST/LambdaCapture.h"
#include "clang/AST/NestedNameSpecifier.h"
#include "clang/AST/OperationKinds.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/StmtObjC.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/TemplateBase.h"
#include "clang/AST/TemplateName.h"
#include "clang/AST/Type.h"
#include "clang/AST/TypeLoc.h"
#include "clang/AST/TypeVisitor.h"
#include "clang/AST/UnresolvedSet.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/ExceptionSpecificationType.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/IdentifierTable.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/Specifiers.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MemoryBuffer.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <memory>
#include <type_traits>
#include <utility>

namespace clang {

  using llvm::make_error;
  using llvm::Error;
  using llvm::Expected;
  using ExpectedTypePtr = llvm::Expected<const Type *>;
  using ExpectedType = llvm::Expected<QualType>;
  using ExpectedStmt = llvm::Expected<Stmt *>;
  using ExpectedExpr = llvm::Expected<Expr *>;
  using ExpectedDecl = llvm::Expected<Decl *>;
  using ExpectedSLoc = llvm::Expected<SourceLocation>;
  using ExpectedName = llvm::Expected<DeclarationName>;

  std::string ImportError::toString() const {
    // FIXME: Improve error texts.
    switch (Error) {
    case NameConflict:
      return "NameConflict";
    case UnsupportedConstruct:
      return "UnsupportedConstruct";
    case Unknown:
      return "Unknown error";
    }
    llvm_unreachable("Invalid error code.");
    return "Invalid error code.";
  }

  void ImportError::log(raw_ostream &OS) const {
    OS << toString();
  }

  std::error_code ImportError::convertToErrorCode() const {
    llvm_unreachable("Function not implemented.");
  }

  char ImportError::ID;

  template <class T>
  SmallVector<Decl *, 2>
  getCanonicalForwardRedeclChain(Redeclarable<T>* D) {
    SmallVector<Decl *, 2> Redecls;
    for (auto *R : D->getFirstDecl()->redecls()) {
      if (R != D->getFirstDecl())
        Redecls.push_back(R);
    }
    Redecls.push_back(D->getFirstDecl());
    std::reverse(Redecls.begin(), Redecls.end());
    return Redecls;
  }

  SmallVector<Decl*, 2> getCanonicalForwardRedeclChain(Decl* D) {
    if (auto *FD = dyn_cast<FunctionDecl>(D))
      return getCanonicalForwardRedeclChain<FunctionDecl>(FD);
    if (auto *VD = dyn_cast<VarDecl>(D))
      return getCanonicalForwardRedeclChain<VarDecl>(VD);
    if (auto *TD = dyn_cast<TagDecl>(D))
      return getCanonicalForwardRedeclChain<TagDecl>(TD);
    llvm_unreachable("Bad declaration kind");
  }

  void updateFlags(const Decl *From, Decl *To) {
    // Check if some flags or attrs are new in 'From' and copy into 'To'.
    // FIXME: Other flags or attrs?
    if (From->isUsed(false) && !To->isUsed(false))
      To->setIsUsed();
  }

  class ASTNodeImporter : public TypeVisitor<ASTNodeImporter, ExpectedType>,
                          public DeclVisitor<ASTNodeImporter, ExpectedDecl>,
                          public StmtVisitor<ASTNodeImporter, ExpectedStmt> {
    ASTImporter &Importer;

    // Use this instead of Importer.importInto .
    template <typename ImportT>
    LLVM_NODISCARD Error importInto(ImportT &To, const ImportT &From) {
      return Importer.importInto(To, From);
    }

    // Use this to import pointers of specific type.
    template <typename ImportT>
    LLVM_NODISCARD Error importInto(ImportT *&To, ImportT *From) {
      auto ToOrErr = Importer.Import(From);
      if (ToOrErr)
        To = cast_or_null<ImportT>(*ToOrErr);
      return ToOrErr.takeError();
    }

    // Call the import function of ASTImporter for a baseclass of type `T` and
    // cast the return value to `T`.
    template <typename T>
    auto import(T *From)
        -> std::conditional_t<std::is_base_of<Type, T>::value,
                              Expected<const T *>, Expected<T *>> {
      auto ToOrErr = Importer.Import(From);
      if (!ToOrErr)
        return ToOrErr.takeError();
      return cast_or_null<T>(*ToOrErr);
    }

    template <typename T>
    auto import(const T *From) {
      return import(const_cast<T *>(From));
    }

    // Call the import function of ASTImporter for type `T`.
    template <typename T>
    Expected<T> import(const T &From) {
      return Importer.Import(From);
    }

    // Import an Optional<T> by importing the contained T, if any.
    template<typename T>
    Expected<Optional<T>> import(Optional<T> From) {
      if (!From)
        return Optional<T>();
      return import(*From);
    }

    ExplicitSpecifier importExplicitSpecifier(Error &Err,
                                              ExplicitSpecifier ESpec);

    // Wrapper for an overload set.
    template <typename ToDeclT> struct CallOverloadedCreateFun {
      template <typename... Args> decltype(auto) operator()(Args &&... args) {
        return ToDeclT::Create(std::forward<Args>(args)...);
      }
    };

    // Always use these functions to create a Decl during import. There are
    // certain tasks which must be done after the Decl was created, e.g. we
    // must immediately register that as an imported Decl.  The parameter `ToD`
    // will be set to the newly created Decl or if had been imported before
    // then to the already imported Decl.  Returns a bool value set to true if
    // the `FromD` had been imported before.
    template <typename ToDeclT, typename FromDeclT, typename... Args>
    LLVM_NODISCARD bool GetImportedOrCreateDecl(ToDeclT *&ToD, FromDeclT *FromD,
                                                Args &&... args) {
      // There may be several overloads of ToDeclT::Create. We must make sure
      // to call the one which would be chosen by the arguments, thus we use a
      // wrapper for the overload set.
      CallOverloadedCreateFun<ToDeclT> OC;
      return GetImportedOrCreateSpecialDecl(ToD, OC, FromD,
                                            std::forward<Args>(args)...);
    }
    // Use this overload if a special Type is needed to be created.  E.g if we
    // want to create a `TypeAliasDecl` and assign that to a `TypedefNameDecl`
    // then:
    // TypedefNameDecl *ToTypedef;
    // GetImportedOrCreateDecl<TypeAliasDecl>(ToTypedef, FromD, ...);
    template <typename NewDeclT, typename ToDeclT, typename FromDeclT,
              typename... Args>
    LLVM_NODISCARD bool GetImportedOrCreateDecl(ToDeclT *&ToD, FromDeclT *FromD,
                                                Args &&... args) {
      CallOverloadedCreateFun<NewDeclT> OC;
      return GetImportedOrCreateSpecialDecl(ToD, OC, FromD,
                                            std::forward<Args>(args)...);
    }
    // Use this version if a special create function must be
    // used, e.g. CXXRecordDecl::CreateLambda .
    template <typename ToDeclT, typename CreateFunT, typename FromDeclT,
              typename... Args>
    LLVM_NODISCARD bool
    GetImportedOrCreateSpecialDecl(ToDeclT *&ToD, CreateFunT CreateFun,
                                   FromDeclT *FromD, Args &&... args) {
      if (Importer.getImportDeclErrorIfAny(FromD)) {
        ToD = nullptr;
        return true; // Already imported but with error.
      }
      ToD = cast_or_null<ToDeclT>(Importer.GetAlreadyImportedOrNull(FromD));
      if (ToD)
        return true; // Already imported.
      ToD = CreateFun(std::forward<Args>(args)...);
      // Keep track of imported Decls.
      Importer.RegisterImportedDecl(FromD, ToD);
      InitializeImportedDecl(FromD, ToD);
      return false; // A new Decl is created.
    }

    void InitializeImportedDecl(Decl *FromD, Decl *ToD) {
      ToD->IdentifierNamespace = FromD->IdentifierNamespace;
      if (FromD->isUsed())
        ToD->setIsUsed();
      if (FromD->isImplicit())
        ToD->setImplicit();
    }

    // Check if we have found an existing definition.  Returns with that
    // definition if yes, otherwise returns null.
    Decl *FindAndMapDefinition(FunctionDecl *D, FunctionDecl *FoundFunction) {
      const FunctionDecl *Definition = nullptr;
      if (D->doesThisDeclarationHaveABody() &&
          FoundFunction->hasBody(Definition))
        return Importer.MapImported(D, const_cast<FunctionDecl *>(Definition));
      return nullptr;
    }

    void addDeclToContexts(Decl *FromD, Decl *ToD) {
      if (Importer.isMinimalImport()) {
        // In minimal import case the decl must be added even if it is not
        // contained in original context, for LLDB compatibility.
        // FIXME: Check if a better solution is possible.
        if (!FromD->getDescribedTemplate() &&
            FromD->getFriendObjectKind() == Decl::FOK_None)
          ToD->getLexicalDeclContext()->addDeclInternal(ToD);
        return;
      }

      DeclContext *FromDC = FromD->getDeclContext();
      DeclContext *FromLexicalDC = FromD->getLexicalDeclContext();
      DeclContext *ToDC = ToD->getDeclContext();
      DeclContext *ToLexicalDC = ToD->getLexicalDeclContext();

      bool Visible = false;
      if (FromDC->containsDeclAndLoad(FromD)) {
        ToDC->addDeclInternal(ToD);
        Visible = true;
      }
      if (ToDC != ToLexicalDC && FromLexicalDC->containsDeclAndLoad(FromD)) {
        ToLexicalDC->addDeclInternal(ToD);
        Visible = true;
      }

      // If the Decl was added to any context, it was made already visible.
      // Otherwise it is still possible that it should be visible.
      if (!Visible) {
        if (auto *FromNamed = dyn_cast<NamedDecl>(FromD)) {
          auto *ToNamed = cast<NamedDecl>(ToD);
          DeclContextLookupResult FromLookup =
              FromDC->lookup(FromNamed->getDeclName());
          if (llvm::is_contained(FromLookup, FromNamed))
            ToDC->makeDeclVisibleInContext(ToNamed);
        }
      }
    }

    void updateLookupTableForTemplateParameters(TemplateParameterList &Params,
                                                DeclContext *OldDC) {
      ASTImporterLookupTable *LT = Importer.SharedState->getLookupTable();
      if (!LT)
        return;

      for (NamedDecl *TP : Params)
        LT->update(TP, OldDC);
    }

    void updateLookupTableForTemplateParameters(TemplateParameterList &Params) {
      updateLookupTableForTemplateParameters(
          Params, Importer.getToContext().getTranslationUnitDecl());
    }

  public:
    explicit ASTNodeImporter(ASTImporter &Importer) : Importer(Importer) {}

    using TypeVisitor<ASTNodeImporter, ExpectedType>::Visit;
    using DeclVisitor<ASTNodeImporter, ExpectedDecl>::Visit;
    using StmtVisitor<ASTNodeImporter, ExpectedStmt>::Visit;

    // Importing types
    ExpectedType VisitType(const Type *T);
    ExpectedType VisitAtomicType(const AtomicType *T);
    ExpectedType VisitBuiltinType(const BuiltinType *T);
    ExpectedType VisitDecayedType(const DecayedType *T);
    ExpectedType VisitComplexType(const ComplexType *T);
    ExpectedType VisitPointerType(const PointerType *T);
    ExpectedType VisitBlockPointerType(const BlockPointerType *T);
    ExpectedType VisitLValueReferenceType(const LValueReferenceType *T);
    ExpectedType VisitRValueReferenceType(const RValueReferenceType *T);
    ExpectedType VisitMemberPointerType(const MemberPointerType *T);
    ExpectedType VisitConstantArrayType(const ConstantArrayType *T);
    ExpectedType VisitIncompleteArrayType(const IncompleteArrayType *T);
    ExpectedType VisitVariableArrayType(const VariableArrayType *T);
    ExpectedType VisitDependentSizedArrayType(const DependentSizedArrayType *T);
    // FIXME: DependentSizedExtVectorType
    ExpectedType VisitVectorType(const VectorType *T);
    ExpectedType VisitExtVectorType(const ExtVectorType *T);
    ExpectedType VisitFunctionNoProtoType(const FunctionNoProtoType *T);
    ExpectedType VisitFunctionProtoType(const FunctionProtoType *T);
    ExpectedType VisitUnresolvedUsingType(const UnresolvedUsingType *T);
    ExpectedType VisitParenType(const ParenType *T);
    ExpectedType VisitTypedefType(const TypedefType *T);
    ExpectedType VisitTypeOfExprType(const TypeOfExprType *T);
    // FIXME: DependentTypeOfExprType
    ExpectedType VisitTypeOfType(const TypeOfType *T);
    ExpectedType VisitDecltypeType(const DecltypeType *T);
    ExpectedType VisitUnaryTransformType(const UnaryTransformType *T);
    ExpectedType VisitAutoType(const AutoType *T);
    ExpectedType VisitDeducedTemplateSpecializationType(
        const DeducedTemplateSpecializationType *T);
    ExpectedType VisitInjectedClassNameType(const InjectedClassNameType *T);
    // FIXME: DependentDecltypeType
    ExpectedType VisitRecordType(const RecordType *T);
    ExpectedType VisitEnumType(const EnumType *T);
    ExpectedType VisitAttributedType(const AttributedType *T);
    ExpectedType VisitTemplateTypeParmType(const TemplateTypeParmType *T);
    ExpectedType VisitSubstTemplateTypeParmType(
        const SubstTemplateTypeParmType *T);
    ExpectedType
    VisitSubstTemplateTypeParmPackType(const SubstTemplateTypeParmPackType *T);
    ExpectedType VisitTemplateSpecializationType(
        const TemplateSpecializationType *T);
    ExpectedType VisitElaboratedType(const ElaboratedType *T);
    ExpectedType VisitDependentNameType(const DependentNameType *T);
    ExpectedType VisitPackExpansionType(const PackExpansionType *T);
    ExpectedType VisitDependentTemplateSpecializationType(
        const DependentTemplateSpecializationType *T);
    ExpectedType VisitObjCInterfaceType(const ObjCInterfaceType *T);
    ExpectedType VisitObjCObjectType(const ObjCObjectType *T);
    ExpectedType VisitObjCObjectPointerType(const ObjCObjectPointerType *T);

    // Importing declarations
    Error ImportDeclParts(NamedDecl *D, DeclarationName &Name, NamedDecl *&ToD,
                          SourceLocation &Loc);
    Error ImportDeclParts(
        NamedDecl *D, DeclContext *&DC, DeclContext *&LexicalDC,
        DeclarationName &Name, NamedDecl *&ToD, SourceLocation &Loc);
    Error ImportDefinitionIfNeeded(Decl *FromD, Decl *ToD = nullptr);
    Error ImportDeclarationNameLoc(
        const DeclarationNameInfo &From, DeclarationNameInfo &To);
    Error ImportDeclContext(DeclContext *FromDC, bool ForceImport = false);
    Error ImportDeclContext(
        Decl *From, DeclContext *&ToDC, DeclContext *&ToLexicalDC);
    Error ImportImplicitMethods(const CXXRecordDecl *From, CXXRecordDecl *To);

    Expected<CXXCastPath> ImportCastPath(CastExpr *E);
    Expected<APValue> ImportAPValue(const APValue &FromValue);

    using Designator = DesignatedInitExpr::Designator;

    /// What we should import from the definition.
    enum ImportDefinitionKind {
      /// Import the default subset of the definition, which might be
      /// nothing (if minimal import is set) or might be everything (if minimal
      /// import is not set).
      IDK_Default,
      /// Import everything.
      IDK_Everything,
      /// Import only the bare bones needed to establish a valid
      /// DeclContext.
      IDK_Basic
    };

    bool shouldForceImportDeclContext(ImportDefinitionKind IDK) {
      return IDK == IDK_Everything ||
             (IDK == IDK_Default && !Importer.isMinimalImport());
    }

    Error ImportInitializer(VarDecl *From, VarDecl *To);
    Error ImportDefinition(
        RecordDecl *From, RecordDecl *To,
        ImportDefinitionKind Kind = IDK_Default);
    Error ImportDefinition(
        EnumDecl *From, EnumDecl *To,
        ImportDefinitionKind Kind = IDK_Default);
    Error ImportDefinition(
        ObjCInterfaceDecl *From, ObjCInterfaceDecl *To,
        ImportDefinitionKind Kind = IDK_Default);
    Error ImportDefinition(
        ObjCProtocolDecl *From, ObjCProtocolDecl *To,
        ImportDefinitionKind Kind = IDK_Default);
    Error ImportTemplateArguments(
        const TemplateArgument *FromArgs, unsigned NumFromArgs,
        SmallVectorImpl<TemplateArgument> &ToArgs);
    Expected<TemplateArgument>
    ImportTemplateArgument(const TemplateArgument &From);

    template <typename InContainerTy>
    Error ImportTemplateArgumentListInfo(
        const InContainerTy &Container, TemplateArgumentListInfo &ToTAInfo);

    template<typename InContainerTy>
    Error ImportTemplateArgumentListInfo(
      SourceLocation FromLAngleLoc, SourceLocation FromRAngleLoc,
      const InContainerTy &Container, TemplateArgumentListInfo &Result);

    using TemplateArgsTy = SmallVector<TemplateArgument, 8>;
    using FunctionTemplateAndArgsTy =
        std::tuple<FunctionTemplateDecl *, TemplateArgsTy>;
    Expected<FunctionTemplateAndArgsTy>
    ImportFunctionTemplateWithTemplateArgsFromSpecialization(
        FunctionDecl *FromFD);
    Error ImportTemplateParameterLists(const DeclaratorDecl *FromD,
                                       DeclaratorDecl *ToD);

    Error ImportTemplateInformation(FunctionDecl *FromFD, FunctionDecl *ToFD);

    Error ImportFunctionDeclBody(FunctionDecl *FromFD, FunctionDecl *ToFD);

    Error ImportDefaultArgOfParmVarDecl(const ParmVarDecl *FromParam,
                                        ParmVarDecl *ToParam);

    Expected<InheritedConstructor>
    ImportInheritedConstructor(const InheritedConstructor &From);

    template <typename T>
    bool hasSameVisibilityContextAndLinkage(T *Found, T *From);

    bool IsStructuralMatch(Decl *From, Decl *To, bool Complain = true);
    ExpectedDecl VisitDecl(Decl *D);
    ExpectedDecl VisitImportDecl(ImportDecl *D);
    ExpectedDecl VisitEmptyDecl(EmptyDecl *D);
    ExpectedDecl VisitAccessSpecDecl(AccessSpecDecl *D);
    ExpectedDecl VisitStaticAssertDecl(StaticAssertDecl *D);
    ExpectedDecl VisitTranslationUnitDecl(TranslationUnitDecl *D);
    ExpectedDecl VisitBindingDecl(BindingDecl *D);
    ExpectedDecl VisitNamespaceDecl(NamespaceDecl *D);
    ExpectedDecl VisitNamespaceAliasDecl(NamespaceAliasDecl *D);
    ExpectedDecl VisitTypedefNameDecl(TypedefNameDecl *D, bool IsAlias);
    ExpectedDecl VisitTypedefDecl(TypedefDecl *D);
    ExpectedDecl VisitTypeAliasDecl(TypeAliasDecl *D);
    ExpectedDecl VisitTypeAliasTemplateDecl(TypeAliasTemplateDecl *D);
    ExpectedDecl VisitLabelDecl(LabelDecl *D);
    ExpectedDecl VisitEnumDecl(EnumDecl *D);
    ExpectedDecl VisitRecordDecl(RecordDecl *D);
    ExpectedDecl VisitEnumConstantDecl(EnumConstantDecl *D);
    ExpectedDecl VisitFunctionDecl(FunctionDecl *D);
    ExpectedDecl VisitCXXMethodDecl(CXXMethodDecl *D);
    ExpectedDecl VisitCXXConstructorDecl(CXXConstructorDecl *D);
    ExpectedDecl VisitCXXDestructorDecl(CXXDestructorDecl *D);
    ExpectedDecl VisitCXXConversionDecl(CXXConversionDecl *D);
    ExpectedDecl VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *D);
    ExpectedDecl VisitFieldDecl(FieldDecl *D);
    ExpectedDecl VisitIndirectFieldDecl(IndirectFieldDecl *D);
    ExpectedDecl VisitFriendDecl(FriendDecl *D);
    ExpectedDecl VisitObjCIvarDecl(ObjCIvarDecl *D);
    ExpectedDecl VisitVarDecl(VarDecl *D);
    ExpectedDecl VisitImplicitParamDecl(ImplicitParamDecl *D);
    ExpectedDecl VisitParmVarDecl(ParmVarDecl *D);
    ExpectedDecl VisitObjCMethodDecl(ObjCMethodDecl *D);
    ExpectedDecl VisitObjCTypeParamDecl(ObjCTypeParamDecl *D);
    ExpectedDecl VisitObjCCategoryDecl(ObjCCategoryDecl *D);
    ExpectedDecl VisitObjCProtocolDecl(ObjCProtocolDecl *D);
    ExpectedDecl VisitLinkageSpecDecl(LinkageSpecDecl *D);
    ExpectedDecl VisitUsingDecl(UsingDecl *D);
    ExpectedDecl VisitUsingShadowDecl(UsingShadowDecl *D);
    ExpectedDecl VisitUsingDirectiveDecl(UsingDirectiveDecl *D);
    ExpectedDecl ImportUsingShadowDecls(BaseUsingDecl *D, BaseUsingDecl *ToSI);
    ExpectedDecl VisitUsingEnumDecl(UsingEnumDecl *D);
    ExpectedDecl VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
    ExpectedDecl VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D);
    ExpectedDecl VisitBuiltinTemplateDecl(BuiltinTemplateDecl *D);
    ExpectedDecl
    VisitLifetimeExtendedTemporaryDecl(LifetimeExtendedTemporaryDecl *D);

    Expected<ObjCTypeParamList *>
    ImportObjCTypeParamList(ObjCTypeParamList *list);

    ExpectedDecl VisitObjCInterfaceDecl(ObjCInterfaceDecl *D);
    ExpectedDecl VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D);
    ExpectedDecl VisitObjCImplementationDecl(ObjCImplementationDecl *D);
    ExpectedDecl VisitObjCPropertyDecl(ObjCPropertyDecl *D);
    ExpectedDecl VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
    ExpectedDecl VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D);
    ExpectedDecl VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D);
    ExpectedDecl VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D);
    ExpectedDecl VisitClassTemplateDecl(ClassTemplateDecl *D);
    ExpectedDecl VisitClassTemplateSpecializationDecl(
                                            ClassTemplateSpecializationDecl *D);
    ExpectedDecl VisitVarTemplateDecl(VarTemplateDecl *D);
    ExpectedDecl VisitVarTemplateSpecializationDecl(VarTemplateSpecializationDecl *D);
    ExpectedDecl VisitFunctionTemplateDecl(FunctionTemplateDecl *D);

    // Importing statements
    ExpectedStmt VisitStmt(Stmt *S);
    ExpectedStmt VisitGCCAsmStmt(GCCAsmStmt *S);
    ExpectedStmt VisitDeclStmt(DeclStmt *S);
    ExpectedStmt VisitNullStmt(NullStmt *S);
    ExpectedStmt VisitCompoundStmt(CompoundStmt *S);
    ExpectedStmt VisitCaseStmt(CaseStmt *S);
    ExpectedStmt VisitDefaultStmt(DefaultStmt *S);
    ExpectedStmt VisitLabelStmt(LabelStmt *S);
    ExpectedStmt VisitAttributedStmt(AttributedStmt *S);
    ExpectedStmt VisitIfStmt(IfStmt *S);
    ExpectedStmt VisitSwitchStmt(SwitchStmt *S);
    ExpectedStmt VisitWhileStmt(WhileStmt *S);
    ExpectedStmt VisitDoStmt(DoStmt *S);
    ExpectedStmt VisitForStmt(ForStmt *S);
    ExpectedStmt VisitGotoStmt(GotoStmt *S);
    ExpectedStmt VisitIndirectGotoStmt(IndirectGotoStmt *S);
    ExpectedStmt VisitContinueStmt(ContinueStmt *S);
    ExpectedStmt VisitBreakStmt(BreakStmt *S);
    ExpectedStmt VisitReturnStmt(ReturnStmt *S);
    // FIXME: MSAsmStmt
    // FIXME: SEHExceptStmt
    // FIXME: SEHFinallyStmt
    // FIXME: SEHTryStmt
    // FIXME: SEHLeaveStmt
    // FIXME: CapturedStmt
    ExpectedStmt VisitCXXCatchStmt(CXXCatchStmt *S);
    ExpectedStmt VisitCXXTryStmt(CXXTryStmt *S);
    ExpectedStmt VisitCXXForRangeStmt(CXXForRangeStmt *S);
    // FIXME: MSDependentExistsStmt
    ExpectedStmt VisitObjCForCollectionStmt(ObjCForCollectionStmt *S);
    ExpectedStmt VisitObjCAtCatchStmt(ObjCAtCatchStmt *S);
    ExpectedStmt VisitObjCAtFinallyStmt(ObjCAtFinallyStmt *S);
    ExpectedStmt VisitObjCAtTryStmt(ObjCAtTryStmt *S);
    ExpectedStmt VisitObjCAtSynchronizedStmt(ObjCAtSynchronizedStmt *S);
    ExpectedStmt VisitObjCAtThrowStmt(ObjCAtThrowStmt *S);
    ExpectedStmt VisitObjCAutoreleasePoolStmt(ObjCAutoreleasePoolStmt *S);

    // Importing expressions
    ExpectedStmt VisitExpr(Expr *E);
    ExpectedStmt VisitSourceLocExpr(SourceLocExpr *E);
    ExpectedStmt VisitVAArgExpr(VAArgExpr *E);
    ExpectedStmt VisitChooseExpr(ChooseExpr *E);
    ExpectedStmt VisitShuffleVectorExpr(ShuffleVectorExpr *E);
    ExpectedStmt VisitGNUNullExpr(GNUNullExpr *E);
    ExpectedStmt VisitGenericSelectionExpr(GenericSelectionExpr *E);
    ExpectedStmt VisitPredefinedExpr(PredefinedExpr *E);
    ExpectedStmt VisitDeclRefExpr(DeclRefExpr *E);
    ExpectedStmt VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
    ExpectedStmt VisitDesignatedInitExpr(DesignatedInitExpr *E);
    ExpectedStmt VisitCXXNullPtrLiteralExpr(CXXNullPtrLiteralExpr *E);
    ExpectedStmt VisitIntegerLiteral(IntegerLiteral *E);
    ExpectedStmt VisitFloatingLiteral(FloatingLiteral *E);
    ExpectedStmt VisitImaginaryLiteral(ImaginaryLiteral *E);
    ExpectedStmt VisitFixedPointLiteral(FixedPointLiteral *E);
    ExpectedStmt VisitCharacterLiteral(CharacterLiteral *E);
    ExpectedStmt VisitStringLiteral(StringLiteral *E);
    ExpectedStmt VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
    ExpectedStmt VisitAtomicExpr(AtomicExpr *E);
    ExpectedStmt VisitAddrLabelExpr(AddrLabelExpr *E);
    ExpectedStmt VisitConstantExpr(ConstantExpr *E);
    ExpectedStmt VisitParenExpr(ParenExpr *E);
    ExpectedStmt VisitParenListExpr(ParenListExpr *E);
    ExpectedStmt VisitStmtExpr(StmtExpr *E);
    ExpectedStmt VisitUnaryOperator(UnaryOperator *E);
    ExpectedStmt VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E);
    ExpectedStmt VisitBinaryOperator(BinaryOperator *E);
    ExpectedStmt VisitConditionalOperator(ConditionalOperator *E);
    ExpectedStmt VisitBinaryConditionalOperator(BinaryConditionalOperator *E);
    ExpectedStmt VisitOpaqueValueExpr(OpaqueValueExpr *E);
    ExpectedStmt VisitArrayTypeTraitExpr(ArrayTypeTraitExpr *E);
    ExpectedStmt VisitExpressionTraitExpr(ExpressionTraitExpr *E);
    ExpectedStmt VisitArraySubscriptExpr(ArraySubscriptExpr *E);
    ExpectedStmt VisitCompoundAssignOperator(CompoundAssignOperator *E);
    ExpectedStmt VisitImplicitCastExpr(ImplicitCastExpr *E);
    ExpectedStmt VisitExplicitCastExpr(ExplicitCastExpr *E);
    ExpectedStmt VisitOffsetOfExpr(OffsetOfExpr *OE);
    ExpectedStmt VisitCXXThrowExpr(CXXThrowExpr *E);
    ExpectedStmt VisitCXXNoexceptExpr(CXXNoexceptExpr *E);
    ExpectedStmt VisitCXXDefaultArgExpr(CXXDefaultArgExpr *E);
    ExpectedStmt VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
    ExpectedStmt VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
    ExpectedStmt VisitCXXTemporaryObjectExpr(CXXTemporaryObjectExpr *E);
    ExpectedStmt VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
    ExpectedStmt VisitPackExpansionExpr(PackExpansionExpr *E);
    ExpectedStmt VisitSizeOfPackExpr(SizeOfPackExpr *E);
    ExpectedStmt VisitCXXNewExpr(CXXNewExpr *E);
    ExpectedStmt VisitCXXDeleteExpr(CXXDeleteExpr *E);
    ExpectedStmt VisitCXXConstructExpr(CXXConstructExpr *E);
    ExpectedStmt VisitCXXMemberCallExpr(CXXMemberCallExpr *E);
    ExpectedStmt VisitCXXDependentScopeMemberExpr(CXXDependentScopeMemberExpr *E);
    ExpectedStmt VisitDependentScopeDeclRefExpr(DependentScopeDeclRefExpr *E);
    ExpectedStmt VisitCXXUnresolvedConstructExpr(CXXUnresolvedConstructExpr *E);
    ExpectedStmt VisitUnresolvedLookupExpr(UnresolvedLookupExpr *E);
    ExpectedStmt VisitUnresolvedMemberExpr(UnresolvedMemberExpr *E);
    ExpectedStmt VisitExprWithCleanups(ExprWithCleanups *E);
    ExpectedStmt VisitCXXThisExpr(CXXThisExpr *E);
    ExpectedStmt VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *E);
    ExpectedStmt VisitCXXPseudoDestructorExpr(CXXPseudoDestructorExpr *E);
    ExpectedStmt VisitMemberExpr(MemberExpr *E);
    ExpectedStmt VisitCallExpr(CallExpr *E);
    ExpectedStmt VisitLambdaExpr(LambdaExpr *LE);
    ExpectedStmt VisitInitListExpr(InitListExpr *E);
    ExpectedStmt VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *E);
    ExpectedStmt VisitCXXInheritedCtorInitExpr(CXXInheritedCtorInitExpr *E);
    ExpectedStmt VisitArrayInitLoopExpr(ArrayInitLoopExpr *E);
    ExpectedStmt VisitArrayInitIndexExpr(ArrayInitIndexExpr *E);
    ExpectedStmt VisitCXXDefaultInitExpr(CXXDefaultInitExpr *E);
    ExpectedStmt VisitCXXNamedCastExpr(CXXNamedCastExpr *E);
    ExpectedStmt VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E);
    ExpectedStmt VisitTypeTraitExpr(TypeTraitExpr *E);
    ExpectedStmt VisitCXXTypeidExpr(CXXTypeidExpr *E);
    ExpectedStmt VisitCXXFoldExpr(CXXFoldExpr *E);

    // Helper for chaining together multiple imports. If an error is detected,
    // subsequent imports will return default constructed nodes, so that failure
    // can be detected with a single conditional branch after a sequence of
    // imports.
    template <typename T> T importChecked(Error &Err, const T &From) {
      // Don't attempt to import nodes if we hit an error earlier.
      if (Err)
        return T{};
      Expected<T> MaybeVal = import(From);
      if (!MaybeVal) {
        Err = MaybeVal.takeError();
        return T{};
      }
      return *MaybeVal;
    }

    template<typename IIter, typename OIter>
    Error ImportArrayChecked(IIter Ibegin, IIter Iend, OIter Obegin) {
      using ItemT = std::remove_reference_t<decltype(*Obegin)>;
      for (; Ibegin != Iend; ++Ibegin, ++Obegin) {
        Expected<ItemT> ToOrErr = import(*Ibegin);
        if (!ToOrErr)
          return ToOrErr.takeError();
        *Obegin = *ToOrErr;
      }
      return Error::success();
    }

    // Import every item from a container structure into an output container.
    // If error occurs, stops at first error and returns the error.
    // The output container should have space for all needed elements (it is not
    // expanded, new items are put into from the beginning).
    template<typename InContainerTy, typename OutContainerTy>
    Error ImportContainerChecked(
        const InContainerTy &InContainer, OutContainerTy &OutContainer) {
      return ImportArrayChecked(
          InContainer.begin(), InContainer.end(), OutContainer.begin());
    }

    template<typename InContainerTy, typename OIter>
    Error ImportArrayChecked(const InContainerTy &InContainer, OIter Obegin) {
      return ImportArrayChecked(InContainer.begin(), InContainer.end(), Obegin);
    }

    Error ImportOverriddenMethods(CXXMethodDecl *ToMethod,
                                  CXXMethodDecl *FromMethod);

    Expected<FunctionDecl *> FindFunctionTemplateSpecialization(
        FunctionDecl *FromFD);

    // Returns true if the given function has a placeholder return type and
    // that type is declared inside the body of the function.
    // E.g. auto f() { struct X{}; return X(); }
    bool hasAutoReturnTypeDeclaredInside(FunctionDecl *D);
  };

template <typename InContainerTy>
Error ASTNodeImporter::ImportTemplateArgumentListInfo(
    SourceLocation FromLAngleLoc, SourceLocation FromRAngleLoc,
    const InContainerTy &Container, TemplateArgumentListInfo &Result) {
  auto ToLAngleLocOrErr = import(FromLAngleLoc);
  if (!ToLAngleLocOrErr)
    return ToLAngleLocOrErr.takeError();
  auto ToRAngleLocOrErr = import(FromRAngleLoc);
  if (!ToRAngleLocOrErr)
    return ToRAngleLocOrErr.takeError();

  TemplateArgumentListInfo ToTAInfo(*ToLAngleLocOrErr, *ToRAngleLocOrErr);
  if (auto Err = ImportTemplateArgumentListInfo(Container, ToTAInfo))
    return Err;
  Result = ToTAInfo;
  return Error::success();
}

template <>
Error ASTNodeImporter::ImportTemplateArgumentListInfo<TemplateArgumentListInfo>(
    const TemplateArgumentListInfo &From, TemplateArgumentListInfo &Result) {
  return ImportTemplateArgumentListInfo(
      From.getLAngleLoc(), From.getRAngleLoc(), From.arguments(), Result);
}

template <>
Error ASTNodeImporter::ImportTemplateArgumentListInfo<
    ASTTemplateArgumentListInfo>(
        const ASTTemplateArgumentListInfo &From,
        TemplateArgumentListInfo &Result) {
  return ImportTemplateArgumentListInfo(
      From.LAngleLoc, From.RAngleLoc, From.arguments(), Result);
}

Expected<ASTNodeImporter::FunctionTemplateAndArgsTy>
ASTNodeImporter::ImportFunctionTemplateWithTemplateArgsFromSpecialization(
    FunctionDecl *FromFD) {
  assert(FromFD->getTemplatedKind() ==
      FunctionDecl::TK_FunctionTemplateSpecialization);

  FunctionTemplateAndArgsTy Result;

  auto *FTSInfo = FromFD->getTemplateSpecializationInfo();
  if (Error Err = importInto(std::get<0>(Result), FTSInfo->getTemplate()))
    return std::move(Err);

  // Import template arguments.
  auto TemplArgs = FTSInfo->TemplateArguments->asArray();
  if (Error Err = ImportTemplateArguments(TemplArgs.data(), TemplArgs.size(),
      std::get<1>(Result)))
    return std::move(Err);

  return Result;
}

template <>
Expected<TemplateParameterList *>
ASTNodeImporter::import(TemplateParameterList *From) {
  SmallVector<NamedDecl *, 4> To(From->size());
  if (Error Err = ImportContainerChecked(*From, To))
    return std::move(Err);

  ExpectedExpr ToRequiresClause = import(From->getRequiresClause());
  if (!ToRequiresClause)
    return ToRequiresClause.takeError();

  auto ToTemplateLocOrErr = import(From->getTemplateLoc());
  if (!ToTemplateLocOrErr)
    return ToTemplateLocOrErr.takeError();
  auto ToLAngleLocOrErr = import(From->getLAngleLoc());
  if (!ToLAngleLocOrErr)
    return ToLAngleLocOrErr.takeError();
  auto ToRAngleLocOrErr = import(From->getRAngleLoc());
  if (!ToRAngleLocOrErr)
    return ToRAngleLocOrErr.takeError();

  return TemplateParameterList::Create(
      Importer.getToContext(),
      *ToTemplateLocOrErr,
      *ToLAngleLocOrErr,
      To,
      *ToRAngleLocOrErr,
      *ToRequiresClause);
}

template <>
Expected<TemplateArgument>
ASTNodeImporter::import(const TemplateArgument &From) {
  switch (From.getKind()) {
  case TemplateArgument::Null:
    return TemplateArgument();

  case TemplateArgument::Type: {
    ExpectedType ToTypeOrErr = import(From.getAsType());
    if (!ToTypeOrErr)
      return ToTypeOrErr.takeError();
    return TemplateArgument(*ToTypeOrErr);
  }

  case TemplateArgument::Integral: {
    ExpectedType ToTypeOrErr = import(From.getIntegralType());
    if (!ToTypeOrErr)
      return ToTypeOrErr.takeError();
    return TemplateArgument(From, *ToTypeOrErr);
  }

  case TemplateArgument::Declaration: {
    Expected<ValueDecl *> ToOrErr = import(From.getAsDecl());
    if (!ToOrErr)
      return ToOrErr.takeError();
    ExpectedType ToTypeOrErr = import(From.getParamTypeForDecl());
    if (!ToTypeOrErr)
      return ToTypeOrErr.takeError();
    return TemplateArgument(*ToOrErr, *ToTypeOrErr);
  }

  case TemplateArgument::NullPtr: {
    ExpectedType ToTypeOrErr = import(From.getNullPtrType());
    if (!ToTypeOrErr)
      return ToTypeOrErr.takeError();
    return TemplateArgument(*ToTypeOrErr, /*isNullPtr*/true);
  }

  case TemplateArgument::Template: {
    Expected<TemplateName> ToTemplateOrErr = import(From.getAsTemplate());
    if (!ToTemplateOrErr)
      return ToTemplateOrErr.takeError();

    return TemplateArgument(*ToTemplateOrErr);
  }

  case TemplateArgument::TemplateExpansion: {
    Expected<TemplateName> ToTemplateOrErr =
        import(From.getAsTemplateOrTemplatePattern());
    if (!ToTemplateOrErr)
      return ToTemplateOrErr.takeError();

    return TemplateArgument(
        *ToTemplateOrErr, From.getNumTemplateExpansions());
  }

  case TemplateArgument::Expression:
    if (ExpectedExpr ToExpr = import(From.getAsExpr()))
      return TemplateArgument(*ToExpr);
    else
      return ToExpr.takeError();

  case TemplateArgument::Pack: {
    SmallVector<TemplateArgument, 2> ToPack;
    ToPack.reserve(From.pack_size());
    if (Error Err = ImportTemplateArguments(
        From.pack_begin(), From.pack_size(), ToPack))
      return std::move(Err);

    return TemplateArgument(
        llvm::makeArrayRef(ToPack).copy(Importer.getToContext()));
  }
  }

  llvm_unreachable("Invalid template argument kind");
}

template <>
Expected<TemplateArgumentLoc>
ASTNodeImporter::import(const TemplateArgumentLoc &TALoc) {
  Expected<TemplateArgument> ArgOrErr = import(TALoc.getArgument());
  if (!ArgOrErr)
    return ArgOrErr.takeError();
  TemplateArgument Arg = *ArgOrErr;

  TemplateArgumentLocInfo FromInfo = TALoc.getLocInfo();

  TemplateArgumentLocInfo ToInfo;
  if (Arg.getKind() == TemplateArgument::Expression) {
    ExpectedExpr E = import(FromInfo.getAsExpr());
    if (!E)
      return E.takeError();
    ToInfo = TemplateArgumentLocInfo(*E);
  } else if (Arg.getKind() == TemplateArgument::Type) {
    if (auto TSIOrErr = import(FromInfo.getAsTypeSourceInfo()))
      ToInfo = TemplateArgumentLocInfo(*TSIOrErr);
    else
      return TSIOrErr.takeError();
  } else {
    auto ToTemplateQualifierLocOrErr =
        import(FromInfo.getTemplateQualifierLoc());
    if (!ToTemplateQualifierLocOrErr)
      return ToTemplateQualifierLocOrErr.takeError();
    auto ToTemplateNameLocOrErr = import(FromInfo.getTemplateNameLoc());
    if (!ToTemplateNameLocOrErr)
      return ToTemplateNameLocOrErr.takeError();
    auto ToTemplateEllipsisLocOrErr =
        import(FromInfo.getTemplateEllipsisLoc());
    if (!ToTemplateEllipsisLocOrErr)
      return ToTemplateEllipsisLocOrErr.takeError();
    ToInfo = TemplateArgumentLocInfo(
        Importer.getToContext(), *ToTemplateQualifierLocOrErr,
        *ToTemplateNameLocOrErr, *ToTemplateEllipsisLocOrErr);
  }

  return TemplateArgumentLoc(Arg, ToInfo);
}

template <>
Expected<DeclGroupRef> ASTNodeImporter::import(const DeclGroupRef &DG) {
  if (DG.isNull())
    return DeclGroupRef::Create(Importer.getToContext(), nullptr, 0);
  size_t NumDecls = DG.end() - DG.begin();
  SmallVector<Decl *, 1> ToDecls;
  ToDecls.reserve(NumDecls);
  for (Decl *FromD : DG) {
    if (auto ToDOrErr = import(FromD))
      ToDecls.push_back(*ToDOrErr);
    else
      return ToDOrErr.takeError();
  }
  return DeclGroupRef::Create(Importer.getToContext(),
                              ToDecls.begin(),
                              NumDecls);
}

template <>
Expected<ASTNodeImporter::Designator>
ASTNodeImporter::import(const Designator &D) {
  if (D.isFieldDesignator()) {
    IdentifierInfo *ToFieldName = Importer.Import(D.getFieldName());

    ExpectedSLoc ToDotLocOrErr = import(D.getDotLoc());
    if (!ToDotLocOrErr)
      return ToDotLocOrErr.takeError();

    ExpectedSLoc ToFieldLocOrErr = import(D.getFieldLoc());
    if (!ToFieldLocOrErr)
      return ToFieldLocOrErr.takeError();

    return Designator(ToFieldName, *ToDotLocOrErr, *ToFieldLocOrErr);
  }

  ExpectedSLoc ToLBracketLocOrErr = import(D.getLBracketLoc());
  if (!ToLBracketLocOrErr)
    return ToLBracketLocOrErr.takeError();

  ExpectedSLoc ToRBracketLocOrErr = import(D.getRBracketLoc());
  if (!ToRBracketLocOrErr)
    return ToRBracketLocOrErr.takeError();

  if (D.isArrayDesignator())
    return Designator(D.getFirstExprIndex(),
                      *ToLBracketLocOrErr, *ToRBracketLocOrErr);

  ExpectedSLoc ToEllipsisLocOrErr = import(D.getEllipsisLoc());
  if (!ToEllipsisLocOrErr)
    return ToEllipsisLocOrErr.takeError();

  assert(D.isArrayRangeDesignator());
  return Designator(
      D.getFirstExprIndex(), *ToLBracketLocOrErr, *ToEllipsisLocOrErr,
      *ToRBracketLocOrErr);
}

template <>
Expected<LambdaCapture> ASTNodeImporter::import(const LambdaCapture &From) {
  VarDecl *Var = nullptr;
  if (From.capturesVariable()) {
    if (auto VarOrErr = import(From.getCapturedVar()))
      Var = *VarOrErr;
    else
      return VarOrErr.takeError();
  }

  auto LocationOrErr = import(From.getLocation());
  if (!LocationOrErr)
    return LocationOrErr.takeError();

  SourceLocation EllipsisLoc;
  if (From.isPackExpansion())
    if (Error Err = importInto(EllipsisLoc, From.getEllipsisLoc()))
      return std::move(Err);

  return LambdaCapture(
      *LocationOrErr, From.isImplicit(), From.getCaptureKind(), Var,
      EllipsisLoc);
}

template <typename T>
bool ASTNodeImporter::hasSameVisibilityContextAndLinkage(T *Found, T *From) {
  if (Found->getLinkageInternal() != From->getLinkageInternal())
    return false;

  if (From->hasExternalFormalLinkage())
    return Found->hasExternalFormalLinkage();
  if (Importer.GetFromTU(Found) != From->getTranslationUnitDecl())
    return false;
  if (From->isInAnonymousNamespace())
    return Found->isInAnonymousNamespace();
  else
    return !Found->isInAnonymousNamespace() &&
           !Found->hasExternalFormalLinkage();
}

template <>
bool ASTNodeImporter::hasSameVisibilityContextAndLinkage(TypedefNameDecl *Found,
                                               TypedefNameDecl *From) {
  if (Found->getLinkageInternal() != From->getLinkageInternal())
    return false;

  if (From->isInAnonymousNamespace() && Found->isInAnonymousNamespace())
    return Importer.GetFromTU(Found) == From->getTranslationUnitDecl();
  return From->isInAnonymousNamespace() == Found->isInAnonymousNamespace();
}

} // namespace clang

//----------------------------------------------------------------------------
// Import Types
//----------------------------------------------------------------------------

using namespace clang;

ExpectedType ASTNodeImporter::VisitType(const Type *T) {
  Importer.FromDiag(SourceLocation(), diag::err_unsupported_ast_node)
    << T->getTypeClassName();
  return make_error<ImportError>(ImportError::UnsupportedConstruct);
}

ExpectedType ASTNodeImporter::VisitAtomicType(const AtomicType *T){
  ExpectedType UnderlyingTypeOrErr = import(T->getValueType());
  if (!UnderlyingTypeOrErr)
    return UnderlyingTypeOrErr.takeError();

  return Importer.getToContext().getAtomicType(*UnderlyingTypeOrErr);
}

ExpectedType ASTNodeImporter::VisitBuiltinType(const BuiltinType *T) {
  switch (T->getKind()) {
#define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
  case BuiltinType::Id: \
    return Importer.getToContext().SingletonId;
#include "clang/Basic/OpenCLImageTypes.def"
#define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
  case BuiltinType::Id: \
    return Importer.getToContext().Id##Ty;
#include "clang/Basic/OpenCLExtensionTypes.def"
#define SVE_TYPE(Name, Id, SingletonId) \
  case BuiltinType::Id: \
    return Importer.getToContext().SingletonId;
#include "clang/Basic/AArch64SVEACLETypes.def"
#define PPC_VECTOR_TYPE(Name, Id, Size) \
  case BuiltinType::Id: \
    return Importer.getToContext().Id##Ty;
#include "clang/Basic/PPCTypes.def"
#define RVV_TYPE(Name, Id, SingletonId)                                        \
  case BuiltinType::Id:                                                        \
    return Importer.getToContext().SingletonId;
#include "clang/Basic/RISCVVTypes.def"
#define SHARED_SINGLETON_TYPE(Expansion)
#define BUILTIN_TYPE(Id, SingletonId) \
  case BuiltinType::Id: return Importer.getToContext().SingletonId;
#include "clang/AST/BuiltinTypes.def"

  // FIXME: for Char16, Char32, and NullPtr, make sure that the "to"
  // context supports C++.

  // FIXME: for ObjCId, ObjCClass, and ObjCSel, make sure that the "to"
  // context supports ObjC.

  case BuiltinType::Char_U:
    // The context we're importing from has an unsigned 'char'. If we're
    // importing into a context with a signed 'char', translate to
    // 'unsigned char' instead.
    if (Importer.getToContext().getLangOpts().CharIsSigned)
      return Importer.getToContext().UnsignedCharTy;

    return Importer.getToContext().CharTy;

  case BuiltinType::Char_S:
    // The context we're importing from has an unsigned 'char'. If we're
    // importing into a context with a signed 'char', translate to
    // 'unsigned char' instead.
    if (!Importer.getToContext().getLangOpts().CharIsSigned)
      return Importer.getToContext().SignedCharTy;

    return Importer.getToContext().CharTy;

  case BuiltinType::WChar_S:
  case BuiltinType::WChar_U:
    // FIXME: If not in C++, shall we translate to the C equivalent of
    // wchar_t?
    return Importer.getToContext().WCharTy;
  }

  llvm_unreachable("Invalid BuiltinType Kind!");
}

ExpectedType ASTNodeImporter::VisitDecayedType(const DecayedType *T) {
  ExpectedType ToOriginalTypeOrErr = import(T->getOriginalType());
  if (!ToOriginalTypeOrErr)
    return ToOriginalTypeOrErr.takeError();

  return Importer.getToContext().getDecayedType(*ToOriginalTypeOrErr);
}

ExpectedType ASTNodeImporter::VisitComplexType(const ComplexType *T) {
  ExpectedType ToElementTypeOrErr = import(T->getElementType());
  if (!ToElementTypeOrErr)
    return ToElementTypeOrErr.takeError();

  return Importer.getToContext().getComplexType(*ToElementTypeOrErr);
}

ExpectedType ASTNodeImporter::VisitPointerType(const PointerType *T) {
  ExpectedType ToPointeeTypeOrErr = import(T->getPointeeType());
  if (!ToPointeeTypeOrErr)
    return ToPointeeTypeOrErr.takeError();

  return Importer.getToContext().getPointerType(*ToPointeeTypeOrErr);
}

ExpectedType ASTNodeImporter::VisitBlockPointerType(const BlockPointerType *T) {
  // FIXME: Check for blocks support in "to" context.
  ExpectedType ToPointeeTypeOrErr = import(T->getPointeeType());
  if (!ToPointeeTypeOrErr)
    return ToPointeeTypeOrErr.takeError();

  return Importer.getToContext().getBlockPointerType(*ToPointeeTypeOrErr);
}

ExpectedType
ASTNodeImporter::VisitLValueReferenceType(const LValueReferenceType *T) {
  // FIXME: Check for C++ support in "to" context.
  ExpectedType ToPointeeTypeOrErr = import(T->getPointeeTypeAsWritten());
  if (!ToPointeeTypeOrErr)
    return ToPointeeTypeOrErr.takeError();

  return Importer.getToContext().getLValueReferenceType(*ToPointeeTypeOrErr);
}

ExpectedType
ASTNodeImporter::VisitRValueReferenceType(const RValueReferenceType *T) {
  // FIXME: Check for C++0x support in "to" context.
  ExpectedType ToPointeeTypeOrErr = import(T->getPointeeTypeAsWritten());
  if (!ToPointeeTypeOrErr)
    return ToPointeeTypeOrErr.takeError();

  return Importer.getToContext().getRValueReferenceType(*ToPointeeTypeOrErr);
}

ExpectedType
ASTNodeImporter::VisitMemberPointerType(const MemberPointerType *T) {
  // FIXME: Check for C++ support in "to" context.
  ExpectedType ToPointeeTypeOrErr = import(T->getPointeeType());
  if (!ToPointeeTypeOrErr)
    return ToPointeeTypeOrErr.takeError();

  ExpectedTypePtr ClassTypeOrErr = import(T->getClass());
  if (!ClassTypeOrErr)
    return ClassTypeOrErr.takeError();

  return Importer.getToContext().getMemberPointerType(*ToPointeeTypeOrErr,
                                                      *ClassTypeOrErr);
}

ExpectedType
ASTNodeImporter::VisitConstantArrayType(const ConstantArrayType *T) {
  Error Err = Error::success();
  auto ToElementType = importChecked(Err, T->getElementType());
  auto ToSizeExpr = importChecked(Err, T->getSizeExpr());
  if (Err)
    return std::move(Err);

  return Importer.getToContext().getConstantArrayType(
      ToElementType, T->getSize(), ToSizeExpr, T->getSizeModifier(),
      T->getIndexTypeCVRQualifiers());
}

ExpectedType
ASTNodeImporter::VisitIncompleteArrayType(const IncompleteArrayType *T) {
  ExpectedType ToElementTypeOrErr = import(T->getElementType());
  if (!ToElementTypeOrErr)
    return ToElementTypeOrErr.takeError();

  return Importer.getToContext().getIncompleteArrayType(*ToElementTypeOrErr,
                                                        T->getSizeModifier(),
                                                T->getIndexTypeCVRQualifiers());
}

ExpectedType
ASTNodeImporter::VisitVariableArrayType(const VariableArrayType *T) {
  Error Err = Error::success();
  QualType ToElementType = importChecked(Err, T->getElementType());
  Expr *ToSizeExpr = importChecked(Err, T->getSizeExpr());
  SourceRange ToBracketsRange = importChecked(Err, T->getBracketsRange());
  if (Err)
    return std::move(Err);
  return Importer.getToContext().getVariableArrayType(
      ToElementType, ToSizeExpr, T->getSizeModifier(),
      T->getIndexTypeCVRQualifiers(), ToBracketsRange);
}

ExpectedType ASTNodeImporter::VisitDependentSizedArrayType(
    const DependentSizedArrayType *T) {
  Error Err = Error::success();
  QualType ToElementType = importChecked(Err, T->getElementType());
  Expr *ToSizeExpr = importChecked(Err, T->getSizeExpr());
  SourceRange ToBracketsRange = importChecked(Err, T->getBracketsRange());
  if (Err)
    return std::move(Err);
  // SizeExpr may be null if size is not specified directly.
  // For example, 'int a[]'.

  return Importer.getToContext().getDependentSizedArrayType(
      ToElementType, ToSizeExpr, T->getSizeModifier(),
      T->getIndexTypeCVRQualifiers(), ToBracketsRange);
}

ExpectedType ASTNodeImporter::VisitVectorType(const VectorType *T) {
  ExpectedType ToElementTypeOrErr = import(T->getElementType());
  if (!ToElementTypeOrErr)
    return ToElementTypeOrErr.takeError();

  return Importer.getToContext().getVectorType(*ToElementTypeOrErr,
                                               T->getNumElements(),
                                               T->getVectorKind());
}

ExpectedType ASTNodeImporter::VisitExtVectorType(const ExtVectorType *T) {
  ExpectedType ToElementTypeOrErr = import(T->getElementType());
  if (!ToElementTypeOrErr)
    return ToElementTypeOrErr.takeError();

  return Importer.getToContext().getExtVectorType(*ToElementTypeOrErr,
                                                  T->getNumElements());
}

ExpectedType
ASTNodeImporter::VisitFunctionNoProtoType(const FunctionNoProtoType *T) {
  // FIXME: What happens if we're importing a function without a prototype
  // into C++? Should we make it variadic?
  ExpectedType ToReturnTypeOrErr = import(T->getReturnType());
  if (!ToReturnTypeOrErr)
    return ToReturnTypeOrErr.takeError();

  return Importer.getToContext().getFunctionNoProtoType(*ToReturnTypeOrErr,
                                                        T->getExtInfo());
}

ExpectedType
ASTNodeImporter::VisitFunctionProtoType(const FunctionProtoType *T) {
  ExpectedType ToReturnTypeOrErr = import(T->getReturnType());
  if (!ToReturnTypeOrErr)
    return ToReturnTypeOrErr.takeError();

  // Import argument types
  SmallVector<QualType, 4> ArgTypes;
  for (const auto &A : T->param_types()) {
    ExpectedType TyOrErr = import(A);
    if (!TyOrErr)
      return TyOrErr.takeError();
    ArgTypes.push_back(*TyOrErr);
  }

  // Import exception types
  SmallVector<QualType, 4> ExceptionTypes;
  for (const auto &E : T->exceptions()) {
    ExpectedType TyOrErr = import(E);
    if (!TyOrErr)
      return TyOrErr.takeError();
    ExceptionTypes.push_back(*TyOrErr);
  }

  FunctionProtoType::ExtProtoInfo FromEPI = T->getExtProtoInfo();
  Error Err = Error::success();
  FunctionProtoType::ExtProtoInfo ToEPI;
  ToEPI.ExtInfo = FromEPI.ExtInfo;
  ToEPI.Variadic = FromEPI.Variadic;
  ToEPI.HasTrailingReturn = FromEPI.HasTrailingReturn;
  ToEPI.TypeQuals = FromEPI.TypeQuals;
  ToEPI.RefQualifier = FromEPI.RefQualifier;
  ToEPI.ExceptionSpec.Type = FromEPI.ExceptionSpec.Type;
  ToEPI.ExceptionSpec.NoexceptExpr =
      importChecked(Err, FromEPI.ExceptionSpec.NoexceptExpr);
  ToEPI.ExceptionSpec.SourceDecl =
      importChecked(Err, FromEPI.ExceptionSpec.SourceDecl);
  ToEPI.ExceptionSpec.SourceTemplate =
      importChecked(Err, FromEPI.ExceptionSpec.SourceTemplate);
  ToEPI.ExceptionSpec.Exceptions = ExceptionTypes;

  if (Err)
    return std::move(Err);

  return Importer.getToContext().getFunctionType(
      *ToReturnTypeOrErr, ArgTypes, ToEPI);
}

ExpectedType ASTNodeImporter::VisitUnresolvedUsingType(
    const UnresolvedUsingType *T) {
  Error Err = Error::success();
  auto ToD = importChecked(Err, T->getDecl());
  auto ToPrevD = importChecked(Err, T->getDecl()->getPreviousDecl());
  if (Err)
    return std::move(Err);

  return Importer.getToContext().getTypeDeclType(
      ToD, cast_or_null<TypeDecl>(ToPrevD));
}

ExpectedType ASTNodeImporter::VisitParenType(const ParenType *T) {
  ExpectedType ToInnerTypeOrErr = import(T->getInnerType());
  if (!ToInnerTypeOrErr)
    return ToInnerTypeOrErr.takeError();

  return Importer.getToContext().getParenType(*ToInnerTypeOrErr);
}

ExpectedType ASTNodeImporter::VisitTypedefType(const TypedefType *T) {
  Expected<TypedefNameDecl *> ToDeclOrErr = import(T->getDecl());
  if (!ToDeclOrErr)
    return ToDeclOrErr.takeError();

  return Importer.getToContext().getTypeDeclType(*ToDeclOrErr);
}

ExpectedType ASTNodeImporter::VisitTypeOfExprType(const TypeOfExprType *T) {
  ExpectedExpr ToExprOrErr = import(T->getUnderlyingExpr());
  if (!ToExprOrErr)
    return ToExprOrErr.takeError();

  return Importer.getToContext().getTypeOfExprType(*ToExprOrErr);
}

ExpectedType ASTNodeImporter::VisitTypeOfType(const TypeOfType *T) {
  ExpectedType ToUnderlyingTypeOrErr = import(T->getUnderlyingType());
  if (!ToUnderlyingTypeOrErr)
    return ToUnderlyingTypeOrErr.takeError();

  return Importer.getToContext().getTypeOfType(*ToUnderlyingTypeOrErr);
}

ExpectedType ASTNodeImporter::VisitDecltypeType(const DecltypeType *T) {
  // FIXME: Make sure that the "to" context supports C++0x!
  ExpectedExpr ToExprOrErr = import(T->getUnderlyingExpr());
  if (!ToExprOrErr)
    return ToExprOrErr.takeError();

  ExpectedType ToUnderlyingTypeOrErr = import(T->getUnderlyingType());
  if (!ToUnderlyingTypeOrErr)
    return ToUnderlyingTypeOrErr.takeError();

  return Importer.getToContext().getDecltypeType(
      *ToExprOrErr, *ToUnderlyingTypeOrErr);
}

ExpectedType
ASTNodeImporter::VisitUnaryTransformType(const UnaryTransformType *T) {
  ExpectedType ToBaseTypeOrErr = import(T->getBaseType());
  if (!ToBaseTypeOrErr)
    return ToBaseTypeOrErr.takeError();

  ExpectedType ToUnderlyingTypeOrErr = import(T->getUnderlyingType());
  if (!ToUnderlyingTypeOrErr)
    return ToUnderlyingTypeOrErr.takeError();

  return Importer.getToContext().getUnaryTransformType(
      *ToBaseTypeOrErr, *ToUnderlyingTypeOrErr, T->getUTTKind());
}

ExpectedType ASTNodeImporter::VisitAutoType(const AutoType *T) {
  // FIXME: Make sure that the "to" context supports C++11!
  ExpectedType ToDeducedTypeOrErr = import(T->getDeducedType());
  if (!ToDeducedTypeOrErr)
    return ToDeducedTypeOrErr.takeError();

  ExpectedDecl ToTypeConstraintConcept = import(T->getTypeConstraintConcept());
  if (!ToTypeConstraintConcept)
    return ToTypeConstraintConcept.takeError();

  SmallVector<TemplateArgument, 2> ToTemplateArgs;
  ArrayRef<TemplateArgument> FromTemplateArgs = T->getTypeConstraintArguments();
  if (Error Err = ImportTemplateArguments(FromTemplateArgs.data(),
                                          FromTemplateArgs.size(),
                                          ToTemplateArgs))
    return std::move(Err);

  return Importer.getToContext().getAutoType(
      *ToDeducedTypeOrErr, T->getKeyword(), /*IsDependent*/false,
      /*IsPack=*/false, cast_or_null<ConceptDecl>(*ToTypeConstraintConcept),
      ToTemplateArgs);
}

ExpectedType ASTNodeImporter::VisitDeducedTemplateSpecializationType(
    const DeducedTemplateSpecializationType *T) {
  // FIXME: Make sure that the "to" context supports C++17!
  Expected<TemplateName> ToTemplateNameOrErr = import(T->getTemplateName());
  if (!ToTemplateNameOrErr)
    return ToTemplateNameOrErr.takeError();
  ExpectedType ToDeducedTypeOrErr = import(T->getDeducedType());
  if (!ToDeducedTypeOrErr)
    return ToDeducedTypeOrErr.takeError();

  return Importer.getToContext().getDeducedTemplateSpecializationType(
      *ToTemplateNameOrErr, *ToDeducedTypeOrErr, T->isDependentType());
}

ExpectedType ASTNodeImporter::VisitInjectedClassNameType(
    const InjectedClassNameType *T) {
  Expected<CXXRecordDecl *> ToDeclOrErr = import(T->getDecl());
  if (!ToDeclOrErr)
    return ToDeclOrErr.takeError();

  ExpectedType ToInjTypeOrErr = import(T->getInjectedSpecializationType());
  if (!ToInjTypeOrErr)
    return ToInjTypeOrErr.takeError();

  // FIXME: ASTContext::getInjectedClassNameType is not suitable for AST reading
  // See comments in InjectedClassNameType definition for details
  // return Importer.getToContext().getInjectedClassNameType(D, InjType);
  enum {
    TypeAlignmentInBits = 4,
    TypeAlignment = 1 << TypeAlignmentInBits
  };

  return QualType(new (Importer.getToContext(), TypeAlignment)
                  InjectedClassNameType(*ToDeclOrErr, *ToInjTypeOrErr), 0);
}

ExpectedType ASTNodeImporter::VisitRecordType(const RecordType *T) {
  Expected<RecordDecl *> ToDeclOrErr = import(T->getDecl());
  if (!ToDeclOrErr)
    return ToDeclOrErr.takeError();

  return Importer.getToContext().getTagDeclType(*ToDeclOrErr);
}

ExpectedType ASTNodeImporter::VisitEnumType(const EnumType *T) {
  Expected<EnumDecl *> ToDeclOrErr = import(T->getDecl());
  if (!ToDeclOrErr)
    return ToDeclOrErr.takeError();

  return Importer.getToContext().getTagDeclType(*ToDeclOrErr);
}

ExpectedType ASTNodeImporter::VisitAttributedType(const AttributedType *T) {
  ExpectedType ToModifiedTypeOrErr = import(T->getModifiedType());
  if (!ToModifiedTypeOrErr)
    return ToModifiedTypeOrErr.takeError();
  ExpectedType ToEquivalentTypeOrErr = import(T->getEquivalentType());
  if (!ToEquivalentTypeOrErr)
    return ToEquivalentTypeOrErr.takeError();

  return Importer.getToContext().getAttributedType(T->getAttrKind(),
      *ToModifiedTypeOrErr, *ToEquivalentTypeOrErr);
}

ExpectedType ASTNodeImporter::VisitTemplateTypeParmType(
    const TemplateTypeParmType *T) {
  Expected<TemplateTypeParmDecl *> ToDeclOrErr = import(T->getDecl());
  if (!ToDeclOrErr)
    return ToDeclOrErr.takeError();

  return Importer.getToContext().getTemplateTypeParmType(
      T->getDepth(), T->getIndex(), T->isParameterPack(), *ToDeclOrErr);
}

ExpectedType ASTNodeImporter::VisitSubstTemplateTypeParmType(
    const SubstTemplateTypeParmType *T) {
  Expected<const TemplateTypeParmType *> ReplacedOrErr =
      import(T->getReplacedParameter());
  if (!ReplacedOrErr)
    return ReplacedOrErr.takeError();

  ExpectedType ToReplacementTypeOrErr = import(T->getReplacementType());
  if (!ToReplacementTypeOrErr)
    return ToReplacementTypeOrErr.takeError();

  return Importer.getToContext().getSubstTemplateTypeParmType(
      *ReplacedOrErr, ToReplacementTypeOrErr->getCanonicalType());
}

ExpectedType ASTNodeImporter::VisitSubstTemplateTypeParmPackType(
    const SubstTemplateTypeParmPackType *T) {
  Expected<const TemplateTypeParmType *> ReplacedOrErr =
      import(T->getReplacedParameter());
  if (!ReplacedOrErr)
    return ReplacedOrErr.takeError();

  Expected<TemplateArgument> ToArgumentPack = import(T->getArgumentPack());
  if (!ToArgumentPack)
    return ToArgumentPack.takeError();

  return Importer.getToContext().getSubstTemplateTypeParmPackType(
      *ReplacedOrErr, *ToArgumentPack);
}

ExpectedType ASTNodeImporter::VisitTemplateSpecializationType(
                                       const TemplateSpecializationType *T) {
  auto ToTemplateOrErr = import(T->getTemplateName());
  if (!ToTemplateOrErr)
    return ToTemplateOrErr.takeError();

  SmallVector<TemplateArgument, 2> ToTemplateArgs;
  if (Error Err = ImportTemplateArguments(
      T->getArgs(), T->getNumArgs(), ToTemplateArgs))
    return std::move(Err);

  QualType ToCanonType;
  if (!T->isCanonicalUnqualified()) {
    QualType FromCanonType
      = Importer.getFromContext().getCanonicalType(QualType(T, 0));
    if (ExpectedType TyOrErr = import(FromCanonType))
      ToCanonType = *TyOrErr;
    else
      return TyOrErr.takeError();
  }
  return Importer.getToContext().getTemplateSpecializationType(*ToTemplateOrErr,
                                                               ToTemplateArgs,
                                                               ToCanonType);
}

ExpectedType ASTNodeImporter::VisitElaboratedType(const ElaboratedType *T) {
  // Note: the qualifier in an ElaboratedType is optional.
  auto ToQualifierOrErr = import(T->getQualifier());
  if (!ToQualifierOrErr)
    return ToQualifierOrErr.takeError();

  ExpectedType ToNamedTypeOrErr = import(T->getNamedType());
  if (!ToNamedTypeOrErr)
    return ToNamedTypeOrErr.takeError();

  Expected<TagDecl *> ToOwnedTagDeclOrErr = import(T->getOwnedTagDecl());
  if (!ToOwnedTagDeclOrErr)
    return ToOwnedTagDeclOrErr.takeError();

  return Importer.getToContext().getElaboratedType(T->getKeyword(),
                                                   *ToQualifierOrErr,
                                                   *ToNamedTypeOrErr,
                                                   *ToOwnedTagDeclOrErr);
}

ExpectedType
ASTNodeImporter::VisitPackExpansionType(const PackExpansionType *T) {
  ExpectedType ToPatternOrErr = import(T->getPattern());
  if (!ToPatternOrErr)
    return ToPatternOrErr.takeError();

  return Importer.getToContext().getPackExpansionType(*ToPatternOrErr,
                                                      T->getNumExpansions(),
                                                      /*ExpactPack=*/false);
}

ExpectedType ASTNodeImporter::VisitDependentTemplateSpecializationType(
    const DependentTemplateSpecializationType *T) {
  auto ToQualifierOrErr = import(T->getQualifier());
  if (!ToQualifierOrErr)
    return ToQualifierOrErr.takeError();

  IdentifierInfo *ToName = Importer.Import(T->getIdentifier());

  SmallVector<TemplateArgument, 2> ToPack;
  ToPack.reserve(T->getNumArgs());
  if (Error Err = ImportTemplateArguments(
      T->getArgs(), T->getNumArgs(), ToPack))
    return std::move(Err);

  return Importer.getToContext().getDependentTemplateSpecializationType(
      T->getKeyword(), *ToQualifierOrErr, ToName, ToPack);
}

ExpectedType
ASTNodeImporter::VisitDependentNameType(const DependentNameType *T) {
  auto ToQualifierOrErr = import(T->getQualifier());
  if (!ToQualifierOrErr)
    return ToQualifierOrErr.takeError();

  IdentifierInfo *Name = Importer.Import(T->getIdentifier());

  QualType Canon;
  if (T != T->getCanonicalTypeInternal().getTypePtr()) {
    if (ExpectedType TyOrErr = import(T->getCanonicalTypeInternal()))
      Canon = (*TyOrErr).getCanonicalType();
    else
      return TyOrErr.takeError();
  }

  return Importer.getToContext().getDependentNameType(T->getKeyword(),
                                                      *ToQualifierOrErr,
                                                      Name, Canon);
}

ExpectedType
ASTNodeImporter::VisitObjCInterfaceType(const ObjCInterfaceType *T) {
  Expected<ObjCInterfaceDecl *> ToDeclOrErr = import(T->getDecl());
  if (!ToDeclOrErr)
    return ToDeclOrErr.takeError();

  return Importer.getToContext().getObjCInterfaceType(*ToDeclOrErr);
}

ExpectedType ASTNodeImporter::VisitObjCObjectType(const ObjCObjectType *T) {
  ExpectedType ToBaseTypeOrErr = import(T->getBaseType());
  if (!ToBaseTypeOrErr)
    return ToBaseTypeOrErr.takeError();

  SmallVector<QualType, 4> TypeArgs;
  for (auto TypeArg : T->getTypeArgsAsWritten()) {
    if (ExpectedType TyOrErr = import(TypeArg))
      TypeArgs.push_back(*TyOrErr);
    else
      return TyOrErr.takeError();
  }

  SmallVector<ObjCProtocolDecl *, 4> Protocols;
  for (auto *P : T->quals()) {
    if (Expected<ObjCProtocolDecl *> ProtocolOrErr = import(P))
      Protocols.push_back(*ProtocolOrErr);
    else
      return ProtocolOrErr.takeError();

  }

  return Importer.getToContext().getObjCObjectType(*ToBaseTypeOrErr, TypeArgs,
                                                   Protocols,
                                                   T->isKindOfTypeAsWritten());
}

ExpectedType
ASTNodeImporter::VisitObjCObjectPointerType(const ObjCObjectPointerType *T) {
  ExpectedType ToPointeeTypeOrErr = import(T->getPointeeType());
  if (!ToPointeeTypeOrErr)
    return ToPointeeTypeOrErr.takeError();

  return Importer.getToContext().getObjCObjectPointerType(*ToPointeeTypeOrErr);
}

//----------------------------------------------------------------------------
// Import Declarations
//----------------------------------------------------------------------------
Error ASTNodeImporter::ImportDeclParts(
    NamedDecl *D, DeclContext *&DC, DeclContext *&LexicalDC,
    DeclarationName &Name, NamedDecl *&ToD, SourceLocation &Loc) {
  // Check if RecordDecl is in FunctionDecl parameters to avoid infinite loop.
  // example: int struct_in_proto(struct data_t{int a;int b;} *d);
  // FIXME: We could support these constructs by importing a different type of
  // this parameter and by importing the original type of the parameter only
  // after the FunctionDecl is created. See
  // VisitFunctionDecl::UsedDifferentProtoType.
  DeclContext *OrigDC = D->getDeclContext();
  FunctionDecl *FunDecl;
  if (isa<RecordDecl>(D) && (FunDecl = dyn_cast<FunctionDecl>(OrigDC)) &&
      FunDecl->hasBody()) {
    auto getLeafPointeeType = [](const Type *T) {
      while (T->isPointerType() || T->isArrayType()) {
        T = T->getPointeeOrArrayElementType();
      }
      return T;
    };
    for (const ParmVarDecl *P : FunDecl->parameters()) {
      const Type *LeafT =
          getLeafPointeeType(P->getType().getCanonicalType().getTypePtr());
      auto *RT = dyn_cast<RecordType>(LeafT);
      if (RT && RT->getDecl() == D) {
        Importer.FromDiag(D->getLocation(), diag::err_unsupported_ast_node)
            << D->getDeclKindName();
        return make_error<ImportError>(ImportError::UnsupportedConstruct);
      }
    }
  }

  // Import the context of this declaration.
  if (Error Err = ImportDeclContext(D, DC, LexicalDC))
    return Err;

  // Import the name of this declaration.
  if (Error Err = importInto(Name, D->getDeclName()))
    return Err;

  // Import the location of this declaration.
  if (Error Err = importInto(Loc, D->getLocation()))
    return Err;

  ToD = cast_or_null<NamedDecl>(Importer.GetAlreadyImportedOrNull(D));
  if (ToD)
    if (Error Err = ASTNodeImporter(*this).ImportDefinitionIfNeeded(D, ToD))
      return Err;

  return Error::success();
}

Error ASTNodeImporter::ImportDeclParts(NamedDecl *D, DeclarationName &Name,
                                       NamedDecl *&ToD, SourceLocation &Loc) {

  // Import the name of this declaration.
  if (Error Err = importInto(Name, D->getDeclName()))
    return Err;

  // Import the location of this declaration.
  if (Error Err = importInto(Loc, D->getLocation()))
    return Err;

  ToD = cast_or_null<NamedDecl>(Importer.GetAlreadyImportedOrNull(D));
  if (ToD)
    if (Error Err = ASTNodeImporter(*this).ImportDefinitionIfNeeded(D, ToD))
      return Err;

  return Error::success();
}

Error ASTNodeImporter::ImportDefinitionIfNeeded(Decl *FromD, Decl *ToD) {
  if (!FromD)
    return Error::success();

  if (!ToD)
    if (Error Err = importInto(ToD, FromD))
      return Err;

  if (RecordDecl *FromRecord = dyn_cast<RecordDecl>(FromD)) {
    if (RecordDecl *ToRecord = cast<RecordDecl>(ToD)) {
      if (FromRecord->getDefinition() && FromRecord->isCompleteDefinition() &&
          !ToRecord->getDefinition()) {
        if (Error Err = ImportDefinition(FromRecord, ToRecord))
          return Err;
      }
    }
    return Error::success();
  }

  if (EnumDecl *FromEnum = dyn_cast<EnumDecl>(FromD)) {
    if (EnumDecl *ToEnum = cast<EnumDecl>(ToD)) {
      if (FromEnum->getDefinition() && !ToEnum->getDefinition()) {
        if (Error Err = ImportDefinition(FromEnum, ToEnum))
          return Err;
      }
    }
    return Error::success();
  }

  return Error::success();
}

Error
ASTNodeImporter::ImportDeclarationNameLoc(
    const DeclarationNameInfo &From, DeclarationNameInfo& To) {
  // NOTE: To.Name and To.Loc are already imported.
  // We only have to import To.LocInfo.
  switch (To.getName().getNameKind()) {
  case DeclarationName::Identifier:
  case DeclarationName::ObjCZeroArgSelector:
  case DeclarationName::ObjCOneArgSelector:
  case DeclarationName::ObjCMultiArgSelector:
  case DeclarationName::CXXUsingDirective:
  case DeclarationName::CXXDeductionGuideName:
    return Error::success();

  case DeclarationName::CXXOperatorName: {
    if (auto ToRangeOrErr = import(From.getCXXOperatorNameRange()))
      To.setCXXOperatorNameRange(*ToRangeOrErr);
    else
      return ToRangeOrErr.takeError();
    return Error::success();
  }
  case DeclarationName::CXXLiteralOperatorName: {
    if (ExpectedSLoc LocOrErr = import(From.getCXXLiteralOperatorNameLoc()))
      To.setCXXLiteralOperatorNameLoc(*LocOrErr);
    else
      return LocOrErr.takeError();
    return Error::success();
  }
  case DeclarationName::CXXConstructorName:
  case DeclarationName::CXXDestructorName:
  case DeclarationName::CXXConversionFunctionName: {
    if (auto ToTInfoOrErr = import(From.getNamedTypeInfo()))
      To.setNamedTypeInfo(*ToTInfoOrErr);
    else
      return ToTInfoOrErr.takeError();
    return Error::success();
  }
  }
  llvm_unreachable("Unknown name kind.");
}

Error
ASTNodeImporter::ImportDeclContext(DeclContext *FromDC, bool ForceImport) {
  if (Importer.isMinimalImport() && !ForceImport) {
    auto ToDCOrErr = Importer.ImportContext(FromDC);
    return ToDCOrErr.takeError();
  }

  // We use strict error handling in case of records and enums, but not
  // with e.g. namespaces.
  //
  // FIXME Clients of the ASTImporter should be able to choose an
  // appropriate error handling strategy for their needs.  For instance,
  // they may not want to mark an entire namespace as erroneous merely
  // because there is an ODR error with two typedefs.  As another example,
  // the client may allow EnumConstantDecls with same names but with
  // different values in two distinct translation units.
  bool AccumulateChildErrors = isa<TagDecl>(FromDC);

  Error ChildErrors = Error::success();
  for (auto *From : FromDC->decls()) {
    ExpectedDecl ImportedOrErr = import(From);

    // If we are in the process of ImportDefinition(...) for a RecordDecl we
    // want to make sure that we are also completing each FieldDecl. There
    // are currently cases where this does not happen and this is correctness
    // fix since operations such as code generation will expect this to be so.
    if (ImportedOrErr) {
      FieldDecl *FieldFrom = dyn_cast_or_null<FieldDecl>(From);
      Decl *ImportedDecl = *ImportedOrErr;
      FieldDecl *FieldTo = dyn_cast_or_null<FieldDecl>(ImportedDecl);
      if (FieldFrom && FieldTo) {
        RecordDecl *FromRecordDecl = nullptr;
        RecordDecl *ToRecordDecl = nullptr;
        // If we have a field that is an ArrayType we need to check if the array
        // element is a RecordDecl and if so we need to import the definition.
        if (FieldFrom->getType()->isArrayType()) {
          // getBaseElementTypeUnsafe(...) handles multi-dimensonal arrays for us.
          FromRecordDecl = FieldFrom->getType()->getBaseElementTypeUnsafe()->getAsRecordDecl();
          ToRecordDecl = FieldTo->getType()->getBaseElementTypeUnsafe()->getAsRecordDecl();
        }

        if (!FromRecordDecl || !ToRecordDecl) {
          const RecordType *RecordFrom =
              FieldFrom->getType()->getAs<RecordType>();
          const RecordType *RecordTo = FieldTo->getType()->getAs<RecordType>();

          if (RecordFrom && RecordTo) {
            FromRecordDecl = RecordFrom->getDecl();
            ToRecordDecl = RecordTo->getDecl();
          }
        }

        if (FromRecordDecl && ToRecordDecl) {
          if (FromRecordDecl->isCompleteDefinition() &&
              !ToRecordDecl->isCompleteDefinition()) {
            Error Err = ImportDefinition(FromRecordDecl, ToRecordDecl);

            if (Err && AccumulateChildErrors)
              ChildErrors =  joinErrors(std::move(ChildErrors), std::move(Err));
            else
              consumeError(std::move(Err));
          }
        }
      }
    } else {
      if (AccumulateChildErrors)
        ChildErrors =
            joinErrors(std::move(ChildErrors), ImportedOrErr.takeError());
      else
        consumeError(ImportedOrErr.takeError());
    }
  }

  // We reorder declarations in RecordDecls because they may have another order
  // in the "to" context than they have in the "from" context. This may happen
  // e.g when we import a class like this:
  //    struct declToImport {
  //        int a = c + b;
  //        int b = 1;
  //        int c = 2;
  //    };
  // During the import of `a` we import first the dependencies in sequence,
  // thus the order would be `c`, `b`, `a`. We will get the normal order by
  // first removing the already imported members and then adding them in the
  // order as they apper in the "from" context.
  //
  // Keeping field order is vital because it determines structure layout.
  //
  // Here and below, we cannot call field_begin() method and its callers on
  // ToDC if it has an external storage. Calling field_begin() will
  // automatically load all the fields by calling
  // LoadFieldsFromExternalStorage(). LoadFieldsFromExternalStorage() would
  // call ASTImporter::Import(). This is because the ExternalASTSource
  // interface in LLDB is implemented by the means of the ASTImporter. However,
  // calling an import at this point would result in an uncontrolled import, we
  // must avoid that.
  const auto *FromRD = dyn_cast<RecordDecl>(FromDC);
  if (!FromRD)
    return ChildErrors;

  auto ToDCOrErr = Importer.ImportContext(FromDC);
  if (!ToDCOrErr) {
    consumeError(std::move(ChildErrors));
    return ToDCOrErr.takeError();
  }

  DeclContext *ToDC = *ToDCOrErr;
  // Remove all declarations, which may be in wrong order in the
  // lexical DeclContext and then add them in the proper order.
  for (auto *D : FromRD->decls()) {
    if (isa<FieldDecl>(D) || isa<IndirectFieldDecl>(D) || isa<FriendDecl>(D)) {
      assert(D && "DC contains a null decl");
      Decl *ToD = Importer.GetAlreadyImportedOrNull(D);
      // Remove only the decls which we successfully imported.
      if (ToD) {
        assert(ToDC == ToD->getLexicalDeclContext() && ToDC->containsDecl(ToD));
        // Remove the decl from its wrong place in the linked list.
        ToDC->removeDecl(ToD);
        // Add the decl to the end of the linked list.
        // This time it will be at the proper place because the enclosing for
        // loop iterates in the original (good) order of the decls.
        ToDC->addDeclInternal(ToD);
      }
    }
  }

  return ChildErrors;
}

Error ASTNodeImporter::ImportDeclContext(
    Decl *FromD, DeclContext *&ToDC, DeclContext *&ToLexicalDC) {
  auto ToDCOrErr = Importer.ImportContext(FromD->getDeclContext());
  if (!ToDCOrErr)
    return ToDCOrErr.takeError();
  ToDC = *ToDCOrErr;

  if (FromD->getDeclContext() != FromD->getLexicalDeclContext()) {
    auto ToLexicalDCOrErr = Importer.ImportContext(
        FromD->getLexicalDeclContext());
    if (!ToLexicalDCOrErr)
      return ToLexicalDCOrErr.takeError();
    ToLexicalDC = *ToLexicalDCOrErr;
  } else
    ToLexicalDC = ToDC;

  return Error::success();
}

Error ASTNodeImporter::ImportImplicitMethods(
    const CXXRecordDecl *From, CXXRecordDecl *To) {
  assert(From->isCompleteDefinition() && To->getDefinition() == To &&
      "Import implicit methods to or from non-definition");

  for (CXXMethodDecl *FromM : From->methods())
    if (FromM->isImplicit()) {
      Expected<CXXMethodDecl *> ToMOrErr = import(FromM);
      if (!ToMOrErr)
        return ToMOrErr.takeError();
    }

  return Error::success();
}

static Error setTypedefNameForAnonDecl(TagDecl *From, TagDecl *To,
                                       ASTImporter &Importer) {
  if (TypedefNameDecl *FromTypedef = From->getTypedefNameForAnonDecl()) {
    if (ExpectedDecl ToTypedefOrErr = Importer.Import(FromTypedef))
      To->setTypedefNameForAnonDecl(cast<TypedefNameDecl>(*ToTypedefOrErr));
    else
      return ToTypedefOrErr.takeError();
  }
  return Error::success();
}

Error ASTNodeImporter::ImportDefinition(
    RecordDecl *From, RecordDecl *To, ImportDefinitionKind Kind) {
  auto DefinitionCompleter = [To]() {
    // There are cases in LLDB when we first import a class without its
    // members. The class will have DefinitionData, but no members. Then,
    // importDefinition is called from LLDB, which tries to get the members, so
    // when we get here, the class already has the DefinitionData set, so we
    // must unset the CompleteDefinition here to be able to complete again the
    // definition.
    To->setCompleteDefinition(false);
    To->completeDefinition();
  };

  if (To->getDefinition() || To->isBeingDefined()) {
    if (Kind == IDK_Everything ||
        // In case of lambdas, the class already has a definition ptr set, but
        // the contained decls are not imported yet. Also, isBeingDefined was
        // set in CXXRecordDecl::CreateLambda.  We must import the contained
        // decls here and finish the definition.
        (To->isLambda() && shouldForceImportDeclContext(Kind))) {
      if (To->isLambda()) {
        auto *FromCXXRD = cast<CXXRecordDecl>(From);
        SmallVector<LambdaCapture, 8> ToCaptures;
        ToCaptures.reserve(FromCXXRD->capture_size());
        for (const auto &FromCapture : FromCXXRD->captures()) {
          if (auto ToCaptureOrErr = import(FromCapture))
            ToCaptures.push_back(*ToCaptureOrErr);
          else
            return ToCaptureOrErr.takeError();
        }
        cast<CXXRecordDecl>(To)->setCaptures(Importer.getToContext(),
                                             ToCaptures);
      }

      Error Result = ImportDeclContext(From, /*ForceImport=*/true);
      // Finish the definition of the lambda, set isBeingDefined to false.
      if (To->isLambda())
        DefinitionCompleter();
      return Result;
    }

    return Error::success();
  }

  To->startDefinition();
  // Complete the definition even if error is returned.
  // The RecordDecl may be already part of the AST so it is better to
  // have it in complete state even if something is wrong with it.
  auto DefinitionCompleterScopeExit =
      llvm::make_scope_exit(DefinitionCompleter);

  if (Error Err = setTypedefNameForAnonDecl(From, To, Importer))
    return Err;

  // Add base classes.
  auto *ToCXX = dyn_cast<CXXRecordDecl>(To);
  auto *FromCXX = dyn_cast<CXXRecordDecl>(From);
  if (ToCXX && FromCXX && ToCXX->dataPtr() && FromCXX->dataPtr()) {

    struct CXXRecordDecl::DefinitionData &ToData = ToCXX->data();
    struct CXXRecordDecl::DefinitionData &FromData = FromCXX->data();

    #define FIELD(Name, Width, Merge) \
    ToData.Name = FromData.Name;
    #include "clang/AST/CXXRecordDeclDefinitionBits.def"

    // Copy over the data stored in RecordDeclBits
    ToCXX->setArgPassingRestrictions(FromCXX->getArgPassingRestrictions());

    SmallVector<CXXBaseSpecifier *, 4> Bases;
    for (const auto &Base1 : FromCXX->bases()) {
      ExpectedType TyOrErr = import(Base1.getType());
      if (!TyOrErr)
        return TyOrErr.takeError();

      SourceLocation EllipsisLoc;
      if (Base1.isPackExpansion()) {
        if (ExpectedSLoc LocOrErr = import(Base1.getEllipsisLoc()))
          EllipsisLoc = *LocOrErr;
        else
          return LocOrErr.takeError();
      }

      // Ensure that we have a definition for the base.
      if (Error Err =
          ImportDefinitionIfNeeded(Base1.getType()->getAsCXXRecordDecl()))
        return Err;

      auto RangeOrErr = import(Base1.getSourceRange());
      if (!RangeOrErr)
        return RangeOrErr.takeError();

      auto TSIOrErr = import(Base1.getTypeSourceInfo());
      if (!TSIOrErr)
        return TSIOrErr.takeError();

      Bases.push_back(
          new (Importer.getToContext()) CXXBaseSpecifier(
              *RangeOrErr,
              Base1.isVirtual(),
              Base1.isBaseOfClass(),
              Base1.getAccessSpecifierAsWritten(),
              *TSIOrErr,
              EllipsisLoc));
    }
    if (!Bases.empty())
      ToCXX->setBases(Bases.data(), Bases.size());
  }

  if (shouldForceImportDeclContext(Kind))
    if (Error Err = ImportDeclContext(From, /*ForceImport=*/true))
      return Err;

  return Error::success();
}

Error ASTNodeImporter::ImportInitializer(VarDecl *From, VarDecl *To) {
  if (To->getAnyInitializer())
    return Error::success();

  Expr *FromInit = From->getInit();
  if (!FromInit)
    return Error::success();

  ExpectedExpr ToInitOrErr = import(FromInit);
  if (!ToInitOrErr)
    return ToInitOrErr.takeError();

  To->setInit(*ToInitOrErr);
  if (EvaluatedStmt *FromEval = From->getEvaluatedStmt()) {
    EvaluatedStmt *ToEval = To->ensureEvaluatedStmt();
    ToEval->HasConstantInitialization = FromEval->HasConstantInitialization;
    ToEval->HasConstantDestruction = FromEval->HasConstantDestruction;
    // FIXME: Also import the initializer value.
  }

  // FIXME: Other bits to merge?
  return Error::success();
}

Error ASTNodeImporter::ImportDefinition(
    EnumDecl *From, EnumDecl *To, ImportDefinitionKind Kind) {
  if (To->getDefinition() || To->isBeingDefined()) {
    if (Kind == IDK_Everything)
      return ImportDeclContext(From, /*ForceImport=*/true);
    return Error::success();
  }

  To->startDefinition();

  if (Error Err = setTypedefNameForAnonDecl(From, To, Importer))
    return Err;

  ExpectedType ToTypeOrErr =
      import(Importer.getFromContext().getTypeDeclType(From));
  if (!ToTypeOrErr)
    return ToTypeOrErr.takeError();

  ExpectedType ToPromotionTypeOrErr = import(From->getPromotionType());
  if (!ToPromotionTypeOrErr)
    return ToPromotionTypeOrErr.takeError();

  if (shouldForceImportDeclContext(Kind))
    if (Error Err = ImportDeclContext(From, /*ForceImport=*/true))
      return Err;

  // FIXME: we might need to merge the number of positive or negative bits
  // if the enumerator lists don't match.
  To->completeDefinition(*ToTypeOrErr, *ToPromotionTypeOrErr,
                         From->getNumPositiveBits(),
                         From->getNumNegativeBits());
  return Error::success();
}

Error ASTNodeImporter::ImportTemplateArguments(
    const TemplateArgument *FromArgs, unsigned NumFromArgs,
    SmallVectorImpl<TemplateArgument> &ToArgs) {
  for (unsigned I = 0; I != NumFromArgs; ++I) {
    if (auto ToOrErr = import(FromArgs[I]))
      ToArgs.push_back(*ToOrErr);
    else
      return ToOrErr.takeError();
  }

  return Error::success();
}

// FIXME: Do not forget to remove this and use only 'import'.
Expected<TemplateArgument>
ASTNodeImporter::ImportTemplateArgument(const TemplateArgument &From) {
  return import(From);
}

template <typename InContainerTy>
Error ASTNodeImporter::ImportTemplateArgumentListInfo(
    const InContainerTy &Container, TemplateArgumentListInfo &ToTAInfo) {
  for (const auto &FromLoc : Container) {
    if (auto ToLocOrErr = import(FromLoc))
      ToTAInfo.addArgument(*ToLocOrErr);
    else
      return ToLocOrErr.takeError();
  }
  return Error::success();
}

static StructuralEquivalenceKind
getStructuralEquivalenceKind(const ASTImporter &Importer) {
  return Importer.isMinimalImport() ? StructuralEquivalenceKind::Minimal
                                    : StructuralEquivalenceKind::Default;
}

bool ASTNodeImporter::IsStructuralMatch(Decl *From, Decl *To, bool Complain) {
  // Eliminate a potential failure point where we attempt to re-import
  // something we're trying to import while completing ToRecord.
  Decl *ToOrigin = Importer.GetOriginalDecl(To);
  if (ToOrigin) {
    To = ToOrigin;
  }

  StructuralEquivalenceContext Ctx(
      Importer.getFromContext(), Importer.getToContext(),
      Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer),
      false, Complain);
  return Ctx.IsEquivalent(From, To);
}

ExpectedDecl ASTNodeImporter::VisitDecl(Decl *D) {
  Importer.FromDiag(D->getLocation(), diag::err_unsupported_ast_node)
    << D->getDeclKindName();
  return make_error<ImportError>(ImportError::UnsupportedConstruct);
}

ExpectedDecl ASTNodeImporter::VisitImportDecl(ImportDecl *D) {
  Importer.FromDiag(D->getLocation(), diag::err_unsupported_ast_node)
      << D->getDeclKindName();
  return make_error<ImportError>(ImportError::UnsupportedConstruct);
}

ExpectedDecl ASTNodeImporter::VisitEmptyDecl(EmptyDecl *D) {
  // Import the context of this declaration.
  DeclContext *DC, *LexicalDC;
  if (Error Err = ImportDeclContext(D, DC, LexicalDC))
    return std::move(Err);

  // Import the location of this declaration.
  ExpectedSLoc LocOrErr = import(D->getLocation());
  if (!LocOrErr)
    return LocOrErr.takeError();

  EmptyDecl *ToD;
  if (GetImportedOrCreateDecl(ToD, D, Importer.getToContext(), DC, *LocOrErr))
    return ToD;

  ToD->setLexicalDeclContext(LexicalDC);
  LexicalDC->addDeclInternal(ToD);
  return ToD;
}

ExpectedDecl ASTNodeImporter::VisitTranslationUnitDecl(TranslationUnitDecl *D) {
  TranslationUnitDecl *ToD =
    Importer.getToContext().getTranslationUnitDecl();

  Importer.MapImported(D, ToD);

  return ToD;
}

ExpectedDecl ASTNodeImporter::VisitBindingDecl(BindingDecl *D) {
  DeclContext *DC, *LexicalDC;
  DeclarationName Name;
  SourceLocation Loc;
  NamedDecl *ToND;
  if (Error Err = ImportDeclParts(D, DC, LexicalDC, Name, ToND, Loc))
    return std::move(Err);
  if (ToND)
    return ToND;

  BindingDecl *ToD;
  if (GetImportedOrCreateDecl(ToD, D, Importer.getToContext(), DC, Loc,
                              Name.getAsIdentifierInfo()))
    return ToD;

  Error Err = Error::success();
  QualType ToType = importChecked(Err, D->getType());
  Expr *ToBinding = importChecked(Err, D->getBinding());
  ValueDecl *ToDecomposedDecl = importChecked(Err, D->getDecomposedDecl());
  if (Err)
    return std::move(Err);

  ToD->setBinding(ToType, ToBinding);
  ToD->setDecomposedDecl(ToDecomposedDecl);
  addDeclToContexts(D, ToD);

  return ToD;
}

ExpectedDecl ASTNodeImporter::VisitAccessSpecDecl(AccessSpecDecl *D) {
  ExpectedSLoc LocOrErr = import(D->getLocation());
  if (!LocOrErr)
    return LocOrErr.takeError();
  auto ColonLocOrErr = import(D->getColonLoc());
  if (!ColonLocOrErr)
    return ColonLocOrErr.takeError();

  // Import the context of this declaration.
  auto DCOrErr = Importer.ImportContext(D->getDeclContext());
  if (!DCOrErr)
    return DCOrErr.takeError();
  DeclContext *DC = *DCOrErr;

  AccessSpecDecl *ToD;
  if (GetImportedOrCreateDecl(ToD, D, Importer.getToContext(), D->getAccess(),
                              DC, *LocOrErr, *ColonLocOrErr))
    return ToD;

  // Lexical DeclContext and Semantic DeclContext
  // is always the same for the accessSpec.
  ToD->setLexicalDeclContext(DC);
  DC->addDeclInternal(ToD);

  return ToD;
}

ExpectedDecl ASTNodeImporter::VisitStaticAssertDecl(StaticAssertDecl *D) {
  auto DCOrErr = Importer.ImportContext(D->getDeclContext());
  if (!DCOrErr)
    return DCOrErr.takeError();
  DeclContext *DC = *DCOrErr;
  DeclContext *LexicalDC = DC;

  Error Err = Error::success();
  auto ToLocation = importChecked(Err, D->getLocation());
  auto ToRParenLoc = importChecked(Err, D->getRParenLoc());
  auto ToAssertExpr = importChecked(Err, D->getAssertExpr());
  auto ToMessage = importChecked(Err, D->getMessage());
  if (Err)
    return std::move(Err);

  StaticAssertDecl *ToD;
  if (GetImportedOrCreateDecl(
      ToD, D, Importer.getToContext(), DC, ToLocation, ToAssertExpr, ToMessage,
      ToRParenLoc, D->isFailed()))
    return ToD;

  ToD->setLexicalDeclContext(LexicalDC);
  LexicalDC->addDeclInternal(ToD);
  return ToD;
}

ExpectedDecl ASTNodeImporter::VisitNamespaceDecl(NamespaceDecl *D) {
  // Import the major distinguishing characteristics of this namespace.
  DeclContext *DC, *LexicalDC;
  DeclarationName Name;
  SourceLocation Loc;
  NamedDecl *ToD;
  if (Error Err = ImportDeclParts(D, DC, LexicalDC, Name, ToD, Loc))
    return std::move(Err);
  if (ToD)
    return ToD;

  NamespaceDecl *MergeWithNamespace = nullptr;
  if (!Name) {
    // This is an anonymous namespace. Adopt an existing anonymous
    // namespace if we can.
    // FIXME: Not testable.
    if (auto *TU = dyn_cast<TranslationUnitDecl>(DC))
      MergeWithNamespace = TU->getAnonymousNamespace();
    else
      MergeWithNamespace = cast<NamespaceDecl>(DC)->getAnonymousNamespace();
  } else {
    SmallVector<NamedDecl *, 4> ConflictingDecls;
    auto FoundDecls = Importer.findDeclsInToCtx(DC, Name);
    for (auto *FoundDecl : FoundDecls) {
      if (!FoundDecl->isInIdentifierNamespace(Decl::IDNS_Namespace))
        continue;

      if (auto *FoundNS = dyn_cast<NamespaceDecl>(FoundDecl)) {
        MergeWithNamespace = FoundNS;
        ConflictingDecls.clear();
        break;
      }

      ConflictingDecls.push_back(FoundDecl);
    }

    if (!ConflictingDecls.empty()) {
      ExpectedName NameOrErr = Importer.HandleNameConflict(
          Name, DC, Decl::IDNS_Namespace, ConflictingDecls.data(),
          ConflictingDecls.size());
      if (NameOrErr)
        Name = NameOrErr.get();
      else
        return NameOrErr.takeError();
    }
  }

  ExpectedSLoc BeginLocOrErr = import(D->getBeginLoc());
  if (!BeginLocOrErr)
    return BeginLocOrErr.takeError();
  ExpectedSLoc RBraceLocOrErr = import(D->getRBraceLoc());
  if (!RBraceLocOrErr)
    return RBraceLocOrErr.takeError();

  // Create the "to" namespace, if needed.
  NamespaceDecl *ToNamespace = MergeWithNamespace;
  if (!ToNamespace) {
    if (GetImportedOrCreateDecl(
            ToNamespace, D, Importer.getToContext(), DC, D->isInline(),
            *BeginLocOrErr, Loc, Name.getAsIdentifierInfo(),
            /*PrevDecl=*/nullptr))
      return ToNamespace;
    ToNamespace->setRBraceLoc(*RBraceLocOrErr);
    ToNamespace->setLexicalDeclContext(LexicalDC);
    LexicalDC->addDeclInternal(ToNamespace);

    // If this is an anonymous namespace, register it as the anonymous
    // namespace within its context.
    if (!Name) {
      if (auto *TU = dyn_cast<TranslationUnitDecl>(DC))
        TU->setAnonymousNamespace(ToNamespace);
      else
        cast<NamespaceDecl>(DC)->setAnonymousNamespace(ToNamespace);
    }
  }
  Importer.MapImported(D, ToNamespace);

  if (Error Err = ImportDeclContext(D))
    return std::move(Err);

  return ToNamespace;
}

ExpectedDecl ASTNodeImporter::VisitNamespaceAliasDecl(NamespaceAliasDecl *D) {
  // Import the major distinguishing characteristics of this namespace.
  DeclContext *DC, *LexicalDC;
  DeclarationName Name;
  SourceLocation Loc;
  NamedDecl *LookupD;
  if (Error Err = ImportDeclParts(D, DC, LexicalDC, Name, LookupD, Loc))
    return std::move(Err);
  if (LookupD)
    return LookupD;

  // NOTE: No conflict resolution is done for namespace aliases now.

  Error Err = Error::success();
  auto ToNamespaceLoc = importChecked(Err, D->getNamespaceLoc());
  auto ToAliasLoc = importChecked(Err, D->getAliasLoc());
  auto ToQualifierLoc = importChecked(Err, D->getQualifierLoc());
  auto ToTargetNameLoc = importChecked(Err, D->getTargetNameLoc());
  auto ToNamespace = importChecked(Err, D->getNamespace());
  if (Err)
    return std::move(Err);

  IdentifierInfo *ToIdentifier = Importer.Import(D->getIdentifier());

  NamespaceAliasDecl *ToD;
  if (GetImportedOrCreateDecl(
      ToD, D, Importer.getToContext(), DC, ToNamespaceLoc, ToAliasLoc,
      ToIdentifier, ToQualifierLoc, ToTargetNameLoc, ToNamespace))
    return ToD;

  ToD->setLexicalDeclContext(LexicalDC);
  LexicalDC->addDeclInternal(ToD);

  return ToD;
}

ExpectedDecl
ASTNodeImporter::VisitTypedefNameDecl(TypedefNameDecl *D, bool IsAlias) {
  // Import the major distinguishing characteristics of this typedef.
  DeclarationName Name;
  SourceLocation Loc;
  NamedDecl *ToD;
  // Do not import the DeclContext, we will import it once the TypedefNameDecl
  // is created.
  if (Error Err = ImportDeclParts(D, Name, ToD, Loc))
    return std::move(Err);
  if (ToD)
    return ToD;

  DeclContext *DC = cast_or_null<DeclContext>(
      Importer.GetAlreadyImportedOrNull(cast<Decl>(D->getDeclContext())));
  DeclContext *LexicalDC =
      cast_or_null<DeclContext>(Importer.GetAlreadyImportedOrNull(
          cast<Decl>(D->getLexicalDeclContext())));

  // If this typedef is not in block scope, determine whether we've
  // seen a typedef with the same name (that we can merge with) or any
  // other entity by that name (which name lookup could conflict with).
  // Note: Repeated typedefs are not valid in C99:
  // 'typedef int T; typedef int T;' is invalid
  // We do not care about this now.
  if (DC && !DC->isFunctionOrMethod()) {
    SmallVector<NamedDecl *, 4> ConflictingDecls;
    unsigned IDNS = Decl::IDNS_Ordinary;
    auto FoundDecls = Importer.findDeclsInToCtx(DC, Name);
    for (auto *FoundDecl : FoundDecls) {
      if (!FoundDecl->isInIdentifierNamespace(IDNS))
        continue;
      if (auto *FoundTypedef = dyn_cast<TypedefNameDecl>(FoundDecl)) {
        if (!hasSameVisibilityContextAndLinkage(FoundTypedef, D))
          continue;

        QualType FromUT = D->getUnderlyingType();
        QualType FoundUT = FoundTypedef->getUnderlyingType();
        if (Importer.IsStructurallyEquivalent(FromUT, FoundUT)) {
          // If the "From" context has a complete underlying type but we
          // already have a complete underlying type then return with that.
          if (!FromUT->isIncompleteType() && !FoundUT->isIncompleteType())
            return Importer.MapImported(D, FoundTypedef);
          // FIXME Handle redecl chain. When you do that make consistent changes
          // in ASTImporterLookupTable too.
        } else {
          ConflictingDecls.push_back(FoundDecl);
        }
      }
    }

    if (!ConflictingDecls.empty()) {
      ExpectedName NameOrErr = Importer.HandleNameConflict(
          Name, DC, IDNS, ConflictingDecls.data(), ConflictingDecls.size());
      if (NameOrErr)
        Name = NameOrErr.get();
      else
        return NameOrErr.takeError();
    }
  }

  Error Err = Error::success();
  auto ToUnderlyingType = importChecked(Err, D->getUnderlyingType());
  auto ToTypeSourceInfo = importChecked(Err, D->getTypeSourceInfo());
  auto ToBeginLoc = importChecked(Err, D->getBeginLoc());
  if (Err)
    return std::move(Err);

  // Create the new typedef node.
  // FIXME: ToUnderlyingType is not used.
  (void)ToUnderlyingType;
  TypedefNameDecl *ToTypedef;
  if (IsAlias) {
    if (GetImportedOrCreateDecl<TypeAliasDecl>(
        ToTypedef, D, Importer.getToContext(), DC, ToBeginLoc, Loc,
        Name.getAsIdentifierInfo(), ToTypeSourceInfo))
      return ToTypedef;
  } else if (GetImportedOrCreateDecl<TypedefDecl>(
      ToTypedef, D, Importer.getToContext(), DC, ToBeginLoc, Loc,
      Name.getAsIdentifierInfo(), ToTypeSourceInfo))
    return ToTypedef;

  // Import the DeclContext and set it to the Typedef.
  if ((Err = ImportDeclContext(D, DC, LexicalDC)))
    return std::move(Err);
  ToTypedef->setDeclContext(DC);
  ToTypedef->setLexicalDeclContext(LexicalDC);
  // Add to the lookupTable because we could not do that in MapImported.
  Importer.AddToLookupTable(ToTypedef);

  ToTypedef->setAccess(D->getAccess());

  // Templated declarations should not appear in DeclContext.
  TypeAliasDecl *FromAlias = IsAlias ? cast<TypeAliasDecl>(D) : nullptr;
  if (!FromAlias || !FromAlias->getDescribedAliasTemplate())
    LexicalDC->addDeclInternal(ToTypedef);

  return ToTypedef;
}

ExpectedDecl ASTNodeImporter::VisitTypedefDecl(TypedefDecl *D) {
  return VisitTypedefNameDecl(D, /*IsAlias=*/false);
}

ExpectedDecl ASTNodeImporter::VisitTypeAliasDecl(TypeAliasDecl *D) {
  return VisitTypedefNameDecl(D, /*IsAlias=*/true);
}

ExpectedDecl
ASTNodeImporter::VisitTypeAliasTemplateDecl(TypeAliasTemplateDecl *D) {
  // Import the major distinguishing characteristics of this typedef.
  DeclContext *DC, *LexicalDC;
  DeclarationName Name;
  SourceLocation Loc;
  NamedDecl *FoundD;
  if (Error Err = ImportDeclParts(D, DC, LexicalDC, Name, FoundD, Loc))
    return std::move(Err);
  if (FoundD)
    return FoundD;

  // If this typedef is not in block scope, determine whether we've
  // seen a typedef with the same name (that we can merge with) or any
  // other entity by that name (which name lookup could conflict with).
  if (!DC->isFunctionOrMethod()) {
    SmallVector<NamedDecl *, 4> ConflictingDecls;
    unsigned IDNS = Decl::IDNS_Ordinary;
    auto FoundDecls = Importer.findDeclsInToCtx(DC, Name);
    for (auto *FoundDecl : FoundDecls) {
      if (!FoundDecl->isInIdentifierNamespace(IDNS))
        continue;
      if (auto *FoundAlias = dyn_cast<TypeAliasTemplateDecl>(FoundDecl))
        return Importer.MapImported(D, FoundAlias);
      ConflictingDecls.push_back(FoundDecl);
    }

    if (!ConflictingDecls.empty()) {
      ExpectedName NameOrErr = Importer.HandleNameConflict(
          Name, DC, IDNS, ConflictingDecls.data(), ConflictingDecls.size());
      if (NameOrErr)
        Name = NameOrErr.get();
      else
        return NameOrErr.takeError();
    }
  }

  Error Err = Error::success();
  auto ToTemplateParameters = importChecked(Err, D->getTemplateParameters());
  auto ToTemplatedDecl = importChecked(Err, D->getTemplatedDecl());
  if (Err)
    return std::move(Err);

  TypeAliasTemplateDecl *ToAlias;
  if (GetImportedOrCreateDecl(ToAlias, D, Importer.getToContext(), DC, Loc,
                              Name, ToTemplateParameters, ToTemplatedDecl))
    return ToAlias;

  ToTemplatedDecl->setDescribedAliasTemplate(ToAlias);

  ToAlias->setAccess(D->getAccess());
  ToAlias->setLexicalDeclContext(LexicalDC);
  LexicalDC->addDeclInternal(ToAlias);
  if (DC != Importer.getToContext().getTranslationUnitDecl())
    updateLookupTableForTemplateParameters(*ToTemplateParameters);
  return ToAlias;
}

ExpectedDecl ASTNodeImporter::VisitLabelDecl(LabelDecl *D) {
  // Import the major distinguishing characteristics of this label.
  DeclContext *DC, *LexicalDC;
  DeclarationName Name;
  SourceLocation Loc;
  NamedDecl *ToD;
  if (Error Err = ImportDeclParts(D, DC, LexicalDC, Name, ToD, Loc))
    return std::move(Err);
  if (ToD)
    return ToD;

  assert(LexicalDC->isFunctionOrMethod());

  LabelDecl *ToLabel;
  if (D->isGnuLocal()) {
    ExpectedSLoc BeginLocOrErr = import(D->getBeginLoc());
    if (!BeginLocOrErr)
      return BeginLocOrErr.takeError();
    if (GetImportedOrCreateDecl(ToLabel, D, Importer.getToContext(), DC, Loc,
                                Name.getAsIdentifierInfo(), *BeginLocOrErr))
      return ToLabel;

  } else {
    if (GetImportedOrCreateDecl(ToLabel, D, Importer.getToContext(), DC, Loc,
                                Name.getAsIdentifierInfo()))
      return ToLabel;

  }

  Expected<LabelStmt *> ToStmtOrErr = import(D->getStmt());
  if (!ToStmtOrErr)
    return ToStmtOrErr.takeError();

  ToLabel->setStmt(*ToStmtOrErr);
  ToLabel->setLexicalDeclContext(LexicalDC);
  LexicalDC->addDeclInternal(ToLabel);
  return ToLabel;
}

ExpectedDecl ASTNodeImporter::VisitEnumDecl(EnumDecl *D) {
  // Import the major distinguishing characteristics of this enum.
  DeclContext *DC, *LexicalDC;
  DeclarationName Name;
  SourceLocation Loc;
  NamedDecl *ToD;
  if (Error Err = ImportDeclParts(D, DC, LexicalDC, Name, ToD, Loc))