Initial skeleton of an AST "importer", which will take AST elements from

one context and import them into another context, merging them
according to language-specific rules. This is a skeleton. It doesn't
work, it isn't testable, but I want it in version control.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@95395 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 650 insertions, 0 deletions

diff --git a/include/clang/AST/ASTImporter.h b/include/clang/AST/ASTImporter.h
new file mode 100644
index 0000000000..d8e1839bea
--- /dev/null
+++ b/include/clang/AST/ASTImporter.h
@@ -0,0 +1,140 @@
+//===--- ASTImporter.h - Importing ASTs from other Contexts -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the ASTImporter class which imports AST nodes from one
+//  context into another context.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_CLANG_AST_ASTIM PORTER_H
+#define LLVM_CLANG_AST_ASTIMPORTER_H
+
+#include "clang/AST/Type.h"
+#include "clang/AST/DeclarationName.h"
+#include "clang/Basic/SourceLocation.h"
+
+namespace clang {
+  class ASTContext;
+  class Decl;
+  class DeclContext;
+  class Diagnostic;
+  class Expr;
+  class IdentifierInfo;
+  class NestedNameSpecifier;
+  class Stmt;
+  class TypeSourceInfo;
+  
+  /// \brief Imports selected nodes from one AST context into another context,
+  /// merging AST nodes where appropriate.
+  class ASTImporter {
+    /// \brief The contexts we're importing to and from.
+    ASTContext &ToContext, &FromContext;
+    
+    /// \brief The diagnostics object that we should use to emit diagnostics
+    /// within the context we're importing to and from.
+    Diagnostic &ToDiags, &FromDiags;
+          
+  public:
+    ASTImporter(ASTContext &ToContext, Diagnostic &ToDiags,
+                ASTContext &FromContext, Diagnostic &FromDiags);
+    
+    ~ASTImporter();
+    
+    /// \brief Import the given type from the "from" context into the "to"
+    /// context.
+    ///
+    /// \returns the equivalent type in the "to" context, or a NULL type if
+    /// an error occurred.
+    QualType Import(QualType FromT);
+
+    /// \brief Import the given type source information from the
+    /// "from" context into the "to" context.
+    ///
+    /// \returns the equivalent type source information in the "to"
+    /// context, or NULL if an error occurred.
+    TypeSourceInfo *Import(TypeSourceInfo *FromTSI);
+
+    /// \brief Import the given declaration from the "from" context into the 
+    /// "to" context.
+    ///
+    /// \returns the equivalent declaration in the "to" context, or a NULL type 
+    /// if an error occurred.
+    Decl *Import(Decl *FromD);
+
+    /// \brief Import the given declaration context from the "from"
+    /// AST context into the "to" AST context.
+    ///
+    /// \returns the equivalent declaration context in the "to"
+    /// context, or a NULL type if an error occurred.
+    DeclContext *ImportContext(DeclContext *FromDC);
+    
+    /// \brief Import the given expression from the "from" context into the
+    /// "to" context.
+    ///
+    /// \returns the equivalent expression in the "to" context, or NULL if
+    /// an error occurred.
+    Expr *Import(Expr *FromE);
+
+    /// \brief Import the given statement from the "from" context into the
+    /// "to" context.
+    ///
+    /// \returns the equivalent statement in the "to" context, or NULL if
+    /// an error occurred.
+    Stmt *Import(Stmt *FromS);
+
+    /// \brief Import the given nested-name-specifier from the "from"
+    /// context into the "to" context.
+    ///
+    /// \returns the equivalent nested-name-specifier in the "to"
+    /// context, or NULL if an error occurred.
+    NestedNameSpecifier *Import(NestedNameSpecifier *FromNNS);
+
+    /// \brief Import the given source location from the "from" context into
+    /// the "to" context.
+    ///
+    /// \returns the equivalent source location in the "to" context, or an
+    /// invalid source location if an error occurred.
+    SourceLocation Import(SourceLocation FromLoc);
+
+    /// \brief Import the given source range from the "from" context into
+    /// the "to" context.
+    ///
+    /// \returns the equivalent source range in the "to" context, or an
+    /// invalid source location if an error occurred.
+    SourceRange Import(SourceRange FromRange);
+
+    /// \brief Import the given declaration name from the "from"
+    /// context into the "to" context.
+    ///
+    /// \returns the equivalent declaration name in the "to" context,
+    /// or an empty declaration name if an error occurred.
+    DeclarationName Import(DeclarationName FromName);
+
+    /// \brief Import the given identifier from the "from" context
+    /// into the "to" context.
+    ///
+    /// \returns the equivalent identifier in the "to" context.
+    IdentifierInfo *Import(IdentifierInfo *FromId);
+
+    /// \brief Retrieve the context that AST nodes are being imported into.
+    ASTContext &getToContext() const { return ToContext; }
+    
+    /// \brief Retrieve the context that AST nodes are being imported from.
+    ASTContext &getFromContext() const { return FromContext; }
+    
+    /// \brief Retrieve the diagnostics object to use to report errors within
+    /// the context we're importing into.
+    Diagnostic &getToDiags() const { return ToDiags; }
+
+    /// \brief Retrieve the diagnostics object to use to report errors within
+    /// the context we're importing from.
+    Diagnostic &getFromDiags() const { return FromDiags; }
+  };
+}
+
+#endif // LLVM_CLANG_AST_ASTIMPORTER_H
diff --git a/lib/AST/ASTImporter.cpp b/lib/AST/ASTImporter.cpp
new file mode 100644
index 0000000000..dc3281afba
--- /dev/null
+++ b/lib/AST/ASTImporter.cpp
@@ -0,0 +1,509 @@
+//===--- ASTImporter.cpp - Importing ASTs from other Contexts ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the ASTImporter class which imports AST nodes from one
+//  context into another context.
+//
+//===----------------------------------------------------------------------===//
+#include "clang/AST/ASTImporter.h"
+
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclObjC.h"
+#include "clang/AST/TypeVisitor.h"
+
+using namespace clang;
+
+namespace {
+  class ASTNodeImporter : public TypeVisitor<ASTNodeImporter, QualType> {
+    ASTImporter &Importer;
+    
+  public:
+    explicit ASTNodeImporter(ASTImporter &Importer) : Importer(Importer) { }
+    
+    using TypeVisitor<ASTNodeImporter, QualType>::Visit;
+
+    // Importing types
+    QualType VisitBuiltinType(BuiltinType *T);
+    QualType VisitComplexType(ComplexType *T);
+    QualType VisitPointerType(PointerType *T);
+    QualType VisitBlockPointerType(BlockPointerType *T);
+    QualType VisitLValueReferenceType(LValueReferenceType *T);
+    QualType VisitRValueReferenceType(RValueReferenceType *T);
+    QualType VisitMemberPointerType(MemberPointerType *T);
+    QualType VisitConstantArrayType(ConstantArrayType *T);
+    QualType VisitIncompleteArrayType(IncompleteArrayType *T);
+    QualType VisitVariableArrayType(VariableArrayType *T);
+    // FIXME: DependentSizedArrayType
+    // FIXME: DependentSizedExtVectorType
+    QualType VisitVectorType(VectorType *T);
+    QualType VisitExtVectorType(ExtVectorType *T);
+    QualType VisitFunctionNoProtoType(FunctionNoProtoType *T);
+    QualType VisitFunctionProtoType(FunctionProtoType *T);
+    // FIXME: UnresolvedUsingType
+    QualType VisitTypedefType(TypedefType *T);
+    QualType VisitTypeOfExprType(TypeOfExprType *T);
+    // FIXME: DependentTypeOfExprType
+    QualType VisitTypeOfType(TypeOfType *T);
+    QualType VisitDecltypeType(DecltypeType *T);
+    // FIXME: DependentDecltypeType
+    QualType VisitRecordType(RecordType *T);
+    QualType VisitEnumType(EnumType *T);
+    QualType VisitElaboratedType(ElaboratedType *T);
+    // FIXME: TemplateTypeParmType
+    // FIXME: SubstTemplateTypeParmType
+    // FIXME: TemplateSpecializationType
+    QualType VisitQualifiedNameType(QualifiedNameType *T);
+    // FIXME: TypenameType
+    QualType VisitObjCInterfaceType(ObjCInterfaceType *T);
+    QualType VisitObjCObjectPointerType(ObjCObjectPointerType *T);
+  };
+}
+
+//----------------------------------------------------------------------------
+// Import Types
+//----------------------------------------------------------------------------
+
+QualType ASTNodeImporter::VisitBuiltinType(BuiltinType *T) {
+  switch (T->getKind()) {
+  case BuiltinType::Void: return Importer.getToContext().VoidTy;
+  case BuiltinType::Bool: return Importer.getToContext().BoolTy;
+    
+  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().getLangOptions().CharIsSigned)
+      return Importer.getToContext().UnsignedCharTy;
+    
+    return Importer.getToContext().CharTy;
+
+  case BuiltinType::UChar: return Importer.getToContext().UnsignedCharTy;
+    
+  case BuiltinType::Char16:
+    // FIXME: Make sure that the "to" context supports C++!
+    return Importer.getToContext().Char16Ty;
+    
+  case BuiltinType::Char32: 
+    // FIXME: Make sure that the "to" context supports C++!
+    return Importer.getToContext().Char32Ty;
+
+  case BuiltinType::UShort: return Importer.getToContext().UnsignedShortTy;
+  case BuiltinType::UInt: return Importer.getToContext().UnsignedIntTy;
+  case BuiltinType::ULong: return Importer.getToContext().UnsignedLongTy;
+  case BuiltinType::ULongLong: 
+    return Importer.getToContext().UnsignedLongLongTy;
+  case BuiltinType::UInt128: return Importer.getToContext().UnsignedInt128Ty;
+    
+  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().getLangOptions().CharIsSigned)
+      return Importer.getToContext().SignedCharTy;
+    
+    return Importer.getToContext().CharTy;
+
+  case BuiltinType::SChar: return Importer.getToContext().SignedCharTy;
+  case BuiltinType::WChar:
+    // FIXME: If not in C++, shall we translate to the C equivalent of
+    // wchar_t?
+    return Importer.getToContext().WCharTy;
+    
+  case BuiltinType::Short : return Importer.getToContext().ShortTy;
+  case BuiltinType::Int : return Importer.getToContext().IntTy;
+  case BuiltinType::Long : return Importer.getToContext().LongTy;
+  case BuiltinType::LongLong : return Importer.getToContext().LongLongTy;
+  case BuiltinType::Int128 : return Importer.getToContext().Int128Ty;
+  case BuiltinType::Float: return Importer.getToContext().FloatTy;
+  case BuiltinType::Double: return Importer.getToContext().DoubleTy;
+  case BuiltinType::LongDouble: return Importer.getToContext().LongDoubleTy;
+
+  case BuiltinType::NullPtr:
+    // FIXME: Make sure that the "to" context supports C++0x!
+    return Importer.getToContext().NullPtrTy;
+    
+  case BuiltinType::Overload: return Importer.getToContext().OverloadTy;
+  case BuiltinType::Dependent: return Importer.getToContext().DependentTy;
+  case BuiltinType::UndeducedAuto: 
+    // FIXME: Make sure that the "to" context supports C++0x!
+    return Importer.getToContext().UndeducedAutoTy;
+
+  case BuiltinType::ObjCId:
+    // FIXME: Make sure that the "to" context supports Objective-C!
+    return Importer.getToContext().ObjCBuiltinIdTy;
+    
+  case BuiltinType::ObjCClass:
+    return Importer.getToContext().ObjCBuiltinClassTy;
+
+  case BuiltinType::ObjCSel:
+    return Importer.getToContext().ObjCBuiltinSelTy;
+  }
+  
+  return QualType();
+}
+
+QualType ASTNodeImporter::VisitComplexType(ComplexType *T) {
+  QualType ToElementType = Importer.Import(T->getElementType());
+  if (ToElementType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getComplexType(ToElementType);
+}
+
+QualType ASTNodeImporter::VisitPointerType(PointerType *T) {
+  QualType ToPointeeType = Importer.Import(T->getPointeeType());
+  if (ToPointeeType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getPointerType(ToPointeeType);
+}
+
+QualType ASTNodeImporter::VisitBlockPointerType(BlockPointerType *T) {
+  // FIXME: Check for blocks support in "to" context.
+  QualType ToPointeeType = Importer.Import(T->getPointeeType());
+  if (ToPointeeType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getBlockPointerType(ToPointeeType);
+}
+
+QualType ASTNodeImporter::VisitLValueReferenceType(LValueReferenceType *T) {
+  // FIXME: Check for C++ support in "to" context.
+  QualType ToPointeeType = Importer.Import(T->getPointeeTypeAsWritten());
+  if (ToPointeeType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getLValueReferenceType(ToPointeeType);
+}
+
+QualType ASTNodeImporter::VisitRValueReferenceType(RValueReferenceType *T) {
+  // FIXME: Check for C++0x support in "to" context.
+  QualType ToPointeeType = Importer.Import(T->getPointeeTypeAsWritten());
+  if (ToPointeeType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getRValueReferenceType(ToPointeeType);  
+}
+
+QualType ASTNodeImporter::VisitMemberPointerType(MemberPointerType *T) {
+  // FIXME: Check for C++ support in "to" context.
+  QualType ToPointeeType = Importer.Import(T->getPointeeType());
+  if (ToPointeeType.isNull())
+    return QualType();
+  
+  QualType ClassType = Importer.Import(QualType(T->getClass(), 0));
+  return Importer.getToContext().getMemberPointerType(ToPointeeType, 
+                                                      ClassType.getTypePtr());
+}
+
+QualType ASTNodeImporter::VisitConstantArrayType(ConstantArrayType *T) {
+  QualType ToElementType = Importer.Import(T->getElementType());
+  if (ToElementType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getConstantArrayType(ToElementType, 
+                                                      T->getSize(),
+                                                      T->getSizeModifier(),
+                                               T->getIndexTypeCVRQualifiers());
+}
+
+QualType ASTNodeImporter::VisitIncompleteArrayType(IncompleteArrayType *T) {
+  QualType ToElementType = Importer.Import(T->getElementType());
+  if (ToElementType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getIncompleteArrayType(ToElementType, 
+                                                        T->getSizeModifier(),
+                                                T->getIndexTypeCVRQualifiers());
+}
+
+QualType ASTNodeImporter::VisitVariableArrayType(VariableArrayType *T) {
+  QualType ToElementType = Importer.Import(T->getElementType());
+  if (ToElementType.isNull())
+    return QualType();
+
+  Expr *Size = Importer.Import(T->getSizeExpr());
+  if (!Size)
+    return QualType();
+  
+  SourceRange Brackets = Importer.Import(T->getBracketsRange());
+  return Importer.getToContext().getVariableArrayType(ToElementType, Size,
+                                                      T->getSizeModifier(),
+                                                T->getIndexTypeCVRQualifiers(),
+                                                      Brackets);
+}
+
+QualType ASTNodeImporter::VisitVectorType(VectorType *T) {
+  QualType ToElementType = Importer.Import(T->getElementType());
+  if (ToElementType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getVectorType(ToElementType, 
+                                               T->getNumElements(),
+                                               T->isAltiVec(),
+                                               T->isPixel());
+}
+
+QualType ASTNodeImporter::VisitExtVectorType(ExtVectorType *T) {
+  QualType ToElementType = Importer.Import(T->getElementType());
+  if (ToElementType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getExtVectorType(ToElementType, 
+                                                  T->getNumElements());
+}
+
+QualType ASTNodeImporter::VisitFunctionNoProtoType(FunctionNoProtoType *T) {
+  // FIXME: What happens if we're importing a function without a prototype 
+  // into C++? Should we make it variadic?
+  QualType ToResultType = Importer.Import(T->getResultType());
+  if (ToResultType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getFunctionNoProtoType(ToResultType,
+                                                        T->getNoReturnAttr(), 
+                                                        T->getCallConv());
+}
+
+QualType ASTNodeImporter::VisitFunctionProtoType(FunctionProtoType *T) {
+  QualType ToResultType = Importer.Import(T->getResultType());
+  if (ToResultType.isNull())
+    return QualType();
+  
+  // Import argument types
+  llvm::SmallVector<QualType, 4> ArgTypes;
+  for (FunctionProtoType::arg_type_iterator A = T->arg_type_begin(),
+                                         AEnd = T->arg_type_end();
+       A != AEnd; ++A) {
+    QualType ArgType = Importer.Import(*A);
+    if (ArgType.isNull())
+      return QualType();
+    ArgTypes.push_back(ArgType);
+  }
+  
+  // Import exception types
+  llvm::SmallVector<QualType, 4> ExceptionTypes;
+  for (FunctionProtoType::exception_iterator E = T->exception_begin(),
+                                          EEnd = T->exception_end();
+       E != EEnd; ++E) {
+    QualType ExceptionType = Importer.Import(*E);
+    if (ExceptionType.isNull())
+      return QualType();
+    ExceptionTypes.push_back(ExceptionType);
+  }
+       
+  return Importer.getToContext().getFunctionType(ToResultType, ArgTypes.data(),
+                                                 ArgTypes.size(),
+                                                 T->isVariadic(),
+                                                 T->getTypeQuals(),
+                                                 T->hasExceptionSpec(), 
+                                                 T->hasAnyExceptionSpec(),
+                                                 ExceptionTypes.size(),
+                                                 ExceptionTypes.data(),
+                                                 T->getNoReturnAttr(),
+                                                 T->getCallConv());
+}
+
+QualType ASTNodeImporter::VisitTypedefType(TypedefType *T) {
+  TypedefDecl *ToDecl
+                 = dyn_cast_or_null<TypedefDecl>(Importer.Import(T->getDecl()));
+  if (!ToDecl)
+    return QualType();
+  
+  return Importer.getToContext().getTypeDeclType(ToDecl);
+}
+
+QualType ASTNodeImporter::VisitTypeOfExprType(TypeOfExprType *T) {
+  Expr *ToExpr = Importer.Import(T->getUnderlyingExpr());
+  if (!ToExpr)
+    return QualType();
+  
+  return Importer.getToContext().getTypeOfExprType(ToExpr);
+}
+
+QualType ASTNodeImporter::VisitTypeOfType(TypeOfType *T) {
+  QualType ToUnderlyingType = Importer.Import(T->getUnderlyingType());
+  if (ToUnderlyingType.isNull())
+    return QualType();
+  
+  return Importer.getToContext().getTypeOfType(ToUnderlyingType);
+}
+
+QualType ASTNodeImporter::VisitDecltypeType(DecltypeType *T) {
+  Expr *ToExpr = Importer.Import(T->getUnderlyingExpr());
+  if (!ToExpr)
+    return QualType();
+  
+  return Importer.getToContext().getDecltypeType(ToExpr);
+}
+
+QualType ASTNodeImporter::VisitRecordType(RecordType *T) {
+  RecordDecl *ToDecl
+    = dyn_cast_or_null<RecordDecl>(Importer.Import(T->getDecl()));
+  if (!ToDecl)
+    return QualType();
+
+  return Importer.getToContext().getTagDeclType(ToDecl);
+}
+
+QualType ASTNodeImporter::VisitEnumType(EnumType *T) {
+  EnumDecl *ToDecl
+    = dyn_cast_or_null<EnumDecl>(Importer.Import(T->getDecl()));
+  if (!ToDecl)
+    return QualType();
+
+  return Importer.getToContext().getTagDeclType(ToDecl);
+}
+
+QualType ASTNodeImporter::VisitElaboratedType(ElaboratedType *T) {
+  QualType ToUnderlyingType = Importer.Import(T->getUnderlyingType());
+  if (ToUnderlyingType.isNull())
+    return QualType();
+
+  return Importer.getToContext().getElaboratedType(ToUnderlyingType,
+                                                   T->getTagKind());
+}
+
+QualType ASTNodeImporter::VisitQualifiedNameType(QualifiedNameType *T) {
+  NestedNameSpecifier *ToQualifier = Importer.Import(T->getQualifier());
+  if (!ToQualifier)
+    return QualType();
+
+  QualType ToNamedType = Importer.Import(T->getNamedType());
+  if (ToNamedType.isNull())
+    return QualType();
+
+  return Importer.getToContext().getQualifiedNameType(ToQualifier, ToNamedType);
+}
+
+QualType ASTNodeImporter::VisitObjCInterfaceType(ObjCInterfaceType *T) {
+  ObjCInterfaceDecl *Class
+    = dyn_cast_or_null<ObjCInterfaceDecl>(Importer.Import(T->getDecl()));
+  if (!Class)
+    return QualType();
+
+  llvm::SmallVector<ObjCProtocolDecl *, 4> Protocols;
+  for (ObjCInterfaceType::qual_iterator P = T->qual_begin(), 
+                                     PEnd = T->qual_end();
+       P != PEnd; ++P) {
+    ObjCProtocolDecl *Protocol
+      = dyn_cast_or_null<ObjCProtocolDecl>(Importer.Import(*P));
+    if (!Protocol)
+      return QualType();
+    Protocols.push_back(Protocol);
+  }
+
+  return Importer.getToContext().getObjCInterfaceType(Class,
+                                                      Protocols.data(),
+                                                      Protocols.size());
+}
+
+QualType ASTNodeImporter::VisitObjCObjectPointerType(ObjCObjectPointerType *T) {
+  QualType ToPointeeType = Importer.Import(T->getPointeeType());
+  if (ToPointeeType.isNull())
+    return QualType();
+
+  llvm::SmallVector<ObjCProtocolDecl *, 4> Protocols;
+  for (ObjCObjectPointerType::qual_iterator P = T->qual_begin(), 
+                                         PEnd = T->qual_end();
+       P != PEnd; ++P) {
+    ObjCProtocolDecl *Protocol
+      = dyn_cast_or_null<ObjCProtocolDecl>(Importer.Import(*P));
+    if (!Protocol)
+      return QualType();
+    Protocols.push_back(Protocol);
+  }
+
+  return Importer.getToContext().getObjCObjectPointerType(ToPointeeType,
+                                                          Protocols.data(),
+                                                          Protocols.size());
+}
+
+ASTImporter::ASTImporter(ASTContext &ToContext, Diagnostic &ToDiags,
+                         ASTContext &FromContext, Diagnostic &FromDiags)
+  : ToContext(ToContext), FromContext(FromContext),
+    ToDiags(ToDiags), FromDiags(FromDiags) { }
+
+QualType ASTImporter::Import(QualType FromT) {
+  if (FromT.isNull())
+    return QualType();
+  
+  // FIXME: Cache type mappings?
+  
+  ASTNodeImporter Importer(*this);
+  QualType ToT = Importer.Visit(FromT.getTypePtr());
+  if (ToT.isNull())
+    return ToT;
+  
+  return ToContext.getQualifiedType(ToT, FromT.getQualifiers());
+}
+
+DeclarationName ASTImporter::Import(DeclarationName FromName) {
+  if (!FromName)
+    return DeclarationName();
+
+  switch (FromName.getNameKind()) {
+  case DeclarationName::Identifier:
+    return Import(FromName.getAsIdentifierInfo());
+
+  case DeclarationName::ObjCZeroArgSelector:
+  case DeclarationName::ObjCOneArgSelector:
+  case DeclarationName::ObjCMultiArgSelector:
+    return Import(FromName.getObjCSelector());
+
+  case DeclarationName::CXXConstructorName: {
+    QualType T = Import(FromName.getCXXNameType());
+    if (T.isNull())
+      return DeclarationName();
+
+    return ToContext.DeclarationNames.getCXXConstructorName(
+                                               ToContext.getCanonicalType(T));
+  }
+
+  case DeclarationName::CXXDestructorName: {
+    QualType T = Import(FromName.getCXXNameType());
+    if (T.isNull())
+      return DeclarationName();
+
+    return ToContext.DeclarationNames.getCXXDestructorName(
+                                               ToContext.getCanonicalType(T));
+  }
+
+  case DeclarationName::CXXConversionFunctionName: {
+    QualType T = Import(FromName.getCXXNameType());
+    if (T.isNull())
+      return DeclarationName();
+
+    return ToContext.DeclarationNames.getCXXConversionFunctionName(
+                                               ToContext.getCanonicalType(T));
+  }
+
+  case DeclarationName::CXXOperatorName:
+    return ToContext.DeclarationNames.getCXXOperatorName(
+                                          FromName.getCXXOverloadedOperator());
+
+  case DeclarationName::CXXLiteralOperatorName:
+    return ToContext.DeclarationNames.getCXXLiteralOperatorName(
+                                   Import(FromName.getCXXLiteralIdentifier()));
+
+  case DeclarationName::CXXUsingDirective:
+    // FIXME: STATICS!
+    return DeclarationName::getUsingDirectiveName();
+  }
+
+  // Silence bogus GCC warning
+  return DeclarationName();
+}
+
+IdentifierInfo *ASTImporter::Import(IdentifierInfo *FromId) {
+  if (!FromId)
+    return 0;
+
+  return &ToContext.Idents.get(FromId->getName());
+}
diff --git a/lib/AST/CMakeLists.txt b/lib/AST/CMakeLists.txt
index dea96e7866..364f7a5ecd 100644
--- a/lib/AST/CMakeLists.txt
+++ b/lib/AST/CMakeLists.txt
@@ -4,6 +4,7 @@ add_clang_library(clangAST
   APValue.cpp
   ASTConsumer.cpp
   ASTContext.cpp
+  ASTImporter.cpp
   AttrImpl.cpp
   CXXInheritance.cpp
   Decl.cpp