Index: cfe/trunk/include/clang/AST/ASTStructuralEquivalence.h
===================================================================
--- cfe/trunk/include/clang/AST/ASTStructuralEquivalence.h
+++ cfe/trunk/include/clang/AST/ASTStructuralEquivalence.h
@@ -0,0 +1,101 @@
+//===--- ASTStructuralEquivalence.h - ---------------------------*- 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 StructuralEquivalenceContext class which checks for
+//  structural equivalence between types.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_AST_ASTSTRUCTURALEQUIVALENCE_H
+#define LLVM_CLANG_AST_ASTSTRUCTURALEQUIVALENCE_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/Optional.h"
+#include <deque>
+
+namespace clang {
+
+class ASTContext;
+class Decl;
+class DiagnosticBuilder;
+class QualType;
+class RecordDecl;
+class SourceLocation;
+
+struct StructuralEquivalenceContext {
+  /// AST contexts for which we are checking structural equivalence.
+  ASTContext &FromCtx, &ToCtx;
+
+  /// The set of "tentative" equivalences between two canonical
+  /// declarations, mapping from a declaration in the first context to the
+  /// declaration in the second context that we believe to be equivalent.
+  llvm::DenseMap<Decl *, Decl *> TentativeEquivalences;
+
+  /// Queue of declarations in the first context whose equivalence
+  /// with a declaration in the second context still needs to be verified.
+  std::deque<Decl *> DeclsToCheck;
+
+  /// Declaration (from, to) pairs that are known not to be equivalent
+  /// (which we have already complained about).
+  llvm::DenseSet<std::pair<Decl *, Decl *>> &NonEquivalentDecls;
+
+  /// Whether we're being strict about the spelling of types when
+  /// unifying two types.
+  bool StrictTypeSpelling;
+
+  /// Whether warn or error on tag type mismatches.
+  bool ErrorOnTagTypeMismatch;
+
+  /// Whether to complain about failures.
+  bool Complain;
+
+  /// \c true if the last diagnostic came from ToCtx.
+  bool LastDiagFromC2;
+
+  StructuralEquivalenceContext(
+      ASTContext &FromCtx, ASTContext &ToCtx,
+      llvm::DenseSet<std::pair<Decl *, Decl *>> &NonEquivalentDecls,
+      bool StrictTypeSpelling = false, bool Complain = true)
+      : FromCtx(FromCtx), ToCtx(ToCtx), NonEquivalentDecls(NonEquivalentDecls),
+        StrictTypeSpelling(StrictTypeSpelling), Complain(Complain),
+        LastDiagFromC2(false) {}
+
+  DiagnosticBuilder Diag1(SourceLocation Loc, unsigned DiagID);
+  DiagnosticBuilder Diag2(SourceLocation Loc, unsigned DiagID);
+
+  /// Determine whether the two declarations are structurally
+  /// equivalent.
+  bool IsStructurallyEquivalent(Decl *D1, Decl *D2);
+
+  /// Determine whether the two types are structurally equivalent.
+  bool IsStructurallyEquivalent(QualType T1, QualType T2);
+
+  /// Find the index of the given anonymous struct/union within its
+  /// context.
+  ///
+  /// \returns Returns the index of this anonymous struct/union in its context,
+  /// including the next assigned index (if none of them match). Returns an
+  /// empty option if the context is not a record, i.e.. if the anonymous
+  /// struct/union is at namespace or block scope.
+  ///
+  /// FIXME: This is needed by ASTImporter and ASTStructureEquivalence. It
+  /// probably makes more sense in some other common place then here.
+  static llvm::Optional<unsigned>
+  findUntaggedStructOrUnionIndex(RecordDecl *Anon);
+
+private:
+  /// Finish checking all of the structural equivalences.
+  ///
+  /// \returns true if an error occurred, false otherwise.
+  bool Finish();
+};
+} // namespace clang
+
+#endif // LLVM_CLANG_AST_ASTSTRUCTURALEQUIVALENCE_H
Index: cfe/trunk/lib/AST/ASTImporter.cpp
===================================================================
--- cfe/trunk/lib/AST/ASTImporter.cpp
+++ cfe/trunk/lib/AST/ASTImporter.cpp
@@ -14,6 +14,7 @@
 #include "clang/AST/ASTImporter.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTDiagnostic.h"
+#include "clang/AST/ASTStructuralEquivalence.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/DeclVisitor.h"
@@ -321,1396 +322,12 @@
   };
 }
 
-using namespace clang;
-
-//----------------------------------------------------------------------------
-// Structural Equivalence
-//----------------------------------------------------------------------------
-
-namespace {
-  struct StructuralEquivalenceContext {
-    /// \brief AST contexts for which we are checking structural equivalence.
-    ASTContext &C1, &C2;
-    
-    /// \brief The set of "tentative" equivalences between two canonical 
-    /// declarations, mapping from a declaration in the first context to the
-    /// declaration in the second context that we believe to be equivalent.
-    llvm::DenseMap<Decl *, Decl *> TentativeEquivalences;
-    
-    /// \brief Queue of declarations in the first context whose equivalence
-    /// with a declaration in the second context still needs to be verified.
-    std::deque<Decl *> DeclsToCheck;
-    
-    /// \brief Declaration (from, to) pairs that are known not to be equivalent
-    /// (which we have already complained about).
-    llvm::DenseSet<std::pair<Decl *, Decl *> > &NonEquivalentDecls;
-    
-    /// \brief Whether we're being strict about the spelling of types when 
-    /// unifying two types.
-    bool StrictTypeSpelling;
-
-    /// \brief Whether to complain about failures.
-    bool Complain;
-
-    /// \brief \c true if the last diagnostic came from C2.
-    bool LastDiagFromC2;
-
-    StructuralEquivalenceContext(ASTContext &C1, ASTContext &C2,
-               llvm::DenseSet<std::pair<Decl *, Decl *> > &NonEquivalentDecls,
-                                 bool StrictTypeSpelling = false,
-                                 bool Complain = true)
-      : C1(C1), C2(C2), NonEquivalentDecls(NonEquivalentDecls),
-        StrictTypeSpelling(StrictTypeSpelling), Complain(Complain),
-        LastDiagFromC2(false) {}
-
-    /// \brief Determine whether the two declarations are structurally
-    /// equivalent.
-    bool IsStructurallyEquivalent(Decl *D1, Decl *D2);
-    
-    /// \brief Determine whether the two types are structurally equivalent.
-    bool IsStructurallyEquivalent(QualType T1, QualType T2);
-
-  private:
-    /// \brief Finish checking all of the structural equivalences.
-    ///
-    /// \returns true if an error occurred, false otherwise.
-    bool Finish();
-    
-  public:
-    DiagnosticBuilder Diag1(SourceLocation Loc, unsigned DiagID) {
-      assert(Complain && "Not allowed to complain");
-      if (LastDiagFromC2)
-        C1.getDiagnostics().notePriorDiagnosticFrom(C2.getDiagnostics());
-      LastDiagFromC2 = false;
-      return C1.getDiagnostics().Report(Loc, DiagID);
-    }
-
-    DiagnosticBuilder Diag2(SourceLocation Loc, unsigned DiagID) {
-      assert(Complain && "Not allowed to complain");
-      if (!LastDiagFromC2)
-        C2.getDiagnostics().notePriorDiagnosticFrom(C1.getDiagnostics());
-      LastDiagFromC2 = true;
-      return C2.getDiagnostics().Report(Loc, DiagID);
-    }
-  };
-}
-
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     QualType T1, QualType T2);
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     Decl *D1, Decl *D2);
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     const TemplateArgument &Arg1,
-                                     const TemplateArgument &Arg2);
-
-/// \brief Determine structural equivalence of two expressions.
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     Expr *E1, Expr *E2) {
-  if (!E1 || !E2)
-    return E1 == E2;
-  
-  // FIXME: Actually perform a structural comparison!
-  return true;
-}
-
-/// \brief Determine whether two identifiers are equivalent.
-static bool IsStructurallyEquivalent(const IdentifierInfo *Name1,
-                                     const IdentifierInfo *Name2) {
-  if (!Name1 || !Name2)
-    return Name1 == Name2;
-  
-  return Name1->getName() == Name2->getName();
-}
-
-/// \brief Determine whether two nested-name-specifiers are equivalent.
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     NestedNameSpecifier *NNS1,
-                                     NestedNameSpecifier *NNS2) {
-  if (NNS1->getKind() != NNS2->getKind())
-    return false;
-
-  NestedNameSpecifier *Prefix1 = NNS1->getPrefix(),
-      *Prefix2 = NNS2->getPrefix();
-  if ((bool)Prefix1 != (bool)Prefix2)
-    return false;
-
-  if (Prefix1)
-    if (!IsStructurallyEquivalent(Context, Prefix1, Prefix2))
-      return false;
-
-  switch (NNS1->getKind()) {
-  case NestedNameSpecifier::Identifier:
-    return IsStructurallyEquivalent(NNS1->getAsIdentifier(),
-                                    NNS2->getAsIdentifier());
-  case NestedNameSpecifier::Namespace:
-    return IsStructurallyEquivalent(Context, NNS1->getAsNamespace(),
-                                    NNS2->getAsNamespace());
-  case NestedNameSpecifier::NamespaceAlias:
-    return IsStructurallyEquivalent(Context, NNS1->getAsNamespaceAlias(),
-                                    NNS2->getAsNamespaceAlias());
-  case NestedNameSpecifier::TypeSpec:
-  case NestedNameSpecifier::TypeSpecWithTemplate:
-    return IsStructurallyEquivalent(Context, QualType(NNS1->getAsType(), 0),
-                                    QualType(NNS2->getAsType(), 0));
-  case NestedNameSpecifier::Global:
-    return true;
-  case NestedNameSpecifier::Super:
-    return IsStructurallyEquivalent(Context, NNS1->getAsRecordDecl(),
-                                    NNS2->getAsRecordDecl());
-  }
-  return false;
-}
-
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     const TemplateName &N1,
-                                     const TemplateName &N2) {
-  if (N1.getKind() != N2.getKind())
-    return false;
-  switch (N1.getKind()) {
-  case TemplateName::Template:
-    return IsStructurallyEquivalent(Context, N1.getAsTemplateDecl(),
-                                    N2.getAsTemplateDecl());
-
-  case TemplateName::OverloadedTemplate: {
-    OverloadedTemplateStorage *OS1 = N1.getAsOverloadedTemplate(),
-        *OS2 = N2.getAsOverloadedTemplate();
-    OverloadedTemplateStorage::iterator I1 = OS1->begin(), I2 = OS2->begin(),
-        E1 = OS1->end(), E2 = OS2->end();
-    for (; I1 != E1 && I2 != E2; ++I1, ++I2)
-      if (!IsStructurallyEquivalent(Context, *I1, *I2))
-        return false;
-    return I1 == E1 && I2 == E2;
-  }
-
-  case TemplateName::QualifiedTemplate: {
-    QualifiedTemplateName *QN1 = N1.getAsQualifiedTemplateName(),
-        *QN2 = N2.getAsQualifiedTemplateName();
-    return IsStructurallyEquivalent(Context, QN1->getDecl(), QN2->getDecl()) &&
-        IsStructurallyEquivalent(Context, QN1->getQualifier(),
-                                 QN2->getQualifier());
-  }
-
-  case TemplateName::DependentTemplate: {
-      DependentTemplateName *DN1 = N1.getAsDependentTemplateName(),
-          *DN2 = N2.getAsDependentTemplateName();
-      if (!IsStructurallyEquivalent(Context, DN1->getQualifier(),
-                                    DN2->getQualifier()))
-        return false;
-      if (DN1->isIdentifier() && DN2->isIdentifier())
-        return IsStructurallyEquivalent(DN1->getIdentifier(),
-                                        DN2->getIdentifier());
-      else if (DN1->isOverloadedOperator() && DN2->isOverloadedOperator())
-        return DN1->getOperator() == DN2->getOperator();
-      return false;
-  }
-
-  case TemplateName::SubstTemplateTemplateParm: {
-    SubstTemplateTemplateParmStorage *TS1 = N1.getAsSubstTemplateTemplateParm(),
-        *TS2 = N2.getAsSubstTemplateTemplateParm();
-    return IsStructurallyEquivalent(Context, TS1->getParameter(),
-                                    TS2->getParameter()) &&
-        IsStructurallyEquivalent(Context, TS1->getReplacement(),
-                                 TS2->getReplacement());
-    }
-  case TemplateName::SubstTemplateTemplateParmPack: {
-    SubstTemplateTemplateParmPackStorage
-        *P1 = N1.getAsSubstTemplateTemplateParmPack(),
-        *P2 = N2.getAsSubstTemplateTemplateParmPack();
-    return IsStructurallyEquivalent(Context, P1->getArgumentPack(),
-                                    P2->getArgumentPack()) &&
-        IsStructurallyEquivalent(Context, P1->getParameterPack(),
-                                 P2->getParameterPack());
-  }
-  }
-  return false;
-}
-
-/// \brief Determine whether two template arguments are equivalent.
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     const TemplateArgument &Arg1,
-                                     const TemplateArgument &Arg2) {
-  if (Arg1.getKind() != Arg2.getKind())
-    return false;
-
-  switch (Arg1.getKind()) {
-  case TemplateArgument::Null:
-    return true;
-      
-  case TemplateArgument::Type:
-    return Context.IsStructurallyEquivalent(Arg1.getAsType(), Arg2.getAsType());
-
-  case TemplateArgument::Integral:
-    if (!Context.IsStructurallyEquivalent(Arg1.getIntegralType(), 
-                                          Arg2.getIntegralType()))
-      return false;
-    
-    return llvm::APSInt::isSameValue(Arg1.getAsIntegral(), Arg2.getAsIntegral());
-      
-  case TemplateArgument::Declaration:
-    return Context.IsStructurallyEquivalent(Arg1.getAsDecl(), Arg2.getAsDecl());
-
-  case TemplateArgument::NullPtr:
-    return true; // FIXME: Is this correct?
-
-  case TemplateArgument::Template:
-    return IsStructurallyEquivalent(Context, 
-                                    Arg1.getAsTemplate(), 
-                                    Arg2.getAsTemplate());
-
-  case TemplateArgument::TemplateExpansion:
-    return IsStructurallyEquivalent(Context, 
-                                    Arg1.getAsTemplateOrTemplatePattern(), 
-                                    Arg2.getAsTemplateOrTemplatePattern());
-
-  case TemplateArgument::Expression:
-    return IsStructurallyEquivalent(Context, 
-                                    Arg1.getAsExpr(), Arg2.getAsExpr());
-      
-  case TemplateArgument::Pack:
-    if (Arg1.pack_size() != Arg2.pack_size())
-      return false;
-      
-    for (unsigned I = 0, N = Arg1.pack_size(); I != N; ++I)
-      if (!IsStructurallyEquivalent(Context, 
-                                    Arg1.pack_begin()[I],
-                                    Arg2.pack_begin()[I]))
-        return false;
-      
-    return true;
-  }
-  
-  llvm_unreachable("Invalid template argument kind");
-}
-
-/// \brief Determine structural equivalence for the common part of array 
-/// types.
-static bool IsArrayStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                          const ArrayType *Array1, 
-                                          const ArrayType *Array2) {
-  if (!IsStructurallyEquivalent(Context, 
-                                Array1->getElementType(), 
-                                Array2->getElementType()))
-    return false;
-  if (Array1->getSizeModifier() != Array2->getSizeModifier())
-    return false;
-  if (Array1->getIndexTypeQualifiers() != Array2->getIndexTypeQualifiers())
-    return false;
-  
-  return true;
-}
-
-/// \brief Determine structural equivalence of two types.
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     QualType T1, QualType T2) {
-  if (T1.isNull() || T2.isNull())
-    return T1.isNull() && T2.isNull();
-  
-  if (!Context.StrictTypeSpelling) {
-    // We aren't being strict about token-to-token equivalence of types,
-    // so map down to the canonical type.
-    T1 = Context.C1.getCanonicalType(T1);
-    T2 = Context.C2.getCanonicalType(T2);
-  }
-  
-  if (T1.getQualifiers() != T2.getQualifiers())
-    return false;
-  
-  Type::TypeClass TC = T1->getTypeClass();
-  
-  if (T1->getTypeClass() != T2->getTypeClass()) {
-    // Compare function types with prototypes vs. without prototypes as if
-    // both did not have prototypes.
-    if (T1->getTypeClass() == Type::FunctionProto &&
-        T2->getTypeClass() == Type::FunctionNoProto)
-      TC = Type::FunctionNoProto;
-    else if (T1->getTypeClass() == Type::FunctionNoProto &&
-             T2->getTypeClass() == Type::FunctionProto)
-      TC = Type::FunctionNoProto;
-    else
-      return false;
-  }
-  
-  switch (TC) {
-  case Type::Builtin:
-    // FIXME: Deal with Char_S/Char_U. 
-    if (cast<BuiltinType>(T1)->getKind() != cast<BuiltinType>(T2)->getKind())
-      return false;
-    break;
-  
-  case Type::Complex:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<ComplexType>(T1)->getElementType(),
-                                  cast<ComplexType>(T2)->getElementType()))
-      return false;
-    break;
-  
-  case Type::Adjusted:
-  case Type::Decayed:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<AdjustedType>(T1)->getOriginalType(),
-                                  cast<AdjustedType>(T2)->getOriginalType()))
-      return false;
-    break;
-
-  case Type::Pointer:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<PointerType>(T1)->getPointeeType(),
-                                  cast<PointerType>(T2)->getPointeeType()))
-      return false;
-    break;
-
-  case Type::BlockPointer:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<BlockPointerType>(T1)->getPointeeType(),
-                                  cast<BlockPointerType>(T2)->getPointeeType()))
-      return false;
-    break;
-
-  case Type::LValueReference:
-  case Type::RValueReference: {
-    const ReferenceType *Ref1 = cast<ReferenceType>(T1);
-    const ReferenceType *Ref2 = cast<ReferenceType>(T2);
-    if (Ref1->isSpelledAsLValue() != Ref2->isSpelledAsLValue())
-      return false;
-    if (Ref1->isInnerRef() != Ref2->isInnerRef())
-      return false;
-    if (!IsStructurallyEquivalent(Context,
-                                  Ref1->getPointeeTypeAsWritten(),
-                                  Ref2->getPointeeTypeAsWritten()))
-      return false;
-    break;
-  }
-      
-  case Type::MemberPointer: {
-    const MemberPointerType *MemPtr1 = cast<MemberPointerType>(T1);
-    const MemberPointerType *MemPtr2 = cast<MemberPointerType>(T2);
-    if (!IsStructurallyEquivalent(Context,
-                                  MemPtr1->getPointeeType(),
-                                  MemPtr2->getPointeeType()))
-      return false;
-    if (!IsStructurallyEquivalent(Context,
-                                  QualType(MemPtr1->getClass(), 0),
-                                  QualType(MemPtr2->getClass(), 0)))
-      return false;
-    break;
-  }
-      
-  case Type::ConstantArray: {
-    const ConstantArrayType *Array1 = cast<ConstantArrayType>(T1);
-    const ConstantArrayType *Array2 = cast<ConstantArrayType>(T2);
-    if (!llvm::APInt::isSameValue(Array1->getSize(), Array2->getSize()))
-      return false;
-    
-    if (!IsArrayStructurallyEquivalent(Context, Array1, Array2))
-      return false;
-    break;
-  }
-
-  case Type::IncompleteArray:
-    if (!IsArrayStructurallyEquivalent(Context, 
-                                       cast<ArrayType>(T1), 
-                                       cast<ArrayType>(T2)))
-      return false;
-    break;
-      
-  case Type::VariableArray: {
-    const VariableArrayType *Array1 = cast<VariableArrayType>(T1);
-    const VariableArrayType *Array2 = cast<VariableArrayType>(T2);
-    if (!IsStructurallyEquivalent(Context, 
-                                  Array1->getSizeExpr(), Array2->getSizeExpr()))
-      return false;
-    
-    if (!IsArrayStructurallyEquivalent(Context, Array1, Array2))
-      return false;
-    
-    break;
-  }
-  
-  case Type::DependentSizedArray: {
-    const DependentSizedArrayType *Array1 = cast<DependentSizedArrayType>(T1);
-    const DependentSizedArrayType *Array2 = cast<DependentSizedArrayType>(T2);
-    if (!IsStructurallyEquivalent(Context, 
-                                  Array1->getSizeExpr(), Array2->getSizeExpr()))
-      return false;
-    
-    if (!IsArrayStructurallyEquivalent(Context, Array1, Array2))
-      return false;
-    
-    break;
-  }
-      
-  case Type::DependentSizedExtVector: {
-    const DependentSizedExtVectorType *Vec1
-      = cast<DependentSizedExtVectorType>(T1);
-    const DependentSizedExtVectorType *Vec2
-      = cast<DependentSizedExtVectorType>(T2);
-    if (!IsStructurallyEquivalent(Context, 
-                                  Vec1->getSizeExpr(), Vec2->getSizeExpr()))
-      return false;
-    if (!IsStructurallyEquivalent(Context, 
-                                  Vec1->getElementType(), 
-                                  Vec2->getElementType()))
-      return false;
-    break;
-  }
-   
-  case Type::Vector: 
-  case Type::ExtVector: {
-    const VectorType *Vec1 = cast<VectorType>(T1);
-    const VectorType *Vec2 = cast<VectorType>(T2);
-    if (!IsStructurallyEquivalent(Context, 
-                                  Vec1->getElementType(),
-                                  Vec2->getElementType()))
-      return false;
-    if (Vec1->getNumElements() != Vec2->getNumElements())
-      return false;
-    if (Vec1->getVectorKind() != Vec2->getVectorKind())
-      return false;
-    break;
-  }
-
-  case Type::FunctionProto: {
-    const FunctionProtoType *Proto1 = cast<FunctionProtoType>(T1);
-    const FunctionProtoType *Proto2 = cast<FunctionProtoType>(T2);
-    if (Proto1->getNumParams() != Proto2->getNumParams())
-      return false;
-    for (unsigned I = 0, N = Proto1->getNumParams(); I != N; ++I) {
-      if (!IsStructurallyEquivalent(Context, Proto1->getParamType(I),
-                                    Proto2->getParamType(I)))
-        return false;
-    }
-    if (Proto1->isVariadic() != Proto2->isVariadic())
-      return false;
-    if (Proto1->getExceptionSpecType() != Proto2->getExceptionSpecType())
-      return false;
-    if (Proto1->getExceptionSpecType() == EST_Dynamic) {
-      if (Proto1->getNumExceptions() != Proto2->getNumExceptions())
-        return false;
-      for (unsigned I = 0, N = Proto1->getNumExceptions(); I != N; ++I) {
-        if (!IsStructurallyEquivalent(Context,
-                                      Proto1->getExceptionType(I),
-                                      Proto2->getExceptionType(I)))
-          return false;
-      }
-    } else if (Proto1->getExceptionSpecType() == EST_ComputedNoexcept) {
-      if (!IsStructurallyEquivalent(Context,
-                                    Proto1->getNoexceptExpr(),
-                                    Proto2->getNoexceptExpr()))
-        return false;
-    }
-    if (Proto1->getTypeQuals() != Proto2->getTypeQuals())
-      return false;
-    
-    // Fall through to check the bits common with FunctionNoProtoType.
-  }
-      
-  case Type::FunctionNoProto: {
-    const FunctionType *Function1 = cast<FunctionType>(T1);
-    const FunctionType *Function2 = cast<FunctionType>(T2);
-    if (!IsStructurallyEquivalent(Context, Function1->getReturnType(),
-                                  Function2->getReturnType()))
-      return false;
-    if (Function1->getExtInfo() != Function2->getExtInfo())
-      return false;
-    break;
-  }
-   
-  case Type::UnresolvedUsing:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<UnresolvedUsingType>(T1)->getDecl(),
-                                  cast<UnresolvedUsingType>(T2)->getDecl()))
-      return false;
-      
-    break;
-
-  case Type::Attributed:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<AttributedType>(T1)->getModifiedType(),
-                                  cast<AttributedType>(T2)->getModifiedType()))
-      return false;
-    if (!IsStructurallyEquivalent(Context,
-                                cast<AttributedType>(T1)->getEquivalentType(),
-                                cast<AttributedType>(T2)->getEquivalentType()))
-      return false;
-    break;
-      
-  case Type::Paren:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<ParenType>(T1)->getInnerType(),
-                                  cast<ParenType>(T2)->getInnerType()))
-      return false;
-    break;
-
-  case Type::Typedef:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<TypedefType>(T1)->getDecl(),
-                                  cast<TypedefType>(T2)->getDecl()))
-      return false;
-    break;
-      
-  case Type::TypeOfExpr:
-    if (!IsStructurallyEquivalent(Context,
-                                cast<TypeOfExprType>(T1)->getUnderlyingExpr(),
-                                cast<TypeOfExprType>(T2)->getUnderlyingExpr()))
-      return false;
-    break;
-      
-  case Type::TypeOf:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<TypeOfType>(T1)->getUnderlyingType(),
-                                  cast<TypeOfType>(T2)->getUnderlyingType()))
-      return false;
-    break;
-
-  case Type::UnaryTransform:
-    if (!IsStructurallyEquivalent(Context,
-                             cast<UnaryTransformType>(T1)->getUnderlyingType(),
-                             cast<UnaryTransformType>(T1)->getUnderlyingType()))
-      return false;
-    break;
-
-  case Type::Decltype:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<DecltypeType>(T1)->getUnderlyingExpr(),
-                                  cast<DecltypeType>(T2)->getUnderlyingExpr()))
-      return false;
-    break;
-
-  case Type::Auto:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<AutoType>(T1)->getDeducedType(),
-                                  cast<AutoType>(T2)->getDeducedType()))
-      return false;
-    break;
-
-  case Type::DeducedTemplateSpecialization: {
-    auto *DT1 = cast<DeducedTemplateSpecializationType>(T1);
-    auto *DT2 = cast<DeducedTemplateSpecializationType>(T2);
-    if (!IsStructurallyEquivalent(Context,
-                                  DT1->getTemplateName(),
-                                  DT2->getTemplateName()))
-      return false;
-    if (!IsStructurallyEquivalent(Context,
-                                  DT1->getDeducedType(),
-                                  DT2->getDeducedType()))
-      return false;
-    break;
-  }
-
-  case Type::Record:
-  case Type::Enum:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<TagType>(T1)->getDecl(),
-                                  cast<TagType>(T2)->getDecl()))
-      return false;
-    break;
-
-  case Type::TemplateTypeParm: {
-    const TemplateTypeParmType *Parm1 = cast<TemplateTypeParmType>(T1);
-    const TemplateTypeParmType *Parm2 = cast<TemplateTypeParmType>(T2);
-    if (Parm1->getDepth() != Parm2->getDepth())
-      return false;
-    if (Parm1->getIndex() != Parm2->getIndex())
-      return false;
-    if (Parm1->isParameterPack() != Parm2->isParameterPack())
-      return false;
-    
-    // Names of template type parameters are never significant.
-    break;
-  }
-      
-  case Type::SubstTemplateTypeParm: {
-    const SubstTemplateTypeParmType *Subst1
-      = cast<SubstTemplateTypeParmType>(T1);
-    const SubstTemplateTypeParmType *Subst2
-      = cast<SubstTemplateTypeParmType>(T2);
-    if (!IsStructurallyEquivalent(Context,
-                                  QualType(Subst1->getReplacedParameter(), 0),
-                                  QualType(Subst2->getReplacedParameter(), 0)))
-      return false;
-    if (!IsStructurallyEquivalent(Context, 
-                                  Subst1->getReplacementType(),
-                                  Subst2->getReplacementType()))
-      return false;
-    break;
-  }
-
-  case Type::SubstTemplateTypeParmPack: {
-    const SubstTemplateTypeParmPackType *Subst1
-      = cast<SubstTemplateTypeParmPackType>(T1);
-    const SubstTemplateTypeParmPackType *Subst2
-      = cast<SubstTemplateTypeParmPackType>(T2);
-    if (!IsStructurallyEquivalent(Context,
-                                  QualType(Subst1->getReplacedParameter(), 0),
-                                  QualType(Subst2->getReplacedParameter(), 0)))
-      return false;
-    if (!IsStructurallyEquivalent(Context, 
-                                  Subst1->getArgumentPack(),
-                                  Subst2->getArgumentPack()))
-      return false;
-    break;
-  }
-  case Type::TemplateSpecialization: {
-    const TemplateSpecializationType *Spec1
-      = cast<TemplateSpecializationType>(T1);
-    const TemplateSpecializationType *Spec2
-      = cast<TemplateSpecializationType>(T2);
-    if (!IsStructurallyEquivalent(Context,
-                                  Spec1->getTemplateName(),
-                                  Spec2->getTemplateName()))
-      return false;
-    if (Spec1->getNumArgs() != Spec2->getNumArgs())
-      return false;
-    for (unsigned I = 0, N = Spec1->getNumArgs(); I != N; ++I) {
-      if (!IsStructurallyEquivalent(Context, 
-                                    Spec1->getArg(I), Spec2->getArg(I)))
-        return false;
-    }
-    break;
-  }
-      
-  case Type::Elaborated: {
-    const ElaboratedType *Elab1 = cast<ElaboratedType>(T1);
-    const ElaboratedType *Elab2 = cast<ElaboratedType>(T2);
-    // CHECKME: what if a keyword is ETK_None or ETK_typename ?
-    if (Elab1->getKeyword() != Elab2->getKeyword())
-      return false;
-    if (!IsStructurallyEquivalent(Context, 
-                                  Elab1->getQualifier(), 
-                                  Elab2->getQualifier()))
-      return false;
-    if (!IsStructurallyEquivalent(Context,
-                                  Elab1->getNamedType(),
-                                  Elab2->getNamedType()))
-      return false;
-    break;
-  }
-
-  case Type::InjectedClassName: {
-    const InjectedClassNameType *Inj1 = cast<InjectedClassNameType>(T1);
-    const InjectedClassNameType *Inj2 = cast<InjectedClassNameType>(T2);
-    if (!IsStructurallyEquivalent(Context,
-                                  Inj1->getInjectedSpecializationType(),
-                                  Inj2->getInjectedSpecializationType()))
-      return false;
-    break;
-  }
-
-  case Type::DependentName: {
-    const DependentNameType *Typename1 = cast<DependentNameType>(T1);
-    const DependentNameType *Typename2 = cast<DependentNameType>(T2);
-    if (!IsStructurallyEquivalent(Context, 
-                                  Typename1->getQualifier(),
-                                  Typename2->getQualifier()))
-      return false;
-    if (!IsStructurallyEquivalent(Typename1->getIdentifier(),
-                                  Typename2->getIdentifier()))
-      return false;
-    
-    break;
-  }
-  
-  case Type::DependentTemplateSpecialization: {
-    const DependentTemplateSpecializationType *Spec1 =
-      cast<DependentTemplateSpecializationType>(T1);
-    const DependentTemplateSpecializationType *Spec2 =
-      cast<DependentTemplateSpecializationType>(T2);
-    if (!IsStructurallyEquivalent(Context, 
-                                  Spec1->getQualifier(),
-                                  Spec2->getQualifier()))
-      return false;
-    if (!IsStructurallyEquivalent(Spec1->getIdentifier(),
-                                  Spec2->getIdentifier()))
-      return false;
-    if (Spec1->getNumArgs() != Spec2->getNumArgs())
-      return false;
-    for (unsigned I = 0, N = Spec1->getNumArgs(); I != N; ++I) {
-      if (!IsStructurallyEquivalent(Context,
-                                    Spec1->getArg(I), Spec2->getArg(I)))
-        return false;
-    }
-    break;
-  }
-
-  case Type::PackExpansion:
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<PackExpansionType>(T1)->getPattern(),
-                                  cast<PackExpansionType>(T2)->getPattern()))
-      return false;
-    break;
-
-  case Type::ObjCInterface: {
-    const ObjCInterfaceType *Iface1 = cast<ObjCInterfaceType>(T1);
-    const ObjCInterfaceType *Iface2 = cast<ObjCInterfaceType>(T2);
-    if (!IsStructurallyEquivalent(Context, 
-                                  Iface1->getDecl(), Iface2->getDecl()))
-      return false;
-    break;
-  }
-
-  case Type::ObjCTypeParam: {
-    const ObjCTypeParamType *Obj1 = cast<ObjCTypeParamType>(T1);
-    const ObjCTypeParamType *Obj2 = cast<ObjCTypeParamType>(T2);
-    if (!IsStructurallyEquivalent(Context, Obj1->getDecl(),
-                                  Obj2->getDecl()))
-      return false;
-
-    if (Obj1->getNumProtocols() != Obj2->getNumProtocols())
-      return false;
-    for (unsigned I = 0, N = Obj1->getNumProtocols(); I != N; ++I) {
-      if (!IsStructurallyEquivalent(Context,
-                                    Obj1->getProtocol(I),
-                                    Obj2->getProtocol(I)))
-        return false;
-    }
-    break;
-  }
-  case Type::ObjCObject: {
-    const ObjCObjectType *Obj1 = cast<ObjCObjectType>(T1);
-    const ObjCObjectType *Obj2 = cast<ObjCObjectType>(T2);
-    if (!IsStructurallyEquivalent(Context,
-                                  Obj1->getBaseType(),
-                                  Obj2->getBaseType()))
-      return false;
-    if (Obj1->getNumProtocols() != Obj2->getNumProtocols())
-      return false;
-    for (unsigned I = 0, N = Obj1->getNumProtocols(); I != N; ++I) {
-      if (!IsStructurallyEquivalent(Context,
-                                    Obj1->getProtocol(I),
-                                    Obj2->getProtocol(I)))
-        return false;
-    }
-    break;
-  }
-
-  case Type::ObjCObjectPointer: {
-    const ObjCObjectPointerType *Ptr1 = cast<ObjCObjectPointerType>(T1);
-    const ObjCObjectPointerType *Ptr2 = cast<ObjCObjectPointerType>(T2);
-    if (!IsStructurallyEquivalent(Context, 
-                                  Ptr1->getPointeeType(),
-                                  Ptr2->getPointeeType()))
-      return false;
-    break;
-  }
-
-  case Type::Atomic: {
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<AtomicType>(T1)->getValueType(),
-                                  cast<AtomicType>(T2)->getValueType()))
-      return false;
-    break;
-  }
-
-  case Type::Pipe: {
-    if (!IsStructurallyEquivalent(Context,
-                                  cast<PipeType>(T1)->getElementType(),
-                                  cast<PipeType>(T2)->getElementType()))
-      return false;
-    break;
-  }
-
-  } // end switch
-
-  return true;
-}
-
-/// \brief Determine structural equivalence of two fields.
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     FieldDecl *Field1, FieldDecl *Field2) {
-  RecordDecl *Owner2 = cast<RecordDecl>(Field2->getDeclContext());
-
-  // For anonymous structs/unions, match up the anonymous struct/union type
-  // declarations directly, so that we don't go off searching for anonymous
-  // types
-  if (Field1->isAnonymousStructOrUnion() &&
-      Field2->isAnonymousStructOrUnion()) {
-    RecordDecl *D1 = Field1->getType()->castAs<RecordType>()->getDecl();
-    RecordDecl *D2 = Field2->getType()->castAs<RecordType>()->getDecl();
-    return IsStructurallyEquivalent(Context, D1, D2);
-  }
-    
-  // Check for equivalent field names.
-  IdentifierInfo *Name1 = Field1->getIdentifier();
-  IdentifierInfo *Name2 = Field2->getIdentifier();
-  if (!::IsStructurallyEquivalent(Name1, Name2))
-    return false;
-
-  if (!IsStructurallyEquivalent(Context,
-                                Field1->getType(), Field2->getType())) {
-    if (Context.Complain) {
-      Context.Diag2(Owner2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-        << Context.C2.getTypeDeclType(Owner2);
-      Context.Diag2(Field2->getLocation(), diag::note_odr_field)
-        << Field2->getDeclName() << Field2->getType();
-      Context.Diag1(Field1->getLocation(), diag::note_odr_field)
-        << Field1->getDeclName() << Field1->getType();
-    }
-    return false;
-  }
-  
-  if (Field1->isBitField() != Field2->isBitField()) {
-    if (Context.Complain) {
-      Context.Diag2(Owner2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-        << Context.C2.getTypeDeclType(Owner2);
-      if (Field1->isBitField()) {
-        Context.Diag1(Field1->getLocation(), diag::note_odr_bit_field)
-        << Field1->getDeclName() << Field1->getType()
-        << Field1->getBitWidthValue(Context.C1);
-        Context.Diag2(Field2->getLocation(), diag::note_odr_not_bit_field)
-        << Field2->getDeclName();
-      } else {
-        Context.Diag2(Field2->getLocation(), diag::note_odr_bit_field)
-        << Field2->getDeclName() << Field2->getType()
-        << Field2->getBitWidthValue(Context.C2);
-        Context.Diag1(Field1->getLocation(), diag::note_odr_not_bit_field)
-        << Field1->getDeclName();
-      }
-    }
-    return false;
-  }
-  
-  if (Field1->isBitField()) {
-    // Make sure that the bit-fields are the same length.
-    unsigned Bits1 = Field1->getBitWidthValue(Context.C1);
-    unsigned Bits2 = Field2->getBitWidthValue(Context.C2);
-    
-    if (Bits1 != Bits2) {
-      if (Context.Complain) {
-        Context.Diag2(Owner2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-          << Context.C2.getTypeDeclType(Owner2);
-        Context.Diag2(Field2->getLocation(), diag::note_odr_bit_field)
-          << Field2->getDeclName() << Field2->getType() << Bits2;
-        Context.Diag1(Field1->getLocation(), diag::note_odr_bit_field)
-          << Field1->getDeclName() << Field1->getType() << Bits1;
-      }
-      return false;
-    }
-  }
-
-  return true;
-}
-
-/// \brief Find the index of the given anonymous struct/union within its
-/// context.
-///
-/// \returns Returns the index of this anonymous struct/union in its context,
-/// including the next assigned index (if none of them match). Returns an
-/// empty option if the context is not a record, i.e.. if the anonymous
-/// struct/union is at namespace or block scope.
-static Optional<unsigned> findUntaggedStructOrUnionIndex(RecordDecl *Anon) {
-  ASTContext &Context = Anon->getASTContext();
-  QualType AnonTy = Context.getRecordType(Anon);
-
-  RecordDecl *Owner = dyn_cast<RecordDecl>(Anon->getDeclContext());
-  if (!Owner)
-    return None;
-
-  unsigned Index = 0;
-  for (const auto *D : Owner->noload_decls()) {
-    const auto *F = dyn_cast<FieldDecl>(D);
-    if (!F)
-      continue;
-
-    if (F->isAnonymousStructOrUnion()) {
-      if (Context.hasSameType(F->getType(), AnonTy))
-        break;
-      ++Index;
-      continue;
-    }
-
-    // If the field looks like this:
-    // struct { ... } A;
-    QualType FieldType = F->getType();
-    if (const auto *RecType = dyn_cast<RecordType>(FieldType)) {
-      const RecordDecl *RecDecl = RecType->getDecl();
-      if (RecDecl->getDeclContext() == Owner &&
-          !RecDecl->getIdentifier()) {
-        if (Context.hasSameType(FieldType, AnonTy))
-          break;
-        ++Index;
-        continue;
-      }
-    }
-  }
-
-  return Index;
-}
-
-/// \brief Determine structural equivalence of two records.
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     RecordDecl *D1, RecordDecl *D2) {
-  if (D1->isUnion() != D2->isUnion()) {
-    if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-        << Context.C2.getTypeDeclType(D2);
-      Context.Diag1(D1->getLocation(), diag::note_odr_tag_kind_here)
-        << D1->getDeclName() << (unsigned)D1->getTagKind();
-    }
-    return false;
-  }
-
-  if (D1->isAnonymousStructOrUnion() && D2->isAnonymousStructOrUnion()) {
-    // If both anonymous structs/unions are in a record context, make sure
-    // they occur in the same location in the context records.
-    if (Optional<unsigned> Index1 = findUntaggedStructOrUnionIndex(D1)) {
-      if (Optional<unsigned> Index2 = findUntaggedStructOrUnionIndex(D2)) {
-        if (*Index1 != *Index2)
-          return false;
-      }
-    }
-  }
-
-  // If both declarations are class template specializations, we know
-  // the ODR applies, so check the template and template arguments.
-  ClassTemplateSpecializationDecl *Spec1
-    = dyn_cast<ClassTemplateSpecializationDecl>(D1);
-  ClassTemplateSpecializationDecl *Spec2
-    = dyn_cast<ClassTemplateSpecializationDecl>(D2);
-  if (Spec1 && Spec2) {
-    // Check that the specialized templates are the same.
-    if (!IsStructurallyEquivalent(Context, Spec1->getSpecializedTemplate(),
-                                  Spec2->getSpecializedTemplate()))
-      return false;
-    
-    // Check that the template arguments are the same.
-    if (Spec1->getTemplateArgs().size() != Spec2->getTemplateArgs().size())
-      return false;
-    
-    for (unsigned I = 0, N = Spec1->getTemplateArgs().size(); I != N; ++I)
-      if (!IsStructurallyEquivalent(Context, 
-                                    Spec1->getTemplateArgs().get(I),
-                                    Spec2->getTemplateArgs().get(I)))
-        return false;
-  }  
-  // If one is a class template specialization and the other is not, these
-  // structures are different.
-  else if (Spec1 || Spec2)
-    return false;
-
-  // Compare the definitions of these two records. If either or both are
-  // incomplete, we assume that they are equivalent.
-  D1 = D1->getDefinition();
-  D2 = D2->getDefinition();
-  if (!D1 || !D2)
-    return true;
-  
-  if (CXXRecordDecl *D1CXX = dyn_cast<CXXRecordDecl>(D1)) {
-    if (CXXRecordDecl *D2CXX = dyn_cast<CXXRecordDecl>(D2)) {
-      if (D1CXX->getNumBases() != D2CXX->getNumBases()) {
-        if (Context.Complain) {
-          Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-            << Context.C2.getTypeDeclType(D2);
-          Context.Diag2(D2->getLocation(), diag::note_odr_number_of_bases)
-            << D2CXX->getNumBases();
-          Context.Diag1(D1->getLocation(), diag::note_odr_number_of_bases)
-            << D1CXX->getNumBases();
-        }
-        return false;
-      }
-      
-      // Check the base classes. 
-      for (CXXRecordDecl::base_class_iterator Base1 = D1CXX->bases_begin(), 
-                                           BaseEnd1 = D1CXX->bases_end(),
-                                                Base2 = D2CXX->bases_begin();
-           Base1 != BaseEnd1;
-           ++Base1, ++Base2) {        
-        if (!IsStructurallyEquivalent(Context, 
-                                      Base1->getType(), Base2->getType())) {
-          if (Context.Complain) {
-            Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-              << Context.C2.getTypeDeclType(D2);
-            Context.Diag2(Base2->getLocStart(), diag::note_odr_base)
-              << Base2->getType()
-              << Base2->getSourceRange();
-            Context.Diag1(Base1->getLocStart(), diag::note_odr_base)
-              << Base1->getType()
-              << Base1->getSourceRange();
-          }
-          return false;
-        }
-        
-        // Check virtual vs. non-virtual inheritance mismatch.
-        if (Base1->isVirtual() != Base2->isVirtual()) {
-          if (Context.Complain) {
-            Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-              << Context.C2.getTypeDeclType(D2);
-            Context.Diag2(Base2->getLocStart(),
-                          diag::note_odr_virtual_base)
-              << Base2->isVirtual() << Base2->getSourceRange();
-            Context.Diag1(Base1->getLocStart(), diag::note_odr_base)
-              << Base1->isVirtual()
-              << Base1->getSourceRange();
-          }
-          return false;
-        }
-      }
-    } else if (D1CXX->getNumBases() > 0) {
-      if (Context.Complain) {
-        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-          << Context.C2.getTypeDeclType(D2);
-        const CXXBaseSpecifier *Base1 = D1CXX->bases_begin();
-        Context.Diag1(Base1->getLocStart(), diag::note_odr_base)
-          << Base1->getType()
-          << Base1->getSourceRange();
-        Context.Diag2(D2->getLocation(), diag::note_odr_missing_base);
-      }
-      return false;
-    }
-  }
-  
-  // Check the fields for consistency.
-  RecordDecl::field_iterator Field2 = D2->field_begin(),
-                             Field2End = D2->field_end();
-  for (RecordDecl::field_iterator Field1 = D1->field_begin(),
-                                  Field1End = D1->field_end();
-       Field1 != Field1End;
-       ++Field1, ++Field2) {
-    if (Field2 == Field2End) {
-      if (Context.Complain) {
-        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-          << Context.C2.getTypeDeclType(D2);
-        Context.Diag1(Field1->getLocation(), diag::note_odr_field)
-          << Field1->getDeclName() << Field1->getType();
-        Context.Diag2(D2->getLocation(), diag::note_odr_missing_field);
-      }
-      return false;
-    }
-    
-    if (!IsStructurallyEquivalent(Context, *Field1, *Field2))
-      return false;    
-  }
-  
-  if (Field2 != Field2End) {
-    if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-        << Context.C2.getTypeDeclType(D2);
-      Context.Diag2(Field2->getLocation(), diag::note_odr_field)
-        << Field2->getDeclName() << Field2->getType();
-      Context.Diag1(D1->getLocation(), diag::note_odr_missing_field);
-    }
-    return false;
-  }
-  
-  return true;
-}
-     
-/// \brief Determine structural equivalence of two enums.
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     EnumDecl *D1, EnumDecl *D2) {
-  EnumDecl::enumerator_iterator EC2 = D2->enumerator_begin(),
-                             EC2End = D2->enumerator_end();
-  for (EnumDecl::enumerator_iterator EC1 = D1->enumerator_begin(),
-                                  EC1End = D1->enumerator_end();
-       EC1 != EC1End; ++EC1, ++EC2) {
-    if (EC2 == EC2End) {
-      if (Context.Complain) {
-        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-          << Context.C2.getTypeDeclType(D2);
-        Context.Diag1(EC1->getLocation(), diag::note_odr_enumerator)
-          << EC1->getDeclName() 
-          << EC1->getInitVal().toString(10);
-        Context.Diag2(D2->getLocation(), diag::note_odr_missing_enumerator);
-      }
-      return false;
-    }
-    
-    llvm::APSInt Val1 = EC1->getInitVal();
-    llvm::APSInt Val2 = EC2->getInitVal();
-    if (!llvm::APSInt::isSameValue(Val1, Val2) || 
-        !IsStructurallyEquivalent(EC1->getIdentifier(), EC2->getIdentifier())) {
-      if (Context.Complain) {
-        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-          << Context.C2.getTypeDeclType(D2);
-        Context.Diag2(EC2->getLocation(), diag::note_odr_enumerator)
-          << EC2->getDeclName() 
-          << EC2->getInitVal().toString(10);
-        Context.Diag1(EC1->getLocation(), diag::note_odr_enumerator)
-          << EC1->getDeclName() 
-          << EC1->getInitVal().toString(10);
-      }
-      return false;
-    }
-  }
-  
-  if (EC2 != EC2End) {
-    if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-        << Context.C2.getTypeDeclType(D2);
-      Context.Diag2(EC2->getLocation(), diag::note_odr_enumerator)
-        << EC2->getDeclName() 
-        << EC2->getInitVal().toString(10);
-      Context.Diag1(D1->getLocation(), diag::note_odr_missing_enumerator);
-    }
-    return false;
-  }
-  
-  return true;
-}
-
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     TemplateParameterList *Params1,
-                                     TemplateParameterList *Params2) {
-  if (Params1->size() != Params2->size()) {
-    if (Context.Complain) {
-      Context.Diag2(Params2->getTemplateLoc(), 
-                    diag::err_odr_different_num_template_parameters)
-        << Params1->size() << Params2->size();
-      Context.Diag1(Params1->getTemplateLoc(), 
-                    diag::note_odr_template_parameter_list);
-    }
-    return false;
-  }
-  
-  for (unsigned I = 0, N = Params1->size(); I != N; ++I) {
-    if (Params1->getParam(I)->getKind() != Params2->getParam(I)->getKind()) {
-      if (Context.Complain) {
-        Context.Diag2(Params2->getParam(I)->getLocation(), 
-                      diag::err_odr_different_template_parameter_kind);
-        Context.Diag1(Params1->getParam(I)->getLocation(),
-                      diag::note_odr_template_parameter_here);
-      }
-      return false;
-    }
-    
-    if (!Context.IsStructurallyEquivalent(Params1->getParam(I),
-                                          Params2->getParam(I))) {
-      
-      return false;
-    }
-  }
-  
-  return true;
-}
-
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     TemplateTypeParmDecl *D1,
-                                     TemplateTypeParmDecl *D2) {
-  if (D1->isParameterPack() != D2->isParameterPack()) {
-    if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
-        << D2->isParameterPack();
-      Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
-        << D1->isParameterPack();
-    }
-    return false;
-  }
-  
-  return true;
-}
-
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     NonTypeTemplateParmDecl *D1,
-                                     NonTypeTemplateParmDecl *D2) {
-  if (D1->isParameterPack() != D2->isParameterPack()) {
-    if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
-        << D2->isParameterPack();
-      Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
-        << D1->isParameterPack();
-    }
-    return false;
-  }
-  
-  // Check types.
-  if (!Context.IsStructurallyEquivalent(D1->getType(), D2->getType())) {
-    if (Context.Complain) {
-      Context.Diag2(D2->getLocation(),
-                    diag::err_odr_non_type_parameter_type_inconsistent)
-        << D2->getType() << D1->getType();
-      Context.Diag1(D1->getLocation(), diag::note_odr_value_here)
-        << D1->getType();
-    }
-    return false;
-  }
-  
-  return true;
-}
-
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     TemplateTemplateParmDecl *D1,
-                                     TemplateTemplateParmDecl *D2) {
-  if (D1->isParameterPack() != D2->isParameterPack()) {
-    if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
-        << D2->isParameterPack();
-      Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
-        << D1->isParameterPack();
-    }
-    return false;
-  }
-
-  // Check template parameter lists.
-  return IsStructurallyEquivalent(Context, D1->getTemplateParameters(),
-                                  D2->getTemplateParameters());
-}
-
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     ClassTemplateDecl *D1, 
-                                     ClassTemplateDecl *D2) {
-  // Check template parameters.
-  if (!IsStructurallyEquivalent(Context,
-                                D1->getTemplateParameters(),
-                                D2->getTemplateParameters()))
-    return false;
-  
-  // Check the templated declaration.
-  return Context.IsStructurallyEquivalent(D1->getTemplatedDecl(), 
-                                          D2->getTemplatedDecl());
-}
-
-/// \brief Determine structural equivalence of two declarations.
-static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     Decl *D1, Decl *D2) {
-  // FIXME: Check for known structural equivalences via a callback of some sort.
-  
-  // Check whether we already know that these two declarations are not
-  // structurally equivalent.
-  if (Context.NonEquivalentDecls.count(std::make_pair(D1->getCanonicalDecl(),
-                                                      D2->getCanonicalDecl())))
-    return false;
-  
-  // Determine whether we've already produced a tentative equivalence for D1.
-  Decl *&EquivToD1 = Context.TentativeEquivalences[D1->getCanonicalDecl()];
-  if (EquivToD1)
-    return EquivToD1 == D2->getCanonicalDecl();
-  
-  // Produce a tentative equivalence D1 <-> D2, which will be checked later.
-  EquivToD1 = D2->getCanonicalDecl();
-  Context.DeclsToCheck.push_back(D1->getCanonicalDecl());
-  return true;
-}
-
-bool StructuralEquivalenceContext::IsStructurallyEquivalent(Decl *D1, 
-                                                            Decl *D2) {
-  if (!::IsStructurallyEquivalent(*this, D1, D2))
-    return false;
-  
-  return !Finish();
-}
-
-bool StructuralEquivalenceContext::IsStructurallyEquivalent(QualType T1, 
-                                                            QualType T2) {
-  if (!::IsStructurallyEquivalent(*this, T1, T2))
-    return false;
-  
-  return !Finish();
-}
-
-bool StructuralEquivalenceContext::Finish() {
-  while (!DeclsToCheck.empty()) {
-    // Check the next declaration.
-    Decl *D1 = DeclsToCheck.front();
-    DeclsToCheck.pop_front();
-    
-    Decl *D2 = TentativeEquivalences[D1];
-    assert(D2 && "Unrecorded tentative equivalence?");
-    
-    bool Equivalent = true;
-    
-    // FIXME: Switch on all declaration kinds. For now, we're just going to
-    // check the obvious ones.
-    if (RecordDecl *Record1 = dyn_cast<RecordDecl>(D1)) {
-      if (RecordDecl *Record2 = dyn_cast<RecordDecl>(D2)) {
-        // Check for equivalent structure names.
-        IdentifierInfo *Name1 = Record1->getIdentifier();
-        if (!Name1 && Record1->getTypedefNameForAnonDecl())
-          Name1 = Record1->getTypedefNameForAnonDecl()->getIdentifier();
-        IdentifierInfo *Name2 = Record2->getIdentifier();
-        if (!Name2 && Record2->getTypedefNameForAnonDecl())
-          Name2 = Record2->getTypedefNameForAnonDecl()->getIdentifier();
-        if (!::IsStructurallyEquivalent(Name1, Name2) ||
-            !::IsStructurallyEquivalent(*this, Record1, Record2))
-          Equivalent = false;
-      } else {
-        // Record/non-record mismatch.
-        Equivalent = false;
-      }
-    } else if (EnumDecl *Enum1 = dyn_cast<EnumDecl>(D1)) {
-      if (EnumDecl *Enum2 = dyn_cast<EnumDecl>(D2)) {
-        // Check for equivalent enum names.
-        IdentifierInfo *Name1 = Enum1->getIdentifier();
-        if (!Name1 && Enum1->getTypedefNameForAnonDecl())
-          Name1 = Enum1->getTypedefNameForAnonDecl()->getIdentifier();
-        IdentifierInfo *Name2 = Enum2->getIdentifier();
-        if (!Name2 && Enum2->getTypedefNameForAnonDecl())
-          Name2 = Enum2->getTypedefNameForAnonDecl()->getIdentifier();
-        if (!::IsStructurallyEquivalent(Name1, Name2) ||
-            !::IsStructurallyEquivalent(*this, Enum1, Enum2))
-          Equivalent = false;
-      } else {
-        // Enum/non-enum mismatch
-        Equivalent = false;
-      }
-    } else if (TypedefNameDecl *Typedef1 = dyn_cast<TypedefNameDecl>(D1)) {
-      if (TypedefNameDecl *Typedef2 = dyn_cast<TypedefNameDecl>(D2)) {
-        if (!::IsStructurallyEquivalent(Typedef1->getIdentifier(),
-                                        Typedef2->getIdentifier()) ||
-            !::IsStructurallyEquivalent(*this,
-                                        Typedef1->getUnderlyingType(),
-                                        Typedef2->getUnderlyingType()))
-          Equivalent = false;
-      } else {
-        // Typedef/non-typedef mismatch.
-        Equivalent = false;
-      }
-    } else if (ClassTemplateDecl *ClassTemplate1 
-                                           = dyn_cast<ClassTemplateDecl>(D1)) {
-      if (ClassTemplateDecl *ClassTemplate2 = dyn_cast<ClassTemplateDecl>(D2)) {
-        if (!::IsStructurallyEquivalent(ClassTemplate1->getIdentifier(),
-                                        ClassTemplate2->getIdentifier()) ||
-            !::IsStructurallyEquivalent(*this, ClassTemplate1, ClassTemplate2))
-          Equivalent = false;
-      } else {
-        // Class template/non-class-template mismatch.
-        Equivalent = false;
-      }
-    } else if (TemplateTypeParmDecl *TTP1= dyn_cast<TemplateTypeParmDecl>(D1)) {
-      if (TemplateTypeParmDecl *TTP2 = dyn_cast<TemplateTypeParmDecl>(D2)) {
-        if (!::IsStructurallyEquivalent(*this, TTP1, TTP2))
-          Equivalent = false;
-      } else {
-        // Kind mismatch.
-        Equivalent = false;
-      }
-    } else if (NonTypeTemplateParmDecl *NTTP1
-                                     = dyn_cast<NonTypeTemplateParmDecl>(D1)) {
-      if (NonTypeTemplateParmDecl *NTTP2
-                                      = dyn_cast<NonTypeTemplateParmDecl>(D2)) {
-        if (!::IsStructurallyEquivalent(*this, NTTP1, NTTP2))
-          Equivalent = false;
-      } else {
-        // Kind mismatch.
-        Equivalent = false;
-      }
-    } else if (TemplateTemplateParmDecl *TTP1
-                                  = dyn_cast<TemplateTemplateParmDecl>(D1)) {
-      if (TemplateTemplateParmDecl *TTP2
-                                    = dyn_cast<TemplateTemplateParmDecl>(D2)) {
-        if (!::IsStructurallyEquivalent(*this, TTP1, TTP2))
-          Equivalent = false;
-      } else {
-        // Kind mismatch.
-        Equivalent = false;
-      }
-    }
-    
-    if (!Equivalent) {
-      // Note that these two declarations are not equivalent (and we already
-      // know about it).
-      NonEquivalentDecls.insert(std::make_pair(D1->getCanonicalDecl(),
-                                               D2->getCanonicalDecl()));
-      return true;
-    }
-    // FIXME: Check other declaration kinds!
-  }
-  
-  return false;
-}
-
 //----------------------------------------------------------------------------
 // Import Types
 //----------------------------------------------------------------------------
 
+using namespace clang;
+
 QualType ASTNodeImporter::VisitType(const Type *T) {
   Importer.FromDiag(SourceLocation(), diag::err_unsupported_ast_node)
     << T->getTypeClassName();
@@ -2634,7 +1251,7 @@
   StructuralEquivalenceContext Ctx(Importer.getFromContext(),
                                    Importer.getToContext(),
                                    Importer.getNonEquivalentDecls());
-  return Ctx.IsStructurallyEquivalent(From, To);  
+  return Ctx.IsStructurallyEquivalent(From, To);
 }
 
 bool ASTNodeImporter::IsStructuralMatch(VarTemplateDecl *From,
@@ -2813,10 +1430,10 @@
                                             FoundTypedef->getUnderlyingType()))
           return Importer.Imported(D, FoundTypedef);
       }
-      
+
       ConflictingDecls.push_back(FoundDecls[I]);
     }
-    
+
     if (!ConflictingDecls.empty()) {
       Name = Importer.HandleNameConflict(Name, DC, IDNS,
                                          ConflictingDecls.data(), 
@@ -2825,7 +1442,7 @@
         return nullptr;
     }
   }
-  
+
   // Import the underlying type of this typedef;
   QualType T = Importer.Import(D->getUnderlyingType());
   if (T.isNull())
@@ -2845,12 +1462,12 @@
                                     StartL, Loc,
                                     Name.getAsIdentifierInfo(),
                                     TInfo);
-  
+
   ToTypedef->setAccess(D->getAccess());
   ToTypedef->setLexicalDeclContext(LexicalDC);
   Importer.Imported(D, ToTypedef);
   LexicalDC->addDeclInternal(ToTypedef);
-  
+
   return ToTypedef;
 }
 
@@ -3024,9 +1641,10 @@
             FoundRecord->isAnonymousStructOrUnion()) {
           // If both anonymous structs/unions are in a record context, make sure
           // they occur in the same location in the context records.
-          if (Optional<unsigned> Index1
-              = findUntaggedStructOrUnionIndex(D)) {
-            if (Optional<unsigned> Index2 =
+          if (Optional<unsigned> Index1 =
+                  StructuralEquivalenceContext::findUntaggedStructOrUnionIndex(
+                      D)) {
+            if (Optional<unsigned> Index2 = StructuralEquivalenceContext::
                     findUntaggedStructOrUnionIndex(FoundRecord)) {
               if (*Index1 != *Index2)
                 continue;
@@ -3216,7 +1834,7 @@
     for (unsigned I = 0, N = FoundDecls.size(); I != N; ++I) {
       if (!FoundDecls[I]->isInIdentifierNamespace(IDNS))
         continue;
-    
+
       if (FunctionDecl *FoundFunction = dyn_cast<FunctionDecl>(FoundDecls[I])) {
         if (FoundFunction->hasExternalFormalLinkage() &&
             D->hasExternalFormalLinkage()) {
@@ -3225,14 +1843,14 @@
             // FIXME: Actually try to merge the body and other attributes.
             return Importer.Imported(D, FoundFunction);
           }
-        
+
           // FIXME: Check for overloading more carefully, e.g., by boosting
           // Sema::IsOverload out to the AST library.
-          
+
           // Function overloading is okay in C++.
           if (Importer.getToContext().getLangOpts().CPlusPlus)
             continue;
-          
+
           // Complain about inconsistent function types.
           Importer.ToDiag(Loc, diag::err_odr_function_type_inconsistent)
             << Name << D->getType() << FoundFunction->getType();
@@ -3241,10 +1859,10 @@
             << FoundFunction->getType();
         }
       }
-      
+
       ConflictingDecls.push_back(FoundDecls[I]);
     }
-    
+
     if (!ConflictingDecls.empty()) {
       Name = Importer.HandleNameConflict(Name, DC, IDNS,
                                          ConflictingDecls.data(), 
@@ -3449,12 +2067,12 @@
       if (!Name && getFieldIndex(D) != getFieldIndex(FoundField))
         continue;
 
-      if (Importer.IsStructurallyEquivalent(D->getType(), 
+      if (Importer.IsStructurallyEquivalent(D->getType(),
                                             FoundField->getType())) {
         Importer.Imported(D, FoundField);
         return FoundField;
       }
-      
+
       Importer.ToDiag(Loc, diag::err_odr_field_type_inconsistent)
         << Name << D->getType() << FoundField->getType();
       Importer.ToDiag(FoundField->getLocation(), diag::note_odr_value_here)
@@ -3514,7 +2132,7 @@
       if (!Name && getFieldIndex(D) != getFieldIndex(FoundField))
         continue;
 
-      if (Importer.IsStructurallyEquivalent(D->getType(), 
+      if (Importer.IsStructurallyEquivalent(D->getType(),
                                             FoundField->getType(),
                                             !Name.isEmpty())) {
         Importer.Imported(D, FoundField);
@@ -3638,12 +2256,12 @@
   if (ToD)
     return ToD;
 
-  // Determine whether we've already imported this ivar 
+  // Determine whether we've already imported this ivar
   SmallVector<NamedDecl *, 2> FoundDecls;
   DC->getRedeclContext()->localUncachedLookup(Name, FoundDecls);
   for (unsigned I = 0, N = FoundDecls.size(); I != N; ++I) {
     if (ObjCIvarDecl *FoundIvar = dyn_cast<ObjCIvarDecl>(FoundDecls[I])) {
-      if (Importer.IsStructurallyEquivalent(D->getType(), 
+      if (Importer.IsStructurallyEquivalent(D->getType(),
                                             FoundIvar->getType())) {
         Importer.Imported(D, FoundIvar);
         return FoundIvar;
@@ -3702,12 +2320,12 @@
     for (unsigned I = 0, N = FoundDecls.size(); I != N; ++I) {
       if (!FoundDecls[I]->isInIdentifierNamespace(IDNS))
         continue;
-      
+
       if (VarDecl *FoundVar = dyn_cast<VarDecl>(FoundDecls[I])) {
         // We have found a variable that we may need to merge with. Check it.
         if (FoundVar->hasExternalFormalLinkage() &&
             D->hasExternalFormalLinkage()) {
-          if (Importer.IsStructurallyEquivalent(D->getType(), 
+          if (Importer.IsStructurallyEquivalent(D->getType(),
                                                 FoundVar->getType())) {
             MergeWithVar = FoundVar;
             break;
@@ -3931,12 +2549,12 @@
       }
 
       // Check parameter types.
-      for (ObjCMethodDecl::param_iterator P = D->param_begin(), 
+      for (ObjCMethodDecl::param_iterator P = D->param_begin(),
              PEnd = D->param_end(), FoundP = FoundMethod->param_begin();
            P != PEnd; ++P, ++FoundP) {
-        if (!Importer.IsStructurallyEquivalent((*P)->getType(), 
+        if (!Importer.IsStructurallyEquivalent((*P)->getType(),
                                                (*FoundP)->getType())) {
-          Importer.FromDiag((*P)->getLocation(), 
+          Importer.FromDiag((*P)->getLocation(),
                             diag::err_odr_objc_method_param_type_inconsistent)
             << D->isInstanceMethod() << Name
             << (*P)->getType() << (*FoundP)->getType();
@@ -4542,7 +3160,7 @@
     if (ObjCPropertyDecl *FoundProp
                                 = dyn_cast<ObjCPropertyDecl>(FoundDecls[I])) {
       // Check property types.
-      if (!Importer.IsStructurallyEquivalent(D->getType(), 
+      if (!Importer.IsStructurallyEquivalent(D->getType(),
                                              FoundProp->getType())) {
         Importer.ToDiag(Loc, diag::err_odr_objc_property_type_inconsistent)
           << Name << D->getType() << FoundProp->getType();
@@ -7597,7 +6215,7 @@
    = ImportedTypes.find(From.getTypePtr());
   if (Pos != ImportedTypes.end() && ToContext.hasSameType(Import(From), To))
     return true;
-      
+
   StructuralEquivalenceContext Ctx(FromContext, ToContext, NonEquivalentDecls,
                                    false, Complain);
   return Ctx.IsStructurallyEquivalent(From, To);
Index: cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
===================================================================
--- cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
+++ cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
@@ -0,0 +1,1318 @@
+//===--- ASTStructuralEquivalence.cpp - -------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implement StructuralEquivalenceContext class and helper functions
+//  for layout matching.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/AST/ASTStructuralEquivalence.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTDiagnostic.h"
+#include "clang/AST/ASTImporter.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclVisitor.h"
+#include "clang/AST/StmtVisitor.h"
+#include "clang/AST/TypeVisitor.h"
+#include "clang/Basic/SourceManager.h"
+
+namespace {
+
+using namespace clang;
+
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     QualType T1, QualType T2);
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     Decl *D1, Decl *D2);
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     const TemplateArgument &Arg1,
+                                     const TemplateArgument &Arg2);
+
+/// Determine structural equivalence of two expressions.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     Expr *E1, Expr *E2) {
+  if (!E1 || !E2)
+    return E1 == E2;
+
+  // FIXME: Actually perform a structural comparison!
+  return true;
+}
+
+/// Determine whether two identifiers are equivalent.
+static bool IsStructurallyEquivalent(const IdentifierInfo *Name1,
+                                     const IdentifierInfo *Name2) {
+  if (!Name1 || !Name2)
+    return Name1 == Name2;
+
+  return Name1->getName() == Name2->getName();
+}
+
+/// Determine whether two nested-name-specifiers are equivalent.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     NestedNameSpecifier *NNS1,
+                                     NestedNameSpecifier *NNS2) {
+  if (NNS1->getKind() != NNS2->getKind())
+    return false;
+
+  NestedNameSpecifier *Prefix1 = NNS1->getPrefix(),
+                      *Prefix2 = NNS2->getPrefix();
+  if ((bool)Prefix1 != (bool)Prefix2)
+    return false;
+
+  if (Prefix1)
+    if (!IsStructurallyEquivalent(Context, Prefix1, Prefix2))
+      return false;
+
+  switch (NNS1->getKind()) {
+  case NestedNameSpecifier::Identifier:
+    return IsStructurallyEquivalent(NNS1->getAsIdentifier(),
+                                    NNS2->getAsIdentifier());
+  case NestedNameSpecifier::Namespace:
+    return IsStructurallyEquivalent(Context, NNS1->getAsNamespace(),
+                                    NNS2->getAsNamespace());
+  case NestedNameSpecifier::NamespaceAlias:
+    return IsStructurallyEquivalent(Context, NNS1->getAsNamespaceAlias(),
+                                    NNS2->getAsNamespaceAlias());
+  case NestedNameSpecifier::TypeSpec:
+  case NestedNameSpecifier::TypeSpecWithTemplate:
+    return IsStructurallyEquivalent(Context, QualType(NNS1->getAsType(), 0),
+                                    QualType(NNS2->getAsType(), 0));
+  case NestedNameSpecifier::Global:
+    return true;
+  case NestedNameSpecifier::Super:
+    return IsStructurallyEquivalent(Context, NNS1->getAsRecordDecl(),
+                                    NNS2->getAsRecordDecl());
+  }
+  return false;
+}
+
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     const TemplateName &N1,
+                                     const TemplateName &N2) {
+  if (N1.getKind() != N2.getKind())
+    return false;
+  switch (N1.getKind()) {
+  case TemplateName::Template:
+    return IsStructurallyEquivalent(Context, N1.getAsTemplateDecl(),
+                                    N2.getAsTemplateDecl());
+
+  case TemplateName::OverloadedTemplate: {
+    OverloadedTemplateStorage *OS1 = N1.getAsOverloadedTemplate(),
+                              *OS2 = N2.getAsOverloadedTemplate();
+    OverloadedTemplateStorage::iterator I1 = OS1->begin(), I2 = OS2->begin(),
+                                        E1 = OS1->end(), E2 = OS2->end();
+    for (; I1 != E1 && I2 != E2; ++I1, ++I2)
+      if (!IsStructurallyEquivalent(Context, *I1, *I2))
+        return false;
+    return I1 == E1 && I2 == E2;
+  }
+
+  case TemplateName::QualifiedTemplate: {
+    QualifiedTemplateName *QN1 = N1.getAsQualifiedTemplateName(),
+                          *QN2 = N2.getAsQualifiedTemplateName();
+    return IsStructurallyEquivalent(Context, QN1->getDecl(), QN2->getDecl()) &&
+           IsStructurallyEquivalent(Context, QN1->getQualifier(),
+                                    QN2->getQualifier());
+  }
+
+  case TemplateName::DependentTemplate: {
+    DependentTemplateName *DN1 = N1.getAsDependentTemplateName(),
+                          *DN2 = N2.getAsDependentTemplateName();
+    if (!IsStructurallyEquivalent(Context, DN1->getQualifier(),
+                                  DN2->getQualifier()))
+      return false;
+    if (DN1->isIdentifier() && DN2->isIdentifier())
+      return IsStructurallyEquivalent(DN1->getIdentifier(),
+                                      DN2->getIdentifier());
+    else if (DN1->isOverloadedOperator() && DN2->isOverloadedOperator())
+      return DN1->getOperator() == DN2->getOperator();
+    return false;
+  }
+
+  case TemplateName::SubstTemplateTemplateParm: {
+    SubstTemplateTemplateParmStorage *TS1 = N1.getAsSubstTemplateTemplateParm(),
+                                     *TS2 = N2.getAsSubstTemplateTemplateParm();
+    return IsStructurallyEquivalent(Context, TS1->getParameter(),
+                                    TS2->getParameter()) &&
+           IsStructurallyEquivalent(Context, TS1->getReplacement(),
+                                    TS2->getReplacement());
+  }
+  case TemplateName::SubstTemplateTemplateParmPack: {
+    SubstTemplateTemplateParmPackStorage
+        *P1 = N1.getAsSubstTemplateTemplateParmPack(),
+        *P2 = N2.getAsSubstTemplateTemplateParmPack();
+    return IsStructurallyEquivalent(Context, P1->getArgumentPack(),
+                                    P2->getArgumentPack()) &&
+           IsStructurallyEquivalent(Context, P1->getParameterPack(),
+                                    P2->getParameterPack());
+  }
+  }
+  return false;
+}
+
+/// Determine whether two template arguments are equivalent.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     const TemplateArgument &Arg1,
+                                     const TemplateArgument &Arg2) {
+  if (Arg1.getKind() != Arg2.getKind())
+    return false;
+
+  switch (Arg1.getKind()) {
+  case TemplateArgument::Null:
+    return true;
+
+  case TemplateArgument::Type:
+    return Context.IsStructurallyEquivalent(Arg1.getAsType(), Arg2.getAsType());
+
+  case TemplateArgument::Integral:
+    if (!Context.IsStructurallyEquivalent(Arg1.getIntegralType(),
+                                          Arg2.getIntegralType()))
+      return false;
+
+    return llvm::APSInt::isSameValue(Arg1.getAsIntegral(),
+                                     Arg2.getAsIntegral());
+
+  case TemplateArgument::Declaration:
+    return Context.IsStructurallyEquivalent(Arg1.getAsDecl(), Arg2.getAsDecl());
+
+  case TemplateArgument::NullPtr:
+    return true; // FIXME: Is this correct?
+
+  case TemplateArgument::Template:
+    return IsStructurallyEquivalent(Context, Arg1.getAsTemplate(),
+                                    Arg2.getAsTemplate());
+
+  case TemplateArgument::TemplateExpansion:
+    return IsStructurallyEquivalent(Context,
+                                    Arg1.getAsTemplateOrTemplatePattern(),
+                                    Arg2.getAsTemplateOrTemplatePattern());
+
+  case TemplateArgument::Expression:
+    return IsStructurallyEquivalent(Context, Arg1.getAsExpr(),
+                                    Arg2.getAsExpr());
+
+  case TemplateArgument::Pack:
+    if (Arg1.pack_size() != Arg2.pack_size())
+      return false;
+
+    for (unsigned I = 0, N = Arg1.pack_size(); I != N; ++I)
+      if (!IsStructurallyEquivalent(Context, Arg1.pack_begin()[I],
+                                    Arg2.pack_begin()[I]))
+        return false;
+
+    return true;
+  }
+
+  llvm_unreachable("Invalid template argument kind");
+}
+
+/// Determine structural equivalence for the common part of array
+/// types.
+static bool IsArrayStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                          const ArrayType *Array1,
+                                          const ArrayType *Array2) {
+  if (!IsStructurallyEquivalent(Context, Array1->getElementType(),
+                                Array2->getElementType()))
+    return false;
+  if (Array1->getSizeModifier() != Array2->getSizeModifier())
+    return false;
+  if (Array1->getIndexTypeQualifiers() != Array2->getIndexTypeQualifiers())
+    return false;
+
+  return true;
+}
+
+/// Determine structural equivalence of two types.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     QualType T1, QualType T2) {
+  if (T1.isNull() || T2.isNull())
+    return T1.isNull() && T2.isNull();
+
+  if (!Context.StrictTypeSpelling) {
+    // We aren't being strict about token-to-token equivalence of types,
+    // so map down to the canonical type.
+    T1 = Context.FromCtx.getCanonicalType(T1);
+    T2 = Context.ToCtx.getCanonicalType(T2);
+  }
+
+  if (T1.getQualifiers() != T2.getQualifiers())
+    return false;
+
+  Type::TypeClass TC = T1->getTypeClass();
+
+  if (T1->getTypeClass() != T2->getTypeClass()) {
+    // Compare function types with prototypes vs. without prototypes as if
+    // both did not have prototypes.
+    if (T1->getTypeClass() == Type::FunctionProto &&
+        T2->getTypeClass() == Type::FunctionNoProto)
+      TC = Type::FunctionNoProto;
+    else if (T1->getTypeClass() == Type::FunctionNoProto &&
+             T2->getTypeClass() == Type::FunctionProto)
+      TC = Type::FunctionNoProto;
+    else
+      return false;
+  }
+
+  switch (TC) {
+  case Type::Builtin:
+    // FIXME: Deal with Char_S/Char_U.
+    if (cast<BuiltinType>(T1)->getKind() != cast<BuiltinType>(T2)->getKind())
+      return false;
+    break;
+
+  case Type::Complex:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<ComplexType>(T1)->getElementType(),
+                                  cast<ComplexType>(T2)->getElementType()))
+      return false;
+    break;
+
+  case Type::Adjusted:
+  case Type::Decayed:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<AdjustedType>(T1)->getOriginalType(),
+                                  cast<AdjustedType>(T2)->getOriginalType()))
+      return false;
+    break;
+
+  case Type::Pointer:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<PointerType>(T1)->getPointeeType(),
+                                  cast<PointerType>(T2)->getPointeeType()))
+      return false;
+    break;
+
+  case Type::BlockPointer:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<BlockPointerType>(T1)->getPointeeType(),
+                                  cast<BlockPointerType>(T2)->getPointeeType()))
+      return false;
+    break;
+
+  case Type::LValueReference:
+  case Type::RValueReference: {
+    const ReferenceType *Ref1 = cast<ReferenceType>(T1);
+    const ReferenceType *Ref2 = cast<ReferenceType>(T2);
+    if (Ref1->isSpelledAsLValue() != Ref2->isSpelledAsLValue())
+      return false;
+    if (Ref1->isInnerRef() != Ref2->isInnerRef())
+      return false;
+    if (!IsStructurallyEquivalent(Context, Ref1->getPointeeTypeAsWritten(),
+                                  Ref2->getPointeeTypeAsWritten()))
+      return false;
+    break;
+  }
+
+  case Type::MemberPointer: {
+    const MemberPointerType *MemPtr1 = cast<MemberPointerType>(T1);
+    const MemberPointerType *MemPtr2 = cast<MemberPointerType>(T2);
+    if (!IsStructurallyEquivalent(Context, MemPtr1->getPointeeType(),
+                                  MemPtr2->getPointeeType()))
+      return false;
+    if (!IsStructurallyEquivalent(Context, QualType(MemPtr1->getClass(), 0),
+                                  QualType(MemPtr2->getClass(), 0)))
+      return false;
+    break;
+  }
+
+  case Type::ConstantArray: {
+    const ConstantArrayType *Array1 = cast<ConstantArrayType>(T1);
+    const ConstantArrayType *Array2 = cast<ConstantArrayType>(T2);
+    if (!llvm::APInt::isSameValue(Array1->getSize(), Array2->getSize()))
+      return false;
+
+    if (!IsArrayStructurallyEquivalent(Context, Array1, Array2))
+      return false;
+    break;
+  }
+
+  case Type::IncompleteArray:
+    if (!IsArrayStructurallyEquivalent(Context, cast<ArrayType>(T1),
+                                       cast<ArrayType>(T2)))
+      return false;
+    break;
+
+  case Type::VariableArray: {
+    const VariableArrayType *Array1 = cast<VariableArrayType>(T1);
+    const VariableArrayType *Array2 = cast<VariableArrayType>(T2);
+    if (!IsStructurallyEquivalent(Context, Array1->getSizeExpr(),
+                                  Array2->getSizeExpr()))
+      return false;
+
+    if (!IsArrayStructurallyEquivalent(Context, Array1, Array2))
+      return false;
+
+    break;
+  }
+
+  case Type::DependentSizedArray: {
+    const DependentSizedArrayType *Array1 = cast<DependentSizedArrayType>(T1);
+    const DependentSizedArrayType *Array2 = cast<DependentSizedArrayType>(T2);
+    if (!IsStructurallyEquivalent(Context, Array1->getSizeExpr(),
+                                  Array2->getSizeExpr()))
+      return false;
+
+    if (!IsArrayStructurallyEquivalent(Context, Array1, Array2))
+      return false;
+
+    break;
+  }
+
+  case Type::DependentSizedExtVector: {
+    const DependentSizedExtVectorType *Vec1 =
+        cast<DependentSizedExtVectorType>(T1);
+    const DependentSizedExtVectorType *Vec2 =
+        cast<DependentSizedExtVectorType>(T2);
+    if (!IsStructurallyEquivalent(Context, Vec1->getSizeExpr(),
+                                  Vec2->getSizeExpr()))
+      return false;
+    if (!IsStructurallyEquivalent(Context, Vec1->getElementType(),
+                                  Vec2->getElementType()))
+      return false;
+    break;
+  }
+
+  case Type::Vector:
+  case Type::ExtVector: {
+    const VectorType *Vec1 = cast<VectorType>(T1);
+    const VectorType *Vec2 = cast<VectorType>(T2);
+    if (!IsStructurallyEquivalent(Context, Vec1->getElementType(),
+                                  Vec2->getElementType()))
+      return false;
+    if (Vec1->getNumElements() != Vec2->getNumElements())
+      return false;
+    if (Vec1->getVectorKind() != Vec2->getVectorKind())
+      return false;
+    break;
+  }
+
+  case Type::FunctionProto: {
+    const FunctionProtoType *Proto1 = cast<FunctionProtoType>(T1);
+    const FunctionProtoType *Proto2 = cast<FunctionProtoType>(T2);
+    if (Proto1->getNumParams() != Proto2->getNumParams())
+      return false;
+    for (unsigned I = 0, N = Proto1->getNumParams(); I != N; ++I) {
+      if (!IsStructurallyEquivalent(Context, Proto1->getParamType(I),
+                                    Proto2->getParamType(I)))
+        return false;
+    }
+    if (Proto1->isVariadic() != Proto2->isVariadic())
+      return false;
+    if (Proto1->getExceptionSpecType() != Proto2->getExceptionSpecType())
+      return false;
+    if (Proto1->getExceptionSpecType() == EST_Dynamic) {
+      if (Proto1->getNumExceptions() != Proto2->getNumExceptions())
+        return false;
+      for (unsigned I = 0, N = Proto1->getNumExceptions(); I != N; ++I) {
+        if (!IsStructurallyEquivalent(Context, Proto1->getExceptionType(I),
+                                      Proto2->getExceptionType(I)))
+          return false;
+      }
+    } else if (Proto1->getExceptionSpecType() == EST_ComputedNoexcept) {
+      if (!IsStructurallyEquivalent(Context, Proto1->getNoexceptExpr(),
+                                    Proto2->getNoexceptExpr()))
+        return false;
+    }
+    if (Proto1->getTypeQuals() != Proto2->getTypeQuals())
+      return false;
+
+    // Fall through to check the bits common with FunctionNoProtoType.
+  }
+
+  case Type::FunctionNoProto: {
+    const FunctionType *Function1 = cast<FunctionType>(T1);
+    const FunctionType *Function2 = cast<FunctionType>(T2);
+    if (!IsStructurallyEquivalent(Context, Function1->getReturnType(),
+                                  Function2->getReturnType()))
+      return false;
+    if (Function1->getExtInfo() != Function2->getExtInfo())
+      return false;
+    break;
+  }
+
+  case Type::UnresolvedUsing:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<UnresolvedUsingType>(T1)->getDecl(),
+                                  cast<UnresolvedUsingType>(T2)->getDecl()))
+      return false;
+
+    break;
+
+  case Type::Attributed:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<AttributedType>(T1)->getModifiedType(),
+                                  cast<AttributedType>(T2)->getModifiedType()))
+      return false;
+    if (!IsStructurallyEquivalent(
+            Context, cast<AttributedType>(T1)->getEquivalentType(),
+            cast<AttributedType>(T2)->getEquivalentType()))
+      return false;
+    break;
+
+  case Type::Paren:
+    if (!IsStructurallyEquivalent(Context, cast<ParenType>(T1)->getInnerType(),
+                                  cast<ParenType>(T2)->getInnerType()))
+      return false;
+    break;
+
+  case Type::Typedef:
+    if (!IsStructurallyEquivalent(Context, cast<TypedefType>(T1)->getDecl(),
+                                  cast<TypedefType>(T2)->getDecl()))
+      return false;
+    break;
+
+  case Type::TypeOfExpr:
+    if (!IsStructurallyEquivalent(
+            Context, cast<TypeOfExprType>(T1)->getUnderlyingExpr(),
+            cast<TypeOfExprType>(T2)->getUnderlyingExpr()))
+      return false;
+    break;
+
+  case Type::TypeOf:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<TypeOfType>(T1)->getUnderlyingType(),
+                                  cast<TypeOfType>(T2)->getUnderlyingType()))
+      return false;
+    break;
+
+  case Type::UnaryTransform:
+    if (!IsStructurallyEquivalent(
+            Context, cast<UnaryTransformType>(T1)->getUnderlyingType(),
+            cast<UnaryTransformType>(T1)->getUnderlyingType()))
+      return false;
+    break;
+
+  case Type::Decltype:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<DecltypeType>(T1)->getUnderlyingExpr(),
+                                  cast<DecltypeType>(T2)->getUnderlyingExpr()))
+      return false;
+    break;
+
+  case Type::Auto:
+    if (!IsStructurallyEquivalent(Context, cast<AutoType>(T1)->getDeducedType(),
+                                  cast<AutoType>(T2)->getDeducedType()))
+      return false;
+    break;
+
+  case Type::DeducedTemplateSpecialization: {
+    auto *DT1 = cast<DeducedTemplateSpecializationType>(T1);
+    auto *DT2 = cast<DeducedTemplateSpecializationType>(T2);
+    if (!IsStructurallyEquivalent(Context, DT1->getTemplateName(),
+                                  DT2->getTemplateName()))
+      return false;
+    if (!IsStructurallyEquivalent(Context, DT1->getDeducedType(),
+                                  DT2->getDeducedType()))
+      return false;
+    break;
+  }
+
+  case Type::Record:
+  case Type::Enum:
+    if (!IsStructurallyEquivalent(Context, cast<TagType>(T1)->getDecl(),
+                                  cast<TagType>(T2)->getDecl()))
+      return false;
+    break;
+
+  case Type::TemplateTypeParm: {
+    const TemplateTypeParmType *Parm1 = cast<TemplateTypeParmType>(T1);
+    const TemplateTypeParmType *Parm2 = cast<TemplateTypeParmType>(T2);
+    if (Parm1->getDepth() != Parm2->getDepth())
+      return false;
+    if (Parm1->getIndex() != Parm2->getIndex())
+      return false;
+    if (Parm1->isParameterPack() != Parm2->isParameterPack())
+      return false;
+
+    // Names of template type parameters are never significant.
+    break;
+  }
+
+  case Type::SubstTemplateTypeParm: {
+    const SubstTemplateTypeParmType *Subst1 =
+        cast<SubstTemplateTypeParmType>(T1);
+    const SubstTemplateTypeParmType *Subst2 =
+        cast<SubstTemplateTypeParmType>(T2);
+    if (!IsStructurallyEquivalent(Context,
+                                  QualType(Subst1->getReplacedParameter(), 0),
+                                  QualType(Subst2->getReplacedParameter(), 0)))
+      return false;
+    if (!IsStructurallyEquivalent(Context, Subst1->getReplacementType(),
+                                  Subst2->getReplacementType()))
+      return false;
+    break;
+  }
+
+  case Type::SubstTemplateTypeParmPack: {
+    const SubstTemplateTypeParmPackType *Subst1 =
+        cast<SubstTemplateTypeParmPackType>(T1);
+    const SubstTemplateTypeParmPackType *Subst2 =
+        cast<SubstTemplateTypeParmPackType>(T2);
+    if (!IsStructurallyEquivalent(Context,
+                                  QualType(Subst1->getReplacedParameter(), 0),
+                                  QualType(Subst2->getReplacedParameter(), 0)))
+      return false;
+    if (!IsStructurallyEquivalent(Context, Subst1->getArgumentPack(),
+                                  Subst2->getArgumentPack()))
+      return false;
+    break;
+  }
+  case Type::TemplateSpecialization: {
+    const TemplateSpecializationType *Spec1 =
+        cast<TemplateSpecializationType>(T1);
+    const TemplateSpecializationType *Spec2 =
+        cast<TemplateSpecializationType>(T2);
+    if (!IsStructurallyEquivalent(Context, Spec1->getTemplateName(),
+                                  Spec2->getTemplateName()))
+      return false;
+    if (Spec1->getNumArgs() != Spec2->getNumArgs())
+      return false;
+    for (unsigned I = 0, N = Spec1->getNumArgs(); I != N; ++I) {
+      if (!IsStructurallyEquivalent(Context, Spec1->getArg(I),
+                                    Spec2->getArg(I)))
+        return false;
+    }
+    break;
+  }
+
+  case Type::Elaborated: {
+    const ElaboratedType *Elab1 = cast<ElaboratedType>(T1);
+    const ElaboratedType *Elab2 = cast<ElaboratedType>(T2);
+    // CHECKME: what if a keyword is ETK_None or ETK_typename ?
+    if (Elab1->getKeyword() != Elab2->getKeyword())
+      return false;
+    if (!IsStructurallyEquivalent(Context, Elab1->getQualifier(),
+                                  Elab2->getQualifier()))
+      return false;
+    if (!IsStructurallyEquivalent(Context, Elab1->getNamedType(),
+                                  Elab2->getNamedType()))
+      return false;
+    break;
+  }
+
+  case Type::InjectedClassName: {
+    const InjectedClassNameType *Inj1 = cast<InjectedClassNameType>(T1);
+    const InjectedClassNameType *Inj2 = cast<InjectedClassNameType>(T2);
+    if (!IsStructurallyEquivalent(Context,
+                                  Inj1->getInjectedSpecializationType(),
+                                  Inj2->getInjectedSpecializationType()))
+      return false;
+    break;
+  }
+
+  case Type::DependentName: {
+    const DependentNameType *Typename1 = cast<DependentNameType>(T1);
+    const DependentNameType *Typename2 = cast<DependentNameType>(T2);
+    if (!IsStructurallyEquivalent(Context, Typename1->getQualifier(),
+                                  Typename2->getQualifier()))
+      return false;
+    if (!IsStructurallyEquivalent(Typename1->getIdentifier(),
+                                  Typename2->getIdentifier()))
+      return false;
+
+    break;
+  }
+
+  case Type::DependentTemplateSpecialization: {
+    const DependentTemplateSpecializationType *Spec1 =
+        cast<DependentTemplateSpecializationType>(T1);
+    const DependentTemplateSpecializationType *Spec2 =
+        cast<DependentTemplateSpecializationType>(T2);
+    if (!IsStructurallyEquivalent(Context, Spec1->getQualifier(),
+                                  Spec2->getQualifier()))
+      return false;
+    if (!IsStructurallyEquivalent(Spec1->getIdentifier(),
+                                  Spec2->getIdentifier()))
+      return false;
+    if (Spec1->getNumArgs() != Spec2->getNumArgs())
+      return false;
+    for (unsigned I = 0, N = Spec1->getNumArgs(); I != N; ++I) {
+      if (!IsStructurallyEquivalent(Context, Spec1->getArg(I),
+                                    Spec2->getArg(I)))
+        return false;
+    }
+    break;
+  }
+
+  case Type::PackExpansion:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<PackExpansionType>(T1)->getPattern(),
+                                  cast<PackExpansionType>(T2)->getPattern()))
+      return false;
+    break;
+
+  case Type::ObjCInterface: {
+    const ObjCInterfaceType *Iface1 = cast<ObjCInterfaceType>(T1);
+    const ObjCInterfaceType *Iface2 = cast<ObjCInterfaceType>(T2);
+    if (!IsStructurallyEquivalent(Context, Iface1->getDecl(),
+                                  Iface2->getDecl()))
+      return false;
+    break;
+  }
+
+  case Type::ObjCTypeParam: {
+    const ObjCTypeParamType *Obj1 = cast<ObjCTypeParamType>(T1);
+    const ObjCTypeParamType *Obj2 = cast<ObjCTypeParamType>(T2);
+    if (!IsStructurallyEquivalent(Context, Obj1->getDecl(), Obj2->getDecl()))
+      return false;
+
+    if (Obj1->getNumProtocols() != Obj2->getNumProtocols())
+      return false;
+    for (unsigned I = 0, N = Obj1->getNumProtocols(); I != N; ++I) {
+      if (!IsStructurallyEquivalent(Context, Obj1->getProtocol(I),
+                                    Obj2->getProtocol(I)))
+        return false;
+    }
+    break;
+  }
+  case Type::ObjCObject: {
+    const ObjCObjectType *Obj1 = cast<ObjCObjectType>(T1);
+    const ObjCObjectType *Obj2 = cast<ObjCObjectType>(T2);
+    if (!IsStructurallyEquivalent(Context, Obj1->getBaseType(),
+                                  Obj2->getBaseType()))
+      return false;
+    if (Obj1->getNumProtocols() != Obj2->getNumProtocols())
+      return false;
+    for (unsigned I = 0, N = Obj1->getNumProtocols(); I != N; ++I) {
+      if (!IsStructurallyEquivalent(Context, Obj1->getProtocol(I),
+                                    Obj2->getProtocol(I)))
+        return false;
+    }
+    break;
+  }
+
+  case Type::ObjCObjectPointer: {
+    const ObjCObjectPointerType *Ptr1 = cast<ObjCObjectPointerType>(T1);
+    const ObjCObjectPointerType *Ptr2 = cast<ObjCObjectPointerType>(T2);
+    if (!IsStructurallyEquivalent(Context, Ptr1->getPointeeType(),
+                                  Ptr2->getPointeeType()))
+      return false;
+    break;
+  }
+
+  case Type::Atomic: {
+    if (!IsStructurallyEquivalent(Context, cast<AtomicType>(T1)->getValueType(),
+                                  cast<AtomicType>(T2)->getValueType()))
+      return false;
+    break;
+  }
+
+  case Type::Pipe: {
+    if (!IsStructurallyEquivalent(Context, cast<PipeType>(T1)->getElementType(),
+                                  cast<PipeType>(T2)->getElementType()))
+      return false;
+    break;
+  }
+
+  } // end switch
+
+  return true;
+}
+
+/// Determine structural equivalence of two fields.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     FieldDecl *Field1, FieldDecl *Field2) {
+  RecordDecl *Owner2 = cast<RecordDecl>(Field2->getDeclContext());
+
+  // For anonymous structs/unions, match up the anonymous struct/union type
+  // declarations directly, so that we don't go off searching for anonymous
+  // types
+  if (Field1->isAnonymousStructOrUnion() &&
+      Field2->isAnonymousStructOrUnion()) {
+    RecordDecl *D1 = Field1->getType()->castAs<RecordType>()->getDecl();
+    RecordDecl *D2 = Field2->getType()->castAs<RecordType>()->getDecl();
+    return IsStructurallyEquivalent(Context, D1, D2);
+  }
+
+  // Check for equivalent field names.
+  IdentifierInfo *Name1 = Field1->getIdentifier();
+  IdentifierInfo *Name2 = Field2->getIdentifier();
+  if (!::IsStructurallyEquivalent(Name1, Name2))
+    return false;
+
+  if (!IsStructurallyEquivalent(Context, Field1->getType(),
+                                Field2->getType())) {
+    if (Context.Complain) {
+      Context.Diag2(Owner2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+          << Context.ToCtx.getTypeDeclType(Owner2);
+      Context.Diag2(Field2->getLocation(), diag::note_odr_field)
+          << Field2->getDeclName() << Field2->getType();
+      Context.Diag1(Field1->getLocation(), diag::note_odr_field)
+          << Field1->getDeclName() << Field1->getType();
+    }
+    return false;
+  }
+
+  if (Field1->isBitField() != Field2->isBitField()) {
+    if (Context.Complain) {
+      Context.Diag2(Owner2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+          << Context.ToCtx.getTypeDeclType(Owner2);
+      if (Field1->isBitField()) {
+        Context.Diag1(Field1->getLocation(), diag::note_odr_bit_field)
+            << Field1->getDeclName() << Field1->getType()
+            << Field1->getBitWidthValue(Context.FromCtx);
+        Context.Diag2(Field2->getLocation(), diag::note_odr_not_bit_field)
+            << Field2->getDeclName();
+      } else {
+        Context.Diag2(Field2->getLocation(), diag::note_odr_bit_field)
+            << Field2->getDeclName() << Field2->getType()
+            << Field2->getBitWidthValue(Context.ToCtx);
+        Context.Diag1(Field1->getLocation(), diag::note_odr_not_bit_field)
+            << Field1->getDeclName();
+      }
+    }
+    return false;
+  }
+
+  if (Field1->isBitField()) {
+    // Make sure that the bit-fields are the same length.
+    unsigned Bits1 = Field1->getBitWidthValue(Context.FromCtx);
+    unsigned Bits2 = Field2->getBitWidthValue(Context.ToCtx);
+
+    if (Bits1 != Bits2) {
+      if (Context.Complain) {
+        Context.Diag2(Owner2->getLocation(),
+                      diag::warn_odr_tag_type_inconsistent)
+            << Context.ToCtx.getTypeDeclType(Owner2);
+        Context.Diag2(Field2->getLocation(), diag::note_odr_bit_field)
+            << Field2->getDeclName() << Field2->getType() << Bits2;
+        Context.Diag1(Field1->getLocation(), diag::note_odr_bit_field)
+            << Field1->getDeclName() << Field1->getType() << Bits1;
+      }
+      return false;
+    }
+  }
+
+  return true;
+}
+
+/// Determine structural equivalence of two records.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     RecordDecl *D1, RecordDecl *D2) {
+  if (D1->isUnion() != D2->isUnion()) {
+    if (Context.Complain) {
+      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+          << Context.ToCtx.getTypeDeclType(D2);
+      Context.Diag1(D1->getLocation(), diag::note_odr_tag_kind_here)
+          << D1->getDeclName() << (unsigned)D1->getTagKind();
+    }
+    return false;
+  }
+
+  if (D1->isAnonymousStructOrUnion() && D2->isAnonymousStructOrUnion()) {
+    // If both anonymous structs/unions are in a record context, make sure
+    // they occur in the same location in the context records.
+    if (Optional<unsigned> Index1 =
+            StructuralEquivalenceContext::findUntaggedStructOrUnionIndex(D1)) {
+      if (Optional<unsigned> Index2 =
+              StructuralEquivalenceContext::findUntaggedStructOrUnionIndex(
+                  D2)) {
+        if (*Index1 != *Index2)
+          return false;
+      }
+    }
+  }
+
+  // If both declarations are class template specializations, we know
+  // the ODR applies, so check the template and template arguments.
+  ClassTemplateSpecializationDecl *Spec1 =
+      dyn_cast<ClassTemplateSpecializationDecl>(D1);
+  ClassTemplateSpecializationDecl *Spec2 =
+      dyn_cast<ClassTemplateSpecializationDecl>(D2);
+  if (Spec1 && Spec2) {
+    // Check that the specialized templates are the same.
+    if (!IsStructurallyEquivalent(Context, Spec1->getSpecializedTemplate(),
+                                  Spec2->getSpecializedTemplate()))
+      return false;
+
+    // Check that the template arguments are the same.
+    if (Spec1->getTemplateArgs().size() != Spec2->getTemplateArgs().size())
+      return false;
+
+    for (unsigned I = 0, N = Spec1->getTemplateArgs().size(); I != N; ++I)
+      if (!IsStructurallyEquivalent(Context, Spec1->getTemplateArgs().get(I),
+                                    Spec2->getTemplateArgs().get(I)))
+        return false;
+  }
+  // If one is a class template specialization and the other is not, these
+  // structures are different.
+  else if (Spec1 || Spec2)
+    return false;
+
+  // Compare the definitions of these two records. If either or both are
+  // incomplete, we assume that they are equivalent.
+  D1 = D1->getDefinition();
+  D2 = D2->getDefinition();
+  if (!D1 || !D2)
+    return true;
+
+  if (CXXRecordDecl *D1CXX = dyn_cast<CXXRecordDecl>(D1)) {
+    if (CXXRecordDecl *D2CXX = dyn_cast<CXXRecordDecl>(D2)) {
+      if (D1CXX->getNumBases() != D2CXX->getNumBases()) {
+        if (Context.Complain) {
+          Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+              << Context.ToCtx.getTypeDeclType(D2);
+          Context.Diag2(D2->getLocation(), diag::note_odr_number_of_bases)
+              << D2CXX->getNumBases();
+          Context.Diag1(D1->getLocation(), diag::note_odr_number_of_bases)
+              << D1CXX->getNumBases();
+        }
+        return false;
+      }
+
+      // Check the base classes.
+      for (CXXRecordDecl::base_class_iterator Base1 = D1CXX->bases_begin(),
+                                              BaseEnd1 = D1CXX->bases_end(),
+                                              Base2 = D2CXX->bases_begin();
+           Base1 != BaseEnd1; ++Base1, ++Base2) {
+        if (!IsStructurallyEquivalent(Context, Base1->getType(),
+                                      Base2->getType())) {
+          if (Context.Complain) {
+            Context.Diag2(D2->getLocation(),
+                          diag::warn_odr_tag_type_inconsistent)
+                << Context.ToCtx.getTypeDeclType(D2);
+            Context.Diag2(Base2->getLocStart(), diag::note_odr_base)
+                << Base2->getType() << Base2->getSourceRange();
+            Context.Diag1(Base1->getLocStart(), diag::note_odr_base)
+                << Base1->getType() << Base1->getSourceRange();
+          }
+          return false;
+        }
+
+        // Check virtual vs. non-virtual inheritance mismatch.
+        if (Base1->isVirtual() != Base2->isVirtual()) {
+          if (Context.Complain) {
+            Context.Diag2(D2->getLocation(),
+                          diag::warn_odr_tag_type_inconsistent)
+                << Context.ToCtx.getTypeDeclType(D2);
+            Context.Diag2(Base2->getLocStart(), diag::note_odr_virtual_base)
+                << Base2->isVirtual() << Base2->getSourceRange();
+            Context.Diag1(Base1->getLocStart(), diag::note_odr_base)
+                << Base1->isVirtual() << Base1->getSourceRange();
+          }
+          return false;
+        }
+      }
+    } else if (D1CXX->getNumBases() > 0) {
+      if (Context.Complain) {
+        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+            << Context.ToCtx.getTypeDeclType(D2);
+        const CXXBaseSpecifier *Base1 = D1CXX->bases_begin();
+        Context.Diag1(Base1->getLocStart(), diag::note_odr_base)
+            << Base1->getType() << Base1->getSourceRange();
+        Context.Diag2(D2->getLocation(), diag::note_odr_missing_base);
+      }
+      return false;
+    }
+  }
+
+  // Check the fields for consistency.
+  RecordDecl::field_iterator Field2 = D2->field_begin(),
+                             Field2End = D2->field_end();
+  for (RecordDecl::field_iterator Field1 = D1->field_begin(),
+                                  Field1End = D1->field_end();
+       Field1 != Field1End; ++Field1, ++Field2) {
+    if (Field2 == Field2End) {
+      if (Context.Complain) {
+        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+            << Context.ToCtx.getTypeDeclType(D2);
+        Context.Diag1(Field1->getLocation(), diag::note_odr_field)
+            << Field1->getDeclName() << Field1->getType();
+        Context.Diag2(D2->getLocation(), diag::note_odr_missing_field);
+      }
+      return false;
+    }
+
+    if (!IsStructurallyEquivalent(Context, *Field1, *Field2))
+      return false;
+  }
+
+  if (Field2 != Field2End) {
+    if (Context.Complain) {
+      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+          << Context.ToCtx.getTypeDeclType(D2);
+      Context.Diag2(Field2->getLocation(), diag::note_odr_field)
+          << Field2->getDeclName() << Field2->getType();
+      Context.Diag1(D1->getLocation(), diag::note_odr_missing_field);
+    }
+    return false;
+  }
+
+  return true;
+}
+
+/// Determine structural equivalence of two enums.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     EnumDecl *D1, EnumDecl *D2) {
+  EnumDecl::enumerator_iterator EC2 = D2->enumerator_begin(),
+                                EC2End = D2->enumerator_end();
+  for (EnumDecl::enumerator_iterator EC1 = D1->enumerator_begin(),
+                                     EC1End = D1->enumerator_end();
+       EC1 != EC1End; ++EC1, ++EC2) {
+    if (EC2 == EC2End) {
+      if (Context.Complain) {
+        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+            << Context.ToCtx.getTypeDeclType(D2);
+        Context.Diag1(EC1->getLocation(), diag::note_odr_enumerator)
+            << EC1->getDeclName() << EC1->getInitVal().toString(10);
+        Context.Diag2(D2->getLocation(), diag::note_odr_missing_enumerator);
+      }
+      return false;
+    }
+
+    llvm::APSInt Val1 = EC1->getInitVal();
+    llvm::APSInt Val2 = EC2->getInitVal();
+    if (!llvm::APSInt::isSameValue(Val1, Val2) ||
+        !IsStructurallyEquivalent(EC1->getIdentifier(), EC2->getIdentifier())) {
+      if (Context.Complain) {
+        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+            << Context.ToCtx.getTypeDeclType(D2);
+        Context.Diag2(EC2->getLocation(), diag::note_odr_enumerator)
+            << EC2->getDeclName() << EC2->getInitVal().toString(10);
+        Context.Diag1(EC1->getLocation(), diag::note_odr_enumerator)
+            << EC1->getDeclName() << EC1->getInitVal().toString(10);
+      }
+      return false;
+    }
+  }
+
+  if (EC2 != EC2End) {
+    if (Context.Complain) {
+      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+          << Context.ToCtx.getTypeDeclType(D2);
+      Context.Diag2(EC2->getLocation(), diag::note_odr_enumerator)
+          << EC2->getDeclName() << EC2->getInitVal().toString(10);
+      Context.Diag1(D1->getLocation(), diag::note_odr_missing_enumerator);
+    }
+    return false;
+  }
+
+  return true;
+}
+
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     TemplateParameterList *Params1,
+                                     TemplateParameterList *Params2) {
+  if (Params1->size() != Params2->size()) {
+    if (Context.Complain) {
+      Context.Diag2(Params2->getTemplateLoc(),
+                    diag::err_odr_different_num_template_parameters)
+          << Params1->size() << Params2->size();
+      Context.Diag1(Params1->getTemplateLoc(),
+                    diag::note_odr_template_parameter_list);
+    }
+    return false;
+  }
+
+  for (unsigned I = 0, N = Params1->size(); I != N; ++I) {
+    if (Params1->getParam(I)->getKind() != Params2->getParam(I)->getKind()) {
+      if (Context.Complain) {
+        Context.Diag2(Params2->getParam(I)->getLocation(),
+                      diag::err_odr_different_template_parameter_kind);
+        Context.Diag1(Params1->getParam(I)->getLocation(),
+                      diag::note_odr_template_parameter_here);
+      }
+      return false;
+    }
+
+    if (!Context.IsStructurallyEquivalent(Params1->getParam(I),
+                                          Params2->getParam(I))) {
+
+      return false;
+    }
+  }
+
+  return true;
+}
+
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     TemplateTypeParmDecl *D1,
+                                     TemplateTypeParmDecl *D2) {
+  if (D1->isParameterPack() != D2->isParameterPack()) {
+    if (Context.Complain) {
+      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
+          << D2->isParameterPack();
+      Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
+          << D1->isParameterPack();
+    }
+    return false;
+  }
+
+  return true;
+}
+
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     NonTypeTemplateParmDecl *D1,
+                                     NonTypeTemplateParmDecl *D2) {
+  if (D1->isParameterPack() != D2->isParameterPack()) {
+    if (Context.Complain) {
+      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
+          << D2->isParameterPack();
+      Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
+          << D1->isParameterPack();
+    }
+    return false;
+  }
+
+  // Check types.
+  if (!Context.IsStructurallyEquivalent(D1->getType(), D2->getType())) {
+    if (Context.Complain) {
+      Context.Diag2(D2->getLocation(),
+                    diag::err_odr_non_type_parameter_type_inconsistent)
+          << D2->getType() << D1->getType();
+      Context.Diag1(D1->getLocation(), diag::note_odr_value_here)
+          << D1->getType();
+    }
+    return false;
+  }
+
+  return true;
+}
+
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     TemplateTemplateParmDecl *D1,
+                                     TemplateTemplateParmDecl *D2) {
+  if (D1->isParameterPack() != D2->isParameterPack()) {
+    if (Context.Complain) {
+      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
+          << D2->isParameterPack();
+      Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
+          << D1->isParameterPack();
+    }
+    return false;
+  }
+
+  // Check template parameter lists.
+  return IsStructurallyEquivalent(Context, D1->getTemplateParameters(),
+                                  D2->getTemplateParameters());
+}
+
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     ClassTemplateDecl *D1,
+                                     ClassTemplateDecl *D2) {
+  // Check template parameters.
+  if (!IsStructurallyEquivalent(Context, D1->getTemplateParameters(),
+                                D2->getTemplateParameters()))
+    return false;
+
+  // Check the templated declaration.
+  return Context.IsStructurallyEquivalent(D1->getTemplatedDecl(),
+                                          D2->getTemplatedDecl());
+}
+
+/// Determine structural equivalence of two declarations.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     Decl *D1, Decl *D2) {
+  // FIXME: Check for known structural equivalences via a callback of some sort.
+
+  // Check whether we already know that these two declarations are not
+  // structurally equivalent.
+  if (Context.NonEquivalentDecls.count(
+          std::make_pair(D1->getCanonicalDecl(), D2->getCanonicalDecl())))
+    return false;
+
+  // Determine whether we've already produced a tentative equivalence for D1.
+  Decl *&EquivToD1 = Context.TentativeEquivalences[D1->getCanonicalDecl()];
+  if (EquivToD1)
+    return EquivToD1 == D2->getCanonicalDecl();
+
+  // Produce a tentative equivalence D1 <-> D2, which will be checked later.
+  EquivToD1 = D2->getCanonicalDecl();
+  Context.DeclsToCheck.push_back(D1->getCanonicalDecl());
+  return true;
+}
+} // namespace
+
+namespace clang {
+
+DiagnosticBuilder StructuralEquivalenceContext::Diag1(SourceLocation Loc,
+                                                      unsigned DiagID) {
+  assert(Complain && "Not allowed to complain");
+  if (LastDiagFromC2)
+    FromCtx.getDiagnostics().notePriorDiagnosticFrom(ToCtx.getDiagnostics());
+  LastDiagFromC2 = false;
+  return FromCtx.getDiagnostics().Report(Loc, DiagID);
+}
+
+DiagnosticBuilder StructuralEquivalenceContext::Diag2(SourceLocation Loc,
+                                                      unsigned DiagID) {
+  assert(Complain && "Not allowed to complain");
+  if (!LastDiagFromC2)
+    ToCtx.getDiagnostics().notePriorDiagnosticFrom(FromCtx.getDiagnostics());
+  LastDiagFromC2 = true;
+  return ToCtx.getDiagnostics().Report(Loc, DiagID);
+}
+
+Optional<unsigned>
+StructuralEquivalenceContext::findUntaggedStructOrUnionIndex(RecordDecl *Anon) {
+  ASTContext &Context = Anon->getASTContext();
+  QualType AnonTy = Context.getRecordType(Anon);
+
+  RecordDecl *Owner = dyn_cast<RecordDecl>(Anon->getDeclContext());
+  if (!Owner)
+    return None;
+
+  unsigned Index = 0;
+  for (const auto *D : Owner->noload_decls()) {
+    const auto *F = dyn_cast<FieldDecl>(D);
+    if (!F)
+      continue;
+
+    if (F->isAnonymousStructOrUnion()) {
+      if (Context.hasSameType(F->getType(), AnonTy))
+        break;
+      ++Index;
+      continue;
+    }
+
+    // If the field looks like this:
+    // struct { ... } A;
+    QualType FieldType = F->getType();
+    if (const auto *RecType = dyn_cast<RecordType>(FieldType)) {
+      const RecordDecl *RecDecl = RecType->getDecl();
+      if (RecDecl->getDeclContext() == Owner && !RecDecl->getIdentifier()) {
+        if (Context.hasSameType(FieldType, AnonTy))
+          break;
+        ++Index;
+        continue;
+      }
+    }
+  }
+
+  return Index;
+}
+
+bool StructuralEquivalenceContext::IsStructurallyEquivalent(Decl *D1,
+                                                            Decl *D2) {
+  if (!::IsStructurallyEquivalent(*this, D1, D2))
+    return false;
+
+  return !Finish();
+}
+
+bool StructuralEquivalenceContext::IsStructurallyEquivalent(QualType T1,
+                                                            QualType T2) {
+  if (!::IsStructurallyEquivalent(*this, T1, T2))
+    return false;
+
+  return !Finish();
+}
+
+bool StructuralEquivalenceContext::Finish() {
+  while (!DeclsToCheck.empty()) {
+    // Check the next declaration.
+    Decl *D1 = DeclsToCheck.front();
+    DeclsToCheck.pop_front();
+
+    Decl *D2 = TentativeEquivalences[D1];
+    assert(D2 && "Unrecorded tentative equivalence?");
+
+    bool Equivalent = true;
+
+    // FIXME: Switch on all declaration kinds. For now, we're just going to
+    // check the obvious ones.
+    if (RecordDecl *Record1 = dyn_cast<RecordDecl>(D1)) {
+      if (RecordDecl *Record2 = dyn_cast<RecordDecl>(D2)) {
+        // Check for equivalent structure names.
+        IdentifierInfo *Name1 = Record1->getIdentifier();
+        if (!Name1 && Record1->getTypedefNameForAnonDecl())
+          Name1 = Record1->getTypedefNameForAnonDecl()->getIdentifier();
+        IdentifierInfo *Name2 = Record2->getIdentifier();
+        if (!Name2 && Record2->getTypedefNameForAnonDecl())
+          Name2 = Record2->getTypedefNameForAnonDecl()->getIdentifier();
+        if (!::IsStructurallyEquivalent(Name1, Name2) ||
+            !::IsStructurallyEquivalent(*this, Record1, Record2))
+          Equivalent = false;
+      } else {
+        // Record/non-record mismatch.
+        Equivalent = false;
+      }
+    } else if (EnumDecl *Enum1 = dyn_cast<EnumDecl>(D1)) {
+      if (EnumDecl *Enum2 = dyn_cast<EnumDecl>(D2)) {
+        // Check for equivalent enum names.
+        IdentifierInfo *Name1 = Enum1->getIdentifier();
+        if (!Name1 && Enum1->getTypedefNameForAnonDecl())
+          Name1 = Enum1->getTypedefNameForAnonDecl()->getIdentifier();
+        IdentifierInfo *Name2 = Enum2->getIdentifier();
+        if (!Name2 && Enum2->getTypedefNameForAnonDecl())
+          Name2 = Enum2->getTypedefNameForAnonDecl()->getIdentifier();
+        if (!::IsStructurallyEquivalent(Name1, Name2) ||
+            !::IsStructurallyEquivalent(*this, Enum1, Enum2))
+          Equivalent = false;
+      } else {
+        // Enum/non-enum mismatch
+        Equivalent = false;
+      }
+    } else if (TypedefNameDecl *Typedef1 = dyn_cast<TypedefNameDecl>(D1)) {
+      if (TypedefNameDecl *Typedef2 = dyn_cast<TypedefNameDecl>(D2)) {
+        if (!::IsStructurallyEquivalent(Typedef1->getIdentifier(),
+                                        Typedef2->getIdentifier()) ||
+            !::IsStructurallyEquivalent(*this, Typedef1->getUnderlyingType(),
+                                        Typedef2->getUnderlyingType()))
+          Equivalent = false;
+      } else {
+        // Typedef/non-typedef mismatch.
+        Equivalent = false;
+      }
+    } else if (ClassTemplateDecl *ClassTemplate1 =
+                   dyn_cast<ClassTemplateDecl>(D1)) {
+      if (ClassTemplateDecl *ClassTemplate2 = dyn_cast<ClassTemplateDecl>(D2)) {
+        if (!::IsStructurallyEquivalent(ClassTemplate1->getIdentifier(),
+                                        ClassTemplate2->getIdentifier()) ||
+            !::IsStructurallyEquivalent(*this, ClassTemplate1, ClassTemplate2))
+          Equivalent = false;
+      } else {
+        // Class template/non-class-template mismatch.
+        Equivalent = false;
+      }
+    } else if (TemplateTypeParmDecl *TTP1 =
+                   dyn_cast<TemplateTypeParmDecl>(D1)) {
+      if (TemplateTypeParmDecl *TTP2 = dyn_cast<TemplateTypeParmDecl>(D2)) {
+        if (!::IsStructurallyEquivalent(*this, TTP1, TTP2))
+          Equivalent = false;
+      } else {
+        // Kind mismatch.
+        Equivalent = false;
+      }
+    } else if (NonTypeTemplateParmDecl *NTTP1 =
+                   dyn_cast<NonTypeTemplateParmDecl>(D1)) {
+      if (NonTypeTemplateParmDecl *NTTP2 =
+              dyn_cast<NonTypeTemplateParmDecl>(D2)) {
+        if (!::IsStructurallyEquivalent(*this, NTTP1, NTTP2))
+          Equivalent = false;
+      } else {
+        // Kind mismatch.
+        Equivalent = false;
+      }
+    } else if (TemplateTemplateParmDecl *TTP1 =
+                   dyn_cast<TemplateTemplateParmDecl>(D1)) {
+      if (TemplateTemplateParmDecl *TTP2 =
+              dyn_cast<TemplateTemplateParmDecl>(D2)) {
+        if (!::IsStructurallyEquivalent(*this, TTP1, TTP2))
+          Equivalent = false;
+      } else {
+        // Kind mismatch.
+        Equivalent = false;
+      }
+    }
+
+    if (!Equivalent) {
+      // Note that these two declarations are not equivalent (and we already
+      // know about it).
+      NonEquivalentDecls.insert(
+          std::make_pair(D1->getCanonicalDecl(), D2->getCanonicalDecl()));
+      return true;
+    }
+    // FIXME: Check other declaration kinds!
+  }
+
+  return false;
+}
+} // namespace clang
Index: cfe/trunk/lib/AST/CMakeLists.txt
===================================================================
--- cfe/trunk/lib/AST/CMakeLists.txt
+++ cfe/trunk/lib/AST/CMakeLists.txt
@@ -7,6 +7,7 @@
   ASTDiagnostic.cpp
   ASTDumper.cpp
   ASTImporter.cpp
+  ASTStructuralEquivalence.cpp
   ASTTypeTraits.cpp
   AttrImpl.cpp
   CXXInheritance.cpp