[ASTImporter] Support LambdaExprs and improve template support

[a.sidorin]

Summary

Also, a number of style and bug fixes was done:

• ASTImporterTest: added sanity check for source node
• ExternalASTMerger: better lookup for template specializations
• ASTImporter: don't add templated declarations into DeclContext
• ASTImporter: introduce a helper, ImportTemplateArgumentListInfo getting SourceLocations
• ASTImporter: proper set ParmVarDecls for imported FunctionProtoTypeLoc

[xazax.hun]

High level note: clang::TypeAliasDecl has the same issue as CXXRecordDecl, so templated versions should not be added to the DeclContext. Could you add that just for the sake of completeness?

[xazax.hun]

I do not see a test for the following changes:

• ASTImporter: don't add templated declarations into DeclContext
• ASTImporter: proper set ParmVarDecls for imported FunctionProtoTypeLoc

lib/AST/ASTImporter.cpp

2085

Use auto to avoid repeating type.

2100

Use auto to avoid repeating type.

2160

Is the switch above meant to be exhaustive? If so, adding LLVM_UNREACHABLE here might be beneficial.

6138

Use auto to avoid repeting type.

lib/AST/ASTStructuralEquivalence.cpp

1267

The name if this function might be misleading. Only looking at the name I would assume that it is also checking for the templated decl itself not just the identifier and the template parameters. I think it would be nice to either change the functionality or the name.

[a.sidorin]

I do not see a test for the following changes:

• ASTImporter: don't add templated declarations into DeclContext

It's in ASTImporterTest. It checks that the templated decl cannot be found in the enclosing TU.

• ASTImporter: proper set ParmVarDecls for imported FunctionProtoTypeLoc

test/ASTMerge/function-cpp. If you remove the change, Sema will segfault.

[xazax.hun]

In D42301#984713, @a.sidorin wrote:

I do not see a test for the following changes:

• ASTImporter: don't add templated declarations into DeclContext

It's in ASTImporterTest. It checks that the templated decl cannot be found in the enclosing TU.

Oh indeed, it looks likeI missed that, thanks :)

• ASTImporter: proper set ParmVarDecls for imported FunctionProtoTypeLoc

test/ASTMerge/function-cpp. If you remove the change, Sema will segfault.

Neat!

[a.sidorin]

Addressed review comments

[a.sidorin]

In D42301#984695, @xazax.hun wrote:

High level note: clang::TypeAliasDecl has the same issue as CXXRecordDecl, so templated versions should not be added to the DeclContext. Could you add that just for the sake of completeness?

I'd rather create a separate patch - this one is already large enough. Is it OK?

[xazax.hun]

In D42301#986583, @a.sidorin wrote:

I'd rather create a separate patch - this one is already large enough. Is it OK?

Yeah, that is fine by me.

[xazax.hun]

Overall looks good! Thanks for working on this!

lib/AST/ExternalASTMerger.cpp

403

Usually, we expect that Import calls might fail and return nullptrs. If this is special for some reason I think it worth a comment.

[a.sidorin]

Thank you, Gabor. I'll change cast<> to cast_or_null<> to enable the assertion below.

lib/AST/ASTImporter.cpp

void ImportDeclarationNameLoc(const DeclarationNameInfo &From,
                                   DeclarationNameInfo& To);
     void ImportDeclContext(DeclContext *FromDC, bool ForceImport = false);
 
     bool ImportCastPath(CastExpr *E, CXXCastPath &Path);
 
     typedef DesignatedInitExpr::Designator Designator;
     Designator ImportDesignator(const Designator &D);
 
+    Optional<LambdaCapture> ImportLambdaCapture(const LambdaCapture &From);
+
                         
     /// \brief What we should import from the definition.
     enum ImportDefinitionKind { 
       /// \brief Import the default subset of the definition, which might be
       /// nothing (if minimal import is set) or might be everything (if minimal
       /// import is not set).
       IDK_Default,
       /// \brief Import everything.
bool ImportDefinition(VarDecl *From, VarDecl *To,
                           ImportDefinitionKind Kind = IDK_Default);
     bool ImportDefinition(EnumDecl *From, EnumDecl *To,
                           ImportDefinitionKind Kind = IDK_Default);
     bool ImportDefinition(ObjCInterfaceDecl *From, ObjCInterfaceDecl *To,
                           ImportDefinitionKind Kind = IDK_Default);
     bool ImportDefinition(ObjCProtocolDecl *From, ObjCProtocolDecl *To,
                           ImportDefinitionKind Kind = IDK_Default);
     TemplateParameterList *ImportTemplateParameterList(
-                                                 TemplateParameterList *Params);
     TemplateArgument ImportTemplateArgument(const TemplateArgument &From);
     Optional<TemplateArgumentLoc> ImportTemplateArgumentLoc(
         const TemplateArgumentLoc &TALoc);
     bool ImportTemplateArguments(const TemplateArgument *FromArgs,
                                  unsigned NumFromArgs,
                                  SmallVectorImpl<TemplateArgument> &ToArgs);
+
     template <typename InContainerTy>
     bool ImportTemplateArgumentListInfo(const InContainerTy &Container,
                                         TemplateArgumentListInfo &ToTAInfo);
+
+    template<typename InContainerTy>
+    bool ImportTemplateArgumentListInfo(SourceLocation FromLAngleLoc,
+                                        SourceLocation FromRAngleLoc,
+                                        const InContainerTy &Container,
+                                        TemplateArgumentListInfo &Result);
+
+    bool ImportTemplateInformation(FunctionDecl *FromFD, FunctionDecl *ToFD);
+
     bool IsStructuralMatch(RecordDecl *FromRecord, RecordDecl *ToRecord,
                            bool Complain = true);
     bool IsStructuralMatch(VarDecl *FromVar, VarDecl *ToVar,
                            bool Complain = true);
     bool IsStructuralMatch(EnumDecl *FromEnum, EnumDecl *ToRecord);
     bool IsStructuralMatch(EnumConstantDecl *FromEC, EnumConstantDecl *ToEC);
     bool IsStructuralMatch(FunctionTemplateDecl *From,
                            FunctionTemplateDecl *To);
public:
     Expr *VisitCXXUnresolvedConstructExpr(CXXUnresolvedConstructExpr *CE);
     Expr *VisitUnresolvedLookupExpr(UnresolvedLookupExpr *E);
     Expr *VisitExprWithCleanups(ExprWithCleanups *EWC);
     Expr *VisitCXXThisExpr(CXXThisExpr *E);
     Expr *VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *E);
     Expr *VisitCXXPseudoDestructorExpr(CXXPseudoDestructorExpr *E);
     Expr *VisitMemberExpr(MemberExpr *E);
     Expr *VisitCallExpr(CallExpr *E);
+    Expr *VisitLambdaExpr(LambdaExpr *LE);
     Expr *VisitInitListExpr(InitListExpr *E);
     Expr *VisitArrayInitLoopExpr(ArrayInitLoopExpr *E);
     Expr *VisitArrayInitIndexExpr(ArrayInitIndexExpr *E);
     Expr *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *E);
     Expr *VisitCXXNamedCastExpr(CXXNamedCastExpr *E);
     Expr *VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E);
     Expr *VisitTypeTraitExpr(TypeTraitExpr *E);
 
if (CXXRecordDecl *ToCXX = dyn_cast<CXXRecordDecl>(To)) {
     ToData.ImplicitCopyConstructorCanHaveConstParamForNonVBase
       = FromData.ImplicitCopyConstructorCanHaveConstParamForNonVBase;
     ToData.ImplicitCopyAssignmentHasConstParam
       = FromData.ImplicitCopyAssignmentHasConstParam;
     ToData.HasDeclaredCopyConstructorWithConstParam
       = FromData.HasDeclaredCopyConstructorWithConstParam;
     ToData.HasDeclaredCopyAssignmentWithConstParam
       = FromData.HasDeclaredCopyAssignmentWithConstParam;
-    ToData.IsLambda = FromData.IsLambda;
 
     SmallVector<CXXBaseSpecifier *, 4> Bases;
     for (const auto &Base1 : FromCXX->bases()) {
       QualType T = Importer.Import(Base1.getType());
       if (T.isNull())
         return true;
 
       SourceLocation EllipsisLoc;
if (To.isNull() && !FromArgs[I].isNull())
       return true;
     
     ToArgs.push_back(To);
   }
   
   return false;
 }
 
+// We cannot use Optional<> pattern here and below because
+// TemplateArgumentListInfo's operator new is declared as deleted so it cannot
+// be stored in Optional.
 template <typename InContainerTy>
 bool ASTNodeImporter::ImportTemplateArgumentListInfo(
     const InContainerTy &Container, TemplateArgumentListInfo &ToTAInfo) {
   for (const auto &FromLoc : Container) {
     if (auto ToLoc = ImportTemplateArgumentLoc(FromLoc))
       ToTAInfo.addArgument(*ToLoc);
     else
       return true;
   }
   return false;
 }
 
+template <typename InContainerTy>
+bool ASTNodeImporter::ImportTemplateArgumentListInfo(
+    SourceLocation FromLAngleLoc, SourceLocation FromRAngleLoc,
+    const InContainerTy &Container, TemplateArgumentListInfo &Result) {
+  TemplateArgumentListInfo ToTAInfo(Importer.Import(FromLAngleLoc),
+                                    Importer.Import(FromRAngleLoc));
+  if (ImportTemplateArgumentListInfo(Container, ToTAInfo))
+    return true;
+  Result = ToTAInfo;
+  return false;
+}
+
 bool ASTNodeImporter::IsStructuralMatch(RecordDecl *FromRecord, 
                                         RecordDecl *ToRecord, bool Complain) {
   // Eliminate a potential failure point where we attempt to re-import
   // something we're trying to import while completing ToRecord.
   Decl *ToOrigin = Importer.GetOriginalDecl(ToRecord);
   if (ToOrigin) {
     RecordDecl *ToOriginRecord = dyn_cast<RecordDecl>(ToOrigin);
     if (ToOriginRecord)
if (CXXRecordDecl *DCXX = llvm::dyn_cast<CXXRecordDecl>(D)) {
                                             DC, TInfo, Loc,
                                             DCXX->isDependentLambda(),
                                             DCXX->isGenericLambda(),
                                             DCXX->getLambdaCaptureDefault());
         Decl *CDecl = Importer.Import(DCXX->getLambdaContextDecl());
         if (DCXX->getLambdaContextDecl() && !CDecl)
           return nullptr;
         D2CXX->setLambdaMangling(DCXX->getLambdaManglingNumber(), CDecl);
-      } else if (DCXX->isInjectedClassName()) {                                                 
-        // We have to be careful to do a similar dance to the one in                            
-        // Sema::ActOnStartCXXMemberDeclarations                                                
-        CXXRecordDecl *const PrevDecl = nullptr;                                                
-        const bool DelayTypeCreation = true;                                                    
-        D2CXX = CXXRecordDecl::Create(                                                          
-            Importer.getToContext(), D->getTagKind(), DC, StartLoc, Loc,                        
-            Name.getAsIdentifierInfo(), PrevDecl, DelayTypeCreation);                           
-        Importer.getToContext().getTypeDeclType(                                                
-            D2CXX, llvm::dyn_cast<CXXRecordDecl>(DC));                                          
+      } else if (DCXX->isInjectedClassName()) {
+        // We have to be careful to do a similar dance to the one in
+        // Sema::ActOnStartCXXMemberDeclarations
+        CXXRecordDecl *const PrevDecl = nullptr;
+        const bool DelayTypeCreation = true;
+        D2CXX = CXXRecordDecl::Create(
+            Importer.getToContext(), D->getTagKind(), DC, StartLoc, Loc,
+            Name.getAsIdentifierInfo(), PrevDecl, DelayTypeCreation);
+        Importer.getToContext().getTypeDeclType(
+            D2CXX, llvm::dyn_cast<CXXRecordDecl>(DC));
       } else {
         D2CXX = CXXRecordDecl::Create(Importer.getToContext(),
                                       D->getTagKind(),
                                       DC, StartLoc, Loc,
                                       Name.getAsIdentifierInfo());
       }
       D2 = D2CXX;
       D2->setAccess(D->getAccess());
+      D2->setLexicalDeclContext(LexicalDC);
+      if (!DCXX->getDescribedClassTemplate())
+        LexicalDC->addDeclInternal(D2);
 
       Importer.Imported(D, D2);
 
       if (ClassTemplateDecl *FromDescribed =
           DCXX->getDescribedClassTemplate()) {
         ClassTemplateDecl *ToDescribed = cast_or_null<ClassTemplateDecl>(
               Importer.Import(FromDescribed));
         if (!ToDescribed)
if (CXXRecordDecl *DCXX = llvm::dyn_cast<CXXRecordDecl>(D)) {
         D2CXX->setInstantiationOfMemberClass(ToInst, SK);
         D2CXX->getMemberSpecializationInfo()->setPointOfInstantiation(
               Importer.Import(MemberInfo->getPointOfInstantiation()));
       }
 
     } else {
       D2 = RecordDecl::Create(Importer.getToContext(), D->getTagKind(),
                               DC, StartLoc, Loc, Name.getAsIdentifierInfo());
+      D2->setLexicalDeclContext(LexicalDC);
+      LexicalDC->addDeclInternal(D2);
     }
     
     D2->setQualifierInfo(Importer.Import(D->getQualifierLoc()));
-    D2->setLexicalDeclContext(LexicalDC);
-    LexicalDC->addDeclInternal(D2);
     if (D->isAnonymousStructOrUnion())
       D2->setAnonymousStructOrUnion(true);
     if (PrevDecl) {
       // FIXME: do this for all Redeclarables, not just RecordDecls.
       D2->setPreviousDecl(PrevDecl);
     }
   }
   
= EnumConstantDecl::Create(Importer.getToContext(), cast<EnumDecl>(DC), Loc,
                                Init, D->getInitVal());
   ToEnumerator->setAccess(D->getAccess());
   ToEnumerator->setLexicalDeclContext(LexicalDC);
   Importer.Imported(D, ToEnumerator);
   LexicalDC->addDeclInternal(ToEnumerator);
   return ToEnumerator;
 }
 
+bool ASTNodeImporter::ImportTemplateInformation(FunctionDecl *FromFD,
+                                                FunctionDecl *ToFD) {
+  switch (FromFD->getTemplatedKind()) {
+  case FunctionDecl::TK_NonTemplate:
+  case FunctionDecl::TK_FunctionTemplate:
+    break;
+
+  case FunctionDecl::TK_MemberSpecialization: {
+    FunctionDecl *InstFD = cast_or_null<FunctionDecl>(
+          Importer.Import(FromFD->getInstantiatedFromMemberFunction()));
+    if (!InstFD)
+      return true;
+
+    TemplateSpecializationKind TSK = FromFD->getTemplateSpecializationKind();
+    SourceLocation POI = Importer.Import(
+          FromFD->getMemberSpecializationInfo()->getPointOfInstantiation());
+    ToFD->setInstantiationOfMemberFunction(InstFD, TSK);
+    ToFD->getMemberSpecializationInfo()->setPointOfInstantiation(POI);
+    break;
+  }
+
+  case FunctionDecl::TK_FunctionTemplateSpecialization: {
+    auto *FTSInfo = FromFD->getTemplateSpecializationInfo();
+    FunctionTemplateDecl *Template = cast_or_null<FunctionTemplateDecl>(
+        Importer.Import(FTSInfo->getTemplate()));
+    if (!Template)
+      return true;
+    TemplateSpecializationKind TSK = FTSInfo->getTemplateSpecializationKind();
+
+    // Import template arguments.
+    auto TemplArgs = FTSInfo->TemplateArguments->asArray();
+    SmallVector<TemplateArgument, 8> ToTemplArgs;
+    if (ImportTemplateArguments(TemplArgs.data(), TemplArgs.size(),
+                                ToTemplArgs))
+      return true;
+
+    TemplateArgumentList *ToTAList = TemplateArgumentList::CreateCopy(
+          Importer.getToContext(), ToTemplArgs);
+
+    TemplateArgumentListInfo ToTAInfo;
+    const auto *FromTAArgsAsWritten = FTSInfo->TemplateArgumentsAsWritten;
+    if (FromTAArgsAsWritten) {
+      if (ImportTemplateArgumentListInfo(
+              FromTAArgsAsWritten->LAngleLoc, FromTAArgsAsWritten->RAngleLoc,
+              FromTAArgsAsWritten->arguments(), ToTAInfo))
+        return true;
+    }
+
+    SourceLocation POI = Importer.Import(FTSInfo->getPointOfInstantiation());
+
+    ToFD->setFunctionTemplateSpecialization(
+        Template, ToTAList, /* InsertPos= */ nullptr,
+        TSK, FromTAArgsAsWritten ? &ToTAInfo : nullptr, POI);
+    break;
+  }
+
+  case FunctionDecl::TK_DependentFunctionTemplateSpecialization: {
+    auto *FromInfo = FromFD->getDependentSpecializationInfo();
+    UnresolvedSet<8> TemplDecls;
+    unsigned NumTemplates = FromInfo->getNumTemplates();
+    for (unsigned I = 0; I < NumTemplates; I++) {
+      if (auto *ToFTD = cast_or_null<FunctionTemplateDecl>(
+              Importer.Import(FromInfo->getTemplate(I))))
+        TemplDecls.addDecl(ToFTD);
+      else
+        return true;
+    }
+
+    // Import TemplateArgumentListInfo.
+    TemplateArgumentListInfo ToTAInfo;
+    if (ImportTemplateArgumentListInfo(
+            FromInfo->getLAngleLoc(), FromInfo->getRAngleLoc(),
+            llvm::makeArrayRef(FromInfo->getTemplateArgs(),
+                               FromInfo->getNumTemplateArgs()),
+            ToTAInfo))
+      return true;
+
+    ToFD->setDependentTemplateSpecialization(Importer.getToContext(),
+                                             TemplDecls, ToTAInfo);
+    break;
+  }
+  }
+
+  return false;
+}
+
 Decl *ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
   // Import the major distinguishing characteristics of this function.
   DeclContext *DC, *LexicalDC;
   DeclarationName Name;
   SourceLocation Loc;
   NamedDecl *ToD;
   if (ImportDeclParts(D, DC, LexicalDC, Name, ToD, Loc))
     return nullptr;
Decl *ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
   for (auto P : D->parameters()) {
     ParmVarDecl *ToP = cast_or_null<ParmVarDecl>(Importer.Import(P));
     if (!ToP)
       return nullptr;
 
     Parameters.push_back(ToP);
   }
   
-  // Create the imported function.
   TypeSourceInfo *TInfo = Importer.Import(D->getTypeSourceInfo());
+  if (D->getTypeSourceInfo() && !TInfo)
+    return nullptr;
+
+  // Create the imported function.
   FunctionDecl *ToFunction = nullptr;
   SourceLocation InnerLocStart = Importer.Import(D->getInnerLocStart());
   if (CXXConstructorDecl *FromConstructor = dyn_cast<CXXConstructorDecl>(D)) {
     ToFunction = CXXConstructorDecl::Create(Importer.getToContext(),
                                             cast<CXXRecordDecl>(DC),
                                             InnerLocStart,
-                                            NameInfo, T, TInfo, 
+                                            NameInfo, T, TInfo,
                                             FromConstructor->isExplicit(),
                                             D->isInlineSpecified(), 
                                             D->isImplicit(),
                                             D->isConstexpr());
     if (unsigned NumInitializers = FromConstructor->getNumCtorInitializers()) {
       SmallVector<CXXCtorInitializer *, 4> CtorInitializers;
       for (CXXCtorInitializer *I : FromConstructor->inits()) {
         CXXCtorInitializer *ToI =
Decl *ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
   ToFunction->setAccess(D->getAccess());
   ToFunction->setLexicalDeclContext(LexicalDC);
   ToFunction->setVirtualAsWritten(D->isVirtualAsWritten());
   ToFunction->setTrivial(D->isTrivial());
   ToFunction->setPure(D->isPure());
   Importer.Imported(D, ToFunction);
 
   // Set the parameters.
-  for (unsigned I = 0, N = Parameters.size(); I != N; ++I) {
-    Parameters[I]->setOwningFunction(ToFunction);
-    ToFunction->addDeclInternal(Parameters[I]);
+  for (ParmVarDecl *Param : Parameters) {
+    Param->setOwningFunction(ToFunction);
+    ToFunction->addDeclInternal(Param);
   }
   ToFunction->setParams(Parameters);
 
   if (FoundWithoutBody) {
     auto *Recent = const_cast<FunctionDecl *>(
           FoundWithoutBody->getMostRecentDecl());
     ToFunction->setPreviousDecl(Recent);
   }
 
+  // We need to complete creation of FunctionProtoTypeLoc manually with setting
+  // params it refers to.
+  if (TInfo) {
+    if (auto ProtoLoc =
+        TInfo->getTypeLoc().IgnoreParens().getAs<FunctionProtoTypeLoc>()) {
+      for (unsigned I = 0, N = Parameters.size(); I != N; ++I)
+        ProtoLoc.setParam(I, Parameters[I]);
+    }
+  }
+
   if (usedDifferentExceptionSpec) {
     // Update FunctionProtoType::ExtProtoInfo.
     QualType T = Importer.Import(D->getType());
     if (T.isNull())
       return nullptr;
     ToFunction->setType(T);
   }
 
   // Import the body, if any.
   if (Stmt *FromBody = D->getBody()) {
     if (Stmt *ToBody = Importer.Import(FromBody)) {
       ToFunction->setBody(ToBody);
     }
   }
 
   // FIXME: Other bits to merge?
 
+  // If it is a template, import all related things.
+  if (ImportTemplateInformation(D, ToFunction))
+    return nullptr;
+
   // Add this function to the lexical context.
+  // NOTE: If the function is templated declaration, it should be not added into
+  // LexicalDC. But described template is imported during import of
+  // FunctionTemplateDecl (it happens later). So, we use source declaration
+  // to determine if we should add the result function.
+  if (!D->getDescribedFunctionTemplate())
     LexicalDC->addDeclInternal(ToFunction);
 
   if (auto *FromCXXMethod = dyn_cast<CXXMethodDecl>(D))
     ImportOverrides(cast<CXXMethodDecl>(ToFunction), FromCXXMethod);
 
   return ToFunction;
 }
 
 Decl *ASTNodeImporter::VisitCXXMethodDecl(CXXMethodDecl *D) {
Decl *ASTNodeImporter::VisitParmVarDecl(ParmVarDecl *D) {
   } else if (D->hasDefaultArg()) {
     FromDefArg = D->getDefaultArg();
     ToDefArg = Importer.Import(FromDefArg);
     ToParm->setDefaultArg(ToDefArg);
   }
   if (FromDefArg && !ToDefArg)
     return nullptr;
 
+  if (D->isObjCMethodParameter()) {
+    ToParm->setObjCMethodScopeInfo(D->getFunctionScopeIndex());
+    ToParm->setObjCDeclQualifier(D->getObjCDeclQualifier());
+  } else {
+    ToParm->setScopeInfo(D->getFunctionScopeDepth(),
+                         D->getFunctionScopeIndex());
+  }
+
   if (D->isUsed())
     ToParm->setIsUsed();
 
   return Importer.Imported(D, ToParm);
 }
 
 Decl *ASTNodeImporter::VisitObjCMethodDecl(ObjCMethodDecl *D) {
   // Import the major distinguishing characteristics of a method.
if (!ConflictingDecls.empty()) {
                                          ConflictingDecls.data(), 
                                          ConflictingDecls.size());
     }
     
     if (!Name)
       return nullptr;
   }
 
-  CXXRecordDecl *DTemplated = D->getTemplatedDecl();
-  
+  CXXRecordDecl *FromTemplated = D->getTemplatedDecl();
   // Create the declaration that is being templated.
-  CXXRecordDecl *D2Templated = cast_or_null<CXXRecordDecl>(
-        Importer.Import(DTemplated));
-  if (!D2Templated)
+  CXXRecordDecl *ToTemplated = cast_or_null<CXXRecordDecl>(
+        Importer.Import(FromTemplated));
+  if (!ToTemplated)
     return nullptr;
 
   // Resolve possible cyclic import.
   if (Decl *AlreadyImported = Importer.GetAlreadyImportedOrNull(D))
     return AlreadyImported;
 
   // Create the class template declaration itself.
-  TemplateParameterList *TemplateParams
-    = ImportTemplateParameterList(D->getTemplateParameters());
+  TemplateParameterList *TemplateParams =
+      ImportTemplateParameterList(D->getTemplateParameters());
   if (!TemplateParams)
     return nullptr;
 
   ClassTemplateDecl *D2 = ClassTemplateDecl::Create(Importer.getToContext(), DC, 
                                                     Loc, Name, TemplateParams, 
-                                                    D2Templated);
-  D2Templated->setDescribedClassTemplate(D2);    
+                                                    ToTemplated);
+  ToTemplated->setDescribedClassTemplate(D2);
   
   D2->setAccess(D->getAccess());
   D2->setLexicalDeclContext(LexicalDC);
   LexicalDC->addDeclInternal(D2);
   
   // Note the relationship between the class templates.
   Importer.Imported(D, D2);
-  Importer.Imported(DTemplated, D2Templated);
+  Importer.Imported(FromTemplated, ToTemplated);
 
-  if (DTemplated->isCompleteDefinition() &&
-      !D2Templated->isCompleteDefinition()) {
+  if (FromTemplated->isCompleteDefinition() &&
+      !ToTemplated->isCompleteDefinition()) {
     // FIXME: Import definition!
   }
   
   return D2;
 }
 
 Decl *ASTNodeImporter::VisitClassTemplateSpecializationDecl(
                                           ClassTemplateSpecializationDecl *D) {
Decl *ASTNodeImporter::VisitClassTemplateSpecializationDecl(
   } else {
     // Create a new specialization.
     if (ClassTemplatePartialSpecializationDecl *PartialSpec =
         dyn_cast<ClassTemplatePartialSpecializationDecl>(D)) {
 
       // Import TemplateArgumentListInfo
       TemplateArgumentListInfo ToTAInfo;
       auto &ASTTemplateArgs = *PartialSpec->getTemplateArgsAsWritten();
-      for (unsigned I = 0, E = ASTTemplateArgs.NumTemplateArgs; I < E; ++I) {
-        if (auto ToLoc = ImportTemplateArgumentLoc(ASTTemplateArgs[I]))
-          ToTAInfo.addArgument(*ToLoc);
-        else
-          return nullptr;
-      }
+      if (ImportTemplateArgumentListInfo(ASTTemplateArgs.arguments(), ToTAInfo))
 
       QualType CanonInjType = Importer.Import(
             PartialSpec->getInjectedSpecializationType());
       if (CanonInjType.isNull())
         return nullptr;
       CanonInjType = CanonInjType.getCanonicalType();
 
       TemplateParameterList *ToTPList = ImportTemplateParameterList(
Expr *ASTNodeImporter::VisitDeclRefExpr(DeclRefExpr *E) {
   QualType T = Importer.Import(E->getType());
   if (T.isNull())
     return nullptr;
 
 
   TemplateArgumentListInfo ToTAInfo;
   TemplateArgumentListInfo *ResInfo = nullptr;
   if (E->hasExplicitTemplateArgs()) {
-    for (const auto &FromLoc : E->template_arguments()) {
-      if (auto ToTALoc = ImportTemplateArgumentLoc(FromLoc))
-        ToTAInfo.addArgument(*ToTALoc);
-      else
-        return nullptr;
-    }
+    if (ImportTemplateArgumentListInfo(E->template_arguments(), ToTAInfo))
     ResInfo = &ToTAInfo;
   }
 
   DeclRefExpr *DRE = DeclRefExpr::Create(Importer.getToContext(), 
                                          Importer.Import(E->getQualifierLoc()),
                                    Importer.Import(E->getTemplateKeywordLoc()),
                                          ToD,
                                         E->refersToEnclosingVariableOrCapture(),
if (!E->isImplicitAccess()) {
     if (!Base)
       return nullptr;
   }
 
   QualType BaseType = Importer.Import(E->getBaseType());
   if (BaseType.isNull())
     return nullptr;
 
-  TemplateArgumentListInfo ToTAInfo(Importer.Import(E->getLAngleLoc()),
-                                    Importer.Import(E->getRAngleLoc()));
-  TemplateArgumentListInfo *ResInfo = nullptr;
+  TemplateArgumentListInfo ToTAInfo, *ResInfo = nullptr;
   if (E->hasExplicitTemplateArgs()) {
-    if (ImportTemplateArgumentListInfo(E->template_arguments(), ToTAInfo))
+    if (ImportTemplateArgumentListInfo(E->getLAngleLoc(), E->getRAngleLoc(),
+                                       E->template_arguments(), ToTAInfo))
       return nullptr;
     ResInfo = &ToTAInfo;
   }
 
   DeclarationName Name = Importer.Import(E->getMember());
   if (!E->getMember().isEmpty() && Name.isEmpty())
     return nullptr;
 
Expr *ASTNodeImporter::VisitUnresolvedLookupExpr(UnresolvedLookupExpr *E) {
   UnresolvedSet<8> ToDecls;
   for (Decl *D : E->decls()) {
     if (NamedDecl *To = cast_or_null<NamedDecl>(Importer.Import(D)))
       ToDecls.addDecl(To);
     else
       return nullptr;
   }
 
-  TemplateArgumentListInfo ToTAInfo(Importer.Import(E->getLAngleLoc()),
-                                    Importer.Import(E->getRAngleLoc()));
-  TemplateArgumentListInfo *ResInfo = nullptr;
+  TemplateArgumentListInfo ToTAInfo, *ResInfo = nullptr;
   if (E->hasExplicitTemplateArgs()) {
-    if (ImportTemplateArgumentListInfo(E->template_arguments(), ToTAInfo))
+    if (ImportTemplateArgumentListInfo(E->getLAngleLoc(), E->getRAngleLoc(),
+                                       E->template_arguments(), ToTAInfo))
       return nullptr;
     ResInfo = &ToTAInfo;
   }
 
   if (ResInfo || E->getTemplateKeywordLoc().isValid())
     return UnresolvedLookupExpr::Create(
         Importer.getToContext(), NamingClass,
         Importer.Import(E->getQualifierLoc()),
for (unsigned ai = 0, ae = NumArgs; ai != ae; ++ai)
     ToArgs_Copied[ai] = ToArgs[ai];
 
   return new (Importer.getToContext())
     CallExpr(Importer.getToContext(), ToCallee, 
              llvm::makeArrayRef(ToArgs_Copied, NumArgs), T, E->getValueKind(),
              Importer.Import(E->getRParenLoc()));
 }
 
+Optional<LambdaCapture>
+ASTNodeImporter::ImportLambdaCapture(const LambdaCapture &From) {
+  VarDecl *Var = nullptr;
+  if (From.capturesVariable()) {
+    Var = cast_or_null<VarDecl>(Importer.Import(From.getCapturedVar()));
+    if (!Var)
+      return None;
+  }
+
+  return LambdaCapture(Importer.Import(From.getLocation()), From.isImplicit(),
+                       From.getCaptureKind(), Var,
+                       From.isPackExpansion()
+                         ? Importer.Import(From.getEllipsisLoc())
+                         : SourceLocation());
+}
+
+Expr *ASTNodeImporter::VisitLambdaExpr(LambdaExpr *LE) {
+  CXXRecordDecl *FromClass = LE->getLambdaClass();
+  CXXRecordDecl *ToClass = dyn_cast_or_null<CXXRecordDecl>(
+        Importer.Import(FromClass));
+  if (!ToClass)
+    return nullptr;
+
+  // NOTE: lambda classes are created with BeingDefined flag set up.
+  // It means that ImportDefinition doesn't work for them and we should fill it
+  // manually.
+  if (ToClass->isBeingDefined()) {
+    for (auto FromField : FromClass->fields()) {
+      auto *ToField = cast_or_null<FieldDecl>(Importer.Import(FromField));
+      if (!ToField)
+        return nullptr;
+    }
+  }
+
+  auto *ToCallOp = dyn_cast_or_null<CXXMethodDecl>(
+        Importer.Import(LE->getCallOperator()));
+  if (!ToCallOp)
+    return nullptr;
+
+  ToClass->completeDefinition();
+
+  unsigned NumCaptures = LE->capture_size();
+  SmallVector<LambdaCapture, 8> Captures;
+  Captures.reserve(NumCaptures);
+  for (const auto &FromCapture : LE->captures()) {
+    if (auto ToCapture = ImportLambdaCapture(FromCapture))
+      Captures.push_back(*ToCapture);
+    else
+      return nullptr;
+  }
+
+  SmallVector<Expr *, 8> InitCaptures(NumCaptures);
+  if (ImportContainerChecked(LE->capture_inits(), InitCaptures))
+    return nullptr;
+
+  return LambdaExpr::Create(Importer.getToContext(), ToClass,
+                            Importer.Import(LE->getIntroducerRange()),
+                            LE->getCaptureDefault(),
+                            Importer.Import(LE->getCaptureDefaultLoc()),
+                            Captures,
+                            LE->hasExplicitParameters(),
+                            LE->hasExplicitResultType(),
+                            InitCaptures,
+                            Importer.Import(LE->getLocEnd()),
+                            LE->containsUnexpandedParameterPack());
+}
+
+
 Expr *ASTNodeImporter::VisitInitListExpr(InitListExpr *ILE) {
   QualType T = Importer.Import(ILE->getType());
   if (T.isNull())
     return nullptr;
 
   llvm::SmallVector<Expr *, 4> Exprs(ILE->getNumInits());
   if (ImportContainerChecked(ILE->inits(), Exprs))
     return nullptr;

lib/AST/ASTStructuralEquivalence.cpp

 bool StructuralEquivalenceContext::IsStructurallyEquivalent(QualType T1,
                                                             QualType T2) {
   if (!::IsStructurallyEquivalent(*this, T1, T2))
     return false;
 
   return !Finish();
 }
 
+static bool IsTemplateDeclStructurallyEquivalent(
+    StructuralEquivalenceContext &Ctx, TemplateDecl *D1, TemplateDecl *D2) {
+  if (!IsStructurallyEquivalent(D1->getIdentifier(), D2->getIdentifier()))
+    return false;
+  if (!D1->getIdentifier()) // Special name
+    if (D1->getNameAsString() != D2->getNameAsString())
+      return false;
+  return IsStructurallyEquivalent(Ctx, D1->getTemplateParameters(),
+                                  D2->getTemplateParameters());
+}
+
 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?");
if (RecordDecl *Record1 = dyn_cast<RecordDecl>(D1)) {
           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))
+        if (!::IsTemplateDeclStructurallyEquivalent(*this, ClassTemplate1,
+                                                    ClassTemplate2) ||
+            !::IsStructurallyEquivalent(*this, ClassTemplate1,
+                                        ClassTemplate2) ||
+            !::IsStructurallyEquivalent(
+              *this, ClassTemplate1->getTemplatedDecl(),
+              ClassTemplate2->getTemplatedDecl()))
+          Equivalent = false;
+      } else {
+        // Class template/non-class-template mismatch.
+        Equivalent = false;
+      }
+    } else if (FunctionTemplateDecl *FunctionTemplate1 =
+               dyn_cast<FunctionTemplateDecl>(D1)) {
+      if (FunctionTemplateDecl *FunctionTemplate2 =
+          dyn_cast<FunctionTemplateDecl>(D2)) {
+        if (!::IsTemplateDeclStructurallyEquivalent(*this, FunctionTemplate1,
+                                                    FunctionTemplate2) ||
+            !::IsStructurallyEquivalent(*this, FunctionTemplate1,
+                                        FunctionTemplate2) ||
+            !::IsStructurallyEquivalent(
+              *this, FunctionTemplate1->getTemplatedDecl()->getType(),
+              FunctionTemplate2->getTemplatedDecl()->getType()))
           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)) {

lib/AST/ExternalASTMerger.cpp

 //  ASTs from several different ASTContext/FileManager pairs
 //
 //===----------------------------------------------------------------------===//
 
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclTemplate.h"
 #include "clang/AST/ExternalASTMerger.h"
 
 using namespace clang;
 
 namespace {
 
 template <typename T> struct Source {
   T t;
for (OriginMap::iterator OI = Origins.begin(), OE = Origins.end(); OI != OE; ) {
     }
     if (Erase)
       OI = Origins.erase(OI);
     else
       ++OI;
   }
 }
 
+template <typename DeclTy>
+static bool importSpecializations(DeclTy *D, ASTImporter *Importer) {
+  for (auto *Spec : D->specializations())
+    if (!Importer->Import(Spec))
+      return true;
+  return false;
+}
+
+/// Imports specializations from template declarations that can be specialized.
+static bool importSpecializationsIfNeeded(Decl *D, ASTImporter *Importer) {
+  if (!isa<TemplateDecl>(D))
+    return false;
+  if (auto *FunctionTD = dyn_cast<FunctionTemplateDecl>(D))
+    return importSpecializations(FunctionTD, Importer);
+  else if (auto *ClassTD = dyn_cast<ClassTemplateDecl>(D))
+    return importSpecializations(ClassTD, Importer);
+  else if (auto *VarTD = dyn_cast<VarTemplateDecl>(D))
+    return importSpecializations(VarTD, Importer);
+  return false;
+}
+
 bool ExternalASTMerger::FindExternalVisibleDeclsByName(const DeclContext *DC,
                                                        DeclarationName Name) {
   llvm::SmallVector<NamedDecl *, 1> Decls;
   llvm::SmallVector<Candidate, 4> Candidates;
 
   auto FilterFoundDecl = [&Candidates](const Candidate &C) {
    if (!HasDeclOfSameType(Candidates, C))
      Candidates.push_back(C);
ForEachMatchingDC(DC, [&](ASTImporter &Forward, ASTImporter &Reverse,
     return false;
   });
 
   if (Candidates.empty())
     return false;
 
   Decls.reserve(Candidates.size());
   for (const Candidate &C : Candidates) {
-    NamedDecl *d = cast<NamedDecl>(C.second->Import(C.first.get()));
-    assert(d);
-    Decls.push_back(d);
+    Decl *LookupRes = C.first.get();
+    ASTImporter *Importer = C.second;
+    NamedDecl *ND = cast<NamedDecl>(Importer->Import(LookupRes));
+    assert(ND);
+    // If we don't import specialization, they are not available via lookup
+    // because the lookup result is imported TemplateDecl and it does not
+    // reference its specializations until they are imported explicitly.
+    bool IsSpecImportFailed =
+        importSpecializationsIfNeeded(LookupRes, Importer);
+    assert(!IsSpecImportFailed);
+    Decls.push_back(ND);
   }
   SetExternalVisibleDeclsForName(DC, Name, Decls);
   return true;
 }
 
 void ExternalASTMerger::FindExternalLexicalDecls(
     const DeclContext *DC, llvm::function_ref<bool(Decl::Kind)> IsKindWeWant,
     SmallVectorImpl<Decl *> &Result) {

test/ASTMerge/class-template/Inputs/class-template1.cpp

 template<typename T>
-struct X0;
+struct X0 {
+  T getValue(T arg) { return arg; }
+};
 
 template<int I>
 struct X1;
 
 template<int I>
 struct X2;
 
 template<int I>

 
 extern X0<int> *x0i;
 extern X0<long> *x0l;
 extern X0<float> *x0r;
 
 template<>
 struct X0<char> {
   int member;
+  char getValue(char ch) { return static_cast<char>(member); }
 };
 
 template<>
 struct X0<wchar_t> {
   int member;
 };

test/ASTMerge/class-template/Inputs/class-template2.cpp

 template<class T>
-struct X0;
+struct X0 {
+  T getValue(T arg);
+};
 
 template<int I>
 struct X1;
 
 template<long I>
 struct X2;
 
 template<typename>

test/ASTMerge/class-template/test.cpp

-// RUN: %clang_cc1 -emit-pch -o %t.1.ast %S/Inputs/class-template1.cpp
-// RUN: %clang_cc1 -emit-pch -o %t.2.ast %S/Inputs/class-template2.cpp
-// RUN: not %clang_cc1 -ast-merge %t.1.ast -ast-merge %t.2.ast -fsyntax-only %s 2>&1 | FileCheck %s
+// RUN: %clang_cc1 -std=c++1z -emit-pch -o %t.1.ast %S/Inputs/class-template1.cpp
+// RUN: %clang_cc1 -std=c++1z -emit-pch -o %t.2.ast %S/Inputs/class-template2.cpp
+// RUN: not %clang_cc1 -std=c++1z  -ast-merge %t.1.ast -ast-merge %t.2.ast -fsyntax-only %s 2>&1 | FileCheck %s
 
-// CHECK: class-template1.cpp:7:14: error: non-type template parameter declared with incompatible types in different translation units ('int' vs. 'long')
-// CHECK: class-template2.cpp:7:15: note: declared here with type 'long'
+static_assert(sizeof(X0<char>().getValue(1)) == sizeof(char));
+static_assert(sizeof(X0<int>().getValue(1)) == sizeof(int));
 
-// CHECK: class-template1.cpp:10:14: error: template parameter has different kinds in different translation units
-// CHECK: class-template2.cpp:10:10: note: template parameter declared here
+// CHECK: class-template1.cpp:9:14: error: non-type template parameter declared with incompatible types in different translation units ('int' vs. 'long')
+// CHECK: class-template2.cpp:9:15: note: declared here with type 'long'
 
-// CHECK: class-template1.cpp:16:23: error: non-type template parameter declared with incompatible types in different translation units ('long' vs. 'int')
-// CHECK: class-template2.cpp:16:23: note: declared here with type 'int'
+// CHECK: class-template1.cpp:12:14: error: template parameter has different kinds in different translation units
+// CHECK: class-template2.cpp:12:10: note: template parameter declared here
 
-// CHECK: class-template1.cpp:19:10: error: template parameter has different kinds in different translation units
-// CHECK: class-template2.cpp:19:10: note: template parameter declared here
+// CHECK: class-template1.cpp:18:23: error: non-type template parameter declared with incompatible types in different translation units ('long' vs. 'int')
+// CHECK: class-template2.cpp:18:23: note: declared here with type 'int'
 
-// CHECK: class-template2.cpp:25:20: error: external variable 'x0r' declared with incompatible types in different translation units ('X0<double> *' vs. 'X0<float> *')
-// CHECK: class-template1.cpp:24:19: note: declared here with type 'X0<float> *'
+// CHECK: class-template1.cpp:21:10: error: template parameter has different kinds in different translation units
+// CHECK: class-template2.cpp:21:10: note: template parameter declared here
 
-// CHECK: class-template1.cpp:32:8: warning: type 'X0<wchar_t>' has incompatible definitions in different translation units
-// CHECK: class-template1.cpp:33:7: note: field 'member' has type 'int' here
-// CHECK: class-template2.cpp:34:9: note: field 'member' has type 'float' here
+// CHECK: class-template2.cpp:27:20: error: external variable 'x0r' declared with incompatible types in different translation units ('X0<double> *' vs. 'X0<float> *')
+// CHECK: class-template1.cpp:26:19: note: declared here with type 'X0<float> *'
+
+// CHECK: class-template1.cpp:35:8: warning: type 'X0<wchar_t>' has incompatible definitions in different translation units
+// CHECK: class-template1.cpp:36:7: note: field 'member' has type 'int' here
+// CHECK: class-template2.cpp:36:9: note: field 'member' has type 'float' here
 
 // CHECK: 1 warning and 5 errors generated.
+// CHECK-NOT: static_assert

test/ASTMerge/exprs-cpp/Inputs/exprs3.cpp

 
 void useTemplateType() {
   testTemplateTypeParmType<char>(4);
 }
 
 const bool ExpressionTrait = __is_lvalue_expr(1);
 const unsigned ArrayRank = __array_rank(int[10][20]);
 const unsigned ArrayExtent = __array_extent(int[10][20], 1);
+
+constexpr int testLambdaAdd(int toAdd) {
+  const int Captured1 = 1, Captured2 = 2;
+  constexpr auto LambdaAdd = [Captured1, Captured2](int k) -> int {
+    return Captured1 + Captured2 + k;
+  };
+  return LambdaAdd(toAdd);
+}
+
+template<typename T>
+struct TestLambdaTemplate {
+  T i, j;
+  TestLambdaTemplate(T i, const T &j) : i(i), j(j) {}
+  T testLambda(T k) {
+    return [this](T k) -> decltype(auto) { return i + j + k; }(k);
+  }
+};

test/ASTMerge/exprs-cpp/test.cpp

 static_assert(bval1 == true);
 static_assert(bval2 == false);
 
 static_assert(ExpressionTrait == false);
 
 static_assert(ArrayRank == 2);
 static_assert(ArrayExtent == 20);
 
+static_assert(testLambdaAdd(3) == 6);
+
 void testImport(int *x, const S1 &cs1, S1 &s1) {
   testNewThrowDelete();
   testArrayElement(nullptr, 12);
   testTernaryOp(0, 1, 2);
   testConstCast(cs1);
   testStaticCast(s1);
   testReinterpretCast(s1);
   testDynamicCast(s1);
   testScalarInit(42);
   testOffsetOf();
   testDefaultArg(12);
   testDefaultArg();
   testDefaultArgExpr();
   useTemplateType();
+  TestLambdaTemplate<int>(1, 2).testLambda(3);
 }

test/ASTMerge/function-cpp/Inputs/function-1.cpp

+
+template<typename T> constexpr T add(T arg1, T arg2) {
+  return arg1 + arg2;
+}
+
+template<> constexpr int add(int arg1, int arg2) {
+  return arg1 + arg2 + 2;
+}

test/ASTMerge/function-cpp/test.cpp

+// RUN: %clang_cc1 -std=c++1z -emit-pch -o %t.1.ast %S/Inputs/function-1.cpp
+// RUN: %clang_cc1 -std=c++1z  -ast-merge %t.1.ast -fsyntax-only %s 2>&1 | FileCheck %s
+// XFAIL: *
+
+static_assert(add(1, 2) == 5);
+
+// FIXME: support of templated function overload is still not implemented.
+static_assert(add('\1', '\2') == 3);
+
+// CHECK-NOT: static_assert

test/Import/template-specialization/Inputs/T.cpp

 template <typename T> struct A {
 };
 
 template <> struct A<int> {
   struct B {
     int f;
   };
 };
 
 template <> struct A<bool> {
   struct B {
     int g;
   };
 };
+
+
+template <typename T> constexpr int f() { return 0; }
+template <> constexpr int f<int>() { return 4; }

test/Import/template-specialization/test.cpp

 // RUN: clang-import-test -import %S/Inputs/T.cpp -expression %s
-// XFAIL: *
+
 void expr() {
   A<int>::B b1;
   A<bool>::B b2;
   b1.f + b2.g;
 }
+
+static_assert(f<char>() == 0, "");
+static_assert(f<int>() == 4, "");

unittests/AST/ASTImporterTest.cpp

 //===- unittest/AST/ASTImporterTest.cpp - AST node import test ------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Tests for the correct import of AST nodes from one AST context to another.
 //
 //===----------------------------------------------------------------------===//
 
+#include "MatchVerifier.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTImporter.h"
-#include "MatchVerifier.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Tooling/Tooling.h"
 #include "gtest/gtest.h"
 
 namespace clang {
 namespace ast_matchers {
 
testImport(const std::string &FromCode, const ArgVector &FromArgs,
   DeclarationName ImportDeclName(ImportedII);
   SmallVector<NamedDecl *, 4> FoundDecls;
   FromCtx.getTranslationUnitDecl()->localUncachedLookup(
         ImportDeclName, FoundDecls);
 
   if (FoundDecls.size() != 1)
     return testing::AssertionFailure() << "Multiple declarations were found!";
 
-  auto Imported = Importer.Import(*FoundDecls.begin());
+  // Sanity check: the node being imported should match in the same way as
+  // the result node.
+  EXPECT_TRUE(Verifier.match(FoundDecls.front(), AMatcher));
+
+  auto Imported = Importer.Import(FoundDecls.front());
   if (!Imported)
     return testing::AssertionFailure() << "Import failed, nullptr returned!";
 
   // This should dump source locations and assert if some source locations
   // were not imported.
   SmallString<1024> ImportChecker;
   llvm::raw_svector_ostream ToNothing(ImportChecker);
   ToCtx.getTranslationUnitDecl()->print(ToNothing);
testImport("typedef int T;"
              Lang_CXX, "", Lang_CXX, Verifier,
              functionDecl(has(compoundStmt(has(
                  callExpr(has(cxxPseudoDestructorExpr())))))));
 }
 
 TEST(ImportDecl, ImportUsingDecl) {
   MatchVerifier<Decl> Verifier;
   testImport("namespace foo { int bar; }"
-             "int declToImport(){ using foo::bar; }",
+             "void declToImport() { using foo::bar; }",
              Lang_CXX, "", Lang_CXX, Verifier,
              functionDecl(
                has(
                  compoundStmt(
                    has(
                      declStmt(
                        has(
                          usingDecl())))))));
TEST(ImportExpr, ImportUnresolvedLookupExpr) {
   MatchVerifier<Decl> Verifier;
   testImport("template<typename T> int foo();"
              "template <typename T> void declToImport() {"
              "  ::foo<T>;"
              "  ::template foo<T>;"
              "}"
              "void instantiate() { declToImport<int>(); }",
              Lang_CXX, "", Lang_CXX, Verifier,
-             functionTemplateDecl(has(functionDecl(has(
-                 compoundStmt(has(unresolvedLookupExpr())))))));
+             functionTemplateDecl(has(functionDecl(
+                 has(compoundStmt(has(unresolvedLookupExpr())))))));
 }
 
 TEST(ImportExpr, ImportCXXUnresolvedConstructExpr) {
   MatchVerifier<Decl> Verifier;
-  testImport("template <typename T> class C { T t; };"
+  testImport("template <typename T> struct C { T t; };"
              "template <typename T> void declToImport() {"
              "  C<T> d;"
              "  d.t = T();"
              "}"
              "void instantiate() { declToImport<int>(); }",
              Lang_CXX, "", Lang_CXX, Verifier,
              functionTemplateDecl(has(functionDecl(has(compoundStmt(has(
                  binaryOperator(has(cxxUnresolvedConstructExpr())))))))));
-  testImport("template <typename T> class C { T t; };"
+  testImport("template <typename T> struct C { T t; };"
              "template <typename T> void declToImport() {"
              "  C<T> d;"
              "  (&d)->t = T();"
              "}"
              "void instantiate() { declToImport<int>(); }",
              Lang_CXX, "", Lang_CXX, Verifier,
              functionTemplateDecl(has(functionDecl(has(compoundStmt(has(
                  binaryOperator(has(cxxUnresolvedConstructExpr())))))))));
 }
 
+/// Check that function "declToImport()" (which is the templated function
+/// for corresponding FunctionTemplateDecl) is not added into DeclContext.
+/// Same for class template declarations.
+TEST(ImportDecl, ImportTemplatedDeclForTemplate) {
+  MatchVerifier<Decl> Verifier;
+  testImport("template <typename T> void declToImport() { T a = 1; }"
+             "void instantiate() { declToImport<int>(); }",
+             Lang_CXX, "", Lang_CXX, Verifier,
+             functionTemplateDecl(hasAncestor(translationUnitDecl(
+                 unless(has(functionDecl(hasName("declToImport"))))))));
+  testImport("template <typename T> struct declToImport { T t; };"
+             "void instantiate() { declToImport<int>(); }",
+             Lang_CXX, "", Lang_CXX, Verifier,
+             classTemplateDecl(hasAncestor(translationUnitDecl(
+                 unless(has(cxxRecordDecl(hasName("declToImport"))))))));
+}
+
 } // end namespace ast_matchers
 } // end namespace clang