[ASTImporter] Import described template (if any) of function.

[balazske]

Summary

When a function is imported, check if it has a described template.
The name lookup is corrected to find the templated entity in this case.
The described template of the function is imported too.

[a_sidorin]

Hello Balasz,
This looks mostly good but I have a question inline.

lib/AST/ASTImporter.cpp

2755

The function template should be already set after getDescribedFunctionTemplate() is imported in VisitFunctionTemplateDecl(). Are there still cases not covered by this?

[balazske]

lib/AST/ASTImporter.cpp

2755

Yes this call can be omitted. But check of return value of Import is needed (the current code is not good: nullptr is not accepted by dyn_cast).

[balazske]

• Removed setDescribedFunctionTemplate call.

[a_sidorin]

LGTM.

lib/AST/ASTImporter.cpp

Decl *ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
   SourceLocation Loc;
   NamedDecl *ToD;
   if (ImportDeclParts(D, DC, LexicalDC, Name, ToD, Loc))
     return nullptr;
   if (ToD)
     return ToD;
 
   const FunctionDecl *FoundByLookup = nullptr;
+  FunctionTemplateDecl *FromFT = D->getDescribedFunctionTemplate();
 
   // If this is a function template specialization, then try to find the same
   // existing specialization in the "to" context. The localUncachedLookup
   // below will not find any specialization, but would find the primary
   // template; thus, we have to skip normal lookup in case of specializations.
   // FIXME handle member function templates (TK_MemberSpecialization) similarly?
   if (D->getTemplatedKind() ==
       FunctionDecl::TK_FunctionTemplateSpecialization) {
else if (!LexicalDC->isFunctionOrMethod()) {
     SmallVector<NamedDecl *, 4> ConflictingDecls;
     unsigned IDNS = Decl::IDNS_Ordinary | Decl::IDNS_OrdinaryFriend;
     SmallVector<NamedDecl *, 2> FoundDecls;
     DC->getRedeclContext()->localUncachedLookup(Name, FoundDecls);
     for (auto *FoundDecl : FoundDecls) {
       if (!FoundDecl->isInIdentifierNamespace(IDNS))
         continue;
 
+      // If template was found, look at the templated function.
+      if (FromFT) {
+        if (auto *Template = dyn_cast<FunctionTemplateDecl>(FoundDecl))
+          FoundDecl = Template->getTemplatedDecl();
+        else
+          continue;
+      }
+
       if (auto *FoundFunction = dyn_cast<FunctionDecl>(FoundDecl)) {
         if (FoundFunction->hasExternalFormalLinkage() &&
             D->hasExternalFormalLinkage()) {
           if (IsStructuralMatch(D, FoundFunction)) {
             const FunctionDecl *Definition = nullptr;
             if (D->doesThisDeclarationHaveABody() &&
                 FoundFunction->hasBody(Definition)) {
               return Importer.MapImported(
Decl *ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
   if (usedDifferentExceptionSpec) {
     // Update FunctionProtoType::ExtProtoInfo.
     QualType T = Importer.Import(D->getType());
     if (T.isNull())
       return nullptr;
     ToFunction->setType(T);
   }
 
+  // Import the describing template function, if any.
+  if (FromFT)
+    if (!Importer.Import(FromFT))
+      return nullptr;
+
   if (D->doesThisDeclarationHaveABody()) {
     if (Stmt *FromBody = D->getBody()) {
       if (Stmt *ToBody = Importer.Import(FromBody)) {
         ToFunction->setBody(ToBody);
       }
     }
   }
 

unittests/AST/ASTImporterTest.cpp

TEST_P(ASTImporterTestBase,
   EXPECT_TRUE(ToTemplated);
   auto ToTU = ToTemplated->getTranslationUnitDecl();
   auto ToFT =
       FirstDeclMatcher<ClassTemplateDecl>().match(ToTU, classTemplateDecl());
   EXPECT_TRUE(ToFT);
 }
 
 TEST_P(ASTImporterTestBase,
-       DISABLED_ImportOfTemplatedDeclShouldImportTheFunctionTemplateDecl) {
+       ImportOfTemplatedDeclShouldImportTheFunctionTemplateDecl) {
   Decl *FromTU = getTuDecl("template<class X> void f(){}", Lang_CXX);
   auto FromFT = FirstDeclMatcher<FunctionTemplateDecl>().match(
       FromTU, functionTemplateDecl());
   ASSERT_TRUE(FromFT);
 
   auto ToTemplated =
       cast<FunctionDecl>(Import(FromFT->getTemplatedDecl(), Lang_CXX));
   EXPECT_TRUE(ToTemplated);