[ASTImporter] Import member expr with explicit template args

[martong]

Summary

Member expressions with explicit template arguments were not imported
correctly: the DeclRefExpr was missing. This patch fixes.

[shafik]

LGTM and I don't see any regressions.

lib/AST/ASTImporter.cpp

ExpectedStmt ASTNodeImporter::VisitMemberExpr(MemberExpr *E) {
   SourceLocation ToLoc, ToLAngleLoc, ToRAngleLoc;
   std::tie(ToDecl, ToName, ToLoc, ToLAngleLoc, ToRAngleLoc) = *Imp2;
 
   DeclAccessPair ToFoundDecl =
       DeclAccessPair::make(ToDecl, E->getFoundDecl().getAccess());
 
   DeclarationNameInfo ToMemberNameInfo(ToName, ToLoc);
 
+  TemplateArgumentListInfo ToTAInfo, *ResInfo = nullptr;
   if (E->hasExplicitTemplateArgs()) {
-    // FIXME: handle template arguments
-    return make_error<ImportError>(ImportError::UnsupportedConstruct);
+    if (Error Err =
+            ImportTemplateArgumentListInfo(E->getLAngleLoc(), E->getRAngleLoc(),
+                                           E->template_arguments(), ToTAInfo))
+      return std::move(Err);
+    ResInfo = &ToTAInfo;
   }
 
   return MemberExpr::Create(
       Importer.getToContext(), ToBase, E->isArrow(), ToOperatorLoc,
       ToQualifierLoc, ToTemplateKeywordLoc, ToMemberDecl, ToFoundDecl,
-      ToMemberNameInfo, nullptr, ToType, E->getValueKind(), E->getObjectKind());
+      ToMemberNameInfo, ResInfo, ToType, E->getValueKind(), E->getObjectKind());
 }
 
 ExpectedStmt
 ASTNodeImporter::VisitCXXPseudoDestructorExpr(CXXPseudoDestructorExpr *E) {
   auto Imp = importSeq(
       E->getBase(), E->getOperatorLoc(), E->getQualifierLoc(),
       E->getScopeTypeInfo(), E->getColonColonLoc(), E->getTildeLoc());
   if (!Imp)

unittests/AST/ASTImporterTest.cpp

TEST_P(ImportFunctions, ImportImplicitFunctionsInLambda) {
   CXXRecordDecl *LambdaRec =
       cast<LambdaExpr>(cast<CStyleCastExpr>(
                            *cast<CompoundStmt>(ToD->getBody())->body_begin())
                            ->getSubExpr())
           ->getLambdaClass();
   EXPECT_TRUE(LambdaRec->getDestructor());
 }
 
+TEST_P(ImportFunctions,
+       CallExprOfMemberFunctionTemplateWithExplicitTemplateArgs) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      struct X {
+        template <typename T>
+        void foo(){}
+      };
+      void f() {
+        X x;
+        x.foo<int>();
+      }
+      )",
+      Lang_CXX);
+  auto *FromD = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("f")));
+  auto *ToD = Import(FromD, Lang_CXX);
+  EXPECT_TRUE(ToD);
+  EXPECT_TRUE(MatchVerifier<FunctionDecl>().match(
+      ToD, functionDecl(hasName("f"), hasDescendant(declRefExpr()))));
+}
+
+TEST_P(ImportFunctions,
+       DependentCallExprOfMemberFunctionTemplateWithExplicitTemplateArgs) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      struct X {
+        template <typename T>
+        void foo(){}
+      };
+      template <typename T>
+      void f() {
+        X x;
+        x.foo<T>();
+      }
+      void g() {
+        f<int>();
+      }
+      )",
+      Lang_CXX);
+  auto *FromD = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("g")));
+  auto *ToD = Import(FromD, Lang_CXX);
+  EXPECT_TRUE(ToD);
+  Decl *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+  EXPECT_TRUE(MatchVerifier<TranslationUnitDecl>().match(
+      ToTU, translationUnitDecl(hasDescendant(
+                functionDecl(hasName("f"), hasDescendant(declRefExpr()))))));
+}
+
 struct ImportFriendFunctions : ImportFunctions {};
 
 TEST_P(ImportFriendFunctions, ImportFriendFunctionRedeclChainProto) {
   auto Pattern = functionDecl(hasName("f"));
 
   Decl *FromTU = getTuDecl("struct X { friend void f(); };"
                            "void f();",
                            Lang_CXX,