[modules] Improve diagnostic for a template-id that's invalid because a default
argument is not visible.

llvm-svn: 239934
diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
index 2544c85..cde497b 100644
--- a/clang/lib/AST/DeclTemplate.cpp
+++ b/clang/lib/AST/DeclTemplate.cpp
@@ -666,6 +666,11 @@
                                nullptr, NumExpansions, nullptr);
 }
 
+SourceLocation TemplateTemplateParmDecl::getDefaultArgumentLoc() const {
+  return hasDefaultArgument() ? getDefaultArgument().getLocation()
+                              : SourceLocation();
+}
+
 void TemplateTemplateParmDecl::setDefaultArgument(
     const ASTContext &C, const TemplateArgumentLoc &DefArg) {
   if (DefArg.getArgument().isNull())