1 files changed, 43 insertions, 9 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index e3c784c..95706fb 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3162,9 +3162,19 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
 
       // We are looking for a qualified typename.
       Token Next = NextToken();
-      if (Next.is(tok::annot_template_id) &&
-          static_cast<TemplateIdAnnotation *>(Next.getAnnotationValue())
-            ->Kind == TNK_Type_template) {
+
+      TemplateIdAnnotation *TemplateId = Next.is(tok::annot_template_id)
+                                             ? takeTemplateIdAnnotation(Next)
+                                             : nullptr;
+      if (TemplateId && TemplateId->hasInvalidName()) {
+        // We found something like 'T::U<Args> x', but U is not a template.
+        // Assume it was supposed to be a type.
+        DS.SetTypeSpecError();
+        ConsumeAnnotationToken();
+        break;
+      }
+
+      if (TemplateId && TemplateId->Kind == TNK_Type_template) {
         // We have a qualified template-id, e.g., N::A<int>
 
         // If this would be a valid constructor declaration with template
@@ -3174,7 +3184,6 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
         //
         // To improve diagnostics for this case, parse the declaration as a
         // constructor (and reject the extra template arguments later).
-        TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Next);
         if ((DSContext == DeclSpecContext::DSC_top_level ||
              DSContext == DeclSpecContext::DSC_class) &&
             TemplateId->Name &&
@@ -3195,9 +3204,7 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
         continue;
       }
 
-      if (Next.is(tok::annot_template_id) &&
-          static_cast<TemplateIdAnnotation *>(Next.getAnnotationValue())
-            ->Kind == TNK_Concept_template &&
+      if (TemplateId && TemplateId->Kind == TNK_Concept_template &&
           GetLookAheadToken(2).isOneOf(tok::kw_auto, tok::kw_decltype)) {
         DS.getTypeSpecScope() = SS;
         // This is a qualified placeholder-specifier, e.g., ::C<int> auto ...
@@ -3459,7 +3466,18 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
       // type-name or placeholder-specifier
     case tok::annot_template_id: {
       TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
+
+      if (TemplateId->hasInvalidName()) {
+        DS.SetTypeSpecError();
+        break;
+      }
+
       if (TemplateId->Kind == TNK_Concept_template) {
+        // If we've already diagnosed that this type-constraint has invalid
+        // arguemnts, drop it and just form 'auto' or 'decltype(auto)'.
+        if (TemplateId->hasInvalidArgs())
+          TemplateId = nullptr;
+
         if (NextToken().is(tok::identifier)) {
           Diag(Loc, diag::err_placeholder_expected_auto_or_decltype_auto)
               << FixItHint::CreateInsertion(NextToken().getLocation(), "auto");
@@ -5197,14 +5215,30 @@ bool Parser::isDeclarationSpecifier(bool DisambiguatingWithExpression) {
 
     // placeholder-type-specifier
   case tok::annot_template_id: {
+    TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
+    if (TemplateId->hasInvalidName())
+      return true;
+    // FIXME: What about type templates that have only been annotated as
+    // annot_template_id, not as annot_typename?
     return isTypeConstraintAnnotation() &&
-        (NextToken().is(tok::kw_auto) || NextToken().is(tok::kw_decltype));
+           (NextToken().is(tok::kw_auto) || NextToken().is(tok::kw_decltype));
   }
-  case tok::annot_cxxscope:
+
+  case tok::annot_cxxscope: {
+    TemplateIdAnnotation *TemplateId =
+        NextToken().is(tok::annot_template_id)
+            ? takeTemplateIdAnnotation(NextToken())
+            : nullptr;
+    if (TemplateId && TemplateId->hasInvalidName())
+      return true;
+    // FIXME: What about type templates that have only been annotated as
+    // annot_template_id, not as annot_typename?
     if (NextToken().is(tok::identifier) && TryAnnotateTypeConstraint())
       return true;
     return isTypeConstraintAnnotation() &&
         GetLookAheadToken(2).isOneOf(tok::kw_auto, tok::kw_decltype);
+  }
+
   case tok::kw___declspec:
   case tok::kw___cdecl:
   case tok::kw___stdcall: