[clang] [clang] require template arg list after template kw (PR #80801)

[via cfe-commits]

================
@@ -3026,13 +3027,23 @@ bool Parser::ParseUnqualifiedId(CXXScopeSpec &SS, ParsedType ObjectType,
           SS, ObjectType, ObjectHadErrors,
           TemplateKWLoc ? *TemplateKWLoc : SourceLocation(), Id, IdLoc,
           EnteringContext, Result, TemplateSpecified);
-    else if (TemplateSpecified &&
-             Actions.ActOnTemplateName(
-                 getCurScope(), SS, *TemplateKWLoc, Result, ObjectType,
-                 EnteringContext, Template,
-                 /*AllowInjectedClassName*/ true) == TNK_Non_template)
-      return true;
 
+    if (TemplateSpecified) {
+      TemplateNameKind TNK =
+          Actions.ActOnTemplateName(getCurScope(), SS, *TemplateKWLoc, Result,
+                                    ObjectType, EnteringContext, Template,
+                                    /*AllowInjectedClassName=*/true);
+      if (TNK == TNK_Non_template)
+        return true;
+
+      // C++ [template.names]p6
----------------
cor3ntin wrote:

```suggestion
      // C++2c [tem.names]p6
```

https://github.com/llvm/llvm-project/pull/80801