Correct error recovery when missing 'class' in a template template parameter.

The diagnostic message correctly informs the user that they have omitted the
'class' keyword, but neither suggests this insertion as a fixit, nor attempts
to recover as if they had provided the keyword.

This fixes the recovery, adds the fixit, and adds a separate diagnostic and
corresponding replacement fixit for cases where the user wrote 'struct' or
'typename' instead of 'class' (suggested by Richard Smith as a possible common
mistake).

I'm not sure the diagnostic message for either the original or new cases feel
very Clang-esque, so I'm open to suggestions there. The fixit hints make it
fairly easy to see what's required, though.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153887 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 6 deletions

diff --git a/lib/Parse/ParseTemplate.cpp b/lib/Parse/ParseTemplate.cpp
index 305f07bc90..474519381e 100644
--- a/lib/Parse/ParseTemplate.cpp
+++ b/lib/Parse/ParseTemplate.cpp
@@ -540,12 +540,17 @@ Parser::ParseTemplateTemplateParameter(unsigned Depth, unsigned Position) {
 
   // Generate a meaningful error if the user forgot to put class before the
   // identifier, comma, or greater.
-  if (!Tok.is(tok::kw_class)) {
-    Diag(Tok.getLocation(), diag::err_expected_class_before)
-      << PP.getSpelling(Tok);
-    return 0;
-  }
-  ConsumeToken();
+  if (Tok.is(tok::kw_typename) || Tok.is(tok::kw_struct)) {
+    Diag(Tok.getLocation(), diag::err_expected_class_instead)
+      << PP.getSpelling(Tok)
+      << FixItHint::CreateReplacement(Tok.getLocation(), "class");
+    ConsumeToken();
+  } else if (!Tok.is(tok::kw_class))
+      Diag(Tok.getLocation(), diag::err_expected_class_before)
+        << PP.getSpelling(Tok)
+        << FixItHint::CreateInsertion(Tok.getLocation(), "class ");
+  else 
+    ConsumeToken();
 
   // Parse the ellipsis, if given.
   SourceLocation EllipsisLoc;