diff -r 4b2762e12b47 -r 03381c41235b src/Pure/Isar/outer_syntax.ML
--- a/src/Pure/Isar/outer_syntax.ML	Tue Sep 25 16:55:32 2012 +0200
+++ b/src/Pure/Isar/outer_syntax.ML	Tue Sep 25 18:24:49 2012 +0200
@@ -275,7 +275,7 @@
 fun cmts (t1 :: t2 :: toks) =
       if Token.keyword_with (fn s => s = "--") t1 then t2 :: cmts toks
       else cmts (t2 :: toks)
-  | cmts toks = [];
+  | cmts _ = [];
 
 in