Per SQL spec (in particular, the grammar in SQL:2008 7.13) we should allow

parentheses around the <query expression body> that follows a WITH clause, eg
	with cte(foo) as ( values(0) ) ((select foo from cte));
This seems to be just an oversight/thinko in gram.y.  Noted while
experimenting with bug #4902.

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.665 2009/06/18 01:27:02 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.666 2009/07/06 02:58:40 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -6879,7 +6879,7 @@ select_no_parens:
 										NULL);
 					$$ = $1;
 				}
-			| with_clause simple_select
+			| with_clause select_clause
 				{
 					insertSelectOptions((SelectStmt *) $2, NULL, NIL,
 										NULL, NULL,