[project @ 2004-10-11 16:12:58 by simonpj]

---------------------------------
	Fix bug in derivable type classes
	---------------------------------

		MERGE TO STABLE (if poss)

The test for not-supported method types for derivable type classes
was broken. This fixes it.

ghc/compiler/typecheck/TcTyClsDecls.lhs

@@ -650,7 +650,7 @@ checkValidClass cls
 
 		-- Check that for a generic method, the type of 
 		-- the method is sufficiently simple
-	; checkTc (dm /= GenDefMeth || validGenericMethodType op_ty)
+	; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
 		  (badGenericMethodType op_name op_ty)
 	}
 	where