| mayDeriveDataTypeable = Nothing
| otherwise = Just why
where
- why = ptext SLIT("You need -fglasgow-exts to derive an instance for this class")
+ why = ptext SLIT("You need -XDeriveDataTypeable to derive an instance for this class")
std_class_via_iso :: Class -> Bool
std_class_via_iso clas -- These standard classes can be derived for a newtype