"Kevin Quick"
I would think that only mutually recursive default methods would require respecification and that there could be any number of default methods that were reasonable as is. Since it's probably quite difficult for the Haskell compiler to analytically detect non-terminating v.s. terminating mutual recursion it may be useful to define an explicit comment flag for this case.
For example:
class Show a where shows = showsPrec 5 showsPrec _ = shows {-# REDEFINE_ONE: shows showsPrec #-}
This would fairly simply allow a warning to be generated for an instance which did not redefine one of the identified methods; it would capture that requirement in the same place the recursive definition was defined, it would avoid false warnings, and it would be backward compatible (and it might be Haddock-able as well).
This should be generalised IMO, since there might be cases where you have to redefine either (foo && bar) || baz; of course, that makes the syntax specification, etc. of the pragma more difficult... -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com