[Haskell-cafe] Instance deriving for Void types.

Hi Cafe. I was wondering if it's possible to have automatic deriving for some classes for the Void type. This would be classes that require a parameter of the type in its functions. This should obviously be trivial as the definition can be undefined since there's no way to supply a value of the type. I guess the obvious one would be Show. data Nada deriving Show {* instance Show Nada where show _ = undefined *} Thoughts?