dreixel/generic-deriving — pull request #4 by spl (2012-12-04 22:14:33+00:00)
Title: Functor instances for representation types

I found myself needing this instances.

I realize this does not change GHC.Generics. Perhaps you can update that yourself.

A downside to these instances is that they require the datatype (via Rec1) to be a Functor. An alternative approach would be to use GFunctor, but then these would not be available from GHC.Generics.