Hi, I'm hitting on an issue when deriving Generic for an associated data type: {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE DeriveGeneric #-} import GHC.Generics class Foo a where data T a :: * instance Foo Int where data T Int = Bla deriving Generic Couldn't match type `Rep (T Int)' with `M1 t0 t1 (M1 t2 t3 U1)' Expected type: Rep (T Int) x Actual type: M1 t0 t1 (M1 t2 t3 U1) x In the pattern: M1 (M1 U1) In an equation for `to': to (M1 (M1 U1)) = Bla In the instance declaration for `Generic (T Int)' The GHC trac seems to be down. Is this a known issue? Cheers, Bas