[Haskell-cafe] Re: Type parameters in type families

I wonder if I am dealing with bugs in the type checker (replying to myself). Curiously if I have class FunctorF d where fmapF :: d -> (x -> y) -> F d x -> F d y fff a = fmapF a id it compiles correctly. If I infer the type signature of fff I get fff :: forall d x. (FunctorF d) => d -> F d x -> F d x On the other side, it fails to compile when this signature is explicit: fff :: forall d x. (FunctorF d) => d -> F d x -> F d x fff a = fmapF a id I am repeating myself in http://hackage.haskell.org/trac/ghc/ticket/2157#comment:6. Sorry for the cascaded messages, hugo