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

On 3/17/08, Hugo Pacheco wrote:

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

Interestingly, this works when you also give a type signature to "id": fff :: forall d x. (FunctorF d) => d -> F d x -> F d x fff a = fmapF a (id :: x -> x) compiles for me (ghc6.8.2). There's probably a bug in the type checker; inference is working with no type signatures, but checking fails.