Hi all, I'd like to make a small plea for PolyKinds. * Haskell is more Haskelly with PolyKinds than without. That is, a key attribute of Haskell is its let-generalization. Yet, oddly, Haskell by default does not generalize its kinds. It should. Here is a motivating example:
data App f a = App (f a)
With PolyKinds, App gets the kind (k -> Type) -> k -> Type. Without PolyKinds, GHC has to use defaulting to get (Type -> Type) -> Type -> Type, which might not work at certain use sites. * PolyKinds is backward compatible, except in obscure cases when a PolyKinds module is imported by a NoPolyKinds module. * Supporting NoPolyKinds is difficult within GHC, and I've been waiting for the right time to propose removing support for it. PolyKinds is conceptually *simpler* than NoPolyKinds, as it doesn't require an awkward defaulting step. Vote for PolyKinds! Thanks, Richard