Dear Cafe, apologies if this is a duplicate question. I want to define an element of a Rank-2 type, use its specialization and then return the general thing. Apparently this is not possible without a newtype. {-# LANGUAGE RankNTypes #-} newtype General = General { useGeneral :: forall a. Integral a => a -> Bool } doesNotWork :: General doesNotWork = let g = even :: forall a. Integral a => a -> Bool b = specializeGeneral g in General g doesWork :: General doesWork = let g = General even b = specializeGeneral (useGeneral g) in g specializeGeneral :: (Int -> Bool) -> Bool specializeGeneral p = p 5 I was under the impression that one can always use a more general type where a more special type is needed. In `doesNotWork` above, despite the explicit Rank-2 type annotation, usage in `specializeGeneral` apparently makes the compiler infer the type of `g` to be (Int -> Bool) and complains that `a` can not me matched with `Bool`. What gets me is that the compiler error is at `General g`, so the compiler must have ignored my Rank-2 type annotation. Should it be allowed to do that? Olaf