Re: [Haskell-cafe] Solved but strange error in type inference

On Wed, Jan 4, 2012 at 7:58 PM, Yves Parès wrote:

f :: forall a. a -> a f x = x :: forall a. a

Which is obviously wrong: when you have entered f, x has been instatiated to a specific type 'a', and then you want it to x to be of any type? That doesn't make sense.

I did not expect the type variables to be scoped. I expected the type of 'x' to be universally quantified, and thus can be unified with 'forall a. a' with no problem.