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

[Yucheng Zhang]

On Wed, Jan 4, 2012 at 2:48 AM, Bardur Arantsson <spam at scientician.net> wrote:
> 'subsome' to a different type than the one you intended -- and indeed one
> which can't be unified with the inferred type. (Unless you use
> ScopedTypeVariables.)

Thanks for the reply.

Actually, my question is why the different type can't be unified with
the inferred type? Could you point me some related resources?