Ganesh Sittampalam:
On Mon, 17 Mar 2008, Manuel M T Chakravarty wrote:
Your are completely right. Unfortunately, superclass equalities (ie, the Id a ~ ida in the class declaration of Foo) aren't fully implemented yet.
OK, thanks. Is there any rough idea of when they will be?
That's a bit difficult to say. The main problem is that the current handling of evidence for classes and access to superclass evidence doesn't mix well with the fact that the evidence for equalities are coercions (ie, type-level things, rather than value level things). It's high up on the list, but some other things like the interaction between GADTs and type families (basically done now) were higher up. If its important to you, I'd try to get to it earlier than if nobody is really waiting for it. Manuel