TypeLits and type families wrt. equality

[Richard Eisenberg]

On Jul 27, 2015, at 9:48 AM, Simon Peyton Jones <simonpj at microsoft.com> wrote:
> 
> Making type inference (and system FC) exploit negative info would be a Big Deal, I think.

Yes. Gabor points out a known infelicity with the interaction between closed type families and GADTs. But I agree with Simon that fixing it would indeed be a Big Deal, and not yet worth the very considerable effort required.

Richard