catch instance Foldable ((, ) a) (Was: What Haskell users are actively maintaining or deving software using ghc <8)

[Richard Eisenberg]

> On May 29, 2020, at 4:47 AM, Ben Gamari <ben at smart-cactus.org> wrote:
>> 
>> https://gitlab.haskell.org/ghc/ghc/issues/11796
>> 
> Indeed. All we need is someone to implement. Admittedly, I don't have
> much insight into how difficult this would be. Richard or Simon
> would likely be more helpful in this regard.

Implementation should be quite easy. The challenge is in the design. The design in the ticket looks plausible, but you would have to start by making a GHC proposal.
>> 
>> Interesting idea. Or would it be better implemented in a type-checker 
>> plugin?
>> 
> That would be another approach but I don't believe this is possible with
> our current typechecker plugin mechanism.. 

I agree with everything Ben said here. We look to plugins only after GHC has failed internally. Maybe that's not the best design, but it's what we have.

Richard