[ghc-steering-committee] Please review #194: Updated partial type signatures, Recommendation: Reject

[Eric Seidel]

Dear Committee,

Richard has proposed an update to the PartialTypeSignatures extension. The proposal is quite detailed and I recommend the Committee read the whole thing as my summary will not do it justice. But the gist is that the `_` has acquired many different meanings in Haskell in different syntactic contexts and under different sets of extensions. And the result is quite confusing! Richard describes four different meanings of `_` in the proposal.

But I don't think Richard's proposal does enough to remedy the situation. I still find the proposed change hard to reason about and would prefer to further simplify the language here.

I suggested an alternate direction[1] on GitHub that I think would make a meaningful improvement. Looking back at the proposal again, it may not be as far from Richard's proposal as I had originally thought. But I think it is important to have different syntax to express the two modalities of "I don't care" (elision/wildcard) and "I don't know" (hole/query).

My recommendation is to not accept this proposal in its current form.

Eric

[1]: https://github.com/ghc-proposals/ghc-proposals/pull/194#discussion_r1257517608

On Thu, May 25, 2023, at 01:55, Joachim Breitner wrote:
> Dear Committee,
>
> Richard resubmits updated partial type signatures:
>
> https://github.com/ghc-proposals/ghc-proposals/pull/194
>
> https://github.com/goldfirere/ghc-proposals/blob/updated-partial-type-sigs/proposals/0000-updated-partial-type-sigs.rst
>
> I’d like to ask Eric to shepherd this proposal.
>
> Please guide us to a conclusion as outlined in 
> https://github.com/ghc-proposals/ghc-proposals#committee-process
>
>
> Cheers,
> Joachim
>
>
> -- 
> Joachim Breitner
>   mail at joachim-breitner.de
>   http://www.joachim-breitner.de/
>
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