[ghc-steering-committee] Proposal #400: COMPLETE set signatures; rec: accept

[Richard Eisenberg]

I support acceptance.

Thanks!
Richard

> On Sep 16, 2021, at 12:07 PM, Vladislav Zavialov (int-index) <vlad.z.4096 at gmail.com> wrote:
> 
> Dear Committee,
> 
> Proposal #400 "COMPLETE set signatures” by Sebastian Graf has been submitted for our consideration.
> 
> Read it here: https://github.com/sgraf812/ghc-proposals/blob/constrained-complete-sigs/proposals/0000-complete-set-signatures.rst
> Discussion here: https://github.com/ghc-proposals/ghc-proposals/pull/400
> 
> The proposal presents an alternative treatment for type annotations on COMPLETE pragmas. Today one could write
> 
>   {-# COMPLETE P, Q :: Either #-}
> 
> where P and Q are some pattern synonyms. But this isn’t even well-kinded.
> 
> Instead, the author proposes that we ask our users to write
> 
>  {-# COMPLETE P, Q :: Either l r #-}
> 
> By requiring a proper type on the RHS, we also gain the ability to talk about more advanced use cases (described in the proposal).
> 
> I recommend acceptance. In fact, I learned about the way these annotations are treated today only from reading the proposal, and it came as a surprise to me. Using proper, well-kinded types there, seems like the right thing to do even if we ignore the new use cases it enables.
> 
> Let me know what you think.
> 
> - Vlad
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