Dear GHC Steering Committee

On 2 April I asked:

I think it's time to vote.   Please so before Monday morning [8 April].  Thank you!

It is now 19 April, of the eight members of the committee only Malte has voted.

Please please vote.  Today!   Use email and record your vote on the spreadsheet.  Vlad you have a vote; since you are the proposer you may choose to abstain but I think it's up to you.

The proposal isn't a huge deal either way, but we owe it to the proposer and to ourselves to deal with our business in a timely way.

Simon

On Tue, 2 Apr 2024 at 17:25, Simon Peyton Jones <simon.peytonjones@gmail.com> wrote:
Dear GHC Steering Committee

Vlad proposes to amend proposal #425 to permit more wildcard binder forms in type declarations:

See my mail below.   I recommend, fairly strongly, to park this until there is evidence of need.
  • it's an unforced change, 
  • with no user demand
  • but some real user impact (notably: it will break some TH users)
  • and some implementation cost (modest but very non-zero)
  • aiming to anticipate as-yet-unknown future requirements -- but YAGNI
I think it's time to vote.   Please so before Monday morning.  Thank you!

Simon

On Thu, 21 Mar 2024 at 09:56, Simon Peyton Jones <simon.peytonjones@gmail.com> wrote:
Dear Steering Committee

Vlad proposes to amend proposal #425 to permit more wildcard binder forms in type declarations:

You may find it easiest to look at the rich diff.

This is a pretty small generalisation which would allow

data T (( (a :: k1) :: k2)) = ...

in which the binder has multiple kind signatures and redundant parens.  The change is not driven by user need, but rather solely by uniformity: these same forms are permitted in function definitions:

f :: forall (a :: k). blah
f @(((a::k1)::k2))) = ...

is permitted.

It imposes a change on Template Haskell syntax too.

The implementation becomes a bit more complicated; more recursive data types, etc.  Nothing hard, but more.

It's not a big deal either way.  Very few people expressed a view on GitHub.  My personal view is that the modest (albeit non-zero) gain does not justify the definite (albeit modest) pain. I would leave this until someone actually wants it.

Vlad argues for future-proofing, but my experience is that an eye to the future is sensible when you are making changes anyway; but making unforced changes solely for the future risks incurring pain now that, when the future comes, turns out to have been a poor investment.  We may have correctly anticipated, or we may not.

So my recommendation is to park this until we get a real user demand.

It's a perfectly sensible proposal, but adopting it is a judgement call. I'll leave a week for committee responses, and then we can just vote.

Simon

On Thu, 21 Mar 2024 at 08:07, Adam Gundry <adam@well-typed.com> wrote:
Dear Committee,

Vlad proposes to amend proposal #425 to permit more wildcard binder
forms in type declarations:

https://github.com/ghc-proposals/ghc-proposals/pull/641

I'd like to nominate Simon PJ as the shepherd.

Please guide us to a conclusion as outlined in
https://github.com/ghc-proposals/ghc-proposals#committee-process

Cheers,

Adam


--
Adam Gundry, Haskell Consultant
Well-Typed LLP, https://www.well-typed.com/

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