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

[Simon Peyton Jones]

I'm in favour of #400.

Simon

PS: I am leaving Microsoft at the end of November 2021, at which point simonpj at microsoft.com will cease to work.  Use simon.peytonjones at gmail.com instead.  (For now, it just forwards to simonpj at microsoft.com.)

|  -----Original Message-----
|  From: ghc-steering-committee <ghc-steering-committee-
|  bounces at haskell.org> On Behalf Of Vladislav Zavialov (int-index)
|  Sent: 16 September 2021 17:07
|  To: ghc-steering-committee <ghc-steering-committee at haskell.org>
|  Subject: [ghc-steering-committee] Proposal #400: COMPLETE set
|  signatures; rec: accept
|  
|  Dear Committee,
|  
|  Proposal #400 "COMPLETE set signatures" by Sebastian Graf has been
|  submitted for our consideration.
|  
|  Read it here:
|  https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
|  ub.com%2Fsgraf812%2Fghc-proposals%2Fblob%2Fconstrained-complete-
|  sigs%2Fproposals%2F0000-complete-set-
|  signatures.rst&data=04%7C01%7Csimonpj%40microsoft.com%7Cccd12e8010
|  654946877608d9792c1a90%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C63
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|  2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=a3j3xlr4FFrJ0%2
|  B6gB80Kb%2FQ%2Faxz0uDyb8HYpLYhNEBg%3D&reserved=0
|  Discussion here:
|  https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
|  ub.com%2Fghc-proposals%2Fghc-
|  proposals%2Fpull%2F400&data=04%7C01%7Csimonpj%40microsoft.com%7Ccc
|  d12e8010654946877608d9792c1a90%7C72f988bf86f141af91ab2d7cd011db47%7C1%
|  7C0%7C637674053577434736%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiL
|  CJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=WPnozLD
|  TtXlaFkUPtyZbzGSn5%2BmpqoTRkRhoy6SJqfg%3D&reserved=0
|  
|  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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