[ghc-steering-committee] Resurrect Pattern Signatures (#119), Recommendation: accept

[Simon Peyton Jones]

I'm ok with this (not particularly keen, but ok), but see my comment:
https://github.com/ghc-proposals/ghc-proposals/pull/119/#issuecomment-385637259

|  -----Original Message-----
|  From: ghc-steering-committee <ghc-steering-committee-
|  bounces at haskell.org> On Behalf Of Christopher Allen
|  Sent: 01 May 2018 01:14
|  To: ghc-steering-committee at haskell.org
|  Subject: [ghc-steering-committee] Resurrect Pattern Signatures (#119),
|  Recommendation: accept
|  
|  This proposal splits out the faculty for assigning type signatures to
|  variables destructured out of a pattern from ScopedTypeVariables.
|  
|  https://github.com/ghc-proposals/ghc-proposals/pull/119/
|  
|  My recommendation is to accept the proposal, with some reservations.
|  
|  ScopedTypeVariables is one of the more popular candidates for "this
|  should always be on regardless." The cases in which STV would be
|  useful greatly outnumber the downsides Gundry cited in my experience.
|  My impression of this upheld by my industrial experience and that of
|  the other industrial programmers I've talked to in the past about
|  ScopedTypeVariables. Almost any time it is brought up almost
|  invariably the conversation touches on, "why isn't this on by
|  default?"
|  
|  I understand STV could break programs with overlapping names that are
|  intended to be independent type variables, I don't presume to litigate
|  or resolve that issue here.
|  
|  Extension fatigue is wearing on the Haskell users I regularly interact
|  with, especially as it's unclear if Haskell Prime will convene and
|  consolidate commonly used extensions into the core language.
|  
|  In my view these aren't sufficient reason to reject the proposed
|  extension on the merits so my recommendation is to accept it as-is. I
|  think the case for this proposal is particularly strong as it would
|  clean up the extension's presently somewhat confusing relationship
|  with STV.
|  
|  If no objections are raised, it should be assumed that this has the
|  assent of the committee.
|  
|  --
|  Chris Allen
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