[ghc-steering-committee] #556: multiple type variables in signatures in type applications in patterns, Recommendation: accept

[Joachim Breitner]

Hi,

ignore this mail. This is already shepherded by Richard.

(I was thrown off by his “I'm happy with the new wording and would
support this in a committee vote.” which sounded like something someone
would say who is not in the position to propose acceptance :-)))

Cheers,
Joachim


Am Freitag, dem 09.12.2022 um 20:07 +0100 schrieb Joachim Breitner:
> Dear all,
> 
> Vlad has submitted a bug fix amendment to #448, to fix the wording around
> type variables in signatures within explicit type annotations:
> 
> https://github.com/ghc-proposals/ghc-proposals/pull/556/files
> 
> I’m shepherding that one myself.
> 
> The gist is that in
>    
>    data Proxy a = P
>    g :: Proxy (Nothing @(a, a)) -> ()
>    g (P @(Nothing :: Maybe (x, x))) = ()
> 
> 
> the multiple occurrences of `a` are non-linear patterns and disallowed,
> but the multiple patterns of `x` are fine, because that’s how type
> variables in signatures in patterns happen to work. Vlad fixed the
> wording with regard to that in #448.
> 
> 
> Simon and Richard already signaled support on the Github thread, which
> I recommend to follow. I don’t expect much further discussion around
> this and will happily merge after a week of silence (or after one or
> two additional confirmations).
> 
> Cheers,
> Joachim
> 
> 
> 

-- 
Joachim Breitner
  mail at joachim-breitner.de
  http://www.joachim-breitner.de/