[ghc-steering-committee] Proposal #281: Visible "forall" in terms; rec: accept

[Richard Eisenberg]

It has been two weeks. I have heard no argument against this proposal, but Simon Marlow (in the springtime) expressed some puzzlement. Simon, what are you thinking about this now? With no further response, I will accept this proposal on Friday.

Others are also very welcome to chime in!

Thanks, all!
Richard

> On Oct 27, 2021, at 5:30 AM, Spiwack, Arnaud <arnaud.spiwack at tweag.io> wrote:
> 
> I think that the proposal makes a great job at listing the issues. It's quite transparent about this, I'm not sure what I could add.
> 
> On Wed, Oct 27, 2021 at 11:29 AM Simon Peyton Jones <simonpj at microsoft.com <mailto:simonpj at microsoft.com>> wrote:
> I was indeed confused! Apologies.
> 
> But my main point remains: enumerating a list of inconvenient side effects and corner cases would be a great service.
> 
> Simon
> 
> PS: I am leaving Microsoft at the end of November 2021, at which point simonpj at microsoft.com <mailto:simonpj at microsoft.com> will cease to work.  Use simon.peytonjones at gmail.com <mailto:simon.peytonjones at gmail.com> instead.  (For now, it just forwards to simonpj at microsoft.com <mailto:simonpj at microsoft.com>.)
> 
> |  -----Original Message-----
> |  From: Vladislav Zavialov (int-index) <vlad.z.4096 at gmail.com <mailto:vlad.z.4096 at gmail.com>>
> |  Sent: 27 October 2021 10:10
> |  To: Simon Peyton Jones <simonpj at microsoft.com <mailto:simonpj at microsoft.com>>
> |  Cc: Spiwack, Arnaud <arnaud.spiwack at tweag.io <mailto:arnaud.spiwack at tweag.io>>; Richard Eisenberg
> |  <rae at richarde.dev <mailto:rae at richarde.dev>>; ghc-steering-committee <ghc-steering-
> |  committee at haskell.org <mailto:committee at haskell.org>>
> |  Subject: Re: [ghc-steering-committee] Proposal #281: Visible "forall"
> |  in terms; rec: accept
> |  
> |  Simon, perhaps you’re thinking of another proposal that is currently
> |  under committee’s consideration?
> |  
> |  Arnaud was commenting on #281, and you seem to be talking about #425.
> |  
> |  - Vlad
> |  
> |  > On 27 Oct 2021, at 12:05, Simon Peyton Jones via ghc-steering-
> |  committee <ghc-steering-committee at haskell.org <mailto:ghc-steering-committee at haskell.org>> wrote:
> |  >
> |  > There are a lot of inconvenient side effects and corner cases
> |  >
> |  > Arnaud, could you enumerate them?  Even if (as I strongly hope) we
> |  accept this proposal, it’s good to have a concrete list of things to
> |  bear in mind.   I for one do not have such list in my head.
> |  >
> |  > One principle that the proposal espouses (but perhaps does not call
> |  out explicitly) is that it should be possible to write an explicit
> |  binder for every in-scope variable.    So instead of
> |  >                 data T (a :: k -> k) = … I want to write
> |  >                 data T @k (a :: k -> k) = … with an explicit binder
> |  > for k.
> |  >
> |  > So I see the proposal as removing an ad-hoc wart in the language.
> |  But I may be blind to the “inconvenient side effects and corner cases”
> |  and I’d welcome a list of such cases.
> |  >
> |  > Simon
> |  >
> |  >
> |  > PS: I am leaving Microsoft at the end of November 2021, at which
> |  point
> |  > simonpj at microsoft.com <mailto:simonpj at microsoft.com> will cease to work.
> |  > Usesimon.peytonjones at gmail.com <mailto:Usesimon.peytonjones at gmail.com> instead.  (For now, it just forwards
> |  to
> |  > simonpj at microsoft.com <mailto:simonpj at microsoft.com>.)
> |  >
> |  > From: ghc-steering-committee
> |  > <ghc-steering-committee-bounces at haskell.org <mailto:ghc-steering-committee-bounces at haskell.org>> On Behalf Of Spiwack,
> |  > Arnaud
> |  > Sent: 27 October 2021 09:20
> |  > To: Richard Eisenberg <rae at richarde.dev <mailto:rae at richarde.dev>>
> |  > Cc: ghc-steering-committee <ghc-steering-committee at haskell.org <mailto:ghc-steering-committee at haskell.org>>
> |  > Subject: Re: [ghc-steering-committee] Proposal #281: Visible
> |  "forall"
> |  > in terms; rec: accept
> |  >
> |  > I've been struggling to have an opinion on this PR. I'm very
> |  sympathetic to the goal of the proposal (and this latest rendition of
> |  the proposal is a really good document). There are a lot of
> |  inconvenient side effects and corner cases (but, to be fair, these are
> |  not special to this proposal: they are inherent to the dependent types
> |  plan). But I'm fairly convinced that this is the best possible
> |  approach, or close enough.
> |  >
> |  >
> |  >
> |  > So yes, I don't really feel strongly about it. But on balance, I
> |  think that I'm in favour.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/ghc-steering-committee/attachments/20211027/cad84dd2/attachment.html>