[ghc-steering-committee] Please review #640: Fix quantification order for a `op` b and a %m -> b (Recommendation: Accept)

[Malte Ott]

Dear all,

I left this lingering for a bit in the hope a consensus might magically appear,
alas it didn’t.

We have consensus on accepting the proposal for the multiplicity annotations. 

For infix type operators I am now trying to convert previously voiced opinions
as faithfully as possible into votes:

Pro:

Eric, Malte, Chris, Matti

Con:

Adam, Arnaud

Undecided:

Simon PJ, Moritz, Simon M

Thus, as it stands we will accept the proposal as is, but it is close.
Please voice your opinion if you want to change your vote until Friday, I will
call the vote on the weekend.

Best
Malte

On 2024-03-21 17:46, Matthías Páll Gissurarson wrote:
> I’m in favor of the proposal:
> 
> For
> 
> a `m` b -> (a,b)
> 
> I think it’s debatable, “forall a m b” vs “forall m a b”
> 
> But what about more nested expressions? If we had
> 
> (a `m` b) `n` (c `o` d) -> (a,b,c,d),
> 
> The current order would give “forall n m a b o c d”, whereas the change
> would give “forall a m b n c o d”. The latter is “less surprising”, and I’m
> in favor of the element of least surprise. Same with linear multiplicities,
> I was surprised to see the m being last in “a %m -> b”.
> 
> As mentioned before, this seems unlikely to cause breakage in the wild, and
> the fix is a simple explicit forall. So I’m in favor of the bug fix.
> 
> /Matti Palli
> 
> 
> On Thu, Mar 21, 2024 at 11:46 Chris Dornan <chris at chrisdornan.com> wrote:
> 
> > I can go either way. We should make the linear change of course. Both
> > Simon and Adam make good arguments for accepting and rejecting the infix
> > operator aspect.
> >
> > I would probably be tempted to stick with the status quo but am happy to
> > accept the whole proposal — as that requires no further change I am coming
> > down on that side — to accept the whole proposal unless someone objects.
> >
> >
> > Chris
> >
> > On 21 Mar 2024, at 10:11, Simon Peyton Jones <simon.peytonjones at gmail.com>
> > wrote:
> >
> > Great summary.
> >
> > I am generally not a fan of enshrining historic coincidence in the
> > language when
> > the cost of fixing it is bareable. On the other hand this is such a minor
> > detail
> > that I don’t think it will matter much in either direction.
> >
> >
> > That's exactly why I am on the fence!
> >
> > Chris, Simon M, Matthias, any opinions?
> >
> > We may just have to vote, as Malte says
> >
> > Simon
> >
> >
> > On Wed, 20 Mar 2024 at 23:42, Malte Ott <malte.ott at maralorn.de> wrote:
> >
> >> Okay, let me summarize the voiced opinions:
> >>
> >> We have agreement on the change to multiplicities.
> >>
> >> On the infix type operator we are a bit stuck:
> >>
> >> * Richard, Eric and I are in favor of fixing the bug.
> >> * Adam and Arnaud are in favor of staying stable, living with the
> >> exception
> >> * Simon was on the fix side but switched to undecided, waiting for more
> >> opinions
> >> * Moritz preferred staying stable, but deferred to Simon before his switch
> >>
> >> Overall slightly more votes for the change but subjectively hold less
> >> strongly
> >> than the opinions against it.
> >>
> >> Since I am unclear on how to proceed I’d love to hear more opinions
> >> (especially
> >> of committee members who haven’t voiced theirs about this proposal).
> >>
> >> I am generally not a fan of enshrining historic coincidence in the
> >> language when
> >> the cost of fixing it is bareable. On the other hand this is such a minor
> >> detail
> >> that I don’t think it will matter much in either direction.
> >>
> >> If we cannot come to a consensus soon I will put it a to a vote. We
> >> shouldn’t spend too much time on this.
> >>
> >> Best
> >> Malte
> >>
> >> On 2024-03-19 15:12, Arnaud Spiwack wrote:
> >> > On Tue, 19 Mar 2024 at 10:26, Simon Peyton Jones <
> >> > simon.peytonjones at gmail.com> wrote:
> >> >
> >> > > But I think you are now saying that *even if a left-to-right order was
> >> > > "best", *there is a long-standing bug in GHC that puts `b` first in (a
> >> > > `b` c`), and it's not worth the risk of change.   So instead we should
> >> > > institutionalise the bug into the spec.
> >> > >
> >> >
> >> > This is, at least, my position. This is a bug fix, but the bug is so
> >> tiny,
> >> > that even if the breakage is rare, it's not necessarily worth it, and it
> >> > may be better to bake the exception into the spec. I'm weakly on the
> >> side
> >> > that baking the exception is better.
> >>
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