[ghc-steering-committee] #626: Amendment of Visible Forall in Types, recommendation: Accept

[Arnaud Spiwack]

I actually hadn't noticed, thanks Richard. For the record: said change
removes the icky ambiguity on `p -> q`, which is always parsed as a view
pattern.


On Fri, 12 Jan 2024 at 02:22, Richard Eisenberg <rae at richarde.dev> wrote:

> (For what it's worth, my suggestion was accepted and has been incorporated
> into the proposal.)
>
> On Jan 9, 2024, at 10:43 AM, Arnaud Spiwack <arnaud.spiwack at tweag.io>
> wrote:
>
> Any other thoughts? If not, I'll consider this proposal accepted at the
> end of this week.
>
> On Tue, 2 Jan 2024 at 13:55, Richard Eisenberg <rae at richarde.dev> wrote:
>
>> I support the amendment. I made one small suggestion, but I wish to vote
>> for acceptance regardless of the status of this suggestion.
>>
>> Richard
>>
>> On Dec 22, 2023, at 9:20 AM, Arnaud Spiwack <arnaud.spiwack at tweag.io>
>> wrote:
>>
>> I realised today that we haven't completed the vote on this. This is
>> really a very simple proposal, let's not spend too long on this. I'll be on
>> holiday for the next two weeks, I'm a bit embarrassed to send this email
>> only now. But please opine soon. I'd like to be able to give an answer soon
>> after I'm back (say on the 12th January)
>>
>> Best,
>> Arnaud
>>
>> On Mon, 11 Dec 2023 at 11:06, Simon Peyton Jones <
>> simon.peytonjones at gmail.com> wrote:
>>
>>> I recommend acceptance too.  It's all very fine detail.
>>>
>>> The actual diff seems quite large but that's because I encouraged Vlad
>>> to take the opportunity to clarity the rather cryptic sentence in the
>>> original #218, namely "The syntactic descriptions here applying to
>>> expressions apply equally to patterns, though we will continue to discuss
>>> only expressions."  Instead it is all spelled out much more explicitly,
>>> which is way better.  Indeed spelling it out showed up a dark corner to do
>>> with view patterns, hence the icky stuff Arnaud mentions.
>>>
>>> Simon
>>>
>>>    -
>>>
>>>
>>> On Mon, 11 Dec 2023 at 09:56, Arnaud Spiwack <arnaud.spiwack at tweag.io>
>>> wrote:
>>>
>>>> Dear all,
>>>>
>>>> Vlad is proposing to amend his own proposal
>>>> https://github.com/ghc-proposals/ghc-proposals/pull/626
>>>>
>>>> Being an amendment, it's, as always, not as straightforward to consume,
>>>> but Vlad gives us a good summary of the changes in his pull-request
>>>> description.
>>>>
>>>> All in all, it's almost entirely straightforward clarification. There
>>>> are two items of notice: patterns for visible forall arguments were
>>>> specified as: only variable or wildcard. The amendment changes it to allow
>>>> data constructors applied to (0 or more) patterns as well. The amended
>>>> version is consistent with how patterns for invisible forall arguments are
>>>> specified. The second, and this one is for Moritz, is a small change in the
>>>> parsing of view patterns (it does break two packages at least on Hackage,
>>>> but I actually don't quite understand how the change can affect semantics.
>>>> It's that tiny. Vlad proposes 3 releases with warning before effecting the
>>>> change).
>>>>
>>>> Maybe there's a third item: `p -> q` parses differently depending on
>>>> whether ViewPattern or RequiredTypeArguments (or both) is turned on. This
>>>> is kind of icky, I suppose. But in the case where both are on, then
>>>> ViewPattern wins, so there's no real harm in it.
>>>>
>>>> Do pay some attention to the new items in the alternatives section.
>>>>
>>>> Anyway, I recommend we accept.
>>>>
>>>> --
>>>> Arnaud Spiwack
>>>> Director, Research at https://moduscreate.com and https://tweag.io.
>>>> _______________________________________________
>>>> ghc-steering-committee mailing list
>>>> ghc-steering-committee at haskell.org
>>>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
>>>>
>>>
>>
>> --
>> Arnaud Spiwack
>> Director, Research at https://moduscreate.com and https://tweag.io.
>> _______________________________________________
>> ghc-steering-committee mailing list
>> ghc-steering-committee at haskell.org
>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
>>
>>
>>
>
> --
> Arnaud Spiwack
> Director, Research at https://moduscreate.com and https://tweag.io.
>
>
>

-- 
Arnaud Spiwack
Director, Research at https://moduscreate.com and https://tweag.io.
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