[ghc-steering-committee] #668: Allow reserved identifiers as fields in OverloadedRecordDot, recommendation: accept
Matthías Páll Gissurarson
mpg at mpg.is
Wed Apr 2 09:26:03 UTC 2025
I have a slight preference for B over A. The point that [2] brings up is a
good one, it seems better to allow row.“foo bar”, especially when reading
CSV or JSON as they mention.
So my preference is B>A>C>D
/Matti Palli
On Wed, Apr 2, 2025 at 07:56 Arnaud Spiwack via ghc-steering-committee <
ghc-steering-committee at haskell.org> wrote:
> My preference is
> A>B>C>D
>
> Though my preference between A and B is weak. Whatever's easier really.
>
> On Thu, 20 Mar 2025 at 19:04, Simon Marlow via ghc-steering-committee <
> ghc-steering-committee at haskell.org> wrote:
>
>> I don't feel all that strongly except that C seems like a bad idea. A = B
>> > D > C
>>
>> Cheers
>> Simon
>>
>> On Wed, 19 Mar 2025 at 21:49, Adam Gundry via ghc-steering-committee <
>> ghc-steering-committee at haskell.org> wrote:
>>
>>> Hi everyone,
>>>
>>> This proposal [0] has been lingering for quite some time, unfortunately.
>>> So we can make progress, I've tried to summarise our options below;
>>> please vote for your preferred option in the next week or two. Once we
>>> have decided on our preferred course of action, I'll make any necessary
>>> editorial changes to the proposal.
>>>
>>> To recap, the idea is to extend OverloadedRecordDot such that it permits
>>> record selection expressions such as
>>>
>>> foo.type -> getField @"type" foo
>>>
>>> even though `type` is a keyword and hence not a valid record field in a
>>> traditional datatype declarations. This is primarily motivated by the
>>> use of OverloadedRecordDot in libraries such as `persistent` (see [1]),
>>> which will generate instances like this:
>>>
>>> instance HasField "type" SomeRecord SomeField1 where
>>> getField = ...
>>>
>>> instance HasField "bar" SomeRecord SomeField2 where
>>> getField = ...
>>>
>>> Both these instances are accepted, so it is quite surprising and
>>> annoying that `foo.type` is a syntax error, even though `foo.bar` will
>>> be accepted (and turn into a call to `getField @"bar"`).
>>>
>>> As a small syntactic change, the proposal has lead to quite some
>>> discussion and a few plausible alternatives:
>>>
>>> A. Accept the proposal as it stands, since it is the smallest change
>>> that resolves the issue.
>>>
>>> B. Extend the proposal to permit still wider syntax, e.g.
>>> `foo.Uppercase` or `foo."quoted string"`, motivated by consistency with
>>> OverloadedLabels and use cases such as [2]. This seems reasonable to me.
>>>
>>> C. Extend the proposal to permit keywords such as `type` to be used as
>>> field names in traditional record syntax, e.g. `data Foo = Foo { type ::
>>> Int }`. In my view this is unnecessary complexity that mistakenly
>>> conflates OverloadedRecordDot with traditional record syntax; the
>>> motivation for keywords as selector names comes from uses of
>>> OverloadedRecordDot that do not involve traditional record syntax.
>>>
>>> D. Reject the proposal entirely, e.g. due to worries about syntax
>>> highlighting.
>>>
>>> Please reply with your preference order amongst these options. My vote
>>> is B > A > C > D.
>>>
>>> Thanks,
>>>
>>> Adam
>>>
>>>
>>> [0] https://github.com/ghc-proposals/ghc-proposals/pull/668
>>>
>>> [1]
>>>
>>> https://github.com/ghc-proposals/ghc-proposals/pull/668#issuecomment-2561282397
>>>
>>> [2]
>>>
>>> https://github.com/ghc-proposals/ghc-proposals/pull/668#issuecomment-2564274901
>>>
>>>
>>>
>>> On 05/11/2024 13:58, Arnaud Spiwack wrote:
>>> > I have no opinion on this. But I've seen two points in the thread
>>> which
>>> > make sense: Vlad, our guardian of the parser, says that it's a good
>>> > idea, and the comparison with OverloadedLabel (made by Vlad and
>>> others)
>>> > is apt, and the symmetry is desirable. Ideally the comparison with
>>> > OverloadedLabel should be made in the Alternatives section, but I
>>> don't
>>> > feel like insisting about it :) .
>>> >
>>> > On Sat, 2 Nov 2024 at 21:21, Simon Peyton Jones
>>> > <simon.peytonjones at gmail.com <mailto:simon.peytonjones at gmail.com>>
>>> wrote:
>>> >
>>> > I'm in support too, but I have made some substantive suggestions on
>>> > the GitHub ticket that I'd like to see addressed before we tie a
>>> bow
>>> > on this.
>>> >
>>> > Simon
>>> >
>>> > On Sat, 2 Nov 2024 at 09:25, Sebastian Graf <sgraf1337 at gmail.com
>>> > <mailto:sgraf1337 at gmail.com>> wrote:
>>> >
>>> > I'm in support as well, but would like to see a single
>>> > clarifying sentence added to the proposal.
>>> >
>>> https://github.com/ghc-proposals/ghc-proposals/pull/668#discussion_r1826533003
>>> <
>>> https://github.com/ghc-proposals/ghc-proposals/pull/668#discussion_r1826533003
>>> >
>>> >
>>> > Am Sa., 2. Nov. 2024 um 07:29 Uhr schrieb Erik de Castro Lopo
>>> > <erikd at mega-nerd.com <mailto:erikd at mega-nerd.com>>:
>>> >
>>> >
>>> >
>>> > I am in support.
>>> >
>>> > Erik
>>> >
>>> > Matthías Páll Gissurarson wrote:
>>> >
>>> > > I’m in support. No need to keep reservations longer than
>>> > necessary.
>>> > >
>>> > > /Matti Palli
>>> > >
>>> > >
>>> > > On Fri, Nov 1, 2024 at 23:22 Malte Ott
>>> > <malte.ott at maralorn.de <mailto:malte.ott at maralorn.de>>
>>> wrote:
>>> > >
>>> > > >
>>> > > > On 2024-10-29 20:12, Adam Gundry wrote:
>>> > > > >
>>> > https://github.com/ghc-proposals/ghc-proposals/pull/668
>>> > <https://github.com/ghc-proposals/ghc-proposals/pull/668>
>>> > > >
>>> > > > I’m in support.
>>> > > >
>>> > > > Best
>>> > > > Malte
>>> > > > _______________________________________________
>>> > > > ghc-steering-committee mailing list
>>> > > > ghc-steering-committee at haskell.org
>>> > <mailto:ghc-steering-committee at haskell.org>
>>> > > >
>>> >
>>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
>>> <
>>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
>>> >
>>> > > >
>>> >
>>> >
>>> > --
>>> >
>>> ----------------------------------------------------------------------
>>> > Erik de Castro Lopo
>>> > http://www.mega-nerd.com/ <http://www.mega-nerd.com/>
>>> > _______________________________________________
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>>> <
>>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
>>> >
>>> >
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>>> >
>>> >
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>>> <
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>>> >
>>> >
>>> >
>>> >
>>> > --
>>> > Arnaud Spiwack
>>> > Director, Research at https://moduscreate.com <https://moduscreate.com>
>>>
>>> > and https://tweag.io <https://tweag.io>.
>>> >
>>> > _______________________________________________
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>>> >
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>>>
>>> --
>>> Adam Gundry, Haskell Consultant
>>> Well-Typed LLP, https://www.well-typed.com/
>>>
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>>
>
>
> --
> Arnaud Spiwack
> Director, Research at https://moduscreate.com and https://tweag.io.
> _______________________________________________
> ghc-steering-committee mailing list
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> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
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