[ghc-steering-committee] #167: Deprecated Entities, rec: accept

Wed Mar 13 15:57:38 UTC 2019

Thank you for this summary, Simon. I didn't realize that the earlier
proposal Require namespacing fixity declarations for type names and
WARNING/DEPRECATED pragmas
<https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0008-type-infix.rst>
affects
DEPRECATED pragmas. They were mentioned in the title but they were not
mentioned in the proposed changes. Now I see in the Motivation section that
«*as well as DEPRECATED pragmas, which accomplish the same thing, so I'll
refer to them henceforth as just WARNING pragmas*».

Joachim, I'm not sure how to proceed here. I don't think that this is the
case for "Needs Revision". I could start another thread with the
recommendation to reject this proposal with the reason that another
(accepted) proposal subsumes this one but it doesn't make too much sense
either.

Vitaly

On Wed, Mar 13, 2019 at 4:35 PM Simon Marlow <marlowsd at gmail.com> wrote:

> On Mon, 11 Mar 2019 at 13:26, Richard Eisenberg <rae at cs.brynmawr.edu>
> wrote:
>
>> "value" would not work as the namespace indicator I envision for the
>> future, as it's a commonly used variable name. (I would advocate against
>> making it a keyword for this reason.) This knob is relatively easy to turn,
>> though, so it's conceivable to use "value" today, and then if/when we start
>> using "data" in the future, allow the use of "data" where we use "value",
>> eventually deprecating and removing "value". It's a bit annoying to users
>> to keep changing it, but only a bit. I've been in this game long enough to
>> know that the future isn't quite predictable, and so I see the sense in
>> choosing the best thing for us now, leaving the door open to fixing it
>> later if necessary. I still advocate for "data", but I won't burst into
>> tears if we choose "value".
>>
>> I could see waiting a day or two for further commentary and then putting
>> it to a committee vote. In the end, I think this choice matters little.
>>
>
>
> For those who (like me) might have been a bit confused about the current
> state of things:
>
>    - There are 5 places that we want namespace specifiers now (possibly
>    more later): import, export, fixity, WARNING, DEPRECATED
>    - GHC's existing *ExplicitNamespaces* option allows *type* and
>    *pattern* keywords to be used in import, export
>    - The earlier proposal Require namespacing fixity declarations for
>    type names and WARNING/DEPRECATED pragmas
>    <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0008-type-infix.rst>
>    was accepted, and allows *type* and *value* keywords in fixity,
>    WARNING, DEPRECATED
>    - This proposal Deprecated Entities
>    <https://github.com/nineonine/ghc-proposals/blob/depr-entities/proposals/0000-deprecated-entities.rst>
>    suggests adding *type* and *pattern* specifiers to DEPRECATED pragmas.
>    (note that DEPRECATED pragmas were covered by the earlier proposal, so this
>    conflicts)
>    - Vitaly's suggested modification of this proposal is to  adopt *type*
>    and *data* instead (for DEPRECATED pragmas), while Simon pointed out
>    that we already accepted a proposal for this, using *type* and *value*,
>    and that whatever we do we should do it consistently across import, export,
>    fixity, WARNING, DEPRECATED (yes!)
>
> I don't think it makes a lot of sense to accept this proposal, since it
> conflicts with the earlier one. Should we instead work on a modification of
> the earlier proposal to extend it to import/export lists, and also resolve
> the debate about *data/pattern/value*?
>
> Richard's concerns about future extensions to add namespacing in
> expressions seem valid to me, it would be unfortunate to use *value* now
> if that will cause problems later.
>
> Cheers
> Simon
>
>
>
>> Richard
>>
>> On Mar 11, 2019, at 9:12 AM, Vitaly Bragilevsky <bravit111 at gmail.com>
>> wrote:
>>
>> Hi Richard,
>>
>> Do you think that using "value" now is a real stopper for the future you
>> are talking about? Maybe we should start thinking about making "value" a
>> reserved keyword because it suits our purposes best as a namespace
>> specifier. It looks like this data/value debate is the only issue before
>> reaching the consensus on this proposal. So we have to do something about
>> it.
>>
>> Regards,
>> Vitaly
>>
>> On Sun, Mar 10, 2019 at 12:10 AM Richard Eisenberg <rae at cs.brynmawr.edu>
>> wrote:
>>
>>> My argument for `data` is as follows (quoted from earlier writing of
>>> mine):
>>>
>>> ---
>>> Though I understand the reasons against it, I'm an unabashed supporter
>>> of using the word "data" to supplant "pattern". My principal argument is
>>> that data can be used freely in the syntax, given that it's a keyword
>>> that has current meaning only as the first lexeme in a top-level
>>> declaration. (Specifically, I pine for a future where types and terms mix.
>>> We can then use type and data in the middle of expressions/types to
>>> denote namespaces.) It also works nicely to mean "data constructor". I
>>> agree that it doesn't work as well with functions or the potential
>>> confusion around "data Bool = True | False" (though, in that last example,
>>> we can pretend hard that the data applies only to the bits after the =
>>> ).
>>> ---
>>>
>>> In other words, I think `data` is more future-compatible than any of the
>>> alternatives, even though I agree that `value` flows more smoothly. We can
>>> think of `data` as meaning "data-level", not "data constructor" (though
>>> that admittedly takes a bit of mental gymnastics).
>>>
>>> Richard
>>>
>>>
>>> On Mar 8, 2019, at 1:12 PM, Vitaly Bragilevsky <bravit111 at gmail.com>
>>> wrote:
>>>
>>> I think we don't have a consensus on the particular word yet: is it data
>>> or value. I'd like to listen to Richard who was strongly in favor of data.
>>> We are in agreement about consistency though.
>>>
>>> Vitaly
>>>
>>>
>>> On Fri, Mar 8, 2019 at 8:45 PM Joachim Breitner <
>>> mail at joachim-breitner.de> wrote:
>>>
>>>> Hi,
>>>>
>>>> I fully support this (I thought I brought it up before, but maybe not
>>>> strongly enough).
>>>>
>>>> Should we just include this change in #167? (If politicians can add
>>>> random riders to laws, so can we). Or does it need more thought?
>>>>
>>>> Cheers,
>>>> Joachim
>>>>
>>>>
>>>> Am Freitag, den 08.03.2019, 14:46 +0000 schrieb Simon Peyton Jones via
>>>> ghc-steering-committee:
>>>> > I also argue that, to be consistent, whatever keyword we agree, we
>>>> should use it
>>>> > In the (accepted) infix/WARNING proposal
>>>> > In import and export lists – presumably for now in addition to
>>>> ‘pattern’, though we might end up deprecating the latter.
>>>> > Simon
>>>> >
>>>> > From: Vitaly Bragilevsky <bravit111 at gmail.com>
>>>> > Sent: 08 March 2019 14:44
>>>> > To: Simon Peyton Jones <simonpj at microsoft.com>
>>>> > Cc: Simon Marlow <marlowsd at gmail.com>; ghc-steering-committee <
>>>> ghc-steering-committee at haskell.org>
>>>> > Subject: Re: [ghc-steering-committee] #167: Deprecated Entities, rec:
>>>> accept
>>>> >
>>>> > Simon PJ argues for "value" over "data" as a specifier:
>>>> https://github.com/ghc-proposals/ghc-proposals/pull/167#issuecomment-470947193
>>>> >
>>>> > I'm fine with this choice either (and I'm satisfied with the argument
>>>> that deprecating or setting fixity for value "value" is a rare case to be
>>>> considered seriously). If you have another opinion, please, speak up.
>>>> >
>>>> > Vitaly
>>>> >
>>>> > On Fri, Mar 8, 2019 at 11:42 AM Simon Peyton Jones <
>>>> simonpj at microsoft.com> wrote:
>>>> > > I’ve made a post on the proposal thread asking why we don’t just
>>>> follow the already-adopted proposal for WARNING and infix pragmas.
>>>> > >
>>>> > > Simon
>>>> > >
>>>> > > From: ghc-steering-committee <
>>>> ghc-steering-committee-bounces at haskell.org> On Behalf Of Simon Marlow
>>>> > > Sent: 08 March 2019 07:57
>>>> > > To: Vitaly Bragilevsky <bravit111 at gmail.com>
>>>> > > Cc: ghc-steering-committee <ghc-steering-committee at haskell.org>
>>>> > > Subject: Re: [ghc-steering-committee] #167: Deprecated Entities,
>>>> rec: accept
>>>> > >
>>>> > > Yes, I think this is the right way to go.
>>>> > >
>>>> > > Cheers
>>>> > > Simon
>>>> > >
>>>> > > On Fri, 8 Mar 2019 at 05:25, Vitaly Bragilevsky <
>>>> bravit111 at gmail.com> wrote:
>>>> > > > Hi everyone,
>>>> > > >
>>>> > > > I was asked to shepherd the proposal #167 (Deprecated Entities,
>>>> https://github.com/nineonine/ghc-proposals/blob/depr-entities/proposals/0000-deprecated-entities.rst).
>>>> It is proposed to extend (nonpositional) DEPRECATED pragma with the two
>>>> specifiers to disambiguate deprecating named type-level and value-level
>>>> things. In its current formulation, the proposal suggests to use the
>>>> specifiers "type" for type-level things and "pattern" for value-level
>>>> things as follows:
>>>> > > >
>>>> > > > data Bar = Bar
>>>> > > > {-# DEPRECATED type Bar "Don't use type Bar" #-}
>>>> > > > data Baz = Baz
>>>> > > > {-# DEPRECATED pattern Baz "Don't use data constructor Baz" #-}
>>>> > > >
>>>> > > > Using this pragma without specifiers should mean deprecating both
>>>> (as is works now).
>>>> > > >
>>>> > > > After discussing this proposal within the committee (see
>>>> https://mail.haskell.org/pipermail/ghc-steering-committee/2019-February/000894.html),
>>>> I recommend acceptance with one change, namely using "data" instead of
>>>> "pattern" for deprecating value-level things.
>>>> > > >
>>>> > > > Reasons for choosing "data":
>>>> > > > * it's a reserved keyword (as opposed to "value", which is
>>>> another option)
>>>> > > > * we are deprecating data constructors here
>>>> > > > * it just feels right (sorry!)
>>>> > > >
>>>> > > > Reasons against "data":
>>>> > > > * it can be confusing whether we mean data type or data
>>>> constructor
>>>> > > > * we use "value" and "pattern" in other places meaning basically
>>>> the same thing
>>>> > > >
>>>> > > > If the committee decides to go this way, then the wider community
>>>> may think about other proposals, such as
>>>> > > > * adding positional DEPRECATED pragmas (including class instances
>>>> deprecation)
>>>> > > > * fixing inconsistencies with the fixity declarations (
>>>> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0008-type-infix.rst)
>>>> and updating ExplicitNamespaces in import/export lists
>>>> > > > * deprecating usage of nonpositional DEPRECATED pragma without
>>>> the specifiers
>>>> > > >
>>>> > > > Silence is understood as agreement.
>>>> > > >
>>>> > > > Regards,
>>>> > > > Vitaly
>>>> > > >
>>>> > > > _______________________________________________
>>>> > > > ghc-steering-committee mailing list
>>>> > > > ghc-steering-committee at haskell.org
>>>> > > >
>>>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
>>>> >
>>>> > _______________________________________________
>>>> > ghc-steering-committee mailing list
>>>> > ghc-steering-committee at haskell.org
>>>> >
>>>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
>>>> --
>>>> Joachim Breitner
>>>>   mail at joachim-breitner.de
>>>>   http://www.joachim-breitner.de/
>>>>
>>>> _______________________________________________
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>>>>
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>>>
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