[Haskell] Treatment of unknown pragmas

[Artem Pelenitsyn]

Hello Daniel,

Annotations API was discussed earlier in this thread. Main points against
are:

Neil:
Significant compilation performance penalty and extra recompilation. ANN
pragmas is what HLint currently uses.

Brandon:
The problem with ANN is it's part of the plugins API, and as such does
things like compiling the expression into the program in case a plugin
generates code using its value, plus things like recompilation checking end
up assuming plugins are in use and doing extra checking. Using it as a
compile-time pragma is actually fairly weird from that standpoint.

--
Best, Artem
On Sat, 27 Oct 2018 at 22:12 Daniel Wagner <dmwit at dmwit.com> wrote:

> I don't have a really strong opinion, but... isn't this (attaching
> string-y data to source constructs) pretty much exactly what GHC's
> annotation pragma is for?
> ~d
>
> On Tue, Oct 16, 2018 at 3:14 PM Ben Gamari <ben at smart-cactus.org> wrote:
>
>> Vladislav Zavialov <vlad.z.4096 at gmail.com> writes:
>>
>> > What about introducing -fno-warn-pragma=XXX? People who use HLint will
>> > add -fno-warn-pragma=HLINT to their build configuration.
>> >
>> A warning flag is an interesting way to deal with the issue. On the
>> other hand, it's not great from an ergonomic perspective; afterall, this
>> would mean that all users of HLint (and any other tool requiring special
>> pragmas) include this flag in their build configuration. A typical
>> Haskell project already needs too much such boilerplate, in my opinion.
>>
>> I think it makes a lot of sense to have a standard way for third-parties
>> to attach string-y information to Haskell source constructs. While it's
>> not strictly speaking necessary to standardize the syntax, doing
>> so minimizes the chance that tools overlap and hopefully reduces
>> the language ecosystem learning curve.
>>
>> Cheers,
>>
>> - Ben
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