[ghc-steering-committee] #390: Fine-grained pragmas, recommendation: accept

[Richard Eisenberg]

I'm happy with this updated proposal, though I've made a small suggestion about making the ;s optional.

Regardless of whether this suggestion is taken, I support acceptance.

Thanks,
Richard

> On Jul 4, 2021, at 5:12 AM, Vitaly Bragilevsky <bravit111 at gmail.com> wrote:
> 
> Dear Committee, 
> 
> I'm happy to repeat my recommendation to accept Alejandro's proposal which is now back from revision:
> Fine-grained pragmas for classes, families, and instances
> https://github.com/ghc-proposals/ghc-proposals/pull/390 <https://github.com/ghc-proposals/ghc-proposals/pull/390>
> https://github.com/serras/ghc-proposals/blob/instance-pragmas/proposals/0000-fine-grained-undecidable.md <https://github.com/serras/ghc-proposals/blob/instance-pragmas/proposals/0000-fine-grained-undecidable.md>
> 
> All the issues that arose in the previous discussion are now resolved. Does anyone have something to add? 
> 
> Vitaly
> 
> 
> 
> сб, 13 мар. 2021 г. в 12:38, Vitaly Bragilevsky <bravit111 at gmail.com <mailto:bravit111 at gmail.com>>:
> чт, 11 мар. 2021 г. в 16:31, Vladislav Zavialov (int-index) <vlad.z.4096 at gmail.com <mailto:vlad.z.4096 at gmail.com>>:
> I like the proposal and I would be happy to vote for its acceptance. However, it requires a little bit of polishing up with regards to its use of modifiers. In particular, it seems to treat modifiers as built-in units, whereas the core idea behind modifiers is that they are based on actual promoted types (with the exception of %1).
> 
> Hence it seems appropriate to send it back for revision until this point is addressed.
> 
> Yes, I agree. There is also another issue. I think we need either a deprecation story for UndecidableInstances, or a statement that it should survive with some motivation behind that. 
> 
> So, I'm sending this proposal back to Alejandro for review and set the "needs revision" label on GitHub.
> 
> Vitaly 
> 
> - Vlad
> 
> > On 20 Feb 2021, at 14:34, Vitaly Bragilevsky <bravit111 at gmail.com <mailto:bravit111 at gmail.com>> wrote:
> > 
> > Dear Committee,
> > 
> > Our own Alejandro has been proposed
> > Fine-grained pragmas for classes, families, and instances
> > https://github.com/ghc-proposals/ghc-proposals/pull/390 <https://github.com/ghc-proposals/ghc-proposals/pull/390>
> > https://github.com/serras/ghc-proposals/blob/instance-pragmas/proposals/0000-fine-grained-undecidable.md <https://github.com/serras/ghc-proposals/blob/instance-pragmas/proposals/0000-fine-grained-undecidable.md>
> > 
> > His idea is to bring the flexibility of overlaps/overlapping/overlappable pragmas to termination checking, type inference, and constraint solving. Alejandro proposes to introduce the following %-modifiers (as in already accepted #370, https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0370-modifiers.rst <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0370-modifiers.rst>):
> > %NoTerminationCheck
> > %LiberalCoverage
> > %LiberalInjectivity
> > %Overlapping
> > %Overlappable
> > %Overlaps
> > to liberate conditions for classes and instances, type families, forall-types, etc. The first three modifiers can be used instead of the scary-sounding UndecidableInstances extension. The last three modifiers are supposed to be used instead of the  overlap*-pragmas for instances we already have. Note that this proposal doesn't suggest deprecating those extensions and pragmas.
> > 
> > I think that this proposal goes in the right direction and recommend accepting it.
> > 
> > As far as I understand, all the committee members, including those with terms about to expire, have the right to either support this proposal or to raise a voice against it either here or at https://github.com/ghc-proposals/ghc-proposals/pull/390 <https://github.com/ghc-proposals/ghc-proposals/pull/390>.
> > 
> > Regards,
> > Vitaly
> > 
> > 
> > 
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