[ghc-steering-committee] Please review: deriving for empty, Shepherd: Iavor Diatchki

[Simon Marlow]

+1 on the proposal, with an extension flag.

I think we should continue to be strict about language extension flags.
Extension flags allow the programmer to signal very clearly which features
they're using, which allows us to write code that will be correctly
rejected with a useful error message both by older versions of GHC and by
hypothetical other compilers that don't support the extension.

If we start to relax the policy of having extension flags, then it's hard
to know where to stop. Yes we have already diverged from Haskell2010, but
so far there was a compelling reason to do so in each case: e.g. we had no
good way to support both versions of the Monad hierarchy, and for
NondecreasingIndentation I think we had been accepting the extended syntax
(without the flag) already in previous versions.

Cheers
Simon


On 17 August 2017 at 17:47, Christopher Allen <cma at bitemyapp.com> wrote:

> I'd tend to agree that we should strictly respect the standard,
> eschewing "benign" augmentations. Part of my discomfort with this is
> my experience talking to programmers who hand-waved effects in general
> as benign. Without a formal definition of benign such as exists in the
> Semantic Versioning standard I'd just as soon not add something like
> this without putting it behind an extension.
>
> I'm a soft +1 on the proposal as an extension.
>
> On Thu, Aug 17, 2017 at 10:05 AM, Richard Eisenberg <rae at cs.brynmawr.edu>
> wrote:
> >
> >> On Aug 16, 2017, at 6:11 PM, Joachim Breitner <mail at joachim-breitner.de>
> wrote:
> >>
> >> that touches on a more fundamental question: How strict do we want to
> >> be with the “every divergence from the standard requires an extension”
> >> rule.
> >
> > I think this is a great question to ask, but I would want more community
> feedback on this point than just us in the committee. My stance is that,
> absent this discussion, we should stay quite strict on that rule.
> >
> > (In the discussion, I would argue that adherence to the standard is less
> necessary.)
> >
> > Richard
> > _______________________________________________
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>
>
>
> --
> Chris Allen
> Currently working on http://haskellbook.com
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