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

OK, I think we've heard from quite a few members of the committee, and the consensus appears to be that we should accept the proposed changes, but guard them with a separate language pragma. I'll post a comment to the thread, requesting that the author makes the change, and then mark it as accepted. -Iavor On Wed, Aug 23, 2017 at 11:44 AM Simon Marlow wrote:

+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 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 wrote:

...

...

On Aug 16, 2017, at 6:11 PM, Joachim Breitner <

mail@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 _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org

https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

-- Chris Allen Currently working on http://haskellbook.com _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

_______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee