[ghc-steering-committee] #409: Exportable named defaults, Recommendation: Partial Accept

[Richard Eisenberg]

Just to chime in now that I'm back in action: I'm reasonably happy with the final result here, but still curious about whether the new warning will be on by default or not.

If it's not: then an unsuspecting user's program could drastically, silently change its meaning just by adding an import -- even if no symbol is used from that import! (I guess this is already true with overlapping instances and orphans. But that doesn't mean we should make the threat worse!)

If it is: the usefulness of the extension is lessened, because any use of it will be noisy.

Richard

> On Jun 27, 2021, at 11:39 AM, Joachim Breitner <mail at joachim-breitner.de> wrote:
> 
> Hi,
> 
> Am Sonntag, dem 20.06.2021 um 22:24 -0400 schrieb Eric Seidel:
>> I recommend we treat defaulting rules like any other importable entity to match how the proposal treats them in export lists
> 
> I am not confident that I can fully predict the practical implications
> of this design, e.g. how well it works for people who advocate for an
> “explicit import lists always” style. But yes, it is a reasonable
> starting point.
> 
> A gut feeling tells me that defaulting rules are a bit more like
> typeclass instances and a bit less like named entities (which you
> import to refer to them in your text). Alejandro voiced that feeling
> too. If we now add a way to mention these typeclass-instancy-thing in
> import and export lists, this _might_ set precendent which could
> eventually lead to syntax for explicitly exporting or importing type
> class instances. This is not a value judgment, just a thought.
> 
> Cheers,
> Joachim
> 
> 
> 
> 
> -- 
> Joachim Breitner
>  mail at joachim-breitner.de
>  http://www.joachim-breitner.de/
> 
> 
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