[swift-evolution] Enhanced existential types proposal discussion

[Joe Groff]

> On May 17, 2016, at 2:04 PM, Austin Zheng <austinzheng at gmail.com> wrote:
> 
> I think this is also probably the best approach. Reskin protocol<> so people can fix their code when 3.0 hits, and then extend its functionality in an additive way.
> 
> Joe, given that this counts as part of "generics and ABI", is it acceptable to continue discussion? Or should all of this be tabled until August?

IMO, discussion on the list is fine, though most of us are probably too busy to deeply participate right now, and any submitted proposals are likely to be deferred until after Swift 3 wraps up.

-Joe

> Austin
> 
> On Tue, May 17, 2016 at 1:55 PM, Joe Groff <jgroff at apple.com> wrote:
> 
> > On May 17, 2016, at 1:27 PM, Matthew Johnson via swift-evolution <swift-evolution at swift.org> wrote:
> >
> >
> >> On May 17, 2016, at 3:06 PM, Austin Zheng <austinzheng at gmail.com> wrote:
> >>
> >> I'm honestly not sure it makes sense to introduce a proposal just for expressing <Class, Protocol, Protocol> style requirements, and then trying to retrofit fuller support for other existentials onto it. I would prefer that the 'basic package' of existential cases be considered together as a single proposal, unless a core team member expresses their preference otherwise.
> >
> > It also renames protocol<> to Any, but fair enough.
> >
> > One reason to keep it separate is that the rename is a breaking change and we should really try to get that into Swift 3.  Generalizing existentials is an additive change.  I would love to have that in Swift 3 as well, but if it’s not going to make it I don’t think it should hold back the smaller change which is a breaking change.
> >
> > Doug, any opinion on this?
> 
> I agree with this. If we're certain we should reskin protocol<> as Any<>, we should frontload that change—in addition to affecting source code, it'd also influence the runtime behavior of type printing/parsing, which can't be statically migrated in the future. I think any discussion of extending existentials has to be considered out of scope for Swift 3, though, so the Any rename deserves its own proposal.
> 
> -Joe
>