> Am 02.06.2016 um 07:42 schrieb Austin Zheng via swift-evolution > <swift-evolution@swift.org>: > > Excellent. > > I put together a PR with a revised proposal containing the core team's > recommended approach. If anyone is curious they can see it here: > https://github.com/austinzheng/swift-evolution/blob/ef6adbe0fe09bff6c44c6aa9d73ee407629235ce/proposals/0095-any-as-existential.md > > Since this is the de-facto second round discussion thread, I'll start with my > personal opinion (which is *not* reflected in the PR): the '&' separators in > lieu of commas are a good idea, but I would still prefer the types to be > wrapped in "Any<>", at least when being used as existentials.
I'm very happy with using `&` as I find this very readable. I would prefer not having to wrap them into `Any<>`. While I can image `Any<>`, or rather `any<>`, for existentials with `where` clauses, I would absolutely hate having to wrap all existentials into that which would introduce a lot of noise. > > My reasons: > > - Jordan Rose brought up a good point in one of the discussion threads today: > a resilience goal is to allow a library to add an associated type to a > protocol that had none and not have it break user code. If this is true > whatever syntax is used for existentials in Swift 3 should be a valid subset > of the generalized existential syntax used to describe protocol compositions > with no associated types. If `P` is an existential there is no problem either, isn't it? No need to require `Any<P>`. > > - I would rather have "Any<>" be used consistently across all existential > types eventually than have it only be used for (e.g.) existential types with > `where` constraints, or allowing two different representations of the same > existential type (one with Any, and one without). Far too much noise! > > - I think any generalized existential syntax without delimiting markers (like > angle braces) is harder to read than syntax with such markers, so I would > prefer a design with those markers. I think markers are only needed if a `where` clause is present and probably not even then. -Thorsten > > Best, > Austin > >>> On Jun 1, 2016, at 10:17 PM, Chris Lattner <clatt...@apple.com> wrote: >>> >>> >>> On Jun 1, 2016, at 9:53 PM, Austin Zheng <austinzh...@gmail.com> wrote: >>> >>> This was indeed a very thorough review by the core team. I'll prepare a v2 >>> proposal with this feedback taken into account so we can continue moving >>> things along. >>> >>> One quick question - is making whatever syntax is chosen for Swift 3 >>> "forward-compatible" with a future generalized existential feature a >>> concern? >> >> Yes it is a concern, but we assume that the “X & Y” syntax will always be >> accepted going forward, as sugar for the more general feature that is yet to >> be designed. >> >> -Chris > > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
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