[swift-evolution] [Returned for Revision] SE-0095: Replace protocol<P1, P2> syntax with Any<P1, P2>

[Jordan Rose]

Yep. I also remain against this syntax, primarily for reasons of learnability.

> On Jun 2, 2016, at 08:25, Austin Zheng via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I'm sure the list is getting sick of me making this point over and
> over again :), so I'll only do it one more time: I find the lack of
> delimiters far worse in terms of readability for type expressions of
> any appreciable complexity than any number of `Any<>` tokens. In fact,
> I'm a bit surprised the core team decided to go in this direction,
> given their stance on parentheses for function types, and replacing
> operators like "&&" or "||" with "and" or "or". I respect their
> decision, though.
> 
> On 6/2/16, Thorsten Seitz <tseitz42 at icloud.com> wrote:
>> 
>> 
>>> Am 02.06.2016 um 07:42 schrieb Austin Zheng via swift-evolution
>>> <swift-evolution at 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 <clattner at apple.com> wrote:
>>>>> 
>>>>> 
>>>>> On Jun 1, 2016, at 9:53 PM, Austin Zheng <austinzheng at 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 at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>> 
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution