These aren't really my points, I just copied them out of the other sub-thread. I'm sure there will be a separate review period, during which many more people will probably join in with their opinions :).
Austin On Fri, May 20, 2016 at 7:59 PM, Matthew Johnson <[email protected]> wrote: > > On May 20, 2016, at 9:10 PM, Austin Zheng <[email protected]> wrote: > > (Trying to move the conversation back to this thread to un-hijack Adrian's > thread.) > > In terms of Any<> vs any<>, I don't have any strong feelings and I think > there are good arguments on both sides. I'm going to leave the proposal as > Any<> but put a section in the 'Alternatives' discussing Any<> vs any<>, so > that if it does go up for review the core team can review arguments and > maybe choose one they like. > > > Thanks for the summary. I think this is helpful. > > > Any<> pros: > - The convention is to capitalize types. 'Any<A, B>' is immediately > apparent as a type, and looks like a type when used in places where types > would be used (like function signatures) > - Having 'Any<>' allows us to keep the well-established 'Any' without > having to typealias to 'any' or 'any<>’ forms > > > How so? you can’t just use `protocol` naked today. You have to say > `protocol<>`. `Any` is a typealias for that. This means we either have a > typealias, we type out `Any<>` or we type out `any<>`. We don’t get to > just type `Any` or `any` without a typealias just because we change the > keyword. > > And I do agree that typealias for existentials should be capitalized. > These are types and behave identically to any other type. > > - any is a keyword, but an argument can be made that keywords that fit > into a particular syntactic slot should be capitalized like normal members > of that slot. Any<> fits into the slot of types, so it should be named like > a type > - In the future, AnySequence and friends can be replaced with, e.g. > Any<Sequence>. > > This increases discoverability of existential features, like a future > "Any<Sequence where .Element == Int>". A number of developers have > mentioned that they suspect protocol<> is rarely used, although GitHub's > search makes it impossible to quantify. > > > If protocol<> is rarely used it is probably because it is a very limited > feature at this point. It becomes extremely useful when we can constrain > associated types. > > When that is possible and the community shares knowledge about how to use > it it will become a widely used feature. I don’t think upper / lower case > or `typealias AnySequnce<T> = Any<Sequence where .Element == T>` will make > much difference either way. > > > any<> pros: > - any<>'s lower case 'a' distinguishes it from other generic types that > use similar syntax, such as "Array<Int>". Perhaps developers, especially > those new to Swift, will be confused as to why "Any<A, B>" isn't a generic > type, but "Dictionary<A, B>" is. > > > The reason this is important is that generic types can be used in ways > that Any cannot. Thus the likely point of confusion is why the following > is not valid: > > struct Foo<T, U> { > func foo(bar: Any<T, U>) { ... } > } > > If we use lowercase it gives the user a hint as to why they might not be > able to use it in all of the same ways as a generic type, *especially* > because Swift is developing strong and consistent conventions for > keywords. If we use uppercase here, not only do we introduce potential > confusion in this case, we *also* water down the meaning of those > conventions and make the language slightly less predictable. (i.e. users > might wonder: are there other uppercase generic-type-like constructs that > don’t quite behave like normal generic types?) > > New developers aside, it may be jarring to have to mentally 'context > switch' between Any<A, B> as an existential, and AnythingButAny<A, B> as a > generic type. > > - any's lower case 'a' makes it clear to users it's not a 'normal' type, > but rather a construction that can be used as a type in some cases, and > can't be used everywhere a concrete type can. > > > Existential types can be used anywhere concrete types can. The difference > is that Any as a* type constructor *behaves much differently than other > type constructors (generic structs, enums, and classes). > > - 'any' isn't a specific type - it's a kind of type (an existential), and > this spelling fits better with the other 'kind' names: 'class', 'struct', > 'enum', 'protocol' > - any is a keyword, and keywords are lower case. Perhaps consistency in > this matter is more important. > > Any other thoughts? I will submit an amendment tonight if people are okay > with this. > > > I have one additional thought. Brent’s rule is based on *exempting* > keywords from the usual rule of lowercase. IMO that exemption should be > reserved for cases where the keyword in question can be used in *all* of > the same was that the similar syntactic form can be used. I believe the > fact that this is not the case for Any is a strong argument to preclude it > from receiving the exemption. > > To be perfectly honest, I do prefer `Any` from an aesthetic / readability > standpoint. But I also think the consistency and usability arguments point > in the other direction. > > When all has been decided I will happily use whatever is decide in my own > code. :-) > > > Austin > > > On May 18, 2016, at 10:35 PM, Austin Zheng <[email protected]> wrote: > > Hello all, > > Swift 3.0 focuses on making breaking changes that prepare the way for > features to be introduced in future releases. In that spirit, I would like > to solicit feedback on a very simple proposal: renaming 'protocol<>' to > 'Any<>', as described in the 'Completing Generics' manifesto. > > The proposal can be found here: > https://github.com/austinzheng/swift-evolution/blob/az-protocol-to-any/proposals/XXXX-any-as-existential.md > > Best, > Austin > > > >
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