[swift-evolution] [Review] SE-0194: Derived Collection of Enum Cases

[Riley Testut]

I’m overall +1, but I’m curious: would you be able to conform an enum from another module to ValueEnumerable via an extension, and still have the compiler generate the protocol requirements for you? I can imagine that the client of a framework with an enum may have a valid use for iterating over all values that the author didn’t foresee, and I would very much like the client to be able to opt-in to the compiler code generation.

(Personally, I’d prefer that all simple enums automatically conform to the protocol and have automatic implementations, since I don’t really see a downside to this that exists for some other compiler-magic protocols like Codable)

> On Jan 9, 2018, at 8:45 AM, Tony Allevato via swift-evolution <swift-evolution at swift.org> wrote:
> 
>> On Mon, Jan 8, 2018 at 11:02 AM Douglas Gregor via swift-evolution <swift-evolution at swift.org> wrote:
>> Hello Swift community,
>> 
>> The review of SE-0194 "Derived Collection of Enum Cases" begins now and runs through January 11, 2018. The proposal is available here:
>> 
>> https://github.com/apple/swift-evolution/blob/master/proposals/0194-derived-collection-of-enum-cases.md
>> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at
>> 
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>> or, if you would like to keep your feedback private, directly to the review manager. When replying, please try to keep the proposal link at the top of the message:
>> 
>> Proposal link:
>> 
>> https://github.com/apple/swift-evolution/blob/master/proposals/0194-derived-collection-of-enum-cases.md
>> Reply text
>> Other replies
>> What goes into a review?
>> 
>> The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:
>> 
>> What is your evaluation of the proposal?
> Big +1. I've been looking forward to something like this for a long time.
> 
> I'm extremely happy with the API chosen here. ValueEnumerable and allValues are absolutely the correct names, because the protocol is not *restricted* to enums, it is merely *synthesized automatically* for enums. That's a very important distinction. Someone could provide their own conformance to ValueEnumerable and use it in generic algorithms and have everything work as expected.
> 
> In a perfect world I would argue that the associated type of allValues should be a Sequence instead of a Collection as this would allow it to be extended to infinite sequences (i.e., cases with associated values that are deeply ValueEnumerable), but I'll admit that I've never come up with a compelling use case for this beyond obscure combinatorial algorithms. Since getting the count of values is important to many users, Collection is a reasonable compromise and I don't have any objections.
>  
>> Is the problem being addressed significant enough to warrant a change to Swift?
> Yes. It's a frequently requested feature and has utility both in UI-driven logic (table view sections based on an enum) and other algorithms.
> 
>  
>> Does this proposal fit well with the feel and direction of Swift?
> Yes. The API design fits right into other stdlib concepts, and the conditions for synthesis align with the synthesis of other synthesized protocols.
> 
>  
>> If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
> Just Java's values() function that is present on all enums. The functionality provided here is what I would expect, similar to other languages.
> 
>  
>> How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
> An in-depth read and I was heavily involved in some of the earlier discussion threads.
> 
>  
>> More information about the Swift evolution process is available at
>> 
>> https://github.com/apple/swift-evolution/blob/master/process.md
>> Thank you,
>> 
>> -Doug Gregor
>> 
>> Review Manager
>> 
>> _______________________________________________
>> 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20180109/42dfce44/attachment.html>