[swift-evolution] [Proposal] Allow enumerating cases in enumerations

[Karl]

> On 5 Jul 2016, at 12:47, Charlie Monroe via swift-evolution <swift-evolution at swift.org> wrote:
> 
> This is mentioned in Gabriel's proposal:
> 
>> Implement a native .cases static var for all enumerations without associated values
> 
> 
> But as has been mentioned in the discussion, this was mentioned by Brent:
> 
>> In previous discussions, the core team specifically asked that this be opt-in so that types which don't want it don't need to "pay" for it.
> 

Looking at the previous discussions, this kind of functionality belongs as part of reflection (once we have a mature reflection API). If you are reflecting a type that is completely known to the compiler (e.g. a concrete value-type, such as a struct or enum), it should be able to statically optimise it.

This is a commonly-enough requested feature that I would like to do it before the reflection API (there’s no public roadmap yet, but I don’t think it’s even under consideration for Swift 4). OTOH, I’m not sure if it makes sense to implement it in hacky way with compiler-generated constants and then replace it once we have a stable ABI.

Probably best to wait for the Swift 4 roadmap discussion and to see what the plans for reflection actually are. So I’m taking back my +1, sorry.

Karl
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