[swift-evolution] Language enhancement: Nest enum declaration into protocol declaration

[Derrick Ho]

Actually this is very consistent. You can not nest data structures like
enums, structs, or classes in a protocol. This is because a protocol is
meant to be a list of variables and functions that data structures may
conform to. A protocol is not a data structure.
On Mon, Nov 21, 2016 at 7:33 AM Jakub Bednář via swift-evolution <
swift-evolution at swift.org> wrote:

> Hi fellow Swifters,
>
> I have just started using the language and was trying to declare an enum
> inside a protocol.
>
> protocol WorkingEngine {
>    enum States {
>         Idle
>         Pending
>         Working
>         Finished
>         Canceled
>   }
>
>   var state: States { get }
> }
>
> The compiler refused this and I had to take the enum outside of the
> protocol:
>
> enum WorkingEngineStates {
>         Idle
>         Pending
>         Working
>         Finished
>         Canceled
>   }
>
> protocol WorkingEngine {
>   var state: WorkingEngineStates { get }
> }
>
> This does not seem coherent with the rest of the language, as enums can be
> nested in classes, structs and even enums, but not to protocols.
> I haven’t found any proposal for this change. Is this the correct place to
> request it or get some opinion on the idea?
>
> Thanks a lot,
>
> Jakub
>
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>
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