[swift-users] Swift 4 protocol with associatedtype conforming to itself

[Jens Persson]

Ok, I thought it was part of SE-0142 (which has status "implemented (Swift
4)".
/Jens

On Wed, Jun 7, 2017 at 9:39 AM, Slava Pestov <spestov at apple.com> wrote:

> This is a rather complex feature that is not actually implemented in Swift
> 4 (or Swift 3 for that matter). Work is underway to support this, though.
> The fact that the second example does not produce a diagnostic is a bug
> (probably you will not be able to define a type that conforms to P2 anyway).
>
> The proposal is here if you’d like to read more about it:
> https://github.com/apple/swift-evolution/blob/master/
> proposals/0157-recursive-protocol-constraints.md
>
> Slava
>
> > On Jun 6, 2017, at 10:37 PM, Jens Persson via swift-users <
> swift-users at swift.org> wrote:
> >
> > In Swift 4:
> >
> > protocol P1 {
> >     associatedtype A: P1 // Error: Type may not reference itself as a
> requirement
> > }
> > protocol P2 {
> >     associatedtype A where A: P2 // OK
> > }
> >
> > What is the rationale behind this?
> >
> > /Jens
> > _______________________________________________
> > swift-users mailing list
> > swift-users at swift.org
> > https://lists.swift.org/mailman/listinfo/swift-users
>
>
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