[swift-evolution] Request for information about constrained protocol inheritance

[Xiaodi Wu]

Replying to swift-users as well, as it's probably the more appropriate
forum.

SE-0142 (Permit where clauses to constrain associated types) is what
brought about this feature. It is now used in the standard library.


On Wed, Jul 5, 2017 at 00:26 Jens Persson via swift-evolution <
swift-evolution at swift.org> wrote:

> The following compiles in Swift 4 (but not in Swift 3.1):
>
> protocol P1 {
>     associatedtype A
> }
> protocol P2 : P1 where A == Int {
> }
>
> I've not been able to find any proposal, discussion or documentation
> mentioning it so any pointers to such would be greatly appreciated.
>
> Also, is this new feature used somewhere in the std lib?
>
> /Jens
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> swift-evolution at swift.org
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>
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