[swift-users] Extensions on Typealiased Existential Protocols

[David Sweeris]

IIUC (which shouldn't be assumed on your part) the difference is that any types which conform to both `A` and `B` will automatically conform to `CProtocol` as well, but not `C`. I suspect the "automatic conformance" bit is why we don't currently allow it.

- Dave Sweeris

> On Jun 19, 2017, at 13:44, Jon Shier via swift-users <swift-users at swift.org> wrote:
> 
> What I usually do here is:
> typealias CProtocol = A & B
> protocol C: CProtocol { } // or just A & B directly, I think
> extension C {}
> 
> So it’s a bit silly to me.
> 
> 
> Jon
> 
> 
>> On Jun 19, 2017, at 3:44 PM, Slava Pestov via swift-users <swift-users at swift.org> wrote:
>> 
>> Hi Steven,
>> 
>>> On Jun 19, 2017, at 11:44 AM, Steven Brunwasser via swift-users <swift-users at swift.org> wrote:
>>> 
>>> Is this error intentional, or a bug?
>> 
>> It’s intentional. We could add support for this as an extra bit of sugar, but note that
>> 
>>> Since extension A where Self: B is the same as extension B where Self: A,
>> 
>> This is not quite true.
>> 
>> Slava
>> 
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