> On Jun 24, 2017, at 6:24 PM, Anders <[email protected]> wrote:

> 
> The feature you called for is generalized existentials. It is on the Generic 
> Manifesto and had a few long discussion threads on the list before. 
> Apparently, it is out of scope for Swift 4, and whether it is in scope of 
> Swift 5 remains to be seen.

Thanks, I wasn’t sure of the right name for the kind of feature.  I’ll be sure 
to watch for any related proposals and vote yes early and often. ;-)
I must have missed the discussions.  I had switched to digests for a while, 
which made following any actual discussion nearly intractable.

> By the way, for your code snippet, apparently you may simply add 
> "doSomething" overloads for `P: B` and `P: C`. The compiler will pick the 
> most specific variant for you at compile time. Deferring to runtime with 
> existentials is not necessarily the only option.

Yes, that’s what I’m doing now, and it felt unnecessary.  There were pieces of 
my logic which had to be duplicated.

-Ben

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