Equivalent of class methods, but for protocols (Factory Methods / Class Clusters)

[ethanjdiamond (Ethan Diamond)]

@Karl

You can just put the known instances somewhere else, which tends to be a better design in most of the real examples I've seen...

That breaks the shorthand in my example without providing extra benefit.

For the core team, there's been a lot of discussion on [Proposal] Factory Initializers - #18 by Charles_Srstka around this, though it was factory methods on classes, not protocols. it seemed to have a lot of interest but then got swept up in ABI stability. It seemed to have a lot of interest at the time.