This is the proposal I'd like to see go before review, and the one I think is 
closest in spirit to the generics roadmap.

Things like adding union types, and rewriting Swift's type system to look like 
Scala's, have very little to do with better representations of existentials, 
and belong in a follow-up proposal.

Austin

> On May 16, 2016, at 11:55 PM, Brent Royal-Gordon via swift-evolution 
> <swift-evolution@swift.org> wrote:
> 
>> But don't you mean the union type of all possible Collection types when you 
>> write Any<Collection>?
> 
> No, I mean "an existential capable of holding any Collection".
> 
> If I write Any<Equatable, Collection>, I mean "an existential capable of 
> holding any Equatable Collection".
> 
> If I write Any<UITableViewCell, CounterDisplaying>, I mean "an existential 
> capable of holding any CounterDisplaying UITableViewCell".
> 
> If I write Any<Collection where .Element: Equatable>, I mean "an existential 
> capable of holding any Collection with an Equatable Element".
> 
> If I write Any<class>, I mean "An existential capable of holding any class 
> instance".
> 
> If I write Any, I mean "An existential capable of holding anything".
> 
> Union types have nothing to do with it.
> 
> -- 
> Brent Royal-Gordon
> Architechies
> 
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