I totally agree. Being able to work properly with existentials (and the other 
generics stuff from the generics manifesto) is more important for Swift than 
adding something like Ceylon's union and intersection types (even though I am a 
fan of them :-)



-Thorsten




Am 17. Mai 2016 um 09:09 schrieb Austin Zheng <[email protected]>:


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 
<[email protected]> 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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