Re: [swift-evolution] Generic types―covariance/contravariance

As Braeden notes, the same compiler magic already works for most standard library container / monadic types. It could probably work in more cases. Let me clarify what I meant: This compiler magic is a very useful machinery that already exists and although the use cases are not wide enough to

Re: [swift-evolution] Generic types―covariance/contravariance

I did some experimenting, and I see that most variance situations are covered by the compiler. Generic collections and wrappers, like Optional or Array, are acceptable with .map and .flatMap, but currently benefit from compiler magic to cast those types. However, not all the standard library

Re: [swift-evolution] Generic types―covariance/contravariance

I wouldn’t keep it that narrow - monadic types like Optional also benefit from variance: func p(_ data:Any?) { if data != nil { data.map { print($0) } } } var a:String? = "foo" p(a) // -> “foo" -DW > On Dec 9, 2016, at 12:24 PM, Hooman Mehr via swift-evolution >

Re: [swift-evolution] Generic types—covariance/contravariance

Yes, please. +1. Charles > On Dec 8, 2016, at 6:45 PM, Braeden Profile via swift-evolution > wrote: > > Has the core team or the community considered the possibility of implementing > covariant/contravariant generic types? It would really be appreciated. > > I

Re: [swift-evolution] Generic types―covariance/contravariance

Siesta’s Entity would certainly profit from being able to opt in to this mechanism: https://bustoutsolutions.github.io/siesta/api/Structs/Entity.html It is _not_ a collection type and does not implement any

Re: [swift-evolution] Generic types―covariance/contravariance

For the specific case of custom collections, I think it is worth providing a protocol as Doug noted before. Quoting Doug Gregor (1/13/16, thread: "Make generics covariant and add generics to protocols”): > Swift’s value-semantic collections are covariant in their generic parameters, > which

Re: [swift-evolution] Generic types―covariance/contravariance

I keep seeing collections brought up whenever this is discussed, so my question is: Have you found a broader use for variance annotations in the Swift you write? Even in Objective-C (perhaps due to their relative obscurity) I don't see (non-Foundation) people make use of the variance

Re: [swift-evolution] Generic types—covariance/contravariance

Huge +1 here. To bring powerful functional approach to Swift I strongly feel like it's a must have. Issue demonstration: //co/invariance type typealias FooFun<-A, +R> = (A)->R //current types typealias BarFun = (A)->R func exact(view:UIView) -> UIView func nonexact(view:NSObject) ->

[swift-evolution] Generic types—covariance/contravariance

Has the core team or the community considered the possibility of implementing covariant/contravariant generic types? It would really be appreciated. I know with Array, vague-ifying or specific-ifying the type ([Int] to [Any]) has help from the compiler—and we can use `map` if all else