[Pitch] Use “some” to express “some specialization of a generic type”

Evolution Pitches
10

This has occurred to me as well, but I suppose it only makes sense for input parameters, e.g. some Array could not be a return type. The function implementer would know what Element is but as a caller you wouldn't. Unless the idea is that the actual type is revealed to you implicitly:

func foo() -> some Array { 
   [1, 2, 3]
}

let x = foo() // x is now [Int]

EDIT:

Turns out this already works for some Collection, so I guess it would make sense for some Array as well.

  func foo() -> some Collection {
    [1, 2, 3]
  }

  func bar() {
    let baz = foo() // some Collection in XCode
    print(type(of: baz)) // prints Array<Int>
  }