Are there any possible explicit uses of instances (values) of empty tuples (), i.e., of instances of typealias 'Void'?

Question

Question:

• Are there any possible explicit uses for the empty tuple (), as a value (and not as a type) in Swift 2.x?

Answer 1

Suppose you have two functions overloading the same name:

func foo()
func foo() -> Int

The first doesn't return anything, the second returns some kind of value. Attempting to call either of these will in most cases get you a compiler error about ambiguity.

foo()
let a = foo()

You'd think that the compiler would know that the first call unambiguously refers to the first function, because it assumes no return value. But in actuality, the return type of a function with no declared return type is Void, or (). So the first call is actually more like this:

let _ = foo()

And absent a type annotation for the discarded lvalue, the compiler can't infer which foo to call. You can use explicit type annotations to disambiguate:

let b: Void = foo()
let c: Int = foo() 

Okay, it's not a very great or common use case for Void, because it's a situation you'd tend to avoid getting into in the first place. But you asked for a use... and it is a use of () as a value and not just a type, because you can retrieve it from b after assignment (for all the good that does you).

Just beware, when you look deeply into the Void, the Void also looks into you. Or something like that.