uninhabited-in-struct.swift

protocol DoSomething {
    func f()
}

enum Empty {}

extension Empty: DoSomething {
    func f() {}
}

struct Container {
    var y: Empty
}

extension Container: DoSomething {
    func f() {
        y.f()
    }
}

func g(_ x: Empty) {
    print(1)
}

/*
a.swift:22:5: warning: will never be executed
    print(1)
    ^
a.swift:21:20: note: 'x' is uninhabited, so this function body can never be executed
func g(_ x: Empty) {
                   ^
a.swift:17:11: warning: will never be executed
        y.f()
          ^
a.swift:17:9: note: a call to a never-returning function
        y.f()
        ^
*/