typealias TwoIntsFn = (_ a: Int, _ b: Int) -> Int
typealias IntPairFn = (_ pair: (Int, Int)) -> Int

func twoIntsFn(_ a: Int, _ b: Int) -> Int { return a + b }
func intPairFn(_ pair: (Int, Int)) -> Int { return pair.0 + pair.1 }

func takesTwoIntsFn(_ twoIntsFn: TwoIntsFn) { print("Two-ints-function!") }
func takesIntPairFn(_ intPairFn: IntPairFn) { print("Int-pair-function!") }

func test() {
    
    let _: TwoIntsFn = twoIntsFn // OK (as expected)
    let _: IntPairFn = intPairFn // OK (as expected)

    //let _: TwoIntsFn = intPairFn // ERROR 1 (as expected)
    //let _: IntPairFn = twoIntsFn // ERROR 2 (as expected)

    takesTwoIntsFn(twoIntsFn) // OK, prints "Two-ints-function!" (as expected)
    takesIntPairFn(intPairFn) // OK, prints "Int-pair-function!" (as expected)

    // BUT, the following also compiles, even though arguments of the wrong
    // type is given. So these should be errors just like ERROR 1 and 2 above:
    takesTwoIntsFn(intPairFn) // Prints "Two-ints-function!" (should be error)
    takesIntPairFn(twoIntsFn) // Prints "Int-pair-function!" (should be error)
}
test()