Info: https://github.com/Kametrixom/The-Swift-Make-It-Compile-Challenge

Challenge3.swift

// This one is quite tricky

let returnN = getReturnN()

func availableToIntCollection<C: CollectionType where C.Generator.Element == Int>(c: C) {}

availableToIntCollection([1, 2, 3].lazy.map(returnN))


var a : Int { returnN (n: 3) }
var b : Int { return N(n: 3) }

typealias N = Int

extension Int {
    init(n: Int) { self = n }
}

@noreturn func returnN(n n: Int) -> Int { fatalError() }

func getReturnN() -> @noreturn (n: Int) -> Int { return returnN }

Edit: Now it's better.

@pyrtsa Sadly this does not compile, it fails on the declaration of a ;)
EDIT: Now it does! Congrats! Will update the github page soon :D

@noreturn Ahhh I was missing this one, nice!!!

It strikes me as strange that we can annotate a closure with @NoReturn when defining its type, but can't define such a closure directly; it must have a named function assigned to it instead. At least we can define nested functions:

func getReturnN() -> @noreturn (n: Int) -> Int {
    // Two n's are not needed; in fact, not even one is!
    // Only the parameter name in the return value matters.
    @noreturn func returnN(_: Int) -> Int {}
    return returnN
}