struct Foo {
  static func foo(a: () -> Int) {}
  func qux(x: Int, y: () -> Int ) {}
}

func testTrailingClosure() -> String {
  Foo.foo(a: { 1 })
  Foo.bar(a: { print(3); return 1 })
  Foo().qux(x: 1, y: { 1 })
  let _ = Foo().quux(x: 1, y: { 1 })

  [1,2,3]
    .filter { $0 % 2 == 0 }
    .map({ $0 + 1 })
}

func foobar(first: String? = nil, closure: () -> Void) { fatalError() }
func blah() {
  _ = foobar(closure: { print("foo") })
}