matching tuple value

tuplematch.swift

protocol Consable {
  typealias Tuple
}

struct HCons<T, U: Consable>: Consable {
  typealias Tuple = (T, U.Tuple)
}

struct HNil: Consable {
  typealias Tuple = ()
}

func ~=<T: Consable>(a: T.Tuple, b: T) -> Bool {
  return true
}

func id<T>(x: T) -> T { return x }

switch (HCons<Int, HCons<Float, HNil>>()) {
  // Need 'id' to trick compiler into thinking this is an expr pattern, not a tuple pattern
  case id(1, (2.0, ())):
    println("ok")
  default: fatalError()
}