class A {
  fun Double.foo(a: Double = 1.0): Double {
      return a
  }

  fun test(): String {
      if (1.0.foo() != 1.0) return "fail"
      if (1.0.foo(2.0) != 2.0) return "fail"
      return "OK"
  }
}

fun box(): String  {
   return A().test()
}