测试方法在类型上不可用的方法

Question

给定游戏的类型层次结构,强烈区分下一轮的转弯:

trait Game
trait BlackToPlay extends Game {
  def move(p: BlackPiece, s: Square): Either[FinishedGame, WhiteToPlay]
}
trait WhiteToPlay extends Game {
  def move(p: WhitePiece, s: Square): Either[FinishedGame, BlackToPlay]
}

我可以在不诉诸反思的情况下做出以下重要断言吗？

"A game with white to play" should {
  "not allow black to play" in {
    // an instance of whiteToPlay should not 
    // have the `move(BlackPiece, Square)` method.
  }
}

编辑:我尝试实施@Martin的解决方案不起作用.对这里有什么不妥的想法？来自REPL:

scala> class B() {
     |   def b(s: String) = s
     | }
defined class B

scala> val b = new B()
b: B = B@420e44

scala> b.c("")
<console>:8: error: value c is not a member of B
       b.c("")
         ^

scala> b match {
     |   case _: { def c(s: String) } => false
     |   case _ => true
     | }
warning: there were unchecked warnings; re-run with -unchecked for details
res7: Boolean = false

res7应该是真的,因为b结构类型不应该匹配{ def c(s: String) }

Answer 1

您不测试系统已经保证的类型.实际上,类型系统已经是对程序某些属性的测试.

你可以进一步测试你保证某种属性的类型(比如没有玩家连续两次移动),但是这种东西仅限于像Agda和Coq这样的语言.