在Scala中,为什么不为类型参数发出不加检查的警告？

class A[K] {
  def receive: PartialFunction[Any,Unit] = {
    case ds: List[Double] =>  // unchecked warning
      println("* List[Double]")
    case kx: Vector[K] =>      // no unchecked warning
      println("* Vector[K]")
  }
}

object TestApp extends App {
  val a = new A[Int]
  a.receive(List("bar"))
  a.receive(Vector("foo"))
}

两个接收电话不幸匹配case子句.编译器确实发出了第一个子句的警告：

Warning: non-variable type argument Double in type pattern List[Double] is unchecked since it is eliminated by erasure.

我知道TypeTag [T]可以用来实现更好的安全性.但我关心的是为什么第二个案例条款没有发出任何不加检查的警告.据我所知,类型参数K也被删除,根据Java Generics FAQ

“unchecked” warnings are also reported when the compiler finds a cast whose target type is either a parameterized type or a type parameter

所以我不知道为什么不会有一个不加检查的警告？