我正在学习scalaZ的monad IO，我无法理解catchAll和catchSome运算符是如何工作的 . 我期待看到一个类似于RxJava的onError或onErrorrResumeNext的行为，但是没有捕获throwable，它只是打破了测试并抛出了NullPointerException .

这是我的两个例子

@Test
  def catchAllOperator(): Unit = {
    val errorSentence: IO[Throwable, String] =
      IO.point[Throwable, String](null)
        .map(value => value.toUpperCase())
        .catchAll(error => IO.fail(error))
    println(unsafePerformIO(errorSentence))

  }

并 grab 一些例子

@Test
  def catchSomeOperator(): Unit = {
    val errorFunction = new PartialFunction[Throwable /*Entry type*/ , IO[Throwable, String] /*Output type*/ ] {

      override def isDefinedAt(x: Throwable): Boolean = x.isInstanceOf[NullPointerException]

      override def apply(v1: Throwable): IO[Throwable, String] = IO.point("Default value")
    }

    val errorSentence = IO.point[Throwable, String](null)
      .map(value => value.toUpperCase())
      .catchSome(errorFunction)
    println(unsafePerformIO(errorSentence))

  }

知道我做错了吗？

问候

scala scalaz scalaz7