bug960.check

来自「JAVA 语言的函数式编程扩展」· CHECK 代码 · 共 11 行

bug960.scala:18: error: ambiguous reference to overloaded definition,
both method unapply in object List of type [a](List[a])Option[Null]
and  method unapply in object List of type [a](List[a])Option[(a, List[a])]
match argument types (List[a])
    case List(x, xs) => 7
         ^
bug960.scala:12: error: method unapply is defined twice
  def unapply[a](xs: List[a]): Option[Null] = xs match {
      ^
two errors found