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sealed abstract class List[+a]
private case object Nil extends List[Nothing]
private final case class Cons[+a](head: a, tail: List[a])
extends List[a]
object List {
def unapply[a](xs: List[a]): Option[(a, List[a])] = xs match {
case Nil => None
case Cons(x, xs) => Some(x, xs)
}
def unapply[a](xs: List[a]): Option[Null] = xs match {
case Nil => Some(null)
case Cons(_, _) => None
}
def foo[a](xs: List[a]) = xs match {
case List(x, xs) => 7
}
def bar(xs: Any) = xs match { // test error message OverloadedUnapplyError
case List(x, xs) => 7
}
}
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