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object Test {
sealed abstract class Foo[T]
case object Bar1 extends Foo[Int]
case object Bar2 extends Foo[String]
case object Bar3 extends Foo[Any]
def ex1[T](xs: List[T]) = xs match {
case ys: List[_] => "ok"
}
def ex2[T](xx: (Foo[T], Foo[T])) = xx match {
case (Bar1, Bar1) => ()
case (_, Bar1) => ()
case (_, Bar3) => ()
case (_, Bar2) => ()
}
def ex3[T](xx: (Foo[T], Foo[T])) = xx match {
case (_: Foo[_], _: Foo[_]) => ()
}
// fails for: ::(_, Nil), ::(_, ::(_, ::(_, _))), ...
def fail1[T](xs: List[T]) = xs match {
case Nil => "ok"
case x :: y :: Nil => "ok"
}
// fails for: Nil
def fail2[T](xs: List[T]) = xs match {
case _ :: _ => "ok"
}
// fails for: ::(<not in (2, 1)>, _)
def fail3a(xs: List[Int]) = xs match {
case 1 :: _ =>
case 2 :: _ =>
case Nil =>
}
// fails for: Bar3
def fail3[T](x: Foo[T]) = x match {
case Bar1 => "ok"
case Bar2 => "ok"
}
// fails for: (Bar1, Bar2)
// fails for: (Bar1, Bar3)
// fails for: (Bar2, Bar2)
// fails for: (Bar2, Bar1)
def fail4[T <: AnyRef](xx: (Foo[T], Foo[T])) = xx match {
case (Bar1, Bar1) => ()
case (Bar2, Bar3) => ()
case (Bar3, _) => ()
}
// fails for: (Bar1, Bar2)
// fails for: (Bar1, Bar3)
// fails for: (Bar2, Bar1)
// fails for: (Bar2, Bar2)
def fail5[T](xx: (Foo[T], Foo[T])) = xx match {
case (Bar1, Bar1) => ()
case (Bar2, Bar3) => ()
case (Bar3, _) => ()
}
}
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