t6963b.scala:2: error: An Array will no longer match as Seq[_].
  def f1(x: Any) = x.isInstanceOf[Seq[_]]
                                 ^
t6963b.scala:4: error: An Array will no longer match as Seq[_].
    case _: Seq[_]  => true
          ^
t6963b.scala:16: error: An Array will no longer match as Seq[_].
    case (Some(_: Seq[_]), Nil, _)        => 1
                ^
t6963b.scala:17: error: An Array will no longer match as Seq[_].
    case (None, List(_: List[_], _), _)   => 2
                    ^
four errors found