Is it possible to extract a higher kind argument in Scala 2 or 3 without using match type?

edit

No, it is not possible to extract a higher kind argument in Scala 2 or 3 without using match type. Match type is the only way to pattern match on a type parameter that has a kind higher than * (i.e., a type constructor).

For example, consider the following code:

trait Functor[F[_]] {
  def map[A, B](fa: F[A])(f: A => B): F[B]
}

To implement the map method, we need to extract the type constructor F from the type parameter F[_]. In Scala 2 or 3, we can only do this using match type:

trait Functor[F[_]] {
  def map[A, B](fa: F[A])(f: A => B): F[B] = fa match {
    case fa: F[t] => ??? // Here we use match type to extract the type constructor F
  }
}

Without match type, we would need to rely on the user of the Functor trait to provide an implicit evidence of the Functor instance for the specific type F, which is less convenient and can lead to boilerplate code.