Possibly spurious warning on type test

Compiler version

3.0.0

Minimized code

sealed trait Action[Page]
case class Renderer[Page, Props]() extends Action[Page]
sealed trait Redirect[Page] extends Action[Page]

final class RouterLogic[Page, Props] {

  def hmm1(a: Action[Page]): Int =
    a match {
      case r: Renderer[Page, Props] => 1
      case _                        => 2
    }

  def hmm2(a: Action[Page]): Int =
    a match {
      case r: Redirect[Page] => 2
      case _                 => 1
    }
}

Output

[warn] 9 |      case r: Renderer[Page, Props] => 1
[warn]   |           ^^^^^^^^^^^^^^^^^^^^^^^^
[warn]   |      the type test for Renderer[Page, Props] cannot be checked at runtime
[warn] one warning found

Expectation

No warnings. (Scala 2.13.6 emits no warnings.)

[som-snytt]

Scala 2 has received a bunch of improvements around pattern checks. This will be on the top of pile where someone might notice it.

[japgolly]

Fantastic! Very glad to hear that Scala 2 will keep getting love and care for a while yet 😁