Exhaustivity checking false positive

[travisbrown]

Minimized code

sealed trait Base[A, +B]
case class Foo[A, +B](f: A => B) extends Base[A, B]

def bar(x: Base[Any, Any]): Unit = x match { case Foo(_) => }

Output

// defined trait Base
// defined case class Foo
4 |def bar(x: Base[Any, Any]): Unit = x match { case Foo(_) => }
  |                                   ^
  |                                   match may not be exhaustive.
  |
  |                                   It would fail on pattern case: Foo(_)
def bar(x: Base[Any, Any]): Unit

Expectation

This should compile without a warning, as it does in Scala 2 and Dotty up until at least 0.23.0. I first noticed it giving this warning in 0.24.0-RC1, but haven't tried to narrow it down beyond that.

I also haven't tried very to hard to minimize it further, but it might be worth noting that making B invariant, A concrete, or changing f: A => B to something like (A, B) all make the warning go away.