false exhaustivity warning for shared inner sealed traits and type parameters

[eejbyfeldt]

Compiler version

3.7.2, 3.3.5

Minimized code

trait Nodes1 {
  sealed trait B
  final case class R1() extends B
}

trait Nodes2 extends Nodes1 {
  final case class R2[T]() extends B
}


object Impl1 extends Nodes1

object test2 {
  val a: Impl1.B = ???
  a match {
    case Impl1.R1() => ???
  }
}

Output

$ ~/Downloads/scala3-3.7.2-x86_64-pc-linux/bin/scalac nodes.scala 
-- [E029] Pattern Match Exhaustivity Warning: nodes.scala:15:2 ----------------------------------------------------------------
15 |  a match {
   |  ^
   |  match may not be exhaustive.
   |
   |  It would fail on pattern case: (Nodes2 & Impl1.type)#R2()
   |
   | longer explanation available when compiling with `-explain`
1 warning found

Expectation

No warnings is produced.

Since Impl1.type is a object instances of Nodes2 & Impl1.type does not exist. Remove the type parameter from R2 makes the warning go away.