Argument identity lost preventing follow-up dependently-typed argument

[japgolly]

Compiler version

3.0.0-RC1

Minimized code

object Hello {

  sealed abstract class X[+A] {
    type This[+A] <: X[A]
    def asThis: This[A]
  }

  class Y[+A] extends X[A] {
    override type This[+AA] = Y[AA]
    override def asThis: This[A] = this
  }

  def hackBackToSelf[F[+u] <: X[u], A](f: F[Any])(f2: f.This[A]): F[A] =
    f2.asInstanceOf[F[A]]

  case class G[F[+u] <: X[u], A](wrapped: F[A]) {

    def mapF[F2[+u] <: X[u]](f: F[A] => F2[A]): G[F2, A] =
      G[F2, A](f(wrapped))

    def test_ko_1: G[F, A] = mapF(ct => hackBackToSelf(ct)(ct.asThis)) // error
    def test_ko_2: G[F, A] = mapF[F](ct => hackBackToSelf(ct)(ct.asThis)) // error
    def test_ok  : G[F, A] = mapF(ct => hackBackToSelf[F, A](ct)(ct.asThis)) // ok
  }
}

Output

-- [E007] Type Mismatch Error: x.scala:21:62 -----------------------------------
21 |    def test_ko_1: G[F, A] = mapF(ct => hackBackToSelf(ct)(ct.asThis)) // error
   |                                                           ^^^^^^^^^
   |                         Found:    ct.This[A]
   |                         Required: ?1.This[A]
   |
   |                         where:    ?1 is an unknown value of type F[Any]
-- [E007] Type Mismatch Error: x.scala:22:65 -----------------------------------
22 |    def test_ko_2: G[F, A] = mapF[F](ct => hackBackToSelf(ct)(ct.asThis)) // error
   |                                                              ^^^^^^^^^
   |                         Found:    ct.This[A]
   |                         Required: ?2.This[A]
   |
   |                         where:    ?2 is an unknown value of type F[Any]
2 errors found

Expectation

It should compile. It does with Scala 2.x.

[abgruszecki]

Possibly related to #11220?

[odersky]

It does look related. There's an asInstanceOf[F[Any]] inserted before it goes wrong.