Broken typecheck for covariant HKT

[DoSOfRedRiver]

minimized code

In Scala 2 following code works just fine:

  class IO[+A]

  trait Functor[F[_]]
  trait Monad[F[_]] extends Functor[F]

  class Stream[+F[_], +A] {
    def take[F1[x] >: F[x]](n: Int)(implicit f: Functor[F1]): Stream[F1, A] = {
      this
    }
  }

  implicit val ioMonad: Monad[IO] = null

  new Stream[IO, Int].take[IO](10)

However, the same code in Dotty results in:
Type argument mains.Test.IO does not conform to lower bound my.package.IO

expectation

Expect the same behavior as in Scala 2.