Missing kind checks when overriding a type

[smarter]

trait A { type L }
trait B extends A { type L[X] }

In scalac this fails with:

 error: The kind of type L does not conform to the expected kind of type L in trait A.
B.this.L's type parameters do not match type L's expected parameters:
type L (in trait B) has one type parameter, but type L (in trait A) has none
trait B extends A { type L[X] }
                         ^

but it succeeds in dotty, which probably leads to interesting issues.

[Blaisorblade]

See also #2771, though there you get an ill-kinded member from intersections.