Difference between HKT and type lambda

[OlivierBlanvillain]

Dotty sees a difference between Option and [A] => Option[A], I think there shoudn't be:

trait Functor[F[_]]

object Functor {
  val a: Functor[Option] = ???
  val b: Functor[[A] => Option[A]] = a

  // Same result with scalac style type lambda:
  // val c: Functor[({ type l[A] = Option[A] })#l] = a
}

23 |  val b: Functor[[A] => Option[A]] = a
   |                                     ^
   |                                   found:    Functor[Option](Functor''.a)
   |                                   required: Functor[Option]
   |
   |                                   where:    Functor  is a trait
   |                                             Functor'' is a object

one error found

[smarter]

Duplicate of #2989

[smarter]

I'm working on a fix, but waiting for the native applied type stuff to be done before finishing it :).

[odersky]

I believe it has to do with variances. Option is [+A] => Option[A] not [A] => Option[A]