Scala's type constructor is not "curried" form. In this example, it is explained that we can emulate type constructor currying using abstract type member.

TypeConstructorCurrying.scala

trait TF {
  type Apply[A]
}
type Curry2[F[_, _]] = TF { type Apply[X] = TF { type Apply[Y] = F[X, Y] } }
type Curry3[F[_, _, _]] = TF { type Apply[X] = Curry2[(TF { type Apply[Y, Z] = F[X, Y, Z] })#Apply] }
// ...

type CurriedMap = Curry2[Map]

val x: CMap#Apply[String]#Apply[Int] = Map("x" -> 1, "y" -> 1) //It is valid code.