path-dependent-type-monad

path-dependent-type-monad.scala

object test {
  trait M[X[_]] {
    def map[A, B](a: X[A])(f: A => B): X[B]
  }

  trait Parsers {
    trait Parser[Y] {
      def map[B](f: Y => B): Parser[B] = null
    }
  }

  def parserM[G <: Parsers with Singleton ]: M[({ type L[T] = G#Parser[T] })#L] =
    new M[({ type L[T] = G#Parser[T] })#L] { 
      def map[A, B](a: G#Parser[A])(f: A => B): G#Parser[B] = a.map(f)
    }

  object a extends Parsers {
    val x = parserM[a.type]
    x: M[a.Parser]
  }
}