resolution_ambigious-typeclass-parameters.scala

import scalaz.meta.Typeclass

trait ambigious_typeclass_parameters {
  trait Functor[F[_]] extends Typeclass {
    def map[A, B](fa: F[A])(f: A => B): F[B]
  }
  trait Applicative[F[_]] extends Functor[F] {
    def unit: F[Unit]
    def product[A, B](fa: F[A], fb: F[B]): F[(A, B)]
  }

  trait Traverse[F[_]] extends Functor[F] {
    def traverse[G[_]: Applicative, A, B](fa: F[A])(f: A => G[B]): G[F[A]]
  }

  // Ambigious instances for typeclasses are okay!
  def test[F[_]: Traverse: Applicative, A](fa: F[A]): F[Unit] =
    implicitly[Functor[F]].map(fa)(_ => ())
}