asOption.scala

// see http://stackoverflow.com/questions/14924707/how-to-write-a-scalaz-isempty-parameter-for-generic-types

import scalaz._
import Scalaz._

object Test {
  def asOption[C](c: C)(implicit ev: IsEmpty[({type F[_] = C})#F]): Option[C] =
    if (ev.isEmpty(c)) None else Some(c)

  implicit def detailedIsEmpty[A, C[_]](implicit ev: IsEmpty[C]) =
    ev.asInstanceOf[IsEmpty[({type F[_] = C[A]})#F]]

  implicit def detailedIsEmptyMap[K, V](implicit ev: IsEmpty[({type F[V] = Map[K, V]})#F]) =
    ev.asInstanceOf[IsEmpty[({type F[_] = Map[K, V]})#F]]
}