listener queue with weak reference to anonymous functions

gistfile1.scala

object E {
    class O {
        val listeners = new ArrayBuffer[E.H]
    }
    trait RO {
        implicit val __ERO__ = new O
    }
    type H = PartialFunction[Any,Any]
}
abstract class E {
    val queue = new ArrayBuffer[WeakReference[E.H]]
    def add(e: E.H)(implicit o: E.O) {
        o.listeners += e
        queue += new WeakReference(e)
    }
}
object U extends E

class M extends E.RO {
    U add { case _ => () }
}
class N extends E.RO {
    U add { case _ => () }
}