toMultiMap

scEnrichColl.scala

  implicit class scEnrichColl[Coll <: Traversable[(_,_)]](val __this: Coll) extends AnyVal {
    def toMultiMap[Result, A, B](implicit view: Coll <:< Traversable[(A, B)],  cbf: CanBuildFrom[Coll, B, Result]): Map[A, Result] = {
      var result = collection.mutable.Map[A, mutable.Builder[B, Result]]()
      result = result.withDefault { a =>  val r = cbf(__this); result.update(a, r); r}

      for((a,b) <- view(__this)) {
        result(a) += b
      }

      result.mapValues(_.result()).toMap
    }
  }