gistfile1.scala

trait StableColl[CC[Elem]] {
  def builder[Elem](): mutable.Builder[Elem, CC[Elem]]
}

object StableColl {
  def apply[CC[Elem]](implicit stableColl: StableColl[CC]): StableColl[CC] = stableColl

  implicit def stableCollSeq: StableColl[Seq] =
    new StableColl[Seq] {
      def builder[Elem]() = new mutable.ListBuffer[Elem]
    }

  implicit def stableCollList: StableColl[List] =
    new StableColl[List] {
      def builder[Elem]() = new mutable.ListBuffer[Elem]
    }

  implicit def stableCollIndexedSeq: StableColl[IndexedSeq] =
    new StableColl[IndexedSeq] {
      def builder[Elem]() = new mutable.ArrayBuffer[Elem]
    }

}