implicitを用いたパケットを扱うクラスを型で自動分岐する例　もっと簡潔に書けそうで思いつかない．

implicit-type-parameter.scala

trait Packet
class ItemPacket extends Packet
class QuestPacket extends Packet

object PacketHandler {
  trait PacketHandler[T <: Packet] {
    def handle(packet: T)
  }

  implicit object ItemPacketHandler extends PacketHandler[ItemPacket] {
    def handle(packet: ItemPacket) = println("item packet!")
  }

  def handle[T <: Packet](packet: T)(implicit handler: PacketHandler[T]) {
    handler.handle(packet)
  }
}

object Main {
  def main(args: Array[String]) {
    PacketHandler.handle(new ItemPacket) // => "item packet!"
  }
}