Scala type classes, dispatch on return type

package tt

object ChannelTest extends App {

  def process[T: Operation](channelId: Long): T = {
    val channel = ChannelService.byId(channelId)
    val op = implicitly[Operation[T]]
    // specific operation depending on concrete T
    val t: T = op.read(channel)
    op.write(channel, t)
    t
  }

  import Implicits._
  val x: Int = process[Int](1L)
  val y: String = process[String](2L)
}


case class Channel(channelId: Long)

object ChannelService {
  def byId(channelId: Long) = Channel(channelId)
}

trait Operation[T] {
  def read(channel: Channel): T
  def write(channel: Channel, t: T): Unit
}

object Implicits {
  implicit val intOp: Operation[Int] = new Operation[Int] {
    def read(channel: Channel): Int = {
      println("intOp.read")
      channel.toString.length
    }
    def write(channel: Channel, t: Int): Unit = {
      println("intOp.write")
    }
  }

  implicit val stringOp: Operation[String] = new Operation[String] {
    def read(channel: Channel): String = {
      println("stringOp.read")
      channel.toString
    }
    def write(channel: Channel, t: String): Unit = {
      println("stringOp.write")
    }
  }

}