using phantom types to keep track of thread pool types carefully

Pools.scala

import java.util.concurrent.ExecutorService

import scalaz.Maybe
import scalaz.syntax.maybe._


final case class Pools(cpu: Maybe[Pool[Pool.Cpu]], io: Maybe[Pool[Pool.Io]])

object Pools {
  def none: Pools = Pools(Maybe.empty, Maybe.empty)
  def both(io: Pool[Pool.Io], cpu: Pool[Pool.Cpu]) = Pools(cpu.just, io.just)
}


final class Pool[A] private (private[kafka] val service: ExecutorService)

object Pool {
  trait Cpu
  trait Io
  def io(service: ExecutorService): Pool[Io] = new Pool(service)
  def cp(service: ExecutorService): Pool[Cpu] = new Pool(service)
}