Custom filter on disjunction, avoid need for Monoid

DisjunctionFilter.scala

import scalaz._
import scalaz.Scalaz._

object Test extends App{
  trait Zero[A] {
    def zero: A
  }
  
  implicit class RichDisjunction[A, B](value: A \/ B) {
    def withFilter(p: B => Boolean)(implicit za: Zero[A]): A \/ B = value match {
      case \/-(b) if !p(b) => -\/(za.zero)
      case _ => value
    }
  }
  
  case class FailType(msg: String)
  implicit val zeroFailType = new Zero[FailType] { val zero = FailType("too bad buddy!") }
  
  
  val result = for {
    age <- 15.right[FailType] if age >= 18
  } yield age
  
  println(result) // Prints -\/(FailType(too bad buddy!))

}