sealed trait Email {
  def email(): String
}


// unvalidated
case class EmailU(email: Email) extends Email

// validated
sealed trait EmailV extends Email {
  def email(): String
}
private case class EmailV_(email: String) extends EmailV
object EmailV {

  def apply(email: String): Either[EmailValidationFailure, EmailV] = {
    Right (EmailV_(email))
  }

  def unapply(arg: EmailV): Option[String] = Some(arg.email())
}

trait EmailValidationFailure
case object InvalidEmail extends EmailValidationFailure