my implementation of scala Option

option.scala

package example

sealed trait OptionZ[+T] {
  def map[U](f: T => U): OptionZ[U]

  def flatMap[U](f: T => OptionZ[U]): OptionZ[U]

  def filter(f: T => Boolean): OptionZ[T]

  def foreach(f: T => Unit): Unit
}

object OptionZ {
  def empty[T]: OptionZ[T] = EmptyZ

  def apply[T](v: T): OptionZ[T] = SomeZ(v)
}

case object EmptyZ extends OptionZ[Nothing] {
  override def map[U](f: Nothing => U): OptionZ[U] = EmptyZ

  override def flatMap[U](f: Nothing => OptionZ[U]): OptionZ[U] = EmptyZ

  override def filter(f: Nothing => Boolean): OptionZ[Nothing] = EmptyZ

  override def foreach(f: Nothing => Unit): Unit = ()
}

final case class SomeZ[T](value: T) extends OptionZ[T] {
  override def map[U](f: T => U): OptionZ[U] = SomeZ(f(value))

  override def flatMap[U](f: T => OptionZ[U]): OptionZ[U] = f(value)

  override def filter(f: T => Boolean): OptionZ[T] = if (f(value)) this else EmptyZ

  override def foreach(f: T => Unit): Unit = f(value)
}