Nested either value extraction

eithers.scala

type NestedEither = Either[Either[String, Int], Double]
val foo: NestedEither = Left(Right(5))

sealed trait Extractor[H, N] {
  def value(a: H): Option[N]
}

implicit def FoundExtractor[A] = new Extractor[A, A] {
  def value(a: A) = Some(a)
}

implicit def GoLeftExtractor[A, B, N](implicit e: Extractor[A, N]) = new Extractor[Either[A, B], N] {
  def value(a: Either[A, B]) = a.left.toOption.flatMap(e.value) 
}

implicit def GoRightExtractor[A, B, N](implicit e: Extractor[B, N]) = new Extractor[Either[A, B], N] {
  def value(a: Either[A, B]) = a.right.toOption.flatMap(e.value) 
}

implicit class Extractable[H](h: H) {
  def find[B](implicit e: Extractor[H, B]) = e.value(h)
}

foo.find[Double] //None
foo.find[Int] //Some(5)
foo.find[String] // None
// foo.as[Float] won't compile as NestedEither does not contain float