http://stackoverflow.com/questions/11164754/scala-method-overloading-oddity

X.scala

object X {
  class EitherProvidesProjection[A, B](e: Either[A, B]) {
    def project[A1](f: A => A1) = e match {
      case Left(l) => Left(f(l)).right
      case Right(r) => Right(r).right
    }
  }
  implicit def EitherProvidesProjection[A, B](e: Either[A, B]) = new EitherProvidesProjection(e)
  
  for {
    a <- Right[String, String]("") project i18n
    b <- Left[String, String]("") project i18n
  } yield a+b
  
  
  def i18n(code: String, args: Any*): String = null
  def i18n(code: String): String = i18n(code, "")
}