gistfile1.scala

// let's us tag primitives with made up types
type Tagged[T] = { type Tag = T }

// have to declare our type annotations for use below
trait BizoIdTag 
trait PartnerIdTag 
trait AppNexusIdTag

// afaik effectively this treats the lhs (ex BizoId) of the alias as a subclass
// of the primitive, only with the added type
type BizoId = String with Tagged[BizoIdTag]
type PartnerId = Long with Tagged[PartnerIdTag]
type AppNexusId =  Long with Tagged[AppNexusIdTag]

// Spark on Scala 2.10 now, which means we can use value classes
// afaik at runtime we don't allocate new objects at all
implicit class TaggedString(val data: String) extends AnyVal {

  // looks scary, but this cast actually can't fail
  def bizoId = data.asInstanceOf[BizoId]
} 

implicit class TaggedLong(val data: Long) extends AnyVal {
  def partnerId =  { 
    require(data >= 1) // oooooo validation!
    data.asInstanceOf[PartnerId]
  }

  def appNexusId = data.asInstanceOf[AppNexusId]
}


def doSomething(bizoId: BizoId, appNexusId: AppNexusId): String = {
  "Hello World"
}


doSomething("129IDKAJDf".bizoId, 12345.appNexusId) // yay!
doSomething("129IDKAJDf".bizoId, 12345.partnerId) // compiler Error!

Playing around with these techniques gives me some errors.

I have

object DomainTypes {
  type Tagged[T] = { type Tag = T }
  trait DeviceIdTag
  type DeviceId = Int with Tagged[DeviceIdTag]

  implicit class TaggedInt(val data: Int) extends AnyVal {

     def deviceId = {
      require(data >= 1)
      data.asInstanceOf[DeviceId]
    }
  }
}

That gives me this stacktrace.

[error] type mismatch;
[error]  found   : Double
[error]  required: AnyRef
[error] Note: an implicit exists from scala.Double => java.lang.Double, but
[error] methods inherited from Object are rendered ambiguous.  This is to avoid
[error] a blanket implicit which would convert any scala.Double to any AnyRef.
[error] You may wish to use a type ascription: `x: java.lang.Double`.
[error] one error found
[error] (compile:compile) Compilation failed

Edit: I left out one important piece.

I then try and use it like :

 case class DeviceIdHolder(odeviceId:DeviceId)

Have you ever seen anything like this? In any case, nice write up . Thanks!