gistfile1.scala

package starfighter.types

sealed abstract class TList
sealed class TNil extends TList
sealed class TCons[A, B <: TList] extends TList

object TList {
  type L[A] = TCons[A, TNil]
  type ::[A, B <: TList] = TCons[A, B] 
}

sealed class OneOfC[A, L <: TList]

sealed class OneOf[L <: TList] { type T[A] = OneOfC[A, L] }
object OneOf {
  implicit def head[A, C <: TList]: OneOfC[A, TCons[A, C]] =
    new OneOfC[A, TCons[A, C]]

  implicit def tail[A, B, C <: TList](implicit foo : OneOfC[A, C]) : OneOfC[A, TCons[B, C]] = 
    new OneOfC[A, TCons[B, C]]
}

object Test {
  import OneOf._
  import TList._

  def example[T: OneOf[ Int :: L[String] ]#T](x:T) = {
  }

  def foo() = { example("hello") } // This works
  def bar() = { example(5) } // This works
  def baz() = { example(new Array[Int](100)) } // This fails
}