sealed trait Color extends LoudColor with CalmColor
object Color {
  case class Black(value: Int) extends Color
  case object White extends Color
}

sealed trait CalmColor
object CalmColor {
  case object Blue extends CalmColor
  case object Green extends CalmColor
}

sealed trait LoudColor
object LoudColor {
  case object Red extends LoudColor
}

object Main {
  def f() {
    var c : Color = null;
    var cc : CalmColor = null;
    var lc : LoudColor = null;

    c = Color.Black(10);
    c = Color.White;
    c = CalmColor.Blue; // expect error
    c = CalmColor.Green; // expect error
    c = LoudColor.Red; // expect error

    cc = Color.Black(10);
    cc = Color.White;
    cc = CalmColor.Blue;
    cc = CalmColor.Green;
    cc = LoudColor.Red; // expect error

    lc = Color.Black(10);
    lc = Color.White;
    lc = CalmColor.Blue; // expect error
    lc = CalmColor.Green; // expect error
    lc = LoudColor.Red;
  }
}