class_initializer_hell.scala

trait T {
  val v = 3

  // if v is overriden, and this is val, this yields not what you'd expect
  // lazy val or def would work ok.
  val version = v
}

class C extends T {
  override val v = 2
}

(new C).version
// get unexpected: Map(3 -> 3, 2 -> 2)



// version two

trait T {
  var metricsData: Map[Int, Int] = Map()

  // missing lazy here
  val v = add(3)

  def add(v: Int) = { metricsData +=  v -> v; v }

  val version = v
}

class C extends T {
  override val v = add(2)
}

(new C).metricsData