foo.scala

implicit def kvPairAsDBObject[A <: Any](kv: (String, A)): DBObject = MongoDBObject(kv)

sealed class NestedListOper(outerField: String) {

  def apply[A <% DBObject](fields: A*): DBObject = {
    val b = Seq.newBuilder[DBObject]
    fields.foreach(x => b += x)
    MongoDBObject(outerField -> b.result())
  }
}

trait OrOp extends BarewordQueryOperator {

/*  def $or[A : ValidBarewordExpressionArgType](fields: A*) =
    MongoDBObject("$or" -> implicitly[ValidBarewordExpressionArgType[A]].listify(fields))*/

  def $or = new NestedListOper("$or")
}