# File lib/methodsig.rb, line 218
    def rest_arg
      args_node = args_node()
      rest = args_node.rest()
      if rest.class == Node::LASGN then
        # subtract 2 to account for implicit vars
        return rest.cnt - 2
      elsif not rest
        return nil
      else
        return rest > 0 ? rest - 2 : nil
      end
    end