# File lib/methodsig.rb, line 242
    def set_optional_args(args, args_node, names)
      opt = args_node.opt
      while opt do
        head = opt.head
        if head.class == Node::LASGN then
          args[head.vid] = Argument.new(head.vid, head.value.as_expression, head.value, false, false)
        else
          raise "Unexpected node type: #{opt.class}"
        end
        opt = opt.next
      end
    end