# File lib/methodsig.rb, line 190
    def argument_names
      local_vars = self.local_vars
      args = self.args_node
      num_required_args = args.cnt
      num_optional_args = 0
      opt = args.opt
      while opt do
        num_optional_args += 1
        opt = opt.next
      end
      num_args = \
        num_required_args + \
        num_optional_args + \
        (rest_arg ? 1 : 0) + \
        (block_arg ? 1 : 0)
      return local_vars[0...num_args]
    end