# File lib/methodsig.rb, line 297
    def argument_names
      local_vars = self.local_vars
      iseq = self.body
      opt_args = iseq.arg_opt_table
      opt_args.pop # last arg is a pointer to the start of the code
      num_args = \
        iseq.argc + \
        opt_args.size + \
        (rest_arg ? 1 : 0) + \
        (block_arg ? 1 : 0)
      return local_vars[0...num_args]
    end