# File lib/thor/base.rb, line 232
      def argument(name, options = {})
        is_thor_reserved_word?(name, :argument)
        no_commands { attr_accessor name }

        required = if options.key?(:optional)
          !options[:optional]
        elsif options.key?(:required)
          options[:required]
        else
          options[:default].nil?
        end

        remove_argument name

        if required
          arguments.each do |argument|
            next if argument.required?
            raise ArgumentError, "You cannot have #{name.to_s.inspect} as required argument after " \
                                "the non-required argument #{argument.human_name.inspect}."
          end
        end

        options[:required] = required

        arguments << Thor::Argument.new(name, options)
      end