# File lib/backports/1.8.7/array/rindex.rb, line 6
    def rindex_with_block(*arg)
      return to_enum(:rindex) if !block_given? && arg.empty?
      return rindex_without_block(*arg) unless block_given? && arg.empty?
      i = 0
      reverse_each{|o| i += 1; return size - i if yield o}
      return nil
    end