class RDoc::MethodAttr

def add_line_numbers(src)
  return unless src.sub!(/\A(.*)(, line (\d+))/, '\1')
  first = $3.to_i - 1
  last  = first + src.count("\n")
  size = last.to_s.length
  line = first
  src.gsub!(/^/) do
    res = if line == first then
            " " * (size + 1)
          else
            "<span class=\"line-num\">%2$*1$d</span> " % [size, line]
          end
    line += 1
    res
  end
end