class RDoc::AnyMethod

def add_line_numbers(src)
  if src =~ /\A.*, line (\d+)/ then
    first = $1.to_i - 1
    last  = first + src.count("\n")
    size = last.to_s.length
    line = first
    src.gsub!(/^/) do
      res = if line == first then
              " " * (size + 2)
            else
              "%2$*1$d: " % [size, line]
            end
      line += 1
      res
    end
  end
end