unmap_file_line (LineCache)

    # File lib/linecache.rb, line 291
      def unmap_file_line(file, line)
        if @@file2file_remap_lines[file]
          @@file2file_remap_lines[file].each do |from_file, range, start|
            if range === line
              from_file = from_file || file
              return [from_file, start+line-range.begin]
            end
          end
        end
        return [file, line]
      end