a part of flymake-vim (or rather: my version of it)

flymake_part.vim

function! s:FlyMakeDisplay(buf, type, msg, regexp)
  let source_file = expand("%")
  let dic = s:FlyMakeParseDictionary(a:msg, a:regexp)
  if len(keys(dic)) == 0
    return 0
  endif
  let sorted_keys = sort(keys(dic), function('s:FlyMakeNumberSort'))

  execute 'match' a:type "'\\%" . sorted_keys[0] . "l'"
  call cursor(sorted_keys[0], 1)
  10 new
  setlocal bufhidden=wipe buftype=nofile noswapfile
  file `=a:buf`
  for n in reverse(sorted_keys)
    for mes in reverse(dic[n])
      call s:FlyMakeSendCommand(a:buf,
      \                         ('call append(line($), "' . source_file . ':' . n . ': '
      \                          . a:type . ' ' . escape(mes, '"()') . '")'))
    endfor
  endfor
  call s:FlyMakeSendCommand(a:buf, 'call cursor(1, 1)')
  cgetbuffer
  call s:FlyMakeSendCommand(a:buf, 'q')
  cwindow
  redr
  return len(keys(dic))
endfunction