The nimsuggest plugin tries to build a unique path for temporary files
for its flycheck checker. This path contains /tmp/emacs-nim-mode/A/B,
where A is the frame ID and B is the full path to the file being checked.
However, the original `nimsuggest--get-dirty-dir' incorrectly extracts
the frame ID from the string representation of `selected-frame' if
frame-title-format has been modified (which Doom has). The result is the
title of the frame, which can contain illegal path characters in
Windows, which in turn causes invalid argument errors when
`nimsuggest--make-tempdir' tries to use it.
This should really be reported upstream!