Hi all,

with the recent updates to style/expl3.el, I think we have an issue with
fontification.  For this small test file:

--8<---------------cut here---------------start------------->8---
% \iffalse
%<package>\NeedsTeXFormat{LaTeX2e}[2005/12/01]
%
%<*driver>
\documentclass{ltxdoc}
\usepackage{expl3}
\begin{document}
\DocInput{dtx-fontification.dtx}
\end{document}
%</driver>
% \fi
%
% \begin{macro}{\next}
%   Implement \cs{next} which is:
%    \begin{macrocode}
\cs_set:Npn \next:nn #1#2 { x #1~y #2 }
\cs_prefix_spec:N \next:nn

\cs_to_str:N \next
\end{macrocode}
% \end{macro}
%
% \endinput
% Local Variables:
% mode: docTeX
% TeX-master: t
% End:
--8<---------------cut here---------------end--------------->8---

The fontification looks like this with 'emacs -Q':