RE: [Emacs-diffs] comment-cache 223d16f 2/3: Apply `comment-depth' text properties when calling `back_comment'.

[Drew Adams]

> > Please don't think of using (nth 9 (snytax-ppss)) in such a high level
> > function.  It's strictly internal stuff used for continuing a parse in
> > the middle of something.  If you do really want to use it, we should
> > consider making that element fully defined at the user level (and
> > possibly stating any further elements are "internal").
> 
> We should document it, indeed.  It's been "stable" for decades and is
> already used at various places in Elisp packages, not all of them
> qualifying as "low-level".

See bug #22890 about defining `file-attributes' accessor macros, to
make code that would otherwise use (nth N SOMETHING) more readable.

http://debbugs.gnu.org/cgi/bugreport.cgi?bug=22890