My distro generally byte compiles all emacs libraries with a command like

/usr/bin/emacs --batch --no-site-file --directory . -f batch-byte-compile ess-tracebug.el

but I am I getting an error:

ess-tracebug.el:1181:36:Error: Garbage following &rest VAR in lambda-list

I don't know much about lisp or emacs, but it seems to me that the line should be changed from

(defun ess-dbg-find-file (filename &rest directory formats)

to

(defun ess-dbg-find-file (filename &optional directory &rest formats)

Thanks Eric for the report. Solved as you've suggested. Other compilation warnings removed as well.

Best, Vitalie.