How to avoid “Unused lexical argument” for condition-case?

Question

Here's a sample of the code that I have:

(define-error 'unsupported-mode-error "Unsupported mode")
(condition-case e
    (if (eq 'a 'a)
        (message "test")
      (signal 'unsupported-mode-error major-mode))
  (unsupported-mode-error
   (signal (car e) (cdr e)))
  (error
   (message "error")))

With lexical-binding in the current file, I get Warning: Unused lexical argument e warning, although I'm clearly using e. Is this a bug or a misunderstanding on my part? And how could I avoid this warning?

Answer 1

This is related to bug #15103, as is now fixed in 25.1.

Earlier Emacs versions can do this to silence the warning:

(setq byte-compile--use-old-handlers nil)