bug#17498: 24.4.50; This function has a compiler macro `yes--cmacro'.

[Nicolas Richard]

Leo Liu <sdl.web@gmail.com> writes:

> Eval the following code
>
> ;;;; BEGIN
> (defun yes ()
>   )
> (when nil
>   (cl-define-compiler-macro yes (&rest _)))
> ;;;; END

FWIW (and because it was not obvious to me), it's due to
eval-and-compile:

(when nil
   (eval-and-compile (message "foo")))
=> foo is shown in *Messages*

Same with this :
(defmacro bar () '(eval-and-compile (message "foo")))
(when nil (bar))

This case could be "fixed" by optimizing `when' for a nil condition :

(defmacro new-when (cond &rest body)
  (declare (indent 1) (debug t))
  (and cond
       (list 'if cond (cons 'progn body))))

Then
(new-when nil (bar))
doesn't show anything.

-- 
Nico.