bug#13023: 24.3.50; lexical binding does not work within defadvice

[Stefan Monnier]

>     ;; -*- lexical-binding: t -*-
>     (funcall (let ((rms "works"))
>                (lambda ()
>                  (message "lex-bind %s" rms))))

>     (defun asdf (b) (funcall b))

>     (defadvice asdf (before rms (b) activate)
>       (setf b (let ((abc 1) (b b)) (lambda () (print abc) (funcall b)))))

>     (asdf 'ding)

> I think this code should work fine.  It doesn't work with trunk and
> emacs-24, though:

Indeed, it doesn't work.  And because of the way advice.el works
(building a new function by combining the code chunks from all the
pieces of advice applied to that function) it's not easy to fix.

This is partly related to the issue mentioned recently that macro calls
in pieces of advice are expanded late (typically when the advised
function is defined).

BTW, this does not affect the new `advice-add' feature in Emacs trunk.


        Stefan