bug#14926: 24.3.50; Warning "`make-variable-buffer-local' should be called at toplevel"

[Michael Heerdegen <michael_heerdegen@web.de>]

Glenn Morris <rgm@gnu.org> writes:

> This feature is 8 years old, BTW.
>
> So "Is this something new?" in Jul 2013 tells you something about how
> much of an issue this has been in practice.

I'll tell you something funny.  When Stefan said that 99% of
non-top-level uses of `make-variable-buffer-local' were wrong, I
searched my large .emacs for counter-examples.  I found 4 such places,
and for every place, it was by mistake!  Of course I knew the difference
when I wrote that code, but these function names sound so similar...

All these occurrences were wrapped inside something like

  (add-hook 'hook (lambda () ... (make-variable-buffer-local ...)))

or inside `with-eval-after-load' (that also wraps the body inside a
lambda) and no warning had been printed all the time.

It would be good to warn also for calls inside lambdas.


Michael.