bug#58513: describe-function should say that defconst variables are constant

[Stefan Kangas]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> The byte-compiler already does warn about it, but only if the assignment
> is in the same file as the `defconst`.

I don't get any warnings with this recipe:

    echo "(defconst foo-bar t) (setq foo-bar nil)" > /tmp/foo.el
    emacs -Q -batch -eval '(byte-compile-file "/tmp/foo.el")'

Am I missing something?