bug#50245: 28.0.50; Instrumenting a function does not show "Edebug:" in the echo area

[Stefan Monnier]

> Here's a new version of the patch, which addresses Stefan's feedback.

Thanks.  One question, tho:

> @@ -1643,7 +1643,10 @@ elisp--eval-defun
>    ;; FIXME: the print-length/level bindings should only be applied while
>    ;; printing, not while evaluating.
>    (defvar elisp--eval-defun-result)
> +  ;; FIXME: This Edebug dependency is undesirable.  See bug#50245
> +  (defvar edebug-all-defs)
>    (let ((debug-on-error eval-expression-debug-on-error)
> +        (edebugging edebug-all-defs)
>          elisp--eval-defun-result)
>      (save-excursion
>        ;; Arrange for eval-region to "read" the (possibly) altered form.

What makes us think that `edebug-all-defs` will always be defined when
we get here?  Doesn't this code signal an error if called before
edebug.el is loaded (e.g. in the case of `emacs -Q` soon followed by
a plain `C-M-x`)?


        Stefan