Re: [Emacs-diffs] comment-cache 223d16f 2/3: Apply `comment-depth' text properties when calling `back_comment'.

[Dmitry Gutov]

On 03/10/2016 11:20 PM, Richard Stallman wrote:

> If you make a concrete proposal for the new behavior, we can think about it.

There's nothing particularly hard about it--we have 
beginning-of-defun-function's implemented for much more complex 
functions than Elisp.

Here's a quick sketch:

(defun elisp-beginning-of-defun (&optional count)
  (setq count (or count 1))
  (dotimes (i count)
    (while (and (re-search-backward "(\\(?:cl-\\)?def" nil t)
                (elisp--form-quoted-p (point))))))

It fails on forms such as (define-key ...), but it's easy to also check 
all positions in (nth 9 (syntax-ppss)), and only pick the outermost 
defun-looking form. We can also make the regexp stricter, to only accept 
[cl-]defun, defmacro, defvar and defconst.

Anyway, like Alan mentioned, this caching proposal is actually 
orthogonal to the use of open-paren-in-column-0-is-defun-start in 
beginning-of-defun in emacs-lisp-mode. We could still keep that 
application, if we so preferred.