bug#73330: 31.0.50; Incorrect completions for 'cond' clauses

[Eli Zaretskii <eliz@gnu.org>]

> From: Eshel Yaron <me@eshelyaron.com>
> Cc: 73330@debbugs.gnu.org
> Date: Thu, 19 Sep 2024 14:25:13 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> Date: Wed, 18 Sep 2024 14:36:18 +0200
> >> From:  Eshel Yaron via "Bug reports for GNU Emacs,
> >>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> >> 
> >> 1. emacs -Q
> >> 2. Insert "(cond (current-p
> >> 3. Hit M-TAB to complete
> >> 
> >> We're completing a symbol in the condition of a cond clause, so it is
> >> expected to be completed as a variable, to current-prefix-argument.
> >> However, Emacs mistakenly thinks that we're completing a function name,
> >> and completes to current-bidi-paragraph-direction.
> >
> > Thanks.  Does the patch below give good results?
> 
> It helps

Does "helps" mean the original scenario is fixed? or are there any
leftovers in that scenario?

> but also seems to cause a regression.  With this change I get:
> 
> 1. emacs -Q
> 2. Insert "(cond ((current-p"
>                   ^note the additional parenthesis
> 3. Hit M-TAB to complete
> 
> This shows an opposite bug: Emacs should complete function names (and
> without the change, it does), but with the change we now get variable
> name completion.

How about the patch below?

diff --git a/lisp/progmodes/elisp-mode.el b/lisp/progmodes/elisp-mode.el
index 9bf6f92..63bd685 100644
--- a/lisp/progmodes/elisp-mode.el
+++ b/lisp/progmodes/elisp-mode.el
@@ -784,13 +784,18 @@ elisp-completion-at-point
                         (list t (elisp--completion-local-symbols)
                               :predicate (lambda (sym)
                                            (get sym 'error-conditions))))
-                       ((and (or ?\( 'let 'let*)
+                       ((and (or ?\( 'let 'let* 'cond 'cond* 'bind*)
                              (guard (save-excursion
                                       (goto-char (1- beg))
                                       (when (eq parent ?\()
                                         (up-list -1))
                                       (forward-symbol -1)
-                                      (looking-at "\\_<let\\*?\\_>"))))
+                                      (or
+                                       (looking-at
+                                        "\\_<\\(let\\*?\\|bind\\*\\)\\_>")
+                                       (and (not (eq parent ?\())
+                                            (looking-at
+                                             "\\_<cond\\*?\\_>"))))))
                         (list t (elisp--completion-local-symbols)
                               :predicate #'elisp--shorthand-aware-boundp
                               :company-kind (lambda (_) 'variable)