bug#15814: 24.3.50; Signal error on malformed bindings in `cl-symbol-macrolet' (patch)

[Nathan Trapuzzano]

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

>> What's the alternative?  Transform malformed let in some undefined way?
>
> Yup.  Just like we've done so far.

I think I understand what you want.  This patch uses
macroexp--warn-and-return.  I'll try to move the checks in
bytecomp.el/cconv.el later.

Nathan

>From 3843a58d0ebcaea9e6c9446ca6b6f52611c8097d Mon Sep 17 00:00:00 2001
From: Nathan Trapuzzano <nbtrap@nbtrap.com>
Date: Tue, 5 Nov 2013 14:36:32 -0500
Subject: [PATCH] Print warning for malformed bindings in cl-symbol-macrolet.

---
 lisp/ChangeLog             |  5 +++++
 lisp/emacs-lisp/cl-macs.el | 18 +++++++++++++-----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 828fcda..824e73c 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2013-11-05  Nathan Trapuzzano  <nbtrap@nbtrap.com>
+
+       * emacs-lisp/cl-macs.el (cl-symbol-macrolet): Print warning for
+       malformed bindings form.
+
 2013-11-05  Eli Zaretskii  <eliz@gnu.org>
 
        * international/quail.el (quail-help): Be more explicit about the
diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index 60fdc09..9cdde5e 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -1992,11 +1992,19 @@ by EXPANSION, and (setq NAME ...) will act like (setf 
EXPANSION ...).
       (unwind-protect
           (progn
             (fset 'macroexpand #'cl--sm-macroexpand)
-            ;; FIXME: For N bindings, this will traverse `body' N times!
-            (macroexpand-all (cons 'progn body)
-                             (cons (list (symbol-name (caar bindings))
-                                         (cl-cadar bindings))
-                                   macroexpand-all-environment)))
+            (let ((expansion
+                   ;; FIXME: For N bindings, this will traverse `body'
+                   ;; N times!
+                   (macroexpand-all (cons 'progn body)
+                                    (cons (list (symbol-name (caar bindings))
+                                                (cl-cadar bindings))
+                                          macroexpand-all-environment))))
+              (if (or (null (cdar bindings)) (cl-cddar bindings))
+                  (macroexp--warn-and-return
+                   (format "Malformed `cl-symbol-macrolet' binding: %S"
+                           (car bindings))
+                   expansion)
+                expansion)))
         (fset 'macroexpand previous-macroexpand))))))
 
 ;;; Multiple values.
-- 
1.8.4.2