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

[Nathan Trapuzzano]

`cl-symbol-macrolet' silently accepts both of the following forms:

(cl-symbol-macrolet ((foo bar baz) ...) ...)
(cl-symbol-macrolet ((foo) ...) ...)

In the former case, baz is ignored; in the latter case, foo is bound to
nil.

According to the CL docs, neither of these is valid.  (Not to mention,
they are both errors in Common Lisp.)  The attached patch asserts
properly formed bindings.

I checked the Emacs source to make sure there's no code in there relying
on this behavior.

>From d6feb1195b8dc8f204d49761bfa828facbb4ba57 Mon Sep 17 00:00:00 2001
From: Nathan Trapuzzano <nbtrap@nbtrap.com>
Date: Tue, 5 Nov 2013 14:36:32 -0500
Subject: [PATCH] Signal error with malformed bindings in cl-symbol-macrolet.

---
 lisp/ChangeLog             | 5 +++++
 lisp/emacs-lisp/cl-macs.el | 2 ++
 2 files changed, 7 insertions(+)

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 828fcda..a4ae0ca 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): Signal error with
+       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..1e277f7 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -1988,6 +1988,8 @@ by EXPANSION, and (setq NAME ...) will act like (setf 
EXPANSION ...).
        (cl-symbol-macrolet ,(cdr bindings) ,@body)))
    ((null bindings) (macroexp-progn body))
    (t
+    (cl-assert (and (cdar bindings) (null (cl-cddar bindings))) nil
+              "Malformed `cl-symbol-macrolet' binding: %S" (car bindings))
     (let ((previous-macroexpand (symbol-function 'macroexpand)))
       (unwind-protect
           (progn
-- 
1.8.4.2