* lisp/emacs-lisp/smie.el (smie-bnf->prec2): Give more understandable error

messages for adjacent non-terminals.

2 files changed, 11 insertions, 2 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 6b5f33a7782..029003c0429 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2011-06-23  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+        * emacs-lisp/smie.el (smie-bnf->prec2): Give more understandable error
+        messages for adjacent non-terminals.
+
 2011-06-23  Richard Stallman  <rms@gnu.org>
 
         * mail/rmail.el (rmail-retry-ignored-headers): Add message-id.
diff --git a/lisp/emacs-lisp/smie.el b/lisp/emacs-lisp/smie.el
index 17cc5668b5f..0206abb9f53 100644
--- a/lisp/emacs-lisp/smie.el
+++ b/lisp/emacs-lisp/smie.el
@@ -229,14 +229,18 @@ one of those elements share the same precedence level and associativity."
               ;; the trouble, and it lets the writer of the BNF
               ;; be a bit more sloppy by skipping uninteresting base
               ;; cases which are terminals but not OPs.
-              (assert (not (member (cadr rhs) nts)))
+              (when (member (cadr rhs) nts)
+                (error "Adjacent non-terminals: %s %s"
+                       (car rhs) (cadr rhs)))
               (pushnew (cadr rhs) first-ops)))
           (let ((shr (reverse rhs)))
             (if (not (member (car shr) nts))
                 (pushnew (car shr) last-ops)
               (pushnew (car shr) last-nts)
               (when (consp (cdr shr))
-                (assert (not (member (cadr shr) nts)))
+                (when (member (cadr rhs) nts)
+                  (error "Adjacent non-terminals: %s %s"
+                         (cadr rhs) (car rhs)))
                 (pushnew (cadr shr) last-ops)))))
         (push (cons nt first-ops) first-ops-table)
         (push (cons nt last-ops) last-ops-table)