(derived-mode-init-mode-variables): Make proper syntax-table.

(derived-mode-merge-syntax-tables): Rewrite using map-char-table.

1 files changed, 9 insertions, 7 deletions

diff --git a/lisp/derived.el b/lisp/derived.el
index 36bf1428125..85466f53899 100644
--- a/lisp/derived.el
+++ b/lisp/derived.el
@@ -221,7 +221,10 @@ the first time the mode is used."
   (if (boundp (derived-mode-syntax-table-name mode))
       t
     (eval (` (defvar (, (derived-mode-syntax-table-name mode))
-               (make-vector 256 nil)
+               ;; Make a syntax table which doesn't specify anything
+               ;; for any char.  Valid data will be merged in by
+               ;; derived-mode-merge-syntax-tables.
+               (make-char-table 'syntax-table nil)
                (, (format "Syntax table for %s." mode)))))
     (put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t))
 
@@ -327,12 +330,11 @@ be automatic inheritance."
 (defun derived-mode-merge-syntax-tables (old new)
   "Merge an old syntax table into a new one.
 Where the new table already has an entry, nothing is copied from the old one."
-  (let ((idx 0)
-        (end (min (length new) (length old))))
-    (while (< idx end)
-      (if (not (aref new idx))
-          (aset new idx (aref old idx)))
-      (setq idx (1+ idx)))))
+  (map-char-table
+   (function (lambda (key value)
+               (or (char-table-range new key)
+                   (set-char-table-range new key value))))
+   old))
 
 ;; Merge an old abbrev table into a new one.
 ;; This function requires internal knowledge of how abbrev tables work,