From ed6cefb42c8847289ff83bf43b5370d878c93697 Mon Sep 17 00:00:00 2001
From: "Richard M. Stallman" <rms@gnu.org>
Date: Sat, 9 Jul 2005 03:42:43 +0000
Subject: [PATCH] (Fdefvar): Allow defvaring a constant to itself quoted.

---
 src/eval.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/eval.c b/src/eval.c
index f625258229..45effae295 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -807,8 +807,16 @@ usage: (defvar SYMBOL &optional INITVALUE DOCSTRING)  */)
 
   sym = Fcar (args);
   if (SYMBOL_CONSTANT_P (sym))
-    error ("Constant symbol `%s' specified in defvar",
-           SDATA (SYMBOL_NAME (sym)));
+    {
+      /* For updward compatibility, allow (defvar :foo (quote :foo)).  */
+      tem = Fcar (Fcdr (args));
+      if (! (CONSP (tem)
+	     && EQ (XCAR (tem), Qquote)
+	     && CONSP (XCDR (tem))
+	     && EQ (XCAR (XCDR (tem)), sym)))
+	error ("Constant symbol `%s' specified in defvar",
+	       SDATA (SYMBOL_NAME (sym)));
+    }
 
   tail = Fcdr (args);
   if (!NILP (Fcdr (Fcdr (tail))))
-- 
2.39.2