Subject: bug#20914: eieio/slot/group

From: Stefan Monnier <[email-masked]>
Date: Tue, 30 Jun 2015 14:09:20 -0400

> The problem comes from use of `copy-sequence' in
> `eieio-copy-parents-into-subclass' function of eieio-core. this
> copy is not reccursive as explained in code comment but it
> should be ! There's a joined patch that fixes the bug.

Thanks for the investigation.  I think the fix should be
applied deeper.  Can you confirm that the patch below works for you
as well?

        Stefan

diff --git a/lisp/emacs-lisp/cl-preloaded.el b/lisp/emacs-lisp/cl-preloaded.el
index ed0639b..2e9bdde 100644
--- a/lisp/emacs-lisp/cl-preloaded.el
+++ b/lisp/emacs-lisp/cl-preloaded.el
@@ -195,7 +195,7 @@
                (:constructor nil)
                (:constructor cl--make-slot-descriptor
                 (name &optional initform type props))
-               (:copier cl--copy-slot-descriptor))
+               (:copier nil))
   ;; FIXME: This is actually not used yet, for circularity reasons!
   "Descriptor of structure slot."
   name                                  ;Attribute name (symbol).
@@ -205,6 +205,11 @@
   ;;  :documentation, :protection, :custom, :label, :group, :printer.
   (props nil :type alist))
 
+(defun cl--copy-slot-descriptor (slot)
+  (let ((new (copy-sequence slot)))
+    (cl-callf copy-sequence (cl--slot-descriptor-props new))
+    new))
+
 (cl-defstruct (cl--class
                (:constructor nil)
                (:copier nil))