1 files changed, 15 insertions, 9 deletions
diff --git a/lisp/emacs-lisp/eieio-core.el b/lisp/emacs-lisp/eieio-core.el
index 59d834837b0..bf3f44206c4 100644
--- a/lisp/emacs-lisp/eieio-core.el
+++ b/lisp/emacs-lisp/eieio-core.el
@@ -88,7 +88,7 @@ Currently under control of this var:
 
 (cl-defstruct (eieio--class
                (:constructor nil)
-               (:constructor eieio--class-make (name &aux (tag 'defclass)))
+               (:constructor eieio--class-make (name))
                (:include cl--class)
                (:copier nil))
   children
@@ -277,12 +277,12 @@ See `defclass' for more information."
   (setq eieio-hook nil)
 
   (let* ((oldc (let ((c (eieio--class-v cname))) (if (eieio--class-p c) c)))
-	 (newc (if (and oldc (not (eieio--class-default-object-cache oldc)))
-                   ;; The oldc class is a stub setup by eieio-defclass-autoload.
-                   ;; Reuse it instead of creating a new one, so that existing
-                   ;; references stay valid.
-                   oldc
-                 (eieio--class-make cname)))
+	 (newc (or oldc
+                   ;; Reuse `oldc' instead of creating a new one, so that
+                   ;; existing references stay valid.  E.g. when
+                   ;; reloading the file that does the `defclass', we don't
+                   ;; want to create a new class object.
+                   (eieio--class-make cname)))
 	 (groups nil) ;; list of groups id'd from slots
 	 (clearparent nil))
 
@@ -292,7 +292,13 @@ See `defclass' for more information."
     ;; method table breakage, particularly when the users is only
     ;; byte compiling an EIEIO file.
     (if oldc
-	(setf (eieio--class-children newc) (eieio--class-children oldc))
+        (progn
+          (cl-assert (eq newc oldc))
+          ;; Reset the fields.
+          (setf (eieio--class-parents newc) nil)
+          (setf (eieio--class-slots newc) nil)
+          (setf (eieio--class-initarg-tuples newc) nil)
+          (setf (eieio--class-class-slots newc) nil))
       ;; If the old class did not exist, but did exist in the autoload map,
       ;; then adopt those children.  This is like the above, but deals with
       ;; autoloads nicely.
@@ -724,7 +730,7 @@ Argument FN is the function calling this verifier."
   (cl-check-type slot symbol)
   (cl-check-type obj (or eieio-object class))
   (let* ((class (cond ((symbolp obj)
-                       (error "eieio-oref called on a class!")
+                       (error "eieio-oref called on a class: %s" obj)
                        (let ((c (eieio--class-v obj)))
                          (if (eieio--class-p c) (eieio-class-un-autoload obj))
                          c))