bug#28489: Acknowledgement (27.0.50; eieio-persistent slot type validation should be a bit smarter)

[Eric Abrahamsen <eric@ericabrahamsen.net>]

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Here's a basic patch that does the bare minimum, and seems to work.


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diff --git a/lisp/emacs-lisp/eieio-base.el b/lisp/emacs-lisp/eieio-base.el
index 6b39b4f262..361c1a4eb9 100644
--- a/lisp/emacs-lisp/eieio-base.el
+++ b/lisp/emacs-lisp/eieio-base.el
@@ -308,14 +308,6 @@ eieio-persistent-validate/fix-slot-value
 		       (= (length proposed-value) 1))
 		  nil)
 
-		  ;; We have a slot with a single object that can be
-		  ;; saved here.  Recurse and evaluate that
-		  ;; sub-object.
-		 ((and classtype (class-p classtype)
-		       (child-of-class-p (car proposed-value) classtype))
-		  (eieio-persistent-convert-list-to-object
-		   proposed-value))
-
 		 ;; List of object constructors.
 		 ((and (eq (car proposed-value) 'list)
 		       ;; 2nd item is a list.
@@ -346,6 +338,16 @@ eieio-persistent-validate/fix-slot-value
 			    objlist))
 		    ;; return the list of objects ... reversed.
 		    (nreverse objlist)))
+                 ;; We have a slot with a single object that can be
+		 ;; saved here.  Recurse and evaluate that
+		 ;; sub-object.
+		 ((and classtype
+                       (seq-some
+                        (lambda (c-type)
+		          (child-of-class-p (car proposed-value) c-type))
+                        (if (listp classtype) classtype (list classtype))))
+		  (eieio-persistent-convert-list-to-object
+		   proposed-value))
 		 (t
 		  proposed-value))))
 
@@ -359,7 +361,7 @@ eieio-persistent-validate/fix-slot-value
   )
 
 (defun eieio-persistent-slot-type-is-class-p (type)
-  "Return the class referred to in TYPE.
+  "Return the class or classes referred to in TYPE.
 If no class is referenced there, then return nil."
   (cond ((class-p type)
 	 ;; If the type is a class, then return it.
@@ -402,13 +404,9 @@ eieio-persistent-slot-type-is-class-p
 	       type))
 
 	((eq (car-safe type) 'or)
-	 ;; If type is a list, and is an or, it is possibly something
-	 ;; like (or null myclass), so check for that.
-	 (let ((ans nil))
-	   (dolist (subtype (cdr type))
-	     (setq ans (eieio-persistent-slot-type-is-class-p
-			subtype)))
-	   ans))
+	 ;; If type is a list, and is an or, it is possible that
+	 ;; multiple classes are acceptable, find them all.
+	 (seq-filter (lambda (elt) (class-p elt)) (cdr type)))
 
 	(t
 	 ;; No match, not a class.