bug#62959: [PATCH] Recognize defstruct slot names in various eieio functions

[Thuna <thuna.cing@gmail.com>]

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The function `eieio--known-slot-name-p' is used by some eieio functions
(specifically eieio-oref, eieio-oref-default, and eieio-oset-default) to
check whether a slot name is known or not, and if not signals an
"Unknown slot" warning.

Structs do not make their slots known to `eieio--known-slot-name-p', so
the warning is signaled even for valid slot names.  Since eieio aims for
compatibility with defstruct, this should probably be considered a bug.

The function `eieio--known-slot-name-p' checks the variable
`eieio--known-slot-names' but also has a fallback for the name's
`slot-name' property.  In the patch I opted to use the latter.


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From 86ed1ed7d024a0d40286d5fe4697258dc98a1b9e Mon Sep 17 00:00:00 2001
From: Thuna <thuna.cing@gmail.com>
Date: Wed, 19 Apr 2023 23:43:22 +0200
Subject: [PATCH] Recognize defstruct slot names in various eieio functions

* lisp/emacs-lisp/cl-preloaded.el (cl-struct-define): Set each slot's
name's `slot-name' property so that `eieio--known-slot-name-p' can
recognize them.
---
 lisp/emacs-lisp/cl-preloaded.el | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lisp/emacs-lisp/cl-preloaded.el b/lisp/emacs-lisp/cl-preloaded.el
index 9445093f143..5235be52996 100644
--- a/lisp/emacs-lisp/cl-preloaded.el
+++ b/lisp/emacs-lisp/cl-preloaded.el
@@ -176,6 +176,7 @@ cl-struct-define
                        (i 0)
                        (offset (if type 0 1)))
                    (dolist (slot slots)
+                     (put (car slot) 'slot-name t)
                      (let* ((props (cl--plist-to-alist (cddr slot)))
                             (typep (assq :type props))
                             (type (if (null typep) t
-- 
2.39.2