Prevent users from accidentally intercept initialize method

#1085

ChangeLog

@@ -1,3 +1,9 @@
+2025-01-11  Shiro Kawai  <[email protected]>
+
+	* src/libobj.scm (initialize): Define locked method for <top> and
+	  <object> to prevent user code accidentally overrides them.
+	  https://github.com/shirok/Gauche/issues/1085
+
 2025-01-10  Shiro Kawai  <[email protected]>
 
 	* lib/control/pmap.scm: Make sure all worker threads are joined,

src/libobj.scm

@@ -746,6 +746,15 @@
   (cond [(assq slot-name (slot-ref class 'accessors)) => cdr]
         [else #f]))
 
+;;----------------------------------------------------------------
+;; Generic initialize
+
+;; These prevent users accidentally define `initialize` on <top>.
+(define-method initialize :locked ((obj <top>) initargs)
+  (next-method))
+(define-method initialize :locked ((obj <object>) initargs)
+  (next-method))
+
 ;;----------------------------------------------------------------
 ;; Generic coercion
 ;;  (should this be in separate file, e.g. coerce.scm?