From 836c1700104c305fa13cbc7b17d114705dd807b2 Mon Sep 17 00:00:00 2001
From: Mike Dalessio <mike@37signals.com>
Date: Mon, 9 Feb 2026 13:45:34 -0500
Subject: Fix UnboundMethod#== for methods from included/extended modules

Method#unbind clones the method entry, preserving its defined_class.
For methods mixed in via include/extend, defined_class is an ICLASS,
causing UnboundMethod#== to return false when comparing against the
same method obtained via Module#instance_method.

Resolve ICLASS defined_class in method_eq.

Fixes [Bug #21873]
---
 proc.c | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'proc.c')

diff --git a/proc.c b/proc.c
index f0cdcae7b1..67963a1b01 100644
--- a/proc.c
+++ b/proc.c
@@ -2006,6 +2006,8 @@ method_eq(VALUE method, VALUE other)
 
     klass1 = method_entry_defined_class(m1->me);
     klass2 = method_entry_defined_class(m2->me);
+    if (RB_TYPE_P(klass1, T_ICLASS)) klass1 = RBASIC_CLASS(klass1);
+    if (RB_TYPE_P(klass2, T_ICLASS)) klass2 = RBASIC_CLASS(klass2);
 
     if (!rb_method_entry_eq(m1->me, m2->me) ||
         klass1 != klass2 ||
-- 
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