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]

1 files changed, 2 insertions, 0 deletions

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 ||