From: "mdalessio (Mike Dalessio) via ruby-core" <ruby-core@...>
Date: 2026-02-09T20:09:02+00:00
Subject: [ruby-core:124742] [Ruby Bug#21873] `UnboundMethod#==` returns false for methods obtained via extend + unbind

Issue #21873 has been updated by mdalessio (Mike Dalessio).


A potential fix for this might be:

```diff
diff --git a/proc.c b/proc.c
index f0cdcae7..67963a1b 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 ||
```


----------------------------------------
Bug #21873: `UnboundMethod#==` returns false for methods obtained via extend + unbind
https://bugs.ruby-lang.org/issues/21873#change-116343

* Author: mdalessio (Mike Dalessio)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
## Description

`UnboundMethod#==` returns `false` when comparing a module's instance method against the same method obtained via `Method#unbind` on a class that includes or extends that module, despite having the same owner and source location.

```ruby
module MyMethods
  def hello = "hello"
end

class Base
  extend MyMethods
end

from_module = MyMethods.instance_method(:hello)
from_unbind = Base.method(:hello).unbind

p from_module.owner == from_unbind.owner                     #=> true
p from_module.source_location == from_unbind.source_location #=> true
p from_module.inspect == from_unbind.inspect                 #=> true

p from_module == from_unbind                                 #=> false (expected true)
```

## Diagnosis

`method_eq` compares method entries using `method_entry_defined_class`. For methods mixed in via `include`/`extend`, the "defined class" will be an ICLASS and not the original class/module. In the example above, `method_eq` is comparing a module's ICLASS entry against the module, and that will always be false.

Related: #18798 (fixed by @ko1 in 59e389af).





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