From: "jeremyevans0 (Jeremy Evans) via ruby-core" <ruby-core@...>
Date: 2026-11-04T04:28:19+00:00
Subject: [ruby-core:127326] [Ruby Bug#22505] UnboundMethod#{bind,bind_call} results in incorrect behavior when method owner is at multiple places in ancestry

Issue #22505 has been reported by jeremyevans0 (Jeremy Evans).

----------------------------------------
Bug #22505: UnboundMethod#{bind,bind_call} results in incorrect behavior when method owner is at multiple places in ancestry
https://bugs.ruby-lang.org/issues/22505

* Author: jeremyevans0 (Jeremy Evans)
* Status: Open
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
If a method owner is at multiple places in the ancestry, `UnboundMethod#bind` can result in incorrect behavior, making an `UnboundMethod` from a superclass method bind to a method defined in a subclass:

```ruby
module M
  def m = [:m, *super]
end
class C
  prepend M
  def m = [:c]
end
class SC < C
  prepend M
  def m = [:sc, *super]
end

C.instance_method(:m).bind_call(SC.new)
# => [:m, :sc, :m, :c]
# Should be: [:m, :c]
```

This was originally discovered while working on #22462, but it's unrelated to method equality.

The incorrect behavior appears to have started in Ruby 2.3, as Ruby 2.0-2.2 give the expected result.

I've submitted a PR to fix this issue: https://github.com/ruby/ruby/pull/19695



-- 
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