From: "jeremyevans0 (Jeremy Evans) via ruby-core" <ruby-core@...>
Date: 2026-11-04T04:44:07+00:00
Subject: [ruby-core:127327] [Ruby Bug#22462] For UnboundMethod, super_method.bind and bind.super_method should return an equal Method

Issue #22462 has been updated by jeremyevans0 (Jeremy Evans).

Subject changed from Method#== can return false for methods that should be considered equal to For UnboundMethod, super_method.bind and bind.super_method should return an equal Method

shugo (Shugo Maeda) wrote in #note-3:
> jeremyevans0 (Jeremy Evans) wrote in #note-2:
> > Since the behavior for the two UnboundMethods is different, I think it makes sense that they are considered unequal.
> 
> I agree that `ua` and `ub` in my example behave differently.
> However, the current behavior of `UnboundMethod#==` was introduced by [Feature #18798], and it only checks whether the method definitions are the same, so `ua == ub` is still true.
> 
> If we accept that `UnboundMethod#==` and `Method#==` are inconsistent in this respect, I think the change in the PR is fine.

Note that my proposal does not change `Method#==` behavior. It only changes `super_method` behavior. The issue here is that the `super_method` and `bind` combination currently returns a `Method` that may be unequal if the order of `super_method` and `bind` is reversed, when it should return a `Method` that is equal regardless of the order. I'm changing the subject to reflect that.

I split out the `bind` issue into a separate bug report (#22505), so that it can be considered separately. Note that the fix for this issue requires the fix for that issue.

----------------------------------------
Bug #22462: For UnboundMethod, super_method.bind and bind.super_method should return an equal Method
https://bugs.ruby-lang.org/issues/22462#change-119757

* Author: jeremyevans0 (Jeremy Evans)
* Status: Open
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
When a `Method` is created using `UnboundMethod#bind` and `#super_method`, the order in which the `#bind` and `#super_method` were applied could result in `Method` objects that were considered unequal.

I believe we should have the invariant: for any `UnboundMethod` `um` where `super_method` is not `nil` and `o` is a valid object to bind to `um`, the following code should be true:

```ruby
um.bind(o).super_method == um.super_method.bind(o)
```

However, that didn't work correctly in some cases:

```ruby
module M; def m = [:M, *super]; end
module N; include M; end
class C; def m = :C; end
class SC < C
  include N
  prepend M
  def m = [:SC, *super]
end
o = SC.new
um = SC.instance_method(:m).super_method.super_method  # M#m below SC (included via N)
um.bind(o).super_method == um.super_method.bind(o)
# => false # should be true
```

There is a similar invariant for Method: for any `Method` `m` where `super_method` is not `nil`, the following code should be true:

```ruby
m.unbind.super_method == m.super_method.unbind
```

This appears to already hold, as the existing refinement tests already checked for this behavior.

I've submitted a PR to fix this issue: https://github.com/ruby/ruby/pull/19474



-- 
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