[ruby-core:108659] [Ruby master Bug#18798] `UnboundMethod#==` with inherited classes

["ko1 (Koichi Sasada)" <noreply@ruby-lang.org>]

Issue #18798 has been reported by ko1 (Koichi Sasada).

----------------------------------------
Bug #18798: `UnboundMethod#==` with inherited classes
https://bugs.ruby-lang.org/issues/18798

* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.0dev (2022-01-14T04:46:12Z gh-4636 c613d79f9b) [x64-mswin64_140]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Now `UnboundMethod` for a same method from a superclass and an inherited class are not `==`.

```ruby
class C
  def foo = :C
  $mc = instance_method(:foo)
end

class D < C
  $md = instance_method(:foo)
end

p $mc == $md #=> false
p $mc.owner #=> C
p $mc.owner == $mc.owner #=> true
p $mc.source_location == $mc.source_location #=> true
p $mc.inspect #=> "#<UnboundMethod: C#foo() t.rb:3>"
p $md.inspect #=> "#<UnboundMethod: D(C)#foo() t.rb:3>"
```

How about to make it `UnboundMethod#==` return true for this case?
Rule: "return true if the UnboundMethod objects points same method definition" seems simple.

FYI: On aliased unbound methods point to a same method are `==`.


```ruby
class C
  def foo = :C
  alias bar foo
  $mfoo = instance_method(:foo)
  $mbar = instance_method(:bar)
end

p $mfoo, $mbar
#=> #<UnboundMethod: C#foo() t.rb:2>
#=> #<UnboundMethod: C#bar(foo)() t.rb:2>

p $mfoo == $mbar #=> true
```




-- 
https://bugs.ruby-lang.org/