[ruby-core:108688] [Ruby master Feature#18798] `UnboundMethod#==` with inherited classes

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

Backport deleted (2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN)
ruby -v deleted (ruby 3.2.0dev (2022-01-14T04:46:12Z gh-4636 c613d79f9b) [x64-mswin64_140])
Tracker changed from Bug to Feature

Ah, yes, it is a feature request.

----------------------------------------
Feature #18798: `UnboundMethod#==` with inherited classes
https://bugs.ruby-lang.org/issues/18798#change-97729

* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
----------------------------------------
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 point to a 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
```




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