Issue #11878 has been updated by matz (Yukihiro Matsumoto).

Status changed from Open to Rejected

For the code like below:

```
module A; end

module I
  include A
end

p A < I #=> false
p A > I #=> true

module P
  prepend A
end

# current: same as include
p A < P #=> false
p A > P #=> true
```

`A > P` does not mean `P` is a subclass of `A`, but `P` *includes* the method sets defined in `A`. So the current behavior should not be changed.

Matz.




----------------------------------------
Bug #11878: Comparison of prepended modules
https://bugs.ruby-lang.org/issues/11878#change-83920

* Author: sawa (Tsuyoshi Sawada)
* Status: Rejected
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 
* ruby -v: 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux]
* Backport: 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED, 2.3: REQUIRED
----------------------------------------
Including module `B` to class/module `A` gives the following results (as expected):

~~~ruby
module A; end
module B; end
A.include B
A < B # => true
B < A # => false
A <=> B # => -1
~~~

And prepending module `C` to `A` gives the following results:

~~~ruby
module C; end
A.prepend C
A < C # => true
C < A # => nil
A <=> C # => -1
~~~

It looks like including and prepending almost do not make difference with respect to module comparison, i.e., `A < B` and `A < C` are the same, and `A <=> B` and `A <=> C` are the same. However, then, the difference between `B < A` and `C < A` stands out unexplained. I suppose this is a bug. If `C < A` were to return `false`, then it would be at least consistent.

However, if that was what was intended, then at least to me, it is strange. In that case, I would like to make this a feature request. I would rather expect:

~~~ruby
A < C # => false
C < A # => true
A <=> C # => 1
~~~




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