From: samuel@...
Date: 2020-01-04T07:21:38+00:00
Subject: [ruby-core:96653] [Ruby master Bug#9573] descendants of a module don't gain its future ancestors, but descendants of a class, do

Issue #9573 has been updated by ioquatix (Samuel Williams).


From @jeremyevans0:

> Previously it wasn't possible because there wasn't a way to go from the module to all iclasses generated from it.
> I think module_subclasses in struct rb_subclass_entry may now contain the necessary pointers, but I'm not sure.
> Actually, looks like the subclasses entry may contain it (module_subclasses is used by iclasses, not modules).  This appears to be a linked list of iclasses for the module.

----------------------------------------
Bug #9573: descendants of a module don't gain its future ancestors, but descendants of a class, do
https://bugs.ruby-lang.org/issues/9573#change-83623

* Author: rits (First Last)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.1.1p76 (2014-02-24 revision 45161) [i686-linux]
* Backport: 
----------------------------------------
```ruby
module Mod1
end

module Mod2
end

class Class1
end

class Class2 < Class1
end

p Class2.ancestors - Object.ancestors # [Class2, Class1]

Class1.include Mod1

p Class2.ancestors - Object.ancestors # [Class2, Class1, Mod1]

Mod1.include Mod2

p Mod1.ancestors - Object.ancestors # [Mod1, Mod2]

p Class2.ancestors - Object.ancestors # [Class2, Class1, Mod1]
```
________________________________________________________________

note that descendants of a class do gain its future ancestors

so 2 issues:

1. It would seem natural that in dynamic language, dynamically added ancestors should propagate to descendants
2. Why is there a difference in ancestor propagation between modules and classes
 



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