[ruby-core:62606] [ruby-trunk - Bug #9475] Behavior change with include + super + alias_method between 1.9.x and 2.x

Issue #9475 has been updated by Tomoyuki Chikanaga.

Backport changed from 1.9.3: DONTNEED, 2.0.0: DONE, 2.1: REQUIRED to 1.9.3: DONTNEED, 2.0.0: DONE, 2.1: DONE

r45367, r45387, r45388 and r45389 were backported into `ruby_2_1` branch at r45955.

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Bug #9475: Behavior change with include + super + alias_method between 1.9.x and 2.x 
https://bugs.ruby-lang.org/issues/9475#change-46746

* Author: Ben Weintraub
* Status: Closed
* Priority: Normal
* Assignee: Nobuyoshi Nakada
* Category: 
* Target version: 
* ruby -v: ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-darwin12.0]
* Backport: 1.9.3: DONTNEED, 2.0.0: DONE, 2.1: DONE
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Ruby 2.0 appears to have introduced a subtle behavior change in method resolution that persists in 2.1.0.

The attached test case (also visible online at https://gist.github.com/benweint/8791007) is extracted from an actual application, and while I won't defend the need to do something like this, it is clear that the behavior changed in 2.0. Note that this sounds similar to https://bugs.ruby-lang.org/issues/9236 but is in fact distinct - the test case given in that bug was fixed in Ruby 2.1.

Steps to reproduce:
1. Run the attached testcase on Ruby 1.9.3 note the output
2. Run the attached testcase on Ruby 2.0.0-p353 or 2.1.0-p0, and note the output

Expected results:
While it's certainly not obvious to me what 'should' happen when executing this code, on 1.9.3, it produces this output:

~~~
foo from C
foo from B
foo from A  
~~~

Actual results:
On 2.0+, I get this instead

~~~
foo from C
foo from B
foo from B (again)
foo from B
foo from B (again)
foo from B
... previous two lines repeated many times ...
test.rb:11: stack level too deep (SystemStackError)
~~~

That is to say, on 2.0, we get into an infinitely recursive loop that doesn't happen with 1.9.3.

---Files--------------------------------
test.rb (340 Bytes)


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