From: benweint@...
Date: 2014-02-03T20:22:52+00:00
Subject: [ruby-core:60431] [ruby-trunk - Bug #9475] [Open] Behavior change with include + super + alias_method between 1.9.x and 2.x

Issue #9475 has been reported by Ben Weintraub.

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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

* Author: Ben Weintraub
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-darwin12.0]
* Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN
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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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