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May 2026

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[ruby-core:125398] [Ruby Bug#22022] Refinement zsuper problems when referenced method changes
by jeremyevans0 (Jeremy Evans) 04 May '26

04 May '26

Issue #22022 has been reported by jeremyevans0 (Jeremy Evans). ---------------------------------------- Bug #22022: Refinement zsuper problems when referenced method changes https://bugs.ruby-lang.org/issues/22022 * Author: jeremyevans0 (Jeremy Evans) * Status: Open * ruby -v: ruby 4.1.0dev (2026-05-03T23:57:21Z master d8d2ed5dc9) +PRISM [x86_64-openbsd7.8] * Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- I've found many problems with refinement zsuper methods. Here's one example: ```ruby module M private def a = :a alias a a end class A include M end class B < A end module R refine B do public :a end end using R B.new.a # false() function is unimplemented on this machine (NotImplementedError) ``` Here's another: ```ruby class A private def a = :a end module R refine A do public :a end end using R A.new.a # => :a module M def a = :b end A.prepend M A.new.a # SystemStackError: stack level too deep ``` The problematic cases are in general can be broken down into: * Method being redefined (in same or closer ancestor) * Method being removed * Method being undef-ed (in same or closer ancestor) * Method being overridden by method in included module * Method being overridden by method in prepended module * Method being defined in an included/prepended module at time of refinement In addition to the `NotImplementedError` and `SystemStackError`, there are other cases where incorrect results are given. One possible approach for fixing this is to turn the zsuper methods into regular methods that call super . This fixes all cases that I found. This is not a perfect solution, due to mildly worse performance (I'm guessing) as well as arity/parameters for the method not as helpful. It may possible to avoid these issues by clearing method caches in more cases. However, I think that would require a lot of extra work, since you cannot just clear the method cache for the current class. You would need to clear it for all subclasses, if this is a module, do the same for all classes that include/prepend the module, as well as any subclasses of those classes. Considering the need for refinement zsuper methods is very rare, the performance and arity/parameters issues seem acceptable (to me). Pull request: https://github.com/ruby/ruby/pull/16844 -- https://bugs.ruby-lang.org/

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