Issue #22309 has been updated by jeremyevans0 (Jeremy Evans). @shugo Thank you for the recommendation for implementing this correctly. I used the approach you recommended, and it ended up being much simpler than I expected, even if there were a couple tricky parts. One of those was how to store the lazily initialized caches. My first approach used an instance variable on an iclass, which apparently is no longer supported due to an optimization involving shapes. In order to avoid increasing the size of rb_classext_struct, I abused the classpath member to hold the cache, as that member is used for classes and modules but unused for iclasses. I'd like to clean this up later and move classpath into the `as` union, so that the iclass member can use a descriptive name. The new approach passes the test suite I built while developing the previous approach. I also added a test case using `Thread.new{super}` (based on your earlier comment), which failed with the previous approach and passes with the new approach. Here's the new pull request: https://github.com/ruby/ruby/pull/18910 ---------------------------------------- Feature #22309: Allow super in a module method to work if method was called by refinement method super https://bugs.ruby-lang.org/issues/22309#change-119074 * Author: jeremyevans0 (Jeremy Evans) * Status: Open ---------------------------------------- Ruby started allowing refinements of modules in 2.4. However, there was one limitation, which is that while the refinement method could call `super` to call the module method, the module method could not call `super`, because it did not have enough information to determine the appropriate ancestor. This limitation was known at the time and was accepted when module refinements were accepted in #12534. As discussed in #22071, `super` wasn't actually prohibited in the module method, it just used the incorrect method lookup, looking for a super method in `BasicObject`. After discussion in #22071, I fixed this to use an explicit exception for this case, so an error was was raised for it. While that addressed the incorrect super method lookup issue, it was an unsatisfying conclusion. I kept thinking about ways to actually fix the issue. My initial idea was to use a separate `T_ICLASS` for the module being refined in every class ancestry chain where it could be called via refinement `super`. However, that approach would result in a large amount of complexity, as well as potentially significant additional memory. I am instead proposing an alternative approach which relies on the fact that when we call `super` in the module method, we know that the current method is a module method, and that the previous method in the call stack is a refinement method. We can walk up the call stack to find the refinement method, look at the previous method calling that to determine the class to use for the super lookup. Note that the previous method may use a different receiver/method, in which case we start with the receiver's class. There are cases where we need to do this multiple times, if there are multiple refinements or multiple modules being refined that have already called super to reach this point. I'm not sure this alternative approach works in all cases, but I have gotten it to work every case I've tried: * Module and refinement appears multiple times in the ancestor chain * `super` calls both directly in method as well as in nested blocks in method * Both refinement method and module method are bmethods * Refinement refines multiple modules and both modules are involved in the same super call chain * Multiple refinements of the same module method * Use of ZSUPER aliases in the super call chain * The `super` call in the module method is not found, and `NoMethodError` is raised correctly We want the behavior of module refinement `super` to be consistent, so in addition to fixing `super` itself, we also need to fix `defined?(super)` as well as `Method#super_method` and `UnboundMethod#super_method`. `defined?(super)` is fixed by sharing the lookup that `super` now uses. However, `Method#super_method` and `UnboundMethod#super_method` require a different approach. Thankfully, `struct METHOD` already has a member named `iclass` that is used to implement `#super_method`. So we just need to make adjustments to the setting of the `iclass` member for `#super_method` to work. Simple example: ```ruby module M def m = [:M, *super] end class C prepend M def m = :C end module R refine M do def m = [:R, *super] end end using R C.new.m # => [:R, :M, :C] ``` I've submitted a pull request to implement this: https://github.com/ruby/ruby/pull/18797 -- https://bugs.ruby-lang.org/