April 2026 - ruby-core - ml.ruby-lang.org

[ruby-core:125124] [Ruby Bug#21964] Fiber stack acquire can expand unnecessarily.
by ioquatix (Samuel Williams) 14 Jun '26

14 Jun '26

Issue #21964 has been reported by ioquatix (Samuel Williams). ---------------------------------------- Bug #21964: Fiber stack acquire can expand unnecessarily. https://bugs.ruby-lang.org/issues/21964 * Author: ioquatix (Samuel Williams) * Status: Open * Assignee: ioquatix (Samuel Williams) * Backport: 3.2: REQUIRED, 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED ---------------------------------------- In several common scenarios, the fiber stack allocator can choose to expand the fiber stack pool even when there are unreachable (effectively dead) fibers. For example, the following program will eventually crash if GC does not run in time: ```ruby loop do Fiber.new{Fiber.yield}.resume end ``` We have a loop that resumes a fiber, that fiber yields, and then becomes unreachable. Eventually, we will exhaust the OS vm map limit and fail with `FiberError`. However, at most only one fiber (stack) is needed to execute the above program, since the fiber immediately becomes unreachable. To fix this, we run GC before trying to expand the fiber stacks. In practice, fiber stacks are expanded on power of 2, up to 1024 fibers per allocation. So GC is only run in scenarios where we hit this limit. If GC is running normally, or fibers are terminating normally, we may never hit this code path. -- https://bugs.ruby-lang.org/

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[ruby-core:123484] [Ruby Bug#21640] Core Pathname is missing 3 methods / is partially-defined
by Eregon (Benoit Daloze) 14 Jun '26

14 Jun '26

Issue #21640 has been reported by Eregon (Benoit Daloze). ---------------------------------------- Bug #21640: Core Pathname is missing 3 methods / is partially-defined https://bugs.ruby-lang.org/issues/21640 * Author: Eregon (Benoit Daloze) * Status: Open * ruby -v: ruby 3.5.0dev (2025-10-09T08:06:20Z master a29c90c3b0) +PRISM [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- ``` $ ruby -e 'puts Pathname.instance_methods(false).sort; puts Pathname.singleton_methods.sort' > core_pathname_methods.txt $ ruby -rpathname -e 'puts Pathname.instance_methods(false).sort; puts Pathname.singleton_methods.sort' > require_pathname_methods.txt $ diff core_pathname_methods.txt require_pathname_methods.txt 36a37 > find 72a74 > rmtree 98a101 > mktmpdir ``` So `#find`, `#rmtree` and `.mktmpdir` are missing from core Pathname. And indeed, they give NoMethodError, e.g. ``` $ ruby -ve 'Pathname.new("doesnotexist").rmtree' ruby 3.5.0dev (2025-10-09T08:06:20Z master a29c90c3b0) +PRISM [x86_64-linux] -e:1:in '<main>': undefined method 'rmtree' for an instance of Pathname (NoMethodError) ``` I think this is confusing and unexpected for most users. Either Pathname should be fully defined or not at all, having a partially-defined Pathname seems particularly confusing (a bit like an autoload that failed in the middle or so). AFAIK the only core class which used to have this was Fiber with `alive?` and `transfer`, that certainly caused its share of confusion, and Fiber has since been fixed, now even without `require "fiber"` Fiber has all methods. Furthermore these 3 methods are not documented as needing `require 'pathname'` in their documentation: https://github.com/ruby/ruby/blob/master/lib/pathname.rb The reason these 3 methods are not in core pathname seems to be (from [this comment](https://github.com/ruby/pathname/issues/64#issuecomment-3388907046)) > That's consensus with akr and me. We should avoid loading other libraries by simply calling methods from the embedded core classes. I understand that concern and I share it, but I think the situation of having a partially-defined Pathname in core is quite problematic. I think there are 2 solutions: * Define all Pathname methods in core. The `require` are done lazily inside the methods so AFAIK there is no technical issue blocking that, but it's not ideal design-wise that a core class can load default gems (i.e. give up that concern for this particular case). * Do not define Pathname in core and let it be a default gem as it was in Ruby 3.4. I discuss the second in more details, because I found more problems than I would have imagined with core Pathname: ## Should Pathname be in core? #17473 proposed to make Pathname core. That sounded great to me at first thought, but as I realize the practical problems with it I'm thinking it's actually better to keep Pathname non-core and as a default gems. Here are concerns with having Pathname in core: 1. Pathname inherently depends on other default gems/stdlib like `find`, `fileutils` and `tmpdir`. This is important to make Pathname useful. The docs even phrase it like this: `ri Pathname` > ... > All functionality from File, FileTest, and some from Dir and > FileUtils is included, in an unsurprising way. It is essentially a > facade for all of these, and more. 2. core Pathname is missing 3 methods compared to gem Pathname (shown above) 3. the pathname gem is likely to gain extra features, methods and bug fixes. For example I see [4 PRs](https://github.com/ruby/pathname/pulls) adding new methods. It means core Pathname will always be outdated and potentially missing some new methods. 4. One can still use the pathname gem even if it's in core, but surprisingly just `require 'pathname'` is not enough: ``` $ gem install pathname Building native extensions. This could take a while... Successfully installed pathname-0.4.0 1 gem installed $ ruby -e 'require "pathname"; puts $".grep(/pathname/)' pathname.so /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+4/pathname.rb ^ wrong that's the stdlib pathname $ ruby -e 'gem "pathname"; require "pathname"; puts $".grep(/pathname/)' # some warnings, reported in https://github.com/ruby/pathname/issues/66 pathname.so /home/eregon/prefix/ruby-master/lib/ruby/gems/3.5.0+4/gems/pathname-0.4.0/lib/pathname.rb ^ correct ``` This is another source of confusion caused by core pathname. It even happens with Bundler! ``` $ cat Gemfile source "https://rubygems.org" gem "pathname" $ bundle install $ ruby -e 'require "bundler/setup"; require "pathname"; puts $".grep(/pathname/); puts; puts $:' pathname.so /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+4/pathname.rb /home/eregon/tmp/bundler-pathname/vendor/bundle/ruby/3.5.0+4/gems/pathname-0.4.0/lib /home/eregon/tmp/bundler-pathname/vendor/bundle/ruby/3.5.0+4/extensions/x86_64-linux/3.5.0+4-static/pathname-0.4.0 /home/eregon/prefix/ruby-master/lib/ruby/gems/3.5.0+4/gems/bundler-2.8.0.dev/lib /home/eregon/prefix/ruby-master/lib/ruby/site_ruby/3.5.0+4 /home/eregon/prefix/ruby-master/lib/ruby/site_ruby/3.5.0+4/x86_64-linux /home/eregon/prefix/ruby-master/lib/ruby/site_ruby /home/eregon/prefix/ruby-master/lib/ruby/vendor_ruby/3.5.0+4 /home/eregon/prefix/ruby-master/lib/ruby/vendor_ruby/3.5.0+4/x86_64-linux /home/eregon/prefix/ruby-master/lib/ruby/vendor_ruby /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+4 /home/eregon/prefix/ruby-master/lib/ruby/3.5.0+4/x86_64-linux $ bundle exec ruby -e 'require "pathname"; puts $".grep(/pathname/); puts; puts $:' same as above ``` I'm not sure why, but that seems a serious bug that the `pathname` gem apparently can't be used at all with Bundler. 4. due to this difference in terms of methods for core & gem pathname it seems complicated to keep core Pathname and gem Pathname in sync, since e.g. everything is naturally in one `.rb` file in the gem, but in two `.rb` files in core 5. the pathname gem has to `remove_const :Pathname` to avoid conflicts and warnings in https://github.com/ruby/pathname/blob/4689b0b78d081ae855f325e086d95803fa5bd…. This is bad for Ruby JITs, especially if core Pathname methods might have been used, as it will invalidate JITs compilations, invalidate some inline caches (also bad for the interpreter), caused the JIT to do more compilations which means slower warmup, makes it much harder to persist JITed code across process executions, etc. Based on all of these I think it would actually be better to not have Pathname in core, and let it be a default gem. Having to `require "pathname"` as one always needed to do so far seems far better than a partially-defined core Pathname with rough edge cases (those concerns). -- https://bugs.ruby-lang.org/

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[ruby-core:125243] [Ruby Bug#21994] If there is a local variable `foo`, calls to a method `foo` with a regexp literal as first argument is always a SyntaxError without parentheses
by jneen (Jeanine Adkisson) 13 Jun '26

13 Jun '26

Issue #21994 has been reported by jneen (Jeanine Adkisson). ---------------------------------------- Bug #21994: If there is a local variable `foo`, calls to a method `foo` with a regexp literal as first argument is always a SyntaxError without parentheses https://bugs.ruby-lang.org/issues/21994 * Author: jneen (Jeanine Adkisson) * Status: Open * ruby -v: 4.0.1 * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ## Quick version: ```bash ruby -e 'p /hello/' # => /hello/ (warning) ruby -e 'p = 1; p /hello/' # syntax error ruby -e 'p %r/hello/' # => /hello/ (no warning) ruby -e 'p = 1; p %r/hello/' # syntax error ``` ## Context In Rouge, our lexing DSL originally looked like this: ```ruby rule /some_regex/, Some::TokenType, :next_state rule /some_other_regex/ do |match| # custom action end ``` In a DSL context like this, I feel that using parentheses for *every* rule definition is a hassle and looks bad, so we leave them off, as is convention. Unfortunately, this warns: ``` warning: ambiguous `/`; wrap regexp in parentheses or add a space after `/` operator ``` Some time ago, to reduce warning-spam on users who run with `-w`, we transitioned all of these to use `%r/.../` or `%r(...)` syntax, which does not warn. The issue here I think is that *both* cases are equivalently ambiguous in some sense, which becomes apparent with the local-scope-dependent behaviour of the parser (putting aside that dependency on local variable scope makes the Ruby syntax highlighting of Rouge more or less impossible to do correctly without a full parse). If there is a local variable named `rule` introduced at any point, even several block scopes above, the entire file errors out in a very confusing manner. At the very least, I feel that the warnings here are inconsistent. If both cases truly are ambiguous and dependent on local variable scope, perhaps it would be better to warn on both - though that would make using a regex literal as a first argument *always* require parentheses to avoid warnings, which would make my DSL much harder. I'm honestly not entirely sure what a good solution would be, but I would like to open a discussion on the topic. Perhaps philosophically related to the other bug I have open ( #21870 ) - is this truly worthy of a warning, or should this be a linter concern? -- https://bugs.ruby-lang.org/

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[ruby-core:125156] [Ruby Feature#21972] Add Date.birthday and Date.age to track Ruby's milestones
by jinroq (Jinroq SAITOH) 12 Jun '26

12 Jun '26

Issue #21972 has been reported by jinroq (Jinroq SAITOH). ---------------------------------------- Feature #21972: Add Date.birthday and Date.age to track Ruby's milestones https://bugs.ruby-lang.org/issues/21972 * Author: jinroq (Jinroq SAITOH) * Status: Open ---------------------------------------- Since its inception in 1993, Ruby has grown beyond a mere programming language to become a rich culture beloved by developers worldwide. However, the standard `date` library surprisingly lacks a formal interface to commemorate Ruby's own historical milestones. The fact that developers cannot programmatically reference Ruby’s heritage is a missed opportunity to foster affection and respect for the language's identity. To rectify this historical oversight, I propose adding the following methods to reference Ruby's key anniversaries and calculate the elapsed years. #### New Features * **`Date.birthday(version = nil)`** Returns the "birthday" of significant moments in Ruby's history. * `nil` (default): **1993-02-24** (The day the name "Ruby" was decided). * `0.95`: **1995-12-21** (The first public release date). * `1.0`: **1996-12-25** (The first stable release date). * **`Date.age(version = nil)`** Calculates the current age (in full years) based on today's date and the specified milestone. * `Date.age`: Years since the name "Ruby" was born. * `Date.age(0.95)`: Years since Ruby was first introduced to the public as OSS. * `Date.age(1.0)`: Years since Ruby began its journey as a stable language. #### Usage Example ```ruby # Check the "age" of each edition puts "Name age: #{Date.age}" # => 33 (as of 2026) puts "OSS age: #{Date.age(0.95)}" # => 30 puts "Stable: #{Date.age(1.0)}" # => 29 # Perform a special action on a specific anniversary if Date.today == Date.birthday(1.0) celebrate_stable_anniversary! end ``` #### Implementation and Testing The attached patch (`birthday_and_age.patch`) includes the implementation of these methods along with a rigorous test suite (`test/date/test_date_birthday.rb`). The tests cover argument dispatching, `ArgumentError` for invalid inputs, and edge cases for age calculation (e.g., boundaries before and after the actual birthday), ensuring production-level quality. Equipping Ruby with the intelligence to reflect upon its own origins is a vital step toward the next 30 or 40 years of its evolution. (Note: This proposal was submitted on a special day that encourages looking at our history with both deep respect and a touch of creative imagination, as is traditional for such a significant date in the calendar.) ---Files-------------------------------- birthday_and_age.patch (8.08 KB) -- https://bugs.ruby-lang.org/

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[ruby-core:125157] [Ruby Feature#21973] Smile argument
by kinoppyd (Yasuhiro Kinoshita) 11 Jun '26

11 Jun '26

Issue #21973 has been reported by kinoppyd (Yasuhiro Kinoshita). ---------------------------------------- Feature #21973: Smile argument https://bugs.ruby-lang.org/issues/21973 * Author: kinoppyd (Yasuhiro Kinoshita) * Status: Open ---------------------------------------- Ruby makes us smile. So I want Ruby to smile too, and that is why I would like to propose this feature. The smile argument makes Ruby smile by allowing a method call to end its argument list with `:)`. smile_method(arg, :) This syntax implicitly supplies keyword arguments by matching the names of local variables in the current scope with the names of the method’s keyword parameters. For example, if a method has the following signature: ```ruby some_method(arg, smile:, hugging:) ``` then these two calls would be equivalent: ```ruby arg = "hello" smile = "smile" hugging = "hugging" some_method(arg, smile:, hugging:) ``` ```ruby arg = "hello" smile = "smile" hugging = "hugging" some_method(arg, :) ``` The motivation behind this feature is the assumption that names used in a method signature are often also used at the call site. For instance, if a library method defines keyword arguments like `(from:, to:)`, I expect that code using that method would often have local variables named `from` and `to` holding the actual values before passing them along. In real application development, when developers adopt a new library, they will usually look at the argument list of the method they want to call. If they intend to use that method as designed, it seems natural that they may also choose the same variable names as those in the method signature. This idea was inspired by Scala’s implicit parameters. It is not exactly the same feature, but as a lazy person, I find the idea of context-driven currying quite appealing. In any case, the real purpose is to make Ruby smile. Happy Ruby! And happy April Fools' Day! -- https://bugs.ruby-lang.org/

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[ruby-core:123958] [Ruby Feature#21720] Add a native Binary Heap / Priority Queue to Ruby's Standard Library (heapify, heappush, heappop)
by rahulk501 (Rahul Kumar) 11 Jun '26

11 Jun '26

Issue #21720 has been reported by rahulk501 (Rahul Kumar). ---------------------------------------- Feature #21720: Add a native Binary Heap / Priority Queue to Ruby's Standard Library (heapify, heappush, heappop) https://bugs.ruby-lang.org/issues/21720 * Author: rahulk501 (Rahul Kumar) * Status: Open ---------------------------------------- **Title:** Add a native Binary Heap / Priority Queue to Ruby's Standard Library (`heapify`, `heappush`, `heappop`) **Problem** Ruby currently lacks a native binary heap / priority queue data structure in the standard library. Users frequently reimplement heaps manually, or install third-party gems, simply to access common operations such as: * `heapify` * `heappush` * `heappop` * efficient priority queues Meanwhile, languages like Python provide a standard `heapq` module which is widely used in algorithms, AI, scheduling, job queues, pathfinding, graph traversal, and competitive programming. Because Ruby does not include a heap implementation, developers often write ad-hoc, buggy, or inconsistent versions of a heap. This leads to fragmentation and duplication. **Proposal** Introduce a lightweight `Heap` or `BinaryHeap` class to Ruby’s standard library with the following minimal API: ```ruby heap = Heap.new(array = []) heap.push(value) heap.pop # returns smallest (min-heap) heap.peek heap.size ``` Or a module-based functional API similar to Python’s `heapq`: ```ruby Heap.heapify(array) Heap.heappush(array, value) Heap.heappop(array) ``` Both designs are simple and allow backward-compatible extension. **Why include it in the standard library?** 1. Heaps are a *fundamental data structure*—used in sorting, algorithms, scheduling, and timers. 2. Many languages include them natively (Python, C++ via STL `priority_queue`, Java, Go, Rust `BinaryHeap`). 3. Adding it reduces unnecessary reimplementations in user codebases. 4. A small heap implementation adds little maintenance burden. 5. Existing Ruby solutions (gems like `algorithms`, `priority_queue`, custom code) are not universally available and often exceed what users need. **Reference Implementation (pure Ruby, minimal example)** ```ruby module Heap def self.heapify(arr) (arr.length / 2 - 1).downto(0) { |i| sift_down(arr, i) } arr end def self.heappush(arr, value) arr << value sift_up(arr, arr.length - 1) end def self.heappop(arr) return nil if arr.empty? arr[0], arr[-1] = arr[-1], arr[0] min = arr.pop sift_down(arr, 0) min end def self.sift_up(arr, i) while i > 0 p = (i - 1) / 2 break if arr[p] <= arr[i] arr[p], arr[i] = arr[i], arr[p] i = p end end def self.sift_down(arr, i) n = arr.length loop do left = 2 * i + 1 right = 2 * i + 2 smallest = i smallest = left if left < n && arr[left] < arr[smallest] smallest = right if right < n && arr[right] < arr[smallest] break if smallest == i arr[i], arr[smallest] = arr[smallest], arr[i] i = smallest end end private_class_method :sift_up, :sift_down end ``` **Optional C implementation** If accepted, I am willing to provide a minimal C version for performance parity with other stdlib containers. **Compatibility** No breaking changes expected. Naming avoids conflict with existing libraries. **Conclusion** Adding a tiny, well-defined heap structure would strengthen Ruby’s built-in algorithmic tools, reduce duplicated code across the ecosystem, and align Ruby with other mainstream languages. -- https://bugs.ruby-lang.org/

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[ruby-core:113430] [Ruby master Feature#19633] Allow passing block to `Kernel#autoload` as alternative to second `filename` argument
by shioyama (Chris Salzberg) 10 Jun '26

10 Jun '26

Issue #19633 has been reported by shioyama (Chris Salzberg). ---------------------------------------- Feature #19633: Allow passing block to `Kernel#autoload` as alternative to second `filename` argument https://bugs.ruby-lang.org/issues/19633 * Author: shioyama (Chris Salzberg) * Status: Open * Priority: Normal ---------------------------------------- `Kernel#autoload` takes two arguments, a symbol `module` representing the constant to be autoloaded, and a `filepath` to load the constant from (with `require`). Currently, Zeitwerk has to [monkeypatch `Kernel#require`](https://github.com/fxn/zeitwerk/blob/a7c4a983df0f4e4058f32c610dac1e8b99f687da/lib/zeitwerk/kernel.rb) to fetch the loader for the file being loaded, then run the original (aliased) `require`, then run autoload callbacks. In addition to the monkeypatch, this also requires a registry (`Zeitwerk::Registry`) to map file paths to loaders, to know which loader should be used for a given autoload-triggered `require`. In fact, Zeitwerk has to _assume_ that the monkey-patched `require` call came from an autoload trigger; there is no way to really be sure of the source. If Ruby allowed passing a block as an alternative to the explicit filepath, then I think this could be improved and would eliminate the need for a monkeypatch. So something like this: ```ruby autoload(:B) do require "lib/b" # trigger callback, etc end ``` I am implementing a gem called [Im](https://github.com/shioyama/im) which is a fork of Zeitwerk, and in the case of this gem, such a feature would be even more useful. Im implements autoloads on anonymous modules by registering an autoload and then "catching" the require and converting it into a `load`, passing the module as the second argument (see [here](https://github.com/shioyama/im/blob/44ce348639a1aae563a5be7a40602761e….) This is currently quite tricky because, again, it's hard to know _where_ a `require` came from. In addition to removing the monkeypatch (inherited from Zeitwerk), Im would further benefit from the block argument because then it could simply access the module via a closure, rather than pulling it from a registry: ```ruby mod.autoload(:Foo) do load "lib/foo.rb", mod end ``` I don't know how hard or easy this would be to implement, but if there is interest in this as a feature I'd be happy to look into implementing it. -- https://bugs.ruby-lang.org/

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[ruby-core:124888] [Ruby Bug#21927] Prism: misleading error message for forwarding in lambda argument
by nobu (Nobuyoshi Nakada) 07 Jun '26

07 Jun '26

Issue #21927 has been reported by nobu (Nobuyoshi Nakada). ---------------------------------------- Bug #21927: Prism: misleading error message for forwarding in lambda argument https://bugs.ruby-lang.org/issues/21927 * Author: nobu (Nobuyoshi Nakada) * Status: Open * Assignee: prism * ruby -v: d256629bf9 * Backport: 3.2: DONTNEED, 3.3: DONTNEED, 3.4: REQUIRED, 4.0: REQUIRED ---------------------------------------- Even in a forwarding method: ```console $ ruby --parser=prism -e 'def m(...) ->(...){}; end' -e: -e:1: syntax error found (SyntaxError) > 1 | def m(...) ->(...){}; end | ^~~ unexpected ... when the parent method is not forwarding ``` This message is proper for method arguments: ```console $ ruby --parser=prism -e 'def m() p(...); end' -e: -e:1: syntax error found (SyntaxError) > 1 | def m() p(...); end | ^~~ unexpected ... when the parent method is not forwarding ``` The message from parse.y is different; "unexpected ... in lambda argument": ```console $ ruby --parser=parse.y -e 'def m(...) ->(...){}; end' -e:1: unexpected ... in lambda argument def m(...) ->(...){}; end ruby: compile error (SyntaxError) ``` -- https://bugs.ruby-lang.org/

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[ruby-core:124885] [Ruby Bug#21925] Prism misparses standalone "in" pattern matching in "case/in"
by knu (Akinori MUSHA) 07 Jun '26

07 Jun '26

Issue #21925 has been reported by knu (Akinori MUSHA). ---------------------------------------- Bug #21925: Prism misparses standalone "in" pattern matching in "case/in" https://bugs.ruby-lang.org/issues/21925 * Author: knu (Akinori MUSHA) * Status: Open * Target version: 4.1 * ruby -v: ruby 4.0.1 (2026-01-13 revision e04267a14b) +PRISM [arm64-darwin23] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- Prism misparses standalone `in` pattern matching in `case/in` when the left-hand side is a method call with a dot receiver ## Summary When a standalone `expr in pattern` one-line pattern match appears inside a `case/in` branch, and `expr` is a method call with a dot receiver (for example, `obj.method`), Prism incorrectly parses `in pattern` as a new branch of the outer `case/in` instead of treating it as a `MatchPredicateNode`. The parse.y parser handles this case correctly. ## Reproduction ``` $ ruby -v ruby 4.0.1 (2026-01-13 revision e04267a14b) +PRISM [arm64-darwin23] ``` It also reproduces on Ruby 3.4.8 (2025-12-17 revision 995b59f666) +PRISM [arm64-darwin25]. ### Minimal script ```ruby x = "x" case x in Integer nil in String p :before x.itself in String p :after end ``` ### Command output ``` $ ruby -e ' x = "x" case x in Integer nil in String p :before x.itself in String p :after end ' :before $ ruby --parser=parse.y -e ' x = "x" case x in Integer nil in String p :before x.itself in String p :after end ' :before :after ``` ### Expected behavior (parse.y) Both `:before` and `:after` are printed. `x.itself in String` is parsed as a standalone pattern match (predicate) inside the `in String` branch. ### Actual behavior (Prism) Only `:before` is printed; `p :after` is never executed. ## Analysis Prism splits `x.itself in String` at the `in` keyword, treating `x.itself` as the last statement of the `in String` branch and `in String` as a third branch of the outer `case/in`. The following script shows how each parser interprets the `case/in` branches: ```ruby code = <<~RUBY x = "x" case x in Integer nil in String x.itself in String p :after end RUBY # Prism require "prism" ast = Prism.parse(code).value.statements.body[1] puts "Prism: conditions: #{ast.conditions.length}" ast.conditions.each_with_index do |c, i| pat = c.pattern name = pat.respond_to?(:name) ? pat.name : pat.class stmts = c.statements&.body&.map { |s| s.class.name.split("::").last } || [] puts " in[#{i}]: pattern=#{name}, body=#{stmts}" end # parse.y (Ripper) require "ripper" sexp = Ripper.sexp(code) case_node = sexp[1][1] def count_in_branches(node) return [] unless node.is_a?(Array) && node[0] == :in pattern_node = node[1] body = node[2] || [] name = pattern_node.is_a?(Array) && pattern_node[1].is_a?(Array) ? pattern_node[1][1] : pattern_node[1] stmts = body.map { |s| s[0].to_s } [{ pattern: name, body: stmts }] + count_in_branches(node[3]) end branches = count_in_branches(case_node[2]) puts "\nparse.y (Ripper): conditions: #{branches.length}" branches.each_with_index do |b, i| puts " in[#{i}]: pattern=#{b[:pattern]}, body=#{b[:body]}" end ``` Output (run with `ruby --parser=parse.y` so Ripper uses parse.y): ``` Prism: conditions: 3 in[0]: pattern=Integer, body=["NilNode"] in[1]: pattern=String, body=["CallNode"] in[2]: pattern=String, body=["CallNode"] parse.y (Ripper): conditions: 2 in[0]: pattern=Integer, body=["var_ref"] in[1]: pattern=String, body=["case", "command"] ``` Prism reports 3 branches, while parse.y reports 2. In the parse.y result, `in[1]` correctly contains both the inner expression (`x.itself in String` parsed as a standalone pattern match) and the `command` (`p :after`). In the Prism result, `x.itself` becomes the sole body of `in[1]`, and `in String` is misinterpreted as a new `in[2]` branch of the outer `case`. ## Consideration From experimentation, the issue appears to be triggered only when all of the following are true: 1. The outer `case/in` has at least two `in` branches before the affected branch. 2. The standalone `in` expression uses a dot-receiver method call as its left-hand side, such as `obj.method in Pattern`. Conditions where this behavior is not observed: - If the expression is a receiver-less call, such as `f(x) in Pattern`, the parser keeps it as a standalone pattern match. - If the receiver expression is parenthesized, such as `(obj.method) in Pattern`, the parser keeps it as a standalone pattern match. - If you assign first, such as `y = obj.method; y in Pattern`, the parser keeps it as a standalone pattern match. -- https://bugs.ruby-lang.org/

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[ruby-core:123731] [Ruby Bug#21674] Possible regression in return case in statement
by jandudulski (Jan Dudulski) 07 Jun '26

07 Jun '26

Issue #21674 has been reported by jandudulski (Jan Dudulski). ---------------------------------------- Bug #21674: Possible regression in return case in statement https://bugs.ruby-lang.org/issues/21674 * Author: jandudulski (Jan Dudulski) * Status: Open * ruby -v: 3.4.6 * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- Suddenly my code started failing in Ruby 3.4.6 and 3.4.7. Shortest code example: ``` ruby args = [:increased] context = Data.define(:event).new(:decreased) case args in [event] context.event in ^event end ``` In Ruby prior to 3.4.6 in returns `false` (as expected) but in 3.4.6 and 3.4.7 it returns `:decreased`. `context.event in ^event` still returns `false`. -- https://bugs.ruby-lang.org/

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