Issue #21558 has been updated by niku (niku _).
Regexp.union creates a new instance, except for a single Regexp argument case.
Ah, that makes perfect sense now. Thank you for the detailed explanation. ```irb irb(main):001> a = /a/ => /a/ irb(main):002> a.__id__ => 7232 irb(main):003> b = Regexp.union(a) => /a/ irb(main):004> b.__id__ => 7232 irb(main):005> c = Regexp.union(a, a) => /(?-mix:a)|(?-mix:a)/ irb(main):006> c.__id__ => 17912 ```
Personally, I think freezing all Regexp instances also may be nice, but that's a different story than Regexp.union.
I agree with your opinion. I'll create a new issue. ---------------------------------------- Bug #21558: Regexp.union with multiple regexps returns a non-shareable object (should be shareable if possible) https://bugs.ruby-lang.org/issues/21558#change-114477 * Author: niku (niku _) * Status: Feedback * ruby -v: ruby 3.5.0dev (2025-08-30T18:24:25Z master 5c7dfe85a1) +PRISM [arm64-darwin24] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- Regexp.union returns a non-shareable object when given multiple Regex arguments. Is this expected behavior? It would be preferable if the resulting Regexp were shareable, since single-argument `Regexp.union` does produce a shareable object. ```irb irb(main):001> a = /a/ => /a/ irb(main):002> b = Regexp.union(a) => /a/ irb(main):003> c = Regexp.union(a, a) => /(?-mix:a)|(?-mix:a)/ irb(main):004> Ractor.shareable?(a) => true irb(main):005> Ractor.shareable?(b) => true irb(main):006> Ractor.shareable?(c) => false ``` -- https://bugs.ruby-lang.org/