From: "jhawthorn (John Hawthorn) via ruby-core" <ruby-core@...>
Date: 2026-06-12T18:07:01+00:00
Subject: [ruby-core:125729] [Ruby Bug#22109] Unexpected or misleading error when subclass of a ractor calls a new method on itself

Issue #22109 has been updated by jhawthorn (John Hawthorn).


I don't think this has anything to do with the method or the subclass. The message could probably be improved, but the warning exists because instance variables on classes like `Ractor` (or other objects which are shareable without being frozen) are only accessible by the main Ractor.

```
��� ruby -ve 'Ractor.new{ @foo = 123 }.join'
ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +PRISM [arm64-darwin25]
-e:1: warning: Ractor API is experimental and may change in future versions of Ruby.
#<Thread:0x0000000120db72b8 run> terminated with exception (report_on_exception is true):
-e:1:in 'block in <main>': can not access instance variables of shareable objects from non-main Ractors (Ractor::IsolationError)
-e:1:in 'Ractor#join': thrown by remote Ractor. (Ractor::RemoteError)
        from -e:1:in '<main>'
-e:1:in 'block in <main>': can not access instance variables of shareable objects from non-main Ractors (Ractor::IsolationError)
```

----------------------------------------
Bug #22109: Unexpected or misleading error when subclass of a ractor calls a new method on itself
https://bugs.ruby-lang.org/issues/22109#change-117613

* Author: miles-georgi (Miles Georgi)
* Status: Open
* ruby -v: ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +PRISM [x86_64-linux]
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
Hey hey!

When I run the following code:

```ruby
class SubRactor < Ractor
  attr_accessor :foo
end

SubRactor.new { puts foo }.join

```

I get the following error:

```
can not access instance variables of shareable objects from non-main Ractors (Ractor::IsolationError)
```

Unclear if I shouldn't get an error of any sort in this situation, but if this is a legitimate error situation, this error seems inaccurate since Ractors can obviously access instance variables of shareable objects.

A tiny script that shows that:


```ruby
class C
  attr_accessor :foo

  def initialize = self.foo = 100
  INSTANCE = new.freeze
end

raise "not shareable!" unless Ractor.shareable?(C::INSTANCE)

Ractor.new { puts C::INSTANCE.foo }.join

```

This prints out 100 as expected instead of giving that error.

This happens on both:

ruby 4.1.0dev (2026-06-11T14:25:18Z master 8e8682fc23) +PRISM [x86_64-linux]

and

ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +PRISM [x86_64-linux]

The script is so puny seems I shouldn't upload the file but let me know if I should just always upload a script file when filing these even when they are trivially small.

Cheers!



-- 
https://bugs.ruby-lang.org/
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