From: ko1@...
Date: 2020-12-18T20:56:28+00:00
Subject: [ruby-core:101521] [Ruby master Feature#17401] The class `Ractor::MovedObject` should not be frozen

Issue #17401 has been updated by ko1 (Koichi Sasada).


Matz prefers to provide a free to shoot the foot.


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Feature #17401: The class `Ractor::MovedObject` should not be frozen
https://bugs.ruby-lang.org/issues/17401#change-89305

* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
----------------------------------------
If `Ractor::MovedObject` can be not frozen that would be more helpful than currently. For example, to implement a helpful `inspect` in pure Ruby 3.0 like in #17393

It is currently possible to go around the fact that it is frozen with refinements:
```ruby
using Module.new {
  refine Ractor::MovedObject do
    def inspect
      "I was moved! Don't use me!"
    end
  end
}
o = Object.new
Ractor.new{ receive }.send(o, move:true)
puts o.inspect # => "I was moved! Don't use me!"
```

Another (ugly) way to bypass the fact that it is frozen without refinements is to modify its ancestor:

```ruby
module Ext
  def inspect
    return super unless Ractor::MovedObject === self

    "I was moved! Don't use me!"
  end
end

BasicObject.prepend Ext

o = Object.new
Ractor.new{ receive }.send(o, move:true)
p o # => "I was moved! Don't use me!"
```

My point remain that this "security" can be bypassed unless it is stricly necessary it, it would be nice to unfreeze the class. It could be documented that this is experimental / not recommended to modify the class in production, for example.



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