From: daniel@...42.com
Date: 2019-12-13T02:43:40+00:00
Subject: [ruby-core:96216] [Ruby master Feature#16377] Regexp literals	should be frozen

Issue #16377 has been updated by Dan0042 (Daniel DeLorme).


> Please don't put ideological thoughts on me, that's not a good basis for debate.

Oh no, I'm not. Sorry for the misunderstanding. I was mostly replying to comments in #8948, but I ended up posting here because this is the ticket that is linked in #16393 DevelopersMeeting20191220Japan.

Yes, of course when one way is blocked there's always an alternate way of doing things. But the point is that if someone is *currently* relying on Regexp literals not being frozen, this change will break their code. Given that the benefit is close to zero, I don't think it's responsible to force anyone to bear that cost. I'm very conservative about backward compatibility.

----------------------------------------
Feature #16377: Regexp literals should be frozen
https://bugs.ruby-lang.org/issues/16377#change-83108

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
The following script:

```ruby
def mutate
  re = /foo/
  state = re.instance_variable_get(:@state)
  re.instance_variable_set(:@state, state.to_i + 1)
  state
end

3.times do
  p mutate
end
```

Output this:

```
nil
1
2
```

IMHO, you shouldn't be able to mutate an unduplicated literal.

GitHub pull request: https://github.com/ruby/ruby/pull/2705



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