[ruby-core:126067] [Ruby Misc#22192] Clarify the scope of default visibility changed inside a block

13 Jul 2026

      Issue #22192 has been updated by shugo (Shugo Maeda).

I checked the behavior of past versions with all-ruby:

```
$ docker run -it --rm rubylang/all-ruby ./all-ruby -e 'class C; [1].each { private; def foo; end }; def afterwards; end; end; p [C.private_instance_methods(false).sort, C.public_instance_methods(false).sort]'
...
ruby-1.1b9_06         -e:1: undefined method `public_instance_methods' for C (NameError)
                  exit 1
ruby-1.1b9_07         [["afterwards", "foo"], []]
...
ruby-1.6.8            [["afterwards", "foo"], []]
ruby-1.8.0            [["foo"], ["afterwards"]]
...
ruby-1.8.7-p374       [["foo"], ["afterwards"]]
ruby-1.9.0-0          [[:afterwards, :foo], []]
...
ruby-4.0.5            [[:afterwards, :foo], []]
```

| Versions        | Behavior                                       |
|-----------------|------------------------------------------------|
| 1.1b9 - 1.6.8   | same as the current behavior                   |
| 1.8.0 - 1.8.7   | same as JRuby (reverted at the end of a block) |
| 1.9.0 - 3.3     | same as the current behavior                   |

----------------------------------------
Misc #22192: Clarify the scope of default visibility changed inside a block
https://bugs.ruby-lang.org/issues/22192#change-118067

* Author: shugo (Shugo Maeda)
* Status: Assigned
* Assignee: matz (Yukihiro Matsumoto)
----------------------------------------
`private` etc. called with no arguments inside a block changes the default visibility of the enclosing lexical scope, and the change survives the block:

```ruby
class C
  %i[foo bar].each do |name|
    private
    define_method(name) { }
  end
  def afterwards; end   # also private
end
C.private_method_defined?(:foo)        #=> true
C.private_method_defined?(:afterwards) #=> true
```

When multiple Procs share the same lexical scope, `private` in a Proc affects all Procs:

```ruby
class Host
  SET_PRIVATE = proc { private }
  DEFINE      = proc { def probe; end }
end
Host::SET_PRIVATE.call
Host::DEFINE.call
Host.private_method_defined?(:probe)   #=> true
```

Neither CRuby nor ruby/spec has corresponding tests. I assume this is intentional, but am I correct?
It seems that the visibility change is effective only within the block on JRuby, so I'd like to clarify this.

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