[ruby-core:126066] [Ruby Misc#22192] Clarify the scope of default visibility changed inside a block

13 Jul 2026

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

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

* Author: shugo (Shugo Maeda)
* Status: Assigned
* Assignee: matz (Yukihiro Matsumoto)
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`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.

-- 
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