From: "itarato (Peter Arato) via ruby-core" <ruby-core@...>
Date: 2023-06-30T14:40:11+00:00
Subject: [ruby-core:114058] [Ruby master Bug#19749] Confirm correct behaviour when attaching private method with `#define_method`

Issue #19749 has been updated by itarato (Peter Arato).


For visibility leaving the examples here that we suspect a CRuby bug:

```ruby
class Foo5
	private

	def bar; end

	public

	define_method(:bar, Foo5.instance_method(:bar))
end

Foo5.new.bar # NoMethodError in CRuby, but should be public
```

and

```ruby
class Foo6
	def bar
		"public"
	end

	private

	define_method(:bar, Foo6.instance_method(:bar))
end

Foo6.new.bar # No error in CRuby but should be NoMethodError
```

----------------------------------------
Bug #19749: Confirm correct behaviour when attaching private method with `#define_method`
https://bugs.ruby-lang.org/issues/19749#change-103727

* Author: itarato (Peter Arato)
* Status: Open
* Priority: Normal
* ruby -v: 3.3.0
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
This issue is a special case of https://bugs.ruby-lang.org/issues/19745:

Should dynamically added private methods via `.singleton_class.send(:define_method,...` at the top-level be accessible publicly?

See the following example:

```ruby
def bar; end

foo = Object.new
foo.singleton_class.define_method(:bar, method(:bar))

foo.bar # No error.
```

The script above runs fine on latest Ruby 3.3. Is this correct to ignore the fact that the visibility in the caller context is the default top-level private visibility?

This came up during a TruffleRuby investigation (https://github.com/oracle/truffleruby/issues/3134) where the result for the same script is: `private method 'bar' called for #<Object:0xc8> (NoMethodError)`




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