[ruby-core:111105] [Ruby master Bug#19047] DelegateClass displays "method redefined" warning when overriding methods

1 Dec 2022

      Issue #19047 has been updated by matz (Yukihiro Matsumoto).

Sorry, but by this change, we missed the warnings from DelegateClass misuse. We will revert this change.

Matz.

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Bug #19047: DelegateClass displays "method redefined" warning when overriding methods
https://bugs.ruby-lang.org/issues/19047#change-100373

* Author: jonathanhefner (Jonathan Hefner)
* Status: Closed
* Priority: Normal
* ruby -v: ruby 3.1.2p20
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
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Perhaps this is not a bug, but it does seem unexpected.

When creating a `DelegateClass` class without an intervening ancestor, overriding a method displays "method redefined" warning:

```ruby
Base = Class.new do
  def foo
    "foo"
  end
end

Delegate1 = DelegateClass(Base) do
  def foo
    super + "1"
  end
end
# warning: method redefined; discarding old foo

Delegate2 = Class.new(DelegateClass(Base)) do
  def foo
    super + "2"
  end
end
# no warning

Delegate1.new(Base.new).foo
# => "foo1"

Delegate2.new(Base.new).foo
# => "foo2"
```

One possible solution would be to evaluate the `DelegateClass` block in a separate module, and prepend that module to the returned class.

Another possible solution would be to silence warnings around [when the block is evaluated](https://github.com/ruby/delegate/blob/df2283b8d8874446086b80355c586397f1b48d...).

I would be happy to submit a PR to https://github.com/ruby/delegate if this is something we want to address.

-- 
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