From: "tenderlovemaking (Aaron Patterson) via ruby-core" <ruby-core@...>
Date: 2024-03-01T20:50:47+00:00
Subject: [ruby-core:117035] [Ruby master Feature#20317] Removing the `allocate` method should cause `new` to fail

Issue #20317 has been updated by tenderlovemaking (Aaron Patterson).


jeremyevans0 (Jeremy Evans) wrote in #note-1:
> The current behavior may be what you want if you want to ensure that new instances of the class have `#initialize` called on them.  I suppose you could switch to making `allocate` private, but that still would allow for `send(:allocate)`.
> 
> If we disallow `.new` if `.allocate` is undefined, should we also disallow `#dup` and `#clone`, both of which also need to allocate an object?

I think that makes sense. For example if you wanted to ensure a particular instance is a singleton:

```ruby
class Foo; end

singleton = Foo.new

Foo.singleton_class.undef_method(:allocate)

# now there can only be one instance of `Foo` as new / allocate / dup / clone will raise
```

----------------------------------------
Feature #20317: Removing the `allocate` method should cause `new` to fail
https://bugs.ruby-lang.org/issues/20317#change-107104

* Author: tenderlovemaking (Aaron Patterson)
* Status: Open
----------------------------------------
When you remove the `allocate` method from a class the you can't allocate the class via the `allocate` method. However, you _can_ allocate the class via the `new` method:

```ruby
class Foo; end

Foo.singleton_class.undef_method(:allocate)

begin
  Foo.allocate # doesn't work, of course
rescue NoMethodError
end

begin
  Class.instance_method(:allocate).bind_call(Foo) # also doesn't work
rescue TypeError
end

Foo.new # works?
```

I think that when we remove the `allocate` method, the `new` method should also fail as there is no `allocate` method for `new` to call.



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