From: "byroot (Jean Boussier)" <noreply@...>
Date: 2022-03-10T12:25:18+00:00
Subject: [ruby-core:107821] [Ruby master Feature#18618] no clobber def

Issue #18618 has been updated by byroot (Jean Boussier).


Note that you could perfectly implement this in pure Ruby today.

```ruby
module ClobberChecker
  def method_added(name)
    super
    no_clobber(name, caller(1, 1).first) if @no_clobber
  end
end

class Class
  def no_clobber(method_name = nil, callsite = caller(1, 1).first)
    if method_name
      if (super_method = instance_method(method_name).super_method)
        warn "Clobbering #{super_method.owner}##{super_method.name} (#{callsite})"
      end
    else
      extend(ClobberChecker)
      @no_clobber = true
    end
  end
end

class A
  def foo
  end

  def bar
  end
end

class B < A
  no_clobber def foo
  end

  no_clobber

  def bar
  end
end
```

There might be some subtleties though, if for instance you include a module after defining a method.

----------------------------------------
Feature #18618: no clobber def
https://bugs.ruby-lang.org/issues/18618#change-96750

* Author: ed_ (Ed Mangimelli)
* Status: Open
* Priority: Normal
----------------------------------------
Sometimes I want to be certain I'm not clobbering/masking a method:

```
class Dog
  def bark
    'bark!'
  end
end

class Poodle < Dog
  raise if method_defined? :bark
  def bark
    'bow-wow'
  end
end
```

I propose creating a shorthand. Maybe something like:

```
class Dog
  def bark
    'bark!'
  end
end

class Poodle < Dog
  ncdef bark        # "no clobber" def
    'bow-wow'
  end
end

=> #<MethodAlreadyDefined: Method `bark' already defined.>
```

This would be useful in scenarios where subclassing a class (or including a mixin) ***you don't own*** is common practice --for instance, subclassing `ApplicationRecord` for your model in Rails.

I agree that `ncdef` is pretty ugly. Maybe `def!` 







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