[ruby-core:72004] [Ruby trunk - Bug #11779] Module#using does not make sense as a method

Issue #11779 has been updated by bug hit.


Shugo Maeda wrote:
> bug hit wrote:
> > > Nobu didn't explain that Module#using should work in methods.
> > > Module#using is designed not for such dynamic use.
> > 
> > Note that when #using is called in a module_eval block, its effect is confined to the body of the block.  So why should it matter if module_eval is called from a method or top level or from another module/class?  ~~Regardless of where it's called, #using inside it works the same.~~  The call site does not influence what #using does nor is influenced by it.
> 
> Because refinement activation should be as static as possible.
> It might be better to prohibit Module#using in module_eval.

Perhaps, since you can apply the refinement outside the module_eval block which will also affect the block:

```ruby
module Refinement
  refine String do
    def refined?
      true
    end
  end
end

module Foo

end

module Bar
  using Refinement

  Foo.module_eval do
    p((''.refined? rescue false))
  end

end
```

so a #using in module_eval is only useful if you want the refinement confined to the block.  There might be uses for that, not sure.

But if this functionality remains, it should work wherever module_eval is invoked.

----------------------------------------
Bug #11779: Module#using does not make sense as a method
https://bugs.ruby-lang.org/issues/11779#change-55413

* Author: bug hit
* Status: Feedback
* Priority: Normal
* Assignee: 
* ruby -v: 2.2.3
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
1. it can't be called from another method
2. the receiver must be self
3. since refinements are lexically scoped the self receiver must match the currently open class

#3 is particularly curious

```ruby
module Refinement
  refine String do
    def refined?
      true
    end
  end
end

module Foo
  def self.refined?
    ''.refined? rescue false
  end
end


module Bar
  def self.refined?
    ''.refined? rescue false
  end
  Foo.module_eval do
    using Refinement

  end
end

p Foo.refined? #false
```

The module_eval `#using` call does not raise (it's not from a method and the receiver is self), but evidently because currently open class does not match self, it does not do anything. So it should at least raise.

So `#using`, though a method, does not function as a method, which is misleading.



-- 
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