[ruby-core:72074] [Ruby trunk - Bug #11779] Module#using does not make sense as a method

Issue #11779 has been updated by Shugo Maeda.

Assignee set to Yukihiro Matsumoto

bug hit wrote:
> > Perhaps, perhaps not.  I depends on what the phrase "whatever the class body can do" mean. 
> > For exmaple, such methods should be able to define constants in a class, but need not to
> > be able to define constants in the same way as in a class body.
> 
> Of course I don't mean in the same exact way, meta-programming is different than native syntax.  However the question of "how" does not apply here, because you are arguing that it should be forbidden (not different), and I'm saying that if a class body can call a module_eval with using, then a class macro method should be able to, as well.

As I stated before, it might be better to introduce Kernel#using, which ignores module_eval blocks as constant lookup do.

```ruby
module Foo
  refine String do
    def foo
      puts "foo"
    end
  end
end

module Bar
end

module Baz
  Bar.module_eval do
    using Foo
    "".foo #=> foo
  end

  "".foo #=> foo
end

"".foo #=> error
```

I'd like to hear Matz's opinion.


----------------------------------------
Bug #11779: Module#using does not make sense as a method
https://bugs.ruby-lang.org/issues/11779#change-55486

* Author: bug hit
* Status: Feedback
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* 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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