From: ko1@...
Date: 2015-05-28T09:57:47+00:00
Subject: [ruby-core:69392] [Ruby trunk - Bug #11182] Refinement with alias causes strange behavior

Issue #11182 has been updated by Koichi Sasada.


Let's discuss with use cases. I don't have good example, but please assume we want to make new Hash class to support something like HashWithIndifferentAccess.

<scenario>
Okay, we need an extra Hash class doing something special.

```ruby
class MyHash < Hash
  def initialize *args
    args.each{|(k, v)|self[k] = v}
  end

  alias iterate each
end

h = MyHash.new([:b, 1], [:a, 2])

h.each{|k, v| p [k, v]} # [:b, 1] [:a, 2]
```

Good.

Next time, I invented a nice refinement to iterate Hash contents by ordered.

```ruby
module OrderedHashEach
  refine Hash do
    def each
      sort.each{|k, v|
        yield k, v
      }
    end
  end
end

using OrderedHashEach
{b: 1, a: 2}.each{|k, v| p [k, v]} # [:a, 2], [:b, 1]
```

Excellent.

And of course, we can combine MyHash and OrderedHashEach.

```ruby
module OrderedHashEach
  refine Hash do
    def each
      sort.each{|k, v|
        yield k, v
      }
    end
  end
end

class MyHash < Hash
  def initialize *args
    args.each{|(k, v)|self[k] = v}
  end
end

h = MyHash.new([:b, 1], [:a, 2])

using OrderedHashEach
h.each{|k, v| p [k, v]} # [:a, 2] [:b, 1]
```

Great.

Wait. `each` is not good terminology for our project. Use `iterate` intead.

```ruby
module OrderedHashEach
  refine Hash do
    def each
      sort.each{|k, v|
        yield k, v
      }
    end
  end
end

class MyHash < Hash
  def initialize *args
    args.each{|(k, v)|self[k] = v}
  end

  alias iterate each
end

h = MyHash.new([:b, 1], [:a, 2])

using OrderedHashEach
h.iterate{|k, v| p [k, v]} # [:b, 1] [:a, 2]
```

It doesn't affect :(  It is unexpected result for me.
</scenario>

Note that I don't want to change this specification. I want to know what is ideal specification.

This time, I made a scenario that we may want to use M::C#foo.


----------------------------------------
Bug #11182: Refinement with alias causes strange behavior
https://bugs.ruby-lang.org/issues/11182#change-52668

* Author: Koichi Sasada
* Status: Feedback
* Priority: Normal
* Assignee: Koichi Sasada
* ruby -v: 2.3dev
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
The following script causes strange behavior.

```ruby
class C
  def foo
    p "C"
  end
end

module M
  refine C do
    def foo
      p "Refiend C"
    end
  end
end

class D < C
  alias bar foo
end

using M
D.new.bar
#=> t.rb:21:in `<main>': undefined method `bar' for #<D:0x29fbf58> (NoMethodError)
```

It seems strange.

Maybe (1) C#foo or (2) M#C#foo should be called. But I'm not sure which is suitable.

Previous versions:

```
ruby 2.0.0p606 (2014-11-28 revision 48636) [i386-mswin32_110]
t.rb:9: warning: Refinements are experimental, and the behavior may change in future versions of Ruby!
"C"

ruby 2.1.5p312 (2015-03-10 revision 49912) [i386-mswin32_110]
"C"
```


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1.PNG (38.7 KB)
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alias_affected_by_original_refinement.diff (1.34 KB)
6.PNG (36.6 KB)
7.PNG (40.7 KB)


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