[ruby-core:102911] [Ruby master Bug#17725] Prepend breaks ability to override optimized methods

Issue #17725 has been updated by xtkoba (Tee KOBAYASHI).


FWIW,
```ruby
# bug17725-test.rb
eval <<EOS
# encoding: ascii-8bit
MY_STRING = ''
EOS

MY_STRING + ''

String.prepend(Module.new)
class String
  def + other
    'blah blah'
  end
end

p 'a' + 'b'
```
gives
```
$ ruby --disable-gems bug17725-test.rb
"ab"
```


----------------------------------------
Bug #17725: Prepend breaks ability to override optimized methods
https://bugs.ruby-lang.org/issues/17725#change-90975

* Author: joshuadreed (Josh Reed)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin19]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
Prepending any module to `String` and `Hash` (and possibly other or all classes?) blocks the ability to `alias` 

As an example:
``` ruby
module Dummy; end
# String.prepend(Dummy)
class String
  alias_method(:old_plus, :+)
  def + other
    puts 'blah blah'
    old_plus(other)
  end
end

'a' + 'b'

> blah blah
```

``` ruby
module Dummy; end
String.prepend(Dummy)
class String
  alias_method(:old_plus, :+)
  def + other
    puts 'blah blah'
    old_plus(other)
  end
end

'a' + 'b'

>
```

Prepending after an `alias` does not affect the previous `alias`



-- 
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