Issue #10276 has been reported by Kazuhiro NISHIYAMA.

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Bug #10276: nil/true/false に singleton メソッドを定義できてしまう
https://bugs.ruby-lang.org/issues/10276

* Author: Kazuhiro NISHIYAMA
* Status: Open
* Priority: Normal
* Assignee: 
* Category: core
* Target version: current: 2.2.0
* ruby -v: ruby 2.2.0dev (2014-09-21 trunk 47672) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
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nil/true/false が frozen object なのに singleton メソッドを定義できてしまいます。

~~~
% cat /tmp/f.rb
def d(o)
  p o.frozen?
  def o.m; end
rescue
  p [o, $!]
end
d(:sym)
d(1)
d(nil)
d(true)
d(false)
d(Object.new.freeze)
% ruby -v /tmp/f.rb
ruby 2.2.0dev (2014-09-21 trunk 47672) [x86_64-linux]
true
[:sym, #<TypeError: can't define singleton>]
true
[1, #<TypeError: can't define singleton>]
true
true
true
true
[#<Object:0x00000002706730>, #<RuntimeError: can't modify frozen object>]
~~~



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