From: Magnus Holm <judofyr@...>
Date: 2011-07-11T01:31:14+09:00
Subject: [ruby-core:37969] Re: [Ruby 1.9 - Bug #5015][Open] method_added" is called in addition to "method_undefined

But undef_method *does* actually add a new method: it adds a method
which prevents the superclass' method being called:

  class Foo < String; def +() end; undef_method :+ end
  Foo.new + "test" # => raises error

  class Bar < String; def +() end; remove_method :+ end
  Bar.new + "test" # => calls String#+

Seems consistant to me.