Issue #10578 has been reported by Peter Zotov.

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Bug #10578: Allow undefining methods in refinements
https://bugs.ruby-lang.org/issues/10578

* Author: Peter Zotov
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-linux]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
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Since refinements are locally scoped monkey patches, and it is possible and useful to undef a method globally, I think refinements should allow to undef methods as well as def them.

For example:

~~~ ruby
module NoPlus
  refine String do
    undef +
  end
end

using NoPlus
"a" + "b"
~~~

Expected behavior: undefined method `+' for "a":String
Actual behavior: undef ignored



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