Ruby

Refinements were added as a feature to scope monkey-patches on ruby core elements. This works for elements such as String, Array (all classes), but not for modules (Enumerable, Timeout...).

This might be related to refinements not working for singleton classes (for example, I can't define a class method inside a refine block).

This code is evaluated, but the method is undefined:

module Extension
refine Array do
def self.foo ; puts "bar" ; end
end
end

This code breaks:

module Extension
refine Kernel do
def foo ; puts "bar" ; end
end
end