Array#extract_options! treat Hashie::Mash data as options

The hashie gem provide a class Hashie::Mash which is a subclass of Hash, allow you use dot syntax to access value of a hash, so you can do things like this:

>> mash = Hashie::Mash.new({:user => {:name => 'Rainux'}, :version => '0.1'})
=> <#Hashie::Mash user=<#Hashie::Mash name="Rainux"> version="0.1">
>> mash.user.name
=> "Rainux"

When I use Hashie::Mash to store data for my Rails 3 app, and use respond_with(@mash) in a show action, it always fails since @mash was treated as an Hash options and be extracted by Array#extract_options!, here is the code in in actionpack-3.0.0.beta/lib/action_controller/meta/mime_responds.rb.

def respond_with(*resources, &block)
  raise "In order to use respond_with, first you need to declare the formats your " <<
        "controller responds to in the class level" if self.class.mimes_for_respond_to.empty?

  if response = retrieve_response_from_mimes(&block)
    options = resources.extract_options!
    options.merge!(:default_response => response)
    (options.delete(:responder) || self.class.responder).call(self, resources, options)
  end
end

Here is the code of Array#extract_options! in activesupport-3.0.0.beta/lib/active_support/core_ext/array/extract_options.rb:

def extract_options!
  last.is_a?(::Hash) ? pop : {}
end

So the question is how do we handle this kind of problems? I think we can't just change the condition to last.instance_of?(Hash) since another subclass of Hash, HashWithIndifferentAccess also widely used as options.

This problem also exists in Rails 2.