class RSpec::Mocks::MethodDouble

def warn_if_nil_class
  if proxy_for_nil_class? & RSpec::Mocks::Proxy.warn_about_expectations_on_nil
    Kernel.warn("An expectation of :#{@method_name} was set on nil. Called from #{caller[4]}. Use allow_message_expectations_on_nil to disable warnings.")
  end
end