class RSpec::Mocks::AnyInstance::MessageChains

def raise_if_second_instance_to_receive_message(instance)
  @instance_with_expectation ||= instance if ExpectationChain === instance
  if ExpectationChain === instance && !@instance_with_expectation.equal?(instance)
    raise RSpec::Mocks::MockExpectationError, "Exactly one instance should have received the following message(s) but didn't: #{unfulfilled_expectations.sort.join(', ')}"
  end
end