thoughtbot/factory_girl — pull request #268 by greyblake (2012-01-16 12:07:11+00:00)
Title: Make traits work after Factory() was called.

Here is a test to reproduce the issue I faced: 7b0f86cfd81f0eb

And that's the fix: 64ad5c0b8b3f

I guess the problem is Factory() call modifies an instance of factory and sets @evaluator_class.
Next time when Factory@with_traits is called it does `self.clone.tap do |factory_with_traits| .. lala .. end`. So it clones an existening factory with `@evaluator_class` already setted.