Xcode 4 "Fix it" - when does it appear?

I would like to know when the "Fix-it" should appear? Is it possible to make appear on all errors (and suggest a change?) Assignment when it should be comparison Clearly an error in my code, which "Fix-it" analyzed and detected. But can it help me even more?

Solution

Unfortunately Fix-it doesn't support all errors/warnings. I've looked for a list of supported ones, with no such luck. It's likely that more will be added in future releases. It's still a very new feature, so Apple will see how things go and improve, adapt, and update.