actionlib feedback: Difference between FooFeedback and FooActionFeedback

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I was implementing an actionlib client with callbacks (API here) and ran into an interesting/annoying problem.

A callback incorrectly-defined with a FooActionFeedbackConstPtr argument gave many errors (unfortunately boost::bind doesn't have the best error messages). For example (using the Fibonacci tutorial example):

void feedbackBad(const learning_actionlib::FibonacciActionFeedbackConstPtr &feedback)

void feedbackGood(const learning_actionlib::FibonacciFeedbackConstPtr& feedback)

and using boost::bind to set the callback function:

actionlib::SimpleActionClient<learning_actionlib::FibonacciAction>
    ::SimpleFeedbackCallback feedbackFun = boost::bind(&feedbackXXX, _1);

What's the difference between a FooActionFeedback and a FooFeedback?