Promise.with_change_func

Description:

[ CCode ( has_construct_function = false ) ]
public Promise.with_change_func (owned PromiseChangeFunc func)

func will be called exactly once when transitioning out of PENDING into any of the other PromiseResult states.

func	a PromiseChangeFunc to call
notify	notification function that `user_data` is no longer needed
user_data	argument to call `func` with