According to Lebanese folklore, my informant said, bad dreams should be interpreted as signs of good fortune.  (This would be reassuring to me, as I have had my share of them!).  The superstition says that once a scenario is played out in a dream, it will not be repeated in reality.  Thus, it is also reflexive: a pleasant dream should not be received as a sign of good fortune to come.
My informant was not aware of the origin of this sign-superstition.  He learned it from his family, none of whom he says actually believe it.  I would most likely postulate monogenesis as a model for the origin of this superstition, as it is unique and counterintuitive.
This is indeed a unique perspective on dreams, one I have never encountered before hearing the superstition from my informant.  As with many superstitions, odds are that there is some element of belief somewhere back in my informant’s family.  Otherwise, it would be unlikely that the superstition would have been passed down and remembered by succeeding generations.