It would be really nice to be able to do something like this:

> data Action = Code | Eat | Sleep deriving (Bounded, Enum)
> randomR :: IO Action
Eat

The implementation for (Enum a, Bounded a) => can cheat a little to get a valid range (psuedo, for randomRIO since it's easier/shorter to show):

let lower = fromEnum (minBound :: a)
let upper = fromEnum (maxBound :: a)
return $ toEnum <$> randomRIO (lower, upper)

Note the usage of the underlying instance for Int to select a constructor.

It would have been magical if we could have just a Enum a => instance, but I can't think of a way to do it.