need help w/ monad comprehension syntax

hello, i am having trouble getting my program below to work. i think i implemented the monad methods correctly, but the function 'g' does not type as i would expect. Hugs thinks that it is just a list (if i remove the explicit typing). i want it to be functionally identical to the function 'h'. what am i missing? thanks konst

newtype State s a = ST (s -> (a,s))

unST (ST m) = m

instance Functor (State s) where fmap f m = ST (\s -> let (a,s') = unST m s in (f a, s'))

instance Monad (State s) where return a = ST (\s -> (a,s)) m >>= f = ST (\s -> let (a,s') = unST m s in unST (f a) s')

--g :: State String Char g = [ x | x <- return 'a' ]

h :: State String Char h = return 'a'