I was under the impression that ResourceT prevents accessing released resources with the type system. Maybe I am not using it correctly...

resource.hs

import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.Resource
import System.IO

main = runResourceT $ do
    (releaseO, output) <- allocate (openFile "output.txt" WriteMode) hClose
    lift $ hPutStrLn output "hallo!"
    release releaseO
    (releaseI, input) <- allocate (openFile "output.txt" ReadMode) hClose
    release releaseI
    -- Too bad the next call doesn't cause a type error...
    lift $ putStr "Contents: " >> hGetContents input >>= hPutStrLn output