haskell - haskell MonadThrow のインスタンスがありません

Question

https://github.com/gertcuykens/haskell-designの完全なコード

application :: MVar ServerState -> WS.Request -> WS.WebSockets WS.Hybi10 ()
application state rq = do
    --snip--
    let a = ("code","test")
    e <- fbEmail $ (\(x,y) -> (C.pack x, C.pack y)) a

私にエラーを与える

src/Server.hs:60:10:
    No instances for (resourcet-0.3.2.2:Control.Monad.Trans.Resource.MonadThrow
                        (WS.WebSockets WS.Hybi10),
                      resourcet-0.3.2.2:Control.Monad.Trans.Resource.MonadUnsafeIO
                        (WS.WebSockets WS.Hybi10),
                      monad-control-0.3.1.3:Control.Monad.Trans.Control.MonadBaseControl
                        IO (WS.WebSockets WS.Hybi10))
      arising from a use of `fbEmail'
    Possible fix:
      add instance declarations for
      (resourcet-0.3.2.2:Control.Monad.Trans.Resource.MonadThrow
         (WS.WebSockets WS.Hybi10),
       resourcet-0.3.2.2:Control.Monad.Trans.Resource.MonadUnsafeIO
         (WS.WebSockets WS.Hybi10),
       monad-control-0.3.1.3:Control.Monad.Trans.Control.MonadBaseControl
         IO (WS.WebSockets WS.Hybi10))
    In the expression: fbEmail
    In a stmt of a 'do' block:
      e <- fbEmail $ (\ (x, y) -> (C.pack x, C.pack y)) a
    In the expression:
      do { WS.acceptRequest rq;
           WS.getVersion >>= liftIO . putStrLn . ("Client version: " ++);
           sink <- WS.getSink;
           msg <- WS.receiveData;
           .... }

私が最終的に達成したいのは交換です

let prefix = "Facebook code"
let client = (T.drop (T.length prefix) msg, sink)

のようなもので

let prefix = "Facebook code"
let code = T.drop (T.length prefix) msg
client = (fbEmail code, sink)

Answer 1

e <- liftIO $ fbEmail $ (\(x,y) -> (C.pack x, C.pack y)) a