I'm currently using the fb package to write a Yesod app that takes data from Facebook. In my Handler, I've managed to get the first step of the authentication to work, but I need to redirect to the url that getUserAccessTokenStep1 returns, which I've defined as fbRedirUrl. I'm having trouble with all the monad wrapping and type checking to make sure I can redirect to this url.

getAccessTokenR :: Handler RepHtml
getAccessTokenR = do
  withManager $ \manager -> do
    FB.runFacebookT creds manager $ do
      fbRedirUrl <- FB.getUserAccessTokenStep1 redirUrl []
      liftIO $ print fbRedirUrl