For example typing ":t control" will lead to message:
:: MonadBaseControl b m =>
(Control.Monad.Trans.Control.RunInBase m b
-> b (Control.Monad.Trans.Control.StM m *** Exception: :hPutChar: invalid argument (invalid character)
This makes working with library less comfortable. Since not all terminals support unicode, I suggest to refrain from the use of unicode in type signatures.
Fix issue #9. Replace all Unicode in type variables.
Thanks for notifying me about this problem.
I uploaded a fix to Hackage.