WCompatWarningsOn.hs:11:5: warning:
    • Could not deduce (MonadFail m)
        arising from the failable pattern ‘Just _’
        (this will become an error a future GHC release)
      from the context: Monad m
        bound by the type signature for:
                   monadFail :: Monad m => m a
        at WCompatWarningsOn.hs:9:1-27
      Possible fix:
        add (MonadFail m) to the context of
          the type signature for:
            monadFail :: Monad m => m a
    • In a stmt of a 'do' block: Just _ <- undefined
      In the expression:
        do { Just _ <- undefined;
             undefined }
      In an equation for ‘monadFail’:
          monadFail
            = do { Just _ <- undefined;
                   undefined }

WCompatWarningsOn.hs:14:1: warning:
    Local definition of ‘<>’ clashes with a future Prelude name.
    This will become an error in a future release.