rw.hs:14:47: error:
    • Couldn't match expected type ‘a’ with actual type ‘Int’
      ‘a’ is a rigid type variable bound by
        the type signature for:
          writeInt :: forall a. T a -> IORef a -> IO ()
        at rw.hs:12:1-34
    • In the second argument of ‘writeIORef’, namely ‘(1 :: Int)’
      In the expression: writeIORef ref (1 :: Int)
      In a case alternative: ~(Li x) -> writeIORef ref (1 :: Int)
    • Relevant bindings include
        ref :: IORef a (bound at rw.hs:13:12)
        v :: T a (bound at rw.hs:13:10)
        writeInt :: T a -> IORef a -> IO () (bound at rw.hs:13:1)

rw.hs:19:43: error:
    • Couldn't match type ‘a’ with ‘Bool’
      ‘a’ is a rigid type variable bound by
        the type signature for:
          readBool :: forall a. T a -> IORef a -> IO ()
        at rw.hs:16:1-34
      Expected type: a -> IO ()
        Actual type: Bool -> IO ()
    • In the second argument of ‘(>>=)’, namely ‘(print . not)’
      In the expression: readIORef ref >>= (print . not)
      In a case alternative: ~(Lb x) -> readIORef ref >>= (print . not)
    • Relevant bindings include
        ref :: IORef a (bound at rw.hs:17:12)
        v :: T a (bound at rw.hs:17:10)
        readBool :: T a -> IORef a -> IO () (bound at rw.hs:17:1)