T8518.hs:14:18: error:
    • Couldn't match expected type ‘Maybe (F c)’ with actual type ‘F c’
    • In the expression: rpt (4 :: Int) c z b
      In an equation for ‘callCont’:
          callCont c z b
            = rpt (4 :: Int) c z b
            where
                rpt 0 c' z' b' = fromJust (fst <$> (continue c' z' b'))
                rpt i c' z' b' = let ... in rpt (i - 1) c''
    • Relevant bindings include
        b :: B c (bound at T8518.hs:14:14)
        z :: Z c (bound at T8518.hs:14:12)
        c :: c (bound at T8518.hs:14:10)
        callCont :: c -> Z c -> B c -> Maybe (F c) (bound at T8518.hs:14:1)

T8518.hs:17:78: error:
    • Couldn't match expected type ‘F a’
                  with actual type ‘Z a -> B a -> F a’
    • In the expression: rpt (i - 1) c''
      In the expression:
        let c'' = fromJust (snd <$> (continue c' z' b')) in rpt (i - 1) c''
      In an equation for ‘rpt’:
          rpt i c' z' b'
            = let c'' = fromJust (snd <$> (continue c' z' b'))
              in rpt (i - 1) c''
    • Relevant bindings include
        c'' :: a (bound at T8518.hs:17:30)
        b' :: B a (bound at T8518.hs:17:21)
        z' :: Z a (bound at T8518.hs:17:18)
        c' :: a (bound at T8518.hs:17:15)
        rpt :: a1 -> a -> Z a -> B a -> F a (bound at T8518.hs:16:9)