T8142.hs:6:10: error: [GHC-83865]
    • Couldn't match type: Nu f0
                     with: c -> f c
      Expected: (c -> f c) -> c -> f c
        Actual: Nu ((,) a0) -> Nu f0
        The type variable ‘f0’ is ambiguous
    • In the expression: h
      In an equation for ‘tracer’:
          tracer
            = h
            where
                h = (\ (_, b) -> ((outI . fmap h) b)) . out
    • Relevant bindings include
        tracer :: (c -> f c) -> c -> f c (bound at T8142.hs:6:1)

T8142.hs:6:57: error: [GHC-83865]
    • Couldn't match type: Nu ((,) a)
                     with: f1 (Nu ((,) a))
      Expected: Nu ((,) a) -> (a, f1 (Nu ((,) a)))
        Actual: Nu ((,) a) -> (a, Nu ((,) a))
    • In the second argument of ‘(.)’, namely ‘out’
      In the expression: (\ (_, b) -> ((outI . fmap h) b)) . out
      In an equation for ‘h’: h = (\ (_, b) -> ((outI . fmap h) b)) . out
    • Relevant bindings include
        h :: Nu ((,) a) -> Nu f1 (bound at T8142.hs:6:18)