T8566.hs:32:9: error:
    • Could not deduce (C ('AA (t (I a ps)) as) ps fs0)
        arising from a use of ‘c’
      from the context: C ('AA (t (I a ps)) as) ps fs
        bound by the instance declaration at T8566.hs:30:10-67
      or from: 'AA t (a : as) ~ 'AA t1 as1
        bound by a pattern with constructor:
                   A :: forall (r :: [*]) v (t :: v) (as :: [U *]). I ('AA t as) r,
                 in an equation for ‘c’
        at T8566.hs:32:5
      The type variable ‘fs0’ is ambiguous
      Relevant bindings include
        c :: I ('AA t (a : as)) ps -> I ('AA t (a : as)) ps
          (bound at T8566.hs:32:3)
    • In the expression: c undefined
      In an equation for ‘c’: c A = c undefined
      In the instance declaration for ‘C ('AA t (a : as)) ps fs’