T19615.hs:17:21: error: [GHC-55287]
    • The argument ‘(f x)’ of ‘lift'’
      does not have a fixed runtime representation.
      Its type is:
        a0 :: TYPE c0
      Cannot unify ‘r'’ with the type variable ‘c0’
      because it is not a concrete ‘RuntimeRep’.
    • In the first argument of ‘lift'’, namely ‘(f x)’
      In the expression: lift' (f x) id
      In an equation for ‘mapF’: mapF f x = lift' (f x) id
    • Relevant bindings include
        f :: a -> b (bound at T19615.hs:17:8)
        mapF :: (a -> b) -> Lev a -> Lev b (bound at T19615.hs:17:3)