T7148a.hs:19:50: error:
    • Couldn't match representation of type ‘b’
                               with that of ‘Result a b’
        arising from the coercion of the method ‘coerce’
          from type ‘forall b. Proxy b -> a -> Result a b’
            to type ‘forall b.
                     Proxy b -> IS_NO_LONGER a -> Result (IS_NO_LONGER a) b’
      ‘b’ is a rigid type variable bound by
        the type Proxy b -> a -> Result a b at T7148a.hs:19:50-56
    • When deriving the instance for (Convert (IS_NO_LONGER a))