T15789.hs:10:80: error:
    • Expected kind ‘k2 -> *’, but ‘cat b’ has kind ‘*’
    • In the first argument of ‘Cat’, namely ‘(forall b. cat b u)’
      In the kind ‘forall (cat :: forall xx. xx -> Type) a.
                   forall b. Cat (forall b. cat b u)’
      In the data type declaration for ‘Zero’