tcfail014.hs:5:33:
    Occurs check: cannot construct the infinite type: t8 ~ t8 -> t7
    Relevant bindings include
      h :: (t8 -> t7) -> t7 (bound at tcfail014.hs:5:25)
      z :: t8 -> t7 (bound at tcfail014.hs:5:27)
    In the first argument of ‛z’, namely ‛z’
    In the expression: z z
    In an equation for ‛h’: h z = z z