readFail003.hs:4:27: error:
    • Occurs check: cannot construct the infinite type:
        t ~ (t, [a], [a1])
    • In the expression: a
      In a pattern binding:
        ~(a, b, c)
          | nullity b = a
          | nullity c = a
          | otherwise = a
          where
              nullity = null
    • Relevant bindings include
        a :: t (bound at readFail003.hs:4:3)
        b :: [a] (bound at readFail003.hs:4:5)
        c :: [a1] (bound at readFail003.hs:4:7)