gadt13.hs:15:13: error:
    • Could not deduce: p ~ (String -> [Char])
      from the context: a ~ Int
        bound by a pattern with constructor: I :: Int -> Term Int,
                 in an equation for ‘shw’
        at gadt13.hs:15:6-8
      ‘p’ is a rigid type variable bound by
        the inferred type of shw :: Term a -> p
        at gadt13.hs:15:1-30
      Possible fix: add a type signature for ‘shw’
    • In the expression: ("I " ++) . shows t
      In an equation for ‘shw’: shw (I t) = ("I " ++) . shows t
    • Relevant bindings include
        shw :: Term a -> p (bound at gadt13.hs:15:1)