gadt21.hs:21:60:
    Could not deduce (Ord a1) arising from a use of ‘f’
    from the context: a ~ Set a1
      bound by a pattern with constructor:
                 TypeSet :: forall a. Type a -> Type (Set a),
               in an equation for ‘withOrdDynExpr’
      at gadt21.hs:21:35-43
    Possible fix:
      add (Ord a1) to the context of the data constructor ‘TypeSet’
    In the first argument of ‘Just’, namely ‘(f e)’
    In the expression: Just (f e)
    In an equation for ‘withOrdDynExpr’:
        withOrdDynExpr (DynExpr e@(Const (TypeSet _) _)) f = Just (f e)