-- Andreas 2021-02-03
-- Cannot use list categories with defined labels.

Bar.  Foo ::= "foo";
cons. [Foo] ::= Foo [Foo];

define cons x xs = x : xs;

-- BNFC-2 says:
--   Bad list formation rule:
--     cons. [Foo] ::= Foo [Foo]
--   List categories [C] can only be formed by rules labeled _, [], (:), or (:[]).