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

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

-- BNFC-2 says:
--   test/check/fail/InvalidListRule.cf:5:1: Bad list formation rule:
--     Cons. [Foo] ::= Foo [Foo]
--   List categories [C] can only be formed by rules labeled _, [], (:), or (:[]).