- DOCUMENT@0..7
    - UNION_TYPE_DEFINITION@0..7
        - union_KW@0..5 "union"
        - WHITESPACE@5..6 " "
        - UNION_MEMBER_TYPES@6..7
            - EQ@6..7 "="
- ERROR@6:7 "expected a Name" =
- ERROR@7:7 "expected Union Member Type" EOF
recursion limit: 500, high: 0