Comment by remram

Rust has the "non_exhaustive" attribute that lets you declare that an enum might get more fields in the future. In practice that means that when you match on an enum value, you have to add a default case. It's like a "other" field in the enum except you can't reference it directly, you use a default case.

IIRC a secret 'other' field (or '__non_exhaustive' or something) is actually how we did thing before non_exhaustive was introduced.