Sum types, 2024 variant

[ElegantBeef]

A possible solution is to use `as` for matching the branches so it'd be `string 
as s` instead. For specific field matching `Type(a, b, c)` would do positional 
matching. With an added `Type(a: fieldName)` it could even be expanded for 
named matching where it'd grab the field of typed branched object.