Are there any ways to achieve exhaustiveness, but enums or sealed classes? I have a bunch of objects and want to provide each of them with some data. (Certainly, I've got DTO schema and want to add platform-specific (SQL-specific, JSON-specific, etc) metadata)

how do you plan on using this? can you provide a hypothetical

when

statement or another snippet that would take advantage of what you're asking for?

Schema sample: https://github.com/Miha-x64/reactive-properties/blob/f9381419ac638c31f4e3f51bc4d856ce4c8ee79e/logic-sample/src/main/kotlin/net/aquadc/propertiesSampleLogic/sql/schema.kt#L27 Metadata sample:

fun jsonMeta(field: FieldDef<User, *>) = when (field) {
    Name -> OverrideName(Prefix("user"))
    Surname -> OverrideName(Prefix("user"))
}