If we decide to improve the type safety of the Swift API (#3969), we can take it a step further by using [String : RealmStorable] and [RealmStorable] to ensure a user does not try to initialize an object with a type that couldn't ever be stored as a property. Though this will not guarantee type safety with these APIs, it'll prevent accidents where a user tries to pass a UInt, some struct, etc.

It also might be a good starting place to think about storing custom types in a Realm, but that's a much more complicated topic…