Prove to compiler that object conforms to protocols after verifying conformance

Question

I'm working on an abstraction to hide the specifics of ObjectBox database from my app.

class ObjectBoxDatabase: Database {
 
    func all<T>(of type: T.Type) throws -> [T] where T : DatabaseEntity {
        let box = self.getBox(for: T.self)
        return box?.all() ?? []
    }

    private func getBox<T>(for type: T.Type) -> Box<T>? where T : DatabaseEntity {
       switch T.self {
        case is SomeEntity.Type:
            return someEntityBox as? Box<T>
        case is SomeOtherEntity.Type:
            return someOtherEntityBox as? Box<T>
        default:
            return nil
        }
    }
}

The implementation of getBox is just a placeholder for now, I'm planning on implementing some more advanced logic there once I figure out the generics.

My problem is that this way, the compiler is complaining when I'm calling getBox that T needs to conform __EntityRelatable, EntityInspectable and T.EntityBindingTypeEntityType == T.

Box<E> : CustomDebugStringConvertible where E : ObjectBox.EntityInspectable, E : ObjectBox.__EntityRelatable, E == E.EntityBindingType.EntityType

I think if it was only one requirement, I could cast T and pass it that way but since these 3 are not related, I don't know what to cast to that is all three and DatabaseEntity at the same time.

An other option I was thinking was to not return Box<T> from getBox but something else, this way T doesn't get restricted. The problem is I don't know what to return then as I don't have a common type (again)

My final try was, (I know from design perspective it is not a good approach at all, but I wanted to see some code running finally) to conform my DatabaseEntity to all those requirements and return Box<DatabaseEntity> but then I still get any DatabaseEntity does not conform EntityInspectable on the return type

EDIT

someEntityBox and someOtherEntityBox are Box<SomeEntity> and Box< SomeOtherEntity> respectively where those entities conform to the Entity protocol from ObjectBox

The database entity protocol is just an empty protocol for now

 protocol DatabaseEntity {}