At the moment:

class Article {
   @Relation
   author: OneRelation<User>;
}

emits:

__metadata('design:type', OneRelation)

My suggestion is that that instead of just type it would also include the type args.

Maybe something like this:

__metadata('design:type', {type: OneRelation, args: [{type: User, args: []}])

With the latter i don't have to repeat myself in decorator that this is a one relation to user as i have already specified this in type.

Thanks,
Reio