export class_NULL?

[t-kalinowski]

Should we add class_NULL? The primary benefit would be improved discoverability through autocompletions on S7::class_* and in the package documentation.

[hadley]

As opposed to just telling people to use NULL?

[t-kalinowski]

I think the core issue is that S7's support for a union class like NULL | class_double is not very discoverable at the moment. Perhaps a better solution is to add examples in ?new_property, ?new_class, and/or ?method<-.

[mmaechler]

I'd also think it's overkill. Knowning about and using NULL should really be part of every intermediate level useR's tools.