[racket] How to get arity of make-object? Found answer

On 2014-06-06 06:31:27 +0100, Matthew Flatt wrote:
> Sorry for being so late to the discussion, but I agree that something
> like `class-constructor-arity` and `class-constructor-arity-includes?`
> should be added to `racket/class`.

Are those even possible to implement?

After all, I can construct a class that has 2 init arguments on
Wednesday and has 3 on Friday (by checking the date and then using
different `super-new` calls in the branches).

Cheers,
Asumu