Context

bson.Zeroer only works when implemented on a struct type. It’d be nice if it could work on any type.

Describe the background behind the problem.
Before I realized that GODRIVER-3223 was a bug (thank you, preston.vasquez@mongodb.com!), I tried implementing Zeroer on our wrapper around Google’s UUID package. Then I saw that the Zeroer docs say it’s only for structs, which is rather a surprise.

Definition of done

The encoder should honor IsZero() on any type, not just structs.

Pitfalls

What should the implementer watch out for? What are the risks?

This could count as a breaking change since IsZero() could conceptually be implemented on some type independently of BSON. IOW, there could be “accidental” Zeroer implementations out there.