[SamReidHughes]

> There's no need to register factory instances inside of some singleton object at startup, the type system can infer which Generic components are needed where.

You would only need to do that if you wanted to define custom behavior, instead of automatically derived behavior, and registering a few delegates is the same amount of work as manually implementing an instance of Arbitrary and CoArbitrary.

[revcbh]

Yep. The only really-real difference is compile time checking.