In #18, I propose letting the factory run in a new turn per #20, and not catching any thrown errors (i.e. they should just crash the program).

The alternative is to catch any errors and transform them into rejections. This gets a bit complicated, though:

1. How should resolve(x); throw y; behave?
2. How should reject(x); throw y; behave?

Plus, it creates a somewhat false parallel between factory and the callbacks to then. The callbacks to then check both return values and thrown errors, while checking return values is not possible for factory.

This is related to what is decided in #20, but in theory any combination could be decided on (same-turn, capture; same-turn, crash; next-turn, capture; next-turn, crash).