1. you usually capture the most general exception in a lib and avoid all refactorings derived of can/cannot fail deep in a stack of calls that needs to be propa

1. you usually capture the most general exception in a lib and avoid all refactorings derived of can/cannot fail deep in a stack of calls that needs to be propagated all the way up. With status it happens the same as with stackless coro. Once something is like that, you need to propagate it all the way up. 2. an exception cannot be ignored either. 3. you can transform an exception into a value or even code them as values. 4. See nested_exception.