I'm proposing this not as a specific feature but as a general strategy: everything the compiler can conceivably recover from in a way that allows the rest of the application to run, should. Think borrow checking, for example. If it could be changed automatically to Arc<Mutex<T>> from &T, when running the test you could say not only the borrow checker error, but also point at the specific runtime case that the borrow checker protected you from if any test exercises it.

Adding `return todo!()` works well enough for some cases, but not all, because it can't confirm against impl Trait return types.

And these strategies are things that people need to be taught about, individually. I'm not saying that the current state is terrible, just that there might be things we can do to make them better.