Write small Rust scripts

Recently I was working on a Rust PR to reduce unreachable_code lint churn after todo!() calls, that basically removes lint messages from unreachable_code after todo!() and instead adds a todo_macro_uses lint which can be turned off while the code is still being worked on. However, once that change was done, I ran into a number of failing tests, because while they had a #![allow(unused)] or some…