I've sometimes wished for a less-strict lint from rustc that only flags non-transitively unused items, i.e. in this case the function that uses CAP could still be flagged while CAP itself would not. Of course the sharper version is important for code that's going to be released, but when I'm working on a crate that's still taking shape I usually want something between full #![warn(unused)] and #![allow(unused)].