rustc-output.txt

 0:10.83 warning: unused variable: `v`
 0:10.83    --> /home/jer/mozilla/src/gecko/obj/toolkit/components/glean/api/src/metrics.rs:411:64
 0:10.83     |
 0:10.83 411 |               let extra = extra.map(|m| m.into_iter().map(|(k, v)| (k.try_into().unwrap(), v)).collect());
 0:10.83     |                                                                ^ help: if this is intentional, prefix it with an underscore: `_v`
 0:10.83     |
 0:10.83     = note: `#[warn(unused_variables)]` on by default
 0:10.83 warning: 1 warning emitted