Function measure_patch_rust_detail 

pub fn measure_patch_rust_detail(
    root: &Path,
    ignore: &[String],
    features: &[String],
) -> Result<BTreeMap<String, RustPatchCoverage>>

Run the Rust unit suite under cargo llvm-cov and return the per-file region detail, keyed by the absolute path llvm-cov reports. ignore is the coverage-rule exemptions, dropped so an exempt file’s changed lines are lifted.