Function rustc_mir_transform::coverage::check_source_region

fn check_source_region(source_region: SourceRegion) -> Option<SourceRegion>

If llvm-cov sees a source region that is improperly ordered (end < start), it will immediately exit with a fatal error. To prevent that from happening, discard regions that are improperly ordered, or might be interpreted in a way that makes them improperly ordered.