Function gather_active_jobs 

pub(crate) fn gather_active_jobs<'tcx, C>(
    query: &'tcx QueryVTable<'tcx, C>,
    tcx: TyCtxt<'tcx>,
    require_complete: bool,
    job_map_out: &mut QueryJobMap<'tcx>,
) -> Option<()>
where
    C: QueryCache<Key: QueryKey + DynSend + DynSync>,
    QueryVTable<'tcx, C>: DynSync,

Internal plumbing for collecting the set of active jobs for this query.

Should only be called from collect_active_jobs_from_all_queries.

(We arbitrarily use the word “gather” when collecting the jobs for each individual query, so that we have distinct function names to grep for.)