Function rustc_mir::borrow_check::type_check::liveness::regions_that_outlive_free_regions

fn regions_that_outlive_free_regions<'tcx>(
    num_region_vars: usize, 
    universal_regions: &UniversalRegions<'tcx>, 
    constraint_set: &OutlivesConstraintSet
) -> FxHashSet<RegionVid>

Computes all regions that are (currently) known to outlive free regions. For these regions, we do not need to compute liveness, since the outlives constraints will ensure that they are live over the whole fn body anyhow.