Function compute_loan_liveness 

pub(super) fn compute_loan_liveness<'tcx>(
    liveness: &LivenessValues,
    outlives_constraints: impl Iterator<Item = OutlivesConstraint<'tcx>>,
    borrow_set: &BorrowSet<'tcx>,
    localized_outlives_constraints: &LocalizedOutlivesConstraintSet,
) -> SparseBitMatrix<PointIndex, BorrowIndex>

Compute loan reachability to approximately trace loan liveness throughout the CFG, by traversing the full graph of constraints that combines:

• the localized constraints (the physical edges),
• with the constraints that hold at all points (the logical edges).