borrow_check:: type_check:: liveness
Combines liveness analysis with initialization analysis to
determine which variables are live at which points, both due to
ordinary uses and drops. Returns a set of (ty, location) pairs
that indicate which types must be live at which point in the CFG.
This vector is consumed by
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.