P4 Description
In ref-processing, references with live referents are dropped from the discovered list, and their referents are mark live by calling `DiscoveredListIterator::make_referent_alive`.
It's not necessary to do so for null referent, and it's confusing as well -- what does it mean to make a null referent live.
Add referent != null as a precondition for make_referent_alive.
It's not necessary to do so for null referent, and it's confusing as well -- what does it mean to make a null referent live.
Add referent != null as a precondition for make_referent_alive.
