The current constraint but with the entry for param updated to entry.
current is used linearly. If it is different from prev it is
known to be dead after the call. Hence it is OK to update destructively
parts of current which are not shared by prev.
The current constraint but with the entry for param updated to entry.
current is used linearly. If it is different from prev it is
known to be dead after the call. Hence it is OK to update destructively
parts of current which are not shared by prev.