reachesIntoOuterContext property
We cannot execute predicates dependent upon local context unless we know for sure we are in the correct context. Because there is no way to do this efficiently, we simply cannot evaluate dependent predicates unless we are in the rule that initially invokes the ATN simulator.
closure() tracks the depth of how far we dip into the outer context: depth > 0. Note that it may not be totally accurate depth since I don't ever decrement. TODO: make it a bool then
For memory efficiency, the {@link #isPrecedenceFilterSuppressed} method is also backed by this field. Since the field is ly accessible, the highest bit which would not cause the value to become negative is used to store this field. This choice minimizes the risk that code which only compares this value to 0 would be affected by the new purpose of the flag. It also ensures the performance of the existing [ATNConfig] constructors as well as certain operations like {@link ATNConfigSet#add(ATNConfig, DoubleKeyMap)} method are completely unaffected by the change.
Implementation
int reachesIntoOuterContext;