Create a new node from an existing node does nothing for BaseTree
as there are no fields other than the children list, which cannot
be copied as the children are not considered part of this node.
A stripped-down version of org.antlr.misc.BitSet that is just
good enough to handle runtime requirements such as FOLLOW sets
for automatic error recovery.
BitSet() -
Constructor for class org.antlr.runtime.BitSet
A blank listener that does nothing; useful for real classes so
they don't have to have lots of blank methods and are less
sensitive to updates to debug interface.