Return an array of the nodes that matched or null if no match. This is the base class so we just throw an exception. All Selector subclasses must provide an implementation of this method.
Selector subclasses all define a toString() method primarily because it makes it easy to write parser tests.
Staticparse
This is the base class for all Selector types. The key method that all selector subclasses must implement is match(). It takes a TraversalState object (from a TreeTransformer traversal) and tests whether the selector matches at the current node. See the comment at the start of this file for more details on the match() method.