@Override
	public Handle range(GrammarAST a, GrammarAST b) {
		ATNState left = newState(a);
		ATNState right = newState(b);
		int t1 = CharSupport.getCharValueFromGrammarCharLiteral(a.getText());
		int t2 = CharSupport.getCharValueFromGrammarCharLiteral(b.getText());
		if (checkRange(a, b, t1, t2)) {
			left.addTransition(createTransition(right, t1, t2, a));
		}
		a.atnState = left;
		b.atnState = left;
		return new Handle(left, right);
	}
Maps from a {@link LexerAction} object to the action index.
tool/src/org/antlr/v4/automata/LexerATNFactory.java