@Override
	public boolean defineRule(Rule r) {
		if (!super.defineRule(r)) {
			return false;
		}

		if ( modes==null ) modes = new MultiMap<String, Rule>();
		modes.map(r.mode, r);
		return true;
	}
DEFAULT_MODE rules are added first due to grammar syntax order
tool/src/org/antlr/v4/tool/LexerGrammar.java