@Override
	public boolean resolvesToListLabel(String x, ActionAST node) {
		LabelElementPair anyLabelDef = getAnyLabelDef(x);
		return anyLabelDef!=null &&
			   (anyLabelDef.type==LabelType.RULE_LIST_LABEL ||
				anyLabelDef.type==LabelType.TOKEN_LIST_LABEL);
	}
$x.y, x can be surrounding rule, token/rule/label ref. y is visible
 attr in that dictionary.  Can't see args on rule refs.
tool/src/org/antlr/v4/tool/Alternative.java