@Override
	public Attribute resolveToAttribute(String x, ActionAST node) {
		if ( args!=null ) {
			Attribute a = args.get(x);   	if ( a!=null ) return a;
		}
		if ( retvals!=null ) {
			Attribute a = retvals.get(x);	if ( a!=null ) return a;
		}
		if ( locals!=null ) {
			Attribute a = locals.get(x);	if ( a!=null ) return a;
		}
		AttributeDict properties = getPredefinedScope(LabelType.RULE_LABEL);
		return properties.get(x);
	}
$x		Attribute: rule arguments, return values, predefined rule prop.
tool/src/org/antlr/v4/tool/Rule.java