@Override
	public void label(GrammarAST op, GrammarAST ID, GrammarAST element) {
		LabelElementPair lp = new LabelElementPair(g, ID, element, op.getType());
		currentRule.alt[currentOuterAltNumber].labelDefs.map(ID.getText(), lp);
	}
Track action name node in @parser::members {...} or @members {...}
tool/src/org/antlr/v4/semantics/SymbolCollector.java