public void trackRef(Token x) {
		List<TerminalAST> xRefs = alt.tokenRefs.get(x.getText());
		if ( xRefs!=null ) {
			alt.tokenRefsInActions.map(x.getText(), node);
		}
		List<GrammarAST> rRefs = alt.ruleRefs.get(x.getText());
		if ( rRefs!=null ) {
			alt.ruleRefsInActions.map(x.getText(), node);
		}
	}
Find token and rule refs plus refs to them in actions;
 side-effect: update Alternatives
tool/src/org/antlr/v4/semantics/ActionSniffer.java