public void setText(String text) {
//		textOverride = text; // don't alt tokens as others might see
		token.setText(text); // we delete surrounding tree, so ok to alter
	}
Walk ancestors of this node until we find ALT with
 alt!=null or leftRecursiveAltInfo!=null. Then grab label if any.
 If not a rule element, just returns null.
tool/src/org/antlr/v4/tool/ast/GrammarAST.java