public List<SrcOp> stringRef(GrammarAST ID, GrammarAST label) {
		List<SrcOp> ops = delegate.stringRef(ID, label);
		for (CodeGeneratorExtension ext : extensions) {
			ops = ext.stringRef(ops);
		}
		return ops;
	}
Create RuleFunction per rule and update sempreds,actions of parser
 output object with stuff found in r.
tool/src/org/antlr/v4/codegen/OutputModelController.java