public Parser parser(ParserFile file) {
		Parser p = delegate.parser(file);
		for (CodeGeneratorExtension ext : extensions) p = ext.parser(p);
		return p;
	}
Build a file with a parser containing rule functions. Use the
 controller as factory in SourceGenTriggers so it triggers codegen
 extensions too, not just the factory functions in this factory.
tool/src/org/antlr/v4/codegen/OutputModelController.java