public ParserFile parserFile(String fileName) {
		ParserFile f = delegate.parserFile(fileName);
		for (CodeGeneratorExtension ext : extensions) f = ext.parserFile(f);
		return f;
	}
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