You typically don't represent that information in the type of the object itself but rather as separate information for the type of the values (ie fields). So ma

You typically don't represent that information in the type of the object itself but rather as separate information for the type of the values (ie fields). So maybe it's "a list, and also the values are lists" or maybe it's "a list, and also the first value is a string, and the other values are integers"... and maybe it's "a list, and the values are strings, and also it has a field named 'foo' that's an integer for some reason". You can still have the same information (depending on the actual system), just represented differently - parametric polymorphism is a bit too rigid here because not everything fits neatly into generic schemas.