trait TypeId {
    fn get_typeid() -> usize;
}

impl TypeId for i32 {
    fn get_typeid() -> usize {return 1;}
}

impl TypeId for String {
    fn get_typeid() -> usize {return 2;}
}

fn is_string<T: ?Sized + TypeId>(_t: &T) -> bool {
    T::get_typeid() == String::get_typeid()
}

fn main() {
    assert_eq!(is_string(&0), false);
    assert_eq!(is_string(&"cookie monster".to_string()), true);
}