Thanks for elaborating on this, now I understand your thoughts. I wanted to write a longer answer, but life got in the middle. So I'll just say: If rust devs d

Thanks for elaborating on this, now I understand your thoughts. I wanted to write a longer answer, but life got in the middle. So I'll just say: If rust devs do not want to add a specialization or traits for this feature and wait for the Right Thing it is fine. It is such a niche (get it?) requirement that it is not worth polluting the standard library. But if you really need it as an user, I don't think the trait solution is an hack at all. I don't see specialization as an hack in general and in fact is important for writing efficient code. Ideally you would be able to encode every possible property of your program elegantly and generically in the type system while keeping the language lean, fast and easy to understand. In practice at any point in time only a language will only have a finite subset of features and an user can't wait forever for the language to reach perfection. Any 50+ year language will necessarily accumulate cruft. Embrace it. Worse is better.