That said, I have personally used newtypes a reasonable amount, mostly for making sure I don't mess up different kinds of database ids.
It is not. `NonZeroUsize` is (though in Rust "newtype" is only a pattern or idiom), and its definition (inside of a macro which provides numeric newtypes a bunch of `impl`s) is:
pub struct NonZeroUsize(usize);
pub struct String {
vec: Vec<u8>,
}
1. Marking the kind of data to prevent mixing up values of different kinds. (e.g. Email)
2. Outlawing some of the values of the underlying type. (e.g. OneToFive)
I do not think it being a tuple-struct or not is important at all when deciding whether something uses the newtype pattern, as long as it has a single field.
(I was going to be cheeky here, but Git history shows you didn't write any of this part.)
There's no real difference between a 1-tuple struct and the regular struct, other than the name. So to me, it feels like either are both newtypes. But, I guess I could see some sort of argument the other way too.