Oddly, I didn’t get a notification for this one and just found it in my email! Anyway - you’re exactly right. There’s no internal benefit to the syntax, I wanted to make sure it was included so that readers wouldn’t be surprised when the ran into it elsewhere.
You do sometimes find it combined with methods to provide a somewhat seamless use of types to represent units - with conversions between them. This can be extended using the repr_transparent feature ( https://doc.rust-lang.org/1.26.2/unstable-book/language-features/repr-transparent.html ) to be seamless, but that’s a bit beyond the scope of the book. Once that feature is stabilized into the main language, I think it’ll see a bit more use.