a576e81b1d
Suggest less bug-prone construction of Duration in docs std::time::Duration has a well-known quirk: Duration::as_nanos() returns u128 [1], but Duration::from_nanos() takes u64 [2]. So these methods cannot easily roundtrip [3]. It is not possible to simply accept u128 in from_nanos [4], because it requires breaking other API [5]. It seems to me that callers have basically only two options: 1. `Duration::from_nanos(d.as_nanos() as u64)`, which is the "obvious" and buggy approach. 2. `Duration::new(d.as_secs(), d.subsecs_nanos())`, which only becomes apparent after reading and digesting the entire Duration struct documentation. I suggest that the documentation of `from_nanos` is changed to make option 2 more easily discoverable. There are two major usecases for this: - "Weird math" operations that should not be supported directly by `Duration`, like squaring. - "Disconnected roundtrips", where the u128 value is passed through various other stack frames, and perhaps reconstructed into a Duration on a different machine. In both cases, it seems like a good idea to not tempt people into thinking "Eh, u64 is good enough, what could possibly go wrong!". That's why I want to add a note that points out the similarly-easy and *safe* way to reconstruct a Duration. [1] https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_nanos [2] https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_nanos [3] https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=fa6bab2b6b72f20c14b5243610ea1dde [4] https://github.com/rust-lang/rust/issues/103332 [5] https://github.com/rust-lang/rust/issues/51107#issuecomment-392353166 |
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The Rust Programming Language
This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.
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