![]() Explanation that fields are being used when deriving `(Partial)Ord` on enums When deriving `std::cmp::Ord` or `std::cmp::PartialOrd` on enums, their fields are compared if the variants are equal. This means that the last assertion in the following snipped panics. ```rust use std::cmp::{PartialEq, Eq, PartialOrd, Ord}; #[derive(PartialEq, Eq, PartialOrd, Ord)] enum Sizes { Small(usize), Big(usize), } fn main() { let a = Sizes::Big(3); let b = Sizes::Big(5); let c = Sizes::Small(10); assert!( c < a); assert_eq!(a, c); } ``` This is more often expected behavior than not, and can be easily circumvented, as discussed in [this thread](https://users.rust-lang.org/t/how-to-sort-enum-variants/52291/4). But it is addressed nowhere in the documentation, yet. So I stumbled across this, as I personally did not expect fields being used in `PartialOrd`. I added the explanation to the documentation. |
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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.
Note: this README is for users rather than contributors. If you wish to contribute to the compiler, you should read CONTRIBUTING.md instead.
Table of Contents
Quick Start
Read "Installation" from The Book.
Installing from source
If you really want to install from source (though this is not recommended), see INSTALL.md.
Getting Help
See https://www.rust-lang.org/community for a list of chat platforms and forums.
Contributing
See CONTRIBUTING.md.
License
Rust is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.
See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details.
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If you want to use these names or brands, please read the media guide.
Third-party logos may be subject to third-party copyrights and trademarks. See Licenses for details.