From 003a636e760d50f4e1e96101f8e9994ac3758135 Mon Sep 17 00:00:00 2001 From: Ariel Davis Date: Fri, 20 Aug 2021 22:24:22 -0400 Subject: [PATCH] Add an example for deriving PartialOrd on enums For some reason, I always forget which variants are smaller and which are larger when you derive PartialOrd on an enum. And the wording in the current docs is not entirely clear to me. So, I often end up making a small enum, deriving PartialOrd on it, and then writing a `#[test]` with an assert that the top one is smaller than the bottom one (or the other way around) to figure out which way the deriving goes. So then I figured, it would be great if the standard library docs just had that example, so if I keep forgetting, at least I can figure it out quickly by looking at std's docs. --- library/core/src/cmp.rs | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/library/core/src/cmp.rs b/library/core/src/cmp.rs index 79610bb409d37..4e82b65539460 100644 --- a/library/core/src/cmp.rs +++ b/library/core/src/cmp.rs @@ -660,6 +660,18 @@ impl Clone for Reverse { /// This trait can be used with `#[derive]`. When `derive`d on structs, it will produce a /// [lexicographic](https://en.wikipedia.org/wiki/Lexicographic_order) ordering based on the top-to-bottom declaration order of the struct's members. /// When `derive`d on enums, variants are ordered by their top-to-bottom discriminant order. +/// This means variants at the top are less than variants at the bottom. +/// Here's an example: +/// +/// ``` +/// #[derive(PartialEq, PartialOrd)] +/// enum Size { +/// Small, +/// Large, +/// } +/// +/// assert!(Size::Small < Size::Large); +/// ``` /// /// ## Lexicographical comparison ///