rustfmt-sorting.md

Rustfmt: Raw identifier sorting

🚧 The 2024 Edition has not yet been released and hence this section is still "under construction".

More information may be found in the tracking issues at rust-lang/rust#123800 and rust-lang/rust#123802.

Summary

rustfmt utilizes a new sorting algorithm.

Details

The Rust Style Guide includes rules for sorting that rustfmt applies in various contexts, such as on imports.

Previous versions of the Style Guide and Rustfmt generally used an "ASCIIbetical" based approach. In the 2024 Edition this is changed to use a version-sort like algorithm that compares Unicode characters lexicographically and provides better results in ASCII digit comparisons.

For example with a given (unsorted) input:

use std::num::{NonZeroU32, NonZeroU16, NonZeroU8, NonZeroU64};
use std::io::{Write, Read, stdout, self};

In the prior Editions, rustfmt would have produced:

use std::io::{self, stdout, Read, Write};
use std::num::{NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8};

In the 2024 Edition, rustfmt now produces:

use std::io::{self, Read, Write, stdout};
use std::num::{NonZeroU8, NonZeroU16, NonZeroU32, NonZeroU64};

Migration

The change can be applied automatically by running cargo fmt or rustfmt with the 2024 Edition.