rust-lang/rust-clippy

Suggest usage of `array.as_slice()` (instead of `&array[..]`) and `array.as_mut_slice()`

Open

#7,633 opened on Sep 4, 2021

View on GitHub
 (6 comments) (2 reactions) (1 assignee)Rust (10,406 stars) (1,391 forks)batch import
A-lintL-restrictiongood first issue

Description

What it does

Lints for example this code:

let array: [u8; 4] = [1, 2, 3, 4];
let slice: &[u8] = &array[..];

and suggests array::as_slice:

let array: [u8; 4] = [1, 2, 3, 4];
let slice: &[u8] = array.as_slice();

(same should be suggested for &mut array[..], which can be replaced with array.as_mut_slice())

Categories (optional)

  • Kind: clippy::pedantic or clippy::style

What is the advantage of the recommended code over the original code?

For example:

  • easier to read for people new to rust (not very obvious what [..] does)
  • there must be a reason why array::as_slice exists? (see rust-lang/rust#76120)

Drawbacks

  • might have a lot of false positives or not much benefit in using the function

Possibly related issues:

  • #728
  • #5598

Stabilization

At the time of writing this issue, the function is still unstable, but with the merging of rust-lang/rust#88353, this feature will be stabilized. (final-comment-period, so will be merged in the next few days)

Contributor guide

Tech stack
rust
Domain
tooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
RustClippy lint internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Review the stabilization of array::as slice and array::as mut slice in rust lang/rust#88353. Examine existing similar lints in the clippy source code, such as those in clippy lints/src/ methods. The implementation should detect the pattern `&array[..]` and suggest `array.as slice()`. The lint should be added under clippy::style or clippy::pedantic category.