Clippy lint · Restriction · checked with Clippy 0.1.99

clippy::deref_by_slicing: slicing when dereferencing would work

What it meansChecks for slicing expressions which are equivalent to dereferencing the value. It is in the restriction group and off by default.

What you see

warning: slicing when dereferencing would work
 --> main.rs:4:13
  |
4 | let slice = &vec[..];
  |             ^^^^^^^^ help: dereference the original value instead: `&*vec`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#deref_by_slicing
  = note: requested on the command line with `-W clippy::deref-by-slicing`

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

Some people may prefer to dereference rather than slice.

Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

let vec = vec![1, 2, 3];
let slice = &vec[..];

Write this instead

let vec = vec![1, 2, 3];
let slice = &*vec;

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
deref_by_slicing = "warn"

In code

#![warn(clippy::deref_by_slicing)]

One run

cargo clippy -- -W clippy::deref-by-slicing

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Restrictiongroup

allowdefault level

yesfixed by cargo clippy --fix

1.61.0added in Rust

Clippy's own documentation

What it does

Checks for slicing expressions which are equivalent to dereferencing the value.

Why restrict this?

Some people may prefer to dereference rather than slice.

Example

let vec = vec![1, 2, 3];
let slice = &vec[..];

Use instead:

let vec = vec![1, 2, 3];
let slice = &*vec;

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

Up next

Also worth your time

Did this answer your question?