Clippy lint · Restriction · checked with Clippy 0.1.99

clippy::get_unwrap: called `.get().unwrap()` on a Vec

What it meansChecks for usage of .get().unwrap() (or .get_mut().unwrap) on a standard library type which implements Index It is in the restriction group and off by default.

What you see

warning: called `.get().unwrap()` on a Vec
 --> main.rs:4:12
  |
4 | let last = some_vec.get(3).unwrap();
  |            ^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#get_unwrap
  = note: requested on the command line with `-W clippy::get-unwrap`
help: using `[]` is clearer and more concise
  |
4 - let last = some_vec.get(3).unwrap();
4 + let last = &some_vec[3];
  |

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?

Using the Index trait ([]) is more clear and more concise.

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 mut some_vec = vec![0, 1, 2, 3];
let last = some_vec.get(3).unwrap();
*some_vec.get_mut(0).unwrap() = 1;

Write this instead

let mut some_vec = vec![0, 1, 2, 3];
let last = some_vec[3];
some_vec[0] = 1;

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]
get_unwrap = "warn"

In code

#![warn(clippy::get_unwrap)]

One run

cargo clippy -- -W clippy::get-unwrap

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

pre 1.29.0added in Rust

Clippy's own documentation

What it does

Checks for usage of .get().unwrap() (or .get_mut().unwrap) on a standard library type which implements Index

Why restrict this?

Using the Index trait ([]) is more clear and more concise.

Known problems

Not a replacement for error handling: Using either .unwrap() or the Index trait ([]) carries the risk of causing a panic if the value being accessed is None. If the use of .get().unwrap() is a temporary placeholder for dealing with the Option type, then this does not mitigate the need for error handling. If there is a chance that .get() will be None in your program, then it is advisable that the None case is handled in a future refactor instead of using .unwrap() or the Index trait.

Example

let mut some_vec = vec![0, 1, 2, 3];
let last = some_vec.get(3).unwrap();
*some_vec.get_mut(0).unwrap() = 1;

The correct use would be:

let mut some_vec = vec![0, 1, 2, 3];
let last = some_vec[3];
some_vec[0] = 1;

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

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