Clippy lint · Complexity · checked with Clippy 0.1.99

clippy::get_last_with_len: accessing last element with `x.get(x.len() - 1)`

What it meansChecks for usage of x.get(x.len() - 1) instead of x.last(). It is in the complexity group and warns by default.

What you see

warning: accessing last element with `x.get(x.len() - 1)`
 --> main.rs:4:20
  |
4 | let last_element = x.get(x.len() - 1);
  |                    ^^^^^^^^^^^^^^^^^^ help: try: `x.last()`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#get_last_with_len
  = note: `#[warn(clippy::get_last_with_len)]` on by default

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 x.last() is easier to read and has the same result. Note that using x[x.len() - 1] is semantically different from x.last(). Indexing into the array will panic on out-of-bounds accesses, while x.get() and x.last() will return None. There is another lint (get_unwrap) that covers the case of using x.get(index).unwrap() instead of x[index].

Code that does something simple in a complicated way. Warns by default.

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 x = vec![2, 3, 5];
let last_element = x.get(x.len() - 1);

Write this instead

let x = vec![2, 3, 5];
let last_element = x.last();

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

On one item

#[allow(clippy::get_last_with_len)]
fn my_function() { /* ... */ }

Whole crate (Cargo.toml)

[lints.clippy]
get_last_with_len = "allow"

One run

cargo clippy -- -A clippy::get-last-with-len

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.

Complexitygroup

warndefault level

yesfixed by cargo clippy --fix

1.37.0added in Rust

Clippy's own documentation

What it does

Checks for usage of x.get(x.len() - 1) instead of x.last().

Why is this bad?

Using x.last() is easier to read and has the same result.

Note that using x[x.len() - 1] is semantically different from x.last(). Indexing into the array will panic on out-of-bounds accesses, while x.get() and x.last() will return None.

There is another lint (get_unwrap) that covers the case of using x.get(index).unwrap() instead of x[index].

Example

let x = vec![2, 3, 5];
let last_element = x.get(x.len() - 1);

Use instead:

let x = vec![2, 3, 5];
let last_element = x.last();

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

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