Clippy lint · Complexity · checked with Clippy 0.1.99

clippy::bytes_count_to_len: using long and hard to read `.bytes().count()`

What it meansIt checks for str::bytes().count() and suggests replacing it with str::len(). It is in the complexity group and warns by default.

What you see

warning: using long and hard to read `.bytes().count()`
 --> main.rs:3:1
  |
3 | "hello".bytes().count();
  | ^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling `.len()` instead: `"hello".len()`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#bytes_count_to_len
  = note: `#[warn(clippy::bytes_count_to_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?

str::bytes().count() is longer and may not be as performant as using str::len().

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

"hello".bytes().count();
String::from("hello").bytes().count();

Write this instead

"hello".len();
String::from("hello").len();

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
bytes_count_to_len = "allow"

One run

cargo clippy -- -A clippy::bytes-count-to-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

1.62.0added in Rust

Clippy's own documentation

What it does

It checks for str::bytes().count() and suggests replacing it with str::len().

Why is this bad?

str::bytes().count() is longer and may not be as performant as using str::len().

Example

"hello".bytes().count();
String::from("hello").bytes().count();

Use instead:

"hello".len();
String::from("hello").len();

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

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