clippy::useless_nonzero_new_unchecked: `NonZeroUsize::new()` and `Option::unwrap()` can be safely used in a `const` context

What you see

warning: `NonZeroUsize::new()` and `Option::unwrap()` can be safely used in a `const` context
 --> main.rs:4:31
  |
4 | const PLAYERS: NonZeroUsize = unsafe { NonZeroUsize::new_unchecked(3) };
  |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use instead: `NonZeroUsize::new(3).unwrap()`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#useless_nonzero_new_unchecked
  = note: `#[warn(clippy::useless_nonzero_new_unchecked)]` 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 NonZero*::new_unchecked() is an unsafe function and requires an unsafe context. When used in a context evaluated at compilation time, NonZero*::new().unwrap() will provide the same result with identical runtime performances while not requiring unsafe.

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

use std::num::NonZeroUsize;
const PLAYERS: NonZeroUsize = unsafe { NonZeroUsize::new_unchecked(3) };

Write this instead

use std::num::NonZeroUsize;
const PLAYERS: NonZeroUsize = NonZeroUsize::new(3).unwrap();

Turn it off, or on

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

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

[lints.clippy]
useless_nonzero_new_unchecked = "allow"

cargo clippy -- -A clippy::useless-nonzero-new-unchecked

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.