clippy::clone_on_copy: using `clone` on type `u64` which implements the `Copy` trait

What you see

warning: using `clone` on type `u64` which implements the `Copy` trait
 --> main.rs:3:1
  |
3 | 42u64.clone();
  | ^^^^^^^^^^^^^ help: try removing the `clone` call: `42u64`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#clone_on_copy
  = note: `#[warn(clippy::clone_on_copy)]` 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?

The only reason Copy types implement Clone is for generics, not for using the clone method on a concrete type.

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

42u64.clone();

Turn it off, or on

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

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

[lints.clippy]
clone_on_copy = "allow"

cargo clippy -- -A clippy::clone-on-copy

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.