RS.CLIPPY.ASSIGNING_CLONES

Assigning the result of cloning may be inefficient

This checker is a Clippy lint created by The Rust Project Contributors. The documentation shown here is a copy of the original documentation for: assigning_clones. Copyright ©2025 The Rust Team. All rights reserved.

What it does

Checks for code like foo = bar.clone();

Why is this bad?

Custom Clone::clone_from() or ToOwned::clone_into implementations allow the objects to share resources and therefore avoid allocations.

Example

struct Thing;

impl Clone for Thing {
    fn clone(&self) -> Self { todo!() }
    fn clone_from(&mut self, other: &Self) { todo!() }
}

pub fn assign_to_ref(a: &mut Thing, b: Thing) {
    *a = b.clone();
}

Use instead:

struct Thing;

impl Clone for Thing {
    fn clone(&self) -> Self { todo!() }
    fn clone_from(&mut self, other: &Self) { todo!() }
}

pub fn assign_to_ref(a: &mut Thing, b: Thing) {
    a.clone_from(&b);
}

Configuration

msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml

(default: current version)