RS.CLIPPY.SUSPICIOUS_TO_OWNED

Calls to `to_owned` on a `Cow<'_, _>` might not do what they are expected

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

What it does

Checks for the usage of _.to_owned(), on a Cow<\'_, _>.

Why is this bad?

Calling to_owned() on a Cow creates a clone of the Cow itself, without taking ownership of the Cow contents (i.e. it's equivalent to calling Cow::clone). The similarly named into_owned method, on the other hand, clones the Cow contents, effectively turning any Cow::Borrowed into a Cow::Owned.

Given the potential ambiguity, consider replacing to_owned with clone for better readability or, if getting a Cow::Owned was the original intent, using into_owned instead.

Example

let s = "Hello world!";
let cow = Cow::Borrowed(s);

let data = cow.to_owned();
assert!(matches!(data, Cow::Borrowed(_)))

Use instead:

let s = "Hello world!";
let cow = Cow::Borrowed(s);

let data = cow.clone();
assert!(matches!(data, Cow::Borrowed(_)))

let s = "Hello world!";
let cow = Cow::Borrowed(s);

let _data: String = cow.into_owned();