Clippy lint · Restriction · checked with Clippy 0.1.99

clippy::str_to_string: `to_string()` called on a `&str`

What it meansThis lint checks for .to_string() method calls on values of type &str. It is in the restriction group and off by default.

What you see

warning: `to_string()` called on a `&str`
 --> main.rs:3:9
  |
3 | let _ = "str".to_string();
  |         ^^^^^^^^^^^^^^^^^ help: try: `"str".to_owned()`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#str_to_string
  = note: requested on the command line with `-W clippy::str-to-string`

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 to_string method is also used on other types to convert them to a string. When called on a &str it turns the &str into the owned variant String, which can be more specifically expressed with .to_owned().

Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.

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

let _ = "str".to_string();

Write this instead

let _ = "str".to_owned();

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
str_to_string = "warn"

In code

#![warn(clippy::str_to_string)]

One run

cargo clippy -- -W clippy::str-to-string

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.

Restrictiongroup

allowdefault level

yesfixed by cargo clippy --fix

pre 1.29.0added in Rust

Clippy's own documentation

What it does

This lint checks for .to_string() method calls on values of type &str.

Why restrict this?

The to_string method is also used on other types to convert them to a string. When called on a &str it turns the &str into the owned variant String, which can be more specifically expressed with .to_owned().

Example

let _ = "str".to_string();

Use instead:

let _ = "str".to_owned();

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

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