Clippy lint · Performance · checked with Clippy 0.1.99

clippy::to_string_in_format_args: Checks for ToString::to_string applied to a type that implements Display in a macro that does formatting

What it meansChecks for ToString::to_string applied to a type that implements Display in a macro that does formatting. It is in the performance group and warns by default.

Does it matter?

Since the type implements Display, the use of to_string is unnecessary.

Code that could be written to run faster. 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

println!("error: something failed at {}", Location::caller().to_string());

Write this instead

println!("error: something failed at {}", Location::caller());

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
to_string_in_format_args = "allow"

One run

cargo clippy -- -A clippy::to-string-in-format-args

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.

Performancegroup

warndefault level

yesfixed by cargo clippy --fix

1.58.0added in Rust

Clippy's own documentation

What it does

Checks for ToString::to_string applied to a type that implements Display in a macro that does formatting.

Why is this bad?

Since the type implements Display, the use of to_string is unnecessary.

Example

println!("error: something failed at {}", Location::caller().to_string());

Use instead:

println!("error: something failed at {}", Location::caller());

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

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