Clippy lint · Suspicious · checked with Clippy 0.1.99

clippy::no_effect_replace: replacing text with itself

What it meansChecks for replace statements which have no effect. It is in the suspicious group and warns by default.

What you see

warning: replacing text with itself
 --> main.rs:3:1
  |
3 | "1234".replace("12", "12");
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#no_effect_replace
  = note: `#[warn(clippy::no_effect_replace)]` 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?

It’s either a mistake or confusing.

Code that is most likely wrong or useless. Warns by default.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

"1234".replace("12", "12");
"1234".replacen("12", "12", 1);

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
no_effect_replace = "allow"

One run

cargo clippy -- -A clippy::no-effect-replace

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.

Suspiciousgroup

warndefault level

nofixed by cargo clippy --fix

1.63.0added in Rust

Clippy's own documentation

What it does

Checks for replace statements which have no effect.

Why is this bad?

It’s either a mistake or confusing.

Example

"1234".replace("12", "12");
"1234".replacen("12", "12", 1);

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

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