Clippy lint · Complexity · checked with Clippy 0.1.99

clippy::double_parens: unnecessary parentheses

What it meansChecks for unnecessary double parentheses. It is in the complexity group and warns by default.

What you see

warning: unnecessary parentheses
 --> main.rs:4:5
  |
4 |     ((0))
  |     ^^^^^ help: remove them: `(0)`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#double_parens
  = note: `#[warn(clippy::double_parens)]` 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?

This makes code harder to read and might indicate a mistake.

Code that does something simple in a complicated way. 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

fn simple_double_parens() -> i32 {
    ((0))
}

foo((0));

Write this instead

fn simple_no_parens() -> i32 {
    (0)
}

foo(0);

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
double_parens = "allow"

One run

cargo clippy -- -A clippy::double-parens

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.

Complexitygroup

warndefault level

yesfixed by cargo clippy --fix

pre 1.29.0added in Rust

Clippy's own documentation

What it does

Checks for unnecessary double parentheses.

Why is this bad?

This makes code harder to read and might indicate a mistake.

Example

fn simple_double_parens() -> i32 {
    ((0))
}

foo((0));

Use instead:

fn simple_no_parens() -> i32 {
    (0)
}

foo(0);

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

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