Clippy lint · Complexity · checked with Clippy 0.1.99

clippy::needless_question_mark: Suggests replacing Ok(x?) or Some(x?) with x in return positions where the ? operator is not needed to convert the type of x

What it meansSuggests replacing Ok(x?) or Some(x?) with x in return positions where the ? operator is not needed to convert the type of x. It is in the complexity group and warns by default.

Does it matter?

There’s no reason to use ? to short-circuit when execution of the body will end there anyway.

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 f(s: &str) -> Option<usize> {
    Some(s.find('x')?)
}

fn g(s: &str) -> Result<usize, ParseIntError> {
    Ok(s.parse()?)
}

Write this instead

fn f(s: &str) -> Option<usize> {
    s.find('x')
}

fn g(s: &str) -> Result<usize, ParseIntError> {
    s.parse()
}

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
needless_question_mark = "allow"

One run

cargo clippy -- -A clippy::needless-question-mark

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

1.51.0added in Rust

Clippy's own documentation

What it does

Suggests replacing Ok(x?) or Some(x?) with x in return positions where the ? operator is not needed to convert the type of x.

Why is this bad?

There’s no reason to use ? to short-circuit when execution of the body will end there anyway.

Example

fn f(s: &str) -> Option<usize> {
    Some(s.find('x')?)
}

fn g(s: &str) -> Result<usize, ParseIntError> {
    Ok(s.parse()?)
}

Use instead:

fn f(s: &str) -> Option<usize> {
    s.find('x')
}

fn g(s: &str) -> Result<usize, ParseIntError> {
    s.parse()
}

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

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