Clippy lint · Complexity · checked with Clippy 0.1.99

clippy::redundant_guards: Checks for unnecessary guards in match expressions

What it meansChecks for unnecessary guards in match expressions. It is in the complexity group and warns by default.

Does it matter?

It’s more complex and much less readable. Making it part of the pattern can improve exhaustiveness checking as well.

Code that does something simple in a complicated way. Warns by default.

How to fix it

Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:

Flagged

match x {
    Some(x) if matches!(x, Some(1)) => ..,
    Some(x) if x == Some(2) => ..,
    _ => todo!(),
}

Write this instead

match x {
    Some(Some(1)) => ..,
    Some(Some(2)) => ..,
    _ => todo!(),
}

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
redundant_guards = "allow"

One run

cargo clippy -- -A clippy::redundant-guards

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

nofixed by cargo clippy --fix

1.73.0added in Rust

Clippy's own documentation

What it does

Checks for unnecessary guards in match expressions.

Why is this bad?

It’s more complex and much less readable. Making it part of the pattern can improve exhaustiveness checking as well.

Example

match x {
    Some(x) if matches!(x, Some(1)) => ..,
    Some(x) if x == Some(2) => ..,
    _ => todo!(),
}

Use instead:

match x {
    Some(Some(1)) => ..,
    Some(Some(2)) => ..,
    _ => todo!(),
}

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

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