clippy::needless_bool: Checks for expressions of the form if c { true } else { false } (or vice versa) and suggests using the condition directly

if x {
    false
} else {
    true
}

!x

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

[lints.clippy]
needless_bool = "allow"

cargo clippy -- -A clippy::needless-bool

Clippy's own documentation

What it does

Checks for expressions of the form if c { true } else { false } (or vice versa) and suggests using the condition directly.

Why is this bad?

Redundant code.

Known problems

Maybe false positives: Sometimes, the two branches are painstakingly documented (which we, of course, do not detect), so they may have some value. Even then, the documentation can be rewritten to match the shorter code.

Example

if x {
    false
} else {
    true
}

Use instead:

!x

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

Related lints

• too_many_argumentsChecks for functions with too many parameters
• clone_on_copyusing `clone` on type `u64` which implements the `Copy` trait
• type_complexityChecks for types used in structs, parameters and let declarations above a certain complexity threshold
• match_single_bindingChecks for useless match that binds to only one value
• needless_arbitrary_self_typethe type of the `self` parameter does not need to be arbitrary
• needless_as_bytesneedless call to `as_bytes`
• needless_bool_assignChecks for expressions of the form if c { x = true } else { x = false } (or vice versa) and suggest assigning the variable directly from the condition
• needless_borrowed_referencethis pattern takes a reference on something that is being dereferenced
• needless_ifsChecks for empty if branches with no else branch

All 847 Clippy lints · Rust compiler errors · Cargo.toml checker