Clippy lint · Style · checked with Clippy 0.1.99

clippy::blocks_in_conditions: Checks for if and match conditions that use blocks containing an expression, statements or conditions that use closures with blocks

What it meansChecks for if and match conditions that use blocks containing an expression, statements or conditions that use closures with blocks. It is in the style group and warns by default.

Does it matter?

Style, using blocks in the condition makes it hard to read.

Code that works but is not idiomatic Rust. 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

if { true } { /* ... */ }

if { let x = somefunc(); x } { /* ... */ }

match { let e = somefunc(); e } {
    // ...
}

Write this instead

if true { /* ... */ }

let res = { let x = somefunc(); x };
if res { /* ... */ }

let res = { let e = somefunc(); e };
match res {
    // ...
}

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
blocks_in_conditions = "allow"

One run

cargo clippy -- -A clippy::blocks-in-conditions

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.

Stylegroup

warndefault level

yesfixed by cargo clippy --fix

1.45.0added in Rust

Clippy's own documentation

What it does

Checks for if and match conditions that use blocks containing an expression, statements or conditions that use closures with blocks.

Why is this bad?

Style, using blocks in the condition makes it hard to read.

Examples

if { true } { /* ... */ }

if { let x = somefunc(); x } { /* ... */ }

match { let e = somefunc(); e } {
    // ...
}

Use instead:

if true { /* ... */ }

let res = { let x = somefunc(); x };
if res { /* ... */ }

let res = { let e = somefunc(); e };
match res {
    // ...
}

Past names

block_in_if_condition_expr
block_in_if_condition_stmt
blocks_in_if_conditions

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

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