Clippy lint · Nursery · checked with Clippy 0.1.99

clippy::useless_let_if_seq: Checks for variable declarations immediately followed by a conditional affectation

What it meansChecks for variable declarations immediately followed by a conditional affectation. It is in the nursery group and off by default.

Does it matter?

This is not idiomatic Rust.

New lints still being finished. Off by default and may have false positives.

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

let foo;

if bar() {
    foo = 42;
} else {
    foo = 0;
}

let mut baz = None;

if bar() {
    baz = Some(42);
}

Write this instead

let foo = if bar() {
    42
} else {
    0
};

let baz = if bar() {
    Some(42)
} else {
    None
};

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
useless_let_if_seq = "warn"

In code

#![warn(clippy::useless_let_if_seq)]

One run

cargo clippy -- -W clippy::useless-let-if-seq

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.

Nurserygroup

allowdefault level

nofixed by cargo clippy --fix

pre 1.29.0added in Rust

Clippy's own documentation

What it does

Checks for variable declarations immediately followed by a conditional affectation.

Why is this bad?

This is not idiomatic Rust.

Example

let foo;

if bar() {
    foo = 42;
} else {
    foo = 0;
}

let mut baz = None;

if bar() {
    baz = Some(42);
}

should be written

let foo = if bar() {
    42
} else {
    0
};

let baz = if bar() {
    Some(42)
} else {
    None
};

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

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