Clippy lint · Suspicious · checked with Clippy 0.1.99

clippy::manual_unwrap_or_default: match can be simplified with `.unwrap_or_default()`

What it meansChecks if a match or if let expression can be simplified using .unwrap_or_default(). It is in the suspicious group and warns by default.

What you see

warning: match can be simplified with `.unwrap_or_default()`
 --> main.rs:4:17
  |
4 |   let y: String = match x {
  |  _________________^
5 | |     Some(v) => v,
6 | |     None => String::new(),
7 | | };
  | |_^ help: replace it with: `x.unwrap_or_default()`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#manual_unwrap_or_default
  = note: `#[warn(clippy::manual_unwrap_or_default)]` on by default

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

It can be done in one call with .unwrap_or_default().

Code that is most likely wrong or useless. 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

let x: Option<String> = Some(String::new());
let y: String = match x {
    Some(v) => v,
    None => String::new(),
};

let x: Option<Vec<String>> = Some(Vec::new());
let y: Vec<String> = if let Some(v) = x {
    v
} else {
    Vec::new()
};

Write this instead

let x: Option<String> = Some(String::new());
let y: String = x.unwrap_or_default();

let x: Option<Vec<String>> = Some(Vec::new());
let y: Vec<String> = x.unwrap_or_default();

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
manual_unwrap_or_default = "allow"

One run

cargo clippy -- -A clippy::manual-unwrap-or-default

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.

Suspiciousgroup

warndefault level

yesfixed by cargo clippy --fix

1.79.0added in Rust

Clippy's own documentation

What it does

Checks if a match or if let expression can be simplified using .unwrap_or_default().

Why is this bad?

It can be done in one call with .unwrap_or_default().

Example

let x: Option<String> = Some(String::new());
let y: String = match x {
    Some(v) => v,
    None => String::new(),
};

let x: Option<Vec<String>> = Some(Vec::new());
let y: Vec<String> = if let Some(v) = x {
    v
} else {
    Vec::new()
};

Use instead:

let x: Option<String> = Some(String::new());
let y: String = x.unwrap_or_default();

let x: Option<Vec<String>> = Some(Vec::new());
let y: Vec<String> = x.unwrap_or_default();

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

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