Clippy lint · Nursery · checked with Clippy 0.1.99

clippy::option_if_let_else: Lints usage of if let Some(v) =

What it meansLints usage of if let Some(v) = ... { y } else { x } and match .. { Some(v) => y, None/_ => x } which are more idiomatically done with Option::map_or (if the else bit is a pure expression) or Option::map_or_else (if the else bit is an impure expression). It is in the nursery group and off by default.

Does it matter?

Using the dedicated functions of the Option type is clearer and more concise than an if let expression.

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 _ = if let Some(foo) = optional {
    foo
} else {
    5
};
let _ = match optional {
    Some(val) => val + 1,
    None => 5
};
let _ = if let Some(foo) = optional {
    foo
} else {
    let y = do_complicated_function();
    y*y
};

Write this instead

let _ = optional.map_or(5, |foo| foo);
let _ = optional.map_or(5, |val| val + 1);
let _ = optional.map_or_else(||{
    let y = do_complicated_function();
    y*y
}, |foo| foo);

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]
option_if_let_else = "warn"

In code

#![warn(clippy::option_if_let_else)]

One run

cargo clippy -- -W clippy::option-if-let-else

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

1.47.0added in Rust

Clippy's own documentation

What it does

Lints usage of if let Some(v) = ... { y } else { x } and match .. { Some(v) => y, None/_ => x } which are more idiomatically done with Option::map_or (if the else bit is a pure expression) or Option::map_or_else (if the else bit is an impure expression).

Why is this bad?

Using the dedicated functions of the Option type is clearer and more concise than an if let expression.

Notes

This lint uses a deliberately conservative metric for checking if the inside of either body contains loop control expressions break or continue (which cannot be used within closures). If these are found, this lint will not be raised.

Example

let _ = if let Some(foo) = optional {
    foo
} else {
    5
};
let _ = match optional {
    Some(val) => val + 1,
    None => 5
};
let _ = if let Some(foo) = optional {
    foo
} else {
    let y = do_complicated_function();
    y*y
};

should be

let _ = optional.map_or(5, |foo| foo);
let _ = optional.map_or(5, |val| val + 1);
let _ = optional.map_or_else(||{
    let y = do_complicated_function();
    y*y
}, |foo| foo);

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

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