Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::match_like_matches_macro: match expression looks like `matches!` macro
What it meansChecks for match or if let expressions producing a bool that could be written using matches! It is in the style group and warns by default.
What you see
warning: match expression looks like `matches!` macro --> main.rs:5:9 | 5 | let a = match x { | _________^ 6 | | Some(0) => true, 7 | | _ => false, 8 | | }; | |_^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#match_like_matches_macro = note: `#[warn(clippy::match_like_matches_macro)]` on by default help: use `matches!` directly | 5 - let a = match x { 6 - Some(0) => true, 7 - _ => false, 8 - }; 5 + let a = matches!(x, Some(0)); |
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?
Readability and needless complexity.
Code that works but is not idiomatic Rust. Warns by default.
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 x = Some(5);
let a = match x {
Some(0) => true,
_ => false,
};
let a = if let Some(0) = x {
true
} else {
false
};
Write this instead
let x = Some(5);
let a = matches!(x, Some(0));
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::match_like_matches_macro)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
match_like_matches_macro = "allow"One run
cargo clippy -- -A clippy::match-like-matches-macroThe [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.
Settings in clippy.toml
msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml
Clippy's own documentation
What it does
Checks for match or if let expressions producing a
bool that could be written using matches!
Why is this bad?
Readability and needless complexity.
Known problems
This lint falsely triggers, if there are arms with
cfg attributes that remove an arm evaluating to false.
Example
let x = Some(5);
let a = match x {
Some(0) => true,
_ => false,
};
let a = if let Some(0) = x {
true
} else {
false
};
Use instead:
let x = Some(5);
let a = matches!(x, Some(0));
Configuration
-
msrv: The minimum rust version that the project supports. Defaults to therust-versionfield inCargo.toml(default:
current version)
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- needless_returnunneeded `return` statement
- new_without_defaultChecks for public types with a pub fn new() -> Self method and no implementation of Default
- len_zeroChecks for getting the length of something via .len() just to compare to zero, and suggests using .is_empty() where applicable
- manual_while_let_someyou seem to be trying to pop elements from a `Vec` in a loop
- map_cloneyou are using an explicit closure for copying elements
- map_collect_result_unit`.map().collect()` can be replaced with `.try_for_each()`
- match_overlapping_armsome ranges overlap
- match_ref_patsChecks for matches where all arms match a reference, suggesting to remove the reference and deref the matched expression instead
- match_result_okChecks for unnecessary ok() in while let
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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