Clippy lints / Pedantic
Clippy lint · Pedantic · checked with Clippy 0.1.99
clippy::unnested_or_patterns: unnested or-patterns
What it meansChecks for unnested or-patterns, e.g., Some(0) | Some(2) and suggests replacing the pattern with a nested one, Some(0 | 2). Another way to think of this is that it rewrites patterns in disjunctive normal form (DNF) into conjunctive normal form (CNF). It is in the pedantic group and off by default.
What you see
warning: unnested or-patterns --> main.rs:2:12 | 2 | if let Some(0) | Some(2) = Some(0) {} | ^^^^^^^^^^^^^^^^^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#unnested_or_patterns = note: `-W clippy::unnested-or-patterns` implied by `-W clippy::pedantic` help: nest the patterns | 2 - if let Some(0) | Some(2) = Some(0) {} 2 + if let Some(0 | 2) = 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?
In the example above, Some is repeated, which unnecessarily complicates the pattern.
Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.
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
fn main() {
if let Some(0) | Some(2) = Some(0) {}
}
Write this instead
fn main() {
if let Some(0 | 2) = Some(0) {}
}
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]
unnested_or_patterns = "warn"In code
#![warn(clippy::unnested_or_patterns)]One run
cargo clippy -- -W clippy::unnested-or-patternsThe [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 unnested or-patterns, e.g., Some(0) | Some(2) and
suggests replacing the pattern with a nested one, Some(0 | 2).
Another way to think of this is that it rewrites patterns in disjunctive normal form (DNF) into conjunctive normal form (CNF).
Why is this bad?
In the example above, Some is repeated, which unnecessarily complicates the pattern.
Example
fn main() {
if let Some(0) | Some(2) = Some(0) {}
}
Use instead:
fn main() {
if let Some(0 | 2) = 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
- too_many_linesChecks for functions with a large amount of lines
- missing_errors_docChecks the doc comments of publicly visible functions that return a Result type and warns if there is no # Errors section
- must_use_candidateChecks for public functions that have no #[must_use] attribute, but return something not already marked must-use, have no mutable arg and mutate no statics
- unnecessary_semicolonChecks for the presence of a semicolon at the end of a match or if statement evaluating to ()
- unnecessary_trailing_commaunnecessary trailing comma
- unnecessary_wrapsthis function's return value is unnecessarily wrapped by `Option`
- unreadable_literallong literal lacking separators
- unsafe_derive_deserializeChecks for deriving serde::Deserialize on a type that has methods using unsafe
- unused_asyncunused `async` for function with no await statements
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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