Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::unneeded_struct_pattern: struct pattern is not needed for a unit variant
What it meansChecks for struct patterns that match against unit variant. It is in the style group and warns by default.
What you see
warning: struct pattern is not needed for a unit variant --> main.rs:5:9 | 5 | None { .. } => 0, | ^^^^^^^ help: remove the struct pattern | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#unneeded_struct_pattern = note: `#[warn(clippy::unneeded_struct_pattern)]` 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?
Struct pattern { } or { .. } is not needed for unit variant.
Code that works but is not idiomatic Rust. 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
match Some(42) {
Some(v) => v,
None { .. } => 0,
};
// Or
match Some(42) {
Some(v) => v,
None { } => 0,
};
Write this instead
match Some(42) {
Some(v) => v,
None => 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::unneeded_struct_pattern)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
unneeded_struct_pattern = "allow"One run
cargo clippy -- -A clippy::unneeded-struct-patternThe [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.
Clippy's own documentation
What it does
Checks for struct patterns that match against unit variant.
Why is this bad?
Struct pattern { } or { .. } is not needed for unit variant.
Example
match Some(42) {
Some(v) => v,
None { .. } => 0,
};
// Or
match Some(42) {
Some(v) => v,
None { } => 0,
};
Use instead:
match Some(42) {
Some(v) => v,
None => 0,
};
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
- unnecessary_map_orthis `map_or` can be simplified
- unnecessary_mut_passedDetects passing a mutable reference to a function that only requires an immutable reference
- unnecessary_owned_empty_stringsusage of `&String::new()` for a function expecting a `&str` argument
- unsafe_removed_from_nameChecks for imports that remove “unsafe” from an item’s name
- unused_enumerate_indexyou seem to use `.enumerate()` and immediately discard the index
- unused_unitunneeded unit expression
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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