Clippy lint · Restriction · checked with Clippy 0.1.99

clippy::unnecessary_rest_pattern: unnecessary rest pattern (`..`)

What it meansDisallow the use of rest patterns that don’t capture any fields. It is in the restriction group and off by default.

What you see

warning: unnecessary rest pattern (`..`)
  --> main.rs:11:5
   |
11 | let S { a, b, c, .. } = s;
   |     ^^^^^^^^^^^^^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#unnecessary_rest_pattern
   = note: requested on the command line with `-W clippy::unnecessary-rest-pattern`
help: consider removing the unnecessary rest pattern (`..`)
   |
11 - let S { a, b, c, .. } = s;
11 + let S { a, b, c,  } = s;
   |

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 might lead to unhandled fields when the struct changes.

Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.

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

struct S {
    a: u8,
    b: u8,
    c: u8,
}

let s = S { a: 1, b: 2, c: 3 };

let S { a, b, c, .. } = s;

Write this instead

struct S {
    a: u8,
    b: u8,
    c: u8,
}

let s = S { a: 1, b: 2, c: 3 };

let S { a, b, c } = s;

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]
unnecessary_rest_pattern = "warn"

In code

#![warn(clippy::unnecessary_rest_pattern)]

One run

cargo clippy -- -W clippy::unnecessary-rest-pattern

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.

Restrictiongroup

allowdefault level

yesfixed by cargo clippy --fix

1.99.0added in Rust

Clippy's own documentation

What it does

Disallow the use of rest patterns that don’t capture any fields.

Why restrict this?

It might lead to unhandled fields when the struct changes.

Example

struct S {
    a: u8,
    b: u8,
    c: u8,
}

let s = S { a: 1, b: 2, c: 3 };

let S { a, b, c, .. } = s;

Use instead:

struct S {
    a: u8,
    b: u8,
    c: u8,
}

let s = S { a: 1, b: 2, c: 3 };

let S { a, b, c } = s;

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

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