Clippy lint · Nursery · checked with Clippy 0.1.99

clippy::use_self: unnecessary structure name repetition

What it meansChecks for unnecessary repetition of structure name when a replacement with Self is applicable. It is in the nursery group and off by default.

What you see

warning: unnecessary structure name repetition
 --> main.rs:5:17
  |
5 |     fn new() -> Foo {
  |                 ^^^ help: use the applicable keyword: `Self`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#use_self
  = note: `-W clippy::use-self` implied by `-W clippy::nursery`

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?

Unnecessary repetition. Mixed use of Self and struct name feels inconsistent.

New lints still being finished. Off by default and may have false positives.

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 Foo;
impl Foo {
    fn new() -> Foo {
        Foo {}
    }
}

Write this instead

struct Foo;
impl Foo {
    fn new() -> Self {
        Self {}
    }
}

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]
use_self = "warn"

In code

#![warn(clippy::use_self)]

One run

cargo clippy -- -W clippy::use-self

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.

Settings in clippy.toml

msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml
recursive-self-in-type-definitions: Whether the type itself in a struct or enum should be replaced with Self when encountering recursive types.

Nurserygroup

allowdefault level

yesfixed by cargo clippy --fix

pre 1.29.0added in Rust

Clippy's own documentation

What it does

Checks for unnecessary repetition of structure name when a replacement with Self is applicable.

Why is this bad?

Unnecessary repetition. Mixed use of Self and struct name feels inconsistent.

Known problems

Unaddressed false negative in fn bodies of trait implementations

Example

struct Foo;
impl Foo {
    fn new() -> Foo {
        Foo {}
    }
}

could be

struct Foo;
impl Foo {
    fn new() -> Self {
        Self {}
    }
}

Configuration

msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml

(default: current version)
recursive-self-in-type-definitions: Whether the type itself in a struct or enum should be replaced with Self when encountering recursive types.

(default: true)

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

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