Clippy lints / Pedantic
Clippy lint · Pedantic · checked with Clippy 0.1.99
clippy::unused_self: unused `self` argument
What it meansChecks methods that contain a self argument but don’t use it It is in the pedantic group and off by default.
What you see
warning: unused `self` argument --> main.rs:5:15 | 5 | fn method(&self) {} | ^^^^^ | = help: consider refactoring to an associated function = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#unused_self = note: `-W clippy::unused-self` implied by `-W clippy::pedantic`
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 may be clearer to define the method as an associated function instead of an instance method if it doesn’t require self.
Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.
How to fix it
Clippy does not fix this one automatically. Change the code by hand:
Flagged
struct A;
impl A {
fn method(&self) {}
}
Write this instead
struct A;
impl A {
fn method() {}
}
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]
unused_self = "warn"In code
#![warn(clippy::unused_self)]One run
cargo clippy -- -W clippy::unused-selfThe [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
avoid-breaking-exported-api: Suppress lints whenever the suggested change would cause breakage for other crates.
Clippy's own documentation
What it does
Checks methods that contain a self argument but don’t use it
Why is this bad?
It may be clearer to define the method as an associated function instead
of an instance method if it doesn’t require self.
Example
struct A;
impl A {
fn method(&self) {}
}
Could be written:
struct A;
impl A {
fn method() {}
}
Configuration
-
avoid-breaking-exported-api: Suppress lints whenever the suggested change would cause breakage for other crates.(default:
true)
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
- unsafe_derive_deserializeChecks for deriving serde::Deserialize on a type that has methods using unsafe
- unused_asyncunused `async` for function with no await statements
- unused_async_trait_implunused `async` for async trait impl function with no `.await` statements
- used_underscore_bindingused underscore-prefixed binding
- used_underscore_itemsused underscore-prefixed item
- verbose_bit_maskChecks for bit masks that can be replaced by a call to trailing_zeros
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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