Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::duplicate_underscore_argument: `a` already exists, having another argument having almost the same name makes code comprehension and documentation more difficult
What it meansChecks for function arguments having the similar names differing by an underscore. It is in the style group and warns by default.
What you see
warning: `a` already exists, having another argument having almost the same name makes code comprehension and documentation more difficult --> main.rs:3:8 | 3 | fn foo(a: i32, _a: i32) {} | ^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#duplicate_underscore_argument = note: `#[warn(clippy::duplicate_underscore_argument)]` 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?
It affects code readability.
Code that works but is not idiomatic Rust. Warns by default.
How to fix it
Clippy does not fix this one automatically. Change the code by hand:
Flagged
fn foo(a: i32, _a: i32) {}
Write this instead
fn bar(a: i32, _b: i32) {}
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::duplicate_underscore_argument)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
duplicate_underscore_argument = "allow"One run
cargo clippy -- -A clippy::duplicate-underscore-argumentThe [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 function arguments having the similar names differing by an underscore.
Why is this bad?
It affects code readability.
Example
fn foo(a: i32, _a: i32) {}
Use instead:
fn bar(a: i32, _b: i32) {}
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
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- doc_lazy_continuationdoc quote line without `>` marker
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- double_must_usethis function has a `#[must_use]` attribute with no message, but returns a type already considered as `#[must_use]`
- enum_variant_namesvariant name ends with the enum's name
- err_expectcalled `.err().expect()` on a `Result` value
- excessive_precisionfloat has excessive precision
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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