Clippy Lints

Guide to Clippy for code quality.

When to Use This Skill

• Running Clippy checks
• Fixing lint warnings
• Configuring lint levels
• Enabling/disabling lints

Running Clippy

cargo clippy
cargo clippy --fix
cargo clippy -- -D warnings
cargo clippy --all-targets --all-features
cargo clippy --workspace -- -D warnings

More flags and CI patterns: references/running-clippy.md.

Allow / Warn / Deny

Use real lint names (not category placeholders):

#[allow(clippy::redundant_clone)]
fn cache_key(s: &String) -> String {
    s.clone()
}

#[deny(clippy::unwrap_used)]
fn parse(s: &str) -> i32 {
    s.parse().unwrap()
}

// Crate-wide
#![warn(clippy::pedantic)]
#![allow(clippy::module_name_repetitions)]

Levels: allow < warn < deny < forbid.

Lint Groups

cargo clippy -- -W clippy::pedantic
cargo clippy -- -W clippy::nursery
cargo clippy -- -A clippy::all -W clippy::perf

# Cargo.toml
[lints.clippy]
all = "deny"
pedantic = "warn"
nursery = "allow"
redundant_clone = "deny"

Common Fixes

Unnecessary clone

// Triggers clippy::redundant_clone when a borrow suffices
let x = some_value.clone();
let x = &some_value;

Redundant closure

.iter().map(|x| foo(x))
.iter().map(foo)

Needless collect

// Prefer iterating without an intermediate Vec when possible
let v: Vec<_> = iter.collect();
for x in v { /* ... */ }
for x in iter { /* ... */ }

Reference Map

• references/running-clippy.md — Commands and flags
• references/common-lints.md — Named lints by category
• references/configuring.md — Attributes, Cargo.toml, clippy.toml

Key References

• Clippy Documentation
• Clippy Lints
• Configuring Clippy