Clippy lints / Complexity
Clippy lint · Complexity · checked with Clippy 0.1.99
clippy::iter_kv_map: Checks for iterating a map (HashMap or BTreeMap) and ignoring either the keys or values
What it meansChecks for iterating a map (HashMap or BTreeMap) and ignoring either the keys or values. It is in the complexity group and warns by default.
Does it matter?
Readability. There are keys and values methods that can be used to express that we only need the keys or the values.
Code that does something simple in a complicated way. Warns by default.
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
let map: HashMap<u32, u32> = HashMap::new();
let values = map.iter().map(|(_, value)| value).collect::<Vec<_>>();
Write this instead
let map: HashMap<u32, u32> = HashMap::new();
let values = map.values().collect::<Vec<_>>();
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::iter_kv_map)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
iter_kv_map = "allow"One run
cargo clippy -- -A clippy::iter-kv-mapThe [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
Clippy's own documentation
What it does
Checks for iterating a map (HashMap or BTreeMap) and
ignoring either the keys or values.
Why is this bad?
Readability. There are keys and values methods that
can be used to express that we only need the keys or the values.
Example
let map: HashMap<u32, u32> = HashMap::new();
let values = map.iter().map(|(_, value)| value).collect::<Vec<_>>();
Use instead:
let map: HashMap<u32, u32> = HashMap::new();
let values = map.values().collect::<Vec<_>>();
Configuration
-
msrv: The minimum rust version that the project supports. Defaults to therust-versionfield inCargo.toml(default:
current version)
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- too_many_argumentsChecks for functions with too many parameters
- clone_on_copyusing `clone` on type `u64` which implements the `Copy` trait
- type_complexityChecks for types used in structs, parameters and let declarations above a certain complexity threshold
- inspect_for_eachcalled `inspect(..).for_each(..)` on an `Iterator`
- int_plus_oneunnecessary `>= y + 1` or `x - 1 >=`
- iter_countcalled `.iter().count()` on a `Vec`
- let_with_type_underscorevariable declared with type underscore
- manual_abs_diffDetects patterns like if a > b { a - b } else { b - a } and suggests using a.abs_diff(b)
- manual_c_str_literalsChecks for the manual creation of C strings (a string with a NUL byte at the end), either through one of the CStr constructor functions, or more plainly by calling .as_ptr() on a (byte) string literal with a hardcoded \0 byte at the end
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
Up next
Related lintclippy::too_many_argumentsChecks for functions with too many parametersRead it next →Did this answer your question?