Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::for_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 style group and warns by default.
Does it matter?
Readability. There are keys and values methods that can be used to express that don’t need the values or keys.
Code that works but is not idiomatic Rust. 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
for (k, _) in &map {
..
}
Write this instead
for k in map.keys() {
..
}
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::for_kv_map)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
for_kv_map = "allow"One run
cargo clippy -- -A clippy::for-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.
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 don’t need the values or keys.
Example
for (k, _) in &map {
..
}
could be replaced by
for k in map.keys() {
..
}
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- needless_returnunneeded `return` statement
- new_without_defaultChecks for public types with a pub fn new() -> Self method and no implementation of Default
- len_zeroChecks for getting the length of something via .len() just to compare to zero, and suggests using .is_empty() where applicable
- filter_map_bool_thenChecks for usage of bool::then in Iterator::filter_map
- fn_to_numeric_castcasting function pointer `fun` to `i64`
- fn_to_numeric_cast_with_truncationcasting function pointer `fn1` to `i32`, which truncates the value
- from_over_intoan implementation of `From` is preferred since it gives you `Into<_>` for free where the reverse isn't true
- from_str_radix_10Checks for function invocations of the form primitive::from_str_radix(s, 10)
- get_firstaccessing first element with `x.get(0)`
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
Up next
Related lintclippy::needless_returnunneeded `return` statementRead it next →Did this answer your question?