Clippy lints / Complexity
Clippy lint · Complexity · checked with Clippy 0.1.99
clippy::unnecessary_sort_by: Checks for usage of Vec::sort_by passing in a closure which compares the two arguments, either directly or indirectly
What it meansChecks for usage of Vec::sort_by passing in a closure which compares the two arguments, either directly or indirectly. It is in the complexity group and warns by default.
Does it matter?
It is more clear to use Vec::sort_by_key (or Vec::sort if possible) than to use Vec::sort_by and a more complicated closure.
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
vec.sort_by(|a, b| a.foo().cmp(&b.foo()));
Write this instead
vec.sort_by_key(|a| a.foo());
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::unnecessary_sort_by)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
unnecessary_sort_by = "allow"One run
cargo clippy -- -A clippy::unnecessary-sort-byThe [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 usage of Vec::sort_by passing in a closure
which compares the two arguments, either directly or indirectly.
Why is this bad?
It is more clear to use Vec::sort_by_key (or Vec::sort if
possible) than to use Vec::sort_by and a more complicated
closure.
Known problems
If the suggested Vec::sort_by_key uses Reverse and it isn’t already
imported by a use statement, then it will need to be added manually.
Example
vec.sort_by(|a, b| a.foo().cmp(&b.foo()));
Use instead:
vec.sort_by_key(|a| a.foo());
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
- unnecessary_map_on_constructorSuggests removing the use of a map() (or map_err()) method when an Option or Result is being constructed
- unnecessary_min_or_max`0` is never greater than `7_u32` and has therefore no effect
- unnecessary_operationChecks for expression statements that can be reduced to a sub-expression
- unnecessary_unwrapChecks for calls of unwrap[_err]() that cannot fail
- unnecessary_unwrap_uncheckedusage of `unwrap_unchecked` when an `_unchecked` variant of the function exists
- unneeded_wildcard_patternthis pattern is unneeded as the `..` pattern can match that element
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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