Clippy lints / Complexity
Clippy lint · Complexity · checked with Clippy 0.1.99
clippy::unnecessary_operation: Checks for expression statements that can be reduced to a sub-expression
What it meansChecks for expression statements that can be reduced to a sub-expression. It is in the complexity group and warns by default.
Does it matter?
Expressions by themselves often have no side-effects. Having such expressions reduces readability.
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
compute_array()[0];
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_operation)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
unnecessary_operation = "allow"One run
cargo clippy -- -A clippy::unnecessary-operationThe [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 expression statements that can be reduced to a sub-expression.
Why is this bad?
Expressions by themselves often have no side-effects. Having such expressions reduces readability.
Example
compute_array()[0];
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_literal_unwrapused `unwrap()` on `Some` value
- 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_sort_byChecks for usage of Vec::sort_by passing in a closure which compares the two arguments, either directly or indirectly
- unnecessary_unwrapChecks for calls of unwrap[_err]() that cannot fail
- unnecessary_unwrap_uncheckedusage of `unwrap_unchecked` when an `_unchecked` variant of the function exists
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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Related lintclippy::too_many_argumentsChecks for functions with too many parametersRead it next →Did this answer your question?