Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::unnecessary_fold: this `.fold` can be written more succinctly using another method
What it meansChecks for usage of fold when a more succinct alternative exists. Specifically, this checks for folds which could be replaced by any, all, sum or product. It is in the style group and warns by default.
What you see
warning: this `.fold` can be written more succinctly using another method --> main.rs:3:8 | 3 | (0..3).fold(false, |acc, x| acc || x > 2); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `any(|x| x > 2)` | = note: the `any` method is short circuiting and may change the program semantics if the iterator has side effects = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#unnecessary_fold = note: `#[warn(clippy::unnecessary_fold)]` on by default
Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.
Does it matter?
Readability.
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
(0..3).fold(false, |acc, x| acc || x > 2);
Write this instead
(0..3).any(|x| x > 2);
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_fold)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
unnecessary_fold = "allow"One run
cargo clippy -- -A clippy::unnecessary-foldThe [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 fold when a more succinct alternative exists.
Specifically, this checks for folds which could be replaced by any, all,
sum or product.
Why is this bad?
Readability.
Example
(0..3).fold(false, |acc, x| acc || x > 2);
Use instead:
(0..3).any(|x| x > 2);
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
- toplevel_ref_arg`ref` directly on a function parameter does not prevent taking ownership of the passed argument. Consider using a reference type instead
- trim_split_whitespacefound call to `str::trim` before `str::split_whitespace`
- unnecessary_fallible_conversionsuse of a fallible conversion when an infallible one could be used
- unnecessary_lazy_evaluationsunnecessary closure used to substitute value for `Option::None`
- unnecessary_map_orthis `map_or` can be simplified
- unnecessary_mut_passedDetects passing a mutable reference to a function that only requires an immutable reference
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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