Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::map_collect_result_unit: `.map().collect()` can be replaced with `.try_for_each()`
What it meansChecks for usage of _.map(_).collect::<Result<(), _>(). It is in the style group and warns by default.
What you see
warning: `.map().collect()` can be replaced with `.try_for_each()` --> main.rs:3:1 | 3 | (0..3).map(|t| Err(t)).collect::<Result<(), _>>(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `(0..3).try_for_each(|t| Err(t))` | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#map_collect_result_unit = note: `#[warn(clippy::map_collect_result_unit)]` 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?
Using try_for_each instead is more readable and idiomatic.
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).map(|t| Err(t)).collect::<Result<(), _>>();
Write this instead
(0..3).try_for_each(|t| Err(t));
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::map_collect_result_unit)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
map_collect_result_unit = "allow"One run
cargo clippy -- -A clippy::map-collect-result-unitThe [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 _.map(_).collect::<Result<(), _>().
Why is this bad?
Using try_for_each instead is more readable and idiomatic.
Example
(0..3).map(|t| Err(t)).collect::<Result<(), _>>();
Use instead:
(0..3).try_for_each(|t| Err(t));
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
- manual_slice_fillmanually filling a slice
- manual_while_let_someyou seem to be trying to pop elements from a `Vec` in a loop
- map_cloneyou are using an explicit closure for copying elements
- match_like_matches_macromatch expression looks like `matches!` macro
- match_overlapping_armsome ranges overlap
- match_ref_patsChecks for matches where all arms match a reference, suggesting to remove the reference and deref the matched expression instead
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?