rust-lang / rust-lang/rust-clippy
`manual_str_repeat` should trigger for `repeat_n` with msrv 1.82
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Description
Summary
Since Rust 1.82.0 users can replace std::iter::repeat(x).take(m).collect::<String>() by the (almost equivalent) std::iter::repeat_n(x,m).collect::<String>(). Both are manual versions of string repeat, but only the former emits a warning.
I would be happy to try to contribute a PR for this if the maintainers agree that this is a false negative.
Thanks for clippy, it's the best!
Lint Name
manual_str_repeat
Reproducer
I tried this code:
fn main() {
let text: String = std::iter::repeat_n('a',5).collect();
println!("{text}");
}
I expected to see this happen:
Checking playground v0.0.1 (/playground)
warning: manual implementation of `str::repeat` using iterators
--> src/main.rs:2:24
|
2 | let text: String = std::iter::repeat_n('a',5).collect();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `"a".repeat(5)`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_str_repeat
= note: `#[warn(clippy::manual_str_repeat)]` on by default
Instead, this happened:
(no warning emitted)
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start at the manual_str_repeat lint entry point and reproduce the issue with the Rust 1.82 repeat_n example from the report. Compare its behavior with the existing repeat(...).take(...) case. Done means the shown repeat_n pattern emits the manual_str_repeat warning and suggests "a".repeat(5).
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 55/100