rust-lang / rust-lang/rust-clippy
Clippy fix makes breaking change on warning: usage of `contains_key` followed by `insert` on a `HashMap`
Nobody has claimed this yet.
- Dominant language
- Rust
- Stars
- 13.5k
- Forks
- 2.2k
- Avg merge
- 2d 10h
- Merged PRs (30d)
- 32
Description
Summary
Clippy attempts to fix the warning: usage of contains_key followed by insert on a HashMap
and creates a borrow after move.
Original:
let name = format!("{}/{}", sensor_driver.namespace, sensor_driver.function);
if sensor_drivers.contains_key(&name) {
res.error(format!("Duplicate sensor driver {} in drivers file.", name));
} else {
sensor_drivers.insert(name, sensor_driver);
}
Clippy Fixed:
let name = format!("{}/{}", sensor_driver.namespace, sensor_driver.function);
if let std::collections::hash_map::Entry::Vacant(e) = sensor_drivers.entry(name) {
e.insert(sensor_driver);
} else {
res.error(format!("Duplicate sensor driver {} in drivers file.", name));
}
The Clippy generated code results in name being moved by HashMap::Entry before being borrowed by format!.
Version
rustc 1.81.0 (eeb90cda1 2024-09-04)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: aarch64-apple-darwin
release: 1.81.0
LLVM version: 18.1.7
Additional Labels
No response
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
Locate the Clippy lint that detects contains_key followed by insert, then reproduce the issue with the Rust snippet in the report. Trace the generated HashMap::Entry suggestion and add a regression test showing that the suggested code does not borrow name after it has been moved; done means the fix compiles without the reported borrow-after-move error.
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
- 48/100