rust-lang / rust-lang/rust-clippy
`needless_borrow` suggestion causes error when using conditional compilation
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Description
Summary
Clippy falsely suggests to remove borrow when using conditional compilation.
Based on the example below, if we listen to clippy and remove borrow (&path -> path), code will compile on any OS but Windows. On Windows however it will throw this error: borrow of moved value: path
Lint Name
clippy::needless_borrow
Reproducer
I tried this code:
use std::{fs, path::PathBuf};
fn main() {
let path = PathBuf::from(".").canonicalize().unwrap();
fs::write(&path, "test").ok();
#[cfg(target_os = "windows")]
println!("{:?}", path);
}
I saw this happen:
main.rs(6, 12): change this to: `path`
I expected to see this happen:
No suggestion at all
Version
rustc 1.73.0 (cc66ad468 2023-10-03)
binary: rustc
commit-hash: cc66ad468955717ab92600c770da8c1601a4ff33
commit-date: 2023-10-03
host: aarch64-apple-darwin
release: 1.73.0
LLVM version: 17.0.2
Additional Labels
@rustbot label I-suggestion-causes-error
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 with the clippy::needless_borrow implementation and reproduce the supplied Rust example with the Windows-only println!. Trace how conditional compilation affects the borrow analysis; done means the lint no longer emits a suggestion that causes a borrow-of-moved-value error on Windows.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers, devtools
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100