Redundant closure lint recommends incorrect code

[iajoiner]

Summary

This is probably a variant of #3071 or #7435. This error is probably dependent on PyO3 which is why I have filed an issue there as well as PyO3/pyo3#2988.

The reason why it is necessary to file an issue here is that the suggestion doesn't actually fix the issue. In fact the same issue exists after refactoring the code according to the suggestion. The next suggestion is for us to directly use Vec::new as a function which causes an error.

Lint Name

redundant-closure

Reproducer

I tried this code:

use pyo3::prelude::*;

#[pyfunction]
#[pyo3(signature = (
    _data = vec![],
))]
pub fn foo(
    _data: Vec<i32>,
) {
}

I saw this happen:

Checking pycatch v0.1.0 (/home/iajoiner/Documents/tests/pycatch)
warning: redundant closure
 --> src/main.rs:5:13
  |
5 |       _data = vec![],
  |  _____________^
6 | | ))]
7 | | pub fn foo(
8 | |     _data: Vec<i32>,
  | |___________________^ help: replace the closure with `Vec::new`: `std::vec::Vec::new`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_closure
  = note: `#[warn(clippy::redundant_closure)]` on by default

warning: `pycatch` (bin "pycatch") generated 1 warning (run `cargo clippy --fix --bin "pycatch"` to apply 1 suggestion)
    Finished dev [unoptimized + debuginfo] target(s) in 0.05s

I expected to see this happen:

Version

rustc 1.67.1 (d5a82bbd2 2023-02-07)
binary: rustc
commit-hash: d5a82bbd26e1ad8b7401f6a718a9c57c96905483
commit-date: 2023-02-07
host: x86_64-unknown-linux-gnu
release: 1.67.1
LLVM version: 15.0.6

Additional Labels

• I-suggestion-causes-error

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[iajoiner]

@rustbot label I-suggestion-causes-error

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[iajoiner]

Minimal example added. This is a weird error that is preventing Python bindings of Apache Arrow Datafusion from using clippy in our CI.

[iajoiner]

Corresponding issue on PyO3: PyO3/pyo3#2988

[iajoiner]

Closed as this is not a Clippy issue. It is a PyO3 one.

[davidhewitt]

Despite having fixed this in PyO3, I would be interested to hear if there are techniques to hint clippy that the PyO3 code is generated and users can't easily correct it.