needless_borrow suggestion doesn't go far enough

[ijackson]

Description

In this code:

fn main() {
    let mut w = [42];
    (&mut w[..]).copy_from_slice(&[43]);
    println!("{:?}", &w);
}

clippy suggests as follows:

4 |     (&mut w[..]).copy_from_slice(&[43]);
  |     ^^^^^^^^^^^^ help: change this to: `w[..]`

This is correct as far as it goes. But a better suggestion would be just w, implying

    w.copy_from_slice(&[43]);

which also DTRT.

FTR, stable doesn't issue this lint in this situation at all. #8367 and #8355 may be relevant.

Version

rustcargo@zealot:/home/ian/Rustup/Arti/experiments$ rustc -Vv
rustc 1.60.0-nightly (a00e130da 2022-01-29)
binary: rustc
commit-hash: a00e130dae74a213338e2b095ec855156d8f3d8a
commit-date: 2022-01-29
host: x86_64-unknown-linux-gnu
release: 1.60.0-nightly
LLVM version: 13.0.0
rustcargo@zealot:/home/ian/Rustup/Arti/experiments$

Additional Labels

No response

[matthiaskrgr]

Hmm, looks like false negative in https://rust-lang.github.io/rust-clippy/master/index.html#redundant_slicing then?