`clippy --fix -- -Dwarnings` does not fail on warnings

Summary

I have cargo clippy -- -Dwarnings correctly fail on warnings.

However, cargo clippy --fix -- -Dwarnings succeeds on warnings (that is, exists with 0 error code).

I'm not sure whether https://github.com/rust-lang/cargo/issues/8424 will help here. Cc #1209 where I got the idea for -Dwarnings.

I'm not sure whether this is a bug or a surprising behavior, but if it is intentional, it should be
mentioned in cargo clippy --help or somewhere, as well as somewhere in https://doc.rust-lang.org/nightly/clippy/usage.html#command-line.

Reproducer

Any code with warnings, e.g.

#![allow(clippy::style)]

#[warn(clippy::double_neg)]
fn main() {
    let x = 1;
    let y = --x;
}

Version

rustc 1.83.0-nightly (7042c269c 2024-09-23)
binary: rustc
commit-hash: 7042c269c166191cd5d8daf0409890903df7af57
commit-date: 2024-09-23
host: aarch64-apple-darwin
release: 1.83.0-nightly
LLVM version: 19.1.0

Additional Labels

No response

Start by reproducing the issue with cargo clippy -- -Dwarnings and cargo clippy --fix -- -Dwarnings using the provided Rust example. Investigate the command-line behavior and determine whether --fix should return a nonzero status for remaining warnings. Done means the behavior is corrected or the difference is documented in cargo clippy --help and the Clippy usage page.