Clippy unexpectedly suggests that clone is redundant

[foresterre]

Excerpt of original output of cargo clippy --fix in console-rs/indicatif#547, which suggested to create an issue here:

Checking indicatif v0.17.4 (C:\foresterre\indicatif)
warning: failed to automatically apply fixes suggested by rustc to crate `multi_autodrop`                                                                                

after fixes were automatically applied the compiler reported errors within these files:

  * tests\multi-autodrop.rs

This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag

indicatif pipeline

I tried this code (can probably be made more minimal):

use std::sync::{atomic::AtomicU32, atomic::Ordering, Arc, Mutex, RwLock};

// Reproduction derived from indicatif::MultiProgress and ProgressBar where this Clippy suggestion was found.
// With Clippy 0.1.71 (2023-06-01 d59363a)
// With Rust 1.70.0

#[derive(Clone)]
struct MultiProgress {
    state: Arc<RwLock<State>>,
}

impl Default for MultiProgress {
    fn default() -> Self {
        Self {
            state: Arc::new(RwLock::new(State)),
        }
    }
}

impl MultiProgress {
    fn add(&self, pb: ProgressBar) -> ProgressBar {
        let state = self.state.write().unwrap();
        drop(state);

        pb.set_remote(self.state.clone());
        pb
    }
}

#[derive(Clone)]
struct ProgressBar {
    value: Arc<AtomicU32>,
    remote: Arc<Mutex<Arc<RwLock<State>>>>,
}

impl Default for ProgressBar {
    fn default() -> Self {
        Self {
            value: Arc::new(AtomicU32::new(0)),
            remote: Arc::new(Mutex::new(Arc::new(RwLock::new(State)))),
        }
    }
}

impl ProgressBar {
    fn set_remote(&self, state: Arc<RwLock<State>>) {
        *self.remote.lock().unwrap() = state;
    }

    fn inc(&self, delta: u32) {
        self.value.fetch_add(delta, Ordering::SeqCst);
    }

    fn reset(&self) {
        self.value.fetch_add(0, Ordering::SeqCst);
    }
}

struct State;

fn main() {
    let pb = {
        let m = MultiProgress::default();
        m.add(ProgressBar::default())
        // m is dropped here
    };

    {
        // Clippy faults here: it suggests to remove the clone.
        let pb2 = pb.clone();
        for _ in 0..10 {
            pb2.inc(1);
        }
    }

    pb.reset();
}

Running cargo clippy:

hecking playground v0.0.1 (/playground)
warning: redundant clone
  --> src/main.rs:70:21
   |
70 |         let pb2 = pb.clone();
   |                     ^^^^^^^^ help: remove this
   |
note: cloned value is neither consumed nor mutated
  --> src/main.rs:70:19
   |
70 |         let pb2 = pb.clone();
   |                   ^^^^^^^^^^
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_clone
   = note: `#[warn(clippy::redundant_clone)]` on by default

warning: `playground` (bin "playground") generated 1 warning (run `cargo clippy --fix --bin "playground"` to apply 1 suggestion)
    Finished dev [unoptimized + debuginfo] target(s) in 0.42s

When applying the suggestion:

 Checking playground v0.0.1 (/playground)
error[E0382]: borrow of moved value: `pb`
  --> src/main.rs:76:5
   |
62 |     let pb = {
   |         -- move occurs because `pb` has type `ProgressBar`, which does not implement the `Copy` trait
...
70 |         let pb2 = pb;
   |                   -- value moved here
...
76 |     pb.reset();
   |     ^^^^^^^^^^ value borrowed here after move
   |
help: consider cloning the value if the performance cost is acceptable
   |
70 |         let pb2 = pb.clone();
   |                     ++++++++

For more information about this error, try `rustc --explain E0382`.
error: could not compile `playground` (bin "playground") due to previous error

Meta

rustc --version --verbose:

rustc 1.70.0 (90c541806 2023-05-31)
binary: rustc
commit-hash: 90c541806f23a127002de5b4038be731ba1458ca
commit-date: 2023-05-31
host: x86_64-pc-windows-msvc
release: 1.70.0
LLVM version: 16.0.2

cargo clippy --version --verbose:

clippy 0.1.70 (90c54180 2023-05-31)

Extra

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[foresterre]

Whoops, wrong repo (altough cargo clippy --fix does suggest creating an issue here). Moved to comment on equivalent issue: rust-lang/rust-clippy#10577 (comment)