needless_return_with_question_mark when inside let ... else

[chris13524]

Summary

I use a return so that my type checks pass, but this lint now wants me to remove the return which breaks my types.

Lint Name

needless_return_with_question_mark

Reproducer

I tried this code:

fn try_fn() -> anyhow::Result<()> {
    let val = Some("hi");
    let Some(val) = val else {
        return Err(anyhow::anyhow!("the error"))?;
    };
    println!("val: {val}");
    Ok(())
}

I saw this happen:

warning: unneeded `return` statement with `?` operator
 --> src/main.rs:8:9
  |
8 |         return Err(anyhow::anyhow!("the error"))?;
  |         ^^^^^^^ help: remove it
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_return_with_question_mark
  = note: `#[warn(clippy::needless_return_with_question_mark)]` on by default

warning: `needless_return_with_question_mark` (bin "needless_return_with_question_mark") generated 1 warning (run `cargo clippy --fix --bin "needless_return_with_question_mark"` to apply 1 suggestion)

But when I fix that:

fn try_fn() -> anyhow::Result<()> {
    let val = Some("hi");
    let Some(val) = val else {
        Err(anyhow::anyhow!("the error"))?;
    };
    println!("val: {val}");
    Ok(())
}

I now get this error:

error[E0308]: `else` clause of `let...else` does not diverge
 --> src/main.rs:7:30
  |
7 |       let Some(val) = val else {
  |  ______________________________^
8 | |         Err(anyhow::anyhow!("the error"))?;
9 | |     };
  | |_____^ expected `!`, found `()`
  |
  = note:   expected type `!`
          found unit type `()`
  = help: try adding a diverging expression, such as `return` or `panic!(..)`
  = help: ...or use `match` instead of `let...else`

For more information about this error, try `rustc --explain E0308`.
error: could not compile `needless_return_with_question_mark` (bin "needless_return_with_question_mark") due to previous error

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

No response

[dswij]

Should be fixed by #11802