clippy::question_mark suggestion makes closure return type ambiguous

Summary

When if let Err(e) = f() { return Err(e) } is used to make the return type of a closure unambiguous, clippy lints this with clippy::question_mark. Applying the suggestion with --fix makes the type ambiguous and causes a compile error.

warning: failed to automatically apply fixes suggested by rustc to crate `a`

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

  * a/src/main.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-clippy/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

The following errors were reported:
error[E0282]: type annotations needed for `std::result::Result<i32, E>`
 --> a/src/main.rs:6:9
  |
6 |     let g = (|| {
  |         ^
  |
help: consider giving `g` an explicit type, where the type for type parameter `E` is specified
  |
6 |     let g: std::result::Result<i32, E> = (|| {
  |          +++++++++++++++++++++++++++++

error: aborting due to previous error

For more information about this error, try `rustc --explain E0282`.
Original diagnostics will follow.

warning: this block may be rewritten with the `?` operator
  --> a/src/main.rs:8:9
   |
8  | /         if let Err(e) = f() {
9  | |             return Err(e);
10 | |         }
   | |_________^ help: replace it with: `f()?;`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#question_mark
   = note: `#[warn(clippy::question_mark)]` on by default

warning: `a` (bin "a") generated 1 warning (run `cargo clippy --fix --bin "a"` to apply 1 suggestion)
warning: `a` (bin "a" test) generated 1 warning (1 duplicate)
    Finished dev [unoptimized + debuginfo] target(s) in 3.58s

Lint Name

clippy::question_mark

Reproducer

fn f() -> Result<u8, u8> {
    Ok(9)
}

fn main() {
    let g = (|| {
        f()?;
        if let Err(e) = f() {
            return Err(e);
        }
        Ok(42)
    })();
    println!("{g:?}");
}

Version

rustc 1.73.0-nightly (db7ff98a7 2023-07-31)
binary: rustc
commit-hash: db7ff98a72f3e742b641f9cb16d0e8c285e87e9b
commit-date: 2023-07-31
host: x86_64-unknown-linux-gnu
release: 1.73.0-nightly
LLVM version: 16.0.5

Additional Labels

@rustbot label I-suggestion-causes-error

Start by reproducing the provided closure example and inspecting the implementation of clippy::question_mark. Verify the suggested replacement with --fix, then add or update coverage so the closure's return type remains unambiguous and the fixed example compiles successfully.