FP: `needless_return_with_question_mark` with implicit Error Conversion
Return with a question mark was triggered in situations where the `?` desuraging was performing error conversion via `Into`/`From`.
The desugared `?` produces a match over an expression with type `std::ops::ControlFlow<B,C>` with `B:Result<Infallible, E:Error>` and `C:Result<_, E':Error>`, and the arms perform the conversion. The patch adds another check in the lint that checks that `E == E'`. If `E == E'`, then the `?` is indeed unnecessary.
changelog: False Positive: [`needless_return_with_question_mark`] when implicit Error Conversion occurs.
fixes: #11982
e7a3cb7ab0