Needless Question Mark Lint

[bengsparks]

Fixes #6410, i.e the needless question mark lint

changelog: [needless_question_mark] New lint

[rust-highfive]

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[bengsparks]

There are a number of matches in test code, most of which seems to be accurate.
However, in $DIR/try_err.rs:56:5, there is a snippet that triggers my lint.

let err: i8 = 1;
// To avoid warnings during rustfix
if true {
    Err(err)?;
}
Ok(i)

While the Err(err)? line is worthy of linting, it should not trigger this lint, correct? @flip1995

[bengsparks]

Upon closer review, it appears that my lint did not trigger the aforementioned lines.

[flip1995]

LGTM overall. After addressing the remaining 2 comments, please squash some of your commits (it doesn't have to be one commit, if you want to split it up a bit).

[flip1995]

The examples in the documentation seem weird to me. Otherwise LGTM.

[flip1995]

@bors r+

Thanks!

[bors]

📌 Commit ba87acb has been approved by flip1995

[bors]

⌛ Testing commit ba87acb with merge 7b727fa...

[bors]

💔 Test failed - checks-action_test

[flip1995]

@bors retry

[bors]

⌛ Testing commit ba87acb with merge ae9ae97...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing ae9ae97 to master...