Fix some problems

[sinkuu]

Fixes #2892, #3199, #2841, #3476

[phansch]

Is there any reason for 328e105? Otherwise r=me 🎇

[bors]

☔ The latest upstream changes (presumably #3529) made this pull request unmergeable. Please resolve the merge conflicts.

[sinkuu]

These are not equivalent:

let _ = if self.opt.is_none() {
    /* no `return` here */ None
} else {
    self.opt
};

let _ = self.opt?;

I'll add this as a comment along with conflict resolution.

if opt.is_none() { None } else { opt } can be changed to opt, but that may be out of scope of this lint ("question_mark").

[oli-obk]

let x = self.opt.is_none() {
    return None;
} else {
    self.op
};

is also not

let _ = self.opt?;

We can always suggest let _ = Some(self.opt?); and have the user take it from there.

[phansch]

@bors r+ thanks!

[bors]

📌 Commit eba44e1 has been approved by phansch

[bors]

⌛ Testing commit eba44e1 with merge 379c934...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: phansch
Pushing 379c934 to master...