Fix false positives of needless_match

[tamaroning]

closes: #9084
made needless_match take into account arm in the form of _ if => ...

changelog: none

[rust-highfive]

r? @llogiq

(rust-highfive has picked a reviewer for you, use r? to override)

[Jarcho]

This should also return false for arm.guard.is_some()

[tamaroning]

@Jarcho
I think my code already works for arms with if guards.
If not, could you raise some cases my code dosen't catch?

• pat => expr_same_as_pat
• pat if some_expr => expr_same_as_pat
• _ => scrutinee
• _ if some_expr => scrutinee
  For now, other cases than these four returns false.

[Jarcho]

Match guards can have side-effects in them. Horrible example:

match 0 {
    0 if { println!("guard"); false } => 0,
    _ => 0,
}

Expr::can_have_side_effects would also solve the problem.

[tamaroning]

Ohhh...I forgot side effects.
OKay. I will use Expr::can_have_side_effects.

[tamaroning]

thank you for your review @Jarcho .
I am a little busy until 8/1 around so I will fix this later.

[tamaroning]

@rustbot label -S-waiting-on-author +S-waiting-on-review

[tamaroning]

hmm..test failed though it passes in the local environment.

[Jarcho]

Try rebasing. Possibly a conflict with #8356.

[llogiq]

I think you just need to bless the needless_match ui test again ( cargo dev bless) and commit+push the resulting diff.

(And sorry for being away for so long, thanks to @Jarcho for picking up the slack)

[tamaroning]

Thank you. My commit somehow does not contained .stderr but fixed :)

[llogiq]

Thank you!

@bors r+

[bors]

📌 Commit f7a376e has been approved by llogiq

It is now in the queue for this repository.

[bors]

⌛ Testing commit f7a376e with merge cc637ba...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing cc637ba to master...