Enhance collapsible_match to cover if-elses

[profetia]

Closes #16558

changelog: [collapsible_match] extend to cover if-elses

[rustbot]

Some changes occurred in clippy_lints/src/doc

cc @notriddle

[rustbot]

r? @llogiq

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[github-actions]

Lintcheck changes for 5be3049

Lint	Added	Removed	Changed
clippy::collapsible_match	15	0	1

This comment will be updated if you push new changes

[llogiq]

Looks good to me. Thank you!

[nbdd0121]

I think this warning should not trigger if clippy::collapsible_if is allowed.

[mkj]

Was this meant to change behaviour without else? I'm hitting it on code without any else, reverting 904a750 removes the warning. (Personally I prefer the code not collapsed in this case).

warning: this `if` can be collapsed into the outer `match`
   --> pldm-fw/src/fd.rs:719:17
    |
719 | /                 if dev.now() - self.update_timestamp_fd_t1 > Self::FD_T1_TIMEOUT
720 | |                 {
721 | |                     // TODO cancel any updates in Device?
722 | |                     self.set_state_idle_timeout();
723 | |                 }
    | |_________________^
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_match
    = note: `#[warn(clippy::collapsible_match)]` on by default
help: collapse nested if block
    |
718 ~             State::Idle { .. }
719 |                 if dev.now() - self.update_timestamp_fd_t1 > Self::FD_T1_TIMEOUT
720 ~                 => {
721 |                     // TODO cancel any updates in Device?
722 |                     self.set_state_idle_timeout();
723 ~                 }
    |

code is
https://github.com/CodeConstruct/mctp-rs/blob/114dee1a7cfbae601ce11901b20516ebe217a4b2/pldm-fw/src/fd.rs#L714-L726

[samueltardieu]

It looks like this is causing bugs in the latest release: #16875, #16864 (fixed in beta) , and #16860 (in less than 48 hours)
Ping @profetia @llogiq

[profetia]

#16749 fixes a few of the bugs. I will also look into the new ones.