Tracking issue for time_checked_add feature

[sgeisler]

This is a tracking issue for PR #55527 .

This feature adds a checked_add(&self, &Duration) -> Option<SystemTime> function to std::time::SystemTime and as a prerequisite also for all platform specific time structs. This also led to the refactoring of many add_duration(&self, &Duration) -> SystemTime functions to avoid redundancy (they now unwrap the result of checked_add_duration).

[Amanieu]

This should be added to Instant as well. We're seeing some need for this in parking_lot to handle wait timeouts.

[faern]

I pushed a PR (#56490) for adding the same functionality to Instant under the same feature gate name. I hope this is fine. They seem extremely related (and share a lot of the implementation) and the feature name fits both.

[faern]

This has now been extended so the feature covers both checked_add and checked_sub on both Instant and SystemTime. Together with the fact that Duration already have these, it's now possible to handle all time types without risking panics on nightly (whenever the next nightly comes out).

[SimonSapin]

Covered by this feature:

impl Instant {
    pub fn checked_add(&self, duration: Duration) -> Option<Instant> {
    pub fn checked_sub(&self, duration: Duration) -> Option<Instant> {
}
impl SystemTime {
    pub fn checked_add(&self, duration: Duration) -> Option<SystemTime> {
    pub fn checked_sub(&self, duration: Duration) -> Option<SystemTime> {
}

Looks good to me.

@rfcbot fcp merge

[rfcbot]

Team member @SimonSapin has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Kimundi
• @SimonSapin
• @alexcrichton
• @dtolnay
• @sfackler
• @withoutboats

No concerns currently listed.

Once a majority of reviewers approve (and none object), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[vi]

Why no Instant::checked_duration_since?

[rfcbot]

The final comment period, with a disposition to merge, as per the review above, is now complete.

[vi]

Implemented checked_duration_since: #58395

[faern]

@vi Could we not keep that as a separate feature? As to not slow this one down. No one reported they might have any need for checked_duration_since when we developed checked_add and checked_sub.

[vi]

OK, renaming the feature in the pull request.