Fix integer overflow in format!("{:.0?}", Duration::MAX)

[beetrees]

Currently format!("{:.0?}", Duration::MAX) causes an integer overflow in the Duration Debug impl (playground link). This is because the carry from the rounding of the fractional_part into the integer_part will cause the integer_part to overflow as it is already u64::MAX. This PR uses a larger integer type to avoid that issue, and adds a test for the correct behaviour.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @scottmcm (or someone else) soon.

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[rustbot]

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[beetrees]

@scottmcm I've added more tests and converted integer_part to be an Option<u64> instead of a u128.

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

[scottmcm]

Thanks for catching this! And I like the checked_add version; definitely better than my overflowing_add sketch.

@bors r+

[bors]

📌 Commit e409ce2 has been approved by scottmcm

It is now in the queue for this repository.

[bors]

⌛ Testing commit e409ce2 with merge 75d3027...

[bors]

☀️ Test successful - checks-actions
Approved by: scottmcm
Pushing 75d3027 to master...

[rust-timer]

Finished benchmarking commit (75d3027): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.4%	[1.2%, 1.6%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	2.5%	[2.5%, 2.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.5%	[-2.5%, -2.5%]	1
Improvements ✅ (secondary)	-4.3%	[-4.3%, -4.3%]	1
All ❌✅ (primary)	0.0%	[-2.5%, 2.5%]	2

Footnotes

1. the arithmetic mean of the percent change ↩ ↩²

2. number of relevant changes ↩ ↩²