Fix println! ICE when parsing percent prefix number

[pymongo]

This PR fixes #125002 ICE occurring, for example, with println!("%100000", 1) or println!("% 100000", 1).

Test Case/Change Explanation

The return type of Num::from_str has been changed to Option<Self> to handle errors when parsing large integers fails.

1. The first println! in the test case covers the change of the first Num::from_str usage in format_foreign.rs:426.
2. The second println! in the test case covers the change of the second Num::from_str usage in line 460.
3. The 3rd to 5th Num::from_str usages behave the same as before.

The 3rd usage would cause an ICE when num > u16::MAX in the previous version, but this commit does not include a fix for the ICE in println!("{:100000$}"). I think we need to emit an error in the compiler and have more discussion in another issue/PR.

[rustbot]

r? @lcnr

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[lcnr]

r? estebank though feel free to reassign if you're also not familiar with this code

[estebank]

Let's get of as many unwraps as possible in this code. It is always "just" providing a suggestion, so a mistake on the translation is better than an ICE.

Thank you for doing this!

[pymongo]

@rustbot ready

[estebank]

r=me after the slight change.

Most of the time you have Option<Option<T>> after a map, what you really wanted is an and_then that does Option<K> -> Option<T> and collapses the Nones.

[pymongo]

Most of the time you have Option<Option<T>> after a map, what you really wanted is an and_then that does Option<K> -> Option<T> and collapses the Nones.

Thanks! I forgot to use and_then to flatten Option<Option>, the second review change is
here pymongo@33d2c87

[estebank]

@bors r+

[bors]

📌 Commit 582fd1f has been approved by estebank

It is now in the queue for this repository.

[bors]

⌛ Testing commit 582fd1f with merge 1c90b9f...

[bors]

☀️ Test successful - checks-actions
Approved by: estebank
Pushing 1c90b9f to master...

[rust-timer]

Finished benchmarking commit (1c90b9f): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary -0.6%)

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.

	mean	range	count
Regressions ❌ (primary)	1.2%	[1.2%, 1.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.5%	[-2.5%, -2.5%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.6%	[-2.5%, 1.2%]	2

Cycles

Results (primary 1.5%)

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.

	mean	range	count
Regressions ❌ (primary)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[1.5%, 1.5%]	1

Binary size

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

Bootstrap: 669.26s -> 667.741s (-0.23%)
Artifact size: 316.04 MiB -> 316.07 MiB (0.01%)