Add expansion info to default bounds

[oli-obk]

Relanding part of #158122

The incremental issues are resolved in this PR, but we still need to check perf

r? @ghost

[oli-obk]

@bors try @rust-timer queue

[oli-obk]

@bors try cancel seems stuck

[rust-bors]

Try build cancelled. Cancelled workflows:

• https://github.com/rust-lang/rust/actions/runs/27962724059

[oli-obk]

@bors try

[rust-bors]

☀️ Try build successful (CI)
Build commit: 6c4a2f9 (6c4a2f95b8d82a704b3d651a5a527b432add2ee8)
Base parent: cddcbec (cddcbec198760511240bf0e728193bf4d700acb4)

[rust-timer]

Finished benchmarking commit (6c4a2f9): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.1%, 3.0%]	80
Regressions ❌ (secondary)	0.6%	[0.0%, 1.8%]	58
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.1%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.6%	[-0.3%, 3.0%]	83

Max RSS (memory usage)

Results (primary 1.6%, secondary 4.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.8%	[0.5%, 3.2%]	28
Regressions ❌ (secondary)	4.5%	[0.7%, 11.5%]	12
Improvements ✅ (primary)	-2.2%	[-2.3%, -2.1%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.6%	[-2.3%, 3.2%]	30

Cycles

Results (primary 3.1%, secondary 2.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	3.4%	[2.0%, 5.2%]	15
Regressions ❌ (secondary)	3.0%	[2.1%, 4.3%]	16
Improvements ✅ (primary)	-1.7%	[-1.7%, -1.7%]	1
Improvements ✅ (secondary)	-4.2%	[-5.3%, -3.1%]	2
All ❌✅ (primary)	3.1%	[-1.7%, 5.2%]	16

Binary size

Results (primary 2.3%, secondary 2.3%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.3%	[0.0%, 11.9%]	78
Regressions ❌ (secondary)	2.3%	[0.0%, 11.4%]	47
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.3%	[0.0%, 11.9%]	78

Bootstrap: 505.379s -> 506.981s (0.32%)
Artifact size: 353.06 MiB -> 353.64 MiB (0.16%)

[oli-obk]

While it would be nice to have this, I don't think it's worth all the extra span information that is necessary for it to work (the perf cost is in metadata encoding and actual generation of those spans, as we generate implicit bounds like Sized everywhere. It may be easier to mark the ones that are not implicitly generated

[oli-obk]

nope that's not a good idea either. It breaks a lot of suggestion logic because that doesn't like expansion info. Ok, giving up 😆