Revert tearing changes to dbg!

[cuviper]

Since the primary change to dbg! in #149869, we've been chasing a few regressions:

• 1.95 beta regression: "temporary value dropped while borrowed" #153850, fixed by don't drop arguments' temporaries in dbg! #154074
• 1.96 beta regression: "lua does not live long enough" #154988, fixed by don't leak internal temporaries from dbg! #154994
• 1.96 beta regression: "lua does not live long enough", take 2 #155902, proposed fix in don't leak internal temporaries from dbg!, even on false unwind paths #155915

We already reverted this once, on beta only to prevent these regressions from shipping in 1.95.

In that most recent PR, we decided that it would be better to revert dbg! to its original state everywhere (main and 1.96-beta), and then we can consider it from scratch later. So here I've reverted the change and its fixes, but kept the regression tests, including the pending one.

cc @joboet @dianne @rust-lang/libs
@rustbot label beta-nominated

[rustbot]

The Clippy subtree was changed

cc @rust-lang/clippy

The Miri subtree was changed

cc @rust-lang/miri

[rustbot]

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[rustbot]

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  • 73931c4
  • c9d9448
  • 9246e19
  • 6f35b83

[cuviper]

r? libs

[the8472]

The principle of the thing was already approved by the team, the reverts look clean, 👍️ for retaining the tests.

@bors r+

[rust-bors]

📌 Commit 6f35b83 has been approved by the8472

It is now in the queue for this repository.

[rust-bors]

☀️ Test successful - CI
Approved by: the8472
Duration: 3h 11m 37s
Pushing 4b97926 to main...

[github-actions]

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing e50aa6f (parent) -> 4b97926 (this PR)

Test differences

Show 32 test diffs

Stage 1

• macros::tests::no_leaking_internal_temps_from_dbg_even_on_false_unwind: [missing] -> pass (J1)

Stage 2

• macros::tests::no_leaking_internal_temps_from_dbg_even_on_false_unwind: [missing] -> pass (J0)

Additionally, 30 doctest diffs were found. These are ignored, as they are noisy.

Job group index

• J0: aarch64-apple, aarch64-gnu, aarch64-gnu-llvm-21-1, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, optional-x86_64-gnu-parallel-frontend, test-various, x86_64-gnu, x86_64-gnu-aux, x86_64-gnu-llvm-21-2, x86_64-gnu-llvm-22-2, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1
• J1: i686-gnu-nopt-2, pr-check-2, x86_64-gnu-llvm-21-3, x86_64-gnu-llvm-22-3, x86_64-gnu-nopt

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 4b9792692fbb675174d4d2082e7c37b2bc930e71 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

1. dist-apple-various: 1h 52m -> 2h 32m (+35.6%)
2. optional-x86_64-gnu-parallel-frontend: 2h 8m -> 2h 44m (+28.2%)
3. dist-x86_64-msvc-alt: 2h 11m -> 2h 47m (+27.3%)
4. dist-i686-msvc: 2h 33m -> 1h 51m (-27.2%)
5. x86_64-gnu-tools: 51m 11s -> 1h 4m (+26.5%)
6. i686-msvc-2: 1h 44m -> 2h 11m (+25.8%)
7. dist-various-2: 35m 15s -> 43m 31s (+23.4%)
8. dist-x86_64-illumos: 1h 50m -> 1h 27m (-21.0%)
9. pr-check-1: 32m 12s -> 27m 53s (-13.4%)
10. x86_64-msvc-ext1: 2h 8m -> 2h 23m (+12.0%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

[rust-timer]

Finished benchmarking commit (4b97926): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This perf run didn't have relevant results for this metric.

Max RSS (memory usage)

Results (primary 2.2%)

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

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.2%	[2.2%, 2.2%]	1

Cycles

Results (primary 1.9%, secondary 4.8%)

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

	mean	range	count
Regressions ❌ (primary)	1.9%	[1.9%, 1.9%]	1
Regressions ❌ (secondary)	4.8%	[4.8%, 4.9%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.9%	[1.9%, 1.9%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 512.018s -> 510.83s (-0.23%)
Artifact size: 400.61 MiB -> 400.58 MiB (-0.01%)

[rustbot]

beta backport approved as per libs team on Zulip. A backport PR will be authored by the release team at the end of the current development cycle. Backport labels are handled by them.