Use the new solver in the impossible_predicates

[compiler-errors]

The old solver is unsound for many reasons. One of which was weaponized by @lcnr in #140212, where the old solver was incompletely considering a dyn vtable method to be impossible and replacing its vtable entry with a null value. This null function could be called post-mono.

The new solver is expected to be less incomplete due to its correct handling of higher-ranked aliases in relate. This PR switches the impossible_predicates query to use the new solver, which patches this UB.

r? lcnr

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 42565da with merge 6aac808...

[bors]

☀️ Try build successful - checks-actions
Build commit: 6aac808 (6aac80825ffa245e49ce6e80bdcfdc433dbb3559)

[rust-timer]

Finished benchmarking commit (6aac808): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.3%, 0.3%]	1
Regressions ❌ (secondary)	0.5%	[0.5%, 0.6%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	3
All ❌✅ (primary)	0.3%	[0.3%, 0.3%]	1

Max RSS (memory usage)

Results (primary -1.6%, secondary -2.9%)

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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.6%	[-2.3%, -0.9%]	2
Improvements ✅ (secondary)	-2.9%	[-3.7%, -2.4%]	3
All ❌✅ (primary)	-1.6%	[-2.3%, -0.9%]	2

Cycles

Results (secondary 2.5%)

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)	-	-	0
Regressions ❌ (secondary)	2.5%	[2.5%, 2.5%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 788.486s -> 790.527s (0.26%)
Artifact size: 347.76 MiB -> 347.72 MiB (-0.01%)

[compiler-errors]

Ok let me fix AFIDT first.

@rustbot author

[compiler-errors]

@bors try @rust-timer queue

(and crater)

[bors]

⌛ Trying commit 40269a1 with merge 4c525d4...

[bors]

☀️ Try build successful - checks-actions
Build commit: 4c525d4 (4c525d43052e921548191f82f6ed9e2f9e98dcb1)

[compiler-errors]

@craterbot check

[craterbot]

👌 Experiment pr-136988 created and queued.
🤖 Automatically detected try build 4c525d4
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[rfcbot]

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

[compiler-errors]

@rustbot ready

[lcnr]

@bors r+ rollup=never

[bors]

📌 Commit 257f687 has been approved by lcnr

It is now in the queue for this repository.

[bors]

⌛ Testing commit 257f687 with merge c4e05e5...

[bors]

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing c4e05e5 to master...

[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 d163a28 (parent) -> c4e05e5 (this PR)

Test differences

Show 4 test diffs

Stage 1

• [ui] tests/ui/traits/vtable/impossible-method.rs#current: [missing] -> pass (J0)
• [ui] tests/ui/traits/vtable/impossible-method.rs#next: [missing] -> pass (J0)

Stage 2

• [ui] tests/ui/traits/vtable/impossible-method.rs#current: [missing] -> pass (J1)
• [ui] tests/ui/traits/vtable/impossible-method.rs#next: [missing] -> pass (J1)

Job group index

• J0: x86_64-gnu-llvm-19-3, x86_64-gnu-llvm-20-3
• J1: aarch64-apple, aarch64-gnu, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, test-various, x86_64-apple-2, x86_64-gnu, x86_64-gnu-llvm-19-1, x86_64-gnu-llvm-19-2, x86_64-gnu-llvm-20-1, x86_64-gnu-llvm-20-2, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard c4e05e53d19b550a358ee8b2e29ecd5a11075800 --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. x86_64-apple-1: 11122.2s -> 7412.5s (-33.4%)
2. dist-apple-various: 10358.5s -> 7424.1s (-28.3%)
3. dist-x86_64-apple: 11586.4s -> 8656.9s (-25.3%)
4. aarch64-apple: 5105.4s -> 4710.9s (-7.7%)
5. dist-x86_64-musl: 7408.3s -> 7962.1s (7.5%)
6. dist-armv7-linux: 5317.7s -> 5711.8s (7.4%)
7. dist-aarch64-apple: 5827.8s -> 5404.2s (-7.3%)
8. x86_64-apple-2: 5290.9s -> 5629.2s (6.4%)
9. dist-aarch64-msvc: 8416.2s -> 8897.4s (5.7%)
10. dist-x86_64-freebsd: 5281.0s -> 4990.2s (-5.5%)

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 (c4e05e5): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

• If the regression was expected or you think it can be justified,
  please write a comment with sufficient written justification, and add
  @rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
• If you think that you know of a way to resolve the regression, try to create
  a new PR with a fix for the regression.
• If you do not understand the regression or you think that it is just noise,
  you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
  were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	0.9%	[0.4%, 1.1%]	5
Regressions ❌ (secondary)	0.5%	[0.3%, 1.0%]	27
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.1%]	1
Improvements ✅ (secondary)	-0.1%	[-0.2%, -0.1%]	6
All ❌✅ (primary)	0.8%	[-0.1%, 1.1%]	6

Max RSS (memory usage)

Results (primary 1.4%, secondary 1.7%)

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)	2.4%	[1.0%, 4.5%]	3
Regressions ❌ (secondary)	1.7%	[1.2%, 2.2%]	2
Improvements ✅ (primary)	-1.5%	[-1.5%, -1.5%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.4%	[-1.5%, 4.5%]	4

Cycles

Results (primary -0.8%)

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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.8%	[-0.8%, -0.8%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.8%	[-0.8%, -0.8%]	1

Binary size

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

Bootstrap: 772.725s -> 773.554s (0.11%)
Artifact size: 365.38 MiB -> 365.48 MiB (0.03%)

[compiler-errors]

Lol. I'm somewhat surprised that perf has diverged so dramatically between March and May.

Previous run: #136988 (comment)

[Kobzol]

The regressions are mostly in helloworld and tiny benchmarks, and they are relatively small, so I think it's fine. We generally expect the perf. of the new solver to improve over time.

@rustbot label: +perf-regression-triaged