Do not return incorrectly constrained opaques in method_autoderef_steps

[adwinwhite]

Fixes rust-lang/trait-system-refactor-initiative#263

r? @lcnr

[lcnr]

Suggested change

	// Previously we return all opaques in `method_auto_deref_steps` which normalizes the opaque
	// to `u32`, causing obligations to fail.
	// We shouldn't return incorrectly constrained opaques in this query.
	// Previously `method_auto_deref_steps` would also return opaque
	// types which have already been defined in the parent context.
	//
	// We then handled these opaque types by emitting `AliasRelate` goals
	// when instantiating its result, assuming that operation to be infallible.
	// By returning opaque type constraints from the parent context and
	// constraining the hidden type without reproving the item bounds of
	// the opaque, this ended up causing ICE.

[lcnr]

r=me after comment nit

thanks ❤️

[lcnr]

@bors r+

[rust-bors]

📌 Commit f6efe7e has been approved by lcnr

It is now in the queue for this repository.

[rust-bors]

☀️ Test successful - CI
Approved by: lcnr
Duration: 3h 18m 56s
Pushing 4742769 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 db6bc0f (parent) -> 4742769 (this PR)

Test differences

Show 14 test diffs

Stage 1

• [ui] tests/ui/traits/next-solver/opaques/method_autoderef_constraints.rs: [missing] -> pass (J0)

Stage 2

• [ui] tests/ui/traits/next-solver/opaques/method_autoderef_constraints.rs: [missing] -> pass (J1)

Additionally, 12 doctest diffs were found. These are ignored, as they are noisy.

Job group index

• J0: x86_64-gnu-llvm-20-3, x86_64-gnu-llvm-21-3
• J1: aarch64-apple, aarch64-gnu, aarch64-gnu-llvm-20-1, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, test-various, x86_64-gnu, x86_64-gnu-debug, x86_64-gnu-gcc, x86_64-gnu-llvm-20, x86_64-gnu-llvm-20-2, x86_64-gnu-llvm-21-2, 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 474276961f48b0d05f4ea260ba400096b027584e --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-aarch64-linux: 9272.8s -> 6669.5s (-28.1%)
2. aarch64-apple: 10339.6s -> 7889.8s (-23.7%)
3. dist-ohos-aarch64: 4478.0s -> 5537.9s (+23.7%)
4. x86_64-gnu-gcc: 3325.9s -> 3852.8s (+15.8%)
5. test-various: 6653.8s -> 7571.1s (+13.8%)
6. dist-apple-various: 4557.0s -> 5157.4s (+13.2%)
7. x86_64-msvc-1: 8247.6s -> 9206.0s (+11.6%)
8. i686-gnu-1: 7344.8s -> 8046.1s (+9.5%)
9. x86_64-gnu-llvm-20-1: 4052.7s -> 4418.5s (+9.0%)
10. i686-gnu-nopt-1: 7350.2s -> 7988.5s (+8.7%)

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 (4742769): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -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
Regressions ❌ (secondary)	0.2%	[0.1%, 0.2%]	4
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 (primary -2.4%, secondary 3.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.9%	[2.9%, 2.9%]	1
Regressions ❌ (secondary)	3.7%	[3.0%, 4.8%]	3
Improvements ✅ (primary)	-3.2%	[-3.9%, -2.1%]	7
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.4%	[-3.9%, 2.9%]	8

Binary size

Results (primary 0.0%, secondary 0.0%)

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

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	4
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	4

Bootstrap: 473.172s -> 473.418s (0.05%)
Artifact size: 383.63 MiB -> 383.64 MiB (0.00%)