`-Znext-solver` Less normalizes-to janks by ShoyuVanilla · Pull Request #156619 · rust-lang/rust

ShoyuVanilla · 2026-05-15T19:20:13Z

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cc rust-lang/trait-system-refactor-initiative#223 (comment)

r? lcnr

rustbot · 2026-05-15T19:20:17Z

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

changes to inspect_obligations.rs

cc @lcnr

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

ShoyuVanilla · 2026-05-15T19:35:00Z

@bors try @rust-timer queue

`-Znext-solver` Less normalizes-to janks

ShoyuVanilla · 2026-05-15T19:46:09Z

I haven't done the nested goals' recursion depth part yet 😅 I'm gonna work on it if the overall design here pan out to be feasible

rust-bors · 2026-05-15T21:45:37Z

☀️ Try build successful (CI)
Build commit: d4c528b (d4c528b37c59bf04c41ddba6375584d284d1a9ba, parent: 88ba7fbe0a6eda36e0adbfd0482856f3784031b9)

rust-timer · 2026-05-15T23:03:40Z

Finished benchmarking commit (d4c528b): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	0.4%	[0.3%, 0.8%]	7
Regressions ❌ (secondary)	22.5%	[0.6%, 46.0%]	12
Improvements ✅ (primary)	-0.3%	[-0.7%, -0.1%]	20
Improvements ✅ (secondary)	-0.3%	[-0.6%, -0.2%]	29
All ❌✅ (primary)	-0.1%	[-0.7%, 0.8%]	27

Max RSS (memory usage)

Results (primary 1.5%, secondary 8.5%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[0.9%, 2.6%]	5
Regressions ❌ (secondary)	11.4%	[2.0%, 25.8%]	8
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-14.8%	[-14.8%, -14.8%]	1
All ❌✅ (primary)	1.5%	[0.9%, 2.6%]	5

Cycles

Results (secondary 26.9%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	26.9%	[17.5%, 41.5%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 510.626s -> 509.733s (-0.17%)
Artifact size: 398.07 MiB -> 398.06 MiB (-0.00%)

ShoyuVanilla · 2026-05-16T00:58:30Z

Oh, the perf regressions are insane 😅 I'll look into them

ShoyuVanilla · 2026-05-16T17:25:25Z

@bors try @rust-timer queue

`-Znext-solver` Less normalizes-to janks

rust-bors · 2026-05-16T19:35:04Z

☀️ Try build successful (CI)
Build commit: 52311d2 (52311d29eb5b4b58f67e481749703829fab93a19, parent: 35143615544ede08a47947901cd4a6b7c5ecd450)

rust-timer · 2026-05-16T20:16:10Z

Finished benchmarking commit (52311d2): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	0.8%	[0.2%, 1.2%]	8
Regressions ❌ (secondary)	26.5%	[0.1%, 45.5%]	10
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.1%]	23
Improvements ✅ (secondary)	-0.4%	[-0.8%, -0.2%]	29
All ❌✅ (primary)	0.0%	[-0.3%, 1.2%]	31

Max RSS (memory usage)

Results (primary 1.7%, secondary 8.4%)

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

	mean	range	count
Regressions ❌ (primary)	1.7%	[1.0%, 2.8%]	6
Regressions ❌ (secondary)	11.3%	[2.1%, 25.8%]	8
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-14.7%	[-14.7%, -14.7%]	1
All ❌✅ (primary)	1.7%	[1.0%, 2.8%]	6

Cycles

Results (primary 2.3%, secondary 22.5%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	25.0%	[2.4%, 43.8%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.4%, -2.4%]	1
All ❌✅ (primary)	2.3%	[2.3%, 2.3%]	1

Binary size

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

Bootstrap: 513.812s -> 509.975s (-0.75%)
Artifact size: 398.43 MiB -> 400.31 MiB (0.47%)

ShoyuVanilla · 2026-05-28T15:44:20Z

If my observation is correct, this would fix the perf regression 🤔
@bors try @rust-timer queue

lcnr · 2026-06-11T09:43:39Z

@@ -39,19 +34,12 @@ where
            ty::AliasTermKind::ProjectionTy { .. } | ty::AliasTermKind::ProjectionConst { .. } => {
                self.normalize_associated_term(goal)


and here you can keep this match as a debug_assert and just inline normalize_associated_term below it :3

View changes since the review

lcnr

a few more nits, r=me on this impl itself

View changes since this review

We had never stepped into recursive replacement with `AliasRelate` goals when replacing aliases because `AliasRelate` goals don't allow normalization

rustbot · 2026-06-11T16:15:12Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

ShoyuVanilla · 2026-06-11T17:38:02Z

@bors r=lcnr

rust-bors · 2026-06-11T17:38:05Z

📌 Commit 54875bf has been approved by lcnr

It is now in the queue for this repository.

`-Znext-solver` Less normalizes-to janks cc rust-lang/trait-system-refactor-initiative#223 (comment) r? lcnr

rust-log-analyzer · 2026-06-12T03:18:58Z

The job dist-loongarch64-linux failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

rust-bors · 2026-06-12T03:19:24Z

💔 Test for 812b7d1 failed: CI. Failed job:

auto - dist-loongarch64-linux (web logs, enhanced plaintext logs)

jhpratt · 2026-06-12T03:29:31Z

The tail of that log shows nothing out of the ordinary, not even a spurious failure.

@bors retry

rust-bors · 2026-06-12T06:42:35Z

☔ The latest upstream changes (presumably #157794) made this pull request unmergeable. Please resolve the merge conflicts.

This pull request was unapproved.

lcnr · 2026-06-12T10:47:35Z

        };

-        self.instantiate_normalizes_to_term(goal, actual);
+        self.push_const_arg_has_type_goal(goal.param_env, goal.predicate.projection_term, actual);


Why are you adding that?

View changes since the review

ah hmm, it's interesting that we add const_arg_has_type here. I guess you're just inlining that function. cc @BoxyUwU why do we do it this way and not more specifically for free consts or sth like that?

It has been introduced in #154853 to fix some ICEs

lcnr · 2026-06-12T10:48:06Z

+            goal.param_env,
+            goal.predicate.projection_term,
+            normalized,
+        );


same 🤔

View changes since the review

lcnr · 2026-06-12T10:49:46Z

+        self.inspect.make_canonical_response(Certainty::AMBIGUOUS);
+
+        // Apply the constraints.
+        self.try_evaluate_added_goals()?;


we don't add any nested goals here. This only handles the goals from replace_alias_with_infer. Move that below the make_canonical_response maybe?

View changes since the review

Yeah, the intention here is to normalize expected term. Without this, structural equating below may fail

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels May 15, 2026

rustbot assigned lcnr May 15, 2026

ShoyuVanilla mentioned this pull request May 15, 2026

-Znext-solver Remove special handling of NormalizesTo goal #154433

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rust-bors Bot pushed a commit that referenced this pull request May 15, 2026

Auto merge of #156619 - ShoyuVanilla:less-normalizes-to-jank, r=<try>

d4c528b

`-Znext-solver` Less normalizes-to janks

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels May 15, 2026

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label May 16, 2026

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rust-bors Bot pushed a commit that referenced this pull request May 16, 2026

Auto merge of #156619 - ShoyuVanilla:less-normalizes-to-jank, r=<try>

52311d2

`-Znext-solver` Less normalizes-to janks

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label May 16, 2026

ShoyuVanilla force-pushed the less-normalizes-to-jank branch from 6bd6498 to 5927eca Compare May 28, 2026 15:43

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lcnr reviewed Jun 11, 2026

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ShoyuVanilla added 8 commits June 11, 2026 23:40

Use ProjectionPredicate for normalizations

adcb6b7

Move files

6675f99

Handle non-trait projections

faef6e6

Handle trait projections

3f06573

Bless tests

be640ae

Reduce might be redundant normalizes-to nested goal evaluations

91065b7

perf: Do not recursively replace aliases in predicates

c801588

We had never stepped into recursive replacement with `AliasRelate` goals when replacing aliases because `AliasRelate` goals don't allow normalization

Apply review feedbacks

54875bf

ShoyuVanilla force-pushed the less-normalizes-to-jank branch from 8cdfcda to 54875bf Compare June 11, 2026 16:15

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 11, 2026

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rust-bors Bot pushed a commit that referenced this pull request Jun 12, 2026

Auto merge of #156619 - ShoyuVanilla:less-normalizes-to-jank, r=lcnr

812b7d1

`-Znext-solver` Less normalizes-to janks cc rust-lang/trait-system-refactor-initiative#223 (comment) r? lcnr

rust-bors Bot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 12, 2026

lcnr reviewed Jun 12, 2026

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		@@ -39,19 +34,12 @@ where
		ty::AliasTermKind::ProjectionTy { .. } \| ty::AliasTermKind::ProjectionConst { .. } => {
		self.normalize_associated_term(goal)

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Overall result: ❌✅ regressions and improvements - please read:

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Overall result: ❌✅ regressions and improvements - please read:

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