`AliasTerm` refactor by WaffleLapkin · Pull Request #155392 · rust-lang/rust

WaffleLapkin · 2026-04-16T13:24:09Z

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follow up to #154758
tracking issue: #154941

rustbot · 2026-04-16T13:24:13Z

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

changes to the core type system

cc @lcnr

HIR ty lowering was modified

cc @fmease

Some changes occurred to the core trait solver

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

changes to the core type system

cc @lcnr

This PR changes rustc_public

cc @oli-obk, @celinval, @ouz-a, @makai410

Some changes occurred in compiler/rustc_sanitizers

cc @rcvalle

BoxyUwU · 2026-04-17T09:17:51Z

r? BoxyUwU

Kivooeo · 2026-04-18T06:41:33Z

a bit concerned about PredicateKind size increase, let's do a perf to make sure it's fine

@bors try @rust-timer queue

`AliasTerm` refactor

rust-bors · 2026-04-18T08:54:25Z

☀️ Try build successful (CI)
Build commit: 8206b39 (8206b39ff9d255d5785bd8d5ad84a4a3d9ef510c, parent: 2f201bccb3a7fb5a85b0fcfcc0a020a946d6d58a)

rust-timer · 2026-04-18T10:56:03Z

Finished benchmarking commit (8206b39): 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)	0.3%	[0.2%, 0.5%]	6
Regressions ❌ (secondary)	0.3%	[0.1%, 0.5%]	5
Improvements ✅ (primary)	-0.3%	[-0.5%, -0.2%]	22
Improvements ✅ (secondary)	-0.3%	[-0.5%, -0.2%]	10
All ❌✅ (primary)	-0.2%	[-0.5%, 0.5%]	28

Max RSS (memory usage)

Results (primary 0.5%, secondary 0.7%)

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

	mean	range	count
Regressions ❌ (primary)	0.8%	[0.6%, 1.2%]	5
Regressions ❌ (secondary)	0.7%	[0.4%, 0.9%]	3
Improvements ✅ (primary)	-0.8%	[-0.8%, -0.8%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[-0.8%, 1.2%]	6

Cycles

Results (secondary -0.5%)

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)	2.3%	[2.3%, 2.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.3%	[-3.3%, -3.3%]	1
All ❌✅ (primary)	-	-	0

Binary size

Results (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
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Bootstrap: 491.618s -> 491.67s (0.01%)
Artifact size: 394.25 MiB -> 394.33 MiB (0.02%)

BoxyUwU

I feel a bit unsure about the with_args method, i feel like it makes the callsites which are obligation.predicate.with_args much less clear what's going on. but I guess thats a more general issue that projection predicates have really confusingly fields.

this PR needs a rebase and can you link to the tracking issue in the description. thx

View changes since this review

rustbot · 2026-04-21T10:29:43Z

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.

I have no idea what caused this change, I don't think other commits changed anything near these lines?..

WaffleLapkin · 2026-04-21T10:50:21Z

Rebased & added the tracking issue to the PR description.

BoxyUwU · 2026-04-21T21:45:12Z

@bors r+ rollup=never p=1 (bitrotty)

rust-bors · 2026-04-21T21:45:15Z

📌 Commit be8bfb2 has been approved by BoxyUwU

It is now in the queue for this repository.

jhpratt · 2026-04-22T02:14:13Z

threading between rollups

@bors p=6

rust-bors · 2026-04-22T06:19:35Z

☀️ Test successful - CI
Approved by: BoxyUwU
Duration: 3h 21m 41s
Pushing 1bfcb28 to main...

github-actions · 2026-04-22T06:22:32Z

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 f9988fe (parent) -> 1bfcb28 (this PR)

Test differences

Show 23 test diffs

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

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 1bfcb284f7a2199ad322daa463e29e708d5bc635 --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

dist-x86_64-llvm-mingw: 1h 29m -> 1h 59m (+33.8%)
dist-armv7-linux: 1h 11m -> 1h 32m (+29.1%)
i686-gnu-1: 1h 48m -> 2h 18m (+27.8%)
dist-i686-msvc: 2h 29m -> 1h 53m (-24.2%)
dist-x86_64-netbsd: 1h 27m -> 1h 9m (-20.8%)
i686-gnu-2: 1h 38m -> 1h 18m (-20.7%)
dist-arm-linux-musl: 1h 40m -> 1h 19m (-20.6%)
x86_64-gnu-tools: 1h 2m -> 49m 44s (-20.0%)
pr-check-2: 35m 10s -> 41m 25s (+17.8%)
x86_64-gnu-gcc: 1h 4m -> 1h 12m (+12.3%)

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 · 2026-04-22T07:01:10Z

Finished benchmarking commit (1bfcb28): comparison URL.

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

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

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

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.1%, 0.9%]	19
Regressions ❌ (secondary)	0.3%	[0.0%, 0.7%]	19
Improvements ✅ (primary)	-0.3%	[-0.4%, -0.2%]	10
Improvements ✅ (secondary)	-0.3%	[-0.5%, -0.2%]	9
All ❌✅ (primary)	0.2%	[-0.4%, 0.9%]	29

Max RSS (memory usage)

Results (primary 0.8%, secondary -0.1%)

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

	mean	range	count
Regressions ❌ (primary)	0.8%	[0.8%, 0.9%]	2
Regressions ❌ (secondary)	1.3%	[0.7%, 2.7%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.8%	[-4.1%, -1.6%]	2
All ❌✅ (primary)	0.8%	[0.8%, 0.9%]	2

Cycles

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

Binary size

Results (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
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Bootstrap: 490.294s -> 491.717s (0.29%)
Artifact size: 394.43 MiB -> 394.44 MiB (0.00%)

Mark-Simulacrum · 2026-04-27T23:06:12Z

@WaffleLapkin / @BoxyUwU it looks like there were some concerns over the size increases (#155392 (comment)), it looks like those have born out in both pre-merge and after-merge results. Do we think the refactor here is worth the slight regressions in instruction counts? I think it's reasonable to accept them given the lack of cycle counts.

lcnr · 2026-04-28T08:32:07Z

            goal.param_env,
            ty::UnevaluatedConst::new(
-                goal.predicate.alias.def_id.try_into().unwrap(),
+                goal.predicate.alias.def_id().try_into().unwrap(),


we should pass in the DefId from the match where we decide to call normalize_anon_const here? 🤔

View changes since the review

lcnr · 2026-04-28T08:32:23Z

        self.add_goals(
            GoalSource::Misc,
-            cx.predicates_of(free_alias.def_id)
+            cx.predicates_of(free_alias.def_id())


same here

View changes since the review

lcnr · 2026-04-28T08:32:49Z

+            cx.type_of(inherent.def_id()).instantiate(cx, inherent_args).skip_norm_wip().into()
        } else {
-            cx.const_of_item(inherent.def_id).instantiate(cx, inherent_args).skip_norm_wip().into()
+            cx.const_of_item(inherent.def_id())


and here, I guess in general, I feel like most calls of AliasXXX::def_id are meh

View changes since the review

i would expect in the long run we just get rid of this method since not everything will have a DefId anymore

BoxyUwU · 2026-04-28T08:49:26Z

@Mark-Simulacrum

Do we think the refactor here is worth the slight regressions in instruction counts?

It would probably be good to look into if we can reduce the size of PredicateKind again and see if that helps. If it's not possible to get the perf back I think this is acceptable as this refactor is necessary for supporting inherent_associated_types and also inherent associated consts in const generics (as well as some other important stuff)

rustbot assigned lcnr Apr 16, 2026

rustbot assigned BoxyUwU and unassigned lcnr Apr 17, 2026

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rust-bors Bot pushed a commit that referenced this pull request Apr 18, 2026

Auto merge of #155392 - WaffleLapkin:alias-termmm, r=<try>

8206b39

`AliasTerm` refactor

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 18, 2026

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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 Apr 18, 2026

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BoxyUwU approved these changes Apr 20, 2026

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BoxyUwU mentioned this pull request Apr 20, 2026

generic_const_args: allow paths to non type consts #155341

Open

WaffleLapkin added 6 commits April 21, 2026 12:28

AliasTermTy refactor: API changes

3484c89

AliasTermTy refactor: fixup compiler

d798694

AliasTermTy refactor: fixup rustdoc

c0ddfb0

AliasTermTy refactor: fixup clippy

c32020d

add AliasTermTy::with_args to simplify a common-ish pattern

0ff2fe8

bless ui tests

59be02e

WaffleLapkin force-pushed the alias-termmm branch from 3112204 to 54abf6d Compare April 21, 2026 10:29

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x fmt

be8bfb2

I have no idea what caused this change, I don't think other commits changed anything near these lines?..

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 Apr 21, 2026

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rust-bors Bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Apr 22, 2026

rust-bors Bot merged commit 1bfcb28 into rust-lang:main Apr 22, 2026
12 checks passed

rustbot added this to the 1.97.0 milestone Apr 22, 2026

WaffleLapkin deleted the alias-termmm branch April 22, 2026 07:29

lcnr reviewed Apr 28, 2026

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

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Test differences

Job duration changes

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rust-timer commented Apr 22, 2026

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

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