Skip walking into param-env component if it has no placeholder/re-var #143500

compiler-errors · 2025-07-05T18:40:27Z

Although it only provides a minor perf improvement, it seems like it could matter in more pathological cases.

…/re-var

compiler-errors · 2025-07-05T18:40:34Z

@bors2 try @rust-timer queue

rust-bors · 2025-07-05T18:40:37Z

⌛ Trying commit e13757e with merge e3ecd5f…

To cancel the try build, run the command @bors2 try cancel.

[perf] Skip walking into param-env component if it has no placeholder/re-var

rust-bors · 2025-07-05T20:56:40Z

☀️ Try build successful (CI)
Build commit: e3ecd5f (e3ecd5f5fd02f50bc278c1f0cd5b4dbd9e07242a, parent: 6dec76f1c2809fded082dd44d3752d3f6220d767)

rust-timer · 2025-07-05T23:21:05Z

Finished benchmarking commit (e3ecd5f): comparison URL.

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

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@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
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.5%	[-0.5%, -0.5%]	3
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

Cycles

Results (secondary 0.2%)

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)	2.4%	[2.4%, 2.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.0%	[-2.0%, -2.0%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 461.008s -> 461.232s (0.05%)
Artifact size: 372.14 MiB -> 372.18 MiB (0.01%)

compiler-errors · 2025-07-06T00:16:33Z

r? lcnr

lcnr · 2025-07-07T08:58:08Z

compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -1069,8 +1070,10 @@ where
            } else {
                ControlFlow::Continue(())
            }
-        } else {
+        } else if ty.has_type_flags(TypeFlags::HAS_PLACEHOLDER | TypeFlags::HAS_RE_INFER) {


why only RE_INFER instead of full infer?

bc we only care about infer regions in this folder's logic -- it would not even be necessary if we didn't replace free regions with infer

why would we care about ty/ct infer for this folder anyways? 🤔

we only care as in: there should never be infer types/consts in the param_env 😁 if we end up with a ty var for whatever reason, then this folder would start incorrectly treating (): Trait<?x> as global evne though it shouldn't be. It currently detects ambiguous aliases in the env as global

I don't see how that is the case and how this behavior would change with this fast path, given that visit_ty does not care about infer types at all and because structurally_normalize_ty just returns Ok(_) for infer types.

Can you explain in more detail, because I am obviously missing something here?

if you've got u32: Trait<AmbiguousAlias>, structurally normalizing that alias results in Ok(_).

At this point we return ControlFlow::Continue(()), treating this where-bound as global. The fast path doesn't matter here 🤔 I generally feel like the way we're handling ambiguous aliases/ty infer vars here isn't right.

I can't really think of an example where this matters. HAving a TAIT in the where-clauses makes it possible to encounter this in theory, but I can't think of a program where this is matters.

I guess 🤷

lcnr · 2025-07-25T10:17:19Z

@bors r+

bors · 2025-07-25T10:17:22Z

📌 Commit e13757e has been approved by lcnr

It is now in the queue for this repository.

bors · 2025-07-26T16:57:49Z

⌛ Testing commit e13757e with merge ce5fdd7...

bors · 2025-07-26T19:57:54Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing ce5fdd7 to master...

github-actions · 2025-07-26T20:01:16Z

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 133798f (parent) -> ce5fdd7 (this PR)

Test differences

Show 8 test diffs

8 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 ce5fdd7d42aba9a2925692e11af2bd39cf37798a --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

x86_64-apple-1: 6290.1s -> 7734.4s (23.0%)
dist-x86_64-apple: 9145.1s -> 7364.4s (-19.5%)
dist-apple-various: 6846.8s -> 5803.0s (-15.2%)
pr-check-2: 2710.7s -> 2445.1s (-9.8%)
arm-android: 6632.2s -> 6062.0s (-8.6%)
aarch64-gnu-debug: 4480.1s -> 4147.5s (-7.4%)
x86_64-gnu-llvm-19-3: 7184.3s -> 6669.5s (-7.2%)
x86_64-gnu-llvm-19: 2948.1s -> 2737.3s (-7.2%)
x86_64-rust-for-linux: 3051.6s -> 2837.7s (-7.0%)
aarch64-gnu-llvm-19-1: 3759.8s -> 3518.1s (-6.4%)

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 · 2025-07-26T21:08:56Z

Finished benchmarking commit (ce5fdd7): comparison URL.

Overall result: ✅ improvements - 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
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.6%	[-0.6%, -0.5%]	3
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -3.2%, secondary -1.0%)

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)	1.0%	[1.0%, 1.0%]	1
Improvements ✅ (primary)	-3.2%	[-3.2%, -3.2%]	1
Improvements ✅ (secondary)	-3.0%	[-3.0%, -3.0%]	1
All ❌✅ (primary)	-3.2%	[-3.2%, -3.2%]	1

Cycles

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

Binary size

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

Bootstrap: 466.195s -> 466.456s (0.06%)
Artifact size: 376.61 MiB -> 376.58 MiB (-0.01%)

[perf] Skip walking into param-env component if it has no placeholder…

e13757e

…/re-var

rustbot added 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 Jul 5, 2025

This comment has been minimized.

Sign in to view

rust-bors bot added a commit that referenced this pull request Jul 5, 2025

Auto merge of #143500 - compiler-errors:characterize-less, r=<try>

e3ecd5f

[perf] Skip walking into param-env component if it has no placeholder/re-var

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 5, 2025

This comment has been minimized.

Sign in to view

rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 5, 2025

compiler-errors changed the title ~~[perf] Skip walking into param-env component if it has no placeholder/re-var~~ Skip walking into param-env component if it has no placeholder/re-var Jul 6, 2025

rustbot assigned lcnr Jul 6, 2025

compiler-errors marked this pull request as ready for review July 6, 2025 17:18

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 6, 2025

lcnr reviewed Jul 7, 2025

View reviewed changes

lcnr added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 11, 2025

compiler-errors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 11, 2025

bors 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 Jul 25, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 26, 2025

bors merged commit ce5fdd7 into rust-lang:master Jul 26, 2025
12 checks passed

rustbot added this to the 1.90.0 milestone Jul 26, 2025

Skip walking into param-env component if it has no placeholder/re-var #143500

Skip walking into param-env component if it has no placeholder/re-var #143500

Conversation

compiler-errors commented Jul 5, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

compiler-errors commented Jul 5, 2025

Uh oh!

This comment has been minimized.

rust-bors bot commented Jul 5, 2025

Uh oh!

rust-bors bot commented Jul 5, 2025

Uh oh!

This comment has been minimized.

rust-timer commented Jul 5, 2025

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

Uh oh!

compiler-errors commented Jul 6, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

compiler-errors Jul 11, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lcnr Jul 25, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lcnr commented Jul 25, 2025

Uh oh!

bors commented Jul 25, 2025

Uh oh!

bors commented Jul 26, 2025

Uh oh!

bors commented Jul 26, 2025

Uh oh!

Uh oh!

github-actions bot commented Jul 26, 2025

Test differences

Job duration changes

Uh oh!

rust-timer commented Jul 26, 2025

Overall result: ✅ improvements - no action needed

Uh oh!

Uh oh!

compiler-errors commented Jul 5, 2025 •

edited

Loading

compiler-errors Jul 11, 2025 •

edited

Loading

lcnr Jul 25, 2025 •

edited

Loading