Instantiate auto trait/`Copy`/`Clone`/`Sized` before computing constituent types binder #143538

compiler-errors · 2025-07-06T20:07:16Z

This makes the binder logic w.r.t. coroutines a bit simpler.

r? lcnr

compiler-errors · 2025-07-06T20:07:33Z

@bors2 try @rust-timer queue

and needs crater too when that's done

rust-bors · 2025-07-06T20:07:37Z

⌛ Trying commit 41eb6d8 with merge ad95a52…

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

Instantiate auto trait before computing higher-ranked constituent types This will need an FCP and a crater run, but I think this makes the binder logic w.r.t. auto traits and coroutines a bit simpler. r? lcnr

rust-bors · 2025-07-06T22:20:25Z

☀️ Try build successful (CI)
Build commit: ad95a52 (ad95a52e03621d91078ef94a829abc288aed9fb5, parent: de031bbcb161b0b7fc0eb16f77b02ce9fbdf4c9e)

rust-timer · 2025-07-07T07:09:44Z

Finished benchmarking commit (ad95a52): comparison URL.

Overall result: no relevant changes - 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

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

Max RSS (memory usage)

Results (primary -2.4%)

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

Cycles

Results (secondary -4.5%)

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.5%	[-4.5%, -4.5%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 460.528s -> 461.621s (0.24%)
Artifact size: 372.13 MiB -> 372.18 MiB (0.01%)

compiler/rustc_trait_selection/src/traits/select/mod.rs

lcnr · 2025-07-07T08:50:53Z

why does this need an FCP? we enter the merged binders right after calling constituent_types_for_ty and whether we've got placeholders from 2 different universes shouldn't matter 🤔 it would only matter if there was a way to create infer vars which can only name some of the placeholders, this shouldn't happen

We always instantiate the binder after calling copy_clone_conditions as well.

compiler-errors · 2025-07-07T22:22:03Z

Yeah, I don't see why this has an FCP. Was just being a bit conservative, but there's no observable behavioral change here that I can see.

compiler-errors · 2025-07-07T22:22:37Z

@bors2 try @rust-timer queue

rust-bors · 2025-07-07T22:22:40Z

⌛ Trying commit 9cb805e with merge 18fd892…

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

Instantiate auto trait before computing higher-ranked constituent types This makes the binder logic w.r.t. auto traits and coroutines a bit simpler. r? lcnr

rust-bors · 2025-07-08T00:35:51Z

☀️ Try build successful (CI)
Build commit: 18fd892 (18fd892b5bfc2ba679fb0c0af2b5b4f5fd09a6bb, parent: 2f8eeb2bba86b8f457ec602c578473c711f85628)

rust-timer · 2025-07-08T01:56:41Z

Finished benchmarking commit (18fd892): comparison URL.

Overall result: ❌ regressions - please read the text below

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.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.2%	[0.2%, 0.2%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	3

Max RSS (memory usage)

Results (secondary 2.2%)

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)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (primary -0.8%, secondary 1.1%)

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

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	4.8%	[4.8%, 4.8%]	1
Improvements ✅ (primary)	-3.8%	[-3.8%, -3.8%]	1
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	1
All ❌✅ (primary)	-0.8%	[-3.8%, 2.2%]	2

Binary size

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

Bootstrap: 465.909s -> 464.854s (-0.23%)
Artifact size: 372.26 MiB -> 372.25 MiB (-0.00%)

compiler-errors · 2025-07-08T02:01:22Z

This is either noise or insignificant wrt the cleanup

@rustbot ready

bors · 2025-07-08T07:36:12Z

☔ The latest upstream changes (presumably #143621) made this pull request unmergeable. Please resolve the merge conflicts.

lcnr · 2025-07-08T07:39:35Z

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

+            | ty::Str
+            | ty::Slice(..)
+            | ty::Foreign(..)
+            | ty::Ref(_, _, hir::Mutability::Mut) => {}


the comment is wrong for &mut _ 🤔

lcnr · 2025-07-08T07:41:20Z

r=me after rebase + nit

rustbot assigned lcnr Jul 6, 2025

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. labels Jul 6, 2025

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compiler-errors added the needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. label Jul 6, 2025

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 6, 2025

compiler-errors added T-types Relevant to the types team, which will review and decide on the PR/issue. and removed T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 6, 2025

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 7, 2025

lcnr reviewed Jul 7, 2025

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compiler/rustc_trait_selection/src/traits/select/mod.rs Show resolved Hide resolved

compiler-errors removed the needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. label Jul 7, 2025

compiler-errors and others added 3 commits July 7, 2025 21:18

Instantiate auto trait before computing higher-ranked constituent types

54c93ab

remove has_nested

f2d8d79

Instantiate binder for Copy/Clone/Sized eagerly

9cb805e

compiler-errors force-pushed the instantiate-auto-trait branch from 41eb6d8 to 9cb805e Compare July 7, 2025 22:21

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 7, 2025

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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 Jul 8, 2025

compiler-errors changed the title ~~Instantiate auto trait before computing higher-ranked constituent types~~ Instantiate auto trait/Copy/Clone/Sized before computing constituent types binder Jul 8, 2025

lcnr reviewed Jul 8, 2025

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Instantiate auto trait/Copy/Clone/Sized before computing constituent types binder #143538

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Instantiate auto trait/Copy/Clone/Sized before computing constituent types binder #143538

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rust-timer commented Jul 7, 2025

Overall result: no relevant changes - no action needed

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rust-timer commented Jul 8, 2025

Overall result: ❌ regressions - please read the text below

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lcnr commented Jul 8, 2025

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Instantiate auto trait/`Copy`/`Clone`/`Sized` before computing constituent types binder #143538

Instantiate auto trait/`Copy`/`Clone`/`Sized` before computing constituent types binder #143538

compiler-errors commented Jul 6, 2025 •

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