Expand free alias types during variance computation by fmease · Pull Request #141030 · rust-lang/rust

fmease · 2025-05-15T11:03:42Z

Instead of computing variances for them since they can never be rigid anyway.

fmease · 2025-05-15T11:03:58Z

[WIP] Expand free alias types during variance computation Instead of computing variances for them since they can never be rigid anyway. Fixes rust-lang#140230.

bors · 2025-05-15T11:05:09Z

⌛ Trying commit 1c11869 with merge 1b77fcd...

bors · 2025-05-15T13:12:13Z

☀️ Try build successful - checks-actions
Build commit: 1b77fcd (1b77fcd0847b6d6dcac3b0857fc0acc504e9f357)

rust-timer · 2025-05-15T14:54:37Z

Finished benchmarking commit (1b77fcd): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	0.7%	[0.7%, 0.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.1%	[1.1%, 1.1%]	1

Max RSS (memory usage)

Results (primary 3.2%, secondary 5.0%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	3.2%	[0.5%, 9.0%]	4
Regressions ❌ (secondary)	5.0%	[4.6%, 5.4%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.2%	[0.5%, 9.0%]	4

Cycles

Results (primary -0.8%, secondary -10.5%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.8%	[-0.8%, -0.8%]	1
Improvements ✅ (secondary)	-10.5%	[-14.0%, -2.6%]	7
All ❌✅ (primary)	-0.8%	[-0.8%, -0.8%]	1

Binary size

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

Bootstrap: 773.561s -> 773.719s (0.02%)
Artifact size: 365.44 MiB -> 365.31 MiB (-0.04%)

fmease · 2025-07-10T15:38:26Z

@bors2 try @rust-timer queue

rust-bors · 2025-07-10T15:38:31Z

⌛ Trying commit 9429c14 with merge f04a108…

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

[WIP] Expand free alias types during variance computation Instead of computing variances for them since they can never be rigid anyway. Fixes #140230.

rust-bors · 2025-07-10T17:53:45Z

☀️ Try build successful (CI)
Build commit: f04a108 (f04a1083ef0335f753c2d52583e8cc33a34e95fb, parent: 119574f83576dc1f3ae067f9a97986d4e2b0826c)

rust-timer · 2025-07-10T19:11:21Z

Finished benchmarking commit (f04a108): 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 -1.5%, secondary 1.4%)

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)	4.6%	[3.1%, 6.1%]	2
Improvements ✅ (primary)	-1.5%	[-1.5%, -1.5%]	1
Improvements ✅ (secondary)	-5.0%	[-5.0%, -5.0%]	1
All ❌✅ (primary)	-1.5%	[-1.5%, -1.5%]	1

Cycles

Results (secondary 2.1%)

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)	2.1%	[2.1%, 2.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
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
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	1
All ❌✅ (primary)	-	-	0

Bootstrap: 463.013s -> 463.287s (0.06%)
Artifact size: 374.51 MiB -> 374.53 MiB (0.01%)

rustbot · 2026-06-10T08:33:41Z

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.

fmease · 2026-06-10T08:39:38Z

#141030 (comment)

addressed @rustbot review

…e aliases

Add more tests that exercise the well-formedness checking of lazy type aliases Split out of PR rust-lang#141030. No behavioral changes.

BoxyUwU · 2026-06-11T00:58:39Z

@bors r+

thanks fmease :) good stuff

rust-bors · 2026-06-11T00:58:42Z

📌 Commit 05aee18 has been approved by BoxyUwU

It is now in the queue for this repository.

Expand free alias types during variance computation Instead of computing variances for them since they can never be rigid anyway. Fixes rust-lang#140230.

Rollup of 31 pull requests Successful merges: - #141030 (Expand free alias types during variance computation) - #154853 (mgca: Register `ConstArgHasType` when normalizing projection consts) - #155527 (Replace printables table with `unicode_data.rs` tables) - #156629 (Stabilize `core::range::{legacy, RangeFull, RangeTo}`) - #157280 (traits: Allow escaping self types in ExistentialTraitRef::with_self_ty) - #157282 (Fix post-monomorphization error note race in the parallel frontend) - #157352 (Make the retained dep graph deterministic under the parallel frontend) - #157601 (Emit error for unused target expression in glob and list delegations) - #157611 (Update `browser-ui-test` version to `0.24.0`) - #157620 (Add a strategy FnMut to inject behavior into the flush cycle) - #157645 (Windows TLS - Only register the `atexit` hook when `cleanup` can be unloaded) - #157646 (Keep rename-imported main alive in dead-code analysis under `--test`) - #157647 (Start using comptime for reflection intrinsics and their wrapper functions) - #157719 (resolve: Partially revert "Remove a special case for dummy imports") - #155153 (Ensure Send/Sync is not implemented for std::env::Vars{,Os}) - #155198 (fix(mgca): Allow specifying generic args (of enum) on enum itself in unit & tuple variant constructions in (direct) const args) - #155323 (refactor `TypeRelativePath::AssocItem` to use `AliasTerm`) - #156497 (fix-155516: Don't suggest wrong unwrap expect) - #156583 (Support defaults for static EIIs) - #157013 (Ensure inferred let pattern types are well-formed) - #157196 (Only suggest reborrowing a moved value where the reborrow is valid) - #157230 (borrowck: avoid ICE describing fields on generic params) - #157288 (platform support: add SNaN erratum to MIPS targets) - #157330 (remove `IsTypeConst` from `hir::TraitItemKind`) - #157350 (compiletest: ignore SVG `y` offset in by-lines comparison) - #157355 (Add `or_try_*` variants for `HashMap` and `BTreeMap` Entry APIs) - #157577 (Fix parser error recovery treating 'dyn' as a strict keyword in Rust 2015 when used in `dyn + dyn`) - #157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N)) - #157691 (Move symbol hiding code to a new file) - #157700 (Rename `errors.rs` file to `diagnostics.rs` (5/N)) - #157703 (Fix doc link to Instant sub in saturating caveat) Failed merges: - #157699 (Arg splat experiment - hir FnDecl impl)

Rollup merge of #141030 - fmease:lta-no-variance, r=BoxyUwU Expand free alias types during variance computation Instead of computing variances for them since they can never be rigid anyway. Fixes #140230.

Rollup of 31 pull requests Successful merges: - rust-lang#141030 (Expand free alias types during variance computation) - rust-lang#154853 (mgca: Register `ConstArgHasType` when normalizing projection consts) - rust-lang#155527 (Replace printables table with `unicode_data.rs` tables) - rust-lang#156629 (Stabilize `core::range::{legacy, RangeFull, RangeTo}`) - rust-lang#157280 (traits: Allow escaping self types in ExistentialTraitRef::with_self_ty) - rust-lang#157282 (Fix post-monomorphization error note race in the parallel frontend) - rust-lang#157352 (Make the retained dep graph deterministic under the parallel frontend) - rust-lang#157601 (Emit error for unused target expression in glob and list delegations) - rust-lang#157611 (Update `browser-ui-test` version to `0.24.0`) - rust-lang#157620 (Add a strategy FnMut to inject behavior into the flush cycle) - rust-lang#157645 (Windows TLS - Only register the `atexit` hook when `cleanup` can be unloaded) - rust-lang#157646 (Keep rename-imported main alive in dead-code analysis under `--test`) - rust-lang#157647 (Start using comptime for reflection intrinsics and their wrapper functions) - rust-lang#157719 (resolve: Partially revert "Remove a special case for dummy imports") - rust-lang#155153 (Ensure Send/Sync is not implemented for std::env::Vars{,Os}) - rust-lang#155198 (fix(mgca): Allow specifying generic args (of enum) on enum itself in unit & tuple variant constructions in (direct) const args) - rust-lang#155323 (refactor `TypeRelativePath::AssocItem` to use `AliasTerm`) - rust-lang#156497 (fix-155516: Don't suggest wrong unwrap expect) - rust-lang#156583 (Support defaults for static EIIs) - rust-lang#157013 (Ensure inferred let pattern types are well-formed) - rust-lang#157196 (Only suggest reborrowing a moved value where the reborrow is valid) - rust-lang#157230 (borrowck: avoid ICE describing fields on generic params) - rust-lang#157288 (platform support: add SNaN erratum to MIPS targets) - rust-lang#157330 (remove `IsTypeConst` from `hir::TraitItemKind`) - rust-lang#157350 (compiletest: ignore SVG `y` offset in by-lines comparison) - rust-lang#157355 (Add `or_try_*` variants for `HashMap` and `BTreeMap` Entry APIs) - rust-lang#157577 (Fix parser error recovery treating 'dyn' as a strict keyword in Rust 2015 when used in `dyn + dyn`) - rust-lang#157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N)) - rust-lang#157691 (Move symbol hiding code to a new file) - rust-lang#157700 (Rename `errors.rs` file to `diagnostics.rs` (5/N)) - rust-lang#157703 (Fix doc link to Instant sub in saturating caveat) Failed merges: - rust-lang#157699 (Arg splat experiment - hir FnDecl impl)

fmease added this to Lazy Type Aliases (LTA) May 15, 2025

fmease moved this to In Progress in Lazy Type Aliases (LTA) May 15, 2025