Resolver: Batched Import Resolution by LorrensP-2158466 · Pull Request #145108 · rust-lang/rust

LorrensP-2158466 · 2025-08-08T15:54:37Z

Transforms the current algorithm for resolving imports to a batched algorithm. Every import in the indeterminate_imports set is resolved in isolation. This is the only real difference from the current algorithm.

r? petrochenkov

compiler/rustc_resolve/src/lib.rs

compiler/rustc_resolve/src/imports.rs

LorrensP-2158466 · 2025-08-11T19:29:42Z

Code looks a little better now and should be more correct than the previous commits, but I have yet to find a way to resolve the current test failures.

LorrensP-2158466 · 2025-08-11T20:34:04Z

Okey, I did fix core not being built, but those other errors happened again. We now resolve the prelude import path when we create such an import at build_reduced_graph phase.

petrochenkov · 2025-08-11T22:39:59Z

Could you update the tests to make CI green, so I can see the difference?
(Even if the changes do not seem correct.)

tests/ui/imports/ambiguous-9.rs

tests/ui/imports/glob-conflict-cross-crate-1.rs

tests/ui/proc-macro/derive-helper-legacy-spurious.rs

petrochenkov · 2025-08-12T17:43:51Z

Moving prelude_import processing to build_reduced_graph may also be necessary for #139493.

LorrensP-2158466 · 2025-08-12T17:49:54Z

I'll create a pr for it.

compiler/rustc_resolve/src/imports.rs

rust-timer · 2026-02-20T15:25:07Z

Finished benchmarking commit (fa4dd1f): 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)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	0.3%	[0.2%, 0.7%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.8%	[-0.8%, -0.8%]	1
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	1

Max RSS (memory usage)

Results (primary -0.0%, secondary 3.2%)

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

	mean	range	count
Regressions ❌ (primary)	1.6%	[0.7%, 3.2%]	3
Regressions ❌ (secondary)	3.2%	[2.1%, 4.8%]	3
Improvements ✅ (primary)	-2.4%	[-2.9%, -2.0%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.0%	[-2.9%, 3.2%]	5

Cycles

Results (primary -3.1%)

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)	-	-	0
Improvements ✅ (primary)	-3.1%	[-3.1%, -3.1%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-3.1%	[-3.1%, -3.1%]	1

Binary size

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

Bootstrap: 481.762s -> 496.521s (3.06%)
Artifact size: 397.93 MiB -> 397.97 MiB (0.01%)

petrochenkov · 2026-02-20T16:41:21Z

Nice.
@craterbot check

craterbot · 2026-02-20T16:41:46Z

👌 Experiment pr-145108-2 created and queued.
🤖 Automatically detected try build fa4dd1f
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-02-21T05:08:28Z

🚧 Experiment pr-145108-2 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-02-23T00:45:10Z

🎉 Experiment pr-145108-2 is completed!
📊 161 regressed and 1 fixed (821749 total)
📊 2472 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-145108-2/retry-regressed-list.txt ↩

petrochenkov · 2026-02-23T06:33:06Z

Looks like rust-embed is still a problem.
Could you rebase, squash commits and re-apply the rust-embed hack commit on top of the other changes?
@rustbot author

LorrensP-2158466 · 2026-02-24T17:04:31Z

Fixed conflicts, squashed and re-applied rust-embed fix. @rustbot ready

compiler/rustc_resolve/src/imports.rs

Import resolution now happens in 2 phases: 1. We resolve all undetermined and collect their resolutions 2. Write all resolutions to the Resolver state. Repeat this untill we reach a fix point. + Bless tests

rustbot · 2026-03-08T15:30:59Z

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.

LorrensP-2158466 · 2026-03-08T15:32:53Z

Rebased to fix the conflicts.

The rustembed hack is a bit more generic, than just checking for RustEmbed.

@rustbot ready

compiler/rustc_resolve/src/imports.rs

petrochenkov · 2026-03-08T18:23:08Z

The rustembed hack is a bit more generic, than just checking for RustEmbed.

Here we need to address a specific set of regressions caused by one specific crate, not bend the language rules in general, the smaller the scope of the hack is the better.
The ambiguous_import_visibilities lint is the more generic solution.

LorrensP-2158466 · 2026-03-09T11:47:18Z

Yes, that's right, I forgot to make myself clear why I made it generic. I couldn't exactly find a way to these 2 points:

X is from macro_use_prelude and has name RustEmbed
module has a macro namespace binding Y with name RustEmbed in it

I couldn't exactly find a way to check exactly with the name RustEmbed. So I wanted to ask how I can search for a binding with identifier RustEmbed or check that X has such an identifier. Sorry

compiler/rustc_resolve/src/imports.rs

LorrensP-2158466 · 2026-03-11T11:23:46Z

Didn't know I could just add a new symbol, thanks!

@rustbot ready

petrochenkov · 2026-03-11T11:34:46Z

@bors try

petrochenkov · 2026-03-11T11:37:02Z

TODO: @craterbot check p=1 crates=https://crater-reports.s3.amazonaws.com/pr-145108-2/retry-regressed-list.txt

rust-bors · 2026-03-11T13:42:45Z

☀️ Try build successful (CI)
Build commit: 0799524 (0799524677c1163b7afa649c7b4006f3d351a1c1, parent: b2fabe39bde5174e8d728bb85f2b8d0572c35b74)

petrochenkov · 2026-03-11T13:47:48Z

@craterbot check p=1 crates=https://crater-reports.s3.amazonaws.com/pr-145108-2/retry-regressed-list.txt

craterbot · 2026-03-11T13:47:54Z

👌 Experiment pr-145108-3 created and queued.
🤖 Automatically detected try build 0799524
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-03-13T13:10:06Z

🚧 Experiment pr-145108-3 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2026-03-13T16:52:26Z

🎉 Experiment pr-145108-3 is completed!
📊 31 regressed and 0 fixed (2551 total)
📊 179 spurious results on the retry-regressed-list.txt, consider a retry¹ if this is a significant amount.
📰 Open the summary report.

⚠️ If you notice any spurious failure please add them to the denylist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

re-run the experiment with crates=https://crater-reports.s3.amazonaws.com/pr-145108-3/retry-regressed-list.txt ↩

petrochenkov · 2026-03-13T17:23:31Z

Need regression analysis, each of the regressions need to fall under one of the deprecation lints we've merged recently.
I'll do it myself in a few days.

rustbot assigned petrochenkov Aug 8, 2025

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 8, 2025

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LorrensP-2158466 marked this pull request as ready for review August 11, 2025 08:37

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LorrensP-2158466 force-pushed the batched-import-resolution branch from a3f8ae2 to 4a2a0dc Compare August 11, 2025 20:37

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LorrensP-2158466 added 2 commits March 8, 2026 16:27

Resolver: Batched import resolution.

a54d3a4

Import resolution now happens in 2 phases: 1. We resolve all undetermined and collect their resolutions 2. Write all resolutions to the Resolver state. Repeat this untill we reach a fix point. + Bless tests

hack for RustEmbed with updated test

fb2ab4b

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make rustembed hack only work for rustembed

5cd22e1

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rust-timer commented Feb 20, 2026

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

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