rustc_resolve: Further reduce mutability in resolver by petrochenkov · Pull Request #160090 · rust-lang/rust

petrochenkov · 2026-07-28T16:04:31Z

resolver.cm() now returns a conditionally mutable reference (RefOrMut) that cannot be mutated, and resolver.cm_mut() returns a conditionally mutable reference that can be mutated.

The "can be mutated" property is checked dynamically, so this can potentially panic in some obscure error reporting cases not covered by the test suite, but they should be easily fixable and will be caught sooner or later, but it's more useful to see which code path actually use resolver in mutable way rather than just take RefOrMut.

The second commit converts RefOrMut to an enum instead of using raw pointers.

r? @mu001999
cc @LorrensP-2158466

petrochenkov · 2026-07-29T08:39:15Z

I'll try changing RefOrMut to an enum to avoid unsafe code.
(I remember why it wasn't made an enum originally, but it should no longer be relevant.)
@rustbot author

rustbot · 2026-07-29T08:39:20Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

mu001999 · 2026-07-29T08:46:17Z

I'm not sure how difficult this would be or whether it's feasible, but could we use different types for Ref and Mut instead of combining them in RefOrMut?

petrochenkov · 2026-07-29T08:55:25Z

I'm not sure how difficult this would be or whether it's feasible, but could we use different types for Ref and Mut instead of combining them in RefOrMut?

Not feasible, functions taking RefOrMut do that because they must work with both mutable and immutable versions, dynamically.

Or rather infeasible without duplicating a large number of resolver functions.
Perhaps the "duplication" could also be done by turning Finalize into a const generic argument, although I'm not sure and it would also be a large change.

petrochenkov · 2026-07-29T10:59:41Z

@bors try @rust-timer queue

rustc_resolve: Further reduce mutability in resolver

rust-bors · 2026-07-29T13:04:55Z

☀️ Try build successful (CI)
Build commit: df44b1a (df44b1aa081b3f74f4d68fe6d1de048820cbb3ca)
Base parent: ce69831 (ce6983167791bf9418726264f8e5cc7abf73d69b)

rust-timer · 2026-07-29T13:45:27Z

Finished benchmarking commit (df44b1a): comparison URL.

Overall result: ❌ regressions - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@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)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 3.7%, secondary 0.4%)

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

	mean	range	count
Regressions ❌ (primary)	3.7%	[1.4%, 5.2%]	3
Regressions ❌ (secondary)	5.3%	[5.3%, 5.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.6%	[-4.6%, -4.6%]	1
All ❌✅ (primary)	3.7%	[1.4%, 5.2%]	3

Cycles

Results (secondary 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)	2.4%	[2.3%, 2.5%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 490.002s -> 491.705s (0.35%)
Artifact size: 390.14 MiB -> 390.21 MiB (0.02%)

rustbot · 2026-07-29T14:18:43Z

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.

petrochenkov · 2026-07-29T14:18:54Z

@rustbot ready

mu001999

@rustbot author

View changes since this review

mu001999 · 2026-07-29T15:42:23Z

@bors r+ rollup

rust-bors · 2026-07-29T15:42:26Z

📌 Commit c9f7b96 has been approved by mu001999

It is now in the queue for this repository.

@mu001999

rustc_resolve: Further reduce mutability in resolver `resolver.cm()` now returns a conditionally mutable reference (`RefOrMut`) that cannot be mutated, and `resolver.cm_mut()` returns a conditionally mutable reference that can be mutated. The "can be mutated" property is checked dynamically, so this can potentially panic in some obscure error reporting cases not covered by the test suite, but they should be easily fixable and will be caught sooner or later, but it's more useful to see which code path *actually* use resolver in mutable way rather than just take `RefOrMut`. The second commit uses standard `NonNull` in the implementation of `RefOrMut`. r? @mu001999 cc @LorrensP-2158466

Rollup of 17 pull requests Successful merges: - #159014 ([rustdoc] Do not take `doc(cfg())` into account when filtering doctests) - #159130 (a bit optimize four-digit chunks in integer formatting) - #159592 (core: implement bounded random sampling) - #159898 (Add intrinsic-test alias and set sample rate) - #158247 (hermit/fs: Return `unsupported()` instead of `from_raw_os_error(22)`) - #158649 (Hermit: fix `readdir()` ) - #159049 (Avoid ICE in From/TryFrom cast suggestion when encountering HRTBs) - #160053 (test: add test suite for the 85681 issue) - #160087 (Add regression test for nested associated-type projection ICE) - #160090 (rustc_resolve: Further reduce mutability in resolver) - #160099 (Resolver: split module resolutions into local and external resolutions) - #160106 (Add suggestions for `must_implement_one_of`) - #160117 (Remove unnecessary format usage) - #160134 (Work around Wine bug 60084 by calling WSAStartup at most once) - #160142 (bootstrap: remove use-lld config alias) - #160148 (Rename `errors.rs` file to `diagnostics.rs` (15/N)) - #160151 (Mark a doctest as requiring unwinding)

@mu001999

rustc_resolve: Further reduce mutability in resolver `resolver.cm()` now returns a conditionally mutable reference (`RefOrMut`) that cannot be mutated, and `resolver.cm_mut()` returns a conditionally mutable reference that can be mutated. The "can be mutated" property is checked dynamically, so this can potentially panic in some obscure error reporting cases not covered by the test suite, but they should be easily fixable and will be caught sooner or later, but it's more useful to see which code path *actually* use resolver in mutable way rather than just take `RefOrMut`. The second commit uses standard `NonNull` in the implementation of `RefOrMut`. r? @mu001999 cc @LorrensP-2158466

Rollup of 18 pull requests Successful merges: - #159130 (a bit optimize four-digit chunks in integer formatting) - #159592 (core: implement bounded random sampling) - #159898 (Add intrinsic-test alias and set sample rate) - #158247 (hermit/fs: Return `unsupported()` instead of `from_raw_os_error(22)`) - #158649 (Hermit: fix `readdir()` ) - #159049 (Avoid ICE in From/TryFrom cast suggestion when encountering HRTBs) - #160053 (test: add test suite for the 85681 issue) - #160087 (Add regression test for nested associated-type projection ICE) - #160090 (rustc_resolve: Further reduce mutability in resolver) - #160099 (Resolver: split module resolutions into local and external resolutions) - #160106 (Add suggestions for `must_implement_one_of`) - #160117 (Remove unnecessary format usage) - #160134 (Work around Wine bug 60084 by calling WSAStartup at most once) - #160139 (iter: specialize Take::count using advance_by) - #160142 (bootstrap: remove use-lld config alias) - #160148 (Rename `errors.rs` file to `diagnostics.rs` (15/N)) - #160151 (Mark a doctest as requiring unwinding) - #160166 (Use correct feature gates for `f16`/`f128` `From` impls)

@mu001999

rustc_resolve: Further reduce mutability in resolver `resolver.cm()` now returns a conditionally mutable reference (`RefOrMut`) that cannot be mutated, and `resolver.cm_mut()` returns a conditionally mutable reference that can be mutated. The "can be mutated" property is checked dynamically, so this can potentially panic in some obscure error reporting cases not covered by the test suite, but they should be easily fixable and will be caught sooner or later, but it's more useful to see which code path *actually* use resolver in mutable way rather than just take `RefOrMut`. The second commit uses standard `NonNull` in the implementation of `RefOrMut`. r? @mu001999 cc @LorrensP-2158466

…uwer Rollup of 18 pull requests Successful merges: - #159898 (Add intrinsic-test alias and set sample rate) - #158247 (hermit/fs: Return `unsupported()` instead of `from_raw_os_error(22)`) - #158649 (Hermit: fix `readdir()` ) - #158693 (Add type-check to offload intrinisc calls) - #159049 (Avoid ICE in From/TryFrom cast suggestion when encountering HRTBs) - #159411 ([rustdoc] Correctly handle output options with --show-coverage) - #160053 (test: add test suite for the 85681 issue) - #160087 (Add regression test for nested associated-type projection ICE) - #160090 (rustc_resolve: Further reduce mutability in resolver) - #160099 (Resolver: split module resolutions into local and external resolutions) - #160106 (Add suggestions for `must_implement_one_of`) - #160117 (Remove unnecessary format usage) - #160134 (Work around Wine bug 60084 by calling WSAStartup at most once) - #160139 (iter: specialize Take::count using advance_by) - #160142 (bootstrap: remove use-lld config alias) - #160148 (Rename `errors.rs` file to `diagnostics.rs` (15/N)) - #160151 (Mark a doctest as requiring unwinding) - #160166 (Use correct feature gates for `f16`/`f128` `From` impls)

Rollup of 20 pull requests Successful merges: - #157669 (cfi: add diag mode support) - #158247 (hermit/fs: Return `unsupported()` instead of `from_raw_os_error(22)`) - #158649 (Hermit: fix `readdir()` ) - #158693 (Add type-check to offload intrinisc calls) - #159049 (Avoid ICE in From/TryFrom cast suggestion when encountering HRTBs) - #159411 ([rustdoc] Correctly handle output options with --show-coverage) - #160053 (test: add test suite for the 85681 issue) - #160087 (Add regression test for nested associated-type projection ICE) - #160090 (rustc_resolve: Further reduce mutability in resolver) - #160099 (Resolver: split module resolutions into local and external resolutions) - #160101 (Add missing `needs-unwind` annotation to `add-spawn-hook-reentrancy-159923` test) - #160106 (Add suggestions for `must_implement_one_of`) - #160117 (Remove unnecessary format usage) - #160134 (Work around Wine bug 60084 by calling WSAStartup at most once) - #160139 (iter: specialize Take::count using advance_by) - #160142 (bootstrap: remove use-lld config alias) - #160148 (Rename `errors.rs` file to `diagnostics.rs` (15/N)) - #160151 (Mark a doctest as requiring unwinding) - #160166 (Use correct feature gates for `f16`/`f128` `From` impls) - #160178 (Remove unused `va_start` intrinsic)

@mu001999

Rollup merge of #160090 - petrochenkov:cmonst, r=mu001999 rustc_resolve: Further reduce mutability in resolver `resolver.cm()` now returns a conditionally mutable reference (`RefOrMut`) that cannot be mutated, and `resolver.cm_mut()` returns a conditionally mutable reference that can be mutated. The "can be mutated" property is checked dynamically, so this can potentially panic in some obscure error reporting cases not covered by the test suite, but they should be easily fixable and will be caught sooner or later, but it's more useful to see which code path *actually* use resolver in mutable way rather than just take `RefOrMut`. The second commit converts `RefOrMut` to an enum instead of using raw pointers. r? @mu001999 cc @LorrensP-2158466

jhpratt · 2026-07-30T23:42:21Z

@rust-timer build 3bb5bfc

rust-timer · 2026-07-31T01:16:53Z

Finished benchmarking commit (3bb5bfc): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@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
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.2%]	2
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -1.2%, 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
Regressions ❌ (secondary)	3.3%	[3.3%, 3.3%]	1
Improvements ✅ (primary)	-1.2%	[-1.2%, -1.2%]	1
Improvements ✅ (secondary)	-0.5%	[-0.6%, -0.4%]	6
All ❌✅ (primary)	-1.2%	[-1.2%, -1.2%]	1

Cycles

Results (primary 0.2%, secondary -3.3%)

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

	mean	range	count
Regressions ❌ (primary)	0.7%	[0.6%, 1.1%]	6
Regressions ❌ (secondary)	1.4%	[0.6%, 2.9%]	3
Improvements ✅ (primary)	-1.5%	[-2.1%, -1.0%]	2
Improvements ✅ (secondary)	-4.4%	[-16.8%, -0.4%]	13
All ❌✅ (primary)	0.2%	[-2.1%, 1.1%]	8

Binary size

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

Bootstrap: 491.471s -> 489.765s (-0.35%)
Artifact size: 390.58 MiB -> 390.47 MiB (-0.03%)

rustbot assigned mu001999 Jul 28, 2026

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 28, 2026

petrochenkov mentioned this pull request Jul 28, 2026

Resolver: Parallelize the import resolution loop #158845

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petrochenkov force-pushed the cmonst branch from 31e0a50 to a6f3450 Compare July 29, 2026 10:59

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rust-bors Bot pushed a commit that referenced this pull request Jul 29, 2026

Auto merge of #160090 - petrochenkov:cmonst, r=<try>

df44b1a

rustc_resolve: Further reduce mutability in resolver

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 29, 2026

petrochenkov added 2 commits July 29, 2026 16:50

rustc_resolve: Further reduce mutability in resolver

6b2608e

rustc_resolve: Turn RefOrMut into an enum

c9f7b96

petrochenkov force-pushed the cmonst branch from a6f3450 to c9f7b96 Compare July 29, 2026 14:18

rustbot 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 29, 2026

mu001999 reviewed Jul 29, 2026

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Comment thread compiler/rustc_resolve/src/lib.rs

Comment thread compiler/rustc_resolve/src/lib.rs

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jhpratt mentioned this pull request Jul 29, 2026

Rollup of 17 pull requests #160168

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jhpratt mentioned this pull request Jul 29, 2026

Rollup of 18 pull requests #160174

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JonathanBrouwer mentioned this pull request Jul 29, 2026

Rollup of 18 pull requests #160182

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jhpratt mentioned this pull request Jul 30, 2026

Rollup of 20 pull requests #160190

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rust-bors Bot merged commit f0fea75 into rust-lang:main Jul 30, 2026
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Overall result: ❌ regressions - no action needed

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Overall result: ✅ improvements - no action needed

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