Resolver: (un)tracked borrows for `CmRefCell` made safe by unsafe speculative flag by LorrensP-2158466 · Pull Request #160510 · rust-lang/rust

LorrensP-2158466 · 2026-08-04T14:04:56Z

Implements the tracked/untracked borrowing of CmRefCell such that we do not mutate any state during speculative resolution. Made safe by an unsafe field that requires any borrows to be dropped before the flag can change.

r? @petrochenkov

petrochenkov · 2026-08-04T14:30:11Z

We already benchmarked this as a regression (due to returning CmRef from borrow and resolution), but we know that #160345 recovers most of the performance, so we can merge this separately.

LorrensP-2158466 · 2026-08-04T14:34:29Z

Unfortunately, we can't "tie" the borrow of the resolver to the CmRef because it conflicts to much. Sometimes we only require a borrow of a CmRefCell but still want to mutate the resolver it self in some way.

petrochenkov · 2026-08-04T14:41:45Z

Unfortunately, we can't "tie" the borrow of the resolver to the CmRef because it conflicts to much. Sometimes we only require a borrow of a CmRefCell but still want to mutate the resolver it self in some way.

Yeah, I expected it to be very inconvenient.

…which does tracked and untracked borrowing

LorrensP-2158466 · 2026-08-04T15:44:46Z

force-pushed to keep it at one commit, @rustbot ready.

petrochenkov · 2026-08-04T16:51:18Z

@bors r+

rust-bors · 2026-08-04T16:51:21Z

📌 Commit e0830fa has been approved by petrochenkov

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 10. This pull request will be tested once the tree is reopened.

Reason for tree closure: manually handling queue due to backlog

@petrochenkov

…ative-flag, r=petrochenkov Resolver: (un)tracked borrows for `CmRefCell` made safe my unsafe speculative flag Implements the tracked/untracked borrowing of `CmRefCell` such that we do not mutate *any* state during speculative resolution. Made safe by an unsafe field that requires any borrows to be dropped before the flag can change. r? @petrochenkov

@petrochenkov

…ative-flag, r=petrochenkov Resolver: (un)tracked borrows for `CmRefCell` made safe my unsafe speculative flag Implements the tracked/untracked borrowing of `CmRefCell` such that we do not mutate *any* state during speculative resolution. Made safe by an unsafe field that requires any borrows to be dropped before the flag can change. r? @petrochenkov

@petrochenkov

…ative-flag, r=petrochenkov Resolver: (un)tracked borrows for `CmRefCell` made safe my unsafe speculative flag Implements the tracked/untracked borrowing of `CmRefCell` such that we do not mutate *any* state during speculative resolution. Made safe by an unsafe field that requires any borrows to be dropped before the flag can change. r? @petrochenkov

…uwer Rollup of 22 pull requests Successful merges: - #158147 (std: fix stack buffer overflow in Windows junction_point) - #159784 (Hint that memchr returns an in-bounds index) - #160130 (Select cache values to verify by key fingerprint, not value fingerprint) - #160343 (Rename `OutlivesPredicate` to `OutlivesClause`) - #160360 (Remove rustc_middle dependency on rustc_hir_pretty) - #160387 (rustc_codegen_ssa: Correctly apply the static `--jobs-backend` limit to backend parallelism) - #160422 (move mir-opt miri tests to CI logic) - #160444 (Avoid resolving path keywords outside `TypeNS`) - #160510 (Resolver: (un)tracked borrows for `CmRefCell` made safe my unsafe speculative flag) - #155424 ([blocked] Link to proposed LLM policy in CONTRIBUTING and pull request template) - #158726 (std: move futex implementations into sys::sync::futex) - #159225 (Split IncrCompSession out of Session) - #159820 (Make the `rustc_unsafe_specialization_marker` attribute actually `unsafe`) - #160198 (Rework `smallest_range_containing` to handle duplicates) - #160362 (Split `SpannedTypeVisitor` into its own crate, `rustc_ty_walk`) - #160390 (autodiff: Handle slice-tailed DSTs in type trees) - #160420 (Suggest `cast_signed()` for overflowing signed integer literals) - #160520 (Add some tests for specialization) - #160522 (fix(bootstrap): Normalize the names of proc macro dependency crates) - #160531 (docs: fix typo in AllowExprMetavar comment) - #160538 (Update expect messages in tcp.rs doc examples to follow the style guide) - #160548 (bootstrap: Register `coverage-map` and `coverage-run` aliases via a separate step)

@petrochenkov

…ative-flag, r=petrochenkov Resolver: (un)tracked borrows for `CmRefCell` made safe my unsafe speculative flag Implements the tracked/untracked borrowing of `CmRefCell` such that we do not mutate *any* state during speculative resolution. Made safe by an unsafe field that requires any borrows to be dropped before the flag can change. r? @petrochenkov

…uwer Rollup of 25 pull requests Successful merges: - #154585 (treat no_mangle_generic_items as hard error instead of lint warning) - #158147 (std: fix stack buffer overflow in Windows junction_point) - #160130 (Select cache values to verify by key fingerprint, not value fingerprint) - #160343 (Rename `OutlivesPredicate` to `OutlivesClause`) - #160360 (Remove rustc_middle dependency on rustc_hir_pretty) - #160387 (rustc_codegen_ssa: Correctly apply the static `--jobs-backend` limit to backend parallelism) - #160422 (move mir-opt miri tests to CI logic) - #160444 (Avoid resolving path keywords outside `TypeNS`) - #160510 (Resolver: (un)tracked borrows for `CmRefCell` made safe my unsafe speculative flag) - #155424 ([blocked] Link to proposed LLM policy in CONTRIBUTING and pull request template) - #158726 (std: move futex implementations into sys::sync::futex) - #158762 (Emit thumb code on VEX V5) - #159225 (Split IncrCompSession out of Session) - #159820 (Make the `rustc_unsafe_specialization_marker` attribute actually `unsafe`) - #160198 (Rework `smallest_range_containing` to handle duplicates) - #160362 (Split `SpannedTypeVisitor` into its own crate, `rustc_ty_walk`) - #160390 (autodiff: Handle slice-tailed DSTs in type trees) - #160420 (Suggest `cast_signed()` for overflowing signed integer literals) - #160516 (Add regression test for HRTB projection in closure) - #160520 (Add some tests for specialization) - #160522 (fix(bootstrap): Normalize the names of proc macro dependency crates) - #160523 (Add regression test for opaque type) - #160531 (docs: fix typo in AllowExprMetavar comment) - #160538 (Update expect messages in tcp.rs doc examples to follow the style guide) - #160548 (bootstrap: Register `coverage-map` and `coverage-run` aliases via a separate step)

…uwer Rollup of 25 pull requests Successful merges: - #158147 (std: fix stack buffer overflow in Windows junction_point) - #160130 (Select cache values to verify by key fingerprint, not value fingerprint) - #160343 (Rename `OutlivesPredicate` to `OutlivesClause`) - #160360 (Remove rustc_middle dependency on rustc_hir_pretty) - #160387 (rustc_codegen_ssa: Correctly apply the static `--jobs-backend` limit to backend parallelism) - #160422 (move mir-opt miri tests to CI logic) - #160444 (Avoid resolving path keywords outside `TypeNS`) - #160510 (Resolver: (un)tracked borrows for `CmRefCell` made safe by unsafe speculative flag) - #155424 ([blocked] Link to proposed LLM policy in CONTRIBUTING and pull request template) - #158726 (std: move futex implementations into sys::sync::futex) - #158762 (Emit thumb code on VEX V5) - #159225 (Split IncrCompSession out of Session) - #159820 (Make the `rustc_unsafe_specialization_marker` attribute actually `unsafe`) - #160198 (Rework `smallest_range_containing` to handle duplicates) - #160362 (Split `SpannedTypeVisitor` into its own crate, `rustc_ty_walk`) - #160390 (autodiff: Handle slice-tailed DSTs in type trees) - #160420 (Suggest `cast_signed()` for overflowing signed integer literals) - #160501 (Add bootstrap CLI snapshot test for testing miri) - #160516 (Add regression test for HRTB projection in closure) - #160520 (Add some tests for specialization) - #160522 (fix(bootstrap): Normalize the names of proc macro dependency crates) - #160523 (Add regression test for opaque type) - #160531 (docs: fix typo in AllowExprMetavar comment) - #160538 (Update expect messages in tcp.rs doc examples to follow the style guide) - #160548 (bootstrap: Register `coverage-map` and `coverage-run` aliases via a separate step)

@petrochenkov

Rollup merge of #160510 - LorrensP-2158466:res-unsafe-speculative-flag, r=petrochenkov Resolver: (un)tracked borrows for `CmRefCell` made safe by unsafe speculative flag Implements the tracked/untracked borrowing of `CmRefCell` such that we do not mutate *any* state during speculative resolution. Made safe by an unsafe field that requires any borrows to be dropped before the flag can change. r? @petrochenkov

JonathanBrouwer · 2026-08-06T20:15:02Z

@rust-timer build 26842a9

rust-timer · 2026-08-06T20:15:05Z

Queued 26842a9 with parent 22950ab, future comparison URL.
There are currently 8 preceding artifacts in the queue.
It will probably take at least ~8.8 hours until the benchmark run finishes.

rustbot assigned petrochenkov Aug 4, 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 Aug 4, 2026

petrochenkov reviewed Aug 4, 2026

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Comment thread compiler/rustc_resolve/src/imports.rs

Comment thread compiler/rustc_resolve/src/lib.rs Outdated

Comment thread compiler/rustc_resolve/src/lib.rs Outdated

Comment thread compiler/rustc_resolve/src/lib.rs Outdated

Comment thread compiler/rustc_resolve/src/lib.rs Outdated

petrochenkov 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 Aug 4, 2026

implement unsafe speculative flag to be used by CmRefCell::borrow, …

e0830fa

…which does tracked and untracked borrowing

LorrensP-2158466 force-pushed the res-unsafe-speculative-flag branch from 17802e1 to e0830fa Compare August 4, 2026 15:44

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 Aug 4, 2026

rust-bors Bot 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 Aug 4, 2026

JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 11 pull requests #160547

Closed

jhpratt mentioned this pull request Aug 5, 2026

Rollup of 16 pull requests #160549

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JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 22 pull requests #160554

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JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 25 pull requests #160557

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LorrensP-2158466 changed the title ~~Resolver: (un)tracked borrows for CmRefCell made safe my unsafe speculative flag~~ Resolver: (un)tracked borrows for CmRefCell made safe by unsafe speculative flag Aug 5, 2026

JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 25 pull requests #160559

Merged

rust-bors Bot merged commit 82c5ef1 into rust-lang:main Aug 5, 2026
13 checks passed

rustbot added this to the 1.99.0 milestone Aug 5, 2026

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Resolver: (un)tracked borrows for `CmRefCell` made safe by unsafe speculative flag - #160510

Resolver: (un)tracked borrows for `CmRefCell` made safe by unsafe speculative flag#160510
rust-bors[bot] merged 1 commit into
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LorrensP-2158466:res-unsafe-speculative-flag

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