fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules - #159881

zalanlevai · 2026-07-25T04:40:20Z

The visible_parent_map query misses putting the child items of #[doc(hidden)] modules into the queue, resulting in the breadth-first search missing them entirely. This results in inconsistent path printing behavior affecting diagnostics: namely that re-exports nested deeply within #[doc(hidden)] modules are not considered as a possible fallback path. See the linked issue (#159880) for more details and an example of how this manifests in diagnostics.

This PR makes sure that #[doc(hidden)] parents in the fallback map are still searched as part of the breadth-first search.

Fixes #159880.

The two tests for this change are based on the inconsistent diagnostics shown in the issue:

tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-transitive-dep-item.rs captures the current, expected behavior in the already working base case where the hidden module is still recorded in the fallback map;
tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-nested-transitive-dep-item.rs is a regression test for the breadth-first search covering nested children of #[doc(hidden)] modules to populate the fallback map by testing whether the diagnostic prefers the hidden but accessible path through the direct dependency crate.

Related PRs/issues:

rustbot · 2026-07-25T04:40:25Z

Thanks for the pull request, and welcome! The Rust Project is excited to review your changes, and you should hear from @fee1-dead (or someone else) some time within the next two weeks.

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zalanlevai · 2026-07-25T04:48:18Z

@rustbot label +A-diagnostics +A-visibility

fee1-dead · 2026-08-01T17:23:33Z

+fn main() {
+    let _: direct_dep::__private::inner::Struct = Struct;
+    //~^ ERROR mismatched types
+    //~| NOTE expected `direct_dep::__private::inner::Struct`, found `Struct`


I think what you want here is //~| LABEL. Also it might just be okay adding the rest of the //~| NOTE too.

View changes since the review

Is //~| LABEL a valid diagnostic kind (more accurately LABEL itself)? When I tried making the following change:

diff --git a/tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-nested-transitive-dep-item.rs b/tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-nested-transitive-dep-item.rs index f8d2f36dc39..305a340cbaf 100644 --- a/tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-nested-transitive-dep-item.rs +++ b/tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-nested-transitive-dep-item.rs @@ -9,5 +9,5 @@ fn main() { let _: direct_dep::__private::inner::Struct = Struct; //~^ ERROR mismatched types - //~| NOTE expected `direct_dep::__private::inner::Struct`, found `Struct` + //~| LABEL expected `direct_dep::__private::inner::Struct`, found `Struct` }

I get the following error from compiletest:

error: 1 diagnostics expected in test file but not reported in JSON output <...>: UNKNOWN: LABEL expected `direct_dep::__private::inner::Struct`, found `Struct` reported with different kind: NOTE with different message: expected `direct_dep::__private::inner::Struct`, found `Struct`

Which reads to me like compiletest recognises that diagnostic as a NOTE.

Oh, I must have misremembered. Yes, just using NOTE for all of these should be fine.

fee1-dead · 2026-08-01T17:25:02Z

                        Entry::Vacant(entry) => {
-                            entry.insert(parent);
+                            if fallback {
+                                fallback_map.push((def_id, parent));


add a note here that we aren't returning early because we still want to do more BFS of its children.

View changes since the review

rustbot · 2026-08-01T17:25:10Z

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

fee1-dead · 2026-08-01T17:25:23Z

@bors try @rust-timer queue

… r=<try> fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules

…hildren of `#[doc(hidden)]` modules

zalanlevai · 2026-08-01T19:08:20Z

I added the requested comment on not returning early and the rest of the diagnostic parts I omitted from the UI tests (I did it for both files, as it was the same kind of change). The only request I could not apply was changing NOTE to LABEL for the expected $PATH, found Struct diagnostics. See #159881 (comment).

@rustbot ready

rust-bors · 2026-08-01T19:33:13Z

☀️ Try build successful (CI)
Build commit: 2e60bec (2e60bec4054dc1ceccef03706c2767908415860a)
Base parent: b430378 (b430378746a835fd5240e2c7169795d7de0547e8)

rust-timer · 2026-08-01T20:15:28Z

Finished benchmarking commit (2e60bec): comparison URL.

Overall result: no relevant changes - 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

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

Max RSS (memory usage)

Results (primary 0.7%, secondary 0.5%)

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

	mean	range	count
Regressions ❌ (primary)	1.1%	[0.4%, 2.3%]	3
Regressions ❌ (secondary)	0.5%	[0.4%, 1.2%]	10
Improvements ✅ (primary)	-0.6%	[-0.6%, -0.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[-0.6%, 2.3%]	4

Cycles

Results (primary 0.2%, 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)	1.0%	[0.4%, 2.5%]	6
Regressions ❌ (secondary)	2.7%	[0.6%, 8.6%]	6
Improvements ✅ (primary)	-0.8%	[-1.3%, -0.4%]	5
Improvements ✅ (secondary)	-1.0%	[-2.3%, -0.4%]	10
All ❌✅ (primary)	0.2%	[-1.3%, 2.5%]	11

Binary size

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

Bootstrap: 489.711s -> 489.974s (0.05%)
Artifact size: 390.35 MiB -> 390.39 MiB (0.01%)

fee1-dead · 2026-08-02T05:31:57Z

Thank you so much! Looks good to me.

@bors r+ rollup

rust-bors · 2026-08-02T05:32:00Z

📌 Commit e5b6364 has been approved by fee1-dead

It is now in the queue for this repository.

…parent-map, r=fee1-dead fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules The `visible_parent_map` query misses putting the child items of `#[doc(hidden)]` modules into the queue, resulting in the breadth-first search missing them entirely. This results in inconsistent path printing behavior affecting diagnostics: namely that re-exports nested deeply within `#[doc(hidden)]` modules are not considered as a possible fallback path. See the linked issue (rust-lang#159880) for more details and an example of how this manifests in diagnostics. This PR makes sure that `#[doc(hidden)]` parents in the fallback map are still searched as part of the breadth-first search. Fixes rust-lang#159880. The two tests for this change are based on the inconsistent diagnostics shown in the issue: * `tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-transitive-dep-item.rs` captures the current, expected behavior in the already working base case where the hidden module is still recorded in the fallback map; * `tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-nested-transitive-dep-item.rs` is a regression test for the breadth-first search covering nested children of `#[doc(hidden)]` modules to populate the fallback map by testing whether the diagnostic prefers the hidden but accessible path through the direct dependency crate. Related PRs/issues: * rust-lang#87349 * rust-lang#153477

Rollup of 6 pull requests Successful merges: - #156527 (Move `std::io` tests to `alloctests` & add prelude) - #159525 (Stabilize passing 128-bit integers via vector registers with `asm!` on x86) - #160342 (Specialize `advance_by` method of `Fuse`) - #106643 (Allow only implementing `Read::read_buf`) - #159729 (allocations are allowed to grow (but not shrink)) - #159881 (fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules)

…parent-map, r=fee1-dead fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules The `visible_parent_map` query misses putting the child items of `#[doc(hidden)]` modules into the queue, resulting in the breadth-first search missing them entirely. This results in inconsistent path printing behavior affecting diagnostics: namely that re-exports nested deeply within `#[doc(hidden)]` modules are not considered as a possible fallback path. See the linked issue (rust-lang#159880) for more details and an example of how this manifests in diagnostics. This PR makes sure that `#[doc(hidden)]` parents in the fallback map are still searched as part of the breadth-first search. Fixes rust-lang#159880. The two tests for this change are based on the inconsistent diagnostics shown in the issue: * `tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-transitive-dep-item.rs` captures the current, expected behavior in the already working base case where the hidden module is still recorded in the fallback map; * `tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-nested-transitive-dep-item.rs` is a regression test for the breadth-first search covering nested children of `#[doc(hidden)]` modules to populate the fallback map by testing whether the diagnostic prefers the hidden but accessible path through the direct dependency crate. Related PRs/issues: * rust-lang#87349 * rust-lang#153477

…uwer Rollup of 12 pull requests Successful merges: - #159906 (Semantic check of `mut` restrictions) - #156527 (Move `std::io` tests to `alloctests` & add prelude) - #159525 (Stabilize passing 128-bit integers via vector registers with `asm!` on x86) - #160342 (Specialize `advance_by` method of `Fuse`) - #160358 (borrowck: Simplify deps to build compiler 30s faster) - #160375 (miri subtree update) - #106643 (Allow only implementing `Read::read_buf`) - #159499 (tests: prefer max-llvm-major-version over open LLVM ranges) - #159729 (allocations are allowed to grow (but not shrink)) - #159881 (fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules) - #160189 (Move codegen_stmt_debuginfo to debuginfo.rs) - #160356 (Add more tests for `must_implement_one_of`)

Rollup merge of #159881 - zalanlevai:fix-incomplete-visible-parent-map, r=fee1-dead fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules The `visible_parent_map` query misses putting the child items of `#[doc(hidden)]` modules into the queue, resulting in the breadth-first search missing them entirely. This results in inconsistent path printing behavior affecting diagnostics: namely that re-exports nested deeply within `#[doc(hidden)]` modules are not considered as a possible fallback path. See the linked issue (#159880) for more details and an example of how this manifests in diagnostics. This PR makes sure that `#[doc(hidden)]` parents in the fallback map are still searched as part of the breadth-first search. Fixes #159880. The two tests for this change are based on the inconsistent diagnostics shown in the issue: * `tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-transitive-dep-item.rs` captures the current, expected behavior in the already working base case where the hidden module is still recorded in the fallback map; * `tests/ui/suggestions/suggest-path-through-direct-dep-crate/hidden-reexport-of-nested-transitive-dep-item.rs` is a regression test for the breadth-first search covering nested children of `#[doc(hidden)]` modules to populate the fallback map by testing whether the diagnostic prefers the hidden but accessible path through the direct dependency crate. Related PRs/issues: * #87349 * #153477

…uwer Rollup of 12 pull requests Successful merges: - rust-lang/rust#159906 (Semantic check of `mut` restrictions) - rust-lang/rust#156527 (Move `std::io` tests to `alloctests` & add prelude) - rust-lang/rust#159525 (Stabilize passing 128-bit integers via vector registers with `asm!` on x86) - rust-lang/rust#160342 (Specialize `advance_by` method of `Fuse`) - rust-lang/rust#160358 (borrowck: Simplify deps to build compiler 30s faster) - rust-lang/rust#160375 (miri subtree update) - rust-lang/rust#106643 (Allow only implementing `Read::read_buf`) - rust-lang/rust#159499 (tests: prefer max-llvm-major-version over open LLVM ranges) - rust-lang/rust#159729 (allocations are allowed to grow (but not shrink)) - rust-lang/rust#159881 (fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules) - rust-lang/rust#160189 (Move codegen_stmt_debuginfo to debuginfo.rs) - rust-lang/rust#160356 (Add more tests for `must_implement_one_of`)

…fallback-entry-check, r=oli-obk fix: Check the fallback map before queueing child in `visible_parent_map` breadth-first search The fix in rust-lang#159881 extended the `visible_parent_map` breadth-first search (BFS) to include items nested within "fallback" items, such as `#[doc(hidden)]` modules and re-exports. However, the fix resulted in fallback entries not being checked before enqueueing new items into the BFS, resulting in fallback items being explored in the BFS multiple times, once for each fallback parent, up until a non-fallback visible parent is found instead, if any. This PR adds a check before new fallback items are recorded and the BFS queue is extended that ensures that the item has not already been searched through a fallback parent item. Fixes the `libc` performance regression described in rust-lang#160439. (Fixes rust-lang#160439.) Unfortunately, I could not think of a way to write a test case that covers the regression that this PR fixes, as it would require a massive crate with a very large number of "fallback" parents, and the test would be performance-based.

Rollup merge of #160464 - zalanlevai:fix-visible-parent-map-fallback-entry-check, r=oli-obk fix: Check the fallback map before queueing child in `visible_parent_map` breadth-first search The fix in #159881 extended the `visible_parent_map` breadth-first search (BFS) to include items nested within "fallback" items, such as `#[doc(hidden)]` modules and re-exports. However, the fix resulted in fallback entries not being checked before enqueueing new items into the BFS, resulting in fallback items being explored in the BFS multiple times, once for each fallback parent, up until a non-fallback visible parent is found instead, if any. This PR adds a check before new fallback items are recorded and the BFS queue is extended that ensures that the item has not already been searched through a fallback parent item. Fixes the `libc` performance regression described in #160439. (Fixes #160439.) Unfortunately, I could not think of a way to write a test case that covers the regression that this PR fixes, as it would require a massive crate with a very large number of "fallback" parents, and the test would be performance-based.

rustbot assigned fee1-dead Jul 25, 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 25, 2026

rustbot added A-diagnostics Area: Messages for errors, warnings, and lints A-visibility Area: Visibility / privacy labels Jul 25, 2026

zalanlevai mentioned this pull request Jul 27, 2026

fix(hygiene): Find paths to transitive dependency items accessible via #[doc(hidden)] re-exports zalanlevai/mutest-rs#24

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rust-bors Bot pushed a commit that referenced this pull request Aug 1, 2026

Auto merge of #159881 - zalanlevai:fix-incomplete-visible-parent-map,…

2e60bec

… r=<try> fix: Do not stop `visible_parent_map` breadth-first search reaching children of `#[doc(hidden)]` modules

fix: Do not stop visible_parent_map breadth-first search reaching c…

e5b6364

…hildren of `#[doc(hidden)]` modules

zalanlevai force-pushed the fix-incomplete-visible-parent-map branch from bc5b71e to e5b6364 Compare August 1, 2026 18:57

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jhpratt mentioned this pull request Aug 2, 2026

Rollup of 6 pull requests #160367

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This was referenced Aug 2, 2026

Rollup of 11 pull requests #160383

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Rollup of 12 pull requests #160388

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rust-bors Bot merged commit d982e2e into rust-lang:main Aug 2, 2026
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rustbot added this to the 1.99.0 milestone Aug 2, 2026

LusterSourav mentioned this pull request Aug 3, 2026

cargo doc freezes on libc with nightly-2026-08-03 #160439

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zalanlevai mentioned this pull request Aug 3, 2026

fix: Check the fallback map before queueing child in visible_parent_map breadth-first search #160464

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This was referenced Aug 4, 2026

dedup fallback LusterSourav/rust#1

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dedup fallback #160487

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Overall result: no relevant changes - no action needed

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