resolve: fix effective visibilities for items in ambiguous glob sets by calvinrp · Pull Request #159039 · rust-lang/rust

calvinrp · 2026-07-09T21:22:09Z

Fixes #159038 (1.96.1 → 1.97.0 regression; details there).

When an item is glob-imported twice at different visibilities, effective visibility was computed from whichever declaration arrived first, not the most visible one. An exported item could then get no MIR encoded, and downstream crates fail with missing optimized MIR.

Fix: also walk the most visible declaration's re-export chain (update_decl_chain, recursing into ambiguity_vis_max). Lint behavior unchanged. Two regression tests added; tests/ui/{imports,privacy,resolve} pass with every #154149 / #156284 test unmodified.

@rustbot label +A-resolve +A-visibility +T-compiler +regression-from-stable-to-stable

rustbot · 2026-07-09T21:22:15Z

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

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Since PR 154149, when one item is glob-imported into a module twice with different visibilities, the first-arrived declaration stays in the resolution slot and the most visible declaration of the ambiguous glob set is only recorded in `ambiguity_vis_max`. `DeclData::vis()` returns the max, so name resolution, metadata reexports and `cross_crate_inlinable` export the item at the maximum visibility, but `set_bindings_effective_visibilities` walked only the slot-resident declaration's reexport chain. When the restricted route arrives first, the definition's effective visibility caps at the restricted visibility while the item is still exported: spurious dead_code, the item missing from reachable_set, should_encode_mir returning false, and downstream crates failing with "missing optimized MIR" (a 1.96.1 -> 1.97.0 stable-to-stable regression). Generalize the one-level `ambiguity_vis_max` update that PR 154149 added in `update_import` (to keep the most visible import from being reported as unused) into a walk of that declaration's whole reexport chain: extract the chain walk into `update_decl_chain` and recurse into `ambiguity_vis_max` at every hop, so the most visible declaration drives the effective visibility of everything on its route, including the final definition. Updates are monotone, so the dual walk is order-independent. The `ambiguous_import_visibilities` lint and the PR 156284 diagnostic suppression are untouched.

petrochenkov · 2026-07-10T12:02:36Z

We can do this, because effective visibilities are not precise and can be conservative.
As it's seen from the diff we previously updated a single ambiguity_vis_max import to "exported", but we need to do it with the whole import chain, and that is what this PR does.
@bors r+

rust-bors · 2026-07-10T12:02:40Z

📌 Commit 299a71d has been approved by petrochenkov

It is now in the queue for this repository.

@rustbot

…biguity, r=petrochenkov resolve: fix effective visibilities for items in ambiguous glob sets Fixes rust-lang#159038 (1.96.1 → 1.97.0 regression; details there). When an item is glob-imported twice at different visibilities, effective visibility was computed from whichever declaration arrived first, not the most visible one. An exported item could then get no MIR encoded, and downstream crates fail with ``missing optimized MIR``. Fix: also walk the most visible declaration's re-export chain (`update_decl_chain`, recursing into `ambiguity_vis_max`). Lint behavior unchanged. Two regression tests added; `tests/ui/{imports,privacy,resolve}` pass with every rust-lang#154149 / rust-lang#156284 test unmodified. @rustbot label +A-resolve +A-visibility +T-compiler +regression-from-stable-to-stable

@rustbot

…biguity, r=petrochenkov resolve: fix effective visibilities for items in ambiguous glob sets Fixes rust-lang#159038 (1.96.1 → 1.97.0 regression; details there). When an item is glob-imported twice at different visibilities, effective visibility was computed from whichever declaration arrived first, not the most visible one. An exported item could then get no MIR encoded, and downstream crates fail with ``missing optimized MIR``. Fix: also walk the most visible declaration's re-export chain (`update_decl_chain`, recursing into `ambiguity_vis_max`). Lint behavior unchanged. Two regression tests added; `tests/ui/{imports,privacy,resolve}` pass with every rust-lang#154149 / rust-lang#156284 test unmodified. @rustbot label +A-resolve +A-visibility +T-compiler +regression-from-stable-to-stable

…uwer Rollup of 10 pull requests Successful merges: - #157690 (codegen_ssa: pack small const aggregates into immediate stores) - #157706 (Deny `todo!()` in tidy) - #159005 (Use `as_lang_item` instead of repeatedly matching) - #156735 (Move NativeLib::filename to the rmeta-link archive member) - #159039 (resolve: fix effective visibilities for items in ambiguous glob sets) - #158930 (Reorganize `tests/ui/issues` [20/N]) - #158965 (Add codegen test for Result is_ok unwrap) - #158979 (Reorganize `tests/ui/issues` [21/N]) - #159050 (assert only opaques with sub unified hidden infer are non-rigid) - #159062 (Remove unused WEAK_ONLY_LANG_ITEMS static) Failed merges: - #158732 (Apply MCP 1003 and move diagnostics.rs into its own module)

@rustbot

…biguity, r=petrochenkov resolve: fix effective visibilities for items in ambiguous glob sets Fixes rust-lang#159038 (1.96.1 → 1.97.0 regression; details there). When an item is glob-imported twice at different visibilities, effective visibility was computed from whichever declaration arrived first, not the most visible one. An exported item could then get no MIR encoded, and downstream crates fail with ``missing optimized MIR``. Fix: also walk the most visible declaration's re-export chain (`update_decl_chain`, recursing into `ambiguity_vis_max`). Lint behavior unchanged. Two regression tests added; `tests/ui/{imports,privacy,resolve}` pass with every rust-lang#154149 / rust-lang#156284 test unmodified. @rustbot label +A-resolve +A-visibility +T-compiler +regression-from-stable-to-stable

lqd · 2026-07-10T16:53:02Z

+// a private facade, lost its exported effective visibility. The defining crate then
+// skipped encoding its optimized MIR (and warned dead_code) while name resolution still
+// exported the item and it remained `cross_crate_inlinable`, so downstream crates failed
+// with "missing optimized MIR". The dead_code half is checked by `#![deny(dead_code)]`


Is this accurate, there is no #![deny(dead_code)] in the auxiliary crate or in this test? There is one in the -reachable test though, so maybe that meant to say the dead code half is checked by that other test?

View changes since the review

Good catch — the comment was inaccurate: there is no #![deny(dead_code)] in this test or its auxiliary crate. The dead-code half of the regression is pinned by the sibling ambiguous-import-visibility-globglob-reachable.rs test (its #![deny(dead_code)] plus the effective-visibility assertions make the pre-fix spurious dead_code fail there); this test pins only the missing-MIR half. Fixed the comment in 159b9a0 to point at the sibling test. I kept deny(dead_code) out of this test's aux crate deliberately — pre-fix it would fail the aux build and mask the missing-MIR failure mode this test exists to pin.

…uwer Rollup of 12 pull requests Successful merges: - #157690 (codegen_ssa: pack small const aggregates into immediate stores) - #159005 (Use `as_lang_item` instead of repeatedly matching) - #156735 (Move NativeLib::filename to the rmeta-link archive member) - #157153 (allow `Allocator`s to be used as `#[global_allocator]`s) - #158767 (merge DefKind::InlineConst into AnonConst) - #159039 (resolve: fix effective visibilities for items in ambiguous glob sets) - #158732 (Apply MCP 1003 and move diagnostics.rs into its own module) - #158930 (Reorganize `tests/ui/issues` [20/N]) - #158965 (Add codegen test for Result is_ok unwrap) - #158979 (Reorganize `tests/ui/issues` [21/N]) - #159050 (assert only opaques with sub unified hidden infer are non-rigid) - #159062 (Remove unused WEAK_ONLY_LANG_ITEMS static)

@rustbot

…biguity, r=petrochenkov resolve: fix effective visibilities for items in ambiguous glob sets Fixes rust-lang#159038 (1.96.1 → 1.97.0 regression; details there). When an item is glob-imported twice at different visibilities, effective visibility was computed from whichever declaration arrived first, not the most visible one. An exported item could then get no MIR encoded, and downstream crates fail with ``missing optimized MIR``. Fix: also walk the most visible declaration's re-export chain (`update_decl_chain`, recursing into `ambiguity_vis_max`). Lint behavior unchanged. Two regression tests added; `tests/ui/{imports,privacy,resolve}` pass with every rust-lang#154149 / rust-lang#156284 test unmodified. @rustbot label +A-resolve +A-visibility +T-compiler +regression-from-stable-to-stable

…reachable test

rust-bors · 2026-07-10T21:17:17Z

⚠️ A new commit 159b9a0c557ed43c9be3d52a58b8cbf10fbc2f4f was pushed.

This pull request was unapproved.

This PR was contained in a rollup (#159104), which was closed.

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 9, 2026

rustbot assigned petrochenkov Jul 9, 2026

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Jul 9, 2026

rustbot added A-resolve Area: Name/path resolution done by `rustc_resolve` specifically A-visibility Area: Visibility / privacy regression-from-stable-to-stable Performance or correctness regression from one stable version to another. labels Jul 9, 2026

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rustbot added the I-prioritize Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical} label Jul 9, 2026

calvinrp mentioned this pull request Jul 9, 2026

Regression 1.96.1 → 1.97.0: "missing optimized MIR" for pub fn glob-reexported alongside a restricted glob duplicate #159038

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calvinrp force-pushed the fix/effective-vis-glob-ambiguity branch from e84a2ff to 299a71d Compare July 9, 2026 21:24

theemathas removed regression-from-stable-to-stable Performance or correctness regression from one stable version to another. I-prioritize Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical} labels Jul 9, 2026

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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 Jul 10, 2026

JonathanBrouwer mentioned this pull request Jul 10, 2026

Rollup of 10 pull requests #159077

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JonathanBrouwer mentioned this pull request Jul 10, 2026

Rollup of 10 pull requests #159080

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theemathas added beta-nominated Nominated for backporting to the compiler in the beta channel. stable-nominated Nominated for backporting to the compiler in the stable channel. labels Jul 10, 2026

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Rollup of 12 pull requests #159095

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lqd reviewed Jul 10, 2026

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JonathanBrouwer mentioned this pull request Jul 10, 2026

Rollup of 14 pull requests #159104

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Fix stale test comment: the dead_code half is pinned by the sibling -…

159b9a0

…reachable test

rust-bors Bot 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 10, 2026

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resolve: fix effective visibilities for items in ambiguous glob sets#159039

resolve: fix effective visibilities for items in ambiguous glob sets#159039
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