don't completely reset HeadUsages by lcnr · Pull Request #148649 · rust-lang/rust (original) (raw)

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This is really subtle ☠️ I've actually went and added testing for search_graph.ignore_candidate_head_usages to https://github.com/lcnr/search_graph_fuzz now. I should have done that when I originally implemented but didn't quite know how to do so back then.

The search graph is far too subtle to think through it manually. I've added the affected proof tree to https://github.com/rust-lang/trait-system-refactor-initiative/blob/main/notes/next-solver/search-graph/general.md#keeping-provisional-cache-entries-on-rerun. It's

• A
  • B
    * C (depends on B and gets dropped when rerunning)
    * D (does not depend on B so we keep it around when rerunning)
    * C (irrevant candidate)
    * A
    * B
    * D
    * C (irrevant candidate)
    * D
    * A
    * rerun
    * C (use provisional cache entry which doesn't depend on B)
    * D (use provisional cache entry which doesn't depend on B)

Fixes the ICE in rust-lang/trait-system-refactor-initiative#246 (comment). I think this issue is brittle enough that adding that as a test isn't really useful. Any small change to the search graph will prevent it from testing this. We do test this fix via the fuzzer.

r? @BoxyUwU

rustbot added S-waiting-on-review

Status: Awaiting review from the assignee but also interested parties.

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Nov 7, 2025

📌 Commit c07f11a has been approved by BoxyUwU

It is now in the queue for this repository.

bors added S-waiting-on-bors

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and removed S-waiting-on-review

Status: Awaiting review from the assignee but also interested parties.

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Nov 7, 2025

jhpratt added a commit to jhpratt/rust that referenced this pull request

Nov 8, 2025

bors added a commit that referenced this pull request

Nov 8, 2025

Rollup of 15 pull requests

Successful merges:

• #147404 (Fix issue with callsite inline attribute not being applied sometimes.)
• #147534 (Implement SIMD funnel shifts in const-eval/Miri)
• #147686 (update isolate_highest_one for NonZero)
• #148020 (Show backtrace on allocation failures when possible)
• #148204 (Modify contributor email entries in .mailmap)
• #148230 (rustdoc: Properly highlight shebang, frontmatter & weak keywords in source code pages and code blocks)
• #148555 (Fix rust-by-example spanish translation)
• #148556 (Fix suggestion for returning async closures)
• #148585 ([rustdoc] Replace print methods with functions to improve code readability)
• #148600 (re-use self.get_all_attrs result for pass indirectly attribute)
• #148612 (Add note for identifier with attempted hygiene violation)
• #148613 (Switch hexagon targets to rust-lld)
• #148644 ([bootstrap] Make --open option work with doc src/tools/error_index_generator)
• #148649 (don't completely reset HeadUsages)
• #148675 (Remove eslint-js from npm dependencies)

r? @ghost @rustbot modify labels: rollup

jhpratt added a commit to jhpratt/rust that referenced this pull request

Nov 8, 2025

bors added a commit that referenced this pull request

Nov 8, 2025

Rollup of 16 pull requests

Successful merges:

• #147534 (Implement SIMD funnel shifts in const-eval/Miri)
• #147686 (update isolate_highest_one for NonZero)
• #148020 (Show backtrace on allocation failures when possible)
• #148204 (Modify contributor email entries in .mailmap)
• #148230 (rustdoc: Properly highlight shebang, frontmatter & weak keywords in source code pages and code blocks)
• #148279 (rustc_builtin_macros: rename bench parameter to avoid collisions with user-defined function names)
• #148555 (Fix rust-by-example spanish translation)
• #148556 (Fix suggestion for returning async closures)
• #148585 ([rustdoc] Replace print methods with functions to improve code readability)
• #148600 (re-use self.get_all_attrs result for pass indirectly attribute)
• #148612 (Add note for identifier with attempted hygiene violation)
• #148613 (Switch hexagon targets to rust-lld)
• #148619 (Enable std locking functions on AIX)
• #148644 ([bootstrap] Make --open option work with doc src/tools/error_index_generator)
• #148649 (don't completely reset HeadUsages)
• #148675 (Remove eslint-js from npm dependencies)

r? @ghost @rustbot modify labels: rollup

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

Nov 8, 2025

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

Nov 8, 2025

bors added a commit that referenced this pull request

Nov 9, 2025

Rollup of 22 pull requests

Successful merges:

• #128666 (Add overflow_checks intrinsic)
• #146305 (Add correct suggestion for multi-references for self type in method)
• #147179 ([DebugInfo] Fix container types failing to find template args)
• #147743 (Show packed field alignment in mir_transform_unaligned_packed_ref)
• #148079 (Rename downcast_[ref|mut]_unchecked -> downcast_unchecked_[ref|mut])
• #148084 (Optimize path components iteration on platforms that don't have prefixes)
• #148126 (Fix rust stdlib build failing for VxWorks)
• #148204 (Modify contributor email entries in .mailmap)
• #148279 (rustc_builtin_macros: rename bench parameter to avoid collisions with user-defined function names)
• #148333 (constify result unwrap unchecked)
• #148539 (Add Allocator proxy impls for Box, Rc, and Arc)
• #148601 (invalid_atomic_ordering: also lint update & try_update)
• #148612 (Add note for identifier with attempted hygiene violation)
• #148613 (Switch hexagon targets to rust-lld)
• #148619 (Enable std locking functions on AIX)
• #148644 ([bootstrap] Make --open option work with doc src/tools/error_index_generator)
• #148649 (don't completely reset HeadUsages)
• #148673 (Remove a remnant of dyn* from the parser)
• #148675 (Remove eslint-js from npm dependencies)
• #148680 (Recover [T: N] as [T; N])
• #148688 (Remove unused argument features from eval_config_entry)
• #148711 (Use the current lint note id when parsing cfg!())

r? @ghost @rustbot modify labels: rollup

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Nov 9, 2025

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Nov 10, 2025

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Nov 10, 2025

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Nov 10, 2025

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Nov 10, 2025

makai410 pushed a commit to makai410/rust that referenced this pull request

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Nov 16, 2025

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Nov 30, 2025

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