autodiff: Handle slice-tailed DSTs in type trees by Dnreikronos · Pull Request #160390 · rust-lang/rust

Dnreikronos · 2026-08-02T16:20:23Z

References to OsStr reach a [u8] tail, but autodiff only recognized direct slices. TypeTree generation then recursed into OsStr and hit the slice arm that ICEd.

TypeTree generation and ABI activity handling now use struct_tail_for_codegen. Slice wrappers keep their element metadata, while prefixed DSTs retain their field offsets. IMO, reusing the existing rustc DST-tail query is cleaner than adding an OsStr special case. BTW, coverage includes the reduced clap_lex reproducer plus a prefixed slice-tail DST.

rustbot · 2026-08-02T16:20:26Z

Some changes occurred in compiler/rustc_codegen_llvm/src/builder/autodiff.rs

cc @ZuseZ4

rustbot · 2026-08-02T16:20:28Z

r? @oli-obk

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Use codegen tail discovery so wrappers such as OsStr keep slice element metadata without losing offsets for prefixed DSTs. Keep recursion tracking scoped to the current traversal path.

rustbot · 2026-08-04T15:29:41Z

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

Clarify that slice-tail layout checks apply to the sized prefix rather than the slice element, and cover zero-sized slice elements in the type-tree run-make test.

oli-obk · 2026-08-04T22:22:48Z

@bors r+ rollup

rust-bors · 2026-08-04T22:22:52Z

📌 Commit 18e0dd9 has been approved by oli-obk

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

…etree, r=oli-obk autodiff: Handle slice-tailed DSTs in type trees Fixes rust-lang#160327 References to `OsStr` reach a `[u8]` tail, but autodiff only recognized direct slices. TypeTree generation then recursed into `OsStr` and hit the slice arm that ICEd. TypeTree generation and ABI activity handling now use `struct_tail_for_codegen`. Slice wrappers keep their element metadata, while prefixed DSTs retain their field offsets. IMO, reusing the existing rustc DST-tail query is cleaner than adding an `OsStr` special case. BTW, coverage includes the reduced `clap_lex` reproducer plus a prefixed slice-tail DST.

…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)

…etree, r=oli-obk autodiff: Handle slice-tailed DSTs in type trees Fixes rust-lang#160327 References to `OsStr` reach a `[u8]` tail, but autodiff only recognized direct slices. TypeTree generation then recursed into `OsStr` and hit the slice arm that ICEd. TypeTree generation and ABI activity handling now use `struct_tail_for_codegen`. Slice wrappers keep their element metadata, while prefixed DSTs retain their field offsets. IMO, reusing the existing rustc DST-tail query is cleaner than adding an `OsStr` special case. BTW, coverage includes the reduced `clap_lex` reproducer plus a prefixed slice-tail DST.

…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)

Rollup merge of #160390 - Dnreikronos:autodiff/slice_dst_typetree, r=oli-obk autodiff: Handle slice-tailed DSTs in type trees Fixes #160327 References to `OsStr` reach a `[u8]` tail, but autodiff only recognized direct slices. TypeTree generation then recursed into `OsStr` and hit the slice arm that ICEd. TypeTree generation and ABI activity handling now use `struct_tail_for_codegen`. Slice wrappers keep their element metadata, while prefixed DSTs retain their field offsets. IMO, reusing the existing rustc DST-tail query is cleaner than adding an `OsStr` special case. BTW, coverage includes the reduced `clap_lex` reproducer plus a prefixed slice-tail DST.

rustbot assigned oli-obk Aug 2, 2026

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Handle slice-tailed DSTs in autodiff type trees

ac1e5f4

Use codegen tail discovery so wrappers such as OsStr keep slice element metadata without losing offsets for prefixed DSTs. Keep recursion tracking scoped to the current traversal path.

Dnreikronos force-pushed the autodiff/slice_dst_typetree branch from 39bb21b to ac1e5f4 Compare August 2, 2026 16:22

oli-obk requested changes Aug 4, 2026

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Comment thread compiler/rustc_codegen_llvm/src/builder/autodiff.rs

Comment thread compiler/rustc_middle/src/ty/typetree.rs

rustbot 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

Document zero-sized autodiff slice handling

18e0dd9

Clarify that slice-tail layout checks apply to the sized prefix rather than the slice element, and cover zero-sized slice elements in the type-tree run-make test.

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 4, 2026

JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 11 pull requests #160547

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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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JonathanBrouwer mentioned this pull request Aug 5, 2026

Rollup of 25 pull requests #160559

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rust-bors Bot merged commit 19ec103 into rust-lang:main Aug 5, 2026
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rustbot added this to the 1.99.0 milestone Aug 5, 2026

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autodiff: Handle slice-tailed DSTs in type trees - #160390

autodiff: Handle slice-tailed DSTs in type trees#160390
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Dnreikronos:autodiff/slice_dst_typetree

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