Fix async drop glue for Box<T> by P8L1 · Pull Request #156067 · rust-lang/rust

P8L1 · 2026-05-01T22:49:06Z

This fixes async drop behavior for boxed values so that async drop glue reaches the boxed value’s async destructor in async drop context.

The change updates async-drop needs-drop analysis so Box<T> is handled specially for async drop by considering the boxed pointee and allocator when deciding whether async drop glue is needed.

This PR intentionally does not change the broader AsyncDrop design. It only fixes behavior under the existing #![feature(async_drop)] implementation.

Reviewer notes:

async-drop-box-allocator.rs already covers async-dropping the allocator of a Box; this PR adds distinct coverage for the boxed value itself.
Boxed dyn pointees are intentionally not pulled into this fix, preserving existing dynamic async-drop limitations.
The change is isolated to async drop analysis; sync needs_drop behavior is unchanged.

@rustbot label F-async_drop

rustbot · 2026-05-01T22:49:11Z

r? @oli-obk

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oli-obk · 2026-05-03T09:21:34Z

oof turns out I didn't see #145316 for 9 months. Gonna review that one first

P8L1 · 2026-05-03T10:04:02Z

oof turns out I didn't see #145316 for 9 months. Gonna review that one first

LMAO Ok gl

P8L1 · 2026-05-06T12:23:59Z

@oli-obk can I close this?

oli-obk · 2026-05-06T12:53:05Z

I'd like to land the sized-only version first. I don't know if the other PR's solution is different from yours. I'll need to compare and figure out whether either solution is one to merge

oli-obk

Do we have tests for dyn? If not, please add one with a note that it needs fixing

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rustbot · 2026-06-08T18:21:58Z

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

rustbot · 2026-06-08T21:47:34Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

P8L1 · 2026-06-08T21:54:37Z

@rustbot ready

P8L1 · 2026-06-09T11:24:03Z

@bors squash

* Fix async drop glue for Box<T> * Adress reviewer concerns * Address more concerns

rust-bors · 2026-06-09T11:24:24Z

🔨 3 commits were squashed into 2bc5e90.

oli-obk · 2026-06-09T11:26:51Z

😅 right that works

@bors r+ rollup

rust-bors · 2026-06-09T11:26:55Z

📌 Commit 2bc5e90 has been approved by oli-obk

It is now in the queue for this repository.

@rustbot

Fix async drop glue for Box<T> Fixes rust-lang#143658. This fixes async drop behavior for boxed values so that async drop glue reaches the boxed value’s async destructor in async drop context. The change updates async-drop needs-drop analysis so `Box<T>` is handled specially for async drop by considering the boxed pointee and allocator when deciding whether async drop glue is needed. This PR intentionally does not change the broader AsyncDrop design. It only fixes behavior under the existing `#![feature(async_drop)]` implementation. Reviewer notes: - `async-drop-box-allocator.rs` already covers async-dropping the allocator of a `Box`; this PR adds distinct coverage for the boxed value itself. - Boxed dyn pointees are intentionally not pulled into this fix, preserving existing dynamic async-drop limitations. - The change is isolated to async drop analysis; sync `needs_drop` behavior is unchanged. @rustbot label F-async_drop

Rollup of 10 pull requests Successful merges: - #157335 (bootstrap: Handle dotted table keys when parsing bootstrap.toml) - #157503 (Disable `tests/debuginfo/pretty-std.rs` `OsString` cdb check) - #148183 (rustdoc: Test & document `test_harness` code block attribute) - #156067 (Fix async drop glue for Box<T>) - #156399 (fix improper ctypes in Znext solver) - #157410 (Implement rustc_public::CrateDef{,Type} for FieldDef) - #157605 (Arg splat experiment - syntax impl) - #157630 (Add multibyte JSON diagnostic regression test) - #157633 (Reorder `impl` restriction rendering and add bottom margin) - #157642 (Report duplicate relaxed bounds during ast lowering)

@rustbot

Fix async drop glue for Box<T> Fixes rust-lang#143658. This fixes async drop behavior for boxed values so that async drop glue reaches the boxed value’s async destructor in async drop context. The change updates async-drop needs-drop analysis so `Box<T>` is handled specially for async drop by considering the boxed pointee and allocator when deciding whether async drop glue is needed. This PR intentionally does not change the broader AsyncDrop design. It only fixes behavior under the existing `#![feature(async_drop)]` implementation. Reviewer notes: - `async-drop-box-allocator.rs` already covers async-dropping the allocator of a `Box`; this PR adds distinct coverage for the boxed value itself. - Boxed dyn pointees are intentionally not pulled into this fix, preserving existing dynamic async-drop limitations. - The change is isolated to async drop analysis; sync `needs_drop` behavior is unchanged. @rustbot label F-async_drop

@rustbot

Fix async drop glue for Box<T> Fixes rust-lang#143658. This fixes async drop behavior for boxed values so that async drop glue reaches the boxed value’s async destructor in async drop context. The change updates async-drop needs-drop analysis so `Box<T>` is handled specially for async drop by considering the boxed pointee and allocator when deciding whether async drop glue is needed. This PR intentionally does not change the broader AsyncDrop design. It only fixes behavior under the existing `#![feature(async_drop)]` implementation. Reviewer notes: - `async-drop-box-allocator.rs` already covers async-dropping the allocator of a `Box`; this PR adds distinct coverage for the boxed value itself. - Boxed dyn pointees are intentionally not pulled into this fix, preserving existing dynamic async-drop limitations. - The change is isolated to async drop analysis; sync `needs_drop` behavior is unchanged. @rustbot label F-async_drop

Rollup of 18 pull requests Successful merges: - #152852 (Remove driver_lint_caps) - #157166 (Change type of async context parameter after state transform.) - #157335 (bootstrap: Handle dotted table keys when parsing bootstrap.toml) - #157503 (Disable `tests/debuginfo/pretty-std.rs` `OsString` cdb check) - #157571 (Remove ProcMacro enum from proc macro ABI) - #148183 (rustdoc: Test & document `test_harness` code block attribute) - #153847 (Fix marker trait winnowing depending on impl order) - #156067 (Fix async drop glue for Box<T>) - #156399 (fix improper ctypes in Znext solver) - #157338 (Make `Literal::byte_character_value` work with bytes as well) - #157410 (Implement rustc_public::CrateDef{,Type} for FieldDef) - #157605 (Arg splat experiment - syntax impl) - #157630 (Add multibyte JSON diagnostic regression test) - #157633 (Reorder `impl` restriction rendering and add bottom margin) - #157642 (Report duplicate relaxed bounds during ast lowering) - #157652 (fix doc for unicode normalization faq on `casefold` APIs) - #157661 (Update to ar_archive_writer v0.5.2) - #157668 (Add test for matches in `rustc_must_match_exhaustively`) Failed merges: - #157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N))

Rollup of 17 pull requests Successful merges: - #157166 (Change type of async context parameter after state transform.) - #157335 (bootstrap: Handle dotted table keys when parsing bootstrap.toml) - #157503 (Disable `tests/debuginfo/pretty-std.rs` `OsString` cdb check) - #157571 (Remove ProcMacro enum from proc macro ABI) - #148183 (rustdoc: Test & document `test_harness` code block attribute) - #153847 (Fix marker trait winnowing depending on impl order) - #156067 (Fix async drop glue for Box<T>) - #156399 (fix improper ctypes in Znext solver) - #157338 (Make `Literal::byte_character_value` work with bytes as well) - #157410 (Implement rustc_public::CrateDef{,Type} for FieldDef) - #157605 (Arg splat experiment - syntax impl) - #157630 (Add multibyte JSON diagnostic regression test) - #157633 (Reorder `impl` restriction rendering and add bottom margin) - #157642 (Report duplicate relaxed bounds during ast lowering) - #157652 (fix doc for unicode normalization faq on `casefold` APIs) - #157661 (Update to ar_archive_writer v0.5.2) - #157668 (Add test for matches in `rustc_must_match_exhaustively`) Failed merges: - #157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N))

@rustbot

Rollup merge of #156067 - P8L1:async-drop-box-fix, r=oli-obk Fix async drop glue for Box<T> Fixes #143658. This fixes async drop behavior for boxed values so that async drop glue reaches the boxed value’s async destructor in async drop context. The change updates async-drop needs-drop analysis so `Box<T>` is handled specially for async drop by considering the boxed pointee and allocator when deciding whether async drop glue is needed. This PR intentionally does not change the broader AsyncDrop design. It only fixes behavior under the existing `#![feature(async_drop)]` implementation. Reviewer notes: - `async-drop-box-allocator.rs` already covers async-dropping the allocator of a `Box`; this PR adds distinct coverage for the boxed value itself. - Boxed dyn pointees are intentionally not pulled into this fix, preserving existing dynamic async-drop limitations. - The change is isolated to async drop analysis; sync `needs_drop` behavior is unchanged. @rustbot label F-async_drop

rustbot assigned oli-obk May 1, 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 May 1, 2026

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Kivooeo closed this May 1, 2026

Kivooeo reopened this May 1, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 1, 2026

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oli-obk added the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label May 3, 2026

oli-obk removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 5, 2026

rustbot added the F-async_drop `#![feature(async_drop)]` label May 22, 2026

oli-obk removed the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Jun 8, 2026

oli-obk requested changes Jun 8, 2026

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Comment thread compiler/rustc_ty_utils/src/needs_drop.rs Outdated

Comment thread compiler/rustc_ty_utils/src/needs_drop.rs Outdated

Comment thread compiler/rustc_ty_utils/src/needs_drop.rs Outdated

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P8L1 force-pushed the async-drop-box-fix branch from 39bb468 to d8aad82 Compare June 8, 2026 21:47

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Fix async drop glue for Box<T>

2bc5e90

* Fix async drop glue for Box<T> * Adress reviewer concerns * Address more concerns

rust-bors Bot force-pushed the async-drop-box-fix branch from 56222cb to 2bc5e90 Compare June 9, 2026 11:24

P8L1 requested a review from oli-obk June 9, 2026 11:25

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 Jun 9, 2026

GuillaumeGomez mentioned this pull request Jun 9, 2026

Rollup of 10 pull requests #157663

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GuillaumeGomez mentioned this pull request Jun 9, 2026

Rollup of 15 pull requests #157673

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jhpratt mentioned this pull request Jun 9, 2026

Rollup of 18 pull requests #157679

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jhpratt mentioned this pull request Jun 9, 2026

Rollup of 17 pull requests #157683

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rust-bors Bot merged commit 9c291fb into rust-lang:main Jun 10, 2026
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rustbot added this to the 1.98.0 milestone Jun 10, 2026

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