Repository: rust
Issue: Tracking Issue for async drop codegen
Labels: T-lang,T-compiler,C-tracking-issue,A-async-await,AsyncAwait-Triaged,WG-async,F-async_drop

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This is a tracking issue for the async drop codegen from MCP "727" (rust-lang/compiler-team#727).
The feature gate for the issue is `#![feature(async_drop))]`.

### About tracking issues

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### Steps
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- [ ] Implement the async drop codegen
  - [x] `AsyncDrop` trait (#121801)
  - [ ] `async_drop_in_place_raw`/async drop glue generation support for
    - [x] Trivially destructible types (integers, bools, floats, string slices, pointers, references, etc.), arrays and slices (array pointer is unsized into slice pointer), ADTs (enums, structs, unions), tuple-like types (tuples, closures) (#121801)
    - [ ] Dynamic types (`dyn Trait`)
      - One proposed design: https://zetanumbers.github.io/book/async-drop-design.html#dyn_trait
    - [ ] Coroutines (#123948)
  - [ ] Type level support (possibly outside of the scope of this tracking issue)
    - [ ] Union rejects non-trivially async destructible fields
    - [ ] `AsyncDrop` implementation requires same bounds as type definition
    - [ ] Synchronously undroppable types
  - [ ] Optimizations
    - [x] Skip trivially destructible fields (optimization) (#124662)
    - [ ] New [`TyKind::AdtAsyncDestructor`](https://zetanumbers.github.io/book/async-drop-design.html#adt-async-destructor-types) and get rid of combinators
  - [ ] Automatic async drop at the end of the scope in async context (#123948)
- [ ] Adjust documentation ([see instructions on rustc-dev-guide][doc-guide])
- [ ] ~~Formatting for new syntax has been added to the [Style Guide] ([nightly-style-procedure])~~
- [ ] Stabilization PR ([see instructions on rustc-dev-guide][stabilization-guide])

[stabilization-guide]: https://rustc-dev-guide.rust-lang.org/stabilization_guide.html#stabilization-pr
[doc-guide]: https://rustc-dev-guide.rust-lang.org/stabilization_guide.html#documentation-prs
[nightly-style-procedure]: https://github.com/rust-lang/style-team/blob/master/nightly-style-procedure.md 
[Style Guide]: https://github.com/rust-lang/rust/tree/master/src/doc/style-guide

### Unresolved Questions
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- [ ] Async drop for dynamic types (`dyn Trait`)
  - One proposed design: https://zetanumbers.github.io/book/async-drop-design.html#dyn_trait
- [ ] Drop of async destructors
- [ ] `AsyncDrop` and `Drop` should somehow be combined to not duplicate implementations (possibly outside of the scope of this tracking issue)

### Implementation history

- #121801
- #124662
- #123948