ICE: elaborate drop: index out of bounds

[matthiaskrgr]

Code

//@compile-flags --edition=2021
#![feature(async_drop)]
use core::future::AsyncDrop;
async fn a<g>(b: g, c: usize) {}
fn d() {
    a(e { field: 1 }2);
}
union e {
    field: i32,
}
impl Drop for e {
    fn drop(&mut self) {}
}
impl AsyncDrop for e {}

Meta

rustc --version --verbose:

rustc 1.89.0-nightly (8405332bd 2025-05-12)
binary: rustc
commit-hash: 8405332bdf09b153e475f83b8b8ebf8d4e8eb81f
commit-date: 2025-05-12
host: x86_64-unknown-linux-gnu
release: 1.89.0-nightly
LLVM version: 20.1.4

Error output

error: expected one of `)`, `,`, `.`, `?`, or an operator, found `2`
 --> code.rs:6:21
  |
6 |     a(e { field: 1 }2);
  |                     ^
  |                     |
  |                     expected one of `)`, `,`, `.`, `?`, or an operator
  |                     help: missing `,`

warning: the feature `async_drop` is incomplete and may not be safe to use and/or cause compiler crashes
 --> code.rs:2:12
  |
2 | #![feature(async_drop)]
  |            ^^^^^^^^^^
  |
  = note: see issue #126482 <https://github.com/rust-lang/rust/issues/126482> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: type parameter `g` should have an upper camel case name
 --> code.rs:4:12
  |
4 | async fn a<g>(b: g, c: usize) {}
  |            ^ help: convert the identifier to upper camel case: `G`
  |
  = note: `#[warn(non_camel_case_types)]` on by default

warning: type `e` should have an upper camel case name
 --> code.rs:8:7
  |
8 | union e {
  |       ^ help: convert the identifier to upper camel case: `E`

error[E0601]: `main` function not found in crate `code`
  --> code.rs:14:24
   |
14 | impl AsyncDrop for e {}
   |                        ^ consider adding a `main` function to `code.rs`

error[E0046]: not all trait items implemented, missing: `drop`
  --> code.rs:14:1
   |
14 | impl AsyncDrop for e {}
   | ^^^^^^^^^^^^^^^^^^^^ missing `drop` in implementation
   |
   = help: implement the missing item: `async fn drop(self: Pin<&mut Self>) { todo!() }`

warning: unused variable: `b`
 --> code.rs:4:15
  |
4 | async fn a<g>(b: g, c: usize) {}
  |               ^ help: if this is intentional, prefix it with an underscore: `_b`
  |
  = note: `#[warn(unused_variables)]` on by default

warning: unused variable: `c`
 --> code.rs:4:21
  |
4 | async fn a<g>(b: g, c: usize) {}
  |                     ^ help: if this is intentional, prefix it with an underscore: `_c`

Backtrace

thread 'rustc' panicked at compiler/rustc_mir_transform/src/elaborate_drop.rs:254:34:
index out of bounds: the len is 0 but the index is 0
stack backtrace:
   0:     0x71f4dd5596c3 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hee27e289fa80eeb0
   1:     0x71f4ddc05987 - core::fmt::write::hcb7a95a553d927d7
   2:     0x71f4decd3411 - std::io::Write::write_fmt::h5f19ce2ac2f30773
   3:     0x71f4dd559522 - std::sys::backtrace::BacktraceLock::print::h967e6c26dabf5676
   4:     0x71f4dd55d11a - std::panicking::default_hook::{{closure}}::h4c9e43e4d632c501
   5:     0x71f4dd55cc9f - std::panicking::default_hook::ha3c41200eaedb148
   6:     0x71f4dc58ac13 - std[a3033ab4cf040dbc]::panicking::update_hook::<alloc[2b9f1e9988cc0e0]::boxed::Box<rustc_driver_impl[2b29d548aa47efe8]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x71f4dd55d993 - std::panicking::rust_panic_with_hook::h614c9e3cb602169a
   8:     0x71f4dd55d68a - std::panicking::begin_panic_handler::{{closure}}::h7175c42c4098b33c
   9:     0x71f4dd559b89 - std::sys::backtrace::__rust_end_short_backtrace::hb28ab4ef577ce3dd
  10:     0x71f4dd55d34d - __rustc[9e838b297ad6583e]::rust_begin_unwind
  11:     0x71f4d9e86220 - core::panicking::panic_fmt::hee3e8e41a6e23382
  12:     0x71f4dbb27553 - core::panicking::panic_bounds_check::h911616a2782ca751
  13:     0x71f4dcda31b5 - <rustc_mir_transform[86a227439405b463]::elaborate_drop::DropCtxt<rustc_mir_transform[86a227439405b463]::shim::DropShimElaborator>>::build_async_drop
  14:     0x71f4de74c486 - <rustc_mir_transform[86a227439405b463]::elaborate_drop::DropCtxt<rustc_mir_transform[86a227439405b463]::shim::DropShimElaborator>>::elaborate_drop
  15:     0x71f4de745d11 - rustc_mir_transform[86a227439405b463]::shim::make_shim
  16:     0x71f4de743cef - rustc_query_impl[c99fb05ce5425a5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c99fb05ce5425a5b]::query_impl::mir_shims::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 8usize]>>
  17:     0x71f4de743ca3 - <rustc_query_impl[c99fb05ce5425a5b]::query_impl::mir_shims::dynamic_query::{closure#2} as core[844c48195e089da5]::ops::function::FnOnce<(rustc_middle[c35c93541fbaf6fb]::ty::context::TyCtxt, rustc_middle[c35c93541fbaf6fb]::ty::instance::InstanceKind)>>::call_once
  18:     0x71f4de4115c8 - rustc_query_system[13fd671b9de95920]::query::plumbing::try_execute_query::<rustc_query_impl[c99fb05ce5425a5b]::DynamicConfig<rustc_query_system[13fd671b9de95920]::query::caches::DefaultCache<rustc_middle[c35c93541fbaf6fb]::ty::instance::InstanceKind, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[c99fb05ce5425a5b]::plumbing::QueryCtxt, false>
  19:     0x71f4de4112e6 - rustc_query_impl[c99fb05ce5425a5b]::query_impl::mir_shims::get_query_non_incr::__rust_end_short_backtrace
  20:     0x71f4dcc3af24 - <rustc_middle[c35c93541fbaf6fb]::ty::context::TyCtxt>::coroutine_layout
  21:     0x71f4de32fc5b - rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached
  22:     0x71f4de322b4e - rustc_ty_utils[c2f95faedb959599]::layout::layout_of
  23:     0x71f4de322aaa - rustc_query_impl[c99fb05ce5425a5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>
  24:     0x71f4de32189c - rustc_query_system[13fd671b9de95920]::query::plumbing::try_execute_query::<rustc_query_impl[c99fb05ce5425a5b]::DynamicConfig<rustc_query_system[13fd671b9de95920]::query::caches::DefaultCache<rustc_middle[c35c93541fbaf6fb]::ty::PseudoCanonicalInput<rustc_middle[c35c93541fbaf6fb]::ty::Ty>, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[c99fb05ce5425a5b]::plumbing::QueryCtxt, false>
  25:     0x71f4de3214e7 - rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
  26:     0x71f4de32039a - <core[844c48195e089da5]::iter::adapters::GenericShunt<core[844c48195e089da5]::iter::adapters::by_ref_sized::ByRefSized<core[844c48195e089da5]::iter::adapters::map::Map<core[844c48195e089da5]::slice::iter::Iter<rustc_middle[c35c93541fbaf6fb]::ty::VariantDef>, rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached::{closure#20}>>, core[844c48195e089da5]::result::Result<core[844c48195e089da5]::convert::Infallible, &rustc_middle[c35c93541fbaf6fb]::ty::layout::LayoutError>> as core[844c48195e089da5]::iter::traits::iterator::Iterator>::next
  27:     0x71f4de327e44 - rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached
  28:     0x71f4de322b4e - rustc_ty_utils[c2f95faedb959599]::layout::layout_of
  29:     0x71f4de322aaa - rustc_query_impl[c99fb05ce5425a5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>
  30:     0x71f4de32189c - rustc_query_system[13fd671b9de95920]::query::plumbing::try_execute_query::<rustc_query_impl[c99fb05ce5425a5b]::DynamicConfig<rustc_query_system[13fd671b9de95920]::query::caches::DefaultCache<rustc_middle[c35c93541fbaf6fb]::ty::PseudoCanonicalInput<rustc_middle[c35c93541fbaf6fb]::ty::Ty>, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[c99fb05ce5425a5b]::plumbing::QueryCtxt, false>
  31:     0x71f4de3214e7 - rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
  32:     0x71f4de32074a - <core[844c48195e089da5]::iter::adapters::GenericShunt<core[844c48195e089da5]::iter::adapters::by_ref_sized::ByRefSized<core[844c48195e089da5]::iter::adapters::map::Map<core[844c48195e089da5]::slice::iter::Iter<rustc_middle[c35c93541fbaf6fb]::ty::VariantDef>, rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached::{closure#20}>>, core[844c48195e089da5]::result::Result<core[844c48195e089da5]::convert::Infallible, &rustc_middle[c35c93541fbaf6fb]::ty::layout::LayoutError>> as core[844c48195e089da5]::iter::traits::iterator::Iterator>::next
  33:     0x71f4de327e44 - rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached
  34:     0x71f4de322b4e - rustc_ty_utils[c2f95faedb959599]::layout::layout_of
  35:     0x71f4de322aaa - rustc_query_impl[c99fb05ce5425a5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>
  36:     0x71f4de32189c - rustc_query_system[13fd671b9de95920]::query::plumbing::try_execute_query::<rustc_query_impl[c99fb05ce5425a5b]::DynamicConfig<rustc_query_system[13fd671b9de95920]::query::caches::DefaultCache<rustc_middle[c35c93541fbaf6fb]::ty::PseudoCanonicalInput<rustc_middle[c35c93541fbaf6fb]::ty::Ty>, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[c99fb05ce5425a5b]::plumbing::QueryCtxt, false>
  37:     0x71f4de3214e7 - rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
  38:     0x71f4de3235c0 - rustc_ty_utils[c2f95faedb959599]::layout::layout_of
  39:     0x71f4de322aaa - rustc_query_impl[c99fb05ce5425a5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>
  40:     0x71f4de32189c - rustc_query_system[13fd671b9de95920]::query::plumbing::try_execute_query::<rustc_query_impl[c99fb05ce5425a5b]::DynamicConfig<rustc_query_system[13fd671b9de95920]::query::caches::DefaultCache<rustc_middle[c35c93541fbaf6fb]::ty::PseudoCanonicalInput<rustc_middle[c35c93541fbaf6fb]::ty::Ty>, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[c99fb05ce5425a5b]::plumbing::QueryCtxt, false>
  41:     0x71f4de3214e7 - rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
  42:     0x71f4de333349 - <rustc_middle[c35c93541fbaf6fb]::ty::layout::LayoutCx as rustc_middle[c35c93541fbaf6fb]::ty::layout::LayoutOf>::spanned_layout_of
  43:     0x71f4dd4c4e30 - <core[844c48195e089da5]::iter::adapters::GenericShunt<core[844c48195e089da5]::iter::adapters::by_ref_sized::ByRefSized<core[844c48195e089da5]::iter::adapters::map::Map<core[844c48195e089da5]::slice::iter::Iter<rustc_middle[c35c93541fbaf6fb]::mir::query::CoroutineSavedTy>, rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached::{closure#12}>>, core[844c48195e089da5]::result::Result<core[844c48195e089da5]::convert::Infallible, &rustc_middle[c35c93541fbaf6fb]::ty::layout::LayoutError>> as core[844c48195e089da5]::iter::traits::iterator::Iterator>::next
  44:     0x71f4dd4aec1a - core[844c48195e089da5]::iter::adapters::try_process::<core[844c48195e089da5]::iter::adapters::by_ref_sized::ByRefSized<core[844c48195e089da5]::iter::adapters::map::Map<core[844c48195e089da5]::slice::iter::Iter<rustc_middle[c35c93541fbaf6fb]::mir::query::CoroutineSavedTy>, rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached::{closure#12}>>, rustc_abi[a261153e5dfc86cc]::layout::ty::TyAndLayout<rustc_middle[c35c93541fbaf6fb]::ty::Ty>, core[844c48195e089da5]::result::Result<core[844c48195e089da5]::convert::Infallible, &rustc_middle[c35c93541fbaf6fb]::ty::layout::LayoutError>, <core[844c48195e089da5]::iter::adapters::map::Map<core[844c48195e089da5]::slice::iter::Iter<rustc_middle[c35c93541fbaf6fb]::mir::query::CoroutineSavedTy>, rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached::{closure#12}> as core[844c48195e089da5]::iter::traits::iterator::Iterator>::try_collect<rustc_index[731be7b9208c99a6]::vec::IndexVec<rustc_middle[c35c93541fbaf6fb]::mir::query::CoroutineSavedLocal, rustc_abi[a261153e5dfc86cc]::layout::ty::TyAndLayout<rustc_middle[c35c93541fbaf6fb]::ty::Ty>>>::{closure#0}, rustc_index[731be7b9208c99a6]::vec::IndexVec<rustc_middle[c35c93541fbaf6fb]::mir::query::CoroutineSavedLocal, rustc_abi[a261153e5dfc86cc]::layout::ty::TyAndLayout<rustc_middle[c35c93541fbaf6fb]::ty::Ty>>>
  45:     0x71f4de33027b - rustc_ty_utils[c2f95faedb959599]::layout::layout_of_uncached
  46:     0x71f4de322b4e - rustc_ty_utils[c2f95faedb959599]::layout::layout_of
  47:     0x71f4de322aaa - rustc_query_impl[c99fb05ce5425a5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>
  48:     0x71f4de32189c - rustc_query_system[13fd671b9de95920]::query::plumbing::try_execute_query::<rustc_query_impl[c99fb05ce5425a5b]::DynamicConfig<rustc_query_system[13fd671b9de95920]::query::caches::DefaultCache<rustc_middle[c35c93541fbaf6fb]::ty::PseudoCanonicalInput<rustc_middle[c35c93541fbaf6fb]::ty::Ty>, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[c99fb05ce5425a5b]::plumbing::QueryCtxt, false>
  49:     0x71f4de3214e7 - rustc_query_impl[c99fb05ce5425a5b]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
  50:     0x71f4dea1d766 - <rustc_mir_transform[86a227439405b463]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[86a227439405b463]::pass_manager::MirLint>::run_lint
  51:     0x71f4ddc0bea7 - rustc_mir_transform[86a227439405b463]::run_analysis_to_runtime_passes
  52:     0x71f4de0bb625 - rustc_mir_transform[86a227439405b463]::mir_drops_elaborated_and_const_checked
  53:     0x71f4de0baff7 - rustc_query_impl[c99fb05ce5425a5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c99fb05ce5425a5b]::query_impl::mir_drops_elaborated_and_const_checked::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 8usize]>>
  54:     0x71f4ddedc4e6 - rustc_query_system[13fd671b9de95920]::query::plumbing::try_execute_query::<rustc_query_impl[c99fb05ce5425a5b]::DynamicConfig<rustc_data_structures[8c4d114b892fc81f]::vec_cache::VecCache<rustc_span[767accb19bf8aef3]::def_id::LocalDefId, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[13fd671b9de95920]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[c99fb05ce5425a5b]::plumbing::QueryCtxt, false>
  55:     0x71f4ddedbdd2 - rustc_query_impl[c99fb05ce5425a5b]::query_impl::mir_drops_elaborated_and_const_checked::get_query_non_incr::__rust_end_short_backtrace
  56:     0x71f4de112210 - rustc_interface[b13b618c5853daff]::passes::run_required_analyses
  57:     0x71f4debdb39e - rustc_interface[b13b618c5853daff]::passes::analysis
  58:     0x71f4debdb375 - rustc_query_impl[c99fb05ce5425a5b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[c99fb05ce5425a5b]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 0usize]>>
  59:     0x71f4deb5363a - rustc_query_system[13fd671b9de95920]::query::plumbing::try_execute_query::<rustc_query_impl[c99fb05ce5425a5b]::DynamicConfig<rustc_query_system[13fd671b9de95920]::query::caches::SingleCache<rustc_middle[c35c93541fbaf6fb]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[c99fb05ce5425a5b]::plumbing::QueryCtxt, false>
  60:     0x71f4deb5330f - rustc_query_impl[c99fb05ce5425a5b]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  61:     0x71f4dee1f0c7 - rustc_interface[b13b618c5853daff]::passes::create_and_enter_global_ctxt::<core[844c48195e089da5]::option::Option<rustc_interface[b13b618c5853daff]::queries::Linker>, rustc_driver_impl[2b29d548aa47efe8]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  62:     0x71f4decf50a6 - rustc_interface[b13b618c5853daff]::interface::run_compiler::<(), rustc_driver_impl[2b29d548aa47efe8]::run_compiler::{closure#0}>::{closure#1}
  63:     0x71f4decca07e - std[a3033ab4cf040dbc]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[b13b618c5853daff]::util::run_in_thread_with_globals<rustc_interface[b13b618c5853daff]::util::run_in_thread_pool_with_globals<rustc_interface[b13b618c5853daff]::interface::run_compiler<(), rustc_driver_impl[2b29d548aa47efe8]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  64:     0x71f4decca4eb - <<std[a3033ab4cf040dbc]::thread::Builder>::spawn_unchecked_<rustc_interface[b13b618c5853daff]::util::run_in_thread_with_globals<rustc_interface[b13b618c5853daff]::util::run_in_thread_pool_with_globals<rustc_interface[b13b618c5853daff]::interface::run_compiler<(), rustc_driver_impl[2b29d548aa47efe8]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[844c48195e089da5]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  65:     0x71f4deccb8eb - std::sys::pal::unix::thread::Thread::new::thread_start::hcb4e67cfc7257238
  66:     0x71f4d8a5d70a - <unknown>
  67:     0x71f4d8ae1aac - <unknown>
  68:                0x0 - <unknown>

error: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: please make sure that you have updated to the latest nightly

note: please attach the file at `/home/matthias/vcs/github/CRED/rustc-ice-2025-05-13T19_00_56-2066440.txt` to your bug report

query stack during panic:
#0 [mir_shims] generating MIR shim for `core::future::async_drop::async_drop_in_place::{closure#0}`, instance=AsyncDropGlue(DefId(2:15267 ~ core[844c]::future::async_drop::async_drop_in_place::{closure#0}), Coroutine(DefId(2:15267 ~ core[844c]::future::async_drop::async_drop_in_place::{closure#0}), [e, (), core::future::ResumeTy, (), (), CoroutineWitness(DefId(2:15267 ~ core[844c]::future::async_drop::async_drop_in_place::{closure#0}), [e]), (*mut e,)]))
#1 [layout_of] computing layout of `{async fn body of core::future::async_drop::async_drop_in_place<e>()}`
#2 [layout_of] computing layout of `core::mem::manually_drop::ManuallyDrop<{async fn body of core::future::async_drop::async_drop_in_place<e>()}>`
#3 [layout_of] computing layout of `core::mem::maybe_uninit::MaybeUninit<{async fn body of core::future::async_drop::async_drop_in_place<e>()}>`
#4 [layout_of] computing layout of `core::mem::maybe_uninit::MaybeUninit<core::future::async_drop::async_drop_in_place::{opaque#0}>`
#5 [layout_of] computing layout of `{async fn body of a<e>()}`
#6 [mir_drops_elaborated_and_const_checked] elaborating drops for `d`
#7 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors; 5 warnings emitted

Some errors have detailed explanations: E0046, E0601.
For more information about an error, try `rustc --explain E0046`.

[moxian]

cleaner:

#![feature(async_drop)]
use core::future::AsyncDrop;

async fn fun(_: HasIncompleteAsyncDrop) {}

struct HasIncompleteAsyncDrop;
impl Drop for HasIncompleteAsyncDrop {
    fn drop(&mut self) {}
}
impl AsyncDrop for HasIncompleteAsyncDrop {
    // not implemented yet..
}

Bisects to initial async drop codegen PR 7d65abf

@rustbot label: +S-has-mcve +requires-incomplete-features -needs-triage +S-has-bisection