rust-lang / rust-lang/rust

[ICE]: broken MIR in AsyncDropGlue

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-Zvalidate-mir C-bug F-async_drop F-async_trait_bounds I-ICE needs-triage T-compiler
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Rust
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Description

auto-reduced (treereduce-rust):

//@compile-flags: --edition=2024 -Zvalidate-mir
#![feature(min_generic_const_args)]
#![feature(async_drop)]
#![feature(async_trait_bounds)]
pub fn block_on<T>(fut: impl Future<Output = T>) -> T {
    loop {}
}

async fn call_once(f: impl async FnOnce(DropMe)) {}

#[derive(Debug)]
struct DropMe(&'static str);

impl Drop for DropMe {
    fn drop(&mut self) {}
}

pub fn main() {
    block_on(async {
        let b = DropMe("hello");
        let async_closure = async move |a: DropMe| {
            println!("{a:?} {b:?}");
        };
        call_once(async_closure).await;
    });
}

original:

#![feature(async_closure, noop_waker, async_fn_traits)]

use std::future::Future;
use std::pin::pin;
use std::task::*;

pub fn block_on<T>(fut: impl Future<Output = T>) -> T {
    let mut fut = pin!(fut);
    let ctx = &mut Context::from_waker(Waker::noop());

    loop {
        match fut.as_mut().poll(ctx) {
            Poll::Pending => {}
            Poll::Ready(t) => break t,
        }
    }
}

async fn call_once(f: impl async FnOnce(DropMe)) {

}

#[derive(Debug)]
struct DropMe(&'static str);

impl Drop for DropMe {
    fn drop(&mut self) {
        println!("{}", self.0);
    }
}

pub fn main() {
    block_on(async {
        let b = DropMe("hello");
        let async_closure = async move |a: DropMe| {
            println!("{a:?} {b:?}");
        };
        call_once(async_closure).await;
    });
}

Version information

rustc 1.96.0-nightly (8db65c717 2026-03-13)
binary: rustc
commit-hash: 8db65c71725664d85d06ec96ee3e575665de1f6a
commit-date: 2026-03-13
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.0

Possibly related line of code:
https://github.com/rust-lang/rust/blob/8db65c71725664d85d06ec96ee3e575665de1f6a/compiler/rustc_mir_transform/src/validate.rs#L75-L87

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --edition=2024 -Zvalidate-mir -Zcrate-attr=feature(min_generic_const_args) -Zcrate-attr=feature(async_drop) -Zcrate-attr=feature(async_trait_bounds)

Program output 

warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:12
  |
1 | #![feature(min_generic_const_args)]
  |            ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #132980 <https://github.com/rust-lang/rust/issues/132980> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: the feature `async_drop` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:12
  |
1 | #![feature(async_drop)]
  |            ^^^^^^^^^^
  |
  = note: see issue #126482 <https://github.com/rust-lang/rust/issues/126482> for more information

warning: unused variable: `fut`
 --> /tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:1:20
  |
1 | pub fn block_on<T>(fut: impl Future<Output = T>) -> T {
  |                    ^^^ help: if this is intentional, prefix it with an underscore: `_fut`
  |
  = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

warning: unused variable: `f`
 --> /tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:5:20
  |
5 | async fn call_once(f: impl async FnOnce(DropMe)) {}
  |                    ^ help: if this is intentional, prefix it with an underscore: `_f`

error: internal compiler error: /rustc-dev/8db65c71725664d85d06ec96ee3e575665de1f6a/compiler/rustc_mir_transform/src/validate.rs:81:25: broken MIR in AsyncDropGlue(DefId(2:16339 ~ core[3557]::future::async_drop::async_drop_in_place::{closure#0}), Coroutine(DefId(2:16339 ~ core[3557]::future::async_drop::async_drop_in_place::{closure#0}), [CoroutineClosure(DefId(0:14 ~ mvce[7a56]::main::{closure#0}::{closure#0}), [i8, Binder { value: extern "RustCall" fn(std::future::ResumeTy, (DropMe,)) -> ((), ()), bound_vars: [] }, (DropMe,), Binder { value: fn() -> (&'^0 DropMe,), bound_vars: [Region(BrAnon)] }]), (), std::future::ResumeTy, (), (), (*mut CoroutineClosure(DefId(0:14 ~ mvce[7a56]::main::{closure#0}::{closure#0}), [i8, Binder { value: extern "RustCall" fn(std::future::ResumeTy, (DropMe,)) -> ((), ()), bound_vars: [] }, (DropMe,), Binder { value: fn() -> (&'^0 DropMe,), bound_vars: [Region(BrAnon)] }]),)])) (after pass MentionedItems) at bb0[0]:
                                place (*(_1.0: *mut {async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51})) has deref as a later projection (it is only permitted as the first projection)
  --> /home/matthias/.rustup/toolchains/master/lib/rustlib/src/rust/library/core/src/future/async_drop.rs:46:70
   |
46 |   pub async unsafe fn async_drop_in_place<T: ?Sized>(_to_drop: *mut T) {
   |  ______________________________________________________________________^
...  |
49 | | }
   | |_^


thread 'rustc' (138316) panicked at /rustc-dev/8db65c71725664d85d06ec96ee3e575665de1f6a/compiler/rustc_mir_transform/src/validate.rs:81:25:
Box<dyn Any>
stack backtrace:
   0:     0x7f852ff41bfb - <<std[528e8317bf3672e6]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[355797217e00999e]::fmt::Display>::fmt
   1:     0x7f853061dd08 - core[355797217e00999e]::fmt::write
   2:     0x7f852ff58c06 - <std[528e8317bf3672e6]::sys::stdio::unix::Stderr as std[528e8317bf3672e6]::io::Write>::write_fmt
   3:     0x7f852ff17ce8 - std[528e8317bf3672e6]::panicking::default_hook::{closure#0}
   4:     0x7f852ff35073 - std[528e8317bf3672e6]::panicking::default_hook
   5:     0x7f852ef2f1ec - std[528e8317bf3672e6]::panicking::update_hook::<alloc[8c63ef3df50c39ca]::boxed::Box<rustc_driver_impl[5188b6df2796d833]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f852ff35352 - std[528e8317bf3672e6]::panicking::panic_with_hook
   7:     0x7f852ef66851 - std[528e8317bf3672e6]::panicking::begin_panic::<rustc_errors[b7386ce73a490176]::ExplicitBug>::{closure#0}
   8:     0x7f852ef5f2b6 - std[528e8317bf3672e6]::sys::backtrace::__rust_end_short_backtrace::<std[528e8317bf3672e6]::panicking::begin_panic<rustc_errors[b7386ce73a490176]::ExplicitBug>::{closure#0}, !>
   9:     0x7f852ef5f29b - std[528e8317bf3672e6]::panicking::begin_panic::<rustc_errors[b7386ce73a490176]::ExplicitBug>
  10:     0x7f852ef71ec1 - <rustc_errors[b7386ce73a490176]::diagnostic::BugAbort as rustc_errors[b7386ce73a490176]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7f852f527adc - <rustc_errors[b7386ce73a490176]::DiagCtxtHandle>::span_bug::<rustc_span[fb50682586f1dcf0]::span_encoding::Span, alloc[8c63ef3df50c39ca]::string::String>
  12:     0x7f852f54f616 - rustc_middle[b50bd0dc9f8ca81a]::util::bug::opt_span_bug_fmt::<rustc_span[fb50682586f1dcf0]::span_encoding::Span>::{closure#0}
  13:     0x7f852f54f7c2 - rustc_middle[b50bd0dc9f8ca81a]::ty::context::tls::with_opt::<rustc_middle[b50bd0dc9f8ca81a]::util::bug::opt_span_bug_fmt<rustc_span[fb50682586f1dcf0]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7f852f54029b - rustc_middle[b50bd0dc9f8ca81a]::ty::context::tls::with_context_opt::<rustc_middle[b50bd0dc9f8ca81a]::ty::context::tls::with_opt<rustc_middle[b50bd0dc9f8ca81a]::util::bug::opt_span_bug_fmt<rustc_span[fb50682586f1dcf0]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x7f852d777cb8 - rustc_middle[b50bd0dc9f8ca81a]::util::bug::span_bug_fmt::<rustc_span[fb50682586f1dcf0]::span_encoding::Span>
  16:     0x7f852db83c65 - <rustc_mir_transform[c4a85a770e98b1c]::validate::CfgChecker>::fail::<alloc[8c63ef3df50c39ca]::string::String>
  17:     0x7f85311d151f - <rustc_mir_transform[c4a85a770e98b1c]::validate::Validator as rustc_mir_transform[c4a85a770e98b1c]::pass_manager::MirPass>::run_pass
  18:     0x7f852db58465 - rustc_mir_transform[c4a85a770e98b1c]::pass_manager::validate_body
  19:     0x7f853061eb70 - rustc_mir_transform[c4a85a770e98b1c]::pass_manager::run_passes_inner
  20:     0x7f85311d67d3 - rustc_mir_transform[c4a85a770e98b1c]::shim::make_shim
  21:     0x7f85311d4c9e - rustc_query_impl[78d760485dcf33b2]::query_impl::mir_shims::invoke_provider_fn::__rust_begin_short_backtrace
  22:     0x7f8531005fd8 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::instance::InstanceKind, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 8usize]>>, false>
  23:     0x7f8531005cd1 - rustc_query_impl[78d760485dcf33b2]::query_impl::mir_shims::execute_query_non_incr::__rust_end_short_backtrace
  24:     0x7f85319a171a - <rustc_middle[b50bd0dc9f8ca81a]::ty::context::TyCtxt>::coroutine_layout
  25:     0x7f8530fd23bc - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  26:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  27:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  28:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  29:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  30:     0x7f8530fc8061 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  31:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  32:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  33:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  34:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  35:     0x7f8530fc8061 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  36:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  37:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  38:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  39:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  40:     0x7f8530fc92a5 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  41:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  42:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  43:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  44:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  45:     0x7f8530fc6d61 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  46:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  47:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  48:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  49:     0x7f8530fc2de1 - <rustc_middle[b50bd0dc9f8ca81a]::ty::layout::LayoutCx as rustc_middle[b50bd0dc9f8ca81a]::ty::layout::LayoutOf>::spanned_layout_of
  50:     0x7f8531ae9da5 - <core[355797217e00999e]::iter::adapters::GenericShunt<core[355797217e00999e]::iter::adapters::by_ref_sized::ByRefSized<core[355797217e00999e]::iter::adapters::map::Map<core[355797217e00999e]::slice::iter::Iter<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedTy>, rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached::{closure#12}>>, core[355797217e00999e]::result::Result<core[355797217e00999e]::convert::Infallible, &rustc_middle[b50bd0dc9f8ca81a]::ty::layout::LayoutError>> as core[355797217e00999e]::iter::traits::iterator::Iterator>::next
  51:     0x7f8531ae9c64 - core[355797217e00999e]::iter::adapters::try_process::<core[355797217e00999e]::iter::adapters::by_ref_sized::ByRefSized<core[355797217e00999e]::iter::adapters::map::Map<core[355797217e00999e]::slice::iter::Iter<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedTy>, rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached::{closure#12}>>, rustc_abi[57d547e7f420776a]::layout::ty::TyAndLayout<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, core[355797217e00999e]::result::Result<core[355797217e00999e]::convert::Infallible, &rustc_middle[b50bd0dc9f8ca81a]::ty::layout::LayoutError>, <core[355797217e00999e]::iter::adapters::map::Map<core[355797217e00999e]::slice::iter::Iter<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedTy>, rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached::{closure#12}> as core[355797217e00999e]::iter::traits::iterator::Iterator>::try_collect<rustc_index[f1d693ef172438f7]::vec::IndexVec<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedLocal, rustc_abi[57d547e7f420776a]::layout::ty::TyAndLayout<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>>>::{closure#0}, rustc_index[f1d693ef172438f7]::vec::IndexVec<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedLocal, rustc_abi[57d547e7f420776a]::layout::ty::TyAndLayout<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>>>
  52:     0x7f8530fd241c - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  53:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  54:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  55:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  56:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  57:     0x7f8530fc8061 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  58:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  59:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  60:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  61:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  62:     0x7f8530fc8061 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  63:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  64:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  65:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  66:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  67:     0x7f8530fc92a5 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  68:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  69:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  70:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  71:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  72:     0x7f8530fc2de1 - <rustc_middle[b50bd0dc9f8ca81a]::ty::layout::LayoutCx as rustc_middle[b50bd0dc9f8ca81a]::ty::layout::LayoutOf>::spanned_layout_of
  73:     0x7f8531ae9da5 - <core[355797217e00999e]::iter::adapters::GenericShunt<core[355797217e00999e]::iter::adapters::by_ref_sized::ByRefSized<core[355797217e00999e]::iter::adapters::map::Map<core[355797217e00999e]::slice::iter::Iter<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedTy>, rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached::{closure#12}>>, core[355797217e00999e]::result::Result<core[355797217e00999e]::convert::Infallible, &rustc_middle[b50bd0dc9f8ca81a]::ty::layout::LayoutError>> as core[355797217e00999e]::iter::traits::iterator::Iterator>::next
  74:     0x7f8531ae9c64 - core[355797217e00999e]::iter::adapters::try_process::<core[355797217e00999e]::iter::adapters::by_ref_sized::ByRefSized<core[355797217e00999e]::iter::adapters::map::Map<core[355797217e00999e]::slice::iter::Iter<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedTy>, rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached::{closure#12}>>, rustc_abi[57d547e7f420776a]::layout::ty::TyAndLayout<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, core[355797217e00999e]::result::Result<core[355797217e00999e]::convert::Infallible, &rustc_middle[b50bd0dc9f8ca81a]::ty::layout::LayoutError>, <core[355797217e00999e]::iter::adapters::map::Map<core[355797217e00999e]::slice::iter::Iter<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedTy>, rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached::{closure#12}> as core[355797217e00999e]::iter::traits::iterator::Iterator>::try_collect<rustc_index[f1d693ef172438f7]::vec::IndexVec<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedLocal, rustc_abi[57d547e7f420776a]::layout::ty::TyAndLayout<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>>>::{closure#0}, rustc_index[f1d693ef172438f7]::vec::IndexVec<rustc_middle[b50bd0dc9f8ca81a]::mir::query::CoroutineSavedLocal, rustc_abi[57d547e7f420776a]::layout::ty::TyAndLayout<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>>>
  75:     0x7f8530fd241c - rustc_ty_utils[83a3898c3774b082]::layout::layout_of_uncached
  76:     0x7f8530fc6c09 - rustc_ty_utils[83a3898c3774b082]::layout::layout_of
  77:     0x7f8530fc6b6f - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::invoke_provider_fn::__rust_begin_short_backtrace
  78:     0x7f8530fc5a47 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::DefaultCache<rustc_middle[b50bd0dc9f8ca81a]::ty::PseudoCanonicalInput<rustc_middle[b50bd0dc9f8ca81a]::ty::Ty>, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 16usize]>>, false>
  79:     0x7f8530fc569e - rustc_query_impl[78d760485dcf33b2]::query_impl::layout_of::execute_query_non_incr::__rust_end_short_backtrace
  80:     0x7f8530d55243 - <rustc_mir_transform[c4a85a770e98b1c]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[c4a85a770e98b1c]::pass_manager::MirLint>::run_lint
  81:     0x7f853060d17c - rustc_mir_transform[c4a85a770e98b1c]::run_analysis_to_runtime_passes
  82:     0x7f8530bc26c4 - rustc_mir_transform[c4a85a770e98b1c]::mir_drops_elaborated_and_const_checked
  83:     0x7f8530bc2119 - rustc_query_impl[78d760485dcf33b2]::query_impl::mir_drops_elaborated_and_const_checked::invoke_provider_fn::__rust_begin_short_backtrace
  84:     0x7f8530706966 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_data_structures[58c9a099e588906a]::vec_cache::VecCache<rustc_span[fb50682586f1dcf0]::def_id::LocalDefId, rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[b50bd0dc9f8ca81a]::dep_graph::graph::DepNodeIndex>, false>
  85:     0x7f85307060c3 - rustc_query_impl[78d760485dcf33b2]::query_impl::mir_drops_elaborated_and_const_checked::execute_query_non_incr::__rust_end_short_backtrace
  86:     0x7f8530708dc8 - <rustc_middle[b50bd0dc9f8ca81a]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[74d89972637901aa]::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}
  87:     0x7f85307081b3 - rustc_interface[74d89972637901aa]::passes::analysis
  88:     0x7f853186e509 - rustc_query_impl[78d760485dcf33b2]::execution::try_execute_query::<rustc_middle[b50bd0dc9f8ca81a]::query::caches::SingleCache<rustc_middle[b50bd0dc9f8ca81a]::query::erase::ErasedData<[u8; 0usize]>>, false>
  89:     0x7f853186e175 - rustc_query_impl[78d760485dcf33b2]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  90:     0x7f8531813248 - rustc_interface[74d89972637901aa]::interface::run_compiler::<(), rustc_driver_impl[5188b6df2796d833]::run_compiler::{closure#0}>::{closure#1}
  91:     0x7f853184cb3e - std[528e8317bf3672e6]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[74d89972637901aa]::util::run_in_thread_with_globals<rustc_interface[74d89972637901aa]::util::run_in_thread_pool_with_globals<rustc_interface[74d89972637901aa]::interface::run_compiler<(), rustc_driver_impl[5188b6df2796d833]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  92:     0x7f853184d3e0 - <std[528e8317bf3672e6]::thread::lifecycle::spawn_unchecked<rustc_interface[74d89972637901aa]::util::run_in_thread_with_globals<rustc_interface[74d89972637901aa]::util::run_in_thread_pool_with_globals<rustc_interface[74d89972637901aa]::interface::run_compiler<(), rustc_driver_impl[5188b6df2796d833]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[355797217e00999e]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  93:     0x7f853184e26c - <std[528e8317bf3672e6]::sys::thread::unix::Thread>::new::thread_start
  94:     0x7f852b2a598b - <unknown>
  95:     0x7f852b329a0c - <unknown>
  96:                0x0 - <unknown>

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: rustc 1.96.0-nightly (8db65c717 2026-03-13) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z validate-mir -Z crate-attr=feature(min_generic_const_args) -Z crate-attr=feature(async_drop) -Z crate-attr=feature(async_trait_bounds) -Z dump-mir-dir=dir

query stack during panic:
#0 [mir_shims] generating MIR shim for `core::future::async_drop::async_drop_in_place::{closure#0}`, instance=AsyncDropGlue(DefId(2:16339 ~ core[3557]::future::async_drop::async_drop_in_place::{closure#0}), Coroutine(DefId(2:16339 ~ core[3557]::future::async_drop::async_drop_in_place::{closure#0}), [CoroutineClosure(DefId(0:14 ~ mvce[7a56]::main::{closure#0}::{closure#0}), [i8, Binder { value: extern "RustCall" fn(core::future::ResumeTy, (DropMe,)) -> ((), ()), bound_vars: [] }, (DropMe,), Binder { value: fn() -> (&'^0 DropMe,), bound_vars: [Region(BrAnon)] }]), (), core::future::ResumeTy, (), (), (*mut CoroutineClosure(DefId(0:14 ~ mvce[7a56]::main::{closure#0}::{closure#0}), [i8, Binder { value: extern "RustCall" fn(core::future::ResumeTy, (DropMe,)) -> ((), ()), bound_vars: [] }, (DropMe,), Binder { value: fn() -> (&'^0 DropMe,), bound_vars: [Region(BrAnon)] }]),)]))
#1 [layout_of] computing layout of `{async fn body of core::future::async_drop::async_drop_in_place<{async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51}>()}`
#2 [layout_of] computing layout of `core::mem::maybe_dangling::MaybeDangling<{async fn body of core::future::async_drop::async_drop_in_place<{async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51}>()}>`
#3 [layout_of] computing layout of `core::mem::manually_drop::ManuallyDrop<{async fn body of core::future::async_drop::async_drop_in_place<{async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51}>()}>`
#4 [layout_of] computing layout of `core::mem::maybe_uninit::MaybeUninit<{async fn body of core::future::async_drop::async_drop_in_place<{async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51}>()}>`
#5 [layout_of] computing layout of `core::mem::maybe_uninit::MaybeUninit<core::future::async_drop::async_drop_in_place::{opaque#0}>`
#6 [layout_of] computing layout of `{async fn body of call_once<{async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51}>()}`
#7 [layout_of] computing layout of `core::mem::maybe_dangling::MaybeDangling<{async fn body of call_once<{async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51}>()}>`
#8 [layout_of] computing layout of `core::mem::manually_drop::ManuallyDrop<{async fn body of call_once<{async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51}>()}>`
#9 [layout_of] computing layout of `core::mem::maybe_uninit::MaybeUninit<{async fn body of call_once<{async closure@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:17:29: 17:51}>()}>`
#10 [layout_of] computing layout of `{async block@/tmp/icemaker_global_tempdir.ZRTrE6gz0GwA/rustc_testrunner_tmpdir_reporting.hFH4jmaKV1GI/mvce.rs:15:14: 15:19}`
#11 [mir_drops_elaborated_and_const_checked] elaborating drops for `main`
#12 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 1 previous error; 4 warnings emitted

@rustbot label +F-async_closure +F-noop_waker +F-async_fn_traits +F-min_generic_const_args +F-async_drop +F-async_trait_bounds +-Zvalidate-mir

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the reduced reproducer and run it using the listed --edition=2024 and -Zvalidate-mir flags. Read compiler/rustc_mir_transform/src/validate.rs around lines 75-87 and core/src/future/async_drop.rs around line 46, then trace the AsyncDropGlue MIR validation failure. Done means the reproducer no longer triggers this ICE and MIR validation accepts the generated body.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Needs clarification
Newbie friendliness
35/100

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