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[ICE]: could not resolve upvar: LocalVarId(HirId(DefId(

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C-bug F-pin_ergonomics I-ICE S-bug-has-test S-has-mcve T-compiler
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Description

auto-reduced (treereduce-rust):

//@compile-flags: --edition=2024
#![feature(pin_ergonomics)]
use core::pin::{pin, Pin};
use core::task::{Context, Poll, Waker};

fn test_idempotency<T>(mut x: Pin<&mut T>) -> impl Future + '_
where
    T: Future<Output = ()>,
{
    core::future::poll_fn(move |cx| {
        assert_eq!(x.as_mut().poll(cx), Poll::Ready(()));

        Poll::Ready(())
    })
}
original code

original:

//@ run-pass
//@ check-run-results

// WARNING: If you would ever want to modify this test,
// please consider modifying miri's async drop test at
// `src/tools/miri/tests/pass/async-drop.rs`.

#![feature(async_drop)]
#![allow(incomplete_features, dead_code)]

//@ edition: 2021

// FIXME(zetanumbers): consider AsyncDestruct::async_drop cleanup tests
use core::future::{async_drop_in_place, AsyncDrop, Future};
use core::hint::black_box;
use core::mem::{self, ManuallyDrop};
use core::pin::{pin, Pin};
use core::task::{Context, Poll, Waker};

async fn test_async_drop<T>(x: T, _size: usize) {
    let mut x = mem::MaybeUninit::new(x);
    let dtor = pin!(unsafe { async_drop_in_place(x.as_mut_ptr()) });

    // FIXME(zetanumbers): This check fully depends on the layout of
    // the coroutine state, since async destructor combinators are just
    // async functions.
    #[cfg(target_pointer_width = "64")]
    assert_eq!(
        mem::size_of_val(&*dtor),
        _size,
        "sizes did not match for async destructor of type {}",
        core::any::type_name::<T>(),
    );

    test_idempotency(dtor).await;
}

fn test_idempotency<T>(mut x: Pin<&mut T>) -> impl Future<Output = ()> + '_
where
    T: Future<Output = ()>,
{
    core::future::poll_fn(move |cx| {
        assert_eq!(x.as_mut().poll(cx), Poll::Ready(()));
        assert_eq!(x.as_mut().poll(cx), Poll::Ready(()));
        Poll::Ready(())
    })
}

fn main() {
    let waker = Waker::noop();
    let mut cx = Context::from_waker(&waker);

    let i = 13;
    let fut = pin!(async {
        test_async_drop(Int(0), 16).await;
        test_async_drop(AsyncInt(0), 32).await;
        test_async_drop([AsyncInt(1), AsyncInt(2)], 104).await;
        test_async_drop((AsyncInt(3), AsyncInt(4)), 120).await;
        test_async_drop(5, 16).await;
        let j = 42;
        test_async_drop(&i, 16).await;
        test_async_drop(&j, 16).await;
        test_async_drop(
            AsyncStruct { b: AsyncInt(8), a: AsyncInt(7), i: 6 },
            136,
        ).await;
        test_async_drop(ManuallyDrop::new(AsyncInt(9)), 16).await;

        let foo = AsyncInt(10);
        test_async_drop(AsyncReference { foo: &foo }, 32).await;
        let _ = ManuallyDrop::new(foo);

        let foo = AsyncInt(11);
        test_async_drop(
            || {
                black_box(foo);
                let foo = AsyncInt(10);
                foo
            },
            48,
        )
        .await;

        test_async_drop(AsyncEnum::A(AsyncInt(12)), 104).await;
        test_async_drop(AsyncEnum::B(SyncInt(13)), 104).await;

        test_async_drop(SyncInt(14), 16).await;
        test_async_drop(
            SyncThenAsync { i: 15, a: AsyncInt(16), b: SyncInt(17), c: AsyncInt(18) },
            120,
        )
        .await;

        let mut ptr19 = mem::MaybeUninit::new(AsyncInt(19));
        let async_drop_fut = pin!(unsafe { async_drop_in_place(ptr19.as_mut_ptr()) });
        test_idempotency(async_drop_fut).await;

        let foo = AsyncInt(20);
        test_async_drop(
            async || {
                black_box(foo);
                let foo = AsyncInt(19);
                // Await point there, but this is async closure so it's fine
                black_box(core::future::ready(())).await;
                foo
            },
            48,
        )
        .await;

        test_async_drop(AsyncUnion { signed: 21 }, 32).await;
    });
    let res = fut.poll(&mut cx);
    assert_eq!(res, Poll::Ready(()));
}

struct AsyncInt(i32);

impl Drop for AsyncInt {
    fn drop(&mut self) {
        println!("AsyncInt::drop: {}", self.0);
    }
}
impl AsyncDrop for AsyncInt {
    async fn drop(self: Pin<&mut Self>) {
        println!("AsyncInt::Dropper::poll: {}", self.0);
    }
}

struct SyncInt(i32);

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

struct SyncThenAsync {
    i: i32,
    a: AsyncInt,
    b: SyncInt,
    c: AsyncInt,
}

impl Drop for SyncThenAsync {
    fn drop(&mut self) {
        println!("SyncThenAsync::drop: {}", self.i);
    }
}

struct AsyncReference<'a> {
    foo: &'a AsyncInt,
}

impl Drop for AsyncReference<'_> {
    fn drop(&mut self) {
        println!("AsyncReference::drop: {}", self.foo.0);
    }
}

impl AsyncDrop for AsyncReference<'_> {
    async fn drop(self: Pin<&mut Self>) {
        println!("AsyncReference::Dropper::poll: {}", self.foo.0);
    }
}

struct Int(i32);

struct AsyncStruct {
    i: i32,
    a: AsyncInt,
    b: AsyncInt,
}

impl Drop for AsyncStruct {
    fn drop(&mut self) {
        println!("AsyncStruct::drop: {}", self.i);
    }
}

impl AsyncDrop for AsyncStruct {
    async fn drop(self: Pin<&mut Self>) {
        println!("AsyncStruct::Dropper::poll: {}", self.i);
    }
}

enum AsyncEnum {
    A(i32),
    B(SyncInt),
}

impl Drop for AsyncEnum {
    fn drop(&mut self) {
        let new_self = match self {
            AsyncEnum::A(foo) => {
                println!("AsyncEnum(A)::drop: {}", foo.0);
                AsyncEnum::B(SyncInt(foo.0))
            }
            AsyncEnum::B(foo) => {
                println!("AsyncEnum(B)::drop: {}", foo.0);
                AsyncEnum::A(AsyncInt(foo.0))
            }
        };
        mem::forget(mem::replace(&mut *self, new_self));
    }
}
impl AsyncDrop for AsyncEnum {
    async fn drop(mut self: Pin<&mut Self>) {
        let new_self = match &*self {
            AsyncEnum::A(foo) => {
                println!("AsyncEnum(A)::Dropper::poll: {}", foo.0);
                AsyncEnum::B(SyncInt(foo.0))
            }
            AsyncEnum::B(foo) => {
                println!("AsyncEnum(B)::Dropper::poll: {}", foo.0);
                AsyncEnum::A(AsyncInt(foo.0))
            }
        };
        mem::forget(mem::replace(&mut *self, new_self));
    }
}

// FIXME(zetanumbers): Disallow types with `AsyncDrop` in unions
union AsyncUnion {
    signed: i32,
    unsigned: u32,
}

impl Drop for AsyncUnion {
    fn drop(&mut self) {
        println!(
            "AsyncUnion::drop: {}, {}",
            unsafe { self.signed },
            unsafe { self.unsigned },
        );
    }
}
impl AsyncDrop for AsyncUnion {
    async fn drop(self: Pin<&mut Self>) {
        println!(
            "AsyncUnion::Dropper::poll: {}, {}",
            unsafe { self.signed },
            unsafe { self.unsigned },
        );
    }
}

Version information

rustc 1.96.0-nightly (2972b5e59 2026-04-03)
binary: rustc
commit-hash: 2972b5e59f1c5529b6ba770437812fd83ab4ebd4
commit-date: 2026-04-03
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.2

Possibly related line of code:
https://github.com/rust-lang/rust/blob/2972b5e59f1c5529b6ba770437812fd83ab4ebd4/compiler/rustc_mir_build/src/builder/expr/as_place.rs#L257-L269

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --edition=2024 -Zcrate-attr=feature(pin_ergonomics)

Program output 

warning: the feature `pin_ergonomics` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:12
  |
1 | #![feature(pin_ergonomics)]
  |            ^^^^^^^^^^^^^^
  |
  = note: see issue #130494 <https://github.com/rust-lang/rust/issues/130494> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: unused import: `pin`
 --> /tmp/icemaker_global_tempdir.eRddSEzN1izY/rustc_testrunner_tmpdir_reporting.mteWNf6k9IrD/mvce.rs:1:17
  |
1 | use core::pin::{pin, Pin};
  |                 ^^^
  |
  = note: `#[warn(unused_imports)]` (part of `#[warn(unused)]`) on by default

warning: unused imports: `Context` and `Waker`
 --> /tmp/icemaker_global_tempdir.eRddSEzN1izY/rustc_testrunner_tmpdir_reporting.mteWNf6k9IrD/mvce.rs:2:18
  |
2 | use core::task::{Context, Poll, Waker};
  |                  ^^^^^^^        ^^^^^

error[E0601]: `main` function not found in crate `mvce`
  --> /tmp/icemaker_global_tempdir.eRddSEzN1izY/rustc_testrunner_tmpdir_reporting.mteWNf6k9IrD/mvce.rs:13:2
   |
13 | }
   |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.eRddSEzN1izY/rustc_testrunner_tmpdir_reporting.mteWNf6k9IrD/mvce.rs`

error: internal compiler error: /rustc-dev/2972b5e59f1c5529b6ba770437812fd83ab4ebd4/compiler/rustc_mir_build/src/builder/expr/as_place.rs:263:67: could not resolve upvar: LocalVarId(HirId(DefId(0:10 ~ mvce[f0d2]::test_idempotency).2)) + []
 --> /tmp/icemaker_global_tempdir.eRddSEzN1izY/rustc_testrunner_tmpdir_reporting.mteWNf6k9IrD/mvce.rs:4:24
  |
4 | fn test_idempotency<T>(mut x: Pin<&mut T>) -> impl Future + '_
  |                        ^^^^^


thread 'rustc' (2745198) panicked at /rustc-dev/2972b5e59f1c5529b6ba770437812fd83ab4ebd4/compiler/rustc_mir_build/src/builder/expr/as_place.rs:263:67:
Box<dyn Any>
stack backtrace:
   0:     0x7f0aaffc0abb - <<std[de416e893de1faf9]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[9f8d6771964fc20c]::fmt::Display>::fmt
   1:     0x7f0ab061e1c8 - core[9f8d6771964fc20c]::fmt::write
   2:     0x7f0aaffd7ac6 - <std[de416e893de1faf9]::sys::stdio::unix::Stderr as std[de416e893de1faf9]::io::Write>::write_fmt
   3:     0x7f0aaff96ac8 - std[de416e893de1faf9]::panicking::default_hook::{closure#0}
   4:     0x7f0aaffb3ec3 - std[de416e893de1faf9]::panicking::default_hook
   5:     0x7f0aaefc2e4c - std[de416e893de1faf9]::panicking::update_hook::<alloc[57804382fb016052]::boxed::Box<rustc_driver_impl[7a9a631d48bc4eca]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f0aaffb41a2 - std[de416e893de1faf9]::panicking::panic_with_hook
   7:     0x7f0aaeff2e01 - std[de416e893de1faf9]::panicking::begin_panic::<rustc_errors[e123dae814032ce5]::ExplicitBug>::{closure#0}
   8:     0x7f0aaefeb976 - std[de416e893de1faf9]::sys::backtrace::__rust_end_short_backtrace::<std[de416e893de1faf9]::panicking::begin_panic<rustc_errors[e123dae814032ce5]::ExplicitBug>::{closure#0}, !>
   9:     0x7f0aaefeb84b - std[de416e893de1faf9]::panicking::begin_panic::<rustc_errors[e123dae814032ce5]::ExplicitBug>
  10:     0x7f0aaeffe441 - <rustc_errors[e123dae814032ce5]::diagnostic::BugAbort as rustc_errors[e123dae814032ce5]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7f0aaf5acbdc - <rustc_errors[e123dae814032ce5]::DiagCtxtHandle>::span_bug::<rustc_span[ae25d23050d7877d]::span_encoding::Span, alloc[57804382fb016052]::string::String>
  12:     0x7f0aaf5d4ad6 - rustc_middle[4d5ddcd23ba200cb]::util::bug::opt_span_bug_fmt::<rustc_span[ae25d23050d7877d]::span_encoding::Span>::{closure#0}
  13:     0x7f0aaf5d4c82 - rustc_middle[4d5ddcd23ba200cb]::ty::context::tls::with_opt::<rustc_middle[4d5ddcd23ba200cb]::util::bug::opt_span_bug_fmt<rustc_span[ae25d23050d7877d]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7f0aaf5c523b - rustc_middle[4d5ddcd23ba200cb]::ty::context::tls::with_context_opt::<rustc_middle[4d5ddcd23ba200cb]::ty::context::tls::with_opt<rustc_middle[4d5ddcd23ba200cb]::util::bug::opt_span_bug_fmt<rustc_span[ae25d23050d7877d]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x7f0aad6cdb18 - rustc_middle[4d5ddcd23ba200cb]::util::bug::span_bug_fmt::<rustc_span[ae25d23050d7877d]::span_encoding::Span>
  16:     0x7f0ab0f36324 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  17:     0x7f0ab06640d3 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_temp::{closure#0}
  18:     0x7f0ab06674d4 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_operand
  19:     0x7f0ab066ae54 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_call_operand
  20:     0x7f0ab066b345 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_call_operand
  21:     0x7f0ab0f2ed01 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  22:     0x7f0ab06640d3 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_temp::{closure#0}
  23:     0x7f0ab11cf5f8 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_as_place
  24:     0x7f0ab11cfc8b - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_as_place
  25:     0x7f0ab11ce68f - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_as_place
  26:     0x7f0ab0f2f4aa - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  27:     0x7f0ab06640d3 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_temp::{closure#0}
  28:     0x7f0ab06674d4 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_operand
  29:     0x7f0ab0f2fb63 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  30:     0x7f0ab06640d3 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_temp::{closure#0}
  31:     0x7f0ab06674d4 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_operand
  32:     0x7f0ab066ae54 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_call_operand
  33:     0x7f0ab066b345 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_call_operand
  34:     0x7f0ab0f2ed01 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  35:     0x7f0ab06640d3 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_temp::{closure#0}
  36:     0x7f0ab11cf5f8 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_as_place
  37:     0x7f0ab11cec73 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_as_place
  38:     0x7f0ab0f2e16f - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  39:     0x7f0ab06640d3 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_temp::{closure#0}
  40:     0x7f0ab06674d4 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_operand
  41:     0x7f0ab0667c17 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_operand
  42:     0x7f0ab0669731 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_rvalue
  43:     0x7f0ab0f2d9d4 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  44:     0x7f0ab06640d3 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_temp::{closure#0}
  45:     0x7f0ab11cf5f8 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_as_place
  46:     0x7f0ab11cec73 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_as_place
  47:     0x7f0ab0f30d8c - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  48:     0x7f0ab06640d3 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::as_temp::{closure#0}
  49:     0x7f0ab0f1eded - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::stmt_expr
  50:     0x7f0ab0f1ecb7 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::stmt_expr
  51:     0x7f0ab15cacda - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::ast_block_stmts
  52:     0x7f0ab15ca121 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::ast_block
  53:     0x7f0ab0f2f57f - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  54:     0x7f0ab0f2e588 - <rustc_mir_build[26ffb09657e2f599]::builder::Builder>::expr_into_dest
  55:     0x7f0ab0f139bb - rustc_mir_build[26ffb09657e2f599]::builder::build_mir_inner_impl
  56:     0x7f0ab060b7f4 - rustc_mir_transform[1f6f3f6d4bd047c6]::mir_built
  57:     0x7f0ab06bb866 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_data_structures[3e48709548f32bc4]::vec_cache::VecCache<rustc_span[ae25d23050d7877d]::def_id::LocalDefId, rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[4d5ddcd23ba200cb]::dep_graph::graph::DepNodeIndex>, false>
  58:     0x7f0ab06bb383 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::mir_built::execute_query_non_incr::__rust_end_short_backtrace
  59:     0x7f0ab062862f - rustc_mir_transform[1f6f3f6d4bd047c6]::ffi_unwind_calls::has_ffi_unwind_calls
  60:     0x7f0ab0628099 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::has_ffi_unwind_calls::invoke_provider_fn::__rust_begin_short_backtrace
  61:     0x7f0ab13891a4 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_data_structures[3e48709548f32bc4]::vec_cache::VecCache<rustc_span[ae25d23050d7877d]::def_id::LocalDefId, rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 1usize]>, rustc_middle[4d5ddcd23ba200cb]::dep_graph::graph::DepNodeIndex>, false>
  62:     0x7f0ab1388d76 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::has_ffi_unwind_calls::execute_query_non_incr::__rust_end_short_backtrace
  63:     0x7f0ab108cf2a - rustc_mir_transform[1f6f3f6d4bd047c6]::mir_promoted
  64:     0x7f0ab108cd92 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::mir_promoted::invoke_provider_fn::__rust_begin_short_backtrace
  65:     0x7f0ab0e20737 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_data_structures[3e48709548f32bc4]::vec_cache::VecCache<rustc_span[ae25d23050d7877d]::def_id::LocalDefId, rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 16usize]>, rustc_middle[4d5ddcd23ba200cb]::dep_graph::graph::DepNodeIndex>, false>
  66:     0x7f0ab0e202c3 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::mir_promoted::execute_query_non_incr::__rust_end_short_backtrace
  67:     0x7f0ab13ab032 - <rustc_borrowck[c4b945395fabc085]::root_cx::BorrowCheckRootCtxt>::do_mir_borrowck
  68:     0x7f0ab13a4eaf - rustc_borrowck[c4b945395fabc085]::mir_borrowck
  69:     0x7f0ab13a4cf7 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::mir_borrowck::invoke_provider_fn::__rust_begin_short_backtrace
  70:     0x7f0ab06bb866 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_data_structures[3e48709548f32bc4]::vec_cache::VecCache<rustc_span[ae25d23050d7877d]::def_id::LocalDefId, rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[4d5ddcd23ba200cb]::dep_graph::graph::DepNodeIndex>, false>
  71:     0x7f0ab06b8f43 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::mir_borrowck::execute_query_non_incr::__rust_end_short_backtrace
  72:     0x7f0ab1787e26 - rustc_hir_analysis[ffc1d045f4785174]::collect::type_of::opaque::find_opaque_ty_constraints_for_rpit
  73:     0x7f0ab1787b66 - rustc_hir_analysis[ffc1d045f4785174]::collect::type_of::type_of_opaque
  74:     0x7f0ab065f00a - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_middle[4d5ddcd23ba200cb]::query::caches::DefIdCache<rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 8usize]>>, false>
  75:     0x7f0ab0d83bce - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::type_of_opaque::execute_query_non_incr::__rust_end_short_backtrace
  76:     0x7f0ab0d90314 - rustc_hir_analysis[ffc1d045f4785174]::collect::type_of::type_of
  77:     0x7f0ab083b9e6 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::type_of::invoke_provider_fn::__rust_begin_short_backtrace
  78:     0x7f0ab065f00a - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_middle[4d5ddcd23ba200cb]::query::caches::DefIdCache<rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 8usize]>>, false>
  79:     0x7f0ab065eb90 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::type_of::execute_query_non_incr::__rust_end_short_backtrace
  80:     0x7f0ab1788510 - rustc_hir_analysis[ffc1d045f4785174]::check::check::check_opaque
  81:     0x7f0ab1392aa1 - rustc_hir_analysis[ffc1d045f4785174]::check::check::check_item_type
  82:     0x7f0ab1389b9c - rustc_hir_analysis[ffc1d045f4785174]::check::wfcheck::check_well_formed
  83:     0x7f0ab1389b6f - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::check_well_formed::invoke_provider_fn::__rust_begin_short_backtrace
  84:     0x7f0ab13891a4 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_data_structures[3e48709548f32bc4]::vec_cache::VecCache<rustc_span[ae25d23050d7877d]::def_id::LocalDefId, rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 1usize]>, rustc_middle[4d5ddcd23ba200cb]::dep_graph::graph::DepNodeIndex>, false>
  85:     0x7f0ab1388f3b - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::check_well_formed::execute_query_non_incr::__rust_end_short_backtrace
  86:     0x7f0ab1385570 - rustc_hir_analysis[ffc1d045f4785174]::check::wfcheck::check_type_wf
  87:     0x7f0ab13853e7 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::check_type_wf::invoke_provider_fn::__rust_begin_short_backtrace
  88:     0x7f0ab1802950 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_middle[4d5ddcd23ba200cb]::query::caches::SingleCache<rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 1usize]>>, false>
  89:     0x7f0ab1802729 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::check_type_wf::execute_query_non_incr::__rust_end_short_backtrace
  90:     0x7f0ab0f06ddb - rustc_hir_analysis[ffc1d045f4785174]::check_crate
  91:     0x7f0ab06b7f61 - rustc_interface[e1d24a92004beaf7]::passes::analysis
  92:     0x7f0ab1805049 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_middle[4d5ddcd23ba200cb]::query::caches::SingleCache<rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 0usize]>>, false>
  93:     0x7f0ab1804cb5 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  94:     0x7f0ab17b1990 - rustc_interface[e1d24a92004beaf7]::interface::run_compiler::<(), rustc_driver_impl[7a9a631d48bc4eca]::run_compiler::{closure#0}>::{closure#1}
  95:     0x7f0ab17e3c3e - std[de416e893de1faf9]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[e1d24a92004beaf7]::util::run_in_thread_with_globals<rustc_interface[e1d24a92004beaf7]::util::run_in_thread_pool_with_globals<rustc_interface[e1d24a92004beaf7]::interface::run_compiler<(), rustc_driver_impl[7a9a631d48bc4eca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  96:     0x7f0ab17e44e0 - <std[de416e893de1faf9]::thread::lifecycle::spawn_unchecked<rustc_interface[e1d24a92004beaf7]::util::run_in_thread_with_globals<rustc_interface[e1d24a92004beaf7]::util::run_in_thread_pool_with_globals<rustc_interface[e1d24a92004beaf7]::interface::run_compiler<(), rustc_driver_impl[7a9a631d48bc4eca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[9f8d6771964fc20c]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  97:     0x7f0ab17e53ec - <std[de416e893de1faf9]::sys::thread::unix::Thread>::new::thread_start
  98:     0x7f0aab2a597a - <unknown>
  99:     0x7f0aab3292bc - <unknown>
 100:                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 (2972b5e59 2026-04-03) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z crate-attr=feature(pin_ergonomics) -Z dump-mir-dir=dir

query stack during panic:
#0 [mir_built] building MIR for `test_idempotency::{closure#0}`
#1 [has_ffi_unwind_calls] checking if `test_idempotency::{closure#0}` contains FFI-unwind calls
#2 [mir_promoted] promoting constants in MIR for `test_idempotency::{closure#0}`
#3 [mir_borrowck] borrow-checking `test_idempotency`
#4 [type_of_opaque] computing type of opaque `test_idempotency::{opaque#0}`
#5 [type_of] computing type of `test_idempotency::{opaque#0}`
#6 [check_well_formed] checking that `test_idempotency::{opaque#0}` is well-formed
#7 [check_type_wf] checking that types are well-formed
#8 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 2 previous errors; 3 warnings emitted

For more information about this error, try `rustc --explain E0601`.

@rustbot label +F-async_drop +F-pin_ergonomics

Contributor guide

Open the contributing guide

First steps

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  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 reproduction in a.rs and reproduce it using the reported rustc command with edition 2024 and pin_ergonomics enabled. Then inspect compiler/rustc_mir_build/src/builder/expr/as_place.rs around lines 257-269, which the issue identifies as the ICE location. Done means the reproduction no longer triggers the internal compiler error.

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
Mostly clear
Newbie friendliness
45/100

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