Unexpected initial operand type

[matthiaskrgr]

I tried this code:

#![feature(async_drop)]
#![feature(coroutines)]
pub fn main() {
  async {
#[coroutine]
    || yield;
  };
}

rustc code.rs --edition=2024 -Clink-dead-code

  WARN rustc_codegen_ssa::mir::locals Unexpected initial operand type:
 expected (),
 found    &'{erased} mut std::task::Context<'{erased}>.
 See <https://github.com/rust-lang/rust/issues/114858>.

Meta

rustc --version --verbose:

rustc 1.97.0-nightly (17584a181 2026-04-13)
binary: rustc
commit-hash: 17584a181979f04f2aaad867332c22db1caa511a
commit-date: 2026-04-13
host: x86_64-unknown-linux-gnu
release: 1.97.0-nightly
LLVM version: 22.1.2

Note adding -Zcodegen-backend=cranelift turns it into an ice

Backtrace

thread 'rustc' (1163411) panicked at /rustc-dev/17584a181979f04f2aaad867332c22db1caa511a/compiler/rustc_codegen_cranelift/src/value_and_place.rs:510:9:
assertion `left == right` failed: Can't write value with incompatible type &'{erased} mut std::task::Context<'{erased}> to place with type ()

[Coroutine(DefId(0:5 ~ code[5fe1]::main::{closure#0}::{closure#0}), [(), (), (), (), ()]), (), std::future::ResumeTy, (), (), (*mut Coroutine(DefId(0:5 ~ code[5fe1]::main::{closure#0}::{closure#0}), [(), (), (), (), ()]),)]
[CPlace { inner: Addr(Pointer { base: Stack(ss0), offset: Offset32(0) }, None), layout: TyAndLayout { ty: Poll<()>, layout: Layout { size: Size(1 bytes), align: AbiAlign { abi: Align(1 bytes) }, backend_repr: Scalar(Initialized { value: Int(I8, false), valid_range: 0..=1 }), fields: Arbitrary { offsets: [Size(0 bytes)], in_memory_order: [0] }, largest_niche: Some(Niche { offset: Size(0 bytes), value: Int(I8, false), valid_range: 0..=1 }), uninhabited: false, variants: Multiple { tag: Initialized { value: Int(I8, false), valid_range: 0..=1 }, tag_encoding: Direct, tag_field: 0, variants: [Layout { size: Size(1 bytes), align: AbiAlign { abi: Align(1 bytes) }, backend_repr: Scalar(Initialized { value: Int(I8, false), valid_range: 0..=1 }), fields: Arbitrary { offsets: [Size(1 bytes)], in_memory_order: [0] }, largest_niche: None, uninhabited: false, variants: Single { index: 0 }, max_repr_align: None, unadjusted_abi_align: Align(1 bytes), randomization_seed: 6371488611584763486 }, Layout { size: Size(1 bytes), align: AbiAlign { abi: Align(1 bytes) }, backend_repr: Memory { sized: true }, fields: Arbitrary { offsets: [], in_memory_order: [] }, largest_niche: None, uninhabited: false, variants: Single { index: 1 }, max_repr_align: None, unadjusted_abi_align: Align(1 bytes), randomization_seed: 6371488611584763486 }] }, max_repr_align: None, unadjusted_abi_align: Align(1 bytes), randomization_seed: 667721761044738842 } } }, CPlace { inner: Addr(Pointer { base: Stack(ss1), offset: Offset32(0) }, None), layout: TyAndLayout { ty: Pin<&mut {async fn body of async_drop_in_place<{coroutine@code.rs:6:5: 6:7}>()}>, layout: Layout { size: Size(8 bytes), align: AbiAlign { abi: Align(8 bytes) }, backend_repr: Scalar(Initialized { value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }), fields: Arbitrary { offsets: [Size(0 bytes)], in_memory_order: [0] }, largest_niche: Some(Niche { offset: Size(0 bytes), value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }), uninhabited: false, variants: Single { index: 0 }, max_repr_align: None, unadjusted_abi_align: Align(8 bytes), randomization_seed: 18365188995968913426 } } }, CPlace { inner: Addr(Pointer { base: Dangling(Align(1 bytes)), offset: Offset32(0) }, None), layout: TyAndLayout { ty: (), layout: Layout { size: Size(0 bytes), align: AbiAlign { abi: Align(1 bytes) }, backend_repr: Memory { sized: true }, fields: Arbitrary { offsets: [], in_memory_order: [] }, largest_niche: None, uninhabited: false, variants: Single { index: 0 }, max_repr_align: None, unadjusted_abi_align: Align(1 bytes), randomization_seed: 0 } } }]

function u0:7(i64, i64) -> i8 uext system_v {
    ss0 = explicit_slot 1
    ss1 = explicit_slot 8, align = 8

block0(v0: i64, v1: i64):
    nop
    stack_store v0, ss1
}


  left: &'{erased} mut std::task::Context<'{erased}>
 right: ()
stack backtrace:
   0:     0x7f30ab4129bb - <<std[82445d07c273dcb0]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[e6c15338c37dc114]::fmt::Display>::fmt
   1:     0x7f30aba21748 - core[e6c15338c37dc114]::fmt::write
   2:     0x7f30ab429c86 - <std[82445d07c273dcb0]::sys::stdio::unix::Stderr as std[82445d07c273dcb0]::io::Write>::write_fmt
   3:     0x7f30ab3e8cb8 - std[82445d07c273dcb0]::panicking::default_hook::{closure#0}
   4:     0x7f30ab406023 - std[82445d07c273dcb0]::panicking::default_hook
   5:     0x7f30aa3e16ec - std[82445d07c273dcb0]::panicking::update_hook::<alloc[8aa01d6867f017eb]::boxed::Box<rustc_driver_impl[b53ec1d8796d19d7]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f30ab406302 - std[82445d07c273dcb0]::panicking::panic_with_hook
   7:     0x7f30ab3e8d78 - std[82445d07c273dcb0]::panicking::panic_handler::{closure#0}
   8:     0x7f30ab3dd2d9 - std[82445d07c273dcb0]::sys::backtrace::__rust_end_short_backtrace::<std[82445d07c273dcb0]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f30ab3ea7dd - __rustc[ccd49f7a2776e796]::rust_begin_unwind
  10:     0x7f30a7f5bdec - core[e6c15338c37dc114]::panicking::panic_fmt
  11:     0x7f30a9c8a893 - core[e6c15338c37dc114]::panicking::assert_failed_inner
  12:     0x7f30aaa00547 - core[e6c15338c37dc114]::panicking::assert_failed::<rustc_middle[f0f16db128b18e3d]::ty::Ty, rustc_middle[f0f16db128b18e3d]::ty::Ty>
  13:     0x7f3098eaeb9e - rustc_codegen_cranelift[c4ed53a42162c0ac]::value_and_place::assert_assignable
  14:     0x7f3098ebd481 - rustc_codegen_cranelift[c4ed53a42162c0ac]::base::codegen_fn_body
  15:     0x7f3098ee796d - rustc_codegen_cranelift[c4ed53a42162c0ac]::driver::aot::codegen_cgu_content
  16:     0x7f3098e81cec - rustc_codegen_cranelift[c4ed53a42162c0ac]::driver::aot::run_aot::{closure#3}::{closure#0}::{closure#0}
  17:     0x7f3098e82e12 - rustc_codegen_cranelift[c4ed53a42162c0ac]::driver::aot::run_aot::{closure#3}::{closure#0}
  18:     0x7f3098ef4a69 - <core[e6c15338c37dc114]::iter::adapters::filter_map::FilterMap<alloc[8aa01d6867f017eb]::vec::into_iter::IntoIter<(usize, &rustc_middle[f0f16db128b18e3d]::mono::CodegenUnit)>, rustc_data_structures[89e4a6a540cc2895]::sync::parallel::par_map<(usize, &rustc_middle[f0f16db128b18e3d]::mono::CodegenUnit), alloc[8aa01d6867f017eb]::vec::Vec<(usize, &rustc_middle[f0f16db128b18e3d]::mono::CodegenUnit)>, rustc_data_structures[89e4a6a540cc2895]::marker::IntoDynSyncSend<rustc_codegen_cranelift[c4ed53a42162c0ac]::driver::aot::OngoingModuleCodegen>, alloc[8aa01d6867f017eb]::vec::Vec<rustc_data_structures[89e4a6a540cc2895]::marker::IntoDynSyncSend<rustc_codegen_cranelift[c4ed53a42162c0ac]::driver::aot::OngoingModuleCodegen>>, rustc_codegen_cranelift[c4ed53a42162c0ac]::driver::aot::run_aot::{closure#3}::{closure#0}>::{closure#0}::{closure#3}> as core[e6c15338c37dc114]::iter::traits::iterator::Iterator>::next
  19:     0x7f3098eec828 - rustc_codegen_cranelift[c4ed53a42162c0ac]::driver::aot::run_aot
  20:     0x7f3098efea05 - <rustc_codegen_cranelift[c4ed53a42162c0ac]::CraneliftCodegenBackend as rustc_codegen_ssa[ebd0a9eafe8c53bd]::traits::backend::CodegenBackend>::codegen_crate
  21:     0x7f30acb904b2 - <rustc_interface[36da19b6867c2d6b]::queries::Linker>::codegen_and_build_linker
  22:     0x7f30acb8a709 - rustc_interface[36da19b6867c2d6b]::interface::run_compiler::<(), rustc_driver_impl[b53ec1d8796d19d7]::run_compiler::{closure#0}>::{closure#1}
  23:     0x7f30acbaa2be - std[82445d07c273dcb0]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[36da19b6867c2d6b]::util::run_in_thread_with_globals<rustc_interface[36da19b6867c2d6b]::util::run_in_thread_pool_with_globals<rustc_interface[36da19b6867c2d6b]::interface::run_compiler<(), rustc_driver_impl[b53ec1d8796d19d7]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  24:     0x7f30acbaab60 - <std[82445d07c273dcb0]::thread::lifecycle::spawn_unchecked<rustc_interface[36da19b6867c2d6b]::util::run_in_thread_with_globals<rustc_interface[36da19b6867c2d6b]::util::run_in_thread_pool_with_globals<rustc_interface[36da19b6867c2d6b]::interface::run_compiler<(), rustc_driver_impl[b53ec1d8796d19d7]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[e6c15338c37dc114]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  25:     0x7f30acbab9ec - <std[82445d07c273dcb0]::sys::thread::unix::Thread>::new::thread_start
  26:     0x7f30a66a597a - <unknown>
  27:     0x7f30a67292bc - <unknown>
  28:                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-2026-04-14T20_36_29-1163401.txt` to your bug report

note: rustc 1.97.0-nightly (17584a181 2026-04-13) running on x86_64-unknown-linux-gnu

note: compiler flags: -C link-dead-code -Z codegen-backend=cranelift

query stack during panic:
end of query stack
fn std::future::async_drop_in_place::{closure#0}(_1: std::pin::Pin<&mut {async fn body of std::future::async_drop_in_place<{coroutine@code.rs:6:5: 6:7}>()}>, _2: ()) -> std::task::Poll<()> {
    let mut _0: std::task::Poll<()>;
    let mut _3: &mut {async fn body of std::future::async_drop_in_place<{coroutine@code.rs:6:5: 6:7}>()};
    let mut _4: *mut {coroutine@code.rs:6:5: 6:7};
    let mut _5: *const ();
    let mut _6: usize;
    let mut _7: usize;
    let mut _8: usize;
    let mut _9: bool;
    let mut _10: *const ();
    let mut _11: usize;
    let mut _12: bool;
    let mut _13: bool;
    let mut _14: bool;

    bb0: {
        _3 = copy (_1.0: &mut {async fn body of std::future::async_drop_in_place<{coroutine@code.rs:6:5: 6:7}>()});
        _4 = copy ((*_3).0: *mut {coroutine@code.rs:6:5: 6:7});
        _5 = copy _4 as *const () (PtrToPtr);
        _6 = copy _5 as usize (Transmute);
        _7 = Sub(const <{coroutine@code.rs:6:5: 6:7} as std::mem::SizedTypeProperties>::ALIGN, const 1_usize);
        _8 = BitAnd(copy _6, copy _7);
        _9 = Eq(copy _8, const 0_usize);
        assert(copy _9, "misaligned pointer dereference: address must be a multiple of {} but is {}", const <{coroutine@code.rs:6:5: 6:7} as std::mem::SizedTypeProperties>::ALIGN, copy _6) -> [success: bb1, unwind unreachable];
    }

    bb1: {
        _10 = copy _4 as *const () (PtrToPtr);
        _11 = copy _10 as usize (Transmute);
        _12 = Eq(copy _11, const 0_usize);
        _13 = BitAnd(copy _12, const true);
        _14 = Not(copy _13);
        assert(copy _14, "null pointer dereference occurred") -> [success: bb2, unwind unreachable];
    }

    bb2: {
        _0 = std::task::Poll::<()>::Ready(const ());
        return;
    }
}

bisects to nightly-2025-04-29, probably #123948