ICE `ArgAbi left behind`

[matthiaskrgr]

auto-reduced (treereduce-rust):

//@compile-flags: --edition=2024 -Zcodegen-backend=cranelift -Clink-dead-code=true
#![feature(async_drop)]
#![feature(gen_blocks)]



fn main() {
    let _ = async {
        let mut gn = gen {
        yield 1;
        2.yield;
    };
        
    };
}

original:

//@ incremental
//@ edition:2021

fn main() {
    let _ = async {
        let mut gn = gen {
        yield 1;
        2.yield;
    };
        //~^ ERROR `[(); _]` is not a future
    };
}

Version information

rustc 1.91.0-nightly (8e3710ef3 2025-08-21)
binary: rustc
commit-hash: 8e3710ef31a0b2cdf5a1c2f3929b7735d1e28c20
commit-date: 2025-08-21
host: x86_64-unknown-linux-gnu
release: 1.91.0-nightly
LLVM version: 21.1.0

Possibly related line of code:
https://github.com/rust-lang/rust/blob/8e3710ef31a0b2cdf5a1c2f3929b7735d1e28c20/compiler/rustc_codegen_cranelift/src/abi/mod.rs#L293-L305

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --edition=2024 -Zcodegen-backend=cranelift -Clink-dead-code=true -Zcrate-attr=feature(async_drop) -Zcrate-attr=feature(gen_blocks)

Program output

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
  = note: `#[warn(incomplete_features)]` on by default

warning: unused variable: `gn`
 --> /tmp/icemaker_global_tempdir.XM6ODE5Hjm0Y/rustc_testrunner_tmpdir_reporting.12FJUATdHBlM/mvce.rs:6:17
  |
6 |         let mut gn = gen {
  |                 ^^ help: if this is intentional, prefix it with an underscore: `_gn`
  |
  = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

warning: variable does not need to be mutable
 --> /tmp/icemaker_global_tempdir.XM6ODE5Hjm0Y/rustc_testrunner_tmpdir_reporting.12FJUATdHBlM/mvce.rs:6:13
  |
6 |         let mut gn = gen {
  |             ----^^
  |             |
  |             help: remove this `mut`
  |
  = note: `#[warn(unused_mut)]` (part of `#[warn(unused)]`) on by default


thread 'rustc' (29598) panicked at compiler/rustc_codegen_cranelift/src/abi/mod.rs:299:5:
ArgAbi left behind
stack backtrace:
   0:     0x7fca4022f453 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h29956387916c7786
   1:     0x7fca40a019d8 - core::fmt::write::hc643e33fb3701c04
   2:     0x7fca40219d23 - std::io::Write::write_fmt::hd8aafd7e0cfa4df0
   3:     0x7fca4022ee02 - std::sys::backtrace::BacktraceLock::print::h7b608780239e41bb
   4:     0x7fca4020fe8e - std::panicking::default_hook::{{closure}}::hb985d7a9c8441027
   5:     0x7fca4020f9b8 - std::panicking::default_hook::h21dd4ceb358d35d5
   6:     0x7fca3f283575 - std[7bbd1c520933e2ca]::panicking::update_hook::<alloc[d048b985160d5cb3]::boxed::Box<rustc_driver_impl[43f25b9ba173297b]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7fca4020f784 - std::panicking::panic_with_hook::h9e10def7ecb801dd
   8:     0x7fca4022f226 - std::panicking::panic_handler::{{closure}}::hcae2f26048275696
   9:     0x7fca4022f1b9 - std::sys::backtrace::__rust_end_short_backtrace::h391fe1ff395ba1e0
  10:     0x7fca4020f8ed - __rustc[27a96dd388c4db29]::rust_begin_unwind
  11:     0x7fca3c8d9840 - core::panicking::panic_fmt::hae068153d2f804a4
  12:     0x7fca2ea3169f - rustc_codegen_cranelift[72d6c50d52a4b85d]::base::codegen_fn_body
  13:     0x7fca2ea51409 - rustc_codegen_cranelift[72d6c50d52a4b85d]::driver::aot::codegen_cgu_content
  14:     0x7fca2ea5e4fc - rustc_codegen_cranelift[72d6c50d52a4b85d]::driver::aot::module_codegen
  15:     0x7fca2eaa9ad9 - rustc_codegen_cranelift[72d6c50d52a4b85d]::driver::aot::run_aot::{closure#3}::{closure#0}
  16:     0x7fca2ea16c89 - <core[944e8f57fc60541e]::iter::adapters::filter_map::FilterMap<alloc[d048b985160d5cb3]::vec::into_iter::IntoIter<(usize, &rustc_middle[984f359684f14d51]::mir::mono::CodegenUnit)>, rustc_data_structures[1992400ef1c04f10]::sync::parallel::par_map<(usize, &rustc_middle[984f359684f14d51]::mir::mono::CodegenUnit), alloc[d048b985160d5cb3]::vec::Vec<(usize, &rustc_middle[984f359684f14d51]::mir::mono::CodegenUnit)>, rustc_data_structures[1992400ef1c04f10]::marker::IntoDynSyncSend<rustc_codegen_cranelift[72d6c50d52a4b85d]::driver::aot::OngoingModuleCodegen>, alloc[d048b985160d5cb3]::vec::Vec<rustc_data_structures[1992400ef1c04f10]::marker::IntoDynSyncSend<rustc_codegen_cranelift[72d6c50d52a4b85d]::driver::aot::OngoingModuleCodegen>>, rustc_codegen_cranelift[72d6c50d52a4b85d]::driver::aot::run_aot::{closure#3}::{closure#0}>::{closure#0}::{closure#3}> as core[944e8f57fc60541e]::iter::traits::iterator::Iterator>::next
  17:     0x7fca2ea59413 - rustc_codegen_cranelift[72d6c50d52a4b85d]::driver::aot::run_aot
  18:     0x7fca2ea7139e - <rustc_codegen_cranelift[72d6c50d52a4b85d]::CraneliftCodegenBackend as rustc_codegen_ssa[8c7a150851651b0c]::traits::backend::CodegenBackend>::codegen_crate
  19:     0x7fca41dacd30 - <rustc_interface[7f26a336caf35539]::queries::Linker>::codegen_and_build_linker
  20:     0x7fca41daa8bc - rustc_interface[7f26a336caf35539]::passes::create_and_enter_global_ctxt::<core[944e8f57fc60541e]::option::Option<rustc_interface[7f26a336caf35539]::queries::Linker>, rustc_driver_impl[43f25b9ba173297b]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  21:     0x7fca41bb8fdf - rustc_interface[7f26a336caf35539]::interface::run_compiler::<(), rustc_driver_impl[43f25b9ba173297b]::run_compiler::{closure#0}>::{closure#1}
  22:     0x7fca41b2c638 - std[7bbd1c520933e2ca]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[7f26a336caf35539]::util::run_in_thread_with_globals<rustc_interface[7f26a336caf35539]::util::run_in_thread_pool_with_globals<rustc_interface[7f26a336caf35539]::interface::run_compiler<(), rustc_driver_impl[43f25b9ba173297b]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  23:     0x7fca41b2c31c - <<std[7bbd1c520933e2ca]::thread::Builder>::spawn_unchecked_<rustc_interface[7f26a336caf35539]::util::run_in_thread_with_globals<rustc_interface[7f26a336caf35539]::util::run_in_thread_pool_with_globals<rustc_interface[7f26a336caf35539]::interface::run_compiler<(), rustc_driver_impl[43f25b9ba173297b]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[944e8f57fc60541e]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  24:     0x7fca41b3238d - std::sys::pal::unix::thread::Thread::new::thread_start::h67ffc5859d05944d
  25:     0x7fca3b2969cb - <unknown>
  26:     0x7fca3b31aa4c - <unknown>
  27:                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: rustc 1.91.0-nightly (8e3710ef3 2025-08-21) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z codegen-backend=cranelift -C link-dead-code=true -Z crate-attr=feature(async_drop) -Z crate-attr=feature(gen_blocks) -Z dump-mir-dir=dir

query stack during panic:
end of query stack
warning: 3 warnings emitted

@rustbot label +F-async_drop +F-gen_blocks

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