ICE: internal compiler error: Unknown(Foo) #150750
Description
I searched using "internal compiler error: Unknown" as the key term and didn't seem to find any similar issues. Is this a new one?
Code
#![feature(repr_simd)]
const C: usize = 16;
#[repr(simd)]
pub struct Foo([u8; C]);
unsafe extern "C" {
static VAR: Foo;
}
fn main() {}Meta
rustc --version --verbose:
rustc 1.94.0-nightly (4fa80a5e7 2026-01-05)
binary: rustc
commit-hash: 4fa80a5e733e2202d7ca4c203c2fdfda41cfe7dc
commit-date: 2026-01-05
host: x86_64-unknown-linux-gnu
release: 1.94.0-nightly
LLVM version: 21.1.8
Program Output
warning: static `VAR` is never used
--> <source>:9:12
|
9 | static VAR: Foo;
| ^^^
|
= note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default
warning: `extern` block uses type `Foo`, which is not FFI-safe
--> <source>:9:17
|
9 | static VAR: Foo;
| ^^^ not FFI-safe
|
= help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
= note: this struct has unspecified layout
note: the type is defined here
--> <source>:6:1
|
6 | pub struct Foo([u8; C]);
| ^^^^^^^^^^^^^^
= note: `#[warn(improper_ctypes)]` on by default
warning: 2 warnings emitted
note: no errors encountered even though delayed bugs were created
note: those delayed bugs will now be shown as internal compiler errors
error: internal compiler error: Unknown(Foo)
--> <source>:9:5
|
9 | static VAR: Foo;
| ^^^^^^^^^^^^^^^
|
note: delayed at /rustc-dev/4fa80a5e733e2202d7ca4c203c2fdfda41cfe7dc/compiler/rustc_hir_analysis/src/check/check.rs:197:23
0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
3: <rustc_errors::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, alloc::string::String>
4: rustc_hir_analysis::check::check::check_item_type
5: rustc_hir_analysis::check::wfcheck::check_well_formed
6: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
7: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 1]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
8: rustc_query_impl::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
9: rustc_hir_analysis::check::wfcheck::check_type_wf
10: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
11: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
12: rustc_query_impl::query_impl::check_type_wf::get_query_non_incr::__rust_end_short_backtrace
13: rustc_hir_analysis::check_crate
14: rustc_interface::passes::analysis
15: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
16: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
17: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
18: <rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
19: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
20: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
21: <std::thread::lifecycle::spawn_unchecked<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
22: <std::sys::thread::unix::Thread>::new::thread_start
23: <unknown>
24: <unknown>
--> <source>:9:5
|
9 | static VAR: Foo;
| ^^^^^^^^^^^^^^^
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 `/app/rustc-ice-2026-01-07T06_31_49-1.txt` to your bug report
note: rustc 1.94.0-nightly (4fa80a5e7 2026-01-05) running on x86_64-unknown-linux-gnu
note: compiler flags: -C debuginfo=2 --crate-type bin -C linker=/opt/compiler-explorer/gcc-15.2.0/bin/gcc
query stack during panic:
end of query stack