ICE: `computed impossible repr (packed enum?): Foo`

[matthiaskrgr]

snippet:

//@compile-flags: --crate-type=lib
#[repr()]
#[repr(packed)]
pub enum Foo {
    Bar,
    Baz(i32),
}

Version information

rustc 1.87.0-nightly (07292cccc 2025-03-08)
binary: rustc
commit-hash: 07292ccccde8b64d87036b2f90b70bc54ab68456
commit-date: 2025-03-08
host: x86_64-unknown-linux-gnu
release: 1.87.0-nightly
LLVM version: 20.1.0

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc --crate-type=lib

Program output

warning: unused attribute
 --> /tmp/icemaker_global_tempdir.hV6iHi5L3CPm/rustc_testrunner_tmpdir_reporting.kj97BZMzsyE0/mvce.rs:1:1
  |
1 | #[repr()]
  | ^^^^^^^^^ help: remove this attribute
  |
  = note: attribute `repr` with an empty list has no effect
  = note: `#[warn(unused_attributes)]` on by default

warning: 1 warning 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: computed impossible repr (packed enum?): Foo
  |
  = note: delayed at compiler/rustc_ty_utils/src/layout.rs:124:18
             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>::delayed_bug::<alloc::string::String>
             4: rustc_ty_utils::layout::map_error
             5: rustc_ty_utils::layout::layout_of_uncached
             6: rustc_ty_utils::layout::layout_of
             7: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 16]>>
             8: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::Ty>, rustc_middle::query::erase::Erased<[u8; 16]>>, false, true, false>, rustc_query_impl::plumbing::QueryCtxt, false>
             9: rustc_query_impl::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
            10: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefaultCache<rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::Ty>, rustc_middle::query::erase::Erased<[u8; 16]>>>
            11: <rustc_lint::BuiltinCombinedModuleLateLintPass as rustc_lint::passes::LateLintPass>::check_item
            12: <rustc_lint::late::LateContextAndPass<rustc_lint::BuiltinCombinedModuleLateLintPass> as rustc_hir::intravisit::Visitor>::visit_nested_item
            13: rustc_lint::lint_mod
            14: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::lint_mod::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
            15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalModDefId, rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            16: rustc_query_impl::query_impl::lint_mod::get_query_non_incr::__rust_end_short_backtrace
            17: rustc_lint::late::check_crate::{closure#1}
            18: rustc_lint::late::check_crate
            19: rustc_interface::passes::analysis
            20: 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]>>
            21: 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>
            22: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
            23: 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}::{closure#0}
            24: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
            25: 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}, ()>
            26: <<std::thread::Builder>::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}
            27: std::sys::pal::unix::thread::Thread::new::thread_start
            28: <unknown>
            29: <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 1.87.0-nightly (07292cccc 2025-03-08) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -Z dump-mir-dir=dir

query stack during panic:
end of query stack

[mu001999]

@rustbot claim