ICE: builtin derive created an unaligned reference

[Robbepop]

I tried this code:

#[derive(PartialEq)]
#[repr(packed)]
pub enum Foo {
    Bar,
    Baz(i32),
}

I expected to see this happen: Proper compiler error stating that #[repr(packed)] cannot be applied to enum.

Instead, this happened: The following ICE:

error[E0517]: attribute should be applied to a struct or union
   --> crates/ir/src/primitive.rs:562:8
    |
562 |   #[repr(packed)]
    |          ^^^^^^
563 | / pub enum Foo {
564 | |     Bar,
565 | |     Baz(i32),
566 | | }
    | |_- not a struct or union

error: internal compiler error: compiler/rustc_mir_transform/src/check_packed_ref.rs:50:21: builtin derive created an unaligned reference
   --> crates/ir/src/primitive.rs:565:9
    |
561 | #[derive(PartialEq)]
    |          --------- in this derive macro expansion
...
565 |     Baz(i32),
    |         ^^^
    |
    = note: this error: internal compiler error originates in the derive macro `PartialEq` (in Nightly builds, run with -Z macro-backtrace for more info)

Meta

The bug also happens on the nightly Rust compiler version.

rustc 1.80.1 (3f5fd8dd4 2024-08-06)
binary: rustc
commit-hash: 3f5fd8dd41153bc5fdca9427e9e05be2c767ba23
commit-date: 2024-08-06
host: aarch64-apple-darwin
release: 1.80.1
LLVM version: 18.1.7

Backtrace:

thread 'rustc' panicked at compiler/rustc_mir_transform/src/check_packed_ref.rs:50:21:
Box<dyn Any>
stack backtrace:
   0:        0x105608c1c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h41035ce174e31160
   1:        0x10564d87c - core::fmt::write::h7e946826fce7616b
   2:        0x1055ff088 - std::io::Write::write_fmt::he3645adfefb23e4a
   3:        0x105608a74 - std::sys_common::backtrace::print::h2efe9ae66fda73dc
   4:        0x10560b080 - std::panicking::default_hook::{{closure}}::hd27200b4fbd3bf40
   5:        0x10560ad4c - std::panicking::default_hook::hb8656334461229c8
   6:        0x10ec8f380 - <alloc[9bfd1da98798fc47]::boxed::Box<rustc_driver_impl[1ef2360f78401c14]::install_ice_hook::{closure#0}> as core[cec0bd9d2fc86fa9]::ops::function::Fn<(&dyn for<'a, 'b> core[cec0bd9d2fc86fa9]::ops::function::Fn<(&'a core[cec0bd9d2fc86fa9]::panic::panic_info::PanicInfo<'b>,), Output = ()> + core[cec0bd9d2fc86fa9]::marker::Sync + core[cec0bd9d2fc86fa9]::marker::Send, &core[cec0bd9d2fc86fa9]::panic::panic_info::PanicInfo)>>::call
   7:        0x10560ba6c - std::panicking::rust_panic_with_hook::h10171cf76e1aed15
   8:        0x10ed18f88 - std[4ec0ba9e3c6d748b]::panicking::begin_panic::<rustc_errors[841c19fe687cbd93]::ExplicitBug>::{closure#0}
   9:        0x10ed18e24 - std[4ec0ba9e3c6d748b]::sys_common::backtrace::__rust_end_short_backtrace::<std[4ec0ba9e3c6d748b]::panicking::begin_panic<rustc_errors[841c19fe687cbd93]::ExplicitBug>::{closure#0}, !>
  10:        0x112d8590c - std[4ec0ba9e3c6d748b]::panicking::begin_panic::<rustc_errors[841c19fe687cbd93]::ExplicitBug>
  11:        0x10ed28144 - <rustc_errors[841c19fe687cbd93]::diagnostic::BugAbort as rustc_errors[841c19fe687cbd93]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:        0x10fa98034 - <rustc_errors[841c19fe687cbd93]::DiagCtxt>::span_bug::<rustc_span[22cad54eabbc67cf]::span_encoding::Span, alloc[9bfd1da98798fc47]::string::String>
  13:        0x10faa107c - rustc_middle[2867706b5eb6f7f9]::util::bug::opt_span_bug_fmt::<rustc_span[22cad54eabbc67cf]::span_encoding::Span>::{closure#0}
  14:        0x10faa10b0 - rustc_middle[2867706b5eb6f7f9]::ty::context::tls::with_opt::<rustc_middle[2867706b5eb6f7f9]::util::bug::opt_span_bug_fmt<rustc_span[22cad54eabbc67cf]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  15:        0x10faa02a4 - rustc_middle[2867706b5eb6f7f9]::ty::context::tls::with_context_opt::<rustc_middle[2867706b5eb6f7f9]::ty::context::tls::with_opt<rustc_middle[2867706b5eb6f7f9]::util::bug::opt_span_bug_fmt<rustc_span[22cad54eabbc67cf]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  16:        0x112e49f8c - rustc_middle[2867706b5eb6f7f9]::util::bug::span_bug_fmt::<rustc_span[22cad54eabbc67cf]::span_encoding::Span>
  17:        0x10f9c5304 - <rustc_mir_transform[ff5c24210d5f1369]::check_packed_ref::PackedRefChecker as rustc_middle[2867706b5eb6f7f9]::mir::visit::Visitor>::visit_place
  18:        0x10f9c4f14 - <rustc_mir_transform[ff5c24210d5f1369]::check_packed_ref::CheckPackedRef as rustc_mir_transform[ff5c24210d5f1369]::pass_manager::MirLint>::run_lint
  19:        0x10fa91cb8 - rustc_mir_transform[ff5c24210d5f1369]::pass_manager::run_passes_inner
  20:        0x10fb59498 - rustc_mir_transform[ff5c24210d5f1369]::mir_built
  21:        0x10ff28f64 - rustc_query_impl[9b9172b7a4c3de5d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[9b9172b7a4c3de5d]::query_impl::mir_built::dynamic_query::{closure#2}::{closure#0}, rustc_middle[2867706b5eb6f7f9]::query::erase::Erased<[u8; 8usize]>>
  22:        0x10ffe46dc - <rustc_query_impl[9b9172b7a4c3de5d]::query_impl::mir_built::dynamic_query::{closure#2} as core[cec0bd9d2fc86fa9]::ops::function::FnOnce<(rustc_middle[2867706b5eb6f7f9]::ty::context::TyCtxt, rustc_span[22cad54eabbc67cf]::def_id::LocalDefId)>>::call_once
  23:        0x10fed5b48 - rustc_query_system[a56a14b00b0e8ff6]::query::plumbing::try_execute_query::<rustc_query_impl[9b9172b7a4c3de5d]::DynamicConfig<rustc_query_system[a56a14b00b0e8ff6]::query::caches::VecCache<rustc_span[22cad54eabbc67cf]::def_id::LocalDefId, rustc_middle[2867706b5eb6f7f9]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[9b9172b7a4c3de5d]::plumbing::QueryCtxt, true>
  24:        0x110093de8 - rustc_query_impl[9b9172b7a4c3de5d]::query_impl::mir_built::get_query_incr::__rust_end_short_backtrace
  25:        0x10f909ae0 - rustc_mir_build[eed3693f0e304215]::check_unsafety::check_unsafety
  26:        0x10ff246b0 - rustc_query_impl[9b9172b7a4c3de5d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[9b9172b7a4c3de5d]::query_impl::check_unsafety::dynamic_query::{closure#2}::{closure#0}, rustc_middle[2867706b5eb6f7f9]::query::erase::Erased<[u8; 0usize]>>
  27:        0x11000e960 - <rustc_query_impl[9b9172b7a4c3de5d]::query_impl::check_unsafety::dynamic_query::{closure#2} as core[cec0bd9d2fc86fa9]::ops::function::FnOnce<(rustc_middle[2867706b5eb6f7f9]::ty::context::TyCtxt, rustc_span[22cad54eabbc67cf]::def_id::LocalDefId)>>::call_once
  28:        0x10fece580 - rustc_query_system[a56a14b00b0e8ff6]::query::plumbing::try_execute_query::<rustc_query_impl[9b9172b7a4c3de5d]::DynamicConfig<rustc_query_system[a56a14b00b0e8ff6]::query::caches::VecCache<rustc_span[22cad54eabbc67cf]::def_id::LocalDefId, rustc_middle[2867706b5eb6f7f9]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[9b9172b7a4c3de5d]::plumbing::QueryCtxt, true>
  29:        0x11009b9f4 - rustc_query_impl[9b9172b7a4c3de5d]::query_impl::check_unsafety::get_query_incr::__rust_end_short_backtrace
  30:        0x10f422344 - std[4ec0ba9e3c6d748b]::panicking::try::<(), core[cec0bd9d2fc86fa9]::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures[961a954d878499e9]::sync::parallel::disabled::par_for_each_in<&[rustc_span[22cad54eabbc67cf]::def_id::LocalDefId], <rustc_middle[2867706b5eb6f7f9]::hir::map::Map>::par_body_owners<rustc_interface[6917c625c882dc9d]::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}>::{closure#0}::{closure#0}::{closure#0}>>
  31:        0x10f3d7c34 - <rustc_data_structures[961a954d878499e9]::sync::parallel::ParallelGuard>::run::<(), rustc_data_structures[961a954d878499e9]::sync::parallel::disabled::par_for_each_in<&[rustc_span[22cad54eabbc67cf]::def_id::LocalDefId], <rustc_middle[2867706b5eb6f7f9]::hir::map::Map>::par_body_owners<rustc_interface[6917c625c882dc9d]::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}>::{closure#0}::{closure#0}::{closure#0}>
  32:        0x10f42048c - <rustc_session[6e72d4e14abb7feb]::session::Session>::time::<(), rustc_interface[6917c625c882dc9d]::passes::run_required_analyses::{closure#1}>
  33:        0x10f3f7284 - rustc_interface[6917c625c882dc9d]::passes::analysis
  34:        0x10ff28c10 - rustc_query_impl[9b9172b7a4c3de5d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[9b9172b7a4c3de5d]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[2867706b5eb6f7f9]::query::erase::Erased<[u8; 1usize]>>
  35:        0x11004ab84 - <rustc_query_impl[9b9172b7a4c3de5d]::query_impl::analysis::dynamic_query::{closure#2} as core[cec0bd9d2fc86fa9]::ops::function::FnOnce<(rustc_middle[2867706b5eb6f7f9]::ty::context::TyCtxt, ())>>::call_once
  36:        0x10fe8f690 - rustc_query_system[a56a14b00b0e8ff6]::query::plumbing::try_execute_query::<rustc_query_impl[9b9172b7a4c3de5d]::DynamicConfig<rustc_query_system[a56a14b00b0e8ff6]::query::caches::SingleCache<rustc_middle[2867706b5eb6f7f9]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[9b9172b7a4c3de5d]::plumbing::QueryCtxt, true>
  37:        0x110090730 - rustc_query_impl[9b9172b7a4c3de5d]::query_impl::analysis::get_query_incr::__rust_end_short_backtrace
  38:        0x10ecac4d8 - <rustc_middle[2867706b5eb6f7f9]::ty::context::GlobalCtxt>::enter::<rustc_driver_impl[1ef2360f78401c14]::run_compiler::{closure#0}::{closure#1}::{closure#3}, core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>
  39:        0x10ec975a4 - <rustc_interface[6917c625c882dc9d]::interface::Compiler>::enter::<rustc_driver_impl[1ef2360f78401c14]::run_compiler::{closure#0}::{closure#1}, core[cec0bd9d2fc86fa9]::result::Result<core[cec0bd9d2fc86fa9]::option::Option<rustc_interface[6917c625c882dc9d]::queries::Linker>, rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>
  40:        0x10ec596b8 - <scoped_tls[1950327f1bf28942]::ScopedKey<rustc_span[22cad54eabbc67cf]::SessionGlobals>>::set::<rustc_interface[6917c625c882dc9d]::util::run_in_thread_with_globals<rustc_interface[6917c625c882dc9d]::interface::run_compiler<core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>, rustc_driver_impl[1ef2360f78401c14]::run_compiler::{closure#0}>::{closure#1}, core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}, core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>
  41:        0x10ec96f18 - rustc_span[22cad54eabbc67cf]::create_session_globals_then::<core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>, rustc_interface[6917c625c882dc9d]::util::run_in_thread_with_globals<rustc_interface[6917c625c882dc9d]::interface::run_compiler<core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>, rustc_driver_impl[1ef2360f78401c14]::run_compiler::{closure#0}>::{closure#1}, core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}>
  42:        0x10ec8dd58 - std[4ec0ba9e3c6d748b]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[6917c625c882dc9d]::util::run_in_thread_with_globals<rustc_interface[6917c625c882dc9d]::interface::run_compiler<core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>, rustc_driver_impl[1ef2360f78401c14]::run_compiler::{closure#0}>::{closure#1}, core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>
  43:        0x10ec6459c - <<std[4ec0ba9e3c6d748b]::thread::Builder>::spawn_unchecked_<rustc_interface[6917c625c882dc9d]::util::run_in_thread_with_globals<rustc_interface[6917c625c882dc9d]::interface::run_compiler<core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>, rustc_driver_impl[1ef2360f78401c14]::run_compiler::{closure#0}>::{closure#1}, core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[cec0bd9d2fc86fa9]::result::Result<(), rustc_span[22cad54eabbc67cf]::ErrorGuaranteed>>::{closure#2} as core[cec0bd9d2fc86fa9]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  44:        0x105614588 - std::sys::pal::unix::thread::Thread::new::thread_start::hb184f2abd415aef7
  45:        0x187025f94 - __pthread_joiner_wake

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: rustc 1.80.1 (3f5fd8dd4 2024-08-06) running on aarch64-apple-darwin

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [mir_built] building MIR for `primitive::<impl at crates/ir/src/primitive.rs:561:10: 561:19>::eq`
#1 [check_unsafety] unsafety-checking `primitive::<impl at crates/ir/src/primitive.rs:561:10: 561:19>::eq`
end of query stack
For more information about this error, try `rustc --explain E0517`.

[matthiaskrgr]

duplicate of #120873

[saethlin]

Ergo, closing