ICE (on stable and nightly): repr(packed) + enum + Box + builtin derive macro

[Ddystopia]

Code

playground

#[derive(Debug)] // The same with `PartialEq`, for example
#[repr(packed)]
enum Enum {
    A(Box<u32>),
}

fn main() {}

Meta

Stable in playground

Error output

Backtrace

Exited with status 101
Standard Error
   Compiling playground v0.0.1 (/playground)
error[[E0517]](https://doc.rust-lang.org/stable/error_codes/E0517.html): attribute should be applied to a struct or union
 --> src/main.rs:2:8
  |
2 |   #[repr(packed)]
  |          ^^^^^^
3 | / enum SlicedIE2 {
4 | |     A(Box<u32>),
5 | | }
  | |_- not a struct or union

error: internal compiler error: compiler/rustc_mir_transform/src/check_packed_ref.rs:49:17: builtin derive created an unaligned reference
 --> src/main.rs:4:7
  |
1 | #[derive(Debug)]
  |          ----- in this derive macro expansion
...
4 |     A(Box<u32>),
  |       ^^^^^^^^
  |
  = note: this error: internal compiler error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)


thread 'rustc' panicked at compiler/rustc_mir_transform/src/check_packed_ref.rs:49:17:
Box<dyn Any>
stack backtrace:
   0:     0x7b35499d6e40 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h6d42cc84fc840290
   1:     0x7b354a22867c - core::fmt::write::h5af61a909e3ec64d
   2:     0x7b354b52ca51 - std::io::Write::write_fmt::h5a7b54aa6e4a315d
   3:     0x7b35499d6ca2 - std::sys::backtrace::BacktraceLock::print::h555579e7396c26ac
   4:     0x7b35499d9122 - std::panicking::default_hook::{{closure}}::h9128866118196224
   5:     0x7b35499d8faa - std::panicking::default_hook::h52e9e7314e0255f6
   6:     0x7b3548b33449 - std[d9e466a2d75004a2]::panicking::update_hook::<alloc[54bfe2542ace865d]::boxed::Box<rustc_driver_impl[680c351c5444d7cd]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7b35499d9ca3 - std::panicking::rust_panic_with_hook::h541791bcc774ef34
   8:     0x7b3548b6e3b1 - std[d9e466a2d75004a2]::panicking::begin_panic::<rustc_errors[90b6e0e1196d63f0]::ExplicitBug>::{closure#0}
   9:     0x7b3548b63326 - std[d9e466a2d75004a2]::sys::backtrace::__rust_end_short_backtrace::<std[d9e466a2d75004a2]::panicking::begin_panic<rustc_errors[90b6e0e1196d63f0]::ExplicitBug>::{closure#0}, !>
  10:     0x7b3548b6330d - std[d9e466a2d75004a2]::panicking::begin_panic::<rustc_errors[90b6e0e1196d63f0]::ExplicitBug>
  11:     0x7b3548b78381 - <rustc_errors[90b6e0e1196d63f0]::diagnostic::BugAbort as rustc_errors[90b6e0e1196d63f0]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7b35490ce80c - <rustc_errors[90b6e0e1196d63f0]::DiagCtxtHandle>::span_bug::<rustc_span[15ded62729b25549]::span_encoding::Span, alloc[54bfe2542ace865d]::string::String>
  13:     0x7b354914ff37 - rustc_middle[a78c8f6c75429410]::util::bug::opt_span_bug_fmt::<rustc_span[15ded62729b25549]::span_encoding::Span>::{closure#0}
  14:     0x7b3549138d6a - rustc_middle[a78c8f6c75429410]::ty::context::tls::with_opt::<rustc_middle[a78c8f6c75429410]::util::bug::opt_span_bug_fmt<rustc_span[15ded62729b25549]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  15:     0x7b3549138bfb - rustc_middle[a78c8f6c75429410]::ty::context::tls::with_context_opt::<rustc_middle[a78c8f6c75429410]::ty::context::tls::with_opt<rustc_middle[a78c8f6c75429410]::util::bug::opt_span_bug_fmt<rustc_span[15ded62729b25549]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  16:     0x7b35478351e7 - rustc_middle[a78c8f6c75429410]::util::bug::span_bug_fmt::<rustc_span[15ded62729b25549]::span_encoding::Span>
  17:     0x7b354aa9287b - <rustc_mir_transform[65d952cda38dbfd0]::check_packed_ref::CheckPackedRef as rustc_mir_transform[65d952cda38dbfd0]::pass_manager::MirLint>::run_lint
  18:     0x7b354a20a265 - rustc_mir_transform[65d952cda38dbfd0]::mir_built
  19:     0x7b354a20a033 - rustc_query_impl[abff21d8349146d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[abff21d8349146d]::query_impl::mir_built::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a78c8f6c75429410]::query::erase::Erased<[u8; 8usize]>>
  20:     0x7b354a609857 - rustc_query_system[9464b8c501ef87f3]::query::plumbing::try_execute_query::<rustc_query_impl[abff21d8349146d]::DynamicConfig<rustc_data_structures[6e992f72641bf6c6]::vec_cache::VecCache<rustc_span[15ded62729b25549]::def_id::LocalDefId, rustc_middle[a78c8f6c75429410]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[9464b8c501ef87f3]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[abff21d8349146d]::plumbing::QueryCtxt, false>
  21:     0x7b354a60940d - rustc_query_impl[abff21d8349146d]::query_impl::mir_built::get_query_non_incr::__rust_end_short_backtrace
  22:     0x7b354ac00058 - rustc_mir_build[b55d8ca8377cfad8]::check_unsafety::check_unsafety
  23:     0x7b354abffec7 - rustc_query_impl[abff21d8349146d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[abff21d8349146d]::query_impl::check_unsafety::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a78c8f6c75429410]::query::erase::Erased<[u8; 0usize]>>
  24:     0x7b354abff1b0 - rustc_query_system[9464b8c501ef87f3]::query::plumbing::try_execute_query::<rustc_query_impl[abff21d8349146d]::DynamicConfig<rustc_data_structures[6e992f72641bf6c6]::vec_cache::VecCache<rustc_span[15ded62729b25549]::def_id::LocalDefId, rustc_middle[a78c8f6c75429410]::query::erase::Erased<[u8; 0usize]>, rustc_query_system[9464b8c501ef87f3]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[abff21d8349146d]::plumbing::QueryCtxt, false>
  25:     0x7b354abfee41 - rustc_query_impl[abff21d8349146d]::query_impl::check_unsafety::get_query_non_incr::__rust_end_short_backtrace
  26:     0x7b354a602e2a - rustc_interface[84ab11ffe8dacd23]::passes::run_required_analyses
  27:     0x7b354ad18f1e - rustc_interface[84ab11ffe8dacd23]::passes::analysis
  28:     0x7b354ad18eef - rustc_query_impl[abff21d8349146d]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[abff21d8349146d]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a78c8f6c75429410]::query::erase::Erased<[u8; 0usize]>>
  29:     0x7b354b191015 - rustc_query_system[9464b8c501ef87f3]::query::plumbing::try_execute_query::<rustc_query_impl[abff21d8349146d]::DynamicConfig<rustc_query_system[9464b8c501ef87f3]::query::caches::SingleCache<rustc_middle[a78c8f6c75429410]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[abff21d8349146d]::plumbing::QueryCtxt, false>
  30:     0x7b354b190d4e - rustc_query_impl[abff21d8349146d]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  31:     0x7b354b19aea9 - rustc_interface[84ab11ffe8dacd23]::passes::create_and_enter_global_ctxt::<core[46aa9df3d3dcdeb1]::option::Option<rustc_interface[84ab11ffe8dacd23]::queries::Linker>, rustc_driver_impl[680c351c5444d7cd]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  32:     0x7b354b1ab726 - rustc_interface[84ab11ffe8dacd23]::interface::run_compiler::<(), rustc_driver_impl[680c351c5444d7cd]::run_compiler::{closure#0}>::{closure#1}
  33:     0x7b354b0e0744 - std[d9e466a2d75004a2]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[84ab11ffe8dacd23]::util::run_in_thread_with_globals<rustc_interface[84ab11ffe8dacd23]::util::run_in_thread_pool_with_globals<rustc_interface[84ab11ffe8dacd23]::interface::run_compiler<(), rustc_driver_impl[680c351c5444d7cd]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  34:     0x7b354b0e0419 - <<std[d9e466a2d75004a2]::thread::Builder>::spawn_unchecked_<rustc_interface[84ab11ffe8dacd23]::util::run_in_thread_with_globals<rustc_interface[84ab11ffe8dacd23]::util::run_in_thread_pool_with_globals<rustc_interface[84ab11ffe8dacd23]::interface::run_compiler<(), rustc_driver_impl[680c351c5444d7cd]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[46aa9df3d3dcdeb1]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  35:     0x7b354b0dfbaf - std::sys::pal::unix::thread::Thread::new::thread_start::hcc5ed016d554f327
  36:     0x7b354528aaa4 - <unknown>
  37:     0x7b3545317a34 - clone
  38:                0x0 - <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: rustc 1.86.0 (05f9846f8 2025-03-31) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2

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

query stack during panic:
#0 [mir_built] building MIR for `<impl at src/main.rs:1:10: 1:15>::fmt`
#1 [check_unsafety] unsafety-checking `<impl at src/main.rs:1:10: 1:15>::fmt`
... and 1 other queries... use `env RUST_BACKTRACE=1` to see the full query stack
For more information about this error, try `rustc --explain E0517`.
error: could not compile `playground` (bin "playground") due to 1 previous error
S

[cyrgani]

duplicate of #133025

[jieyouxu]

Indeed.