ICE `non-Aggregate field with matching ABI but differing alignment`

auto-reduced (treereduce-rust):

#[repr(packed)]
#[repr(u32)]
enum E {
    A,
    B,
    C,
}

fn main() {
    union InvalidTag {
        int: u32,
        e: E,
    }
    let _invalid_tag = InvalidTag { int: 4 };
}

original:

// Regression test for issue 123710.
// Tests that the we do not ICE in KnownPanicsLint
// when a union contains an enum with an repr(packed),
// which is a repr not supported for enums

#[repr(packed)]
//~^ ERROR attribute should be applied to a struct or union
#[repr(u32)]
enum E {
    A,
    B,
    C,
}

fn main() {
    union InvalidTag {
        int: u32,
        e: E,
//~^ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
    }
    let _invalid_tag = InvalidTag { int: 4 };
}

Version information

rustc 1.82.0-nightly (97e72524a 2024-08-09)
binary: rustc
commit-hash: 97e72524a34994541810438258115802f8b85543
commit-date: 2024-08-09
host: x86_64-unknown-linux-gnu
release: 1.82.0-nightly
LLVM version: 19.1.0

Command: /home/matthias/.rustup/toolchains/master/bin/rustc -Zvalidate-mir

Program output

``` error[E0517]: attribute should be applied to a struct or union --> /tmp/icemaker_global_tempdir.iOHXDC03JcDS/rustc_testrunner_tmpdir_reporting.IwiBfGzE7qtZ/mvce.rs:1:8 | 1 | #[repr(packed)] | ^^^^^^ 2 | #[repr(u32)] 3 | / enum E { 4 | | A, 5 | | B, 6 | | C, 7 | | } | |_- not a struct or union error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union --> /tmp/icemaker_global_tempdir.iOHXDC03JcDS/rustc_testrunner_tmpdir_reporting.IwiBfGzE7qtZ/mvce.rs:12:9 | 12 | e: E, | ^^^^ | = note: union fields must not have drop side-effects, which is currently enforced via either `Copy` or `ManuallyDrop<...>` help: wrap the field type in `ManuallyDrop<...>` | 12 | e: std::mem::ManuallyDrop, | +++++++++++++++++++++++ + thread 'rustc' panicked at /rustc/97e72524a34994541810438258115802f8b85543/compiler/rustc_abi/src/layout.rs:287:29: assertion `left == right` failed: non-Aggregate field with matching ABI but differing alignment left: Align(4 bytes) right: Align(1 bytes) stack backtrace: 0: 0x7b1c4dc78c9d - std::backtrace_rs::backtrace::libunwind::trace::h6d8f9caaadd7fb58 at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5 1: 0x7b1c4dc78c9d - std::backtrace_rs::backtrace::trace_unsynchronized::h17be7deb44f4a166 at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5 2: 0x7b1c4dc78c9d - std::sys::backtrace::_print_fmt::h9644a3e199661ff7 at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/sys/backtrace.rs:66:9 3: 0x7b1c4dc78c9d - ::fmt::h19f5bb40323ef90a at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/sys/backtrace.rs:39:26 4: 0x7b1c4dcc942b - core::fmt::rt::Argument::fmt::h04004c0c7b9c8c68 at /rustc/97e72524a34994541810438258115802f8b85543/library/core/src/fmt/rt.rs:173:76 5: 0x7b1c4dcc942b - core::fmt::write::h038b15e88d4c08dd at /rustc/97e72524a34994541810438258115802f8b85543/library/core/src/fmt/mod.rs:1178:21 6: 0x7b1c4dc6cb33 - std::io::Write::write_fmt::h336c1ed0f6805c7d at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/io/mod.rs:1823:15 7: 0x7b1c4dc7b492 - std::sys::backtrace::BacktraceLock::print::h32f152afdca981eb at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/sys/backtrace.rs:42:9 8: 0x7b1c4dc7b492 - std::panicking::default_hook::{{closure}}::h2a41f7f3fcf3abf5 at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/panicking.rs:266:22 9: 0x7b1c4dc7b0fe - std::panicking::default_hook::h83a4d780a2fde4cb at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/panicking.rs:293:9 10: 0x7b1c4a0c0177 - std[8905f2cde1cc7662]::panicking::update_hook::>::{closure#0} 11: 0x7b1c4dc7be82 - as core::ops::function::Fn>::call::ha95e7459ace54ce3 at /rustc/97e72524a34994541810438258115802f8b85543/library/alloc/src/boxed.rs:2164:9 12: 0x7b1c4dc7be82 - std::panicking::rust_panic_with_hook::h69861f8a9f68140e at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/panicking.rs:805:13 13: 0x7b1c4dc7bb37 - std::panicking::begin_panic_handler::{{closure}}::haee2c71d9d77450d at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/panicking.rs:671:13 14: 0x7b1c4dc79189 - std::sys::backtrace::__rust_end_short_backtrace::h13dd402901136d07 at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/sys/backtrace.rs:170:18 15: 0x7b1c4dc7b7c4 - rust_begin_unwind at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/panicking.rs:662:5 16: 0x7b1c4dcc5a83 - core::panicking::panic_fmt::haa28ca6654179c80 at /rustc/97e72524a34994541810438258115802f8b85543/library/core/src/panicking.rs:74:14 17: 0x7b1c4dcc605f - core::panicking::assert_failed_inner::hb8e7362e4cbedd62 at /rustc/97e72524a34994541810438258115802f8b85543/library/core/src/panicking.rs:407:23 18: 0x7b1c4aeb9477 - core[ed2708e6dfab5976]::panicking::assert_failed:: 19: 0x7b1c4bffeba5 - rustc_ty_utils[8fe1d6497c51be38]::layout::layout_of_uncached 20: 0x7b1c4bff653d - rustc_ty_utils[8fe1d6497c51be38]::layout::layout_of 21: 0x7b1c4bff64d1 - rustc_query_impl[a3ff9df8c87d6bf9]::plumbing::__rust_begin_short_backtrace::> 22: 0x7b1c4bff57d2 - rustc_query_system[ae5d59fa4dc61faf]::query::plumbing::try_execute_query::, rustc_middle[4c63caae2dc30deb]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[a3ff9df8c87d6bf9]::plumbing::QueryCtxt, false> 23: 0x7b1c4bff546f - rustc_query_impl[a3ff9df8c87d6bf9]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace 24: 0x7b1c48d498a8 - ::run_pass 25: 0x7b1c4b601d35 - rustc_mir_transform[eb83fea80f9dad86]::pass_manager::run_passes_inner 26: 0x7b1c4c180b61 - rustc_mir_transform[eb83fea80f9dad86]::optimized_mir 27: 0x7b1c4c1649db - rustc_query_impl[a3ff9df8c87d6bf9]::plumbing::__rust_begin_short_backtrace::> 28: 0x7b1c4b95a11f - rustc_query_system[ae5d59fa4dc61faf]::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl[a3ff9df8c87d6bf9]::plumbing::QueryCtxt, false> 29: 0x7b1c4b9598f3 - rustc_query_impl[a3ff9df8c87d6bf9]::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace 30: 0x7b1c485ba7a8 - ::instance_mir 31: 0x7b1c4b977e55 - rustc_interface[69b3ddcd41152fad]::passes::run_required_analyses 32: 0x7b1c4c21381e - rustc_interface[69b3ddcd41152fad]::passes::analysis 33: 0x7b1c4c2137f1 - rustc_query_impl[a3ff9df8c87d6bf9]::plumbing::__rust_begin_short_backtrace::> 34: 0x7b1c4c5ec0ae - rustc_query_system[ae5d59fa4dc61faf]::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl[a3ff9df8c87d6bf9]::plumbing::QueryCtxt, false> 35: 0x7b1c4c5ebe0f - rustc_query_impl[a3ff9df8c87d6bf9]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace 36: 0x7b1c4c46efe0 - rustc_interface[69b3ddcd41152fad]::interface::run_compiler::, rustc_driver_impl[409c18a6a244b347]::run_compiler::{closure#0}>::{closure#1} 37: 0x7b1c4c409509 - std[8905f2cde1cc7662]::sys::backtrace::__rust_begin_short_backtrace::, rustc_driver_impl[409c18a6a244b347]::run_compiler::{closure#0}>::{closure#1}, core[ed2708e6dfab5976]::result::Result<(), rustc_span[b1343f73fcced4f1]::ErrorGuaranteed>>::{closure#0}, core[ed2708e6dfab5976]::result::Result<(), rustc_span[b1343f73fcced4f1]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[ed2708e6dfab5976]::result::Result<(), rustc_span[b1343f73fcced4f1]::ErrorGuaranteed>> 38: 0x7b1c4c4092b2 - <::spawn_unchecked_, rustc_driver_impl[409c18a6a244b347]::run_compiler::{closure#0}>::{closure#1}, core[ed2708e6dfab5976]::result::Result<(), rustc_span[b1343f73fcced4f1]::ErrorGuaranteed>>::{closure#0}, core[ed2708e6dfab5976]::result::Result<(), rustc_span[b1343f73fcced4f1]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[ed2708e6dfab5976]::result::Result<(), rustc_span[b1343f73fcced4f1]::ErrorGuaranteed>>::{closure#1} as core[ed2708e6dfab5976]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 39: 0x7b1c4dc85b9b - as core::ops::function::FnOnce>::call_once::h706c4c27c8278947 at /rustc/97e72524a34994541810438258115802f8b85543/library/alloc/src/boxed.rs:2150:9 40: 0x7b1c4dc85b9b - as core::ops::function::FnOnce>::call_once::h267b705fa7be0ba5 at /rustc/97e72524a34994541810438258115802f8b85543/library/alloc/src/boxed.rs:2150:9 41: 0x7b1c4dc85b9b - std::sys::pal::unix::thread::Thread::new::thread_start::h109d3e899700b4bb at /rustc/97e72524a34994541810438258115802f8b85543/library/std/src/sys/pal/unix/thread.rs:110:17 42: 0x7b1c46aa6ded - 43: 0x7b1c46b2a0dc - 44: 0x0 - 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 1.82.0-nightly (97e72524a 2024-08-09) running on x86_64-unknown-linux-gnu note: compiler flags: -Z validate-mir -Z dump-mir-dir=dir query stack during panic: #0 [layout_of] computing layout of `main::InvalidTag` #1 [optimized_mir] optimizing MIR for `main` end of query stack error: aborting due to 2 previous errors Some errors have detailed explanations: E0517, E0740. For more information about an error, try `rustc --explain E0517`. ```

rust-lang / rust

ICE `non-Aggregate field with matching ABI but differing alignment` #128870