ICE: `assertion failed: self.is_struct() || self.is_union()`

Code

#![feature(repr_simd)]

use std::arch::asm;

#[repr(simd)]
enum Es {}
static CLs: Es;

pub fn main() {
    let mut b = 4i32;
    unsafe {
        asm!("{}", out(reg) CLs);
    }
}

A mutant of tests/pretty/asm.rs

Error output

Command: rustc

error: free static item without body
 --> 14.rs:7:1
  |
7 | static CLs: Es;
  | ^^^^^^^^^^^^^^-
  |               |
  |               help: provide a definition for the static: `= <expr>;`

error[E0517]: attribute should be applied to a struct
 --> 14.rs:5:8
  |
5 | #[repr(simd)]
  |        ^^^^
6 | enum Es {}
  | ---------- not a struct

error[E0084]: unsupported representation for zero-variant enum
 --> 14.rs:5:8
  |
5 | #[repr(simd)]
  |        ^^^^
6 | enum Es {}
  | ------- zero-variant enum


thread 'rustc' (6698172) panicked at compiler/rustc_middle/src/ty/adt.rs:462:9:
assertion failed: self.is_struct() || self.is_union()

Backtrace

thread 'rustc' (6698172) panicked at compiler/rustc_middle/src/ty/adt.rs:462:9:
assertion failed: self.is_struct() || self.is_union()
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: <rustc_hir_typeck::inline_asm::InlineAsmCtxt>::check_asm_operand_type
   4: rustc_hir_typeck::typeck_with_inspect::{closure#0}
   5: rustc_hir_typeck::typeck
      [... omitted 1 frame ...]
   6: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis::check_crate::{closure#2}>::{closure#0}
   7: rustc_hir_analysis::check_crate
   8: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
   9: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
  10: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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: please attach the file at `/Users/jb/Library/CloudStorage/Dropbox/Desk/2503_rustc_ice/20251106 ice 보고용/rustc-ice-2025-11-07T07_18_16-4837.txt` to your bug report

query stack during panic:
#0 [typeck] type-checking `main`
#1 [analysis] running analysis passes on crate `14`
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0084, E0517.
For more information about an error, try `rustc --explain E0084`.

Notes

ICE location: compiler/rustc_middle/src/ty/adt.rs Line-462

rust/compiler/rustc_middle/src/ty/adt.rs

Lines 460 to 464 in c90bcb9

    
               /// Asserts this is a struct or union and returns its unique variant. 
        
               pub fn non_enum_variant(self) -> &'tcx VariantDef { 
        
                   assert!(self.is_struct() || self.is_union()); 
        
                   self.variant(FIRST_VARIANT) 
        
               }

In my guess, the non_enum_variant call comes from here:

rust/compiler/rustc_hir_typeck/src/inline_asm.rs

Lines 168 to 189 in c90bcb9

    
           let asm_ty = match *ty.kind() { 
        
               // `!` is allowed for input but not for output (issue #87802) 
        
               ty::Never if is_input => return None, 
        
               _ if ty.references_error() => return None, 
        
               ty::Adt(adt, args) if self.tcx().is_lang_item(adt.did(), LangItem::MaybeUninit) => { 
        
                   let fields = &adt.non_enum_variant().fields; 
        
                   let ty = fields[FieldIdx::ONE].ty(self.tcx(), args); 
        
                   // FIXME: Are we just trying to map to the `T` in `MaybeUninit<T>`? 
        
                   // If so, just get it from the args. 
        
                   let ty::Adt(ty, args) = ty.kind() else { 
        
                       unreachable!("expected first field of `MaybeUninit` to be an ADT") 
        
                   }; 
        
                   assert!( 
        
                       ty.is_manually_drop(), 
        
                       "expected first field of `MaybeUninit` to be `ManuallyDrop`" 
        
                   ); 
        
                   let fields = &ty.non_enum_variant().fields; 
        
                   let ty = fields[FieldIdx::ZERO].ty(self.tcx(), args); 
        
                   self.get_asm_ty(expr.span, ty) 
        
               } 
        
               _ => self.get_asm_ty(expr.span, ty), 
        
           };

Duplication Check
- I searched "self.is_struct()" ICE (Github issue page with query), and there are no opened issues there.

use std::arch::asm;

#[repr(simd)]
enum Es {
    T,
}

fn main() {
    unsafe {
        asm!("{}", out(reg) Es::T);
    }
}

cargo-bisect-rustc --start=2022-01-01 --end=2025-11-07 --regress ice --preserve --script rustc -- 148634.rs

********************************************************************************
Regression in nightly-2022-05-28
********************************************************************************

fetching https://static.rust-lang.org/dist/2022-05-27/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2022-05-27: 40 B / 40 B [==================================================================================================================================================] 100.00 % 1.03 MB/s converted 2022-05-27 to 490324f7b29d5f1a1e063a563045d790091ed639
fetching https://static.rust-lang.org/dist/2022-05-28/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2022-05-28: 40 B / 40 B [==================================================================================================================================================] 100.00 % 1.02 MB/s converted 2022-05-28 to ebbcbfc236ced21d5e6a92269edb704692ff26b8
looking for regression commit between 2022-05-27 and 2022-05-28
fetching (via remote github) commits from max(490324f7b29d5f1a1e063a563045d790091ed639, 2022-05-25) to ebbcbfc236ced21d5e6a92269edb704692ff26b8
ending github query because we found starting sha: 490324f7b29d5f1a1e063a563045d790091ed639
get_commits_between returning commits, len: 8
  commit[0] 2022-05-26: Auto merge of #97434 - matthiaskrgr:rollup-7j3y16l, r=matthiaskrgr
  commit[1] 2022-05-26: Auto merge of #97386 - nnethercote:optimize-pos-adjustments, r=bjorn3
  commit[2] 2022-05-27: Auto merge of #96298 - petrochenkov:fromgen, r=estebank
  commit[3] 2022-05-27: Auto merge of #97444 - compiler-errors:rollup-2gvdav6, r=compiler-errors
  commit[4] 2022-05-27: Auto merge of #97004 - nnethercote:proc-macro-tweaks, r=eddyb
  commit[5] 2022-05-27: Auto merge of #97442 - hafeoz:master, r=GuillaumeGomez
  commit[6] 2022-05-27: Auto merge of #96046 - oli-obk:const_typeck, r=cjgillot
  commit[7] 2022-05-27: Auto merge of #96790 - lqd:update_jemalloc, r=Mark-Simulacrum
ERROR: no CI builds available between 490324f7b29d5f1a1e063a563045d790091ed639 and ebbcbfc236ced21d5e6a92269edb704692ff26b8 within last 167 days

	/// Asserts this is a struct or union and returns its unique variant.
	pub fn non_enum_variant(self) -> &'tcx VariantDef {
	assert!(self.is_struct() \|\| self.is_union());
	self.variant(FIRST_VARIANT)
	}

	let asm_ty = match *ty.kind() {
	// `!` is allowed for input but not for output (issue #87802)
	ty::Never if is_input => return None,
	_ if ty.references_error() => return None,
	ty::Adt(adt, args) if self.tcx().is_lang_item(adt.did(), LangItem::MaybeUninit) => {
	let fields = &adt.non_enum_variant().fields;
	let ty = fields[FieldIdx::ONE].ty(self.tcx(), args);
	// FIXME: Are we just trying to map to the `T` in `MaybeUninit<T>`?
	// If so, just get it from the args.
	let ty::Adt(ty, args) = ty.kind() else {
	unreachable!("expected first field of `MaybeUninit` to be an ADT")
	};
	assert!(
	ty.is_manually_drop(),
	"expected first field of `MaybeUninit` to be `ManuallyDrop`"
	);
	let fields = &ty.non_enum_variant().fields;
	let ty = fields[FieldIdx::ZERO].ty(self.tcx(), args);
	self.get_asm_ty(expr.span, ty)
	}
	_ => self.get_asm_ty(expr.span, ty),
	};

Code

Meta

Error output

Notes