[ICE]: autodiff normalize_erasing_regions fails when moving a struct with reference + unnormalised type

Ran into this ICE when using the std::autodiff feature on nightly, I get the compiler error when I have the combination of an unnormalised type and a Box/reference. See MRE below (generated with help of an LLM):

Code

trait Op { type V; }
struct Eqn;
impl Op for Eqn { type V = f64; }
struct State<V> { y: V }
struct Inner<'a, E: Op> { s: &'a State<E::V>, a: u64, b: u64 }

fn main() {
    let s = State { y: 1.0f64 };
    let i = Inner::<Eqn> { s: &s, a: 1, b: 2 };
    let m = std::hint::black_box(i);
    println!("{}", m.a + m.b + m.s.y as u64);
}

Meta

rustc --version --verbose:

rustc 1.98.1 (48a229cea 2026-09-01)
binary: rustc
commit-hash: 48a229ceaefd4985c50990b14116b6d856af0985
commit-date: 2026-09-01
host: x86_64-unknown-linux-gnu
release: 1.98.1
LLVM version: 22.1.8

Error output

❯ RUSTFLAGS="-Zautodiff=Enable" cargo +nightly run --release
   Compiling autodiff-ice v0.1.0 (/home/mrobins/git/tmp/autodiff-ice)

thread 'rustc' (1294985) panicked at /rustc-dev/0ed41eb4142dda2df61eb1145a312c1a9d62eb56/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:76:13:
assertion `left == right` failed
  left: State<Alias(No, Alias { kind: Projection { def_id: DefId(0:4 ~ autodiff_ice[349e]::Op::V) }, args: [Eqn], .. })>
 right: State<f64>
stack backtrace:
   0:     0x79257a091516 - <<std[d4c1480f659289a4]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[645f4c3e01480c61]::fmt::Display>::fmt
   1:     0x79257a80ba8f - core[645f4c3e01480c61]::fmt::write
   2:     0x79257a0a660c - <std[d4c1480f659289a4]::sys::stdio::unix::Stderr as core[645f4c3e01480c61]::io::write::Write>::write_fmt
   3:     0x79257a063dba - std[d4c1480f659289a4]::panicking::default_hook::{closure#0}
   4:     0x79257a085813 - std[d4c1480f659289a4]::panicking::default_hook
   5:     0x792578fdcaef - std[d4c1480f659289a4]::panicking::update_hook::<alloc[85239869be382ab2]::boxed::Box<rustc_driver_impl[52b061d793d3365c]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x79257a085cb2 - std[d4c1480f659289a4]::panicking::panic_with_hook
   7:     0x79257a063e72 - std[d4c1480f659289a4]::panicking::panic_handler::{closure#0}
   8:     0x79257a05ccd9 - std[d4c1480f659289a4]::sys::backtrace::__rust_end_short_backtrace::<std[d4c1480f659289a4]::panicking::panic_handler::{closure#0}, !>
   9:     0x79257a065a4d - __rustc[d3fd7ef964226397]::rust_begin_unwind
  10:     0x792576db721c - core[645f4c3e01480c61]::panicking::panic_fmt
  11:     0x792578960c93 - core[645f4c3e01480c61]::panicking::assert_failed_inner
  12:     0x79257959c5b3 - core[645f4c3e01480c61]::panicking::assert_failed::<rustc_middle[7aa4fce01e3768ef]::ty::Ty, rustc_middle[7aa4fce01e3768ef]::ty::Ty>
  13:     0x79257b0210df - <rustc_middle[7aa4fce01e3768ef]::ty::context::TyCtxt>::struct_tail_for_codegen
  14:     0x7925795ed5c5 - rustc_middle[7aa4fce01e3768ef]::ty::typetree::handle_indirection
  15:     0x7925795ee22e - rustc_middle[7aa4fce01e3768ef]::ty::typetree::typetree_from_ty_impl_inner
  16:     0x7925795ee367 - rustc_middle[7aa4fce01e3768ef]::ty::typetree::typetree_from_ty_impl_inner
  17:     0x79257ab97ef5 - <rustc_codegen_ssa[ce71d2ce136ae586]::mir::operand::OperandValue<&rustc_codegen_llvm[757fffd0e17f0ef5]::llvm::ffi::Value>>::store_with_flags::<rustc_codegen_llvm[757fffd0e17f0ef5]::builder::GenericBuilder<rustc_codegen_llvm[757fffd0e17f0ef5]::context::FullCx>>
  18:     0x79257bbabb11 - <rustc_codegen_llvm[757fffd0e17f0ef5]::builder::GenericBuilder<rustc_codegen_llvm[757fffd0e17f0ef5]::context::FullCx> as rustc_codegen_ssa[ce71d2ce136ae586]::traits::intrinsic::IntrinsicCallBuilderMethods>::codegen_intrinsic_call
  19:     0x79257bba70c0 - <rustc_codegen_ssa[ce71d2ce136ae586]::mir::FunctionCx<rustc_codegen_llvm[757fffd0e17f0ef5]::builder::GenericBuilder<rustc_codegen_llvm[757fffd0e17f0ef5]::context::FullCx>>>::codegen_intrinsic_call
  20:     0x79257be62343 - rustc_codegen_ssa[ce71d2ce136ae586]::mir::codegen_mir::<rustc_codegen_llvm[757fffd0e17f0ef5]::builder::GenericBuilder<rustc_codegen_llvm[757fffd0e17f0ef5]::context::FullCx>>
  21:     0x79257aba749c - rustc_codegen_llvm[757fffd0e17f0ef5]::base::compile_codegen_unit::module_codegen
  22:     0x79257b983a36 - <rustc_codegen_llvm[757fffd0e17f0ef5]::LlvmCodegenBackend as rustc_codegen_ssa[ce71d2ce136ae586]::traits::backend::ExtraBackendMethods>::compile_codegen_unit
  23:     0x79257b97f958 - rustc_codegen_ssa[ce71d2ce136ae586]::base::codegen_crate::<rustc_codegen_llvm[757fffd0e17f0ef5]::LlvmCodegenBackend, rustc_codegen_llvm[757fffd0e17f0ef5]::ModuleLlvm>
  24:     0x79257b97e30c - <rustc_codegen_llvm[757fffd0e17f0ef5]::LlvmCodegenBackend as rustc_codegen_ssa[ce71d2ce136ae586]::traits::backend::CodegenBackend>::codegen_crate
  25:     0x79257bc037cc - <rustc_interface[facc905b6ccf4600]::queries::Linker>::codegen_and_build_linker
  26:     0x79257bbfae41 - rustc_interface[facc905b6ccf4600]::interface::run_compiler::<(), rustc_driver_impl[52b061d793d3365c]::run_compiler::{closure#0}>::{closure#2}
  27:     0x79257bc89602 - std[d4c1480f659289a4]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[facc905b6ccf4600]::util::run_in_thread_with_globals<rustc_interface[facc905b6ccf4600]::util::run_in_thread_pool_with_globals<rustc_interface[facc905b6ccf4600]::interface::run_compiler<(), rustc_driver_impl[52b061d793d3365c]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  28:     0x79257bc893ad - <std[d4c1480f659289a4]::thread::lifecycle::spawn_unchecked<rustc_interface[facc905b6ccf4600]::util::run_in_thread_with_globals<rustc_interface[facc905b6ccf4600]::util::run_in_thread_pool_with_globals<rustc_interface[facc905b6ccf4600]::interface::run_compiler<(), rustc_driver_impl[52b061d793d3365c]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[645f4c3e01480c61]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  29:     0x79257bc86f47 - <std[d4c1480f659289a4]::sys::thread::unix::Thread>::new::thread_start
  30:     0x792574e8307a - start_thread
                               at ./nptl/pthread_create.c:454:8
  31:     0x792574f16534 - clone
                               at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:100:0
  32:                0x0 - <unknown>

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 `/home/mrobins/git/tmp/autodiff-ice/rustc-ice-2026-09-05T08_00_20-1294983.txt` to your bug report

note: rustc 1.100.0-nightly (0ed41eb41 2026-09-04) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C opt-level=3 -C embed-bitcode=no -C strip=debuginfo -Z autodiff=Enable

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

query stack during panic:
end of query stack
error: could not compile `autodiff-ice` (bin "autodiff-ice")

Reproduce the ICE with the supplied MRE using nightly and RUSTFLAGS="-Zautodiff=Enable". Start at compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:76, then follow the typetree and codegen paths named in the stack trace. Done means the example no longer panics and coverage protects this autodiff case.