[ICE]: `ptr_metadata_ty_or_tail applied to unexpected type`

[cushionbadak]

Code

trait Trait {
    type Assoc2;
}

struct Bar;
impl Trait for Bar {
    type Assoc2 = Result<(), <Bar as Trait>::Assoc2>;
}

struct Foo {
    field: <Bar as Trait>::Assoc2,
}

static BAR: u8 = 42;
static FOO2: &Foo = unsafe { std::mem::transmute(&BAR) };

fn main() {}

A mutant of tests/ui/type-alias-impl-trait/bad-transmute-itiat.rs

Meta

rustc --version --verbose:

rustc 1.96.0-nightly (b90dc1e59 2026-03-04)
binary: rustc
commit-hash: b90dc1e597db0bbc0cab0eccb39747b1a9d7e607
commit-date: 2026-03-04
host: x86_64-apple-darwin
release: 1.96.0-nightly
LLVM version: 22.1.0

Error output

Command: rustc

error[E0275]: overflow evaluating the requirement `<Bar as Trait>::Assoc2 == _`
 --> asdf.rs:7:19
  |
7 |     type Assoc2 = Result<(), <Bar as Trait>::Assoc2>;
  |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0275]: overflow evaluating the requirement `<Bar as Trait>::Assoc2 == _`
  --> asdf.rs:11:12
   |
11 |     field: <Bar as Trait>::Assoc2,
   |            ^^^^^^^^^^^^^^^^^^^^^^

error: internal compiler error: /rustc-dev/b90dc1e597db0bbc0cab0eccb39747b1a9d7e607/compiler/rustc_middle/src/ty/sty.rs:1740:86: `ptr_metadata_ty_or_tail` applied to unexpected type: Foo (tail = ?1t)


thread 'rustc' (9080132) panicked at /rustc-dev/b90dc1e597db0bbc0cab0eccb39747b1a9d7e607/compiler/rustc_middle/src/ty/sty.rs:1740:86:
Box<dyn Any>

Backtrace

thread 'rustc' (9080132) panicked at /rustc-dev/b90dc1e597db0bbc0cab0eccb39747b1a9d7e607/compiler/rustc_middle/src/ty/sty.rs:1740:86:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   3: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   4: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   5: rustc_middle::util::bug::bug_fmt
   6: rustc_trait_selection::traits::project::confirm_builtin_candidate
   7: rustc_trait_selection::traits::project::opt_normalize_projection_term
   8: rustc_trait_selection::traits::project::normalize_projection_term
   9: rustc_traits::normalize_projection_ty::normalize_canonicalized_projection
  10: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefaultCache<rustc_type_ir::canonical::CanonicalQueryInput<rustc_middle::ty::context::TyCtxt, rustc_middle::ty::ParamEnvAnd<rustc_type_ir::predicate::AliasTerm<rustc_middle::ty::context::TyCtxt>>>, rustc_middle::query::erase::ErasedData<[u8; 8]>>, false>
  11: <rustc_trait_selection::traits::query::normalize::QueryNormalizer>::try_fold_free_or_assoc
  12: <rustc_trait_selection::traits::query::normalize::QueryNormalizer as rustc_type_ir::fold::FallibleTypeFolder<rustc_middle::ty::context::TyCtxt>>::try_fold_ty
  13: <rustc_traits::normalize_erasing_regions::provide::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::generic_args::GenericArg>)>>::call_once
  14: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefaultCache<rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::generic_args::GenericArg>, rustc_middle::query::erase::ErasedData<[u8; 8]>>, false>
  15: <rustc_middle::ty::normalize_erasing_regions::TryNormalizeAfterErasingRegionsFolder>::try_normalize_generic_arg_after_erasing_regions
  16: <rustc_middle::ty::context::TyCtxt>::try_normalize_erasing_regions::<rustc_middle::ty::Ty>
  17: rustc_ty_utils::layout::layout_of
      [... omitted 1 frame ...]
  18: rustc_ty_utils::layout::layout_of
      [... omitted 1 frame ...]
  19: rustc_hir_analysis::check::check::check_item_type
  20: rustc_hir_analysis::check::wfcheck::check_well_formed
      [... omitted 1 frame ...]
  21: rustc_hir_analysis::check::wfcheck::check_type_wf
      [... omitted 1 frame ...]
  22: rustc_hir_analysis::check_crate
  23: rustc_interface::passes::analysis
  24: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>, false>
  25: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
  26: 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.

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 `/Volumes/T7/workspace/scratch_250918/rustc-ice-2026-03-05T05_18_01-87285.txt` to your bug report

note: rustc 1.96.0-nightly (b90dc1e59 2026-03-04) running on x86_64-apple-darwin

query stack during panic:
#0 [normalize_canonicalized_projection] normalizing `<Foo as core::ptr::metadata::Pointee>::Metadata`
#1 [try_normalize_generic_arg_after_erasing_regions] normalizing `<Foo as core::ptr::metadata::Pointee>::Metadata`
#2 [layout_of] computing layout of `&Foo`
#3 [layout_of] computing layout of `&'static Foo`
#4 [check_well_formed] checking that `FOO2` is well-formed
#5 [check_type_wf] checking that types are well-formed
#6 [analysis] running analysis passes on crate `asdf`
end of query stack
error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0275`.

Regression In

Regression in nightly-2025-07-02

Command: cargo bisect-rustc --start=2025-01-01 --end=2026-03-05 --regress ice --preserve --script rustc -- asdf.rs

Log

searched toolchains nightly-2025-01-01 through nightly-2026-03-05


********************************************************************************
Regression in nightly-2025-07-02
********************************************************************************

fetching https://static.rust-lang.org/dist/2025-07-01/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2025-07-01: 40 B / 40 B [================================================================] 100.00 % 847.05 KB/s converted 2025-07-01 to f26e58023071e71636a3c72ac3a2bf89b1f76706
fetching https://static.rust-lang.org/dist/2025-07-02/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2025-07-02: 40 B / 40 B [================================================================] 100.00 % 921.52 KB/s converted 2025-07-02 to 71e4c005caa812a16fcb08d0bf1e6f1eda7c8381
looking for regression commit between 2025-07-01 and 2025-07-02
fetching (via remote github) commits from max(f26e58023071e71636a3c72ac3a2bf89b1f76706, 2025-06-29) to 71e4c005caa812a16fcb08d0bf1e6f1eda7c8381
ending github query because we found starting sha: f26e58023071e71636a3c72ac3a2bf89b1f76706
get_commits_between returning commits, len: 8
  commit[0] 2025-06-30: Auto merge of #143239 - GuillaumeGomez:subtree-update_cg_gcc_2025-06-30, r=GuillaumeGomez
  commit[1] 2025-06-30: Auto merge of #143254 - matthiaskrgr:rollup-7x8bxek, r=matthiaskrgr
  commit[2] 2025-07-01: Auto merge of #141875 - nnethercote:ByteSymbol, r=petrochenkov
  commit[3] 2025-07-01: Auto merge of #143267 - matthiaskrgr:rollup-suvzar6, r=matthiaskrgr
  commit[4] 2025-07-01: Auto merge of #142921 - JonathanBrouwer:rustc_attributes_parser, r=oli-obk
  commit[5] 2025-07-01: Auto merge of #143013 - bjorn3:split_exported_symbols, r=oli-obk
  commit[6] 2025-07-01: Auto merge of #142030 - oli-obk:wfck-less-hir, r=compiler-errors
  commit[7] 2025-07-01: Auto merge of #143287 - GuillaumeGomez:rollup-fdjcti9, r=GuillaumeGomez
ERROR: no CI builds available between f26e58023071e71636a3c72ac3a2bf89b1f76706 and 71e4c005caa812a16fcb08d0bf1e6f1eda7c8381 within last 167 days

Notes

• ICE location: compiler/rustc_middle/src/ty/sty.rs Line-1740
  

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

  Lines 1736 to 1742 in b90dc1e

  	ty::Infer(ty::TyVar(_))
  	| ty::Pat(..)
  	| ty::Bound(..)
  	| ty::Placeholder(..)
  	| ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => bug!(
  	"`ptr_metadata_ty_or_tail` applied to unexpected type: {self:?} (tail = {tail:?})"
  	),

• Duplication Check:

  • No duplicated ICE reports, when searched with "ptr_metadata_ty_or_tail"

[RaghavenderSingh]

@rustbot claim