ICE: Failed to normalize Alias(Projection, AliasTy...

[rucsesec]

I tried this code:

Code

trait Trait {
    type Assoc;
}

impl Trait for u8 {
    type Assoc = i8;
}

struct Struct<T: Trait> {
    member: T::Assoc,
}

unsafe extern "C" {
    static VAR: Struct<i8>;
}


fn main() {}

Meta

rustc --version --verbose:

rustc 1.92.0-nightly (4068bafed 2025-10-20)
binary: rustc
commit-hash: 4068bafedd8ba724e332a5221c06a6fa531a30d2
commit-date: 2025-10-20
host: x86_64-unknown-linux-gnu
release: 1.92.0-nightly
LLVM version: 21.1.3

I expected to see error: the trait bound i8: Trait is not satisfied.

However, it triggered ICE.(It can also be triggered on the stable version.)

Program Output

error: internal compiler error: compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:171:13: Failed to normalize Alias(Projection, AliasTy { args: [i8], def_id: DefId(0:4 ~ example[cbae]::Trait::Assoc), .. }) in typing_env=TypingEnv { typing_mode: Analysis { defining_opaque_types_and_generators: [] }, param_env: ParamEnv { caller_bounds: [] } }, maybe try to call `try_normalize_erasing_regions` instead


thread 'rustc' (3) panicked at compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:171:13:
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_middle::ty::normalize_erasing_regions::NormalizeAfterErasingRegionsFolder>::normalize_generic_arg_after_erasing_regions
   7: <rustc_middle::ty::context::TyCtxt>::struct_tail_for_codegen
   8: rustc_hir_analysis::check::wfcheck::check_static_item
   9: rustc_hir_analysis::collect::type_of::type_of
      [... omitted 1 frame ...]
  10: rustc_hir_analysis::check::check::check_item_type
  11: rustc_hir_analysis::check::wfcheck::check_well_formed
      [... omitted 1 frame ...]
  12: rustc_hir_analysis::check::wfcheck::check_type_wf
      [... omitted 1 frame ...]
  13: rustc_hir_analysis::check_crate
  14: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
  15: <rustc_interface::passes::create_and_enter_global_ctxt<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  16: 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 `/app/rustc-ice-2025-10-27T03_51_24-1.txt` to your bug report

note: compiler flags: -C debuginfo=2 --crate-type bin -C linker=/opt/compiler-explorer/gcc-15.2.0/bin/gcc

query stack during panic:
#0 [type_of] computing type of `VAR`
#1 [check_well_formed] checking that `` is well-formed
#2 [check_type_wf] checking that types are well-formed
#3 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 1 previous error

[bjorn3]

With the unsafe removed this somehow compiles on rustc 1.30, gives a proper error for 1.31 through 1.37 and starts giving an ICE from 1.38 onwards.

[nikunj-kohli]

I would like to contribute here, I request you to assign me

[Noratrieb]

@nikunj-kohli You've commented this on a lot of different issues, I recommend not try to claim so many at the same time but instead only starting with the next one once you've fixed the first one, to ensure there isn't too much assigned to you. As for how to do it, someone else already linked you the contribution guide on another issue so that should be clear now.