ICE: delegation: unreachable

[matthiaskrgr]

auto-reduced (treereduce-rust):

mod to_reuse { pub fn foo() {} }
struct S< S >;
impl Item for S<S> {
    reuse to_reuse::foo;
}

original:

mod to_reuse { pub fn foo() {} }
struct S< S >;
impl Item for S<S> {
    reuse to_reuse::foo;
}
fn main() {}

Version information

rustc 1.94.0-nightly (07a5b02a2 2025-12-19)
binary: rustc
commit-hash: 07a5b02a2dfa2f1d7fc51b0133d545afc13849dd
commit-date: 2025-12-19
host: x86_64-unknown-linux-gnu
release: 1.94.0-nightly
LLVM version: 21.1.8

Possibly related line of code:

rust/compiler/rustc_hir_analysis/src/delegation.rs

Lines 339 to 351 in 07a5b02

	),
	// For trait impl's `sig_id` is always equal to the corresponding trait method.
	// For inherent methods delegation is not yet supported.
	(FnKind::AssocTraitImpl, _)
	| (_, FnKind::AssocTraitImpl)
	| (_, FnKind::AssocInherentImpl) => unreachable!(),
	}
	}
	pub(crate) fn inherit_predicates_for_delegation_item<'tcx>(
	tcx: TyCtxt<'tcx>,
	def_id: LocalDefId,

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error[E0405]: cannot find trait `Item` in this scope
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Wr4SrHda33Rx/mvce.rs:3:6
  |
3 | impl Item for S<S> {
  |      ^^^^ not found in this scope

error[E0658]: functions delegation is not yet fully implemented
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Wr4SrHda33Rx/mvce.rs:4:5
  |
4 |     reuse to_reuse::foo;
  |     ^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #118212 <https://github.com/rust-lang/rust/issues/118212> for more information
  = help: add `#![feature(fn_delegation)]` to the crate attributes to enable
  = note: this compiler was built on 2025-12-19; consider upgrading it if it is out of date

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Wr4SrHda33Rx/mvce.rs:5:2
  |
5 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Wr4SrHda33Rx/mvce.rs`


thread 'rustc' (658477) panicked at compiler/rustc_hir_analysis/src/delegation.rs:345:45:
internal error: entered unreachable code
stack backtrace:
   0:     0x7f0ed82073b3 - <<std[4c74a2fce9bf2c5f]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[9fe61ba2d6da4b2d]::fmt::Display>::fmt
   1:     0x7f0ed8810648 - core[9fe61ba2d6da4b2d]::fmt::write
   2:     0x7f0ed821db26 - <std[4c74a2fce9bf2c5f]::sys::stdio::unix::Stderr as std[4c74a2fce9bf2c5f]::io::Write>::write_fmt
   3:     0x7f0ed81ddaa8 - std[4c74a2fce9bf2c5f]::panicking::default_hook::{closure#0}
   4:     0x7f0ed81fb223 - std[4c74a2fce9bf2c5f]::panicking::default_hook
   5:     0x7f0ed71e7ed7 - std[4c74a2fce9bf2c5f]::panicking::update_hook::<alloc[74f421483eb98d63]::boxed::Box<rustc_driver_impl[a2c782fc25686226]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f0ed81fb502 - std[4c74a2fce9bf2c5f]::panicking::panic_with_hook
   7:     0x7f0ed81ddb9a - std[4c74a2fce9bf2c5f]::panicking::panic_handler::{closure#0}
   8:     0x7f0ed81d2369 - std[4c74a2fce9bf2c5f]::sys::backtrace::__rust_end_short_backtrace::<std[4c74a2fce9bf2c5f]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f0ed81df71d - __rustc[b4174ff09eddacad]::rust_begin_unwind
  10:     0x7f0ed527358c - core[9fe61ba2d6da4b2d]::panicking::panic_fmt
  11:     0x7f0ed49a6c72 - core[9fe61ba2d6da4b2d]::panicking::panic
  12:     0x7f0ed9055639 - rustc_hir_analysis[23d422958f87a7df]::collect::generics_of::generics_of
  13:     0x7f0ed8818529 - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::generics_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 8usize]>>
  14:     0x7f0ed8818c06 - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_query_system[864220176bb95b8e]::query::caches::DefIdCache<rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  15:     0x7f0ed881892b - rustc_query_impl[a0a98bf419192c37]::query_impl::generics_of::get_query_non_incr::__rust_end_short_backtrace
  16:     0x7f0ed55d66f8 - rustc_hir_analysis[23d422958f87a7df]::variance::crate_variances
  17:     0x7f0ed99b5faa - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::crate_variances::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 8usize]>>
  18:     0x7f0ed99b55dd - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_query_system[864220176bb95b8e]::query::caches::SingleCache<rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  19:     0x7f0ed99b4cc0 - rustc_query_impl[a0a98bf419192c37]::query_impl::crate_variances::get_query_non_incr::__rust_end_short_backtrace
  20:     0x7f0ed9f27ad2 - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::variances_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 16usize]>>.warm
  21:     0x7f0ed88f0dd1 - <rustc_query_impl[a0a98bf419192c37]::query_impl::variances_of::dynamic_query::{closure#2} as core[9fe61ba2d6da4b2d]::ops::function::FnOnce<(rustc_middle[3d58750448771592]::ty::context::TyCtxt, rustc_span[e672eaeb0cbdeb6f]::def_id::DefId)>>::call_once
  22:     0x7f0ed88ef3a1 - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_query_system[864220176bb95b8e]::query::caches::DefIdCache<rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  23:     0x7f0ed88eeef2 - rustc_query_impl[a0a98bf419192c37]::query_impl::variances_of::get_query_non_incr::__rust_end_short_backtrace
  24:     0x7f0ed9058a85 - rustc_hir_analysis[23d422958f87a7df]::check::wfcheck::check_variances_for_type_defn
  25:     0x7f0ed8f2472f - rustc_hir_analysis[23d422958f87a7df]::check::check::check_item_type
  26:     0x7f0ed8f1f036 - rustc_hir_analysis[23d422958f87a7df]::check::wfcheck::check_well_formed
  27:     0x7f0ed8f1f017 - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 1usize]>>
  28:     0x7f0ed8f1e88d - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_data_structures[e44aecb238e9f44f]::vec_cache::VecCache<rustc_span[e672eaeb0cbdeb6f]::def_id::LocalDefId, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[864220176bb95b8e]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  29:     0x7f0ed8f1e396 - rustc_query_impl[a0a98bf419192c37]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  30:     0x7f0ed8f1bb30 - rustc_hir_analysis[23d422958f87a7df]::check::wfcheck::check_type_wf
  31:     0x7f0ed8f1ba1d - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::check_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 1usize]>>
  32:     0x7f0ed99b2e54 - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_query_system[864220176bb95b8e]::query::caches::SingleCache<rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  33:     0x7f0ed99b2c36 - rustc_query_impl[a0a98bf419192c37]::query_impl::check_type_wf::get_query_non_incr::__rust_end_short_backtrace
  34:     0x7f0ed9304518 - rustc_hir_analysis[23d422958f87a7df]::check_crate
  35:     0x7f0ed8b93d1b - rustc_interface[d43cea5cb0259171]::passes::analysis
  36:     0x7f0ed8b93965 - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 0usize]>>
  37:     0x7f0ed99b4626 - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_query_system[864220176bb95b8e]::query::caches::SingleCache<rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  38:     0x7f0ed99b41f6 - rustc_query_impl[a0a98bf419192c37]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  39:     0x7f0ed9b7fed4 - <rustc_interface[d43cea5cb0259171]::passes::create_and_enter_global_ctxt<core[9fe61ba2d6da4b2d]::option::Option<rustc_interface[d43cea5cb0259171]::queries::Linker>, rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[9fe61ba2d6da4b2d]::ops::function::FnOnce<(&rustc_session[cb9669c7b5ad4b36]::session::Session, rustc_middle[3d58750448771592]::ty::context::CurrentGcx, alloc[74f421483eb98d63]::sync::Arc<rustc_data_structures[e44aecb238e9f44f]::jobserver::Proxy>, &std[4c74a2fce9bf2c5f]::sync::once_lock::OnceLock<rustc_middle[3d58750448771592]::ty::context::GlobalCtxt>, &rustc_data_structures[e44aecb238e9f44f]::sync::worker_local::WorkerLocal<rustc_middle[3d58750448771592]::arena::Arena>, &rustc_data_structures[e44aecb238e9f44f]::sync::worker_local::WorkerLocal<rustc_hir[4ee98cbafbf8416b]::Arena>, rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  40:     0x7f0ed98fd01a - rustc_interface[d43cea5cb0259171]::interface::run_compiler::<(), rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}>::{closure#1}
  41:     0x7f0ed98e7f4e - std[4c74a2fce9bf2c5f]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[d43cea5cb0259171]::util::run_in_thread_with_globals<rustc_interface[d43cea5cb0259171]::util::run_in_thread_pool_with_globals<rustc_interface[d43cea5cb0259171]::interface::run_compiler<(), rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  42:     0x7f0ed98e7d20 - <std[4c74a2fce9bf2c5f]::thread::lifecycle::spawn_unchecked<rustc_interface[d43cea5cb0259171]::util::run_in_thread_with_globals<rustc_interface[d43cea5cb0259171]::util::run_in_thread_pool_with_globals<rustc_interface[d43cea5cb0259171]::interface::run_compiler<(), rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[9fe61ba2d6da4b2d]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  43:     0x7f0ed98e60f8 - <std[4c74a2fce9bf2c5f]::sys::thread::unix::Thread>::new::thread_start
  44:     0x7f0ed329698b - <unknown>
  45:     0x7f0ed331a9cc - <unknown>
  46:                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: rustc 1.94.0-nightly (07a5b02a2 2025-12-19) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [generics_of] computing generics of `<impl at /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Wr4SrHda33Rx/mvce.rs:3:1: 3:19>::foo`
#1 [crate_variances] computing the variances for items in this crate
#2 [variances_of] computing the variances of `S`
#3 [check_well_formed] checking that `S` is well-formed
#4 [check_type_wf] checking that types are well-formed
#5 [analysis] running analysis passes on crate `mvce`
end of query stack
error[E0107]: missing generics for struct `S`
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Wr4SrHda33Rx/mvce.rs:3:17
  |
3 | impl Item for S<S> {
  |                 ^ expected 1 generic argument
  |
note: struct defined here, with 1 generic parameter: `S`
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Wr4SrHda33Rx/mvce.rs:2:8
  |
2 | struct S< S >;
  |        ^  -
help: add missing generic argument
  |
3 | impl Item for S<S<S>> {
  |                  +++

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0107, E0405, E0601, E0658.
For more information about an error, try `rustc --explain E0107`.

[matthiaskrgr]

hitting the same unreachable although with different stacktrace:

auto-reduced (treereduce-rust):

trait Trait {
    reuse to_reuse::foo;
}
mod to_reuse {
    fn foo() {}
}
impl Trait for S {
    reuse foo;
}

original:

trait Trait {
    reuse to_reuse::foo;
}
mod to_reuse {
    fn foo() {}
}
impl Trait for S {
    reuse foo;
}

fn main() {}

Version information

rustc 1.94.0-nightly (07a5b02a2 2025-12-19)
binary: rustc
commit-hash: 07a5b02a2dfa2f1d7fc51b0133d545afc13849dd
commit-date: 2025-12-19
host: x86_64-unknown-linux-gnu
release: 1.94.0-nightly
LLVM version: 21.1.8

Possibly related line of code:

rust/compiler/rustc_hir_analysis/src/delegation.rs

Lines 339 to 351 in 07a5b02

	),
	// For trait impl's `sig_id` is always equal to the corresponding trait method.
	// For inherent methods delegation is not yet supported.
	(FnKind::AssocTraitImpl, _)
	| (_, FnKind::AssocTraitImpl)
	| (_, FnKind::AssocInherentImpl) => unreachable!(),
	}
	}
	pub(crate) fn inherit_predicates_for_delegation_item<'tcx>(
	tcx: TyCtxt<'tcx>,
	def_id: LocalDefId,

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error[E0425]: cannot find type `S` in this scope
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:7:16
  |
7 | impl Trait for S {
  |                ^ not found in this scope

error[E0425]: cannot find function `foo` in this scope
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:8:11
  |
8 |     reuse foo;
  |           ^^^ not found in this scope
  |
note: function `to_reuse::foo` exists but is inaccessible
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:5:5
  |
5 |     fn foo() {}
  |     ^^^^^^^^ not accessible

error[E0603]: function `foo` is private
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:2:21
  |
2 |     reuse to_reuse::foo;
  |                     ^^^ private function
  |
note: the function `foo` is defined here
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:5:5
  |
5 |     fn foo() {}
  |     ^^^^^^^^

error[E0658]: functions delegation is not yet fully implemented
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:2:5
  |
2 |     reuse to_reuse::foo;
  |     ^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #118212 <https://github.com/rust-lang/rust/issues/118212> for more information
  = help: add `#![feature(fn_delegation)]` to the crate attributes to enable
  = note: this compiler was built on 2025-12-19; consider upgrading it if it is out of date

error[E0658]: functions delegation is not yet fully implemented
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:8:5
  |
8 |     reuse foo;
  |     ^^^^^^^^^^
  |
  = note: see issue #118212 <https://github.com/rust-lang/rust/issues/118212> for more information
  = help: add `#![feature(fn_delegation)]` to the crate attributes to enable
  = note: this compiler was built on 2025-12-19; consider upgrading it if it is out of date

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:9:2
  |
9 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs`


thread 'rustc' (658478) panicked at compiler/rustc_hir_analysis/src/delegation.rs:345:45:
internal error: entered unreachable code
stack backtrace:
   0:     0x7f68ff6073b3 - <<std[4c74a2fce9bf2c5f]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[9fe61ba2d6da4b2d]::fmt::Display>::fmt
   1:     0x7f68ffc10648 - core[9fe61ba2d6da4b2d]::fmt::write
   2:     0x7f68ff61db26 - <std[4c74a2fce9bf2c5f]::sys::stdio::unix::Stderr as std[4c74a2fce9bf2c5f]::io::Write>::write_fmt
   3:     0x7f68ff5ddaa8 - std[4c74a2fce9bf2c5f]::panicking::default_hook::{closure#0}
   4:     0x7f68ff5fb223 - std[4c74a2fce9bf2c5f]::panicking::default_hook
   5:     0x7f68fe5e7ed7 - std[4c74a2fce9bf2c5f]::panicking::update_hook::<alloc[74f421483eb98d63]::boxed::Box<rustc_driver_impl[a2c782fc25686226]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f68ff5fb502 - std[4c74a2fce9bf2c5f]::panicking::panic_with_hook
   7:     0x7f68ff5ddb9a - std[4c74a2fce9bf2c5f]::panicking::panic_handler::{closure#0}
   8:     0x7f68ff5d2369 - std[4c74a2fce9bf2c5f]::sys::backtrace::__rust_end_short_backtrace::<std[4c74a2fce9bf2c5f]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f68ff5df71d - __rustc[b4174ff09eddacad]::rust_begin_unwind
  10:     0x7f68fc67358c - core[9fe61ba2d6da4b2d]::panicking::panic_fmt
  11:     0x7f68fbda6c72 - core[9fe61ba2d6da4b2d]::panicking::panic
  12:     0x7f6900455639 - rustc_hir_analysis[23d422958f87a7df]::collect::generics_of::generics_of
  13:     0x7f68ffc18529 - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::generics_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 8usize]>>
  14:     0x7f68ffc18c06 - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_query_system[864220176bb95b8e]::query::caches::DefIdCache<rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  15:     0x7f68ffc1892b - rustc_query_impl[a0a98bf419192c37]::query_impl::generics_of::get_query_non_incr::__rust_end_short_backtrace
  16:     0x7f6900320715 - rustc_hir_analysis[23d422958f87a7df]::check::check::check_item_type
  17:     0x7f690031f036 - rustc_hir_analysis[23d422958f87a7df]::check::wfcheck::check_well_formed
  18:     0x7f690031f017 - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 1usize]>>
  19:     0x7f690031e88d - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_data_structures[e44aecb238e9f44f]::vec_cache::VecCache<rustc_span[e672eaeb0cbdeb6f]::def_id::LocalDefId, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[864220176bb95b8e]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  20:     0x7f690031e396 - rustc_query_impl[a0a98bf419192c37]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  21:     0x7f690031bb48 - rustc_hir_analysis[23d422958f87a7df]::check::wfcheck::check_type_wf
  22:     0x7f690031ba1d - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::check_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 1usize]>>
  23:     0x7f6900db2e54 - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_query_system[864220176bb95b8e]::query::caches::SingleCache<rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  24:     0x7f6900db2c36 - rustc_query_impl[a0a98bf419192c37]::query_impl::check_type_wf::get_query_non_incr::__rust_end_short_backtrace
  25:     0x7f6900704518 - rustc_hir_analysis[23d422958f87a7df]::check_crate
  26:     0x7f68fff93d1b - rustc_interface[d43cea5cb0259171]::passes::analysis
  27:     0x7f68fff93965 - rustc_query_impl[a0a98bf419192c37]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a0a98bf419192c37]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 0usize]>>
  28:     0x7f6900db4626 - rustc_query_system[864220176bb95b8e]::query::plumbing::try_execute_query::<rustc_query_impl[a0a98bf419192c37]::DynamicConfig<rustc_query_system[864220176bb95b8e]::query::caches::SingleCache<rustc_middle[3d58750448771592]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[a0a98bf419192c37]::plumbing::QueryCtxt, false>
  29:     0x7f6900db41f6 - rustc_query_impl[a0a98bf419192c37]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  30:     0x7f6900f7fed4 - <rustc_interface[d43cea5cb0259171]::passes::create_and_enter_global_ctxt<core[9fe61ba2d6da4b2d]::option::Option<rustc_interface[d43cea5cb0259171]::queries::Linker>, rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[9fe61ba2d6da4b2d]::ops::function::FnOnce<(&rustc_session[cb9669c7b5ad4b36]::session::Session, rustc_middle[3d58750448771592]::ty::context::CurrentGcx, alloc[74f421483eb98d63]::sync::Arc<rustc_data_structures[e44aecb238e9f44f]::jobserver::Proxy>, &std[4c74a2fce9bf2c5f]::sync::once_lock::OnceLock<rustc_middle[3d58750448771592]::ty::context::GlobalCtxt>, &rustc_data_structures[e44aecb238e9f44f]::sync::worker_local::WorkerLocal<rustc_middle[3d58750448771592]::arena::Arena>, &rustc_data_structures[e44aecb238e9f44f]::sync::worker_local::WorkerLocal<rustc_hir[4ee98cbafbf8416b]::Arena>, rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  31:     0x7f6900cfd01a - rustc_interface[d43cea5cb0259171]::interface::run_compiler::<(), rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}>::{closure#1}
  32:     0x7f6900ce7f4e - std[4c74a2fce9bf2c5f]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[d43cea5cb0259171]::util::run_in_thread_with_globals<rustc_interface[d43cea5cb0259171]::util::run_in_thread_pool_with_globals<rustc_interface[d43cea5cb0259171]::interface::run_compiler<(), rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  33:     0x7f6900ce7d20 - <std[4c74a2fce9bf2c5f]::thread::lifecycle::spawn_unchecked<rustc_interface[d43cea5cb0259171]::util::run_in_thread_with_globals<rustc_interface[d43cea5cb0259171]::util::run_in_thread_pool_with_globals<rustc_interface[d43cea5cb0259171]::interface::run_compiler<(), rustc_driver_impl[a2c782fc25686226]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[9fe61ba2d6da4b2d]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  34:     0x7f6900ce60f8 - <std[4c74a2fce9bf2c5f]::sys::thread::unix::Thread>::new::thread_start
  35:     0x7f68fa69698b - <unknown>
  36:     0x7f68fa71a9cc - <unknown>
  37:                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: rustc 1.94.0-nightly (07a5b02a2 2025-12-19) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [generics_of] computing generics of `<impl at /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:7:1: 7:17>::foo`
#1 [check_well_formed] checking that `<impl at /tmp/icemaker_global_tempdir.knj0uoUcipRR/rustc_testrunner_tmpdir_reporting.Dnh4sDRgjKmR/mvce.rs:7:1: 7:17>::foo` is well-formed
#2 [check_type_wf] checking that types are well-formed
#3 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 6 previous errors

Some errors have detailed explanations: E0425, E0601, E0603, E0658.
For more information about an error, try `rustc --explain E0425`.

[matthiaskrgr]

both of these bisect to #150024

[petrochenkov]

cc @aerooneqq