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[ICE]: `type variables should not be hashed: ?0t`

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C-bug F-transmutability F-unboxed_closures I-ICE T-compiler WG-trait-system-refactor
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Rust
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Description

Code

rustc code.rs -Znext-solver=globally --edition=2021

#![feature(transmutability)]
#![feature(unboxed_closures)]
fn main() {
   &async {} as &dyn Service;
}
impl<T: std::mem::TransmuteFrom()> Service for T {}
trait Service {}
Meta

rustc --version --verbose:

rustc 1.94.0-nightly (fe98ddcfc 2026-01-17)
binary: rustc
commit-hash: fe98ddcfcfb6f185dbf4adeaf439d8a756da0273
commit-date: 2026-01-17
host: x86_64-unknown-linux-gnu
release: 1.94.0-nightly
LLVM version: 21.1.8
Error output
error[E0220]: associated type `Output` not found for `TransmuteFrom`
 --> code.rs:6:19
  |
6 | impl<T: std::mem::TransmuteFrom()> Service for T {}
  |                   ^^^^^^^^^^^^^^^ associated type `Output` not found
Backtrace 

thread 'rustc' (2187337) panicked at /rustc-dev/fe98ddcfcfb6f185dbf4adeaf439d8a756da0273/compiler/rustc_type_ir/src/ty_kind.rs:680:17:
type variables should not be hashed: ?0t
stack backtrace:
   0:     0x7f1170642f93 - <<std[7637d35b2e73f491]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[e59341b65d367131]::fmt::Display>::fmt
   1:     0x7f1170c0e2c8 - core[e59341b65d367131]::fmt::write
   2:     0x7f1170659986 - <std[7637d35b2e73f491]::sys::stdio::unix::Stderr as std[7637d35b2e73f491]::io::Write>::write_fmt
   3:     0x7f1170619008 - std[7637d35b2e73f491]::panicking::default_hook::{closure#0}
   4:     0x7f11706366c3 - std[7637d35b2e73f491]::panicking::default_hook
   5:     0x7f116f60b7fa - std[7637d35b2e73f491]::panicking::update_hook::<alloc[e4cd1c42012959c4]::boxed::Box<rustc_driver_impl[1a3eae45778b1a3a]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f11706369a2 - std[7637d35b2e73f491]::panicking::panic_with_hook
   7:     0x7f11706190c8 - std[7637d35b2e73f491]::panicking::panic_handler::{closure#0}
   8:     0x7f117060d579 - std[7637d35b2e73f491]::sys::backtrace::__rust_end_short_backtrace::<std[7637d35b2e73f491]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f117061ab9d - __rustc[f6c708c0d8e4bdd6]::rust_begin_unwind
  10:     0x7f116d8e91fc - core[e59341b65d367131]::panicking::panic_fmt
  11:     0x7f117135b12a - <rustc_type_ir[a44b4988878e9ab6]::ty_kind::TyKind<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt> as rustc_data_structures[ab77da159d78a1fb]::stable_hasher::HashStable<rustc_query_system[11b36a7129bd2e9f]::ich::hcx::StableHashingContext>>::hash_stable
  12:     0x7f1171354b52 - <rustc_middle[f49c2f37af7e8c7e]::ty::generic_args::GenericArg as rustc_data_structures[ab77da159d78a1fb]::stable_hasher::HashStable<rustc_query_system[11b36a7129bd2e9f]::ich::hcx::StableHashingContext>>::hash_stable
  13:     0x7f11713543f6 - <&rustc_middle[f49c2f37af7e8c7e]::ty::list::RawList<(), rustc_middle[f49c2f37af7e8c7e]::ty::generic_args::GenericArg> as rustc_data_structures[ab77da159d78a1fb]::stable_hasher::HashStable<rustc_query_system[11b36a7129bd2e9f]::ich::hcx::StableHashingContext>>::hash_stable
  14:     0x7f1170ceec00 - <rustc_type_ir[a44b4988878e9ab6]::ty_info::WithCachedTypeInfo<rustc_type_ir[a44b4988878e9ab6]::ty_kind::TyKind<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>> as rustc_data_structures[ab77da159d78a1fb]::stable_hasher::HashStable<rustc_query_system[11b36a7129bd2e9f]::ich::hcx::StableHashingContext>>::hash_stable
  15:     0x7f117001fcbd - rustc_query_impl[f993d76296ac3ede]::plumbing::create_query_frame::<rustc_middle[f49c2f37af7e8c7e]::ty::PseudoCanonicalInput<rustc_middle[f49c2f37af7e8c7e]::ty::Ty>>
  16:     0x7f117013f9a0 - <rustc_query_impl[f993d76296ac3ede]::query_impl::layout_of::collect_active_jobs::{closure#0} as core[e59341b65d367131]::ops::function::FnOnce<(rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt, rustc_middle[f49c2f37af7e8c7e]::ty::PseudoCanonicalInput<rustc_middle[f49c2f37af7e8c7e]::ty::Ty>)>>::call_once
  17:     0x7f1170002302 - <rustc_query_system[11b36a7129bd2e9f]::query::plumbing::QueryState<rustc_middle[f49c2f37af7e8c7e]::ty::PseudoCanonicalInput<rustc_middle[f49c2f37af7e8c7e]::ty::Ty>>>::collect_active_jobs::<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>
  18:     0x7f11700aa7c1 - rustc_query_impl[f993d76296ac3ede]::query_impl::layout_of::collect_active_jobs
  19:     0x7f11700be46f - <rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt as rustc_query_system[11b36a7129bd2e9f]::query::QueryContext>::collect_active_jobs
  20:     0x7f11700257a3 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::cycle_error::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_query_system[11b36a7129bd2e9f]::query::caches::DefaultCache<rustc_type_ir[a44b4988878e9ab6]::canonical::CanonicalQueryInput<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt, rustc_middle[f49c2f37af7e8c7e]::ty::ParamEnvAnd<rustc_middle[f49c2f37af7e8c7e]::traits::query::type_op::Normalize<rustc_middle[f49c2f37af7e8c7e]::ty::Ty>>>, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt>
  21:     0x7f1170d6f27c - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_data_structures[ab77da159d78a1fb]::vec_cache::VecCache<rustc_span[d2f47af3535269a]::def_id::LocalDefId, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[11b36a7129bd2e9f]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  22:     0x7f1170d6e589 - rustc_query_impl[f993d76296ac3ede]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  23:     0x7f1171987c71 - rustc_hir_typeck[cda3b2c1a48d49f5]::typeck_with_inspect::{closure#0}
  24:     0x7f117197b674 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>
  25:     0x7f1170d6ecaa - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_data_structures[ab77da159d78a1fb]::vec_cache::VecCache<rustc_span[d2f47af3535269a]::def_id::LocalDefId, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[11b36a7129bd2e9f]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  26:     0x7f1170d6e589 - rustc_query_impl[f993d76296ac3ede]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  27:     0x7f1171126cf6 - rustc_mir_build[916b7e25050224b]::thir::pattern::check_match::check_match
  28:     0x7f117112609f - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::check_match::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 1usize]>>
  29:     0x7f117137b4f8 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_data_structures[ab77da159d78a1fb]::vec_cache::VecCache<rustc_span[d2f47af3535269a]::def_id::LocalDefId, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[11b36a7129bd2e9f]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  30:     0x7f117137b1bd - rustc_query_impl[f993d76296ac3ede]::query_impl::check_match::get_query_non_incr::__rust_end_short_backtrace
  31:     0x7f11711022eb - rustc_mir_build[916b7e25050224b]::builder::build_mir_inner_impl
  32:     0x7f1170c08dea - rustc_mir_transform[8e6f1eb7ff0fdc6d]::mir_built
  33:     0x7f1170c08db3 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::mir_built::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>
  34:     0x7f1170d6ecaa - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_data_structures[ab77da159d78a1fb]::vec_cache::VecCache<rustc_span[d2f47af3535269a]::def_id::LocalDefId, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[11b36a7129bd2e9f]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  35:     0x7f1170d6e709 - rustc_query_impl[f993d76296ac3ede]::query_impl::mir_built::get_query_non_incr::__rust_end_short_backtrace
  36:     0x7f1170c4f797 - rustc_mir_transform[8e6f1eb7ff0fdc6d]::ffi_unwind_calls::has_ffi_unwind_calls
  37:     0x7f1170c4f1a9 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::has_ffi_unwind_calls::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 1usize]>>
  38:     0x7f117137b4f8 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_data_structures[ab77da159d78a1fb]::vec_cache::VecCache<rustc_span[d2f47af3535269a]::def_id::LocalDefId, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[11b36a7129bd2e9f]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  39:     0x7f117137b07d - rustc_query_impl[f993d76296ac3ede]::query_impl::has_ffi_unwind_calls::get_query_non_incr::__rust_end_short_backtrace
  40:     0x7f117190eda9 - rustc_mir_transform[8e6f1eb7ff0fdc6d]::mir_promoted
  41:     0x7f117190ebd2 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::mir_promoted::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 16usize]>>
  42:     0x7f117165bcb5 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_data_structures[ab77da159d78a1fb]::vec_cache::VecCache<rustc_span[d2f47af3535269a]::def_id::LocalDefId, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 16usize]>, rustc_query_system[11b36a7129bd2e9f]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  43:     0x7f117165b84c - rustc_query_impl[f993d76296ac3ede]::query_impl::mir_promoted::get_query_non_incr::__rust_end_short_backtrace
  44:     0x7f1171fb50bf - rustc_mir_transform[8e6f1eb7ff0fdc6d]::coroutine::mir_coroutine_witnesses
  45:     0x7f1171fb4a27 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::mir_coroutine_witnesses::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>
  46:     0x7f1170c17c45 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_query_system[11b36a7129bd2e9f]::query::caches::DefIdCache<rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  47:     0x7f11722cc1b4 - rustc_query_impl[f993d76296ac3ede]::query_impl::mir_coroutine_witnesses::get_query_non_incr::__rust_end_short_backtrace
  48:     0x7f11719736a5 - rustc_mir_transform[8e6f1eb7ff0fdc6d]::mir_drops_elaborated_and_const_checked
  49:     0x7f11719727d9 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::mir_drops_elaborated_and_const_checked::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>
  50:     0x7f1170d6ecaa - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_data_structures[ab77da159d78a1fb]::vec_cache::VecCache<rustc_span[d2f47af3535269a]::def_id::LocalDefId, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[11b36a7129bd2e9f]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  51:     0x7f1170d6e34d - rustc_query_impl[f993d76296ac3ede]::query_impl::mir_drops_elaborated_and_const_checked::get_query_non_incr::__rust_end_short_backtrace
  52:     0x7f1170fe2f16 - rustc_mir_transform[8e6f1eb7ff0fdc6d]::optimized_mir
  53:     0x7f1170fe29af - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>
  54:     0x7f1170c17c45 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_query_system[11b36a7129bd2e9f]::query::caches::DefIdCache<rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  55:     0x7f1170c1721b - rustc_query_impl[f993d76296ac3ede]::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace
  56:     0x7f1171eee441 - <rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>::coroutine_layout
  57:     0x7f117157f535 - rustc_ty_utils[f823f1d5efade7eb]::layout::layout_of_uncached
  58:     0x7f1171574589 - rustc_ty_utils[f823f1d5efade7eb]::layout::layout_of
  59:     0x7f11715744f0 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 16usize]>>
  60:     0x7f11715735d7 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_query_system[11b36a7129bd2e9f]::query::caches::DefaultCache<rustc_middle[f49c2f37af7e8c7e]::ty::PseudoCanonicalInput<rustc_middle[f49c2f37af7e8c7e]::ty::Ty>, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  61:     0x7f11715731f4 - rustc_query_impl[f993d76296ac3ede]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
  62:     0x7f117055f028 - rustc_transmute[a79904f2c7e85e92]::layout::rustc::layout_of
  63:     0x7f117055d0a2 - <rustc_transmute[a79904f2c7e85e92]::layout::tree::Tree<rustc_transmute[a79904f2c7e85e92]::layout::rustc::Def, rustc_middle[f49c2f37af7e8c7e]::ty::region::Region, rustc_middle[f49c2f37af7e8c7e]::ty::Ty>>::from_ty
  64:     0x7f1170556d84 - <rustc_transmute[a79904f2c7e85e92]::rustc::TransmuteTypeEnv>::is_transmutable
  65:     0x7f117048a775 - <rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate as rustc_next_trait_solver[170a8c4b65e982f7]::delegate::SolverDelegate>::is_transmutable
  66:     0x7f117047be7f - <rustc_type_ir[a44b4988878e9ab6]::predicate::TraitPredicate<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt> as rustc_next_trait_solver[170a8c4b65e982f7]::solve::assembly::GoalKind<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::consider_builtin_transmute_candidate
  67:     0x7f1171abfc20 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::assemble_builtin_impl_candidates::<rustc_type_ir[a44b4988878e9ab6]::predicate::TraitPredicate<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>
  68:     0x7f1171ab157e - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::compute_trait_goal
  69:     0x7f117183044f - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate> as rustc_type_ir[a44b4988878e9ab6]::search_graph::Delegate>::compute_goal::{closure#0}
  70:     0x7f117184705a - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::evaluate_goal_raw
  71:     0x7f1171836bf4 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::try_evaluate_added_goals
  72:     0x7f1171829e0f - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::evaluate_added_goals_and_make_canonical_response
  73:     0x7f1171aadcb4 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::assemble_impl_candidates::<rustc_type_ir[a44b4988878e9ab6]::predicate::TraitPredicate<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::{closure#0}
  74:     0x7f1171ab2768 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::compute_trait_goal
  75:     0x7f117183044f - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate> as rustc_type_ir[a44b4988878e9ab6]::search_graph::Delegate>::compute_goal::{closure#0}
  76:     0x7f117184705a - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::evaluate_goal_raw
  77:     0x7f1171836bf4 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::try_evaluate_added_goals
  78:     0x7f1171829e0f - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::evaluate_added_goals_and_make_canonical_response
  79:     0x7f1171abe476 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::assemble_builtin_impl_candidates::<rustc_type_ir[a44b4988878e9ab6]::predicate::TraitPredicate<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>
  80:     0x7f1171ab157e - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::compute_trait_goal
  81:     0x7f117183044f - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate> as rustc_type_ir[a44b4988878e9ab6]::search_graph::Delegate>::compute_goal::{closure#0}
  82:     0x7f117184705a - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::evaluate_goal_raw
  83:     0x7f1171836bf4 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::try_evaluate_added_goals
  84:     0x7f1171829e0f - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::evaluate_added_goals_and_make_canonical_response
  85:     0x7f1171aadcb4 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::assemble_impl_candidates::<rustc_type_ir[a44b4988878e9ab6]::predicate::TraitPredicate<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::{closure#0}
  86:     0x7f1171ab2384 - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::compute_trait_goal
  87:     0x7f117183044f - <rustc_next_trait_solver[170a8c4b65e982f7]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate> as rustc_type_ir[a44b4988878e9ab6]::search_graph::Delegate>::compute_goal::{closure#0}
  88:     0x7f117182ed97 - <rustc_type_ir[a44b4988878e9ab6]::search_graph::SearchGraph<rustc_next_trait_solver[170a8c4b65e982f7]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate>, rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>>::evaluate_goal_in_task
  89:     0x7f117182e891 - rustc_trait_selection[ea11fdd225b236a7]::solve::evaluate_root_goal_for_proof_tree_raw
  90:     0x7f117182e6bf - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::evaluate_root_goal_for_proof_tree_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 48usize]>>
  91:     0x7f117182e677 - <rustc_query_impl[f993d76296ac3ede]::query_impl::evaluate_root_goal_for_proof_tree_raw::dynamic_query::{closure#2} as core[e59341b65d367131]::ops::function::FnOnce<(rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt, rustc_type_ir[a44b4988878e9ab6]::canonical::CanonicalQueryInput<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt, rustc_type_ir[a44b4988878e9ab6]::solve::QueryInput<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt, rustc_middle[f49c2f37af7e8c7e]::ty::predicate::Predicate>>)>>::call_once
  92:     0x7f1171817d21 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_query_system[11b36a7129bd2e9f]::query::caches::DefaultCache<rustc_type_ir[a44b4988878e9ab6]::canonical::CanonicalQueryInput<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt, rustc_type_ir[a44b4988878e9ab6]::solve::QueryInput<rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt, rustc_middle[f49c2f37af7e8c7e]::ty::predicate::Predicate>>, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 48usize]>>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
  93:     0x7f117181a3c2 - rustc_query_impl[f993d76296ac3ede]::query_impl::evaluate_root_goal_for_proof_tree_raw::get_query_non_incr::__rust_end_short_backtrace
  94:     0x7f117181a2c1 - <rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt as rustc_type_ir[a44b4988878e9ab6]::interner::Interner>::evaluate_root_goal_for_proof_tree_raw
  95:     0x7f1171819b83 - <rustc_trait_selection[ea11fdd225b236a7]::solve::delegate::SolverDelegate as rustc_next_trait_solver[170a8c4b65e982f7]::solve::eval_ctxt::SolverDelegateEvalExt>::evaluate_root_goal_for_proof_tree
  96:     0x7f1170ca6ac2 - <rustc_hir_typeck[cda3b2c1a48d49f5]::fn_ctxt::FnCtxt>::coerce
  97:     0x7f117197fee2 - rustc_hir_typeck[cda3b2c1a48d49f5]::typeck_with_inspect::{closure#0}
  98:     0x7f117197b674 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>>
  99:     0x7f1170d6ecaa - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_data_structures[ab77da159d78a1fb]::vec_cache::VecCache<rustc_span[d2f47af3535269a]::def_id::LocalDefId, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[11b36a7129bd2e9f]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
 100:     0x7f1170d6e589 - rustc_query_impl[f993d76296ac3ede]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
 101:     0x7f1171414d35 - <rustc_middle[f49c2f37af7e8c7e]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis[5017dacce67ac1a4]::check_crate::{closure#2}>::{closure#0}
 102:     0x7f1171414744 - rustc_hir_analysis[5017dacce67ac1a4]::check_crate
 103:     0x7f1170d62e5b - rustc_interface[70956b6af7f02b7a]::passes::analysis
 104:     0x7f1170d62ab5 - rustc_query_impl[f993d76296ac3ede]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f993d76296ac3ede]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 0usize]>>
 105:     0x7f1171df9e23 - rustc_query_system[11b36a7129bd2e9f]::query::plumbing::try_execute_query::<rustc_query_impl[f993d76296ac3ede]::DynamicConfig<rustc_query_system[11b36a7129bd2e9f]::query::caches::SingleCache<rustc_middle[f49c2f37af7e8c7e]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[f993d76296ac3ede]::plumbing::QueryCtxt, false>
 106:     0x7f1171df9c0e - rustc_query_impl[f993d76296ac3ede]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
 107:     0x7f1171e17dd1 - <rustc_interface[70956b6af7f02b7a]::passes::create_and_enter_global_ctxt<core[e59341b65d367131]::option::Option<rustc_interface[70956b6af7f02b7a]::queries::Linker>, rustc_driver_impl[1a3eae45778b1a3a]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[e59341b65d367131]::ops::function::FnOnce<(&rustc_session[ef90395b1d579b60]::session::Session, rustc_middle[f49c2f37af7e8c7e]::ty::context::CurrentGcx, alloc[e4cd1c42012959c4]::sync::Arc<rustc_data_structures[ab77da159d78a1fb]::jobserver::Proxy>, &std[7637d35b2e73f491]::sync::once_lock::OnceLock<rustc_middle[f49c2f37af7e8c7e]::ty::context::GlobalCtxt>, &rustc_data_structures[ab77da159d78a1fb]::sync::worker_local::WorkerLocal<rustc_middle[f49c2f37af7e8c7e]::arena::Arena>, &rustc_data_structures[ab77da159d78a1fb]::sync::worker_local::WorkerLocal<rustc_hir[78cba43770fa9cc1]::Arena>, rustc_driver_impl[1a3eae45778b1a3a]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
 108:     0x7f1171d98cf4 - rustc_interface[70956b6af7f02b7a]::interface::run_compiler::<(), rustc_driver_impl[1a3eae45778b1a3a]::run_compiler::{closure#0}>::{closure#1}
 109:     0x7f1171d35dba - std[7637d35b2e73f491]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[70956b6af7f02b7a]::util::run_in_thread_with_globals<rustc_interface[70956b6af7f02b7a]::util::run_in_thread_pool_with_globals<rustc_interface[70956b6af7f02b7a]::interface::run_compiler<(), rustc_driver_impl[1a3eae45778b1a3a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
 110:     0x7f1171d35b7e - <std[7637d35b2e73f491]::thread::lifecycle::spawn_unchecked<rustc_interface[70956b6af7f02b7a]::util::run_in_thread_with_globals<rustc_interface[70956b6af7f02b7a]::util::run_in_thread_pool_with_globals<rustc_interface[70956b6af7f02b7a]::interface::run_compiler<(), rustc_driver_impl[1a3eae45778b1a3a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[e59341b65d367131]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
 111:     0x7f1171d37944 - <std[7637d35b2e73f491]::sys::thread::unix::Thread>::new::thread_start
 112:     0x7f116b69698b - <unknown>
 113:     0x7f116b71a9cc - <unknown>
 114:                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/matthias/vcs/github/CRED/rustc-ice-2026-01-18T18_32_40-2187319.txt` to your bug report

note: rustc 1.94.0-nightly (fe98ddcfc 2026-01-17) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z next-solver=globally

query stack during panic:
panicked at /rustc-dev/fe98ddcfcfb6f185dbf4adeaf439d8a756da0273/compiler/rustc_type_ir/src/ty_kind.rs:680:17:

thread panicked while processing panic. aborting.
[1]    2187319 IOT instruction  rustc code.rs -Znext-solver=globally --edition=2021

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the ICE with the command and example in code.rs, using -Znext-solver=globally and the supplied nightly version. Then inspect rustc_type_ir/src/ty_kind.rs around line 680 and the stack-trace path; done means the reproducer no longer panics and reports an appropriate compiler diagnostic.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
35/100

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