rust-lang / rust-lang/rust

ICE: called `Option::unwrap()` on a `None` value

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A-dyn-trait C-bug F-type_alias_impl_trait I-ICE S-bug-has-test S-has-mcve T-compiler
Dominant language
Rust
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Description

I tried this code:

#![feature(type_alias_impl_trait)]
type Tait = impl Sized;
trait Foo: Bar<Tait> {}
trait Bar<T> {
    fn bar(&self);
}
fn test_correct2(x: &dyn Foo) {
    x.bar();
}
fn main() {}
Release channel Result
Current Stable ICE
Current Nightly ICE
Current Nightly（-Z next-solver=globally） ICE
Meta

rustc --version --verbose:

rustc 1.95.0-nightly (db3e99bba 2026-02-04)
binary: rustc
commit-hash: db3e99bbab28c6ca778b13222becdea54533d908
commit-date: 2026-02-04
host: x86_64-unknown-linux-gnu
release: 1.95.0-nightly
LLVM version: 22.1.0
Backtrace 

thread 'rustc' panicked at /rustc-dev/db3e99bbab28c6ca778b13222becdea54533d908/compiler/rustc_trait_selection/src/traits/vtable.rs:363:77:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7f522125af4b - <std[5b6453b30570829a]::backtrace::Backtrace>::create
   1:     0x7f522125ae95 - <std[5b6453b30570829a]::backtrace::Backtrace>::force_capture
   2:     0x7f522025d7b5 - std[5b6453b30570829a]::panicking::update_hook::<alloc[4b4e8be454901a39]::boxed::Box<rustc_driver_impl[70175e87f37eb535]::install_ice_hook::{closure#1}>>::{closure#0}
   3:     0x7f522126da42 - std[5b6453b30570829a]::panicking::panic_with_hook
   4:     0x7f522125047a - std[5b6453b30570829a]::panicking::panic_handler::{closure#0}
   5:     0x7f52212449b9 - std[5b6453b30570829a]::sys::backtrace::__rust_end_short_backtrace::<std[5b6453b30570829a]::panicking::panic_handler::{closure#0}, !>
   6:     0x7f5221251ead - __rustc[c8a7c5c4b6a2cdce]::rust_begin_unwind
   7:     0x7f521e4b610c - core[94716341d7c778ad]::panicking::panic_fmt
   8:     0x7f521da0ea82 - core[94716341d7c778ad]::panicking::panic
   9:     0x7f521e5727e9 - core[94716341d7c778ad]::option::unwrap_failed
  10:     0x7f52228830cb - rustc_trait_selection[b1d9eac621a96b17]::traits::vtable::first_method_vtable_slot
  11:     0x7f5222881d96 - rustc_query_impl[5ce950bad06ac490]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[5ce950bad06ac490]::query_impl::first_method_vtable_slot::make_query_vtable::{closure#1}::{closure#0}, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 8usize]>>
  12:     0x7f5222881d69 - <rustc_query_impl[5ce950bad06ac490]::query_impl::first_method_vtable_slot::make_query_vtable::{closure#1} as core[94716341d7c778ad]::ops::function::FnOnce<(rustc_middle[945890ed1064710a]::ty::context::TyCtxt, rustc_type_ir[e35c5fdc9bc4ed54]::predicate::TraitRef<rustc_middle[945890ed1064710a]::ty::context::TyCtxt>)>>::call_once
  13:     0x7f5222886947 - rustc_query_system[cb5650c2b33f578c]::query::plumbing::try_execute_query::<rustc_query_impl[5ce950bad06ac490]::SemiDynamicQueryDispatcher<rustc_query_system[cb5650c2b33f578c]::query::caches::DefaultCache<rustc_type_ir[e35c5fdc9bc4ed54]::predicate::TraitRef<rustc_middle[945890ed1064710a]::ty::context::TyCtxt>, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 8usize]>>, {rustc_query_impl[5ce950bad06ac490]::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: false }}>, false>
  14:     0x7f522288668c - rustc_query_impl[5ce950bad06ac490]::query_impl::first_method_vtable_slot::get_query_non_incr::__rust_end_short_backtrace
  15:     0x7f5221f918cf - rustc_ty_utils[208ab547c572f55d]::instance::resolve_instance_raw
  16:     0x7f5221f8f33c - rustc_query_impl[5ce950bad06ac490]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[5ce950bad06ac490]::query_impl::resolve_instance_raw::make_query_vtable::{closure#1}::{closure#0}, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 32usize]>>
  17:     0x7f5221f8e640 - rustc_query_system[cb5650c2b33f578c]::query::plumbing::try_execute_query::<rustc_query_impl[5ce950bad06ac490]::SemiDynamicQueryDispatcher<rustc_query_system[cb5650c2b33f578c]::query::caches::DefaultCache<rustc_middle[945890ed1064710a]::ty::PseudoCanonicalInput<(rustc_span[64ec0f452ae8c55c]::def_id::DefId, &rustc_middle[945890ed1064710a]::ty::list::RawList<(), rustc_middle[945890ed1064710a]::ty::generic_args::GenericArg>)>, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 32usize]>>, {rustc_query_impl[5ce950bad06ac490]::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: false }}>, false>
  18:     0x7f5221f8e283 - rustc_query_impl[5ce950bad06ac490]::query_impl::resolve_instance_raw::get_query_non_incr::__rust_end_short_backtrace
  19:     0x7f5221d1257f - <rustc_middle[945890ed1064710a]::ty::instance::Instance>::try_resolve
  20:     0x7f5221d0e714 - <rustc_mir_transform[7868ec3e499e053b]::check_call_recursion::CheckCallRecursion as rustc_mir_transform[7868ec3e499e053b]::pass_manager::MirLint>::run_lint
  21:     0x7f522183fe79 - rustc_mir_transform[7868ec3e499e053b]::mir_built
  22:     0x7f522183fba3 - rustc_query_impl[5ce950bad06ac490]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[5ce950bad06ac490]::query_impl::mir_built::make_query_vtable::{closure#1}::{closure#0}, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 8usize]>>
  23:     0x7f5221b2535b - rustc_query_system[cb5650c2b33f578c]::query::plumbing::try_execute_query::<rustc_query_impl[5ce950bad06ac490]::SemiDynamicQueryDispatcher<rustc_data_structures[1e615b1a93145c8c]::vec_cache::VecCache<rustc_span[64ec0f452ae8c55c]::def_id::LocalDefId, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 8usize]>, rustc_query_system[cb5650c2b33f578c]::dep_graph::graph::DepNodeIndex>, {rustc_query_impl[5ce950bad06ac490]::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: true }}>, false>
  24:     0x7f5221b24c59 - rustc_query_impl[5ce950bad06ac490]::query_impl::mir_built::get_query_non_incr::__rust_end_short_backtrace
  25:     0x7f5221d9efb0 - rustc_mir_build[92fa072902886eb8]::check_unsafety::check_unsafety
  26:     0x7f5221d9ed59 - rustc_query_impl[5ce950bad06ac490]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[5ce950bad06ac490]::query_impl::check_unsafety::make_query_vtable::{closure#1}::{closure#0}, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 0usize]>>
  27:     0x7f5221da67d6 - rustc_query_system[cb5650c2b33f578c]::query::plumbing::try_execute_query::<rustc_query_impl[5ce950bad06ac490]::SemiDynamicQueryDispatcher<rustc_data_structures[1e615b1a93145c8c]::vec_cache::VecCache<rustc_span[64ec0f452ae8c55c]::def_id::LocalDefId, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 0usize]>, rustc_query_system[cb5650c2b33f578c]::dep_graph::graph::DepNodeIndex>, {rustc_query_impl[5ce950bad06ac490]::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: false }}>, false>
  28:     0x7f5221da654b - rustc_query_impl[5ce950bad06ac490]::query_impl::check_unsafety::get_query_non_incr::__rust_end_short_backtrace
  29:     0x7f5221da5708 - <rustc_middle[945890ed1064710a]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[391380b3dd77dca3]::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}
  30:     0x7f5221da324a - rustc_interface[391380b3dd77dca3]::passes::analysis
  31:     0x7f5221da266b - rustc_query_impl[5ce950bad06ac490]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[5ce950bad06ac490]::query_impl::analysis::make_query_vtable::{closure#1}::{closure#0}, rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 0usize]>>
  32:     0x7f52229c15e6 - rustc_query_system[cb5650c2b33f578c]::query::plumbing::try_execute_query::<rustc_query_impl[5ce950bad06ac490]::SemiDynamicQueryDispatcher<rustc_query_system[cb5650c2b33f578c]::query::caches::SingleCache<rustc_middle[945890ed1064710a]::query::erase::ErasedData<[u8; 0usize]>>, {rustc_query_impl[5ce950bad06ac490]::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: false }}>, false>
  33:     0x7f52229c1348 - rustc_query_impl[5ce950bad06ac490]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  34:     0x7f5222b31da7 - <rustc_interface[391380b3dd77dca3]::passes::create_and_enter_global_ctxt<core[94716341d7c778ad]::option::Option<rustc_interface[391380b3dd77dca3]::queries::Linker>, rustc_driver_impl[70175e87f37eb535]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[94716341d7c778ad]::ops::function::FnOnce<(&rustc_session[79dda06290ce4e69]::session::Session, rustc_middle[945890ed1064710a]::ty::context::CurrentGcx, alloc[4b4e8be454901a39]::sync::Arc<rustc_data_structures[1e615b1a93145c8c]::jobserver::Proxy>, &std[5b6453b30570829a]::sync::once_lock::OnceLock<rustc_middle[945890ed1064710a]::ty::context::GlobalCtxt>, &rustc_data_structures[1e615b1a93145c8c]::sync::worker_local::WorkerLocal<rustc_middle[945890ed1064710a]::arena::Arena>, &rustc_data_structures[1e615b1a93145c8c]::sync::worker_local::WorkerLocal<rustc_hir[a9e131cadb307f85]::Arena>, rustc_driver_impl[70175e87f37eb535]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  35:     0x7f52229e30be - rustc_interface[391380b3dd77dca3]::interface::run_compiler::<(), rustc_driver_impl[70175e87f37eb535]::run_compiler::{closure#0}>::{closure#1}
  36:     0x7f5222a256fe - std[5b6453b30570829a]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[391380b3dd77dca3]::util::run_in_thread_with_globals<rustc_interface[391380b3dd77dca3]::util::run_in_thread_pool_with_globals<rustc_interface[391380b3dd77dca3]::interface::run_compiler<(), rustc_driver_impl[70175e87f37eb535]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  37:     0x7f5222a25c20 - <std[5b6453b30570829a]::thread::lifecycle::spawn_unchecked<rustc_interface[391380b3dd77dca3]::util::run_in_thread_with_globals<rustc_interface[391380b3dd77dca3]::util::run_in_thread_pool_with_globals<rustc_interface[391380b3dd77dca3]::interface::run_compiler<(), rustc_driver_impl[70175e87f37eb535]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[94716341d7c778ad]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  38:     0x7f5222a26aac - <std[5b6453b30570829a]::sys::thread::unix::Thread>::new::thread_start
  39:     0x7f521c5de609 - start_thread
                               at /build/glibc-B3wQXB/glibc-2.31/nptl/pthread_create.c:477:8
  40:     0x7f521c503353 - clone
                               at /build/glibc-B3wQXB/glibc-2.31/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95:0
  41:                0x0 - <unknown>


rustc version: 1.95.0-nightly (db3e99bba 2026-02-04)
platform: x86_64-unknown-linux-gnu

query stack during panic:
#0 [first_method_vtable_slot] finding the slot within the vtable of `dyn Foo<'_>` for the implementation of `Bar`
#1 [resolve_instance_raw] resolving instance `<dyn Foo<'_> as Bar<'_, '_, Tait>>::bar`
#2 [mir_built] building MIR for `test_correct2`
#3 [check_unsafety] unsafety-checking `test_correct2`
#4 [analysis] running analysis passes on crate `bug`
end of query stack

@rustbot label +I-ICE +T-compiler +C-bug

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  3. Fork the repository and make your change on a branch.
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Research direction

Reproduce the ICE with the provided type_alias_impl_trait and trait-object example, then inspect compiler/rustc_trait_selection/src/traits/vtable.rs around first_method_vtable_slot. Trace the related resolve_instance_raw path shown in the backtrace and add a regression test for the example; done means compilation no longer panics on stable, nightly, or the listed next-solver mode.

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
Mostly clear
Newbie friendliness
35/100

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