[ICE]: `virtual dispatches have no instance MIR`

[matthiaskrgr]

Code

//@ compiler-flags: -Clink-dead-code
#![feature(lazy_type_alias)]
impl Trait for Struct {}
pub trait Trait {
  fn a(&self) {}
}
pub type Struct = Trait;

pub fn main() {}

Meta

rustc --version --verbose:

rustc 1.98.0-nightly (973ad0d0a 2026-06-25)
binary: rustc
commit-hash: 973ad0d0ab149bde2e96422833c1265c7a5be217
commit-date: 2026-06-25
host: x86_64-unknown-linux-gnu
release: 1.98.0-nightly
LLVM version: 22.1.7

Error output

<output>

Backtrace

error: internal compiler error: /rustc-dev/973ad0d0ab149bde2e96422833c1265c7a5be217/compiler/rustc_middle/src/ty/mod.rs:1807:46: virtual dispatches have no instance MIR


thread 'rustc' (4179870) panicked at /rustc-dev/973ad0d0ab149bde2e96422833c1265c7a5be217/compiler/rustc_middle/src/ty/mod.rs:1807:46:
Box<dyn Any>
stack backtrace:
   0:     0x7fdacf07f7c9 - <<std[93d08488200afbe9]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[f7e291d2543430ab]::fmt::Display>::fmt
   1:     0x7fdacf60ed5e - core[f7e291d2543430ab]::fmt::write
   2:     0x7fdacf095e36 - <std[93d08488200afbe9]::sys::stdio::unix::Stderr as std[93d08488200afbe9]::io::Write>::write_fmt
   3:     0x7fdacf054a8e - std[93d08488200afbe9]::panicking::default_hook::{closure#0}
   4:     0x7fdacf0724b3 - std[93d08488200afbe9]::panicking::default_hook
   5:     0x7fdace0b9da1 - std[93d08488200afbe9]::panicking::update_hook::<alloc[53d916e428402608]::boxed::Box<rustc_driver_impl[979a081fdb5de70a]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7fdacf072792 - std[93d08488200afbe9]::panicking::panic_with_hook
   7:     0x7fdace0e7511 - std[93d08488200afbe9]::panicking::begin_panic::<rustc_errors[264333f2c4fc38ce]::ExplicitBug>::{closure#0}
   8:     0x7fdace0e0506 - std[93d08488200afbe9]::sys::backtrace::__rust_end_short_backtrace::<std[93d08488200afbe9]::panicking::begin_panic<rustc_errors[264333f2c4fc38ce]::ExplicitBug>::{closure#0}, !>
   9:     0x7fdace0de217 - std[93d08488200afbe9]::panicking::begin_panic::<rustc_errors[264333f2c4fc38ce]::ExplicitBug>
  10:     0x7fdace0f26a1 - <rustc_errors[264333f2c4fc38ce]::diagnostic::BugAbort as rustc_errors[264333f2c4fc38ce]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7fdace641859 - rustc_middle[bcc3288a6814d0a4]::util::bug::opt_span_bug_fmt::<rustc_span[35a08c5840550152]::span_encoding::Span>::{closure#0}
  12:     0x7fdace6419c2 - rustc_middle[bcc3288a6814d0a4]::ty::context::tls::with_opt::<rustc_middle[bcc3288a6814d0a4]::util::bug::opt_span_bug_fmt<rustc_span[35a08c5840550152]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  13:     0x7fdace62e01b - rustc_middle[bcc3288a6814d0a4]::ty::context::tls::with_context_opt::<rustc_middle[bcc3288a6814d0a4]::ty::context::tls::with_opt<rustc_middle[bcc3288a6814d0a4]::util::bug::opt_span_bug_fmt<rustc_span[35a08c5840550152]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  14:     0x7fdacb8f1984 - rustc_middle[bcc3288a6814d0a4]::util::bug::bug_fmt
  15:     0x7fdacfff9d9d - <rustc_middle[bcc3288a6814d0a4]::ty::context::TyCtxt>::instance_mir
  16:     0x7fdacfffcb4b - rustc_monomorphize[e5a33d18fbf7dfd7]::collector::items_of_instance
  17:     0x7fdacfffcad1 - rustc_query_impl[17a4b120598da42c]::query_impl::items_of_instance::invoke_provider_fn::__rust_begin_short_backtrace
  18:     0x7fdad0015230 - rustc_query_impl[17a4b120598da42c]::execution::try_execute_query::<rustc_middle[bcc3288a6814d0a4]::query::caches::DefaultCache<(rustc_middle[bcc3288a6814d0a4]::ty::instance::Instance, rustc_middle[bcc3288a6814d0a4]::mono::CollectionMode), rustc_middle[bcc3288a6814d0a4]::query::erase::ErasedData<[u8; 32usize]>>, false>
  19:     0x7fdad0014e9b - rustc_query_impl[17a4b120598da42c]::query_impl::items_of_instance::execute_query_non_incr::__rust_end_short_backtrace
  20:     0x7fdad0013854 - rustc_monomorphize[e5a33d18fbf7dfd7]::collector::collect_items_rec::{closure#0}
  21:     0x7fdad0a5f13a - rustc_monomorphize[e5a33d18fbf7dfd7]::collector::collect_items_rec
  22:     0x7fdacfdb92a1 - rustc_monomorphize[e5a33d18fbf7dfd7]::collector::collect_crate_mono_items::{closure#1}::{closure#0}
  23:     0x7fdad0264f4f - rustc_monomorphize[e5a33d18fbf7dfd7]::partitioning::collect_and_partition_mono_items
  24:     0x7fdad079dc68 - rustc_query_impl[17a4b120598da42c]::query_impl::collect_and_partition_mono_items::invoke_provider_fn::__rust_begin_short_backtrace
  25:     0x7fdad079d5c1 - rustc_query_impl[17a4b120598da42c]::execution::try_execute_query::<rustc_middle[bcc3288a6814d0a4]::query::caches::SingleCache<rustc_middle[bcc3288a6814d0a4]::query::erase::ErasedData<[u8; 24usize]>>, false>
  26:     0x7fdad079d27c - rustc_query_impl[17a4b120598da42c]::query_impl::collect_and_partition_mono_items::execute_query_non_incr::__rust_end_short_backtrace
  27:     0x7fdacfeabca4 - rustc_codegen_ssa[147effa7f152b327]::back::symbol_export::exported_generic_symbols_provider_local
  28:     0x7fdad0425468 - rustc_query_impl[17a4b120598da42c]::query_impl::exported_generic_symbols::invoke_provider_fn::__rust_begin_short_backtrace
  29:     0x7fdad042376d - rustc_query_impl[17a4b120598da42c]::execution::try_execute_query::<rustc_data_structures[4869b7949a113a92]::vec_cache::VecCache<rustc_span[35a08c5840550152]::def_id::CrateNum, rustc_middle[bcc3288a6814d0a4]::query::erase::ErasedData<[u8; 16usize]>, rustc_middle[bcc3288a6814d0a4]::dep_graph::graph::DepNodeIndex>, false>
  30:     0x7fdad0423283 - rustc_query_impl[17a4b120598da42c]::query_impl::exported_generic_symbols::execute_query_non_incr::__rust_end_short_backtrace
  31:     0x7fdacfe7d867 - <rustc_metadata[62f2524ca2ba8bcb]::rmeta::encoder::EncodeContext>::encode_crate_root
  32:     0x7fdad05157d5 - rustc_metadata[62f2524ca2ba8bcb]::rmeta::encoder::encode_metadata::{closure#3}
  33:     0x7fdad0512fa1 - rustc_metadata[62f2524ca2ba8bcb]::rmeta::encoder::encode_metadata
  34:     0x7fdad051d105 - rustc_metadata[62f2524ca2ba8bcb]::fs::encode_and_write_metadata
  35:     0x7fdad0762c3b - <rustc_interface[71cd11911924984b]::queries::Linker>::codegen_and_build_linker
  36:     0x7fdad075d9bd - rustc_interface[71cd11911924984b]::interface::run_compiler::<(), rustc_driver_impl[979a081fdb5de70a]::run_compiler::{closure#0}>::{closure#1}
  37:     0x7fdad078dc7a - std[93d08488200afbe9]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[71cd11911924984b]::util::run_in_thread_with_globals<rustc_interface[71cd11911924984b]::util::run_in_thread_pool_with_globals<rustc_interface[71cd11911924984b]::interface::run_compiler<(), rustc_driver_impl[979a081fdb5de70a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  38:     0x7fdad078da2d - <std[93d08488200afbe9]::thread::lifecycle::spawn_unchecked<rustc_interface[71cd11911924984b]::util::run_in_thread_with_globals<rustc_interface[71cd11911924984b]::util::run_in_thread_pool_with_globals<rustc_interface[71cd11911924984b]::interface::run_compiler<(), rustc_driver_impl[979a081fdb5de70a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[f7e291d2543430ab]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  39:     0x7fdad0783f10 - <std[93d08488200afbe9]::sys::thread::unix::Thread>::new::thread_start
  40:     0x7fdaca2981b9 - <unknown>
  41:     0x7fdaca31d21c - <unknown>
  42:                0x0 - <unknown>

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-2026-06-25T16_55_05-4179868.txt` to your bug report

note: rustc 1.98.0-nightly (973ad0d0a 2026-06-25) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C link-dead-code

query stack during panic:
#0 [items_of_instance] collecting items used by `<dyn Trait as Trait>::a - virtual#3`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
#2 [exported_generic_symbols] collecting exported generic symbols for crate `0`
end of query stack
error: aborting due to 1 previous error; 2 warnings emitted