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

[jacob-greenfield-ll]

Code

#![allow(unused)]

trait StageTrait {
    type Fallback: StageTrait;

    fn run<G: StageFinder<Target = Self>>(head: &mut G::Head) {
        StageTrait::run::<FindFallback<G>>(head);
    }
}

trait StageFinder {
    type Head;
    type Target: StageTrait;
}

struct FindHead<H>(H);
impl<H: StageTrait> StageFinder for FindHead<H> {
    type Head = H;
    type Target = H;
}

struct FindFallback<G>(G);
impl<G: StageFinder> StageFinder for FindFallback<G> {
    type Head = G::Head;
    type Target = <G::Target as StageTrait>::Fallback;
}

struct Loop;
impl StageTrait for Loop {
    type Fallback = Loop;
}

struct MyStage<T: StageTrait>(T);

impl<T: StageTrait> StageTrait for MyStage<T> {
    type Fallback = T;

    fn run<G: StageFinder<Target = Self>>(head: &mut G::Head) {
        StageTrait::run::<FindFallback<G>>(head);
    }
}

fn main() {
    StageTrait::run::<FindHead<_>>(&mut MyStage(Loop));
}

My second issue of the day unfortunately (#143097).

Meta

rustc --version --verbose:

rustc 1.88.0 (6b00bc388 2025-06-23)
binary: rustc
commit-hash: 6b00bc3880198600130e1cf62b8f8a93494488cc
commit-date: 2025-06-23
host: aarch64-apple-darwin
release: 1.88.0
LLVM version: 20.1.5

Error output

thread 'rustc' panicked at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/compiler/rustc_type_ir/src/ty_kind.rs:864:17:
type variables should not be hashed: ?0t

Backtrace (`RUST_BACKTRACE=1`)

   Compiling rustc-hang v0.1.0 (/Users/ja33827/Downloads/rustc-hang)

thread 'rustc' panicked at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/compiler/rustc_type_ir/src/ty_kind.rs:864:17:
type variables should not be hashed: ?0t
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: <rustc_type_ir::ty_kind::TyKind<rustc_middle::ty::context::TyCtxt> as rustc_data_structures::stable_hasher::HashStable<rustc_query_system::ich::hcx::StableHashingContext>>::hash_stable
   3: <rustc_type_ir::ty_info::WithCachedTypeInfo<rustc_type_ir::ty_kind::TyKind<rustc_middle::ty::context::TyCtxt>> as rustc_data_structures::stable_hasher::HashStable<rustc_query_system::ich::hcx::StableHashingContext>>::hash_stable
   4: <rustc_type_ir::ty_kind::TyKind<rustc_middle::ty::context::TyCtxt> as rustc_data_structures::stable_hasher::HashStable<rustc_query_system::ich::hcx::StableHashingContext>>::hash_stable
   5: <rustc_type_ir::ty_info::WithCachedTypeInfo<rustc_type_ir::ty_kind::TyKind<rustc_middle::ty::context::TyCtxt>> as rustc_data_structures::stable_hasher::HashStable<rustc_query_system::ich::hcx::StableHashingContext>>::hash_stable
   6: <rustc_query_impl::query_impl::try_normalize_generic_arg_after_erasing_regions::dynamic_query::{closure#7} as core::ops::function::FnOnce<(&mut rustc_query_system::ich::hcx::StableHashingContext, &rustc_middle::query::erase::Erased<[u8; 8]>)>>::call_once
   7: <rustc_query_system::dep_graph::graph::DepGraphData<rustc_middle::dep_graph::DepsType>>::hash_result_and_alloc_node::<rustc_middle::ty::context::TyCtxt, rustc_middle::query::erase::Erased<[u8; 8]>>
   8: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_middle::ty::PseudoCanonicalInput<rustc_middle::ty::generic_args::GenericArg>, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, true>
   9: <rustc_middle::ty::normalize_erasing_regions::NormalizeAfterErasingRegionsFolder>::normalize_generic_arg_after_erasing_regions
  10: rustc_ty_utils::abi::fn_abi_new_uncached
  11: rustc_ty_utils::abi::fn_abi_of_instance
      [... omitted 2 frames ...]
  12: rustc_monomorphize::mono_checks::check_mono_item
      [... omitted 2 frames ...]
  13: rustc_monomorphize::collector::items_of_instance
      [... omitted 2 frames ...]
  14: rustc_monomorphize::collector::collect_items_rec::{closure#0}
  15: rustc_monomorphize::collector::collect_items_rec
  16: rustc_monomorphize::collector::collect_items_rec
  17: rustc_monomorphize::collector::collect_items_rec
  18: rustc_monomorphize::collector::collect_items_rec
  19: rustc_monomorphize::collector::collect_items_rec
  20: rustc_monomorphize::collector::collect_items_rec
  21: rustc_monomorphize::collector::collect_items_rec
  22: rustc_monomorphize::collector::collect_items_rec
  23: rustc_monomorphize::collector::collect_items_rec
  24: rustc_monomorphize::collector::collect_items_rec
  25: rustc_monomorphize::collector::collect_items_rec
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  27: rustc_monomorphize::collector::collect_items_rec
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  29: rustc_monomorphize::collector::collect_items_rec
  30: rustc_monomorphize::collector::collect_items_rec
  31: rustc_monomorphize::collector::collect_items_rec
  32: rustc_monomorphize::collector::collect_items_rec
  33: rustc_monomorphize::collector::collect_items_rec
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  36: rustc_monomorphize::collector::collect_items_rec
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  38: rustc_monomorphize::collector::collect_items_rec
  39: rustc_monomorphize::collector::collect_items_rec
  40: rustc_monomorphize::collector::collect_items_rec
  41: rustc_monomorphize::collector::collect_items_rec
  42: rustc_monomorphize::collector::collect_items_rec
  43: rustc_monomorphize::collector::collect_items_rec
  44: rustc_monomorphize::collector::collect_items_rec
  45: rustc_monomorphize::collector::collect_items_rec
  46: rustc_monomorphize::collector::collect_items_rec
  47: rustc_monomorphize::collector::collect_items_rec
  48: rustc_monomorphize::collector::collect_items_rec
  49: rustc_monomorphize::collector::collect_items_rec
  50: rustc_monomorphize::collector::collect_items_rec
  51: rustc_monomorphize::collector::collect_items_rec
  52: rustc_monomorphize::collector::collect_items_rec
  53: rustc_monomorphize::collector::collect_items_rec
  54: rustc_monomorphize::collector::collect_items_rec
  55: rustc_monomorphize::collector::collect_items_rec
  56: rustc_monomorphize::collector::collect_items_rec
  57: rustc_monomorphize::collector::collect_items_rec
  58: rustc_monomorphize::collector::collect_items_rec
  59: rustc_monomorphize::collector::collect_items_rec
  60: rustc_monomorphize::collector::collect_items_rec
  61: rustc_monomorphize::collector::collect_items_rec
  62: rustc_monomorphize::collector::collect_items_rec
  63: rustc_monomorphize::collector::collect_items_rec
  64: rustc_monomorphize::collector::collect_items_rec
  65: rustc_monomorphize::collector::collect_items_rec
  66: rustc_monomorphize::collector::collect_items_rec
  67: rustc_monomorphize::collector::collect_items_rec
  68: rustc_monomorphize::collector::collect_items_rec
  69: rustc_monomorphize::collector::collect_items_rec
  70: rustc_monomorphize::collector::collect_items_rec
  71: rustc_monomorphize::collector::collect_items_rec
  72: rustc_monomorphize::collector::collect_items_rec
  73: rustc_monomorphize::collector::collect_items_rec
  74: rustc_monomorphize::collector::collect_items_rec
  75: rustc_monomorphize::collector::collect_items_rec
  76: rustc_monomorphize::collector::collect_items_rec
  77: rustc_monomorphize::collector::collect_items_rec
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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: rustc 1.88.0 (6b00bc388 2025-06-23) running on aarch64-apple-darwin

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [try_normalize_generic_arg_after_erasing_regions] normalizing `&mut <FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindHead<MyStage<Loop>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> as StageFinder>::Head`
#1 [fn_abi_of_instance] computing call ABI of `<Loop as StageTrait>::run::<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindHead<MyStage<Loop>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
#2 [check_mono_item] monomorphization-time checking
#3 [items_of_instance] collecting items used by `<Loop as StageTrait>::run::<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindHead<MyStage<Loop>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
#4 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: could not compile `rustc-hang` (bin "rustc-hang")

Caused by:
  process didn't exit successfully: `/Users/ja33827/.rustup/toolchains/stable-aarch64-apple-darwin/bin/rustc --crate-name rustc_hang --edition=2024 src/main.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=108 --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values())' -C metadata=d4a19bba085308e7 -C extra-filename=-4cd3b9647ea4d87d --out-dir /Users/ja33827/Downloads/rustc-hang/target/debug/deps -C incremental=/Users/ja33827/Downloads/rustc-hang/target/debug/incremental -L dependency=/Users/ja33827/Downloads/rustc-hang/target/debug/deps` (exit status: 101)

Backtrace (`RUST_BACKTRACE=full`)

   Compiling rustc-hang v0.1.0 (/Users/ja33827/Downloads/rustc-hang)

thread 'rustc' panicked at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/compiler/rustc_type_ir/src/ty_kind.rs:864:17:
type variables should not be hashed: ?0t
stack backtrace:
   0:        0x1102a17e4 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h2c3f7b4c4ce00f07
   1:        0x10d891558 - core::fmt::write::h1dbafa36e52e01c5
   2:        0x110296118 - std::io::Write::write_fmt::he72d49f3084ee601
   3:        0x1102a16a4 - std::sys::backtrace::BacktraceLock::print::h1fb87370474572ed
   4:        0x1102a6360 - std::panicking::default_hook::{{closure}}::h195a9b2c829547eb
   5:        0x1102a6030 - std::panicking::default_hook::h18c3aa3e3a3584d5
   6:        0x10e3fc724 - std[72c7846bd0c5b2df]::panicking::update_hook::<alloc[546c5ff29fefb371]::boxed::Box<rustc_driver_impl[8a44d88c4f0f23]::install_ice_hook::{closure#1}>>::{closure#0}
   7:        0x1102a6d48 - std::panicking::rust_panic_with_hook::h02a9fa3cad928562
   8:        0x1102a693c - std::panicking::begin_panic_handler::{{closure}}::hd1cc56578f819958
   9:        0x1102a1c88 - std::sys::backtrace::__rust_end_short_backtrace::h52c1e479035e4bc4
  10:        0x1102a6604 - __rustc[4794b31dd7191200]::rust_begin_unwind
  11:        0x112ee155c - core::panicking::panic_fmt::heec96bfc27e6c546
  12:        0x10efb014c - <rustc_type_ir[5c54c4d31ec23536]::ty_kind::TyKind<rustc_middle[be4ece2d81dbf2e4]::ty::context::TyCtxt> as rustc_data_structures[f8a49ce7c8670f7e]::stable_hasher::HashStable<rustc_query_system[e5df0f758f72467d]::ich::hcx::StableHashingContext>>::hash_stable
  13:        0x10efea858 - <rustc_type_ir[5c54c4d31ec23536]::ty_info::WithCachedTypeInfo<rustc_type_ir[5c54c4d31ec23536]::ty_kind::TyKind<rustc_middle[be4ece2d81dbf2e4]::ty::context::TyCtxt>> as rustc_data_structures[f8a49ce7c8670f7e]::stable_hasher::HashStable<rustc_query_system[e5df0f758f72467d]::ich::hcx::StableHashingContext>>::hash_stable
  14:        0x10efafbc8 - <rustc_type_ir[5c54c4d31ec23536]::ty_kind::TyKind<rustc_middle[be4ece2d81dbf2e4]::ty::context::TyCtxt> as rustc_data_structures[f8a49ce7c8670f7e]::stable_hasher::HashStable<rustc_query_system[e5df0f758f72467d]::ich::hcx::StableHashingContext>>::hash_stable
  15:        0x10efea858 - <rustc_type_ir[5c54c4d31ec23536]::ty_info::WithCachedTypeInfo<rustc_type_ir[5c54c4d31ec23536]::ty_kind::TyKind<rustc_middle[be4ece2d81dbf2e4]::ty::context::TyCtxt>> as rustc_data_structures[f8a49ce7c8670f7e]::stable_hasher::HashStable<rustc_query_system[e5df0f758f72467d]::ich::hcx::StableHashingContext>>::hash_stable
  16:        0x10f9cb744 - <rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::try_normalize_generic_arg_after_erasing_regions::dynamic_query::{closure#7} as core[27359fb985a9eb5]::ops::function::FnOnce<(&mut rustc_query_system[e5df0f758f72467d]::ich::hcx::StableHashingContext, &rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 8usize]>)>>::call_once
  17:        0x10f782138 - <rustc_query_system[e5df0f758f72467d]::dep_graph::graph::DepGraphData<rustc_middle[be4ece2d81dbf2e4]::dep_graph::DepsType>>::hash_result_and_alloc_node::<rustc_middle[be4ece2d81dbf2e4]::ty::context::TyCtxt, rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 8usize]>>
  18:        0x10f7ff1d4 - rustc_query_system[e5df0f758f72467d]::query::plumbing::try_execute_query::<rustc_query_impl[f2b4fd6c2e4cdec6]::DynamicConfig<rustc_query_system[e5df0f758f72467d]::query::caches::DefaultCache<rustc_middle[be4ece2d81dbf2e4]::ty::PseudoCanonicalInput<rustc_middle[be4ece2d81dbf2e4]::ty::generic_args::GenericArg>, rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::QueryCtxt, true>
  19:        0x10fa74fbc - rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::try_normalize_generic_arg_after_erasing_regions::get_query_incr::__rust_end_short_backtrace
  20:        0x10f048a10 - <rustc_middle[be4ece2d81dbf2e4]::ty::normalize_erasing_regions::NormalizeAfterErasingRegionsFolder>::normalize_generic_arg_after_erasing_regions
  21:        0x110225f60 - rustc_ty_utils[f56567f23be2c806]::abi::fn_abi_new_uncached
  22:        0x11020b7ec - rustc_ty_utils[f56567f23be2c806]::abi::fn_abi_of_instance
  23:        0x10f9fbecc - rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::fn_abi_of_instance::dynamic_query::{closure#2}::{closure#0}, rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 16usize]>>
  24:        0x10f9aa0b0 - <rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::fn_abi_of_instance::dynamic_query::{closure#2} as core[27359fb985a9eb5]::ops::function::FnOnce<(rustc_middle[be4ece2d81dbf2e4]::ty::context::TyCtxt, rustc_middle[be4ece2d81dbf2e4]::ty::PseudoCanonicalInput<(rustc_middle[be4ece2d81dbf2e4]::ty::instance::Instance, &rustc_middle[be4ece2d81dbf2e4]::ty::list::RawList<(), rustc_middle[be4ece2d81dbf2e4]::ty::Ty>)>)>>::call_once
  25:        0x10f807d9c - rustc_query_system[e5df0f758f72467d]::query::plumbing::try_execute_query::<rustc_query_impl[f2b4fd6c2e4cdec6]::DynamicConfig<rustc_query_system[e5df0f758f72467d]::query::caches::DefaultCache<rustc_middle[be4ece2d81dbf2e4]::ty::PseudoCanonicalInput<(rustc_middle[be4ece2d81dbf2e4]::ty::instance::Instance, &rustc_middle[be4ece2d81dbf2e4]::ty::list::RawList<(), rustc_middle[be4ece2d81dbf2e4]::ty::Ty>)>, rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::QueryCtxt, true>
  26:        0x10fa54794 - rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::fn_abi_of_instance::get_query_incr::__rust_end_short_backtrace
  27:        0x10f466aa8 - rustc_monomorphize[3cd78c9f076272f8]::mono_checks::check_mono_item
  28:        0x10f9fa458 - rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::check_mono_item::dynamic_query::{closure#2}::{closure#0}, rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 0usize]>>
  29:        0x10f9989d4 - <rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::check_mono_item::dynamic_query::{closure#2} as core[27359fb985a9eb5]::ops::function::FnOnce<(rustc_middle[be4ece2d81dbf2e4]::ty::context::TyCtxt, rustc_middle[be4ece2d81dbf2e4]::ty::instance::Instance)>>::call_once
  30:        0x10f81da78 - rustc_query_system[e5df0f758f72467d]::query::plumbing::try_execute_query::<rustc_query_impl[f2b4fd6c2e4cdec6]::DynamicConfig<rustc_query_system[e5df0f758f72467d]::query::caches::DefaultCache<rustc_middle[be4ece2d81dbf2e4]::ty::instance::Instance, rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::QueryCtxt, true>
  31:        0x10fa94538 - rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::check_mono_item::get_query_incr::__rust_end_short_backtrace
  32:        0x10f464208 - rustc_monomorphize[3cd78c9f076272f8]::collector::items_of_instance
  33:        0x10f9fb888 - rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::items_of_instance::dynamic_query::{closure#2}::{closure#0}, rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 32usize]>>
  34:        0x10f9a6d50 - <rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::items_of_instance::dynamic_query::{closure#2} as core[27359fb985a9eb5]::ops::function::FnOnce<(rustc_middle[be4ece2d81dbf2e4]::ty::context::TyCtxt, (rustc_middle[be4ece2d81dbf2e4]::ty::instance::Instance, rustc_middle[be4ece2d81dbf2e4]::mir::mono::CollectionMode))>>::call_once
  35:        0x10f842f50 - rustc_query_system[e5df0f758f72467d]::query::plumbing::try_execute_query::<rustc_query_impl[f2b4fd6c2e4cdec6]::DynamicConfig<rustc_query_system[e5df0f758f72467d]::query::caches::DefaultCache<(rustc_middle[be4ece2d81dbf2e4]::ty::instance::Instance, rustc_middle[be4ece2d81dbf2e4]::mir::mono::CollectionMode), rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 32usize]>>, false, false, false>, rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::QueryCtxt, true>
  36:        0x10fa95e38 - rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::items_of_instance::get_query_incr::__rust_end_short_backtrace
  37:        0x10f478888 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec::{closure#0}
  38:        0x10f476a38 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  39:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  40:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  41:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  42:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  43:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  44:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  45:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  46:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  47:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  48:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  49:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  50:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  51:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  52:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  53:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  54:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  55:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  56:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  57:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  58:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  59:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  60:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  61:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  62:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  63:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  64:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  65:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  66:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  67:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  68:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  69:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  70:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  71:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  72:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  73:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  74:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  75:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  76:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  77:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  78:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  79:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  80:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  81:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  82:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  83:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  84:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  85:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  86:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  87:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  88:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  89:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  90:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  91:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  92:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  93:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  94:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  95:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  96:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  97:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  98:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
  99:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 100:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 101:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 102:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 103:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 104:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 105:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 106:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 107:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 108:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 109:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 110:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 111:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 112:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 113:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 114:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 115:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 116:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 117:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 118:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 119:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 120:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 121:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 122:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 123:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 124:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 125:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 126:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 127:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 128:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 129:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 130:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 131:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 132:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 133:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 134:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 135:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 136:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 137:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 138:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 139:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 140:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 141:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 142:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 143:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 144:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 145:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 146:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 147:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 148:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 149:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 150:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 151:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 152:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 153:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 154:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 155:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 156:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 157:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 158:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 159:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 160:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 161:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 162:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 163:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 164:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 165:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 166:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 167:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 168:        0x10f477da8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_items_rec
 169:        0x10f47cca8 - rustc_monomorphize[3cd78c9f076272f8]::collector::collect_crate_mono_items::{closure#1}::{closure#0}
 170:        0x10f4721c0 - rustc_monomorphize[3cd78c9f076272f8]::partitioning::collect_and_partition_mono_items
 171:        0x10f9fea60 - rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 40usize]>>
 172:        0x10f7d7a48 - rustc_query_system[e5df0f758f72467d]::query::plumbing::try_execute_query::<rustc_query_impl[f2b4fd6c2e4cdec6]::DynamicConfig<rustc_query_system[e5df0f758f72467d]::query::caches::SingleCache<rustc_middle[be4ece2d81dbf2e4]::query::erase::Erased<[u8; 40usize]>>, false, false, false>, rustc_query_impl[f2b4fd6c2e4cdec6]::plumbing::QueryCtxt, true>
 173:        0x10fa72564 - rustc_query_impl[f2b4fd6c2e4cdec6]::query_impl::collect_and_partition_mono_items::get_query_incr::__rust_end_short_backtrace
 174:        0x10e051b04 - rustc_codegen_ssa[b73cc951c071280a]::base::codegen_crate::<rustc_codegen_llvm[bff1d3324f93f84c]::LlvmCodegenBackend>
 175:        0x10e14a86c - <rustc_codegen_llvm[bff1d3324f93f84c]::LlvmCodegenBackend as rustc_codegen_ssa[b73cc951c071280a]::traits::backend::CodegenBackend>::codegen_crate
 176:        0x10ecec888 - <rustc_interface[3c49f4d970e728]::queries::Linker>::codegen_and_build_linker
 177:        0x10e3addd8 - rustc_interface[3c49f4d970e728]::passes::create_and_enter_global_ctxt::<core[27359fb985a9eb5]::option::Option<rustc_interface[3c49f4d970e728]::queries::Linker>, rustc_driver_impl[8a44d88c4f0f23]::run_compiler::{closure#0}::{closure#2}>
 178:        0x10e3f9524 - rustc_interface[3c49f4d970e728]::interface::run_compiler::<(), rustc_driver_impl[8a44d88c4f0f23]::run_compiler::{closure#0}>::{closure#1}
 179:        0x10e3ea47c - std[72c7846bd0c5b2df]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[3c49f4d970e728]::util::run_in_thread_with_globals<rustc_interface[3c49f4d970e728]::util::run_in_thread_pool_with_globals<rustc_interface[3c49f4d970e728]::interface::run_compiler<(), rustc_driver_impl[8a44d88c4f0f23]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
 180:        0x10e3ffee0 - <<std[72c7846bd0c5b2df]::thread::Builder>::spawn_unchecked_<rustc_interface[3c49f4d970e728]::util::run_in_thread_with_globals<rustc_interface[3c49f4d970e728]::util::run_in_thread_pool_with_globals<rustc_interface[3c49f4d970e728]::interface::run_compiler<(), rustc_driver_impl[8a44d88c4f0f23]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[27359fb985a9eb5]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
 181:        0x1102a928c - std::sys::pal::unix::thread::Thread::new::thread_start::hf0cf67e969add794
 182:        0x1a01b6c0c - __pthread_cond_wait

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: rustc 1.88.0 (6b00bc388 2025-06-23) running on aarch64-apple-darwin

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [try_normalize_generic_arg_after_erasing_regions] normalizing `&mut <FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindHead<MyStage<Loop>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> as StageFinder>::Head`
#1 [fn_abi_of_instance] computing call ABI of `<Loop as StageTrait>::run::<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindHead<MyStage<Loop>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
#2 [check_mono_item] monomorphization-time checking
#3 [items_of_instance] collecting items used by `<Loop as StageTrait>::run::<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindFallback<FindHead<MyStage<Loop>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
#4 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: could not compile `rustc-hang` (bin "rustc-hang")

Caused by:
  process didn't exit successfully: `/Users/ja33827/.rustup/toolchains/stable-aarch64-apple-darwin/bin/rustc --crate-name rustc_hang --edition=2024 src/main.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values())' -C metadata=d4a19bba085308e7 -C extra-filename=-4cd3b9647ea4d87d --out-dir /Users/ja33827/Downloads/rustc-hang/target/debug/deps -C incremental=/Users/ja33827/Downloads/rustc-hang/target/debug/incremental -L dependency=/Users/ja33827/Downloads/rustc-hang/target/debug/deps` (exit status: 101)

[cyrgani]

simpler:

fn run<G: StageFinder>(head: G::Head) {
    run::<FindFallback<G>>(head);
}

trait StageFinder {
    type Head;
}

impl StageFinder for MyStage {
    type Head = MyStage;
}

struct FindFallback<G>(G);
impl<G: StageFinder> StageFinder for FindFallback<G> {
    type Head = G::Head;
}

struct MyStage;

fn main() {
    run::<FindFallback<MyStage>>(MyStage);
}

[matthiaskrgr]

might be duplicate of #122823

[cyrgani]

unlike that issue, this one also reproduces in release builds though