[ICE]: `cycle detected when computing function signature` / `Not enough bound vars:`

[matthiaskrgr]

Code

#![feature(return_type_notation)]
struct a<const b: usize >;
trait c {
    fn d(&self) -> impl c<d(..): >;
}

fn main() {}

Meta

rustc --version --verbose:

rustc 1.99.0-nightly (da86f4d07 2026-07-24)
binary: rustc
commit-hash: da86f4d0726be475afbbffe40cb2f65741c51ad3
commit-date: 2026-07-24
host: x86_64-unknown-linux-gnu
release: 1.99.0-nightly
LLVM version: 22.1.8

Error output

<output>

Backtrace

warning: type `a` should have an upper camel case name
 --> code.rs:2:8
  |
2 | struct a<const b: usize >;
  |        ^ help: convert the identifier to upper camel case: `A`
  |
  = note: `#[warn(non_camel_case_types)]` (part of `#[warn(nonstandard_style)]`) on by default

warning: trait `c` should have an upper camel case name
 --> code.rs:3:7
  |
3 | trait c {
  |       ^ help: convert the identifier to upper camel case (notice the capitalization): `C`

warning: struct `a` is never constructed
 --> code.rs:2:8
  |
2 | struct a<const b: usize >;
  |        ^
  |
  = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default

warning: trait `c` is never used
 --> code.rs:3:7
  |
3 | trait c {
  |       ^

warning: const parameter `b` should have an upper case name
 --> code.rs:2:16
  |
2 | struct a<const b: usize >;
  |                ^ help: convert the identifier to upper case: `B`
  |
  = note: `#[warn(non_upper_case_globals)]` (part of `#[warn(nonstandard_style)]`) on by default

warning: 5 warnings emitted

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error[E0391]: cycle detected when computing function signature of `c::d`
 --> code.rs:4:5
  |
4 |     fn d(&self) -> impl c<d(..): >;
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: ...which requires looking up late bound vars inside `c::d`...
  = note: ...which requires resolving lifetimes for `c::d`...
  = note: ...which again requires computing function signature of `c::d`, completing the cycle
  = note: cycle used when computing the variances for items in this crate
  = note: for more information, see <https://rustc-dev-guide.rust-lang.org/overview.html#queries> and <https://rustc-dev-guide.rust-lang.org/query.html>
note: delayed at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/job.rs:487:24
         0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
         1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
         2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
         3: <rustc_errors::diagnostic::Diag>::delay_as_bug
         4: <rustc_query_impl::query_impl::fn_sig::make_query_vtable::{closure#1} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId, rustc_middle::query::plumbing::Cycle, rustc_errors::diagnostic::Diag)>>::call_once
         5: rustc_query_impl::execution::handle_cycle::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 24]>>>
         6: rustc_query_impl::execution::find_and_handle_cycle::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 24]>>>
         7: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 24]>>, false>
         8: rustc_query_impl::query_impl::fn_sig::execute_query_non_incr::__rust_end_short_backtrace
         9: <rustc_hir_analysis::collect::resolve_bound_vars::BoundVarContext as rustc_hir::intravisit::Visitor>::visit_path
        10: <rustc_hir_analysis::collect::resolve_bound_vars::BoundVarContext>::visit_poly_trait_ref_inner
        11: <rustc_hir_analysis::collect::resolve_bound_vars::BoundVarContext as rustc_hir::intravisit::Visitor>::visit_opaque_ty
        12: <rustc_hir_analysis::collect::resolve_bound_vars::BoundVarContext as rustc_hir::intravisit::Visitor>::visit_trait_item
        13: rustc_query_impl::query_impl::resolve_bound_vars::invoke_provider_fn::__rust_begin_short_backtrace
        14: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_hir_id::OwnerId, rustc_middle::query::erase::ErasedData<[u8; 8]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        15: rustc_query_impl::query_impl::resolve_bound_vars::execute_query_non_incr::__rust_end_short_backtrace
        16: rustc_query_impl::query_impl::late_bound_vars_map::invoke_provider_fn::__rust_begin_short_backtrace
        17: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_hir_id::OwnerId, rustc_middle::query::erase::ErasedData<[u8; 8]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        18: rustc_query_impl::query_impl::late_bound_vars_map::execute_query_non_incr::__rust_end_short_backtrace
        19: <dyn rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::lower_fn_ty
        20: rustc_hir_analysis::collect::fn_sig
        21: rustc_query_impl::query_impl::fn_sig::invoke_provider_fn::__rust_begin_short_backtrace
        22: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 24]>>, false>
        23: rustc_query_impl::query_impl::fn_sig::execute_query_non_incr::__rust_end_short_backtrace
        24: <rustc_hir_analysis::variance::constraints::ConstraintContext>::build_constraints_for_item
        25: rustc_hir_analysis::variance::crate_variances
        26: rustc_query_impl::query_impl::crate_variances::invoke_provider_fn::__rust_begin_short_backtrace
        27: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 8]>>, false>
        28: rustc_query_impl::query_impl::crate_variances::execute_query_non_incr::__rust_end_short_backtrace
        29: rustc_query_impl::query_impl::variances_of::invoke_provider_fn::__rust_begin_short_backtrace.warm
        30: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 16]>>, false>
        31: rustc_query_impl::query_impl::variances_of::execute_query_non_incr::__rust_end_short_backtrace
        32: rustc_hir_analysis::check::wfcheck::check_variances_for_type_defn
        33: rustc_hir_analysis::check::check::check_item_type
        34: rustc_hir_analysis::check::wfcheck::check_well_formed
        35: rustc_query_impl::query_impl::check_well_formed::invoke_provider_fn::__rust_begin_short_backtrace
        36: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 1]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        37: rustc_query_impl::query_impl::check_well_formed::execute_query_non_incr::__rust_end_short_backtrace
        38: rustc_hir_analysis::check::wfcheck::check_type_wf
        39: rustc_query_impl::query_impl::check_type_wf::invoke_provider_fn::__rust_begin_short_backtrace
        40: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 1]>>, false>
        41: rustc_query_impl::query_impl::check_type_wf::execute_query_non_incr::__rust_end_short_backtrace
        42: rustc_hir_analysis::check_crate
        43: rustc_interface::passes::analysis
        44: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>, false>
        45: rustc_query_impl::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
        46: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#2}
        47: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
        48: <std::thread::lifecycle::spawn_unchecked<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        49: <std::sys::thread::unix::Thread>::new::thread_start
        50: <unknown>
        51: <unknown>

 --> code.rs:4:5
  |
4 |     fn d(&self) -> impl c<d(..): >;
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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-2026-07-25T10_03_58-2301471.txt` to your bug report

note: rustc 1.99.0-nightly (da86f4d07 2026-07-24) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack

[matthiaskrgr]

might be related to #154056 but already ICEs without -Zthreads or mgca

with debug assertions:

thread 'rustc' (2302541) panicked at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_type_ir/src/binder.rs:288:21:
Not enough bound vars: '^0.Named(DefId(0:10 ~ code[ec3d]::c::d::'_)) not found in []
stack backtrace:
   0:     0x7f70b4e07180 - std[4957aea88bdd0f88]::backtrace_rs::backtrace::libunwind::trace
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
   1:     0x7f70b4e07180 - std[4957aea88bdd0f88]::backtrace_rs::backtrace::trace_unsynchronized::<std[4957aea88bdd0f88]::sys::backtrace::_print_fmt::{closure#1}>
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/../../backtrace/src/backtrace/mod.rs:66:14
   2:     0x7f70b4e07180 - std[4957aea88bdd0f88]::sys::backtrace::_print_fmt
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/sys/backtrace.rs:74:9
   3:     0x7f70b4e07180 - <<std[4957aea88bdd0f88]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[da6cea203c5b5d33]::fmt::Display>::fmt
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/sys/backtrace.rs:44:26
   4:     0x7f70b0695afe - <core[da6cea203c5b5d33]::fmt::rt::Argument>::fmt
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/core/src/fmt/rt.rs:152:76
   5:     0x7f70b0695afe - core[da6cea203c5b5d33]::fmt::write
   6:     0x7f70b4e1e11c - core[da6cea203c5b5d33]::io::write::default_write_fmt::<std[4957aea88bdd0f88]::sys::stdio::unix::Stderr>
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/core/src/io/write.rs:402:11
   7:     0x7f70b4e1e11c - <std[4957aea88bdd0f88]::sys::stdio::unix::Stderr as core[da6cea203c5b5d33]::io::write::Write>::write_fmt
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/core/src/io/write.rs:335:13
   8:     0x7f70b4dc6544 - <std[4957aea88bdd0f88]::sys::backtrace::BacktraceLock>::print
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/sys/backtrace.rs:47:9
   9:     0x7f70b4dc6544 - std[4957aea88bdd0f88]::panicking::default_hook::{closure#0}
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/panicking.rs:292:27
  10:     0x7f70b4df37e1 - std[4957aea88bdd0f88]::panicking::default_hook
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/panicking.rs:319:9
  11:     0x7f70b19b9738 - <alloc[741620e15a3c417e]::boxed::Box<dyn for<'a, 'b> core[da6cea203c5b5d33]::ops::function::Fn<(&'a std[4957aea88bdd0f88]::panic::PanicHookInfo<'b>,), Output = ()> + core[da6cea203c5b5d33]::marker::Sync + core[da6cea203c5b5d33]::marker::Send> as core[da6cea203c5b5d33]::ops::function::Fn<(&std[4957aea88bdd0f88]::panic::PanicHookInfo,)>>::call
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/alloc/src/boxed.rs:2340:9
  12:     0x7f70b19b9738 - rustc_driver_impl[cb05b4e96be3d0e4]::install_ice_hook::{closure#1}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_driver_impl/src/lib.rs:1482:17
  13:     0x7f70b19b9738 - <alloc[741620e15a3c417e]::boxed::Box<rustc_driver_impl[cb05b4e96be3d0e4]::install_ice_hook::{closure#1}> as core[da6cea203c5b5d33]::ops::function::Fn<(&dyn for<'a, 'b> core[da6cea203c5b5d33]::ops::function::Fn<(&'a std[4957aea88bdd0f88]::panic::PanicHookInfo<'b>,), Output = ()> + core[da6cea203c5b5d33]::marker::Sync + core[da6cea203c5b5d33]::marker::Send, &std[4957aea88bdd0f88]::panic::PanicHookInfo)>>::call
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/alloc/src/boxed.rs:2340:9
  14:     0x7f70b19b9738 - std[4957aea88bdd0f88]::panicking::update_hook::<alloc[741620e15a3c417e]::boxed::Box<rustc_driver_impl[cb05b4e96be3d0e4]::install_ice_hook::{closure#1}>>::{closure#0}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/panicking.rs:235:47
  15:     0x7f70b4df3c6a - <alloc[741620e15a3c417e]::boxed::Box<dyn for<'a, 'b> core[da6cea203c5b5d33]::ops::function::Fn<(&'a std[4957aea88bdd0f88]::panic::PanicHookInfo<'b>,), Output = ()> + core[da6cea203c5b5d33]::marker::Sync + core[da6cea203c5b5d33]::marker::Send> as core[da6cea203c5b5d33]::ops::function::Fn<(&std[4957aea88bdd0f88]::panic::PanicHookInfo,)>>::call
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/alloc/src/boxed.rs:2340:9
  16:     0x7f70b4df3c6a - std[4957aea88bdd0f88]::panicking::panic_with_hook
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/panicking.rs:823:13
  17:     0x7f70b4dc6612 - std[4957aea88bdd0f88]::panicking::panic_handler::{closure#0}
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/panicking.rs:688:13
  18:     0x7f70b4db6919 - std[4957aea88bdd0f88]::sys::backtrace::__rust_end_short_backtrace::<std[4957aea88bdd0f88]::panicking::panic_handler::{closure#0}, !>
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/sys/backtrace.rs:182:18
  19:     0x7f70b4dc850d - __rustc[b6a9bdc199f3cce9]::rust_begin_unwind
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/panicking.rs:679:5
  20:     0x7f70b069684c - core[da6cea203c5b5d33]::panicking::panic_fmt
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/core/src/panicking.rs:80:14
  21:     0x7f70b1ff9800 - <rustc_type_ir[a2ec8591d3d5b635]::binder::ValidateBoundVars<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt> as rustc_type_ir[a2ec8591d3d5b635]::visit::TypeVisitor<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>::visit_region
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_type_ir/src/binder.rs:288:21
  22:     0x7f70b1d6d735 - <rustc_type_ir[a2ec8591d3d5b635]::sty::Region<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt> as rustc_type_ir[a2ec8591d3d5b635]::visit::TypeVisitable<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>::visit_with::<rustc_type_ir[a2ec8591d3d5b635]::binder::ValidateBoundVars<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_type_ir/src/sty/mod.rs:151:17
  23:     0x7f70b1d6d735 - <rustc_middle[66530f1cd38cda85]::ty::generic_args::GenericArg as rustc_type_ir[a2ec8591d3d5b635]::visit::TypeVisitable<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>::visit_with::<rustc_type_ir[a2ec8591d3d5b635]::binder::ValidateBoundVars<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/ty/generic_args.rs:356:48
  24:     0x7f70b1d6d735 - <&rustc_middle[66530f1cd38cda85]::ty::list::RawList<(), rustc_middle[66530f1cd38cda85]::ty::generic_args::GenericArg> as rustc_type_ir[a2ec8591d3d5b635]::visit::TypeVisitable<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>::visit_with::<rustc_type_ir[a2ec8591d3d5b635]::binder::ValidateBoundVars<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/ty/generic_args.rs:710:9
  25:     0x7f70b1e2c5a4 - <rustc_type_ir[a2ec8591d3d5b635]::ty::alias::Alias<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt, rustc_type_ir[a2ec8591d3d5b635]::term_kind::AliasTermKind<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>> as rustc_type_ir[a2ec8591d3d5b635]::visit::TypeVisitable<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>::visit_with::<rustc_type_ir[a2ec8591d3d5b635]::binder::ValidateBoundVars<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_type_ir/src/ty/alias.rs:16:10
  26:     0x7f70b1e2c5a4 - <rustc_type_ir[a2ec8591d3d5b635]::binder::Binder<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt, rustc_type_ir[a2ec8591d3d5b635]::ty::alias::Alias<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt, rustc_type_ir[a2ec8591d3d5b635]::term_kind::AliasTermKind<rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>>>>::bind_with_vars
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_type_ir/src/binder.rs:56:27
  27:     0x7f70b1e2c5a4 - <dyn rustc_hir_analysis[330d207a830ca3ff]::hir_ty_lowering::HirTyLowerer>::lower_assoc_item_constraint
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs:455:13
  28:     0x7f70b1e2c5a4 - <dyn rustc_hir_analysis[330d207a830ca3ff]::hir_ty_lowering::HirTyLowerer>::lower_poly_trait_ref
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs:1160:54
  29:     0x7f70b1c60d9e - <dyn rustc_hir_analysis[330d207a830ca3ff]::hir_ty_lowering::HirTyLowerer>::lower_bounds::<&[rustc_hir[e492e04751bc083d]::hir::GenericBound]>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs:337:34
  30:     0x7f70b1f22f63 - rustc_hir_analysis[330d207a830ca3ff]::collect::item_bounds::associated_type_bounds
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/collect/item_bounds.rs:43:23
  31:     0x7f70b1f244a9 - rustc_hir_analysis[330d207a830ca3ff]::collect::item_bounds::explicit_item_bounds_with_filter
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/collect/item_bounds.rs:434:17
  32:     0x7f70b1f223b6 - rustc_hir_analysis[330d207a830ca3ff]::collect::item_bounds::explicit_item_bounds
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/collect/item_bounds.rs:413:5
  33:     0x7f70b3db7aaa - rustc_query_impl[caac36dfda81a9d7]::query_impl::explicit_item_bounds::invoke_provider_fn::__rust_begin_short_backtrace
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/query_impl.rs:112:29
  34:     0x7f70b3b14db6 - rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr::<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/execution.rs:422:59
  35:     0x7f70b3b14db6 - rustc_middle[66530f1cd38cda85]::ty::context::tls::enter_context::<rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>::{closure#0}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/ty/context/tls.rs:56:9
  36:     0x7f70b3b14db6 - <std[4957aea88bdd0f88]::thread::local::LocalKey<core[da6cea203c5b5d33]::cell::Cell<*const ()>>>::try_with::<rustc_middle[66530f1cd38cda85]::ty::context::tls::enter_context<rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/thread/local.rs:464:12
  37:     0x7f70b3b14db6 - <std[4957aea88bdd0f88]::thread::local::LocalKey<core[da6cea203c5b5d33]::cell::Cell<*const ()>>>::with::<rustc_middle[66530f1cd38cda85]::ty::context::tls::enter_context<rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/thread/local.rs:428:20
  38:     0x7f70b3b14db6 - rustc_middle[66530f1cd38cda85]::ty::context::tls::enter_context::<rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/ty/context/tls.rs:53:9
  39:     0x7f70b3b14db6 - rustc_query_impl[caac36dfda81a9d7]::plumbing::start_query::<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>, rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}>::{closure#0}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/plumbing.rs:74:9
  40:     0x7f70b3b14db6 - rustc_middle[66530f1cd38cda85]::ty::context::tls::with_context::<rustc_query_impl[caac36dfda81a9d7]::plumbing::start_query<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>, rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>::{closure#0}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/ty/context/tls.rs:86:36
  41:     0x7f70b3b14db6 - rustc_middle[66530f1cd38cda85]::ty::context::tls::with_context_opt::<rustc_middle[66530f1cd38cda85]::ty::context::tls::with_context<rustc_query_impl[caac36dfda81a9d7]::plumbing::start_query<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>, rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/ty/context/tls.rs:75:18
  42:     0x7f70b3b14db6 - rustc_middle[66530f1cd38cda85]::ty::context::tls::with_context::<rustc_query_impl[caac36dfda81a9d7]::plumbing::start_query<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>, rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}>::{closure#0}, rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/ty/context/tls.rs:86:5
  43:     0x7f70b3b14db6 - rustc_query_impl[caac36dfda81a9d7]::plumbing::start_query::<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>, rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/plumbing.rs:61:5
  44:     0x7f70b3b14db6 - rustc_query_impl[caac36dfda81a9d7]::execution::execute_job_non_incr::<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/execution.rs:422:17
  45:     0x7f70b3b14db6 - rustc_query_impl[caac36dfda81a9d7]::execution::try_execute_query::<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>, false>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/execution.rs:330:17
  46:     0x7f70b3db7e76 - rustc_query_impl[caac36dfda81a9d7]::execution::execute_query_non_incr_inner::<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/execution.rs:616:32
  47:     0x7f70b3db7e76 - stacker[63f11707587470ee]::maybe_grow::<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>, rustc_query_impl[caac36dfda81a9d7]::execution::execute_query_non_incr_inner<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}>
                               at /rust/deps/stacker-0.1.21/src/lib.rs:57:9
  48:     0x7f70b3db7e76 - rustc_data_structures[8b14e35dea0ad776]::stack::ensure_sufficient_stack::<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>, rustc_query_impl[caac36dfda81a9d7]::execution::execute_query_non_incr_inner<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>::{closure#0}>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_data_structures/src/stack.rs:21:5
  49:     0x7f70b3db7e76 - rustc_query_impl[caac36dfda81a9d7]::execution::execute_query_non_incr_inner::<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/execution.rs:616:5
  50:     0x7f70b3db7e76 - rustc_query_impl[caac36dfda81a9d7]::query_impl::explicit_item_bounds::execute_query_non_incr::__rust_end_short_backtrace
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/query_impl.rs:82:30
  51:     0x7f70b1cee874 - rustc_middle[66530f1cd38cda85]::query::inner::query_get_at::<rustc_middle[66530f1cd38cda85]::query::caches::DefIdCache<rustc_middle[66530f1cd38cda85]::query::erase::ErasedData<[u8; 16usize]>>>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/query/inner.rs:45:17
  52:     0x7f70b1cee874 - <rustc_middle[66530f1cd38cda85]::query::plumbing::TyCtxtAt>::explicit_item_bounds::<rustc_span[de76fed82ebe26ff]::def_id::DefId>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/query/plumbing.rs:564:46
  53:     0x7f70b1cee874 - <rustc_middle[66530f1cd38cda85]::ty::context::TyCtxt>::explicit_item_bounds::<rustc_span[de76fed82ebe26ff]::def_id::DefId>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_middle/src/query/plumbing.rs:552:39
  54:     0x7f70b1cee874 - rustc_hir_analysis[330d207a830ca3ff]::check::wfcheck::check_associated_type_bounds
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/check/wfcheck.rs:1121:29
  55:     0x7f70b1cee874 - rustc_hir_analysis[330d207a830ca3ff]::check::wfcheck::check_associated_item::{closure#0}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/check/wfcheck.rs:961:21
  56:     0x7f70b1cee874 - rustc_hir_analysis[330d207a830ca3ff]::check::wfcheck::enter_wf_checking_ctxt::<rustc_hir_analysis[330d207a830ca3ff]::check::wfcheck::check_associated_item::{closure#0}>
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/check/wfcheck.rs:178:5
  57:     0x7f70b1f10d19 - rustc_hir_analysis[330d207a830ca3ff]::check::wfcheck::check_associated_item
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_hir_analysis/src/check/wfcheck.rs:913:5

< snip >

 177:     0x7f70b19c1d09 - std[4957aea88bdd0f88]::thread::lifecycle::spawn_unchecked::<rustc_interface[b0e8760c305ddcff]::util::run_in_thread_with_globals<rustc_interface[b0e8760c305ddcff]::util::run_in_thread_pool_with_globals<rustc_interface[b0e8760c305ddcff]::interface::run_compiler<(), rustc_driver_impl[cb05b4e96be3d0e4]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/thread/lifecycle.rs:68:26
 178:     0x7f70b19c1d09 - <std[4957aea88bdd0f88]::thread::lifecycle::spawn_unchecked<rustc_interface[b0e8760c305ddcff]::util::run_in_thread_with_globals<rustc_interface[b0e8760c305ddcff]::util::run_in_thread_pool_with_globals<rustc_interface[b0e8760c305ddcff]::interface::run_compiler<(), rustc_driver_impl[cb05b4e96be3d0e4]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[da6cea203c5b5d33]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
                               at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/core/src/ops/function.rs:250:5
 179:     0x7f70b4e02cef - <alloc[741620e15a3c417e]::boxed::Box<dyn core[da6cea203c5b5d33]::ops::function::FnOnce<(), Output = ()> + core[da6cea203c5b5d33]::marker::Send> as core[da6cea203c5b5d33]::ops::function::FnOnce<()>>::call_once
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/alloc/src/boxed.rs:2326:9
 180:     0x7f70b4e02cef - <std[4957aea88bdd0f88]::sys::thread::unix::Thread>::new::thread_start
                               at /rustc/da86f4d0726be475afbbffe40cb2f65741c51ad3/library/std/src/sys/thread/unix.rs:123:17
 181:     0x7f70aec97739 - <unknown>
 182:     0x7f70aed1bedc - <unknown>
 183:                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-2026-07-25T10_05_53-2302539.txt` to your bug report

note: rustc 1.99.0-nightly (da86f4d07 2026-07-24) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [explicit_item_bounds] finding item bounds for `c::d::{anon_assoc#0}`
#1 [check_well_formed] checking that `c::d` is well-formed
#2 [check_type_wf] checking that types are well-formed
#3 [analysis] running analysis passes on crate `code`
end of query stack
warning: 2 warnings emitted

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error[E0391]: cycle detected when computing function signature of `c::d`
 --> code.rs:4:5
  |
4 |     fn d(&self) -> impl c<d(..): >;
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: ...which requires looking up late bound vars inside `c::d`...
  = note: ...which requires resolving lifetimes for `c::d`...
  = note: ...which again requires computing function signature of `c::d`, completing the cycle
  = note: cycle used when computing the variances for items in this crate
  = note: for more information, see <https://rustc-dev-guide.rust-lang.org/overview.html#queries> and <https://rustc-dev-guide.rust-lang.org/query.html>
note: delayed at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_query_impl/src/job.rs:487:24
         0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
                   at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_errors/src/lib.rs:1275:41
         1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
                   at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_errors/src/lib.rs:868:33
         2: <rustc_errors::diagnostic::Diag>::emit_producing_error_guaranteed
                   at /rustc-dev/da86f4d0726be475afbbffe40cb2f65741c51ad3/compiler/rustc_errors/src/diagnostic.rs:1325:29
....