warning: the feature `fn_delegation` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.pYoYXAah8KAR/rustc_testrunner_tmpdir_reporting.7dx1EBXRKZmJ/mvce.rs:1:12
  |
1 | #![feature(fn_delegation)]
  |            ^^^^^^^^^^^^^
  |
  = note: see issue #118212 <https://github.com/rust-lang/rust/issues/118212> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: function `default` is never used
 --> /tmp/icemaker_global_tempdir.pYoYXAah8KAR/rustc_testrunner_tmpdir_reporting.7dx1EBXRKZmJ/mvce.rs:2:16
  |
2 | reuse Default::default;
  |                ^^^^^^^
  |
  = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default

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: the self type must be specified
 --> /tmp/icemaker_global_tempdir.pYoYXAah8KAR/rustc_testrunner_tmpdir_reporting.7dx1EBXRKZmJ/mvce.rs:2:16
  |
2 | reuse Default::default;
  |                ^^^^^^^
  |
note: delayed at /rustc-dev/ce89c898570852a1bb441d77570596e50bf362c2/compiler/rustc_hir_analysis/src/delegation.rs:287:13
         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::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, &str>
         4: rustc_hir_analysis::delegation::get_delegation_self_ty_or_err
         5: rustc_hir_analysis::delegation::create_folder_and_args
         6: rustc_hir_analysis::collect::predicates_of::gather_explicit_predicates_of::{closure#0}
         7: rustc_query_impl::query_impl::explicit_predicates_of::invoke_provider_fn::__rust_begin_short_backtrace
         8: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 24]>>, false>
         9: rustc_query_impl::query_impl::explicit_predicates_of::execute_query_non_incr::__rust_end_short_backtrace
        10: rustc_query_impl::query_impl::predicates_of::invoke_provider_fn::__rust_begin_short_backtrace
        11: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 24]>>, false>
        12: rustc_query_impl::query_impl::predicates_of::execute_query_non_incr::__rust_end_short_backtrace
        13: rustc_hir_analysis::check::check::check_item_type
        14: rustc_hir_analysis::check::wfcheck::check_well_formed
        15: rustc_query_impl::query_impl::check_well_formed::invoke_provider_fn::__rust_begin_short_backtrace
        16: 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>
        17: rustc_query_impl::query_impl::check_well_formed::execute_query_non_incr::__rust_end_short_backtrace
        18: rustc_hir_analysis::check::wfcheck::check_type_wf
        19: rustc_query_impl::query_impl::check_type_wf::invoke_provider_fn::__rust_begin_short_backtrace
        20: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 1]>>, false>
        21: rustc_query_impl::query_impl::check_type_wf::execute_query_non_incr::__rust_end_short_backtrace
        22: rustc_hir_analysis::check_crate
        23: rustc_interface::passes::analysis
        24: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>, false>
        25: rustc_query_impl::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
        26: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        27: 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#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
        28: <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#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        29: <std::sys::thread::unix::Thread>::new::thread_start
        30: <unknown>
        31: <unknown>
      
 --> /tmp/icemaker_global_tempdir.pYoYXAah8KAR/rustc_testrunner_tmpdir_reporting.7dx1EBXRKZmJ/mvce.rs:2:16
  |
2 | reuse Default::default;
  |                ^^^^^^^

error: internal compiler error: the self type must be specified
 --> /tmp/icemaker_global_tempdir.pYoYXAah8KAR/rustc_testrunner_tmpdir_reporting.7dx1EBXRKZmJ/mvce.rs:2:16
  |
2 | reuse Default::default;
  |                ^^^^^^^
  |
note: delayed at /rustc-dev/ce89c898570852a1bb441d77570596e50bf362c2/compiler/rustc_hir_analysis/src/delegation.rs:287:13
         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::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, &str>
         4: rustc_hir_analysis::delegation::get_delegation_self_ty_or_err
         5: rustc_hir_analysis::delegation::create_folder_and_args
         6: rustc_hir_analysis::delegation::inherit_sig_for_delegation_item
         7: rustc_query_impl::query_impl::inherit_sig_for_delegation_item::invoke_provider_fn::__rust_begin_short_backtrace
         8: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 16]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
         9: rustc_query_impl::query_impl::inherit_sig_for_delegation_item::execute_query_non_incr::__rust_end_short_backtrace
        10: <dyn rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::lower_ty
        11: <dyn rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::lower_fn_ty
        12: rustc_hir_analysis::collect::lower_fn_sig_recovering_infer_ret_ty
        13: rustc_hir_analysis::collect::fn_sig
        14: rustc_query_impl::query_impl::fn_sig::invoke_provider_fn::__rust_begin_short_backtrace
        15: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 24]>>, false>
        16: rustc_query_impl::query_impl::fn_sig::execute_query_non_incr::__rust_end_short_backtrace
        17: rustc_hir_analysis::check::check::check_item_type
        18: rustc_hir_analysis::check::wfcheck::check_well_formed
        19: rustc_query_impl::query_impl::check_well_formed::invoke_provider_fn::__rust_begin_short_backtrace
        20: 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>
        21: rustc_query_impl::query_impl::check_well_formed::execute_query_non_incr::__rust_end_short_backtrace
        22: rustc_hir_analysis::check::wfcheck::check_type_wf
        23: rustc_query_impl::query_impl::check_type_wf::invoke_provider_fn::__rust_begin_short_backtrace
        24: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 1]>>, false>
        25: rustc_query_impl::query_impl::check_type_wf::execute_query_non_incr::__rust_end_short_backtrace
        26: rustc_hir_analysis::check_crate
        27: rustc_interface::passes::analysis
        28: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>, false>
        29: rustc_query_impl::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
        30: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        31: 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#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
        32: <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#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        33: <std::sys::thread::unix::Thread>::new::thread_start
        34: <unknown>
        35: <unknown>
      
 --> /tmp/icemaker_global_tempdir.pYoYXAah8KAR/rustc_testrunner_tmpdir_reporting.7dx1EBXRKZmJ/mvce.rs:2:16
  |
2 | reuse Default::default;
  |                ^^^^^^^

error: internal compiler error: mir_const_qualif: MIR had errors
 --> /tmp/icemaker_global_tempdir.pYoYXAah8KAR/rustc_testrunner_tmpdir_reporting.7dx1EBXRKZmJ/mvce.rs:2:16
  |
2 | reuse Default::default;
  |                ^^^^^^^
  |
note: delayed at /rustc-dev/ce89c898570852a1bb441d77570596e50bf362c2/compiler/rustc_mir_transform/src/lib.rs:373:19
         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::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, &str>
         4: rustc_mir_transform::mir_const_qualif
         5: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::DefIdCache<rustc_middle::query::erase::ErasedData<[u8; 4]>>, false>
         6: rustc_query_impl::query_impl::mir_const_qualif::execute_query_non_incr::__rust_end_short_backtrace
         7: rustc_mir_transform::mir_promoted
         8: rustc_query_impl::query_impl::mir_promoted::invoke_provider_fn::__rust_begin_short_backtrace
         9: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 16]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        10: rustc_query_impl::query_impl::mir_promoted::execute_query_non_incr::__rust_end_short_backtrace
        11: rustc_borrowck::mir_borrowck
        12: rustc_query_impl::query_impl::mir_borrowck::invoke_provider_fn::__rust_begin_short_backtrace
        13: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::ErasedData<[u8; 8]>, rustc_middle::dep_graph::graph::DepNodeIndex>, false>
        14: rustc_query_impl::query_impl::mir_borrowck::execute_query_non_incr::__rust_end_short_backtrace
        15: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface::passes::run_required_analyses::{closure#2}::{closure#0}>::{closure#0}
        16: rustc_interface::passes::analysis
        17: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>, false>
        18: rustc_query_impl::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
        19: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        20: 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#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
        21: <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#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        22: <std::sys::thread::unix::Thread>::new::thread_start
        23: <unknown>
        24: <unknown>
      
 --> /tmp/icemaker_global_tempdir.pYoYXAah8KAR/rustc_testrunner_tmpdir_reporting.7dx1EBXRKZmJ/mvce.rs:2:16
  |
2 | reuse Default::default;
  |                ^^^^^^^

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: rustc 1.97.0-nightly (ce89c8985 2026-05-09) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack