ICE on recursive fn which returns impl T

[jruderman]

Valid according to stable (1.64.0), but ICEs beta (1.65.0-beta.4) and ICEs nightly:

trait T {}

fn wrap(x: impl T) -> impl T {
    wrap(wrap(x))
}

fn main() {}

Reduced from a fuzzer mutation of src/test/ui/impl-trait/issue-87450.rs

Error output

Two ICEs:

thread 'rustc' panicked at 'assertion failed: !infcx.is_in_snapshot() || self.usable_in_snapshot', compiler/rustc_trait_selection/src/traits/fulfill.rs:177:9

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: VecMap([(OpaqueTypeKey { def_id: DefId(0:7 ~ main[d88a]::wrap::{opaque#1}), substs: [impl T] }, OpaqueTypeDecl { hidden_type: OpaqueHiddenType { span: cyz/src/main.rs:7:5: 7:18 (#0), ty: impl T }, origin: FnReturn(DefId(0:4 ~ main[d88a]::wrap)) })])
  |
  = note: delayed at compiler/rustc_infer/src/infer/opaque_types/table.rs:50:26

Full output with both backtraces

thread 'rustc' panicked at 'assertion failed: !infcx.is_in_snapshot() || self.usable_in_snapshot', compiler/rustc_trait_selection/src/traits/fulfill.rs:177:9
stack backtrace:
   0:        0x105c92882 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h25d806a113d8ecc4
   1:        0x105cea72a - core::fmt::write::h27951ddb40e14403
   2:        0x105c8484c - std::io::Write::write_fmt::h7266f2429fcf12b5
   3:        0x105c9264a - std::sys_common::backtrace::print::h73136d09f0ffc17b
   4:        0x105c95a56 - std::panicking::default_hook::{{closure}}::h914a4530f160715f
   5:        0x105c957a7 - std::panicking::default_hook::h66c12acf767bf01f
   6:        0x114bcbbfd - rustc_driver[8de3e851f3511a86]::DEFAULT_HOOK::{closure#0}::{closure#0}
   7:        0x105c96251 - std::panicking::rust_panic_with_hook::h54847cdb3a29a411
   8:        0x105c95fa2 - std::panicking::begin_panic_handler::{{closure}}::h2f6619e41c119eb6
   9:        0x105c92d18 - std::sys_common::backtrace::__rust_end_short_backtrace::hbf07852adff27aef
  10:        0x105c95cad - _rust_begin_unwind
  11:        0x105d17193 - core::panicking::panic_fmt::h4ef0f61efac12a83
  12:        0x105d17267 - core::panicking::panic::h2dceeeaec9419bf8
  13:        0x11910fe16 - <rustc_trait_selection[a15beaa728f912ec]::traits::fulfill::FulfillmentContext as rustc_infer[6fee85a783c5345a]::traits::engine::TraitEngine>::register_predicate_obligation
  14:        0x117e9611f - rustc_trait_selection[a15beaa728f912ec]::traits::fully_solve_obligations::<alloc[30a41e7aafccdad0]::vec::Vec<rustc_infer[6fee85a783c5345a]::traits::Obligation<rustc_middle[c9d78f14285fe0f2]::ty::Predicate>>>
  15:        0x117ee3f7e - rustc_trait_selection[a15beaa728f912ec]::traits::query::type_op::custom::scrape_region_constraints::<rustc_borrowck[91564686624f537b]::type_check::InstantiateOpaqueType, (), <rustc_borrowck[91564686624f537b]::type_check::InstantiateOpaqueType as rustc_trait_selection[a15beaa728f912ec]::traits::query::type_op::TypeOp>::fully_perform::{closure#0}>
  16:        0x117ec4b54 - <rustc_borrowck[91564686624f537b]::type_check::InstantiateOpaqueType as rustc_trait_selection[a15beaa728f912ec]::traits::query::type_op::TypeOp>::fully_perform
  17:        0x117ec5cd8 - <rustc_borrowck[91564686624f537b]::type_check::TypeChecker>::fully_perform_op::<(), rustc_borrowck[91564686624f537b]::type_check::InstantiateOpaqueType>
  18:        0x117fb9c3b - <rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate as rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelatingDelegate>::register_opaque_type
  19:        0x117eb7d19 - <rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate>>::relate_opaques
  20:        0x117eb6f89 - <rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate> as rustc_middle[c9d78f14285fe0f2]::ty::relate::TypeRelation>::relate::<rustc_middle[c9d78f14285fe0f2]::ty::Ty>
  21:        0x117e992dc - <rustc_middle[c9d78f14285fe0f2]::ty::subst::GenericArg as rustc_middle[c9d78f14285fe0f2]::ty::relate::Relate>::relate::<rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate>>
  22:        0x117e556ec - <core[2c87c43c7709eb65]::result::Result<rustc_middle[c9d78f14285fe0f2]::ty::subst::GenericArg, rustc_middle[c9d78f14285fe0f2]::ty::error::TypeError> as rustc_type_ir[92625cb12ceab9e2]::InternIteratorElement<rustc_middle[c9d78f14285fe0f2]::ty::subst::GenericArg, &rustc_middle[c9d78f14285fe0f2]::ty::list::List<rustc_middle[c9d78f14285fe0f2]::ty::subst::GenericArg>>>::intern_with::<core[2c87c43c7709eb65]::iter::adapters::map::Map<core[2c87c43c7709eb65]::iter::adapters::zip::Zip<core[2c87c43c7709eb65]::iter::adapters::copied::Copied<core[2c87c43c7709eb65]::slice::iter::Iter<rustc_middle[c9d78f14285fe0f2]::ty::subst::GenericArg>>, core[2c87c43c7709eb65]::iter::adapters::copied::Copied<core[2c87c43c7709eb65]::slice::iter::Iter<rustc_middle[c9d78f14285fe0f2]::ty::subst::GenericArg>>>, rustc_middle[c9d78f14285fe0f2]::ty::relate::relate_substs<rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate>>::{closure#0}>, <rustc_middle[c9d78f14285fe0f2]::ty::context::TyCtxt>::mk_substs<core[2c87c43c7709eb65]::iter::adapters::map::Map<core[2c87c43c7709eb65]::iter::adapters::zip::Zip<core[2c87c43c7709eb65]::iter::adapters::copied::Copied<core[2c87c43c7709eb65]::slice::iter::Iter<rustc_middle[c9d78f14285fe0f2]::ty::subst::GenericArg>>, core[2c87c43c7709eb65]::iter::adapters::copied::Copied<core[2c87c43c7709eb65]::slice::iter::Iter<rustc_middle[c9d78f14285fe0f2]::ty::subst::GenericArg>>>, rustc_middle[c9d78f14285fe0f2]::ty::relate::relate_substs<rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate>>::{closure#0}>>::{closure#0}>
  23:        0x117f9c182 - rustc_middle[c9d78f14285fe0f2]::ty::relate::relate_substs::<rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate>>
  24:        0x117f9d3bb - rustc_middle[c9d78f14285fe0f2]::ty::relate::super_relate_tys::<rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate>>
  25:        0x117df2b42 - <rustc_infer[6fee85a783c5345a]::infer::InferCtxt>::super_combine_tys::<rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate>>
  26:        0x117eb6f32 - <rustc_infer[6fee85a783c5345a]::infer::nll_relate::TypeRelating<rustc_borrowck[91564686624f537b]::type_check::relate_tys::NllTypeRelatingDelegate> as rustc_middle[c9d78f14285fe0f2]::ty::relate::TypeRelation>::relate::<rustc_middle[c9d78f14285fe0f2]::ty::Ty>
  27:        0x117ec76e4 - <rustc_borrowck[91564686624f537b]::type_check::TypeChecker>::relate_types
  28:        0x117ecfe43 - <rustc_borrowck[91564686624f537b]::type_check::TypeChecker>::typeck_mir
  29:        0x117ebbfcb - rustc_borrowck[91564686624f537b]::type_check::type_check
  30:        0x117e0e962 - rustc_borrowck[91564686624f537b]::nll::compute_regions
  31:        0x117f31f90 - rustc_borrowck[91564686624f537b]::do_mir_borrowck
  32:        0x117f23b9f - rustc_borrowck[91564686624f537b]::mir_borrowck
  33:        0x117f04425 - <rustc_borrowck[91564686624f537b]::provide::{closure#0} as core[2c87c43c7709eb65]::ops::function::FnOnce<(rustc_middle[c9d78f14285fe0f2]::ty::context::TyCtxt, rustc_span[81b003e947b8ff3]::def_id::LocalDefId)>>::call_once
  34:        0x1183a38f9 - rustc_query_system[6dacc3bd586c32a5]::query::plumbing::try_execute_query::<rustc_query_impl[8431c9b77d4d37fe]::plumbing::QueryCtxt, rustc_query_system[6dacc3bd586c32a5]::query::caches::DefaultCache<rustc_span[81b003e947b8ff3]::def_id::LocalDefId, &rustc_middle[c9d78f14285fe0f2]::mir::query::BorrowCheckResult>>
  35:        0x118494be3 - rustc_query_system[6dacc3bd586c32a5]::query::plumbing::get_query::<rustc_query_impl[8431c9b77d4d37fe]::queries::mir_borrowck, rustc_query_impl[8431c9b77d4d37fe]::plumbing::QueryCtxt>
  36:        0x11765de7a - rustc_hir_analysis[30e39910cbeda8e1]::collect::type_of::find_opaque_ty_constraints_for_rpit
  37:        0x11765cfc6 - rustc_hir_analysis[30e39910cbeda8e1]::collect::type_of::type_of
  38:        0x1183c4215 - rustc_query_system[6dacc3bd586c32a5]::query::plumbing::try_execute_query::<rustc_query_impl[8431c9b77d4d37fe]::plumbing::QueryCtxt, rustc_query_system[6dacc3bd586c32a5]::query::caches::DefaultCache<rustc_span[81b003e947b8ff3]::def_id::DefId, rustc_middle[c9d78f14285fe0f2]::ty::Ty>>
  39:        0x1184a8174 - rustc_query_system[6dacc3bd586c32a5]::query::plumbing::get_query::<rustc_query_impl[8431c9b77d4d37fe]::queries::type_of, rustc_query_impl[8431c9b77d4d37fe]::plumbing::QueryCtxt>
  40:        0x1176113cc - rustc_hir_analysis[30e39910cbeda8e1]::check::check::check_item_type
  41:        0x11761ad5e - rustc_hir_analysis[30e39910cbeda8e1]::check::check::check_mod_item_types
  42:        0x1183a6f75 - rustc_query_system[6dacc3bd586c32a5]::query::plumbing::try_execute_query::<rustc_query_impl[8431c9b77d4d37fe]::plumbing::QueryCtxt, rustc_query_system[6dacc3bd586c32a5]::query::caches::DefaultCache<rustc_span[81b003e947b8ff3]::def_id::LocalDefId, ()>>
  43:        0x11849e2b5 - rustc_query_system[6dacc3bd586c32a5]::query::plumbing::get_query::<rustc_query_impl[8431c9b77d4d37fe]::queries::check_mod_item_types, rustc_query_impl[8431c9b77d4d37fe]::plumbing::QueryCtxt>
  44:        0x11763f898 - <rustc_middle[c9d78f14285fe0f2]::hir::map::Map>::for_each_module::<rustc_hir_analysis[30e39910cbeda8e1]::check_crate::{closure#6}::{closure#0}>
  45:        0x11762fcc9 - <rustc_session[82219efc93061be6]::session::Session>::time::<(), rustc_hir_analysis[30e39910cbeda8e1]::check_crate::{closure#6}>
  46:        0x1175e434f - rustc_hir_analysis[30e39910cbeda8e1]::check_crate
  47:        0x114c98d4a - rustc_interface[7f8f58d06d0d17dc]::passes::analysis
  48:        0x11842e0fc - rustc_query_system[6dacc3bd586c32a5]::query::plumbing::try_execute_query::<rustc_query_impl[8431c9b77d4d37fe]::plumbing::QueryCtxt, rustc_query_system[6dacc3bd586c32a5]::query::caches::DefaultCache<(), core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>>
  49:        0x1184a8289 - rustc_query_system[6dacc3bd586c32a5]::query::plumbing::get_query::<rustc_query_impl[8431c9b77d4d37fe]::queries::analysis, rustc_query_impl[8431c9b77d4d37fe]::plumbing::QueryCtxt>
  50:        0x114b5aeb6 - <rustc_interface[7f8f58d06d0d17dc]::passes::QueryContext>::enter::<rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}::{closure#2}::{closure#3}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>
  51:        0x114b9f71d - rustc_span[81b003e947b8ff3]::with_source_map::<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_interface[7f8f58d06d0d17dc]::interface::run_compiler<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}>::{closure#0}::{closure#1}>
  52:        0x114b8ee1c - <scoped_tls[ea35ba321eba8f32]::ScopedKey<rustc_span[81b003e947b8ff3]::SessionGlobals>>::set::<rustc_interface[7f8f58d06d0d17dc]::interface::run_compiler<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}>::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>
  53:        0x114b5ea3a - std[4f43db94453d85b3]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[7f8f58d06d0d17dc]::util::run_in_thread_pool_with_globals<rustc_interface[7f8f58d06d0d17dc]::interface::run_compiler<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}>::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>
  54:        0x114b4462b - <<std[4f43db94453d85b3]::thread::Builder>::spawn_unchecked_<rustc_interface[7f8f58d06d0d17dc]::util::run_in_thread_pool_with_globals<rustc_interface[7f8f58d06d0d17dc]::interface::run_compiler<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}>::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>::{closure#1} as core[2c87c43c7709eb65]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  55:        0x105c9f367 - std::sys::unix::thread::Thread::new::thread_start::h87910746f103bc71
  56:     0x7ff81000f4e1 - __pthread_start

error: internal compiler error: unexpected panic

note: 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 1.66.0-nightly (bed4ad65b 2022-10-25) running on x86_64-apple-darwin

query stack during panic:
#0 [mir_borrowck] borrow-checking `wrap`
#1 [type_of] computing type of `wrap::{opaque#1}`
#2 [check_mod_item_types] checking item types in top-level module
#3 [analysis] running analysis passes on this crate
end of query stack
error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: VecMap([(OpaqueTypeKey { def_id: DefId(0:7 ~ main[d88a]::wrap::{opaque#1}), substs: [impl T] }, OpaqueTypeDecl { hidden_type: OpaqueHiddenType { span: cyz/src/main.rs:7:5: 7:18 (#0), ty: impl T }, origin: FnReturn(DefId(0:4 ~ main[d88a]::wrap)) })])
  |
  = note: delayed at compiler/rustc_infer/src/infer/opaque_types/table.rs:50:26

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1553:13
stack backtrace:
   0:        0x105c92882 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h25d806a113d8ecc4
   1:        0x105cea72a - core::fmt::write::h27951ddb40e14403
   2:        0x105c8484c - std::io::Write::write_fmt::h7266f2429fcf12b5
   3:        0x105c9264a - std::sys_common::backtrace::print::h73136d09f0ffc17b
   4:        0x105c95a56 - std::panicking::default_hook::{{closure}}::h914a4530f160715f
   5:        0x105c957a7 - std::panicking::default_hook::h66c12acf767bf01f
   6:        0x114bcbbfd - rustc_driver[8de3e851f3511a86]::DEFAULT_HOOK::{closure#0}::{closure#0}
   7:        0x105c96251 - std::panicking::rust_panic_with_hook::h54847cdb3a29a411
   8:        0x11959cb87 - std[4f43db94453d85b3]::panicking::begin_panic::<rustc_errors[daa152a9571d4543]::ExplicitBug>::{closure#0}
   9:        0x11959abb9 - std[4f43db94453d85b3]::sys_common::backtrace::__rust_end_short_backtrace::<std[4f43db94453d85b3]::panicking::begin_panic<rustc_errors[daa152a9571d4543]::ExplicitBug>::{closure#0}, !>
  10:        0x119961e69 - std[4f43db94453d85b3]::panicking::begin_panic::<rustc_errors[daa152a9571d4543]::ExplicitBug>
  11:        0x11958cd19 - std[4f43db94453d85b3]::panic::panic_any::<rustc_errors[daa152a9571d4543]::ExplicitBug>
  12:        0x119593e3e - <rustc_errors[daa152a9571d4543]::HandlerInner>::flush_delayed::<alloc[30a41e7aafccdad0]::vec::Vec<rustc_errors[daa152a9571d4543]::diagnostic::Diagnostic>, &str>
  13:        0x11958fca9 - <rustc_errors[daa152a9571d4543]::HandlerInner as core[2c87c43c7709eb65]::ops::drop::Drop>::drop
  14:        0x114b4dd5a - core[2c87c43c7709eb65]::ptr::drop_in_place::<rustc_session[82219efc93061be6]::parse::ParseSess>
  15:        0x114b4f4db - core[2c87c43c7709eb65]::ptr::drop_in_place::<rustc_session[82219efc93061be6]::session::Session>
  16:        0x114bb4e1e - core[2c87c43c7709eb65]::ptr::drop_in_place::<rustc_interface[7f8f58d06d0d17dc]::interface::Compiler>
  17:        0x114b9fc0f - rustc_span[81b003e947b8ff3]::with_source_map::<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_interface[7f8f58d06d0d17dc]::interface::run_compiler<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}>::{closure#0}::{closure#1}>
  18:        0x114b8ee1c - <scoped_tls[ea35ba321eba8f32]::ScopedKey<rustc_span[81b003e947b8ff3]::SessionGlobals>>::set::<rustc_interface[7f8f58d06d0d17dc]::interface::run_compiler<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}>::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>
  19:        0x114b5ea3a - std[4f43db94453d85b3]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[7f8f58d06d0d17dc]::util::run_in_thread_pool_with_globals<rustc_interface[7f8f58d06d0d17dc]::interface::run_compiler<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}>::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>
  20:        0x114b4462b - <<std[4f43db94453d85b3]::thread::Builder>::spawn_unchecked_<rustc_interface[7f8f58d06d0d17dc]::util::run_in_thread_pool_with_globals<rustc_interface[7f8f58d06d0d17dc]::interface::run_compiler<core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>, rustc_driver[8de3e851f3511a86]::run_compiler::{closure#1}>::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2c87c43c7709eb65]::result::Result<(), rustc_errors[daa152a9571d4543]::ErrorGuaranteed>>::{closure#1} as core[2c87c43c7709eb65]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  21:        0x105c9f367 - std::sys::unix::thread::Thread::new::thread_start::h87910746f103bc71
  22:     0x7ff81000f4e1 - __pthread_start

note: 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 1.66.0-nightly (bed4ad65b 2022-10-25) running on x86_64-apple-darwin

query stack during panic:
end of query stack
thread panicked while panicking. aborting.
Abort trap: 6

Version

rustc --version --verbose:

rustc 1.66.0-nightly (bed4ad65b 2022-10-25)
binary: rustc
commit-hash: bed4ad65bf7a1cef39e3d66b3670189581b3b073
commit-date: 2022-10-25
host: x86_64-apple-darwin
release: 1.66.0-nightly
LLVM version: 15.0.2

Regression

Bisected with cargo-bisect-rustc on x86_64-apple-darwin:

searched nightlies: from nightly-2022-08-23 to nightly-2022-10-26
regressed nightly: nightly-2022-08-31
searched commit range: bc4b39c...02654a0
regressed commit: 0631ea5 (rollup)

Among the commits in the rollup, my guess is #100092 (CC @compiler-errors):

• It added the function relate_opaques (frame 19 on the first stack).
• It added a regression test with some similarities: an unconditionally recursive function with impl in return position.

@rustbot label +regression-from-stable-to-beta +A-impl-trait

[compiler-errors]

yup, ez fix incoming