ice: `bug!()` in mir building

[matthiaskrgr]

auto-reduced (treereduce-rust):

trait Foo {}

trait ThreeCellFragment {
    fn ext_cells<'a>(&'a self) -> impl Foo + 'a {
        self.ext_adjacent_cells(|()| 3)
    }
}

original:

// check-pass


trait Foo {}

impl Foo for () {}

trait ThreeCellFragment {
    fn ext_cells<'a>(&'a self) -> impl Foo + 'a {
        self.ext_adjacent_cells(|()| 3)
    }

    fn ext_adjacent_cells<'a>(&'a self) -> impl Foo + 'a;
}

fn main() {}

Version information

rustc 1.75.0-nightly (17d0a45f5 2023-11-10)
binary: rustc
commit-hash: 17d0a45f5df31f218b84c3275bb05c3227348b5b
commit-date: 2023-11-10
host: x86_64-unknown-linux-gnu
release: 1.75.0-nightly
LLVM version: 17.0.4

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.sMhjD6Mc1Nu9/rustc_testrunner_tmpdir_reporting.f0KwVpsVTJF1/mvce.rs:7:2
  |
7 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.sMhjD6Mc1Nu9/rustc_testrunner_tmpdir_reporting.f0KwVpsVTJF1/mvce.rs`

error[E0599]: no method named `ext_adjacent_cells` found for reference `&'a Self` in the current scope
 --> /tmp/icemaker_global_tempdir.sMhjD6Mc1Nu9/rustc_testrunner_tmpdir_reporting.f0KwVpsVTJF1/mvce.rs:5:14
  |
5 |         self.ext_adjacent_cells(|()| 3)
  |              ^^^^^^^^^^^^^^^^^^ help: there is a method with a similar name: `ext_cells`

error: internal compiler error: compiler/rustc_mir_build/src/build/mod.rs:643:65: impossible case reached

thread 'rustc' panicked at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/compiler/rustc_errors/src/lib.rs:1661:9:
Box<dyn Any>
stack backtrace:
   0:     0x7fc8a9b8b62c - std::backtrace_rs::backtrace::libunwind::trace::h46374b84341786bc
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7fc8a9b8b62c - std::backtrace_rs::backtrace::trace_unsynchronized::he7815f30c698ee16
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fc8a9b8b62c - std::sys_common::backtrace::_print_fmt::hf3ac027a6e20df81
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7fc8a9b8b62c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h6350b6493143b1fc
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7fc8a9bde630 - core::fmt::rt::Argument::fmt::haac38874886df8e7
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/core/src/fmt/rt.rs:142:9
   5:     0x7fc8a9bde630 - core::fmt::write::hf0e822b6d8ad56b2
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/core/src/fmt/mod.rs:1120:17
   6:     0x7fc8a9b7f54f - std::io::Write::write_fmt::h1a44df357aa13b6e
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/io/mod.rs:1762:15
   7:     0x7fc8a9b8b414 - std::sys_common::backtrace::_print::h95329df2b370286a
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7fc8a9b8b414 - std::sys_common::backtrace::print::hd1549e5974c3fa44
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7fc8a9b8e0a7 - std::panicking::default_hook::{{closure}}::hfc23d70499246b08
  10:     0x7fc8a9b8de0f - std::panicking::default_hook::h0d66df0a095a3bd0
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/panicking.rs:292:9
  11:     0x7fc8ac8ee150 - std[4df474cf7c0204ae]::panicking::update_hook::<alloc[ca626be192fcf572]::boxed::Box<rustc_driver_impl[ec4025a53c2103e9]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7fc8a9b8e7e8 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h44f7f870300bcc1d
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/alloc/src/boxed.rs:2021:9
  13:     0x7fc8a9b8e7e8 - std::panicking::rust_panic_with_hook::h652875067b2fe609
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/panicking.rs:783:13
  14:     0x7fc8acd39a74 - std[4df474cf7c0204ae]::panicking::begin_panic::<rustc_errors[1bc87cf102603fe6]::ExplicitBug>::{closure#0}
  15:     0x7fc8acd2e0e6 - std[4df474cf7c0204ae]::sys_common::backtrace::__rust_end_short_backtrace::<std[4df474cf7c0204ae]::panicking::begin_panic<rustc_errors[1bc87cf102603fe6]::ExplicitBug>::{closure#0}, !>
  16:     0x7fc8acd1c5d6 - std[4df474cf7c0204ae]::panicking::begin_panic::<rustc_errors[1bc87cf102603fe6]::ExplicitBug>
  17:     0x7fc8acd13714 - <rustc_errors[1bc87cf102603fe6]::HandlerInner>::bug::<alloc[ca626be192fcf572]::string::String>
  18:     0x7fc8acd1341a - <rustc_errors[1bc87cf102603fe6]::Handler>::bug::<alloc[ca626be192fcf572]::string::String>
  19:     0x7fc8acdb514d - rustc_middle[dadee63cb0feb6d5]::util::bug::opt_span_bug_fmt::<rustc_span[9afbaaf51cc05e3]::span_encoding::Span>::{closure#0}
  20:     0x7fc8acd9c0aa - rustc_middle[dadee63cb0feb6d5]::ty::context::tls::with_opt::<rustc_middle[dadee63cb0feb6d5]::util::bug::opt_span_bug_fmt<rustc_span[9afbaaf51cc05e3]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7fc8acd9bf28 - rustc_middle[dadee63cb0feb6d5]::ty::context::tls::with_context_opt::<rustc_middle[dadee63cb0feb6d5]::ty::context::tls::with_opt<rustc_middle[dadee63cb0feb6d5]::util::bug::opt_span_bug_fmt<rustc_span[9afbaaf51cc05e3]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7fc8aad158c0 - rustc_middle[dadee63cb0feb6d5]::util::bug::bug_fmt
  23:     0x7fc8ace10c52 - rustc_mir_build[a72c6cb2b0bc5327]::build::construct_error
  24:     0x7fc8ae15c1e7 - rustc_mir_build[a72c6cb2b0bc5327]::build::mir_built
  25:     0x7fc8ae15aa07 - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::mir_built::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>
  26:     0x7fc8adce2083 - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::VecCache<rustc_span[9afbaaf51cc05e3]::def_id::LocalDefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  27:     0x7fc8adce1a10 - rustc_query_impl[d9d242dab8718f47]::query_impl::mir_built::get_query_non_incr::__rust_end_short_backtrace
  28:     0x7fc8ab07bc1e - rustc_mir_transform[68e77d7196a8ecec]::check_unsafety::unsafety_check_result
  29:     0x7fc8adce1e07 - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::unsafety_check_result::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>
  30:     0x7fc8adce2083 - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::VecCache<rustc_span[9afbaaf51cc05e3]::def_id::LocalDefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  31:     0x7fc8adce1b90 - rustc_query_impl[d9d242dab8718f47]::query_impl::unsafety_check_result::get_query_non_incr::__rust_end_short_backtrace
  32:     0x7fc8adce3076 - rustc_mir_transform[68e77d7196a8ecec]::mir_const
  33:     0x7fc8adce2fa1 - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::mir_const::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>
  34:     0x7fc8adce2083 - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::VecCache<rustc_span[9afbaaf51cc05e3]::def_id::LocalDefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  35:     0x7fc8adce1ad0 - rustc_query_impl[d9d242dab8718f47]::query_impl::mir_const::get_query_non_incr::__rust_end_short_backtrace
  36:     0x7fc8abe6c490 - rustc_mir_transform[68e77d7196a8ecec]::mir_promoted
  37:     0x7fc8ae0e3092 - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::mir_promoted::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 16usize]>>
  38:     0x7fc8ae0e3345 - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::VecCache<rustc_span[9afbaaf51cc05e3]::def_id::LocalDefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  39:     0x7fc8ae0e2f93 - rustc_query_impl[d9d242dab8718f47]::query_impl::mir_promoted::get_query_non_incr::__rust_end_short_backtrace
  40:     0x7fc8aea1ffcb - rustc_borrowck[44740cb65e3b9e2a]::mir_borrowck
  41:     0x7fc8aea1ff17 - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>
  42:     0x7fc8adce2083 - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::VecCache<rustc_span[9afbaaf51cc05e3]::def_id::LocalDefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  43:     0x7fc8adce1c50 - rustc_query_impl[d9d242dab8718f47]::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
  44:     0x7fc8aec19ff1 - <rustc_hir_analysis[3fdc3bc95e806e7]::collect::type_of::opaque::RpitConstraintChecker>::check
  45:     0x7fc8ac181bf5 - <rustc_hir_analysis[3fdc3bc95e806e7]::collect::type_of::opaque::RpitConstraintChecker as rustc_hir[8da2da2e6769dc1f]::intravisit::Visitor>::visit_expr
  46:     0x7fc8ac181bdb - <rustc_hir_analysis[3fdc3bc95e806e7]::collect::type_of::opaque::RpitConstraintChecker as rustc_hir[8da2da2e6769dc1f]::intravisit::Visitor>::visit_expr
  47:     0x7fc8ae96aa70 - rustc_hir_analysis[3fdc3bc95e806e7]::collect::type_of::type_of_opaque
  48:     0x7fc8ae96a19b - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::type_of_opaque::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>
  49:     0x7fc8adc531d4 - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::DefaultCache<rustc_span[9afbaaf51cc05e3]::def_id::DefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  50:     0x7fc8aec4ff9e - rustc_query_impl[d9d242dab8718f47]::query_impl::type_of_opaque::get_query_non_incr::__rust_end_short_backtrace
  51:     0x7fc8adcc1f38 - rustc_middle[dadee63cb0feb6d5]::query::plumbing::query_get_at::<rustc_query_system[6b6f1c30493de844]::query::caches::DefaultCache<rustc_span[9afbaaf51cc05e3]::def_id::DefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>>
  52:     0x7fc8abdd3c1f - rustc_hir_analysis[3fdc3bc95e806e7]::collect::type_of::type_of
  53:     0x7fc8adc54336 - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>
  54:     0x7fc8adc531d4 - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::DefaultCache<rustc_span[9afbaaf51cc05e3]::def_id::DefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  55:     0x7fc8adc52d9b - rustc_query_impl[d9d242dab8718f47]::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
  56:     0x7fc8adcc1f38 - rustc_middle[dadee63cb0feb6d5]::query::plumbing::query_get_at::<rustc_query_system[6b6f1c30493de844]::query::caches::DefaultCache<rustc_span[9afbaaf51cc05e3]::def_id::DefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 8usize]>>>
  57:     0x7fc8ae32088c - rustc_hir_analysis[3fdc3bc95e806e7]::check::check::check_mod_item_types
  58:     0x7fc8ae31f293 - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::check_mod_item_types::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 0usize]>>
  59:     0x7fc8ae60757b - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::DefaultCache<rustc_span[9afbaaf51cc05e3]::def_id::LocalModDefId, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  60:     0x7fc8ae606f57 - rustc_query_impl[d9d242dab8718f47]::query_impl::check_mod_item_types::get_query_non_incr::__rust_end_short_backtrace
  61:     0x7fc8ae1ce7d5 - rustc_hir_analysis[3fdc3bc95e806e7]::check_crate
  62:     0x7fc8adfaa8d7 - rustc_interface[b3bf249fff60da9a]::passes::analysis
  63:     0x7fc8adfaa537 - rustc_query_impl[d9d242dab8718f47]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d9d242dab8718f47]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 1usize]>>
  64:     0x7fc8aeb98824 - rustc_query_system[6b6f1c30493de844]::query::plumbing::try_execute_query::<rustc_query_impl[d9d242dab8718f47]::DynamicConfig<rustc_query_system[6b6f1c30493de844]::query::caches::SingleCache<rustc_middle[dadee63cb0feb6d5]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[d9d242dab8718f47]::plumbing::QueryCtxt, false>
  65:     0x7fc8aeb98615 - rustc_query_impl[d9d242dab8718f47]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  66:     0x7fc8aeba123f - rustc_interface[b3bf249fff60da9a]::interface::run_compiler::<core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>, rustc_driver_impl[ec4025a53c2103e9]::run_compiler::{closure#1}>::{closure#0}
  67:     0x7fc8aeba855a - std[4df474cf7c0204ae]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[b3bf249fff60da9a]::util::run_in_thread_with_globals<rustc_interface[b3bf249fff60da9a]::util::run_in_thread_pool_with_globals<rustc_interface[b3bf249fff60da9a]::interface::run_compiler<core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>, rustc_driver_impl[ec4025a53c2103e9]::run_compiler::{closure#1}>::{closure#0}, core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>>::{closure#0}, core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>>
  68:     0x7fc8aeba8383 - <<std[4df474cf7c0204ae]::thread::Builder>::spawn_unchecked_<rustc_interface[b3bf249fff60da9a]::util::run_in_thread_with_globals<rustc_interface[b3bf249fff60da9a]::util::run_in_thread_pool_with_globals<rustc_interface[b3bf249fff60da9a]::interface::run_compiler<core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>, rustc_driver_impl[ec4025a53c2103e9]::run_compiler::{closure#1}>::{closure#0}, core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>>::{closure#0}, core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[f248d18e5721e18e]::result::Result<(), rustc_span[9afbaaf51cc05e3]::ErrorGuaranteed>>::{closure#1} as core[f248d18e5721e18e]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  69:     0x7fc8a9b986a5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h473dfddbf197f5bf
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/alloc/src/boxed.rs:2007:9
  70:     0x7fc8a9b986a5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h8959fbdf8cbf8098
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/alloc/src/boxed.rs:2007:9
  71:     0x7fc8a9b986a5 - std::sys::unix::thread::Thread::new::thread_start::hab410919d7ef6e45
                               at /rustc/17d0a45f5df31f218b84c3275bb05c3227348b5b/library/std/src/sys/unix/thread.rs:108:17
  72:     0x7fc8a99899eb - <unknown>
  73:     0x7fc8a9a0d7cc - <unknown>
  74:                0x0 - <unknown>

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.75.0-nightly (17d0a45f5 2023-11-10) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [mir_built] building MIR for `ThreeCellFragment::ext_cells::{closure#0}`
#1 [unsafety_check_result] unsafety-checking `ThreeCellFragment::ext_cells::{closure#0}`
#2 [mir_const] preparing `ThreeCellFragment::ext_cells::{closure#0}` for borrow checking
#3 [mir_promoted] promoting constants in MIR for `ThreeCellFragment::ext_cells::{closure#0}`
#4 [mir_borrowck] borrow-checking `ThreeCellFragment::ext_cells::{closure#0}`
#5 [type_of_opaque] computing type of opaque `ThreeCellFragment::ext_cells::{opaque#0}`
#6 [type_of] computing type of `ThreeCellFragment::ext_cells::{opaque#0}`
#7 [check_mod_item_types] checking item types in top-level module
#8 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0599, E0601.
For more information about an error, try `rustc --explain E0599`.

[matthiaskrgr]

Regression in nightly-2023-11-08
504f63e / #117418 ping @compiler-errors

[compiler-errors]

This should be fixed by #117686

[bvanjoi]

@compiler-errors I'm intrigued as to why you believe #117686 could rectify this problem.

The issue can be distilled as follows:

trait Foo {}

trait T {
    fn a(&self) -> impl Foo {
        self.b(|| 0)
    }
}

fn main() {}

It results in a panic at bug! due to the closure utilizing the type from its outermost function, eventually returning ty::Error. This issue appears to be unrelated to DefKind::Coroutine.

[compiler-errors]

@bvanjoi: You're provably correct, and I am likely wrong about the root cause of the issue. I will look tomorrow. Feel free to claim this issue if you've already found a solution in the process of investigation.