ice: auto traits: `unexpected builtin trait with associated type`

[matthiaskrgr]

auto-reduced (treereduce-rust):

auto trait Z<'a, T: ?Sized>
where
    T: Z<'a, u16>,

    for<'b> <T as Z<'b, u16>>::W: Clone,
{
    type W: ?Sized;
}

original:

// check-pass

#[cfg(x2, y2, const { [3u32, 0, 1, 2] })]
auto trait Z<'a, T: ?Sized>
where
    T: Z<'a, u16>,
    //~^ the trait bound `str: Clone` is not satisfied
    //~| the trait bound `str: Clone` is not satisfied
    for<'b> <T as Z<'b, u16>>::W: Clone,
{
    type W: ?Sized;
    fn h(&self, x: &T::W) {
        <T::W>::clone(x);
    }
}
// Values for testing *size
//~| WARN unstable syntax can change at any point in the future, causing a hard error!

fn main(x: <T as Try>::Output) {}

Version information

rustc 1.76.0-nightly (a04d56b36 2023-11-12)
binary: rustc
commit-hash: a04d56b36d8f634abd7bdd64dd859a30655f1818
commit-date: 2023-11-12
host: x86_64-unknown-linux-gnu
release: 1.76.0-nightly
LLVM version: 17.0.4

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

Program output

error[E0567]: auto traits cannot have generic parameters
 --> /tmp/icemaker_global_tempdir.mZwoYuuERxJE/rustc_testrunner_tmpdir_reporting.QEWekm25QZ3t/mvce.rs:1:13
  |
1 | auto trait Z<'a, T: ?Sized>
  |            -^^^^^^^^^^^^^^^ help: remove the parameters
  |            |
  |            auto trait cannot have generic parameters

error[E0568]: auto traits cannot have super traits or lifetime bounds
 --> /tmp/icemaker_global_tempdir.mZwoYuuERxJE/rustc_testrunner_tmpdir_reporting.QEWekm25QZ3t/mvce.rs:2:1
  |
1 |   auto trait Z<'a, T: ?Sized>
  |              - auto traits cannot have super traits or lifetime bounds
2 | / where
3 | |     T: Z<'a, u16>,
4 | |
5 | |     for<'b> <T as Z<'b, u16>>::W: Clone,
  | |________________________________________^ help: remove the super traits or lifetime bounds

error[E0380]: auto traits cannot have associated items
 --> /tmp/icemaker_global_tempdir.mZwoYuuERxJE/rustc_testrunner_tmpdir_reporting.QEWekm25QZ3t/mvce.rs:7:10
  |
1 | auto trait Z<'a, T: ?Sized>
  |            - auto traits cannot have associated items
...
7 |     type W: ?Sized;
  |     -----^--------- help: remove these associated items

error[E0658]: auto traits are experimental and possibly buggy
 --> /tmp/icemaker_global_tempdir.mZwoYuuERxJE/rustc_testrunner_tmpdir_reporting.QEWekm25QZ3t/mvce.rs:1:1
  |
1 | / auto trait Z<'a, T: ?Sized>
2 | | where
3 | |     T: Z<'a, u16>,
4 | |
... |
7 | |     type W: ?Sized;
8 | | }
  | |_^
  |
  = note: see issue #13231 <https://github.com/rust-lang/rust/issues/13231> for more information
  = help: add `#![feature(auto_traits)]` to the crate attributes to enable

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.mZwoYuuERxJE/rustc_testrunner_tmpdir_reporting.QEWekm25QZ3t/mvce.rs:8:2
  |
8 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.mZwoYuuERxJE/rustc_testrunner_tmpdir_reporting.QEWekm25QZ3t/mvce.rs`

error: internal compiler error: compiler/rustc_trait_selection/src/traits/project.rs:1912:21: unexpected builtin trait with associated type: <u16 as Z<'b, u16>>

thread 'rustc' panicked at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/compiler/rustc_errors/src/lib.rs:1661:9:
Box<dyn Any>
stack backtrace:
   0:     0x7fad9758561c - std::backtrace_rs::backtrace::libunwind::trace::ha7d8e18371214dc5
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7fad9758561c - std::backtrace_rs::backtrace::trace_unsynchronized::h4ab7ef5b35b18e6e
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fad9758561c - std::sys_common::backtrace::_print_fmt::ha4aed865ff21cdc6
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7fad9758561c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h89cdffe584387f6a
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7fad975d8620 - core::fmt::rt::Argument::fmt::he4d350492cf5a41f
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/core/src/fmt/rt.rs:142:9
   5:     0x7fad975d8620 - core::fmt::write::ha0b883466b3eea5c
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/core/src/fmt/mod.rs:1120:17
   6:     0x7fad9757953f - std::io::Write::write_fmt::hbeb259dcdb178e61
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/io/mod.rs:1762:15
   7:     0x7fad97585404 - std::sys_common::backtrace::_print::hfd400ec6542a93b9
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7fad97585404 - std::sys_common::backtrace::print::hf891cc8f835583e3
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7fad97588097 - std::panicking::default_hook::{{closure}}::hd1b01d54ca05bedb
  10:     0x7fad97587dff - std::panicking::default_hook::he9fe70984bc0a99b
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/panicking.rs:292:9
  11:     0x7fad942ec420 - std[abb76f1550ab564c]::panicking::update_hook::<alloc[c5d6ca6f2be9df74]::boxed::Box<rustc_driver_impl[be7a3904fcdd9e27]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7fad975887d8 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hd181986705e402fb
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/alloc/src/boxed.rs:2021:9
  13:     0x7fad975887d8 - std::panicking::rust_panic_with_hook::hab5502e98b8d3256
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/panicking.rs:783:13
  14:     0x7fad9473a744 - std[abb76f1550ab564c]::panicking::begin_panic::<rustc_errors[635868a7a4dff52f]::ExplicitBug>::{closure#0}
  15:     0x7fad94733c96 - std[abb76f1550ab564c]::sys_common::backtrace::__rust_end_short_backtrace::<std[abb76f1550ab564c]::panicking::begin_panic<rustc_errors[635868a7a4dff52f]::ExplicitBug>::{closure#0}, !>
  16:     0x7fad9472e2d6 - std[abb76f1550ab564c]::panicking::begin_panic::<rustc_errors[635868a7a4dff52f]::ExplicitBug>
  17:     0x7fad94713cd4 - <rustc_errors[635868a7a4dff52f]::HandlerInner>::bug::<alloc[c5d6ca6f2be9df74]::string::String>
  18:     0x7fad947139da - <rustc_errors[635868a7a4dff52f]::Handler>::bug::<alloc[c5d6ca6f2be9df74]::string::String>
  19:     0x7fad947b5bdd - rustc_middle[c8990ecd71a144c7]::util::bug::opt_span_bug_fmt::<rustc_span[4a6542c0fe2e5cc4]::span_encoding::Span>::{closure#0}
  20:     0x7fad9479d13a - rustc_middle[c8990ecd71a144c7]::ty::context::tls::with_opt::<rustc_middle[c8990ecd71a144c7]::util::bug::opt_span_bug_fmt<rustc_span[4a6542c0fe2e5cc4]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7fad9479cfd8 - rustc_middle[c8990ecd71a144c7]::ty::context::tls::with_context_opt::<rustc_middle[c8990ecd71a144c7]::ty::context::tls::with_opt<rustc_middle[c8990ecd71a144c7]::util::bug::opt_span_bug_fmt<rustc_span[4a6542c0fe2e5cc4]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7fad927152b0 - rustc_middle[c8990ecd71a144c7]::util::bug::bug_fmt
  23:     0x7fad95874c11 - rustc_trait_selection[d994e538aea3acdf]::traits::project::opt_normalize_projection_type
  24:     0x7fad9586753e - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_ty
  25:     0x7fad958657aa - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_predicate
  26:     0x7fad95b9cd02 - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::vtable_auto_impl::{closure#0}
  27:     0x7fad9270354f - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::poly_select
  28:     0x7fad95868cc6 - rustc_trait_selection[d994e538aea3acdf]::traits::project::opt_normalize_projection_type
  29:     0x7fad9586753e - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_ty
  30:     0x7fad958657aa - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_predicate
  31:     0x7fad95b9cd02 - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::vtable_auto_impl::{closure#0}
  32:     0x7fad9270354f - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::poly_select
  33:     0x7fad95868cc6 - rustc_trait_selection[d994e538aea3acdf]::traits::project::opt_normalize_projection_type
  34:     0x7fad9586753e - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_ty
  35:     0x7fad958657aa - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_predicate
  36:     0x7fad95b9cd02 - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::vtable_auto_impl::{closure#0}
  37:     0x7fad9270354f - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::poly_select
  38:     0x7fad95868cc6 - rustc_trait_selection[d994e538aea3acdf]::traits::project::opt_normalize_projection_type
  39:     0x7fad9586753e - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_ty
  40:     0x7fad958657aa - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_predicate
  41:     0x7fad95b9cd02 - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::vtable_auto_impl::{closure#0}
  42:     0x7fad9270354f - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::poly_select
  43:     0x7fad95868cc6 - rustc_trait_selection[d994e538aea3acdf]::traits::project::opt_normalize_projection_type
  44:     0x7fad9586753e - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_ty
  45:     0x7fad958657aa - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_predicate
  46:     0x7fad95b9cd02 - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::vtable_auto_impl::{closure#0}
  47:     0x7fad9270354f - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::poly_select
  48:     0x7fad95868cc6 - rustc_trait_selection[d994e538aea3acdf]::traits::project::opt_normalize_projection_type
<snip>

 656:     0x7fad95b9cd02 - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::vtable_auto_impl::{closure#0}
 657:     0x7fad9270354f - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::poly_select
 658:     0x7fad95868cc6 - rustc_trait_selection[d994e538aea3acdf]::traits::project::opt_normalize_projection_type
 659:     0x7fad9586753e - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_ty
 660:     0x7fad958657aa - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_predicate
 661:     0x7fad95b9cd02 - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::vtable_auto_impl::{closure#0}
 662:     0x7fad9270354f - <rustc_trait_selection[d994e538aea3acdf]::traits::select::SelectionContext>::poly_select
 663:     0x7fad95868cc6 - rustc_trait_selection[d994e538aea3acdf]::traits::project::opt_normalize_projection_type
 664:     0x7fad9586753e - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_ty
 665:     0x7fad958657aa - <rustc_trait_selection[d994e538aea3acdf]::traits::project::AssocTypeNormalizer as rustc_type_ir[14c467366cccebac]::fold::TypeFolder<rustc_middle[c8990ecd71a144c7]::ty::context::TyCtxt>>::fold_predicate
 666:     0x7fad95838eca - rustc_trait_selection[d994e538aea3acdf]::traits::wf::clause_obligations
 667:     0x7fad95d0827a - rustc_hir_analysis[d3ef41151e11064]::check::wfcheck::check_where_clauses
 668:     0x7fad960723e9 - rustc_hir_analysis[d3ef41151e11064]::check::wfcheck::check_trait
 669:     0x7fad95e0719d - rustc_hir_analysis[d3ef41151e11064]::check::wfcheck::check_well_formed
 670:     0x7fad95e06187 - rustc_query_impl[1dbe5d39a1f7335]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[1dbe5d39a1f7335]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c8990ecd71a144c7]::query::erase::Erased<[u8; 1usize]>>
 671:     0x7fad95e058b7 - rustc_query_system[de6aa3eb6381c13]::query::plumbing::try_execute_query::<rustc_query_impl[1dbe5d39a1f7335]::DynamicConfig<rustc_query_system[de6aa3eb6381c13]::query::caches::VecCache<rustc_hir[9844e3a9044970e3]::hir_id::OwnerId, rustc_middle[c8990ecd71a144c7]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[1dbe5d39a1f7335]::plumbing::QueryCtxt, false>
 672:     0x7fad95e05643 - rustc_query_impl[1dbe5d39a1f7335]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
 673:     0x7fad95e04a06 - rustc_hir_analysis[d3ef41151e11064]::check::wfcheck::check_mod_type_wf
 674:     0x7fad95e0493b - rustc_query_impl[1dbe5d39a1f7335]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[1dbe5d39a1f7335]::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c8990ecd71a144c7]::query::erase::Erased<[u8; 1usize]>>
 675:     0x7fad95e03b3b - rustc_query_system[de6aa3eb6381c13]::query::plumbing::try_execute_query::<rustc_query_impl[1dbe5d39a1f7335]::DynamicConfig<rustc_query_system[de6aa3eb6381c13]::query::caches::DefaultCache<rustc_span[4a6542c0fe2e5cc4]::def_id::LocalModDefId, rustc_middle[c8990ecd71a144c7]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[1dbe5d39a1f7335]::plumbing::QueryCtxt, false>
 676:     0x7fad95e038cd - rustc_query_impl[1dbe5d39a1f7335]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
 677:     0x7fad95bc4c9a - <rustc_middle[c8990ecd71a144c7]::hir::map::Map>::try_par_for_each_module::<rustc_hir_analysis[d3ef41151e11064]::check_crate::{closure#4}::{closure#0}>::{closure#0}
 678:     0x7fad95bc5495 - rustc_hir_analysis[d3ef41151e11064]::check_crate
 679:     0x7fad95983317 - rustc_interface[2eb8f42114fb09b1]::passes::analysis
 680:     0x7fad95982f77 - rustc_query_impl[1dbe5d39a1f7335]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[1dbe5d39a1f7335]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c8990ecd71a144c7]::query::erase::Erased<[u8; 1usize]>>
 681:     0x7fad965962a4 - rustc_query_system[de6aa3eb6381c13]::query::plumbing::try_execute_query::<rustc_query_impl[1dbe5d39a1f7335]::DynamicConfig<rustc_query_system[de6aa3eb6381c13]::query::caches::SingleCache<rustc_middle[c8990ecd71a144c7]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[1dbe5d39a1f7335]::plumbing::QueryCtxt, false>
 682:     0x7fad96596095 - rustc_query_impl[1dbe5d39a1f7335]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
 683:     0x7fad9659ecbf - rustc_interface[2eb8f42114fb09b1]::interface::run_compiler::<core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>, rustc_driver_impl[be7a3904fcdd9e27]::run_compiler::{closure#1}>::{closure#0}
 684:     0x7fad965a5fda - std[abb76f1550ab564c]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[2eb8f42114fb09b1]::util::run_in_thread_with_globals<rustc_interface[2eb8f42114fb09b1]::util::run_in_thread_pool_with_globals<rustc_interface[2eb8f42114fb09b1]::interface::run_compiler<core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>, rustc_driver_impl[be7a3904fcdd9e27]::run_compiler::{closure#1}>::{closure#0}, core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>>::{closure#0}, core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>>
 685:     0x7fad965a5e03 - <<std[abb76f1550ab564c]::thread::Builder>::spawn_unchecked_<rustc_interface[2eb8f42114fb09b1]::util::run_in_thread_with_globals<rustc_interface[2eb8f42114fb09b1]::util::run_in_thread_pool_with_globals<rustc_interface[2eb8f42114fb09b1]::interface::run_compiler<core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>, rustc_driver_impl[be7a3904fcdd9e27]::run_compiler::{closure#1}>::{closure#0}, core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>>::{closure#0}, core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3c289e99ef9ba493]::result::Result<(), rustc_span[4a6542c0fe2e5cc4]::ErrorGuaranteed>>::{closure#1} as core[3c289e99ef9ba493]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
 686:     0x7fad97592695 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4543cbb2476eec39
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/alloc/src/boxed.rs:2007:9
 687:     0x7fad97592695 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h33bb6ebf49fc4745
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/alloc/src/boxed.rs:2007:9
 688:     0x7fad97592695 - std::sys::unix::thread::Thread::new::thread_start::h9f68884c308aa5fe
                               at /rustc/a04d56b36d8f634abd7bdd64dd859a30655f1818/library/std/src/sys/unix/thread.rs:108:17
 689:     0x7fad914759eb - <unknown>
 690:     0x7fad914f97cc - <unknown>
 691:                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 1.76.0-nightly (a04d56b36 2023-11-12) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [check_well_formed] checking that `Z` is well-formed
#1 [check_mod_type_wf] checking that types are well-formed in top-level module
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 6 previous errors

Some errors have detailed explanations: E0380, E0567, E0568, E0601, E0658.
For more information about an error, try `rustc --explain E0380`.

[matthiaskrgr]

Regression in nightly-2023-06-18
Regression in f90d57d / #112687 ping @compiler-errors

[jruderman]

The depth of the stack at the ICE depends on the recursion limit. Add #![recursion_limit="8"] and it still ICEs, but with only 8 repeated stack portions.

[jruderman]

Simplified to use only locally defined traits, not use a lifetime parameter, and hit fewer errors:

#![feature(auto_traits)]

trait B {}

auto trait Z<T>
where
    T: Z<u16>,
    <T as Z<u16>>::W: B,
{
    type W;
}

fn main() {}

Oddly enough, this variant hits the same ICE but without such a deep stack.

[asquared31415]

You can replace the bound : B with a lifetime bound to reproduce too, such as <T as Z<u16>>::W: 'static.