ICE: `rustc_specialization_trait` and circular associated type

[ChaiTRex]

Code

[Playground link]

#![feature(min_specialization, rustc_attrs)]

#[rustc_specialization_trait]
pub trait Trait {}

struct Struct
where
    Self: Iterator<Item = <Self as Iterator>::Item>, {}

impl Trait for Struct {}

Meta

rustc --version --verbose:

rustc 1.64.0 (a55dd71d5 2022-09-19)
binary: rustc
commit-hash: a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52
commit-date: 2022-09-19
host: x86_64-unknown-linux-gnu
release: 1.64.0
LLVM version: 14.0.6

rustc 1.65.0-beta.2 (e5da98475 2022-09-24)
binary: rustc
commit-hash: e5da98475e88b52384bac96923bba7cd45941d69
commit-date: 2022-09-24
host: x86_64-unknown-linux-gnu
release: 1.65.0-beta.2
LLVM version: 15.0.0

rustc 1.66.0-nightly (3f83906b3 2022-09-24)
binary: rustc
commit-hash: 3f83906b30798bf61513fa340524cebf6676f9db
commit-date: 2022-09-24
host: x86_64-unknown-linux-gnu
release: 1.66.0-nightly
LLVM version: 15.0.0

Error output

   Compiling ice v0.0.0 (/home/ubuntu/dev/ice)
thread 'rustc' panicked at 'assertion failed: !obligations.needs_infer()', compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs:358:13

[Backtrace removed]

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 (3f83906b3 2022-09-24) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [check_mod_impl_wf] checking that impls are well-formed in top-level module
#1 [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: implied_outlives_bounds failed to solve all obligations
  --> src/lib.rs:10:1
   |
10 | impl Trait for Struct {}
   | ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: delayed at compiler/rustc_trait_selection/src/traits/outlives_bounds.rs:63:31

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1530:13

[Backtrace removed]

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 (3f83906b3 2022-09-24) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
thread panicked while panicking. aborting.
error: could not compile `ice`

Caused by:
  process didn't exit successfully: `rustc --crate-name ice --edition=2021 src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debuginfo=2 -C metadata=2cc8a57eb73b0fe5 -C extra-filename=-2cc8a57eb73b0fe5 --out-dir /home/ubuntu/dev/ice/target/debug/deps -C incremental=/home/ubuntu/dev/ice/target/debug/incremental -L dependency=/home/ubuntu/dev/ice/target/debug/deps` (signal: 6, SIGABRT: process abort signal)

Backtrace

   Compiling ice v0.0.0 (/home/ubuntu/dev/ice)
thread 'rustc' panicked at 'assertion failed: !obligations.needs_infer()', compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs:358:13
stack backtrace:
   0: rust_begin_unwind
             at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/panicking.rs:556:5
   1: core::panicking::panic_fmt
             at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/core/src/panicking.rs:142:14
   2: core::panicking::panic
             at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/core/src/panicking.rs:48:5
   3: <rustc_infer::infer::InferCtxtBuilder>::enter::<(), rustc_typeck::impl_wf_check::min_specialization::check_predicates::{closure#3}>
   4: rustc_typeck::impl_wf_check::min_specialization::check_min_specialization
   5: rustc_typeck::impl_wf_check::check_mod_impl_wf
   6: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId, ()>
   7: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalDefId, ()>>
   8: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::check_mod_impl_wf, rustc_query_impl::plumbing::QueryCtxt>
   9: <rustc_middle::hir::map::Map>::for_each_module::<rustc_typeck::check_crate::{closure#2}::{closure#0}::{closure#0}>
  10: <rustc_session::session::Session>::track_errors::<rustc_typeck::check_crate::{closure#2}, ()>
  11: rustc_typeck::check_crate
  12: rustc_interface::passes::analysis
  13: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (), core::result::Result<(), rustc_errors::ErrorGuaranteed>>
  14: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(), core::result::Result<(), rustc_errors::ErrorGuaranteed>>>
  15: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt>
  16: <rustc_interface::passes::QueryContext>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}::{closure#3}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
  17: rustc_interface::interface::create_compiler_and_run::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>
  18: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 (3f83906b3 2022-09-24) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [check_mod_impl_wf] checking that impls are well-formed in top-level module
#1 [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: implied_outlives_bounds failed to solve all obligations
  --> src/lib.rs:10:1
   |
10 | impl Trait for Struct {}
   | ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: delayed at compiler/rustc_trait_selection/src/traits/outlives_bounds.rs:63:31

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1530:13
stack backtrace:
   0:     0x7f3a43cd1fc0 - std::backtrace_rs::backtrace::libunwind::trace::h83db09f97ba446e0
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   1:     0x7f3a43cd1fc0 - std::backtrace_rs::backtrace::trace_unsynchronized::hbc692a375382599a
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f3a43cd1fc0 - std::sys_common::backtrace::_print_fmt::h5d9374f1dc540502
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7f3a43cd1fc0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h678bc20029fef91d
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7f3a43d2cdfe - core::fmt::write::h3ff59c1e0cfd7af2
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/core/src/fmt/mod.rs:1202:17
   5:     0x7f3a43cc2c05 - std::io::Write::write_fmt::h57bc84b9ab3e4292
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/io/mod.rs:1679:15
   6:     0x7f3a43cd4d43 - std::sys_common::backtrace::_print::h58613138e3b60a1b
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7f3a43cd4d43 - std::sys_common::backtrace::print::h182e9bde2e8d07ea
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7f3a43cd4d43 - std::panicking::default_hook::{{closure}}::h829771b46ce932f3
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/panicking.rs:267:22
   9:     0x7f3a43cd4a2f - std::panicking::default_hook::h167447d609e3453b
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/panicking.rs:286:9
  10:     0x7f3a4650c431 - <rustc_driver[615eae184240f2d1]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[d525c930f060fa4e]::ops::function::FnOnce<(&core[d525c930f060fa4e]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
  11:     0x7f3a43cd557b - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h8a7c5a65eb87446d
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/alloc/src/boxed.rs:1954:9
  12:     0x7f3a43cd557b - std::panicking::rust_panic_with_hook::haa7a7aef616e6ae8
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/panicking.rs:673:13
  13:     0x7f3a4761e931 - std[590eaa09bda9df92]::panicking::begin_panic::<rustc_errors[a92f92f3abe4e548]::ExplicitBug>::{closure#0}
  14:     0x7f3a4761e306 - std[590eaa09bda9df92]::sys_common::backtrace::__rust_end_short_backtrace::<std[590eaa09bda9df92]::panicking::begin_panic<rustc_errors[a92f92f3abe4e548]::ExplicitBug>::{closure#0}, !>
  15:     0x7f3a4761dfa6 - std[590eaa09bda9df92]::panicking::begin_panic::<rustc_errors[a92f92f3abe4e548]::ExplicitBug>
  16:     0x7f3a4761bd06 - std[590eaa09bda9df92]::panic::panic_any::<rustc_errors[a92f92f3abe4e548]::ExplicitBug>
  17:     0x7f3a46055338 - <rustc_errors[a92f92f3abe4e548]::HandlerInner as core[d525c930f060fa4e]::ops::drop::Drop>::drop
  18:     0x7f3a452da348 - core[d525c930f060fa4e]::ptr::drop_in_place::<rustc_session[c2bba8d08c637bfa]::parse::ParseSess>
  19:     0x7f3a452985c8 - <alloc[10be8beb537b5cb7]::rc::Rc<rustc_session[c2bba8d08c637bfa]::session::Session> as core[d525c930f060fa4e]::ops::drop::Drop>::drop
  20:     0x7f3a4529529d - core[d525c930f060fa4e]::ptr::drop_in_place::<rustc_interface[c48cc815669d5993]::interface::Compiler>
  21:     0x7f3a45293444 - rustc_interface[c48cc815669d5993]::interface::create_compiler_and_run::<core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>, rustc_driver[615eae184240f2d1]::run_compiler::{closure#1}>
  22:     0x7f3a45290f41 - <scoped_tls[cad2a7494d31e12]::ScopedKey<rustc_span[199ab19abca3e97b]::SessionGlobals>>::set::<rustc_interface[c48cc815669d5993]::interface::run_compiler<core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>, rustc_driver[615eae184240f2d1]::run_compiler::{closure#1}>::{closure#0}, core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>>
  23:     0x7f3a45290c2f - std[590eaa09bda9df92]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[c48cc815669d5993]::util::run_in_thread_pool_with_globals<rustc_interface[c48cc815669d5993]::interface::run_compiler<core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>, rustc_driver[615eae184240f2d1]::run_compiler::{closure#1}>::{closure#0}, core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>>::{closure#0}, core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>>
  24:     0x7f3a46362ff0 - <<std[590eaa09bda9df92]::thread::Builder>::spawn_unchecked_<rustc_interface[c48cc815669d5993]::util::run_in_thread_pool_with_globals<rustc_interface[c48cc815669d5993]::interface::run_compiler<core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>, rustc_driver[615eae184240f2d1]::run_compiler::{closure#1}>::{closure#0}, core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>>::{closure#0}, core[d525c930f060fa4e]::result::Result<(), rustc_errors[a92f92f3abe4e548]::ErrorGuaranteed>>::{closure#1} as core[d525c930f060fa4e]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  25:     0x7f3a43cdf363 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hc33c8b6114373b1d
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/alloc/src/boxed.rs:1940:9
  26:     0x7f3a43cdf363 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h477ba7c62d8daaed
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/alloc/src/boxed.rs:1940:9
  27:     0x7f3a43cdf363 - std::sys::unix::thread::Thread::new::thread_start::h7a4a94e6bf66c5d5
                               at /rustc/3f83906b30798bf61513fa340524cebf6676f9db/library/std/src/sys/unix/thread.rs:108:17
  28:     0x7f3a43a33b43 - <unknown>
  29:     0x7f3a43ac5a00 - <unknown>
  30:                0x0 - <unknown>

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 (3f83906b3 2022-09-24) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
thread panicked while panicking. aborting.
error: could not compile `ice`

Caused by:
  process didn't exit successfully: `rustc --crate-name ice --edition=2021 src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debuginfo=2 -C metadata=2cc8a57eb73b0fe5 -C extra-filename=-2cc8a57eb73b0fe5 --out-dir /home/ubuntu/dev/ice/target/debug/deps -C incremental=/home/ubuntu/dev/ice/target/debug/incremental -L dependency=/home/ubuntu/dev/ice/target/debug/deps` (signal: 6, SIGABRT: process abort signal)

[ChaiTRex]

It looks like it was introduced some time between 1.43.1 and 1.44.1.

Meta

rustc --version --verbose:

rustc 1.44.1 (c7087fe00 2020-06-17)
binary: rustc
commit-hash: c7087fe00d2ba919df1d813c040a5d47e43b0fe7
commit-date: 2020-06-17
host: x86_64-unknown-linux-gnu
release: 1.44.1
LLVM version: 9.0

Error output

   Compiling ice v0.0.0 (/home/ubuntu/dev/ice)
error[E0554]: `#![feature]` may not be used on the stable release channel
 --> src/lib.rs:1:1
  |
1 | #![feature(min_specialization, rustc_attrs)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

thread 'rustc' panicked at 'region constraints already solved', src/librustc_infer/infer/mod.rs:209:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.44.1 (c7087fe00 2020-06-17) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental --crate-type lib

note: some of the compiler flags provided by cargo are hidden

error: aborting due to previous error

For more information about this error, try `rustc --explain E0554`.
error: could not compile `ice`.

To learn more, run the command again with --verbose.

Backtrace

   Compiling ice v0.0.0 (/home/ubuntu/dev/ice)
error[E0554]: `#![feature]` may not be used on the stable release channel
 --> src/lib.rs:1:1
  |
1 | #![feature(min_specialization, rustc_attrs)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

thread 'rustc' panicked at 'region constraints already solved', src/librustc_infer/infer/mod.rs:209:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1069
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1504
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:515
  12: rust_begin_unwind
             at src/libstd/panicking.rs:419
  13: core::panicking::panic_fmt
             at src/libcore/panicking.rs:111
  14: core::option::expect_failed
             at src/libcore/option.rs:1260
  15: rustc_infer::infer::InferCtxt::start_snapshot
  16: rustc_infer::infer::InferCtxt::commit_if_ok
  17: rustc_trait_selection::traits::project::opt_normalize_projection_type
  18: rustc_trait_selection::traits::project::normalize_projection_type
  19: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  20: rustc_middle::ty::fold::TypeFoldable::fold_with
  21: rustc_trait_selection::traits::project::normalize_to
  22: rustc_trait_selection::traits::wf::WfPredicates::normalize
  23: rustc_trait_selection::traits::wf::obligations
  24: rustc_typeck::impl_wf_check::min_specialization::check_always_applicable
  25: rustc_infer::infer::InferCtxtBuilder::enter
  26: rustc_typeck::impl_wf_check::min_specialization::check_min_specialization
  27: <rustc_typeck::impl_wf_check::ImplWfCheck as rustc_hir::itemlikevisit::ItemLikeVisitor>::visit_item
  28: rustc_middle::hir::map::Map::visit_item_likes_in_module
  29: rustc_typeck::impl_wf_check::check_mod_impl_wf
  30: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::check_mod_impl_wf>::compute
  31: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  32: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  33: rustc_query_system::query::plumbing::get_query
  34: rustc_query_system::query::plumbing::ensure_query
  35: rustc_typeck::impl_wf_check::impl_wf_check
  36: rustc_typeck::check_crate
  37: rustc_interface::passes::analysis
  38: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  39: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  40: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  41: rustc_query_system::query::plumbing::get_query
  42: rustc_middle::ty::context::tls::enter_global
  43: rustc_interface::interface::run_compiler_in_existing_thread_pool
  44: scoped_tls::ScopedKey<T>::set
  45: rustc_ast::attr::with_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.44.1 (c7087fe00 2020-06-17) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental --crate-type lib

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [check_mod_impl_wf] checking that impls are well-formed in top-level module
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

For more information about this error, try `rustc --explain E0554`.
error: could not compile `ice`.

To learn more, run the command again with --verbose.

[matthiaskrgr]

updated stacktrace

warning: the feature `rustc_attrs` is internal to the compiler or standard library
 --> f.rs:1:32
  |
1 | #![feature(min_specialization, rustc_attrs)]
  |                                ^^^^^^^^^^^
  |
  = note: using it is strongly discouraged
  = note: `#[warn(internal_features)]` on by default

error[E0601]: `main` function not found in crate `f`
  --> f.rs:10:25
   |
10 | impl Trait for Struct {}
   |                         ^ consider adding a `main` function to `f.rs`

error[E0275]: overflow evaluating the requirement `<Struct as Iterator>::Item == _`
 --> f.rs:6:1
  |
6 | struct Struct
  | ^^^^^^^^^^^^^

thread 'rustc' panicked at compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs:420:9:
assertion failed: !obligations.has_infer()
stack backtrace:
   0:     0x7cc880835b35 - std::backtrace_rs::backtrace::libunwind::trace::hf6436e929f7909b2
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/../../backtrace/src/backtrace/libunwind.rs:105:5
   1:     0x7cc880835b35 - std::backtrace_rs::backtrace::trace_unsynchronized::h66804002fba2d9a2
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7cc880835b35 - std::sys_common::backtrace::_print_fmt::h37691a73293ec221
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7cc880835b35 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h0c103d3d357450b2
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7cc880884cfb - core::fmt::rt::Argument::fmt::h7dd3a77f3202738e
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/core/src/fmt/rt.rs:165:63
   5:     0x7cc880884cfb - core::fmt::write::h14fe62b4f0765a22
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/core/src/fmt/mod.rs:1157:21
   6:     0x7cc88082a87f - std::io::Write::write_fmt::h65dcc5485b0907ac
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/io/mod.rs:1835:15
   7:     0x7cc88083590e - std::sys_common::backtrace::_print::h494af3712379749e
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7cc88083590e - std::sys_common::backtrace::print::h033d8e5cb8f913e7
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7cc880838279 - std::panicking::default_hook::{{closure}}::h2c9a1c60f356f72b
  10:     0x7cc880837fbd - std::panicking::default_hook::h5eb86e5b9864f803
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/panicking.rs:298:9
  11:     0x7cc87d2ba1af - std[c2942707aeb3fecf]::panicking::update_hook::<alloc[7183c8e6e494c79b]::boxed::Box<rustc_driver_impl[183fefe8278e000e]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7cc880838976 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h687983cf8c8b1924
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/alloc/src/boxed.rs:2036:9
  13:     0x7cc880838976 - std::panicking::rust_panic_with_hook::he27185849116e75a
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/panicking.rs:799:13
  14:     0x7cc8808386eb - std::panicking::begin_panic_handler::{{closure}}::h4c49ba09408244b3
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/panicking.rs:656:13
  15:     0x7cc880835ff9 - std::sys_common::backtrace::__rust_end_short_backtrace::hd35c2e6a82fff9df
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x7cc880838457 - rust_begin_unwind
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/panicking.rs:652:5
  17:     0x7cc8808812c3 - core::panicking::panic_fmt::h9ce34dba3d434a10
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/core/src/panicking.rs:72:14
  18:     0x7cc88088136c - core::panicking::panic::h97f5e163faee8a89
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/core/src/panicking.rs:146:5
  19:     0x7cc87d4253bf - rustc_hir_analysis[7270adfa0a603d34]::impl_wf_check::min_specialization::check_always_applicable
  20:     0x7cc87ef13772 - rustc_hir_analysis[7270adfa0a603d34]::check::wfcheck::check_well_formed
  21:     0x7cc87ef1019d - rustc_query_impl[b0b6e1adda5b8627]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[b0b6e1adda5b8627]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[ad05dbfce6aa193f]::query::erase::Erased<[u8; 1usize]>>
  22:     0x7cc87ef0f940 - rustc_query_system[a96a8a7004732019]::query::plumbing::try_execute_query::<rustc_query_impl[b0b6e1adda5b8627]::DynamicConfig<rustc_query_system[a96a8a7004732019]::query::caches::VecCache<rustc_hir[923df9bef2e89365]::hir_id::OwnerId, rustc_middle[ad05dbfce6aa193f]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[b0b6e1adda5b8627]::plumbing::QueryCtxt, false>
  23:     0x7cc87ef0f6bf - rustc_query_impl[b0b6e1adda5b8627]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  24:     0x7cc87ef0d5f7 - rustc_hir_analysis[7270adfa0a603d34]::check::wfcheck::check_mod_type_wf
  25:     0x7cc87ef0d427 - rustc_query_impl[b0b6e1adda5b8627]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[b0b6e1adda5b8627]::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[ad05dbfce6aa193f]::query::erase::Erased<[u8; 1usize]>>
  26:     0x7cc87eefc2b0 - rustc_query_system[a96a8a7004732019]::query::plumbing::try_execute_query::<rustc_query_impl[b0b6e1adda5b8627]::DynamicConfig<rustc_query_system[a96a8a7004732019]::query::caches::DefaultCache<rustc_span[2022bdb1e52fe685]::def_id::LocalModDefId, rustc_middle[ad05dbfce6aa193f]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[b0b6e1adda5b8627]::plumbing::QueryCtxt, false>
  27:     0x7cc87eefc05b - rustc_query_impl[b0b6e1adda5b8627]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
  28:     0x7cc87ec9fcde - rustc_hir_analysis[7270adfa0a603d34]::check_crate
  29:     0x7cc87efe2423 - rustc_interface[4e3bc9a91fb7f25c]::passes::analysis
  30:     0x7cc87efe1f61 - rustc_query_impl[b0b6e1adda5b8627]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[b0b6e1adda5b8627]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[ad05dbfce6aa193f]::query::erase::Erased<[u8; 1usize]>>
  31:     0x7cc87f3d3d65 - rustc_query_system[a96a8a7004732019]::query::plumbing::try_execute_query::<rustc_query_impl[b0b6e1adda5b8627]::DynamicConfig<rustc_query_system[a96a8a7004732019]::query::caches::SingleCache<rustc_middle[ad05dbfce6aa193f]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[b0b6e1adda5b8627]::plumbing::QueryCtxt, false>
  32:     0x7cc87f3d3ac9 - rustc_query_impl[b0b6e1adda5b8627]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  33:     0x7cc87f23988e - rustc_interface[4e3bc9a91fb7f25c]::interface::run_compiler::<core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>, rustc_driver_impl[183fefe8278e000e]::run_compiler::{closure#0}>::{closure#1}
  34:     0x7cc87f225609 - std[c2942707aeb3fecf]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[4e3bc9a91fb7f25c]::util::run_in_thread_with_globals<rustc_interface[4e3bc9a91fb7f25c]::util::run_in_thread_pool_with_globals<rustc_interface[4e3bc9a91fb7f25c]::interface::run_compiler<core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>, rustc_driver_impl[183fefe8278e000e]::run_compiler::{closure#0}>::{closure#1}, core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>>::{closure#0}, core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>>
  35:     0x7cc87f2253b8 - <<std[c2942707aeb3fecf]::thread::Builder>::spawn_unchecked_<rustc_interface[4e3bc9a91fb7f25c]::util::run_in_thread_with_globals<rustc_interface[4e3bc9a91fb7f25c]::util::run_in_thread_pool_with_globals<rustc_interface[4e3bc9a91fb7f25c]::interface::run_compiler<core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>, rustc_driver_impl[183fefe8278e000e]::run_compiler::{closure#0}>::{closure#1}, core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>>::{closure#0}, core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[719ca24346e77cd2]::result::Result<(), rustc_span[2022bdb1e52fe685]::ErrorGuaranteed>>::{closure#2} as core[719ca24346e77cd2]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  36:     0x7cc8808427bb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h8fd56e044d024af5
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/alloc/src/boxed.rs:2022:9
  37:     0x7cc8808427bb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h0e2ea69a6bf35e42
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/alloc/src/boxed.rs:2022:9
  38:     0x7cc8808427bb - std::sys::pal::unix::thread::Thread::new::thread_start::h02710c0b1a3f6241
                               at /rustc/9c9b568792ef20d8459c745345dd3e79b7c7fa8c/library/std/src/sys/pal/unix/thread.rs:108:17
  39:     0x7cc87a0a955a - <unknown>
  40:     0x7cc87a126a3c - <unknown>
  41:                0x0 - <unknown>

error: the compiler unexpectedly panicked. this is a bug.

note: using internal features is not supported and expected to cause internal compiler errors when used incorrectly

note: please attach the file at `/tmp/im/rustc-ice-2024-05-06T16_12_59-1062772.txt` to your bug report

query stack during panic:
#0 [check_well_formed] checking that `<impl at f.rs:10:1: 10:22>` 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 2 previous errors; 1 warning emitted

Some errors have detailed explanations: E0275, E0601.
For more information about an error, try `rustc --explain E0275`.