ICE: `unexpected builtin trait with associated type:` <{closure@./... } as Fn>

[Naserume]

Code

#![feature(auto_traits)]
#![feature(unboxed_closures)]

trait T {}

fn f() -> impl Fn(T) {
    let p = ();
    |_| p
}

auto trait Fn {
    type Output;
}

fn main() {}

Meta

rustc --version --verbose:

rustc 1.81.0-nightly (fcaa6fdfb 2024-07-13)
binary: rustc
commit-hash: fcaa6fdfbee1316184e7ad98c53241d52cd30a5f
commit-date: 2024-07-13
host: x86_64-apple-darwin
release: 1.81.0-nightly
LLVM version: 18.1.7

Error output

error[E0380]: auto traits cannot have associated items
  --> ./6A4A7.rs:12:10
   |
11 | auto trait Fn {
   |            -- auto traits cannot have associated items
12 |     type Output; //~ ERROR E0380
   |     -----^^^^^^- help: remove these associated items

error[E0107]: trait takes 0 generic arguments but 1 generic argument was supplied
  --> ./6A4A7.rs:6:16
   |
6  | fn f() -> impl Fn(T) {
   |                ^^--- help: remove these parenthetical generics
   |                |
   |                expected 0 generic arguments
   |
note: trait defined here, with 0 generic parameters
  --> ./6A4A7.rs:11:12
   |
11 | auto trait Fn {
   |            ^^

Backtrace

error: internal compiler error: compiler/rustc_trait_selection/src/traits/project.rs:1206:21: unexpected builtin trait with associated type: <{closure@./6A4A7.rs:8:5: 8:8} as Fn>

thread 'rustc' panicked at compiler/rustc_trait_selection/src/traits/project.rs:1206:21:
Box<dyn Any>
stack backtrace:
   0:        0x10f6f6373 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h605d51fc858e32d3
   1:        0x10f7412fb - core::fmt::write::he70b1f5b242a09e4
   2:        0x10f6ec0be - std::io::Write::write_fmt::hbfde528b9dfff91a
   3:        0x10f6f8c1a - std::panicking::default_hook::{{closure}}::hfdc91bfcaaf40c09
   4:        0x10f6f88ca - std::panicking::default_hook::h8673ceadddb8316e
   5:        0x118a7d8dc - std[8bfe66706d3bd117]::panicking::update_hook::<alloc[ea04c33bd6f71985]::boxed::Box<rustc_driver_impl[d8a49a9463f03e6]::install_ice_hook::{closure#0}>>::{closure#0}
   6:        0x10f6f9a09 - std::panicking::rust_panic_with_hook::h206b639ed4704bb1
   7:        0x118af0bb7 - std[8bfe66706d3bd117]::panicking::begin_panic::<rustc_errors[7f155011d809a3bf]::ExplicitBug>::{closure#0}
   8:        0x118adc9f9 - std[8bfe66706d3bd117]::sys::backtrace::__rust_end_short_backtrace::<std[8bfe66706d3bd117]::panicking::begin_panic<rustc_errors[7f155011d809a3bf]::ExplicitBug>::{closure#0}, !>
   9:        0x11d557469 - std[8bfe66706d3bd117]::panicking::begin_panic::<rustc_errors[7f155011d809a3bf]::ExplicitBug>
  10:        0x118b02c06 - <rustc_errors[7f155011d809a3bf]::diagnostic::BugAbort as rustc_errors[7f155011d809a3bf]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:        0x1197c8b45 - rustc_middle[66eaac359ba8a608]::util::bug::opt_span_bug_fmt::<rustc_span[9df13b32b3ae4eb2]::span_encoding::Span>::{closure#0}
  12:        0x11977f0b7 - rustc_middle[66eaac359ba8a608]::ty::context::tls::with_opt::<rustc_middle[66eaac359ba8a608]::util::bug::opt_span_bug_fmt<rustc_span[9df13b32b3ae4eb2]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  13:        0x11977ebf5 - rustc_middle[66eaac359ba8a608]::ty::context::tls::with_context_opt::<rustc_middle[66eaac359ba8a608]::ty::context::tls::with_opt<rustc_middle[66eaac359ba8a608]::util::bug::opt_span_bug_fmt<rustc_span[9df13b32b3ae4eb2]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  14:        0x11d61ff9b - rustc_middle[66eaac359ba8a608]::util::bug::bug_fmt
  15:        0x11a7ce9a0 - rustc_trait_selection[bf739c384407ce51]::traits::project::opt_normalize_projection_term
  16:        0x11a5db9be - <rustc_infer[3da7f7f7e3fca22e]::infer::InferCtxt>::commit_if_ok::<rustc_trait_selection[bf739c384407ce51]::traits::project::ProjectAndUnifyResult, rustc_infer[3da7f7f7e3fca22e]::traits::project::MismatchedProjectionTypes, rustc_trait_selection[bf739c384407ce51]::traits::project::poly_project_and_unify_term::{closure#0}>
  17:        0x11a72a112 - <rustc_trait_selection[bf739c384407ce51]::traits::fulfill::FulfillProcessor>::process_projection_obligation
  18:        0x11a7c016f - <rustc_trait_selection[bf739c384407ce51]::traits::fulfill::FulfillProcessor as rustc_data_structures[1d3e240332809550]::obligation_forest::ObligationProcessor>::process_obligation
  19:        0x118ed2759 - <rustc_data_structures[1d3e240332809550]::obligation_forest::ObligationForest<rustc_trait_selection[bf739c384407ce51]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[bf739c384407ce51]::traits::fulfill::FulfillProcessor>
  20:        0x118fcb9b2 - <rustc_trait_selection[bf739c384407ce51]::traits::fulfill::FulfillmentContext<rustc_trait_selection[bf739c384407ce51]::traits::FulfillmentError> as rustc_infer[3da7f7f7e3fca22e]::traits::engine::TraitEngine<rustc_trait_selection[bf739c384407ce51]::traits::FulfillmentError>>::select_where_possible
  21:        0x11912a8c2 - <rustc_hir_typeck[a7633e0d641b9efc]::fn_ctxt::FnCtxt>::resolve_vars_with_obligations
  22:        0x119133aa2 - <rustc_hir_typeck[a7633e0d641b9efc]::fn_ctxt::FnCtxt>::try_structurally_resolve_type
  23:        0x119022626 - <rustc_hir_typeck[a7633e0d641b9efc]::fn_ctxt::FnCtxt>::coerce
  24:        0x11910c014 - <rustc_hir_typeck[a7633e0d641b9efc]::coercion::CoerceMany<&rustc_hir[d0540023df9f77a9]::hir::Expr>>::coerce_inner::<<rustc_hir_typeck[a7633e0d641b9efc]::coercion::CoerceMany<&rustc_hir[d0540023df9f77a9]::hir::Expr>>::coerce::{closure#0}>
  25:        0x119040d9a - <rustc_hir_typeck[a7633e0d641b9efc]::fn_ctxt::FnCtxt>::check_return_expr
  26:        0x119101e36 - rustc_hir_typeck[a7633e0d641b9efc]::check::check_fn
  27:        0x1190fd551 - rustc_hir_typeck[a7633e0d641b9efc]::typeck
  28:        0x11a16666c - rustc_query_impl[ab99e8e391ad42b2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ab99e8e391ad42b2]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>
  29:        0x119fe3fae - rustc_query_system[55587a8be6cb95b6]::query::plumbing::try_execute_query::<rustc_query_impl[ab99e8e391ad42b2]::DynamicConfig<rustc_query_system[55587a8be6cb95b6]::query::caches::VecCache<rustc_span[9df13b32b3ae4eb2]::def_id::LocalDefId, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[ab99e8e391ad42b2]::plumbing::QueryCtxt, false>
  30:        0x11a189dab - rustc_query_impl[ab99e8e391ad42b2]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  31:        0x118cb1923 - rustc_middle[66eaac359ba8a608]::query::plumbing::query_get_at::<rustc_query_system[55587a8be6cb95b6]::query::caches::VecCache<rustc_span[9df13b32b3ae4eb2]::def_id::LocalDefId, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>>
  32:        0x118e25646 - rustc_hir_analysis[c06ca58d4f3a4935]::collect::type_of::type_of_opaque
  33:        0x11a160c1c - rustc_query_impl[ab99e8e391ad42b2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ab99e8e391ad42b2]::query_impl::type_of_opaque::dynamic_query::{closure#2}::{closure#0}, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>
  34:        0x119f3390f - rustc_query_system[55587a8be6cb95b6]::query::plumbing::try_execute_query::<rustc_query_impl[ab99e8e391ad42b2]::DynamicConfig<rustc_query_system[55587a8be6cb95b6]::query::caches::DefIdCache<rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[ab99e8e391ad42b2]::plumbing::QueryCtxt, false>
  35:        0x11a16fad9 - rustc_query_impl[ab99e8e391ad42b2]::query_impl::type_of_opaque::get_query_non_incr::__rust_end_short_backtrace
  36:        0x118cb0cde - rustc_middle[66eaac359ba8a608]::query::plumbing::query_get_at::<rustc_query_system[55587a8be6cb95b6]::query::caches::DefIdCache<rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>>
  37:        0x118e246f7 - rustc_hir_analysis[c06ca58d4f3a4935]::collect::type_of::type_of
  38:        0x11a1666e8 - rustc_query_impl[ab99e8e391ad42b2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ab99e8e391ad42b2]::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>
  39:        0x119f3390f - rustc_query_system[55587a8be6cb95b6]::query::plumbing::try_execute_query::<rustc_query_impl[ab99e8e391ad42b2]::DynamicConfig<rustc_query_system[55587a8be6cb95b6]::query::caches::DefIdCache<rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[ab99e8e391ad42b2]::plumbing::QueryCtxt, false>
  40:        0x11a16f729 - rustc_query_impl[ab99e8e391ad42b2]::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
  41:        0x118cb0cde - rustc_middle[66eaac359ba8a608]::query::plumbing::query_get_at::<rustc_query_system[55587a8be6cb95b6]::query::caches::DefIdCache<rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 8usize]>>>
  42:        0x118d87ec5 - rustc_hir_analysis[c06ca58d4f3a4935]::check::check::check_item_type
  43:        0x118dbd0f1 - rustc_hir_analysis[c06ca58d4f3a4935]::check::wfcheck::check_well_formed
  44:        0x11a1620dc - rustc_query_impl[ab99e8e391ad42b2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ab99e8e391ad42b2]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 1usize]>>
  45:        0x119ff02df - rustc_query_system[55587a8be6cb95b6]::query::plumbing::try_execute_query::<rustc_query_impl[ab99e8e391ad42b2]::DynamicConfig<rustc_query_system[55587a8be6cb95b6]::query::caches::VecCache<rustc_hir[d0540023df9f77a9]::hir_id::OwnerId, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[ab99e8e391ad42b2]::plumbing::QueryCtxt, false>
  46:        0x11a1ac7d0 - rustc_query_impl[ab99e8e391ad42b2]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  47:        0x118cb1d22 - rustc_middle[66eaac359ba8a608]::query::plumbing::query_ensure_error_guaranteed::<rustc_query_system[55587a8be6cb95b6]::query::caches::VecCache<rustc_hir[d0540023df9f77a9]::hir_id::OwnerId, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 1usize]>>, ()>
  48:        0x118dcbd51 - rustc_hir_analysis[c06ca58d4f3a4935]::check::wfcheck::check_mod_type_wf
  49:        0x11a1620ac - rustc_query_impl[ab99e8e391ad42b2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ab99e8e391ad42b2]::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 1usize]>>
  50:        0x119f8d589 - rustc_query_system[55587a8be6cb95b6]::query::plumbing::try_execute_query::<rustc_query_impl[ab99e8e391ad42b2]::DynamicConfig<rustc_query_system[55587a8be6cb95b6]::query::caches::DefaultCache<rustc_span[9df13b32b3ae4eb2]::def_id::LocalModDefId, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[ab99e8e391ad42b2]::plumbing::QueryCtxt, false>
  51:        0x11a189200 - rustc_query_impl[ab99e8e391ad42b2]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
  52:        0x118e4c0bc - rustc_hir_analysis[c06ca58d4f3a4935]::check_crate
  53:        0x11940ce37 - rustc_interface[f3798eed8f7e14ff]::passes::run_required_analyses
  54:        0x11940f2d3 - rustc_interface[f3798eed8f7e14ff]::passes::analysis
  55:        0x11a16671c - rustc_query_impl[ab99e8e391ad42b2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[ab99e8e391ad42b2]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 1usize]>>
  56:        0x119f3ebfe - rustc_query_system[55587a8be6cb95b6]::query::plumbing::try_execute_query::<rustc_query_impl[ab99e8e391ad42b2]::DynamicConfig<rustc_query_system[55587a8be6cb95b6]::query::caches::SingleCache<rustc_middle[66eaac359ba8a608]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[ab99e8e391ad42b2]::plumbing::QueryCtxt, false>
  57:        0x11a170c77 - rustc_query_impl[ab99e8e391ad42b2]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  58:        0x118a23537 - <rustc_interface[f3798eed8f7e14ff]::queries::QueryResult<&rustc_middle[66eaac359ba8a608]::ty::context::GlobalCtxt>>::enter::<core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>, rustc_driver_impl[d8a49a9463f03e6]::run_compiler::{closure#0}::{closure#1}::{closure#5}>
  59:        0x118a84c1b - rustc_interface[f3798eed8f7e14ff]::interface::run_compiler::<core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>, rustc_driver_impl[d8a49a9463f03e6]::run_compiler::{closure#0}>::{closure#1}
  60:        0x118a6ffc1 - std[8bfe66706d3bd117]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[f3798eed8f7e14ff]::util::run_in_thread_with_globals<rustc_interface[f3798eed8f7e14ff]::util::run_in_thread_pool_with_globals<rustc_interface[f3798eed8f7e14ff]::interface::run_compiler<core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>, rustc_driver_impl[d8a49a9463f03e6]::run_compiler::{closure#0}>::{closure#1}, core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>>::{closure#0}, core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>>
  61:        0x118a8b5e6 - <<std[8bfe66706d3bd117]::thread::Builder>::spawn_unchecked_<rustc_interface[f3798eed8f7e14ff]::util::run_in_thread_with_globals<rustc_interface[f3798eed8f7e14ff]::util::run_in_thread_pool_with_globals<rustc_interface[f3798eed8f7e14ff]::interface::run_compiler<core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>, rustc_driver_impl[d8a49a9463f03e6]::run_compiler::{closure#0}>::{closure#1}, core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>>::{closure#0}, core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[84f3396b7379d157]::result::Result<(), rustc_span[9df13b32b3ae4eb2]::ErrorGuaranteed>>::{closure#2} as core[84f3396b7379d157]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  62:        0x10f7029bb - std::sys::pal::unix::thread::Thread::new::thread_start::hff8a09cc296b9c2d
  63:     0x7ff801f5318b - __pthread_start

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

note: please make sure that you have updated to the latest nightly

note: please attach the file at `/Users/sal/Documents/240714/rustc-ice-2024-07-15T02_02_55-63072.txt` to your bug report

query stack during panic:
#0 [typeck] type-checking `f`
#1 [type_of_opaque] computing type of opaque `f::{opaque#0}`
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0107, E0380.
For more information about an error, try `rustc --explain E0107`.

Note

ICE location

rust/compiler/rustc_trait_selection/src/traits/project.rs

Lines 1122 to 1207 in fcaa6fd

	} else if tcx.is_lang_item(trait_ref.def_id, LangItem::PointeeTrait) {
	let tail = selcx.tcx().struct_tail_with_normalize(
	self_ty,
	|ty| {
	// We throw away any obligations we get from this, since we normalize
	// and confirm these obligations once again during confirmation
	normalize_with_depth(
	selcx,
	obligation.param_env,
	obligation.cause.clone(),
	obligation.recursion_depth + 1,
	ty,
	)
	.value
	},
	|| {},
	);
	match tail.kind() {
	ty::Bool
	| ty::Char
	| ty::Int(_)
	| ty::Uint(_)
	| ty::Float(_)
	| ty::Str
	| ty::Array(..)
	| ty::Pat(..)
	| ty::Slice(_)
	| ty::RawPtr(..)
	| ty::Ref(..)
	| ty::FnDef(..)
	| ty::FnPtr(..)
	| ty::Dynamic(..)
	| ty::Closure(..)
	| ty::CoroutineClosure(..)
	| ty::Coroutine(..)
	| ty::CoroutineWitness(..)
	| ty::Never
	// Extern types have unit metadata, according to RFC 2850
	| ty::Foreign(_)
	// If returned by `struct_tail_without_normalization` this is a unit struct
	// without any fields, or not a struct, and therefore is Sized.
	| ty::Adt(..)
	// If returned by `struct_tail_without_normalization` this is the empty tuple.
	| ty::Tuple(..)
	// Integers and floats are always Sized, and so have unit type metadata.
	| ty::Infer(ty::InferTy::IntVar(_) | ty::InferTy::FloatVar(..)) => true,
	// We normalize from `Wrapper<Tail>::Metadata` to `Tail::Metadata` if able.
	// Otherwise, type parameters, opaques, and unnormalized projections have
	// unit metadata if they're known (e.g. by the param_env) to be sized.
	ty::Param(_) | ty::Alias(..)
	if self_ty != tail
	|| selcx.infcx.predicate_must_hold_modulo_regions(
	&obligation.with(
	selcx.tcx(),
	ty::TraitRef::new(
	selcx.tcx(),
	selcx.tcx().require_lang_item(
	LangItem::Sized,
	Some(obligation.cause.span()),
	),
	[self_ty],
	),
	),
	) =>
	{
	true
	}
	// FIXME(compiler-errors): are Bound and Placeholder types ever known sized?
	ty::Param(_)
	| ty::Alias(..)
	| ty::Bound(..)
	| ty::Placeholder(..)
	| ty::Infer(..)
	| ty::Error(_) => {
	if tail.has_infer_types() {
	candidate_set.mark_ambiguous();
	}
	false
	}
	}
	} else {
	bug!("unexpected builtin trait with associated type: {trait_ref:?}")
	}

@rustbot label +A-auto-traits +F-unboxed_closures

[theemathas]

Minimized:

#![feature(auto_traits)]

auto trait Trait {
    type Output;
}

fn f() {
    let _: <i32 as Trait>::Output = 1_i64;
}

Error output

   Compiling playground v0.0.1 (/playground)
error[E0380]: auto traits cannot have associated items
 --> src/lib.rs:4:10
  |
3 | auto trait Trait {
  |            ----- auto traits cannot have associated items
4 |     type Output;
  |     -----^^^^^^- help: remove these associated items

error: internal compiler error: compiler/rustc_trait_selection/src/traits/project.rs:1206:21: unexpected builtin trait with associated type: <i32 as Trait>

thread 'rustc' panicked at compiler/rustc_trait_selection/src/traits/project.rs:1206:21:
Box<dyn Any>
stack backtrace:
   0:     0x7fd2c0a22ab5 - std::backtrace_rs::backtrace::libunwind::trace::h90ef53671b8f35e2
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:     0x7fd2c0a22ab5 - std::backtrace_rs::backtrace::trace_unsynchronized::h4f56cd06e6931e36
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fd2c0a22ab5 - std::sys::backtrace::_print_fmt::hc7ca1bfe672db1b4
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/sys/backtrace.rs:68:5
   3:     0x7fd2c0a22ab5 - <std::sys::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h103b2337102fecbf
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/sys/backtrace.rs:44:22
   4:     0x7fd2c0a7250b - core::fmt::rt::Argument::fmt::h1c3f905c574b7e34
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/core/src/fmt/rt.rs:173:76
   5:     0x7fd2c0a7250b - core::fmt::write::h7386266427c35607
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/core/src/fmt/mod.rs:1182:21
   6:     0x7fd2c0a173ef - std::io::Write::write_fmt::h6342dfcd770ba156
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/io/mod.rs:1835:15
   7:     0x7fd2c0a2288e - std::sys::backtrace::_print::h4286525352765247
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/sys/backtrace.rs:47:5
   8:     0x7fd2c0a2288e - std::sys::backtrace::print::hc98e431c340084b2
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/sys/backtrace.rs:34:9
   9:     0x7fd2c0a251d9 - std::panicking::default_hook::{{closure}}::h2ab543053f1e54a6
  10:     0x7fd2c0a24f7c - std::panicking::default_hook::ha284c4ce18b0445e
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/panicking.rs:292:9
  11:     0x7fd2c3ea21fa - std[85c3ca4c170da0bb]::panicking::update_hook::<alloc[d335478de6b4a53f]::boxed::Box<rustc_driver_impl[dc4b00a9cfefcaac]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7fd2c0a25aff - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hbe29137bf798c82c
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/alloc/src/boxed.rs:2078:9
  13:     0x7fd2c0a25aff - std::panicking::rust_panic_with_hook::h869b30cecbb157c4
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/panicking.rs:804:13
  14:     0x7fd2c3edd151 - std[85c3ca4c170da0bb]::panicking::begin_panic::<rustc_errors[24d2db88e61fdfbe]::ExplicitBug>::{closure#0}
  15:     0x7fd2c3ed0106 - std[85c3ca4c170da0bb]::sys::backtrace::__rust_end_short_backtrace::<std[85c3ca4c170da0bb]::panicking::begin_panic<rustc_errors[24d2db88e61fdfbe]::ExplicitBug>::{closure#0}, !>
  16:     0x7fd2c3ed00b6 - std[85c3ca4c170da0bb]::panicking::begin_panic::<rustc_errors[24d2db88e61fdfbe]::ExplicitBug>
  17:     0x7fd2c3ee6391 - <rustc_errors[24d2db88e61fdfbe]::diagnostic::BugAbort as rustc_errors[24d2db88e61fdfbe]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  18:     0x7fd2c44f3664 - rustc_middle[aeeec62211ae3a75]::util::bug::opt_span_bug_fmt::<rustc_span[67819806738ee56d]::span_encoding::Span>::{closure#0}
  19:     0x7fd2c44d9eda - rustc_middle[aeeec62211ae3a75]::ty::context::tls::with_opt::<rustc_middle[aeeec62211ae3a75]::util::bug::opt_span_bug_fmt<rustc_span[67819806738ee56d]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  20:     0x7fd2c44d9d5b - rustc_middle[aeeec62211ae3a75]::ty::context::tls::with_context_opt::<rustc_middle[aeeec62211ae3a75]::ty::context::tls::with_opt<rustc_middle[aeeec62211ae3a75]::util::bug::opt_span_bug_fmt<rustc_span[67819806738ee56d]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  21:     0x7fd2c1e89d50 - rustc_middle[aeeec62211ae3a75]::util::bug::bug_fmt
  22:     0x7fd2c5cdfe22 - rustc_trait_selection[32a10b8e227ae023]::traits::project::opt_normalize_projection_term
  23:     0x7fd2c5ccbc0d - <rustc_trait_selection[32a10b8e227ae023]::traits::normalize::AssocTypeNormalizer as rustc_type_ir[33d27c6bc9b48538]::fold::TypeFolder<rustc_middle[aeeec62211ae3a75]::ty::context::TyCtxt>>::fold_ty
  24:     0x7fd2c5d252fb - <rustc_hir_typeck[4115a8e785646128]::fn_ctxt::FnCtxt>::normalize::<rustc_middle[aeeec62211ae3a75]::ty::Ty>
  25:     0x7fd2c5d2628b - <dyn rustc_hir_analysis[45c875b93a141787]::hir_ty_lowering::HirTyLowerer>::lower_ty_common::{closure#0}
  26:     0x7fd2c5d455c4 - <rustc_hir_typeck[4115a8e785646128]::gather_locals::GatherLocalsVisitor>::declare
  27:     0x7fd2c2daa1a2 - <rustc_hir_typeck[4115a8e785646128]::gather_locals::GatherLocalsVisitor as rustc_hir[b204fec8ca04ef98]::intravisit::Visitor>::visit_expr
  28:     0x7fd2c57fe56d - rustc_hir_typeck[4115a8e785646128]::check::check_fn
  29:     0x7fd2c5e6ee07 - rustc_hir_typeck[4115a8e785646128]::typeck
  30:     0x7fd2c5e6e79d - rustc_query_impl[1a70eeac4d27cd99]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[1a70eeac4d27cd99]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 8usize]>>
  31:     0x7fd2c5820073 - rustc_query_system[a1535082eb398a6e]::query::plumbing::try_execute_query::<rustc_query_impl[1a70eeac4d27cd99]::DynamicConfig<rustc_query_system[a1535082eb398a6e]::query::caches::VecCache<rustc_span[67819806738ee56d]::def_id::LocalDefId, rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[1a70eeac4d27cd99]::plumbing::QueryCtxt, false>
  32:     0x7fd2c581f24d - rustc_query_impl[1a70eeac4d27cd99]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  33:     0x7fd2c581ee44 - <rustc_middle[aeeec62211ae3a75]::hir::map::Map>::par_body_owners::<rustc_hir_analysis[45c875b93a141787]::check_crate::{closure#4}>::{closure#0}
  34:     0x7fd2c581cc7c - rustc_hir_analysis[45c875b93a141787]::check_crate
  35:     0x7fd2c5813355 - rustc_interface[a6452cf60fc426fe]::passes::analysis
  36:     0x7fd2c5812f07 - rustc_query_impl[1a70eeac4d27cd99]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[1a70eeac4d27cd99]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 1usize]>>
  37:     0x7fd2c6389665 - rustc_query_system[a1535082eb398a6e]::query::plumbing::try_execute_query::<rustc_query_impl[1a70eeac4d27cd99]::DynamicConfig<rustc_query_system[a1535082eb398a6e]::query::caches::SingleCache<rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[1a70eeac4d27cd99]::plumbing::QueryCtxt, false>
  38:     0x7fd2c63893cf - rustc_query_impl[1a70eeac4d27cd99]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  39:     0x7fd2c6259745 - rustc_interface[a6452cf60fc426fe]::interface::run_compiler::<core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>, rustc_driver_impl[dc4b00a9cfefcaac]::run_compiler::{closure#0}>::{closure#1}
  40:     0x7fd2c6226589 - std[85c3ca4c170da0bb]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[a6452cf60fc426fe]::util::run_in_thread_with_globals<rustc_interface[a6452cf60fc426fe]::util::run_in_thread_pool_with_globals<rustc_interface[a6452cf60fc426fe]::interface::run_compiler<core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>, rustc_driver_impl[dc4b00a9cfefcaac]::run_compiler::{closure#0}>::{closure#1}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#0}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>
  41:     0x7fd2c622633a - <<std[85c3ca4c170da0bb]::thread::Builder>::spawn_unchecked_<rustc_interface[a6452cf60fc426fe]::util::run_in_thread_with_globals<rustc_interface[a6452cf60fc426fe]::util::run_in_thread_pool_with_globals<rustc_interface[a6452cf60fc426fe]::interface::run_compiler<core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>, rustc_driver_impl[dc4b00a9cfefcaac]::run_compiler::{closure#0}>::{closure#1}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#0}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#2} as core[2213ecb858fb81d5]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  42:     0x7fd2c0a2f95b - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7aa527871fe5008e
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/alloc/src/boxed.rs:2064:9
  43:     0x7fd2c0a2f95b - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h661f413d6ffad84b
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/alloc/src/boxed.rs:2064:9
  44:     0x7fd2c0a2f95b - std::sys::pal::unix::thread::Thread::new::thread_start::h77623da8b368e6ce
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/sys/pal/unix/thread.rs:108:17
  45:     0x7fd2c0939609 - start_thread
  46:     0x7fd2c085c353 - clone
  47:                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: please make sure that you have updated to the latest nightly

note: please attach the file at `/playground/rustc-ice-2024-07-15T03_34_45-244.txt` to your bug report

note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2

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

query stack during panic:
#0 [typeck] type-checking `f`
#1 [analysis] running analysis passes on this crate
end of query stack
For more information about this error, try `rustc --explain E0380`.
error: could not compile `playground` (lib) due to 1 previous error

@rustbot label -F-unboxed_closures +F-auto_traits

[GrigorenkoPV]

#![feature(auto_traits)]
#![feature(unboxed_closures)]

trait T {}

fn f() -> impl Fn(T) {
    let p = ();
    |_| p
}

auto trait Fn {
    type Output;
}

fn main() {}

Regression in nightly-2024-01-11 (190f4c9...a2d9d73)

Minimized:

#![feature(auto_traits)]

auto trait Trait {
    type Output;
}

fn f() {
    let _: <i32 as Trait>::Output = 1_i64;
}

Regression in nightly-2023-06-18 (6bba061...3b2073f)

[matthiaskrgr]

probably just another duplicate of #117829