ICE when specifiyng invalid `{}` as the associated type for `impl Iterator` as a return type

[rmurrells]

Code

fn get_iter(vec: &[i32]) -> impl Iterator<Item = {}> + '_ {
    vec.iter()
}

fn main() {
    let vec = Vec::new();
    let mut iter = get_iter(&vec);
    iter.next();
}

Meta

rustc --version --verbose:

rustc 1.62.1 (e092d0b6b 2022-07-16)
binary: rustc
commit-hash: e092d0b6b43f2de967af0887873151bb1c0b18d3
commit-date: 2022-07-16
host: x86_64-apple-darwin
release: 1.62.1
LLVM version: 14.0.5

Error output

error[E0658]: associated const equality is incomplete
 --> src/main.rs:1:43
  |
1 | fn get_iter(vec: &[i32]) -> impl Iterator<Item = {}> + '_ {
  |                                           ^^^^^^^^^
  |
  = note: see issue #92827 <https://github.com/rust-lang/rust/issues/92827> for more information

error: mismatch in bind of associated type, got const
  --> src/main.rs:1:43
   |
1  | fn get_iter(vec: &[i32]) -> impl Iterator<Item = {}> + '_ {
   |                                           ^^^^^^^^^
   |
note: associated type defined here does not match const

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', compiler/rustc_trait_selection/src/traits/project.rs:565:36

Backtrace

stack backtrace:
   0:        0x1111434e4 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h33d4544161da9cd0
   1:        0x11119df5b - core::fmt::write::h22b56d6d417c492d
   2:        0x111135a38 - std::io::Write::write_fmt::h515a8855c6a84843
   3:        0x11114689d - std::panicking::default_hook::{{closure}}::hedda119dcd298b7b
   4:        0x111146581 - std::panicking::default_hook::hc602c1312aa18d98
   5:        0x10870fddd - rustc_driver[7138d63f5c135eca]::DEFAULT_HOOK::{closure#0}::{closure#0}
   6:        0x111147006 - std::panicking::rust_panic_with_hook::h3147bfce63989ccb
   7:        0x111146e0a - std::panicking::begin_panic_handler::{{closure}}::h354f8ce5af2f2ce8
   8:        0x111143967 - std::sys_common::backtrace::__rust_end_short_backtrace::h63e1494bcfb6c060
   9:        0x111146b1a - _rust_begin_unwind
  10:        0x1111c7633 - core::panicking::panic_fmt::h6e7523bddca0f9b8
  11:        0x1111c7517 - core::panicking::panic::h9ad5b84e0d6bc108
  12:        0x10c827def - <rustc_trait_selection[a6f455bbcb9cbb54]::traits::project::AssocTypeNormalizer as rustc_middle[82d07da5c7c19032]::ty::fold::TypeFolder>::fold_ty
  13:        0x10c8a4653 - <&rustc_middle[82d07da5c7c19032]::ty::list::List<rustc_middle[82d07da5c7c19032]::ty::subst::GenericArg> as rustc_middle[82d07da5c7c19032]::ty::fold::TypeFoldable>::try_super_fold_with::<rustc_trait_selection[a6f455bbcb9cbb54]::traits::project::AssocTypeNormalizer>
  14:        0x10c8db83a - <rustc_middle[82d07da5c7c19032]::ty::Ty as rustc_middle[82d07da5c7c19032]::ty::fold::TypeFoldable>::super_fold_with::<rustc_trait_selection[a6f455bbcb9cbb54]::traits::project::AssocTypeNormalizer>
  15:        0x10c827752 - <rustc_trait_selection[a6f455bbcb9cbb54]::traits::project::AssocTypeNormalizer as rustc_middle[82d07da5c7c19032]::ty::fold::TypeFolder>::fold_ty
  16:        0x10b1a80ff - <&rustc_middle[82d07da5c7c19032]::ty::list::List<rustc_middle[82d07da5c7c19032]::ty::Ty> as rustc_middle[82d07da5c7c19032]::ty::fold::TypeFoldable>::try_fold_with::<rustc_trait_selection[a6f455bbcb9cbb54]::traits::project::AssocTypeNormalizer>
  17:        0x10b2d9315 - <rustc_trait_selection[a6f455bbcb9cbb54]::traits::project::AssocTypeNormalizer>::fold::<(rustc_middle[82d07da5c7c19032]::ty::sty::FnSig, rustc_middle[82d07da5c7c19032]::ty::InstantiatedPredicates)>
  18:        0x10b2df9fe - rustc_trait_selection[a6f455bbcb9cbb54]::traits::project::normalize::<(rustc_middle[82d07da5c7c19032]::ty::sty::FnSig, rustc_middle[82d07da5c7c19032]::ty::InstantiatedPredicates)>
  19:        0x10b256eb1 - <rustc_infer[dfa359709b99501c]::infer::InferCtxt as rustc_trait_selection[a6f455bbcb9cbb54]::infer::InferCtxtExt>::partially_normalize_associated_types_in::<(rustc_middle[82d07da5c7c19032]::ty::sty::FnSig, rustc_middle[82d07da5c7c19032]::ty::InstantiatedPredicates)>
  20:        0x10b354c66 - <rustc_typeck[aefb7a72b7b1d0e8]::check::inherited::Inherited>::normalize_associated_types_in::<(rustc_middle[82d07da5c7c19032]::ty::sty::FnSig, rustc_middle[82d07da5c7c19032]::ty::InstantiatedPredicates)>
  21:        0x10b282d63 - <rustc_typeck[aefb7a72b7b1d0e8]::check::method::confirm::ConfirmContext>::confirm
  22:        0x10b156577 - <rustc_typeck[aefb7a72b7b1d0e8]::check::fn_ctxt::FnCtxt>::lookup_method
  23:        0x10b14a4f8 - <rustc_typeck[aefb7a72b7b1d0e8]::check::fn_ctxt::FnCtxt>::check_expr_kind
  24:        0x10b101d47 - <rustc_typeck[aefb7a72b7b1d0e8]::check::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  25:        0x10b1159bb - <rustc_typeck[aefb7a72b7b1d0e8]::check::fn_ctxt::FnCtxt>::check_stmt
  26:        0x10b1161ef - <rustc_typeck[aefb7a72b7b1d0e8]::check::fn_ctxt::FnCtxt>::check_block_with_expected
  27:        0x10b14af0d - <rustc_typeck[aefb7a72b7b1d0e8]::check::fn_ctxt::FnCtxt>::check_expr_kind
  28:        0x10b101d47 - <rustc_typeck[aefb7a72b7b1d0e8]::check::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  29:        0x10b1028c5 - <rustc_typeck[aefb7a72b7b1d0e8]::check::fn_ctxt::FnCtxt>::check_return_expr
  30:        0x10b366052 - rustc_typeck[aefb7a72b7b1d0e8]::check::check::check_fn
  31:        0x10b23cc27 - <rustc_infer[dfa359709b99501c]::infer::InferCtxtBuilder>::enter::<&rustc_middle[82d07da5c7c19032]::ty::context::TypeckResults, <rustc_typeck[aefb7a72b7b1d0e8]::check::inherited::InheritedBuilder>::enter<rustc_typeck[aefb7a72b7b1d0e8]::check::typeck_with_fallback<rustc_typeck[aefb7a72b7b1d0e8]::check::typeck::{closure#0}>::{closure#1}, &rustc_middle[82d07da5c7c19032]::ty::context::TypeckResults>::{closure#0}>
  32:        0x10b1b5a61 - rustc_typeck[aefb7a72b7b1d0e8]::check::typeck
  33:        0x10bf096eb - <rustc_query_system[4126f90d2148db6f]::dep_graph::graph::DepGraph<rustc_middle[82d07da5c7c19032]::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle[82d07da5c7c19032]::ty::context::TyCtxt, rustc_span[5a76e2efa0e4796c]::def_id::LocalDefId, &rustc_middle[82d07da5c7c19032]::ty::context::TypeckResults>
  34:        0x10bca7c05 - rustc_query_system[4126f90d2148db6f]::query::plumbing::try_execute_query::<rustc_query_impl[16d321854c18bb84]::plumbing::QueryCtxt, rustc_query_system[4126f90d2148db6f]::query::caches::DefaultCache<rustc_span[5a76e2efa0e4796c]::def_id::LocalDefId, &rustc_middle[82d07da5c7c19032]::ty::context::TypeckResults>>
  35:        0x10bda1c0e - rustc_query_system[4126f90d2148db6f]::query::plumbing::get_query::<rustc_query_impl[16d321854c18bb84]::queries::typeck, rustc_query_impl[16d321854c18bb84]::plumbing::QueryCtxt>
  36:        0x10b2d7b23 - <rustc_middle[82d07da5c7c19032]::hir::map::Map>::par_body_owners::<rustc_typeck[aefb7a72b7b1d0e8]::check::typeck_item_bodies::{closure#0}>
  37:        0x10b1bae15 - rustc_typeck[aefb7a72b7b1d0e8]::check::typeck_item_bodies
  38:        0x10bf3e8e4 - <rustc_query_system[4126f90d2148db6f]::dep_graph::graph::DepGraph<rustc_middle[82d07da5c7c19032]::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle[82d07da5c7c19032]::ty::context::TyCtxt, (), ()>
  39:        0x10bd0f4b7 - rustc_query_system[4126f90d2148db6f]::query::plumbing::try_execute_query::<rustc_query_impl[16d321854c18bb84]::plumbing::QueryCtxt, rustc_query_system[4126f90d2148db6f]::query::caches::DefaultCache<(), ()>>
  40:        0x10bd7bf82 - rustc_query_system[4126f90d2148db6f]::query::plumbing::get_query::<rustc_query_impl[16d321854c18bb84]::queries::typeck_item_bodies, rustc_query_impl[16d321854c18bb84]::plumbing::QueryCtxt>
  41:        0x10b22e8b2 - <rustc_session[a4ff899d744b243a]::session::Session>::time::<(), rustc_typeck[aefb7a72b7b1d0e8]::check_crate::{closure#7}>
  42:        0x10b20bf7d - rustc_typeck[aefb7a72b7b1d0e8]::check_crate
  43:        0x1087f698a - rustc_interface[221574002a4ca70c]::passes::analysis
  44:        0x10bf33ec7 - <rustc_query_system[4126f90d2148db6f]::dep_graph::graph::DepGraph<rustc_middle[82d07da5c7c19032]::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle[82d07da5c7c19032]::ty::context::TyCtxt, (), core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>
  45:        0x10bd026a6 - rustc_query_system[4126f90d2148db6f]::query::plumbing::try_execute_query::<rustc_query_impl[16d321854c18bb84]::plumbing::QueryCtxt, rustc_query_system[4126f90d2148db6f]::query::caches::DefaultCache<(), core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>>
  46:        0x10bda1fef - rustc_query_system[4126f90d2148db6f]::query::plumbing::get_query::<rustc_query_impl[16d321854c18bb84]::queries::analysis, rustc_query_impl[16d321854c18bb84]::plumbing::QueryCtxt>
  47:        0x1086d02c2 - <rustc_interface[221574002a4ca70c]::passes::QueryContext>::enter::<rustc_driver[7138d63f5c135eca]::run_compiler::{closure#1}::{closure#2}::{closure#3}, core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>
  48:        0x1086b214a - <rustc_interface[221574002a4ca70c]::interface::Compiler>::enter::<rustc_driver[7138d63f5c135eca]::run_compiler::{closure#1}::{closure#2}, core[8afb26d279e869ce]::result::Result<core[8afb26d279e869ce]::option::Option<rustc_interface[221574002a4ca70c]::queries::Linker>, rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>
  49:        0x108716018 - rustc_span[5a76e2efa0e4796c]::with_source_map::<core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>, rustc_interface[221574002a4ca70c]::interface::create_compiler_and_run<core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>, rustc_driver[7138d63f5c135eca]::run_compiler::{closure#1}>::{closure#1}>
  50:        0x1086b2d4a - rustc_interface[221574002a4ca70c]::interface::create_compiler_and_run::<core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>, rustc_driver[7138d63f5c135eca]::run_compiler::{closure#1}>
  51:        0x1086acdc5 - <scoped_tls[39d586c33eb6f7eb]::ScopedKey<rustc_span[5a76e2efa0e4796c]::SessionGlobals>>::set::<rustc_interface[221574002a4ca70c]::interface::run_compiler<core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>, rustc_driver[7138d63f5c135eca]::run_compiler::{closure#1}>::{closure#0}, core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>
  52:        0x1086d3499 - std[8b12c7306df28d12]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[221574002a4ca70c]::util::run_in_thread_pool_with_globals<rustc_interface[221574002a4ca70c]::interface::run_compiler<core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>, rustc_driver[7138d63f5c135eca]::run_compiler::{closure#1}>::{closure#0}, core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>::{closure#0}, core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>
  53:        0x1086d42f1 - <<std[8b12c7306df28d12]::thread::Builder>::spawn_unchecked_<rustc_interface[221574002a4ca70c]::util::run_in_thread_pool_with_globals<rustc_interface[221574002a4ca70c]::interface::run_compiler<core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>, rustc_driver[7138d63f5c135eca]::run_compiler::{closure#1}>::{closure#0}, core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>::{closure#0}, core[8afb26d279e869ce]::result::Result<(), rustc_errors[9b765dd3664f2226]::ErrorGuaranteed>>::{closure#1} as core[8afb26d279e869ce]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  54:        0x1111502b7 - std::sys::unix::thread::Thread::new::thread_start::h5be690079b7ad7fa
  55:     0x7fff204558fc - __pthread_start

error: internal compiler error: unexpected panic

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

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

note: rustc 1.62.1 (e092d0b6b 2022-07-16) running on x86_64-apple-darwin

note: compiler flags: --crate-type bin -C embed-bitcode=no -C split-debuginfo=unpacked -C debuginfo=2 -C incremental

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

query stack during panic:
#0 [typeck] type-checking `main`
#1 [typeck_item_bodies] type-checking all item bodies
#2 [analysis] running analysis passes on this crate
end of query stack

[compiler-errors]

@TaKO8Ki are you working on this? I started working on a solution but didn't claim it, and I saw you claimed a few other issues recently too so I didn't know if it was planned or started yet 😆

If you've already gotten started on it, then that's ok, but if you just claimed so that you can work on it later, I'd like to finish up my solution.

[TaKO8Ki]

@compiler-errors I've already started working on this, but I spent only a little time on it, so I have no problem with you taking it over!

[compiler-errors]

Thanks. I will try my best to claim issues I am working on earlier in the process so I don't have to bother you like this.