rustc crashes when impl Iterator for X {} has a function with a return type containing Item

[xrdelectro]

Code

impl<T> Iterator for S<T> {
    fn next(&mut self) -> Option<Item> {}
}

even more minimal:

impl Iterator for S {
  fn n() -> Item {}
}

Meta

rustc --version --verbose:

rustc 1.83.0-nightly (c2f74c3f9 2024-09-09)
binary: rustc
commit-hash: c2f74c3f928aeb503f15b4e9ef5778e77f3058b8
commit-date: 2024-09-09
host: aarch64-apple-darwin
release: 1.83.0-nightly
LLVM version: 19.1.0

Error output

RUST_BACKTRACE=1 rustc --edition 2021 rustc_crash_code.rs:

thread 'rustc' panicked at compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs:244:1:
DefId(2:8887 ~ core[5321]::iter::traits::iterator::Iterator::Item) does not have a "fn_arg_names"
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: rustc_metadata::rmeta::decoder::cstore_impl::provide_extern::fn_arg_names::{closure#2}
   3: rustc_metadata::rmeta::decoder::cstore_impl::provide_extern::fn_arg_names
      [... omitted 2 frames ...]
   4: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 16]>>>
   5: <rustc_resolve::late::LateResolutionVisitor>::try_lookup_name_relaxed
   6: <rustc_resolve::late::LateResolutionVisitor>::smart_resolve_report_errors
   7: <rustc_resolve::late::LateResolutionVisitor>::smart_resolve_path_fragment::{closure#0}
   8: <rustc_resolve::late::LateResolutionVisitor>::smart_resolve_path_fragment
   9: <rustc_resolve::late::LateResolutionVisitor>::smart_resolve_path
  10: <rustc_resolve::late::LateResolutionVisitor as rustc_ast::visit::Visitor>::visit_ty
  11: <rustc_resolve::late::LateResolutionVisitor as rustc_ast::visit::Visitor>::visit_generic_arg
  12: rustc_ast::visit::walk_generic_args::<rustc_resolve::late::LateResolutionVisitor>
  13: rustc_ast::visit::walk_path::<rustc_resolve::late::LateResolutionVisitor>
  14: <rustc_resolve::late::LateResolutionVisitor as rustc_ast::visit::Visitor>::visit_ty
  15: <rustc_resolve::late::LateResolutionVisitor as rustc_ast::visit::Visitor>::visit_fn
  16: <rustc_ast::ast::AssocItemKind as rustc_ast::visit::WalkItemKind>::walk::<rustc_resolve::late::LateResolutionVisitor>
  17: <rustc_resolve::late::LateResolutionVisitor>::resolve_impl_item
  18: <rustc_resolve::late::LateResolutionVisitor>::resolve_item
  19: <rustc_resolve::late::LateResolutionVisitor as rustc_ast::visit::Visitor>::visit_item
  20: <rustc_resolve::Resolver>::late_resolve_crate
  21: <rustc_session::session::Session>::time::<(), <rustc_resolve::Resolver>::resolve_crate::{closure#0}>
  22: rustc_interface::passes::resolver_for_lowering_raw
      [... omitted 2 frames ...]
  23: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}::{closure#3}, &rustc_data_structures::steal::Steal<(rustc_middle::ty::ResolverAstLowering, alloc::sync::Arc<rustc_ast::ast::Crate>)>>
  24: <rustc_interface::interface::Compiler>::enter::<rustc_driver_impl::run_compiler::{closure#0}::{closure#1}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
  25: rustc_span::create_session_globals_then::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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

note: please attach the file at `/Users/zigmars/Documents/sandbox/comprehensive-rust/rustc-ice-2024-09-10T13_56_41-37663.txt` to your bug report

query stack during panic:
#0 [fn_arg_names] looking up function parameter names for `core::iter::traits::iterator::Iterator::Item`
#1 [resolver_for_lowering_raw] getting the resolver for lowering
end of query stack

Backtrace

<backtrace>

rustc-ice-2024-09-10T13_56_41-37663.txt

[rustc-ice-2024-09-10T13_56_41-37663.txt](https://github.com/user-attachments/files/16945965/rustc-ice-2024-09-10T13_56_41-37663.txt)

[xrdelectro]

When e.g., Item -> Self::Item, it does not crash anymore.

[compiler-errors]

Fixed by #130033

[fmease]

Duplicate of #130015