ICE: eii: fn / macro rules `None` in find_attr()

[matthiaskrgr]

snippet:

macro_rules! foo_impl {}
#[eii]
fn foo_impl() {}

Version information

rustc 1.94.0-nightly (3f4dc1e02 2025-12-14)
binary: rustc
commit-hash: 3f4dc1e02d759aa3c3807d4efc1f7f6e293536a5
commit-date: 2025-12-14
host: x86_64-unknown-linux-gnu
release: 1.94.0-nightly
LLVM version: 21.1.5

Possibly related line of code:

rust/compiler/rustc_metadata/src/eii.rs

Lines 28 to 40 in 3f4dc1e

	for i in
	find_attr!(tcx.get_all_attrs(id), AttributeKind::EiiImpls(e) => e).into_iter().flatten()
	{
	eiis.entry(i.eii_macro)
	.or_insert_with(|| {
	// find the decl for this one if it wasn't in yet (maybe it's from the local crate? not very useful but not illegal)
	(find_attr!(tcx.get_all_attrs(i.eii_macro), AttributeKind::EiiExternTarget(d) => *d).unwrap(), Default::default())
	}).1.insert(id.into(), *i);
	}
	// if we find a new declaration, add it to the list without a known implementation
	if let Some(decl) =
	find_attr!(tcx.get_all_attrs(id), AttributeKind::EiiExternTarget(d) => *d)

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

Program output

error: macros must contain at least one rule
 --> /tmp/icemaker_global_tempdir.H7kAaxdihhDG/rustc_testrunner_tmpdir_reporting.S9gL24J8ZiLI/mvce.rs:1:1
  |
1 | macro_rules! foo_impl {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^

error[E0658]: use of unstable library feature `extern_item_impls`
 --> /tmp/icemaker_global_tempdir.H7kAaxdihhDG/rustc_testrunner_tmpdir_reporting.S9gL24J8ZiLI/mvce.rs:2:3
  |
2 | #[eii]
  |   ^^^
  |
  = note: see issue #125418 <https://github.com/rust-lang/rust/issues/125418> for more information
  = help: add `#![feature(extern_item_impls)]` to the crate attributes to enable
  = note: this compiler was built on 2025-12-14; consider upgrading it if it is out of date

warning: unused macro definition: `foo_impl`
 --> /tmp/icemaker_global_tempdir.H7kAaxdihhDG/rustc_testrunner_tmpdir_reporting.S9gL24J8ZiLI/mvce.rs:1:14
  |
1 | macro_rules! foo_impl {}
  |              ^^^^^^^^
  |
  = note: `#[warn(unused_macros)]` (part of `#[warn(unused)]`) on by default

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.H7kAaxdihhDG/rustc_testrunner_tmpdir_reporting.S9gL24J8ZiLI/mvce.rs:3:17
  |
3 | fn foo_impl() {}
  |                 ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.H7kAaxdihhDG/rustc_testrunner_tmpdir_reporting.S9gL24J8ZiLI/mvce.rs`


thread 'rustc' (3711046) panicked at compiler/rustc_metadata/src/eii.rs:34:106:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7f791af90173 - <<std[e49fa185a119b89b]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[17865207963548b5]::fmt::Display>::fmt
   1:     0x7f791b610648 - core[17865207963548b5]::fmt::write
   2:     0x7f791afa67c6 - <std[e49fa185a119b89b]::sys::stdio::unix::Stderr as std[e49fa185a119b89b]::io::Write>::write_fmt
   3:     0x7f791af66938 - std[e49fa185a119b89b]::panicking::default_hook::{closure#0}
   4:     0x7f791af84043 - std[e49fa185a119b89b]::panicking::default_hook
   5:     0x7f7919f741d7 - std[e49fa185a119b89b]::panicking::update_hook::<alloc[756b9f94e2773738]::boxed::Box<rustc_driver_impl[e1c4671be5271ce8]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f791af84322 - std[e49fa185a119b89b]::panicking::panic_with_hook
   7:     0x7f791af66a2a - std[e49fa185a119b89b]::panicking::panic_handler::{closure#0}
   8:     0x7f791af5dab9 - std[e49fa185a119b89b]::sys::backtrace::__rust_end_short_backtrace::<std[e49fa185a119b89b]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f791af685ad - __rustc[df3bb69314ad135f]::rust_begin_unwind
  10:     0x7f791826df0c - core[17865207963548b5]::panicking::panic_fmt
  11:     0x7f7917775122 - core[17865207963548b5]::panicking::panic
  12:     0x7f7918767e39 - core[17865207963548b5]::option::unwrap_failed
  13:     0x7f791c77747e - rustc_metadata[2002d9e21ce78884]::eii::collect
  14:     0x7f791c77759e - rustc_query_impl[462c6a5584cea8d4]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[462c6a5584cea8d4]::query_impl::externally_implementable_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle[7055997c00c0bb98]::query::erase::Erased<[u8; 8usize]>>
  15:     0x7f791bad7a77 - rustc_query_system[5be0c069f6d5c539]::query::plumbing::try_execute_query::<rustc_query_impl[462c6a5584cea8d4]::DynamicConfig<rustc_data_structures[30161969bbcb553f]::vec_cache::VecCache<rustc_span[ce53af16555a42ff]::def_id::CrateNum, rustc_middle[7055997c00c0bb98]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[5be0c069f6d5c539]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[462c6a5584cea8d4]::plumbing::QueryCtxt, false>
  16:     0x7f791bad0f49 - rustc_query_impl[462c6a5584cea8d4]::query_impl::externally_implementable_items::get_query_non_incr::__rust_end_short_backtrace
  17:     0x7f791bad02ba - rustc_passes[9766a5655bde9e6]::eii::check_externally_implementable_items
  18:     0x7f791bad022f - rustc_query_impl[462c6a5584cea8d4]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[462c6a5584cea8d4]::query_impl::check_externally_implementable_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle[7055997c00c0bb98]::query::erase::Erased<[u8; 0usize]>>
  19:     0x7f791c7725a6 - rustc_query_system[5be0c069f6d5c539]::query::plumbing::try_execute_query::<rustc_query_impl[462c6a5584cea8d4]::DynamicConfig<rustc_query_system[5be0c069f6d5c539]::query::caches::SingleCache<rustc_middle[7055997c00c0bb98]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[462c6a5584cea8d4]::plumbing::QueryCtxt, false>
  20:     0x7f791c77238e - rustc_query_impl[462c6a5584cea8d4]::query_impl::check_externally_implementable_items::get_query_non_incr::__rust_end_short_backtrace
  21:     0x7f791b6ec481 - rustc_interface[50af632e35c6bce3]::passes::analysis
  22:     0x7f791b6ec2e5 - rustc_query_impl[462c6a5584cea8d4]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[462c6a5584cea8d4]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[7055997c00c0bb98]::query::erase::Erased<[u8; 0usize]>>
  23:     0x7f791c7725a6 - rustc_query_system[5be0c069f6d5c539]::query::plumbing::try_execute_query::<rustc_query_impl[462c6a5584cea8d4]::DynamicConfig<rustc_query_system[5be0c069f6d5c539]::query::caches::SingleCache<rustc_middle[7055997c00c0bb98]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[462c6a5584cea8d4]::plumbing::QueryCtxt, false>
  24:     0x7f791c772176 - rustc_query_impl[462c6a5584cea8d4]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  25:     0x7f791c92cdd4 - <rustc_interface[50af632e35c6bce3]::passes::create_and_enter_global_ctxt<core[17865207963548b5]::option::Option<rustc_interface[50af632e35c6bce3]::queries::Linker>, rustc_driver_impl[e1c4671be5271ce8]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[17865207963548b5]::ops::function::FnOnce<(&rustc_session[307f8e7a4263bd4]::session::Session, rustc_middle[7055997c00c0bb98]::ty::context::CurrentGcx, alloc[756b9f94e2773738]::sync::Arc<rustc_data_structures[30161969bbcb553f]::jobserver::Proxy>, &std[e49fa185a119b89b]::sync::once_lock::OnceLock<rustc_middle[7055997c00c0bb98]::ty::context::GlobalCtxt>, &rustc_data_structures[30161969bbcb553f]::sync::worker_local::WorkerLocal<rustc_middle[7055997c00c0bb98]::arena::Arena>, &rustc_data_structures[30161969bbcb553f]::sync::worker_local::WorkerLocal<rustc_hir[5d00f225b65c0257]::Arena>, rustc_driver_impl[e1c4671be5271ce8]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  26:     0x7f791c7c19da - rustc_interface[50af632e35c6bce3]::interface::run_compiler::<(), rustc_driver_impl[e1c4671be5271ce8]::run_compiler::{closure#0}>::{closure#1}
  27:     0x7f791c731d8e - std[e49fa185a119b89b]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[50af632e35c6bce3]::util::run_in_thread_with_globals<rustc_interface[50af632e35c6bce3]::util::run_in_thread_pool_with_globals<rustc_interface[50af632e35c6bce3]::interface::run_compiler<(), rustc_driver_impl[e1c4671be5271ce8]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  28:     0x7f791c731b60 - <std[e49fa185a119b89b]::thread::lifecycle::spawn_unchecked<rustc_interface[50af632e35c6bce3]::util::run_in_thread_with_globals<rustc_interface[50af632e35c6bce3]::util::run_in_thread_pool_with_globals<rustc_interface[50af632e35c6bce3]::interface::run_compiler<(), rustc_driver_impl[e1c4671be5271ce8]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[17865207963548b5]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  29:     0x7f791c7374f8 - <std[e49fa185a119b89b]::sys::thread::unix::Thread>::new::thread_start
  30:     0x7f79160969cb - <unknown>
  31:     0x7f791611aa0c - <unknown>
  32:                0x0 - <unknown>

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: rustc 1.94.0-nightly (3f4dc1e02 2025-12-14) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [externally_implementable_items] looking up the externally implementable items of a crate
#1 [check_externally_implementable_items] check externally implementable items
#2 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 3 previous errors; 1 warning emitted

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