[ICE]: DefId does not have a "fn_sig"

auto-reduced (treereduce-rust):

fn main() {
    if None::<str>() {}
}

original:

fn main() {
  if None::<str>() {}
}

Version information

rustc 1.99.0-nightly (87212cef7 2026-08-05)
binary: rustc
commit-hash: 87212cef77e7bfa92ba0c4850be1d089745ba6fc
commit-date: 2026-08-05
host: x86_64-unknown-linux-gnu
release: 1.99.0-nightly
LLVM version: 23.1.0

Possibly related line of code:
https://github.com/rust-lang/rust/blob/87212cef77e7bfa92ba0c4850be1d089745ba6fc/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs#L224-L236

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

error[E0618]: expected function, found enum variant `None<str>`
 --> /tmp/icemaker_global_tempdir.zwqcIgjvUqIE/rustc_testrunner_tmpdir_reporting.xJ97gJejYS8G/mvce.rs:2:8
  |
2 |     if None::<str>() {}
  |        ^^^^^^^^^^^--
  |        |
  |        call expression requires function
  |
help: `None<str>` is a unit enum variant, and does not take parentheses to be constructed
  |
2 -     if None::<str>() {}
2 +     if None::<str> {}
  |


thread 'rustc' (1771207) panicked at /rustc-dev/87212cef77e7bfa92ba0c4850be1d089745ba6fc/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs:230:1:
DefId(2:53128 ~ core[e730]::option::Option::None::{constructor#0}) does not have a "fn_sig"
stack backtrace:
   0:     0x7f2935f49af6 - <<std[76c4f663cfdf9de9]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[e73040c94e2c05fb]::fmt::Display>::fmt
   1:     0x7f293660a40f - core[e73040c94e2c05fb]::fmt::write
   2:     0x7f2935f5ea1c - <std[76c4f663cfdf9de9]::sys::stdio::unix::Stderr as core[e73040c94e2c05fb]::io::write::Write>::write_fmt
   3:     0x7f2935f1c8da - std[76c4f663cfdf9de9]::panicking::default_hook::{closure#0}
   4:     0x7f2935f3d673 - std[76c4f663cfdf9de9]::panicking::default_hook
   5:     0x7f2934e8101a - std[76c4f663cfdf9de9]::panicking::update_hook::<alloc[6c3988ddb1173fa]::boxed::Box<rustc_driver_impl[babd6b97ed827c3b]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f2935f3db12 - std[76c4f663cfdf9de9]::panicking::panic_with_hook
   7:     0x7f2935f1c992 - std[76c4f663cfdf9de9]::panicking::panic_handler::{closure#0}
   8:     0x7f2935f14609 - std[76c4f663cfdf9de9]::sys::backtrace::__rust_end_short_backtrace::<std[76c4f663cfdf9de9]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f2935f1e36d - __rustc[597bf519f21c5b2a]::rust_begin_unwind
  10:     0x7f2932b0cf2c - core[e73040c94e2c05fb]::panicking::panic_fmt
  11:     0x7f29353f8971 - rustc_metadata[983eb2c9ed2f2131]::rmeta::decoder::cstore_impl::provide_extern::fn_sig::{closure#1}
  12:     0x7f2936a211ac - rustc_metadata[983eb2c9ed2f2131]::rmeta::decoder::cstore_impl::provide_extern::fn_sig
  13:     0x7f2936e0030b - rustc_query_impl[13b9a2342661e590]::query_impl::fn_sig::invoke_provider_fn::__rust_begin_short_backtrace
  14:     0x7f2936e01c52 - rustc_query_impl[13b9a2342661e590]::execution::try_execute_query::<rustc_middle[398bfe4e000b8183]::query::caches::DefIdCache<rustc_middle[398bfe4e000b8183]::query::erase::ErasedData<[u8; 24usize]>>, false>
  15:     0x7f2936e0179e - rustc_query_impl[13b9a2342661e590]::query_impl::fn_sig::execute_query_non_incr::__rust_end_short_backtrace
  16:     0x7f2935d9e2e1 - <rustc_trait_selection[80cf404ec0a5bee9]::error_reporting::TypeErrCtxt>::suggest_add_reference_to_arg
  17:     0x7f2935d4c31c - <rustc_trait_selection[80cf404ec0a5bee9]::error_reporting::TypeErrCtxt>::report_selection_error
  18:     0x7f2935d70e5f - <rustc_trait_selection[80cf404ec0a5bee9]::error_reporting::TypeErrCtxt>::report_fulfillment_error
  19:     0x7f2934788b69 - <rustc_trait_selection[80cf404ec0a5bee9]::error_reporting::TypeErrCtxt>::report_fulfillment_errors
  20:     0x7f293796d35c - rustc_hir_typeck[44769868edd0f557]::typeck_with_inspect::{closure#0}
  21:     0x7f293795fc70 - rustc_query_impl[13b9a2342661e590]::query_impl::typeck_root::invoke_provider_fn::__rust_begin_short_backtrace
  22:     0x7f293715b0b5 - rustc_query_impl[13b9a2342661e590]::execution::try_execute_query::<rustc_data_structures[1fe83761f21b0d17]::vec_cache::VecCache<rustc_span[130017d5cd07ffae]::def_id::LocalDefId, rustc_middle[398bfe4e000b8183]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[398bfe4e000b8183]::dep_graph::graph::DepNodeIndex>, false>
  23:     0x7f293715aa43 - rustc_query_impl[13b9a2342661e590]::query_impl::typeck_root::execute_query_non_incr::__rust_end_short_backtrace
  24:     0x7f2936e35390 - rustc_hir_analysis[81d558729a90fdc1]::check_crate
  25:     0x7f293715c5ba - rustc_interface[f85a6de8440246ff]::passes::analysis
  26:     0x7f293780b50a - rustc_query_impl[13b9a2342661e590]::execution::try_execute_query::<rustc_middle[398bfe4e000b8183]::query::caches::SingleCache<rustc_middle[398bfe4e000b8183]::query::erase::ErasedData<[u8; 0usize]>>, false>
  27:     0x7f293780b2e9 - rustc_query_impl[13b9a2342661e590]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  28:     0x7f29378722f5 - rustc_interface[f85a6de8440246ff]::interface::run_compiler::<(), rustc_driver_impl[babd6b97ed827c3b]::run_compiler::{closure#0}>::{closure#2}
  29:     0x7f29378b2ea4 - std[76c4f663cfdf9de9]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[f85a6de8440246ff]::util::run_in_thread_with_globals<rustc_interface[f85a6de8440246ff]::util::run_in_thread_pool_with_globals<rustc_interface[f85a6de8440246ff]::interface::run_compiler<(), rustc_driver_impl[babd6b97ed827c3b]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  30:     0x7f29378b2c6d - <std[76c4f663cfdf9de9]::thread::lifecycle::spawn_unchecked<rustc_interface[f85a6de8440246ff]::util::run_in_thread_with_globals<rustc_interface[f85a6de8440246ff]::util::run_in_thread_pool_with_globals<rustc_interface[f85a6de8440246ff]::interface::run_compiler<(), rustc_driver_impl[babd6b97ed827c3b]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[e73040c94e2c05fb]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  31:     0x7f29378af8fa - <std[76c4f663cfdf9de9]::sys::thread::unix::Thread>::new::thread_start
  32:     0x7f2930c97739 - <unknown>
  33:     0x7f2930d1bedc - <unknown>
  34:                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 1.99.0-nightly (87212cef7 2026-08-05) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [fn_sig] computing function signature of `core::option::Option::None`
#1 [typeck_root] type-checking `main`
#2 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0618`.