ICE: autodiff: `expected autodiff function`

[matthiaskrgr]

auto-reduced (treereduce-rust):

//@compile-flags: -Clink-dead-code=true --crate-type=lib
#![feature(autodiff)]
#[core::autodiff::autodiff_forward(fd_inner, Const, Dual)]
fn _zst(_zst: (), d: f64) {}

original:

#![feature(autodiff)]
#[core::autodiff::autodiff_forward(fd_inner, Const, Dual)]
fn _zst(_zst : (), d : f64) {}

Version information

rustc 1.94.0-nightly (2ca7bcd03 2025-12-23)
binary: rustc
commit-hash: 2ca7bcd03b87b52f7055a59b817443b0ac4a530d
commit-date: 2025-12-23
host: x86_64-unknown-linux-gnu
release: 1.94.0-nightly
LLVM version: 21.1.8

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Clink-dead-code=true --crate-type=lib

Program output

warning: unused variable: `d`
 --> /tmp/icemaker_global_tempdir.4K5QMhZtihrW/rustc_testrunner_tmpdir_reporting.xgmodUgqMMc5/mvce.rs:3:19
  |
3 | fn _zst(_zst: (), d: f64) {}
  |                   ^ help: if this is intentional, prefix it with an underscore: `_d`
  |
  = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

error: internal compiler error: /rustc-dev/2ca7bcd03b87b52f7055a59b817443b0ac4a530d/compiler/rustc_monomorphize/src/collector/autodiff.rs:44:18: expected autodiff function


thread 'rustc' (3569155) panicked at /rustc-dev/2ca7bcd03b87b52f7055a59b817443b0ac4a530d/compiler/rustc_monomorphize/src/collector/autodiff.rs:44:18:
Box<dyn Any>
stack backtrace:
   0:     0x7f6c07a2c3a3 - <<std[243ef3771c46e43a]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[c088ff38143eb53e]::fmt::Display>::fmt
   1:     0x7f6c08010648 - core[c088ff38143eb53e]::fmt::write
   2:     0x7f6c07a42af6 - <std[243ef3771c46e43a]::sys::stdio::unix::Stderr as std[243ef3771c46e43a]::io::Write>::write_fmt
   3:     0x7f6c07a02b48 - std[243ef3771c46e43a]::panicking::default_hook::{closure#0}
   4:     0x7f6c07a20213 - std[243ef3771c46e43a]::panicking::default_hook
   5:     0x7f6c06a10d77 - std[243ef3771c46e43a]::panicking::update_hook::<alloc[baa86124b2c3e6f2]::boxed::Box<rustc_driver_impl[e986b619aabff65e]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f6c07a204f2 - std[243ef3771c46e43a]::panicking::panic_with_hook
   7:     0x7f6c06a4dec1 - std[243ef3771c46e43a]::panicking::begin_panic::<rustc_errors[c64784b3ec03c9d3]::ExplicitBug>::{closure#0}
   8:     0x7f6c06a3e166 - std[243ef3771c46e43a]::sys::backtrace::__rust_end_short_backtrace::<std[243ef3771c46e43a]::panicking::begin_panic<rustc_errors[c64784b3ec03c9d3]::ExplicitBug>::{closure#0}, !>
   9:     0x7f6c06a3b7a9 - std[243ef3771c46e43a]::panicking::begin_panic::<rustc_errors[c64784b3ec03c9d3]::ExplicitBug>
  10:     0x7f6c06a6beb1 - <rustc_errors[c64784b3ec03c9d3]::diagnostic::BugAbort as rustc_errors[c64784b3ec03c9d3]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7f6c0700d2e9 - rustc_middle[395a2484b1db1a27]::util::bug::opt_span_bug_fmt::<rustc_span[f0a4c422aa13deb9]::span_encoding::Span>::{closure#0}
  12:     0x7f6c0700d472 - rustc_middle[395a2484b1db1a27]::ty::context::tls::with_opt::<rustc_middle[395a2484b1db1a27]::util::bug::opt_span_bug_fmt<rustc_span[f0a4c422aa13deb9]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  13:     0x7f6c06ffe77b - rustc_middle[395a2484b1db1a27]::ty::context::tls::with_context_opt::<rustc_middle[395a2484b1db1a27]::ty::context::tls::with_opt<rustc_middle[395a2484b1db1a27]::util::bug::opt_span_bug_fmt<rustc_span[f0a4c422aa13deb9]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  14:     0x7f6c0541a5b4 - rustc_middle[395a2484b1db1a27]::util::bug::bug_fmt
  15:     0x7f6c0841ce27 - <rustc_monomorphize[890c893552912303]::collector::MirUsedCollector as rustc_middle[395a2484b1db1a27]::mir::visit::Visitor>::visit_terminator
  16:     0x7f6c084117a2 - rustc_monomorphize[890c893552912303]::collector::items_of_instance
  17:     0x7f6c08411032 - rustc_query_impl[3af702bc24a35b84]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[3af702bc24a35b84]::query_impl::items_of_instance::dynamic_query::{closure#2}::{closure#0}, rustc_middle[395a2484b1db1a27]::query::erase::Erased<[u8; 32usize]>>
  18:     0x7f6c086fb094 - rustc_query_system[fae14337e0c02060]::query::plumbing::try_execute_query::<rustc_query_impl[3af702bc24a35b84]::DynamicConfig<rustc_query_system[fae14337e0c02060]::query::caches::DefaultCache<(rustc_middle[395a2484b1db1a27]::ty::instance::Instance, rustc_middle[395a2484b1db1a27]::mir::mono::CollectionMode), rustc_middle[395a2484b1db1a27]::query::erase::Erased<[u8; 32usize]>>, false, false, false>, rustc_query_impl[3af702bc24a35b84]::plumbing::QueryCtxt, false>
  19:     0x7f6c086facb7 - rustc_query_impl[3af702bc24a35b84]::query_impl::items_of_instance::get_query_non_incr::__rust_end_short_backtrace
  20:     0x7f6c086f95d7 - rustc_monomorphize[890c893552912303]::collector::collect_items_rec::{closure#0}
  21:     0x7f6c0943d157 - rustc_monomorphize[890c893552912303]::collector::collect_items_rec
  22:     0x7f6c083a8921 - rustc_monomorphize[890c893552912303]::collector::collect_crate_mono_items::{closure#1}::{closure#0}
  23:     0x7f6c089b733a - rustc_monomorphize[890c893552912303]::partitioning::collect_and_partition_mono_items
  24:     0x7f6c094fa896 - rustc_query_impl[3af702bc24a35b84]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[3af702bc24a35b84]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle[395a2484b1db1a27]::query::erase::Erased<[u8; 24usize]>>
  25:     0x7f6c094fa85b - <rustc_query_impl[3af702bc24a35b84]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2} as core[c088ff38143eb53e]::ops::function::FnOnce<(rustc_middle[395a2484b1db1a27]::ty::context::TyCtxt, ())>>::call_once
  26:     0x7f6c094fa3b6 - rustc_query_system[fae14337e0c02060]::query::plumbing::try_execute_query::<rustc_query_impl[3af702bc24a35b84]::DynamicConfig<rustc_query_system[fae14337e0c02060]::query::caches::SingleCache<rustc_middle[395a2484b1db1a27]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[3af702bc24a35b84]::plumbing::QueryCtxt, false>
  27:     0x7f6c094fa15b - rustc_query_impl[3af702bc24a35b84]::query_impl::collect_and_partition_mono_items::get_query_non_incr::__rust_end_short_backtrace
  28:     0x7f6c08c866fe - rustc_codegen_ssa[21f8591ee52006ec]::back::symbol_export::exported_generic_symbols_provider_local
  29:     0x7f6c08f00b75 - rustc_query_impl[3af702bc24a35b84]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[3af702bc24a35b84]::query_impl::exported_generic_symbols::dynamic_query::{closure#2}::{closure#0}, rustc_middle[395a2484b1db1a27]::query::erase::Erased<[u8; 16usize]>>
  30:     0x7f6c08f00b4b - <rustc_query_impl[3af702bc24a35b84]::query_impl::exported_generic_symbols::dynamic_query::{closure#2} as core[c088ff38143eb53e]::ops::function::FnOnce<(rustc_middle[395a2484b1db1a27]::ty::context::TyCtxt, rustc_span[f0a4c422aa13deb9]::def_id::CrateNum)>>::call_once
  31:     0x7f6c08efe9a6 - rustc_query_system[fae14337e0c02060]::query::plumbing::try_execute_query::<rustc_query_impl[3af702bc24a35b84]::DynamicConfig<rustc_data_structures[75601f20e3d68749]::vec_cache::VecCache<rustc_span[f0a4c422aa13deb9]::def_id::CrateNum, rustc_middle[395a2484b1db1a27]::query::erase::Erased<[u8; 16usize]>, rustc_query_system[fae14337e0c02060]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[3af702bc24a35b84]::plumbing::QueryCtxt, false>
  32:     0x7f6c08efe4cc - rustc_query_impl[3af702bc24a35b84]::query_impl::exported_generic_symbols::get_query_non_incr::__rust_end_short_backtrace
  33:     0x7f6c08ac1653 - <rustc_metadata[39a13e8e21b894d2]::rmeta::encoder::EncodeContext>::encode_crate_root
  34:     0x7f6c09507b90 - <rustc_metadata[39a13e8e21b894d2]::rmeta::encoder::encode_metadata::{closure#3} as core[c088ff38143eb53e]::ops::function::FnOnce<(rustc_middle[395a2484b1db1a27]::ty::context::TyCtxt, &std[243ef3771c46e43a]::path::Path)>>::call_once
  35:     0x7f6c09504893 - rustc_metadata[39a13e8e21b894d2]::rmeta::encoder::encode_metadata
  36:     0x7f6c09025a01 - rustc_metadata[39a13e8e21b894d2]::fs::encode_and_write_metadata
  37:     0x7f6c093ac56e - <rustc_interface[577997324878ea43]::queries::Linker>::codegen_and_build_linker
  38:     0x7f6c093a9299 - <rustc_interface[577997324878ea43]::passes::create_and_enter_global_ctxt<core[c088ff38143eb53e]::option::Option<rustc_interface[577997324878ea43]::queries::Linker>, rustc_driver_impl[e986b619aabff65e]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[c088ff38143eb53e]::ops::function::FnOnce<(&rustc_session[9908f9ef7e13fd8d]::session::Session, rustc_middle[395a2484b1db1a27]::ty::context::CurrentGcx, alloc[baa86124b2c3e6f2]::sync::Arc<rustc_data_structures[75601f20e3d68749]::jobserver::Proxy>, &std[243ef3771c46e43a]::sync::once_lock::OnceLock<rustc_middle[395a2484b1db1a27]::ty::context::GlobalCtxt>, &rustc_data_structures[75601f20e3d68749]::sync::worker_local::WorkerLocal<rustc_middle[395a2484b1db1a27]::arena::Arena>, &rustc_data_structures[75601f20e3d68749]::sync::worker_local::WorkerLocal<rustc_hir[38bedddefeb6b9a6]::Arena>, rustc_driver_impl[e986b619aabff65e]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  39:     0x7f6c0923cc8a - rustc_interface[577997324878ea43]::interface::run_compiler::<(), rustc_driver_impl[e986b619aabff65e]::run_compiler::{closure#0}>::{closure#1}
  40:     0x7f6c0918ffce - std[243ef3771c46e43a]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[577997324878ea43]::util::run_in_thread_with_globals<rustc_interface[577997324878ea43]::util::run_in_thread_pool_with_globals<rustc_interface[577997324878ea43]::interface::run_compiler<(), rustc_driver_impl[e986b619aabff65e]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  41:     0x7f6c0918fda0 - <std[243ef3771c46e43a]::thread::lifecycle::spawn_unchecked<rustc_interface[577997324878ea43]::util::run_in_thread_with_globals<rustc_interface[577997324878ea43]::util::run_in_thread_pool_with_globals<rustc_interface[577997324878ea43]::interface::run_compiler<(), rustc_driver_impl[e986b619aabff65e]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[c088ff38143eb53e]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  42:     0x7f6c09195b38 - <std[243ef3771c46e43a]::sys::thread::unix::Thread>::new::thread_start
  43:     0x7f6c02a9698b - <unknown>
  44:     0x7f6c02b1a9cc - <unknown>
  45:                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: rustc 1.94.0-nightly (2ca7bcd03 2025-12-23) running on x86_64-unknown-linux-gnu

note: compiler flags: -C link-dead-code=true --crate-type lib -Z dump-mir-dir=dir

query stack during panic:
#0 [items_of_instance] collecting items used by `fd_inner`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
#2 [exported_generic_symbols] collecting exported generic symbols for crate `0`
end of query stack
error: aborting due to 1 previous error; 1 warning emitted

@rustbot label +F-autodiff

[Aditya-PS-05]

@rustbot claim