[ICE]: encountered incremental compilation error with evaluate_obligation

Code

I don't have a minimal reproducer yet, but I have a branch where I can repro the ICE consistently.

git clone https://gitlab.torproject.org/gabi-250/arti.git -b ice-min-g2
cd arti
git checkout HEAD^
cargo check --all-features
git checkout -
cargo check --all-features

The second cargo check --all-features triggers the ICE.

Meta

It reproduces consistently on rustc 1.97.1.

rustc --version --verbose:

rustc 1.97.1 (8bab26f4f 2026-07-14)
binary: rustc
commit-hash: 8bab26f4f68e0e26f0bb7960be334d5b520ea452
commit-date: 2026-07-14
host: x86_64-unknown-linux-gnu
release: 1.97.1
LLVM version: 22.1.6

It doesn't reproduce on nightly, so I suppose it's possible this was already fixed (but I figured I'd file an issue just in case)

rustc 1.100.0-nightly (bba531001 2026-09-20)
binary: rustc
commit-hash: bba531001d4de6d7f49693e0836a2668ca063282
commit-date: 2026-09-20
host: x86_64-unknown-linux-gnu
release: 1.100.0-nightly
LLVM version: 23.1.1

Error output

Using 1.97.1:

error[E0425]: cannot find type `FromUtf8Error` in module `std::str`
  --> crates/arti-relay/src/stream/dns/resolver/err.rs:12:31
   |
12 |     InvalidHostname(std::str::FromUtf8Error),
   |                               ^^^^^^^^^^^^^
   |
  --> /rustc/8bab26f4f68e0e26f0bb7960be334d5b520ea452/library/core/src/str/error.rs:47:0
   |
   = note: similarly named struct `Utf8Error` defined here
help: a struct with a similar name exists
   |
12 -     InvalidHostname(std::str::FromUtf8Error),
12 +     InvalidHostname(std::str::Utf8Error),
   |
help: consider importing this struct
   |
 3 + use std::string::FromUtf8Error;
   |
help: if you import `FromUtf8Error`, refer to it directly
   |
12 -     InvalidHostname(std::str::FromUtf8Error),
12 +     InvalidHostname(FromUtf8Error),
   |

warning: unused imports: `LookupAnswers` and `LookupError`
 --> crates/arti-relay/src/stream/dns.rs:5:29
  |
5 | use resolver::{DnsResolver, LookupAnswers, LookupError};
  |                             ^^^^^^^^^^^^^  ^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` (part of `#[warn(unused)]`) on by default

error: internal compiler error: encountered incremental compilation error with evaluate_obligation(939cab13c00586cf-1d23fe1e6676f246)
  |
  = note: please follow the instructions below to create a bug report with the provided information
  = note: for incremental compilation bugs, having a reproduction is vital
  = note: an ideal reproduction consists of the code before and some patch that then triggers the bug when applied and compiled again
  = note: as a workaround, you can run `cargo clean -p arti_relay` or `cargo clean` to allow your project to compile


thread 'rustc' (273233) panicked at /rustc-dev/8bab26f4f68e0e26f0bb7960be334d5b520ea452/compiler/rustc_middle/src/verify_ich.rs:82:9:
Found unstable fingerprints for evaluate_obligation(939cab13c00586cf-1d23fe1e6676f246): Ok(EvaluatedToOk)
stack backtrace:
   0:     0x7f5af06901f9 - <<std[1e3c4ec04c5261a9]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[37f591cfbe66b0b1]::fmt::Display>::fmt
   1:     0x7f5af0e20cc8 - core[37f591cfbe66b0b1]::fmt::write
   2:     0x7f5af220d936 - <std[1e3c4ec04c5261a9]::sys::stdio::unix::Stderr as std[1e3c4ec04c5261a9]::io::Write>::write_fmt
   3:     0x7f5af06663fe - std[1e3c4ec04c5261a9]::panicking::default_hook::{closure#0}
   4:     0x7f5af0683b33 - std[1e3c4ec04c5261a9]::panicking::default_hook
   5:     0x7f5aef476c31 - std[1e3c4ec04c5261a9]::panicking::update_hook::<alloc[24b8200b0946867]::boxed::Box<rustc_driver_impl[4e5b0da0f4005eeb]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f5af0683e12 - std[1e3c4ec04c5261a9]::panicking::panic_with_hook
   7:     0x7f5af06664c2 - std[1e3c4ec04c5261a9]::panicking::panic_handler::{closure#0}
   8:     0x7f5af065a9a9 - std[1e3c4ec04c5261a9]::sys::backtrace::__rust_end_short_backtrace::<std[1e3c4ec04c5261a9]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f5af0667f2d - __rustc[6ef78fba13ac776c]::rust_begin_unwind
  10:     0x7f5aed1192dc - core[37f591cfbe66b0b1]::panicking::panic_fmt
  11:     0x7f5aefb71e27 - rustc_middle[8a940fbd8c5d50e6]::verify_ich::incremental_verify_ich_failed
  12:     0x7f5af159eeda - rustc_middle[8a940fbd8c5d50e6]::verify_ich::incremental_verify_ich::<rustc_middle[8a940fbd8c5d50e6]::query::erase::ErasedData<[u8; 2usize]>>
  13:     0x7f5af1c56adc - rustc_query_impl[bdb42d22f02e134a]::execution::try_execute_query::<rustc_middle[8a940fbd8c5d50e6]::query::caches::DefaultCache<rustc_type_ir[f110db280fa5959f]::canonical::CanonicalQueryInput<rustc_middle[8a940fbd8c5d50e6]::ty::context::TyCtxt, rustc_middle[8a940fbd8c5d50e6]::ty::ParamEnvAnd<rustc_middle[8a940fbd8c5d50e6]::ty::predicate::Predicate>>, rustc_middle[8a940fbd8c5d50e6]::query::erase::ErasedData<[u8; 2usize]>>, true>
  14:     0x7f5af1c55182 - rustc_query_impl[bdb42d22f02e134a]::query_impl::evaluate_obligation::execute_query_incr::__rust_end_short_backtrace
  15:     0x7f5af140c5a0 - <rustc_trait_selection[c5d69b98270b4c69]::traits::fulfill::FulfillProcessor as rustc_data_structures[6314a90323e5c320]::obligation_forest::ObligationProcessor>::process_obligation
  16:     0x7f5af0e05d95 - <rustc_data_structures[6314a90323e5c320]::obligation_forest::ObligationForest<rustc_trait_selection[c5d69b98270b4c69]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[c5d69b98270b4c69]::traits::fulfill::FulfillProcessor>
  17:     0x7f5af16cb979 - rustc_hir_analysis[1956eea595525479]::check::check::check_coroutine_obligations
  18:     0x7f5af16cb2d9 - rustc_query_impl[bdb42d22f02e134a]::query_impl::check_coroutine_obligations::invoke_provider_fn::__rust_begin_short_backtrace
  19:     0x7f5af104cf3f - rustc_query_impl[bdb42d22f02e134a]::execution::try_execute_query::<rustc_data_structures[6314a90323e5c320]::vec_cache::VecCache<rustc_span[d86c6dd34b0962f8]::def_id::LocalDefId, rustc_middle[8a940fbd8c5d50e6]::query::erase::ErasedData<[u8; 1usize]>, rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepNodeIndex>, true>
  20:     0x7f5af1f81911 - rustc_query_impl[bdb42d22f02e134a]::execution::force_query_dep_node::<rustc_data_structures[6314a90323e5c320]::vec_cache::VecCache<rustc_span[d86c6dd34b0962f8]::def_id::LocalDefId, rustc_middle[8a940fbd8c5d50e6]::query::erase::ErasedData<[u8; 1usize]>, rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepNodeIndex>>
  21:     0x7f5af00b13ed - <rustc_query_impl[bdb42d22f02e134a]::dep_kind_vtables::make_dep_kind_vtable_for_query<rustc_query_impl[bdb42d22f02e134a]::query_impl::check_coroutine_obligations::VTableGetter>::{closure#0} as core[37f591cfbe66b0b1]::ops::function::FnOnce<(rustc_middle[8a940fbd8c5d50e6]::ty::context::TyCtxt, rustc_middle[8a940fbd8c5d50e6]::dep_graph::dep_node::DepNode, rustc_middle[8a940fbd8c5d50e6]::dep_graph::serialized::SerializedDepNodeIndex)>>::call_once
  22:     0x7f5af1044b66 - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  23:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  24:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  25:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  26:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  27:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  28:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  29:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  30:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  31:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  32:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  33:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  34:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  35:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  36:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  37:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  38:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  39:     0x7f5af1044acf - <rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepGraphData>::try_mark_previous_green
  40:     0x7f5af25528cc - rustc_query_impl[bdb42d22f02e134a]::execution::ensure_can_skip_execution::<rustc_data_structures[6314a90323e5c320]::vec_cache::VecCache<rustc_span[d86c6dd34b0962f8]::def_id::LocalDefId, rustc_middle[8a940fbd8c5d50e6]::query::erase::ErasedData<[u8; 1usize]>, rustc_middle[8a940fbd8c5d50e6]::dep_graph::graph::DepNodeIndex>>.warm
  41:     0x7f5af104c95b - rustc_query_impl[bdb42d22f02e134a]::query_impl::check_well_formed::execute_query_incr::__rust_end_short_backtrace
  42:     0x7f5af15bdca6 - rustc_hir_analysis[1956eea595525479]::check::wfcheck::check_type_wf
  43:     0x7f5af15bdb39 - rustc_query_impl[bdb42d22f02e134a]::query_impl::check_type_wf::invoke_provider_fn::__rust_begin_short_backtrace
  44:     0x7f5af21e80f1 - rustc_query_impl[bdb42d22f02e134a]::execution::try_execute_query::<rustc_middle[8a940fbd8c5d50e6]::query::caches::SingleCache<rustc_middle[8a940fbd8c5d50e6]::query::erase::ErasedData<[u8; 1usize]>>, true>
  45:     0x7f5af21e790b - rustc_query_impl[bdb42d22f02e134a]::query_impl::check_type_wf::execute_query_incr::__rust_end_short_backtrace
  46:     0x7f5af10bb469 - rustc_hir_analysis[1956eea595525479]::check_crate
  47:     0x7f5af10b6e33 - rustc_interface[6818d3a8678689ee]::passes::analysis
  48:     0x7f5af1f66c35 - rustc_query_impl[bdb42d22f02e134a]::execution::try_execute_query::<rustc_middle[8a940fbd8c5d50e6]::query::caches::SingleCache<rustc_middle[8a940fbd8c5d50e6]::query::erase::ErasedData<[u8; 0usize]>>, true>
  49:     0x7f5af1f665ea - rustc_query_impl[bdb42d22f02e134a]::query_impl::analysis::execute_query_incr::__rust_end_short_backtrace
  50:     0x7f5af1f26f1b - rustc_interface[6818d3a8678689ee]::interface::run_compiler::<(), rustc_driver_impl[4e5b0da0f4005eeb]::run_compiler::{closure#0}>::{closure#1}
  51:     0x7f5af1f5407a - std[1e3c4ec04c5261a9]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[6818d3a8678689ee]::util::run_in_thread_with_globals<rustc_interface[6818d3a8678689ee]::util::run_in_thread_pool_with_globals<rustc_interface[6818d3a8678689ee]::interface::run_compiler<(), rustc_driver_impl[4e5b0da0f4005eeb]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  52:     0x7f5af1f5476d - <std[1e3c4ec04c5261a9]::thread::lifecycle::spawn_unchecked<rustc_interface[6818d3a8678689ee]::util::run_in_thread_with_globals<rustc_interface[6818d3a8678689ee]::util::run_in_thread_pool_with_globals<rustc_interface[6818d3a8678689ee]::interface::run_compiler<(), rustc_driver_impl[4e5b0da0f4005eeb]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[37f591cfbe66b0b1]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  53:     0x7f5af1f5556c - <std[1e3c4ec04c5261a9]::sys::thread::unix::Thread>::new::thread_start
  54:     0x7f5aeb4980a2 - <unknown>
  55:     0x7f5aeb52080c - <unknown>
  56:                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: rustc 1.97.1 (8bab26f4f 2026-07-14) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

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

query stack during panic:
#0 [evaluate_obligation] evaluating trait selection obligation `alloc::boxed::Box<hickory_proto::error::ProtoError>: core::marker::Send`
#1 [check_coroutine_obligations] verify auto trait bounds for coroutine interior type `stream::handle_circuit_incoming_streams`
... and 2 other queries... use `env RUST_BACKTRACE=1` to see the full query stack
there was a panic while trying to force a dep node
try_mark_green dep node stack:
#0 mir_borrowck(arti_relay[adc4]::stream::handle_circuit_incoming_streams)
#1 type_of_opaque(arti_relay[adc4]::stream::handle_circuit_incoming_streams::{opaque#0})
#2 typeck_root(arti_relay[adc4]::stream::handle_incoming_streams)
#3 check_match(arti_relay[adc4]::stream::handle_incoming_streams)
#4 mir_built(arti_relay[adc4]::stream::handle_incoming_streams)
#5 has_ffi_unwind_calls(arti_relay[adc4]::stream::handle_incoming_streams)
#6 mir_promoted(arti_relay[adc4]::stream::handle_incoming_streams)
#7 mir_borrowck(arti_relay[adc4]::stream::handle_incoming_streams)
#8 type_of_opaque(arti_relay[adc4]::stream::handle_incoming_streams::{opaque#0})
#9 typeck_root(arti_relay[adc4]::relay::{impl#1}::run)
#10 check_match(arti_relay[adc4]::relay::{impl#1}::run)
#11 mir_built(arti_relay[adc4]::relay::{impl#1}::run)
#12 has_ffi_unwind_calls(arti_relay[adc4]::relay::{impl#1}::run)
#13 mir_promoted(arti_relay[adc4]::relay::{impl#1}::run)
#14 mir_borrowck(arti_relay[adc4]::relay::{impl#1}::run)
#15 type_of_opaque(arti_relay[adc4]::relay::{impl#1}::run::{opaque#0})
#16 type_of(arti_relay[adc4]::relay::{impl#1}::run::{opaque#0})
#17 check_well_formed(arti_relay[adc4]::relay::{impl#1}::run::{opaque#0})
end of try_mark_green dep node stack
For more information about this error, try `rustc --explain E0425`.
warning: `arti-relay` (bin "arti-relay") generated 1 warning
error: could not compile `arti-relay` (bin "arti-relay") due to 2 previous errors; 1 warning emitted

Backtrace

<backtrace>