internal compiler error: compiler/rustc_borrowck/src/universal_regions.rs:930:36: cannot convert `'de/#0` to a region vid

[zesterer]

Summary

We've been seeing regular ICEs recently when compiling Veloren.

I've observed similar crashes on my own machine, as well as on CI machines - so it doesn't seem to be hardware-specific or due to cosmic particles.

I've observed that when running locally, immediately attempting a recompile (even without cargo clean-ing) often results in a successful build, implying that it may not be deterministic.

Version

rustc 1.91.0-nightly (12eb345e5 2025-09-07)
binary: rustc
commit-hash: 12eb345e5593a10e61b4aef766076c8bd552fea6
commit-date: 2025-09-07
host: x86_64-unknown-linux-gnu
release: 1.91.0-nightly
LLVM version: 21.1.0

Error output

Backtrace

error: internal compiler error: compiler/rustc_borrowck/src/universal_regions.rs:930:36: cannot convert `'de/#0` to a region vid
thread 'rustc' (5423) panicked at compiler/rustc_borrowck/src/universal_regions.rs:930:36:
Box<dyn Any>
stack backtrace:
 0:     0x7eff947c3033 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h2ad4b81e0a1d141a
 1:     0x7eff94e019d8 - core::fmt::write::hb0774556d3dc7b30
 2:     0x7eff94777e51 - std::io::Write::write_fmt::hbc4aae9967b6aa1f
 3:     0x7eff94788f12 - std::sys::backtrace::BacktraceLock::print::h009225ea673dcb39
 4:     0x7eff9478ee99 - std::panicking::default_hook::{{closure}}::h0ee7758b43152b02
 5:     0x7eff9478e9c3 - std::panicking::default_hook::hd7f22928c5f2b4e9
 6:     0x7eff937e90c5 - std[4955be27840904f9]::panicking::update_hook::<alloc[205488731dce6b4a]::boxed::Box<rustc_driver_impl[26f42f34adb8177b]::install_ice_hook::{closure#1}>>::{closure#0}
 7:     0x7eff9478f2bf - std::panicking::panic_with_hook::hb199e027d0d73c56
 8:     0x7eff93825451 - std[4955be27840904f9]::panicking::begin_panic::<rustc_errors[d69bd3777161a3f7]::ExplicitBug>::{closure#0}
 9:     0x7eff93818cd6 - std[4955be27840904f9]::sys::backtrace::__rust_end_short_backtrace::<std[4955be27840904f9]::panicking::begin_panic<rustc_errors[d69bd3777161a3f7]::ExplicitBug>::{closure#0}, !>
10:     0x7eff938169bb - std[4955be27840904f9]::panicking::begin_panic::<rustc_errors[d69bd3777161a3f7]::ExplicitBug>
11:     0x7eff93830be1 - <rustc_errors[d69bd3777161a3f7]::diagnostic::BugAbort as rustc_errors[d69bd3777161a3f7]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
12:     0x7eff93dc521a - rustc_middle[c20b1833d2103cd4]::util::bug::opt_span_bug_fmt::<rustc_span[9207591e1bacc259]::span_encoding::Span>::{closure#0}
13:     0x7eff93dc527a - rustc_middle[c20b1833d2103cd4]::ty::context::tls::with_opt::<rustc_middle[c20b1833d2103cd4]::util::bug::opt_span_bug_fmt<rustc_span[9207591e1bacc259]::span_encoding::Span>::{closure#0}, !>::{closure#0}
14:     0x7eff93db39cb - rustc_middle[c20b1833d2103cd4]::ty::context::tls::with_context_opt::<rustc_middle[c20b1833d2103cd4]::ty::context::tls::with_opt<rustc_middle[c20b1833d2103cd4]::util::bug::opt_span_bug_fmt<rustc_span[9207591e1bacc259]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
15:     0x7eff90ed1f50 - rustc_middle[c20b1833d2103cd4]::util::bug::bug_fmt
16:     0x7eff9574b119 - <rustc_borrowck[87b5e164cf2e6b95]::type_check::TypeChecker>::fully_perform_op::<(), rustc_middle[c20b1833d2103cd4]::ty::ParamEnvAnd<rustc_middle[c20b1833d2103cd4]::traits::query::type_op::ProvePredicate>>
17:     0x7eff91c984f7 - <rustc_borrowck[87b5e164cf2e6b95]::type_check::TypeChecker as rustc_middle[c20b1833d2103cd4]::mir::visit::Visitor>::visit_operand
18:     0x7eff95e43285 - <rustc_borrowck[87b5e164cf2e6b95]::type_check::TypeChecker as rustc_middle[c20b1833d2103cd4]::mir::visit::Visitor>::visit_body
19:     0x7eff95e126f8 - rustc_borrowck[87b5e164cf2e6b95]::type_check::type_check
20:     0x7eff9602c247 - <rustc_borrowck[87b5e164cf2e6b95]::root_cx::BorrowCheckRootCtxt>::do_mir_borrowck
21:     0x7eff960246e4 - rustc_borrowck[87b5e164cf2e6b95]::mir_borrowck
22:     0x7eff960244ad - rustc_query_impl[a53c7e3147e2afca]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a53c7e3147e2afca]::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c20b1833d2103cd4]::query::erase::Erased<[u8; 8usize]>>
23:     0x7eff94fdea45 - rustc_query_system[f188b7b83fb6d746]::query::plumbing::try_execute_query::<rustc_query_impl[a53c7e3147e2afca]::DynamicConfig<rustc_data_structures[9410bdb10db28c4b]::vec_cache::VecCache<rustc_span[9207591e1bacc259]::def_id::LocalDefId, rustc_middle[c20b1833d2103cd4]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[f188b7b83fb6d746]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a53c7e3147e2afca]::plumbing::QueryCtxt, false>
24:     0x7eff94fde249 - rustc_query_impl[a53c7e3147e2afca]::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
25:     0x7eff94fd924f - <rustc_middle[c20b1833d2103cd4]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[304babcac9c0794b]::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}
26:     0x7eff94fd6ad9 - rustc_interface[304babcac9c0794b]::passes::analysis
27:     0x7eff94fd5f8b - rustc_query_impl[a53c7e3147e2afca]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a53c7e3147e2afca]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c20b1833d2103cd4]::query::erase::Erased<[u8; 0usize]>>
28:     0x7eff95edb8e6 - rustc_query_system[f188b7b83fb6d746]::query::plumbing::try_execute_query::<rustc_query_impl[a53c7e3147e2afca]::DynamicConfig<rustc_query_system[f188b7b83fb6d746]::query::caches::SingleCache<rustc_middle[c20b1833d2103cd4]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[a53c7e3147e2afca]::plumbing::QueryCtxt, false>
29:     0x7eff95edb53c - rustc_query_impl[a53c7e3147e2afca]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
30:     0x7eff9608bc63 - rustc_interface[304babcac9c0794b]::passes::create_and_enter_global_ctxt::<core[dc33fea427b8ae3c]::option::Option<rustc_interface[304babcac9c0794b]::queries::Linker>, rustc_driver_impl[26f42f34adb8177b]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
31:     0x7eff9607b97e - rustc_interface[304babcac9c0794b]::interface::run_compiler::<(), rustc_driver_impl[26f42f34adb8177b]::run_compiler::{closure#0}>::{closure#1}
32:     0x7eff95fcc078 - std[4955be27840904f9]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[304babcac9c0794b]::util::run_in_thread_with_globals<rustc_interface[304babcac9c0794b]::util::run_in_thread_pool_with_globals<rustc_interface[304babcac9c0794b]::interface::run_compiler<(), rustc_driver_impl[26f42f34adb8177b]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
33:     0x7eff95fcbd5c - <<std[4955be27840904f9]::thread::Builder>::spawn_unchecked_<rustc_interface[304babcac9c0794b]::util::run_in_thread_with_globals<rustc_interface[304babcac9c0794b]::util::run_in_thread_pool_with_globals<rustc_interface[304babcac9c0794b]::interface::run_compiler<(), rustc_driver_impl[26f42f34adb8177b]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[dc33fea427b8ae3c]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
34:     0x7eff95fd23cd - std::sys::pal::unix::thread::Thread::new::thread_start::h131e81087b96dc19
35:     0x7eff8fa8aaa4 - <unknown>
36:     0x7eff8fb17c6c - <unknown>
37:                0x0 - <unknown>

[samueltardieu]

Clippy doesn't appear anywhere in this backtrace. It looks like this is a rustc problem, which would happen when running cargo check as well.

@rustbot transfer rust

[reddevilmidzy]

Thank you for reporting, Could you please try to find the minimum code that triggers ICE?

[theemathas]

Do you use any non-default configuration, such as parallel compilation?

[zesterer]

Thank you for reporting, Could you please try to find the minimum code that triggers ICE?

That's... going to be difficult. Veloren is an extremely large project and this issue seems to be intermittent. I'm still not entirely convinced that it's not just dodgy hardware.

Do you use any non-default configuration, such as parallel compilation?

Only what is listed here.