[ICE][ICE->Error] Explicit naming of parameter leads to ICE

[miki4625]

Code playground

struct LifetimeMarker<'a>(std::marker::PhantomData<&'a ()>);

fn example<T: Default>() -> impl FnMut(&mut LifetimeMarker) {
    // This line invokes ICE
    |marker: &mut LifetimeMarker| {
    //This works
    //|_| {
        || {
            let obj = T::default();
            needs_static_lifetime(obj);
        };
    }
}

fn needs_static_lifetime<T: 'static>(obj: T) {}

Code should result in:

error[E0310]: the parameter type `T` may not live long enough

But result is:

error: internal compiler error: compiler/rustc_borrowck/src/universal_regions.rs:928:36: cannot convert `ReLateParam(DefId(0:10 ~ playground[961a]::example::{closure#0}), LateNamed(DefId(0:14 ~ playground[961a]::example::'_), '_))` to a region vid

Meta (local)

rustc --version --verbose:
Same behavior on playground (both stable and nightly)

rustc 1.90.0-nightly (8f08b3a32 2025-07-18)
binary: rustc
commit-hash: 8f08b3a32478b8d0507732800ecb548a76e0fd0c
commit-date: 2025-07-18
host: x86_64-pc-windows-msvc
release: 1.90.0-nightly
LLVM version: 20.1.8

Error output

thread 'rustc' panicked at compiler/rustc_borrowck/src/universal_regions.rs:928:36:
Box<dyn Any>
stack backtrace:
   0:     0x7174a1546543 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h46a716bba2450163
   1:     0x7174a1c05947 - core::fmt::write::h275e5980d7008551
   2:     0x7174a2cc16d1 - std::io::Write::write_fmt::h561a66a0340b6995
   3:     0x7174a15463a2 - std::sys::backtrace::BacktraceLock::print::hafb9d5969adc39a0
   4:     0x7174a1549f9a - std::panicking::default_hook::{{closure}}::hae2e97a5c4b2b777
   5:     0x7174a1549b1f - std::panicking::default_hook::h3db1b505cfc4eb79
   6:     0x7174a0575b93 - std[61bb86a81f0491]::panicking::update_hook::<alloc[7c55b5a5cf9e3c5f]::boxed::Box<rustc_driver_impl[b7d73271a09ede7d]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7174a154a813 - std::panicking::rust_panic_with_hook::h409da73ddef13937
   8:     0x7174a05b1f41 - std[61bb86a81f0491]::panicking::begin_panic::<rustc_errors[38d461c0e4a8a2b3]::ExplicitBug>::{closure#0}
   9:     0x7174a05a5e16 - std[61bb86a81f0491]::sys::backtrace::__rust_end_short_backtrace::<std[61bb86a81f0491]::panicking::begin_panic<rustc_errors[38d461c0e4a8a2b3]::ExplicitBug>::{closure#0}, !>
  10:     0x7174a05a5bf3 - std[61bb86a81f0491]::panicking::begin_panic::<rustc_errors[38d461c0e4a8a2b3]::ExplicitBug>
  11:     0x7174a05bc5c1 - <rustc_errors[38d461c0e4a8a2b3]::diagnostic::BugAbort as rustc_errors[38d461c0e4a8a2b3]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7174a0c2adaa - rustc_middle[1134768a56a896b4]::util::bug::opt_span_bug_fmt::<rustc_span[1f7aec696a0836ce]::span_encoding::Span>::{closure#0}
  13:     0x7174a0c0331a - rustc_middle[1134768a56a896b4]::ty::context::tls::with_opt::<rustc_middle[1134768a56a896b4]::util::bug::opt_span_bug_fmt<rustc_span[1f7aec696a0836ce]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7174a0c0318b - rustc_middle[1134768a56a896b4]::ty::context::tls::with_context_opt::<rustc_middle[1134768a56a896b4]::ty::context::tls::with_opt<rustc_middle[1134768a56a896b4]::util::bug::opt_span_bug_fmt<rustc_span[1f7aec696a0836ce]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x71749de85ff0 - rustc_middle[1134768a56a896b4]::util::bug::bug_fmt
  16:     0x7174a22b316a - <rustc_infer[90ea0da8f705ff7b]::infer::outlives::obligations::TypeOutlives<&mut rustc_borrowck[177ef636edd0ce33]::type_check::constraint_conversion::ConstraintConversion>>::components_must_outlive
  17:     0x7174a2c2c477 - <rustc_borrowck[177ef636edd0ce33]::type_check::constraint_conversion::ConstraintConversion>::convert
  18:     0x7174a2c2ae2f - <rustc_borrowck[177ef636edd0ce33]::type_check::TypeChecker>::prove_closure_bounds
  19:     0x71749eed40d0 - <rustc_borrowck[177ef636edd0ce33]::type_check::TypeChecker as rustc_middle[1134768a56a896b4]::mir::visit::Visitor>::visit_rvalue
  20:     0x7174a2f9d233 - <rustc_borrowck[177ef636edd0ce33]::type_check::TypeChecker as rustc_middle[1134768a56a896b4]::mir::visit::Visitor>::visit_body
  21:     0x7174a2c3fd14 - rustc_borrowck[177ef636edd0ce33]::do_mir_borrowck
  22:     0x7174a2c2cbf6 - <rustc_borrowck[177ef636edd0ce33]::root_cx::BorrowCheckRootCtxt>::get_or_insert_nested
  23:     0x7174a1fca8ef - rustc_borrowck[177ef636edd0ce33]::mir_borrowck
  24:     0x7174a1fca59f - rustc_query_impl[6f0ca6887c150a69]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[6f0ca6887c150a69]::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 8usize]>>
  25:     0x7174a1fc9366 - rustc_query_system[48caa8a8a4cfcb68]::query::plumbing::try_execute_query::<rustc_query_impl[6f0ca6887c150a69]::DynamicConfig<rustc_data_structures[e24569e090b577b3]::vec_cache::VecCache<rustc_span[1f7aec696a0836ce]::def_id::LocalDefId, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[48caa8a8a4cfcb68]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[6f0ca6887c150a69]::plumbing::QueryCtxt, false>
  26:     0x7174a1fc8d12 - rustc_query_impl[6f0ca6887c150a69]::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
  27:     0x7174a2e547eb - rustc_hir_analysis[5a87eb6962d34b42]::collect::type_of::opaque::find_opaque_ty_constraints_for_rpit
  28:     0x7174a2e54574 - rustc_hir_analysis[5a87eb6962d34b42]::collect::type_of::type_of_opaque
  29:     0x7174a2e54437 - rustc_query_impl[6f0ca6887c150a69]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[6f0ca6887c150a69]::query_impl::type_of_opaque::dynamic_query::{closure#2}::{closure#0}, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 8usize]>>
  30:     0x7174a20800bf - rustc_query_system[48caa8a8a4cfcb68]::query::plumbing::try_execute_query::<rustc_query_impl[6f0ca6887c150a69]::DynamicConfig<rustc_query_system[48caa8a8a4cfcb68]::query::caches::DefIdCache<rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[6f0ca6887c150a69]::plumbing::QueryCtxt, false>
  31:     0x7174a2ed7dfc - rustc_query_impl[6f0ca6887c150a69]::query_impl::type_of_opaque::get_query_non_incr::__rust_end_short_backtrace
  32:     0x7174a2086b48 - rustc_hir_analysis[5a87eb6962d34b42]::collect::type_of::type_of
  33:     0x7174a2081476 - rustc_query_impl[6f0ca6887c150a69]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[6f0ca6887c150a69]::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 8usize]>>
  34:     0x7174a20800bf - rustc_query_system[48caa8a8a4cfcb68]::query::plumbing::try_execute_query::<rustc_query_impl[6f0ca6887c150a69]::DynamicConfig<rustc_query_system[48caa8a8a4cfcb68]::query::caches::DefIdCache<rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[6f0ca6887c150a69]::plumbing::QueryCtxt, false>
  35:     0x7174a207fc6b - rustc_query_impl[6f0ca6887c150a69]::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
  36:     0x7174a2e54d19 - rustc_hir_analysis[5a87eb6962d34b42]::check::check::check_opaque
  37:     0x7174a21ce682 - rustc_hir_analysis[5a87eb6962d34b42]::check::check::check_item_type
  38:     0x7174a24199e9 - rustc_hir_analysis[5a87eb6962d34b42]::check::wfcheck::check_well_formed
  39:     0x7174a241704b - rustc_query_impl[6f0ca6887c150a69]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[6f0ca6887c150a69]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 1usize]>>
  40:     0x7174a24168f1 - rustc_query_system[48caa8a8a4cfcb68]::query::plumbing::try_execute_query::<rustc_query_impl[6f0ca6887c150a69]::DynamicConfig<rustc_data_structures[e24569e090b577b3]::vec_cache::VecCache<rustc_span[1f7aec696a0836ce]::def_id::LocalDefId, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[48caa8a8a4cfcb68]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[6f0ca6887c150a69]::plumbing::QueryCtxt, false>
  41:     0x7174a24163e6 - rustc_query_impl[6f0ca6887c150a69]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  42:     0x7174a2413d23 - rustc_hir_analysis[5a87eb6962d34b42]::check::wfcheck::check_mod_type_wf
  43:     0x7174a241375f - rustc_query_impl[6f0ca6887c150a69]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[6f0ca6887c150a69]::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 1usize]>>
  44:     0x7174a2beda84 - rustc_query_system[48caa8a8a4cfcb68]::query::plumbing::try_execute_query::<rustc_query_impl[6f0ca6887c150a69]::DynamicConfig<rustc_query_system[48caa8a8a4cfcb68]::query::caches::DefaultCache<rustc_span[1f7aec696a0836ce]::def_id::LocalModDefId, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[6f0ca6887c150a69]::plumbing::QueryCtxt, false>
  45:     0x7174a2bed811 - rustc_query_impl[6f0ca6887c150a69]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
  46:     0x7174a1fc6f72 - rustc_hir_analysis[5a87eb6962d34b42]::check_crate
  47:     0x7174a25e0237 - rustc_interface[a43b584b4c4124b4]::passes::run_required_analyses
  48:     0x7174a2aedb5e - rustc_interface[a43b584b4c4124b4]::passes::analysis
  49:     0x7174a2aedb35 - rustc_query_impl[6f0ca6887c150a69]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[6f0ca6887c150a69]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 0usize]>>
  50:     0x7174a2aefc3a - rustc_query_system[48caa8a8a4cfcb68]::query::plumbing::try_execute_query::<rustc_query_impl[6f0ca6887c150a69]::DynamicConfig<rustc_query_system[48caa8a8a4cfcb68]::query::caches::SingleCache<rustc_middle[1134768a56a896b4]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[6f0ca6887c150a69]::plumbing::QueryCtxt, false>
  51:     0x7174a2aef90f - rustc_query_impl[6f0ca6887c150a69]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  52:     0x7174a2daa0c7 - rustc_interface[a43b584b4c4124b4]::passes::create_and_enter_global_ctxt::<core[105cb658ab12d76f]::option::Option<rustc_interface[a43b584b4c4124b4]::queries::Linker>, rustc_driver_impl[b7d73271a09ede7d]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  53:     0x7174a2cfe966 - rustc_interface[a43b584b4c4124b4]::interface::run_compiler::<(), rustc_driver_impl[b7d73271a09ede7d]::run_compiler::{closure#0}>::{closure#1}
  54:     0x7174a2cb523e - std[61bb86a81f0491]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[a43b584b4c4124b4]::util::run_in_thread_with_globals<rustc_interface[a43b584b4c4124b4]::util::run_in_thread_pool_with_globals<rustc_interface[a43b584b4c4124b4]::interface::run_compiler<(), rustc_driver_impl[b7d73271a09ede7d]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  55:     0x7174a2cb56b4 - <<std[61bb86a81f0491]::thread::Builder>::spawn_unchecked_<rustc_interface[a43b584b4c4124b4]::util::run_in_thread_with_globals<rustc_interface[a43b584b4c4124b4]::util::run_in_thread_pool_with_globals<rustc_interface[a43b584b4c4124b4]::interface::run_compiler<(), rustc_driver_impl[b7d73271a09ede7d]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[105cb658ab12d76f]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  56:     0x7174a2cb6aab - std::sys::pal::unix::thread::Thread::new::thread_start::h1822d22fde68314f
  57:     0x71749ca8aaa4 - <unknown>
  58:     0x71749cb17a34 - clone
  59:                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: rustc 1.88.0 (6b00bc388 2025-06-23) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `example`
#1 [type_of_opaque] computing type of opaque `example::{opaque#0}`
... and 4 other queries... use `env RUST_BACKTRACE=1` to see the full query stack
warning: `playground` (lib) generated 1 warning
error: could not compile `playground` (lib); 1 warning emitted

Caused by:
  process didn't exit successfully: `/playground/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/bin/rustc --crate-name playground --edition=2024 src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values())' -C metadata=88d75c911cfddd04 -C extra-filename=-013ef0dffb93ce85 --out-dir /playground/target/debug/deps -L dependency=/playground/target/debug/deps [...] (deleted bcs 65536 character limit)` (exit status: 101)

Backtrace

thread 'rustc' panicked at compiler/rustc_borrowck/src/universal_regions.rs:928:36:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   3: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   4: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   5: rustc_middle::util::bug::bug_fmt
   6: <rustc_infer::infer::outlives::obligations::TypeOutlives<&mut rustc_borrowck::type_check::constraint_conversion::ConstraintConversion>>::components_must_outlive
   7: <rustc_borrowck::type_check::constraint_conversion::ConstraintConversion>::convert
   8: <rustc_borrowck::type_check::TypeChecker>::prove_closure_bounds
   9: <rustc_borrowck::type_check::TypeChecker as rustc_middle::mir::visit::Visitor>::visit_rvalue
  10: <rustc_borrowck::type_check::TypeChecker as rustc_middle::mir::visit::Visitor>::visit_body
  11: rustc_borrowck::do_mir_borrowck
  12: <rustc_borrowck::root_cx::BorrowCheckRootCtxt>::get_or_insert_nested
  13: rustc_borrowck::mir_borrowck
      [... omitted 1 frame ...]
  14: rustc_hir_analysis::collect::type_of::opaque::find_opaque_ty_constraints_for_rpit
  15: rustc_hir_analysis::collect::type_of::type_of_opaque
      [... omitted 1 frame ...]
  16: rustc_hir_analysis::collect::type_of::type_of
      [... omitted 1 frame ...]
  17: rustc_hir_analysis::check::check::check_opaque
  18: rustc_hir_analysis::check::check::check_item_type
  19: rustc_hir_analysis::check::wfcheck::check_well_formed
      [... omitted 1 frame ...]
  20: rustc_hir_analysis::check::wfcheck::check_mod_type_wf
      [... omitted 1 frame ...]
  21: rustc_hir_analysis::check_crate
  22: rustc_interface::passes::run_required_analyses
  23: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
  24: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  25: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 1.88.0 (6b00bc388 2025-06-23) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `example`
#1 [type_of_opaque] computing type of opaque `example::{opaque#0}`
#2 [type_of] computing type of `example::{opaque#0}`
#3 [check_well_formed] checking that `example::{opaque#0}` is well-formed
#4 [check_mod_type_wf] checking that types are well-formed in top-level module
#5 [analysis] running analysis passes on this crate
end of query stack
warning: `playground` (lib) generated 1 warning
error: could not compile `playground` (lib); 1 warning emitted

[cyrgani]

a bit shorter:

fn example<T>(x: T) -> impl FnMut(&mut ()) {
    |_: &mut ()| {
        || needs_static_lifetime(x);
    }
}

fn needs_static_lifetime<T: 'static>(obj: T) {}

[lqd]

This is actually a 1.85 to 1.86 regression, from nightly-2025-01-15.

[Subway2023]

Hello, I would like to ask how an ICE (Internal Compiler Error) is identified. Sometimes it's just a normal compilation error, such as a syntax or semantic issue.

In other compilers like Solidity, normal errors usually include the keyword error in the output, while an ICE often results in vague messages without the error keyword.

[lqd]

while an ICE often results in vague messages without the error keyword.

ICE is internal compiler error.

From the OP:

error: internal compiler error: compiler/rustc_borrowck/src/universal_regions.rs:928:36