Repository navigation
ICE inferred lifetime in signature #148949
Description
snippet:
#![feature(min_generic_const_args)]
#![feature(inherent_associated_types)]
struct Foo<'a> {
x: &'a (),
}
impl<'a> Foo<'a> {
fn foo(_: [u8; Foo::X]) {}
}
fn main() {}Version information
rustc 1.93.0-nightly (c91009892 2025-11-14)
binary: rustc
commit-hash: c91009892b4cd1776d4c9d85793166612195a03d
commit-date: 2025-11-14
host: x86_64-unknown-linux-gnu
release: 1.93.0-nightly
LLVM version: 21.1.5
Command:
/home/matthias/.rustup/toolchains/master/bin/rustc
Program output
warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
--> /tmp/icemaker_global_tempdir.C4RdvOM2TnqW/rustc_testrunner_tmpdir_reporting.FKNzgy6tMw5C/mvce.rs:1:12
|
1 | #![feature(min_generic_const_args)]
| ^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #132980 <https://github.com/rust-lang/rust/issues/132980> for more information
= note: `#[warn(incomplete_features)]` on by default
warning: the feature `inherent_associated_types` is incomplete and may not be safe to use and/or cause compiler crashes
--> /tmp/icemaker_global_tempdir.C4RdvOM2TnqW/rustc_testrunner_tmpdir_reporting.FKNzgy6tMw5C/mvce.rs:2:12
|
2 | #![feature(inherent_associated_types)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #8995 <https://github.com/rust-lang/rust/issues/8995> for more information
warning: struct `Foo` is never constructed
--> /tmp/icemaker_global_tempdir.C4RdvOM2TnqW/rustc_testrunner_tmpdir_reporting.FKNzgy6tMw5C/mvce.rs:3:8
|
3 | struct Foo<'a> {
| ^^^
|
= note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default
warning: associated function `foo` is never used
--> /tmp/icemaker_global_tempdir.C4RdvOM2TnqW/rustc_testrunner_tmpdir_reporting.FKNzgy6tMw5C/mvce.rs:8:8
|
7 | impl<'a> Foo<'a> {
| ---------------- associated function in this implementation
8 | fn foo(_: [u8; Foo::X]) {}
| ^^^
warning: 4 warnings emitted
note: no errors encountered even though delayed bugs were created
note: those delayed bugs will now be shown as internal compiler errors
error: internal compiler error: unelided lifetime in signature
--> /tmp/icemaker_global_tempdir.C4RdvOM2TnqW/rustc_testrunner_tmpdir_reporting.FKNzgy6tMw5C/mvce.rs:8:20
|
8 | fn foo(_: [u8; Foo::X]) {}
| ^^^
|
note: delayed at compiler/rustc_hir_analysis/src/collect.rs:334:13
0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
3: <rustc_errors::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, &str>
4: <rustc_hir_analysis::collect::ItemCtxt as rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::re_infer
5: <dyn rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::lower_resolved_ty_path
6: <dyn rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::lower_ty::{closure#0}
7: <dyn rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::lower_const_arg
8: <dyn rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::lower_ty::{closure#0}
9: <dyn rustc_hir_analysis::hir_ty_lowering::HirTyLowerer>::lower_fn_ty
10: rustc_hir_analysis::collect::lower_fn_sig_recovering_infer_ret_ty
11: rustc_hir_analysis::collect::fn_sig
12: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::fn_sig::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 24]>>
13: <rustc_query_impl::query_impl::fn_sig::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once
14: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 24]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
15: rustc_query_impl::query_impl::fn_sig::get_query_non_incr::__rust_end_short_backtrace
16: <rustc_hir_analysis::variance::constraints::ConstraintContext>::build_constraints_for_item
17: rustc_hir_analysis::variance::crate_variances
18: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::crate_variances::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
19: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
20: rustc_query_impl::query_impl::crate_variances::get_query_non_incr::__rust_end_short_backtrace
21: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::variances_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 16]>>.warm
22: <rustc_query_impl::query_impl::variances_of::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::DefId)>>::call_once
23: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 16]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
24: rustc_query_impl::query_impl::variances_of::get_query_non_incr::__rust_end_short_backtrace
25: rustc_hir_analysis::check::wfcheck::check_variances_for_type_defn
26: rustc_hir_analysis::check::check::check_item_type
27: rustc_hir_analysis::check::wfcheck::check_well_formed
28: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
29: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 1]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
30: rustc_query_impl::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
31: rustc_hir_analysis::check::wfcheck::check_type_wf
32: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
33: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
34: rustc_query_impl::query_impl::check_type_wf::get_query_non_incr::__rust_end_short_backtrace
35: rustc_hir_analysis::check_crate
36: rustc_interface::passes::analysis
37: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
38: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
39: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
40: <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} as core::ops::function::FnOnce<(&rustc_session::session::Session, rustc_middle::ty::context::CurrentGcx, alloc::sync::Arc<rustc_data_structures::jobserver::Proxy>, &std::sync::once_lock::OnceLock<rustc_middle::ty::context::GlobalCtxt>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_middle::arena::Arena>, &rustc_data_structures::sync::worker_local::WorkerLocal<rustc_hir::Arena>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
41: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
42: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
43: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
44: std::sys::thread::unix::Thread::new::thread_start
45: <unknown>
46: <unknown>
--> /tmp/icemaker_global_tempdir.C4RdvOM2TnqW/rustc_testrunner_tmpdir_reporting.FKNzgy6tMw5C/mvce.rs:8:20
|
8 | fn foo(_: [u8; Foo::X]) {}
| ^^^
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 1.93.0-nightly (c91009892 2025-11-14) running on x86_64-unknown-linux-gnu
query stack during panic:
end of query stack
@rustbot label +F-min_generic_const_args +F-inherent_associated_types
Activity
matthiaskrgr commentedon Nov 14, 2025
since #148771
charmitro commentedon Nov 24, 2025
I believe this is happening because PR #148771's early bailout doesn't account for error-containing self types (like Foo without a lifetime), causing the delayed bug from lifetime inference failure to surface as an ICE.
reddevilmidzy commentedon Dec 9, 2025
@rustbot claim
reddevilmidzy commentedon Dec 9, 2025
This code also causes
the sameICE, but it occurs before the PR mentioned.Program output
it's since: #139558
EDIT: Oh, it's not exactly the same. created a new issue #149809
inferred lifetime in signature#157777 as a duplicate of this issuereddevilmidzy commentedon Jun 12, 2026
new program output
[-]ICE `unelided lifetime in signature`[/-][+]ICE `inferred lifetime in signature`[/+]