[ICE]: snapshot_vec: index out of bounds: the len is 0 but the index is 0
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C-bug
F-non_lifetime_binders
I-ICE
needs-triage
T-compiler
WG-trait-system-refactor
- Dominant language
- Rust
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Description
auto-reduced (treereduce-rust):
//@compile-flags: -Znext-solver=globally
#![feature(non_lifetime_binders)]
impl<'b, Itemm> IntoIterator for IterRef
where
for<'a, T, Item, IntoIter> &'a T:,
for<'a, T, Item, IntoIter> &'a T: IntoIterator<Item = Item, IntoIter = IntoIter>,
{
fn into_iter(self) -> Self::IntoIter {}
}
original:
#![feature(non_lifetime_binders)]
impl<'b, Itemm> IntoIterator for IterRef<IntoIter = Itemm>
where
for<'a, T, Item, IntoIter> &'a T:,
for<'a, T, Item, IntoIter> &'a T: IntoIterator<Item = Item, IntoIter = IntoIter>,
{
fn into_iter(self) -> Self::IntoIter {}
}
fn main() {}
Version information
rustc 1.96.0-nightly (d2218f5f5 2026-03-03)
binary: rustc
commit-hash: d2218f5f5ca3f502772ec4cb69fc2ee44e096512
commit-date: 2026-03-03
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.0
Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Znext-solver=globally
Program output
error[E0425]: cannot find type `IterRef` in this scope
--> /tmp/icemaker_global_tempdir.ScxgzaNVLgAH/rustc_testrunner_tmpdir_reporting.lDJFySxN2Gpp/mvce.rs:3:34
|
3 | impl<'b, Itemm> IntoIterator for IterRef
| ^^^^^^^ not found in this scope
warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
--> /tmp/icemaker_global_tempdir.ScxgzaNVLgAH/rustc_testrunner_tmpdir_reporting.lDJFySxN2Gpp/mvce.rs:1:12
|
1 | #![feature(non_lifetime_binders)]
| ^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
= note: `#[warn(incomplete_features)]` on by default
error[E0601]: `main` function not found in crate `mvce`
--> /tmp/icemaker_global_tempdir.ScxgzaNVLgAH/rustc_testrunner_tmpdir_reporting.lDJFySxN2Gpp/mvce.rs:9:2
|
9 | }
| ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.ScxgzaNVLgAH/rustc_testrunner_tmpdir_reporting.lDJFySxN2Gpp/mvce.rs`
thread 'rustc' (512111) panicked at /rust/deps/ena-0.14.4/src/snapshot_vec.rs:199:10:
index out of bounds: the len is 0 but the index is 0
stack backtrace:
0: 0x7f0ce9762aab - <<std[76599d2169901dc8]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[d5ffb84325ed5c2a]::fmt::Display>::fmt
1: 0x7f0ce9e228c8 - core[d5ffb84325ed5c2a]::fmt::write
2: 0x7f0ce9779ab6 - <std[76599d2169901dc8]::sys::stdio::unix::Stderr as std[76599d2169901dc8]::io::Write>::write_fmt
3: 0x7f0ce9738b88 - std[76599d2169901dc8]::panicking::default_hook::{closure#0}
4: 0x7f0ce9755f13 - std[76599d2169901dc8]::panicking::default_hook
5: 0x7f0ce87424cc - std[76599d2169901dc8]::panicking::update_hook::<alloc[f847baa7d3d2ac55]::boxed::Box<rustc_driver_impl[ffd722fd6c32666a]::install_ice_hook::{closure#1}>>::{closure#0}
6: 0x7f0ce97561f2 - std[76599d2169901dc8]::panicking::panic_with_hook
7: 0x7f0ce9738c48 - std[76599d2169901dc8]::panicking::panic_handler::{closure#0}
8: 0x7f0ce972f979 - std[76599d2169901dc8]::sys::backtrace::__rust_end_short_backtrace::<std[76599d2169901dc8]::panicking::panic_handler::{closure#0}, !>
9: 0x7f0ce973a6ad - __rustc[7dea9537d06e225e]::rust_begin_unwind
10: 0x7f0ce631975c - core[d5ffb84325ed5c2a]::panicking::panic_fmt
11: 0x7f0ce66fa982 - core[d5ffb84325ed5c2a]::panicking::panic_bounds_check
12: 0x7f0cea84cc10 - <rustc_trait_selection[502c21a12406236f]::solve::delegate::SolverDelegate as rustc_next_trait_solver[beb9dc5464000fde]::delegate::SolverDelegate>::compute_goal_fast_path
13: 0x7f0cea84e71c - <rustc_trait_selection[502c21a12406236f]::solve::fulfill::FulfillmentCtxt<rustc_infer[a106829e2b559cfc]::traits::engine::ScrubbedTraitError> as rustc_infer[a106829e2b559cfc]::traits::engine::TraitEngine<rustc_infer[a106829e2b559cfc]::traits::engine::ScrubbedTraitError>>::evaluate_obligations_error_on_ambiguity
14: 0x7f0ce9edc625 - rustc_trait_selection[502c21a12406236f]::traits::type_known_to_meet_bound_modulo_regions
15: 0x7f0ce9edb292 - rustc_ty_utils[23782f25fc8ac972]::common_traits::is_copy_raw
16: 0x7f0ce9edae87 - rustc_query_impl[89f9236b2ac04da0]::query_impl::is_copy_raw::invoke_provider_fn::__rust_begin_short_backtrace
17: 0x7f0cea3bcce7 - rustc_query_impl[89f9236b2ac04da0]::execution::try_execute_query::<rustc_middle[7c9cbe436035c5a4]::query::caches::DefaultCache<rustc_middle[7c9cbe436035c5a4]::ty::PseudoCanonicalInput<rustc_middle[7c9cbe436035c5a4]::ty::Ty>, rustc_middle[7c9cbe436035c5a4]::query::erase::ErasedData<[u8; 1usize]>>, false>
18: 0x7f0cea3bc8c9 - rustc_query_impl[89f9236b2ac04da0]::query_impl::is_copy_raw::execute_query_non_incr::__rust_end_short_backtrace
19: 0x7f0cea3be4f0 - rustc_ty_utils[23782f25fc8ac972]::needs_drop::needs_drop_raw
20: 0x7f0cea3bde67 - rustc_query_impl[89f9236b2ac04da0]::query_impl::needs_drop_raw::invoke_provider_fn::__rust_begin_short_backtrace
21: 0x7f0cea3bcc59 - rustc_query_impl[89f9236b2ac04da0]::execution::try_execute_query::<rustc_middle[7c9cbe436035c5a4]::query::caches::DefaultCache<rustc_middle[7c9cbe436035c5a4]::ty::PseudoCanonicalInput<rustc_middle[7c9cbe436035c5a4]::ty::Ty>, rustc_middle[7c9cbe436035c5a4]::query::erase::ErasedData<[u8; 1usize]>>, false>
22: 0x7f0cea3bc839 - rustc_query_impl[89f9236b2ac04da0]::query_impl::needs_drop_raw::execute_query_non_incr::__rust_end_short_backtrace
23: 0x7f0ce6715c96 - <rustc_mir_transform[c7b522523fe3a5eb]::elaborate_drops::ElaborateDrops as rustc_mir_transform[c7b522523fe3a5eb]::pass_manager::MirPass>::run_pass
24: 0x7f0ce9e0ce6a - rustc_mir_transform[c7b522523fe3a5eb]::run_analysis_to_runtime_passes
25: 0x7f0ceac1c5c4 - rustc_mir_transform[c7b522523fe3a5eb]::mir_drops_elaborated_and_const_checked
26: 0x7f0ceac1c021 - rustc_query_impl[89f9236b2ac04da0]::query_impl::mir_drops_elaborated_and_const_checked::invoke_provider_fn::__rust_begin_short_backtrace
27: 0x7f0ce9f6d18a - rustc_query_impl[89f9236b2ac04da0]::execution::try_execute_query::<rustc_data_structures[79f5f180de225010]::vec_cache::VecCache<rustc_span[8a71b77c74bc13cb]::def_id::LocalDefId, rustc_middle[7c9cbe436035c5a4]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[7c9cbe436035c5a4]::dep_graph::graph::DepNodeIndex>, false>
28: 0x7f0ce9f6c8c3 - rustc_query_impl[89f9236b2ac04da0]::query_impl::mir_drops_elaborated_and_const_checked::execute_query_non_incr::__rust_end_short_backtrace
29: 0x7f0ce9f6ac48 - <rustc_middle[7c9cbe436035c5a4]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[400bc27e64bfd912]::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}
30: 0x7f0ce9f6a02f - rustc_interface[400bc27e64bfd912]::passes::analysis
31: 0x7f0ceb03175c - rustc_query_impl[89f9236b2ac04da0]::execution::try_execute_query::<rustc_middle[7c9cbe436035c5a4]::query::caches::SingleCache<rustc_middle[7c9cbe436035c5a4]::query::erase::ErasedData<[u8; 0usize]>>, false>
32: 0x7f0ceb0314bb - rustc_query_impl[89f9236b2ac04da0]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
33: 0x7f0ceafeda2d - rustc_interface[400bc27e64bfd912]::interface::run_compiler::<(), rustc_driver_impl[ffd722fd6c32666a]::run_compiler::{closure#0}>::{closure#1}
34: 0x7f0ceafd20be - std[76599d2169901dc8]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[400bc27e64bfd912]::util::run_in_thread_with_globals<rustc_interface[400bc27e64bfd912]::util::run_in_thread_pool_with_globals<rustc_interface[400bc27e64bfd912]::interface::run_compiler<(), rustc_driver_impl[ffd722fd6c32666a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
35: 0x7f0ceafd2720 - <std[76599d2169901dc8]::thread::lifecycle::spawn_unchecked<rustc_interface[400bc27e64bfd912]::util::run_in_thread_with_globals<rustc_interface[400bc27e64bfd912]::util::run_in_thread_pool_with_globals<rustc_interface[400bc27e64bfd912]::interface::run_compiler<(), rustc_driver_impl[ffd722fd6c32666a]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[d5ffb84325ed5c2a]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
36: 0x7f0ceafd35ac - <std[76599d2169901dc8]::sys::thread::unix::Thread>::new::thread_start
37: 0x7f0ce4aa598b - <unknown>
38: 0x7f0ce4b29a0c - <unknown>
39: 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: please make sure that you have updated to the latest nightly
note: rustc 1.96.0-nightly (d2218f5f5 2026-03-03) running on x86_64-unknown-linux-gnu
note: compiler flags: -Z next-solver=globally -Z dump-mir-dir=dir
query stack during panic:
#0 [is_copy_raw] computing whether `_` is `Copy`
#1 [needs_drop_raw] computing whether `_` needs drop
#2 [mir_drops_elaborated_and_const_checked] elaborating drops for `<impl at /tmp/icemaker_global_tempdir.ScxgzaNVLgAH/rustc_testrunner_tmpdir_reporting.lDJFySxN2Gpp/mvce.rs:3:1: 6:86>::into_iter`
#3 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 2 previous errors; 1 warning emitted
Some errors have detailed explanations: E0425, E0601.
For more information about an error, try `rustc --explain E0425`.
@rustbot label +F-non_lifetime_binders +WG-trait-system-refactor
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by compiling the reduced Rust program with -Znext-solver=globally and compare the query stack around rustc_trait_selection::solve::delegate::compute_goal_fast_path. Trace the snapshot_vec panic through trait solving and drop elaboration; done means the reproducer no longer causes an internal compiler error while reporting its ordinary diagnostics.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 38/100