[ICE]: assertion failed: !parts.is_empty()

auto-reduced (treereduce-rust):

trait Reference: 'static {
    type Ref<'a>;
}

struct SliceRef<'a, T: ?Sized + 'static> {
    inner: &'static T,
}

impl<SR: 'static> Reference for Vec<SR> {
    type Ref<'a> = SliceRef<'a, [SR]>;

    fn get_ref(&self) -> Self::Ref<'_> {
        SliceRef { inner: self }
    }
}

original:

trait Reference: 'static {
    type Ref<'a>;
    fn get_ref(&self) -> Self::Ref<'_>;
}

struct SliceRef<'a, T: ?Sized + 'static> {
    inner: &'static T,
}

impl<SR: 'static> Reference for Vec<SR> {
    type Ref<'a> = SliceRef<'a, [SR]>;

    fn get_ref(&self) -> Self::Ref<'_> {
        SliceRef { inner: self }
    }
}

fn main() {}

Version information

rustc 1.101.0-nightly (16d1ffac1 2026-10-26)
binary: rustc
commit-hash: 16d1ffac17ad8b739e32483ac2e65fe7e1804977
commit-date: 2026-10-26
host: x86_64-unknown-linux-gnu
release: 1.101.0-nightly
LLVM version: 23.1.4

Possibly related line of code:

rust/compiler/rustc_errors/src/diagnostic.rs

Lines 789 to 801 in 16d1ffa

    
           let parts = suggestion 
        
               .into_iter() 
        
               .map(|(span, snippet)| SubstitutionPart { snippet, span }) 
        
               .collect::<Vec<_>>(); 
        
           assert!(!parts.is_empty()); 
        
           debug_assert_eq!( 
        
               parts.iter().find(|part| part.span.is_empty() && part.snippet.is_empty()), 
        
               None, 
        
               "Span must not be empty and have no suggestion", 
        
           ); 
        
           debug_assert_eq!(

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

`--edition` is unspecified, defaulting to `2015` while the latest is `2024`; it must be one of: <2015|2018|2021|2024|future>

error[E0407]: method `get_ref` is not a member of trait `Reference`
  --> /tmp/icemaker_global_tempdir.O89QqsIytXhi/rustc_testrunner_tmpdir_reporting.ax0HfJtwB3vR/mvce.rs:12:5
   |
12 | /     fn get_ref(&self) -> Self::Ref<'_> {
13 | |         SliceRef { inner: self }
14 | |     }
   | |_____^ not a member of trait `Reference`

error[E0601]: `main` function not found in crate `mvce`
  --> /tmp/icemaker_global_tempdir.O89QqsIytXhi/rustc_testrunner_tmpdir_reporting.ax0HfJtwB3vR/mvce.rs:15:2
   |
15 | }
   |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.O89QqsIytXhi/rustc_testrunner_tmpdir_reporting.ax0HfJtwB3vR/mvce.rs`

error[E0392]: lifetime parameter `'a` is never used
 --> /tmp/icemaker_global_tempdir.O89QqsIytXhi/rustc_testrunner_tmpdir_reporting.ax0HfJtwB3vR/mvce.rs:5:17
  |
5 | struct SliceRef<'a, T: ?Sized + 'static> {
  |                 ^^ unused lifetime parameter
  |
  = help: consider removing `'a`, referring to it in a field, or using a marker such as `PhantomData`


thread 'rustc' (146452) panicked at /rustc-dev/16d1ffac17ad8b739e32483ac2e65fe7e1804977/compiler/rustc_errors/src/diagnostic.rs:795:9:
assertion failed: !parts.is_empty()
stack backtrace:
   0:     0x7f1aafc1bc66 - <<std[330264cedda0dde7]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[c3c47457b203f732]::fmt::Display>::fmt
   1:     0x7f1ab020bf69 - core[c3c47457b203f732]::fmt::write
   2:     0x7f1aafc31d4c - <std[330264cedda0dde7]::sys::stdio::unix::Stderr as core[c3c47457b203f732]::io::write::Write>::write_fmt
   3:     0x7f1aafbecdaa - std[330264cedda0dde7]::panicking::default_hook::{closure#0}
   4:     0x7f1aafc0f5b3 - std[330264cedda0dde7]::panicking::default_hook
   5:     0x7f1aae9d7dd9 - std[330264cedda0dde7]::panicking::update_hook::<alloc[af84d0cd032748a3]::boxed::Box<rustc_driver_impl[854d066a38aab513]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f1aafc0fa52 - std[330264cedda0dde7]::panicking::panic_with_hook
   7:     0x7f1aafbece94 - std[330264cedda0dde7]::panicking::panic_handler::{closure#0}
   8:     0x7f1aafbe3509 - std[330264cedda0dde7]::sys::backtrace::__rust_end_short_backtrace::<std[330264cedda0dde7]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f1aafbeebbd - __rustc[a38ff76b5c4f9c0]::rust_begin_unwind
  10:     0x7f1aac4eb5dc - core[c3c47457b203f732]::panicking::panic_fmt
  11:     0x7f1aacf512d2 - core[c3c47457b203f732]::panicking::panic
  12:     0x7f1aae58b6d1 - <rustc_errors[9ab7b5d3ce2cdd56]::diagnostic::Diag>::multipart_suggestion_with_style::<&str>
  13:     0x7f1aae677631 - <rustc_borrowck[e1fd4d0d9c3617a1]::MirBorrowckCtxt>::report_general_error
  14:     0x7f1aae66fdd2 - <rustc_borrowck[e1fd4d0d9c3617a1]::MirBorrowckCtxt>::report_region_error
  15:     0x7f1aae67885c - <rustc_borrowck[e1fd4d0d9c3617a1]::MirBorrowckCtxt>::report_region_errors
  16:     0x7f1ab15d31d5 - rustc_borrowck[e1fd4d0d9c3617a1]::borrowck_check_region_constraints
  17:     0x7f1ab15a7e5b - <rustc_borrowck[e1fd4d0d9c3617a1]::root_cx::BorrowCheckRootCtxt>::do_mir_borrowck
  18:     0x7f1ab05741d5 - rustc_borrowck[e1fd4d0d9c3617a1]::mir_borrowck
  19:     0x7f1ab0573ef9 - rustc_query_impl[41e30d1e9fe6e894]::query_vtables::mir_borrowck::invoke_provider_fn::__rust_begin_short_backtrace
  20:     0x7f1ab057290e - rustc_query_impl[41e30d1e9fe6e894]::execution::try_execute_query::<rustc_data_structures[f4d1bc18c8885aa4]::vec_cache::VecCache<rustc_span[fd67e99fbaac7070]::def_id::LocalDefId, rustc_middle[3fdf4e28e066cfea]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[3fdf4e28e066cfea]::dep_graph::graph::DepNodeIndex>, false>
  21:     0x7f1ab0572475 - rustc_query_impl[41e30d1e9fe6e894]::query_vtables::mir_borrowck::execute_query_non_incr::__rust_end_short_backtrace
  22:     0x7f1ab05704e9 - <rustc_middle[3fdf4e28e066cfea]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[330c1f918d396dc7]::passes::run_required_analyses::{closure#2}::{closure#0}>::{closure#0}
  23:     0x7f1ab056f7b1 - rustc_interface[330c1f918d396dc7]::passes::analysis
  24:     0x7f1ab13aff87 - rustc_query_impl[41e30d1e9fe6e894]::execution::try_execute_query::<rustc_middle[3fdf4e28e066cfea]::query::caches::SingleCache<rustc_middle[3fdf4e28e066cfea]::query::erase::ErasedData<[u8; 0usize]>>, false>
  25:     0x7f1ab13afd6b - rustc_query_impl[41e30d1e9fe6e894]::query_vtables::analysis::execute_query_non_incr::__rust_end_short_backtrace
  26:     0x7f1ab14e3e05 - rustc_interface[330c1f918d396dc7]::interface::run_compiler::<(), rustc_driver_impl[854d066a38aab513]::compiler_entrypoint::{closure#0}>::{closure#2}
  27:     0x7f1ab15637c1 - std[330264cedda0dde7]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[330c1f918d396dc7]::util::run_in_thread_with_globals<rustc_interface[330c1f918d396dc7]::util::run_in_thread_pool_with_globals<rustc_interface[330c1f918d396dc7]::interface::run_compiler<(), rustc_driver_impl[854d066a38aab513]::compiler_entrypoint::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  28:     0x7f1ab156356d - <std[330264cedda0dde7]::thread::lifecycle::spawn_unchecked<rustc_interface[330c1f918d396dc7]::util::run_in_thread_with_globals<rustc_interface[330c1f918d396dc7]::util::run_in_thread_pool_with_globals<rustc_interface[330c1f918d396dc7]::interface::run_compiler<(), rustc_driver_impl[854d066a38aab513]::compiler_entrypoint::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[c3c47457b203f732]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  29:     0x7f1ab142e82d - <std[330264cedda0dde7]::sys::thread::unix::Thread>::new::thread_start
  30:     0x7f1aaa4980a2 - <unknown>
  31:     0x7f1aaa52080c - <unknown>
  32:                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 1.101.0-nightly (16d1ffac1 2026-10-26) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [mir_borrowck] borrow-checking `<impl at /tmp/icemaker_global_tempdir.O89QqsIytXhi/rustc_testrunner_tmpdir_reporting.ax0HfJtwB3vR/mvce.rs:9:1: 9:40>::get_ref`
#1 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 3 previous errors

Some errors have detailed explanations: E0392, E0407, E0601.
For more information about an error, try `rustc --explain E0392`.

Regression in nightly-2026-10-27.

searched nightlies: from nightly-2026-01-01 to nightly-2026-10-28
regressed nightly: nightly-2026-10-27
searched commit range: 76456a6...16d1ffa
regressed commit: 16d1ffa

bisected with cargo-bisect-rustc v0.6.12

Host triple: x86_64-apple-darwin
Reproduce with:

cargo bisect-rustc --start=2026-01-01 --end=2026-10-28 --regress ice --preserve --script rustc -- 165052.rs --edition 2024

simpler:

struct S<'a> {
    n: &'static u8, // changing 'static to 'a makes it compile
}
fn b(n: &u8) -> S {
    S { n }
}

fn main() {}

Let's also mark this as a regression, going from pass -> ice by just misnaming a single lifetime is a bit bad 😅

also available with free RegionError

enum Ast<'a> {
    Add(&'a Ast<'static>, &'a Ast<'a>),
}
fn mk_add_bad1<'a, 'b>(x: &'a Ast, y: &'b Ast) -> Ast<'a> {
    Ast::Add(x, y)
}

fn main() {}

`--edition` is unspecified, defaulting to `2015` while the latest is `2024`; it must be one of: <2015|2018|2021|2024|future>


thread 'rustc' (2524641) panicked at /rustc-dev/92ffebeceaa0a071066f233873c2438e73d70fe7/compiler/rustc_errors/src/diagnostic.rs:795:9:
assertion failed: !parts.is_empty()
stack backtrace:
   0:     0x7f945b62aa86 - <<std[79e685616d8acb06]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[37f3b5327d2a8d81]::fmt::Display>::fmt
   1:     0x7f945bc0c3e9 - core[37f3b5327d2a8d81]::fmt::write
   2:     0x7f945b640b6c - <std[79e685616d8acb06]::sys::stdio::unix::Stderr as core[37f3b5327d2a8d81]::io::write::Write>::write_fmt
   3:     0x7f945b5fbbda - std[79e685616d8acb06]::panicking::default_hook::{closure#0}
   4:     0x7f945b61e3d3 - std[79e685616d8acb06]::panicking::default_hook
   5:     0x7f945a3df1c9 - std[79e685616d8acb06]::panicking::update_hook::<alloc[c9af9d88734a640]::boxed::Box<rustc_driver_impl[a9bc65168640fad2]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f945b61e872 - std[79e685616d8acb06]::panicking::panic_with_hook
   7:     0x7f945b5fbcc4 - std[79e685616d8acb06]::panicking::panic_handler::{closure#0}
   8:     0x7f945b5f30c9 - std[79e685616d8acb06]::sys::backtrace::__rust_end_short_backtrace::<std[79e685616d8acb06]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f945b5fd9ed - __rustc[24b41f7b1eaff5c4]::rust_begin_unwind
  10:     0x7f9457e9d34c - core[37f3b5327d2a8d81]::panicking::panic_fmt
  11:     0x7f94589cfd02 - core[37f3b5327d2a8d81]::panicking::panic
  12:     0x7f9459f91ca1 - <rustc_errors[562a20e589be4a37]::diagnostic::Diag>::multipart_suggestion_with_style::<&str>
  13:     0x7f945a07e8a1 - <rustc_borrowck[473f42d474e5f443]::MirBorrowckCtxt>::report_general_error
  14:     0x7f945a077042 - <rustc_borrowck[473f42d474e5f443]::MirBorrowckCtxt>::report_region_error
  15:     0x7f945a07facc - <rustc_borrowck[473f42d474e5f443]::MirBorrowckCtxt>::report_region_errors
  16:     0x7f945d01a318 - rustc_borrowck[473f42d474e5f443]::borrowck_check_region_constraints
  17:     0x7f945cfeef9b - <rustc_borrowck[473f42d474e5f443]::root_cx::BorrowCheckRootCtxt>::do_mir_borrowck
  18:     0x7f945bf3d355 - rustc_borrowck[473f42d474e5f443]::mir_borrowck
  19:     0x7f945bf3d079 - rustc_query_impl[94ea310137c91be9]::query_vtables::mir_borrowck::invoke_provider_fn::__rust_begin_short_backtrace
  20:     0x7f945bf3ba8e - rustc_query_impl[94ea310137c91be9]::execution::try_execute_query::<rustc_data_structures[765348a730531b4f]::vec_cache::VecCache<rustc_span[8d99a68682bc74a4]::def_id::LocalDefId, rustc_middle[65aed009adb63715]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[65aed009adb63715]::dep_graph::graph::DepNodeIndex>, false>
  21:     0x7f945bf3b5f5 - rustc_query_impl[94ea310137c91be9]::query_vtables::mir_borrowck::execute_query_non_incr::__rust_end_short_backtrace
  22:     0x7f945bf39669 - <rustc_middle[65aed009adb63715]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[ee1467d4bce41807]::passes::run_required_analyses::{closure#2}::{closure#0}>::{closure#0}
  23:     0x7f945bf389d2 - rustc_interface[ee1467d4bce41807]::passes::analysis
  24:     0x7f945ccdcf5f - rustc_query_impl[94ea310137c91be9]::execution::try_execute_query::<rustc_middle[65aed009adb63715]::query::caches::SingleCache<rustc_middle[65aed009adb63715]::query::erase::ErasedData<[u8; 0usize]>>, false>
  25:     0x7f945ccdcd53 - rustc_query_impl[94ea310137c91be9]::query_vtables::analysis::execute_query_non_incr::__rust_end_short_backtrace
  26:     0x7f945cf009c0 - rustc_interface[ee1467d4bce41807]::interface::run_compiler::<(), rustc_driver_impl[a9bc65168640fad2]::compiler_entrypoint::{closure#0}>::{closure#2}
  27:     0x7f945cf59101 - std[79e685616d8acb06]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[ee1467d4bce41807]::util::run_in_thread_with_globals<rustc_interface[ee1467d4bce41807]::util::run_in_thread_pool_with_globals<rustc_interface[ee1467d4bce41807]::interface::run_compiler<(), rustc_driver_impl[a9bc65168640fad2]::compiler_entrypoint::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  28:     0x7f945cf58ead - <std[79e685616d8acb06]::thread::lifecycle::spawn_unchecked<rustc_interface[ee1467d4bce41807]::util::run_in_thread_with_globals<rustc_interface[ee1467d4bce41807]::util::run_in_thread_pool_with_globals<rustc_interface[ee1467d4bce41807]::interface::run_compiler<(), rustc_driver_impl[a9bc65168640fad2]::compiler_entrypoint::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[37f3b5327d2a8d81]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  29:     0x7f945cf53e6d - <std[79e685616d8acb06]::sys::thread::unix::Thread>::new::thread_start
  30:     0x7f9455e980a2 - <unknown>
  31:     0x7f9455f2080c - <unknown>
  32:                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: please attach the file at `/home/matthias/vcs/github/CRED/rustc-ice-2026-10-29T18_54_40-2524572.txt` to your bug report

note: rustc 1.101.0-nightly (92ffebece 2026-10-28) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [mir_borrowck] borrow-checking `mk_add_bad1`
#1 [analysis] running analysis passes on crate `code`
end of query stack
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: RegionError { fr_origin: FreeRegion, longer_fr: '?2, shorter_fr: '?1, is_reported: true }
  |
  = note: delayed at /rustc-dev/92ffebeceaa0a071066f233873c2438e73d70fe7/compiler/rustc_borrowck/src/region_infer/region_context.rs:1522:31 - disabled backtrace

error: internal compiler error: RegionError { fr_origin: FreeRegion, longer_fr: '?3, shorter_fr: '?0, is_reported: true }
  |
  = note: delayed at /rustc-dev/92ffebeceaa0a071066f233873c2438e73d70fe7/compiler/rustc_borrowck/src/region_infer/region_context.rs:1500:31 - disabled backtrace

error: internal compiler error: RegionError { fr_origin: FreeRegion, longer_fr: '?4, shorter_fr: '?1, is_reported: true }
  |
  = note: delayed at /rustc-dev/92ffebeceaa0a071066f233873c2438e73d70fe7/compiler/rustc_borrowck/src/region_infer/region_context.rs:1522:31 - disabled 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: please make sure that you have updated to the latest nightly

note: please attach the file at `/home/matthias/vcs/github/CRED/rustc-ice-2026-10-29T18_54_40-2524572.txt` to your bug report

note: rustc 1.101.0-nightly (92ffebece 2026-10-28) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack

@estebank

Regression in e1057ef. Note that if it is a legacy rollup build, it might be available in rust-lang-ci@e1057ef.
The PR introducing the regression in this rollup is #164776: Account for trait object with implicit 'static lifetime i…

cc @estebank

bisected with cargo-bisect-rustc v0.6.12

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --regress ice --preserve --start 2026-10-22

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[ICE]: `assertion failed: !parts.is_empty()` #165052

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	let parts = suggestion
	.into_iter()
	.map(\|(span, snippet)\| SubstitutionPart { snippet, span })
	.collect::<Vec<_>>();

	assert!(!parts.is_empty());
	debug_assert_eq!(
	parts.iter().find(\|part\| part.span.is_empty() && part.snippet.is_empty()),
	None,
	"Span must not be empty and have no suggestion",
	);
	debug_assert_eq!(

[ICE]: assertion failed: !parts.is_empty() #165052

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cushionbadak commented on Oct 28, 2026

matthiaskrgr commented on Oct 29, 2026

matthiaskrgr commented on Oct 29, 2026

matthiaskrgr commented on Oct 29, 2026

zachs18 commented on Oct 29, 2026

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[ICE]: `assertion failed: !parts.is_empty()` #165052