Code
#![feature(return_type_notation)]
pub trait Foo {
async fn bar();
}
trait Bar {}
impl<T: Foo<bar(..): Send>> Foo for T where T: Bar {
}
fn needs_foo(_: impl Foo) {}
trait Mirror {
type Mirror;
}
impl<T> Mirror for T {
type Mirror = T;
}
fn hello<T>() where <T as Mirror>::Mirror: Foo {
needs_foo(());
}
fn main() {}Mutant of tests/ui/traits/next-solver/diagnostics/where-clause-doesnt-apply.rs
Meta
rustc --version --verbose:
rustc 1.95.0-nightly (7f99507f5 2026-02-19)
binary: rustc
commit-hash: 7f99507f57e6c4aa0dce3daf6a13cca8cd4dd312
commit-date: 2026-02-19
host: x86_64-apple-darwin
release: 1.95.0-nightly
LLVM version: 22.1.0
Error output
Command: rustc --edition=2024
It ICEs at no-edition too, but put it to reduce error message length.
error[E0046]: not all trait items implemented, missing: `bar`
--> iter9_23c3d7db5173f2ab.rs:7:1
|
3 | async fn bar();
| --------------- `bar` from trait
...
7 | impl<T: Foo<bar(..): Send>> Foo for T where T: Bar {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `bar` in implementation
error[E0277]: the trait bound `(): Foo` is not satisfied
--> iter9_23c3d7db5173f2ab.rs:19:15
|
19 | needs_foo(());
| --------- ^^ the trait `Bar` is not implemented for `()`
| |
| required by a bound introduced by this call
|
help: this trait has no implementations, consider adding one
--> iter9_23c3d7db5173f2ab.rs:5:1
|
5 | trait Bar {}
| ^^^^^^^^^
note: required for `()` to implement `Foo`
--> iter9_23c3d7db5173f2ab.rs:7:29
|
7 | impl<T: Foo<bar(..): Send>> Foo for T where T: Bar {
| ^^^ ^ --- unsatisfied trait bound introduced here
= note: 1 redundant requirement hidden
= note: required for `()` to implement `Foo`
note: required by a bound in `needs_foo`
--> iter9_23c3d7db5173f2ab.rs:9:22
|
9 | fn needs_foo(_: impl Foo) {}
| ^^^ required by this bound in `needs_foo`
error: internal compiler error: /rustc-dev/7f99507f57e6c4aa0dce3daf6a13cca8cd4dd312/compiler/rustc_middle/src/ty/mod.rs:1556:13: item_name: no name for DefPath { data: [DisambiguatedDefPathData { data: TypeNs("Foo"), disambiguator: 0 }, DisambiguatedDefPathData { data: AnonAssocTy("bar"), disambiguator: 0 }], krate: crate0 }
thread 'rustc' (15452564) panicked at /rustc-dev/7f99507f57e6c4aa0dce3daf6a13cca8cd4dd312/compiler/rustc_middle/src/ty/mod.rs:1556:13:
Box<dyn Any>
Backtrace
thread 'rustc' (15452564) panicked at /rustc-dev/7f99507f57e6c4aa0dce3daf6a13cca8cd4dd312/compiler/rustc_middle/src/ty/mod.rs:1556:13:
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_middle::ty::context::TyCtxt>::item_name::<rustc_span::def_id::DefId>::{closure#0}
7: rustc_trait_selection::error_reporting::traits::suggestions::point_at_assoc_type_restriction::<rustc_span::ErrorGuaranteed>
8: <rustc_trait_selection::error_reporting::TypeErrCtxt>::note_obligation_cause_code::<rustc_span::ErrorGuaranteed, rustc_middle::ty::predicate::Predicate>
9: <rustc_trait_selection::error_reporting::TypeErrCtxt>::report_overflow_error::<<rustc_trait_selection::error_reporting::TypeErrCtxt>::report_overflow_obligation<rustc_middle::ty::predicate::Predicate>::{closure#0}>
10: <rustc_trait_selection::error_reporting::TypeErrCtxt>::report_overflow_obligation::<rustc_middle::ty::predicate::Predicate>
11: <rustc_trait_selection::error_reporting::TypeErrCtxt>::report_overflow_obligation_cycle
12: <rustc_trait_selection::error_reporting::TypeErrCtxt>::report_fulfillment_errors
13: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_argument_types
14: <rustc_hir_typeck::fn_ctxt::FnCtxt>::confirm_builtin_call
15: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_kind
16: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
17: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_block
18: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
19: <rustc_hir_typeck::fn_ctxt::FnCtxt>::check_return_or_body_tail
20: rustc_hir_typeck::check::check_fn
21: rustc_hir_typeck::typeck_with_inspect::{closure#0}
22: rustc_hir_typeck::typeck
23: rustc_query_impl::execution::try_execute_query::<rustc_data_structures::vec_cache::VecCache<rustc_hir_id::OwnerId, rustc_middle::query::erase::ErasedData<[u8; 8]>, rustc_middle::dep_graph::graph::DepNodeIndex>, {rustc_query_impl::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: false }}, false>
24: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis::check_crate::{closure#2}>::{closure#0}
25: rustc_hir_analysis::check_crate
26: rustc_interface::passes::analysis
27: rustc_query_impl::execution::try_execute_query::<rustc_middle::query::caches::SingleCache<rustc_middle::query::erase::ErasedData<[u8; 0]>>, {rustc_query_impl::QueryFlags { is_anon: false, is_depth_limit: false, is_feedable: false }}, false>
28: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>
29: 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: please make sure that you have updated to the latest nightly
note: please attach the file at `/Volumes/T7/workspace/out-260219/scratch/rustc-ice-2026-02-20T07_47_13-46327.txt` to your bug report
note: rustc 1.95.0-nightly (7f99507f5 2026-02-19) running on x86_64-apple-darwin
query stack during panic:
#0 [typeck] type-checking `hello`
#1 [analysis] running analysis passes on crate `iter9_23c3d7db5173f2ab`
end of query stack
error: aborting due to 3 previous errors
Some errors have detailed explanations: E0046, E0277.
For more information about an error, try `rustc --explain E0046`.
Regression
Regression in 2024-01-26
Command: cargo bisect-rustc --start=2024-01-01 --end=2026-02-18 --regress ice --preserve --script rustc -- noname.rs
Log
searched toolchains nightly-2024-01-01 through nightly-2026-02-18
********************************************************************************
Regression in nightly-2024-01-26
********************************************************************************
fetching https://static.rust-lang.org/dist/2024-01-25/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2024-01-25: 40 B / 40 B [==================================================================] 100.00 % 1.03 MB/s converted 2024-01-25 to 7ffc697ce10f19447c0ce338428ae4b9bc0c041c
fetching https://static.rust-lang.org/dist/2024-01-26/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2024-01-26: 40 B / 40 B [================================================================] 100.00 % 850.92 KB/s converted 2024-01-26 to 5bd5d214effd494f4bafb29b3a7a2f6c2070ca5c
looking for regression commit between 2024-01-25 and 2024-01-26
fetching (via remote github) commits from max(7ffc697ce10f19447c0ce338428ae4b9bc0c041c, 2024-01-23) to 5bd5d214effd494f4bafb29b3a7a2f6c2070ca5c
ending github query because we found starting sha: 7ffc697ce10f19447c0ce338428ae4b9bc0c041c
get_commits_between returning commits, len: 5
commit[0] 2024-01-24: Auto merge of #120309 - fmease:rollup-kr7wqy6, r=fmease
commit[1] 2024-01-25: Auto merge of #119627 - oli-obk:const_prop_lint_n̵o̵n̵sense, r=cjgillot
commit[2] 2024-01-25: Auto merge of #119911 - NCGThompson:is-statically-known, r=oli-obk
commit[3] 2024-01-25: Auto merge of #119955 - kamalesh0406:master, r=WaffleLapkin
commit[4] 2024-01-25: Auto merge of #120335 - matthiaskrgr:rollup-2a0y3rd, r=matthiaskrgr
ERROR: no CI builds available between 7ffc697ce10f19447c0ce338428ae4b9bc0c041c and 5bd5d214effd494f4bafb29b3a7a2f6c2070ca5c within last 167 days
Notes
@rustbot label +F-return_type_notation
Code
Mutant of
tests/ui/traits/next-solver/diagnostics/where-clause-doesnt-apply.rsMeta
rustc --version --verbose:Error output
Command:
rustc --edition=2024It ICEs at no-edition too, but put it to reduce error message length.
Backtrace
Regression
Regression in 2024-01-26
Command:
cargo bisect-rustc --start=2024-01-01 --end=2026-02-18 --regress ice --preserve --script rustc -- noname.rsLog
Notes
ICE location:
compiler/rustc_middle/src/ty/mod.rs Line-1556rust/compiler/rustc_middle/src/ty/mod.rs
Lines 1547 to 1558 in 7f99507
Duplication Check
@rustbot label +F-return_type_notation