ICE: unreachable in compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs #148631
Description
Code
struct C; struct S<T>(Option<T>); trait Tr { type Out; } impl<T> Clone for S<C> where S<T>: Tr<Out = T>, { fn clone(&self) -> Self { *self } } fn main() {}A mutant of tests/ui/associated-types/issue-25700-1.rs
Meta
rustc --version --verbose:
rustc 1.93.0-nightly (c90bcb957 2025-11-06) binary: rustc commit-hash: c90bcb9571b7aab0d8beaa2ce8a998ffaf079d38 commit-date: 2025-11-06 host: x86_64-apple-darwin release: 1.93.0-nightly LLVM version: 21.1.3 Error output
Command: rustc
error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predicates --> 08.rs:9:6 | 9 | impl<T> Clone for S<C> | ^ unconstrained type parameter thread 'rustc' (6161155) panicked at compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs:1353:27: internal error: entered unreachable code Backtrace
thread 'rustc' (6161155) panicked at compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs:1353:27: internal error: entered unreachable code stack backtrace: 0: __rustc::rust_begin_unwind 1: core::panicking::panic_fmt 2: core::panicking::panic 3: <rustc_borrowck::MirBorrowckCtxt>::suggest_cloning 4: <rustc_borrowck::MirBorrowckCtxt>::report 5: <rustc_borrowck::MirBorrowckCtxt>::report_move_errors 6: rustc_borrowck::borrowck_check_region_constraints 7: <rustc_borrowck::root_cx::BorrowCheckRootCtxt>::do_mir_borrowck 8: rustc_borrowck::mir_borrowck [... omitted 1 frame ...] 9: <rustc_middle::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0} 10: rustc_interface::passes::analysis [... omitted 1 frame ...] 11: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}> 12: 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. 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 `/Users/jb/Library/CloudStorage/Dropbox/Desk/2503_rustc_ice/20251106 ice 보고용/rustc-ice-2025-11-07T05_57_22-5613.txt` to your bug report query stack during panic: #0 [mir_borrowck] borrow-checking `<impl at 08.rs:9:1: 11:23>::clone` #1 [analysis] running analysis passes on crate `08` end of query stack error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0207`. Notes
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ICE location:
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs Line-1353
rust/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
Lines 1346 to 1358 in c90bcb9
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Duplication Check
- I searched "conflict_errors.rs" ICE (Github issue page with query), and there are no opened issues there.