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ICE: unexpected ambiguity #105299
Description
Activity
Also you could try to see if this repros on the latest stable 1.65. If possible you can also try the latest nightly 1.67.
Possibly the same bug or a closely related one can be triggered with the following MCVE on both current stable and nightly. If this is a different bug, I can open a new issue or comment on another issue.
pub trait Foo: Clone {} pub struct Bar<'a, T: Clone> { pub cow: std::borrow::Cow<'a, [T]>, pub THIS_CAUSES_ICE: (), // #1 } impl<T> Bar<'_, T> where T: Clone, [T]: Foo, { pub fn MOVES_SELF(self) {} // #2 }
results in
error: internal compiler error: unexpected ambiguity: Canonical { max_universe: U0, variables: [], value: ParamEnvAnd { param_env: ParamEnv { caller_bounds: [Binder(TraitPredicate(<[T] as Foo>, polarity:Positive), []), Binder(TraitPredicate(<[T] as std::clone::Clone>, polarity:Positive), []), Binder(TraitPredicate(<[T] as std::marker::Sized>, polarity:Positive), []), Binder(TraitPredicate(<T as std::clone::Clone>, polarity:Positive), []), Binder(TraitPredicate(<T as std::marker::Sized>, polarity:Positive), [])], reveal: UserFacing, constness: NotConst }, value: ProjectionTy { substs: [[T]], item_def_id: DefId(5:859 ~ alloc[d987]::borrow::ToOwned::Owned) } } } Canonical { max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], value: QueryResponse { var_values: CanonicalVarValues { var_values: [] }, region_constraints: QueryRegionConstraints { outlives: [], member_constraints: [] }, certainty: Ambiguous, opaque_types: [], value: NormalizationResult { normalized_ty: ^0 } } }Full compiler output
Compiling playground v0.0.1 (/playground) thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: NoSolution', compiler/rustc_borrowck/src/type_check/liveness/trace.rs:574:88 stack backtrace: 0: 0x7efcb7fab9a0 - std::backtrace_rs::backtrace::libunwind::trace::he615646ea344481f at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5 1: 0x7efcb7fab9a0 - std::backtrace_rs::backtrace::trace_unsynchronized::h6ea8eaac68705b9c at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5 2: 0x7efcb7fab9a0 - std::sys_common::backtrace::_print_fmt::h7ac486a935ce0bf7 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:65:5 3: 0x7efcb7fab9a0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1b5a095d3db2e28f at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:44:22 4: 0x7efcb800798e - core::fmt::write::h445545b92224a1cd at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/fmt/mod.rs:1209:17 5: 0x7efcb7f9bb15 - std::io::Write::write_fmt::h55a43474c6520b00 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/io/mod.rs:1682:15 6: 0x7efcb7fab765 - std::sys_common::backtrace::_print::h65d20526fdb736b0 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:47:5 7: 0x7efcb7fab765 - std::sys_common::backtrace::print::h6555fbe12a1cc41b at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:34:9 8: 0x7efcb7fae56f - std::panicking::default_hook::{{closure}}::hbdf58083140e7ac6 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:267:22 9: 0x7efcb7fae2aa - std::panicking::default_hook::haef8271c56b74d85 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:286:9 10: 0x7efcb7faed78 - std::panicking::rust_panic_with_hook::hfd45b6b6c12d9fa5 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:688:13 11: 0x7efcb7faeb17 - std::panicking::begin_panic_handler::{{closure}}::hf591e8609a75bd4b at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:579:13 12: 0x7efcb7fabe4c - std::sys_common::backtrace::__rust_end_short_backtrace::h81899558795e4ff7 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:137:18 13: 0x7efcb7fae832 - rust_begin_unwind at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:575:5 14: 0x7efcb8004373 - core::panicking::panic_fmt::h4235fa9b4675b332 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/panicking.rs:65:14 15: 0x7efcb80048e3 - core::result::unwrap_failed::ha17dbf463031a5e1 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/result.rs:1791:5 16: 0x7efcb9f9aefa - rustc_borrowck[60153a3fde5c674a]::type_check::liveness::trace::trace 17: 0x7efcb9f6bc67 - rustc_borrowck[60153a3fde5c674a]::type_check::liveness::generate 18: 0x7efcb9f66f76 - rustc_borrowck[60153a3fde5c674a]::type_check::type_check 19: 0x7efcb9f5730a - rustc_borrowck[60153a3fde5c674a]::nll::compute_regions 20: 0x7efcb9f3865f - rustc_borrowck[60153a3fde5c674a]::do_mir_borrowck 21: 0x7efcb9f1e996 - rustc_borrowck[60153a3fde5c674a]::mir_borrowck 22: 0x7efcba29651c - rustc_query_system[330b635d327008f7]::query::plumbing::try_execute_query::<rustc_query_impl[969f89a88b0ee9ca]::plumbing::QueryCtxt, rustc_query_system[330b635d327008f7]::query::caches::DefaultCache<rustc_span[14998722174c1bca]::def_id::LocalDefId, &rustc_middle[1bbcd7fc39987e50]::mir::query::BorrowCheckResult>> 23: 0x7efcb954e072 - rustc_data_structures[e8a5264856147ea5]::sync::par_for_each_in::<&[rustc_span[14998722174c1bca]::def_id::LocalDefId], <rustc_middle[1bbcd7fc39987e50]::hir::map::Map>::par_body_owners<rustc_interface[ee1a3f92e887e004]::passes::analysis::{closure#2}::{closure#0}>::{closure#0}> 24: 0x7efcb954cb4f - <rustc_session[87e5e219eb43521c]::session::Session>::time::<(), rustc_interface[ee1a3f92e887e004]::passes::analysis::{closure#2}> 25: 0x7efcb954aa87 - rustc_interface[ee1a3f92e887e004]::passes::analysis 26: 0x7efcba987ac4 - rustc_query_system[330b635d327008f7]::query::plumbing::try_execute_query::<rustc_query_impl[969f89a88b0ee9ca]::plumbing::QueryCtxt, rustc_query_system[330b635d327008f7]::query::caches::DefaultCache<(), core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>> 27: 0x7efcba9877c7 - rustc_query_system[330b635d327008f7]::query::plumbing::get_query::<rustc_query_impl[969f89a88b0ee9ca]::queries::analysis, rustc_query_impl[969f89a88b0ee9ca]::plumbing::QueryCtxt> 28: 0x7efcba4c9acd - <rustc_interface[ee1a3f92e887e004]::passes::QueryContext>::enter::<rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}::{closure#2}::{closure#3}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>> 29: 0x7efcba4c5f7f - <rustc_interface[ee1a3f92e887e004]::interface::Compiler>::enter::<rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}::{closure#2}, core[b97a30f8df81432d]::result::Result<core[b97a30f8df81432d]::option::Option<rustc_interface[ee1a3f92e887e004]::queries::Linker>, rustc_errors[21897ed46328f955]::ErrorGuaranteed>> 30: 0x7efcba4bdac2 - rustc_span[14998722174c1bca]::with_source_map::<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}::{closure#1}> 31: 0x7efcba4bd5b9 - <scoped_tls[23afcff80b89ba49]::ScopedKey<rustc_span[14998722174c1bca]::SessionGlobals>>::set::<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>> 32: 0x7efcba4bcbc8 - std[bbad73ae434e23e5]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[ee1a3f92e887e004]::util::run_in_thread_pool_with_globals<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>> 33: 0x7efcba4bc8ec - <<std[bbad73ae434e23e5]::thread::Builder>::spawn_unchecked_<rustc_interface[ee1a3f92e887e004]::util::run_in_thread_pool_with_globals<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#1} as core[b97a30f8df81432d]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 34: 0x7efcbbe666a3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4273f95ec44459b3 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/alloc/src/boxed.rs:1987:9 35: 0x7efcbbe666a3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h70f28fa4ddc269e5 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/alloc/src/boxed.rs:1987:9 36: 0x7efcbbe666a3 - std::sys::unix::thread::Thread::new::thread_start::h85a9c16b988e2bd0 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys/unix/thread.rs:108:17 37: 0x7efcb7e8a609 - start_thread 38: 0x7efcb7dad133 - clone 39: 0x0 - <unknown> error: internal compiler error: no errors encountered even though `delay_span_bug` issued error: internal compiler error: unexpected ambiguity: Canonical { max_universe: U0, variables: [], value: ParamEnvAnd { param_env: ParamEnv { caller_bounds: [Binder(TraitPredicate(<[T] as Foo>, polarity:Positive), []), Binder(TraitPredicate(<[T] as std::clone::Clone>, polarity:Positive), []), Binder(TraitPredicate(<[T] as std::marker::Sized>, polarity:Positive), []), Binder(TraitPredicate(<T as std::clone::Clone>, polarity:Positive), []), Binder(TraitPredicate(<T as std::marker::Sized>, polarity:Positive), [])], reveal: UserFacing, constness: NotConst }, value: ProjectionTy { substs: [[T]], item_def_id: DefId(5:859 ~ alloc[d987]::borrow::ToOwned::Owned) } } } Canonical { max_universe: U0, variables: [CanonicalVarInfo { kind: Ty(General(U0)) }], value: QueryResponse { var_values: CanonicalVarValues { var_values: [] }, region_constraints: QueryRegionConstraints { outlives: [], member_constraints: [] }, certainty: Ambiguous, opaque_types: [], value: NormalizationResult { normalized_ty: ^0 } } } | = note: delayed at compiler/rustc_trait_selection/src/traits/query/normalize.rs:260:34 thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1553:13 stack backtrace: 0: 0x7efcbbe5ce20 - std::backtrace_rs::backtrace::libunwind::trace::he615646ea344481f at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5 1: 0x7efcbbe5ce20 - std::backtrace_rs::backtrace::trace_unsynchronized::h6ea8eaac68705b9c at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5 2: 0x7efcbbe5ce20 - std::sys_common::backtrace::_print_fmt::h7ac486a935ce0bf7 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:65:5 3: 0x7efcbbe5ce20 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1b5a095d3db2e28f at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:44:22 4: 0x7efcb800798e - core::fmt::write::h445545b92224a1cd at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/fmt/mod.rs:1209:17 5: 0x7efcbbe50ad5 - std::io::Write::write_fmt::h55a43474c6520b00 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/io/mod.rs:1682:15 6: 0x7efcbbe5cbe5 - std::sys_common::backtrace::_print::h65d20526fdb736b0 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:47:5 7: 0x7efcbbe5cbe5 - std::sys_common::backtrace::print::h6555fbe12a1cc41b at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:34:9 8: 0x7efcbbe5ef3f - std::panicking::default_hook::{{closure}}::hbdf58083140e7ac6 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:267:22 9: 0x7efcbbe5ec7a - std::panicking::default_hook::haef8271c56b74d85 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:286:9 10: 0x7efcbb122cd4 - <rustc_driver[9c4183344b2d0066]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[b97a30f8df81432d]::ops::function::FnOnce<(&core[b97a30f8df81432d]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0} 11: 0x7efcbbe5f729 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h44df53ea2a13204b at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/alloc/src/boxed.rs:2001:9 12: 0x7efcbbe5f729 - std::panicking::rust_panic_with_hook::hfd45b6b6c12d9fa5 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:692:13 13: 0x7efcbb1510b1 - std[bbad73ae434e23e5]::panicking::begin_panic::<rustc_errors[21897ed46328f955]::ExplicitBug>::{closure#0} 14: 0x7efcbb14f846 - std[bbad73ae434e23e5]::sys_common::backtrace::__rust_end_short_backtrace::<std[bbad73ae434e23e5]::panicking::begin_panic<rustc_errors[21897ed46328f955]::ExplicitBug>::{closure#0}, !> 15: 0x7efcbb149636 - std[bbad73ae434e23e5]::panicking::begin_panic::<rustc_errors[21897ed46328f955]::ExplicitBug> 16: 0x7efcbb14bcc6 - std[bbad73ae434e23e5]::panic::panic_any::<rustc_errors[21897ed46328f955]::ExplicitBug> 17: 0x7efcba6c4b71 - <rustc_errors[21897ed46328f955]::HandlerInner>::flush_delayed::<alloc[d987cf4402e5b40a]::vec::Vec<rustc_errors[21897ed46328f955]::diagnostic::Diagnostic>, &str> 18: 0x7efcba6c3bb2 - <rustc_errors[21897ed46328f955]::HandlerInner as core[b97a30f8df81432d]::ops::drop::Drop>::drop 19: 0x7efcba50cd58 - core[b97a30f8df81432d]::ptr::drop_in_place::<rustc_session[87e5e219eb43521c]::parse::ParseSess> 20: 0x7efcba4bedf8 - core[b97a30f8df81432d]::ptr::drop_in_place::<rustc_session[87e5e219eb43521c]::session::Session> 21: 0x7efcba4beb19 - core[b97a30f8df81432d]::ptr::drop_in_place::<rustc_interface[ee1a3f92e887e004]::interface::Compiler> 22: 0x7efcba4bdf2e - rustc_span[14998722174c1bca]::with_source_map::<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}::{closure#1}> 23: 0x7efcba4bd5b9 - <scoped_tls[23afcff80b89ba49]::ScopedKey<rustc_span[14998722174c1bca]::SessionGlobals>>::set::<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>> 24: 0x7efcba4bcbc8 - std[bbad73ae434e23e5]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[ee1a3f92e887e004]::util::run_in_thread_pool_with_globals<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>> 25: 0x7efcba4bc8ec - <<std[bbad73ae434e23e5]::thread::Builder>::spawn_unchecked_<rustc_interface[ee1a3f92e887e004]::util::run_in_thread_pool_with_globals<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#1} as core[b97a30f8df81432d]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 26: 0x7efcbbe666a3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4273f95ec44459b3 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/alloc/src/boxed.rs:1987:9 27: 0x7efcbbe666a3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h70f28fa4ddc269e5 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/alloc/src/boxed.rs:1987:9 28: 0x7efcbbe666a3 - std::sys::unix::thread::Thread::new::thread_start::h85a9c16b988e2bd0 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys/unix/thread.rs:108:17 29: 0x7efcb7e8a609 - start_thread 30: 0x7efcb7dad133 - clone 31: 0x0 - <unknown> note: 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: rustc 1.66.0 (69f9c33d7 2022-12-12) running on x86_64-unknown-linux-gnu note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 note: some of the compiler flags provided by cargo are hidden query stack during panic: end of query stack thread '<unnamed>' panicked at 'panic in a function that cannot unwind', library/core/src/panicking.rs:90:58 stack backtrace: 0: 0x7efcb7fab9a0 - std::backtrace_rs::backtrace::libunwind::trace::he615646ea344481f at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5 1: 0x7efcb7fab9a0 - std::backtrace_rs::backtrace::trace_unsynchronized::h6ea8eaac68705b9c at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5 2: 0x7efcb7fab9a0 - std::sys_common::backtrace::_print_fmt::h7ac486a935ce0bf7 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:65:5 3: 0x7efcb7fab9a0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1b5a095d3db2e28f at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:44:22 4: 0x7efcb800798e - core::fmt::write::h445545b92224a1cd at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/fmt/mod.rs:1209:17 5: 0x7efcb7f9bb15 - std::io::Write::write_fmt::h55a43474c6520b00 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/io/mod.rs:1682:15 6: 0x7efcb7fab765 - std::sys_common::backtrace::_print::h65d20526fdb736b0 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:47:5 7: 0x7efcb7fab765 - std::sys_common::backtrace::print::h6555fbe12a1cc41b at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:34:9 8: 0x7efcb7fae56f - std::panicking::default_hook::{{closure}}::hbdf58083140e7ac6 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:267:22 9: 0x7efcb7fae2aa - std::panicking::default_hook::haef8271c56b74d85 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:286:9 10: 0x7efcb7faed78 - std::panicking::rust_panic_with_hook::hfd45b6b6c12d9fa5 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:688:13 11: 0x7efcb7faead1 - std::panicking::begin_panic_handler::{{closure}}::hf591e8609a75bd4b at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:577:13 12: 0x7efcb7fabe4c - std::sys_common::backtrace::__rust_end_short_backtrace::h81899558795e4ff7 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys_common/backtrace.rs:137:18 13: 0x7efcb7fae832 - rust_begin_unwind at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/panicking.rs:575:5 14: 0x7efcb80043f3 - core::panicking::panic_str_nounwind::h2959ea310e934ac1 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/panicking.rs:93:14 15: 0x7efcb8004563 - core::panicking::panic_no_unwind::h31a06247391473ac at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/core/src/panicking.rs:164:5 16: 0x7efcba4bdf45 - rustc_span[14998722174c1bca]::with_source_map::<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}::{closure#1}> 17: 0x7efcba4bd5b9 - <scoped_tls[23afcff80b89ba49]::ScopedKey<rustc_span[14998722174c1bca]::SessionGlobals>>::set::<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>> 18: 0x7efcba4bcbc8 - std[bbad73ae434e23e5]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[ee1a3f92e887e004]::util::run_in_thread_pool_with_globals<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>> 19: 0x7efcba4bc8ec - <<std[bbad73ae434e23e5]::thread::Builder>::spawn_unchecked_<rustc_interface[ee1a3f92e887e004]::util::run_in_thread_pool_with_globals<rustc_interface[ee1a3f92e887e004]::interface::run_compiler<core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>, rustc_driver[9c4183344b2d0066]::run_compiler::{closure#1}>::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[b97a30f8df81432d]::result::Result<(), rustc_errors[21897ed46328f955]::ErrorGuaranteed>>::{closure#1} as core[b97a30f8df81432d]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 20: 0x7efcbbe666a3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4273f95ec44459b3 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/alloc/src/boxed.rs:1987:9 21: 0x7efcbbe666a3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h70f28fa4ddc269e5 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/alloc/src/boxed.rs:1987:9 22: 0x7efcbbe666a3 - std::sys::unix::thread::Thread::new::thread_start::h85a9c16b988e2bd0 at /rustc/69f9c33d71c871fc16ac445211281c6e7a340943/library/std/src/sys/unix/thread.rs:108:17 23: 0x7efcb7e8a609 - start_thread 24: 0x7efcb7dad133 - clone 25: 0x0 - <unknown> thread panicked while panicking. aborting. error: could not compile `playground`The critical lines are marked as
#1and#2; commenting out#1prevents the ICE and gives the following error which is presumably caused by the compiler not being able to prove thatCow<'_, [T]>isSized(presumably caused by missingToOwnedbound?) Removing line#2, or changing it to borrowselfmakes the code compile, as expected.EDIT
Seems this is related to the fact that a DST can be the last field, but only the last field, of a struct. Moving
#1one line up also makes the ICE go away.error[[E0284]](https://doc.rust-lang.org/stable/error-index.html#E0284): type annotations needed --> src/lib.rs:17:23 | 17 | pub fn MOVES_SELF(self) {} | ^^^^ cannot infer type | = note: cannot satisfy `<[T] as ToOwned>::Owned == _` note: required because it appears within the type `Bar<'_, T>` --> src/lib.rs:3:12 | 3 | pub struct Bar<'a, T> | ^^^ help: function arguments must have a statically known size, borrowed types always have a known size | 17 | pub fn MOVES_SELF(&self) {} | +This was fixed by #136539
Reacted by Johannes Dahlström
Today I encountered a compiler panic with rustc 1.64.0.
Code
Unfortunately I cannot provide the code at this point, as it's not released, yet. The project makes heavy use of (const) generics. There were some errors in the code which probably lead to the compiler panic. After fixing some errors, the panic went away, too.
Meta
rustc --version --verbose:Error output
Backtrace