ICE: "region constraints already solved'": with_negative_coherence

[matthiaskrgr]

Code

./src/test/ui/coherence/coherence-negative-outlives-lifetimes.rs

#![feature(negative_impls)]

// FIXME: this should compile

trait MyPredicate<'a> {}
impl<'a, T> !MyPredicate<'a> for &T where T: 'a {}
trait MyTrait<'a> {}
impl<'a, T: MyPredicate<'a>> MyTrait<'a> for T {}
impl<'a, T> MyTrait<'a> for &'a T {}
//~^ ERROR: conflicting implementations of trait `MyTrait<'_>` for type `&_`

fn main() {}

Meta

rustc --version --verbose:

rustc 1.64.0-nightly (93ffde6f0 2022-07-23)
binary: rustc
commit-hash: 93ffde6f04d3d24327a4e17a2a2bf4f63c246235
commit-date: 2022-07-23
host: x86_64-unknown-linux-gnu
release: 1.64.0-nightly
LLVM version: 14.0.6

Error output

rustc ./src/test/ui/coherence/coherence-negative-outlives-lifetimes.rs "-Zcrate-attr=feature(with_negative_coherence)"

<output>

Backtrace

thread 'rustc' panicked at 'region constraints already solved', compiler/rustc_infer/src/infer/mod.rs:235:9
stack backtrace:
   0:     0x7fabb70a37a0 - std::backtrace_rs::backtrace::libunwind::trace::h763ecd2b1c94eb47
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   1:     0x7fabb70a37a0 - std::backtrace_rs::backtrace::trace_unsynchronized::h7346e33da5e91dc9
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fabb70a37a0 - std::sys_common::backtrace::_print_fmt::h8ca9befc16375e7f
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7fabb70a37a0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h35a76e8acc949815
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7fabb70fda2c - core::fmt::write::h1966177bbb3b1b76
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/core/src/fmt/mod.rs:1198:17
   5:     0x7fabb7094f85 - std::io::Write::write_fmt::he17142a652adbfaa
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/io/mod.rs:1672:15
   6:     0x7fabb70a6471 - std::sys_common::backtrace::_print::h58fd682547bc6ff7
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7fabb70a6471 - std::sys_common::backtrace::print::hb71ddfedfd79ba3f
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7fabb70a6471 - std::panicking::default_hook::{{closure}}::h866ffdcbb9391663
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/panicking.rs:295:22
   9:     0x7fabb70a6143 - std::panicking::default_hook::hc53d610bee87e7b5
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/panicking.rs:314:9
  10:     0x7fabb7953731 - rustc_driver[ee492072531d29b9]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7fabb70a6c46 - std::panicking::rust_panic_with_hook::h1f2457f8494b1ce0
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/panicking.rs:702:17
  12:     0x7fabb70a6a97 - std::panicking::begin_panic_handler::{{closure}}::h84de84c919a48b08
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/panicking.rs:588:13
  13:     0x7fabb70a3cc4 - std::sys_common::backtrace::__rust_end_short_backtrace::h50976962eb12c97a
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/sys_common/backtrace.rs:138:18
  14:     0x7fabb70a67c2 - rust_begin_unwind
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/panicking.rs:584:5
  15:     0x7fabb7069b63 - core::panicking::panic_fmt::hb7aeecf8ae8bdd28
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/core/src/panicking.rs:142:14
  16:     0x7fabb70fa651 - core::panicking::panic_display::h8a507b84231c6858
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/core/src/panicking.rs:72:5
  17:     0x7fabb70fa5fb - core::panicking::panic_str::he42b786850f072a3
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/core/src/panicking.rs:56:5
  18:     0x7fabb70699d6 - core::option::expect_failed::h87ab6556ec5701cd
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/core/src/option.rs:1874:5
  19:     0x7fabb98d048d - <rustc_infer[bfbf07e5440e77e9]::infer::InferCtxt>::start_snapshot
  20:     0x7fabb989471a - <rustc_middle[ba567b0c63397382]::ty::context::TyCtxt>::for_each_relevant_impl::<<rustc_trait_selection[620490483a22fe27]::traits::select::SelectionContext>::assemble_candidates_from_impls::{closure#0}>
  21:     0x7fabb88151dc - <rustc_trait_selection[620490483a22fe27]::traits::select::SelectionContext>::assemble_candidates_from_impls
  22:     0x7fabb9815a82 - <rustc_trait_selection[620490483a22fe27]::traits::select::SelectionContext>::assemble_candidates
  23:     0x7fabb9801b41 - <rustc_trait_selection[620490483a22fe27]::traits::select::SelectionContext>::candidate_from_obligation_no_cache
  24:     0x7fabb98232e0 - <rustc_trait_selection[620490483a22fe27]::traits::select::SelectionContext>::select
  25:     0x7fabb986b388 - <rustc_trait_selection[620490483a22fe27]::traits::fulfill::FulfillProcessor as rustc_data_structures[c16dd9bc0e209753]::obligation_forest::ObligationProcessor>::process_obligation
  26:     0x7fabb98917fe - <rustc_data_structures[c16dd9bc0e209753]::obligation_forest::ObligationForest<rustc_trait_selection[620490483a22fe27]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[620490483a22fe27]::traits::fulfill::FulfillProcessor, rustc_data_structures[c16dd9bc0e209753]::obligation_forest::Outcome<rustc_trait_selection[620490483a22fe27]::traits::fulfill::PendingPredicateObligation, rustc_infer[bfbf07e5440e77e9]::traits::FulfillmentErrorCode>>
  27:     0x7fabb98664ea - <rustc_trait_selection[620490483a22fe27]::traits::fulfill::FulfillmentContext as rustc_infer[bfbf07e5440e77e9]::traits::engine::TraitEngine>::select_all_or_error
  28:     0x7fabb8896bfa - rustc_trait_selection[620490483a22fe27]::traits::coherence::resolve_negative_obligation
  29:     0x7fabb88960ec - rustc_trait_selection[620490483a22fe27]::traits::coherence::equate::<core[7b47b893e00d8dca]::iter::adapters::chain::Chain<core[7b47b893e00d8dca]::iter::adapters::chain::Chain<core[7b47b893e00d8dca]::iter::adapters::map::Map<core[7b47b893e00d8dca]::iter::adapters::zip::Zip<alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_middle[ba567b0c63397382]::ty::Predicate>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_span[e8a062c38fd06fcf]::span_encoding::Span>>, rustc_trait_selection[620490483a22fe27]::traits::util::predicates_for_generics::{closure#0}>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_infer[bfbf07e5440e77e9]::traits::Obligation<rustc_middle[ba567b0c63397382]::ty::Predicate>>>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_infer[bfbf07e5440e77e9]::traits::Obligation<rustc_middle[ba567b0c63397382]::ty::Predicate>>>>::{closure#0}
  30:     0x7fabb884d082 - <core[7b47b893e00d8dca]::iter::adapters::map::Map<core[7b47b893e00d8dca]::iter::adapters::zip::Zip<alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_middle[ba567b0c63397382]::ty::Predicate>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_span[e8a062c38fd06fcf]::span_encoding::Span>>, rustc_trait_selection[620490483a22fe27]::traits::util::predicates_for_generics::{closure#0}> as core[7b47b893e00d8dca]::iter::traits::iterator::Iterator>::try_fold::<(), core[7b47b893e00d8dca]::iter::traits::iterator::Iterator::find::check<rustc_infer[bfbf07e5440e77e9]::traits::Obligation<rustc_middle[ba567b0c63397382]::ty::Predicate>, &mut &mut &mut rustc_trait_selection[620490483a22fe27]::traits::coherence::equate<core[7b47b893e00d8dca]::iter::adapters::chain::Chain<core[7b47b893e00d8dca]::iter::adapters::chain::Chain<core[7b47b893e00d8dca]::iter::adapters::map::Map<core[7b47b893e00d8dca]::iter::adapters::zip::Zip<alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_middle[ba567b0c63397382]::ty::Predicate>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_span[e8a062c38fd06fcf]::span_encoding::Span>>, rustc_trait_selection[620490483a22fe27]::traits::util::predicates_for_generics::{closure#0}>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_infer[bfbf07e5440e77e9]::traits::Obligation<rustc_middle[ba567b0c63397382]::ty::Predicate>>>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_infer[bfbf07e5440e77e9]::traits::Obligation<rustc_middle[ba567b0c63397382]::ty::Predicate>>>>::{closure#0}>::{closure#0}, core[7b47b893e00d8dca]::ops::control_flow::ControlFlow<rustc_infer[bfbf07e5440e77e9]::traits::Obligation<rustc_middle[ba567b0c63397382]::ty::Predicate>>>
  31:     0x7fabb8895b22 - rustc_trait_selection[620490483a22fe27]::traits::coherence::equate::<core[7b47b893e00d8dca]::iter::adapters::chain::Chain<core[7b47b893e00d8dca]::iter::adapters::chain::Chain<core[7b47b893e00d8dca]::iter::adapters::map::Map<core[7b47b893e00d8dca]::iter::adapters::zip::Zip<alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_middle[ba567b0c63397382]::ty::Predicate>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_span[e8a062c38fd06fcf]::span_encoding::Span>>, rustc_trait_selection[620490483a22fe27]::traits::util::predicates_for_generics::{closure#0}>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_infer[bfbf07e5440e77e9]::traits::Obligation<rustc_middle[ba567b0c63397382]::ty::Predicate>>>, alloc[327c298d5f7f3986]::vec::into_iter::IntoIter<rustc_infer[bfbf07e5440e77e9]::traits::Obligation<rustc_middle[ba567b0c63397382]::ty::Predicate>>>>
  32:     0x7fabb87e76ed - <rustc_infer[bfbf07e5440e77e9]::infer::InferCtxtBuilder>::enter::<bool, rustc_trait_selection[620490483a22fe27]::traits::coherence::negative_impl::{closure#0}>
  33:     0x7fabb88956b8 - rustc_trait_selection[620490483a22fe27]::traits::coherence::negative_impl
  34:     0x7fabba2f9b0a - rustc_trait_selection[620490483a22fe27]::traits::coherence::overlap_within_probe
  35:     0x7fabba2d1b39 - <rustc_infer[bfbf07e5440e77e9]::infer::InferCtxt>::probe_maybe_skip_leak_check::<core[7b47b893e00d8dca]::option::Option<rustc_trait_selection[620490483a22fe27]::traits::coherence::OverlapResult>, rustc_trait_selection[620490483a22fe27]::traits::coherence::overlap::{closure#0}>
  36:     0x7fabba2d09c1 - <rustc_infer[bfbf07e5440e77e9]::infer::InferCtxtBuilder>::enter::<bool, rustc_trait_selection[620490483a22fe27]::traits::coherence::overlapping_impls<<rustc_middle[ba567b0c63397382]::traits::specialization_graph::Children as rustc_trait_selection[620490483a22fe27]::traits::specialize::specialization_graph::ChildrenExt>::insert::{closure#2}, <rustc_middle[ba567b0c63397382]::traits::specialization_graph::Children as rustc_trait_selection[620490483a22fe27]::traits::specialize::specialization_graph::ChildrenExt>::insert::{closure#3}, core[7b47b893e00d8dca]::result::Result<(bool, bool), rustc_trait_selection[620490483a22fe27]::traits::specialize::OverlapError>>::{closure#1}>
  37:     0x7fabb98a2fdc - <rustc_middle[ba567b0c63397382]::traits::specialization_graph::Children as rustc_trait_selection[620490483a22fe27]::traits::specialize::specialization_graph::ChildrenExt>::insert
  38:     0x7fabb98a3bb8 - <rustc_middle[ba567b0c63397382]::traits::specialization_graph::Graph as rustc_trait_selection[620490483a22fe27]::traits::specialize::specialization_graph::GraphExt>::insert
  39:     0x7fabb9868f04 - rustc_trait_selection[620490483a22fe27]::traits::specialize::specialization_graph_provider
  40:     0x7fabba06318a - rustc_query_system[b49264403dc3266]::query::plumbing::try_execute_query::<rustc_query_impl[7dace536525edc45]::plumbing::QueryCtxt, rustc_query_system[b49264403dc3266]::query::caches::ArenaCache<rustc_span[e8a062c38fd06fcf]::def_id::DefId, rustc_middle[ba567b0c63397382]::traits::specialization_graph::Graph>>
  41:     0x7fabba0efeb9 - rustc_query_system[b49264403dc3266]::query::plumbing::get_query::<rustc_query_impl[7dace536525edc45]::queries::specialization_graph_of, rustc_query_impl[7dace536525edc45]::plumbing::QueryCtxt>
  42:     0x7fabb9de5288 - rustc_typeck[ba18a5ea3a172631]::coherence::coherent_trait
  43:     0x7fabb952d2f5 - rustc_query_system[b49264403dc3266]::query::plumbing::try_execute_query::<rustc_query_impl[7dace536525edc45]::plumbing::QueryCtxt, rustc_query_system[b49264403dc3266]::query::caches::DefaultCache<rustc_span[e8a062c38fd06fcf]::def_id::DefId, ()>>
  44:     0x7fabba0d4842 - rustc_query_system[b49264403dc3266]::query::plumbing::get_query::<rustc_query_impl[7dace536525edc45]::queries::coherent_trait, rustc_query_impl[7dace536525edc45]::plumbing::QueryCtxt>
  45:     0x7fabb9dbf7a9 - <rustc_session[82687f0a78807d1f]::session::Session>::track_errors::<rustc_typeck[ba18a5ea3a172631]::check_crate::{closure#3}, ()>
  46:     0x7fabb9e1834f - rustc_typeck[ba18a5ea3a172631]::check_crate
  47:     0x7fabb9b49e97 - rustc_interface[c2045ebdcb88575c]::passes::analysis
  48:     0x7fabba0a2735 - rustc_query_system[b49264403dc3266]::query::plumbing::try_execute_query::<rustc_query_impl[7dace536525edc45]::plumbing::QueryCtxt, rustc_query_system[b49264403dc3266]::query::caches::DefaultCache<(), core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>>>
  49:     0x7fabba101b9e - rustc_query_system[b49264403dc3266]::query::plumbing::get_query::<rustc_query_impl[7dace536525edc45]::queries::analysis, rustc_query_impl[7dace536525edc45]::plumbing::QueryCtxt>
  50:     0x7fabb9b2328e - <rustc_interface[c2045ebdcb88575c]::passes::QueryContext>::enter::<rustc_driver[ee492072531d29b9]::run_compiler::{closure#1}::{closure#2}::{closure#3}, core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>>
  51:     0x7fabb9b06c6e - <rustc_interface[c2045ebdcb88575c]::interface::Compiler>::enter::<rustc_driver[ee492072531d29b9]::run_compiler::{closure#1}::{closure#2}, core[7b47b893e00d8dca]::result::Result<core[7b47b893e00d8dca]::option::Option<rustc_interface[c2045ebdcb88575c]::queries::Linker>, rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>>
  52:     0x7fabb9b02f3a - rustc_span[e8a062c38fd06fcf]::with_source_map::<core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>, rustc_interface[c2045ebdcb88575c]::interface::create_compiler_and_run<core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>, rustc_driver[ee492072531d29b9]::run_compiler::{closure#1}>::{closure#1}>
  53:     0x7fabb9b1f360 - rustc_interface[c2045ebdcb88575c]::interface::create_compiler_and_run::<core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>, rustc_driver[ee492072531d29b9]::run_compiler::{closure#1}>
  54:     0x7fabb9b33362 - <scoped_tls[7afe57960397b723]::ScopedKey<rustc_span[e8a062c38fd06fcf]::SessionGlobals>>::set::<rustc_interface[c2045ebdcb88575c]::interface::run_compiler<core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>, rustc_driver[ee492072531d29b9]::run_compiler::{closure#1}>::{closure#0}, core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>>
  55:     0x7fabb9b0532f - std[af12de6c3337c1b7]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[c2045ebdcb88575c]::util::run_in_thread_pool_with_globals<rustc_interface[c2045ebdcb88575c]::interface::run_compiler<core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>, rustc_driver[ee492072531d29b9]::run_compiler::{closure#1}>::{closure#0}, core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>>::{closure#0}, core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>>
  56:     0x7fabb9b1f7b9 - <<std[af12de6c3337c1b7]::thread::Builder>::spawn_unchecked_<rustc_interface[c2045ebdcb88575c]::util::run_in_thread_pool_with_globals<rustc_interface[c2045ebdcb88575c]::interface::run_compiler<core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>, rustc_driver[ee492072531d29b9]::run_compiler::{closure#1}>::{closure#0}, core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>>::{closure#0}, core[7b47b893e00d8dca]::result::Result<(), rustc_errors[30e8870fe27fb8ba]::ErrorGuaranteed>>::{closure#1} as core[7b47b893e00d8dca]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  57:     0x7fabb70b0693 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h2535c4f17d1ae00a
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/alloc/src/boxed.rs:1935:9
  58:     0x7fabb70b0693 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h9555fa64d2fdcc1f
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/alloc/src/boxed.rs:1935:9
  59:     0x7fabb70b0693 - std::sys::unix::thread::Thread::new::thread_start::hcd4b7b87c76163e2
                               at /rustc/93ffde6f04d3d24327a4e17a2a2bf4f63c246235/library/std/src/sys/unix/thread.rs:108:17
  60:     0x7fabb6e8054d - <unknown>
  61:     0x7fabb6f05874 - clone
  62:                0x0 - <unknown>

error: internal compiler error: unexpected panic

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 1.64.0-nightly (93ffde6f0 2022-07-23) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z crate-attr=feature(with_negative_coherence)

query stack during panic:
#0 [specialization_graph_of] building specialization graph of trait `MyTrait`
#1 [coherent_trait] coherence checking all impls of trait `MyTrait`
#2 [analysis] running analysis passes on this crate
end of query stack