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ICE: unexpected const placeholder #131538

Open matthiaskrgr opened 1 week ago

matthiaskrgr commented 1 week ago

Code

#![feature(return_type_notation)]
#![feature(generic_associated_types_extended)]
#![feature(trivial_bounds)]

trait HealthCheck {
    async fn check<const N: usize>() -> bool;
}

async fn do_health_check_par<HC>()
where
    HealthCheck: HealthCheck<Send(): Send> + Send + 'static,
{
}

Meta

rustc --version --verbose:

binary: rustc
commit-hash: 52fd9983996d9fcfb719749838336be66dee68f9
commit-date: 2024-10-10
host: x86_64-unknown-linux-gnu
release: 1.83.0-nightly
LLVM version: 19.1.1

Error output

warning: the feature `generic_associated_types_extended` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/crash.rs:2:12
  |
2 | #![feature(generic_associated_types_extended)]
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #95451 <https://github.com/rust-lang/rust/issues/95451> for more information
  = note: `#[warn(incomplete_features)]` on by default

error: parenthesized generic arguments cannot be used in associated type constraints
  --> /tmp/crash.rs:11:30
   |
11 |     HealthCheck: HealthCheck<Send(): Send> + Send + 'static,
   |                              ^^^^--
   |                                  |
   |                                  help: remove these parentheses

error[E0220]: associated type `Send` not found for `HealthCheck`
  --> /tmp/crash.rs:11:30
   |
11 |     HealthCheck: HealthCheck<Send(): Send> + Send + 'static,
   |                              ^^^^ associated type `Send` not found
Backtrace

``` error: internal compiler error: compiler/rustc_infer/src/infer/freshen.rs:178:17: unexpected const !130_0 thread 'rustc' panicked at compiler/rustc_infer/src/infer/freshen.rs:178:17: Box stack backtrace: 0: 0x7714989dd24a - ::fmt::h87acf85b5211808c 1: 0x7714992034a6 - core::fmt::write::h1830300cff8013e6 2: 0x77149a40bb91 - std::io::Write::write_fmt::hff4c51c59db7db45 3: 0x7714989dd0a2 - std::sys::backtrace::BacktraceLock::print::h5e8429acc66fa0b4 4: 0x7714989df576 - std::panicking::default_hook::{{closure}}::h47c5621b8a2933e4 5: 0x7714989df3c0 - std::panicking::default_hook::h4c51255dc678cdff 6: 0x771497a315df - std[39bba8b06d71f7a0]::panicking::update_hook::>::{closure#0} 7: 0x7714989dfc88 - std::panicking::rust_panic_with_hook::hfa48cfa9339c55df 8: 0x771497a6b7c1 - std[39bba8b06d71f7a0]::panicking::begin_panic::::{closure#0} 9: 0x771497a5e866 - std[39bba8b06d71f7a0]::sys::backtrace::__rust_end_short_backtrace::::{closure#0}, !> 10: 0x771497a59d99 - std[39bba8b06d71f7a0]::panicking::begin_panic:: 11: 0x771497a75051 - ::emit_producing_guarantee 12: 0x7714980d1124 - rustc_middle[29f16e95e513605a]::util::bug::opt_span_bug_fmt::::{closure#0} 13: 0x7714980b6f9a - rustc_middle[29f16e95e513605a]::ty::context::tls::with_opt::::{closure#0}, !>::{closure#0} 14: 0x7714980b6e2b - rustc_middle[29f16e95e513605a]::ty::context::tls::with_context_opt::::{closure#0}, !>::{closure#0}, !> 15: 0x7714955faad0 - rustc_middle[29f16e95e513605a]::util::bug::bug_fmt 16: 0x771499f446fb - >::fold_const 17: 0x771499337449 - >::try_super_fold_with:: 18: 0x771499e990c5 - ::poly_select::{closure#0} 19: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 20: 0x771499a89bea - rustc_trait_selection[51e218581841b494]::traits::project::poly_project_and_unify_term 21: 0x771495defc36 - ::candidate_from_obligation_no_cache 22: 0x771499e9d1f5 - ::poly_select::{closure#0} 23: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 24: 0x771499a915b3 - >::fold_ty 25: 0x771499a909c1 - <&rustc_middle[29f16e95e513605a]::ty::list::RawList<(), rustc_middle[29f16e95e513605a]::ty::generic_args::GenericArg> as rustc_type_ir[aeae2260a8e42b9a]::fold::TypeFoldable>::try_fold_with:: 26: 0x771499a901e0 - >::fold_predicate 27: 0x77149999fd89 - rustc_trait_selection[51e218581841b494]::traits::normalize::normalize_with_depth_to:: 28: 0x771499aef3ae - ::confirm_candidate 29: 0x771495decd8d - ::candidate_from_obligation_no_cache 30: 0x771499e9d1f5 - ::poly_select::{closure#0} 31: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 32: 0x771499a915b3 - >::fold_ty 33: 0x771499a909c1 - <&rustc_middle[29f16e95e513605a]::ty::list::RawList<(), rustc_middle[29f16e95e513605a]::ty::generic_args::GenericArg> as rustc_type_ir[aeae2260a8e42b9a]::fold::TypeFoldable>::try_fold_with:: 34: 0x771499a901e0 - >::fold_predicate 35: 0x77149999fd89 - rustc_trait_selection[51e218581841b494]::traits::normalize::normalize_with_depth_to:: 36: 0x771499aef3ae - ::confirm_candidate 37: 0x771495decd8d - ::candidate_from_obligation_no_cache 38: 0x771499e9d1f5 - ::poly_select::{closure#0} 39: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 40: 0x771499a915b3 - >::fold_ty 41: 0x771499a909c1 - <&rustc_middle[29f16e95e513605a]::ty::list::RawList<(), rustc_middle[29f16e95e513605a]::ty::generic_args::GenericArg> as rustc_type_ir[aeae2260a8e42b9a]::fold::TypeFoldable>::try_fold_with:: 42: 0x771499a901e0 - >::fold_predicate 43: 0x77149999fd89 - rustc_trait_selection[51e218581841b494]::traits::normalize::normalize_with_depth_to:: 44: 0x771499aef3ae - ::confirm_candidate 45: 0x771495decd8d - ::candidate_from_obligation_no_cache 46: 0x771499e9d1f5 - ::poly_select::{closure#0} 47: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 48: 0x771499a915b3 - >::fold_ty 49: 0x771499a909c1 - <&rustc_middle[29f16e95e513605a]::ty::list::RawList<(), rustc_middle[29f16e95e513605a]::ty::generic_args::GenericArg> as rustc_type_ir[aeae2260a8e42b9a]::fold::TypeFoldable>::try_fold_with:: 50: 0x771499a901e0 - >::fold_predicate 51: 0x77149999fd89 - rustc_trait_selection[51e218581841b494]::traits::normalize::normalize_with_depth_to:: 52: 0x771499aef3ae - ::confirm_candidate 53: 0x771495decd8d - ::candidate_from_obligation_no_cache 54: 0x771499e9d1f5 - ::poly_select::{closure#0} 55: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 56: 0x771499a915b3 - >::fold_ty 57: 0x771499a909c1 - <&rustc_middle[29f16e95e513605a]::ty::list::RawList<(), rustc_middle[29f16e95e513605a]::ty::generic_args::GenericArg> as rustc_type_ir[aeae2260a8e42b9a]::fold::TypeFoldable>::try_fold_with:: 58: 0x771499a901e0 - >::fold_predicate 59: 0x77149999fd89 - rustc_trait_selection[51e218581841b494]::traits::normalize::normalize_with_depth_to:: 60: 0x771499aef3ae - ::confirm_candidate 61: 0x771495decd8d - ::candidate_from_obligation_no_cache 62: 0x771499e9d1f5 - ::poly_select::{closure#0} 63: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 64: 0x771499a915b3 - >::fold_ty 65: 0x771499a909c1 - <&rustc_middle[29f16e95e513605a]::ty::list::RawList<(), rustc_middle[29f16e95e513605a]::ty::generic_args::GenericArg> as rustc_type_ir[aeae2260a8e42b9a]::fold::TypeFoldable>::try_fold_with:: 1010: 0x771499a901e0 - >::fold_predicate 1011: 0x77149999fd89 - rustc_trait_selection[51e218581841b494]::traits::normalize::normalize_with_depth_to:: 1012: 0x771499aef3ae - ::confirm_candidate 1013: 0x771495decd8d - ::candidate_from_obligation_no_cache 1014: 0x771499e9d1f5 - ::poly_select::{closure#0} 1015: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 1016: 0x771499a915b3 - >::fold_ty 1017: 0x771499a909c1 - <&rustc_middle[29f16e95e513605a]::ty::list::RawList<(), rustc_middle[29f16e95e513605a]::ty::generic_args::GenericArg> as rustc_type_ir[aeae2260a8e42b9a]::fold::TypeFoldable>::try_fold_with:: 1018: 0x771499a901e0 - >::fold_predicate 1019: 0x77149999fd89 - rustc_trait_selection[51e218581841b494]::traits::normalize::normalize_with_depth_to:: 1020: 0x771499aef3ae - ::confirm_candidate 1021: 0x771495decd8d - ::candidate_from_obligation_no_cache 1022: 0x771499e9d1f5 - ::poly_select::{closure#0} 1023: 0x771499a94890 - rustc_trait_selection[51e218581841b494]::traits::project::opt_normalize_projection_term 1024: 0x771499a915b3 - >::fold_ty 1025: 0x771499a909c1 - <&rustc_middle[29f16e95e513605a]::ty::list::RawList<(), rustc_middle[29f16e95e513605a]::ty::generic_args::GenericArg> as rustc_type_ir[aeae2260a8e42b9a]::fold::TypeFoldable>::try_fold_with:: 1026: 0x771499a901e0 - >::fold_predicate 1027: 0x77149999fd89 - rustc_trait_selection[51e218581841b494]::traits::normalize::normalize_with_depth_to:: 1028: 0x771499aef3ae - ::confirm_candidate 1029: 0x771495decd8d - ::candidate_from_obligation_no_cache 1030: 0x771495e1a435 - ::candidate_from_obligation 1031: 0x771499ab03bc - ::evaluate_trait_predicate_recursively 1032: 0x7714992e9c5e - ::evaluate_root_obligation 1033: 0x7714992e8212 - rustc_traits[f9de722fbc0fac2a]::evaluate_obligation::evaluate_obligation 1034: 0x7714992e7ca9 - rustc_query_impl[577202e9d6ff7d36]::plumbing::__rust_begin_short_backtrace::> 1035: 0x7714992e722b - rustc_query_system[e421b998c28443f5]::query::plumbing::try_execute_query::>, rustc_middle[29f16e95e513605a]::query::erase::Erased<[u8; 2usize]>>, false, false, false>, rustc_query_impl[577202e9d6ff7d36]::plumbing::QueryCtxt, false> 1036: 0x7714992e6e7a - rustc_query_impl[577202e9d6ff7d36]::query_impl::evaluate_obligation::get_query_non_incr::__rust_end_short_backtrace 1037: 0x77149569bcc7 - ::process_obligation 1038: 0x7714993f32c1 - >::process_obligations:: 1039: 0x7714993efcc1 - >::assumed_wf_types_and_report_errors 1040: 0x7714999836f5 - rustc_hir_analysis[7d1658e465b44263]::check::wfcheck::check_item_fn 1041: 0x771496b5386f - rustc_hir_analysis[7d1658e465b44263]::check::wfcheck::check_well_formed 1042: 0x771499bd53eb - rustc_query_impl[577202e9d6ff7d36]::plumbing::__rust_begin_short_backtrace::> 1043: 0x771499bd4b51 - rustc_query_system[e421b998c28443f5]::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl[577202e9d6ff7d36]::plumbing::QueryCtxt, false> 1044: 0x771499bd47d0 - rustc_query_impl[577202e9d6ff7d36]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace 1045: 0x771499bd567f - rustc_hir_analysis[7d1658e465b44263]::check::wfcheck::check_mod_type_wf 1046: 0x771499bd54a5 - rustc_query_impl[577202e9d6ff7d36]::plumbing::__rust_begin_short_backtrace::> 1047: 0x77149a101d3b - rustc_query_system[e421b998c28443f5]::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl[577202e9d6ff7d36]::plumbing::QueryCtxt, false> 1048: 0x77149a101aed - rustc_query_impl[577202e9d6ff7d36]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace 1049: 0x77149963387b - rustc_hir_analysis[7d1658e465b44263]::check_crate 1050: 0x7714996305d7 - rustc_interface[3d22ab4a16c914f1]::passes::run_required_analyses 1051: 0x771499f29a5e - rustc_interface[3d22ab4a16c914f1]::passes::analysis 1052: 0x771499f29a31 - rustc_query_impl[577202e9d6ff7d36]::plumbing::__rust_begin_short_backtrace::> 1053: 0x77149a1138ae - rustc_query_system[e421b998c28443f5]::query::plumbing::try_execute_query::>, false, false, false>, rustc_query_impl[577202e9d6ff7d36]::plumbing::QueryCtxt, false> 1054: 0x77149a11358f - rustc_query_impl[577202e9d6ff7d36]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace 1055: 0x771499f39a5e - rustc_interface[3d22ab4a16c914f1]::interface::run_compiler::, rustc_driver_impl[2b16dbb9274b0adb]::run_compiler::{closure#0}>::{closure#1} 1056: 0x771499fc1d50 - std[39bba8b06d71f7a0]::sys::backtrace::__rust_begin_short_backtrace::, rustc_driver_impl[2b16dbb9274b0adb]::run_compiler::{closure#0}>::{closure#1}, core[5ae4016a0c652b3c]::result::Result<(), rustc_span[6ca13cbf14de63a0]::ErrorGuaranteed>>::{closure#0}, core[5ae4016a0c652b3c]::result::Result<(), rustc_span[6ca13cbf14de63a0]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[5ae4016a0c652b3c]::result::Result<(), rustc_span[6ca13cbf14de63a0]::ErrorGuaranteed>> 1057: 0x771499fc2417 - <::spawn_unchecked_, rustc_driver_impl[2b16dbb9274b0adb]::run_compiler::{closure#0}>::{closure#1}, core[5ae4016a0c652b3c]::result::Result<(), rustc_span[6ca13cbf14de63a0]::ErrorGuaranteed>>::{closure#0}, core[5ae4016a0c652b3c]::result::Result<(), rustc_span[6ca13cbf14de63a0]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[5ae4016a0c652b3c]::result::Result<(), rustc_span[6ca13cbf14de63a0]::ErrorGuaranteed>>::{closure#1} as core[5ae4016a0c652b3c]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 1058: 0x771499fc3301 - std::sys::pal::unix::thread::Thread::new::thread_start::hc0595517bea46b79 1059: 0x77149b80139d - 1060: 0x77149b88649c - 1061: 0x0 - 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 `/tmp/rustc-ice-2024-10-11T09_35_41-93078.txt` to your bug report note: compiler flags: --crate-type lib query stack during panic: #0 [evaluate_obligation] evaluating trait selection obligation `(dyn HealthCheck + 'a): HealthCheck` #1 [check_well_formed] checking that `do_health_check_par` is well-formed end of query stack error[E0782]: trait objects must include the `dyn` keyword --> /tmp/crash.rs:11:5 | 11 | HealthCheck: HealthCheck + Send + 'static, | ^^^^^^^^^^^ | help: add `dyn` keyword before this trait | 11 | dyn HealthCheck: HealthCheck + Send + 'static, | +++ error: aborting due to 4 previous errors; 1 warning emitted Some errors have detailed explanations: E0220, E0782. For more information about an error, try `rustc --explain E0220`. ```

cyrgani commented 1 week ago

Reduced:

#![feature(generic_associated_types_extended)]
#![feature(trivial_bounds)]

trait HealthCheck {
    async fn check<const N: usize>();
}

fn do_health_check_par()
where
    HealthCheck: HealthCheck,
{
}

Removing #![feature(trivial_bounds)] causes the compiler to hang, instead of ICEing.

szbergeron commented 1 day ago

Hi All! Do we know what the expected behavior for this case should be?

As is, it runs into recursion limits and then bugs when TypeFreshener tries to fold a ConstKind::Placeholder left over afterwards.

My intuition is that it should behave exactly as it does when check is fn check<const N: usize>(); or fn check<const N: usize>(&self);: complain that HealthCheck is not object safe due to missing self or generic parameters and then exit gracefully.

Is this a reasonable/accurate assumption? (I'm new to reading rustc so my understanding may very well be off base!)

szbergeron commented 20 hours ago

663da008760a0f6d38dbd5e7db4c9bb67fa64798 does change the behavior here for the current minified example, though I think there should still be a way of triggering the ICE now. I'll try to produce a new test that still exhibits the behavior after that.

EDIT: new repro that accommodates the changes:

#![feature(generic_associated_types_extended)]
#![feature(trivial_bounds)]

trait HealthCheck {
    async fn check<const N: usize>();
}

fn do_health_check_par()
where
    dyn HealthCheck: HealthCheck,
{
}