#![feature(generic_const_exprs)] ICE on evaluating constans both for type of generic const parameter and trait bound at the same type definition

[AnthonyMikh]

Code

#![feature(generic_const_exprs)]

struct Foo<const A: [(); 0 + 0]>
    where [(); 0 + 0]: Sized;

Note that it is required for both array lengths to be not a literal in order to trigger this bug.

Meta

Quite surprisingly, despite using #![feature], it works not only on nightly but on beta and stable as well. Although backtraces differ, the failed assertion is the same.

rustc --version --verbose:

rustc 1.56.1 (59eed8a2a 2021-11-01)
binary: rustc
commit-hash: 59eed8a2aac0230a8b53e89d4e99d55912ba6b35
commit-date: 2021-11-01
host: x86_64-pc-windows-msvc
release: 1.56.1
LLVM version: 13.0.0

Error output

error[E0554]: `#![feature]` may not be used on the stable release channel
 --> lib.rs:1:1
  |
1 | #![feature(generic_const_exprs)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> lib.rs:1:12
  |
1 | #![feature(generic_const_exprs)]
  |            ^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default
  = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information

thread 'rustc' panicked at 'assertion failed: !arg.has_type_flags(!allowed_flags)', compiler\rustc_typeck\src\collect\type_of.rs:297:9
stack backtrace:
<snip, see below>

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 1.56.1 (59eed8a2a 2021-11-01) running on x86_64-pc-windows-msvc

query stack during panic:
#0 [default_anon_const_substs] computing the default generic arguments for `Foo::{constant#1}`
#1 [param_env] computing normalized predicates of `Foo`
#2 [check_item_well_formed] checking that `Foo` is well-formed
#3 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error; 1 warning emitted

Setting RUST_BACKTRACE=1 revealed no stack frames at all so I used RUST_BACKTRACE=full.

Backtrace

   0:     0x7ffd4de87a9e - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h90fc78c6027cfe27
   1:     0x7ffd4deb268a - core::fmt::write::h8afcb1031f89d60b
   2:     0x7ffd4de7ae08 - <std::io::IoSliceMut as core::fmt::Debug>::fmt::hb4b34c43836aedaf
   3:     0x7ffd4de8b586 - std::panicking::take_hook::h8b2fe3f8f4cf4b43
   4:     0x7ffd4de8b074 - std::panicking::take_hook::h8b2fe3f8f4cf4b43
   5:       0x86d770a525 - <serde_json::value::WriterFormatter as std::io::Write>::flush::hc1d196eaca04d7a8
   6:     0x7ffd4de8be99 - std::panicking::rust_panic_with_hook::h844a8dc19bbe524e
   7:     0x7ffd4de8b90f - rust_begin_unwind
   8:     0x7ffd4de883e7 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h90fc78c6027cfe27
   9:     0x7ffd4de8b899 - rust_begin_unwind
  10:     0x7ffd4dee8d10 - core::panicking::panic_fmt::h27a79246687269a4
  11:     0x7ffd4dee8c5c - core::panicking::panic::h4b6e61fc90377b73
  12:       0x86d9fa5c7e - <rustc_typeck::coherence::unsafety::UnsafetyChecker as rustc_hir::itemlikevisit::ItemLikeVisitor>::visit_item::h682aa4275916ccf2
  13:       0x86dab4d8cc - <fixedbitset::FixedBitSet as core::fmt::Debug>::fmt::hedf20157683d04ae
  14:       0x86daee596d - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_mark_green::h02f98d8f46101c14
  15:       0x86db8241cf - <rustc_trait_selection::traits::on_unimplemented::OnUnimplementedDirective as core::fmt::Debug>::fmt::hdad6ed0876437135
  16:       0x86db8c3ca2 - <rustc_trait_selection::opaque_types::GenerateMemberConstraints as core::fmt::Debug>::fmt::h6351a5ad34a7afd7
  17:       0x86db8f1c43 - <rustc_infer::infer::lub::Lub as rustc_middle::ty::relate::TypeRelation>::tcx::hd8dcd1498c2c37da
  18:       0x86db83ff39 - <rustc_trait_selection::traits::specialize::OverlapError as core::fmt::Debug>::fmt::h82cecc3e256aff77
  19:       0x86db8f0927 - rustc_trait_selection::traits::project::AssocTypeNormalizer::new::hf5a40d1813a3e002
  20:       0x86db8ee8cd - <rustc_trait_selection::traits::wf::Elaborate as core::fmt::Debug>::fmt::h98a2adc5ad82cba2
  21:       0x86db88ad3d - rustc_trait_selection::traits::normalize_param_env_or_error::h6c082e5471b3c0d8
  22:       0x86db7a1b51 - <unicode_normalization::stream_safe::Decomposition as core::fmt::Debug>::fmt::h4cb36b1bc76a44b4
  23:       0x86db889f8b - rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions::h6d992d2ac142b395
  24:       0x86db88a1c2 - rustc_trait_selection::traits::normalize_param_env_or_error::h6c082e5471b3c0d8
  25:       0x86da083bd1 - rustc_ty_utils::provide::hb69364e707605161
  26:       0x86dab833cc - <fixedbitset::FixedBitSet as core::fmt::Debug>::fmt::hedf20157683d04ae
  27:       0x86daeed260 - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_mark_green::h02f98d8f46101c14
  28:       0x86da05f805 - rustc_typeck::check::intrinsic::check_platform_intrinsic_type::h1f8cb0a40e4e11fe
  29:       0x86da05cece - rustc_typeck::check::intrinsic::check_platform_intrinsic_type::h1f8cb0a40e4e11fe
  30:       0x86dab4ff32 - <fixedbitset::FixedBitSet as core::fmt::Debug>::fmt::hedf20157683d04ae
  31:       0x86daeee981 - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_mark_green::h02f98d8f46101c14
  32:       0x86da066c9a - <rustc_typeck::check::wfcheck::CheckTypeWellFormedVisitor as rustc_hir::intravisit::Visitor>::visit_item::ha4fd906560a43a45
  33:       0x86d9fcee58 - <rustc_typeck::check::writeback::Resolver as rustc_middle::ty::fold::TypeFolder>::fold_const::he13d4a92cbd78022
  34:       0x86d9f89199 - <rustc_typeck::check::method::confirm::ConfirmResult as core::fmt::Debug>::fmt::h12133a562210cf53
  35:       0x86d9eb3d01 - <rustc_typeck::check::PlaceOp as core::fmt::Debug>::fmt::h8616b96de76e95b0
  36:       0x86d9e82ef1 - rustc_typeck::check_crate::h72808c5b688a43c3
  37:       0x86d7849bd2 - rustc_interface::passes::analysis::h213d2025de663219
  38:       0x86dab6cbd2 - <fixedbitset::FixedBitSet as core::fmt::Debug>::fmt::hedf20157683d04ae
  39:       0x86daee5afc - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_mark_green::h02f98d8f46101c14
  40:       0x86d775f28d - regex_syntax::hir::Error::pattern::h26de5cae1e560f3c
  41:       0x86d77297b5 - rustc_driver::pretty::print_after_hir_lowering::h8daab7168b9a121b
  42:       0x86d77614c7 - regex_syntax::hir::Error::pattern::h26de5cae1e560f3c
  43:       0x86d772dfc0 - <tracing_subscriber::util::TryInitError as core::fmt::Display>::fmt::h6e9774f2c0dd7eb3
  44:       0x86d772a248 - rustc_driver::pretty::print_after_hir_lowering::h8daab7168b9a121b
  45:       0x86d771e67d - <rustc_driver::Compilation as core::fmt::Debug>::fmt::ha388fa55e25fcec9
  46:     0x7ffd4de9a1cc - std::sys::windows::thread::Thread::new::h5ab92c811b2297f5
  47:     0x7ffd825213d2 - BaseThreadInitThunk
  48:     0x7ffd832754f4 - RtlUserThreadStart

[Alexendoo]

No longer ICEs since #92805

[cameron1024]

@rustbot claim

[AnthonyMikh]

Closing as it was fixed and have a regression test