ICE: unexpected const !2: usize

[matthiaskrgr]

snippet:

#![feature(generic_const_exprs, with_negative_coherence)]

use std::ops::Mul;

pub trait Indices<const N: usize> {
    const NUM_ELEMS: usize;
}

impl<I: Indices<N>, J: Indices<N>, const N: usize> Mul for Tensor<I, N>
where
    I: Concat<J>,
    <I as Concat<J>>::Output: Indices<N>,
    [u8; I::NUM_ELEMS]: Sized,
    [u8; J::NUM_ELEMS]: Sized,
    [u8; <I as Concat<J>>::Output::NUM_ELEMS]: Sized,
{
}

pub trait Concat<J> {}

pub struct Tensor<I: Indices<N>, const N: usize> {}

impl<I: Indices<N>, J: Indices<N>, const N: usize> Mul for Tensor<I, N>
where
    I: Concat<J>,
    <I as Concat<J>>::Output: Indices<N>,
    [u8; I::NUM_ELEMS]: Sized,
    [u8; J::NUM_ELEMS]: Sized,
    [u8; <I as Concat<J>>::Output::NUM_ELEMS]: Sized,
{
}

Version information

rustc 1.78.0-nightly (a84bb95a1 2024-02-13)
binary: rustc
commit-hash: a84bb95a1f65bfe25038f188763a18e096a86ab2
commit-date: 2024-02-13
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 18.1.0

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error[E0576]: cannot find associated type `Output` in trait `Concat`
  --> /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:12:23
   |
12 |     <I as Concat<J>>::Output: Indices<N>,
   |                       ^^^^^^ not found in `Concat`

error[E0576]: cannot find associated type `Output` in trait `Concat`
  --> /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:15:28
   |
15 |     [u8; <I as Concat<J>>::Output::NUM_ELEMS]: Sized,
   |                            ^^^^^^ not found in `Concat`

error[E0576]: cannot find associated type `Output` in trait `Concat`
  --> /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:26:23
   |
26 |     <I as Concat<J>>::Output: Indices<N>,
   |                       ^^^^^^ not found in `Concat`

error[E0576]: cannot find associated type `Output` in trait `Concat`
  --> /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:29:28
   |
29 |     [u8; <I as Concat<J>>::Output::NUM_ELEMS]: Sized,
   |                            ^^^^^^ not found in `Concat`

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:1:12
  |
1 | #![feature(generic_const_exprs, with_negative_coherence)]
  |            ^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
  = note: `#[warn(incomplete_features)]` on by default

error[E0601]: `main` function not found in crate `mvce`
  --> /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:31:2
   |
31 | }
   |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs`

error[E0207]: the type parameter `J` is not constrained by the impl trait, self type, or predicates
 --> /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:9:21
  |
9 | impl<I: Indices<N>, J: Indices<N>, const N: usize> Mul for Tensor<I, N>
  |                     ^ unconstrained type parameter

error[E0207]: the type parameter `J` is not constrained by the impl trait, self type, or predicates
  --> /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:23:21
   |
23 | impl<I: Indices<N>, J: Indices<N>, const N: usize> Mul for Tensor<I, N>
   |                     ^ unconstrained type parameter

error: internal compiler error: compiler/rustc_infer/src/infer/freshen.rs:176:17: unexpected const !2: usize

thread 'rustc' panicked at compiler/rustc_middle/src/util/bug.rs:35:44:
Box<dyn Any>
stack backtrace:
   0:     0x7f8228f8d086 - std::backtrace_rs::backtrace::libunwind::trace::h350c9bbd0d629e5a
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f8228f8d086 - std::backtrace_rs::backtrace::trace_unsynchronized::hb5ce80cf0732c5cf
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f8228f8d086 - std::sys_common::backtrace::_print_fmt::he116d0f55fe00810
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f8228f8d086 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h71fa05f97c99f332
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f8228fdd51c - core::fmt::rt::Argument::fmt::hfafe0bdb999ad9e2
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/core/src/fmt/rt.rs:142:9
   5:     0x7f8228fdd51c - core::fmt::write::h6115470fc2d68b0c
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/core/src/fmt/mod.rs:1120:17
   6:     0x7f8228f80abf - std::io::Write::write_fmt::hdc66f4e88b29f74f
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/io/mod.rs:1854:15
   7:     0x7f8228f8ce34 - std::sys_common::backtrace::_print::hcb29a46764838669
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f8228f8ce34 - std::sys_common::backtrace::print::h05e4e1c5c9b1d560
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f8228f8fb7b - std::panicking::default_hook::{{closure}}::h8d5ead34896ab42d
  10:     0x7f8228f8f8c9 - std::panicking::default_hook::h78047fe2f192a868
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/panicking.rs:292:9
  11:     0x7f822bd463bc - std[466eff1cc2ed908f]::panicking::update_hook::<alloc[4ead1f6995f5264c]::boxed::Box<rustc_driver_impl[c431125988ed1f11]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7f8228f902e0 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hcfe839bef410f29b
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/alloc/src/boxed.rs:2030:9
  13:     0x7f8228f902e0 - std::panicking::rust_panic_with_hook::h1e5f7f410afd2444
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/panicking.rs:785:13
  14:     0x7f822bd73d24 - std[466eff1cc2ed908f]::panicking::begin_panic::<rustc_errors[1de830c8c65656ce]::ExplicitBug>::{closure#0}
  15:     0x7f822bd70c36 - std[466eff1cc2ed908f]::sys_common::backtrace::__rust_end_short_backtrace::<std[466eff1cc2ed908f]::panicking::begin_panic<rustc_errors[1de830c8c65656ce]::ExplicitBug>::{closure#0}, !>
  16:     0x7f822bd70636 - std[466eff1cc2ed908f]::panicking::begin_panic::<rustc_errors[1de830c8c65656ce]::ExplicitBug>
  17:     0x7f822bd7f671 - <rustc_errors[1de830c8c65656ce]::diagnostic_builder::BugAbort as rustc_errors[1de830c8c65656ce]::diagnostic_builder::EmissionGuarantee>::emit_producing_guarantee
  18:     0x7f822c138b6e - <rustc_errors[1de830c8c65656ce]::DiagCtxt>::bug::<alloc[4ead1f6995f5264c]::string::String>
  19:     0x7f822c1d265b - rustc_middle[80ff7a15503a7fbe]::util::bug::opt_span_bug_fmt::<rustc_span[f008fc136599d052]::span_encoding::Span>::{closure#0}
  20:     0x7f822c1b9ffa - rustc_middle[80ff7a15503a7fbe]::ty::context::tls::with_opt::<rustc_middle[80ff7a15503a7fbe]::util::bug::opt_span_bug_fmt<rustc_span[f008fc136599d052]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7f822c1b9e98 - rustc_middle[80ff7a15503a7fbe]::ty::context::tls::with_context_opt::<rustc_middle[80ff7a15503a7fbe]::ty::context::tls::with_opt<rustc_middle[80ff7a15503a7fbe]::util::bug::opt_span_bug_fmt<rustc_span[f008fc136599d052]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7f822a6a9470 - rustc_middle[80ff7a15503a7fbe]::util::bug::bug_fmt
  23:     0x7f822d3dd2af - <rustc_infer[fc90b6d353db46a7]::infer::freshen::TypeFreshener as rustc_type_ir[ebc5bf0fdfdb0d04]::fold::TypeFolder<rustc_middle[80ff7a15503a7fbe]::ty::context::TyCtxt>>::fold_const
  24:     0x7f822a693797 - <rustc_trait_selection[4b445828abf7ba1d]::traits::select::SelectionContext>::poly_select
  25:     0x7f822d29381f - rustc_traits[ab147ed71eb77be]::codegen::codegen_select_candidate
  26:     0x7f822d2932ef - rustc_query_impl[56a5a1cad20ac6aa]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[56a5a1cad20ac6aa]::query_impl::codegen_select_candidate::dynamic_query::{closure#2}::{closure#0}, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 16usize]>>
  27:     0x7f822d292824 - rustc_query_system[790ca29724b87fee]::query::plumbing::try_execute_query::<rustc_query_impl[56a5a1cad20ac6aa]::DynamicConfig<rustc_query_system[790ca29724b87fee]::query::caches::DefaultCache<(rustc_middle[80ff7a15503a7fbe]::ty::ParamEnv, rustc_middle[80ff7a15503a7fbe]::ty::predicate::TraitRef), rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[56a5a1cad20ac6aa]::plumbing::QueryCtxt, false>
  28:     0x7f822d2924dd - rustc_query_impl[56a5a1cad20ac6aa]::query_impl::codegen_select_candidate::get_query_non_incr::__rust_end_short_backtrace
  29:     0x7f822aa2daf7 - rustc_ty_utils[1f3d0eb1fe395dcd]::instance::resolve_instance
  30:     0x7f822d24acc5 - rustc_query_impl[56a5a1cad20ac6aa]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[56a5a1cad20ac6aa]::query_impl::resolve_instance::dynamic_query::{closure#2}::{closure#0}, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 32usize]>>
  31:     0x7f822d24b004 - rustc_query_system[790ca29724b87fee]::query::plumbing::try_execute_query::<rustc_query_impl[56a5a1cad20ac6aa]::DynamicConfig<rustc_query_system[790ca29724b87fee]::query::caches::DefaultCache<rustc_middle[80ff7a15503a7fbe]::ty::ParamEnvAnd<(rustc_span[f008fc136599d052]::def_id::DefId, &rustc_middle[80ff7a15503a7fbe]::ty::list::List<rustc_middle[80ff7a15503a7fbe]::ty::generic_args::GenericArg>)>, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 32usize]>>, false, false, false>, rustc_query_impl[56a5a1cad20ac6aa]::plumbing::QueryCtxt, false>
  32:     0x7f822d24ac5d - rustc_query_impl[56a5a1cad20ac6aa]::query_impl::resolve_instance::get_query_non_incr::__rust_end_short_backtrace
  33:     0x7f822b223c71 - <rustc_middle[80ff7a15503a7fbe]::ty::context::TyCtxt>::const_eval_resolve
  34:     0x7f822de55553 - rustc_const_eval[b73c79410a5da8b8]::const_eval::eval_queries::eval_body_using_ecx::{closure#0}
  35:     0x7f822de52870 - rustc_const_eval[b73c79410a5da8b8]::const_eval::eval_queries::eval_in_interpreter
  36:     0x7f822d55771a - rustc_const_eval[b73c79410a5da8b8]::const_eval::eval_queries::eval_to_allocation_raw_provider
  37:     0x7f822d557576 - rustc_query_impl[56a5a1cad20ac6aa]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[56a5a1cad20ac6aa]::query_impl::eval_to_allocation_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 24usize]>>
  38:     0x7f822d8b2451 - rustc_query_system[790ca29724b87fee]::query::plumbing::try_execute_query::<rustc_query_impl[56a5a1cad20ac6aa]::DynamicConfig<rustc_query_system[790ca29724b87fee]::query::caches::DefaultCache<rustc_middle[80ff7a15503a7fbe]::ty::ParamEnvAnd<rustc_middle[80ff7a15503a7fbe]::mir::interpret::GlobalId>, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[56a5a1cad20ac6aa]::plumbing::QueryCtxt, false>
  39:     0x7f822d8b202c - rustc_query_impl[56a5a1cad20ac6aa]::query_impl::eval_to_allocation_raw::get_query_non_incr::__rust_end_short_backtrace
  40:     0x7f822dd1e114 - rustc_const_eval[b73c79410a5da8b8]::const_eval::valtrees::eval_to_valtree
  41:     0x7f822dd1df30 - <rustc_const_eval[b73c79410a5da8b8]::provide::{closure#0} as core[16c6da236be526b4]::ops::function::FnOnce<(rustc_middle[80ff7a15503a7fbe]::ty::context::TyCtxt, rustc_middle[80ff7a15503a7fbe]::ty::ParamEnvAnd<rustc_middle[80ff7a15503a7fbe]::mir::interpret::GlobalId>)>>::call_once
  42:     0x7f822dd1df04 - rustc_query_impl[56a5a1cad20ac6aa]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[56a5a1cad20ac6aa]::query_impl::eval_to_valtree::dynamic_query::{closure#2}::{closure#0}, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 24usize]>>
  43:     0x7f822dd1dec5 - <rustc_query_impl[56a5a1cad20ac6aa]::query_impl::eval_to_valtree::dynamic_query::{closure#2} as core[16c6da236be526b4]::ops::function::FnOnce<(rustc_middle[80ff7a15503a7fbe]::ty::context::TyCtxt, rustc_middle[80ff7a15503a7fbe]::ty::ParamEnvAnd<rustc_middle[80ff7a15503a7fbe]::mir::interpret::GlobalId>)>>::call_once
  44:     0x7f822d8b252c - rustc_query_system[790ca29724b87fee]::query::plumbing::try_execute_query::<rustc_query_impl[56a5a1cad20ac6aa]::DynamicConfig<rustc_query_system[790ca29724b87fee]::query::caches::DefaultCache<rustc_middle[80ff7a15503a7fbe]::ty::ParamEnvAnd<rustc_middle[80ff7a15503a7fbe]::mir::interpret::GlobalId>, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[56a5a1cad20ac6aa]::plumbing::QueryCtxt, false>
  45:     0x7f822d8b1e2c - rustc_query_impl[56a5a1cad20ac6aa]::query_impl::eval_to_valtree::get_query_non_incr::__rust_end_short_backtrace
  46:     0x7f822d9abeee - rustc_middle[80ff7a15503a7fbe]::query::plumbing::query_get_at::<rustc_query_system[790ca29724b87fee]::query::caches::DefaultCache<rustc_middle[80ff7a15503a7fbe]::ty::ParamEnvAnd<rustc_middle[80ff7a15503a7fbe]::mir::interpret::GlobalId>, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 24usize]>>>
  47:     0x7f822d9abb19 - <rustc_middle[80ff7a15503a7fbe]::ty::context::TyCtxt>::const_eval_global_id_for_typeck
  48:     0x7f822d9ab39e - <rustc_middle[80ff7a15503a7fbe]::ty::context::TyCtxt>::const_eval_resolve_for_typeck
  49:     0x7f822c02d826 - <rustc_infer[fc90b6d353db46a7]::infer::InferCtxt>::const_eval_resolve
  50:     0x7f822c00fafa - <rustc_infer[fc90b6d353db46a7]::infer::InferCtxt>::try_const_eval_resolve
  51:     0x7f822c7c37a5 - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::try_const_eval_resolve
  52:     0x7f822c7d1278 - <rustc_trait_selection[4b445828abf7ba1d]::solve::search_graph::SearchGraph>::with_new_goal::<<rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_canonical_goal::{closure#0}::{closure#0}::{closure#0}>::{closure#3}
  53:     0x7f822c7ce013 - <rustc_trait_selection[4b445828abf7ba1d]::solve::search_graph::SearchGraph>::with_new_goal::<<rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_canonical_goal::{closure#0}::{closure#0}::{closure#0}>
  54:     0x7f822c7c2478 - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_goal
  55:     0x7f822c83379f - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::try_evaluate_added_goals
  56:     0x7f822c830c8d - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::try_normalize_term
  57:     0x7f822c7d1d65 - <rustc_trait_selection[4b445828abf7ba1d]::solve::search_graph::SearchGraph>::with_new_goal::<<rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_canonical_goal::{closure#0}::{closure#0}::{closure#0}>::{closure#3}
  58:     0x7f822c7ce013 - <rustc_trait_selection[4b445828abf7ba1d]::solve::search_graph::SearchGraph>::with_new_goal::<<rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_canonical_goal::{closure#0}::{closure#0}::{closure#0}>
  59:     0x7f822c7c2478 - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_goal
  60:     0x7f822c83379f - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::try_evaluate_added_goals
  61:     0x7f822c8310f1 - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_added_goals_and_make_canonical_response
  62:     0x7f822c7d5d21 - <rustc_middle[80ff7a15503a7fbe]::ty::predicate::TraitPredicate as rustc_trait_selection[4b445828abf7ba1d]::solve::assembly::GoalKind>::probe_and_match_goal_against_assumption::<<rustc_middle[80ff7a15503a7fbe]::ty::predicate::TraitPredicate as rustc_trait_selection[4b445828abf7ba1d]::solve::assembly::GoalKind>::consider_implied_clause<[rustc_middle[80ff7a15503a7fbe]::traits::solve::Goal<rustc_middle[80ff7a15503a7fbe]::ty::predicate::Predicate>; 0usize]>::{closure#0}>
  63:     0x7f822c830d18 - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::assemble_param_env_candidates::<rustc_middle[80ff7a15503a7fbe]::ty::predicate::TraitPredicate>
  64:     0x7f822c7b9055 - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::assemble_and_evaluate_candidates::<rustc_middle[80ff7a15503a7fbe]::ty::predicate::TraitPredicate>
  65:     0x7f822c7d197b - <rustc_trait_selection[4b445828abf7ba1d]::solve::search_graph::SearchGraph>::with_new_goal::<<rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_canonical_goal::{closure#0}::{closure#0}::{closure#0}>::{closure#3}
  66:     0x7f822c7ce013 - <rustc_trait_selection[4b445828abf7ba1d]::solve::search_graph::SearchGraph>::with_new_goal::<<rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_canonical_goal::{closure#0}::{closure#0}::{closure#0}>
  67:     0x7f822c7c2478 - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::evaluate_goal
  68:     0x7f822c7c1e6c - <rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::EvalCtxt>::enter_root::<core[16c6da236be526b4]::result::Result<(bool, rustc_middle[80ff7a15503a7fbe]::traits::solve::Certainty, alloc[4ead1f6995f5264c]::vec::Vec<rustc_middle[80ff7a15503a7fbe]::traits::solve::Goal<rustc_middle[80ff7a15503a7fbe]::ty::predicate::Predicate>>), rustc_middle[80ff7a15503a7fbe]::traits::query::NoSolution>, <rustc_infer[fc90b6d353db46a7]::infer::InferCtxt as rustc_trait_selection[4b445828abf7ba1d]::solve::eval_ctxt::InferCtxtEvalExt>::evaluate_root_goal::{closure#0}>
  69:     0x7f822c7c3ff3 - <rustc_trait_selection[4b445828abf7ba1d]::solve::fulfill::FulfillmentCtxt as rustc_infer[fc90b6d353db46a7]::traits::engine::TraitEngine>::select_where_possible
  70:     0x7f822d2911a5 - <rustc_trait_selection[4b445828abf7ba1d]::traits::engine::ObligationCtxt>::select_all_or_error
  71:     0x7f822c7e0837 - rustc_trait_selection[4b445828abf7ba1d]::traits::coherence::impl_intersection_has_negative_obligation
  72:     0x7f822d2406a6 - rustc_trait_selection[4b445828abf7ba1d]::traits::coherence::overlap
  73:     0x7f822da3d42b - <rustc_middle[80ff7a15503a7fbe]::traits::specialization_graph::Children as rustc_trait_selection[4b445828abf7ba1d]::traits::specialize::specialization_graph::ChildrenExt>::insert
  74:     0x7f822da3c991 - <rustc_middle[80ff7a15503a7fbe]::traits::specialization_graph::Graph as rustc_trait_selection[4b445828abf7ba1d]::traits::specialize::specialization_graph::GraphExt>::insert
  75:     0x7f822da3fb77 - rustc_trait_selection[4b445828abf7ba1d]::traits::specialize::specialization_graph_provider
  76:     0x7f822da3f60d - rustc_query_impl[56a5a1cad20ac6aa]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[56a5a1cad20ac6aa]::query_impl::specialization_graph_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 8usize]>>
  77:     0x7f822d0827a0 - rustc_query_system[790ca29724b87fee]::query::plumbing::try_execute_query::<rustc_query_impl[56a5a1cad20ac6aa]::DynamicConfig<rustc_query_system[790ca29724b87fee]::query::caches::DefIdCache<rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[56a5a1cad20ac6aa]::plumbing::QueryCtxt, false>
  78:     0x7f822d583f9e - rustc_query_impl[56a5a1cad20ac6aa]::query_impl::specialization_graph_of::get_query_non_incr::__rust_end_short_backtrace
  79:     0x7f822d58438d - rustc_hir_analysis[46d1d11b50942035]::coherence::coherent_trait
  80:     0x7f822d584135 - rustc_query_impl[56a5a1cad20ac6aa]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[56a5a1cad20ac6aa]::query_impl::coherent_trait::dynamic_query::{closure#2}::{closure#0}, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 1usize]>>
  81:     0x7f822d0f2a16 - rustc_query_system[790ca29724b87fee]::query::plumbing::try_execute_query::<rustc_query_impl[56a5a1cad20ac6aa]::DynamicConfig<rustc_query_system[790ca29724b87fee]::query::caches::DefIdCache<rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[56a5a1cad20ac6aa]::plumbing::QueryCtxt, false>
  82:     0x7f822d615e55 - rustc_query_impl[56a5a1cad20ac6aa]::query_impl::coherent_trait::get_query_non_incr::__rust_end_short_backtrace
  83:     0x7f822d1c8396 - rustc_hir_analysis[46d1d11b50942035]::check_crate
  84:     0x7f822d9e8c13 - rustc_interface[b495b14b2a666c1a]::passes::analysis
  85:     0x7f822d9e8869 - rustc_query_impl[56a5a1cad20ac6aa]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[56a5a1cad20ac6aa]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 1usize]>>
  86:     0x7f822daaf3a5 - rustc_query_system[790ca29724b87fee]::query::plumbing::try_execute_query::<rustc_query_impl[56a5a1cad20ac6aa]::DynamicConfig<rustc_query_system[790ca29724b87fee]::query::caches::SingleCache<rustc_middle[80ff7a15503a7fbe]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[56a5a1cad20ac6aa]::plumbing::QueryCtxt, false>
  87:     0x7f822daaf109 - rustc_query_impl[56a5a1cad20ac6aa]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  88:     0x7f822dcea77b - rustc_interface[b495b14b2a666c1a]::interface::run_compiler::<core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>, rustc_driver_impl[c431125988ed1f11]::run_compiler::{closure#0}>::{closure#0}
  89:     0x7f822df7e854 - std[466eff1cc2ed908f]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[b495b14b2a666c1a]::util::run_in_thread_with_globals<rustc_interface[b495b14b2a666c1a]::util::run_in_thread_pool_with_globals<rustc_interface[b495b14b2a666c1a]::interface::run_compiler<core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>, rustc_driver_impl[c431125988ed1f11]::run_compiler::{closure#0}>::{closure#0}, core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>>::{closure#0}, core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>>
  90:     0x7f822df7e680 - <<std[466eff1cc2ed908f]::thread::Builder>::spawn_unchecked_<rustc_interface[b495b14b2a666c1a]::util::run_in_thread_with_globals<rustc_interface[b495b14b2a666c1a]::util::run_in_thread_pool_with_globals<rustc_interface[b495b14b2a666c1a]::interface::run_compiler<core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>, rustc_driver_impl[c431125988ed1f11]::run_compiler::{closure#0}>::{closure#0}, core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>>::{closure#0}, core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[16c6da236be526b4]::result::Result<(), rustc_span[f008fc136599d052]::ErrorGuaranteed>>::{closure#1} as core[16c6da236be526b4]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  91:     0x7f8228f99425 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hf2f3f78227db386b
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/alloc/src/boxed.rs:2016:9
  92:     0x7f8228f99425 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hfde7215efc7d46f6
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/alloc/src/boxed.rs:2016:9
  93:     0x7f8228f99425 - std::sys::pal::unix::thread::Thread::new::thread_start::hca4f71b4c325cea0
                               at /rustc/a84bb95a1f65bfe25038f188763a18e096a86ab2/library/std/src/sys/pal/unix/thread.rs:108:17
  94:     0x7f8228d819eb - <unknown>
  95:     0x7f8228e057cc - <unknown>
  96:                0x0 - <unknown>

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 1.78.0-nightly (a84bb95a1 2024-02-13) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [codegen_select_candidate] computing candidate for `<!1 as Indices<!2>>`
#1 [resolve_instance] resolving instance `<!1 as Indices<!2>>::NUM_ELEMS`
#2 [eval_to_allocation_raw] const-evaluating + checking `<impl at /tmp/icemaker_global_tempdir.JmhHu65RE3t8/rustc_testrunner_tmpdir_reporting.SAuTnLQ72a4e/mvce.rs:9:1: 15:54>::{constant#1}`
#3 [eval_to_valtree] evaluating type-level constant
#4 [specialization_graph_of] building specialization graph of trait `core::ops::arith::Mul`
#5 [coherent_trait] coherence checking all impls of trait `core::ops::arith::Mul`
#6 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 8 previous errors; 1 warning emitted

Some errors have detailed explanations: E0207, E0576, E0601.
For more information about an error, try `rustc --explain E0207`.

[matthiaskrgr]

This bisects to #120836 cc @lcnr 🤔

[lcnr]

the new solver ends up calling into the old one via const evaluation 😅 the old solver cannot handle placeholder consts 🤔 🤷

i think this can impact -Znext-solver=coherence by itself, cc @compiler-errors

[lcnr]

though, given that it relies on gce this seems alright to delay until after the stabilization