[ICE] with const generics without feature

[leonardo-m]

fn foo<const N: usize>(x: &[u8; N]) -> &[u8; N - 1] {
    match x { [_, ref xs @ ..] => xs }
}
fn main() {}

Gives:

error[E0658]: const generics are unstable
 --> ...\test.rs:1:14
  |
1 | fn foo<const N: usize>(x: &[u8; N]) -> &[u8; N - 1] {
  |              ^
  |
  = note: see issue #74878 <https://github.com/rust-lang/rust/issues/74878> for more information
  = help: add `#![feature(min_const_generics)]` to the crate attributes to enable

error: internal compiler error: compiler\rustc_middle\src\ty\subst.rs:568:17: const parameter `N/#0` (Const { ty: usize, val: Param(N/#0) }/0) out of range when substituting substs=[]

thread 'rustc' panicked at 'Box<Any>', /rustc/1700ca07c6dd7becff85678409a5df6ad4cf4f47\compiler\rustc_errors\src\lib.rs:904:9
stack backtrace:
   0: std::panicking::begin_panic
   1: rustc_errors::HandlerInner::span_bug
   2: rustc_errors::Handler::span_bug
   3: rustc_middle::util::bug::opt_span_bug_fmt::{{closure}}
   4: rustc_middle::ty::context::tls::with_opt::{{closure}}
   5: rustc_middle::ty::context::tls::with_opt
   6: rustc_middle::util::bug::opt_span_bug_fmt
   7: rustc_middle::util::bug::span_bug_fmt
   8: <rustc_middle::ty::subst::SubstFolder as rustc_middle::ty::fold::TypeFolder>::fold_const
   9: rustc_middle::ty::normalize_erasing_regions::<impl rustc_middle::ty::context::TyCtxt>::subst_and_normalize_erasing_regions
  10: rustc_mir::interpret::operand::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_operand
  11: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_rvalue_into_place
  12: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::run
  13: rustc_mir::const_eval::eval_queries::eval_to_allocation_raw_provider
  14: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::eval_to_allocation_raw>::compute
  15: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  16: rustc_query_system::query::plumbing::get_query_impl
  17: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  18: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::eval_to_const_value_raw>::compute
  19: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  20: rustc_query_system::query::plumbing::get_query_impl
  21: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  22: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::eval_to_const_value_raw>::compute
  23: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  24: rustc_data_structures::stack::ensure_sufficient_stack
  25: rustc_query_system::query::plumbing::get_query_impl
  26: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_global_id
  27: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_resolve
  28: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_const
  29: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::TyS>::super_fold_with
  30: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  31: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::TyS>::super_fold_with
  32: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  33: rustc_middle::ty::util::fold_list
  34: rustc_trait_selection::traits::project::AssocTypeNormalizer::fold
  35: rustc_trait_selection::traits::project::normalize
  36: <rustc_infer::infer::InferCtxt as rustc_trait_selection::infer::InferCtxtExt>::partially_normalize_associated_types_in
  37: rustc_typeck::check::inherited::Inherited::normalize_associated_types_in
  38: rustc_infer::infer::InferCtxtBuilder::enter
  39: rustc_typeck::check::wfcheck::check_item_fn
  40: rustc_typeck::check::wfcheck::check_item_well_formed
  41: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::check_item_well_formed>::compute
  42: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  43: rustc_data_structures::stack::ensure_sufficient_stack
  44: rustc_query_system::query::plumbing::get_query_impl
  45: rustc_query_system::query::plumbing::ensure_query_impl
  46: rustc_data_structures::sync::par_for_each_in
  47: rustc_hir::hir::Crate::par_visit_all_item_likes
  48: rustc_session::session::Session::track_errors
  49: rustc_typeck::check_crate
  50: rustc_interface::passes::analysis
  51: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  52: rustc_query_system::dep_graph::graph::DepGraph<K>::with_eval_always_task
  53: rustc_data_structures::stack::ensure_sufficient_stack
  54: rustc_query_system::query::plumbing::get_query_impl
  55: rustc_interface::passes::QueryContext::enter
  56: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  57: rustc_span::with_source_map
  58: rustc_interface::interface::create_compiler_and_run
  59: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 1.50.0-nightly (1700ca07c 2020-12-08) running on x86_64-pc-windows-gnu

query stack during panic:
#0 [eval_to_allocation_raw] const-evaluating + checking `foo::{constant#1}`
#1 [eval_to_const_value_raw] simplifying constant for the type system `foo::{constant#1}`
#2 [eval_to_const_value_raw] simplifying constant for the type system `foo::{constant#1}`
#3 [check_item_well_formed] checking that `foo` is well-formed
#4 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.

[matthiaskrgr]

This crashes on stable as well, and even on 1.44.
@rustbot label regression-from-stable-to-stable

[apiraino]

Assigning P-medium as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.

[lcnr]

this is a duplicate of #67945

will be fixed with #[feature(min_const_generics)]