Repository: rust
Issue: ICE: cannot relate bound region: ReLateBound
Labels: E-needs-test,T-compiler,C-bug,A-const-generics,requires-nightly,F-const_generics,glacier

<!--
Thank you for finding an Internal Compiler Error! 🧊  If possible, try to provide
a minimal verifiable example. You can read "Rust Bug Minimization Patterns" for
how to create smaller examples.

http://blog.pnkfx.org/blog/2019/11/18/rust-bug-minimization-patterns/

-->

### Code

```Rust
trait MyTrait<T> {}

fn bug<'a, T>() -> &'static dyn MyTrait<[(); { |x: &'a u32| { x }; 4 }]> {
    todo!()
}
```


### Meta
<!--
If you're using the stable version of the compiler, you should also check if the
bug also exists in the beta or nightly versions.
-->

`rustc --version --verbose`:
```
rustc 1.46.0 (04488afe3 2020-08-24)
rustc 1.47.0-beta.5 (9f0e6fa94 2020-09-29)
rustc 1.48.0-nightly (381b445ff 2020-09-29)
```

### Error output

```
error: internal compiler error: compiler/rustc_infer/src/infer/region_constraints/mod.rs:576:17: cannot relate bound region: ReLateBound(DebruijnIndex(1), BrNamed(DefId(0:6 ~ playground[efd4]::bug::'a), 'a)) <= '_#1r
```

<!--
Include a backtrace in the code block by setting `RUST_BACKTRACE=1` in your
environment. E.g. `RUST_BACKTRACE=1 cargo build`.
-->
<details><summary><strong>Backtrace</strong></summary>
<p>

```
thread 'rustc' panicked at 'Box<Any>', /rustc/381b445ff5751f9f39ec672b623372dff09c276e/compiler/rustc_errors/src/lib.rs:891:9
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_infer::infer::region_constraints::RegionConstraintCollector::make_subregion
   9: rustc_infer::infer::region_constraints::RegionConstraintCollector::make_eqregion
  10: <rustc_infer::infer::equate::Equate as rustc_middle::ty::relate::TypeRelation>::regions
  11: rustc_middle::ty::relate::super_relate_tys
  12: rustc_infer::infer::combine::<impl rustc_infer::infer::InferCtxt>::super_combine_tys
  13: <rustc_infer::infer::equate::Equate as rustc_middle::ty::relate::TypeRelation>::tys
  14: <rustc_middle::ty::subst::GenericArg as rustc_middle::ty::relate::Relate>::relate
  15: <core::result::Result<T,E> as rustc_middle::ty::context::InternIteratorElement<T,R>>::intern_with
  16: <rustc_middle::ty::sty::TraitRef as rustc_middle::ty::relate::Relate>::relate
  17: rustc_infer::infer::InferCtxt::commit_if_ok
  18: rustc_trait_selection::traits::select::SelectionContext::match_impl
  19: rustc_infer::infer::InferCtxt::probe
  20: rustc_middle::ty::trait_def::<impl rustc_middle::ty::context::TyCtxt>::for_each_relevant_impl
  21: rustc_trait_selection::traits::select::candidate_assembly::<impl rustc_trait_selection::traits::select::SelectionContext>::assemble_candidates_from_impls
  22: rustc_trait_selection::traits::select::candidate_assembly::<impl rustc_trait_selection::traits::select::SelectionContext>::assemble_candidates
  23: rustc_trait_selection::traits::select::SelectionContext::candidate_from_obligation_no_cache
  24: rustc_query_system::dep_graph::graph::DepGraph<K>::with_anon_task
  25: rustc_trait_selection::traits::select::candidate_assembly::<impl rustc_trait_selection::traits::select::SelectionContext>::candidate_from_obligation
  26: rustc_trait_selection::traits::select::SelectionContext::select
  27: rustc_typeck::check::coercion::Coerce::coerce
  28: rustc_infer::infer::InferCtxt::commit_if_ok
  29: rustc_typeck::check::coercion::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::try_coerce
  30: rustc_typeck::check::coercion::CoerceMany<E>::coerce_inner
  31: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_return_expr
  32: rustc_typeck::check::check::check_fn
  33: rustc_typeck::check::closure::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_closure
  34: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  35: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  36: rustc_typeck::check::fn_ctxt::FnCtxt::check_stmt
  37: rustc_typeck::check::fn_ctxt::FnCtxt::check_block_with_expected
  38: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  39: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  40: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_coercable_to_type
  41: rustc_infer::infer::InferCtxtBuilder::enter
  42: rustc_typeck::check::typeck
  43: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  44: rustc_data_structures::stack::ensure_sufficient_stack
  45: rustc_query_system::query::plumbing::get_query_impl
  46: rustc_middle::ty::context::TyCtxt::typeck_opt_const_arg
  47: rustc_mir::const_eval::eval_queries::eval_to_allocation_raw_provider
  48: 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
  49: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  50: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  51: rustc_query_system::query::plumbing::get_query_impl
  52: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  53: 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
  54: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  55: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  56: rustc_query_system::query::plumbing::get_query_impl
  57: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  58: 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
  59: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  60: rustc_data_structures::stack::ensure_sufficient_stack
  61: rustc_query_system::query::plumbing::get_query_impl
  62: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_global_id
  63: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_resolve
  64: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_const
  65: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::TyS>::super_fold_with
  66: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  67: rustc_middle::ty::fold::TypeFoldable::fold_with
  68: rustc_middle::ty::structural_impls::fold_list
  69: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::TyS>::super_fold_with
  70: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  71: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::TyS>::super_fold_with
  72: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  73: rustc_middle::ty::structural_impls::fold_list
  74: rustc_trait_selection::traits::project::AssocTypeNormalizer::fold
  75: rustc_trait_selection::traits::project::normalize
  76: <rustc_infer::infer::InferCtxt as rustc_trait_selection::infer::InferCtxtExt>::partially_normalize_associated_types_in
  77: rustc_typeck::check::inherited::Inherited::normalize_associated_types_in
  78: rustc_infer::infer::InferCtxtBuilder::enter
  79: rustc_typeck::check::wfcheck::check_item_well_formed
  80: 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
  81: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  82: rustc_data_structures::stack::ensure_sufficient_stack
  83: rustc_query_system::query::plumbing::get_query_impl
  84: rustc_query_system::query::plumbing::ensure_query_impl
  85: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  86: rustc_hir::hir::Crate::par_visit_all_item_likes
  87: rustc_session::session::Session::track_errors
  88: rustc_typeck::check_crate
  89: rustc_interface::passes::analysis
  90: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  91: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
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 1.48.0-nightly (381b445ff 2020-09-29) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2 --crate-type lib

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [typeck] type-checking `bug::{constant#0}`
#1 [eval_to_allocation_raw] const-evaluating + checking `bug::{constant#0}`
#2 [eval_to_const_value_raw] simplifying constant for the type system `bug::{constant#0}`
#3 [eval_to_const_value_raw] simplifying constant for the type system `bug::{constant#0}`
#4 [check_item_well_formed] checking that `bug` is well-formed
#5 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

error: could not compile `playground`
```

</p>
</details>

Maybe related to https://github.com/rust-lang/rust/issues/73375 , https://github.com/rust-lang/rust/issues/75883 and https://github.com/rust-lang/rust/issues/66152 ? Feel free to close if so :)