ICE initializing impl Fn() constant with closure

[rodrimati1992]

Code

#![feature(impl_trait_in_bindings)]
const _: impl Fn() = ||();

Meta

rustc --version --verbose:

1.45.0-nightly (2020-06-03 56daaf669ebc3d5083db)

Error output

warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes
 --> src/lib.rs:1:12
  |
1 | #![feature(impl_trait_in_bindings)]
  |            ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default
  = note: see issue #63065 <https://github.com/rust-lang/rust/issues/63065> for more information

error: internal compiler error: src/librustc_trait_selection/traits/structural_match.rs:216: unexpected type during structural-match checking: [closure@src/lib.rs:2:22: 2:31]

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:907:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.45.0-nightly (56daaf669 2020-06-03) 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

error: aborting due to previous error; 1 warning emitted

error: could not compile `playground`.

To learn more, run the command again with --verbose.

Backtrace

error: internal compiler error: src/librustc_trait_selection/traits/structural_match.rs:216: unexpected type during structural-match checking: [closure@src/lib.rs:2:22: 2:31]

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:907:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1076
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1537
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:490
  12: std::panicking::begin_panic
  13: rustc_errors::HandlerInner::bug
  14: rustc_errors::Handler::bug
  15: rustc_middle::util::bug::opt_span_bug_fmt::{{closure}}
  16: rustc_middle::ty::context::tls::with_opt::{{closure}}
  17: rustc_middle::ty::context::tls::with_opt
  18: rustc_middle::util::bug::opt_span_bug_fmt
  19: rustc_middle::util::bug::bug_fmt
  20: <rustc_trait_selection::traits::structural_match::Search as rustc_middle::ty::fold::TypeVisitor>::visit_ty
  21: rustc_middle::ty::context::GlobalCtxt::enter_local
  22: rustc_trait_selection::traits::structural_match::search_for_structural_match_violation
  23: <rustc_mir::transform::check_consts::qualifs::CustomEq as rustc_mir::transform::check_consts::qualifs::Qualif>::in_any_value_of_ty
  24: rustc_mir::transform::check_consts::validation::Validator::qualifs_in_return_place
  25: rustc_mir::transform::mir_const_qualif
  26: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_const_qualif>::compute
  27: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  28: rustc_query_system::query::plumbing::get_query_impl::{{closure}}
  29: rustc_query_system::query::plumbing::get_query_impl
  30: rustc_mir::transform::mir_validated
  31: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_validated>::compute
  32: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  33: rustc_query_system::query::plumbing::get_query_impl::{{closure}}
  34: rustc_query_system::query::plumbing::get_query_impl
  35: rustc_mir::borrow_check::mir_borrowck
  36: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_borrowck>::compute
  37: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  38: rustc_data_structures::stack::ensure_sufficient_stack
  39: rustc_query_system::query::plumbing::get_query_impl
  40: rustc_typeck::collect::type_of::find_opaque_ty_constraints::ConstraintLocator::check
  41: rustc_typeck::collect::type_of::find_opaque_ty_constraints
  42: rustc_typeck::collect::type_of::type_of
  43: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::type_of>::compute
  44: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  45: rustc_data_structures::stack::ensure_sufficient_stack
  46: rustc_query_system::query::plumbing::get_query_impl
  47: rustc_query_system::query::plumbing::ensure_query_impl
  48: <rustc_typeck::collect::CollectItemTypesVisitor as rustc_hir::intravisit::Visitor>::visit_item
  49: rustc_middle::hir::map::Map::visit_item_likes_in_module
  50: rustc_typeck::collect::collect_mod_item_types
  51: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::collect_mod_item_types>::compute
  52: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  53: rustc_data_structures::stack::ensure_sufficient_stack
  54: rustc_query_system::query::plumbing::get_query_impl
  55: rustc_query_system::query::plumbing::ensure_query_impl
  56: rustc_session::session::Session::track_errors
  57: rustc_typeck::check_crate
  58: rustc_interface::passes::analysis
  59: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  60: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  61: rustc_data_structures::stack::ensure_sufficient_stack
  62: rustc_query_system::query::plumbing::get_query_impl
  63: rustc_middle::ty::context::tls::enter_global
  64: rustc_interface::interface::run_compiler_in_existing_thread_pool
  65: rustc_ast::attr::with_globals
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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.45.0-nightly (56daaf669 2020-06-03) 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 [mir_const_qualif] const checking `_`
#1 [mir_validated] processing `_`
#2 [mir_borrowck] borrow-checking `_`
#3 [type_of] computing type of `_::{{opaque}}#0`
#4 [collect_mod_item_types] collecting item types in top-level module
#5 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error; 1 warning emitted

error: could not compile `playground`.