Closure in array length ICE's

[DutchGhost]

The following ICE's in beta and nightly:

struct Bug {
    a: [(); (|| { 0 })()]
}

Backtrace:

Compiling playground v0.0.1 (/playground)
error[E0015]: calls in constants are limited to constant functions, tuple structs and tuple variants
 --> src/lib.rs:2:13
  |
2 |     a: [(); (|| { 0 })()]
  |             ^^^^^^^^^^^^

error: internal compiler error: src/librustc_typeck/collect.rs:1969: to get the signature of a closure, use `closure_sig()` not `fn_sig()`

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:882:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.1485827954.workers.dev-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.1485827954.workers.dev-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:77
   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:1052
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1426
   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:204
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:224
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:476
  12: std::panicking::begin_panic
  13: rustc_errors::HandlerInner::bug
  14: rustc_errors::Handler::bug
  15: rustc::util::bug::opt_span_bug_fmt::{{closure}}
  16: rustc::ty::context::tls::with_opt::{{closure}}
  17: rustc::ty::context::tls::with_opt
  18: rustc::util::bug::opt_span_bug_fmt
  19: rustc::util::bug::bug_fmt
  20: rustc_typeck::collect::fn_sig
  21: rustc::ty::query::__query_compute::fn_sig
  22: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  23: rustc_mir::const_eval::fn_queries::provide::is_const_fn_raw
  24: rustc::ty::query::__query_compute::is_const_fn_raw
  25: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  26: <rustc_mir::const_eval::machine::CompileTimeInterpreter as rustc_mir::interpret::machine::Machine>::find_mir_or_eval_fn
  27: rustc_mir::interpret::terminator::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_fn_call
  28: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::step
  29: rustc_mir::const_eval::eval_queries::const_eval_raw_provider
  30: rustc::ty::query::__query_compute::const_eval_raw
  31: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  32: rustc_mir::const_eval::eval_queries::const_eval_validated_provider
  33: rustc::ty::query::__query_compute::const_eval_validated
  34: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  35: rustc_mir::const_eval::eval_queries::const_eval_validated_provider
  36: rustc::ty::query::__query_compute::const_eval_validated
  37: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::const_eval_validated>::compute
  38: rustc::dep_graph::graph::DepGraph::with_task_impl
  39: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  40: rustc::mir::interpret::queries::<impl rustc::ty::context::TyCtxt>::const_eval_instance
  41: rustc::mir::interpret::queries::<impl rustc::ty::context::TyCtxt>::const_eval_resolve
  42: <rustc::traits::project::AssocTypeNormalizer as rustc::ty::fold::TypeFolder>::fold_const
  43: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::TyS>::super_fold_with
  44: <rustc::traits::project::AssocTypeNormalizer as rustc::ty::fold::TypeFolder>::fold_ty
  45: rustc::traits::project::normalize
  46: rustc_typeck::check::FnCtxt::normalize_associated_types_in
  47: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  48: rustc::ty::context::GlobalCtxt::enter_local
  49: rustc_typeck::check::wfcheck::check_item_well_formed
  50: rustc::ty::query::__query_compute::check_item_well_formed
  51: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::check_item_well_formed>::compute
  52: rustc::dep_graph::graph::DepGraph::with_task_impl
  53: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  54: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::ensure_query
  55: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:86
  56: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  57: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:86
  58: rustc_hir::hir::Crate::par_visit_all_item_likes
  59: rustc_typeck::check_crate
  60: rustc_interface::passes::analysis
  61: rustc::ty::query::__query_compute::analysis
  62: rustc::dep_graph::graph::DepGraph::with_task_impl
  63: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  64: rustc::ty::context::tls::enter_global
  65: rustc_interface::interface::run_compiler_in_existing_thread_pool
  66: scoped_tls::ScopedKey<T>::set
  67: syntax::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 1.42.0-nightly (c2d141df5 2020-01-24) running on x86_64-unknown-linux-gnu

note: compiler flags: -C opt-level=3 -C codegen-units=1 --crate-type lib

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [fn_sig] processing `Bug::a::{{constant}}#0::{{closure}}#0`
#1 [is_const_fn_raw] checking if item is const fn: `Bug::a::{{constant}}#0::{{closure}}#0`
#2 [const_eval_raw] const-evaluating `Bug::a::{{constant}}#0`
#3 [const_eval_validated] const-evaluating + checking `Bug::a::{{constant}}#0`
#4 [const_eval_validated] const-evaluating + checking `Bug::a::{{constant}}#0`
#5 [check_item_well_formed] processing `Bug`
#6 [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 E0015`.
error: could not compile `playground`.

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