HRTB closure ICE

[DutchGhost]

Returning a Higher Ranked Trait Bound closure ICE's on stable (1.28), beta and nightly:

fn bug() -> impl for <'r> Fn() -> &'r () { || { &() } }

fn main() {
    let f = bug();
}

Backtrace:

error: internal compiler error: librustc/infer/higher_ranked/mod.rs:160: no representative region for `ReSkolemized(UniverseIndex(2), BrAnon(1))` in `{ReSkolemized(UniverseIndex(2), BrAnon(1))}`

thread 'main' panicked at 'Box<Any>', librustc_errors/lib.rs:554:9
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:71
             at libstd/sys_common/backtrace.rs:59
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:211
   3: std::panicking::default_hook
             at libstd/panicking.rs:227
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:515
   6: std::panicking::begin_panic
   7: rustc_errors::Handler::bug
   8: rustc::session::opt_span_bug_fmt::{{closure}}
   9: rustc::ty::context::tls::with_opt::{{closure}}
  10: rustc::ty::context::tls::with_context_opt
  11: rustc::ty::context::tls::with_opt
  12: rustc::session::opt_span_bug_fmt
  13: rustc::session::bug_fmt
  14: rustc::infer::higher_ranked::<impl rustc::infer::combine::CombineFields<'a, 'gcx, 'tcx>>::higher_ranked_match::{{closure}}::{{closure}}::{{closure}}
  15: <std::collections::hash::map::HashMap<K, V, S> as core::iter::traits::FromIterator<(K, V)>>::from_iter
  16: rustc::infer::InferCtxt::commit_if_ok
  17: rustc::infer::InferCtxt::match_poly_projection_predicate
  18: rustc::traits::project::confirm_param_env_candidate
  19: rustc::traits::project::confirm_callable_candidate
  20: rustc::traits::project::opt_normalize_projection_type
  21: rustc::traits::project::project_and_unify_type
  22: rustc::infer::InferCtxt::commit_if_ok
  23: <rustc::traits::fulfill::FulfillmentContext<'tcx> as rustc::traits::engine::TraitEngine<'tcx>>::select_where_possible
  24: rustc_typeck::check::FnCtxt::select_obligations_where_possible
  25: rustc::ty::context::tls::with_related_context
  26: rustc::infer::InferCtxtBuilder::enter
  27: rustc_typeck::check::typeck_tables_of
  28: rustc::ty::query::__query_compute::typeck_tables_of
  29: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_tables_of<'tcx>>::compute
  30: rustc::dep_graph::graph::DepGraph::with_task_impl
  31: rustc::ty::context::tls::with_related_context
  32: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job
  33: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
  34: rustc::ty::query::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::typeck_tables_of
  35: rustc_typeck::collect::type_of
  36: rustc::ty::query::__query_compute::type_of
  37: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::type_of<'tcx>>::compute
  38: rustc::dep_graph::graph::DepGraph::with_task_impl
  39: rustc::ty::context::tls::with_related_context
  40: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job
  41: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
  42: rustc::ty::query::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::type_of
  43: <rustc_typeck::collect::CollectItemTypesVisitor<'a, 'tcx> as rustc::hir::intravisit::Visitor<'tcx>>::visit_item
  44: rustc::hir::Crate::visit_all_item_likes
  45: rustc::session::Session::track_errors
  46: rustc_typeck::check_crate
  47: rustc::ty::context::tls::enter_context
  48: <std::thread::local::LocalKey<T>>::with
  49: rustc::ty::context::TyCtxt::create_and_enter
  50: rustc_driver::driver::compile_input
  51: rustc_driver::run_compiler_with_pool
  52: <scoped_tls::ScopedKey<T>>::set
  53: syntax::with_globals
  54: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  55: __rust_maybe_catch_panic
             at libpanic_unwind/lib.rs:105
  56: rustc_driver::run
  57: rustc_driver::main
  58: std::rt::lang_start::{{closure}}
  59: std::panicking::try::do_call
             at libstd/rt.rs:59
             at libstd/panicking.rs:310
  60: __rust_maybe_catch_panic
             at libpanic_unwind/lib.rs:105
  61: std::rt::lang_start_internal
             at libstd/panicking.rs:289
             at libstd/panic.rs:392
             at libstd/rt.rs:58
  62: main
  63: __libc_start_main
  64: <unknown>
query stack during panic:
#0 [typeck_tables_of] processing `bug`
#1 [type_of] processing `bug::{{exist-impl-Trait}}`
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0582`.

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 1.28.0 (9634041f0 2018-07-30) running on x86_64-unknown-linux-gnu

note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type bin

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

error: Could not compile `playground`.

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

[DutchGhost]

I suppose this is a duplicate of #52812 , #53943 , and perhaps some other HRTB ICE's.

[hellow554]

The ICE cannot be reproduces with 1.26.2 .

error[E0582]: binding for associated type `Output` references lifetime `'r`, which does not appear in the trait input types
  --> file.rs on line 5:35
   |
10 | fn bug() -> impl for <'r> Fn() -> &'r () { || { &() } }
   |                                   ^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0582`.

[DutchGhost]

The ICE cannot be reproduces with 1.26.2 .

error[E0582]: binding for associated type `Output` references lifetime `'r`, which does not appear in the trait input types
  --> file.rs on line 5:35
   |
10 | fn bug() -> impl for <'r> Fn() -> &'r () { || { &() } }
   |                                   ^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0582`.

1.27 also just errors, the ICE seems to have slipped in with 1.28

[DutchGhost]

As of 1.33, this just gives back a normal error, and no longer ICE's. issue can be closed?