thread 'rustc' panicked at 'no representative region', /checkout/src/libcore/option.rs:819:4

[realcr]

I tried to compile a piece of code and the compiler crashed.
This is the code that causes the problem:

trait MockFutureTrait {
    type Item;
}

struct MockFuture<T> {
    item: T,
}

impl<T> MockFutureTrait for MockFuture<T> {
    type Item=T;
}

struct FragMsgReceiver<'a,'c:'a> {
    recv_dgram: &'a FnMut(&mut [u8]) -> Box<MockFutureTrait<Item=&mut [u8]> + 'c>,
}
fn constrain_handler<F>(f: F) -> F
where F: for <'r> FnMut(&'r mut [u8]) -> Box<MockFutureTrait<Item=&'r mut [u8]>> {
    f
}

fn main() {
    let mut recv_dgram = constrain_handler(|buf: &mut [u8]| {
        Box::new(MockFuture {
            item: buf,
        }) as Box<MockFutureTrait<Item=&mut [u8]>>
    });

    let ref_recv_dgram = &mut recv_dgram;
    let fmr = FragMsgReceiver {
        recv_dgram: ref_recv_dgram,
    };
}

I suspect that the line where F: for <'r> FnMut(&'r mut [u8]) -> Box<MockFutureTrait<Item=&'r mut [u8]>> { is related to the crash.

I hoped the code to compile, or at least not compile and give me a nice error message.
This is also related to my SO question here.

Meta

$ rustc --version --verbose
rustc 1.21.0-nightly (13d94d5fa 2017-08-10)
binary: rustc
commit-hash: 13d94d5fa8129a34f5c77a1bcd76983f5aed2434
commit-date: 2017-08-10
host: x86_64-unknown-linux-gnu
release: 1.21.0-nightly
LLVM version: 4.0

Backtrace

$ RUST_BACKTRACE=full cargo check
   Compiling noncompiling_lifetime_trait v0.1.0 (.../noncompiling/noncompiling_lifetime_trait)
error: internal compiler error: unexpected panic

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 1.21.0-nightly (13d94d5fa 2017-08-10) running on x86_64-unknown-linux-gnu

note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'no representative region', /checkout/src/libcore/option.rs:819:4
stack backtrace:
   0:     0x7f613ecb0c83 - std::sys::imp::backtrace::tracing::imp::unwind_backtrace::hc9320db76922c77f
                               at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1:     0x7f613ecab414 - std::sys_common::backtrace::_print::hd1cad143436e7e7b
                               at /checkout/src/libstd/sys_common/backtrace.rs:71
   2:     0x7f613ecbe493 - std::panicking::default_hook::{{closure}}::h8ce44357afd55c76
                               at /checkout/src/libstd/sys_common/backtrace.rs:60
                               at /checkout/src/libstd/panicking.rs:380
   3:     0x7f613ecbe18a - std::panicking::default_hook::h85c58325ebacf8fb
                               at /checkout/src/libstd/panicking.rs:390
   4:     0x7f613ecbe997 - std::panicking::rust_panic_with_hook::hfa335e60391f47d9
                               at /checkout/src/libstd/panicking.rs:610
   5:     0x7f613ecbe7f4 - std::panicking::begin_panic::h30d278ec64e447d3
                               at /checkout/src/libstd/panicking.rs:571
   6:     0x7f613ecbe769 - std::panicking::begin_panic_fmt::hcd587d71433b1406
                               at /checkout/src/libstd/panicking.rs:521
   7:     0x7f613ecbe6fa - rust_begin_unwind
                               at /checkout/src/libstd/panicking.rs:497
   8:     0x7f613ecfefa0 - core::panicking::panic_fmt::h39daae460f714f61
                               at /checkout/src/libcore/panicking.rs:71
   9:     0x7f613ecff00d - core::option::expect_failed::h950b5744b96e90a4
                               at /checkout/src/libcore/option.rs:819
  10:     0x7f613bb8274d - rustc::infer::InferCtxt::match_poly_projection_predicate::h7cdea5d9923c1547
  11:     0x7f613bc0a028 - rustc::traits::project::confirm_param_env_candidate::h9272de6f49d53275
  12:     0x7f613bc09dde - rustc::traits::project::confirm_callable_candidate::h65de99afd0ee75f4
  13:     0x7f613bc09a92 - rustc::traits::project::confirm_closure_candidate::h4d1b6993371710c1
  14:     0x7f613bc08928 - rustc::traits::project::confirm_candidate::h3d4c618bc3cc9ea9
  15:     0x7f613bc06e35 - rustc::traits::project::opt_normalize_projection_type::h91fef886d54f4389
  16:     0x7f613bc0283f - rustc::traits::project::poly_project_and_unify_type::{{closure}}::h4c1f58cafeb751d1
  17:     0x7f613bc02406 - rustc::traits::project::poly_project_and_unify_type::h00e4d6f4aed39050
  18:     0x7f613bc0043b - <rustc::traits::fulfill::FulfillProcessor<'a, 'b, 'gcx, 'tcx> as rustc_data_structures::obligation_forest::ObligationProcessor>::process_obligation::he3ca956ae5013358
  19:     0x7f613bbff29f - rustc::traits::fulfill::FulfillmentContext::select::hefab09daa26270d9
  20:     0x7f613bbfe947 - rustc::traits::fulfill::FulfillmentContext::select_where_possible::h61b467f90f61b84a
  21:     0x7f613c10934e - rustc_typeck::check::FnCtxt::select_obligations_where_possible::h52bef7c97c0eb449
  22:     0x7f613c1079d6 - rustc_typeck::check::FnCtxt::resolve_type_vars_with_obligations::h8c5e37d40475b2c4
  23:     0x7f613c0b8ad8 - rustc_typeck::check::demand::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::demand_coerce::ha42166c66a50b636
  24:     0x7f613c11e2c3 - rustc_typeck::check::FnCtxt::check_decl_local::hd2968d1d52af8618
  25:     0x7f613c11ec81 - rustc_typeck::check::FnCtxt::check_block_with_expected::{{closure}}::h82a74948a706d3f2
  26:     0x7f613c11e688 - rustc_typeck::check::FnCtxt::check_block_with_expected::h689be9ae83db888e
  27:     0x7f613c112241 - rustc_typeck::check::FnCtxt::check_expr_kind::h0e034806c0640e1d
  28:     0x7f613c110cd2 - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h8a32a773ec83482f
  29:     0x7f613c10cc71 - rustc_typeck::check::FnCtxt::check_return_expr::h2a6b3f2954cd404d
  30:     0x7f613c0feaed - rustc_typeck::check::check_fn::he6fe52d652431556
  31:     0x7f613c0f8dc6 - rustc_typeck::check::typeck_tables_of::{{closure}}::h729ebe10d2f47787
  32:     0x7f613c0f8930 - rustc_typeck::check::typeck_tables_of::h29cbfeec62f1849e
  33:     0x7f613bacd4dd - rustc::dep_graph::graph::DepGraph::with_task::h450f55c1a9fcbd74
  34:     0x7f613bceb2ea - rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_tables_of<'tcx>>::try_get::h556c3eb09c2c7d21
  35:     0x7f613bd2353a - rustc::ty::maps::TyCtxtAt::typeck_tables_of::h78c1a7f7ca156eb2
  36:     0x7f613bd1f9d6 - rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::typeck_tables_of::h837a829971c907ae
  37:     0x7f613c0f7eb7 - rustc_typeck::check::typeck_item_bodies::h0f8ae19b232d2120
  38:     0x7f613bacf8ed - rustc::dep_graph::graph::DepGraph::with_task::ha14cbe06d8885f55
  39:     0x7f613bce9ff5 - rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_item_bodies<'tcx>>::try_get::h3c646c870f54cabf
  40:     0x7f613bd233f5 - rustc::ty::maps::TyCtxtAt::typeck_item_bodies::h271de086ad24efe2
  41:     0x7f613bd1f9a6 - rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::typeck_item_bodies::h2e56734515ae4638
  42:     0x7f613c14f831 - rustc_typeck::check_crate::he7514f54bbc90a21
  43:     0x7f613efe25b0 - rustc::ty::context::TyCtxt::create_and_enter::hf0b1401af74e7747
  44:     0x7f613f03fed1 - rustc_driver::driver::compile_input::h7e4322197bc87ab7
  45:     0x7f613f059782 - rustc_driver::run_compiler::h7ff66578813a854d
  46:     0x7f613ef97261 - std::sys_common::backtrace::__rust_begin_short_backtrace::h2a0cfbdf7b97e796
  47:     0x7f613ecededc - __rust_maybe_catch_panic
                               at /checkout/src/libpanic_unwind/lib.rs:98
  48:     0x7f613efca900 - <F as alloc::boxed::FnBox<A>>::call_box::hb763c222ac18e463
  49:     0x7f613ecbd3cb - std::sys::imp::thread::Thread::new::thread_start::h79a2d07a57977c8b
                               at /checkout/src/liballoc/boxed.rs:692
                               at /checkout/src/libstd/sys_common/thread.rs:21
                               at /checkout/src/libstd/sys/unix/thread.rs:84
  50:     0x7f6139ea76b9 - start_thread
  51:     0x7f613e96c3dc - clone
  52:                0x0 - <unknown>

error: Could not compile `noncompiling_lifetime_trait`.

[arielb1]

Doesn't ICE on either stable, beta, or nightly. Closing.