thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err`

[IllusiveS]

I tried this code:

#![allow(dead_code)]
#![allow(unused_must_use)]

use std::collections::HashMap;
use std::any::{Any, TypeId};
use std::result::Result::Ok;
use std::hash::Hash;

trait State {
	type EventType;

	fn on_enter(&mut self);
	fn on_event_enter(&mut self, event: Self::EventType);

	fn get_type_id_of_state(&self) -> TypeId;
}

struct StateMachine<EventType : Hash + Eq> {
	current_state : Box<State<EventType=EventType>>,
	transition_table : HashMap<TypeId, HashMap<EventType, fn() -> Box<State<EventType=EventType>>>>
}

impl <EventType : Hash + Eq> StateMachine<EventType> {
	fn process_event(&mut self, event : EventType) {
		self.inner_process_event(event);
	}

	fn is_state<T: ?Sized + Any>(&mut self) -> bool {
		self.current_state.get_type_id_of_state() == TypeId::of::<T>()
	}

	fn inner_process_event(&mut self, event : EventType) -> Result<(), i8> {
		let new_state_creation_function = self.transition_table
			.iter()
			.find(|(&event_typeid, _)| event_typeid == self.current_state.get_type_id_of_state())
			.ok_or(1)?
			.1
			.iter()
			.find(|(&event_type, _)|event == event_type)
			.ok_or(2)?
			.1;

		//TODO on_exit from state
		self.current_state = new_state_creation_function();
		Ok(())
	}
}

#[cfg(test)]
mod tests {
    #[test]
    fn it_works() {
        assert_eq!(2 + 2, 4);
    }
}

I expected to see this happen: for this code to compile, or throw an error

Instead, this happened: i broke the compiler

Meta

rustc --version --verbose:
rustc 1.26.1 (827013a 2018-05-25)
binary: rustc
commit-hash: 827013a
commit-date: 2018-05-25
host: x86_64-unknown-linux-gnu
release: 1.26.1
LLVM version: 6.0

Backtrace:

thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: (MoveData { move_paths: [MovePath { place: _0 }, MovePath { place: _1 }, MovePath { place: _2 }, MovePath { place: _3 }, MovePath { place: _4 }, MovePath { place: _5 }], moves: [mp4@bb0[6], mp5@bb0[6], mp5@bb2[0], mp4@bb2[1], mp3@bb2[2], mp3@bb3[0], mp3@bb4[0], mp0@bb4[1]], loc_map: LocationMap { map: [[[], [], [], [], [], [], [mo0, mo1]], [[]], [[mo2], [mo3], [mo4]], [[mo5]], [[mo6], [mo7]]] }, path_map: [[mo7], [], [], [mo4, mo5, mo6], [mo0, mo3], [mo1, mo2]], rev_lookup: MovePathLookup { locals: [mp0, mp1, mp2, mp3, mp4, mp5], projections: {} }, inits: [mp1@src/lib.rs:39:10: 39:47 (Deep), mp2@src/lib.rs:39:11: 39:27 (Deep), mp3@src/lib.rs:39:13: 39:23 (Deep), mp4@src/lib.rs:39:28: 39:33 (Deep), mp5@src/lib.rs:39:37: 39:47 (Deep), mp0@src/lib.rs:39:28: 39:47 (NonPanicPathOnly)], init_loc_map: LocationMap { map: [[[], [in2], [], [in3], [], [in4], [in5]], [[]], [[], [], []], [[]], [[], []]] }, init_path_map: [[in5], [in0], [in1], [in2], [in3], [in4]] }, [IllegalMove { cannot_move_out_of: IllegalMoveOrigin { span: src/lib.rs:39:13: 39:23, kind: BorrowedContent } }])', libcore/result.rs:945:5
stack backtrace:
   0:     0x7f65eff6366b - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::hc94fccaa2a711028
                               at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1:     0x7f65eff317f0 - std::sys_common::backtrace::print::h8c9041d44f9f1a2c
                               at libstd/sys_common/backtrace.rs:71
                               at libstd/sys_common/backtrace.rs:59
   2:     0x7f65eff570ad - std::panicking::default_hook::{{closure}}::ha2f043e73975ac4b
                               at libstd/panicking.rs:207
   3:     0x7f65eff56e0b - std::panicking::default_hook::h1db43126ea6aa931
                               at libstd/panicking.rs:223
   4:     0x7f65ec581c7d - core::ops::function::Fn::call::h4c0721031e98bbc2
   5:     0x7f65eff575f9 - std::panicking::rust_panic_with_hook::h4de9fd85b55cffd7
                               at libstd/panicking.rs:403
   6:     0x7f65eff573e2 - std::panicking::begin_panic_fmt::h2cd49505797e619d
                               at libstd/panicking.rs:349
   7:     0x7f65eff57312 - rust_begin_unwind
                               at libstd/panicking.rs:325
   8:     0x7f65effc9650 - core::panicking::panic_fmt::h2bc4e257e1a74d55
                               at libcore/panicking.rs:72
   9:     0x7f65ed222fe8 - core::result::unwrap_failed::h3a709c5b32360d64
  10:     0x7f65ed0f354e - <rustc_mir::transform::elaborate_drops::ElaborateDrops as rustc_mir::transform::MirPass>::run_pass::h660045041abc7571
  11:     0x7f65ed173de7 - rustc_mir::transform::optimized_mir::{{closure}}::h7cb0d0add4eb4184
  12:     0x7f65ed16e4e6 - rustc_mir::transform::optimized_mir::h7cb7fa1e30d4354e
  13:     0x7f65ec19d2c4 - rustc::dep_graph::graph::DepGraph::with_task_impl::h878c22fb5122f9c6
  14:     0x7f65ec130299 - rustc_errors::Handler::track_diagnostics::h918b4586db0c6597
  15:     0x7f65ec3f46f7 - rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check::h0eef73757e8f6ac7
  16:     0x7f65ec062c10 - rustc::ty::maps::<impl rustc::ty::maps::queries::optimized_mir<'tcx>>::force::hf2f063865577b696
  17:     0x7f65ec063569 - rustc::ty::maps::<impl rustc::ty::maps::queries::optimized_mir<'tcx>>::try_get::hce2244b4b273c61b
  18:     0x7f65ec4759fa - rustc::ty::maps::TyCtxtAt::optimized_mir::hc7898fa6d1e4cf46
  19:     0x7f65ec4728e0 - rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::optimized_mir::h151511e9befcfbcc
  20:     0x7f65ee1996d7 - rustc_metadata::encoder::<impl rustc_metadata::isolated_encoder::IsolatedEncoder<'a, 'b, 'tcx>>::encode_optimized_mir::hc555dd2c28fae047
  21:     0x7f65ee19b2ed - rustc_metadata::encoder::<impl rustc_metadata::isolated_encoder::IsolatedEncoder<'a, 'b, 'tcx>>::encode_info_for_closure::h16853ae6f89c1dc6
  22:     0x7f65ee0b09fa - rustc::dep_graph::graph::DepGraph::with_ignore::h05704be9e04a9fb6
  23:     0x7f65ee1864da - rustc_metadata::encoder::<impl rustc_metadata::index_builder::IndexBuilder<'a, 'b, 'tcx>>::encode_info_for_expr::hbcf521968e6680b1
  24:     0x7f65ee088569 - rustc::hir::intravisit::walk_expr::haa934655629b9d52
  25:     0x7f65ee08855a - rustc::hir::intravisit::walk_expr::haa934655629b9d52
  26:     0x7f65ee08875a - rustc::hir::intravisit::walk_expr::haa934655629b9d52
  27:     0x7f65ee088783 - rustc::hir::intravisit::walk_expr::haa934655629b9d52
  28:     0x7f65ee088bc6 - rustc::hir::intravisit::walk_expr::haa934655629b9d52
  29:     0x7f65ee08503e - rustc::hir::intravisit::walk_local::hfbe4bc5f617e268b
  30:     0x7f65ee08897f - rustc::hir::intravisit::walk_expr::haa934655629b9d52
  31:     0x7f65edff2dd4 - rustc::hir::intravisit::Visitor::visit_nested_body::hef2dfe74809641b6
  32:     0x7f65ee1a9ada - rustc::hir::Crate::visit_all_item_likes::hbf8265e514e7d5ba
  33:     0x7f65ee04388b - rustc_metadata::encoder::encode_metadata::he4cc4242b9c6db42
  34:     0x7f65ee1bca41 - rustc_metadata::cstore_impl::<impl rustc::middle::cstore::CrateStore for rustc_metadata::cstore::CStore>::encode_metadata::h8690a83dd23db74e
  35:     0x7f65ec459c40 - rustc::ty::context::TyCtxt::encode_metadata::h4066fda02cc5f5b3
  36:     0x7f65e484b4f4 - rustc_trans::base::write_metadata::h92808802d3f10fb1
  37:     0x7f65e48eeb86 - rustc::util::common::time::h7afbe841455208f3
  38:     0x7f65e484bd99 - rustc_trans::base::trans_crate::h14dc7fce48712af1
  39:     0x7f65e47fa367 - <rustc_trans::LlvmTransCrate as rustc_trans_utils::trans_crate::TransCrate>::trans_crate::hdaf690ee5d727ebc
  40:     0x7f65f02edce5 - rustc::util::common::time::h3cd3b736e582b0e7
  41:     0x7f65f02e1d64 - rustc_driver::driver::phase_4_translate_to_llvm::h464b5474b0ef515a
  42:     0x7f65f036a159 - rustc_driver::driver::compile_input::{{closure}}::h23e22af9bd83b9e4
  43:     0x7f65f036650a - <std::thread::local::LocalKey<T>>::with::hc77f0fdf41eb34ff
  44:     0x7f65f0362c96 - <std::thread::local::LocalKey<T>>::with::h62237ca090d08843
  45:     0x7f65f03e029e - rustc::ty::context::TyCtxt::create_and_enter::hbfec67eee3dde235
  46:     0x7f65f02db217 - rustc_driver::driver::compile_input::hef0281f2d009ea71
  47:     0x7f65f038facf - rustc_driver::run_compiler_impl::hfe6dafc265c4aa95
  48:     0x7f65f02b5578 - syntax::with_globals::h0c3db56419a08c06
  49:     0x7f65f02f5b8d - std::sys_common::backtrace::__rust_begin_short_backtrace::h78942b1d792cc36a
  50:     0x7f65eff71cce - __rust_maybe_catch_panic
                               at libpanic_unwind/lib.rs:102
  51:     0x7f65f030189d - <F as alloc::boxed::FnBox<A>>::call_box::h7dcda0c9ae6259a6
  52:     0x7f65eff68d57 - std::sys_common::thread::start_thread::hbdb0265288bf7dcc
                               at /checkout/src/liballoc/boxed.rs:794
                               at libstd/sys_common/thread.rs:24
  53:     0x7f65eff37e18 - std::sys::unix::thread::Thread::new::thread_start::h99a7fe00c40fd1be
                               at libstd/sys/unix/thread.rs:90
  54:     0x7f65ea2db6b9 - start_thread
  55:     0x7f65efc1741c - clone
  56:                0x0 - <unknown>

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 1.26.1 (827013a31 2018-05-25) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental --crate-type lib

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

error: Could not compile `rust_state_machine`.
warning: build failed, waiting for other jobs to finish...
error: build failed

Process finished with exit code 101

[shingtaklam1324]

Latest nightly seems to give more information, it might be a mir issue.

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: (MoveData { move_paths: [MovePath { place: _0 }, MovePath { place: _1 }, MovePath { place: _2 }, MovePath { place: _3 }, MovePath { place: _4 }, MovePath { place: _5 }], moves: [mp4@bb0[6], mp5@bb0[6], mp5@bb2[0], mp4@bb2[1], mp3@bb2[2], mp3@bb3[0], mp3@bb4[0], mp0@bb4[1]], loc_map: LocationMap { map: [[[], [], [], [], [], [], [mo0, mo1]], [[]], [[mo2], [mo3], [mo4]], [[mo5]], [[mo6], [mo7]]] }, path_map: [[mo7], [], [], [mo4, mo5, mo6], [mo0, mo3], [mo1, mo2]], rev_lookup: MovePathLookup { locals: [mp0, mp1, mp2, mp3, mp4, mp5], projections: {} }, inits: [mp1@src/lib.rs:40:19: 40:57 (Deep), mp2@src/lib.rs:40:20: 40:36 (Deep), mp3@src/lib.rs:40:22: 40:32 (Deep), mp4@src/lib.rs:40:38: 40:43 (Deep), mp5@src/lib.rs:40:47: 40:57 (Deep), mp0@src/lib.rs:40:38: 40:57 (NonPanicPathOnly)], init_loc_map: LocationMap { map: [[[], [in2], [], [in3], [], [in4], [in5]], [[]], [[], [], []], [[]], [[], []]] }, init_path_map: [[in5], [in0], [in1], [in2], [in3], [in4]] }, [IllegalMove { cannot_move_out_of: IllegalMoveOrigin { span: src/lib.rs:40:22: 40:32, kind: BorrowedContent } }])', libcore/result.rs:945:5
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::continue_panic_fmt
             at libstd/panicking.rs:426
   7: rust_begin_unwind
             at libstd/panicking.rs:337
   8: core::panicking::panic_fmt
             at libcore/panicking.rs:92
   9: core::result::unwrap_failed
  10: <rustc_mir::transform::elaborate_drops::ElaborateDrops as rustc_mir::transform::MirPass>::run_pass
  11: rustc_mir::transform::optimized_mir::{{closure}}
  12: rustc_mir::transform::optimized_mir
  13: rustc::ty::maps::__query_compute::optimized_mir
  14: rustc::ty::maps::<impl rustc::ty::maps::config::QueryConfig<'tcx> for rustc::ty::maps::queries::optimized_mir<'tcx>>::compute
  15: rustc::ty::context::tls::with_context
  16: rustc::dep_graph::graph::DepGraph::with_task_impl
  17: rustc::ty::context::tls::with_related_context
  18: rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job
  19: rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
  20: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::optimized_mir
  21: rustc_metadata::encoder::<impl rustc_metadata::isolated_encoder::IsolatedEncoder<'a, 'b, 'tcx>>::encode_optimized_mir
  22: rustc_metadata::encoder::<impl rustc_metadata::isolated_encoder::IsolatedEncoder<'a, 'b, 'tcx>>::encode_info_for_closure
  23: rustc::ty::context::tls::with_context
  24: rustc_metadata::encoder::<impl rustc_metadata::index_builder::IndexBuilder<'a, 'b, 'tcx>>::encode_info_for_expr
  25: rustc::hir::intravisit::walk_expr
  26: rustc::hir::intravisit::walk_expr
  27: rustc::hir::intravisit::walk_expr
  28: rustc::hir::intravisit::walk_expr
  29: rustc::hir::intravisit::walk_expr
  30: rustc::hir::intravisit::walk_local
  31: rustc::hir::intravisit::walk_expr
  32: rustc::hir::intravisit::Visitor::visit_nested_body
  33: rustc::hir::Crate::visit_all_item_likes
  34: rustc_metadata::encoder::encode_metadata
  35: rustc_metadata::cstore_impl::<impl rustc::middle::cstore::CrateStore for rustc_metadata::cstore::CStore>::encode_metadata
  36: rustc::ty::context::TyCtxt::encode_metadata
  37: rustc_codegen_llvm::base::write_metadata
  38: rustc::util::common::time
  39: rustc_codegen_llvm::base::codegen_crate
  40: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_utils::codegen_backend::CodegenBackend>::codegen_crate
  41: rustc::util::common::time
  42: rustc_driver::driver::phase_4_codegen
  43: rustc_driver::driver::compile_input::{{closure}}
  44: rustc::ty::context::tls::enter_context
  45: <std::thread::local::LocalKey<T>>::with
  46: rustc::ty::context::TyCtxt::create_and_enter
  47: rustc_driver::driver::compile_input
  48: rustc_driver::run_compiler_with_pool
  49: <scoped_tls::ScopedKey<T>>::set
  50: syntax::with_globals
  51: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  52: __rust_maybe_catch_panic
             at libpanic_unwind/lib.rs:105
  53: rustc_driver::run
  54: rustc_driver::main
  55: std::rt::lang_start::{{closure}}
  56: std::panicking::try::do_call
             at libstd/rt.rs:59
             at libstd/panicking.rs:310
  57: __rust_maybe_catch_panic
             at libpanic_unwind/lib.rs:105
  58: std::rt::lang_start_internal
             at libstd/panicking.rs:289
             at libstd/panic.rs:374
             at libstd/rt.rs:58
  59: main
  60: __libc_start_main
  61: <unknown>
query stack during panic:
#0 [optimized_mir] processing `<StateMachine<EventType>>::inner_process_event::{{closure}}`
end of query stack

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 1.28.0-nightly (29f48ccf3 2018-06-03) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental --crate-type lib

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

error: Could not compile `tst`.

[estebank]

Current output (fixed to run):

error[E0507]: cannot move out of borrowed content
  --> src/lib.rs:39:11
   |
39 |             .find(|(&event_type, _)|event == event_type)
   |                    ^^----------^^^^
   |                    | |
   |                    | data moved here
   |                    cannot move out of borrowed content
   |
note: move occurs because `event_type` has type `EventType`, which does not implement the `Copy` trait
  --> src/lib.rs:39:13
   |
39 |             .find(|(&event_type, _)|event == event_type)
   |                      ^^^^^^^^^^

[tesuji]

Is this test OK? Where can I store this?

use std::any::TypeId;
use std::collections::HashMap;
use std::hash::Hash;

trait State {
    type EventType;
    fn get_type_id_of_state(&self) -> TypeId;
}

struct StateMachine<EventType: Hash + Eq> {
    current_state: Box<dyn State<EventType = EventType>>,
    transition_table:
        HashMap<TypeId, HashMap<EventType, fn() -> Box<dyn State<EventType = EventType>>>>,
}

impl<EventType: Hash + Eq> StateMachine<EventType> {
    fn inner_process_event(&mut self, event: EventType) -> Result<(), i8> {
        let new_state_creation_function = self
            .transition_table
            .iter()
            .find(|(&event_typeid, _)| event_typeid == self.current_state.get_type_id_of_state())
            .ok_or(1)?
            .1
            .iter()
            .find(|(&event_type, _)| event == event_type)
            .ok_or(2)?
            .1;

        self.current_state = new_state_creation_function();
        Ok(())
    }
}

[estebank]

That seems about right add the file to src/test/ui/issues and run ./x.py test src/test/ui --stage 1 --bless.