thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', compiler/rustc_query_impl/src/on_disk_cache.rs:890:14 stack backtrace: 0: _rust_begin_unwind 1: core::panicking::panic_fmt 2: core::panicking::panic 3: rustc_middle::ty::generics::_DERIVE_rustc_serialize_Decodable_D_FOR_GenericParamDef::<impl rustc_serialize::serialize::Decodable<__D> for rustc_middle::ty::generics::GenericParamDef>::decode 4: rustc_serialize::serialize::Decoder::read_seq 5: rustc_middle::ty::generics::_DERIVE_rustc_serialize_Decodable_D_FOR_Generics::<impl rustc_serialize::serialize::Decodable<__D> for rustc_middle::ty::generics::Generics>::decode 6: rustc_query_impl::on_disk_cache::OnDiskCache::try_load_query_result 7: rustc_query_impl::plumbing::<impl rustc_query_system::query::config::QueryDescription<rustc_query_impl::plumbing::QueryCtxt> for rustc_query_impl::queries::generics_of>::try_load_from_disk 8: rustc_query_system::query::plumbing::load_from_disk_and_cache_in_memory 9: rustc_data_structures::stack::ensure_sufficient_stack 10: rustc_query_system::query::plumbing::get_query_impl 11: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::generics_of 12: rustc_middle::ty::subst::<impl rustc_middle::ty::list::List<rustc_middle::ty::subst::GenericArg>>::for_item 13: rustc_infer::infer::InferCtxt::fresh_substs_for_item 14: rustc_trait_selection::traits::select::SelectionContext::match_impl 15: rustc_infer::infer::InferCtxt::probe 16: rustc_middle::ty::trait_def::<impl rustc_middle::ty::context::TyCtxt>::for_each_relevant_impl 17: rustc_trait_selection::traits::select::candidate_assembly::<impl rustc_trait_selection::traits::select::SelectionContext>::assemble_candidates_from_impls 18: rustc_trait_selection::traits::select::candidate_assembly::<impl rustc_trait_selection::traits::select::SelectionContext>::assemble_candidates 19: rustc_trait_selection::traits::select::candidate_assembly::<impl rustc_trait_selection::traits::select::SelectionContext>::candidate_from_obligation_no_cache 20: rustc_query_system::dep_graph::graph::DepGraph<K>::with_anon_task 21: rustc_trait_selection::traits::select::candidate_assembly::<impl rustc_trait_selection::traits::select::SelectionContext>::candidate_from_obligation 22: rustc_trait_selection::traits::select::SelectionContext::select 23: rustc_trait_selection::traits::fulfill::FulfillProcessor::process_trait_obligation 24: rustc_trait_selection::traits::fulfill::FulfillProcessor::progress_changed_obligations 25: rustc_data_structures::obligation_forest::ObligationForest<O>::process_obligations 26: <rustc_trait_selection::traits::fulfill::FulfillmentContext as rustc_infer::traits::engine::TraitEngine>::select_where_possible 27: rustc_typeck::check::op::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::lookup_op_method 28: rustc_typeck::check::op::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_overloaded_binop 29: rustc_typeck::check::op::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_binop 30: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation 31: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_coercable_to_type 32: rustc_typeck::check::op::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_binop 33: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation 34: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation 35: rustc_typeck::check::_match::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_match 36: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind 37: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation 38: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected 39: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_no_value 40: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind 41: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation 42: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_stmt 43: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected 44: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation 45: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_return_expr 46: rustc_typeck::check::check::check_fn 47: rustc_infer::infer::InferCtxtBuilder::enter 48: rustc_typeck::check::typeck 49: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl 50: rustc_data_structures::stack::ensure_sufficient_stack 51: rustc_query_system::query::plumbing::force_query_with_job 52: rustc_query_system::query::plumbing::get_query_impl 53: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck 54: rustc_middle::ty::<impl rustc_middle::ty::context::TyCtxt>::par_body_owners 55: rustc_typeck::check::typeck_item_bodies 56: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl 57: rustc_data_structures::stack::ensure_sufficient_stack 58: rustc_query_system::query::plumbing::force_query_with_job 59: rustc_query_system::query::plumbing::get_query_impl 60: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::typeck_item_bodies 61: rustc_session::utils::<impl rustc_session::session::Session>::time 62: rustc_typeck::check_crate 63: rustc_interface::passes::analysis 64: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl 65: rustc_data_structures::stack::ensure_sufficient_stack 66: rustc_query_system::query::plumbing::force_query_with_job 67: rustc_query_system::query::plumbing::get_query_impl 68: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis 69: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter 70: rustc_span::with_source_map 71: rustc_interface::interface::create_compiler_and_run 72: scoped_tls::ScopedKey<T>::set note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace. error: internal compiler error: unexpected panic note: the compiler unexpectedly panicked. this is a bug.