error: internal compiler error: src/librustc/traits/codegen/mod.rs:104: Encountered errors `[FulfillmentError(Obligation(predicate=Binder(TraitPredicate(<dyn std::iter::Iterator<Item = u8> as std::ops::Fn<()>>)), depth=1),Unimplemented)]` resolving bounds after type-checking thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:883:9 stack backtrace: 0: backtrace::backtrace::libunwind::trace at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88 1: backtrace::backtrace::trace_unsynchronized at /cargo/registry/src/github.com-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::traits::codegen::<impl rustc::infer::InferCtxt>::drain_fulfillment_cx_or_panic 21: rustc::ty::context::GlobalCtxt::enter_local 22: rustc::traits::codegen::codegen_fulfill_obligation 23: rustc::ty::query::__query_compute::codegen_fulfill_obligation 24: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::codegen_fulfill_obligation>::compute 25: rustc::dep_graph::graph::DepGraph::with_task_impl 26: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query 27: rustc::ty::instance::Instance::resolve 28: <rustc_mir::monomorphize::collector::MirNeighborCollector as rustc::mir::visit::Visitor>::visit_terminator_kind 29: rustc_mir::monomorphize::collector::collect_items_rec 30: rustc_mir::monomorphize::collector::collect_items_rec 31: rustc_session::utils::<impl rustc_session::session::Session>::time 32: rustc_mir::monomorphize::collector::collect_crate_mono_items 33: rustc_mir::monomorphize::partitioning::collect_and_partition_mono_items 34: rustc::ty::query::__query_compute::collect_and_partition_mono_items 35: rustc::dep_graph::graph::DepGraph::with_task_impl 36: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query 37: rustc_codegen_ssa::base::codegen_crate 38: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_utils::codegen_backend::CodegenBackend>::codegen_crate 39: rustc_session::utils::<impl rustc_session::session::Session>::time 40: rustc_interface::passes::QueryContext::enter 41: rustc_interface::queries::Queries::ongoing_codegen 42: rustc_interface::interface::run_compiler_in_existing_thread_pool 43: scoped_tls::ScopedKey<T>::set 44: 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 (3761dcd34 2020-01-28) 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 query stack during panic: #0 [codegen_fulfill_obligation] checking if `std::ops::Fn` fulfills its obligations #1 [collect_and_partition_mono_items] collect_and_partition_mono_items end of query stack error: aborting due to previous error error: could not compile `playground`. To learn more, run the command again with --verbose.