Closed
Description
An underscore (aka wildcard aka _) nested within a type declaration is causing problems for some new code that tries to project out the inner types after normalization is finished. Here is an example (play):
struct X;
struct Y;
struct Z;
pub fn join<A, B, RA, RB>(_oper_a: A, _oper_b: B) -> (RA, RB)
where A: FnOnce() -> RA + Send,
B: FnOnce() -> RB + Send,
RA: Send,
RB: Send
{
loop { }
}
fn main() {
let ((_x, _y), _z): (_, Z) = join(|| (X, Y),
|| Z);
}Original bug report follows
Running cargo test here
error: internal compiler error: librustc/mir/tcx.rs:68: extracting field of non-tuple non-adt: Ty { ty: _ }
thread 'main' panicked at 'Box<Any>', librustc_errors/lib.rs:600:9
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
2: std::panicking::default_hook::{{closure}}
at libstd/sys_common/backtrace.rs:59
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:480
6: std::panicking::begin_panic
7: rustc_errors::Handler::bug
8: rustc::util::bug::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::util::bug::opt_span_bug_fmt
13: rustc::util::bug::bug_fmt
14: rustc::mir::tcx::PlaceTy::field_ty
15: rustc::mir::tcx::PlaceTy::projection_ty_core
16: rustc_mir::borrow_check::nll::type_check::TypeChecker::relate_type_and_user_type
17: <rustc_mir::borrow_check::nll::type_check::TypeVerifier<'a, 'b, 'gcx, 'tcx> as rustc::mir::visit::Visitor<'tcx>>::visit_local_decl
18: <rustc_mir::borrow_check::nll::type_check::TypeVerifier<'a, 'b, 'gcx, 'tcx> as rustc::mir::visit::Visitor<'tcx>>::visit_mir
19: rustc_mir::borrow_check::nll::type_check::type_check_internal
20: rustc::ty::context::tls::with_related_context
21: rustc::infer::InferCtxtBuilder::enter
22: <rustc_mir::borrow_check::nll::type_check::TypeckMir as rustc_mir::transform::MirPass>::run_pass
23: rustc_mir::transform::run_passes::{{closure}}
24: rustc_mir::transform::run_passes
25: rustc_mir::transform::mir_const
26: rustc::ty::query::__query_compute::mir_const
27: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::mir_const<'tcx>>::compute
28: rustc::ty::context::tls::with_context
29: rustc::dep_graph::graph::DepGraph::with_task_impl
30: rustc::ty::context::tls::with_related_context
31: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job
32: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
33: rustc::ty::query::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::mir_const
34: rustc_mir::transform::mir_validated
35: rustc::ty::query::__query_compute::mir_validated
36: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::mir_validated<'tcx>>::compute
37: rustc::ty::context::tls::with_context
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::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::ensure_query
43: rustc_borrowck::borrowck::borrowck
44: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::borrowck<'tcx>>::compute
45: rustc::ty::context::tls::with_context
46: rustc::dep_graph::graph::DepGraph::with_task_impl
47: rustc::ty::context::tls::with_related_context [22/3644]
48: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job
49: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
50: rustc::ty::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::par_body_owners
51: rustc_borrowck::borrowck::check_crate
52: rustc::util::common::time
53: rustc::ty::context::tls::enter_context
54: <std::thread::local::LocalKey<T>>::with
55: rustc::ty::context::TyCtxt::create_and_enter
56: rustc_driver::driver::compile_input
57: rustc_driver::run_compiler_with_pool
58: rustc_driver::driver::spawn_thread_pool
59: rustc_driver::run_compiler
60: <scoped_tls::ScopedKey<T>>::set
61: syntax::with_globals
62: __rust_maybe_catch_panic
at libpanic_unwind/lib.rs:102
63: rustc_driver::run
64: rustc_driver::main
65: std::rt::lang_start::{{closure}}
66: std::panicking::try::do_call
at libstd/rt.rs:59
at libstd/panicking.rs:310
67: __rust_maybe_catch_panic
at libpanic_unwind/lib.rs:102
68: std::rt::lang_start_internal
at libstd/panicking.rs:289
at libstd/panic.rs:392
at libstd/rt.rs:58
69: main
70: __libc_start_main
71: <unknown>
query stack during panic:
#0 [mir_const] processing `artifact::determine_artifacts`
#1 [mir_validated] processing `artifact::determine_artifacts`
#2 [borrowck] processing `artifact::determine_artifacts`
end of query stack
error: aborting due to previous error
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 1.31.0-nightly (1cf82fd9c 2018-10-30) 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 `artifact_data`.
```