Closed
Description
The following minimal example causes an internal compiler error.
struct Foo;
impl Iterator for Foo {
type Item<'b> = &'b Foo;
fn next(&mut self) -> Option<Self::Item> {
None
}
}
fn main() {}
Error in question:
> RUST_BACKTRACE=1 cargo +stable build
Compiling icetest v0.1.0 (/tmp/icetest)
error[E0658]: generic associated types are unstable (see issue #44265)
--> src/main.rs:4:5
|
4 | type Item<'b> = &'b Foo;
| ^^^^^^^^^^^^^^^^^^^^^^^^
error: internal compiler error: src/librustc/ty/subst.rs:426: Region parameter out of range when substituting in region 'b (root type=Some(&'b Foo)) (index=0)
thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:558:9
stack backtrace:
0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
1: std::sys_common::backtrace::_print
at src/libstd/sys_common/backtrace.rs:70
2: std::panicking::default_hook::{{closure}}
at src/libstd/sys_common/backtrace.rs:58
at src/libstd/panicking.rs:200
3: std::panicking::default_hook
at src/libstd/panicking.rs:215
4: rustc::util::common::panic_hook
5: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:482
6: std::panicking::begin_panic
7: rustc_errors::Handler::span_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::span_bug_fmt
14: <rustc::ty::subst::SubstFolder<'a, 'gcx, 'tcx> as rustc::ty::fold::TypeFolder<'gcx, 'tcx>>::fold_region
15: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable<'tcx> for &'tcx rustc::ty::TyS<'tcx>>::super_fold_with
16: <rustc::ty::subst::SubstFolder<'a, 'gcx, 'tcx> as rustc::ty::fold::TypeFolder<'gcx, 'tcx>>::fold_ty
17: rustc::traits::project::opt_normalize_projection_type
18: rustc::traits::project::normalize_projection_type
19: <rustc::traits::project::AssociatedTypeNormalizer<'a, 'b, 'gcx, 'tcx> as rustc::ty::fold::TypeFolder<'gcx, 'tcx>>::fold_ty
20: <smallvec::SmallVec<A> as core::iter::traits::collect::FromIterator<<A as smallvec::Array>::Item>>::from_iter
21: rustc::ty::fold::TypeFoldable::fold_with
22: rustc::ty::fold::TypeFoldable::fold_with
23: rustc::ty::fold::TypeFoldable::fold_with
24: rustc::traits::project::normalize
25: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &mut F>::call_once
26: <core::iter::adapters::flatten::FlatMap<I, U, F> as core::iter::traits::iterator::Iterator>::next
27: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
28: rustc::ty::wf::trait_obligations
29: rustc::ty::context::GlobalCtxt::enter_local
30: rustc_typeck::check::wfcheck::check_item_well_formed
31: rustc::ty::query::__query_compute::check_item_well_formed
32: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::check_item_well_formed<'tcx>>::compute
33: rustc::dep_graph::graph::DepGraph::with_task_impl
34: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
35: rustc::hir::Crate::visit_all_item_likes
36: rustc::util::common::time
37: rustc_typeck::check_crate
38: <std::thread::local::LocalKey<T>>::with
39: rustc::ty::context::TyCtxt::create_and_enter
40: rustc_driver::driver::compile_input
41: rustc_driver::run_compiler_with_pool
42: <scoped_tls::ScopedKey<T>>::set
43: rustc_driver::run_compiler
44: syntax::with_globals
45: __rust_maybe_catch_panic
at src/libpanic_unwind/lib.rs:87
46: <F as alloc::boxed::FnBox<A>>::call_box
47: std::sys::unix::thread::Thread::new::thread_start
at /rustc/fc50f328b0353b285421b8ff5d4100966387a997/src/liballoc/boxed.rs:759
at src/libstd/sys_common/thread.rs:14
at src/libstd/sys/unix/thread.rs:81
48: start_thread
49: __clone
query stack during panic:
#0 [check_item_well_formed] processing `<Foo as std::iter::Iterator>`
end of query stack
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0658`.
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 1.34.1 (fc50f328b 2019-04-24) running on x86_64-unknown-linux-gnu
note: compiler flags: -C debuginfo=2 -C incremental --crate-type bin
note: some of the compiler flags provided by cargo are hidden
error: Could not compile `icetest`.
To learn more, run the command again with --verbose.
rustc version:
> rustc +stable --version --verbose
rustc 1.34.1 (fc50f328b 2019-04-24)
binary: rustc
commit-hash: fc50f328b0353b285421b8ff5d4100966387a997
commit-date: 2019-04-24
host: x86_64-unknown-linux-gnu
release: 1.34.1
LLVM version: 8.0
This error was encountered on stable, but I can confirm that it also occurs on the latest nightly (1.36.0-nightly (cfdc84a00 2019-05-07)).