ICE with lifetime'd associated type on stable

[TheDan64]

Playground: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=8f737364785513fd20d1ef32c1c03bd6

Tested on 1.33, 1.34.2

[hellow554]

Backtrace

error: internal compiler error: src/librustc/ty/subst.rs:426: Region parameter out of range when substituting in region 'a (root type=Some(&'a Bar)) (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/6c2484dc3c532c052f159264e970278d8b77cdc9/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 FooBar>`
end of query stack
error: aborting due to 3 previous errors

Some errors occurred: E0412, E0658.
For more information about an error, try `rustc --explain E0412`.

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 1.34.2 (6c2484dc3 2019-05-13) running on x86_64-unknown-linux-gnu

note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type bin

There has been a few issues lately with const generics, because the ICE happen altough the feature gate is missing.

Possible dup of #60814, #60813, #60724, #60619

[TheDan64]

I would think this isn't a const generics issue, but rather an issue with associated types? Since lifetimes aren't currently allowed on the type definition.

[pnkfelix]

yes, this is a dupe of #60654

[pnkfelix]

triage: P-medium. Removing nomination since I do not think this needs discussion. Closing as dupe of #60654.

But since this (#61064) and #60654 are clearly biting people (who are then rightfully filing bugs, the compiler is asking them to do so, I'm going to assign both bugs to myself, and hopefully fix (by issuing the error diagnostic but not the ICE).

[hellow554]

but rather an issue with associated types

Yes, you're right. Haven't payed enough attention. Sorry for that!