ICE impl_trait_in_bindings with elided lifetime

[pandaman64]

#![feature(impl_trait_in_bindings)]

struct A<'a>(&'a ());

trait Trait<T> {
}

impl<T> Trait<T> for () {
}

fn main() {
    let x: impl Trait<A> = ();
}

Backtrace

thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', src/libcore/option.rs:347:21
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
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:71
   2: std::panicking::default_hook::{{closure}}
             at src/libstd/sys_common/backtrace.rs:59
             at src/libstd/panicking.rs:197
   3: std::panicking::default_hook
             at src/libstd/panicking.rs:211
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:478
   6: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:381
   7: rust_begin_unwind
             at src/libstd/panicking.rs:308
   8: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
   9: core::panicking::panic
             at src/libcore/panicking.rs:49
  10: rustc_typeck::check::writeback::WritebackCx::visit_opaque_types
  11: rustc_typeck::check::writeback::<impl rustc_typeck::check::FnCtxt>::resolve_type_vars_in_body
  12: rustc::ty::context::GlobalCtxt::enter_local
  13: rustc_typeck::check::typeck_tables_of
  14: rustc::ty::query::__query_compute::typeck_tables_of
  15: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::typeck_tables_of>::compute
  16: rustc::dep_graph::graph::DepGraph::with_task_impl
  17: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  18: rustc_typeck::collect::checked_type_of
  19: rustc_typeck::collect::type_of
  20: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::type_of>::compute
  21: rustc::dep_graph::graph::DepGraph::with_task_impl
  22: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  23: rustc::ty::util::<impl rustc::ty::context::TyCtxt>::try_expand_impl_trait_type::OpaqueTypeExpander::expand_opaque_ty
  24: rustc::ty::util::<impl rustc::ty::context::TyCtxt>::try_expand_impl_trait_type
  25: rustc_typeck::check::check_item_type
  26: rustc::hir::map::Map::visit_item_likes_in_module
  27: rustc_typeck::check::check_mod_item_types
  28: rustc::ty::query::__query_compute::check_mod_item_types
  29: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::check_mod_item_types>::compute
  30: rustc::dep_graph::graph::DepGraph::with_task_impl
  31: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  32: rustc_typeck::check_crate::{{closure}}
  33: rustc::util::common::time
  34: rustc_typeck::check_crate
  35: rustc_interface::passes::analysis
  36: rustc::ty::query::__query_compute::analysis
  37: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::analysis>::compute
  38: rustc::dep_graph::graph::DepGraph::with_task_impl
  39: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  40: rustc::ty::context::tls::enter_global
  41: rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}}
  42: rustc_interface::passes::create_global_ctxt::{{closure}}
  43: rustc_interface::interface::run_compiler_in_existing_thread_pool
  44: std::thread::local::LocalKey<T>::with
  45: scoped_tls::ScopedKey<T>::set
  46: syntax::with_globals
query stack during panic:
#0 [typeck_tables_of] processing `main`
#1 [type_of] processing `main::{{opaque}}#0`
#2 [check_mod_item_types] checking item types in top-level module
#3 [analysis] running analysis passes on this crate
end of query stack

error: internal compiler error: unexpected panic

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 1.36.0-nightly (00859e3e6 2019-04-29) 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

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=540971beb17a2f712b41a5a5e8888f51

If you give the lifetime explicitly, it compiles:
https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=ccd7cdc4e4d0e3952f518070fae7fba8

[Centril]

Unstable buggy feature: suggested P-medium;
Might also want to add to INCOMPLETE_FEATURES and P-high that aspect alone.

[davidtwco]

I think this is a duplicate of #60371.

[nikomatsakis]

Closing as duplicate.

[varkor]

This ICEs in a different place after #60714, hitting:

rust/src/librustc_mir/util/elaborate_drops.rs

Line 829 in aa9369c

_ => bug!("open drop from non-ADT `{:?}`", ty)

[pnkfelix]

triage: P-medium. Removing nomination tag.

[Alexendoo]

Fixed by #67681