ICE: opaque type with non-universal region substs

[chengniansun]

Code

#![feature(impl_trait_in_bindings)]
struct A<'a>(&'a ());
trait Trait<T> {}
impl<T> Trait<T> for () {}
fn foo<'a: 'a>() {
    let _x: impl Trait<A<'a>> = ();
}

Meta

rustc --version --verbose:

rustc 1.54.0-nightly (716394d65 2021-05-03)
binary: rustc
commit-hash: 716394d6581b60c75cfdd88b8e5b876f2db88b62
commit-date: 2021-05-03
host: x86_64-unknown-linux-gnu
release: 1.54.0-nightly
LLVM version: 12.0.0

Error output

warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:1:12
  |
1 | #![feature(impl_trait_in_bindings)]
  |            ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default
  = note: see issue #63065 <https://github.com/rust-lang/rust/issues/63065> for more information

warning: struct is never constructed: `A`
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:2:8
  |
2 | struct A<'a>(&'a ());
  |        ^
  |
  = note: `#[warn(dead_code)]` on by default

warning: function is never used: `foo`
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:5:4
  |
5 | fn foo<'a: 'a>() {
  |    ^^^

warning: 3 warnings emitted

error: internal compiler error: opaque type with non-universal region substs
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:5:1
  |
5 | / fn foo<'a: 'a>() {
6 | |     let _x: impl Trait<A<'a>> = ();
7 | | }
  | |_^
  |
  = note: delayed at compiler/rustc_mir/src/borrow_check/region_infer/opaque_types.rs:68:48

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:1018:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.54.0-nightly (716394d65 2021-05-03) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type staticlib

query stack during panic:
end of query stack

Backtrace

warning: the feature `impl_trait_in_bindings` is incomplete and may not be safe to use and/or cause compiler crashes
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:1:12
  |
1 | #![feature(impl_trait_in_bindings)]
  |            ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default
  = note: see issue #63065 <https://github.com/rust-lang/rust/issues/63065> for more information

warning: struct is never constructed: `A`
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:2:8
  |
2 | struct A<'a>(&'a ());
  |        ^
  |
  = note: `#[warn(dead_code)]` on by default

warning: function is never used: `foo`
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:5:4
  |
5 | fn foo<'a: 'a>() {
  |    ^^^

warning: 3 warnings emitted

error: internal compiler error: opaque type with non-universal region substs
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:5:1
  |
5 | / fn foo<'a: 'a>() {
6 | |     let _x: impl Trait<A<'a>> = ();
7 | | }
  | |_^
  |
  = note: delayed at compiler/rustc_mir/src/borrow_check/region_infer/opaque_types.rs:68:48

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:1018:13
stack backtrace:
   0: rust_begin_unwind
             at /rustc/716394d6581b60c75cfdd88b8e5b876f2db88b62/library/std/src/panicking.rs:493:5
   1: std::panicking::begin_panic_fmt
             at /rustc/716394d6581b60c75cfdd88b8e5b876f2db88b62/library/std/src/panicking.rs:435:5
   2: rustc_errors::HandlerInner::flush_delayed
   3: <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop
   4: core::ptr::drop_in_place<rustc_session::parse::ParseSess>
   5: <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop
   6: core::ptr::drop_in_place<rustc_interface::interface::Compiler>
   7: rustc_span::with_source_map
   8: rustc_interface::interface::create_compiler_and_run
   9: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.54.0-nightly (716394d65 2021-05-03) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type staticlib

query stack during panic:
end of query stack

[jyn514]

Slightly smaller:

#![feature(impl_trait_in_bindings)]

trait Trait {}
impl Trait for () {}

fn foo<'a: 'a>() {
    let _x: impl Trait = ();
}