Repository: rust
Issue: ICE: add_outlives_bounds: unexpected regions
Labels: I-ICE,E-needs-test,T-compiler,regression-from-stable-to-stable,C-bug

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### Code


```rust
trait Gat {
    type FooArg<'a, 'b: 'b>;
}

impl Gat for () {
    type FooArg<'a, 'b: 'b> = &'a dyn ToString;
}

struct Test;

impl Iterator for Test {
    type Item = Box<dyn Fn(<() as Gat>::FooArg<'_, '_>)>;

    fn next(&mut self) -> Option<Self::Item> { None }
}

pub fn main() {}
```


### Meta
<!--
If you're using the stable version of the compiler, you should also check if the
bug also exists in the beta or nightly versions.
-->

`rustc --version --verbose`:
```
rustc 1.73.0-nightly (1a8d09468 2023-07-17)
binary: rustc
commit-hash: 1a8d09468f045d75c5072af0a3e9b23443d484dd
commit-date: 2023-07-17
host: x86_64-unknown-linux-gnu
release: 1.73.0-nightly
LLVM version: 16.0.5
```

### Error output

```
```

<!--
Include a backtrace in the code block by setting `RUST_BACKTRACE=1` in your
environment. E.g. `RUST_BACKTRACE=1 cargo build`.
-->
<details><summary><strong>Backtrace</strong></summary>
<p>

```
error: internal compiler error: /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/compiler/rustc_infer/src/infer/outlives/env.rs:148:26: add_outlives_bounds: unexpected regions: (RePlaceholder(Placeholder { universe: U3, bound: BoundRegion { var: 1, kind: BrNamed(DefId(0:18 ~ playground[4e9f]::{impl#1}::Item::'_#1), '_) } }), RePlaceholder(Placeholder { universe: U3, bound: BoundRegion { var: 1, kind: BrNamed(DefId(0:18 ~ playground[4e9f]::{impl#1}::Item::'_#1), '_) } }))

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/compiler/rustc_errors/src/lib.rs:1651:9
stack backtrace:
   0:     0x7fb0e822a071 - std::backtrace_rs::backtrace::libunwind::trace::h6aeaf83abc038fe6
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7fb0e822a071 - std::backtrace_rs::backtrace::trace_unsynchronized::h4f9875212db0ad97
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fb0e822a071 - std::sys_common::backtrace::_print_fmt::h3f820027e9c39d3b
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7fb0e822a071 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hded4932df41373b3
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7fb0e8289d9f - core::fmt::rt::Argument::fmt::hc8ead7746b2406d6
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/core/src/fmt/rt.rs:138:9
   5:     0x7fb0e8289d9f - core::fmt::write::hb1cb56105a082ad9
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/core/src/fmt/mod.rs:1094:21
   6:     0x7fb0e821d271 - std::io::Write::write_fmt::h797fda7085c97e57
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/io/mod.rs:1713:15
   7:     0x7fb0e8229e85 - std::sys_common::backtrace::_print::h492d3c92d7400346
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7fb0e8229e85 - std::sys_common::backtrace::print::hf74aa2eef05af215
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7fb0e822cb47 - std::panicking::default_hook::{{closure}}::h8cad394227ea3de8
  10:     0x7fb0e822c934 - std::panicking::default_hook::h249cc184fec99a8a
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/panicking.rs:288:9
  11:     0x7fb0eb3a9b5b - rustc_driver_impl[55b27a31f76e3fb7]::install_ice_hook::{closure#0}
  12:     0x7fb0e822d28d - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h0be7fc2421582b49
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/alloc/src/boxed.rs:1999:9
  13:     0x7fb0e822d28d - std::panicking::rust_panic_with_hook::h82ebcd5d5ed2fad4
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/panicking.rs:709:13
  14:     0x7fb0eb8b6dc1 - std[a2d7a4c8dd6a1366]::panicking::begin_panic::<rustc_errors[ac1621e430503503]::ExplicitBug>::{closure#0}
  15:     0x7fb0eb8b2b96 - std[a2d7a4c8dd6a1366]::sys_common::backtrace::__rust_end_short_backtrace::<std[a2d7a4c8dd6a1366]::panicking::begin_panic<rustc_errors[ac1621e430503503]::ExplicitBug>::{closure#0}, !>
  16:     0x7fb0eb8aece6 - std[a2d7a4c8dd6a1366]::panicking::begin_panic::<rustc_errors[ac1621e430503503]::ExplicitBug>
  17:     0x7fb0eb8ac204 - <rustc_errors[ac1621e430503503]::HandlerInner>::bug::<alloc[af44278adca4aa3a]::string::String>
  18:     0x7fb0eb8abfa6 - <rustc_errors[ac1621e430503503]::Handler>::bug::<alloc[af44278adca4aa3a]::string::String>
  19:     0x7fb0eb93a92c - rustc_middle[69e8a450f04f22d]::util::bug::opt_span_bug_fmt::<rustc_span[b25f563e2e6d20a1]::span_encoding::Span>::{closure#0}
  20:     0x7fb0eb936ffa - rustc_middle[69e8a450f04f22d]::ty::context::tls::with_opt::<rustc_middle[69e8a450f04f22d]::util::bug::opt_span_bug_fmt<rustc_span[b25f563e2e6d20a1]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7fb0eb936fca - rustc_middle[69e8a450f04f22d]::ty::context::tls::with_context_opt::<rustc_middle[69e8a450f04f22d]::ty::context::tls::with_opt<rustc_middle[69e8a450f04f22d]::util::bug::opt_span_bug_fmt<rustc_span[b25f563e2e6d20a1]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7fb0e9a7632d - rustc_middle[69e8a450f04f22d]::util::bug::bug_fmt
  23:     0x7fb0e9e096db - <rustc_infer[ab09412129cf3116]::infer::outlives::env::OutlivesEnvironment>::with_bounds::<core[3d2408b9a7974bb]::iter::adapters::flatten::FlatMap<indexmap[35ddfa7bf58f02e4]::set::IntoIter<rustc_middle[69e8a450f04f22d]::ty::Ty>, alloc[af44278adca4aa3a]::vec::Vec<rustc_middle[69e8a450f04f22d]::traits::query::OutlivesBound>, <rustc_infer[ab09412129cf3116]::infer::InferCtxt as rustc_trait_selection[fd75ccd2de8cef13]::traits::outlives_bounds::InferCtxtExt>::implied_bounds_tys::{closure#0}>>
  24:     0x7fb0ea310490 - rustc_hir_analysis[367b7eb6b2106fd1]::check::compare_impl_item::compare_method_predicate_entailment
  25:     0x7fb0ea3065b0 - rustc_hir_analysis[367b7eb6b2106fd1]::check::compare_impl_item::compare_impl_method
  26:     0x7fb0ea2fa9d3 - rustc_hir_analysis[367b7eb6b2106fd1]::check::check::check_mod_item_types
  27:     0x7fb0e9feac5c - rustc_query_impl[9640443f3247e199]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[9640443f3247e199]::query_impl::check_mod_item_types::dynamic_query::{closure#2}::{closure#0}, rustc_middle[69e8a450f04f22d]::query::erase::Erased<[u8; 0usize]>>
  28:     0x7fb0e9feac3e - <rustc_query_impl[9640443f3247e199]::query_impl::check_mod_item_types::dynamic_query::{closure#2} as core[3d2408b9a7974bb]::ops::function::FnOnce<(rustc_middle[69e8a450f04f22d]::ty::context::TyCtxt, rustc_span[b25f563e2e6d20a1]::def_id::LocalDefId)>>::call_once
  29:     0x7fb0e9b688ef - rustc_query_system[18feb85a2a4aa83f]::query::plumbing::try_execute_query::<rustc_query_impl[9640443f3247e199]::DynamicConfig<rustc_query_system[18feb85a2a4aa83f]::query::caches::VecCache<rustc_span[b25f563e2e6d20a1]::def_id::LocalDefId, rustc_middle[69e8a450f04f22d]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[9640443f3247e199]::plumbing::QueryCtxt, false>
  30:     0x7fb0ead65a14 - rustc_query_impl[9640443f3247e199]::query_impl::check_mod_item_types::get_query_non_incr::__rust_end_short_backtrace
  31:     0x7fb0ea88fdd7 - <rustc_middle[69e8a450f04f22d]::hir::map::Map>::for_each_module::<rustc_hir_analysis[367b7eb6b2106fd1]::check_crate::{closure#6}::{closure#0}>
  32:     0x7fb0ea88f20d - <rustc_session[3eaa31a6c81d371]::session::Session>::time::<(), rustc_hir_analysis[367b7eb6b2106fd1]::check_crate::{closure#6}>
  33:     0x7fb0ea88d247 - rustc_hir_analysis[367b7eb6b2106fd1]::check_crate
  34:     0x7fb0ea88843d - rustc_interface[2ac6857faa489841]::passes::analysis
  35:     0x7fb0ea8c624a - rustc_query_impl[9640443f3247e199]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[9640443f3247e199]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[69e8a450f04f22d]::query::erase::Erased<[u8; 1usize]>>
  36:     0x7fb0ea8c6239 - <rustc_query_impl[9640443f3247e199]::query_impl::analysis::dynamic_query::{closure#2} as core[3d2408b9a7974bb]::ops::function::FnOnce<(rustc_middle[69e8a450f04f22d]::ty::context::TyCtxt, ())>>::call_once
  37:     0x7fb0eaa7b8e8 - rustc_query_system[18feb85a2a4aa83f]::query::plumbing::try_execute_query::<rustc_query_impl[9640443f3247e199]::DynamicConfig<rustc_query_system[18feb85a2a4aa83f]::query::caches::SingleCache<rustc_middle[69e8a450f04f22d]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[9640443f3247e199]::plumbing::QueryCtxt, false>
  38:     0x7fb0eaa7b6b9 - rustc_query_impl[9640443f3247e199]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  39:     0x7fb0ea632f22 - <rustc_interface[2ac6857faa489841]::queries::QueryResult<&rustc_middle[69e8a450f04f22d]::ty::context::GlobalCtxt>>::enter::<core[3d2408b9a7974bb]::result::Result<(), rustc_span[b25f563e2e6d20a1]::ErrorGuaranteed>, rustc_driver_impl[55b27a31f76e3fb7]::run_compiler::{closure#1}::{closure#2}::{closure#4}>
  40:     0x7fb0ea631e85 - <rustc_interface[2ac6857faa489841]::interface::Compiler>::enter::<rustc_driver_impl[55b27a31f76e3fb7]::run_compiler::{closure#1}::{closure#2}, core[3d2408b9a7974bb]::result::Result<core[3d2408b9a7974bb]::option::Option<rustc_interface[2ac6857faa489841]::queries::Linker>, rustc_span[b25f563e2e6d20a1]::ErrorGuaranteed>>
  41:     0x7fb0ea62f683 - std[a2d7a4c8dd6a1366]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[2ac6857faa489841]::util::run_in_thread_pool_with_globals<rustc_interface[2ac6857faa489841]::interface::run_compiler<core[3d2408b9a7974bb]::result::Result<(), rustc_span[b25f563e2e6d20a1]::ErrorGuaranteed>, rustc_driver_impl[55b27a31f76e3fb7]::run_compiler::{closure#1}>::{closure#0}, core[3d2408b9a7974bb]::result::Result<(), rustc_span[b25f563e2e6d20a1]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3d2408b9a7974bb]::result::Result<(), rustc_span[b25f563e2e6d20a1]::ErrorGuaranteed>>
  42:     0x7fb0eac5b165 - <<std[a2d7a4c8dd6a1366]::thread::Builder>::spawn_unchecked_<rustc_interface[2ac6857faa489841]::util::run_in_thread_pool_with_globals<rustc_interface[2ac6857faa489841]::interface::run_compiler<core[3d2408b9a7974bb]::result::Result<(), rustc_span[b25f563e2e6d20a1]::ErrorGuaranteed>, rustc_driver_impl[55b27a31f76e3fb7]::run_compiler::{closure#1}>::{closure#0}, core[3d2408b9a7974bb]::result::Result<(), rustc_span[b25f563e2e6d20a1]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3d2408b9a7974bb]::result::Result<(), rustc_span[b25f563e2e6d20a1]::ErrorGuaranteed>>::{closure#1} as core[3d2408b9a7974bb]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  43:     0x7fb0e82377b5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h9adfc2ae43657457
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/alloc/src/boxed.rs:1985:9
  44:     0x7fb0e82377b5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h14fefbfa7b574396
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/alloc/src/boxed.rs:1985:9
  45:     0x7fb0e82377b5 - std::sys::unix::thread::Thread::new::thread_start::ha211bb47f6f5cedc
                               at /rustc/8ede3aae28fe6e4d52b38157d7bfe0d3bceef225/library/std/src/sys/unix/thread.rs:108:17
  46:     0x7fb0e8107609 - start_thread
  47:     0x7fb0e802a133 - clone
  48:                0x0 - <unknown>

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 1.71.0 (8ede3aae2 2023-07-12) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [check_mod_item_types] checking item types in top-level module
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0412`.
```

</p>
</details>