ICE with generic associated types and HRTBs

[moulins]

Got an ICE while experimenting with GATs:

use std::marker::PhantomData as Boo;

struct Gc<'gc, T: 'gc>(Boo<fn(&'gc T) -> &'gc T>);

trait Rootable<'env> {
    type AsRoot<'r>: Rootable<'r> + 'r where 'env: 'r;
}

impl<'env, T: Rootable<'env>> Rootable<'env> for Gc<'env, T> {
    type AsRoot<'r> = Gc<'r, T::AsRoot<'r>> where 'env: 'r;
}

impl<'env> Rootable<'env> for i32 {
    type AsRoot<'r> = i32 where 'env: 'r;
}

fn reroot<'gc, T: Rootable<'gc>>(_t: T, _f: for<'a> fn(T::AsRoot<'a>)) {
}

fn test<'gc>(t: Gc<'gc, i32>) {
    reroot(t, |_| ());
}

This crashes with the following error:

   Compiling playground v0.0.1 (/playground)
error: internal compiler error: compiler/rustc_borrowck/src/universal_regions.rs:828:36: cannot convert `RePlaceholder(Placeholder { universe: U1, name: BrAnon(0, None) })` to a region vid

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/compiler/rustc_errors/src/lib.rs:1609:9
stack backtrace:
   0:     0x7fc1a3ccf36a - std::backtrace_rs::backtrace::libunwind::trace::heb3166a6cb1fd02b
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7fc1a3ccf36a - std::backtrace_rs::backtrace::trace_unsynchronized::h34837841e045a1d4
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fc1a3ccf36a - std::sys_common::backtrace::_print_fmt::h4348a4b63f328ee4
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7fc1a3ccf36a - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h1bad440d01eeeb29
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7fc1a3d3152e - core::fmt::write::hb5a073c651a6cb64
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/core/src/fmt/mod.rs:1232:17
   5:     0x7fc1a3cbf9b5 - std::io::Write::write_fmt::h97cc768331421fb2
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/io/mod.rs:1682:15
   6:     0x7fc1a3ccf135 - std::sys_common::backtrace::_print::h23bd93d6897965f3
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7fc1a3ccf135 - std::sys_common::backtrace::print::h4d41ae33ce7a824f
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7fc1a3cd1eff - std::panicking::default_hook::{{closure}}::h8ab48635107c713a
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/panicking.rs:267:22
   9:     0x7fc1a3cd1c3b - std::panicking::default_hook::h6305ca3c910e41d2
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/panicking.rs:286:9
  10:     0x7fc1a703e444 - rustc_driver[d1d90693eba3e117]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7fc1a3cd273a - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h60fe4dd8262b5528
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/alloc/src/boxed.rs:2002:9
  12:     0x7fc1a3cd273a - std::panicking::rust_panic_with_hook::ha8dfad8ee636a9a3
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/panicking.rs:692:13
  13:     0x7fc1a754dc21 - std[ef0604d174e11cd5]::panicking::begin_panic::<rustc_errors[6cf9ff966b0b62fb]::ExplicitBug>::{closure#0}
  14:     0x7fc1a754cad6 - std[ef0604d174e11cd5]::sys_common::backtrace::__rust_end_short_backtrace::<std[ef0604d174e11cd5]::panicking::begin_panic<rustc_errors[6cf9ff966b0b62fb]::ExplicitBug>::{closure#0}, !>
  15:     0x7fc1a75db2a6 - std[ef0604d174e11cd5]::panicking::begin_panic::<rustc_errors[6cf9ff966b0b62fb]::ExplicitBug>
  16:     0x7fc1a75909c6 - std[ef0604d174e11cd5]::panic::panic_any::<rustc_errors[6cf9ff966b0b62fb]::ExplicitBug>
  17:     0x7fc1a758b376 - <rustc_errors[6cf9ff966b0b62fb]::HandlerInner>::bug::<&alloc[9ea3c9e5c77b7621]::string::String>
  18:     0x7fc1a7589fd0 - <rustc_errors[6cf9ff966b0b62fb]::Handler>::bug::<&alloc[9ea3c9e5c77b7621]::string::String>
  19:     0x7fc1a759f4bb - rustc_middle[526e0ca739798ee2]::util::bug::opt_span_bug_fmt::<rustc_span[6b0f4bf036ac788e]::span_encoding::Span>::{closure#0}
  20:     0x7fc1a759f2ea - rustc_middle[526e0ca739798ee2]::ty::context::tls::with_opt::<rustc_middle[526e0ca739798ee2]::util::bug::opt_span_bug_fmt<rustc_span[6b0f4bf036ac788e]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x7fc1a759f2ba - rustc_middle[526e0ca739798ee2]::ty::context::tls::with_context_opt::<rustc_middle[526e0ca739798ee2]::ty::context::tls::with_opt<rustc_middle[526e0ca739798ee2]::util::bug::opt_span_bug_fmt<rustc_span[6b0f4bf036ac788e]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x7fc1a759f406 - rustc_middle[526e0ca739798ee2]::util::bug::opt_span_bug_fmt::<rustc_span[6b0f4bf036ac788e]::span_encoding::Span>
  23:     0x7fc1a52d57c3 - rustc_middle[526e0ca739798ee2]::util::bug::bug_fmt
  24:     0x7fc1a5f6f38e - <&mut <rustc_borrowck[2e52752a89f891f4]::type_check::free_region_relations::UniversalRegionRelationsBuilder>::create::{closure#0} as core[3a3cbeb512a16fa3]::ops::function::FnOnce<(rustc_middle[526e0ca739798ee2]::ty::Ty,)>>::call_once
  25:     0x7fc1a5f6e402 - <alloc[9ea3c9e5c77b7621]::vec::Vec<&rustc_middle[526e0ca739798ee2]::infer::canonical::QueryRegionConstraints> as alloc[9ea3c9e5c77b7621]::vec::spec_from_iter::SpecFromIter<&rustc_middle[526e0ca739798ee2]::infer::canonical::QueryRegionConstraints, core[3a3cbeb512a16fa3]::iter::adapters::flatten::FlatMap<core[3a3cbeb512a16fa3]::iter::adapters::chain::Chain<core[3a3cbeb512a16fa3]::iter::adapters::cloned::Cloned<core[3a3cbeb512a16fa3]::slice::iter::Iter<rustc_middle[526e0ca739798ee2]::ty::Ty>>, core[3a3cbeb512a16fa3]::option::IntoIter<rustc_middle[526e0ca739798ee2]::ty::Ty>>, core[3a3cbeb512a16fa3]::iter::adapters::chain::Chain<core[3a3cbeb512a16fa3]::iter::adapters::chain::Chain<core[3a3cbeb512a16fa3]::option::IntoIter<&rustc_middle[526e0ca739798ee2]::infer::canonical::QueryRegionConstraints>, core[3a3cbeb512a16fa3]::option::IntoIter<&rustc_middle[526e0ca739798ee2]::infer::canonical::QueryRegionConstraints>>, core[3a3cbeb512a16fa3]::option::IntoIter<&rustc_middle[526e0ca739798ee2]::infer::canonical::QueryRegionConstraints>>, <rustc_borrowck[2e52752a89f891f4]::type_check::free_region_relations::UniversalRegionRelationsBuilder>::create::{closure#0}>>>::from_iter
  26:     0x7fc1a5f69709 - rustc_borrowck[2e52752a89f891f4]::type_check::free_region_relations::create
  27:     0x7fc1a5f5480d - rustc_borrowck[2e52752a89f891f4]::nll::compute_regions
  28:     0x7fc1a5f23e5e - rustc_borrowck[2e52752a89f891f4]::do_mir_borrowck
  29:     0x7fc1a5f06f85 - rustc_borrowck[2e52752a89f891f4]::mir_borrowck
  30:     0x7fc1a582238d - rustc_query_system[decabb1eb79370b7]::query::plumbing::try_execute_query::<rustc_query_impl[ff3c18b748312d2f]::queries::mir_borrowck, rustc_query_impl[ff3c18b748312d2f]::plumbing::QueryCtxt>
  31:     0x7fc1a69f6c8d - <rustc_query_impl[ff3c18b748312d2f]::Queries as rustc_middle[526e0ca739798ee2]::ty::query::QueryEngine>::mir_borrowck
  32:     0x7fc1a6001124 - <rustc_borrowck[2e52752a89f891f4]::type_check::TypeChecker>::prove_closure_bounds
  33:     0x7fc1a5fdd78b - <rustc_borrowck[2e52752a89f891f4]::type_check::TypeChecker>::typeck_mir
  34:     0x7fc1a5f54b8d - rustc_borrowck[2e52752a89f891f4]::nll::compute_regions
  35:     0x7fc1a5f23e5e - rustc_borrowck[2e52752a89f891f4]::do_mir_borrowck
  36:     0x7fc1a5f06f85 - rustc_borrowck[2e52752a89f891f4]::mir_borrowck
  37:     0x7fc1a582238d - rustc_query_system[decabb1eb79370b7]::query::plumbing::try_execute_query::<rustc_query_impl[ff3c18b748312d2f]::queries::mir_borrowck, rustc_query_impl[ff3c18b748312d2f]::plumbing::QueryCtxt>
  38:     0x7fc1a568f5cd - rustc_data_structures[439cdbfa31de989]::sync::par_for_each_in::<&[rustc_span[6b0f4bf036ac788e]::def_id::LocalDefId], <rustc_middle[526e0ca739798ee2]::hir::map::Map>::par_body_owners<rustc_interface[d4b4ad1a0cb81775]::passes::analysis::{closure#2}::{closure#0}>::{closure#0}>
  39:     0x7fc1a568f1d3 - <rustc_session[8c42e6c16859134b]::session::Session>::time::<(), rustc_interface[d4b4ad1a0cb81775]::passes::analysis::{closure#2}>
  40:     0x7fc1a568d2b7 - rustc_interface[d4b4ad1a0cb81775]::passes::analysis
  41:     0x7fc1a67c588e - rustc_query_system[decabb1eb79370b7]::query::plumbing::try_execute_query::<rustc_query_impl[ff3c18b748312d2f]::queries::analysis, rustc_query_impl[ff3c18b748312d2f]::plumbing::QueryCtxt>
  42:     0x7fc1a69ef64a - <rustc_query_impl[ff3c18b748312d2f]::Queries as rustc_middle[526e0ca739798ee2]::ty::query::QueryEngine>::analysis
  43:     0x7fc1a66f8a60 - <rustc_interface[d4b4ad1a0cb81775]::passes::QueryContext>::enter::<rustc_driver[d1d90693eba3e117]::run_compiler::{closure#1}::{closure#2}::{closure#3}, core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>>
  44:     0x7fc1a624a296 - rustc_span[6b0f4bf036ac788e]::with_source_map::<core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>, rustc_interface[d4b4ad1a0cb81775]::interface::run_compiler<core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>, rustc_driver[d1d90693eba3e117]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
  45:     0x7fc1a6242654 - <scoped_tls[6607de7944b4e913]::ScopedKey<rustc_span[6b0f4bf036ac788e]::SessionGlobals>>::set::<rustc_interface[d4b4ad1a0cb81775]::interface::run_compiler<core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>, rustc_driver[d1d90693eba3e117]::run_compiler::{closure#1}>::{closure#0}, core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>>
  46:     0x7fc1a6241d52 - std[ef0604d174e11cd5]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[d4b4ad1a0cb81775]::util::run_in_thread_pool_with_globals<rustc_interface[d4b4ad1a0cb81775]::interface::run_compiler<core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>, rustc_driver[d1d90693eba3e117]::run_compiler::{closure#1}>::{closure#0}, core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>>
  47:     0x7fc1a6241afa - <<std[ef0604d174e11cd5]::thread::Builder>::spawn_unchecked_<rustc_interface[d4b4ad1a0cb81775]::util::run_in_thread_pool_with_globals<rustc_interface[d4b4ad1a0cb81775]::interface::run_compiler<core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>, rustc_driver[d1d90693eba3e117]::run_compiler::{closure#1}>::{closure#0}, core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3a3cbeb512a16fa3]::result::Result<(), rustc_errors[6cf9ff966b0b62fb]::ErrorGuaranteed>>::{closure#1} as core[3a3cbeb512a16fa3]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  48:     0x7fc1a3cdc803 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h9646bd6a135081c9
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/alloc/src/boxed.rs:1988:9
  49:     0x7fc1a3cdc803 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h180d98f11b902552
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/alloc/src/boxed.rs:1988:9
  50:     0x7fc1a3cdc803 - std::sys::unix::thread::Thread::new::thread_start::h83489d4028ebb6e1
                               at /rustc/ef982929c0b653436a6ea6892a2a839fba7c8b57/library/std/src/sys/unix/thread.rs:108:17
  51:     0x7fc1a3b9f609 - start_thread
  52:     0x7fc1a3ac2133 - clone
  53:                0x0 - <unknown>

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 1.69.0-nightly (ef982929c 2023-01-27) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [mir_borrowck] borrow-checking `test::{closure#0}`
#1 [mir_borrowck] borrow-checking `test`
#2 [analysis] running analysis passes on this crate
end of query stack
error: could not compile `playground`

Playground link