rustdoc: ICE: synthetic auto trait impls: `unexpected region: RePlaceholder[…]` involving TAIT

[Sherlock-Holo]

Code

this commit codes Sherlock-Holo/compio_compat@468c054

Meta

rustc --version --verbose:

rustc 1.77.0-nightly (bf3c6c5be 2024-02-01)
binary: rustc
commit-hash: bf3c6c5bed498f41ad815641319a1ad9bcecb8e8
commit-date: 2024-02-01
host: x86_64-unknown-linux-gnu
release: 1.77.0-nightly
LLVM version: 17.0.6

Error output

error: internal compiler error: src/librustdoc/clean/auto_trait.rs:745:18: unexpected region: RePlaceholder(!1_BoundRegion { var: 0, kind: BrAnon })

thread 'rustc' panicked at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/compiler/rustc_errors/src/lib.rs:932:30:
Box<dyn Any>
stack backtrace:
   0:     0x75078af8cd16 - std::backtrace_rs::backtrace::libunwind::trace::he544685250360e22
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x75078af8cd16 - std::backtrace_rs::backtrace::trace_unsynchronized::h664adef12633380a
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x75078af8cd16 - std::sys_common::backtrace::_print_fmt::hba7ee045aeee07b0
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x75078af8cd16 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hc80b7ff177a688f2
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x75078afdf770 - core::fmt::rt::Argument::fmt::h605309ab4829b6b5
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/core/src/fmt/rt.rs:142:9
   5:     0x75078afdf770 - core::fmt::write::h5f24f526de99e105
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/core/src/fmt/mod.rs:1120:17
   6:     0x75078af8061f - std::io::Write::write_fmt::h711c920f97cd3d8c
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/io/mod.rs:1846:15
   7:     0x75078af8caf4 - std::sys_common::backtrace::_print::ha279702af2871260
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x75078af8caf4 - std::sys_common::backtrace::print::hc1f3820f405abdd3
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x75078af8f887 - std::panicking::default_hook::{{closure}}::h5058841d19c78172
  10:     0x75078af8f5e9 - std::panicking::default_hook::h60a42497ec033f97
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/panicking.rs:292:9
  11:     0x750787b371fc - std[4337b1e3d1c66af6]::panicking::update_hook::<alloc[6a28242b4f343ab9]::boxed::Box<rustc_driver_impl[e51f6499da6a94b9]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x75078af8ffd6 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h437fd8fcb0ff0cea
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/alloc/src/boxed.rs:2029:9
  13:     0x75078af8ffd6 - std::panicking::rust_panic_with_hook::h294fbe090fe44fa4
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/panicking.rs:785:13
  14:     0x750787b693b4 - std[4337b1e3d1c66af6]::panicking::begin_panic::<rustc_errors[37e82e04e08bc148]::ExplicitBug>::{closure#0}
  15:     0x750787b65aa6 - std[4337b1e3d1c66af6]::sys_common::backtrace::__rust_end_short_backtrace::<std[4337b1e3d1c66af6]::panicking::begin_panic<rustc_errors[37e82e04e08bc148]::ExplicitBug>::{closure#0}, !>
  16:     0x750787b60d06 - std[4337b1e3d1c66af6]::panicking::begin_panic::<rustc_errors[37e82e04e08bc148]::ExplicitBug>
  17:     0x750787b74591 - <rustc_errors[37e82e04e08bc148]::diagnostic_builder::BugAbort as rustc_errors[37e82e04e08bc148]::diagnostic_builder::EmissionGuarantee>::emit_producing_guarantee
  18:     0x750787f2cbcb - <rustc_errors[37e82e04e08bc148]::DiagCtxt>::bug::<alloc[6a28242b4f343ab9]::string::String>
  19:     0x750787fc3ceb - rustc_middle[9b442554c155189d]::util::bug::opt_span_bug_fmt::<rustc_span[ecf473d7733698d2]::span_encoding::Span>::{closure#0}
  20:     0x750787faca2a - rustc_middle[9b442554c155189d]::ty::context::tls::with_opt::<rustc_middle[9b442554c155189d]::util::bug::opt_span_bug_fmt<rustc_span[ecf473d7733698d2]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x750787fac8c8 - rustc_middle[9b442554c155189d]::ty::context::tls::with_context_opt::<rustc_middle[9b442554c155189d]::ty::context::tls::with_opt<rustc_middle[9b442554c155189d]::util::bug::opt_span_bug_fmt<rustc_span[ecf473d7733698d2]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x750785f61d40 - rustc_middle[9b442554c155189d]::util::bug::bug_fmt
  23:     0x5aba61135c63 - <rustdoc[3384abbdb6741cf]::clean::auto_trait::RegionReplacer as rustc_type_ir[d836307668432e47]::fold::TypeFolder<rustc_middle[9b442554c155189d]::ty::context::TyCtxt>>::fold_region
  24:     0x5aba61077b2e - <&rustc_middle[9b442554c155189d]::ty::list::List<rustc_middle[9b442554c155189d]::ty::generic_args::GenericArg> as rustc_type_ir[d836307668432e47]::fold::TypeFoldable<rustc_middle[9b442554c155189d]::ty::context::TyCtxt>>::try_fold_with::<rustdoc[3384abbdb6741cf]::clean::auto_trait::RegionReplacer>
  25:     0x5aba61071bcb - <rustc_middle[9b442554c155189d]::ty::Ty as rustc_type_ir[d836307668432e47]::fold::TypeSuperFoldable<rustc_middle[9b442554c155189d]::ty::context::TyCtxt>>::try_super_fold_with::<rustdoc[3384abbdb6741cf]::clean::auto_trait::RegionReplacer>
  26:     0x5aba61077e9e - <&rustc_middle[9b442554c155189d]::ty::list::List<rustc_middle[9b442554c155189d]::ty::generic_args::GenericArg> as rustc_type_ir[d836307668432e47]::fold::TypeFoldable<rustc_middle[9b442554c155189d]::ty::context::TyCtxt>>::try_fold_with::<rustdoc[3384abbdb6741cf]::clean::auto_trait::RegionReplacer>
  27:     0x5aba61130ad5 - <rustdoc[3384abbdb6741cf]::clean::auto_trait::AutoTraitFinder>::param_env_to_generics
  28:     0x5aba60fd2be6 - <rustc_trait_selection[549d5aadac124ff9]::traits::auto_trait::AutoTraitFinder>::find_auto_trait_generics::<rustdoc[3384abbdb6741cf]::clean::types::Generics, <rustdoc[3384abbdb6741cf]::clean::auto_trait::AutoTraitFinder>::generate_for_trait::{closure#0}>
  29:     0x5aba6112fb56 - <rustdoc[3384abbdb6741cf]::clean::auto_trait::AutoTraitFinder>::generate_for_trait
  30:     0x5aba6114e477 - rustdoc[3384abbdb6741cf]::clean::utils::get_auto_trait_and_blanket_impls
  31:     0x5aba612614ae - <rustdoc[3384abbdb6741cf]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[3384abbdb6741cf]::visit::DocVisitor>::visit_item
  32:     0x5aba6126182a - <rustdoc[3384abbdb6741cf]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[3384abbdb6741cf]::visit::DocVisitor>::visit_item
  33:     0x5aba6126182a - <rustdoc[3384abbdb6741cf]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[3384abbdb6741cf]::visit::DocVisitor>::visit_item
  34:     0x5aba6125e225 - rustdoc[3384abbdb6741cf]::passes::collect_trait_impls::collect_trait_impls
  35:     0x5aba611833fe - rustdoc[3384abbdb6741cf]::core::run_global_ctxt
  36:     0x5aba6128edb6 - rustdoc[3384abbdb6741cf]::main_args::{closure#1}::{closure#0}::{closure#0}
  37:     0x5aba6108585e - rustc_interface[e57535df52585ed5]::interface::run_compiler::<core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>, rustdoc[3384abbdb6741cf]::main_args::{closure#1}>::{closure#0}
  38:     0x5aba610488d0 - std[4337b1e3d1c66af6]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[e57535df52585ed5]::util::run_in_thread_with_globals<rustc_interface[e57535df52585ed5]::util::run_in_thread_pool_with_globals<rustc_interface[e57535df52585ed5]::interface::run_compiler<core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>, rustdoc[3384abbdb6741cf]::main_args::{closure#1}>::{closure#0}, core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>>::{closure#0}, core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>>
  39:     0x5aba61090ade - <<std[4337b1e3d1c66af6]::thread::Builder>::spawn_unchecked_<rustc_interface[e57535df52585ed5]::util::run_in_thread_with_globals<rustc_interface[e57535df52585ed5]::util::run_in_thread_pool_with_globals<rustc_interface[e57535df52585ed5]::interface::run_compiler<core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>, rustdoc[3384abbdb6741cf]::main_args::{closure#1}>::{closure#0}, core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>>::{closure#0}, core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[cc6cd760d986f799]::result::Result<(), rustc_span[ecf473d7733698d2]::ErrorGuaranteed>>::{closure#1} as core[cc6cd760d986f799]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  40:     0x75078af99675 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hc4b9a6efba849e51
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/alloc/src/boxed.rs:2015:9
  41:     0x75078af99675 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hc525ee5ac423ddcd
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/alloc/src/boxed.rs:2015:9
  42:     0x75078af99675 - std::sys::pal::unix::thread::Thread::new::thread_start::h31b81f67226864c0
                               at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/library/std/src/sys/pal/unix/thread.rs:108:17
  43:     0x750784caa9eb - <unknown>
  44:     0x750784d2e8ac - <unknown>
  45:                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-rustdoc&template=ice.md

note: please attach the file at `/home/sherlock/git/compio_compat/rustc-ice-2024-02-03T11_08_13-130160.txt` to your bug report

note: compiler flags: --crate-type lib

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

query stack during panic:
end of query stack
error: could not document `compio_compat`

Caused by:
  process didn't exit successfully: `/home/sherlock/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustdoc --edition=2021 --crate-type lib --crate-name compio_compat src/lib.rs -o /home/sherlock/git/compio_compat/target/doc --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=150 -C metadata=82bf5ac2095ab40f -L dependency=/home/sherlock/git/compio_compat/target/debug/deps --extern compio_buf=/home/sherlock/git/compio_compat/target/debug/deps/libcompio_buf-3f6a7492d880a9a6.rmeta --extern compio_io=/home/sherlock/git/compio_compat/target/debug/deps/libcompio_io-6ba0a1a4d4aab3c6.rmeta --extern futures_util=/home/sherlock/git/compio_compat/target/debug/deps/libfutures_util-9f338ae92a96bae3.rmeta --crate-version 0.1.0` (exit status: 101)

rustc-ice-2024-02-03T11_08_13-130160.txt

Backtrace

 Documenting compio_compat v0.1.0 (/home/sherlock/git/compio_compat)
error: internal compiler error: src/librustdoc/clean/auto_trait.rs:745:18: unexpected region: RePlaceholder(!1_BoundRegion { var: 0, kind: BrAnon })

thread 'rustc' panicked at /rustc/bf3c6c5bed498f41ad815641319a1ad9bcecb8e8/compiler/rustc_errors/src/lib.rs:932:30:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic_builder::BugAbort as rustc_errors::diagnostic_builder::EmissionGuarantee>::emit_producing_guarantee
   2: <rustc_errors::DiagCtxt>::bug::<alloc::string::String>
   3: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   4: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   5: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   6: rustc_middle::util::bug::bug_fmt
   7: <rustdoc::clean::auto_trait::RegionReplacer as rustc_type_ir::fold::TypeFolder<rustc_middle::ty::context::TyCtxt>>::fold_region
   8: <&rustc_middle::ty::list::List<rustc_middle::ty::generic_args::GenericArg> as rustc_type_ir::fold::TypeFoldable<rustc_middle::ty::context::TyCtxt>>::try_fold_with::<rustdoc::clean::auto_trait::RegionReplacer>
   9: <rustc_middle::ty::Ty as rustc_type_ir::fold::TypeSuperFoldable<rustc_middle::ty::context::TyCtxt>>::try_super_fold_with::<rustdoc::clean::auto_trait::RegionReplacer>
  10: <&rustc_middle::ty::list::List<rustc_middle::ty::generic_args::GenericArg> as rustc_type_ir::fold::TypeFoldable<rustc_middle::ty::context::TyCtxt>>::try_fold_with::<rustdoc::clean::auto_trait::RegionReplacer>
  11: <rustdoc::clean::auto_trait::AutoTraitFinder>::param_env_to_generics
  12: <rustc_trait_selection::traits::auto_trait::AutoTraitFinder>::find_auto_trait_generics::<rustdoc::clean::types::Generics, <rustdoc::clean::auto_trait::AutoTraitFinder>::generate_for_trait::{closure#0}>
  13: <rustdoc::clean::auto_trait::AutoTraitFinder>::generate_for_trait
  14: rustdoc::clean::utils::get_auto_trait_and_blanket_impls
  15: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector as rustdoc::visit::DocVisitor>::visit_item
  16: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector as rustdoc::visit::DocVisitor>::visit_item
  17: <rustdoc::passes::collect_trait_impls::SyntheticImplCollector as rustdoc::visit::DocVisitor>::visit_item
  18: rustdoc::passes::collect_trait_impls::collect_trait_impls
  19: rustdoc::core::run_global_ctxt
  20: rustdoc::main_args::{closure#1}::{closure#0}::{closure#0}
  21: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustdoc::main_args::{closure#1}>::{closure#0}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-rustdoc&template=ice.md

note: please attach the file at `/home/sherlock/git/compio_compat/rustc-ice-2024-02-03T11_11_10-133512.txt` to your bug report

note: compiler flags: --crate-type lib

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

query stack during panic:
end of query stack
error: could not document `compio_compat`

Caused by:
  process didn't exit successfully: `/home/sherlock/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/rustdoc --edition=2021 --crate-type lib --crate-name compio_compat src/lib.rs -o /home/sherlock/git/compio_compat/target/doc --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=150 -C metadata=82bf5ac2095ab40f -L dependency=/home/sherlock/git/compio_compat/target/debug/deps --extern compio_buf=/home/sherlock/git/compio_compat/target/debug/deps/libcompio_buf-3f6a7492d880a9a6.rmeta --extern compio_io=/home/sherlock/git/compio_compat/target/debug/deps/libcompio_io-6ba0a1a4d4aab3c6.rmeta --extern futures_util=/home/sherlock/git/compio_compat/target/debug/deps/libfutures_util-9f338ae92a96bae3.rmeta --crate-version 0.1.0` (exit status: 101)

[Luk-ESC]

Minimized:

#![feature(type_alias_impl_trait)]
use std::future::Future;

type Fut<Io: IoAsyncRead> = impl Future;

pub struct CompatRead<Io: IoAsyncRead> {
    fut: Fut<Io>,
}

impl<Io: IoAsyncRead> CompatRead<Io> {
    fn poll_fill_buf(self, io: Io) {
        let _: Fut<Io> = async move { io.read().await };
    }
}


trait IoAsyncRead {
    async fn read(&self);
}

Note that a different ICE can be triggered with a few changes:

#![feature(type_alias_impl_trait)]
use std::future::Future;

type Fut = impl Future;

pub struct CompatRead {
    fut: Fut,
}

New Backtrace

thread 'rustc' panicked at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/compiler/rustc_trait_selection/src/traits/auto_trait.rs:178:13:
Unable to fulfill trait DefId(2:3029 ~ core[8e56]::marker::Freeze) for 'CompatRead': [FulfillmentError(Obligation(predicate=Binder { value: TraitPredicate(<{type error} as std::marker::Freeze>, polarity:Positive), bound_vars: [] }, depth=2),Ambiguity)]
stack backtrace:
 0:     0x713e310c02fe - std::backtrace_rs::backtrace::libunwind::trace::hfff812496cb2354e
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
 1:     0x713e310c02fe - std::backtrace_rs::backtrace::trace_unsynchronized::h06db600873ee163d
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
 2:     0x713e310c02fe - std::backtrace::Backtrace::create::hbb2edd00479d55d5
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/backtrace.rs:331:13
 3:     0x713e310c0240 - std::backtrace::Backtrace::force_capture::h0633e9373bbbc7ea
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/backtrace.rs:312:9
 4:     0x713e2dd55380 - std[673c07b0c8518b8]::panicking::update_hook::<alloc[2c6c21add906cb03]::boxed::Box<rustc_driver_impl[c60de66b38787e5]::install_ice_hook::{closure#0}>>::{closure#0}
 5:     0x713e310dc736 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hc543a528b9bc2dd2
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/alloc/src/boxed.rs:2030:9
 6:     0x713e310dc736 - std::panicking::rust_panic_with_hook::haac9f65a4111ce33
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/panicking.rs:785:13
 7:     0x713e310dc482 - std::panicking::begin_panic_handler::{{closure}}::h6a452ac7fecf7288
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/panicking.rs:659:13
 8:     0x713e310d9916 - std::sys_common::backtrace::__rust_end_short_backtrace::ha4c176c669fc3286
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/sys_common/backtrace.rs:171:18
 9:     0x713e310dc1d4 - rust_begin_unwind
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/panicking.rs:647:5
10:     0x713e311286e5 - core::panicking::panic_fmt::hfae197985af26789
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/core/src/panicking.rs:72:14
11:     0x5cd0c05cf953 - <rustc_trait_selection[74e74ff542f4a57a]::traits::auto_trait::AutoTraitFinder>::find_auto_trait_generics::<rustdoc[ea5f4756bf6af5b9]::clean::types::Generics, <rustdoc[ea5f4756bf6af5b9]::clean::auto_trait::AutoTraitFinder>::generate_for_trait::{closure#0}>
12:     0x5cd0c072e836 - <rustdoc[ea5f4756bf6af5b9]::clean::auto_trait::AutoTraitFinder>::generate_for_trait
13:     0x5cd0c074d9b7 - rustdoc[ea5f4756bf6af5b9]::clean::utils::get_auto_trait_and_blanket_impls
14:     0x5cd0c085fb51 - <rustdoc[ea5f4756bf6af5b9]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[ea5f4756bf6af5b9]::visit::DocVisitor>::visit_item
15:     0x5cd0c085feaa - <rustdoc[ea5f4756bf6af5b9]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[ea5f4756bf6af5b9]::visit::DocVisitor>::visit_item
16:     0x5cd0c085c915 - rustdoc[ea5f4756bf6af5b9]::passes::collect_trait_impls::collect_trait_impls
17:     0x5cd0c0781ca0 - rustdoc[ea5f4756bf6af5b9]::core::run_global_ctxt
18:     0x5cd0c088d840 - rustdoc[ea5f4756bf6af5b9]::main_args::{closure#1}::{closure#0}::{closure#0}
19:     0x5cd0c0684490 - rustc_interface[9911b9828ae39d39]::interface::run_compiler::<core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>, rustdoc[ea5f4756bf6af5b9]::main_args::{closure#1}>::{closure#0}
20:     0x5cd0c06566f0 - std[673c07b0c8518b8]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[9911b9828ae39d39]::util::run_in_thread_with_globals<rustc_interface[9911b9828ae39d39]::util::run_in_thread_pool_with_globals<rustc_interface[9911b9828ae39d39]::interface::run_compiler<core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>, rustdoc[ea5f4756bf6af5b9]::main_args::{closure#1}>::{closure#0}, core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>>::{closure#0}, core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>>
21:     0x5cd0c068fa06 - <<std[673c07b0c8518b8]::thread::Builder>::spawn_unchecked_<rustc_interface[9911b9828ae39d39]::util::run_in_thread_with_globals<rustc_interface[9911b9828ae39d39]::util::run_in_thread_pool_with_globals<rustc_interface[9911b9828ae39d39]::interface::run_compiler<core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>, rustdoc[ea5f4756bf6af5b9]::main_args::{closure#1}>::{closure#0}, core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>>::{closure#0}, core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[8e561eb1b9dc85d8]::result::Result<(), rustc_span[81dd5176fffc21b7]::ErrorGuaranteed>>::{closure#1} as core[8e561eb1b9dc85d8]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
22:     0x713e310e5925 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h882bc548fde6b0fb
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/alloc/src/boxed.rs:2016:9
23:     0x713e310e5925 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h95e2a93069d2a4eb
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/alloc/src/boxed.rs:2016:9
24:     0x713e310e5925 - std::sys::pal::unix::thread::Thread::new::thread_start::hbe34808929695de9
                             at /rustc/1a648b397dedc98ada3dd3360f6d661ec2436c56/library/std/src/sys/pal/unix/thread.rs:108:17
25:     0x713e2aea955a - <unknown>
26:     0x713e2af26a3c - <unknown>
27:                0x0 - <unknown>

Not sure how related they are.