rustdoc: ice: has escaping bound vars, so it cannot be wrapped in a dummy binder

[matthiaskrgr]

I tried this code:

#![crate_type="lib"]
#![feature(associated_type_bounds)]

trait A<'a> {}
trait B<'b> {}

trait C<'c>: for<'a> A<'a> + for<'b> B<'b> {
    type As;
}

trait E<'e> {
    type As;
}
trait F<'f>: for<'a> A<'a> + for<'e> E<'e> {}
struct G<T>
where
    T: for<'l, 'i> H<'l, 'i, As: for<'a> A<'a> + 'i>
{
    t: std::marker::PhantomData<T>,
}

trait I<'a, 'b, 'c> {
    type As;
}

trait H<'d, 'e>: for<'f> I<'d, 'f, 'e> + 'd {}

I expected to see this happen: explanation

Instead, this happened: explanation

Meta

rustc --version --verbose:

rustdoc 1.71.0-nightly (1c42cb4ef 2023-04-26)
binary: rustdoc
commit-hash: 1c42cb4ef0544fbfaa500216e53382d6b079c001
commit-date: 2023-04-26
host: x86_64-unknown-linux-gnu
release: 1.71.0-nightly
LLVM version: 16.0.2

Backtrace

warning: struct `G` is never constructed
  --> 30B0262E00C316EA1B4121A3F74A7B40BD0A1BBD6F303232F9C8C1438A7EEDA4.rs:15:8
   |
15 | struct G<T>
   |        ^
   |
   = note: `#[warn(dead_code)]` on by default

warning: 1 warning emitted

thread 'rustc' panicked at '`<T as I<'l, 'f, 'i>>::As` has escaping bound vars, so it cannot be wrapped in a dummy binder.', src/librustdoc/clean/mod.rs:367:29
stack backtrace:
   0:     0x7f741af68e73 - std::backtrace_rs::backtrace::libunwind::trace::h0c8179e89cc9893e
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f741af68e73 - std::backtrace_rs::backtrace::trace_unsynchronized::hfadffaff9fceb6ba
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f741af68e73 - std::sys_common::backtrace::_print_fmt::ha49f609af156c4cb
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7f741af68e73 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h0ad104dc9ebb0bab
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f741afc9c8f - core::fmt::write::h076b507083203424
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/core/src/fmt/mod.rs:1247:17
   5:     0x7f741af5bea1 - std::io::Write::write_fmt::ha4c326e8c8c981e1
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/io/mod.rs:1712:15
   6:     0x7f741af68c85 - std::sys_common::backtrace::_print::hbc9e8503f2c8583b
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7f741af68c85 - std::sys_common::backtrace::print::he24fec1d9c5516a7
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7f741af6b847 - std::panicking::default_hook::{{closure}}::hf29caaf6379226a6
   9:     0x7f741af6b635 - std::panicking::default_hook::h0765c9476c979227
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/panicking.rs:288:9
  10:     0x7f741e1bf8c5 - <rustc_driver_impl[b4ece89b41fa04d8]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[a53159a38bb5d97c]::ops::function::FnOnce<(&core[a53159a38bb5d97c]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
  11:     0x7f741af6bf85 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h7a83df3f1b1b39ec
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/alloc/src/boxed.rs:1976:9
  12:     0x7f741af6bf85 - std::panicking::rust_panic_with_hook::h060701a46b500fdf
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/panicking.rs:695:13
  13:     0x7f741af6bcf9 - std::panicking::begin_panic_handler::{{closure}}::hcfb53c4ced379f9a
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/panicking.rs:582:13
  14:     0x7f741af692b6 - std::sys_common::backtrace::__rust_end_short_backtrace::h2100286b873f9af0
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/sys_common/backtrace.rs:150:18
  15:     0x7f741af6ba52 - rust_begin_unwind
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/panicking.rs:578:5
  16:     0x7f741afc5f23 - core::panicking::panic_fmt::hcbb1fb2c2e65f651
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/core/src/panicking.rs:67:14
  17:     0x55866dce60d7 - rustdoc[91caa3b57dab4aa7]::clean::clean_predicate
  18:     0x55866dba144b - <alloc[5698eed4a099ff47]::vec::Vec<rustdoc[91caa3b57dab4aa7]::clean::types::WherePredicate> as alloc[5698eed4a099ff47]::vec::spec_from_iter::SpecFromIter<rustdoc[91caa3b57dab4aa7]::clean::types::WherePredicate, core[a53159a38bb5d97c]::iter::adapters::flatten::FlatMap<alloc[5698eed4a099ff47]::vec::into_iter::IntoIter<&rustc_middle[74d31bc1c7288efd]::ty::Predicate>, core[a53159a38bb5d97c]::option::Option<rustdoc[91caa3b57dab4aa7]::clean::types::WherePredicate>, rustdoc[91caa3b57dab4aa7]::clean::clean_ty_generics::{closure#3}>>>::from_iter
  19:     0x55866dcea18d - rustdoc[91caa3b57dab4aa7]::clean::clean_ty_generics
  20:     0x55866da0e618 - <rustdoc[91caa3b57dab4aa7]::clean::auto_trait::AutoTraitFinder>::param_env_to_generics
  21:     0x55866dc7df0a - <rustc_trait_selection[ce8ecfa74af62748]::traits::auto_trait::AutoTraitFinder>::find_auto_trait_generics::<rustdoc[91caa3b57dab4aa7]::clean::types::Generics, <rustdoc[91caa3b57dab4aa7]::clean::auto_trait::AutoTraitFinder>::generate_for_trait::{closure#0}>
  22:     0x55866da0afdd - <rustdoc[91caa3b57dab4aa7]::clean::auto_trait::AutoTraitFinder>::generate_for_trait
  23:     0x55866dbb9e11 - <alloc[5698eed4a099ff47]::vec::Vec<rustdoc[91caa3b57dab4aa7]::clean::types::Item> as alloc[5698eed4a099ff47]::vec::spec_from_iter::SpecFromIter<rustdoc[91caa3b57dab4aa7]::clean::types::Item, core[a53159a38bb5d97c]::iter::adapters::filter_map::FilterMap<alloc[5698eed4a099ff47]::vec::into_iter::IntoIter<rustc_span[5acbb0d3e38bbf81]::def_id::DefId>, <rustdoc[91caa3b57dab4aa7]::clean::auto_trait::AutoTraitFinder>::get_auto_trait_impls::{closure#0}>>>::from_iter
  24:     0x55866da0b957 - <rustdoc[91caa3b57dab4aa7]::clean::auto_trait::AutoTraitFinder>::get_auto_trait_impls
  25:     0x55866da8eb13 - rustdoc[91caa3b57dab4aa7]::clean::utils::get_auto_trait_and_blanket_impls
  26:     0x55866dd0ff1f - <rustdoc[91caa3b57dab4aa7]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[91caa3b57dab4aa7]::visit::DocVisitor>::visit_item
  27:     0x55866dd1002a - <rustdoc[91caa3b57dab4aa7]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[91caa3b57dab4aa7]::visit::DocVisitor>::visit_item
  28:     0x55866dd112e6 - <rustdoc[91caa3b57dab4aa7]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[91caa3b57dab4aa7]::visit::DocVisitor>::visit_crate
  29:     0x55866db27e11 - <rustc_session[86cf650fda0448f5]::session::Session>::time::<alloc[5698eed4a099ff47]::vec::Vec<rustdoc[91caa3b57dab4aa7]::clean::types::Item>, rustdoc[91caa3b57dab4aa7]::passes::collect_trait_impls::collect_trait_impls::{closure#0}>
  30:     0x55866dd0d1e3 - rustdoc[91caa3b57dab4aa7]::passes::collect_trait_impls::collect_trait_impls
  31:     0x55866db28442 - <rustc_session[86cf650fda0448f5]::session::Session>::time::<rustdoc[91caa3b57dab4aa7]::clean::types::Crate, rustdoc[91caa3b57dab4aa7]::core::run_global_ctxt::{closure#8}>
  32:     0x55866dc7068d - rustdoc[91caa3b57dab4aa7]::core::run_global_ctxt
  33:     0x55866db286be - <rustc_session[86cf650fda0448f5]::session::Session>::time::<(rustdoc[91caa3b57dab4aa7]::clean::types::Crate, rustdoc[91caa3b57dab4aa7]::config::RenderOptions, rustdoc[91caa3b57dab4aa7]::formats::cache::Cache), rustdoc[91caa3b57dab4aa7]::main_args::{closure#1}::{closure#0}::{closure#0}::{closure#0}>
  34:     0x55866dcced90 - <rustc_middle[74d31bc1c7288efd]::ty::context::GlobalCtxt>::enter::<rustdoc[91caa3b57dab4aa7]::main_args::{closure#1}::{closure#0}::{closure#0}, core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>>
  35:     0x55866da59c25 - <rustc_interface[69aa8c17999313ff]::interface::Compiler>::enter::<rustdoc[91caa3b57dab4aa7]::main_args::{closure#1}::{closure#0}, core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>>
  36:     0x55866dc7754b - rustc_span[5acbb0d3e38bbf81]::set_source_map::<core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>, rustc_interface[69aa8c17999313ff]::interface::run_compiler<core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>, rustdoc[91caa3b57dab4aa7]::main_args::{closure#1}>::{closure#0}::{closure#0}>
  37:     0x55866dd1771d - <scoped_tls[f608a97ff3f9cbb]::ScopedKey<rustc_span[5acbb0d3e38bbf81]::SessionGlobals>>::set::<rustc_interface[69aa8c17999313ff]::interface::run_compiler<core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>, rustdoc[91caa3b57dab4aa7]::main_args::{closure#1}>::{closure#0}, core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>>
  38:     0x55866db35219 - std[b0e36382822581c2]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[69aa8c17999313ff]::util::run_in_thread_pool_with_globals<rustc_interface[69aa8c17999313ff]::interface::run_compiler<core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>, rustdoc[91caa3b57dab4aa7]::main_args::{closure#1}>::{closure#0}, core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>>
  39:     0x55866dc60e6d - <<std[b0e36382822581c2]::thread::Builder>::spawn_unchecked_<rustc_interface[69aa8c17999313ff]::util::run_in_thread_pool_with_globals<rustc_interface[69aa8c17999313ff]::interface::run_compiler<core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>, rustdoc[91caa3b57dab4aa7]::main_args::{closure#1}>::{closure#0}, core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[a53159a38bb5d97c]::result::Result<(), rustc_span[5acbb0d3e38bbf81]::ErrorGuaranteed>>::{closure#1} as core[a53159a38bb5d97c]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  40:     0x7f741af76365 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h2b4cb02d9a218e1d
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/alloc/src/boxed.rs:1962:9
  41:     0x7f741af76365 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hbd8144eacfab6e10
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/alloc/src/boxed.rs:1962:9
  42:     0x7f741af76365 - std::sys::unix::thread::Thread::new::thread_start::h95499a4b2fca6f4a
                               at /rustc/1c42cb4ef0544fbfaa500216e53382d6b079c001/library/std/src/sys/unix/thread.rs:108:17
  43:     0x7f741ac1ebb5 - <unknown>
  44:     0x7f741aca0d90 - <unknown>
  45:                0x0 - <unknown>

error: 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 1.71.0-nightly (1c42cb4ef 2023-04-26) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack

[fmease]

@rustbot claim