ICE: rustdoc: unable to fulfill trait

[matthiaskrgr]

Code

code from glacier/fixed ./82830.rs

trait A<Y, N> {
    type B;
}
type MaybeBox<T> = <T as A<T, Box<T>>>::B;
struct P {
    t: MaybeBox<P>
}
impl<Y, N> A<Y, N> for P {
    type B = N;
}
fn main() {
    let t: MaybeBox<P>;
}

Meta

rustc --version --verbose:

rustdoc 1.66.0-nightly (89e4e1f1b 2022-09-22)
binary: rustdoc
commit-hash: 89e4e1f1b32e2a88cf696337f77e10273142c1a0
commit-date: 2022-09-22
host: x86_64-unknown-linux-gnu
release: 1.66.0-nightly
LLVM version: 15.0.0

Error output

rustdoc ./82830.rs

<output>

Backtrace

thread 'rustc' panicked at 'Unable to fulfill trait DefId(2:9577 ~ core[18c4]::panic::unwind_safe::RefUnwindSafe) for 'P': [FulfillmentError(Obligation(predicate=Binder(TraitPredicate(<P as std::marker::Sized>, polarity:Positive), []), depth=2),Cycle([Obligation(predicate=Binder(TraitPredicate(<P as std::marker::Sized>, polarity:Positive), []), depth=2)]))]', /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/compiler/rustc_trait_selection/src/traits/auto_trait.rs:212:17
stack backtrace:
   0:     0x7fadeada2ff0 - std::backtrace_rs::backtrace::libunwind::trace::h2ca6883764224c50
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   1:     0x7fadeada2ff0 - std::backtrace_rs::backtrace::trace_unsynchronized::hc8d7bf16fbb24a66
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fadeada2ff0 - std::sys_common::backtrace::_print_fmt::h8131a70362d50711
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7fadeada2ff0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h90d935aa8f152cc4
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7fadeadfde1e - core::fmt::write::he269743b74f5c696
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/core/src/fmt/mod.rs:1202:17
   5:     0x7fadead93af5 - std::io::Write::write_fmt::hc8f981841522dcb7
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/io/mod.rs:1679:15
   6:     0x7fadeada5d73 - std::sys_common::backtrace::_print::hc472289dfed76ac5
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7fadeada5d73 - std::sys_common::backtrace::print::hb5cbce6ae3413adf
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7fadeada5d73 - std::panicking::default_hook::{{closure}}::h2cd9e26e5a4d26cf
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/panicking.rs:267:22
   9:     0x7fadeada5a5f - std::panicking::default_hook::h285a577a219daf6b
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/panicking.rs:286:9
  10:     0x7faded5a9f11 - rustc_driver[3f123be23da454cf]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7fadeada65ab - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hb82c925d16f3379b
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/alloc/src/boxed.rs:1954:9
  12:     0x7fadeada65ab - std::panicking::rust_panic_with_hook::hb93707af70744542
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/panicking.rs:673:13
  13:     0x7fadeada6407 - std::panicking::begin_panic_handler::{{closure}}::hd681f529bfde9833
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/panicking.rs:560:13
  14:     0x7fadeada349c - std::sys_common::backtrace::__rust_end_short_backtrace::h0a1c018d6d45d3ac
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/sys_common/backtrace.rs:138:18
  15:     0x7fadeada6122 - rust_begin_unwind
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/panicking.rs:556:5
  16:     0x7fadeadfa9f3 - core::panicking::panic_fmt::h9c23657a9510a693
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/core/src/panicking.rs:142:14
  17:     0x55fe41d697a1 - <rustc_trait_selection[85ad35dc24063c91]::traits::auto_trait::AutoTraitFinder>::find_auto_trait_generics::<rustdoc[49db050148857d76]::clean::types::Generics, <rustdoc[49db050148857d76]::clean::auto_trait::AutoTraitFinder>::generate_for_trait::{closure#0}>
  18:     0x55fe41cf7926 - <rustdoc[49db050148857d76]::clean::auto_trait::AutoTraitFinder>::generate_for_trait
  19:     0x55fe41d50c41 - <alloc[e78ec9fa308054ee]::vec::Vec<rustdoc[49db050148857d76]::clean::types::Item> as alloc[e78ec9fa308054ee]::vec::spec_from_iter::SpecFromIter<rustdoc[49db050148857d76]::clean::types::Item, core[18c4b1d7071fd1cd]::iter::adapters::filter_map::FilterMap<alloc[e78ec9fa308054ee]::vec::into_iter::IntoIter<rustc_span[8952443004196ec6]::def_id::DefId>, <rustdoc[49db050148857d76]::clean::auto_trait::AutoTraitFinder>::get_auto_trait_impls::{closure#0}>>>::from_iter
  20:     0x55fe41cf8682 - <rustdoc[49db050148857d76]::clean::auto_trait::AutoTraitFinder>::get_auto_trait_impls
  21:     0x55fe41dbdc31 - rustdoc[49db050148857d76]::clean::utils::get_auto_trait_and_blanket_impls
  22:     0x55fe41eeb69a - <rustdoc[49db050148857d76]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[49db050148857d76]::visit::DocVisitor>::visit_item
  23:     0x55fe41eeb7da - <rustdoc[49db050148857d76]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[49db050148857d76]::visit::DocVisitor>::visit_item
  24:     0x55fe41eec70d - <rustdoc[49db050148857d76]::passes::collect_trait_impls::SyntheticImplCollector as rustdoc[49db050148857d76]::visit::DocVisitor>::visit_crate
  25:     0x55fe41f64b82 - <rustc_session[116fffadb813d920]::session::Session>::time::<alloc[e78ec9fa308054ee]::vec::Vec<rustdoc[49db050148857d76]::clean::types::Item>, rustdoc[49db050148857d76]::passes::collect_trait_impls::collect_trait_impls::{closure#0}>
  26:     0x55fe41ee9540 - rustdoc[49db050148857d76]::passes::collect_trait_impls::collect_trait_impls
  27:     0x55fe41f64dfd - <rustc_session[116fffadb813d920]::session::Session>::time::<rustdoc[49db050148857d76]::clean::types::Crate, rustdoc[49db050148857d76]::core::run_global_ctxt::{closure#7}>
  28:     0x55fe41e3e8a8 - rustdoc[49db050148857d76]::core::run_global_ctxt
  29:     0x55fe41f650df - <rustc_session[116fffadb813d920]::session::Session>::time::<(rustdoc[49db050148857d76]::clean::types::Crate, rustdoc[49db050148857d76]::config::RenderOptions, rustdoc[49db050148857d76]::formats::cache::Cache), rustdoc[49db050148857d76]::main_options::{closure#0}::{closure#0}::{closure#1}::{closure#0}>
  30:     0x55fe41eb0801 - <rustc_interface[7e3736c909effbd2]::passes::QueryContext>::enter::<rustdoc[49db050148857d76]::main_options::{closure#0}::{closure#0}::{closure#1}, core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>>
  31:     0x55fe41c961fa - <rustc_interface[7e3736c909effbd2]::interface::Compiler>::enter::<rustdoc[49db050148857d76]::main_options::{closure#0}::{closure#0}, core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>>
  32:     0x55fe41fdbbf0 - rustc_span[8952443004196ec6]::with_source_map::<core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>, rustc_interface[7e3736c909effbd2]::interface::create_compiler_and_run<core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>, rustdoc[49db050148857d76]::main_options::{closure#0}>::{closure#1}>
  33:     0x55fe41cd9025 - rustdoc[49db050148857d76]::main_options
  34:     0x55fe41eae59b - <scoped_tls[b33617bf2807a620]::ScopedKey<rustc_span[8952443004196ec6]::SessionGlobals>>::set::<rustdoc[49db050148857d76]::main_args::{closure#0}, core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>>
  35:     0x55fe41f7ac70 - std[e75007de79557301]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[7e3736c909effbd2]::util::run_in_thread_pool_with_globals<rustdoc[49db050148857d76]::main_args::{closure#0}, core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>>::{closure#0}, core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>>
  36:     0x55fe41e2b8fc - <<std[e75007de79557301]::thread::Builder>::spawn_unchecked_<rustc_interface[7e3736c909effbd2]::util::run_in_thread_pool_with_globals<rustdoc[49db050148857d76]::main_args::{closure#0}, core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>>::{closure#0}, core[18c4b1d7071fd1cd]::result::Result<(), rustc_errors[34b5fd58e2bb12db]::ErrorGuaranteed>>::{closure#1} as core[18c4b1d7071fd1cd]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  37:     0x7fadeadb0393 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hf8eb4b8b28ab25ff
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/alloc/src/boxed.rs:1940:9
  38:     0x7fadeadb0393 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7b97191167d4a57f
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/alloc/src/boxed.rs:1940:9
  39:     0x7fadeadb0393 - std::sys::unix::thread::Thread::new::thread_start::h6566f949dcab60e6
                               at /rustc/89e4e1f1b32e2a88cf696337f77e10273142c1a0/library/std/src/sys/unix/thread.rs:108:17
  40:     0x7fadeaae878d - <unknown>
  41:     0x7fadeab698e4 - clone
  42:                0x0 - <unknown>

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 1.66.0-nightly (89e4e1f1b 2022-09-22) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack

[matthiaskrgr]

Two files from the repo that reproduce this since yesterday:
./src/test/ui/generic-associated-types/bugs/issue-80626.rs
./src/test/ui/traits/issue-82830.rs

[GuillaumeGomez]

I think it's because of a change in the compiler. Maybe you know about this @oli-obk ?

[matthiaskrgr]

cargo-bisect-rustc points to 89e4e1f

[oli-obk]

This is almost certainly #102037 (the ice mentions cycles). Likely rustdoc is unwrapping something in generate_for_trait in the closure arg for the call to find_auto_trait_generics

[Alexendoo]

No longer ICEs since #104293

[aDotInTheVoid]

@rustbot claim