GAT + RPTIT + Refined lifetimes = ICE

[clarfonthey]

Code

Playground: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=e5dcadac111f6d397f4554167e2aa03e

#![feature(return_position_impl_trait_in_trait)]
trait Iterable {
    type Item<'a>
    where
        Self: 'a;
    fn iter(&self) -> impl '_ + Iterator<Item = Self::Item<'_>>;
}
impl<'a, I: 'a + Iterable> Iterable for &'a I {
    type Item<'b> = I::Item<'a>
    where
        'a: 'b;
    fn iter(&self) -> impl 'a + Iterator<Item = I::Item<'a>> {
        (*self).iter()
    }
}

Meta

rustc --version --verbose:

rustc 1.73.0-nightly (0d95f9132 2023-07-26)
binary: rustc
commit-hash: 0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8
commit-date: 2023-07-26
host: x86_64-unknown-linux-gnu
release: 1.73.0-nightly
LLVM version: 16.0.5

Error output

error: internal compiler error: compiler/rustc_middle/src/ty/mod.rs:2342:13: item_name: no name for DefPath { data: [DisambiguatedDefPathData { data: Impl, disambiguator: 0 }, DisambiguatedDefPathData { data: ImplTraitAssocTy, disambiguator: 0 }], krate: crate0 }

Backtrace

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/compiler/rustc_errors/src/lib.rs:1640:9
stack backtrace:
   0:     0x657efec74fc1 - std::backtrace_rs::backtrace::libunwind::trace::hf6e154905f06aaf4
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x657efec74fc1 - std::backtrace_rs::backtrace::trace_unsynchronized::h18cebe760f1510fa
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x657efec74fc1 - std::sys_common::backtrace::_print_fmt::hffe418505cdd97e8
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x657efec74fc1 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h19176839053c7e42
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x657efecdb49c - core::fmt::rt::Argument::fmt::hf19c9b9307d45f5d
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/core/src/fmt/rt.rs:138:9
   5:     0x657efecdb49c - core::fmt::write::h79cbf0496735b1b7
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/core/src/fmt/mod.rs:1094:21
   6:     0x657efec675ce - std::io::Write::write_fmt::h11f28dab14e62928
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/io/mod.rs:1714:15
   7:     0x657efec74dd5 - std::sys_common::backtrace::_print::he32b2def77c6f779
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x657efec74dd5 - std::sys_common::backtrace::print::h6be21ee209c4bf2f
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x657efec77e2a - std::panicking::panic_hook_with_disk_dump::{{closure}}::h9e13983d414e65b8
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/panicking.rs:278:22
  10:     0x657efec77ac3 - std::panicking::panic_hook_with_disk_dump::he404d3925670a989
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/panicking.rs:312:9
  11:     0x657f01e98f79 - rustc_driver_impl[11f9c42ddd32a232]::install_ice_hook::{closure#0}
  12:     0x657efec786d0 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h8ce3cd052223b94b
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/alloc/src/boxed.rs:2021:9
  13:     0x657efec786d0 - std::panicking::rust_panic_with_hook::h1fcb49fe91d725f0
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/panicking.rs:733:13
  14:     0x657f02465711 - std[2e963e9f253cdd71]::panicking::begin_panic::<rustc_errors[16c9db0e0ca0a6f7]::ExplicitBug>::{closure#0}
  15:     0x657f02463396 - std[2e963e9f253cdd71]::sys_common::backtrace::__rust_end_short_backtrace::<std[2e963e9f253cdd71]::panicking::begin_panic<rustc_errors[16c9db0e0ca0a6f7]::ExplicitBug>::{closure#0}, !>
  16:     0x657f023d4e96 - std[2e963e9f253cdd71]::panicking::begin_panic::<rustc_errors[16c9db0e0ca0a6f7]::ExplicitBug>
  17:     0x657f02481b24 - <rustc_errors[16c9db0e0ca0a6f7]::HandlerInner>::bug::<alloc[d59d314c1498fc03]::string::String>
  18:     0x657f02481788 - <rustc_errors[16c9db0e0ca0a6f7]::Handler>::bug::<alloc[d59d314c1498fc03]::string::String>
  19:     0x657f0247d10c - rustc_middle[2dbe2ef140938139]::util::bug::opt_span_bug_fmt::<rustc_span[6541493927a8eee4]::span_encoding::Span>::{closure#0}
  20:     0x657f0247bf0a - rustc_middle[2dbe2ef140938139]::ty::context::tls::with_opt::<rustc_middle[2dbe2ef140938139]::util::bug::opt_span_bug_fmt<rustc_span[6541493927a8eee4]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  21:     0x657f0247bed8 - rustc_middle[2dbe2ef140938139]::ty::context::tls::with_context_opt::<rustc_middle[2dbe2ef140938139]::ty::context::tls::with_opt<rustc_middle[2dbe2ef140938139]::util::bug::opt_span_bug_fmt<rustc_span[6541493927a8eee4]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  22:     0x657f0098af90 - rustc_middle[2dbe2ef140938139]::util::bug::bug_fmt
  23:     0x657f004bc816 - <rustc_middle[2dbe2ef140938139]::ty::context::TyCtxt>::item_name
  24:     0x657f02189692 - <rustc_infer[d209e7ec2feaa707]::infer::error_reporting::TypeErrCtxt>::report_concrete_failure
  25:     0x657f02191d3c - <rustc_infer[d209e7ec2feaa707]::infer::error_reporting::TypeErrCtxt>::report_region_errors
  26:     0x657f00aea542 - <rustc_trait_selection[29a196fad0f1dedf]::traits::engine::ObligationCtxt>::resolve_regions_and_report_errors
  27:     0x657f00f8b94f - rustc_hir_analysis[7376a6bdbe652c9c]::check::compare_impl_item::check_type_bounds
  28:     0x657f00f7e352 - rustc_hir_analysis[7376a6bdbe652c9c]::check::compare_impl_item::compare_impl_ty
  29:     0x657f00f73fd6 - rustc_hir_analysis[7376a6bdbe652c9c]::check::check::check_mod_item_types
  30:     0x657f00bf216c - rustc_query_impl[764276e1d4d25526]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[764276e1d4d25526]::query_impl::check_mod_item_types::dynamic_query::{closure#2}::{closure#0}, rustc_middle[2dbe2ef140938139]::query::erase::Erased<[u8; 0usize]>>
  31:     0x657f00bf214e - <rustc_query_impl[764276e1d4d25526]::query_impl::check_mod_item_types::dynamic_query::{closure#2} as core[5cd17d5b9f662bec]::ops::function::FnOnce<(rustc_middle[2dbe2ef140938139]::ty::context::TyCtxt, rustc_span[6541493927a8eee4]::def_id::LocalDefId)>>::call_once
  32:     0x657f007fa79f - rustc_query_system[455882a7c9f92b0a]::query::plumbing::try_execute_query::<rustc_query_impl[764276e1d4d25526]::DynamicConfig<rustc_query_system[455882a7c9f92b0a]::query::caches::VecCache<rustc_span[6541493927a8eee4]::def_id::LocalDefId, rustc_middle[2dbe2ef140938139]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[764276e1d4d25526]::plumbing::QueryCtxt, false>
  33:     0x657f018000a2 - rustc_query_impl[764276e1d4d25526]::query_impl::check_mod_item_types::get_query_non_incr::__rust_end_short_backtrace
  34:     0x657f013371e7 - <rustc_middle[2dbe2ef140938139]::hir::map::Map>::for_each_module::<rustc_hir_analysis[7376a6bdbe652c9c]::check_crate::{closure#6}::{closure#0}>
  35:     0x657f01335e5f - rustc_hir_analysis[7376a6bdbe652c9c]::check_crate
  36:     0x657f0132fe9a - rustc_interface[7f8477932cb20ad4]::passes::analysis
  37:     0x657f0139739a - rustc_query_impl[764276e1d4d25526]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[764276e1d4d25526]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[2dbe2ef140938139]::query::erase::Erased<[u8; 1usize]>>
  38:     0x657f01397389 - <rustc_query_impl[764276e1d4d25526]::query_impl::analysis::dynamic_query::{closure#2} as core[5cd17d5b9f662bec]::ops::function::FnOnce<(rustc_middle[2dbe2ef140938139]::ty::context::TyCtxt, ())>>::call_once
  39:     0x657f0153e818 - rustc_query_system[455882a7c9f92b0a]::query::plumbing::try_execute_query::<rustc_query_impl[764276e1d4d25526]::DynamicConfig<rustc_query_system[455882a7c9f92b0a]::query::caches::SingleCache<rustc_middle[2dbe2ef140938139]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[764276e1d4d25526]::plumbing::QueryCtxt, false>
  40:     0x657f0153e5a7 - rustc_query_impl[764276e1d4d25526]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  41:     0x657f010bead5 - <rustc_middle[2dbe2ef140938139]::ty::context::GlobalCtxt>::enter::<rustc_driver_impl[11f9c42ddd32a232]::run_compiler::{closure#1}::{closure#2}::{closure#4}, core[5cd17d5b9f662bec]::result::Result<(), rustc_span[6541493927a8eee4]::ErrorGuaranteed>>
  42:     0x657f010be102 - <rustc_interface[7f8477932cb20ad4]::interface::Compiler>::enter::<rustc_driver_impl[11f9c42ddd32a232]::run_compiler::{closure#1}::{closure#2}, core[5cd17d5b9f662bec]::result::Result<core[5cd17d5b9f662bec]::option::Option<rustc_interface[7f8477932cb20ad4]::queries::Linker>, rustc_span[6541493927a8eee4]::ErrorGuaranteed>>
  43:     0x657f010b71a8 - std[2e963e9f253cdd71]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[7f8477932cb20ad4]::util::run_in_thread_pool_with_globals<rustc_interface[7f8477932cb20ad4]::interface::run_compiler<core[5cd17d5b9f662bec]::result::Result<(), rustc_span[6541493927a8eee4]::ErrorGuaranteed>, rustc_driver_impl[11f9c42ddd32a232]::run_compiler::{closure#1}>::{closure#0}, core[5cd17d5b9f662bec]::result::Result<(), rustc_span[6541493927a8eee4]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[5cd17d5b9f662bec]::result::Result<(), rustc_span[6541493927a8eee4]::ErrorGuaranteed>>
  44:     0x657f010b692e - <<std[2e963e9f253cdd71]::thread::Builder>::spawn_unchecked_<rustc_interface[7f8477932cb20ad4]::util::run_in_thread_pool_with_globals<rustc_interface[7f8477932cb20ad4]::interface::run_compiler<core[5cd17d5b9f662bec]::result::Result<(), rustc_span[6541493927a8eee4]::ErrorGuaranteed>, rustc_driver_impl[11f9c42ddd32a232]::run_compiler::{closure#1}>::{closure#0}, core[5cd17d5b9f662bec]::result::Result<(), rustc_span[6541493927a8eee4]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[5cd17d5b9f662bec]::result::Result<(), rustc_span[6541493927a8eee4]::ErrorGuaranteed>>::{closure#1} as core[5cd17d5b9f662bec]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  45:     0x657efec82dc5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h6a397ffa79ce97be
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/alloc/src/boxed.rs:2007:9
  46:     0x657efec82dc5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hd63e3cd46e3d7a48
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/alloc/src/boxed.rs:2007:9
  47:     0x657efec82dc5 - std::sys::unix::thread::Thread::new::thread_start::h06e8fe5bf1fac20c
                               at /rustc/0d95f9132909ae7c5f2456748d0ffd1c3ba4a8e8/library/std/src/sys/unix/thread.rs:108:17
  48:     0x657efe9b244b - <unknown>
  49:     0x657efea35e40 - <unknown>
  50:                0x0 - <unknown>

Additional notes

• I am aware that refined implementations are not yet implemented. This should still not cause an ICE, only an error.
• The addition of the GAT Item<'a> is required to trigger this error. If Item is an ordinary, non-generic associated type, the ICE does not occur.
• This seems related to ICE: rpitit: item_name: no name for DefPath {..} #113794 but I felt it was worth opening a new issue in case they're not related.