ICE: "no errors encountered even though delay_span_bug issued" in recursive impl

Some code I wrote for the 2022 advent of code fails to compile under the newly released 1.69. It compiled previously under 1.67 and 1.68.

Code

use std::{collections::BTreeMap, num::ParseIntError, str::FromStr};

enum FileSystem {
    File(usize),
    Directory(BTreeMap<String, FileSystem>),
}

impl FromStr for FileSystem {
    type Err = ParseIntError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s.starts_with("dir") {
            Ok(Self::new_dir())
        } else {
            Ok(Self::File(s.split_whitespace().next().unwrap().parse()?))
        }
    }
}

impl FileSystem {
    fn new_dir() -> FileSystem {
        FileSystem::Directory(BTreeMap::new())
    }

    fn insert(&mut self, name: String, other: FileSystem) -> Option<FileSystem> {
        match self {
            FileSystem::File(_) => panic!("can only insert into directory!"),
            FileSystem::Directory(tree) => tree.insert(name, other),
        }
    }

    // Recursively build a tree from commands. This uses (abuses?)
    // the fact that `cd /` only appears at the start and that
    // subsequent `cd`s can only move ONE level to use the recursion
    // stack as the filesystem stack
    fn build<'a>(
        &mut self,
        mut commands: impl Iterator<Item = &'a str> + 'a,
    ) -> Option<impl Iterator<Item = &'a str> + 'a> {
        let cmd = commands.next()?;
        let mut elements = cmd.lines();
        match elements.next().map(str::trim) {
            Some("cd /") | None => self.build(commands),
            Some("cd ..") => {
                // return to higher scope
                Some(commands)
            }
            Some("ls") => {
                for item in elements {
                    let name = item.split_whitespace().last().unwrap();
                    let prior = self.insert(name.to_string(), item.parse().unwrap());
                    debug_assert!(prior.is_none());
                }
                // continue on
                self.build(commands)
            }
            Some(other_cd) => {
                let name = other_cd
                    .trim()
                    .strip_prefix("cd ")
                    .expect("expected a cd command");
                let mut directory = FileSystem::new_dir();
                let further_commands = directory.build(commands);
                self.insert(name.to_string(), directory);
                self.build(further_commands?) // THIS LINE FAILS TO COMPILE
            }
        }
    }
}

fn main() {}

Error output

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: opaque type with non-universal region substs
  --> 7/src/main.rs:65:17
   |
65 |                 self.build(further_commands?)
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: delayed at    0: <rustc_errors::HandlerInner>::emit_diagnostic
              1: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
              2: <rustc_borrowck::region_infer::RegionInferenceContext>::infer_opaque_types::{closure#0}::{closure#2}
              3: rustc_middle::ty::util::fold_list::<rustc_middle::ty::fold::RegionFolder, rustc_middle::ty::subst::GenericArg, <&rustc_middle::ty::list::List<rustc_middle::ty::subst::GenericArg> as rustc_type_ir::fold::TypeFoldable<rustc_middle::ty::context::TyCtxt>>::try_fold_with<rustc_middle::ty::fold::RegionFolder>::{closure#0}>
              4: <rustc_borrowck::region_infer::RegionInferenceContext>::infer_opaque_types
              5: rustc_borrowck::nll::compute_regions
              6: rustc_borrowck::do_mir_borrowck
              7: rustc_borrowck::mir_borrowck
              8: <rustc_borrowck::provide::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)>>::call_once
              9: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::mir_borrowck, rustc_query_impl::plumbing::QueryCtxt>
             10: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_borrowck
             11: rustc_hir_analysis::collect::type_of::type_of
             12: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::type_of, rustc_query_impl::plumbing::QueryCtxt>
             13: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::type_of
             14: rustc_hir_analysis::check::check::check_mod_item_types
             15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::check_mod_item_types, rustc_query_impl::plumbing::QueryCtxt>
             16: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::check_mod_item_types
             17: <rustc_middle::hir::map::Map>::for_each_module::<rustc_hir_analysis::check_crate::{closure#6}::{closure#0}>
             18: rustc_hir_analysis::check_crate
             19: rustc_interface::passes::analysis
             20: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt>
             21: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
             22: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_driver_impl::run_compiler::{closure#1}::{closure#2}::{closure#4}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
             23: rustc_span::with_source_map::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
             24: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
             25: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
             26: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                        at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library/alloc/src/boxed.rs:1987:9
             27: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                        at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library/alloc/src/boxed.rs:1987:9
             28: std::sys::unix::thread::Thread::new::thread_start
                        at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library/std/src/sys/unix/thread.rs:108:17
             29: start_thread
                        at ./nptl/./nptl/pthread_create.c:442:8
             30: clone3
                        at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
           

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 (84c898d65 2023-04-16) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

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

query stack during panic:
end of query stack
warning: `seven` (bin "seven") generated 2 warnings
error: could not compile `seven`; 2 warnings emitted

Backtrace

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: opaque type with non-universal region substs
  --> 7/src/main.rs:65:17
   |
65 |                 self.build(further_commands?)
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: delayed at    0: <rustc_errors::HandlerInner>::emit_diagnostic
              1: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
              2: <rustc_borrowck::region_infer::RegionInferenceContext>::infer_opaque_types::{closure#0}::{closure#2}
              3: rustc_middle::ty::util::fold_list::<rustc_middle::ty::fold::RegionFolder, rustc_middle::ty::subst::GenericArg, <&rustc_middle::ty::list::List<rustc_middle::ty::subst::GenericArg> as rustc_type_ir::fold::TypeFoldable<rustc_middle::ty::context::TyCtxt>>::try_fold_with<rustc_middle::ty::fold::RegionFolder>::{closure#0}>
              4: <rustc_borrowck::region_infer::RegionInferenceContext>::infer_opaque_types
              5: rustc_borrowck::nll::compute_regions
              6: rustc_borrowck::do_mir_borrowck
              7: rustc_borrowck::mir_borrowck
              8: <rustc_borrowck::provide::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)>>::call_once
              9: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::mir_borrowck, rustc_query_impl::plumbing::QueryCtxt>
             10: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_borrowck
             11: rustc_hir_analysis::collect::type_of::type_of
             12: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::type_of, rustc_query_impl::plumbing::QueryCtxt>
             13: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::type_of
             14: rustc_hir_analysis::check::check::check_mod_item_types
             15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::check_mod_item_types, rustc_query_impl::plumbing::QueryCtxt>
             16: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::check_mod_item_types
             17: <rustc_middle::hir::map::Map>::for_each_module::<rustc_hir_analysis::check_crate::{closure#6}::{closure#0}>
             18: rustc_hir_analysis::check_crate
             19: rustc_interface::passes::analysis
             20: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt>
             21: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
             22: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_driver_impl::run_compiler::{closure#1}::{closure#2}::{closure#4}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
             23: rustc_span::with_source_map::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
             24: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
             25: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
             26: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                        at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library/alloc/src/boxed.rs:1987:9
             27: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                        at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library/alloc/src/boxed.rs:1987:9
             28: std::sys::unix::thread::Thread::new::thread_start
                        at /rustc/84c898d65adf2f39a5a98507f1fe0ce10a2b8dbc/library/std/src/sys/unix/thread.rs:108:17
             29: start_thread
                        at ./nptl/./nptl/pthread_create.c:442:8
             30: clone3
                        at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
           

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 (84c898d65 2023-04-16) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

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

query stack during panic:
end of query stack
warning: `seven` (bin "seven") generated 2 warnings
error: could not compile `seven`; 2 warnings emitted

reduced

struct FileSystem;

impl FileSystem {
    fn build<'a>(
        &mut self,
        commands: impl Iterator<Item = &'a str> + 'a,
    ) -> Option<impl Iterator<Item = &'a str> + 'a> {
        let further_commands = self.build(commands);
        self.build(further_commands?)
    }
}

fn main() {}

@oli-obk

searched toolchains nightly-2022-03-30 through nightly-2023-04-20
Regression in nightly-2022-03-31

fetching (via local git) commits from 9c06e1b to c5cf08d
opening existing repository at "rust.git"
Found origin remote under name origin
refreshing repository at "rust.git"
looking up first commit
looking up second commit
checking that commits are by bors and thus have ci artifacts...
finding bors merge commits
found 8 bors merge commits in the specified range
commit[0] 2022-03-29: Auto merge of #95448 - Dylan-DPC:rollup-wpj5yto, r=Dylan-DPC
commit[1] 2022-03-30: Auto merge of #95455 - RalfJung:miri, r=RalfJung
commit[2] 2022-03-30: Auto merge of #94081 - oli-obk:lazy_tait_take_two, r=nikomatsakis
commit[3] 2022-03-30: Auto merge of #95466 - Dylan-DPC:rollup-g7ddr8y, r=Dylan-DPC
commit[4] 2022-03-30: Auto merge of #95241 - Gankra:cleaned-provenance, r=workingjubilee
commit[5] 2022-03-30: Auto merge of #94963 - lcnr:inherent-impls-std, r=oli-obk,m-ou-se
commit[6] 2022-03-30: Auto merge of #95458 - calebcartwright:sync-rustfmt-subtree, r=calebcartwright
commit[7] 2022-03-30: Auto merge of #95425 - nnethercote:yet-more-parse_tt-improvements, r=petrochenkov
ERROR: no CI builds available between 9c06e1b and c5cf08d within last 167 days

ouff, a bit more than a year 😆

#94081 by @oli-obk looks a bit suspicious imo 🙃

reduced

trait S {}

fn foo<'a>(x: impl S + 'a) -> impl S + 'a {
    foo(foo(x))
}

@rustbot

I will try fix this.

@rustbot claim

Auto merge of rust-lang#116891 - aliemjay:opaque-region-infer-rework-…

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ICE: "no errors encountered even though `delay_span_bug` issued" in recursive impl #110623

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ICE: "no errors encountered even though delay_span_bug issued" in recursive impl #110623

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matthiaskrgr commented on Apr 20, 2023

matthiaskrgr commented on Apr 20, 2023

zirconium-n commented on Apr 21, 2023

zirconium-n commented on Apr 21, 2023

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ICE: "no errors encountered even though `delay_span_bug` issued" in recursive impl #110623