ICE: lifetime_capture_rules_2024: None in region_infer/opaque_types.rs

[matthiaskrgr]

auto-reduced (treereduce-rust):

#![feature(lifetime_capture_rules_2024)]


struct FileSystem;

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

original:

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() {}

Version information

rustc 1.79.0-nightly (a128516cf 2024-03-20)
binary: rustc
commit-hash: a128516cf9de352ae1f9d430ed730363c7ca3c0c
commit-date: 2024-03-20
host: x86_64-unknown-linux-gnu
release: 1.79.0-nightly
LLVM version: 18.1.2

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zcrate-attr=feature(lifetime_capture_rules_2024)

Program output

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.5DyaYG8WNdcy/rustc_testrunner_tmpdir_reporting.vVpwcwBvw9uo/mvce.rs:8:2
  |
8 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.5DyaYG8WNdcy/rustc_testrunner_tmpdir_reporting.vVpwcwBvw9uo/mvce.rs`

warning: function cannot return without recursing
 --> /tmp/icemaker_global_tempdir.5DyaYG8WNdcy/rustc_testrunner_tmpdir_reporting.vVpwcwBvw9uo/mvce.rs:4:5
  |
4 |     fn build<'a>(&mut self, commands: impl Iterator + 'a) -> Option<impl Iterator + 'a> {
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot return without recursing
5 |         let further_commands = self.build(commands);
  |                                -------------------- recursive call site
  |
  = help: a `loop` may express intention better if this is on purpose
  = note: `#[warn(unconditional_recursion)]` on by default

thread 'rustc' panicked at compiler/rustc_borrowck/src/region_infer/opaque_types.rs:73:54:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x753296040fa5 - std::backtrace_rs::backtrace::libunwind::trace::hb238178a600e7640
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/../../backtrace/src/backtrace/libunwind.rs:105:5
   1:     0x753296040fa5 - std::backtrace_rs::backtrace::trace_unsynchronized::h18a64faf849956d4
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x753296040fa5 - std::sys_common::backtrace::_print_fmt::hdae976156d449368
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x753296040fa5 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hdb9b5e3e983ce460
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x753296091feb - core::fmt::rt::Argument::fmt::h5ad447117290599a
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/core/src/fmt/rt.rs:142:9
   5:     0x753296091feb - core::fmt::write::hcec2d8528418f27e
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/core/src/fmt/mod.rs:1153:17
   6:     0x753296035cbf - std::io::Write::write_fmt::haa636139e96e53ba
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/io/mod.rs:1843:15
   7:     0x753296040d7e - std::sys_common::backtrace::_print::hdbf81feba9c817a4
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x753296040d7e - std::sys_common::backtrace::print::h112b76c74c4834e6
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7532960439f9 - std::panicking::default_hook::{{closure}}::hc5e53ea3fc429948
  10:     0x753296043763 - std::panicking::default_hook::hf72e5bd4be2b44da
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/panicking.rs:292:9
  11:     0x753292bbd84e - std[a5db6e0d1910bc78]::panicking::update_hook::<alloc[18bd171651bd487c]::boxed::Box<rustc_driver_impl[97baef311a2c4da5]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x753296044150 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h3f12fab570b3bdb9
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/alloc/src/boxed.rs:2029:9
  13:     0x753296044150 - std::panicking::rust_panic_with_hook::h87df935cb16f0257
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/panicking.rs:783:13
  14:     0x753296043e6d - std::panicking::begin_panic_handler::{{closure}}::h8437e08ccc24881f
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/panicking.rs:649:13
  15:     0x753296041469 - std::sys_common::backtrace::__rust_end_short_backtrace::h3ca2dfcfb7935be2
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x753296043bd7 - rust_begin_unwind
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/panicking.rs:645:5
  17:     0x75329608e486 - core::panicking::panic_fmt::hb044fd902962ba9f
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/core/src/panicking.rs:72:14
  18:     0x75329608e52f - core::panicking::panic::h81980bd19ca17c53
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/core/src/panicking.rs:141:5
  19:     0x75329608e229 - core::option::unwrap_failed::h058372a1f2d8fc7f
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/core/src/option.rs:1985:5
  20:     0x75329173df12 - rustc_borrowck[aed012f9190e468d]::nll::compute_regions
  21:     0x753294dcd306 - rustc_borrowck[aed012f9190e468d]::do_mir_borrowck
  22:     0x753294107ce8 - rustc_borrowck[aed012f9190e468d]::mir_borrowck
  23:     0x7532941077d7 - rustc_query_impl[d6f091b6e43d27d5]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d6f091b6e43d27d5]::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>
  24:     0x7532941097ee - rustc_query_system[b807d52738406a3e]::query::plumbing::try_execute_query::<rustc_query_impl[d6f091b6e43d27d5]::DynamicConfig<rustc_query_system[b807d52738406a3e]::query::caches::VecCache<rustc_span[124ba900a2a510f4]::def_id::LocalDefId, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d6f091b6e43d27d5]::plumbing::QueryCtxt, false>
  25:     0x75329410930c - rustc_query_impl[d6f091b6e43d27d5]::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
  26:     0x75329487c1cb - rustc_middle[798b1e6edaf341c7]::query::plumbing::query_get_at::<rustc_query_system[b807d52738406a3e]::query::caches::VecCache<rustc_span[124ba900a2a510f4]::def_id::LocalDefId, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>>
  27:     0x7532948740ad - rustc_hir_analysis[423f0ab376009544]::collect::type_of::type_of_opaque
  28:     0x753294873f37 - rustc_query_impl[d6f091b6e43d27d5]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d6f091b6e43d27d5]::query_impl::type_of_opaque::dynamic_query::{closure#2}::{closure#0}, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>
  29:     0x753293ef5b59 - rustc_query_system[b807d52738406a3e]::query::plumbing::try_execute_query::<rustc_query_impl[d6f091b6e43d27d5]::DynamicConfig<rustc_query_system[b807d52738406a3e]::query::caches::DefIdCache<rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d6f091b6e43d27d5]::plumbing::QueryCtxt, false>
  30:     0x753294da71de - rustc_query_impl[d6f091b6e43d27d5]::query_impl::type_of_opaque::get_query_non_incr::__rust_end_short_backtrace
  31:     0x7532944eb696 - rustc_middle[798b1e6edaf341c7]::query::plumbing::query_get_at::<rustc_query_system[b807d52738406a3e]::query::caches::DefIdCache<rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>>
  32:     0x753291c5ce3a - rustc_hir_analysis[423f0ab376009544]::collect::type_of::type_of
  33:     0x753293ef6f22 - rustc_query_impl[d6f091b6e43d27d5]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d6f091b6e43d27d5]::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>
  34:     0x753293ef5b59 - rustc_query_system[b807d52738406a3e]::query::plumbing::try_execute_query::<rustc_query_impl[d6f091b6e43d27d5]::DynamicConfig<rustc_query_system[b807d52738406a3e]::query::caches::DefIdCache<rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d6f091b6e43d27d5]::plumbing::QueryCtxt, false>
  35:     0x753293ef565b - rustc_query_impl[d6f091b6e43d27d5]::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
  36:     0x7532944eb696 - rustc_middle[798b1e6edaf341c7]::query::plumbing::query_get_at::<rustc_query_system[b807d52738406a3e]::query::caches::DefIdCache<rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 8usize]>>>
  37:     0x7532944f1873 - rustc_hir_analysis[423f0ab376009544]::check::check::check_item_type
  38:     0x753294517bd2 - rustc_hir_analysis[423f0ab376009544]::check::wfcheck::check_well_formed
  39:     0x7532945166b5 - rustc_query_impl[d6f091b6e43d27d5]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d6f091b6e43d27d5]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 1usize]>>
  40:     0x753294515e40 - rustc_query_system[b807d52738406a3e]::query::plumbing::try_execute_query::<rustc_query_impl[d6f091b6e43d27d5]::DynamicConfig<rustc_query_system[b807d52738406a3e]::query::caches::VecCache<rustc_hir[37495ea4fccba01b]::hir_id::OwnerId, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[d6f091b6e43d27d5]::plumbing::QueryCtxt, false>
  41:     0x753294515bbf - rustc_query_impl[d6f091b6e43d27d5]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  42:     0x753294513afa - rustc_hir_analysis[423f0ab376009544]::check::wfcheck::check_mod_type_wf
  43:     0x753294513921 - rustc_query_impl[d6f091b6e43d27d5]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d6f091b6e43d27d5]::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 1usize]>>
  44:     0x7532948e7c70 - rustc_query_system[b807d52738406a3e]::query::plumbing::try_execute_query::<rustc_query_impl[d6f091b6e43d27d5]::DynamicConfig<rustc_query_system[b807d52738406a3e]::query::caches::DefaultCache<rustc_span[124ba900a2a510f4]::def_id::LocalModDefId, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[d6f091b6e43d27d5]::plumbing::QueryCtxt, false>
  45:     0x7532948e7a1b - rustc_query_impl[d6f091b6e43d27d5]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
  46:     0x753294104f0b - rustc_hir_analysis[423f0ab376009544]::check_crate
  47:     0x7532942a226a - rustc_interface[b2729804a80bd186]::passes::analysis
  48:     0x7532942a1dd9 - rustc_query_impl[d6f091b6e43d27d5]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d6f091b6e43d27d5]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 1usize]>>
  49:     0x753294c3c8c3 - rustc_query_system[b807d52738406a3e]::query::plumbing::try_execute_query::<rustc_query_impl[d6f091b6e43d27d5]::DynamicConfig<rustc_query_system[b807d52738406a3e]::query::caches::SingleCache<rustc_middle[798b1e6edaf341c7]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[d6f091b6e43d27d5]::plumbing::QueryCtxt, false>
  50:     0x753294c3c63f - rustc_query_impl[d6f091b6e43d27d5]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  51:     0x753294a8d684 - rustc_interface[b2729804a80bd186]::interface::run_compiler::<core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>, rustc_driver_impl[97baef311a2c4da5]::run_compiler::{closure#0}>::{closure#0}
  52:     0x753294b97a05 - std[a5db6e0d1910bc78]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[b2729804a80bd186]::util::run_in_thread_with_globals<rustc_interface[b2729804a80bd186]::util::run_in_thread_pool_with_globals<rustc_interface[b2729804a80bd186]::interface::run_compiler<core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>, rustc_driver_impl[97baef311a2c4da5]::run_compiler::{closure#0}>::{closure#0}, core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>>::{closure#0}, core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>>
  53:     0x753294b97832 - <<std[a5db6e0d1910bc78]::thread::Builder>::spawn_unchecked_<rustc_interface[b2729804a80bd186]::util::run_in_thread_with_globals<rustc_interface[b2729804a80bd186]::util::run_in_thread_pool_with_globals<rustc_interface[b2729804a80bd186]::interface::run_compiler<core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>, rustc_driver_impl[97baef311a2c4da5]::run_compiler::{closure#0}>::{closure#0}, core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>>::{closure#0}, core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[980ed62ddb44d8e4]::result::Result<(), rustc_span[124ba900a2a510f4]::ErrorGuaranteed>>::{closure#1} as core[980ed62ddb44d8e4]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  54:     0x75329604d919 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hce41d8367d913790
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/alloc/src/boxed.rs:2015:9
  55:     0x75329604d919 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h2459e445e1bb3b38
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/alloc/src/boxed.rs:2015:9
  56:     0x75329604d919 - std::sys::pal::unix::thread::Thread::new::thread_start::h51f8e470692041f5
                               at /rustc/a128516cf9de352ae1f9d430ed730363c7ca3c0c/library/std/src/sys/pal/unix/thread.rs:108:17
  57:     0x75328faa955a - <unknown>
  58:     0x75328fb26a3c - <unknown>
  59:                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 1.79.0-nightly (a128516cf 2024-03-20) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z crate-attr=feature(lifetime_capture_rules_2024) -Z dump-mir-dir=dir

query stack during panic:
#0 [mir_borrowck] borrow-checking `<impl at /tmp/icemaker_global_tempdir.5DyaYG8WNdcy/rustc_testrunner_tmpdir_reporting.vVpwcwBvw9uo/mvce.rs:3:1: 3:16>::build`
#1 [type_of_opaque] computing type of opaque `<impl at /tmp/icemaker_global_tempdir.5DyaYG8WNdcy/rustc_testrunner_tmpdir_reporting.vVpwcwBvw9uo/mvce.rs:3:1: 3:16>::build::{opaque#0}`
#2 [type_of] computing type of `<impl at /tmp/icemaker_global_tempdir.5DyaYG8WNdcy/rustc_testrunner_tmpdir_reporting.vVpwcwBvw9uo/mvce.rs:3:1: 3:16>::build::{opaque#0}`
#3 [check_well_formed] checking that `<impl at /tmp/icemaker_global_tempdir.5DyaYG8WNdcy/rustc_testrunner_tmpdir_reporting.vVpwcwBvw9uo/mvce.rs:3:1: 3:16>::build::{opaque#0}` is well-formed
#4 [check_mod_type_wf] checking that types are well-formed in top-level module
#5 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 1 previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0601`.

[matthiaskrgr]

cc @oli-obk seems to happen since #116935

[aliemjay]

minimized:

#![feature(type_alias_impl_trait)]

type Opq<'a, X> = impl Sized;

fn build<'a, X>() -> Option<Opq<'a, X>> {
    match true {
        true => None::<Opq<'_, Opq<'_, X>>>,
        false => None::<Opq<'_, Opq<'_, X>>>,
    }
}

[aliemjay]

futher:

#![feature(type_alias_impl_trait)]

type Opq<'a> = impl Sized;

fn build<'a>() -> Opq<'a> {
    let _: Opq<'_> = ();
}