ICE: None in region infer

[matthiaskrgr]

auto-reduced (treereduce-rust):

//@compile-flags: --edition=2024
trait Owned: 'static {}
fn ice() -> impl Future<Output = &'static dyn Owned> {
    async {
        let not_static = 0;
        force_send(async_load(&not_static));
        loop {}
    }
}

fn force_send<T: Send>(_: T) {}

fn async_load<'a, T: LoadQuery<'a>>(this: T) -> impl Future {
    async {
        this.get_future().await;
    }
}

trait LoadQuery<'a>: Sized {
    type LoadFuture: Future;

    fn get_future(self) -> Self::LoadFuture {
        loop {}
    }
}

impl<'a> LoadQuery<'a> for &'a u8 {
    type LoadFuture = ();
}

original:

use std::future::Future;

trait Owned: 'static {}
fn ice() -> impl Future<Output = &'static dyn Owned> {
    async {
        let not_static = 0;
        force_send(async_load(&not_static));
        loop {}
    }
}

fn force_send<T: Send>(_: T) {
    bar(0usize);
}

fn async_load<'a, T: LoadQuery<'a>>(this: T) -> impl Future {
    async {
        this.get_future().await;
    }
}

trait LoadQuery<'a>: Sized {
    type LoadFuture: Future;

    fn get_future(self) -> Self::LoadFuture {
        loop {}
    }
}

impl<'a> LoadQuery<'a> for &'a u8 {
    type LoadFuture = SimpleFuture;
}

struct SimpleFuture;
impl Future for SimpleFuture {
    type Output = ();
    fn poll(
        self: std::pin::Pin<&mut Self>,
        _: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Self::Output> {
        loop {}
    }
}

Version information

rustc 1.85.0-nightly (a2bcfae5c 2024-12-22)
binary: rustc
commit-hash: a2bcfae5c5d05dd7806a79194cda39108ed6cd7d
commit-date: 2024-12-22
host: x86_64-unknown-linux-gnu
release: 1.85.0-nightly
LLVM version: 19.1.6

Possibly related line of code:

rust/compiler/rustc_borrowck/src/region_infer/mod.rs

Lines 1948 to 1960 in a2bcfae

	from_region: RegionVid,
	from_region_origin: NllRegionVariableOrigin,
	target_test: impl Fn(RegionVid) -> bool,
	) -> (BlameConstraint<'tcx>, Vec<ExtraConstraintInfo>) {
	// Find all paths
	let (path, target_region) =
	self.find_constraint_paths_between_regions(from_region, target_test).unwrap();
	debug!(
	"path={:#?}",
	path.iter()
	.map(|c| format!(
	"{:?} ({:?}: {:?})",
	c,

Command:
/home/gh-matthiaskrgr/.rustup/toolchains/master/bin/rustc --edition=2024

Program output

error[E0601]: `main` function not found in crate `mvce`
  --> /tmp/icemaker_global_tempdir.BHiqrJV6LOIy/rustc_testrunner_tmpdir_reporting.rdn3fbZeLICY/mvce.rs:28:2
   |
28 | }
   |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.BHiqrJV6LOIy/rustc_testrunner_tmpdir_reporting.rdn3fbZeLICY/mvce.rs`

error[E0277]: `()` is not a future
  --> /tmp/icemaker_global_tempdir.BHiqrJV6LOIy/rustc_testrunner_tmpdir_reporting.rdn3fbZeLICY/mvce.rs:27:23
   |
27 |     type LoadFuture = ();
   |                       ^^ `()` is not a future
   |
   = help: the trait `Future` is not implemented for `()`
note: required by a bound in `LoadQuery::LoadFuture`
  --> /tmp/icemaker_global_tempdir.BHiqrJV6LOIy/rustc_testrunner_tmpdir_reporting.rdn3fbZeLICY/mvce.rs:19:22
   |
19 |     type LoadFuture: Future;
   |                      ^^^^^^ required by this bound in `LoadQuery::LoadFuture`

thread 'rustc' panicked at compiler/rustc_borrowck/src/region_infer/mod.rs:1954:82:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x72263dcb775a - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::he57e0fea652ab9fd
   1:     0x72263e413866 - core::fmt::write::hd55e7fc717febc4b
   2:     0x72263f348bd1 - std::io::Write::write_fmt::h78281f831863065d
   3:     0x72263dcb75b2 - std::sys::backtrace::BacktraceLock::print::h7acbe748d8539c38
   4:     0x72263dcb9aaa - std::panicking::default_hook::{{closure}}::hea23bfd5c34c8db7
   5:     0x72263dcb98f3 - std::panicking::default_hook::hff2113baba127713
   6:     0x72263ce2ecc8 - std[e6d36fd50c659ae0]::panicking::update_hook::<alloc[4740fe411def7ec4]::boxed::Box<rustc_driver_impl[89e0991809749e6d]::install_ice_hook::{closure#0}>>::{closure#0}
   7:     0x72263dcba2a8 - std::panicking::rust_panic_with_hook::hfc1c16069db4c6ff
   8:     0x72263dcb9f66 - std::panicking::begin_panic_handler::{{closure}}::hb21d96c911822c44
   9:     0x72263dcb7c09 - std::sys::backtrace::__rust_end_short_backtrace::h8e09f77e03188563
  10:     0x72263dcb9c5d - rust_begin_unwind
  11:     0x72263a99c340 - core::panicking::panic_fmt::hfa3a678dda58d831
  12:     0x72263b402d7c - core::panicking::panic::hdf786271010df6cf
  13:     0x72263ba1d049 - core::option::unwrap_failed::hbc04c4e08213af89
  14:     0x72263c7aebd6 - <rustc_borrowck[620ce4e9c4d33f0c]::MirBorrowckCtxt>::explain_why_borrow_contains_point
  15:     0x72263c6cf825 - <rustc_borrowck[620ce4e9c4d33f0c]::MirBorrowckCtxt>::report_borrowed_value_does_not_live_long_enough
  16:     0x72263f4de964 - rustc_borrowck[620ce4e9c4d33f0c]::do_mir_borrowck
  17:     0x72263f4b066a - rustc_query_impl[a3a64fb382d359d2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a3a64fb382d359d2]::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>>
  18:     0x72263e6ef411 - rustc_query_system[7ed8f12aa9c699c]::query::plumbing::try_execute_query::<rustc_query_impl[a3a64fb382d359d2]::DynamicConfig<rustc_data_structures[3e783a0e36352b79]::vec_cache::VecCache<rustc_span[458074075485def8]::def_id::LocalDefId, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[7ed8f12aa9c699c]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a3a64fb382d359d2]::plumbing::QueryCtxt, false>
  19:     0x72263e6eef0d - rustc_query_impl[a3a64fb382d359d2]::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
  20:     0x72263eef1a0a - rustc_middle[5e0371d42ed41497]::query::plumbing::query_get_at::<rustc_data_structures[3e783a0e36352b79]::vec_cache::VecCache<rustc_span[458074075485def8]::def_id::LocalDefId, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[7ed8f12aa9c699c]::dep_graph::graph::DepNodeIndex>>
  21:     0x72263eef1a6a - <rustc_borrowck[620ce4e9c4d33f0c]::type_check::TypeChecker>::prove_closure_bounds
  22:     0x72263e752cbb - <rustc_borrowck[620ce4e9c4d33f0c]::type_check::TypeChecker>::typeck_mir
  23:     0x72263f49aad0 - rustc_borrowck[620ce4e9c4d33f0c]::type_check::type_check
  24:     0x72263e4c39d7 - rustc_borrowck[620ce4e9c4d33f0c]::nll::compute_regions
  25:     0x72263f4bda78 - rustc_borrowck[620ce4e9c4d33f0c]::do_mir_borrowck
  26:     0x72263f4b066a - rustc_query_impl[a3a64fb382d359d2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a3a64fb382d359d2]::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>>
  27:     0x72263e6ef411 - rustc_query_system[7ed8f12aa9c699c]::query::plumbing::try_execute_query::<rustc_query_impl[a3a64fb382d359d2]::DynamicConfig<rustc_data_structures[3e783a0e36352b79]::vec_cache::VecCache<rustc_span[458074075485def8]::def_id::LocalDefId, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[7ed8f12aa9c699c]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a3a64fb382d359d2]::plumbing::QueryCtxt, false>
  28:     0x72263e6eef0d - rustc_query_impl[a3a64fb382d359d2]::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
  29:     0x72263ed1c118 - rustc_middle[5e0371d42ed41497]::query::plumbing::query_get_at::<rustc_data_structures[3e783a0e36352b79]::vec_cache::VecCache<rustc_span[458074075485def8]::def_id::LocalDefId, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[7ed8f12aa9c699c]::dep_graph::graph::DepNodeIndex>>
  30:     0x72263f36c6de - rustc_hir_analysis[17bd3daf66b8921d]::collect::type_of::type_of_opaque
  31:     0x72263f36c551 - rustc_query_impl[a3a64fb382d359d2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a3a64fb382d359d2]::query_impl::type_of_opaque::dynamic_query::{closure#2}::{closure#0}, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>>
  32:     0x72263e50f21f - rustc_query_system[7ed8f12aa9c699c]::query::plumbing::try_execute_query::<rustc_query_impl[a3a64fb382d359d2]::DynamicConfig<rustc_query_system[7ed8f12aa9c699c]::query::caches::DefIdCache<rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a3a64fb382d359d2]::plumbing::QueryCtxt, false>
  33:     0x72263f5e2035 - rustc_query_impl[a3a64fb382d359d2]::query_impl::type_of_opaque::get_query_non_incr::__rust_end_short_backtrace
  34:     0x72263ed4c5ec - rustc_middle[5e0371d42ed41497]::query::plumbing::query_get_at::<rustc_query_system[7ed8f12aa9c699c]::query::caches::DefIdCache<rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>>>
  35:     0x72263e5157e1 - rustc_hir_analysis[17bd3daf66b8921d]::collect::type_of::type_of
  36:     0x72263e514326 - rustc_query_impl[a3a64fb382d359d2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a3a64fb382d359d2]::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>>
  37:     0x72263e50f21f - rustc_query_system[7ed8f12aa9c699c]::query::plumbing::try_execute_query::<rustc_query_impl[a3a64fb382d359d2]::DynamicConfig<rustc_query_system[7ed8f12aa9c699c]::query::caches::DefIdCache<rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a3a64fb382d359d2]::plumbing::QueryCtxt, false>
  38:     0x72263e50edab - rustc_query_impl[a3a64fb382d359d2]::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
  39:     0x72263ed4c5ec - rustc_middle[5e0371d42ed41497]::query::plumbing::query_get_at::<rustc_query_system[7ed8f12aa9c699c]::query::caches::DefIdCache<rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 8usize]>>>
  40:     0x72263ed69c75 - rustc_hir_analysis[17bd3daf66b8921d]::check::check::check_item_type
  41:     0x72263bbafafa - rustc_hir_analysis[17bd3daf66b8921d]::check::wfcheck::check_well_formed
  42:     0x72263edce7bb - rustc_query_impl[a3a64fb382d359d2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a3a64fb382d359d2]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 1usize]>>
  43:     0x72263edce269 - rustc_query_system[7ed8f12aa9c699c]::query::plumbing::try_execute_query::<rustc_query_impl[a3a64fb382d359d2]::DynamicConfig<rustc_data_structures[3e783a0e36352b79]::vec_cache::VecCache<rustc_span[458074075485def8]::def_id::LocalDefId, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[7ed8f12aa9c699c]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a3a64fb382d359d2]::plumbing::QueryCtxt, false>
  44:     0x72263edcdccb - rustc_query_impl[a3a64fb382d359d2]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  45:     0x72263edce82b - rustc_middle[5e0371d42ed41497]::query::plumbing::query_ensure_error_guaranteed::<rustc_data_structures[3e783a0e36352b79]::vec_cache::VecCache<rustc_span[458074075485def8]::def_id::LocalDefId, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[7ed8f12aa9c699c]::dep_graph::graph::DepNodeIndex>, ()>
  46:     0x72263edced1b - rustc_hir_analysis[17bd3daf66b8921d]::check::wfcheck::check_mod_type_wf
  47:     0x72263edce84b - rustc_query_impl[a3a64fb382d359d2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a3a64fb382d359d2]::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 1usize]>>
  48:     0x72263f3816c8 - rustc_query_system[7ed8f12aa9c699c]::query::plumbing::try_execute_query::<rustc_query_impl[a3a64fb382d359d2]::DynamicConfig<rustc_query_system[7ed8f12aa9c699c]::query::caches::DefaultCache<rustc_span[458074075485def8]::def_id::LocalModDefId, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[a3a64fb382d359d2]::plumbing::QueryCtxt, false>
  49:     0x72263f381470 - rustc_query_impl[a3a64fb382d359d2]::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
  50:     0x72263e6ebeec - rustc_hir_analysis[17bd3daf66b8921d]::check_crate
  51:     0x72263e6bb6aa - rustc_interface[36124661c84dc53c]::passes::run_required_analyses
  52:     0x72263f34ca5e - rustc_interface[36124661c84dc53c]::passes::analysis
  53:     0x72263f34ca2f - rustc_query_impl[a3a64fb382d359d2]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a3a64fb382d359d2]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 0usize]>>
  54:     0x72263f3a7855 - rustc_query_system[7ed8f12aa9c699c]::query::plumbing::try_execute_query::<rustc_query_impl[a3a64fb382d359d2]::DynamicConfig<rustc_query_system[7ed8f12aa9c699c]::query::caches::SingleCache<rustc_middle[5e0371d42ed41497]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[a3a64fb382d359d2]::plumbing::QueryCtxt, false>
  55:     0x72263f3a758e - rustc_query_impl[a3a64fb382d359d2]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  56:     0x72263f4437de - rustc_interface[36124661c84dc53c]::passes::create_and_enter_global_ctxt::<core[a17736bada842104]::option::Option<rustc_interface[36124661c84dc53c]::queries::Linker>, rustc_driver_impl[89e0991809749e6d]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  57:     0x72263f3c2aa8 - rustc_interface[36124661c84dc53c]::interface::run_compiler::<(), rustc_driver_impl[89e0991809749e6d]::run_compiler::{closure#0}>::{closure#1}
  58:     0x72263f251311 - std[e6d36fd50c659ae0]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[36124661c84dc53c]::util::run_in_thread_with_globals<rustc_interface[36124661c84dc53c]::util::run_in_thread_pool_with_globals<rustc_interface[36124661c84dc53c]::interface::run_compiler<(), rustc_driver_impl[89e0991809749e6d]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  59:     0x72263f2517a6 - <<std[e6d36fd50c659ae0]::thread::Builder>::spawn_unchecked_<rustc_interface[36124661c84dc53c]::util::run_in_thread_with_globals<rustc_interface[36124661c84dc53c]::util::run_in_thread_pool_with_globals<rustc_interface[36124661c84dc53c]::interface::run_compiler<(), rustc_driver_impl[89e0991809749e6d]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[a17736bada842104]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  60:     0x72263f252d81 - std::sys::pal::unix::thread::Thread::new::thread_start::h0cedf7b69d2cc02b
  61:     0x72263949ca94 - start_thread
                               at ./nptl/pthread_create.c:447:8
  62:     0x722639529c3c - clone3
                               at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:78
  63:                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: please make sure that you have updated to the latest nightly

note: rustc 1.85.0-nightly (a2bcfae5c 2024-12-22) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z dump-mir-dir=dir

query stack during panic:
#0 [mir_borrowck] borrow-checking `ice::{closure#0}`
#1 [mir_borrowck] borrow-checking `ice`
end of query stack
error: aborting due to 2 previous errors

Some errors have detailed explanations: E0277, E0601.
For more information about an error, try `rustc --explain E0277`.

[matthiaskrgr]

seems to bisect to nightly-2024-07-04

[cyrgani]

Isn't this just #133252 (comment)?

[matthiaskrgr]

ah, yes 😆

[matthiaskrgr]

thanks!