ICE: "fn pointer should not capture bound vars from predicate" using HRTB on fn and FnMut

[Stock84-dev]

Code

fn ice()
where
    for<'w> fn(&'w ()): FnMut(&'w ()),
{
}

fn main() {
    ice();
}

Meta

Exists on stable, beta and nightly.

rustc --version --verbose:

rustc 1.67.1 (d5a82bbd2 2023-02-07)
binary: rustc
commit-hash: d5a82bbd26e1ad8b7401f6a718a9c57c96905483
commit-date: 2023-02-07
host: x86_64-unknown-linux-gnu
release: 1.67.1
LLVM version: 15.0.6

Error output

thread 'rustc' panicked at 'fn pointer should not capture bound vars from predicate', compiler/rustc_trait_selection/src/traits/select/confirmation.rs:605:23

Backtrace

stack backtrace:
   0:     0x7f5f29f656fa - std::backtrace_rs::backtrace::libunwind::trace::h79937bc171ada62c
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f5f29f656fa - std::backtrace_rs::backtrace::trace_unsynchronized::h2292bca8571cb919
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f5f29f656fa - std::sys_common::backtrace::_print_fmt::h9c461f248e4ae90d
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7f5f29f656fa - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::he9fe6bf1a39182e1
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f5f29fc825e - core::fmt::write::h032658c119c720d7
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/core/src/fmt/mod.rs:1208:17
   5:     0x7f5f29f55a85 - std::io::Write::write_fmt::h299fc90dfae41c0d
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/io/mod.rs:1682:15
   6:     0x7f5f29f654c5 - std::sys_common::backtrace::_print::heb70d25df9937e3f
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7f5f29f654c5 - std::sys_common::backtrace::print::had745c0a76b8b521
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7f5f29f6820f - std::panicking::default_hook::{{closure}}::h1ea782cdfa2fd097
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/panicking.rs:267:22
   9:     0x7f5f29f67f4b - std::panicking::default_hook::h1cc3af63455a163c
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/panicking.rs:286:9
  10:     0x7f5f2d260ab1 - <rustc_driver[5c3b90d1fb3964ba]::DEFAULT_HOOK::{closure#0}::{closure#0} as core[e6a29f2585b3d454]::ops::function::FnOnce<(&core[e6a29f2585b3d454]::panic::panic_info::PanicInfo,)>>::call_once::{shim:vtable#0}
  11:     0x7f5f29f68a4d - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h6e4950ba7c0fd82a
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/alloc/src/boxed.rs:2032:9
  12:     0x7f5f29f68a4d - std::panicking::rust_panic_with_hook::h5cafdc4b3bfd5528
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/panicking.rs:692:13
  13:     0x7f5f29f687c9 - std::panicking::begin_panic_handler::{{closure}}::hf31c60f40775892c
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/panicking.rs:579:13
  14:     0x7f5f29f65bac - std::sys_common::backtrace::__rust_end_short_backtrace::h28a5c7be595826cd
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/sys_common/backtrace.rs:137:18
  15:     0x7f5f29f684d2 - rust_begin_unwind
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/panicking.rs:575:5
  16:     0x7f5f29fc4c43 - core::panicking::panic_fmt::h8fa27a0b37dd98b7
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/core/src/panicking.rs:64:14
  17:     0x7f5f29fc4d91 - core::panicking::panic_display::hf704d87f83545eb6
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/core/src/panicking.rs:135:5
  18:     0x7f5f29fc4d3b - core::panicking::panic_str::hdc01f81137c4de19
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/core/src/panicking.rs:119:5
  19:     0x7f5f29fc49c6 - core::option::expect_failed::hc5e8507006410982
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/core/src/option.rs:1879:5
  20:     0x7f5f2b4dc733 - <rustc_trait_selection[945b70100f8dd3ec]::traits::select::SelectionContext>::confirm_candidate
  21:     0x7f5f2bb4f39a - <rustc_trait_selection[945b70100f8dd3ec]::traits::select::SelectionContext>::evaluate_stack
  22:     0x7f5f2bcfd8c5 - <rustc_trait_selection[945b70100f8dd3ec]::traits::select::SelectionContext>::evaluate_predicate_recursively
  23:     0x7f5f2ba518cd - rustc_traits[6faae80c4e587721]::evaluate_obligation::evaluate_obligation
  24:     0x7f5f2ba4f25a - rustc_query_system[7dbbccfee5a2d054]::query::plumbing::get_query::<rustc_query_impl[e214cefb6de2a99d]::queries::evaluate_obligation, rustc_query_impl[e214cefb6de2a99d]::plumbing::QueryCtxt>
  25:     0x7f5f2b51313f - <rustc_infer[ce51c2dc4d9f2303]::infer::InferCtxt as rustc_trait_selection[945b70100f8dd3ec]::traits::query::evaluate_obligation::InferCtxtExt>::predicate_must_hold_considering_regions
  26:     0x7f5f2b4b55b4 - <rustc_trait_selection[945b70100f8dd3ec]::traits::fulfill::FulfillProcessor as rustc_data_structures[1026114362f98086]::obligation_forest::ObligationProcessor>::process_obligation
  27:     0x7f5f2b4a77a2 - <rustc_data_structures[1026114362f98086]::obligation_forest::ObligationForest<rustc_trait_selection[945b70100f8dd3ec]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[945b70100f8dd3ec]::traits::fulfill::FulfillProcessor>
  28:     0x7f5f2b489a11 - <rustc_hir_typeck[1edef3791817899d]::fn_ctxt::FnCtxt>::check_argument_types
  29:     0x7f5f2b68e0f6 - <rustc_hir_typeck[1edef3791817899d]::fn_ctxt::FnCtxt>::check_call
  30:     0x7f5f2b5e6645 - <rustc_hir_typeck[1edef3791817899d]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  31:     0x7f5f2b63930a - <rustc_hir_typeck[1edef3791817899d]::fn_ctxt::FnCtxt>::check_block_with_expected
  32:     0x7f5f2b5e6a49 - <rustc_hir_typeck[1edef3791817899d]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  33:     0x7f5f2b5d23d3 - <rustc_hir_typeck[1edef3791817899d]::fn_ctxt::FnCtxt>::check_return_expr
  34:     0x7f5f2b5c9b3b - rustc_hir_typeck[1edef3791817899d]::check::check_fn
  35:     0x7f5f2b5b4d80 - <rustc_hir_typeck[1edef3791817899d]::inherited::InheritedBuilder>::enter::<rustc_hir_typeck[1edef3791817899d]::typeck_with_fallback<rustc_hir_typeck[1edef3791817899d]::typeck::{closure#0}>::{closure#0}::{closure#1}, &rustc_middle[83f907612b22699d]::ty::context::TypeckResults>
  36:     0x7f5f2b5a76c1 - rustc_hir_typeck[1edef3791817899d]::typeck
  37:     0x7f5f2b5b1b3c - <rustc_query_system[7dbbccfee5a2d054]::dep_graph::graph::DepGraph<rustc_middle[83f907612b22699d]::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle[83f907612b22699d]::ty::context::TyCtxt, rustc_span[41a321a6411ba4fa]::def_id::LocalDefId, &rustc_middle[83f907612b22699d]::ty::context::TypeckResults>
  38:     0x7f5f2b5a5e31 - rustc_query_system[7dbbccfee5a2d054]::query::plumbing::try_execute_query::<rustc_query_impl[e214cefb6de2a99d]::plumbing::QueryCtxt, rustc_query_system[7dbbccfee5a2d054]::query::caches::VecCache<rustc_span[41a321a6411ba4fa]::def_id::LocalDefId, &rustc_middle[83f907612b22699d]::ty::context::TypeckResults>>
  39:     0x7f5f2c9b0085 - rustc_data_structures[1026114362f98086]::sync::par_for_each_in::<&[rustc_span[41a321a6411ba4fa]::def_id::LocalDefId], <rustc_middle[83f907612b22699d]::hir::map::Map>::par_body_owners<rustc_hir_typeck[1edef3791817899d]::typeck_item_bodies::{closure#0}>::{closure#0}>
  40:     0x7f5f2c9afdc3 - rustc_hir_typeck[1edef3791817899d]::typeck_item_bodies
  41:     0x7f5f2c8a5c7a - <rustc_query_system[7dbbccfee5a2d054]::dep_graph::graph::DepGraph<rustc_middle[83f907612b22699d]::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle[83f907612b22699d]::ty::context::TyCtxt, (), ()>
  42:     0x7f5f2c8a49f0 - rustc_query_system[7dbbccfee5a2d054]::query::plumbing::try_execute_query::<rustc_query_impl[e214cefb6de2a99d]::plumbing::QueryCtxt, rustc_query_system[7dbbccfee5a2d054]::query::caches::DefaultCache<(), ()>>
  43:     0x7f5f2c8a4370 - rustc_query_system[7dbbccfee5a2d054]::query::plumbing::get_query::<rustc_query_impl[e214cefb6de2a99d]::queries::typeck_item_bodies, rustc_query_impl[e214cefb6de2a99d]::plumbing::QueryCtxt>
  44:     0x7f5f2b75bfb2 - <rustc_session[b89b9f24749004e7]::session::Session>::time::<(), rustc_hir_analysis[44326659f1d3f01d]::check_crate::{closure#7}>
  45:     0x7f5f2b75ad6c - rustc_hir_analysis[44326659f1d3f01d]::check_crate
  46:     0x7f5f2b75a98b - rustc_interface[65dcc5dffb099e04]::passes::analysis
  47:     0x7f5f2ca1291f - <rustc_query_system[7dbbccfee5a2d054]::dep_graph::graph::DepGraph<rustc_middle[83f907612b22699d]::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle[83f907612b22699d]::ty::context::TyCtxt, (), core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>
  48:     0x7f5f2ca11a17 - rustc_query_system[7dbbccfee5a2d054]::query::plumbing::try_execute_query::<rustc_query_impl[e214cefb6de2a99d]::plumbing::QueryCtxt, rustc_query_system[7dbbccfee5a2d054]::query::caches::DefaultCache<(), core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>>
  49:     0x7f5f2ca11470 - rustc_query_system[7dbbccfee5a2d054]::query::plumbing::get_query::<rustc_query_impl[e214cefb6de2a99d]::queries::analysis, rustc_query_impl[e214cefb6de2a99d]::plumbing::QueryCtxt>
  50:     0x7f5f2c4241b3 - <rustc_interface[65dcc5dffb099e04]::passes::QueryContext>::enter::<rustc_driver[5c3b90d1fb3964ba]::run_compiler::{closure#1}::{closure#2}::{closure#2}, core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>
  51:     0x7f5f2c420733 - <rustc_interface[65dcc5dffb099e04]::interface::Compiler>::enter::<rustc_driver[5c3b90d1fb3964ba]::run_compiler::{closure#1}::{closure#2}, core[e6a29f2585b3d454]::result::Result<core[e6a29f2585b3d454]::option::Option<rustc_interface[65dcc5dffb099e04]::queries::Linker>, rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>
  52:     0x7f5f2c41b788 - rustc_span[41a321a6411ba4fa]::with_source_map::<core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>, rustc_interface[65dcc5dffb099e04]::interface::run_compiler<core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>, rustc_driver[5c3b90d1fb3964ba]::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
  53:     0x7f5f2c41b275 - <scoped_tls[393dd8f8fd825c8d]::ScopedKey<rustc_span[41a321a6411ba4fa]::SessionGlobals>>::set::<rustc_interface[65dcc5dffb099e04]::interface::run_compiler<core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>, rustc_driver[5c3b90d1fb3964ba]::run_compiler::{closure#1}>::{closure#0}, core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>
  54:     0x7f5f2c41a862 - std[359ab902947f5f0b]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[65dcc5dffb099e04]::util::run_in_thread_pool_with_globals<rustc_interface[65dcc5dffb099e04]::interface::run_compiler<core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>, rustc_driver[5c3b90d1fb3964ba]::run_compiler::{closure#1}>::{closure#0}, core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>
  55:     0x7f5f2cb13b7a - <<std[359ab902947f5f0b]::thread::Builder>::spawn_unchecked_<rustc_interface[65dcc5dffb099e04]::util::run_in_thread_pool_with_globals<rustc_interface[65dcc5dffb099e04]::interface::run_compiler<core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>, rustc_driver[5c3b90d1fb3964ba]::run_compiler::{closure#1}>::{closure#0}, core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[e6a29f2585b3d454]::result::Result<(), rustc_errors[d24ea2395205e4f0]::ErrorGuaranteed>>::{closure#1} as core[e6a29f2585b3d454]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  56:     0x7f5f29f72803 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hb77d8d72ebcf79c4
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/alloc/src/boxed.rs:2000:9
  57:     0x7f5f29f72803 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hc08c3353e1568487
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/alloc/src/boxed.rs:2000:9
  58:     0x7f5f29f72803 - std::sys::unix::thread::Thread::new::thread_start::h7168e596cd5e5ce6
                               at /rustc/d5a82bbd26e1ad8b7401f6a718a9c57c96905483/library/std/src/sys/unix/thread.rs:108:17
  59:     0x7f5f29d058fd - <unknown>
  60:     0x7f5f29d87a60 - <unknown>
  61:                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 1.67.1 (d5a82bbd2 2023-02-07) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED] -C link-arg=-fuse-ld=lld

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

query stack during panic:
#0 [evaluate_obligation] evaluating trait selection obligation `for<'w> fn(&'w ()): core::ops::function::FnMut<(&'w (),)>`
#1 [typeck] type-checking `main`
#2 [typeck_item_bodies] type-checking all item bodies
#3 [analysis] running analysis passes on this crate
end of query stack

[compiler-errors]

I tried to fix this in #104929.

I'll probably at least put up a PR that turns this into an error from an ICE.

[JohnTitor]

Triage: #108834 removes an ICE (but it doesn't fix the issue itself, see #108834 (comment)), dropping the I-ICE label.

[Enselic]

Triage: #108834 adds a regression test that passes in the new solver. Also making it work in the old solver is probably a waste of time? Let's close this as "sufficiently fixed".

[compiler-errors]

@Enselic: Do not close anything that is fixed by the new solver. The new solver is far from stable.