ICE while trying to field project out of opaque value by utilizing type ascription #134838

fmease · 2024-12-28T01:25:42Z

Reproducer:

#![feature(type_ascription)]
#![allow(dead_code)]

struct Ty(());

fn mk() -> impl Sized {
    if false {
         let _ = type_ascribe!(mk(), Ty).0;
    }
    Ty(())
}

fn main() {}

Compiler output (backtrace disabled):

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error: broken MIR in DefId(0:6 ~ ice[df8a]::mk) ((_3.0: ())): can't project out of PlaceTy { ty: Alias(Opaque, AliasTy { args: [], def_id: DefId(0:7 ~ ice[df8a]::mk::{opaque#0}), .. }), variant_index: None }
 --> ice.rs:8:18
  |
8 |          let _ = type_ascribe!(mk(), Ty).0;
  |                  ^^^^^^^^^^^^^^^^^^^^^^^^^
  |
note: delayed at compiler/rustc_borrowck/src/type_check/mod.rs:809:31 - disabled backtrace
 --> ice.rs:8:18
  |
8 |          let _ = type_ascribe!(mk(), Ty).0;
  |                  ^^^^^^^^^^^^^^^^^^^^^^^^^

error: internal compiler error: TyKind::Error constructed but no error reported
  |
  = note: delayed at compiler/rustc_borrowck/src/type_check/mod.rs:726:9 - disabled backtrace

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 (6d9f6ae36 2024-12-16) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack

Compiler output (backtrace enabled)

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error: broken MIR in DefId(0:6 ~ ice[df8a]::mk) ((_3.0: ())): can't project out of PlaceTy { ty: Alias(Opaque, AliasTy { args: [], def_id: DefId(0:7 ~ ice[df8a]::mk::{opaque#0}), .. }), variant_index: None }
 --> ice.rs:8:18
  |
8 |          let _ = type_ascribe!(mk(), Ty).0;
  |                  ^^^^^^^^^^^^^^^^^^^^^^^^^
  |
note: delayed at compiler/rustc_borrowck/src/type_check/mod.rs:809:31
         0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
         1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
         2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
         3: <rustc_errors::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, alloc::string::String>
         4: <rustc_borrowck::type_check::TypeVerifier as rustc_middle::mir::visit::Visitor>::visit_place
         5: <rustc_borrowck::type_check::TypeVerifier as rustc_middle::mir::visit::Visitor>::visit_body
         6: rustc_borrowck::type_check::type_check
         7: rustc_borrowck::nll::compute_regions
         8: rustc_borrowck::do_mir_borrowck
         9: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        10: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        11: rustc_query_impl::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
        12: rustc_middle::query::plumbing::query_get_at::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>>
        13: rustc_hir_analysis::collect::type_of::type_of_opaque
        14: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::type_of_opaque::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        16: rustc_query_impl::query_impl::type_of_opaque::get_query_non_incr::__rust_end_short_backtrace
        17: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
        18: rustc_hir_analysis::collect::type_of::type_of
        19: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
        20: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        21: rustc_query_impl::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
        22: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
        23: rustc_hir_analysis::check::check::check_item_type
        24: rustc_hir_analysis::check::wfcheck::check_well_formed
        25: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
        26: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 1]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        27: rustc_query_impl::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
        28: rustc_middle::query::plumbing::query_ensure_error_guaranteed::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 1]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, ()>
        29: rustc_hir_analysis::check::wfcheck::check_mod_type_wf
        30: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
        31: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalModDefId, rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        32: rustc_query_impl::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
        33: rustc_hir_analysis::check_crate
        34: rustc_interface::passes::run_required_analyses
        35: rustc_interface::passes::analysis
        36: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
        37: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
        38: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
        39: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        40: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
        41: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
        42: std::sys::pal::unix::thread::Thread::new::thread_start
        43: <unknown>
        44: <unknown>
 --> ice.rs:8:18
  |
8 |          let _ = type_ascribe!(mk(), Ty).0;
  |                  ^^^^^^^^^^^^^^^^^^^^^^^^^

error: internal compiler error: TyKind::Error constructed but no error reported
  |
  = note: delayed at compiler/rustc_borrowck/src/type_check/mod.rs:726:9
             0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
             1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
             2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
             3: <rustc_errors::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, &str>
             4: <rustc_middle::ty::Ty>::new_misc_error
             5: <rustc_borrowck::type_check::TypeVerifier as rustc_middle::mir::visit::Visitor>::visit_place
             6: <rustc_borrowck::type_check::TypeVerifier as rustc_middle::mir::visit::Visitor>::visit_body
             7: rustc_borrowck::type_check::type_check
             8: rustc_borrowck::nll::compute_regions
             9: rustc_borrowck::do_mir_borrowck
            10: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
            11: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            12: rustc_query_impl::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
            13: rustc_middle::query::plumbing::query_get_at::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>>
            14: rustc_hir_analysis::collect::type_of::type_of_opaque
            15: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::type_of_opaque::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
            16: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            17: rustc_query_impl::query_impl::type_of_opaque::get_query_non_incr::__rust_end_short_backtrace
            18: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
            19: rustc_hir_analysis::collect::type_of::type_of
            20: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
            21: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            22: rustc_query_impl::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
            23: rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>>
            24: rustc_hir_analysis::check::check::check_item_type
            25: rustc_hir_analysis::check::wfcheck::check_well_formed
            26: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
            27: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 1]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            28: rustc_query_impl::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
            29: rustc_middle::query::plumbing::query_ensure_error_guaranteed::<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 1]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, ()>
            30: rustc_hir_analysis::check::wfcheck::check_mod_type_wf
            31: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::check_mod_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
            32: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalModDefId, rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            33: rustc_query_impl::query_impl::check_mod_type_wf::get_query_non_incr::__rust_end_short_backtrace
            34: rustc_hir_analysis::check_crate
            35: rustc_interface::passes::run_required_analyses
            36: rustc_interface::passes::analysis
            37: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 0]>>
            38: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 0]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            39: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
            40: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
            41: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
            42: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
            43: std::sys::pal::unix::thread::Thread::new::thread_start
            44: <unknown>
            45: <unknown>


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 (6d9f6ae36 2024-12-16) running on x86_64-unknown-linux-gnu

query stack during panic:
end of query stack

The text was updated successfully, but these errors were encountered:

fmease · 2024-12-28T01:26:28Z

P-low because type_ascription's future is uncertain.

fmease · 2024-12-28T01:34:50Z

Ofc it would be better if I could find a reproducer that doesn't rely on type_ascription.

Replacing the type_ascribe!(mk(), Ty) with (mk() as Ty) doesn't lead to an ICE. I don't know the systems involved very well but I guess what's happening is

the cast / explicit coercion leads to the expression "taking on" the hidden type during typeck and borrowck while
the type ascription only leads to the hidden type getting revealed during typeck but not during borrowck

theemathas · 2024-12-28T03:27:37Z

Recursive RPIT calls also seem to have very strange behavior in general.

#![allow(dead_code)]

#[derive(Copy, Clone)]
struct Ty(());

fn mk() -> impl Copy {
    if false {
        let a: [_; 2] = [mk(), Ty(())];
        let mut b @ Ty(()) = a[0];
        let c: Ty = b;
        let _ = c.0;
        let d = b as Ty;
        let _ = d.0;
        let _ = (b as Ty).0;
        b = Ty(());
        // compile error: no field `0` on type `impl Copy`
        let _ = b.0;
    }
    Ty(())
}

compiler-errors · 2024-12-30T16:46:01Z

I believe this is generally fixed by the approach to opaques taken by the new solver. I don't expect this to be possible to fix in the old solver (or at least any fix approach would probably not be worth landing) given the way it handles opaque types.

fmease · 2024-12-30T17:12:47Z

Makes sense, let's not fix it in the old solver (how did I not check if it's fixed in the next solver? I usually check that for every trait system related issue..)

rustbot added the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Dec 28, 2024

fmease removed the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Dec 28, 2024

fmease changed the title ~~ICE trying to field project out of opaque value by utilizing type ascription~~ ICE while trying to field project out of opaque value by utilizing type ascription Dec 28, 2024

compiler-errors added the fixed-by-next-solver Fixed by the next-generation trait solver, `-Znext-solver`. label Dec 30, 2024

matthiaskrgr added the S-bug-has-test Status: This bug is tracked inside the repo by a `known-bug` test. label Jan 5, 2025

theemathas mentioned this issue Apr 4, 2025

Recursive RPIT causes E0792 (an error about TAIT): "this generic parameter must be used with a generic type parameter" #139350

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ICE while trying to field project out of opaque value by utilizing type ascription #134838

ICE while trying to field project out of opaque value by utilizing type ascription #134838

fmease commented Dec 28, 2024

fmease commented Dec 28, 2024

fmease commented Dec 28, 2024 •

edited

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theemathas commented Dec 28, 2024

compiler-errors commented Dec 30, 2024

fmease commented Dec 30, 2024

ICE while trying to field project out of opaque value by utilizing type ascription #134838

ICE while trying to field project out of opaque value by utilizing type ascription #134838

Comments

fmease commented Dec 28, 2024

fmease commented Dec 28, 2024

fmease commented Dec 28, 2024 • edited Loading

theemathas commented Dec 28, 2024

compiler-errors commented Dec 30, 2024

fmease commented Dec 30, 2024

fmease commented Dec 28, 2024 •

edited

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