rust-lang / rust-lang/rust

ICE: "error performing operation: fully_perform" on type inference for trait object with HRTB over GAT

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A-dyn-trait A-GATs A-higher-ranked A-lifetimes A-trait-system C-bug fixed-by-next-solver I-ICE S-bug-has-test T-compiler
Dominant language
Rust
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PR metrics pending

Description

Another ICE when using a HRTB in a trait object similar to #130524, but in a slightly different context and with a different error.

Code
trait Transform {
    type Output<'a>;
}
trait Propagate<O> {}
trait AddChild<C> {}

pub struct Node<T>(T);
impl<T> AddChild<Box<dyn for<'b> Propagate<T::Output<'b>>>> for Node<T> where
    T: Transform
{
}

fn make_graph_root() {
    add_children(Node(Dummy));
}

fn add_children<T, C>(_node: T)
where
    T: AddChild<C>,
{
}

struct Dummy;
impl Transform for Dummy {
    type Output<'a> = ();
}
Meta

rustc --version --verbose:

rustc 1.81.0 (eeb90cda1 2024-09-04)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: x86_64-unknown-linux-gnu
release: 1.81.0
LLVM version: 18.1.7

Also reproduced on nightly via the playground

Error output
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: error performing operation: fully_perform
  --> repro/src/lib.rs:14:5
   |
14 |     add_children(Node(Dummy));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: delayed at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs:85:25 - disabled backtrace
  --> repro/src/lib.rs:14:5
   |
14 |     add_children(Node(Dummy));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^

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 1.81.0 (eeb90cda1 2024-09-04) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -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
Backtrace 

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: error performing operation: fully_perform
  --> repro/src/lib.rs:14:5
   |
14 |     add_children(Node(Dummy));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: delayed at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs:85:25
         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::TypeChecker>::fully_perform_op::<(), rustc_middle::ty::ParamEnvAnd<rustc_middle::traits::query::type_op::ProvePredicate>>
         5: <rustc_borrowck::type_check::TypeChecker>::normalize_and_prove_instantiated_predicates
         6: <rustc_borrowck::type_check::TypeVerifier as rustc_middle::mir::visit::Visitor>::visit_const_operand
         7: <rustc_borrowck::type_check::TypeVerifier as rustc_middle::mir::visit::Visitor>::visit_body
         8: rustc_borrowck::type_check::type_check
         9: rustc_borrowck::nll::compute_regions
        10: rustc_borrowck::do_mir_borrowck
        11: 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]>>
        12: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, true>
        13: rustc_query_impl::query_impl::mir_borrowck::get_query_incr::__rust_end_short_backtrace
        14: rustc_interface::passes::analysis
        15: 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; 1]>>
        16: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, true>
        17: rustc_query_impl::query_impl::analysis::get_query_incr::__rust_end_short_backtrace
        18: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
        19: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
        20: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, 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}
        21: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                   at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/boxed.rs:2070:9
        22: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                   at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/boxed.rs:2070:9
        23: std::sys::pal::unix::thread::Thread::new::thread_start
                   at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/pal/unix/thread.rs:108:17
        24: <unknown>
        25: <unknown>
  --> repro/src/lib.rs:14:5
   |
14 |     add_children(Node(Dummy));
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^

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 1.81.0 (eeb90cda1 2024-09-04) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -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

Contributor guide

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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by compiling the provided reproducer with the reported Rust 1.81.0 toolchain or nightly and inspect the borrow-checking path in TypeChecker::fully_perform_op, along with rustc_trait_selection/src/traits/query/type_op/custom.rs:85 from the backtrace. Done means the reproducer no longer emits the reported internal compiler error.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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