Internal Compiler Error with generic const parameters
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Nobody has claimed this yet.
C-bug
F-generic_const_exprs
I-ICE
P-low
S-bug-has-test
T-compiler
- Dominant language
- Rust
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- 119k
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Description
rustc-ice-2025-02-02T02_19_03-370381.txt
Code
#![feature(generic_const_exprs)]
struct State<const S : usize = {}> where[(); S] :;
I think this should be a parser error? I reduced it from a much more complicated test case that I think was hitting an actual logic bug, but this is the smallest program that triggers a failure in the same way.
Meta
rustc --version --verbose:
rustc 1.86.0-nightly (8239a37f9 2025-02-01)
binary: rustc
commit-hash: 8239a37f9c0951a037cfc51763ea52a20e71e6bd
commit-date: 2025-02-01
host: x86_64-unknown-linux-gnu
release: 1.86.0-nightly
LLVM version: 19.1.7
Error output
query stack during panic:
#0 [check_well_formed] checking that `State` is well-formed
#1 [check_mod_type_wf] checking that types are well-formed in top-level module
#2 [analysis] running analysis passes on this crate
end of query stack
Backtrace
thread 'rustc' panicked at /rustc/8239a37f9c0951a037cfc51763ea52a20e71e6bd/compiler/rustc_type_ir/src/binder.rs:776:9:
const parameter `S/#0` (S/#0/0) out of range when instantiating args=[]
stack backtrace:
0: rust_begin_unwind
1: core::panicking::panic_fmt
2: <rustc_type_ir::binder::ArgFolder<rustc_middle::ty::context::TyCtxt>>::const_param_out_of_range
3: <rustc_type_ir::binder::ArgFolder<rustc_middle::ty::context::TyCtxt> as rustc_type_ir::fold::TypeFolder<rustc_middle::ty::context::TyCtxt>>::fold_ty
4: <rustc_middle::ty::generics::GenericPredicates>::instantiate_into
5: <rustc_trait_selection::traits::wf::WfPredicates>::nominal_obligations
6: <rustc_trait_selection::traits::wf::WfPredicates as rustc_type_ir::visit::TypeVisitor<rustc_middle::ty::context::TyCtxt>>::visit_const
7: <rustc_trait_selection::traits::fulfill::FulfillProcessor as rustc_data_structures::obligation_forest::ObligationProcessor>::process_obligation
8: <rustc_data_structures::obligation_forest::ObligationForest<rustc_trait_selection::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection::traits::fulfill::FulfillProcessor>
9: <rustc_trait_selection::traits::fulfill::FulfillmentContext<rustc_trait_selection::traits::FulfillmentError> as rustc_infer::traits::engine::TraitEngine<rustc_trait_selection::traits::FulfillmentError>>::select_all_or_error
10: rustc_hir_analysis::check::wfcheck::check_type_defn
11: rustc_hir_analysis::check::wfcheck::check_well_formed
[... omitted 1 frame ...]
12: rustc_hir_analysis::check::wfcheck::check_mod_type_wf
[... omitted 1 frame ...]
13: rustc_hir_analysis::check_crate
14: rustc_interface::passes::run_required_analyses
15: rustc_interface::passes::analysis
[... omitted 1 frame ...]
16: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
17: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
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- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by compiling the reduced example and confirming the ICE and query stack. Read compiler/rustc_type_ir/src/binder.rs around line 776 and the rustc_hir_analysis well-formedness path named in the backtrace. Done means the example produces an appropriate parser or compiler diagnostic without panicking, with a regression test covering it.
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
- Clearly specified
- Newbie friendliness
- 45/100