Crash on const generics code

rust-analyzer version: 0.4.2999-standalone (6817dd3094 2026-08-05)

rustc version: rustc 1.99.0-nightly (1ed2df61a 2026-08-04)

editor or extension: VSCode

code snippet to reproduce:

// main.rs
#![allow(incomplete_features)]
#![feature(min_generic_const_args, macroless_generic_const_args)]
trait T0 {
    type const N: usize;
}
struct S0<T: T0>([(); T::N]);

fn f1<T: T0>(_: &S0<T>) {}
fn f0<T: T0>(f: &S0<T>) {
    f1(f);
}

fn main() {}

> rust-analyzer analysis-stats .

Database loaded:     333.66ms, 0b (metadata 197.76ms, 0b; build 16.73ms, 0b)
  item trees: 1
  dependency lines of code: 1_469_547, item trees: 2_948
  dependency item stats: traits: 849, impl: 9_703, mods: 3_058, macro calls: 5_590, macro rules: 1_051
Item Tree Collection: 1.22s, 0b
  Total Statistics:
    crates: 1, mods: 1, decls: 5, bodies: 3, adts: 1, consts: 0, signatures: 5, variants: 1
  Workspace:
    traits: 1, macro_rules macros: 0, proc_macros: 0
    lines of code: 14, item trees: 1
    usages: traits: 1, impl: 0, mods: 0, macro calls: 0, macro rules: 0
  Dependencies:
    lines of code: 1_469_547, item trees: 2_948
    declarations: traits: 849, impl: 9_703, mods: 3_058, macro calls: 5_590, macro rules: 1_051
Item Collection:     560.98ms, 0b
Crate lang items:    176.81ms, 0b
Expression Store Lowering: 176.96µs, 0b

thread 'main' (2869738) panicked at /Users/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ena-0.14.4/src/snapshot_vec.rs:199:10:
index out of bounds: the len is 0 but the index is 0
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic_bounds_check
   3: <ra_ap_rustc_next_trait_solver::resolve::EagerResolver<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner> as ra_ap_rustc_type_ir::fold::TypeFolder<hir_ty::next_solver::interner::DbInterner>>::fold_ty
   4: <hir_ty::next_solver::generic_arg::GenericArgs as ra_ap_rustc_type_ir::fold::TypeFoldable<hir_ty::next_solver::interner::DbInterner>>::fold_with::<ra_ap_rustc_next_trait_solver::resolve::EagerResolver<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>
   5: <ra_ap_rustc_type_ir::solve::Goal<hir_ty::next_solver::interner::DbInterner, hir_ty::next_solver::predicate::Predicate> as ra_ap_rustc_type_ir::fold::TypeFoldable<hir_ty::next_solver::interner::DbInterner>>::fold_with::<ra_ap_rustc_next_trait_solver::resolve::EagerResolver<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>
   6: ra_ap_rustc_next_trait_solver::resolve::eager_resolve_vars::<hir_ty::next_solver::solver::SolverContext, (ra_ap_rustc_type_ir::solve::Goal<hir_ty::next_solver::interner::DbInterner, hir_ty::next_solver::predicate::Predicate>, alloc::vec::Vec<(ra_ap_rustc_type_ir::opaque_ty::OpaqueTypeKey<hir_ty::next_solver::interner::DbInterner>, hir_ty::next_solver::ty::Ty)>)>
   7: <hir_ty::next_solver::solver::SolverContext as ra_ap_rustc_next_trait_solver::solve::eval_ctxt::SolverDelegateEvalExt>::evaluate_root_goal_for_proof_tree
   8: <hir_ty::next_solver::infer::InferCtxt>::select
   9: hir_ty::method_resolution::lookup_impl_assoc_item_for_trait_ref
  10: hir_ty::method_resolution::lookup_impl_const
  11: <hir_ty::mir::eval::Evaluator>::eval_operand
  12: <hir_ty::mir::eval::Evaluator>::eval_rvalue
  13: hir_ty::mir::eval::interpret_mir
  14: <hir_ty::consteval::anon_const_eval::_::anon_const_eval_query_Configuration_ as salsa::function::Configuration>::execute
  15: <salsa::function::IngredientImpl<hir_ty::consteval::anon_const_eval::_::anon_const_eval_query_Configuration_>>::execute
  16: hir_ty::consteval::anon_const_eval
  17: <hir_ty::next_solver::solver::SolverContext as ra_ap_rustc_next_trait_solver::delegate::SolverDelegate>::evaluate_const
  18: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::evaluate_const_and_instantiate_normalizes_to_term
  19: <ra_ap_rustc_type_ir::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver::solve::search_graph::SearchGraphDelegate<hir_ty::next_solver::solver::SolverContext>, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal_in_task
  20: <ra_ap_rustc_type_ir::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver::solve::search_graph::SearchGraphDelegate<hir_ty::next_solver::solver::SolverContext>, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal
  21: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::try_evaluate_added_goals
  22: <ra_ap_rustc_type_ir::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver::solve::search_graph::SearchGraphDelegate<hir_ty::next_solver::solver::SolverContext>, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal_in_task
  23: <ra_ap_rustc_type_ir::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver::solve::search_graph::SearchGraphDelegate<hir_ty::next_solver::solver::SolverContext>, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal
  24: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal
  25: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::try_evaluate_added_goals
  26: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::evaluate_added_goals_and_make_canonical_response
  27: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::compute_trait_goal
  28: <ra_ap_rustc_type_ir::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver::solve::search_graph::SearchGraphDelegate<hir_ty::next_solver::solver::SolverContext>, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal_in_task
  29: <ra_ap_rustc_type_ir::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver::solve::search_graph::SearchGraphDelegate<hir_ty::next_solver::solver::SolverContext>, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal
  30: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal
  31: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::try_evaluate_added_goals
  32: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::evaluate_added_goals_and_make_canonical_response
  33: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::assemble_impl_candidates::<ra_ap_rustc_type_ir::predicate::TraitPredicate<hir_ty::next_solver::interner::DbInterner>>::{closure#0}
  34: <ra_ap_rustc_next_trait_solver::solve::eval_ctxt::EvalCtxt<hir_ty::next_solver::solver::SolverContext, hir_ty::next_solver::interner::DbInterner>>::compute_trait_goal
  35: <ra_ap_rustc_type_ir::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver::solve::search_graph::SearchGraphDelegate<hir_ty::next_solver::solver::SolverContext>, hir_ty::next_solver::interner::DbInterner>>::evaluate_goal_in_task
  36: <hir_ty::infer::coerce::Coerce<hir_ty::infer::coerce::InferenceCoercionDelegate>>::coerce
  37: <hir_ty::infer::InferenceContext>::check_call_arguments
  38: <hir_ty::infer::InferenceContext>::infer_call
  39: <hir_ty::infer::InferenceContext>::infer_expr_inner
  40: <hir_ty::infer::InferenceContext>::infer_expr_inner
  41: <hir_ty::infer::InferenceContext>::infer_return
  42: hir_ty::infer::infer_query_with_inspect
  43: <salsa::function::IngredientImpl<<hir_ty::infer::InferenceResult>::for_body::_::for_body__Configuration_>>::execute
  44: <hir_ty::infer::InferenceResult>::for_body
  45: <rust_analyzer::cli::flags::AnalysisStats>::run_inference
  46: <rust_analyzer::cli::flags::AnalysisStats>::run::{closure#4}
  47: <rust_analyzer::cli::flags::AnalysisStats>::run
  48: rust_analyzer::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
infer panicked for bugrepro::f0: index out of bounds: the len is 0 but the index is 0
  exprs: 2, ??ty: 0 (0%), ?ty: 0 (0%), !ty: 0
  pats: 1, ??ty: 0 (0%), ?ty: 0 (0%), !ty: 0
  panics: 1
Inference:           111.18ms, 0b
2026-08-05T14:27:04.550361-05:00  WARN Propagating panic for cycle head that panicked in an earlier execution in that revision

Run the provided const-generics snippet with rust-analyzer analysis-stats . and confirm the panic. Trace the stack through hir_ty::next_solver, method_resolution, consteval, and inference, then ensure this reproducer no longer panics and has regression coverage.