panic: mir lowering `no entry found for key`

fn main() { let _: [(); { |x: u32| { x }; 4 }]; }

code sompiles with rustc

RUST_BACKTRACE=full ~/.rustup/toolchains/master/bin/rust-analyzer analysis-stats --run-all-ide-things .

Database loaded:     344.53ms, 224minstr, 48mb (metadata 193.23ms, 926kinstr, 150kb; build 18.90ms, 165kinstr, 1088b)
  item trees: 1
  dependency lines of code: 1_462_980, item trees: 2_900
  dependency item stats: traits: 851, impl: 9_703, mods: 3_013, macro calls: 5_502, macro rules: 1_053
Item Tree Collection: 2.07s, 22ginstr, 425mb
  Total Statistics:
1    crates: 1, mods: 1, decls: 1, bodies: 1, adts: 0, consts: 0, signatures: 1, variants: 0
  Workspace:
    traits: 0, macro_rules macros: 0, proc_macros: 0
    lines of code: 5, item trees: 1
    usages: traits: 0, impl: 0, mods: 0, macro calls: 0, macro rules: 0
  Dependencies:
    lines of code: 1_462_980, item trees: 2_900
    declarations: traits: 851, impl: 9_703, mods: 3_013, macro calls: 5_502, macro rules: 1_053
Item Collection:     1.15s, 11ginstr, 177mb
Crate lang items:    233.20ms, 2471minstr, 31mb
Expression Store Lowering: 125.69µs, 165kinstr, 3968b
0/1 0% processing: a::main
thread 'main' (826510) panicked at src/tools/rust-analyzer/crates/hir-ty/src/mir/lower.rs:1258:61:
no entry found for key
stack backtrace:
   0:     0x7f1b0e62a786 - <<std[1e37345aeca07a33]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[702fd8b52481f6b]::fmt::Display>::fmt
   1:     0x7f1b0ec0f108 - core[702fd8b52481f6b]::fmt::write
   2:     0x7f1b0e63f9ec - <std[1e37345aeca07a33]::sys::stdio::unix::Stderr as core[702fd8b52481f6b]::io::write::Write>::write_fmt
   3:     0x7f1b0e5fc40a - std[1e37345aeca07a33]::panicking::default_hook::{closure#0}
   4:     0x7f1b0e61cea3 - std[1e37345aeca07a33]::panicking::default_hook
   5:     0x7f1b0e61d30b - std[1e37345aeca07a33]::panicking::panic_with_hook
   6:     0x7f1b0e5fc4c2 - std[1e37345aeca07a33]::panicking::panic_handler::{closure#0}
   7:     0x7f1b0e5f3959 - std[1e37345aeca07a33]::sys::backtrace::__rust_end_short_backtrace::<std[1e37345aeca07a33]::panicking::panic_handler::{closure#0}, !>
   8:     0x7f1b0e5fde1d - __rustc[c13b5280399c33fa]::rust_begin_unwind
   9:     0x7f1b0b2ea73c - core[702fd8b52481f6b]::panicking::panic_fmt
  10:     0x7f1b0c2ef724 - core[702fd8b52481f6b]::option::expect_failed
  11:     0x55fe3915fbf3 - <hir_ty[e0bea5ffe6249590]::mir::lower::MirLowerCtx>::lower_expr_to_place_without_adjust
  12:     0x55fe390f6325 - <hir_ty[e0bea5ffe6249590]::mir::lower::MirLowerCtx>::lower_expr_to_some_place_without_adjust
  13:     0x55fe39157eb4 - <hir_ty[e0bea5ffe6249590]::mir::lower::MirLowerCtx>::lower_block_to_place
  14:     0x55fe3915b07a - <hir_ty[e0bea5ffe6249590]::mir::lower::MirLowerCtx>::lower_expr_to_place_without_adjust
  15:     0x55fe39157b71 - <hir_ty[e0bea5ffe6249590]::mir::lower::MirLowerCtx>::lower_expr_to_place
  16:     0x55fe39207175 - hir_ty[e0bea5ffe6249590]::mir::lower::lower_body_to_mir
  17:     0x55fe39282bb1 - <hir_ty[e0bea5ffe6249590]::mir::lower::_::mir_body_query_Configuration_ as salsa[6da196d40d999542]::function::Configuration>::execute
  18:     0x55fe3909054b - <salsa[6da196d40d999542]::function::IngredientImpl<hir_ty[e0bea5ffe6249590]::mir::lower::_::mir_body_query_Configuration_>>::execute
  19:     0x55fe39206507 - hir_ty[e0bea5ffe6249590]::mir::lower::mir_body_query
  20:     0x55fe3a042117 - <ide_db[638de82cedb9c87c]::RootDatabase as hir_ty[e0bea5ffe6249590]::db::HirDatabase>::mir_body
  21:     0x55fe3927f867 - <hir_ty[e0bea5ffe6249590]::mir::monomorphization::_::monomorphized_mir_body_query_Configuration_ as salsa[6da196d40d999542]::function::Configuration>::execute
  22:     0x55fe3908ce5d - <salsa[6da196d40d999542]::function::IngredientImpl<hir_ty[e0bea5ffe6249590]::mir::monomorphization::_::monomorphized_mir_body_query_Configuration_>>::execute
  23:     0x55fe39200279 - hir_ty[e0bea5ffe6249590]::mir::monomorphization::monomorphized_mir_body_query
  24:     0x55fe3a041e67 - <ide_db[638de82cedb9c87c]::RootDatabase as hir_ty[e0bea5ffe6249590]::db::HirDatabase>::monomorphized_mir_body
  25:     0x55fe3928556a - <hir_ty[e0bea5ffe6249590]::consteval::anon_const_eval::_::anon_const_eval_query_Configuration_ as salsa[6da196d40d999542]::function::Configuration>::execute
  26:     0x55fe390a602b - <salsa[6da196d40d999542]::function::IngredientImpl<hir_ty[e0bea5ffe6249590]::consteval::anon_const_eval::_::anon_const_eval_query_Configuration_>>::execute
  27:     0x55fe391f813c - hir_ty[e0bea5ffe6249590]::consteval::anon_const_eval
  28:     0x55fe3a041cc4 - <ide_db[638de82cedb9c87c]::RootDatabase as hir_ty[e0bea5ffe6249590]::db::HirDatabase>::anon_const_eval
  29:     0x55fe392639c3 - <hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext as ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::delegate::SolverDelegate>::evaluate_const
  30:     0x55fe3917fc5b - <ra_ap_rustc_type_ir[e97d49aadf028198]::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::search_graph::SearchGraphDelegate<hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext>, hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::evaluate_goal_in_task
  31:     0x55fe39174d98 - <ra_ap_rustc_type_ir[e97d49aadf028198]::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::search_graph::SearchGraphDelegate<hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext>, hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::evaluate_goal
  32:     0x55fe3910a85a - <ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::eval_ctxt::EvalCtxt<hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext, hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::evaluate_goal_raw
  33:     0x55fe3910ba6f - <ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::eval_ctxt::EvalCtxt<hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext, hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::try_evaluate_added_goals
  34:     0x55fe3917d374 - <ra_ap_rustc_type_ir[e97d49aadf028198]::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::search_graph::SearchGraphDelegate<hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext>, hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::evaluate_goal_in_task
  35:     0x55fe39174d98 - <ra_ap_rustc_type_ir[e97d49aadf028198]::search_graph::SearchGraph<ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::search_graph::SearchGraphDelegate<hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext>, hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::evaluate_goal
  36:     0x55fe3910a85a - <ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::eval_ctxt::EvalCtxt<hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext, hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::evaluate_goal_raw
  37:     0x55fe39109779 - <ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::eval_ctxt::EvalCtxt<hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext, hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::evaluate_goal
  38:     0x55fe39333f27 - <hir_ty[e0bea5ffe6249590]::next_solver::solver::SolverContext as ra_ap_rustc_next_trait_solver[550ca1f3e128fc40]::solve::eval_ctxt::SolverDelegateEvalExt>::evaluate_root_goal
  39:     0x55fe3911d3b5 - <hir_ty[e0bea5ffe6249590]::next_solver::fulfill::FulfillmentCtxt>::try_evaluate_obligations
  40:     0x55fe390b7c89 - <hir_ty[e0bea5ffe6249590]::next_solver::normalize::NormalizationFolder>::normalize_alias_term
  41:     0x55fe393383c5 - <hir_ty[e0bea5ffe6249590]::next_solver::normalize::NormalizationFolder as ra_ap_rustc_type_ir[e97d49aadf028198]::fold::FallibleTypeFolder<hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::try_fold_const
  42:     0x55fe390022d5 - <hir_ty[e0bea5ffe6249590]::next_solver::ty::Ty as ra_ap_rustc_type_ir[e97d49aadf028198]::fold::TypeSuperFoldable<hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::try_super_fold_with::<hir_ty[e0bea5ffe6249590]::next_solver::normalize::NormalizationFolder>
  43:     0x55fe39337e72 - <hir_ty[e0bea5ffe6249590]::next_solver::normalize::NormalizationFolder as ra_ap_rustc_type_ir[e97d49aadf028198]::fold::FallibleTypeFolder<hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::try_fold_ty
  44:     0x55fe38f64d59 - hir_ty[e0bea5ffe6249590]::next_solver::normalize::deeply_normalize_with_skipped_universes_and_ambiguous_coroutine_goals::<hir_ty[e0bea5ffe6249590]::next_solver::ty::Ty>
  45:     0x55fe38ebbac2 - <hir_ty[e0bea5ffe6249590]::infer::unify::resolve_completely::Resolver>::handle_term::<hir_ty[e0bea5ffe6249590]::next_solver::ty::Ty, <hir_ty[e0bea5ffe6249590]::infer::unify::resolve_completely::Resolver as ra_ap_rustc_type_ir[e97d49aadf028198]::fold::TypeFolder<hir_ty[e0bea5ffe6249590]::next_solver::interner::DbInterner>>::fold_ty::{closure#0}>
  46:     0x55fe38ea1d8b - <hir_ty[e0bea5ffe6249590]::infer::unify::resolve_completely::WriteBackCtxt>::resolve_completely::<hir_ty[e0bea5ffe6249590]::next_solver::ty::StoredTy>
  47:     0x55fe391d58de - hir_ty[e0bea5ffe6249590]::infer::infer_finalize
  48:     0x55fe391de9cf - hir_ty[e0bea5ffe6249590]::infer::infer_query_with_inspect
  49:     0x55fe39099584 - <salsa[6da196d40d999542]::function::IngredientImpl<<hir_ty[e0bea5ffe6249590]::infer::InferenceResult>::for_body::_::for_body__Configuration_>>::execute
  50:     0x55fe38e98eb7 - <salsa[6da196d40d999542]::attach::Attached>::attach::<dyn hir_ty[e0bea5ffe6249590]::db::HirDatabase, &hir_ty[e0bea5ffe6249590]::infer::InferenceResult, <hir_ty[e0bea5ffe6249590]::infer::InferenceResult>::for_body::for_body_::{closure#0}>
  51:     0x55fe39e3bdbf - <rust_analyzer[29694c28a86a0685]::cli::flags::AnalysisStats>::run_inference
  52:     0x55fe39de9534 - <rust_analyzer[29694c28a86a0685]::cli::flags::AnalysisStats>::run::{closure#3}
  53:     0x55fe39e47fb9 - <rust_analyzer[29694c28a86a0685]::cli::flags::AnalysisStats>::run
  54:     0x55fe3a0f1d62 - rust_analyzer[b45ee5f09a5d6ebe]::main
  55:     0x55fe3a088593 - std[1e37345aeca07a33]::sys::backtrace::__rust_begin_short_backtrace::<fn() -> core[702fd8b52481f6b]::result::Result<std[1e37345aeca07a33]::process::ExitCode, anyhow[f29ba2bc3bec5daa]::Error>, core[702fd8b52481f6b]::result::Result<std[1e37345aeca07a33]::process::ExitCode, anyhow[f29ba2bc3bec5daa]::Error>>
  56:     0x55fe3a0eaf02 - std[1e37345aeca07a33]::rt::lang_start::<core[702fd8b52481f6b]::result::Result<std[1e37345aeca07a33]::process::ExitCode, anyhow[f29ba2bc3bec5daa]::Error>>::{closure#0}
  57:     0x7f1b0fd9d099 - std[1e37345aeca07a33]::rt::lang_start_internal
  58:     0x55fe3a10afe8 - main
  59:     0x7f1b09627741 - <unknown>
  60:     0x7f1b09627879 - __libc_start_main
  61:     0x55fe389fc629 - <unknown>
  62:                0x0 - <unknown>
infer panicked for a::main: no entry found for key
  exprs: 0, ??ty: 0 (100%), ?ty: 0 (100%), !ty: 0
  pats: 0, ??ty: 0 (100%), ?ty: 0 (100%), !ty: 0
  panics: 1
Inference:           12.47ms, 62minstr, 7mb
1/1 100% mir lowering: a::main2026-07-17T17:33:46.238777284+02:00  WARN Propagating panic for cycle head that panicked in an earlier execution in that revision

Reproduce the panic with the minimal Rust snippet and the analysis-stats command from the issue. Start at src/tools/rust-analyzer/crates/hir-ty/src/mir/lower.rs:1258 and trace the MIR lowering path shown in the backtrace; done means analysis-stats completes without the "no entry found for key" panic.