ICE: `generics_of: unexpected node kind ConstArg(ConstArg`

[matthiaskrgr]

auto-reduced (treereduce-rust):

#![feature(min_generic_const_args)]
#![feature(generic_const_exprs)]
struct Both<const is_123: u32 = 3, T> {
    a: A<{ B::<1>::M }>,
}

original:

#![non_upper_case_globals = "ABCD"]
#![yes_ord(dead_code)]

struct Both<const is_123: u32=3, T> {
    a: A<{ B::<1>::M }>,
}

Version information

rustc 1.93.0-nightly (2636cb4c1 2025-11-11)
binary: rustc
commit-hash: 2636cb4c1328f5a3ab05b8d13a666ac5f3a48a08
commit-date: 2025-11-11
host: x86_64-unknown-linux-gnu
release: 1.93.0-nightly
LLVM version: 21.1.5

Possibly related line of code:

rust/compiler/rustc_hir_analysis/src/collect/generics_of.rs

Lines 206 to 218 in 2636cb4

	Node::Synthetic => span_bug!(
	tcx.def_span(def_id),
	"synthetic HIR should have its `generics_of` explicitly fed"
	),
	_ => span_bug!(tcx.def_span(def_id), "generics_of: unexpected node kind {node:?}"),
	};
	// Add in the self type parameter.
	let opt_self = if let Node::Item(item) = node
	&& let ItemKind::Trait(..) | ItemKind::TraitAlias(..) = item.kind
	{

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zcrate-attr=feature(min_generic_const_args) -Zcrate-attr=feature(generic_const_exprs)

Program output

error: generic parameters with a default must be trailing
 --> /tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs:1:19
  |
1 | struct Both<const is_123: u32 = 3, T> {
  |                   ^^^^^^

error[E0412]: cannot find type `A` in this scope
 --> /tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs:2:8
  |
1 | struct Both<const is_123: u32 = 3, T> {
  |                                    - similarly named type parameter `T` defined here
2 |     a: A<{ B::<1>::M }>,
  |        ^ help: a type parameter with a similar name exists: `T`

warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:12
  |
1 | #![feature(min_generic_const_args)]
  |            ^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #132980 <https://github.com/rust-lang/rust/issues/132980> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> <crate attribute>:1:12
  |
1 | #![feature(generic_const_exprs)]
  |            ^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs:3:2
  |
3 | }
  |  ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs`

error: internal compiler error: compiler/rustc_hir_analysis/src/collect/generics_of.rs:212:14: generics_of: unexpected node kind ConstArg(ConstArg { hir_id: HirId(DefId(0:3 ~ mvce[f463]::Both).14), kind: Path(Resolved(None, Path { span: /tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs:2:12: 2:21 (#0), res: Err, segments: [PathSegment { ident: B#0, hir_id: HirId(DefId(0:3 ~ mvce[f463]::Both).12), res: Err, args: Some(GenericArgs { args: [Const(ConstArg { hir_id: HirId(DefId(0:3 ~ mvce[f463]::Both).11), kind: Anon(AnonConst { hir_id: HirId(DefId(0:3 ~ mvce[f463]::Both).9), def_id: DefId(0:9 ~ mvce[f463]::Both::a::{constant#0}::{constant#0}), body: BodyId { hir_id: HirId(DefId(0:3 ~ mvce[f463]::Both).10) }, span: /tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs:2:16: 2:17 (#0) }) })], constraints: [], parenthesized: No, span_ext: /tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs:2:15: 2:18 (#0) }), infer_args: false }, PathSegment { ident: M#0, hir_id: HirId(DefId(0:3 ~ mvce[f463]::Both).13), res: Err, args: None, infer_args: false }] })) })
 --> /tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs:2:12
  |
2 |     a: A<{ B::<1>::M }>,
  |            ^^^^^^^^^


thread 'rustc' (1550694) panicked at compiler/rustc_hir_analysis/src/collect/generics_of.rs:212:14:
Box<dyn Any>
stack backtrace:
   0:     0x7fe014e77793 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h8508b8692a67f424
   1:     0x7fe015601afc - core::fmt::write::h892b976990d68807
   2:     0x7fe014e2c113 - std::io::Write::write_fmt::h2cfb6ae7ceafc18f
   3:     0x7fe014e3d722 - std::sys::backtrace::BacktraceLock::print::h6b401f5a90fe0615
   4:     0x7fe014e438b9 - std::panicking::default_hook::{{closure}}::h4bcd3e8272ea6e1e
   5:     0x7fe014e433e3 - std::panicking::default_hook::hc47768de8da9bf00
   6:     0x7fe013e32f01 - std[2b52140d45a5d53]::panicking::update_hook::<alloc[f328c0b594c54d96]::boxed::Box<rustc_driver_impl[ff76f056f877a8d6]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7fe014e43cdb - std::panicking::panic_with_hook::h50a148ea39b0e607
   8:     0x7fe013e6ee31 - std[2b52140d45a5d53]::panicking::begin_panic::<rustc_errors[76704593d079f0be]::ExplicitBug>::{closure#0}
   9:     0x7fe013e61576 - std[2b52140d45a5d53]::sys::backtrace::__rust_end_short_backtrace::<std[2b52140d45a5d53]::panicking::begin_panic<rustc_errors[76704593d079f0be]::ExplicitBug>::{closure#0}, !>
  10:     0x7fe013e610d7 - std[2b52140d45a5d53]::panicking::begin_panic::<rustc_errors[76704593d079f0be]::ExplicitBug>
  11:     0x7fe013e8d641 - <rustc_errors[76704593d079f0be]::diagnostic::BugAbort as rustc_errors[76704593d079f0be]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7fe0143f588c - <rustc_errors[76704593d079f0be]::DiagCtxtHandle>::span_bug::<rustc_span[1859fa485aa88c5d]::span_encoding::Span, alloc[f328c0b594c54d96]::string::String>
  13:     0x7fe014418dc7 - rustc_middle[48f5e10766353194]::util::bug::opt_span_bug_fmt::<rustc_span[1859fa485aa88c5d]::span_encoding::Span>::{closure#0}
  14:     0x7fe0144190ca - rustc_middle[48f5e10766353194]::ty::context::tls::with_opt::<rustc_middle[48f5e10766353194]::util::bug::opt_span_bug_fmt<rustc_span[1859fa485aa88c5d]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  15:     0x7fe014409ecb - rustc_middle[48f5e10766353194]::ty::context::tls::with_context_opt::<rustc_middle[48f5e10766353194]::ty::context::tls::with_opt<rustc_middle[48f5e10766353194]::util::bug::opt_span_bug_fmt<rustc_span[1859fa485aa88c5d]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  16:     0x7fe012710ec7 - rustc_middle[48f5e10766353194]::util::bug::span_bug_fmt::<rustc_span[1859fa485aa88c5d]::span_encoding::Span>
  17:     0x7fe015fa2578 - rustc_hir_analysis[95d84e02a3e62ea1]::collect::generics_of::generics_of
  18:     0x7fe01561b969 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::generics_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>>
  19:     0x7fe01561c046 - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_query_system[636933bf47b8a8e3]::query::caches::DefIdCache<rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  20:     0x7fe01561bd6b - rustc_query_impl[d248f320eda2a0f9]::query_impl::generics_of::get_query_non_incr::__rust_end_short_backtrace
  21:     0x7fe015fa080f - rustc_hir_analysis[95d84e02a3e62ea1]::collect::generics_of::generics_of
  22:     0x7fe01561b969 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::generics_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>>
  23:     0x7fe01561c046 - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_query_system[636933bf47b8a8e3]::query::caches::DefIdCache<rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  24:     0x7fe01561bd6b - rustc_query_impl[d248f320eda2a0f9]::query_impl::generics_of::get_query_non_incr::__rust_end_short_backtrace
  25:     0x7fe015fe8f82 - rustc_hir_analysis[95d84e02a3e62ea1]::collect::predicates_of::gather_explicit_predicates_of::{closure#0}
  26:     0x7fe015fe6c10 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::explicit_predicates_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 24usize]>>
  27:     0x7fe01574449a - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_query_system[636933bf47b8a8e3]::query::caches::DefIdCache<rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  28:     0x7fe015743da2 - rustc_query_impl[d248f320eda2a0f9]::query_impl::explicit_predicates_of::get_query_non_incr::__rust_end_short_backtrace
  29:     0x7fe015743183 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::predicates_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 24usize]>>
  30:     0x7fe0157444b9 - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_query_system[636933bf47b8a8e3]::query::caches::DefIdCache<rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  31:     0x7fe015743ca2 - rustc_query_impl[d248f320eda2a0f9]::query_impl::predicates_of::get_query_non_incr::__rust_end_short_backtrace
  32:     0x7fe015ae3748 - rustc_ty_utils[8aae495b601b2150]::ty::param_env
  33:     0x7fe015ae2cd9 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::param_env::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>>
  34:     0x7fe01561c046 - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_query_system[636933bf47b8a8e3]::query::caches::DefIdCache<rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  35:     0x7fe01561bb31 - rustc_query_impl[d248f320eda2a0f9]::query_impl::param_env::get_query_non_incr::__rust_end_short_backtrace
  36:     0x7fe01631b6c3 - rustc_hir_typeck[429764d9bd7be61f]::typeck_with_inspect::{closure#0}
  37:     0x7fe0163162c6 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>>
  38:     0x7fe015889777 - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_data_structures[e91f46092e6bce0]::vec_cache::VecCache<rustc_span[1859fa485aa88c5d]::def_id::LocalDefId, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[636933bf47b8a8e3]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  39:     0x7fe015889109 - rustc_query_impl[d248f320eda2a0f9]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  40:     0x7fe01588a5d7 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::used_trait_imports::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>>
  41:     0x7fe015889777 - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_data_structures[e91f46092e6bce0]::vec_cache::VecCache<rustc_span[1859fa485aa88c5d]::def_id::LocalDefId, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[636933bf47b8a8e3]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  42:     0x7fe015889049 - rustc_query_impl[d248f320eda2a0f9]::query_impl::used_trait_imports::get_query_non_incr::__rust_end_short_backtrace
  43:     0x7fe015888abd - rustc_hir_analysis[95d84e02a3e62ea1]::check_unused::check_unused_traits
  44:     0x7fe0158889a9 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::check_unused_traits::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 0usize]>>
  45:     0x7fe0166917e6 - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_query_system[636933bf47b8a8e3]::query::caches::SingleCache<rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  46:     0x7fe0166914c2 - rustc_query_impl[d248f320eda2a0f9]::query_impl::check_unused_traits::get_query_non_incr::__rust_end_short_backtrace
  47:     0x7fe0160fc86f - rustc_hir_analysis[95d84e02a3e62ea1]::check_crate
  48:     0x7fe01655f770 - rustc_interface[5c2f13e94b4905f7]::passes::analysis
  49:     0x7fe01655f433 - rustc_query_impl[d248f320eda2a0f9]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[d248f320eda2a0f9]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 0usize]>>
  50:     0x7fe0166917e6 - rustc_query_system[636933bf47b8a8e3]::query::plumbing::try_execute_query::<rustc_query_impl[d248f320eda2a0f9]::DynamicConfig<rustc_query_system[636933bf47b8a8e3]::query::caches::SingleCache<rustc_middle[48f5e10766353194]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[d248f320eda2a0f9]::plumbing::QueryCtxt, false>
  51:     0x7fe01669143c - rustc_query_impl[d248f320eda2a0f9]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  52:     0x7fe0168d83c3 - <rustc_interface[5c2f13e94b4905f7]::passes::create_and_enter_global_ctxt<core[38695eb0a3e4dc55]::option::Option<rustc_interface[5c2f13e94b4905f7]::queries::Linker>, rustc_driver_impl[ff76f056f877a8d6]::run_compiler::{closure#0}::{closure#2}>::{closure#2} as core[38695eb0a3e4dc55]::ops::function::FnOnce<(&rustc_session[e86e12dfad9d04f]::session::Session, rustc_middle[48f5e10766353194]::ty::context::CurrentGcx, alloc[f328c0b594c54d96]::sync::Arc<rustc_data_structures[e91f46092e6bce0]::jobserver::Proxy>, &std[2b52140d45a5d53]::sync::once_lock::OnceLock<rustc_middle[48f5e10766353194]::ty::context::GlobalCtxt>, &rustc_data_structures[e91f46092e6bce0]::sync::worker_local::WorkerLocal<rustc_middle[48f5e10766353194]::arena::Arena>, &rustc_data_structures[e91f46092e6bce0]::sync::worker_local::WorkerLocal<rustc_hir[9e147bcb7655fc56]::Arena>, rustc_driver_impl[ff76f056f877a8d6]::run_compiler::{closure#0}::{closure#2})>>::call_once::{shim:vtable#0}
  53:     0x7fe0167a7b29 - rustc_interface[5c2f13e94b4905f7]::interface::run_compiler::<(), rustc_driver_impl[ff76f056f877a8d6]::run_compiler::{closure#0}>::{closure#1}
  54:     0x7fe01673ad87 - std[2b52140d45a5d53]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[5c2f13e94b4905f7]::util::run_in_thread_with_globals<rustc_interface[5c2f13e94b4905f7]::util::run_in_thread_pool_with_globals<rustc_interface[5c2f13e94b4905f7]::interface::run_compiler<(), rustc_driver_impl[ff76f056f877a8d6]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  55:     0x7fe01673aa68 - <<std[2b52140d45a5d53]::thread::Builder>::spawn_unchecked_<rustc_interface[5c2f13e94b4905f7]::util::run_in_thread_with_globals<rustc_interface[5c2f13e94b4905f7]::util::run_in_thread_pool_with_globals<rustc_interface[5c2f13e94b4905f7]::interface::run_compiler<(), rustc_driver_impl[ff76f056f877a8d6]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[38695eb0a3e4dc55]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  56:     0x7fe016740bef - std::sys::thread::unix::Thread::new::thread_start::h91d6dca458fee5fb
  57:     0x7fe00fe969cb - <unknown>
  58:     0x7fe00ff1aa0c - <unknown>
  59:                0x0 - <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 1.93.0-nightly (2636cb4c1 2025-11-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z crate-attr=feature(min_generic_const_args) -Z crate-attr=feature(generic_const_exprs) -Z dump-mir-dir=dir

query stack during panic:
#0 [generics_of] computing generics of `Both::a::{constant#0}`
#1 [generics_of] computing generics of `Both::a::{constant#0}::{constant#0}`
#2 [explicit_predicates_of] computing explicit predicates of `Both::a::{constant#0}::{constant#0}`
#3 [predicates_of] computing predicates of `Both::a::{constant#0}::{constant#0}`
#4 [param_env] computing normalized predicates of `Both::a::{constant#0}::{constant#0}`
#5 [typeck] type-checking `Both::a::{constant#0}::{constant#0}`
#6 [used_trait_imports] finding used_trait_imports `Both::a::{constant#0}::{constant#0}`
#7 [check_unused_traits] checking unused trait imports in crate
#8 [analysis] running analysis passes on crate `mvce`
end of query stack
error[E0433]: failed to resolve: use of undeclared type `B`
 --> /tmp/icemaker_global_tempdir.pMUmmFc3ZGer/rustc_testrunner_tmpdir_reporting.aRsqC0nvtFAY/mvce.rs:2:12
  |
2 |     a: A<{ B::<1>::M }>,
  |            ^
  |            |
  |            use of undeclared type `B`
  |            help: a type parameter with a similar name exists: `T`

error: aborting due to 5 previous errors; 2 warnings emitted

Some errors have detailed explanations: E0412, E0433, E0601.
For more information about an error, try `rustc --explain E0412`.

@rustbot label +F-min_generic_const_args +F-generic_const_exprs

[InvalidPathException]

rust/compiler/rustc_hir_analysis/src/collect/generics_of.rs

Lines 76 to 90 in 2636cb4

	// FIXME(#43408) always enable this once `lazy_normalization` is
	// stable enough and does not need a feature gate anymore.
	Node::AnonConst(_) => {
	let parent_did = tcx.parent(def_id.to_def_id());
	debug!(?parent_did);
	let mut in_param_ty = false;
	for (_parent, node) in tcx.hir_parent_iter(hir_id) {
	if let Some(generics) = node.generics() {
	let mut visitor = AnonConstInParamTyDetector { in_param_ty: false, ct: hir_id };
	in_param_ty = visitor.visit_generics(generics).is_break();
	break;
	}
	}

Seems like there is a missing branch which should be similar to the above
Could look like the below:

        Node::ConstArg(_) => {
            let parent_did = tcx.parent(def_id.to_def_id());
            debug!(?parent_did);

            if let Node::GenericParam(hir::GenericParam {
                def_id: param_id,
                kind: hir::GenericParamKind::Const { .. },
                ..
            }) = tcx.parent_hir_node(hir_id)
            {
                let generics = tcx.generics_of(parent_did);
                let param_def_idx = generics.param_def_id_to_index[&param_id.to_def_id()];
                let own_params = generics.params_to(param_def_idx as usize, tcx).to_owned();
                let param_def_id_to_index =
                    own_params.iter().map(|param| (param.def_id, param.index)).collect();

                return ty::Generics {
                    parent: generics.parent,
                    parent_count: generics.parent_count,
                    own_params,
                    param_def_id_to_index,
                    has_self: generics.has_self,
                    has_late_bound_regions: generics.has_late_bound_regions,
                };
            }

            Some(parent_did)
        }

[BoxyUwU]

git whoopsie dropped the fix for this from the PR that closed this