ICE: `cannot find 'N/#0' in param-env: ParamEnv`

[matthiaskrgr]

Code

#![feature(generic_const_exprs)]
#![feature(generic_const_parameter_types)]
#![feature(adt_const_params)]
#[derive(Clone)]
struct Foo<const N : [u8; Self::FOO]>;

pub fn main() {}

Version information

rustc 1.90.0-nightly (fe5f3dedf 2025-06-27)
binary: rustc
commit-hash: fe5f3dedf7b4d6bea2cadb17343f747d70b4c66b
commit-date: 2025-06-27
host: x86_64-unknown-linux-gnu
release: 1.90.0-nightly
LLVM version: 20.1.7

Possibly related line of code:

rust/compiler/rustc_middle/src/ty/sty.rs

Lines 366 to 378 in fe5f3de

	// `Option<Ty<'tcx>>` instead of `Ty<'tcx>`; however, this is generally
	// considered to be a bandaid solution, since it hides more important
	// underlying issues with how we construct generics and predicates of
	// items. It's advised to fix the underlying issue rather than trying
	// to modify this function.
	let ty = candidates.next().unwrap_or_else(|| {
	bug!("cannot find `{self:?}` in param-env: {env:#?}");
	});
	assert!(
	candidates.next().is_none(),
	"did not expect duplicate `ConstParamHasTy` for `{self:?}` in param-env: {env:#?}"
	);
	ty

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc

Program output

error: cannot use `Self` in const parameter type
 --> /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:5:26
  |
5 | struct Foo<const N: [u8; Self::FOO]>;
  |                          ^^^^^^^^^

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:1:12
  |
1 | #![feature(generic_const_exprs)]
  |            ^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: the feature `generic_const_parameter_types` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:2:12
  |
2 | #![feature(generic_const_parameter_types)]
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #137626 <https://github.com/rust-lang/rust/issues/137626> for more information

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:5:38
  |
5 | struct Foo<const N: [u8; Self::FOO]>;
  |                                      ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs`

error: `[u8; Self::FOO]` is forbidden as the type of a const generic parameter
 --> /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:5:21
  |
5 | struct Foo<const N: [u8; Self::FOO]>;
  |                     ^^^^^^^^^^^^^^^
  |
  = note: the only supported types are integers, `bool`, and `char`
help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
  |
4 + #![feature(adt_const_params)]
  |

error: internal compiler error: compiler/rustc_middle/src/ty/sty.rs:372:13: cannot find `N/#0` in param-env: ParamEnv {
                                    caller_bounds: [],
                                }


thread 'rustc' panicked at compiler/rustc_middle/src/ty/sty.rs:372:13:
Box<dyn Any>
stack backtrace:
   0:     0x7dc6aa1096f3 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h48b24be8297e4a9c
   1:     0x7dc6aa802c37 - core::fmt::write::h44ef114fca1e3410
   2:     0x7dc6aa0ff213 - std::io::Write::write_fmt::h48f3596bb626dcaa
   3:     0x7dc6aa109552 - std::sys::backtrace::BacktraceLock::print::h08fe9f4d0c0a723f
   4:     0x7dc6aa10d04a - std::panicking::default_hook::{{closure}}::h470a325c2f4bb1be
   5:     0x7dc6aa10cbcf - std::panicking::default_hook::h375895b5d6b84766
   6:     0x7dc6a91ea173 - std[7a7d327c4bb6bc11]::panicking::update_hook::<alloc[95fe608572e1da2a]::boxed::Box<rustc_driver_impl[1d35d6f9d2799e05]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7dc6aa10d89b - std::panicking::rust_panic_with_hook::h3f9361c44c0dd63d
   8:     0x7dc6a9224261 - std[7a7d327c4bb6bc11]::panicking::begin_panic::<rustc_errors[46b8c952c97445c4]::ExplicitBug>::{closure#0}
   9:     0x7dc6a9218936 - std[7a7d327c4bb6bc11]::sys::backtrace::__rust_end_short_backtrace::<std[7a7d327c4bb6bc11]::panicking::begin_panic<rustc_errors[46b8c952c97445c4]::ExplicitBug>::{closure#0}, !>
  10:     0x7dc6a9215139 - std[7a7d327c4bb6bc11]::panicking::begin_panic::<rustc_errors[46b8c952c97445c4]::ExplicitBug>
  11:     0x7dc6a922dd41 - <rustc_errors[46b8c952c97445c4]::diagnostic::BugAbort as rustc_errors[46b8c952c97445c4]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7dc6a97f6bca - rustc_middle[421a23b7571f26a5]::util::bug::opt_span_bug_fmt::<rustc_span[dd092a92122222c1]::span_encoding::Span>::{closure#0}
  13:     0x7dc6a97d66ba - rustc_middle[421a23b7571f26a5]::ty::context::tls::with_opt::<rustc_middle[421a23b7571f26a5]::util::bug::opt_span_bug_fmt<rustc_span[dd092a92122222c1]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7dc6a97d652b - rustc_middle[421a23b7571f26a5]::ty::context::tls::with_context_opt::<rustc_middle[421a23b7571f26a5]::ty::context::tls::with_opt<rustc_middle[421a23b7571f26a5]::util::bug::opt_span_bug_fmt<rustc_span[dd092a92122222c1]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x7dc6a689f860 - rustc_middle[421a23b7571f26a5]::util::bug::bug_fmt
  16:     0x7dc6ab279cb9 - <rustc_trait_selection[e32a2b5ce67343b3]::traits::fulfill::FulfillProcessor as rustc_data_structures[d5f78031b72118ca]::obligation_forest::ObligationProcessor>::process_obligation
  17:     0x7dc6aa805902 - <rustc_data_structures[d5f78031b72118ca]::obligation_forest::ObligationForest<rustc_trait_selection[e32a2b5ce67343b3]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[e32a2b5ce67343b3]::traits::fulfill::FulfillProcessor>
  18:     0x7dc6ab68a4f6 - <rustc_hir_typeck[e45be9a4afc83985]::fn_ctxt::FnCtxt>::check_expr_path
  19:     0x7dc6ab341e96 - <rustc_hir_typeck[e45be9a4afc83985]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
  20:     0x7dc6ab9f3e01 - rustc_hir_typeck[e45be9a4afc83985]::typeck_with_inspect::{closure#0}
  21:     0x7dc6ab9f23b0 - rustc_query_impl[a46554db2076a7e1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a46554db2076a7e1]::query_impl::typeck::dynamic_query::{closure#2}::{closure#0}, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 8usize]>>
  22:     0x7dc6aaa0bcee - rustc_query_system[9da031a4e4fdb32b]::query::plumbing::try_execute_query::<rustc_query_impl[a46554db2076a7e1]::DynamicConfig<rustc_data_structures[d5f78031b72118ca]::vec_cache::VecCache<rustc_span[dd092a92122222c1]::def_id::LocalDefId, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[9da031a4e4fdb32b]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a46554db2076a7e1]::plumbing::QueryCtxt, false>
  23:     0x7dc6aaa0b689 - rustc_query_impl[a46554db2076a7e1]::query_impl::typeck::get_query_non_incr::__rust_end_short_backtrace
  24:     0x7dc6ab24104b - rustc_mir_build[4861131aeeb73c8e]::thir::cx::thir_body
  25:     0x7dc6ab23fdb4 - rustc_query_impl[a46554db2076a7e1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a46554db2076a7e1]::query_impl::thir_body::dynamic_query::{closure#2}::{closure#0}, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 16usize]>>
  26:     0x7dc6ab20d382 - rustc_query_system[9da031a4e4fdb32b]::query::plumbing::try_execute_query::<rustc_query_impl[a46554db2076a7e1]::DynamicConfig<rustc_data_structures[d5f78031b72118ca]::vec_cache::VecCache<rustc_span[dd092a92122222c1]::def_id::LocalDefId, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 16usize]>, rustc_query_system[9da031a4e4fdb32b]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a46554db2076a7e1]::plumbing::QueryCtxt, false>
  27:     0x7dc6ab20cfcc - rustc_query_impl[a46554db2076a7e1]::query_impl::thir_body::get_query_non_incr::__rust_end_short_backtrace
  28:     0x7dc6aac82047 - rustc_query_impl[a46554db2076a7e1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a46554db2076a7e1]::query_impl::thir_abstract_const::dynamic_query::{closure#2}::{closure#0}, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 16usize]>>
  29:     0x7dc6aac81f8d - <rustc_query_impl[a46554db2076a7e1]::query_impl::thir_abstract_const::dynamic_query::{closure#2} as core[df8911376af37c8c]::ops::function::FnOnce<(rustc_middle[421a23b7571f26a5]::ty::context::TyCtxt, rustc_span[dd092a92122222c1]::def_id::DefId)>>::call_once
  30:     0x7dc6aa9c19fb - rustc_query_system[9da031a4e4fdb32b]::query::plumbing::try_execute_query::<rustc_query_impl[a46554db2076a7e1]::DynamicConfig<rustc_query_system[9da031a4e4fdb32b]::query::caches::DefIdCache<rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[a46554db2076a7e1]::plumbing::QueryCtxt, false>
  31:     0x7dc6aa9c1632 - rustc_query_impl[a46554db2076a7e1]::query_impl::thir_abstract_const::get_query_non_incr::__rust_end_short_backtrace
  32:     0x7dc6abef5d37 - <<rustc_middle[421a23b7571f26a5]::ty::context::TyCtxt>::expand_abstract_consts::Expander as rustc_type_ir[b99847d00467586e]::fold::TypeFolder<rustc_middle[421a23b7571f26a5]::ty::context::TyCtxt>>::fold_const.warm
  33:     0x7dc6aa841031 - rustc_trait_selection[e32a2b5ce67343b3]::traits::const_evaluatable::is_const_evaluatable
  34:     0x7dc6ab27dfad - <rustc_trait_selection[e32a2b5ce67343b3]::traits::fulfill::FulfillProcessor as rustc_data_structures[d5f78031b72118ca]::obligation_forest::ObligationProcessor>::process_obligation
  35:     0x7dc6aa805902 - <rustc_data_structures[d5f78031b72118ca]::obligation_forest::ObligationForest<rustc_trait_selection[e32a2b5ce67343b3]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[e32a2b5ce67343b3]::traits::fulfill::FulfillProcessor>
  36:     0x7dc6ab1de967 - <rustc_trait_selection[e32a2b5ce67343b3]::traits::fulfill::FulfillmentContext<rustc_trait_selection[e32a2b5ce67343b3]::traits::FulfillmentError> as rustc_infer[cb3f45674935538]::traits::engine::TraitEngine<rustc_trait_selection[e32a2b5ce67343b3]::traits::FulfillmentError>>::select_all_or_error
  37:     0x7dc6ab1e0ec3 - rustc_hir_analysis[bda1b381e8c255de]::check::wfcheck::check_item
  38:     0x7dc6ab1d9bd9 - rustc_hir_analysis[bda1b381e8c255de]::check::wfcheck::check_well_formed
  39:     0x7dc6ab1d9a59 - rustc_query_impl[a46554db2076a7e1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a46554db2076a7e1]::query_impl::check_well_formed::dynamic_query::{closure#2}::{closure#0}, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 1usize]>>
  40:     0x7dc6ab1d928d - rustc_query_system[9da031a4e4fdb32b]::query::plumbing::try_execute_query::<rustc_query_impl[a46554db2076a7e1]::DynamicConfig<rustc_data_structures[d5f78031b72118ca]::vec_cache::VecCache<rustc_span[dd092a92122222c1]::def_id::LocalDefId, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 1usize]>, rustc_query_system[9da031a4e4fdb32b]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[a46554db2076a7e1]::plumbing::QueryCtxt, false>
  41:     0x7dc6ab1d8dc2 - rustc_query_impl[a46554db2076a7e1]::query_impl::check_well_formed::get_query_non_incr::__rust_end_short_backtrace
  42:     0x7dc6ab1d651f - rustc_hir_analysis[bda1b381e8c255de]::check::wfcheck::check_type_wf
  43:     0x7dc6ab1d641d - rustc_query_impl[a46554db2076a7e1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a46554db2076a7e1]::query_impl::check_type_wf::dynamic_query::{closure#2}::{closure#0}, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 1usize]>>
  44:     0x7dc6ab8af9f0 - rustc_query_system[9da031a4e4fdb32b]::query::plumbing::try_execute_query::<rustc_query_impl[a46554db2076a7e1]::DynamicConfig<rustc_query_system[9da031a4e4fdb32b]::query::caches::SingleCache<rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[a46554db2076a7e1]::plumbing::QueryCtxt, false>
  45:     0x7dc6ab8af7ce - rustc_query_impl[a46554db2076a7e1]::query_impl::check_type_wf::get_query_non_incr::__rust_end_short_backtrace
  46:     0x7dc6aaa0343a - rustc_hir_analysis[bda1b381e8c255de]::check_crate
  47:     0x7dc6aaa077a7 - rustc_interface[b6aba49ee050940e]::passes::analysis
  48:     0x7dc6aaa073cb - rustc_query_impl[a46554db2076a7e1]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a46554db2076a7e1]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 0usize]>>
  49:     0x7dc6ab8b113c - rustc_query_system[9da031a4e4fdb32b]::query::plumbing::try_execute_query::<rustc_query_impl[a46554db2076a7e1]::DynamicConfig<rustc_query_system[9da031a4e4fdb32b]::query::caches::SingleCache<rustc_middle[421a23b7571f26a5]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[a46554db2076a7e1]::plumbing::QueryCtxt, false>
  50:     0x7dc6ab8b0e12 - rustc_query_impl[a46554db2076a7e1]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  51:     0x7dc6abaa99d6 - rustc_interface[b6aba49ee050940e]::passes::create_and_enter_global_ctxt::<core[df8911376af37c8c]::option::Option<rustc_interface[b6aba49ee050940e]::queries::Linker>, rustc_driver_impl[1d35d6f9d2799e05]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  52:     0x7dc6aba9ae2f - rustc_interface[b6aba49ee050940e]::interface::run_compiler::<(), rustc_driver_impl[1d35d6f9d2799e05]::run_compiler::{closure#0}>::{closure#1}
  53:     0x7dc6aba460b8 - std[7a7d327c4bb6bc11]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[b6aba49ee050940e]::util::run_in_thread_with_globals<rustc_interface[b6aba49ee050940e]::util::run_in_thread_pool_with_globals<rustc_interface[b6aba49ee050940e]::interface::run_compiler<(), rustc_driver_impl[1d35d6f9d2799e05]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  54:     0x7dc6aba45d96 - <<std[7a7d327c4bb6bc11]::thread::Builder>::spawn_unchecked_<rustc_interface[b6aba49ee050940e]::util::run_in_thread_with_globals<rustc_interface[b6aba49ee050940e]::util::run_in_thread_pool_with_globals<rustc_interface[b6aba49ee050940e]::interface::run_compiler<(), rustc_driver_impl[1d35d6f9d2799e05]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[df8911376af37c8c]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  55:     0x7dc6aba443bd - std::sys::pal::unix::thread::Thread::new::thread_start::h10083fa6b51603a6
  56:     0x7dc6a54a57eb - <unknown>
  57:     0x7dc6a552918c - <unknown>
  58:                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 1.90.0-nightly (fe5f3dedf 2025-06-27) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `<impl at /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:4:10: 4:15>::{constant#0}`
#1 [thir_body] building THIR for `<impl at /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:4:10: 4:15>::{constant#0}`
#2 [thir_abstract_const] building an abstract representation for `<impl at /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:4:10: 4:15>::{constant#0}`
#3 [check_well_formed] checking that `<impl at /tmp/icemaker_global_tempdir.09Cy251VhU78/rustc_testrunner_tmpdir_reporting.l9Ia4P1qfQIs/mvce.rs:4:10: 4:15>` is well-formed
#4 [check_type_wf] checking that types are well-formed
#5 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 4 previous errors; 2 warnings emitted

For more information about this error, try `rustc --explain E0601`.

@rustbot label +F-generic_const_exprs +F-generic_const_parameter_types +F-adt_const_params