rust-lang / rust-lang/rust

ICE: `failed to normalize const, but it is not generic`

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C-bug F-generic_const_exprs I-ICE T-compiler
Dominant language
Rust
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PR metrics pending

Description

auto-reduced (treereduce-rust):

#![feature(generic_const_exprs)]

fn can_double<const N: usize>(x: [(); N])
where
    [(); N * 2]:,
{
    x[0];
}

fn foo<const N: usize>()
where
    [(); (N + 1) * 2]:,
{
    can_double([(); { N + 1 }]);
}

fn main() {
    foo::<1>();
}

original:

#![feature(generic_const_exprs)]
#![allow(incomplete_features)]

fn can_double<const N: usize>(x: [(); N])
where
    [(); N * 2]:,
{
    x[0];
    unimplemented!()
}

fn foo<const N: usize>()
where
    [(); (N + 1) * 2]:,
{
    can_double([(); { N + 1 }]);
    // can_double::<{N + 1}>([(); { N + 1 }]);
    // can_double::<{N + 1}>([(); { N + 1 }]);
}

fn main() {
    foo::<1>();
}

Version information

rustc 1.92.0-nightly (ce4beebec 2025-09-22)
binary: rustc
commit-hash: ce4beebecb77821734079cff47d8af08f9f27f11
commit-date: 2025-09-22
host: x86_64-unknown-linux-gnu
release: 1.92.0-nightly
LLVM version: 21.1.1

Possibly related line of code:
https://github.com/rust-lang/rust/blob/ce4beebecb77821734079cff47d8af08f9f27f11/compiler/rustc_ty_utils/src/layout.rs#L142-L154

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

Program output 

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.xLfdc4uD19aC/rustc_testrunner_tmpdir_reporting.NJBgu9wYiPWw/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

error: internal compiler error: compiler/rustc_ty_utils/src/layout.rs:148:17: failed to normalize const, but it is not generic: (Add: (1_usize: usize), (1_usize: usize))


thread 'rustc' (312868) panicked at compiler/rustc_ty_utils/src/layout.rs:148:17:
Box<dyn Any>
stack backtrace:
   0:     0x7f826e202753 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h3e5bd3a23c0347a9
   1:     0x7f826ea02044 - core::fmt::write::heee6829eb564c27d
   2:     0x7f826e1b7101 - std::io::Write::write_fmt::ha453775b50cc97a5
   3:     0x7f826e1c84c2 - std::sys::backtrace::BacktraceLock::print::h71d64778f60f39dd
   4:     0x7f826e1ce429 - std::panicking::default_hook::{{closure}}::h0c1df9123d837333
   5:     0x7f826e1cdf53 - std::panicking::default_hook::h1518572259f2e3d5
   6:     0x7f826d1f1e47 - std[18d792bd9b3d078a]::panicking::update_hook::<alloc[cb65cdfa434cac9f]::boxed::Box<rustc_driver_impl[477d964a0f4cf97e]::install_ice_hook::{closure#1}>>::{closure#0}
   7:     0x7f826e1ce84f - std::panicking::panic_with_hook::hec947c027cbe77e3
   8:     0x7f826d22e701 - std[18d792bd9b3d078a]::panicking::begin_panic::<rustc_errors[93e6452cd29fe3a8]::ExplicitBug>::{closure#0}
   9:     0x7f826d221f16 - std[18d792bd9b3d078a]::sys::backtrace::__rust_end_short_backtrace::<std[18d792bd9b3d078a]::panicking::begin_panic<rustc_errors[93e6452cd29fe3a8]::ExplicitBug>::{closure#0}, !>
  10:     0x7f826d21f9b9 - std[18d792bd9b3d078a]::panicking::begin_panic::<rustc_errors[93e6452cd29fe3a8]::ExplicitBug>
  11:     0x7f826d239df1 - <rustc_errors[93e6452cd29fe3a8]::diagnostic::BugAbort as rustc_errors[93e6452cd29fe3a8]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x7f826d7cc0ca - rustc_middle[168a57e624ed4250]::util::bug::opt_span_bug_fmt::<rustc_span[150c1f29595c3fc1]::span_encoding::Span>::{closure#0}
  13:     0x7f826d7cc12a - rustc_middle[168a57e624ed4250]::ty::context::tls::with_opt::<rustc_middle[168a57e624ed4250]::util::bug::opt_span_bug_fmt<rustc_span[150c1f29595c3fc1]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7f826d7ba90b - rustc_middle[168a57e624ed4250]::ty::context::tls::with_context_opt::<rustc_middle[168a57e624ed4250]::ty::context::tls::with_opt<rustc_middle[168a57e624ed4250]::util::bug::opt_span_bug_fmt<rustc_span[150c1f29595c3fc1]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x7f826bfd83f0 - rustc_middle[168a57e624ed4250]::util::bug::bug_fmt
  16:     0x7f82705eb970 - rustc_ty_utils[3896a6e1d26d46a]::layout::extract_const_value.cold
  17:     0x7f826f28b8ee - rustc_ty_utils[3896a6e1d26d46a]::layout::layout_of_uncached
  18:     0x7f826f27fa89 - rustc_ty_utils[3896a6e1d26d46a]::layout::layout_of
  19:     0x7f826f27f9ee - rustc_query_impl[e799cb834319d50f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e799cb834319d50f]::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 16usize]>>
  20:     0x7f826f27e8fd - rustc_query_system[fc44913d20ec5c31]::query::plumbing::try_execute_query::<rustc_query_impl[e799cb834319d50f]::DynamicConfig<rustc_query_system[fc44913d20ec5c31]::query::caches::DefaultCache<rustc_middle[168a57e624ed4250]::ty::PseudoCanonicalInput<rustc_middle[168a57e624ed4250]::ty::Ty>, rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[e799cb834319d50f]::plumbing::QueryCtxt, false>
  21:     0x7f826f27e528 - rustc_query_impl[e799cb834319d50f]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
  22:     0x7f826f3c934a - <core[524b22d1fd644b30]::iter::adapters::enumerate::Enumerate<_> as core[524b22d1fd644b30]::iter::traits::iterator::Iterator>::try_fold::enumerate::<rustc_middle[168a57e624ed4250]::ty::Ty, (), core[524b22d1fd644b30]::ops::control_flow::ControlFlow<core[524b22d1fd644b30]::ops::control_flow::ControlFlow<rustc_target[1989c676991791d8]::callconv::ArgAbi<rustc_middle[168a57e624ed4250]::ty::Ty>>>, core[524b22d1fd644b30]::iter::adapters::map::map_try_fold<(usize, rustc_middle[168a57e624ed4250]::ty::Ty), core[524b22d1fd644b30]::result::Result<rustc_target[1989c676991791d8]::callconv::ArgAbi<rustc_middle[168a57e624ed4250]::ty::Ty>, &rustc_middle[168a57e624ed4250]::ty::layout::FnAbiError>, (), core[524b22d1fd644b30]::ops::control_flow::ControlFlow<core[524b22d1fd644b30]::ops::control_flow::ControlFlow<rustc_target[1989c676991791d8]::callconv::ArgAbi<rustc_middle[168a57e624ed4250]::ty::Ty>>>, rustc_ty_utils[3896a6e1d26d46a]::abi::fn_abi_new_uncached::{closure#3}, <core[524b22d1fd644b30]::iter::adapters::GenericShunt<core[524b22d1fd644b30]::iter::adapters::map::Map<core[524b22d1fd644b30]::iter::adapters::enumerate::Enumerate<core[524b22d1fd644b30]::iter::adapters::chain::Chain<core[524b22d1fd644b30]::iter::adapters::chain::Chain<core[524b22d1fd644b30]::iter::adapters::copied::Copied<core[524b22d1fd644b30]::slice::iter::Iter<rustc_middle[168a57e624ed4250]::ty::Ty>>, core[524b22d1fd644b30]::iter::adapters::copied::Copied<core[524b22d1fd644b30]::slice::iter::Iter<rustc_middle[168a57e624ed4250]::ty::Ty>>>, core[524b22d1fd644b30]::option::IntoIter<rustc_middle[168a57e624ed4250]::ty::Ty>>>, rustc_ty_utils[3896a6e1d26d46a]::abi::fn_abi_new_uncached::{closure#3}>, core[524b22d1fd644b30]::result::Result<core[524b22d1fd644b30]::convert::Infallible, &rustc_middle[168a57e624ed4250]::ty::layout::FnAbiError>> as core[524b22d1fd644b30]::iter::traits::iterator::Iterator>::try_fold<(), core[524b22d1fd644b30]::iter::traits::iterator::Iterator::try_for_each::call<rustc_target[1989c676991791d8]::callconv::ArgAbi<rustc_middle[168a57e624ed4250]::ty::Ty>, core[524b22d1fd644b30]::ops::control_flow::ControlFlow<rustc_target[1989c676991791d8]::callconv::ArgAbi<rustc_middle[168a57e624ed4250]::ty::Ty>>, core[524b22d1fd644b30]::ops::control_flow::ControlFlow<rustc_target[1989c676991791d8]::callconv::ArgAbi<rustc_middle[168a57e624ed4250]::ty::Ty>>::Break>::{closure#0}, core[524b22d1fd644b30]::ops::control_flow::ControlFlow<rustc_target[1989c676991791d8]::callconv::ArgAbi<rustc_middle[168a57e624ed4250]::ty::Ty>>>::{closure#0}>::{closure#0}>::{closure#0}
  23:     0x7f826f5b2d64 - rustc_ty_utils[3896a6e1d26d46a]::abi::fn_abi_new_uncached
  24:     0x7f826f5ad710 - rustc_ty_utils[3896a6e1d26d46a]::abi::fn_abi_of_instance
  25:     0x7f826f5acdbc - rustc_query_impl[e799cb834319d50f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e799cb834319d50f]::query_impl::fn_abi_of_instance::dynamic_query::{closure#2}::{closure#0}, rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 16usize]>>
  26:     0x7f826f79debc - rustc_query_system[fc44913d20ec5c31]::query::plumbing::try_execute_query::<rustc_query_impl[e799cb834319d50f]::DynamicConfig<rustc_query_system[fc44913d20ec5c31]::query::caches::DefaultCache<rustc_middle[168a57e624ed4250]::ty::PseudoCanonicalInput<(rustc_middle[168a57e624ed4250]::ty::instance::Instance, &rustc_middle[168a57e624ed4250]::ty::list::RawList<(), rustc_middle[168a57e624ed4250]::ty::Ty>)>, rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[e799cb834319d50f]::plumbing::QueryCtxt, false>
  27:     0x7f826f79da4f - rustc_query_impl[e799cb834319d50f]::query_impl::fn_abi_of_instance::get_query_non_incr::__rust_end_short_backtrace
  28:     0x7f826bdad552 - rustc_monomorphize[2c4283d798154e0c]::mono_checks::check_mono_item
  29:     0x7f826ea0d8a0 - rustc_query_impl[e799cb834319d50f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e799cb834319d50f]::query_impl::check_mono_item::dynamic_query::{closure#2}::{closure#0}, rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 0usize]>>
  30:     0x7f826f600c92 - rustc_query_system[fc44913d20ec5c31]::query::plumbing::try_execute_query::<rustc_query_impl[e799cb834319d50f]::DynamicConfig<rustc_query_system[fc44913d20ec5c31]::query::caches::DefaultCache<rustc_middle[168a57e624ed4250]::ty::instance::Instance, rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[e799cb834319d50f]::plumbing::QueryCtxt, false>
  31:     0x7f826f600911 - rustc_query_impl[e799cb834319d50f]::query_impl::check_mono_item::get_query_non_incr::__rust_end_short_backtrace
  32:     0x7f826bd961c7 - rustc_monomorphize[2c4283d798154e0c]::collector::items_of_instance
  33:     0x7f826ebf0732 - rustc_query_impl[e799cb834319d50f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e799cb834319d50f]::query_impl::items_of_instance::dynamic_query::{closure#2}::{closure#0}, rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 32usize]>>
  34:     0x7f826f4524d5 - rustc_query_system[fc44913d20ec5c31]::query::plumbing::try_execute_query::<rustc_query_impl[e799cb834319d50f]::DynamicConfig<rustc_query_system[fc44913d20ec5c31]::query::caches::DefaultCache<(rustc_middle[168a57e624ed4250]::ty::instance::Instance, rustc_middle[168a57e624ed4250]::mir::mono::CollectionMode), rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 32usize]>>, false, false, false>, rustc_query_impl[e799cb834319d50f]::plumbing::QueryCtxt, false>
  35:     0x7f826f4520e9 - rustc_query_impl[e799cb834319d50f]::query_impl::items_of_instance::get_query_non_incr::__rust_end_short_backtrace
  36:     0x7f826f45534e - rustc_monomorphize[2c4283d798154e0c]::collector::collect_items_rec::{closure#0}
  37:     0x7f826f45646c - rustc_monomorphize[2c4283d798154e0c]::collector::collect_items_rec
  38:     0x7f826f4570f0 - rustc_monomorphize[2c4283d798154e0c]::collector::collect_items_rec
  39:     0x7f826f4570f0 - rustc_monomorphize[2c4283d798154e0c]::collector::collect_items_rec
  40:     0x7f826ef557e1 - rustc_monomorphize[2c4283d798154e0c]::collector::collect_crate_mono_items::{closure#1}::{closure#0}
  41:     0x7f826f0bb138 - rustc_monomorphize[2c4283d798154e0c]::partitioning::collect_and_partition_mono_items
  42:     0x7f826f0badd6 - rustc_query_impl[e799cb834319d50f]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[e799cb834319d50f]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 24usize]>>
  43:     0x7f826f0badb9 - <rustc_query_impl[e799cb834319d50f]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2} as core[524b22d1fd644b30]::ops::function::FnOnce<(rustc_middle[168a57e624ed4250]::ty::context::TyCtxt, ())>>::call_once
  44:     0x7f826feb2b5e - rustc_query_system[fc44913d20ec5c31]::query::plumbing::try_execute_query::<rustc_query_impl[e799cb834319d50f]::DynamicConfig<rustc_query_system[fc44913d20ec5c31]::query::caches::SingleCache<rustc_middle[168a57e624ed4250]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[e799cb834319d50f]::plumbing::QueryCtxt, false>
  45:     0x7f826feb2903 - rustc_query_impl[e799cb834319d50f]::query_impl::collect_and_partition_mono_items::get_query_non_incr::__rust_end_short_backtrace
  46:     0x7f826fbaafee - <rustc_codegen_llvm[d0043158dff2f39a]::LlvmCodegenBackend as rustc_codegen_ssa[ac50efdacbb25cbe]::traits::backend::CodegenBackend>::codegen_crate
  47:     0x7f826fc77070 - <rustc_interface[60bc46e8fdb58ac8]::queries::Linker>::codegen_and_build_linker
  48:     0x7f826fc74bc0 - rustc_interface[60bc46e8fdb58ac8]::passes::create_and_enter_global_ctxt::<core[524b22d1fd644b30]::option::Option<rustc_interface[60bc46e8fdb58ac8]::queries::Linker>, rustc_driver_impl[477d964a0f4cf97e]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  49:     0x7f826fc121be - rustc_interface[60bc46e8fdb58ac8]::interface::run_compiler::<(), rustc_driver_impl[477d964a0f4cf97e]::run_compiler::{closure#0}>::{closure#1}
  50:     0x7f826fb74778 - std[18d792bd9b3d078a]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[60bc46e8fdb58ac8]::util::run_in_thread_with_globals<rustc_interface[60bc46e8fdb58ac8]::util::run_in_thread_pool_with_globals<rustc_interface[60bc46e8fdb58ac8]::interface::run_compiler<(), rustc_driver_impl[477d964a0f4cf97e]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  51:     0x7f826fb7445c - <<std[18d792bd9b3d078a]::thread::Builder>::spawn_unchecked_<rustc_interface[60bc46e8fdb58ac8]::util::run_in_thread_with_globals<rustc_interface[60bc46e8fdb58ac8]::util::run_in_thread_pool_with_globals<rustc_interface[60bc46e8fdb58ac8]::interface::run_compiler<(), rustc_driver_impl[477d964a0f4cf97e]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[524b22d1fd644b30]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  52:     0x7f826fb7a34d - std::sys::thread::unix::Thread::new::thread_start::hd35e43a00d992682
  53:     0x7f82692969cb - <unknown>
  54:     0x7f826931aa0c - <unknown>
  55:                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 1.92.0-nightly (ce4beebec 2025-09-22) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [layout_of] computing layout of `[(); ValTree(Leaf(0x0000000000000001): usize) + ValTree(Leaf(0x0000000000000001): usize)]`
#1 [fn_abi_of_instance] computing call ABI of `can_double::<ValTree(Leaf(0x0000000000000001): usize) + ValTree(Leaf(0x0000000000000001): usize)>`
#2 [check_mono_item] monomorphization-time checking
#3 [items_of_instance] collecting items used by `can_double::<ValTree(Leaf(0x0000000000000001): usize) + ValTree(Leaf(0x0000000000000001): usize)>`
#4 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to 1 previous error; 1 warning emitted

@rustbot label +F-generic_const_exprs

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Compile the reduced reproducer with the nightly rustc version described in the issue and confirm the ICE. Then inspect compiler/rustc_ty_utils/src/layout.rs around lines 142-154, especially the layout path leading to extract_const_value. Done means the reproducer no longer triggers an internal compiler error and has appropriate compiler behavior for this case.

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
Mostly clear
Newbie friendliness
35/100

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