rust-lang / rust-lang/rust

[ICE]: `primitive read not possible for type`

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C-bug F-generic_const_args F-generic_const_items F-min_generic_const_args I-ICE T-compiler
Dominant language
Rust
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Description

auto-reduced (treereduce-rust):

#![feature(min_generic_const_args)]
#![feature(generic_const_args)]
type const ADD1<const N: usize>: usize = const { N + 1 };
type const ONE: usize = ADD1::<b"">;

original:

#![feature(min_generic_const_args)]
#![feature(generic_const_items)]
#![feature(generic_const_args)]
type const ADD1<const N: usize>: usize = const { N + 1 };
type const ONE: usize = ADD1::<b"">;
fn main() {}

Version information

rustc 1.96.0-nightly (2972b5e59 2026-04-03)
binary: rustc
commit-hash: 2972b5e59f1c5529b6ba770437812fd83ab4ebd4
commit-date: 2026-04-03
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.2

Possibly related line of code:
https://github.com/rust-lang/rust/blob/2972b5e59f1c5529b6ba770437812fd83ab4ebd4/compiler/rustc_const_eval/src/interpret/operand.rs#L673-L685

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

Program output 

error[E0658]: generic const items are experimental
 --> /tmp/icemaker_global_tempdir.v3sG33Ug8t3x/rustc_testrunner_tmpdir_reporting.SvoBhCeWrxKl/mvce.rs:3:16
  |
3 | type const ADD1<const N: usize>: usize = const { N + 1 };
  |                ^^^^^^^^^^^^^^^^
  |
  = note: see issue #113521 <https://github.com/rust-lang/rust/issues/113521> for more information
  = help: add `#![feature(generic_const_items)]` to the crate attributes to enable
  = note: this compiler was built on 2026-04-03; consider upgrading it if it is out of date

warning: the feature `min_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.v3sG33Ug8t3x/rustc_testrunner_tmpdir_reporting.SvoBhCeWrxKl/mvce.rs: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

error[E0601]: `main` function not found in crate `mvce`
 --> /tmp/icemaker_global_tempdir.v3sG33Ug8t3x/rustc_testrunner_tmpdir_reporting.SvoBhCeWrxKl/mvce.rs:4:37
  |
4 | type const ONE: usize = ADD1::<b"">;
  |                                     ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.v3sG33Ug8t3x/rustc_testrunner_tmpdir_reporting.SvoBhCeWrxKl/mvce.rs`

error: internal compiler error: /rustc-dev/2972b5e59f1c5529b6ba770437812fd83ab4ebd4/compiler/rustc_const_eval/src/interpret/operand.rs:679:13: primitive read not possible for type: [u8; 0]
 --> /tmp/icemaker_global_tempdir.v3sG33Ug8t3x/rustc_testrunner_tmpdir_reporting.SvoBhCeWrxKl/mvce.rs:3:50
  |
3 | type const ADD1<const N: usize>: usize = const { N + 1 };
  |                                                  ^^^^^


thread 'rustc' (3250000) panicked at /rustc-dev/2972b5e59f1c5529b6ba770437812fd83ab4ebd4/compiler/rustc_const_eval/src/interpret/operand.rs:679:13:
Box<dyn Any>
stack backtrace:
   0:     0x7effd23c0abb - <<std[de416e893de1faf9]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[9f8d6771964fc20c]::fmt::Display>::fmt
   1:     0x7effd2a1e1c8 - core[9f8d6771964fc20c]::fmt::write
   2:     0x7effd23d7ac6 - <std[de416e893de1faf9]::sys::stdio::unix::Stderr as std[de416e893de1faf9]::io::Write>::write_fmt
   3:     0x7effd2396ac8 - std[de416e893de1faf9]::panicking::default_hook::{closure#0}
   4:     0x7effd23b3ec3 - std[de416e893de1faf9]::panicking::default_hook
   5:     0x7effd13c2e4c - std[de416e893de1faf9]::panicking::update_hook::<alloc[57804382fb016052]::boxed::Box<rustc_driver_impl[7a9a631d48bc4eca]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7effd23b41a2 - std[de416e893de1faf9]::panicking::panic_with_hook
   7:     0x7effd13f2e01 - std[de416e893de1faf9]::panicking::begin_panic::<rustc_errors[e123dae814032ce5]::ExplicitBug>::{closure#0}
   8:     0x7effd13eb976 - std[de416e893de1faf9]::sys::backtrace::__rust_end_short_backtrace::<std[de416e893de1faf9]::panicking::begin_panic<rustc_errors[e123dae814032ce5]::ExplicitBug>::{closure#0}, !>
   9:     0x7effd13eb84b - std[de416e893de1faf9]::panicking::begin_panic::<rustc_errors[e123dae814032ce5]::ExplicitBug>
  10:     0x7effd13fe441 - <rustc_errors[e123dae814032ce5]::diagnostic::BugAbort as rustc_errors[e123dae814032ce5]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7effd19acbdc - <rustc_errors[e123dae814032ce5]::DiagCtxtHandle>::span_bug::<rustc_span[ae25d23050d7877d]::span_encoding::Span, alloc[57804382fb016052]::string::String>
  12:     0x7effd19d4ad6 - rustc_middle[4d5ddcd23ba200cb]::util::bug::opt_span_bug_fmt::<rustc_span[ae25d23050d7877d]::span_encoding::Span>::{closure#0}
  13:     0x7effd19d4c82 - rustc_middle[4d5ddcd23ba200cb]::ty::context::tls::with_opt::<rustc_middle[4d5ddcd23ba200cb]::util::bug::opt_span_bug_fmt<rustc_span[ae25d23050d7877d]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7effd19c523b - rustc_middle[4d5ddcd23ba200cb]::ty::context::tls::with_context_opt::<rustc_middle[4d5ddcd23ba200cb]::ty::context::tls::with_opt<rustc_middle[4d5ddcd23ba200cb]::util::bug::opt_span_bug_fmt<rustc_span[ae25d23050d7877d]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x7effcfacdb18 - rustc_middle[4d5ddcd23ba200cb]::util::bug::span_bug_fmt::<rustc_span[ae25d23050d7877d]::span_encoding::Span>
  16:     0x7effd3aef530 - <rustc_const_eval[b70cca6f81c4b47b]::interpret::eval_context::InterpCx<rustc_const_eval[b70cca6f81c4b47b]::const_eval::machine::CompileTimeMachine>>::eval_rvalue_into_place
  17:     0x7effd3aaa6df - rustc_const_eval[b70cca6f81c4b47b]::const_eval::eval_queries::eval_to_allocation_raw_provider
  18:     0x7effd3aa8ed6 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
  19:     0x7effd2e2abd3 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_middle[4d5ddcd23ba200cb]::query::caches::DefaultCache<rustc_middle[4d5ddcd23ba200cb]::ty::PseudoCanonicalInput<rustc_middle[4d5ddcd23ba200cb]::mir::interpret::GlobalId>, rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 24usize]>>, false>
  20:     0x7effd2e2a5d1 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
  21:     0x7effd30bb353 - rustc_const_eval[b70cca6f81c4b47b]::const_eval::valtrees::eval_to_valtree
  22:     0x7effd30bb126 - <rustc_const_eval[b70cca6f81c4b47b]::provide::{closure#0} as core[9f8d6771964fc20c]::ops::function::FnOnce<(rustc_middle[4d5ddcd23ba200cb]::ty::context::TyCtxt, rustc_middle[4d5ddcd23ba200cb]::ty::PseudoCanonicalInput<rustc_middle[4d5ddcd23ba200cb]::mir::interpret::GlobalId>)>>::call_once
  23:     0x7effd30bb0e2 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::eval_to_valtree::invoke_provider_fn::__rust_begin_short_backtrace
  24:     0x7effd3559426 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_middle[4d5ddcd23ba200cb]::query::caches::DefaultCache<rustc_middle[4d5ddcd23ba200cb]::ty::PseudoCanonicalInput<rustc_middle[4d5ddcd23ba200cb]::mir::interpret::GlobalId>, rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 16usize]>>, false>
  25:     0x7effd355903e - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::eval_to_valtree::execute_query_non_incr::__rust_end_short_backtrace
  26:     0x7effcfa4f1e1 - <rustc_middle[4d5ddcd23ba200cb]::ty::context::TyCtxt>::const_eval_resolve_for_typeck
  27:     0x7effd2e04ec9 - rustc_trait_selection[68aaf85cf2f33f59]::traits::try_evaluate_const
  28:     0x7effd2e0878d - <rustc_trait_selection[68aaf85cf2f33f59]::traits::normalize::AssocTypeNormalizer as rustc_type_ir[51f94517df34cb9f]::fold::TypeFolder<rustc_middle[4d5ddcd23ba200cb]::ty::context::TyCtxt>>::fold_const
  29:     0x7effd3e6fef7 - <rustc_trait_selection[68aaf85cf2f33f59]::traits::normalize::AssocTypeNormalizer>::normalize_free_alias::{closure#0}
  30:     0x7effd2e08d8f - <rustc_trait_selection[68aaf85cf2f33f59]::traits::normalize::AssocTypeNormalizer as rustc_type_ir[51f94517df34cb9f]::fold::TypeFolder<rustc_middle[4d5ddcd23ba200cb]::ty::context::TyCtxt>>::fold_const
  31:     0x7effd1500b52 - <rustc_infer[eac98fb965f9dc66]::infer::at::At as rustc_trait_selection[68aaf85cf2f33f59]::traits::normalize::NormalizeExt>::normalize::<rustc_middle[4d5ddcd23ba200cb]::ty::consts::Const>
  32:     0x7effd157eef8 - rustc_hir_analysis[ffc1d045f4785174]::check::wfcheck::check_type_const
  33:     0x7effd3796cec - rustc_hir_analysis[ffc1d045f4785174]::check::check::check_item_type
  34:     0x7effd3789b9c - rustc_hir_analysis[ffc1d045f4785174]::check::wfcheck::check_well_formed
  35:     0x7effd3789b6f - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::check_well_formed::invoke_provider_fn::__rust_begin_short_backtrace
  36:     0x7effd37891a4 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_data_structures[3e48709548f32bc4]::vec_cache::VecCache<rustc_span[ae25d23050d7877d]::def_id::LocalDefId, rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 1usize]>, rustc_middle[4d5ddcd23ba200cb]::dep_graph::graph::DepNodeIndex>, false>
  37:     0x7effd3788f3b - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::check_well_formed::execute_query_non_incr::__rust_end_short_backtrace
  38:     0x7effd37854f3 - rustc_hir_analysis[ffc1d045f4785174]::check::wfcheck::check_type_wf
  39:     0x7effd37853e7 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::check_type_wf::invoke_provider_fn::__rust_begin_short_backtrace
  40:     0x7effd3c02950 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_middle[4d5ddcd23ba200cb]::query::caches::SingleCache<rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 1usize]>>, false>
  41:     0x7effd3c02729 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::check_type_wf::execute_query_non_incr::__rust_end_short_backtrace
  42:     0x7effd3306ddb - rustc_hir_analysis[ffc1d045f4785174]::check_crate
  43:     0x7effd2ab7f61 - rustc_interface[e1d24a92004beaf7]::passes::analysis
  44:     0x7effd3c05049 - rustc_query_impl[fdd9a9cd73aeb4]::execution::try_execute_query::<rustc_middle[4d5ddcd23ba200cb]::query::caches::SingleCache<rustc_middle[4d5ddcd23ba200cb]::query::erase::ErasedData<[u8; 0usize]>>, false>
  45:     0x7effd3c04cb5 - rustc_query_impl[fdd9a9cd73aeb4]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  46:     0x7effd3bb1990 - rustc_interface[e1d24a92004beaf7]::interface::run_compiler::<(), rustc_driver_impl[7a9a631d48bc4eca]::run_compiler::{closure#0}>::{closure#1}
  47:     0x7effd3be3c3e - std[de416e893de1faf9]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[e1d24a92004beaf7]::util::run_in_thread_with_globals<rustc_interface[e1d24a92004beaf7]::util::run_in_thread_pool_with_globals<rustc_interface[e1d24a92004beaf7]::interface::run_compiler<(), rustc_driver_impl[7a9a631d48bc4eca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  48:     0x7effd3be44e0 - <std[de416e893de1faf9]::thread::lifecycle::spawn_unchecked<rustc_interface[e1d24a92004beaf7]::util::run_in_thread_with_globals<rustc_interface[e1d24a92004beaf7]::util::run_in_thread_pool_with_globals<rustc_interface[e1d24a92004beaf7]::interface::run_compiler<(), rustc_driver_impl[7a9a631d48bc4eca]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[9f8d6771964fc20c]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  49:     0x7effd3be53ec - <std[de416e893de1faf9]::sys::thread::unix::Thread>::new::thread_start
  50:     0x7effcd6a597a - <unknown>
  51:     0x7effcd7292bc - <unknown>
  52:                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 1.96.0-nightly (2972b5e59 2026-04-03) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [eval_to_allocation_raw] const-evaluating + checking `ADD1::{constant#0}`
#1 [eval_to_valtree] evaluating type-level constant
#2 [check_well_formed] checking that `ONE` is well-formed
#3 [check_type_wf] checking that types are well-formed
#4 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 3 previous errors; 1 warning emitted

Some errors have detailed explanations: E0601, E0658.
For more information about an error, try `rustc --explain E0601`.

@rustbot label +F-min_generic_const_args +F-generic_const_items +F-generic_const_args

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

Start with the reduced program in the issue and the referenced code in compiler/rustc_const_eval/src/interpret/operand.rs around lines 673-685. Run the shown rustc reproduction, then trace the const-evaluation path in the backtrace through eval_rvalue_into_place and valtree evaluation. Done means the program no longer triggers an internal compiler error.

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
Quiet
Clarity
Mostly clear
Newbie friendliness
38/100

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