[ICE]: `invalid immediate for given destination place: scalar value has wrong size`
Open
Nobody has claimed this yet.
C-bug
F-generic_const_args
F-generic_const_items
F-min_generic_const_args
I-ICE
needs-triage
T-compiler
- Dominant language
- Rust
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Description
auto-reduced (treereduce-rust):
#![feature(generic_const_args)]
trait Owner {
const K<const N : u16>: u16;
}
impl Owner for () {
const K<const N : u32> : u32 = N;
}
fn take1(_: impl Owner<K<9> = 0>) {
take1(())
}
original:
#![feature(generic_const_args)]
#![feature(min_generic_const_args)]
#![feature(generic_const_items)]
trait Owner {
const K<const N : u16>: u16;
}
impl Owner for () {
const K<const N : u32> : u32 = N;
}
fn take1(_: impl Owner<K<9> = 0>) {
take1(())
}
fn main() {}
Version information
rustc 1.100.0-nightly (8536f4de9 2026-08-22)
binary: rustc
commit-hash: 8536f4de90e5e781c06e584f8a88de860adc798b
commit-date: 2026-08-22
host: x86_64-unknown-linux-gnu
release: 1.100.0-nightly
LLVM version: 23.1.0
Possibly related line of code:
https://github.com/rust-lang/rust/blob/8536f4de90e5e781c06e584f8a88de860adc798b/compiler/rustc_const_eval/src/interpret/operand.rs#L116-L128
Command:
/home/matthias/.rustup/toolchains/master/bin/rustc
Program output
error: `generic_const_args` requires `min_generic_const_args` to be enabled
--> /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:1:12
|
1 | #![feature(generic_const_args)]
| ^^^^^^^^^^^^^^^^^^
|
= help: enable all of these features
error[E0658]: generic const items are experimental
--> /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:4:12
|
4 | const K<const N : u16>: u16;
| ^^^^^^^^^^^^^^^
|
= 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= note: this compiler was built on 2026-08-22; consider upgrading it if it is out of date
error[E0658]: generic const items are experimental
--> /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:7:12
|
7 | const K<const N : u32> : u32 = N;
| ^^^^^^^^^^^^^^^
|
= 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 2026-08-22; consider upgrading it if it is out of date
error[E0658]: associated const equality is incomplete
--> /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:9:24
|
9 | fn take1(_: impl Owner<K<9> = 0>) {
| ^^^^^^^^
|
= note: see issue #132980 <https://github.com/rust-lang/rust/issues/132980> for more information
= help: add `#![feature(min_generic_const_args)]` to the crate attributes to enable
= note: this compiler was built on 2026-08-22; consider upgrading it if it is out of date
warning: the feature `generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
--> /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:1:12
|
1 | #![feature(generic_const_args)]
| ^^^^^^^^^^^^^^^^^^
|
= note: see issue #151972 <https://github.com/rust-lang/rust/issues/151972> for more information
= note: `#[warn(incomplete_features)]` on by default
error[E0601]: `main` function not found in crate `mvce`
--> /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:11:2
|
11 | }
| ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs`
error[E0053]: associated constant `K` has an incompatible generic parameter for trait `Owner`
--> /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:7:13
|
3 | trait Owner {
| -----
4 | const K<const N : u16>: u16;
| ------------- expected const parameter of type `u16`
5 | }
6 | impl Owner for () {
| -----------------
7 | const K<const N : u32> : u32 = N;
| ^^^^^^^^^^^^^ found const parameter of type `u32`
thread 'rustc' (3624088) panicked at /rustc-dev/8536f4de90e5e781c06e584f8a88de860adc798b/compiler/rustc_const_eval/src/interpret/operand.rs:122:17:
assertion `left == right` failed: invalid immediate for given destination place: scalar value has wrong size
left: Size(2 bytes)
right: Size(4 bytes)
stack backtrace:
0: 0x7f1c36fef966 - <<std[6a2a162ccd49bd24]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[34df38ed1aeeb409]::fmt::Display>::fmt
1: 0x7f1c3760b063 - core[34df38ed1aeeb409]::fmt::write
2: 0x7f1c37004e4c - <std[6a2a162ccd49bd24]::sys::stdio::unix::Stderr as core[34df38ed1aeeb409]::io::write::Write>::write_fmt
3: 0x7f1c36fc2bea - std[6a2a162ccd49bd24]::panicking::default_hook::{closure#0}
4: 0x7f1c36fe3c03 - std[6a2a162ccd49bd24]::panicking::default_hook
5: 0x7f1c35f9f25a - std[6a2a162ccd49bd24]::panicking::update_hook::<alloc[d780ca98ca945870]::boxed::Box<rustc_driver_impl[914da1ef5f0db717]::install_ice_hook::{closure#1}>>::{closure#0}
6: 0x7f1c36fe40a2 - std[6a2a162ccd49bd24]::panicking::panic_with_hook
7: 0x7f1c36fc2ca2 - std[6a2a162ccd49bd24]::panicking::panic_handler::{closure#0}
8: 0x7f1c36fbadd9 - std[6a2a162ccd49bd24]::sys::backtrace::__rust_end_short_backtrace::<std[6a2a162ccd49bd24]::panicking::panic_handler::{closure#0}, !>
9: 0x7f1c36fc46ad - __rustc[8236491043d97613]::rust_begin_unwind
10: 0x7f1c33c2f00c - core[34df38ed1aeeb409]::panicking::panic_fmt
11: 0x7f1c359332b3 - core[34df38ed1aeeb409]::panicking::assert_failed_inner
12: 0x7f1c36527f00 - core[34df38ed1aeeb409]::panicking::assert_failed::<rustc_abi[a860a93160536fb1]::Size, rustc_abi[a860a93160536fb1]::Size>
13: 0x7f1c37d6466c - <rustc_const_eval[972a1eb05da00dbd]::interpret::eval_context::InterpCx<rustc_const_eval[972a1eb05da00dbd]::const_eval::machine::CompileTimeMachine>>::copy_op_no_validate::<rustc_const_eval[972a1eb05da00dbd]::interpret::operand::OpTy, rustc_const_eval[972a1eb05da00dbd]::interpret::place::PlaceTy>
14: 0x7f1c351027d7 - rustc_const_eval[972a1eb05da00dbd]::const_eval::eval_queries::eval_to_allocation_raw_provider
15: 0x7f1c3763bcd6 - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
16: 0x7f1c3865bdfa - rustc_query_impl[7883aff223ddbf83]::execution::try_execute_query::<rustc_middle[e13af1fab9e07cac]::query::caches::DefaultCache<rustc_middle[e13af1fab9e07cac]::ty::PseudoCanonicalInput<rustc_middle[e13af1fab9e07cac]::mir::interpret::GlobalId>, rustc_middle[e13af1fab9e07cac]::query::erase::ErasedData<[u8; 24usize]>>, false>
17: 0x7f1c3865b367 - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
18: 0x7f1c350ffc9a - rustc_const_eval[972a1eb05da00dbd]::const_eval::eval_queries::eval_to_allocation_raw_provider
19: 0x7f1c3763bcd6 - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
20: 0x7f1c3865bdfa - rustc_query_impl[7883aff223ddbf83]::execution::try_execute_query::<rustc_middle[e13af1fab9e07cac]::query::caches::DefaultCache<rustc_middle[e13af1fab9e07cac]::ty::PseudoCanonicalInput<rustc_middle[e13af1fab9e07cac]::mir::interpret::GlobalId>, rustc_middle[e13af1fab9e07cac]::query::erase::ErasedData<[u8; 24usize]>>, false>
21: 0x7f1c3865b367 - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
22: 0x7f1c3474d8d6 - rustc_const_eval[972a1eb05da00dbd]::const_eval::valtrees::eval_to_valtree
23: 0x7f1c383a7fe6 - <rustc_const_eval[972a1eb05da00dbd]::provide::{closure#0} as core[34df38ed1aeeb409]::ops::function::FnOnce<(rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt, rustc_middle[e13af1fab9e07cac]::ty::PseudoCanonicalInput<rustc_middle[e13af1fab9e07cac]::mir::interpret::GlobalId>)>>::call_once
24: 0x7f1c383a7fa2 - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_valtree::invoke_provider_fn::__rust_begin_short_backtrace
25: 0x7f1c383a7676 - rustc_query_impl[7883aff223ddbf83]::execution::try_execute_query::<rustc_middle[e13af1fab9e07cac]::query::caches::DefaultCache<rustc_middle[e13af1fab9e07cac]::ty::PseudoCanonicalInput<rustc_middle[e13af1fab9e07cac]::mir::interpret::GlobalId>, rustc_middle[e13af1fab9e07cac]::query::erase::ErasedData<[u8; 16usize]>>, false>
26: 0x7f1c383a733f - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_valtree::execute_query_non_incr::__rust_end_short_backtrace
27: 0x7f1c3773fef1 - <rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>::const_eval_global_id_for_typeck
28: 0x7f1c3773f9f2 - <rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>::const_eval_resolve_for_typeck
29: 0x7f1c3773ecbe - <rustc_next_trait_solver[71fb316e451aa38c]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[c751c4991df8534b]::solve::delegate::SolverDelegate, rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>>::evaluate_const
30: 0x7f1c3772b2f5 - <rustc_next_trait_solver[71fb316e451aa38c]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[c751c4991df8534b]::solve::delegate::SolverDelegate, rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>>::evaluate_const_and_instantiate_projection_term
31: 0x7f1c38da7ede - <rustc_next_trait_solver[71fb316e451aa38c]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[c751c4991df8534b]::solve::delegate::SolverDelegate, rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>>::assemble_and_evaluate_candidates::<rustc_type_ir[277fd484b88c078f]::predicate::NormalizesTo<rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>>
32: 0x7f1c344e7520 - <rustc_type_ir[277fd484b88c078f]::search_graph::SearchGraph<rustc_next_trait_solver[71fb316e451aa38c]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[c751c4991df8534b]::solve::delegate::SolverDelegate>, rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>>::evaluate_goal::{closure#0}
33: 0x7f1c38561928 - <rustc_next_trait_solver[71fb316e451aa38c]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[c751c4991df8534b]::solve::delegate::SolverDelegate, rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>>::evaluate_goal_raw
34: 0x7f1c344e6a07 - <rustc_type_ir[277fd484b88c078f]::search_graph::SearchGraph<rustc_next_trait_solver[71fb316e451aa38c]::solve::search_graph::SearchGraphDelegate<rustc_trait_selection[c751c4991df8534b]::solve::delegate::SolverDelegate>, rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>>::evaluate_goal::{closure#0}
35: 0x7f1c383e5430 - <rustc_next_trait_solver[71fb316e451aa38c]::solve::eval_ctxt::EvalCtxt<rustc_trait_selection[c751c4991df8534b]::solve::delegate::SolverDelegate, rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>>::evaluate_goal_no_fast_paths
36: 0x7f1c3760c001 - <rustc_trait_selection[c751c4991df8534b]::traits::engine::FulfillmentEngine<rustc_trait_selection[c751c4991df8534b]::traits::FulfillmentError> as rustc_infer[d9cb6d70c198d788]::traits::engine::TraitEngine<rustc_trait_selection[c751c4991df8534b]::traits::FulfillmentError>>::try_evaluate_obligations
37: 0x7f1c377adbe1 - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::check_expr_call
38: 0x7f1c37fe6675 - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
39: 0x7f1c37fdf7fd - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::check_expr_block
40: 0x7f1c37fe6692 - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
41: 0x7f1c37766861 - rustc_hir_typeck[794a63979e72c52d]::check::check_fn
42: 0x7f1c381184d8 - rustc_hir_typeck[794a63979e72c52d]::typeck_with_inspect::{closure#0}
43: 0x7f1c38116a4a - rustc_query_impl[7883aff223ddbf83]::query_vtables::typeck_root::invoke_provider_fn::__rust_begin_short_backtrace
44: 0x7f1c380f0f35 - rustc_query_impl[7883aff223ddbf83]::execution::try_execute_query::<rustc_data_structures[f27dd378dd25622a]::vec_cache::VecCache<rustc_span[e5991a1499837571]::def_id::LocalDefId, rustc_middle[e13af1fab9e07cac]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[e13af1fab9e07cac]::dep_graph::graph::DepNodeIndex>, false>
45: 0x7f1c380f0ba7 - rustc_query_impl[7883aff223ddbf83]::query_vtables::typeck_root::execute_query_non_incr::__rust_end_short_backtrace
46: 0x7f1c37eb8914 - rustc_hir_analysis[6c6705371eee3cd0]::check_crate
47: 0x7f1c380f243a - rustc_interface[4cb4cba335c0809d]::passes::analysis
48: 0x7f1c3882ef4a - rustc_query_impl[7883aff223ddbf83]::execution::try_execute_query::<rustc_middle[e13af1fab9e07cac]::query::caches::SingleCache<rustc_middle[e13af1fab9e07cac]::query::erase::ErasedData<[u8; 0usize]>>, false>
49: 0x7f1c3882ecd3 - rustc_query_impl[7883aff223ddbf83]::query_vtables::analysis::execute_query_non_incr::__rust_end_short_backtrace
50: 0x7f1c389afb6b - rustc_interface[4cb4cba335c0809d]::interface::run_compiler::<(), rustc_driver_impl[914da1ef5f0db717]::run_compiler::{closure#0}>::{closure#2}
51: 0x7f1c389da7e4 - std[6a2a162ccd49bd24]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[4cb4cba335c0809d]::util::run_in_thread_with_globals<rustc_interface[4cb4cba335c0809d]::util::run_in_thread_pool_with_globals<rustc_interface[4cb4cba335c0809d]::interface::run_compiler<(), rustc_driver_impl[914da1ef5f0db717]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
52: 0x7f1c389da5ad - <std[6a2a162ccd49bd24]::thread::lifecycle::spawn_unchecked<rustc_interface[4cb4cba335c0809d]::util::run_in_thread_with_globals<rustc_interface[4cb4cba335c0809d]::util::run_in_thread_pool_with_globals<rustc_interface[4cb4cba335c0809d]::interface::run_compiler<(), rustc_driver_impl[914da1ef5f0db717]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[34df38ed1aeeb409]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
53: 0x7f1c389d82c7 - <std[6a2a162ccd49bd24]::sys::thread::unix::Thread>::new::thread_start
54: 0x7f1c31c97739 - <unknown>
55: 0x7f1c31d1bedc - <unknown>
56: 0x0 - <unknown>
error: the compiler unexpectedly panicked. This is a bug
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 1.100.0-nightly (8536f4de9 2026-08-22) running on x86_64-unknown-linux-gnu
query stack during panic:
#0 [eval_to_allocation_raw] const-evaluating + checking `<impl at /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:6:1: 6:18>::K`
#1 [eval_to_allocation_raw] const-evaluating + checking `<impl at /tmp/icemaker_global_tempdir.o4FI5rQou7VT/rustc_testrunner_tmpdir_reporting.0AJls2wI4xES/mvce.rs:6:1: 6:18>::K`
#2 [eval_to_valtree] evaluating type-level constant
#3 [typeck_root] type-checking `take1`
#4 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 6 previous errors; 1 warning emitted
Some errors have detailed explanations: E0053, E0601, E0658.
For more information about an error, try `rustc --explain E0053`.
@rustbot label +F-generic_const_args +F-min_generic_const_args +F-generic_const_items
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by compiling the reduced b.rs reproducer with the nightly rustc version reported in the issue. Then inspect compiler/rustc_const_eval/src/interpret/operand.rs around lines 116-128 and trace the const-evaluation path shown in the backtrace. Done means the reproducer no longer causes the scalar-size assertion ICE and instead produces an appropriate compiler result or diagnostic.
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
- Active
- Clarity
- Mostly clear
- Newbie friendliness
- 48/100