[ICE]: `ScalarInt has size 8 but expected 1`
Open
Nobody has claimed this yet.
C-bug
F-generic_const_exprs
F-min_generic_const_args
I-ICE
needs-triage
T-compiler
- Dominant language
- Rust
- Stars
- 119k
- Forks
- 16.1k
- PR merge metrics
- PR metrics pending
Description
auto-reduced (treereduce-rust):
#![feature(macroless_generic_const_args)]
#![feature(generic_const_exprs)]
struct Foo<const B: bool>;
fn test<const N: usize>() -> Foo<{ N > 0 }> {
test::<true>
}
original:
#![feature(macroless_generic_const_args)]
#![feature(generic_const_exprs)]
#![feature(min_generic_const_args)]
struct Foo<const B : bool>;
fn test<const N : usize>() ->Foo<{N > 0}> { test::<true> }
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_middle/src/ty/consts/int.rs#L261-L273
Command:
/home/matthias/.rustup/toolchains/master/bin/rustc
Program output
error: `macroless_generic_const_args` requires `min_generic_const_args` to be enabled
--> /tmp/icemaker_global_tempdir.z3xn6cNlkIRr/rustc_testrunner_tmpdir_reporting.8BSwG7Hva398/mvce.rs:1:12
|
1 | #![feature(macroless_generic_const_args)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: enable all of these features
warning: `feature(generic_const_exprs)` is not supported with the next-generation trait solver
--> /tmp/icemaker_global_tempdir.z3xn6cNlkIRr/rustc_testrunner_tmpdir_reporting.8BSwG7Hva398/mvce.rs:2:12
|
2 | #![feature(generic_const_exprs)]
| ^^^^^^^^^^^^^^^^^^^
|
= note: `-Znext-solver=globally` is currently enabled by default for testing
= note: reverted the setting to `-Znext-solver=coherence` for this crate
= note: the currently stable trait solver will be used for this crate
= note: see issues #160895 <https://github.com/rust-lang/rust/issues/160895> for more information
warning: the feature `macroless_generic_const_args` is incomplete and may not be safe to use and/or cause compiler crashes
--> /tmp/icemaker_global_tempdir.z3xn6cNlkIRr/rustc_testrunner_tmpdir_reporting.8BSwG7Hva398/mvce.rs:1:12
|
1 | #![feature(macroless_generic_const_args)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #159006 <https://github.com/rust-lang/rust/issues/159006> 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
--> /tmp/icemaker_global_tempdir.z3xn6cNlkIRr/rustc_testrunner_tmpdir_reporting.8BSwG7Hva398/mvce.rs:2:12
|
2 | #![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.z3xn6cNlkIRr/rustc_testrunner_tmpdir_reporting.8BSwG7Hva398/mvce.rs:7:2
|
7 | }
| ^ consider adding a `main` function to `/tmp/icemaker_global_tempdir.z3xn6cNlkIRr/rustc_testrunner_tmpdir_reporting.8BSwG7Hva398/mvce.rs`
thread 'rustc' (3555206) panicked at /rustc-dev/8536f4de90e5e781c06e584f8a88de860adc798b/compiler/rustc_middle/src/ty/consts/int.rs:267:9:
assertion `left == right` failed: ScalarInt has size 8 but expected 1
left: 1
right: 8
stack backtrace:
0: 0x7f33435ef966 - <<std[6a2a162ccd49bd24]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[34df38ed1aeeb409]::fmt::Display>::fmt
1: 0x7f3343c0b063 - core[34df38ed1aeeb409]::fmt::write
2: 0x7f3343604e4c - <std[6a2a162ccd49bd24]::sys::stdio::unix::Stderr as core[34df38ed1aeeb409]::io::write::Write>::write_fmt
3: 0x7f33435c2bea - std[6a2a162ccd49bd24]::panicking::default_hook::{closure#0}
4: 0x7f33435e3c03 - std[6a2a162ccd49bd24]::panicking::default_hook
5: 0x7f334259f25a - std[6a2a162ccd49bd24]::panicking::update_hook::<alloc[d780ca98ca945870]::boxed::Box<rustc_driver_impl[914da1ef5f0db717]::install_ice_hook::{closure#1}>>::{closure#0}
6: 0x7f33435e40a2 - std[6a2a162ccd49bd24]::panicking::panic_with_hook
7: 0x7f33435c2ca2 - std[6a2a162ccd49bd24]::panicking::panic_handler::{closure#0}
8: 0x7f33435badd9 - std[6a2a162ccd49bd24]::sys::backtrace::__rust_end_short_backtrace::<std[6a2a162ccd49bd24]::panicking::panic_handler::{closure#0}, !>
9: 0x7f33435c46ad - __rustc[8236491043d97613]::rust_begin_unwind
10: 0x7f334022f00c - core[34df38ed1aeeb409]::panicking::panic_fmt
11: 0x7f3341f332b3 - core[34df38ed1aeeb409]::panicking::assert_failed_inner
12: 0x7f3341f29205 - core[34df38ed1aeeb409]::panicking::assert_failed::<u64, u64>
13: 0x7f3343cad53a - <rustc_const_eval[972a1eb05da00dbd]::interpret::eval_context::InterpCx<rustc_const_eval[972a1eb05da00dbd]::const_eval::machine::CompileTimeMachine>>::binary_op
14: 0x7f3341709ff9 - <rustc_const_eval[972a1eb05da00dbd]::interpret::eval_context::InterpCx<rustc_const_eval[972a1eb05da00dbd]::const_eval::machine::CompileTimeMachine>>::eval_rvalue_into_place
15: 0x7f3341702423 - rustc_const_eval[972a1eb05da00dbd]::const_eval::eval_queries::eval_to_allocation_raw_provider
16: 0x7f3343c3bcd6 - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
17: 0x7f3344c5bdfa - 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>
18: 0x7f3344c5b367 - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
19: 0x7f3340d4d8d6 - rustc_const_eval[972a1eb05da00dbd]::const_eval::valtrees::eval_to_valtree
20: 0x7f33449a7fe6 - <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
21: 0x7f33449a7fa2 - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_valtree::invoke_provider_fn::__rust_begin_short_backtrace
22: 0x7f33449a7676 - 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>
23: 0x7f33449a733f - rustc_query_impl[7883aff223ddbf83]::query_vtables::eval_to_valtree::execute_query_non_incr::__rust_end_short_backtrace
24: 0x7f3343d3fef1 - <rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>::const_eval_global_id_for_typeck
25: 0x7f3343d3f9f2 - <rustc_middle[e13af1fab9e07cac]::ty::context::TyCtxt>::const_eval_resolve_for_typeck
26: 0x7f33433c11d8 - <rustc_trait_selection[c751c4991df8534b]::traits::fulfill::FulfillProcessor as rustc_data_structures[f27dd378dd25622a]::obligation_forest::ObligationProcessor>::process_obligation::{closure#0}
27: 0x7f3343fffe33 - <rustc_trait_selection[c751c4991df8534b]::traits::fulfill::FulfillProcessor as rustc_data_structures[f27dd378dd25622a]::obligation_forest::ObligationProcessor>::process_obligation
28: 0x7f3343ff2ba0 - <rustc_data_structures[f27dd378dd25622a]::obligation_forest::ObligationForest<rustc_trait_selection[c751c4991df8534b]::traits::fulfill::PendingPredicateObligation>>::process_obligations::<rustc_trait_selection[c751c4991df8534b]::traits::fulfill::FulfillProcessor>
29: 0x7f3343da76da - <rustc_trait_selection[c751c4991df8534b]::traits::engine::ObligationCtxt>::try_evaluate_obligations
30: 0x7f3342895680 - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::may_coerce
31: 0x7f3342873b0e - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::suggest_deref_ref_or_into
32: 0x7f334286886f - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::emit_type_mismatch_suggestions
33: 0x7f3342863f1e - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::emit_coerce_suggestions
34: 0x7f33445e293e - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::check_expr_block
35: 0x7f33445e6692 - <rustc_hir_typeck[794a63979e72c52d]::fn_ctxt::FnCtxt>::check_expr_with_expectation_and_args
36: 0x7f3343d66861 - rustc_hir_typeck[794a63979e72c52d]::check::check_fn
37: 0x7f33447184d8 - rustc_hir_typeck[794a63979e72c52d]::typeck_with_inspect::{closure#0}
38: 0x7f3344716a4a - rustc_query_impl[7883aff223ddbf83]::query_vtables::typeck_root::invoke_provider_fn::__rust_begin_short_backtrace
39: 0x7f33446f0f35 - 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>
40: 0x7f33446f0ba7 - rustc_query_impl[7883aff223ddbf83]::query_vtables::typeck_root::execute_query_non_incr::__rust_end_short_backtrace
41: 0x7f33444b8914 - rustc_hir_analysis[6c6705371eee3cd0]::check_crate
42: 0x7f33446f243a - rustc_interface[4cb4cba335c0809d]::passes::analysis
43: 0x7f3344e2ef4a - rustc_query_impl[7883aff223ddbf83]::execution::try_execute_query::<rustc_middle[e13af1fab9e07cac]::query::caches::SingleCache<rustc_middle[e13af1fab9e07cac]::query::erase::ErasedData<[u8; 0usize]>>, false>
44: 0x7f3344e2ecd3 - rustc_query_impl[7883aff223ddbf83]::query_vtables::analysis::execute_query_non_incr::__rust_end_short_backtrace
45: 0x7f3344fafb6b - rustc_interface[4cb4cba335c0809d]::interface::run_compiler::<(), rustc_driver_impl[914da1ef5f0db717]::run_compiler::{closure#0}>::{closure#2}
46: 0x7f3344fda7e4 - 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}, ()>
47: 0x7f3344fda5ad - <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}
48: 0x7f3344fd82c7 - <std[6a2a162ccd49bd24]::sys::thread::unix::Thread>::new::thread_start
49: 0x7f333e297739 - <unknown>
50: 0x7f333e31bedc - <unknown>
51: 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 `test::{constant#0}`
#1 [eval_to_valtree] evaluating type-level constant
#2 [typeck_root] type-checking `test`
#3 [analysis] running analysis passes on crate `mvce`
end of query stack
error: aborting due to 2 previous errors; 3 warnings emitted
For more information about this error, try `rustc --explain E0601`.
@rustbot label +F-macroless_generic_const_args +F-generic_const_exprs +F-min_generic_const_args
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 with the minimized reproducer and run it using the nightly rustc command shown in the issue. Read compiler/rustc_middle/src/ty/consts/int.rs around lines 261-273, then trace the const-evaluation path shown in the backtrace. Done means this input no longer causes the ScalarInt size assertion or 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
- Active
- Clarity
- Clearly specified
- Newbie friendliness
- 55/100