rust-lang / rust-lang/rust

[ICE]: `Got a scalar pair where a scalar was expected`

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@GokhanKabar is already working on this.

Since Apr 13, 2026.

C-bug I-ICE P-low regression-from-stable-to-nightly T-compiler WG-trait-system-refactor
Dominant language
Rust
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PR metrics pending

Description

auto-reduced (treereduce-rust):

//@compile-flags: -Znext-solver=globally
impl<'a, T: ?Sized> Sized for T {}

fn main() {
    const {
        unsafe {
            let value = [1, 2];
            let ptr = value.as_ptr().add(2);
        }
    }
}

original:

#![feature(min_specialization)]

trait MySpecTrait {
    fn f();
}

impl<'a, T: ?Sized> Sized for T {
    default fn f() {}
}

impl<T> MySpecTrait for &'a T {
    fn f() {}
}

fn main() {
    const {
        unsafe {
            let value = [1, 2];
            let ptr = value.as_ptr().add(2);
            let fat = std::ptr::slice_from_raw_parts(ptr, usize::MAX);
            let _ice = (*fat)[ + 0 + 1 + 1
        + 1 + 1];
        }
    }
}

Version information

rustc 1.97.0-nightly (dab8d9d10 2026-04-12)
binary: rustc
commit-hash: dab8d9d1066c4c95008163c7babf275106ce3f32
commit-date: 2026-04-12
host: x86_64-unknown-linux-gnu
release: 1.97.0-nightly
LLVM version: 22.1.2

Possibly related line of code:
https://github.com/rust-lang/rust/blob/dab8d9d1066c4c95008163c7babf275106ce3f32/compiler/rustc_const_eval/src/interpret/operand.rs#L81-L93

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Znext-solver=globally

Program output 

error[E0322]: explicit impls for the `Sized` trait are not permitted
 --> /tmp/icemaker_global_tempdir.ijetyTEoRrg7/rustc_testrunner_tmpdir_reporting.vqmJqRh8PV63/mvce.rs:1:1
  |
1 | impl<'a, T: ?Sized> Sized for T {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of `Sized` not allowed

error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
 --> /tmp/icemaker_global_tempdir.ijetyTEoRrg7/rustc_testrunner_tmpdir_reporting.vqmJqRh8PV63/mvce.rs:1:10
  |
1 | impl<'a, T: ?Sized> Sized for T {}
  |          ^ type parameter `T` must be used as the type parameter for some local type
  |
  = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local
  = note: only traits defined in the current crate can be implemented for a type parameter

warning: unused variable: `ptr`
 --> /tmp/icemaker_global_tempdir.ijetyTEoRrg7/rustc_testrunner_tmpdir_reporting.vqmJqRh8PV63/mvce.rs:7:17
  |
7 |             let ptr = value.as_ptr().add(2);
  |                 ^^^ help: if this is intentional, prefix it with an underscore: `_ptr`
  |
  = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

error: internal compiler error: /rustc-dev/dab8d9d1066c4c95008163c7babf275106ce3f32/compiler/rustc_const_eval/src/interpret/operand.rs:87:42: Got a scalar pair where a scalar was expected


thread 'rustc' (36528) panicked at /rustc-dev/dab8d9d1066c4c95008163c7babf275106ce3f32/compiler/rustc_const_eval/src/interpret/operand.rs:87:42:
Box<dyn Any>
stack backtrace:
   0:     0x7f617c62f00b - <<std[8da0d64ac8131bdc]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[f9890b7f281801e7]::fmt::Display>::fmt
   1:     0x7f617cc20ac8 - core[f9890b7f281801e7]::fmt::write
   2:     0x7f617c6462d6 - <std[8da0d64ac8131bdc]::sys::stdio::unix::Stderr as std[8da0d64ac8131bdc]::io::Write>::write_fmt
   3:     0x7f617c605308 - std[8da0d64ac8131bdc]::panicking::default_hook::{closure#0}
   4:     0x7f617c622673 - std[8da0d64ac8131bdc]::panicking::default_hook
   5:     0x7f617b5fea1c - std[8da0d64ac8131bdc]::panicking::update_hook::<alloc[d917484f94c95b6d]::boxed::Box<rustc_driver_impl[b2ed678f474368d]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f617c622952 - std[8da0d64ac8131bdc]::panicking::panic_with_hook
   7:     0x7f617b62e901 - std[8da0d64ac8131bdc]::panicking::begin_panic::<rustc_errors[da4fca7d51b28372]::ExplicitBug>::{closure#0}
   8:     0x7f617b627366 - std[8da0d64ac8131bdc]::sys::backtrace::__rust_end_short_backtrace::<std[8da0d64ac8131bdc]::panicking::begin_panic<rustc_errors[da4fca7d51b28372]::ExplicitBug>::{closure#0}, !>
   9:     0x7f617b625278 - std[8da0d64ac8131bdc]::panicking::begin_panic::<rustc_errors[da4fca7d51b28372]::ExplicitBug>
  10:     0x7f617b639e51 - <rustc_errors[da4fca7d51b28372]::diagnostic::BugAbort as rustc_errors[da4fca7d51b28372]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7f617bc336d9 - rustc_middle[854472fbb2a70fbb]::util::bug::opt_span_bug_fmt::<rustc_span[3bf58ae8b6d8fa24]::span_encoding::Span>::{closure#0}
  12:     0x7f617bc33862 - rustc_middle[854472fbb2a70fbb]::ty::context::tls::with_opt::<rustc_middle[854472fbb2a70fbb]::util::bug::opt_span_bug_fmt<rustc_span[3bf58ae8b6d8fa24]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  13:     0x7f617bc2400b - rustc_middle[854472fbb2a70fbb]::ty::context::tls::with_context_opt::<rustc_middle[854472fbb2a70fbb]::ty::context::tls::with_opt<rustc_middle[854472fbb2a70fbb]::util::bug::opt_span_bug_fmt<rustc_span[3bf58ae8b6d8fa24]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  14:     0x7f6178d35ce4 - rustc_middle[854472fbb2a70fbb]::util::bug::bug_fmt
  15:     0x7f617e10d3e0 - <rustc_const_eval[aec75a2448d811d3]::interpret::eval_context::InterpCx<rustc_const_eval[aec75a2448d811d3]::const_eval::machine::CompileTimeMachine>>::binary_op
  16:     0x7f617a4e3af3 - <rustc_const_eval[aec75a2448d811d3]::interpret::eval_context::InterpCx<rustc_const_eval[aec75a2448d811d3]::const_eval::machine::CompileTimeMachine>>::eval_rvalue_into_place
  17:     0x7f617a4dc0e1 - rustc_const_eval[aec75a2448d811d3]::const_eval::eval_queries::eval_to_allocation_raw_provider
  18:     0x7f617d40cc16 - rustc_query_impl[e8c0d15e0ce1a66c]::query_impl::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
  19:     0x7f617d40c2c3 - rustc_query_impl[e8c0d15e0ce1a66c]::execution::try_execute_query::<rustc_middle[854472fbb2a70fbb]::query::caches::DefaultCache<rustc_middle[854472fbb2a70fbb]::ty::PseudoCanonicalInput<rustc_middle[854472fbb2a70fbb]::mir::interpret::GlobalId>, rustc_middle[854472fbb2a70fbb]::query::erase::ErasedData<[u8; 24usize]>>, false>
  20:     0x7f617d40bcc7 - rustc_query_impl[e8c0d15e0ce1a66c]::query_impl::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
  21:     0x7f617d40ab40 - rustc_const_eval[aec75a2448d811d3]::const_eval::eval_queries::eval_to_const_value_raw_provider
  22:     0x7f617d40a696 - rustc_query_impl[e8c0d15e0ce1a66c]::query_impl::eval_to_const_value_raw::invoke_provider_fn::__rust_begin_short_backtrace
  23:     0x7f617d40c1bb - rustc_query_impl[e8c0d15e0ce1a66c]::execution::try_execute_query::<rustc_middle[854472fbb2a70fbb]::query::caches::DefaultCache<rustc_middle[854472fbb2a70fbb]::ty::PseudoCanonicalInput<rustc_middle[854472fbb2a70fbb]::mir::interpret::GlobalId>, rustc_middle[854472fbb2a70fbb]::query::erase::ErasedData<[u8; 24usize]>>, false>
  24:     0x7f617d40bd7f - rustc_query_impl[e8c0d15e0ce1a66c]::query_impl::eval_to_const_value_raw::execute_query_non_incr::__rust_end_short_backtrace
  25:     0x7f617d73689f - <rustc_middle[854472fbb2a70fbb]::ty::context::TyCtxt>::const_eval_resolve
  26:     0x7f617d64b5b1 - <rustc_mir_transform[529351ae2b1b511b]::known_panics_lint::ConstPropagator as rustc_middle[854472fbb2a70fbb]::mir::visit::Visitor>::visit_assign
  27:     0x7f617d6474fd - <rustc_mir_transform[529351ae2b1b511b]::known_panics_lint::ConstPropagator as rustc_middle[854472fbb2a70fbb]::mir::visit::Visitor>::visit_body
  28:     0x7f617d641c4d - <rustc_mir_transform[529351ae2b1b511b]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[529351ae2b1b511b]::pass_manager::MirLint>::run_lint
  29:     0x7f617cc0d13c - rustc_mir_transform[529351ae2b1b511b]::run_analysis_to_runtime_passes
  30:     0x7f617d842ab7 - rustc_mir_transform[529351ae2b1b511b]::mir_drops_elaborated_and_const_checked
  31:     0x7f617d842559 - rustc_query_impl[e8c0d15e0ce1a66c]::query_impl::mir_drops_elaborated_and_const_checked::invoke_provider_fn::__rust_begin_short_backtrace
  32:     0x7f617cf12c26 - rustc_query_impl[e8c0d15e0ce1a66c]::execution::try_execute_query::<rustc_data_structures[eff972d194685d0b]::vec_cache::VecCache<rustc_span[3bf58ae8b6d8fa24]::def_id::LocalDefId, rustc_middle[854472fbb2a70fbb]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[854472fbb2a70fbb]::dep_graph::graph::DepNodeIndex>, false>
  33:     0x7f617cf1369b - rustc_query_impl[e8c0d15e0ce1a66c]::query_impl::mir_drops_elaborated_and_const_checked::execute_query_non_incr::__rust_end_short_backtrace
  34:     0x7f617db123dc - <rustc_middle[854472fbb2a70fbb]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[8e9c025ebfbd6215]::passes::run_required_analyses::{closure#2}::{closure#0}>::{closure#0}
  35:     0x7f617db1169d - rustc_interface[8e9c025ebfbd6215]::passes::analysis
  36:     0x7f617ddc7d09 - rustc_query_impl[e8c0d15e0ce1a66c]::execution::try_execute_query::<rustc_middle[854472fbb2a70fbb]::query::caches::SingleCache<rustc_middle[854472fbb2a70fbb]::query::erase::ErasedData<[u8; 0usize]>>, false>
  37:     0x7f617ddc7969 - rustc_query_impl[e8c0d15e0ce1a66c]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  38:     0x7f617dd9f610 - rustc_interface[8e9c025ebfbd6215]::interface::run_compiler::<(), rustc_driver_impl[b2ed678f474368d]::run_compiler::{closure#0}>::{closure#1}
  39:     0x7f617dd8c77e - std[8da0d64ac8131bdc]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[8e9c025ebfbd6215]::util::run_in_thread_with_globals<rustc_interface[8e9c025ebfbd6215]::util::run_in_thread_pool_with_globals<rustc_interface[8e9c025ebfbd6215]::interface::run_compiler<(), rustc_driver_impl[b2ed678f474368d]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  40:     0x7f617dd8d020 - <std[8da0d64ac8131bdc]::thread::lifecycle::spawn_unchecked<rustc_interface[8e9c025ebfbd6215]::util::run_in_thread_with_globals<rustc_interface[8e9c025ebfbd6215]::util::run_in_thread_pool_with_globals<rustc_interface[8e9c025ebfbd6215]::interface::run_compiler<(), rustc_driver_impl[b2ed678f474368d]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[f9890b7f281801e7]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  41:     0x7f617dd8deac - <std[8da0d64ac8131bdc]::sys::thread::unix::Thread>::new::thread_start
  42:     0x7f61778a597a - <unknown>
  43:     0x7f61779292bc - <unknown>
  44:                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 1.97.0-nightly (dab8d9d10 2026-04-12) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z next-solver=globally -Z dump-mir-dir=dir

query stack during panic:
#0 [eval_to_allocation_raw] const-evaluating + checking `main::{constant#0}`
#1 [eval_to_const_value_raw] simplifying constant for the type system `main::{constant#0}`
#2 [mir_drops_elaborated_and_const_checked] elaborating drops for `main`
#3 [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: E0210, E0322.
For more information about an error, try `rustc --explain E0210`.

@rustbot label +F-min_specialization +WG-trait-system-refactor

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