[ICE]: invalid immediate for given destination place: scalar value has wrong size

@rustbot

auto-reduced (treereduce-rust):

#![feature(field_projections)]
use std::field::{field_of, Field};
use std::mem::offset_of;

#[repr(C)]
pub struct Struct {
    a: i32,
    b: i64,
}

fn main() {
    assert_eq!(<field_of!(Struct, b)>::OFFSET, offset_of!((), ()));
}

original code

original:

//@ revisions: old next
//@ [next] compile-flags: -Znext-solver
//@ run-pass
#![expect(incomplete_features)]
#![feature(field_projections)]

use std::field::{Field, field_of};
use std::mem::offset_of;
use std::ptr;

#[repr(C)]
pub struct Struct {
    a: i32,
    b: i64,
}

// FIXME(FRTs): need to mark these fields as used by the `field_of!` macro.
#[expect(dead_code)]
pub union Union {
    a: i32,
    b: i64,
}

#[repr(C, i8)]
pub enum Enum {
    A { a: i32, b: i64 },
    B { x: i64, y: i32 },
}

fn project_ref<'a, T, F: Field<Base = T>>(r: &'a T) -> &'a F::Type {
    unsafe { &*ptr::from_ref(r).byte_add(F::OFFSET).cast() }
}

fn main() {
    assert_eq!(<field_of!(Struct, a)>::OFFSET, offset_of!(Struct, a));
    assert_eq!(<field_of!(Struct, b)>::OFFSET, offset_of!((), ()));

    let _: field_of!(Union, a);
    let _: field_of!(Union, b);

    let _: field_of!(Enum, A.a);
    let _: field_of!(Enum, A.b);
    let _: field_of!(Enum, B.x);
    let _: field_of!(Enum, B.y);

    let s = Struct { a: 42, b: 24 };
    let r = &s;
    let a = project_ref::<Struct, field_of!(Struct, a)>(r);
    let b = project_ref::<Struct, field_of!(Struct, b)>(r);
    assert_eq!(*a, 42);
    assert_eq!(*b, 24);
}

Version information

rustc 1.96.0-nightly (ba1567989 2026-02-28)
binary: rustc
commit-hash: ba1567989ee7774a1fb53aa680a8e4e8daa0f519
commit-date: 2026-02-28
host: x86_64-unknown-linux-gnu
release: 1.96.0-nightly
LLVM version: 22.1.0

Possibly related line of code:

rust/compiler/rustc_const_eval/src/interpret/operand.rs

Lines 116 to 128 in ba15679

    
               } 
        
               /// Assert that this immediate is a valid value for the given ABI. 
        
               pub fn assert_matches_abi(self, abi: BackendRepr, msg: &str, cx: &impl HasDataLayout) { 
        
                   match (self, abi) { 
        
                       (Immediate::Scalar(scalar), BackendRepr::Scalar(s)) => { 
        
                           assert_eq!(scalar.size(), s.size(cx), "{msg}: scalar value has wrong size"); 
        
                           if !matches!(s.primitive(), abi::Primitive::Pointer(..)) { 
        
                               // This is not a pointer, it should not carry provenance. 
        
                               assert!( 
        
                                   matches!(scalar, Scalar::Int(..)), 
        
                                   "{msg}: scalar value should be an integer, but has provenance" 
        
                               );

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

Program output

error: offset_of expects dot-separated field and variant names
  --> b.rs:13:63
   |
13 |     assert_eq!(<field_of!(Struct, b)>::OFFSET, offset_of!((), ()));
   |                                                               ^^

warning: the feature `field_projections` is incomplete and may not be safe to use and/or cause compiler crashes
 --> b.rs:1:12
  |
1 | #![feature(field_projections)]
  |            ^^^^^^^^^^^^^^^^^
  |
  = note: see issue #145383 <https://github.com/rust-lang/rust/issues/145383> for more information
  = note: `#[warn(incomplete_features)]` on by default


thread 'rustc' (2095317) panicked at /rustc-dev/ba1567989ee7774a1fb53aa680a8e4e8daa0f519/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(4 bytes)
 right: Size(8 bytes)
stack backtrace:
   0:     0x7f13cf9aa67b - <<std[fec5da352f41df64]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[655421083fc59668]::fmt::Display>::fmt
   1:     0x7f13d0020288 - core[655421083fc59668]::fmt::write
   2:     0x7f13cf9c1686 - <std[fec5da352f41df64]::sys::stdio::unix::Stderr as std[fec5da352f41df64]::io::Write>::write_fmt
   3:     0x7f13cf980758 - std[fec5da352f41df64]::panicking::default_hook::{closure#0}
   4:     0x7f13cf99dae3 - std[fec5da352f41df64]::panicking::default_hook
   5:     0x7f13ce975070 - std[fec5da352f41df64]::panicking::update_hook::<alloc[c081135bcfa9263a]::boxed::Box<rustc_driver_impl[a0a5e0825e3525c3]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f13cf99ddc2 - std[fec5da352f41df64]::panicking::panic_with_hook
   7:     0x7f13cf980818 - std[fec5da352f41df64]::panicking::panic_handler::{closure#0}
   8:     0x7f13cf977549 - std[fec5da352f41df64]::sys::backtrace::__rust_end_short_backtrace::<std[fec5da352f41df64]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f13cf98227d - __rustc[70948dbd69585b06]::rust_begin_unwind
  10:     0x7f13cc51fefc - core[655421083fc59668]::panicking::panic_fmt
  11:     0x7f13ce2c0243 - core[655421083fc59668]::panicking::assert_failed_inner
  12:     0x7f13cef743ce - core[655421083fc59668]::panicking::assert_failed::<rustc_abi[efb49786af623574]::Size, rustc_abi[efb49786af623574]::Size>
  13:     0x7f13d046cbd7 - <rustc_const_eval[60546f5659a7e5b8]::interpret::eval_context::InterpCx<rustc_const_eval[60546f5659a7e5b8]::const_eval::machine::CompileTimeMachine>>::copy_op_no_validate::<rustc_const_eval[60546f5659a7e5b8]::interpret::operand::OpTy, rustc_const_eval[60546f5659a7e5b8]::interpret::place::PlaceTy>
  14:     0x7f13d10ac948 - rustc_const_eval[60546f5659a7e5b8]::const_eval::eval_queries::eval_to_allocation_raw_provider
  15:     0x7f13d10aae1c - rustc_query_impl[83437f7fc475934b]::query_impl::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
  16:     0x7f13d0e6df83 - rustc_query_impl[83437f7fc475934b]::execution::try_execute_query::<rustc_middle[487438de6df3e06a]::query::caches::DefaultCache<rustc_middle[487438de6df3e06a]::ty::PseudoCanonicalInput<rustc_middle[487438de6df3e06a]::mir::interpret::GlobalId>, rustc_middle[487438de6df3e06a]::query::erase::ErasedData<[u8; 24usize]>>, false>
  17:     0x7f13d0e6d8eb - rustc_query_impl[83437f7fc475934b]::query_impl::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
  18:     0x7f13d0e6f521 - rustc_const_eval[60546f5659a7e5b8]::const_eval::eval_queries::eval_to_const_value_raw_provider
  19:     0x7f13d0e6f0a8 - rustc_query_impl[83437f7fc475934b]::query_impl::eval_to_const_value_raw::invoke_provider_fn::__rust_begin_short_backtrace
  20:     0x7f13d0e6de87 - rustc_query_impl[83437f7fc475934b]::execution::try_execute_query::<rustc_middle[487438de6df3e06a]::query::caches::DefaultCache<rustc_middle[487438de6df3e06a]::ty::PseudoCanonicalInput<rustc_middle[487438de6df3e06a]::mir::interpret::GlobalId>, rustc_middle[487438de6df3e06a]::query::erase::ErasedData<[u8; 24usize]>>, false>
  21:     0x7f13d0e6d9eb - rustc_query_impl[83437f7fc475934b]::query_impl::eval_to_const_value_raw::execute_query_non_incr::__rust_end_short_backtrace
  22:     0x7f13d0c5db20 - <rustc_middle[487438de6df3e06a]::ty::context::TyCtxt>::const_eval_resolve
  23:     0x7f13d0761d8e - <rustc_mir_transform[375a1252ba647aa9]::known_panics_lint::ConstPropagator as rustc_middle[487438de6df3e06a]::mir::visit::Visitor>::visit_assign
  24:     0x7f13d075dc36 - <rustc_mir_transform[375a1252ba647aa9]::known_panics_lint::ConstPropagator as rustc_middle[487438de6df3e06a]::mir::visit::Visitor>::visit_body
  25:     0x7f13d075afe8 - <rustc_mir_transform[375a1252ba647aa9]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[375a1252ba647aa9]::pass_manager::MirLint>::run_lint
  26:     0x7f13d000ca6a - rustc_mir_transform[375a1252ba647aa9]::run_analysis_to_runtime_passes
  27:     0x7f13d0de3034 - rustc_mir_transform[375a1252ba647aa9]::promoted_mir
  28:     0x7f13d0de2cb3 - rustc_query_impl[83437f7fc475934b]::query_impl::promoted_mir::invoke_provider_fn::__rust_begin_short_backtrace
  29:     0x7f13d005a4e8 - rustc_query_impl[83437f7fc475934b]::execution::try_execute_query::<rustc_middle[487438de6df3e06a]::query::caches::DefIdCache<rustc_middle[487438de6df3e06a]::query::erase::ErasedData<[u8; 8usize]>>, false>
  30:     0x7f13d0059764 - rustc_query_impl[83437f7fc475934b]::query_impl::promoted_mir::execute_query_non_incr::__rust_end_short_backtrace
  31:     0x7f13d10aa9e4 - <rustc_const_eval[60546f5659a7e5b8]::interpret::eval_context::InterpCx<rustc_const_eval[60546f5659a7e5b8]::const_eval::machine::CompileTimeMachine>>::load_mir
  32:     0x7f13d10ab59a - rustc_const_eval[60546f5659a7e5b8]::const_eval::eval_queries::eval_to_allocation_raw_provider
  33:     0x7f13d10aae1c - rustc_query_impl[83437f7fc475934b]::query_impl::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
  34:     0x7f13d0e6df83 - rustc_query_impl[83437f7fc475934b]::execution::try_execute_query::<rustc_middle[487438de6df3e06a]::query::caches::DefaultCache<rustc_middle[487438de6df3e06a]::ty::PseudoCanonicalInput<rustc_middle[487438de6df3e06a]::mir::interpret::GlobalId>, rustc_middle[487438de6df3e06a]::query::erase::ErasedData<[u8; 24usize]>>, false>
  35:     0x7f13d0e6d8eb - rustc_query_impl[83437f7fc475934b]::query_impl::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
  36:     0x7f13d0e6f521 - rustc_const_eval[60546f5659a7e5b8]::const_eval::eval_queries::eval_to_const_value_raw_provider
  37:     0x7f13d0e6f0a8 - rustc_query_impl[83437f7fc475934b]::query_impl::eval_to_const_value_raw::invoke_provider_fn::__rust_begin_short_backtrace
  38:     0x7f13d0e6de87 - rustc_query_impl[83437f7fc475934b]::execution::try_execute_query::<rustc_middle[487438de6df3e06a]::query::caches::DefaultCache<rustc_middle[487438de6df3e06a]::ty::PseudoCanonicalInput<rustc_middle[487438de6df3e06a]::mir::interpret::GlobalId>, rustc_middle[487438de6df3e06a]::query::erase::ErasedData<[u8; 24usize]>>, false>
  39:     0x7f13d0e6d9eb - rustc_query_impl[83437f7fc475934b]::query_impl::eval_to_const_value_raw::execute_query_non_incr::__rust_end_short_backtrace
  40:     0x7f13d0c5db20 - <rustc_middle[487438de6df3e06a]::ty::context::TyCtxt>::const_eval_resolve
  41:     0x7f13d0761d8e - <rustc_mir_transform[375a1252ba647aa9]::known_panics_lint::ConstPropagator as rustc_middle[487438de6df3e06a]::mir::visit::Visitor>::visit_assign
  42:     0x7f13d075dc36 - <rustc_mir_transform[375a1252ba647aa9]::known_panics_lint::ConstPropagator as rustc_middle[487438de6df3e06a]::mir::visit::Visitor>::visit_body
  43:     0x7f13d075afe8 - <rustc_mir_transform[375a1252ba647aa9]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[375a1252ba647aa9]::pass_manager::MirLint>::run_lint
  44:     0x7f13d000ca6a - rustc_mir_transform[375a1252ba647aa9]::run_analysis_to_runtime_passes
  45:     0x7f13d0de1784 - rustc_mir_transform[375a1252ba647aa9]::mir_drops_elaborated_and_const_checked
  46:     0x7f13d0de11e1 - rustc_query_impl[83437f7fc475934b]::query_impl::mir_drops_elaborated_and_const_checked::invoke_provider_fn::__rust_begin_short_backtrace
  47:     0x7f13d016790a - rustc_query_impl[83437f7fc475934b]::execution::try_execute_query::<rustc_data_structures[e05ccdf9cc6e0e20]::vec_cache::VecCache<rustc_span[8c85abb5df2f449]::def_id::LocalDefId, rustc_middle[487438de6df3e06a]::query::erase::ErasedData<[u8; 8usize]>, rustc_middle[487438de6df3e06a]::dep_graph::graph::DepNodeIndex>, false>
  48:     0x7f13d0167043 - rustc_query_impl[83437f7fc475934b]::query_impl::mir_drops_elaborated_and_const_checked::execute_query_non_incr::__rust_end_short_backtrace
  49:     0x7f13d01653c8 - <rustc_middle[487438de6df3e06a]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_interface[b660c6c936fc555e]::passes::run_required_analyses::{closure#1}::{closure#0}>::{closure#0}
  50:     0x7f13d01647af - rustc_interface[b660c6c936fc555e]::passes::analysis
  51:     0x7f13d120925a - rustc_query_impl[83437f7fc475934b]::execution::try_execute_query::<rustc_middle[487438de6df3e06a]::query::caches::SingleCache<rustc_middle[487438de6df3e06a]::query::erase::ErasedData<[u8; 0usize]>>, false>
  52:     0x7f13d1209029 - rustc_query_impl[83437f7fc475934b]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  53:     0x7f13d1229c2d - rustc_interface[b660c6c936fc555e]::interface::run_compiler::<(), rustc_driver_impl[a0a5e0825e3525c3]::run_compiler::{closure#0}>::{closure#1}
  54:     0x7f13d11f653e - std[fec5da352f41df64]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[b660c6c936fc555e]::util::run_in_thread_with_globals<rustc_interface[b660c6c936fc555e]::util::run_in_thread_pool_with_globals<rustc_interface[b660c6c936fc555e]::interface::run_compiler<(), rustc_driver_impl[a0a5e0825e3525c3]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  55:     0x7f13d11f6ba0 - <std[fec5da352f41df64]::thread::lifecycle::spawn_unchecked<rustc_interface[b660c6c936fc555e]::util::run_in_thread_with_globals<rustc_interface[b660c6c936fc555e]::util::run_in_thread_pool_with_globals<rustc_interface[b660c6c936fc555e]::interface::run_compiler<(), rustc_driver_impl[a0a5e0825e3525c3]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[655421083fc59668]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  56:     0x7f13d11f7a2c - <std[fec5da352f41df64]::sys::thread::unix::Thread>::new::thread_start
  57:     0x7f13caca598b - <unknown>
  58:     0x7f13cad29a0c - <unknown>
  59:                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: please attach the file at `/tmp/im/rustc-ice-2026-02-28T20_48_10-2095315.txt` to your bug report

note: rustc 1.96.0-nightly (ba1567989 2026-02-28) running on x86_64-unknown-linux-gnu

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}`
  |
  = note: this failure-note originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)
#2 [promoted_mir] optimizing promoted MIR for `main`
#3 [eval_to_allocation_raw] const-evaluating + checking `main::promoted[1]`
#4 [eval_to_const_value_raw] simplifying constant for the type system `main::promoted[1]`
#5 [mir_drops_elaborated_and_const_checked] elaborating drops for `main`
#6 [analysis] running analysis passes on crate `b`
end of query stack
error: aborting due to 1 previous error; 1 warning emitted

@rustbot label +F-field_projections

seems to trigger without field projections as well:

use std::mem::offset_of;

struct S {
	x: ()
}

impl S {
    fn a() {
        offset_of!(Self, Self::x);
    }
}

fn main() {}

bisects to #148151

Rollup merge of rust-lang#153495 - TaKO8Ki:fix-153236-offset-of-recov…

Unrolled build for #153495

Rollup merge of #153495 - TaKO8Ki:fix-153236-offset-of-recovery, r=pe…

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[ICE]: `invalid immediate for given destination place: scalar value has wrong size` #153236

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	}

	/// Assert that this immediate is a valid value for the given ABI.
	pub fn assert_matches_abi(self, abi: BackendRepr, msg: &str, cx: &impl HasDataLayout) {
	match (self, abi) {
	(Immediate::Scalar(scalar), BackendRepr::Scalar(s)) => {
	assert_eq!(scalar.size(), s.size(cx), "{msg}: scalar value has wrong size");
	if !matches!(s.primitive(), abi::Primitive::Pointer(..)) {
	// This is not a pointer, it should not carry provenance.
	assert!(
	matches!(scalar, Scalar::Int(..)),
	"{msg}: scalar value should be an integer, but has provenance"
	);

[ICE]: invalid immediate for given destination place: scalar value has wrong size #153236

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matthiaskrgr commented on Mar 2, 2026

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[ICE]: `invalid immediate for given destination place: scalar value has wrong size` #153236