[ICE]: reborrow: size mismatch: compiler/rustc_const_eval/src/interpret/place.rs

[matthiaskrgr]

Code

#![feature(const_block_items)]
#![feature(reborrow)]
use std::marker::CoerceShared;
struct MyMut<'a>(&'a u8);
struct MyRef<'a> {
    x: &'a (),
    y: &'a (),
}

impl<'a> CoerceShared<MyRef<'a>> for MyMut<'a> {}
const {
    let value = 1;
    foo(MyMut(&value));
}
const fn foo(x: MyRef) {}

fn main() {}

Meta

rustc --version --verbose:

rustc 1.98.0-nightly (bc2112ed5 2026-06-18)
binary: rustc
commit-hash: bc2112ed56c99fa649e09ab3ab286afab3d9059a
commit-date: 2026-06-18
host: x86_64-unknown-linux-gnu
release: 1.98.0-nightly
LLVM version: 22.1.7

Error output

error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
  --> a.rs:10:10
   |
10 | impl<'a> CoerceShared<MyRef<'a>> for MyMut<'a> {}
   |          ^^^^^^^^^^^^^^^^^^^^^^^

Backtrace

thread 'rustc' (1255357) panicked at /rustc-dev/bc2112ed56c99fa649e09ab3ab286afab3d9059a/compiler/rustc_const_eval/src/interpret/place.rs:936:17:
assertion `left == right` failed
  left: Size(8 bytes)
 right: Size(16 bytes)
stack backtrace:
   0:     0x7f38d19fd889 - <<std[9155b05baf46f0b5]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[b26e7c5dab710dcd]::fmt::Display>::fmt
   1:     0x7f38d200ebde - core[b26e7c5dab710dcd]::fmt::write
   2:     0x7f38d1a13cb6 - <std[9155b05baf46f0b5]::sys::stdio::unix::Stderr as std[9155b05baf46f0b5]::io::Write>::write_fmt
   3:     0x7f38d19d2b7e - std[9155b05baf46f0b5]::panicking::default_hook::{closure#0}
   4:     0x7f38d19f0573 - std[9155b05baf46f0b5]::panicking::default_hook
   5:     0x7f38d0a49fc1 - std[9155b05baf46f0b5]::panicking::update_hook::<alloc[4a86d35f348a3b04]::boxed::Box<rustc_driver_impl[b791fc15675dcea2]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f38d19f0852 - std[9155b05baf46f0b5]::panicking::panic_with_hook
   7:     0x7f38d19d2c42 - std[9155b05baf46f0b5]::panicking::panic_handler::{closure#0}
   8:     0x7f38d19c7169 - std[9155b05baf46f0b5]::sys::backtrace::__rust_end_short_backtrace::<std[9155b05baf46f0b5]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f38d19d46ad - __rustc[b4c4dac14d05b73]::rust_begin_unwind
  10:     0x7f38ce90455c - core[b26e7c5dab710dcd]::panicking::panic_fmt
  11:     0x7f38d040bbd3 - core[b26e7c5dab710dcd]::panicking::assert_failed_inner
  12:     0x7f38d0faf839 - core[b26e7c5dab710dcd]::panicking::assert_failed::<rustc_abi[c68f683fea65e658]::Size, rustc_abi[c68f683fea65e658]::Size>
  13:     0x7f38d2704b02 - <rustc_const_eval[a05529753b3711cc]::interpret::eval_context::InterpCx<rustc_const_eval[a05529753b3711cc]::const_eval::machine::CompileTimeMachine>>::copy_op_no_validate::<rustc_const_eval[a05529753b3711cc]::interpret::operand::OpTy, rustc_const_eval[a05529753b3711cc]::interpret::place::PlaceTy>
  14:     0x7f38d3040cc2 - <rustc_const_eval[a05529753b3711cc]::interpret::eval_context::InterpCx<rustc_const_eval[a05529753b3711cc]::const_eval::machine::CompileTimeMachine>>::eval_rvalue_into_place
  15:     0x7f38d300360d - rustc_const_eval[a05529753b3711cc]::const_eval::eval_queries::eval_to_allocation_raw_provider
  16:     0x7f38d3001c56 - rustc_query_impl[f814d044a8094e2a]::query_impl::eval_to_allocation_raw::invoke_provider_fn::__rust_begin_short_backtrace
  17:     0x7f38d26d3970 - rustc_query_impl[f814d044a8094e2a]::execution::try_execute_query::<rustc_middle[cb7c4bb37f51aac1]::query::caches::DefaultCache<rustc_middle[cb7c4bb37f51aac1]::ty::PseudoCanonicalInput<rustc_middle[cb7c4bb37f51aac1]::mir::interpret::GlobalId>, rustc_middle[cb7c4bb37f51aac1]::query::erase::ErasedData<[u8; 24usize]>>, false>
  18:     0x7f38d26d3297 - rustc_query_impl[f814d044a8094e2a]::query_impl::eval_to_allocation_raw::execute_query_non_incr::__rust_end_short_backtrace
  19:     0x7f38d26d18ca - rustc_const_eval[a05529753b3711cc]::const_eval::eval_queries::eval_to_const_value_raw_provider
  20:     0x7f38d26d151e - rustc_query_impl[f814d044a8094e2a]::query_impl::eval_to_const_value_raw::invoke_provider_fn::__rust_begin_short_backtrace
  21:     0x7f38d26d37ac - rustc_query_impl[f814d044a8094e2a]::execution::try_execute_query::<rustc_middle[cb7c4bb37f51aac1]::query::caches::DefaultCache<rustc_middle[cb7c4bb37f51aac1]::ty::PseudoCanonicalInput<rustc_middle[cb7c4bb37f51aac1]::mir::interpret::GlobalId>, rustc_middle[cb7c4bb37f51aac1]::query::erase::ErasedData<[u8; 24usize]>>, false>
  22:     0x7f38d26d334f - rustc_query_impl[f814d044a8094e2a]::query_impl::eval_to_const_value_raw::execute_query_non_incr::__rust_end_short_backtrace
  23:     0x7f38d26d23c5 - rustc_const_eval[a05529753b3711cc]::const_eval::eval_queries::eval_to_const_value_raw_provider
  24:     0x7f38d26d151e - rustc_query_impl[f814d044a8094e2a]::query_impl::eval_to_const_value_raw::invoke_provider_fn::__rust_begin_short_backtrace
  25:     0x7f38d26d37ac - rustc_query_impl[f814d044a8094e2a]::execution::try_execute_query::<rustc_middle[cb7c4bb37f51aac1]::query::caches::DefaultCache<rustc_middle[cb7c4bb37f51aac1]::ty::PseudoCanonicalInput<rustc_middle[cb7c4bb37f51aac1]::mir::interpret::GlobalId>, rustc_middle[cb7c4bb37f51aac1]::query::erase::ErasedData<[u8; 24usize]>>, false>
  26:     0x7f38d26d334f - rustc_query_impl[f814d044a8094e2a]::query_impl::eval_to_const_value_raw::execute_query_non_incr::__rust_end_short_backtrace
  27:     0x7f38d24a842a - <rustc_middle[cb7c4bb37f51aac1]::ty::context::TyCtxt>::par_hir_body_owners::<rustc_hir_analysis[f8649c0bc5b32aaa]::check_crate::{closure#1}>::{closure#0}
  28:     0x7f38d24a7a25 - rustc_hir_analysis[f8649c0bc5b32aaa]::check_crate
  29:     0x7f38d24a9d0c - rustc_interface[84e7048b04034882]::passes::analysis
  30:     0x7f38d317f906 - rustc_query_impl[f814d044a8094e2a]::execution::try_execute_query::<rustc_middle[cb7c4bb37f51aac1]::query::caches::SingleCache<rustc_middle[cb7c4bb37f51aac1]::query::erase::ErasedData<[u8; 0usize]>>, false>
  31:     0x7f38d317f5e9 - rustc_query_impl[f814d044a8094e2a]::query_impl::analysis::execute_query_non_incr::__rust_end_short_backtrace
  32:     0x7f38d3199c52 - rustc_interface[84e7048b04034882]::interface::run_compiler::<(), rustc_driver_impl[b791fc15675dcea2]::run_compiler::{closure#0}>::{closure#1}
  33:     0x7f38d31ceffa - std[9155b05baf46f0b5]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[84e7048b04034882]::util::run_in_thread_with_globals<rustc_interface[84e7048b04034882]::util::run_in_thread_pool_with_globals<rustc_interface[84e7048b04034882]::interface::run_compiler<(), rustc_driver_impl[b791fc15675dcea2]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  34:     0x7f38d31cedad - <std[9155b05baf46f0b5]::thread::lifecycle::spawn_unchecked<rustc_interface[84e7048b04034882]::util::run_in_thread_with_globals<rustc_interface[84e7048b04034882]::util::run_in_thread_pool_with_globals<rustc_interface[84e7048b04034882]::interface::run_compiler<(), rustc_driver_impl[b791fc15675dcea2]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[b26e7c5dab710dcd]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  35:     0x7f38d31c5290 - <std[9155b05baf46f0b5]::sys::thread::unix::Thread>::new::thread_start
  36:     0x7f38ccc981b9 - <unknown>
  37:     0x7f38ccd1d21c - <unknown>
  38:                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-2026-06-19T19_06_42-1255347.txt` to your bug report

note: rustc 1.98.0-nightly (bc2112ed5 2026-06-18) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [eval_to_allocation_raw] const-evaluating + checking `_`
#1 [eval_to_const_value_raw] simplifying constant for the type system `_`
#2 [eval_to_const_value_raw] simplifying constant for the type system `_`
#3 [analysis] running analysis passes on crate `a`
end of query stack
error: aborting due to 1 previous error