ICE from transmuting pointer to TypeId then comparing in const

[theemathas]

Code

#![feature(const_trait_impl, const_cmp)]

use std::any::TypeId;
use std::mem::transmute;

const X: bool = {
    let a = ();
    let id: TypeId = unsafe { transmute([&raw const a; 2]) };
    id == id
};

@rustbot labels +A-const-eval +F-const_trait_impl

cc @oli-obk

Meta

Reproducible on the playground with version 1.90.0-nightly (2025-07-20 9982d6462bedf1e793f7)

Error output

error: internal compiler error: compiler/rustc_const_eval/src/interpret/memory.rs:1000:51: could not find allocation for alloc3

Backtrace

thread 'rustc' panicked at compiler/rustc_const_eval/src/interpret/memory.rs:1000:51:
Box<dyn Any>
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: <rustc_errors::diagnostic::BugAbort as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
   2: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
   3: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
   4: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
   5: rustc_middle::util::bug::bug_fmt
   6: <rustc_const_eval::interpret::eval_context::InterpCx<rustc_const_eval::const_eval::machine::CompileTimeMachine>>::read_type_id
   7: <rustc_const_eval::interpret::eval_context::InterpCx<rustc_const_eval::const_eval::machine::CompileTimeMachine>>::eval_intrinsic
   8: <rustc_const_eval::const_eval::machine::CompileTimeMachine as rustc_const_eval::interpret::machine::Machine>::call_intrinsic
   9: <rustc_const_eval::interpret::eval_context::InterpCx<rustc_const_eval::const_eval::machine::CompileTimeMachine>>::init_fn_call
  10: rustc_const_eval::const_eval::eval_queries::eval_to_allocation_raw_provider
      [... omitted 1 frame ...]
  11: rustc_const_eval::const_eval::eval_queries::eval_to_const_value_raw_provider
      [... omitted 1 frame ...]
  12: rustc_hir_analysis::check_crate
  13: rustc_interface::passes::analysis
      [... omitted 1 frame ...]
  14: rustc_interface::passes::create_and_enter_global_ctxt::<core::option::Option<rustc_interface::queries::Linker>, rustc_driver_impl::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
  15: rustc_interface::interface::run_compiler::<(), rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 `/playground/rustc-ice-2025-07-21T12_22_43-25.txt` to your bug report

note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [eval_to_allocation_raw] const-evaluating + checking `X`
#1 [eval_to_const_value_raw] simplifying constant for the type system `X`
#2 [analysis] running analysis passes on this crate
end of query stack
error: could not compile `playground` (lib)