ICE in Miri: "primitive read failed for type", due to reading a Boxed slice with an allocator?

[saethlin]

Unclear if this is a Miri issue or a rustc issue, but it looks to me like the issue is squarely in the CTFE code so I'm reporting it here.

I'm trying to improve on the experimental PR to use Box to implement Vec: #96607 and I'm using miri-test-libstd to see how things are going. I've gotten all the way to running tests, but I immediately ran into an ICE:

     Running unittests ../liballoc/src/lib.rs (/home/ben/miri-test-libstd/target/miri/x86_64-unknown-linux-gnu/debug/deps/alloc_miri_test-1f894794e44196e9)

running 308 tests
test alloc::tests::alloc_owned_small ... ignored
test alloc::tests::allocate_zeroed ... ok
test box_storage::tests::allocator_param ... error: internal compiler error: /rustc/18b53cefdf7456bf68937b08e377b7e622a115c2/compiler/rustc_const_eval/src/interpret/operand.rs:328:13: primitive read failed for type: std::boxed::Box<[core::mem::MaybeUninit<u8>], box_storage::tests::allocator_param::BoundedAlloc>
    --> /home/ben/rust/library/alloc/src/boxed.rs:1007:9
     |
1007 |         Box(unsafe { Unique::new_unchecked(raw) }, alloc)
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/18b53cefdf7456bf68937b08e377b7e622a115c2/compiler/rustc_errors/src/lib.rs:1253:9
...

This can be reproduced by running miri-test-libstd on #96607. (the PR is very hacked-up right now)

There have been issues along this code path before, but none of them seem relevant to this particular situation?

cc @oli-obk @RalfJung

[oli-obk]

Possibly related to nonzst allocators ICEs everywhere?

May get fixed by #95576

[beepster4096]

@rustbot claim

[RalfJung]

Yeah, can you find out what the allocator type is there?
Sounds like a duplicate of #95453.

[RalfJung]

Closing as duplicate of #95453.