BorshSerialize derive fails for structs with packed attribute about borsh-rs HOT 4 OPEN

#[derive(serde::Serialize)]
#[repr(packed)]
struct Bar {
    x: u8,
    y: u64,
}

#[derive(serde::Serialize)]
#[repr(packed)]
struct Foo {
    x: RefCell<u8>,
    y: u64,
}

use core::mem;
use core::ops::Deref;
use core::ptr;
use std::rc::Rc;

#[repr(packed)]
struct Foo {
    x: Rc<u8>,
    y: u64,
}

impl borsh::ser::BorshSerialize for Foo {
    fn serialize<W: borsh::io::Write>(
        &self,
        writer: &mut W,
    ) -> ::core::result::Result<(), borsh::io::Error> {
        borsh::BorshSerialize::serialize(
            mem::ManuallyDrop::new(unsafe { ptr::read_unaligned(ptr::addr_of!(self.x)) }).deref(),
            writer,
        )?;
        borsh::BorshSerialize::serialize(
            mem::ManuallyDrop::new(unsafe { ptr::read_unaligned(ptr::addr_of!(self.y)) }).deref(),
            writer,
        )?;
        Ok(())
    }
}

fn main() {
    let foo = Foo {
        x: Rc::new(42),
        y: 182,
    };
    println!("{:?}", borsh::to_vec(&foo).unwrap());
}