Code shared from the Rust Playground

playground.rs

#[derive(Debug)]
#[repr(C)]
struct MyStruct<T, U> {
    height: Option<T>,
    width: Option<T>,
    age: u32,
    othertype: U,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut value: MyStruct<i32, u8> = MyStruct {
        height: Some(22003),
        width: None,
        age: 100,
        othertype: 25u8,
    };

    println!("value == {:#?}", value);

    let value_bytes =
        unsafe { &mut *(&mut value as *mut MyStruct<i32, u8> as *mut [u8; std::mem::size_of::<MyStruct<i32, u8>>()]) };

    println!("value_bytes = {:?}", value_bytes);

    let value_reconstructed = 
        unsafe { &mut *(value_bytes as *mut [u8; std::mem::size_of::<MyStruct<i32, u8>>()] as *mut MyStruct<i32, u8>) };

    println!("value_reconstructed == {:#?}", value_reconstructed);

    println!("Modify value_reconstructed");
    value_reconstructed.height = None;
    value_reconstructed.age = 101;
    value_reconstructed.width = Some(35);

    println!("value_reconstructed == {:#?}", value_reconstructed);

    println!("value == {:#?}", value);
    
    println!("value_bytes = {:?}", value_bytes);

    Ok(())
}