pub fn new_zeroed() -> Arc<mem::MaybeUninit<T>> {
        unsafe {
            Arc::from_ptr(Arc::allocate_for_layout(
                Layout::new::<T>(),
                |layout| Global.allocate_zeroed(layout),
                |mem| mem as *mut ArcInner<mem::MaybeUninit<T>>,
            ))
        }
    }
Constructs a new `Arc` with uninitialized contents, with the memory
being filled with `0` bytes, returning an error if allocation fails.

See [`MaybeUninit::zeroed`][zeroed] for examples of correct and incorrect usage
of this method.
benchmarks/haystacks/code/rust-library.rs