unsafe fn copy_from_slice(v: &[T]) -> Rc<[T]> {
        unsafe {
            let ptr = Self::allocate_for_slice(v.len());
            ptr::copy_nonoverlapping(v.as_ptr(), &mut (*ptr).value as *mut [T] as *mut T, v.len());
            Self::from_ptr(ptr)
        }
    }
Drops the `Rc`.

This will decrement the strong reference count. If the strong reference
benchmarks/haystacks/code/rust-library.rs