pub(crate) unsafe fn box_free<T: ?Sized, A: Allocator>(ptr: Unique<T>, alloc: A) {
    unsafe {
        let size = size_of_val(ptr.as_ref());
        let align = min_align_of_val(ptr.as_ref());
        let layout = Layout::from_size_align_unchecked(size, align);
        alloc.deallocate(ptr.cast().into(), layout)
    }
}
Specialize clones into pre-allocated, uninitialized memory.
Used by `Box::clone` and `R
benchmarks/haystacks/code/rust-library.rs