Fix unsound aliasing into Box<[T]> when converting them into NumPy arrays

[adamreichold]

No description provided.

[adamreichold]

I would like to ignore the coverage failure here as we do have a doctest for the offending method, it is just that doctests are currently not supported by cargo-llvm-cov and thereby not counted against our coverage. Duplicating the test into a unit or integration test just to increase the patch coverage seems like a maintainability loss to me.

[mejrs]

Thanks, you're quick 👍 We're still taking pointers and then moving vecs/arrays, but that should be fine, because those aren't noalias. :)

[adamreichold]

We're still taking pointers and then moving vecs/arrays, but that should be fine, because those aren't noalias. :)

I considered doing the same change for Vec and Array for consistency, but the problem is that the pointer owning the allocating is not necessarily equals the pointer to the first element for arrays, so deriving the pointer from PySliceContainer does not work for Array (which is backed by Vec) that easily. Hence, I decided for the minimum required change.