How to use DataOwned::MaybeUninit ?

[cassiersg]

I am trying to migrate ndarray-linalg away from the use of ArrayBase::uninitialized to ArrayBase::uninit. I do not see how to do the conversion in the following case (simplified from ndarray_linalg::convert::clone_with_layout:

fn foo<A, Si, So>(a: &ArrayBase<Si, Ix2>) -> ArrayBase<So, Ix2>
where
    A: Copy,
    Si: Data<Elem = A>,
    So: DataOwned<Elem = A> + DataMut,
{
    let layout: (usize, usize) = (1, 1); // simplified from the original
    let mut b = ArrayBase::uninitialized(layout);
    b.assign(a);
    b
}

My best attempt is:

fn foo<A, Si, So>(l: MatrixLayout, a: &ArrayBase<Si, Ix2>) -> ArrayBase<So, Ix2>
where
    A: Copy,
    Si: Data<Elem = A>,
    So: DataOwned<Elem = A> + DataMut,
{
    let layout: (usize, usize) = (1, 1); // simplified from the original
    let mut b: ArrayBase<<So as DataOwned>::MaybeUninit, Ix2> =  ArrayBase::uninit(layout);
    a.assign_to(&mut);
    unsafe { b.assume_init() }
}

which does not work because the storage for b does not impl DataMut.

Is the use of DataOwned::MaybeUninit::uninit the way to go ? Then how can I initialize it, since it doesn't implement DataMut ?

[bluss]

Threre is an internal way to do that (see build_uninit in the source) - but it's not quite ready for public consumption - needs to use an ArrayViewMut instead. At the moment there is no clean (it's possible with extra bounds) way to do this generically for all owned arrays.

In other words, it should currently be good enough for using specific owned arrays directly but maybe the build_uninit method needs exposing for generic methods.