Function clip_to_plane_uninit_unchecked 

pub unsafe fn clip_to_plane_uninit_unchecked<Vertex: Copy, Plane: AttributedClipPlane<Vertex>>(
    source: &[Vertex],
    destination: &mut [MaybeUninit<Vertex>],
    plane: &Plane,
    traversal: ClipTraversal,
) -> usize

clip_to_plane_uninit without the bounds check on each write. The first returned-count entries of destination are initialised.

Safety

clip_to_plane_unchecked’s capacity contract.