Function build_slice_type_di_node 

fn build_slice_type_di_node<'ll, 'tcx>(
    cx: &GenericCx<'ll, FullCx<'ll, 'tcx>>,
    slice_type: Ty<'tcx>,
    unique_type_id: UniqueTypeId<'tcx>,
    span: Span,
) -> DINodeCreationResult<'ll>

Create debuginfo for [T] and str. These are unsized.