Fix return type of layout_padded operator

[Quntized]

I was testing layout_padded while doing in layout_padded indices operator -> The return type was size_t but in compute_offset is returned by as index_type .

    using extint32 = MDSPAN_IMPL_STANDARD_NAMESPACE::extents<int, 2, 3, 4>;
    using layout_left = Kokkos::Experimental::layout_left_padded<16>::mapping<extint32>;
    layout_left l1(extint32{});
    static_assert(std::is_same_v<decltype(l1(0,0,0)),extint32::index_type>," not int");

->

/home/sajid/kokkos_internal/kokkos_tree/mdspan/kokkos_extent_inv.hpp(78): error: static assertion failed with " not int"
      static_assert(std::is_same_v<decltype(l1(0,0,0)),extint32::index_type>," not int");
      ^

[Quntized]

I checked P2642R6 (the standard proposal this implementation follows), and it explicitly specifies constexpr size_t operator()(...) for the padded layouts, unlike the general LayoutMapping requirement of returning index_type. My test's premise was wrong. Closing this .

[mhoemmen]

C++26 specifies the return type as index_type. See e.g., the layout_left_padded::mapping class synopsis and the paragraphs that describe its call operator.

[mhoemmen]

Thanks for the fix!

[Quntized]

Thanks for the reference. I had been checking an older draft of the proposal.
Sorry for that.