#include <linalg> causes compiler error in VS2022

Putting

#include <linalg>

in a source file in Visual Studio 2022, using the VS compiler, results in a compiler error. There is no error when I switch to the LLVM Platform Toolset in my project settings, however.

Details and repro follow:

My VS project name is lin_alg_examples (VS creates a directory of the same name). Under this directory, I created the following subdirectory:

...lin_alg_examples\kokkos\experimental

Under experimental, I placed the mdspan and linalg header files, and the __p0009_bits and __p1673_bits directories:

In the project settings, I am using the VS compiler with the latest C++ working draft:

I then write an empty main() function:

#include <experimental/mdspan>
#include <experimental/linalg>
#include <vector>#include <cstdlib>
#include <iostream>#include <format>
using std::vector, std::size_t, std::cout, std::format;
namespace stdex = std::experimental;
int main()
{

}

When I build the project, I get the following compiler error messages:

\lin_alg_examples\kokkos\experimental\__p1673_bits\transposed.hpp(255,57): error C2653: 'original_mapping_type': is not a class or namespace name

\lin_alg_examples\kokkos\experimental\__p1673_bits\transposed.hpp(253,17): message : This diagnostic occurred in the compiler generated function 'auto std::experimental::__p1673_version_0::linalg::impl::transposed_layout<std::experimental::layout_stride>::mapping(const std::experimental::layout_stride::mapping<Extents> &)'

It identifies lines 253 and 255 in transposed.hpp; lines 252-255 are as follows:

    template<class OriginalExtents>
    static auto mapping(const typename layout_stride::template mapping<OriginalExtents>& orig_map) {
      using original_mapping_type = typename layout_stride::template mapping<OriginalExtents>;
      using extents_type = transpose_extents_t<typename original_mapping_type::extents_type>;

I tried inserting the "ugly hack" referenced in Issue #242, but this did not fix the problem, even though it seemed it might be related.

If I comment out #include <experimental/linalg>, however, the project builds successfully.

Furthermore, if I restore the file so that the linalg file is included again, and I change the compiler Platform Toolset to the LLVM setting:

the code will compile successfully.

One final remark is that the exact same behavior is seen after changing the C++ Language Standard setting to C++20:

Reproduce the issue with the provided empty main and the MSVC Platform Toolset, comparing it with the LLVM toolset and the C++20 setting. Start in kokkos/experimental/__p1673_bits/transposed.hpp around lines 252-255, where original_mapping_type is used, and compare the behavior when experimental/linalg is included. Done means the example builds with the VS compiler without breaking the reported LLVM case.