MSVC 19.x is not working

The mdspan library doesn't compile when using it in Visual Studio 2022 and MSVC 19.35.

With the following cMake and example source results in a compilation error:

CMakeLists.txt.

cmake_minimum_required(VERSION 3.13 FATAL_ERROR)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED Yes)

project(mdspanTest
	VERSION 0.0.1
)

set(MDSPAN_CXX_STANDARD ${CMAKE_CXX_STANDARD} CACHE INTERNAL "Use CMAKE_CXX_STANDARD .")
include(FetchContent)
FetchContent_Declare(mdspan
	GIT_REPOSITORY https://github.com/kokkos/mdspan.git
	GIT_TAG mdspan-0.6.0
)
FetchContent_GetProperties(mdspan)
if(NOT mdspan_POPULATED)
	FetchContent_Populate(mdspan)
	add_subdirectory(${mdspan_SOURCE_DIR} ${mdspan_BINARY_DIR} EXCLUDE_FROM_ALL)
endif()

add_executable(${PROJECT_NAME}
  main.cpp
)

target_link_libraries(${PROJECT_NAME} 
	std::mdspan
)

main.cpp

#include <cstddef>
#include <iostream>
#include <experimental/mdspan>
#include <vector>

int main()
{
    std::vector v{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
    auto ms2 = std::experimental::mdspan(v.data(), 2, 6);
}

Error

  [1/2] Building CXX object CMakeFiles\mdspanTest.dir\main.cpp.obj
  FAILED: CMakeFiles/mdspanTest.dir/main.cpp.obj 
  C:\PROGRA~1\MIB055~1\2022\COMMUN~1\VC\Tools\MSVC\1435~1.322\bin\Hostx64\x64\cl.exe  /nologo /TP  -IC:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include /DWIN32 /D_WINDOWS /W3 /GR /EHsc /MDd /Zi /Ob0 /Od /RTC1 -std:c++17 /showIncludes /FoCMakeFiles\mdspanTest.dir\main.cpp.obj /FdCMakeFiles\mdspanTest.dir\ /FS -c C:\Projects\Mdspan_Test\main.cpp
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(375): warning C4346: 'Extents::rank': dependent name is not a type
  C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(375): note: prefix with 'typename' to indicate a type
  C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(475): note: see reference to class template instantiation 'std::experimental::layout_stride::mapping<Extents>' being compiled
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(375): error C2059: syntax error: '...'
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(382): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(382): error C2062: type 'unknown-type' unexpected
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(384): error C2334: unexpected token(s) preceding '{'; skipping apparent function body
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(395): error C2270: 'is_exhaustive': modifiers not allowed on nonmember functions
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_stride.hpp(406): error C2270: 'stride': modifiers not allowed on nonmember functions
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(159): warning C4346: 'std::experimental::layout_right::mapping<Extents>::std::experimental::layout_right::mapping<Extents>::extents_type::rank': dependent name is not a type
  C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(159): note: prefix with 'typename' to indicate a type
  C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(220): note: see reference to class template instantiation 'std::experimental::layout_right::mapping<Extents>' being compiled
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(159): error C2059: syntax error: '...'
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(168): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(168): error C2062: type 'unknown-type' unexpected
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(170): error C2334: unexpected token(s) preceding '{'; skipping apparent function body
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(177): error C2270: 'is_unique': modifiers not allowed on nonmember functions
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(178): error C2270: 'is_exhaustive': modifiers not allowed on nonmember functions
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(179): error C2270: 'is_strided': modifiers not allowed on nonmember functions
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\layout_right.hpp(186): error C2270: 'stride': modifiers not allowed on nonmember functions
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\mdspan.hpp(110): error C2059: syntax error: '...'
  C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits/mdspan.hpp(372): note: see reference to class template instantiation 'std::experimental::mdspan<ElementType,Extents,LayoutPolicy,AccessorPolicy>' being compiled
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\mdspan.hpp(119): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\mdspan.hpp(119): error C2062: type 'unknown-type' unexpected
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\mdspan.hpp(123): error C2334: unexpected token(s) preceding ':'; skipping apparent function body
C:\Projects\Mdspan_Test\out\build\x64-Debug\_deps\mdspan-src\include\experimental\__p0009_bits\mdspan.hpp(26): fatal error C1075: '{': no matching token found
  ninja: build stopped: subcommand failed.

Or here in the online demo: https://godbolt.org/z/W9bhGxzqf

Any idea where the error is from? And how it can be fixed?

Thanks,
Silvan

Reproduce the failure with the provided CMakeLists.txt and main.cpp using Visual Studio 2022 with MSVC 19.35. Start with include/experimental/__p0009_bits/layout_stride.hpp, layout_right.hpp, and mdspan.hpp, then compare the compiler diagnostics with the Godbolt example. Done means the example compiles successfully with the reported MSVC version.