Standard Library Modules: bogus error C2504: 'std::filesystem::_Dir_enum_impl': base class undefined

[StephanTLavavej]

On Discord, @davidhunter22 provided the following test case which is very similar to #3330, but which isn't helped by @fsb4000's workaround #3331:

D:\GitHub\STL\out\x64>type woof.cpp

import std;

int main() {
    std::filesystem::directory_iterator x{"."};
}

D:\GitHub\STL\out\x64>cl /EHsc /nologo /W4 /std:c++latest /MTd /Od out\modules\std.ixx woof.cpp /Fewoof.exe
std.ixx
woof.cpp
woof.cpp(5): error C2504: 'std::filesystem::_Dir_enum_impl': base class undefined
Generating Code...

I was unable to work around this by adding _EXPORT_STD and/or extern "C++", so it appears that we need to report an additional compiler bug beyond DevCom-10247495.

[StephanTLavavej]

Reported internally as VSO-1715231 "Standard Library Modules: Bogus error C2504: 'std::filesystem::_Dir_enum_impl': base class undefined".

[huangqinjin]

I also reported C2504 long time ago in DevCom-10091963. No idea if they are same issue.

[StephanTLavavej]

This compiler bug has been fixed for VS 2022 17.6 Preview 2. 🎉

[ChemistAion]

It still appears for std::filesystem::is_empty(...)

Microsoft Visual Studio Community 2022
Version 17.5.0 Preview 6.0

[fsb4000]

@ChemistAion

17.6 Preview 2 > 17.5 Preview 6

17.6 Preview 2 has not been released yet

[ChemistAion]

@fsb4000: yep, I get it... that part I am missing here with these :hooray: reacts (yours included) - so we are celebrating fix of a regression bug in std::filesystem in VS that is not available yet? ;)

[fsb4000]

Yeah, we like emojis and celebrating anything 😺 🎉

[ChemistAion]

ack, I joined 🐰