Steps to reproduce the bug:
- First open a VS developer shell using Visual Studio Version 17.5.0 Preview 6.0
- Compile first with
cl /nologo /std:c++latest /EHsc main.cpp
compilation should succeed. - Compile again with
cl /nologo /std:c++latest /EHsc /DMODULES mod.ixx main.cpp
you will now see an error like
C:\Users\anon\dev\TestInclude.h(13): error C2079: 'storage<Object>::value' uses undefined class 'Object'
main.cpp(8): note: see reference to class template instantiation 'storage<Object>' being compiled