VisualStudio is unable to compile mathplot

[sebsjames]

VisualStudio (both the "Windows 2022" github runner version and the "Windows 2025" github runner version) chokes on some code that I believe to be valid C++.

The file is VisualOwnable.cppm and the error message is:

D:\a\mathplot\mathplot\mplot\VisualOwnable.cppm(1067,27): error C2079: 'fout' uses undefined class 'std::basic_ofstream<char,std::char_traits<char>>' [D:\a\mathplot\mathplot\build\examples\anneal_asa.vcxproj]
  (compiling source file '../../examples/anneal_asa.cpp')
      D:\a\mathplot\mathplot\mplot\VisualOwnable.cppm(1067,27):
      the template instantiation context (the oldest one first) is
          D:\a\mathplot\mathplot\examples\anneal_asa.cpp(101,21):
          see reference to class template instantiation 'mplot::Visual<262145>' being compiled
          D:\a\mathplot\mathplot\mplot\Visual.cppm(59,34):
          see reference to class template instantiation 'mplot::VisualOwnable<262145>' being compiled
          D:\a\mathplot\mathplot\mplot\VisualOwnable.cppm(1065,22):
          while compiling class template member function 'void mplot::VisualOwnable<262145>::savegltf(const std::string &)'

I've yet to try to make a report on this to Microsoft.

[sebsjames]

I think this issue may be a similar problem; I added to it:

https://developercommunity.microsoft.com/t/MSVC-1452-regression:-C2079-in-std::get/11092704