error ‘stdfilesystem’ has not been declared

This error can occur when the standard library header file for the filesystem library is not included in your code. To fix this error, add the following line to the top of your code:

#include <filesystem>

If you are using an older version of C++, you may need to use the experimental filesystem library instead:

#include <experimental/filesystem>

Note that the experimental filesystem library is not available in all compilers and may have different functionality compared to the standard filesystem library.