https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100583
--- Comment #4 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> --- As pointed out in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103118#c3: > What works is including them in a non-module unit translation unit. > > ```C++ > #if defined(__GNUC__) and not defined(__clang__) > # include <chrono> // Workaround GCC bug 103118. > # include <span> // Workaround GCC bug 100583. > #endif > import waarudo.geometries; > import waarudo.numbers; > import waarudo.quantities; > #include <cassert> > ```