return &items[pos].id; ^~~ ../include/bits/list.hpp: In member function 'T& bits::flat_list<T>::iterator::operator*() const': ../include/bits/list.hpp:324:26: error: 'pos' was not declared in this scope return items[pos].id; ^~~ [3/6] Building CXX object CMakeFiles/test_parameter.dir/test/parameter.cpp.o ninja: build stopped: subcommand failed. ERROR: Job failed: exit code 1