how to resolve c build error: 'declaration of anonymous class must be a definition' [closed]

Getting the following error when running make using c++11 on a mac m1:

./Continuous.h:623:1: error: declaration of anonymous class must be a definition
class LTI_ODE  
^

the code snippet is:

class LTI_ODE
{
protected:
    iMatrix A;
    iMatrix B;
    iMatrix C;
    iMatrix constant;

    bMatrix connectivity;

    std::vector<Interval> dist_range;

public:
    LTI_ODE(iMatrix & A_input, iMatrix & B_input, iMatrix & C_input, iMatrix & constant_input, const std::vector<Interval> & dist_range_input);
    ~LTI_ODE();

    void one_step_trans(iMatrix & Phi, iMatrix & Psi, iMatrix & trans_constant, Zonotope & dist, const double step, const int order);
};

I don't think it's an anonymous class, hence, I don't know how to fix it?