Returning a reference == int(int (*)()) ??

[manasij7479]

I have a member function:

        T& at(int n)
        {
            return coeff.at(n);
        }

where coeff is a std::vector<T>

When I attempt to use the returned value in a multiplication with another T instantiated to integers, I get the following error:

polynomial.hpp:76:4: error: invalid operands of types ‘int(int (*)())’ and ‘int’ to binary ‘operator*’

Here is the complete code:
polynomial.hpp

#ifndef MM_POLY
#define MM_POLY
#include<vector>
#include<string>
#include<sstream>
#include<initializer_list>
#include<stdexcept>
namespace mm
{
    
    template<typename T=double>
    class Polynomial
    {
    public:
        Polynomial(std::initializer_list<T> dat)
        {
            for(auto x:dat)
                coeff.push_back(x);
        }
        Polynomial(int n)
        {
            coeff.reserve(n+1);
        }
        std::string str(std::string var) const
        {
            std::ostringstream os;
            for(uint i=0;i<coeff.size()-1;++i)
                os<<coeff[i]<<"*"<<var<<"^"<<i<<" + ";
            os<<coeff[coeff.size()-1]<<"*"<<var<<"^"<<coeff.size()-1;
            return os.str();
        }
        T eval(T t) const
        {
            T result = T(0);
            T mul = T(1); 
            for(int i=0;i<=degree();++i,mul*=t)
                result+=mul*coeff[i];
            return result;
        }
        
        
        int degree() const
        {
            return coeff.size()-1;
        }
        T& at(int n)
        {
            return coeff.at(n);
        }
    private:
        std::vector<T> coeff;
    };
    
    template
    <
    typename T
    >
    std::pair
    <
    Polynomial<T>
    ,T
    >
    SyntheticDivision(Polynomial<T> dividend,Polynomial<T> divisor)
    {
        int qdeg = dividend.degree()-1;
        Polynomial<T> quotient(qdeg);
        T remainder(T());
        if(divisor.degree()!=1)
            throw(std::logic_error("SyntheticDivision:Divisor.Degree !=1"));
        

        T h=- divisor.at(0)/divisor.at(1);

        for(int i=qdeg;i>=0;--i)
        {
            remainder = dividend.at(i+1) + remainder*h;
            quotient.at(i)=remainder;
        }
        
        return std::pair<Polynomial<T>,T>(quotient,remainder);
    }
}

#endif

Similar errors are reported at lines 76,77 and 80.
main.cpp

#include "polynomial.hpp"
#include<iostream>
int main()
{
    mm::Polynomial<int> dn({2,-3,1}),dv({-1,1});
    auto result = mm::SyntheticDivision<int>(dn,dv);
    std::cout<<result.first.str("x");
}

I couldn't produce the problem with a simpler example:

template<typename T>
class Foo
{
public:
    Foo(T t):foo(t){};
    T& val()
    {
        return foo;
    }
private:
    T foo;
};
int main()
{
    Foo<int> bar(6);
    int xip = 5;
    int bas  = xip * bar.val();
}