Problem with template (unresolved overloaded function type)

Question

The following code fail to compile because function g but I don't know why.

template <int N>
struct  A{
    template <int n>
    int f() {return n;}
};

template <int N>
int g(A<N>& a)
{
    return a.f<10>();
}

int main()
{
   A<1> a;
   g(a);
}

You can compile it in: https://godbolt.org/z/sysQwj

The error is

error: expected primary-expression before ')' token return a.f<10>();

In instantiation of 'int g(A<N>&) [with int N = 1]':

error: invalid operands of types '<unresolved overloaded function type>' 
and 'int' to binary 'operator<': return a.f<10>();