Thread: I thought overloading on return type isn't allowed !

I thought overloading on return type *wasn't allowed.. but apparently something changes when templates are involved.

Consider the following code:

Code:

#include <termios.h>
#include <unistd.h>
#include <functional>
#include <string>
#include <utility>
#include <iostream>

class NonCanInput
{
public:
    template <typename F>
    typename std::result_of<F()>::type
    operator()(F arbitrary)
    {
        TurnOn t;
        return arbitrary();
    }
    
    int operator()(std::function<int(void)> arbitrary= [](){return std::cin.get();} )
    {
        TurnOn t;
        return arbitrary();
    }
    //overload >> if required
private:
    class TurnOn
    {
    public:
        TurnOn()
        {
            tcgetattr( STDIN_FILENO, &oldt );
            newt = oldt;
            newt.c_lflag &= ~( ICANON | ECHO );
            tcsetattr( STDIN_FILENO, TCSANOW, &newt );
        }
        ~TurnOn()
        {
            tcsetattr( STDIN_FILENO, TCSANOW, &oldt );
        }
    private:
        struct termios oldt, newt;
        
    };
};

The above code works fine.
I thought a template<> would be needed at the bolded part, but that shows an error called "explicit specialization in non-namespace scope".
Removing the 'template <>' works fine....and I am not not sure why (as I intended that to be a specialzation of the above) .
Any explanation?