Why can't I use aggrigate/uniform initialisation when assigning the new value into a std::map? [duplicate]

This question already has an answer here:

• Initializer list not working with vector in Visual Studio 2012? [duplicate] 1 answer

following on from my last question: here

I have:

struct test
{
    int a;
    int b;
    std::string str;
};

int main()
{   
    std::map<int, test> test_map;
    test t1 = {1, 2, "hello"};
    test_map[0] = t1;    
    return 0;
}

This works ok, but I don't really want to create a variable just to insert into the map.

Can I use uniform/aggregate initialisation to help me here, something like this:

int main()
{   
    std::map<int, test> test_map;
    test_map[0] = {1, 2, "hello"};    
    return 0;
}