different case of function reutrn value

func_reutrn_value.cc

#include <iostream>
using namespace std;

struct A
{
int a;
int b;
int c;
};

A func()
{
	A tmp;
	tmp.a = 1;
	tmp.b = 2;
	tmp.c = 3;
	return tmp;
}

int fun2()
{
	int i = 0;
	return i;
}

int main()
{

	A tmp;
	tmp.a = 4;
	tmp.b = 5;
	tmp.c = 6;
	cout << (func() = tmp).c << endl;

	//fun2() = 10; //Error lvalue required as left operand of assignment
}