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#include <vector>
#include <unordered_set>
#include <algorithm>
#include <functional>
 
template<typename V, typename... Args>
void autoEmplace(V& vec, Args&& ...args)
{
	return autoEmplace(typename std::is_pod<
		typename V::value_type>::type(), vec,
		std::forward<Args>(args)...);
}
 
template<typename V, typename... Args>
void autoEmplace(std::true_type, V& vec, Args&& ...args)
{
	vec.push_back({std::forward<Args>(args)...});
}
 
template<typename V, typename... Args>
void autoEmplace(std::false_type, V& vec, Args&& ...args)
{
	vec.emplace_back(std::forward<Args>(args)...);
}
 
#include <iostream>
 
struct Foo {
	int i;
	short n;
};
 
struct Bars {
	int i;
	double n;
};
 
using Lol = std::unordered_set<int>;
 
int main() {
	Foo foo{42}; //fine
	std::vector<Foo> v;
	std::vector<Bars> b;
	std::vector<Lol> h;
	autoEmplace(v, 42);
	autoEmplace(b, 42, 3.14159265358979323);
	autoEmplace(h, 10, std::hash<int>(), std::equal_to<int>());
	std::cout << v.back().i << std::endl;
	std::cout << b.back().n << std::endl;
}

prog.cpp: In instantiation of 'void autoEmplace(V&, Args&& ...) [with V = std::vector<std::unordered_set<int> >; Args = {int, std::hash<int>, std::equal_to<int>}]':
prog.cpp:47:59:   required from here
prog.cpp:9:20: error: invalid initialization of non-const reference of type 'std::integral_constant<bool, false>&' from an rvalue of type 'std::integral_constant<bool, false>::type {aka std::integral_constant<bool, false>}'
  return autoEmplace(typename std::is_pod<
                    ^
prog.cpp:7:6: note:   initializing argument 1 of 'void autoEmplace(V&, Args&& ...) [with V = std::integral_constant<bool, false>; Args = {std::vector<std::unordered_set<int, std::hash<int>, std::equal_to<int>, std::allocator<int> >, std::allocator<std::unordered_set<int, std::hash<int>, std::equal_to<int>, std::allocator<int> > > >&, int, std::hash<int>, std::equal_to<int>}]'
 void autoEmplace(V& vec, Args&& ...args)
      ^
prog.cpp:11:30: error: return-statement with a value, in function returning 'void' [-fpermissive]
   std::forward<Args>(args)...);
                              ^

Standard output is empty