#include <iostream>
#include <set>
#include <string>
#include <vector>
using namespace std;
 
template<typename T>
void check_emplace_back(T& t, ...) {
	cout << "T does not have emplace_back()" << endl;
}
 
template<typename T>
auto check_emplace_back(T& t, int)
		-> decltype((void)t.emplace_back()) {
	cout << "T does have emplace_back()!" << endl;
	t.emplace_back();
}
 
 
int main() {
	double d{};
	check_emplace_back(d, 0);
 
	set<string> ss{};
	check_emplace_back(ss, 0);
 
	vector<int> vi{};
	check_emplace_back(vi, 0);
 
	return 0;
}

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