不完整类型错误(E0409、E0070、E0515）

在我的代码Main.cpp中，我有如下所示。我用tuple<int, int, int>遇到的问题我一直收到这三个错误

function "sPA" returns incomplete type "trie"、incomplete type is not allowed和cannot convert to incomplete class "trie"

我做错了什么才犯了这个错误？

// Main.cpp
#include <iostream>
#include <string>
using namespace std;
typedef pair<int, int> int_pair;
typedef tuple<int, int, int> trie;

int_pair sum_and_product(int a, int b) {
return int_pair(a + b, a * b);
}
trie sPA(int a, int b, int c) {
trie t{ a + b + c,a * b * c,((a + b + c) / 3) };
return t;
} 
void consuming_templates() {
int a = 2, b = 3, c = 4;
auto results = sum_and_product(a,b);
cout << "sum = " << results.first << "|product = " << results.second << endl;
auto r2 = sPA(a, b, c);
}
int main(int argc, char* argv[]) {
consuming_templates();
return 0;
}