Use of 'auto func(int)' before deduction of 'auto' in C++14

I have compiled following program in GCC using C++14.

#include <iostream>
using namespace std;

auto func(int i);

int main() 
{
    auto ret = func(5);
    return 0;
}

auto func(int i) 
{
  if (i == 1)
    return i;              
  else
    return func(i-1) + i;  
}

But, I get the following error.

In function 'int main()': 8:16: error: use of 'auto func(int)' before
deduction of 'auto'
 auto ret = func(5);

So, what am I missing here?