Unable to take same type in std::variant

Question

I'm using c++17, and would like to write the code something like this,

#include <variant>
typedef int NewInt;
int main() {
    std::variant<NewInt, int> n = 1;
}

But it emits compile error,

po.cpp: In function ‘int main()’:
po.cpp:5:35: error: conversion from ‘int’ to non-scalar type ‘std::variant<int, int>’ requested
     std::variant<NewInt, int> n = 1;
                               ^

How could I define the type like std::variant<NewInt, int> or is it impossible?

Answer 1

A type alias is just another name for an existing type, not a new type. So you have a variant of two ints. And while it's allowed, you must address the ambiguity explicitly. std::variant has a suitable constructor:

std::variant<NewInt, int> n{ std::in_place_index<0>, 1 };

The above will construct the first integer member (your NewInt). If you want to construct the second, it's the obvious:

std::variant<NewInt, int> n{ std::in_place_index<1>, 1 };