CppQuiz.org - Question #117

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Question #117 Difficulty:

According to the C++23 standard, what is the output of this program?

    #include <iostream>

template <template <typename> class>
struct X {
  X() { std::cout << "1"; }
};

template <typename>
struct Y {};

template <typename T>
using Z = Y<T>;

template <>
struct X<Y> {
  X() { std::cout << "2"; }
};

int main() {
  X<Y> x1;
  X<Z> x2;
}

Hint:

Is a template alias a new family of types?

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