assigning members of a pair to variables

The C++17 already let you to use the Structured binding declaration syntax:

#include <iostream>

std::pair<bool, int> foo() {
    return std::make_pair(false, 3);
}

int main() {
    auto [y, x] = foo();               //Structured binding attribution
    std::cout << x << ',' << y << '\n';
}

Yes; std::tie was invented for this:

#include <tuple>
#include <iostream>

std::pair<bool, int> foo()
{
    return std::make_pair(false, 3);
}

int main()
{
    int x;
    bool y;

    std::tie(y, x) = foo();
    std::cout << x << ',' << y << '\n';
}

// Output: 3,0

(live demo)

Of course you are still going to have a temporary object somewhere (modulo constant optimisations), but this is the most direct you can write the code unless you initialise x and y directly from their eventual values rather than first creating a pair inside foo().