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Structured binding: referencing an existing variable

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I was cleaning up some code and getting rid of an obscure in-out 
reference parameter by replacing it by a tuple return. E.g. with a 
simplified example, instead of former

A foo(int& pos_in_out);

we now have

std::pair<A, int> foo(int pos_in);

where the updated pos is returned explicitly.

Now how do I capture these results when calling it? In the old call it was:

int pos = 0;
while(pos < N) {
    A a = foo(pos);
    // ...
}

How should I replace it? The thing is A does not have a default ctor and 
should be created afresh each time when foo is called, while pos should 
be updated instead.

std::tie(a, pos) = foo(pos);  // Does not work for A as it cannot be 
pre-constructed.

An alternative is to use C++17 structured binding:

auto [a, pos] = foo(pos); // Does not work for pos as it creates a new 
variable, instead of updating the old one.

In short, I would want to use structured binding for A and effectively 
std::tie() for the other member. Is that somehow possible?

For now I resorted to:

auto [a, newPos] = foo(pos);
pos = newPos;

but this introduces an unneeded extra variable and does not look like so 
great improvement over the old code.

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Structured binding: referencing an existing variable Paavo Helde <eesnimi@osa.pri.ee> - 2022-02-16 08:46 +0200
  Re: Structured binding: referencing an existing variable Manfred <noname@add.invalid> - 2022-02-16 21:43 +0100
  Re: Structured binding: referencing an existing variable Vir Campestris <vir.campestris@invalid.invalid> - 2022-02-16 22:00 +0000
    Re: Structured binding: referencing an existing variable Paavo Helde <eesnimi@osa.pri.ee> - 2022-02-17 16:00 +0200

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