Is it a missed optimization, when a compile-time known reference takes space in a non-aggregate struct?

Question

Note: this is a follow-up question to: Is it a missed optimization, when a compile-time known reference takes space in a struct?, which showed that aggregate initialization

Answer 1

In the following example y.b refers to x.a.

int main ()
{
    Foo     x;
    Foo     y(x);

    return 0;
}