Little quiz

[bearophile]

A little quiz for people here: guess the output of this little D2 program (it 
compiles correctly and doesn't crash at run time, so it's a fair question):


import std.typecons: tuple;
import std.c.stdio: printf;

auto foo() {
    printf("foo\n");
    return tuple(1, 2);
}

void main() {
    foreach (x; foo().tupleof)
        printf("%d\n", x);
}


Bye,
bearophile