struct First {
    uint type = 0;
    int data;

    this( int d ) {
        data = d;
    }
}

struct Second {
    uint type = 1;
    double data;

    this( double d ) {
        data = d;
    }
}

First returnFirst( int data ) {
    return First( data );
}

Second returnSecond( double data ) {
    return Second( data );
}

void printAny( uint * type ) {
    if( *type == 0 ) {
        writeln( (cast(First *)type).data );
    } else if( *type == 1 ) {
        writeln( (cast(Second *)type).data );
    } else {
        writeln( "Error" );
    }
}

int main() {

    printAny( &returnFirst( 42 ).type );
    printAny( &returnSecond( 3.14 ).type );

    return 0;
}