Is this a desing rationale? (static array object member)

[Brian Hsu]

I posted a similar post at D.learn newsgroup and got a explanation about this. But I have a question after got that answer: is this reasonable? 

Here is my code:

class Test
{
    int [] z = [1,1,1,1,1];
    void addByOne () { //Increase all elements in x by 1}
}

void fun1 (int y)
{
    int [] x = [1,1,1,1,1];
    foreach (int i, int v; x ) {
        x[i] = x[i]+y;
    }
}

void fun2 ()
{
    int [] y = [1,1,1,1,1];

    foreach (int i, int v; y ) {
        Stdout.format ("{} ", v);
    }

    Stdout.newline;
}

void main ()
{
    Test a = new Test();
    Test b = new Test();
    a.addByOne(); 
    // Now b.z will be [2,2,2,2,2]
    
    fun1(3);
    fun2(); // Still print [1,1,1,1,1]
}

So a.z and b.z pointed to same array, but int [] y and int [] z are still different array instance.

Regan mentioned that this is because the array literal [1,1,1,1,1] create only one instance of array*, so at first time I suspect that when compiler see [1,1,1,1,1], it would translate that to a fixed memory address of something like that. 

* http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.learn&article_id=9580

But it clearly that int [] x and int [] y is still a different array instance even they have same array literal initialization.  

So, after all, when is a.z and b.z point to same array instance exactly? Since I believe it should be runtime, not compile time to do initialization of object member, then why a.z and b.z is same array instance but int [] x and int [] y is different array instance? 

Finally, is this behavior reasonable? Since I didn't declare that int [] as a static class member, even though they have same initialization array literal, but I would expect that a.z/b.z they should be different array have same content. (As in Java or C++)

Or is there special reasons of this strange behaver?