associative array: unexpected results after static initialization

[kdevel]

This program

```
void aa_stat(T, U) (T[U] aa)
{
    import std.stdio;
    writefln ("aa        : %s", aa);
    writefln ("aa.length : %d", aa.length);
    writefln ("aa.keys   : %s", aa.keys);
    writefln ("aa.values : %s", aa.values);
    foreach (k, v; aa)
       writeln (k, ": ", v);
}

void main ()
{
    string[int] aa = [
       0: "null",
       0: "eins"
    ];
    aa.aa_stat;
}
```

produces this output:

    aa        : [0:"eins", ]
    aa.length : 2
    aa.keys   : [0, 32767]
    aa.values : ["eins", ""]
    0: eins

I would have expected either a compile time or a runtime error or 
this result:

    aa        : [0:"eins"]
    aa.length : 1
    aa.keys   : [0]
    aa.values : ["eins"]
    0: eins

What's happening here?