Make == for associative arrays test for equality, not identity. _aaEq was added to runtime/internal/aaA.d which forwards to TypeInfo_AssociativeArray.equals in genobj.d. On the codegen side, DtoAAEquals was added to gen/aa.cpp and is called from EqualExp::toElem in gen/toir.cpp. I assume that the frontend will produce an error if == is used on associative arrays of different type. This fixes DMD bug 1429.

module multiarr1;

void main()
{
    int[16][16] a;
    assert(a[0][0] == 0);
    assert(a[0][1] == 0);
    assert(a[0][2] == 0);
    assert(a[0][3] == 0);
    assert(a[10][13] == 0);
    assert(a[15][15] == 0);
    a[10][13] = 42;
    assert(a[0][0] == 0);
    assert(a[10][13] == 42);
    assert(a[15][15] == 0);
    {
        int* l = cast(int*)a;
        l += 10*16+13;
        assert(*l == 42);
    }
}