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 tangotests.marray2;

void main()
{
    int[][] ma = new int[][](2,4);
    assert(ma.length == 2);
    assert(ma[0].length == 4);
    assert(ma[1].length == 4);
    ma[0][3] = 32;
    ma[1][2] = 123;
    ma[0][0] = 55;
    assert(ma[0][3] == 32);
    assert(ma[1][2] == 123);
    assert(ma[0][0] == 55);
}