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 classes10;

class C
{
    int i;
    override char[] toString()
    {
        return "foobar";
    }
}

void main()
{
    Object o = new C;
    char[] s = o.toString();
    assert(s == "foobar");
}