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 memory1;

extern(C) int printf(char*,...);

void main()
{
    auto a = new int[16];
    {printf("array.length = %u\n", a.length);}
    {a.length = a.length + 1;}
    {printf("array.length = %u\n", a.length);}
    {assert(a.length == 17);}
}