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 bug59;

void main()
{
    int[2] a = 0;
    //func(a);
    a[0] = 1;
    int i = a[0];
    int* p = &a[0];
}

void func(int[2] a)
{
    int* p = cast(int*)a;
}

void func2(int[4] a)
{
    int* p = 3+cast(int*)a;
}