[REG2.111] Indexing a *cast* AA yields no lvalue anymore

[kinke]

This works with v2.110.0, but fails to compile with v2.111.0-beta.1:

shared struct Queue
{
    int[int] map;
}

void main()
{
    auto queue = Queue();
    (cast(int[int]) queue.map)[1] = 2;
    assert(queue.map[1] == 2);
}

bug.d(9): Error: cannot modify expression `(cast(int[int])queue.map)[1]` because it is not an lvalue