Clean up some suspicious code. There's no guarantee a constant of integer type is a ConstantInt, so it's not safe to just cast<> these to ConstantInt. (It could be a constant expression, for example) The code is shorter this way too :).

module aa5;

void main()
{
    int[int] aa;
    aa[42] = 1;
    int i = aa[42];
    assert(i == 1);
}