Consequences of casting away immutable from pointers

[jmh530]

I'm trying to understand the consequences of casting away 
immutable from a pointer. The code below has some weird things 
going on like the pointers still point to the correct address but 
when you dereference them they don't point to the correct value 
anymore.

Should I just assume this is undefined behavior and not bother 
with it? Or is there a use case for this?


void main()
{
     immutable(int) x = 5;
     auto p_x = &x;
     int* p_x_alt = cast(int*)p_x;
     (*p_x_alt)++;

     //addresses remain unchanged
     assert(&x == p_x);
     assert(p_x == p_x_alt);

     assert(*p_x_alt == 6);
     assert(*p_x == *p_x_alt); //but p_x and p_x_alt point to same 
value
     assert(x != *p_x); //yet that is not the case for x
     assert(x == 5); //which still is 5
}