Dealing with the interior pointers bug

[ag0aep6g via Digitalmars-d-learn]

On 06/22/2017 08:38 PM, Boris-Barboris wrote:
> Casts are part of the type system. Yes, D type system allows invalid 
> operations. It's not the compiler's fault, it's type system's fault.
> 
> unittest
> {
>      immutable int a = 4;
>      int* b = cast(int*) &a;
>      *b = 5;
>      assert(*(&a) == 5);
>      assert(a == 4);
> }

This is just arguing semantics, of course, but I wouldn't say that the 
type system allows this specific invalid operation. Rather, with casting 
you can step out of the type system, and break its guarantees.

Point is, you need a way to say that the operation is invalid. It's 
invalid because it breaks what `immutable` promises. `immutable` is part 
of the type, so I'd say the guarantee is part of the type system.