Copying structs with pointers

[Peter Alexander]

On 20/07/11 11:06 PM, Jonathan M Davis wrote:
> Postblit doesn't work with const or immutable right now:
> http://d.puremagic.com/issues/show_bug.cgi?id=4867

Is that the issue though? I believe it's a deeper issue.

An example:

struct Ptr
{
   int* p;
   this(int x) { p = new int; *p = x; }
   this(this) { /+ do nothing +/ } // (!!!)
   const int get() { return *p; }
   void set(int x) { *p = x; }
}

void main()
{
   const Ptr a = Ptr(1);
   Ptr b = a; // shallow copy! const removed!
   b.set(2);
   assert(a.get() == 1); // FAIL
}


If you allow this then it means that you can get a non-const pointer 
through a const object, which breaks the transitivity of const.