Workarounds for Lack of Mutable Keyword

[Craig Black]

I did it and it was very easy.  I didn't know you could cast away const so 
easily in D.  This works for const, but not invariant.  Since we have the 
ability to subvert const so easily, there should be no problem living 
without mutable fields.

import std.stdio;

void ConstAssign(T)(ref const T x, T y) { *cast(T*)&x = y; }

class A
{
public:
  int x;
  int y;
  void setY(int ny) const { ConstAssign(y, ny); }
}

void foo(const A a) { a.setY(2); }

int main(char[][] args)
{
  A a = new A;
  a.y = 1;
  foo(a);
  writefln(a.y);
  return 0;
}