Ctor, setters and invariant

[simendsjo]

invariant is called when a method enters. This creates problems 
if the constructor calls a setter:

import std.exception;
struct S {
   private int _i;
   public:
   this(int i) {
     this.i = i;
   }
   @property void i(int v) {
     enforce(v > 1);
     _i = v;
   }
   invariant() {
     assert(_i > 1);
   }
}
unittest {
   S(10);
}
void main() {}


In this example, invariant is called at the start if the property 
i called through the constructor. Calling setters in constructors 
is sometimes a good way to make sure everything is initialized 
properly, but as invariant is called, this becomes impossible.

Is it possible that invariant() is only called at the end of ctor 
instead of at the beginning and end of each setter when called 
from the ctor? The ctor will often have the object in an invalid 
state while constructing the object, so calling invariant() while 
in ctor will almost always create problems.

Or does anyone know a better way to solve this that doesn't 
require code duplication?