[boost] [TypeErasure] assignment operator of any references

Hi, The References section constains this example: int i, j; any<typeid_<>, _self&> x(i), y(j); x = y; // error The following basic c++ code int i=1, j=0; int& x(i); int& y(j); x = y; // [1] works and the expected value of x after [1] is 0. Which concept requirements should I add to make the following work? assignable? int i, j; any<mpl::vector<typeid_<>, ...>, _self&> x(i), y(j); x = y; // no error Best, Vicente