It seems like an horribly expensive shenanigan to me. F# can do all the work that you described at compile time using type providers with no runtime cost and no need for a call to pledge()... What will happen if someone forgets to call pledge? Or, even worse, if someone calls pledge and then he does some other dynamic operation? Or if he calls pledge at the right time but one thread has been rescheduled and when it is executed again it will continue to issue dynamic instructions?