internal override void TrySetFaulted(out State state, out Func <bool> postscript, Exception exception)
 {
     state      = new FaultedState(exception);
     postscript = TryPostscript;
 }
 internal override void SetFaulted(out State state, out Action postscript, Exception exception)
 {
     state      = new FaultedState(exception);
     postscript = Postscript;
 }