Introducing Nullable Reference Types in C#. Is there hope for D, too?

[RomanZ]

Is it possible to somehow change the concept of uninitialized 
values to something like 'zeroOrOne' instead of 'null'?


   Instrument instrument1 = new Instrument();
   Instrument instrument2 = new Instrument();

   zeroOrOne!Instrument getInstrument() {
	  zeroOrOne!Instrument instrument;
	  if( instrument1.power > 10 ) instrument = instrument1;
	  else if( instrument2.power > 5 ) instrument = instrument2;
	  return instrument;
   }

   //zeroOrOne!Instrument instead of 'InstrumentOrNull'
   auto instrument = getInstrument();

   /*1*/ instrument.setPower( 20.4f );
   /*2*/ instrument.doit();

   /*3*/ instrument1.setPower = 20;

   instrument = getInstrument();
   /*4*/ instrument.doit();
   /*5*/ instrument.setPower( 20.4f );

   /*
   1: opDispatch: setPower
   2: opDispatch: doit

   3: Instrument.setPower: 20

   4: opDispatch: doit
   4: Instrument.doit;
   5: opDispatch: setPower
   5: Instrument.setPower: 20.4
   */