From @TimToady

22​:28 < TimToady> m​: say class { has Int​:D $.foo is default(0) }.new
22​:29 <+camelia> rakudo-moar 472ea0​: OUTPUT«===SORRY!=== Error while
compiling /tmp/WV7JjqRYN7␤Variable definition of type Int​:D requires an
  initializer␤at /tmp/WV7JjqRYN7​:1␤------> class { has
Int​:D $.foo is default(0) ⏏}.new␤ expecting any of​:␤
  constraint␤»
22​:29 < TimToady> I don't think that one should require an initializer
22​:29 -!- coetry [~allen@​c-50-171-35-243.hsd1.tx.comcast.net] has quit
[Quit​: Lost terminal]
22​:29 -!- allen [~allen@​c-50-171-35-243.hsd1.tx.comcast.net] has quit
[Quit​: Lost terminal]
22​:30 < TimToady> m​: my Int​:D $x is default(0);
22​:30 <+camelia> rakudo-moar 472ea0​: OUTPUT«===SORRY!=== Error while
compiling /tmp/p5BBLy48x8␤Default value '0' will never bind to a
  parameter of type Int​:D␤at /tmp/p5BBLy48x8​:1␤------> my
Int​:D $x is default(0)⏏;␤ expecting any of​:␤ constraint␤»
22​:30 < TimToady> say wot?
22​:31 < TimToady> is that one bug or two?
22​:32 < TimToady> m​: my Int​:D @​array is default(0); @​array[0] = Nil;
22​:32 <+camelia> rakudo-moar 472ea0​: OUTPUT«===SORRY!=== Error while
compiling /tmp/MpVmByHAQM␤Default value '0' will never bind to a
  parameter of type Array[Int​:D]␤at
/tmp/MpVmByHAQM​:1␤------> my Int​:D @​array is default(0)⏏; @​array[0] =
Nil;␤ expecting
  any of​:␤ co…»
22​:33 < TimToady> two and a half?

From @FROGGS

Patch​: rakudo/rakudo@80a3d07235
Tests​: Raku/roast@071720b28d

Closing ticket.

@FROGGS - Status changed from 'new' to 'resolved'