How do I convert integer to cardinal on the fly?

[ToddAndMargo via perl6-users]

Hi All,

What am I doing wrong here?

> my int16 $x = 0xABCD;
-21555

> say $x.base(16);
-5433

> my uint16 $y = $x.uint16;
No such method 'uint16' for invocant of type 'Int'
  in block <unit> at <unknown file> line 1

Many thanks,
-T