From @AlexDaniel

Submitting this ticket just to add some context for the upcoming test. The issue is already resolved after rakudo/rakudo@3de6f33 .

Code​:
role Rule {
  has Int $.number;
  has $.foo = $!number.say;
}

class Wolfram does Rule {
  has Rule $.rule .= new(​:$!number);
}

Wolfram.new​: number => 30

Result (2017.08,dea0a08545a^)​:
30
30

Result (dea0a08,HEAD(ac8e099))​:
(Int)
30

This was causing a problem with Automata​::Cellular tests ( https://github.com/dbrunton/Automata-Cellular ).