parameterize

role Bop[::Zub] {
   has Zub $.bap;
};
role Foo[::Bap] {
   has Bap $.bop;
};

my $f = Str;
my $d = class {} but Bop.^parameterize($f);

my $c = class {} but Foo.^parameterize($d);

for $c.^attributes -> $a {
   my $t =  $a.type;
   say $t;
   for $t.^attributes -> $a {
      say $a.type;
   }
}