From andjrob@gmail.com

The spec says you should be able to use <​::($name)>, but rakudo doesn't work.

me>
n​: grammar G { rule TOP {^ <A>+ $}; regex B($what) { <​::($what)> };
regex C { 'test' }; regex A { <B('C')> }; }; say G.parse('testtest')

p6eval>
niecza v24-35-g5c06e28​: OUTPUT«｢testtest｣␤ A => ｢test｣␤ B => ｢test｣␤
:​:($what) => ｢test｣␤ A => ｢test｣␤ B => ｢test｣␤ :​:($what) =>
｢test｣␤␤»

me>
r​: grammar G { rule TOP {^ <A>+ $}; regex B($what) { <​::($what)> };
regex C { 'test' }; regex A { <B('C')> }; }; say G.parse('testtest')

p6eval>
rakudo 25a9d6​: OUTPUT«No such method 'QAST​::Var<1988309812>' for
invocant of type 'G'␤ in regex B at /tmp/RtzoutigI0​:1␤ in regex A at
/tmp/RtzoutigI0​:1␤ in regex TOP at /tmp/RtzoutigI0​:1␤ in method
parse at src/gen/CORE.setting​:10941␤ in block at
/tmp/RtzoutigI0​:1␤␤»

From @diakopter

14​:17 <diakopter> m​: grammar G { rule TOP {^ <A>+ $}; regex B($what) { <​::($what)> }; regex C { 'test' }; regex A {
  <B('C')> }; }; say G.parse('testtest')
14​:17 <camelia> rakudo-moar 61d231​: OUTPUT«｢testtest｣␤ A => ｢test｣␤ B => ｢test｣␤ A => ｢test｣␤ B => ｢test｣␤»

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