fake-trust.raku

use v6.d;

class A {
    has $!a = 'private';
    method !a { $!a }
}

multi sub trait_mod:<is>(Mu:U \obj, :$spying!) {
    A.^add_trustee(obj);
    A.^compose;
}

class B is spying(A) {
    has A $.a = A.new;
    method m { say $!a!A::a }
}

B.new.m;