gistfile1.txt

multi trait_mod:<will>(Attribute:D $attr, $block, :$lazy!) {
    $attr does role {
        method compose(|) {
            callsame();
            $attr.package.^method_table{$attr.name.substr(2)}.wrap(-> \self {
                callsame() // $attr.set_value(self, $block())
            });
        }
    }
}

class A {
    has $.a will lazy { say 'omg now'; 42 }
}

my $a = A.new;
say 'not yet';
say $a.a;
say $a.a;