my %is-no-serialize;
my SetHash $is-no-serialize .= new;

multi sub trait_mod:<is>(Attribute $a, :$no-serialize) {
    %is-no-serialize{$a.WHICH.Str} = True;
    $is-no-serialize{$a.WHICH.Str} = True;
}
class Foo {
    has u32 $.bar is required is no-serialize = 1;
    has u64 $.baz is no-serialize;
}
class Bar {
    has u32 $.bar is required is no-serialize = 1;
    has u64 $.baz is no-serialize;
}

say %is-no-serialize.keys;
say $is-no-serialize.keys;