Yes, still going with this. My impression is that there's this powerful facility in Raku, which is not really easy to use, and there's so little documentation for that. I'd like to kind of mitigate that.

In this case, I'm trying to force attributes to be read-only by default, to make immutable classes. Here's my attempt:

my class MetamodelX::Frozen is Metamodel::ClassHOW {

    method compose_attributes($the-obj, :$compiler_services) {
        my $attribute-container = callsame;
        my $new-container = Perl6::Metamodel::AttributeContainer.new(
                :attributes($attribute-container.attributes),
                :attribute_lookup($attribute-container.attribute_table),
                :0attr_rw_by_default
                );
        $new-container.compose_attributes($the-obj, $compiler_services);
    }
}

my package EXPORTHOW {
    package DECLARE {
        constant frozen = MetamodelX::Frozen;
    }
}

I'm calling that from a main function that looks like this:

use Frozen;

frozen Foo {
    has $.bar;

    method gist() {
        return "→ $!bar";
    }
}

my $foo = Foo.new(:3bar);

say $foo.bar;

$foo.bar(33);

I'm trying to follow the source, that does not really give a lot of facilities to change attribute stuff, so there seems to be no other way that creating a new instance of the container. And that might fail in impredictable ways, and that's what it does:

Type check failed in binding to parameter '$the-obj'; expected Any but got Foo (Foo)
at /home/jmerelo/Code/raku/my-raku-examples/frozen.raku:7

Not clear if this is the first the-obj or the second one, but any way, some help is appreciated.