gistfile1.txt

multi trait_mod:<is>(Attribute:D $attr, :$chainymutable!) {
    $attr does role {
        method compose(Mu \package) {
            my constant NO_ARG = Mu.new;
            my $this_attr = self;
            package.^add_method:
                $this_attr.name.substr(2), # strip sigil
                method (Mu \value = NO_ARG) {
                    if value =:= NO_ARG {
                        $this_attr.get_value(self)
                    }
                    else {
                        $this_attr.set_value(self, value);
                        self
                    }
                }
            nextsame();
        }
    }
}

class Point {
    has $.x is chainymutable;
    has $.y is chainymutable;
}

my $p = Point.new.x(42).y(69);
say $p.x;
say $p.y;