Protections, ACCEPTS, and NQPRotine.md

Hello, Perl6'ers.

When dealing with objects, sometimes you'd like to keep outside code from running methods from your class. To this effect, I have tried to bring a semblance of the protected method to Perl6.

I can sum up much of the problem with the following few pieces of code.

role GTK::Roles::Protection {
  has @!prefixes;

  # cw: This is a HACK, but it should work with careful use.
  method CALLING-METHOD($nf is copy = 3) {
    my $c = callframe($nf).code;
    while $c !~~ Routine {
      my $cf = callframe(++$nf);
      die 'Exceeded backtrace when searching for calling routine' 
        if $cf ~~ Failure;
      $c = $cf.code;
      # Special casing. It's (not) FUUUN!
      next if $c.^name eq <NQPRoutine Block>.any;
      # Special casing is hell! -- Allow for shortcircuit
      $c.^name.say;
      unless  
        $c.package.^name ne <
          GLOBAL Any::IterateOneWithoutPhasers List
        >.any
        ##||
        #'is-hidden-from-backtrace' ∈ $c.^roles.map( .^name )
      { 
        $c = False;
        next;
      }
    }
    "{ $c.package.^name }.{ $c.name }";
  }

  # Do NOT use this method unless you are adding a widget. If adding widgets,
  # please be sure to use a discrete namespace for them.
  #
  # For example:
  #   - It is not sufficient to self.ADD-PREFIX('YourProject') if
  #     the YourProject:: code has non-GTK derivative code. In that case, it
  #     would be appreciated if you would put all widgets into the
  #     YourProject::Widgets namespace and then you can do:
  #         self.ADD-PREFIX('YourProject::Widgets::')
  #     in submethod BUILD.
  #
  # THANKS!
  method ADD-PREFIX($p) {
    @!prefixes.push: $p;
  }

  # Should never be called ouside of the GTK::Widget hierarchy, but
  # how can the watcher watch itself?
  method IS-PROTECTED {
    # Really kinda violates someone's idea of "object-oriented" somewhere,
    # but I am more results-oriened.
    my $c = self.CALLING-METHOD;
    # Must be done, otherwise error. Note: Regexes do not like attributes.
    #my @p = @!prefixes;
    my $t = False;
    # Hardcoded 'GTK::'. There should be a better mechanism to do this, but
    # we use what works.
    for 'GTK::', |@!prefixes {
      last if ( $t = $c.starts-with($_) );
    }
    die "Cannot call method from outside of a GTK:: object ({ $c })"
      unless $t;
    True;
  }
}

The point of this piece of code is to use the callframe function to step back through the frames to find the first non-internal routine and check if its name is acceptable.

However I am now getting this error from a piece of code that uses this protection. I thought an --ll-exception would shed some light on the topic, but unfortunately, it does not.

perl6 --ll-exception -I../cairo-p6-paths/lib -I../p6-Pango/lib -I../p6-GtkPlus/lib -Ilib t/04-simple-ui.t Cannot resolve caller ACCEPTS(Routine:U: NQPRoutine); none of these signatures match:
    (Mu:U: \topic, *%_)
    (Mu:U: Mu:U \topic, *%_)
    (Any:D: Mu:D \a, *%_)
    (Any:D: Mu:U, *%_ --> Bool::False)
    (Any:U: \topic, *%_ --> Bool)
    (Code:D $self: Mu $topic is raw, *%_)
  in method CALLING-METHOD at /home/cbwood/Projects/p6-WebkitGtk/../p6-GtkPlus/lib/GTK/Roles/Protection.pm6 (GTK::Roles::Protection) line 8
  in method IS-PROTECTED at /home/cbwood/Projects/p6-WebkitGtk/../p6-GtkPlus/lib/GTK/Roles/Protection.pm6 (GTK::Roles::Protection) line 53
  in method RESOLVE-UINT at /home/cbwood/Projects/p6-WebkitGtk/../p6-GtkPlus/lib/GTK/Roles/Types.pm6 (GTK::Roles::Types) line 80
  in block  at /home/cbwood/Projects/p6-WebkitGtk/../p6-GtkPlus/lib/GTK/Widget.pm6 (GTK::Widget) line 1169
  in block <unit> at t/04-simple-ui.t line 76

Any ideas on how to sidestep or solve this problem?