scopes of $?SELF and $?CLASS

[Stevan Little]

Hello all,

I tried to search for this answer in AES12, but I did not see anything, 
and a perl6.lang search just brought up the whole $_.method vs. 
./method debate (which was too much to shlog through).

So, onto my question, I am wondering what are the valid scopes for 
$?SELF and $?CLASS.

Are these (magical) globals who only have bound values in certain 
contexts? If that is so, what value do they have outside of a valid 
context? undef? or is attempting to accessing the value a runtime 
exception?

Or ...

Is it a syntax error to access them outside of a valid scope, and 
therefore caught at compile time? In this case, then it seems to me 
that they are not behaving as global variables so much as they are 
behaving like language keywords.

Now as for the valid contexts.

The obvious one is that they are both valid within a method. I asumme 
that $?SELF is bound to the invocant, and $?CLASS is bound to the class 
the method was defined within. It seems to me that this also mean that 
in a class method, that $?SELF == $?CLASS?

Also (IIRC) we discussed $?CLASS being valid inside a class Foo { ... } 
block at the hackathon. Would mean that something like this should be 
possible.

  class FooLoggerProxy is Foo {
      has Logger $.logger;
      for ($?CLASS.meta.superclasses()) -> $super {
          for ($super.meta.getmethods()) -> $method {
             $?CLASS.meta.add_method($method.label => method {
                  $?SELF.logger.log($method.label ~ " has been called");
                  return $method.do([EMAIL PROTECTED])
             });
                }
      }
  }

I am not sure if there are any other valid contexts other than inside a 
method or a class composition block. At least none that I can think of.

Thanks,

Stevan