# Lexical class

    my $grammar = grammar {...};  # anonymous
    my grammar x {...};  # named
    our grammar x {...};  # named, visible from outside

    grammar.rule - looks up in "current-namespace"::grammar
    # lookup_method( $grammar, 'rule' )
    
    'our' classes have also a native-namespace representation, for p5 compatibility
    
AST operations
    
- enumerate seen classes
because unseen classes need wrapping
mark the unseen class as 'native', because it may be a p5 class
which doesn't have lookup_method()

- replace meth(...) with lookup_method(...)
- replace sub(...) with %class{sub}(...)

- add 'is export' classes to @EXPORT
if it makes sense

---
# xxx desugaring a class
# create a metaclass
# the class definition is itself inside a closure
INIT { _build_metaclass() }
my $_METACLASS_X := create_metaclass();
my $_CLASS_X := $_METACLASS_X.create_instance;  # 'our' also generates a namespace
_build_metaclass {
    my $meta = $_METACLASS_X.HOW;
    $meta.add_method( 'x', sub { ... } );
}
$_CLASS_X.call_method( 'x' );

---
# xxx desugaring a class
# create a prototype
# the class definition is itself inside a closure
INIT { _build_class() }
my $_CLASS_X := create_class( 'Class' );  # 'our' also generates a namespace
_build_class {
    my $meta = $_CLASS_X.HOW;
    $meta.add_method( 'x', sub { ... } );
}
$_CLASS_X.HOW.call_method( 'x' );