problems with grammar attributes and a solution

One could say one cannot _declare_ grammar attributes but rakudo barks only when we use them.
For more context:

https://rt.perl.org/Ticket/Display.html?id=122253
http://irclog.perlgeek.de/perl6/2015-03-11#i_10262331
rakudo/rakudo@858ac4e

Author: cognominal

S12-objects.pod

@@ -205,6 +205,12 @@ handled with lexical scoping in Perl 6.  The fact that importation
 is lexical by default also means that any names your class imports
 are also private by default.
 
+In grammars, one cannot use grammar attributes so one can call
+a grammar rule from an unrelated grammar.
+One can emulate that behavior with lexically scoped grammars created 
+within a closure. The lexical variables captured by the closure can then 
+be used where grammar attributes would be.
+
 =head2 Class composition
 
 Class declarations (in particular, role composition) are strictly