anchor.diff:  
   editdecl
      : '@edit' property
  +   ;
  +
  +addaliasdecl
  +   : '@addalias' name (',' name)* 'to' expression
      ;
   
   statement
  
positive.code:    | noteditdecl
     | createdecl
     | editdecl
     ;
  
  programdecl
  
negative.code:    ;
  
  describedecl
     : '@describe' property 'as' expression
     ;
  
  contentsdecl
  