anchor.diff:     | noteditdecl
      | createdecl
      | editdecl
  +   | addaliasdecl
      ;
   
   programdecl
  
positive.code: 
  editdecl
     : '@edit' property
     ;
  
  statement
  
negative.code:    ;
  
  describedecl
     : '@describe' property 'as' expression
     ;
  
  contentsdecl
  