anchor.diff:  parser grammar WrenParser;
   
   options { tokenVocab=WrenLexer; }
  -
   
   script: fileAtom+ EOF;
   
  
positive.code: // class statement
  classStatement
      : function
      | classGetter
      | classSetter
      | classSubscriptGet
      | classSubscriptSet
      | classOpGetter
      | classOpSetter
      | classConstructor
      ;
  
negative.code:     | GE
      | NOTEQUAL
      | IS
      ;
  classOpGetter: operatorGetter block?;
  classOpSetter: operatorSetter oneArgument block;
  oneArgument: LPAREN id RPAREN;
  subscript: LBRACK enumeration RBRACK;
  classSubscriptGet:  subscript block;
  classSubscriptSet:  subscript ASSIGN oneArgument block;
  classSetter: id assignmentSetter block;
  assignmentSetter:ASSIGN oneArgument;
  arguments: LPAREN (id (COMMA id)*)? RPAREN;
  