anchor.diff:      ;
   
   forBlock
  -    : 'for' '(' forIterator ')' block
  -    -> forIterator ^(LOOP_BLOCK block)
  +    : 'for'^ '('! forIterator ')'! block
       ;
   
   failBlock
  -    : 'fail' block
  -    -> ^(FAIL_BLOCK block)
  +    : 'fail'^ block
       ;
   
   forIterator
  
positive.code:     POS_ARG_LIST;
      POSTFIX_EXPR;
      PRIMARY;
      RET_STMT;
      RETRY_STMT;
      SATISFIES_EXPR;
      SEQ_ARG;
      SPECIAL_ARG;
      THROW_STMT;
      TRY_BLOCK;
      TRY_CATCH_STMT;
      TRY_RESOURCE;
      TRY_STMT;
      TYPE_ARG_LIST;
      TYPE_DECL;
      TYPE_NAME;
      TYPE_PARAMETER_LIST;
      TYPE_SPECIFIER;
      WHILE_BLOCK;
      WHILE_STMT;
      SWITCH_STMT;
      SWITCH_EXPR;
      SWITCH_CASE_LIST;
      TYPE_CONSTRAINT_LIST;
      TYPE;
  
negative.code:     ;
  
  objectDeclaration
      : 'object'! memberName extendedType? satisfiedTypes? classBody
      ;
  
  voidMethodDeclaration
  