anchor.diff:  
   parenthesized_expression : '(' expression_element_list? ')'  ;
   expression_element_list : expression_element (',' expression_element)* ;
  -expression_element : expression | identifier ':' expression  ;
  +expression_element : expression | identifier ':' expression | operator ;
   
   // GRAMMAR OF A WILDCARD EXPRESSION
   
  
positive.code:  : '('  balanced_tokens? ')'
   | '[' balanced_tokens? ']'
   | '{' balanced_tokens? '}'
   | identifier | expression | context_sensitive_keyword | literal | operator
  // | Any punctuation except ( ,  ')' , '[' , ']' , { , or } TODO add?
   ;
  
  
negative.code: /*
   * alexsaveliev: added comma-separate tokens to support
   * @available(*, unavailable, message="Please wrap your tuple argument in parentheses: 'print((...))'")
   * alexsaveliev: multiple identiiers/literals in a row to support "@available(iOS 9.0, OSX 10.11, *)"
   */
  balanced_tokens
   : balanced_token+
  