anchor.diff:        // also test for expression content.
       }
     }
  -  
  +
     void parserExpressionTestInvalid() {
       Map invalidCases = {
                           '': throwsArgumentError,
  
positive.code:                       new Token(")", TokenType.RBRACE)]);
      rpnTokenStreams.add([new Token("1", TokenType.VAL),
                           new Token("_", TokenType.UNMINUS)]);
      
      inputStrings.add("_(1)");
      tokenStreams.add([new Token("_", TokenType.UNMINUS),
                        new Token("(", TokenType.LBRACE),
  
negative.code: //                        'log(1,)': throws,
                          'log(1,': throwsStateError,
      };
  
      for (String expr in invalidCases.keys) {
        expect(() => lex.tokenizeToRPN(expr), invalidCases[expr]);
      }
  