anchor.diff:      Expression expression = parsePrimaryExpression('[]');
       expect(expression, isNotNull);
       assertNoErrors();
  -    expect(expression, new isInstanceOf<ListLiteral>());
  -    ListLiteral literal = expression;
  +    var literal = expression as ListLiteral;
       expect(literal, isNotNull);
     }
   
  
positive.code:     TypedLiteral literal = parseListOrMapLiteral(null, '[1]');
      expect(literal, isNotNull);
      assertNoErrors();
      expect(literal, new isInstanceOf<ListLiteral>());
      ListLiteral listLiteral = literal;
      expect(listLiteral.constKeyword, isNull);
      expect(listLiteral.typeArguments, isNull);
      expect(listLiteral.leftBracket, isNotNull);
  
negative.code:     Expression expression = parseAssignableExpression('super.y', false);
      expect(expression, isNotNull);
      assertNoErrors();
      var propertyAccess = expression as PropertyAccess;
      EngineTestCase.assertInstanceOf((obj) => obj is SuperExpression,
          SuperExpression, propertyAccess.target);
      expect(propertyAccess.operator, isNotNull);
  