==== tests/cases/conformance/expressions/binaryOperators/additionOperator/additionOperatorWithOnlyNullValueOrUndefinedValue.ts (4 errors) ====
    // bug 819721
    var r1 = null + null;
             ~~~~~~~~~~~
!!! Operator '+' cannot be applied to types 'null' and 'null'.
    var r2 = null + undefined;
             ~~~~~~~~~~~~~~~~
!!! Operator '+' cannot be applied to types 'undefined' and 'undefined'.
    var r3 = undefined + null;
             ~~~~~~~~~~~~~~~~
!!! Operator '+' cannot be applied to types 'null' and 'null'.
    var r4 = undefined + undefined;
             ~~~~~~~~~~~~~~~~~~~~~
!!! Operator '+' cannot be applied to types 'undefined' and 'undefined'.