text: //// [additionOperatorWithNullValueAndInvalidOperator.ts]
  // If one operand is the null or undefined value, it is treated as having the type of the other operand.
  
  function foo(): void { return undefined }
  
  var a: boolean;
  var b: Object;
  var c: void;
  var d: Number;
  
  // null + boolean/Object
  var r1 = null + a;
  var r2 = null + b;
  var r3 = null + c;
  var r4 = a + null;
  var r5 = b + null;
  var r6 = null + c;
  
  // other cases
  var r7 = null + d;
  var r8 = null + true;
  var r9 = null + { a: '' };
  var r10 = null + foo();
  var r11 = null + (() => { });
  
  //// [additionOperatorWithNullValueAndInvalidOperator.js]
  // If one operand is the null or undefined value, it is treated as having the type of the other operand.
  function foo() { return undefined; }
  var a;
  var b;
  var c;
  var d;
  // null + boolean/Object
  var r1 = null + a;
  var r2 = null + b;
  var r3 = null + c;
  var r4 = a + null;
  var r5 = b + null;
  var r6 = null + c;
  // other cases
  var r7 = null + d;
  var r8 = null + true;
  var r9 = null + { a: '' };
  var r10 = null + foo();
  var r11 = null + (function () { });
  