anchor.diff:     */
     void _assertNegated(DartObjectImpl expected, DartObjectImpl operand) {
       if (expected == null) {
  -      try {
  +      expect(() {
           operand.negated(_typeProvider);
  -        fail("Expected an EvaluationException");
  -      } on EvaluationException {}
  +      }, throwsEvaluationException);
       } else {
         DartObjectImpl result = operand.negated(_typeProvider);
         expect(result, isNotNull);
  
positive.code:   void _assertShiftRight(
        DartObjectImpl expected, DartObjectImpl left, DartObjectImpl right) {
      if (expected == null) {
        try {
          left.shiftRight(_typeProvider, right);
          fail("Expected an EvaluationException");
        } on EvaluationException {}
      } else {
        DartObjectImpl result = left.shiftRight(_typeProvider, right);
        expect(result, isNotNull);
  
negative.code:   void _assertAdd(
        DartObjectImpl expected, DartObjectImpl left, DartObjectImpl right) {
      if (expected == null) {
        expect(() {
          left.add(_typeProvider, right);
        }, throwsEvaluationException);
      } else {
        DartObjectImpl result = left.add(_typeProvider, right);
        expect(result, isNotNull);
  