anchor.diff:    void _assertBitOr(
         DartObjectImpl expected, DartObjectImpl left, DartObjectImpl right) {
       if (expected == null) {
  -      try {
  +      expect(() {
           left.bitOr(_typeProvider, right);
  -        fail("Expected an EvaluationException");
  -      } on EvaluationException {}
  +      }, throwsEvaluationException);
       } else {
         DartObjectImpl result = left.bitOr(_typeProvider, right);
         expect(result, isNotNull);
  
positive.code:    */
    void _assertStringLength(DartObjectImpl expected, DartObjectImpl operand) {
      if (expected == null) {
        try {
          operand.stringLength(_typeProvider);
          fail("Expected an EvaluationException");
        } on EvaluationException {}
      } else {
        DartObjectImpl result = operand.stringLength(_typeProvider);
        expect(result, isNotNull);
  
negative.code:   void _assertLogicalAnd(
        DartObjectImpl expected, DartObjectImpl left, DartObjectImpl right) {
      if (expected == null) {
        expect(() {
          left.logicalAnd(_typeProvider, right);
        }, throwsEvaluationException);
      } else {
        DartObjectImpl result = left.logicalAnd(_typeProvider, right);
        expect(result, isNotNull);
  