anchor.diff:      expect.putIfAbsent(val, func0).equals.putIfAbsent(val, func0);
       expect.remove(val).equals.remove(val);
       expect.values.equals.values;
  -    expect.toString().equals.toString();
  +    expect.asString().equals.toString();
     }
   
     // Runs tests of Set behavior.
  
positive.code:     testInvocations(m, m2);
    }));
  
    toString() => new _Equals(equals = getWrappedObject((m2) {
      testInvocations(TO_STRING_INVOCATION, m2);
    }));
  }
  
negative.code:     expect.toList(growable: true).equals.toList(growable: true);
      expect.toList(growable: false).equals.toList(growable: false);
      expect.toSet().equals.toSet();
      expect.asString().equals.toString();
      expect.where(func1).equals.where(func1);
    }
  
  