I unintentionally compiled the following statement:

```
manager.groupName - lastGroupName;

```

Instead of:

```
manager.groupName = lastGroupName;

```

I am trying to understand why the compiler does not even provide a warning for the former statement I unintentionally provided. The statement has no effect, even it if is legal to subtract pointers from one another.

Both groupName and lastGroupName are of type (NSString \*).
The groupName property is declared as:

```
@property (nonatomic, retain) NSString *groupName;

```

Wondering if I should visit bugreporter or if there is a reason that XCode isn't providing a diagnostic.