Open Radar

 
Summary:
With the first developer seed of Xcode 8, clang has gotten much stricter regarding nullability — which is good! Unfortunately, it also reports false positives — which is sad.

Steps to Reproduce:
Compile the following function with `-Wnullable-to-nonnull-conversion` in the specified Xcode version as Objective–C and as Objective-C++:
```
static BOOL IsValidJSONData(NSData *const _Nullable data) {
    if (data == nil) return NO;

    return nil != [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:NULL];
}
```

Expected Results:
While the implementation is absurdly wasteful, the code above should compile without warnings (let alone errors). This happens regardless if compiled as Objective–C or Objective–C++.

Actual Results:
When compiled as Objective–C, the code compiles without errors or warnings. When compiled as Objective–C++, however, there’s a warning that the parameter passed to `+[NSJSONSerialization JSONObjectWithData:options:error:]` could be nil — which is obviously wrong, since there is no way that the constant could have been changed.

Notes:
This does not happen on Xcode 7. In fact, marking a nullable parameter as const, and then performing a nil check is how I silenced these warnings without casts or additional local variables.