Open Radar

 
Summary:
When a C-function is passed a weak variable for a nonnull argument the compiler should elicit a warning that the provided variable could be `nil` and therefore is not save to pass to a nonnull argument.

Example:


// Function
static void _Foo(MyObject * __nonnull bar)
{
    bar->_fooCount++;
}

// MyObject
@implementation MyObject
{
    NSInteger _fooCount;
}

- (void)asyncFoo
{
    __weak typeof(self) weakSelf = self;
    dispatch_async(SomeQueue(), ^{
        _Foo(weakSelf); // <-- should warn against nil being passed!  Will crash!
    });
}

@end


Steps to Reproduce:
Implement code like the example above

Expected Results:
Compiler elicits a warning (which we'd elect to treat as an error)

Actual Results:
No compiler warning.  In fact, the static analyzer does not yield a warning either!

Notes:
We consider this critical to safety and stability

Version/Build:
Xcode 9.3

Configuration:
macOS High Sierra