Best Warning Message Ever

From my diagnostic warning messages today:

Instantiating NSNavExpansionButtonCell (superclass of the also dead NSDisclosureButtonCell), which is a private class not used by the AppKit and will be removed. Use an NSButton with NSRoundedDisclosureBezelStyle instead. You can drag one out in IB. Break on _NSInstantiatingDeadDisclosureButton to debug. This will be logged only once. This may break in the future.

Now that is how to deprecate a function. It explains what the problem is, what you should do to fix it, how to generate the code to fix it, and how to find where you're using it. Awesome.