Incredible. STILL NOT FIXED IN CS6.
Architecture example. Educational or Gaming Software. Main program. Thousands of "Lesson" or "Levels"s. Cannot define "Lesson" in main movie's SWC and reference from Lesson1, Lesson2, etc., because Flash CS6 doesn't allow document class of "LessonX.swf" to reside in a linked SWC of the main movie.
Instead, one must create and maintain hundreds of "dummy" lesson document classes that do absolutely nothing but inherit directly from the "Lesson" class in the SWC. Why the hel1 I cannot just assign the document class directly to the "Lesson" class in the SWC is PURE NEGLECT on Adobe's part, IMO.
The class and the symbol contents are separate. Their instantiation is separate. This is an under-the-hood problem that hasn't' been fixed. The linkage between library symbol contents and classes is ill-defined. This is why, for example, you cannot assign classes to library symbols which extend each other and expect the symbols contents to stack when you instantiate the most-derived symbol as you'd expect from an inheritance chain. Instead, only the most-derived class's symbol contents are included, and the base class, which are linked to symbols as well, do not have their symbol contents instantiated. It's incorrectly functioning, because instantiating any of those classes individually is synonymous with constructing their symbol contents, yet when instantiated as base classes, the content is simply omitted.
As far as I'm concerned, the feature is broken. I cannot use the class I need to use via a linked SWC, so the feature is broken. I'm not paying for it until it's fixed, just like I didn't pay for CS4 when I needed the "unloadAndStop" command to properly unload Captivate files I was told I could load in CS3, but couldn't because the "unload" method didn't completely unload the loaded content. I'm not paying for falsely advertised features, and since I'm not being compensated for the hundreds of hours I have to spend working around those falsely advertised and broken features, I'm not paying for them. Please fix these critical issues that are making and breaking Flash itself as a viable development platform.