I'd be easier to see those if you could send me a project that shows just the specific syntax problems you are seeing. in a project with 89 errors, most of them "expected", its hard to find the ones that are legitimate bugs; on a cursory glance, the one above was the only one that struck out as not being caused by unknown types, directly or indirectly.
e.g. ar these compiler bugs or bugs with the code base? hard to tell, given the operators you define on AppendableData themselves fail to compile due to calls to Cocoa specific APIs:
packet.variableHeader += nextMessageId() // E64 Type mismatch, cannot find operator to evaluate "AppendableData" + "UInt16"
packet.payload += topic // E62 Type mismatch, cannot assign "String!" to "AppendableData"