When the wrappers come across an expression that is used as default parameter value, e.g. "x=SomeType::SomeVal", they must add qualifiers as necessary so that the wrapper code will compile. For example, the qualified expression might be "vtkMyClass::SomeType::SomeVal".
There was already some code in the wrappers that did this, but it was only able to handle constants that were members of the class, and wasn't capable of handling typedefs or enum classes. The new code is more compact and more complete.