Allow serialising anonymous classes

[kashike]

I can totally understand not allowing deserialising anonymous classes, but serialising anonymous classes should be permitted.

[kashike]

Is this something that can happen at some point? I can look into sending a pull request if so.

[Marcono1234]

See #298 and #1510, especially the discussion on #1510. The current handling of anonymous and local classes is definitely problematic. Do you still want to submit a pull request for this?

Though I am not sure if the project members will merge it in the end if there are too many compatibility concerns.