swift234

Mark decls that are illegal due to generic inside non-generic decl or non-generic inside generic decl with setInvalid(), and avoid assertions
trying to set the superclass on classes in such situations by setting the superclass of an invalid decl to the error type.

This fixes a bunch of compiler crashes, and also changes some errors in other tests where the main error is the invalid declaration and now the
downstream errors can be a bit different because the decl has been invalidated.