[ruby/rdoc] ClassModule#superclass= accepts a ClassModule as an

argument
(https://github.com/ruby/rdoc/pull/1222)

It is necessary for ClassModule's instance variable @superclass to
always be a String (or nil) so that the class can be saved with
`#marshal_dump` and loaded with `#marshal_load`.

However, there's no type checking being done, which allows a bug like
the one reported in #1221 (which was introduced in #1217) that sets
superclass to a ClassModule. That bug requires:

- setting a superclass to a NormalClass
- marshal_save
- marshal_load (which raises an exception)

With this change, passing a ClassModule to ClassModule#superclass= is
explicitly allowed by saving the full name of the ClassModule in the
@superclass instance variable.

9ced6d534c

lib/rdoc/code_object/class_module.rb

@@ -705,10 +705,23 @@ class RDoc::ClassModule < RDoc::Context
 
   ##
   # Set the superclass of this class to +superclass+
+  #
+  # where +superclass+ is one of:
+  #
+  # - +nil+
+  # - a String containing the full name of the superclass
+  # - the RDoc::ClassModule representing the superclass
 
   def superclass=(superclass)
     raise NoMethodError, "#{full_name} is a module" if module?
-    @superclass = superclass
+    case superclass
+    when RDoc::ClassModule
+      @superclass = superclass.full_name
+    when nil, String
+      @superclass = superclass
+    else
+      raise TypeError, "superclass must be a String or RDoc::ClassModule, not #{superclass.class}"
+    end
   end
 
   ##