Refactor extracting method visibility arguments

lib/rdoc/parser/prism_ruby.rb

@@ -885,12 +885,24 @@ def visibility_method_arguments(call_node, singleton:)
       arguments_node = call_node.arguments
       return unless arguments_node
       symbols = symbol_arguments(call_node)
-      return symbols.map(&:to_s) if symbols # module_function :foo, :bar
-      return unless arguments_node.arguments.size == 1
-      arg = arguments_node.arguments.first
-      return unless arg.is_a?(Prism::DefNode)
-      # `module_function def foo; end` or `private_class_method def self.foo; end`
-      [arg.name.to_s] if singleton ? arg.receiver.is_a?(Prism::SelfNode) : arg.receiver.nil?
+      if symbols
+        # module_function :foo, :bar
+        return symbols.map(&:to_s)
+      else
+        return unless arguments_node.arguments.size == 1
+        arg = arguments_node.arguments.first
+        return unless arg.is_a?(Prism::DefNode)
+
+        if singleton
+          # `private_class_method def foo; end` `private_class_method def not_self.foo; end` should be ignored
+          return unless arg.receiver.is_a?(Prism::SelfNode)
+        else
+          # `module_function def something.foo` should be ignored
+          return if arg.receiver
+        end
+        # `module_function def foo; end` or `private_class_method def self.foo; end`
+        [arg.name.to_s]
+      end
     end
 
     def constant_path_string(node)

test/rdoc/test_rdoc_parser_prism_ruby.rb

@@ -1007,11 +1007,17 @@ def test_undocumentable_change_visibility
     util_parser <<~RUBY
       class A
         def m1; end
-        private 42, :m1 # maybe not Module#private
+        def self.m2; end
+        private 42, :m # maybe not Module#private
+        # ignore all non-standard `private def` and `private_class_method def`
+        private def self.m1; end
+        private_class_method def m2; end
+        private def to_s.m1; end
+        private_class_method def to_s.m2; end
       end
     RUBY
     klass = @store.find_class_named 'A'
-    assert_equal [:public], klass.method_list.map(&:visibility)
+    assert_equal [:public] * 4, klass.method_list.map(&:visibility)
   end
 
   def test_method_visibility_change_in_subclass