Cannot parse def self.use(...) in Ruby 2.6

actionpack/lib/action_controller/metal.rb

@@ -218,16 +218,13 @@ def self.inherited(base) # :nodoc:
       super
     end
 
-    # Pushes the given Rack middleware and its arguments to the bottom of the
-    # middleware stack.
-    if RUBY_VERSION >= "2.7"
-      def self.use(...)
-        middleware_stack.use(...)
-      end
-    else
-      def self.use(*args, &block)
+    class << self
+      # Pushes the given Rack middleware and its arguments to the bottom of the
+      # middleware stack.
+      def use(*args, &block)
         middleware_stack.use(*args, &block)
       end
+      ruby2_keywords(:use) if respond_to?(:ruby2_keywords, true)
     end
 
     # Alias for +middleware_stack+.