DefNode: Optimize by avoiding intermediate array

lib/rubocop/ast/node/def_node.rb

@@ -31,14 +31,14 @@ def argument_forwarding?
       #
       # @return [Symbol] the name of the defined method
       def method_name
-        node_parts[2]
+        children[-3]
       end
 
       # An array containing the arguments of the method definition.
       #
       # @return [Array<Node>] the arguments of the method definition
       def arguments
-        node_parts[1]
+        children[-2]
       end
 
       # The body of the method definition.
@@ -49,33 +49,14 @@ def arguments
       #
       # @return [Node] the body of the method definition
       def body
-        node_parts[0]
+        children[-1]
       end
 
       # The receiver of the method definition, if any.
       #
       # @return [Node, nil] the receiver of the method definition, or `nil`.
       def receiver
-        node_parts[3]
-      end
-
-      # Custom destructuring method. This can be used to normalize
-      # destructuring for different variations of the node.
-      #
-      # In this case, the `def` node destructures into:
-      #
-      #   `method_name, arguments, body`
-      #
-      # while the `defs` node destructures into:
-      #
-      #   `receiver, method_name, arguments, body`
-      #
-      # so we reverse the destructured array to get the optional receiver
-      # at the end, where it can be discarded.
-      #
-      # @return [Array] the different parts of the `def` or `defs` node
-      def node_parts
-        to_a.reverse
+        children[-4]
       end
     end
   end