Extend with a module instead of aliasing on the singleton class

Library/Homebrew/cmd/doctor.rb

@@ -1151,15 +1151,14 @@ module Homebrew
   end
 
   def inject_dump_stats checks
-    class << checks
+    checks.extend Module.new {
-      alias_method :oldsend, :send
+      def send(method, *)
-      def send method
         time = Time.now
-        oldsend(method)
+        super
       ensure
         $times[method] = Time.now - time
       end
-    end
+    }
     $times = {}
     at_exit {
       puts $times.sort_by{|k, v| v }.map{|k, v| "#{k}: #{v}"}