Reduce object allocation

actionview/lib/action_view/template.rb

@@ -313,7 +313,7 @@ def handle_render_error(view, e) #:nodoc:
 
       def locals_code #:nodoc:
         # Double assign to suppress the dreaded 'assigned but unused variable' warning
-        @locals.map { |key| "#{key} = #{key} = local_assigns[:#{key}];" }.join
+        @locals.each_with_object('') { |key, code| code << "#{key} = #{key} = local_assigns[:#{key}];" }
       end
 
       def method_name #:nodoc: