fix(class): use rawset during instantiation

If classes use a __newindex method it may lead to unexpected behaviour.

imports/class/shared.lua

@@ -63,17 +63,17 @@ function mixins.new(class, ...)
     if constructor then
         local parent = class
 
-        function obj:super(...)
+        rawset(obj, 'super', function(self, ...)
             parent = getmetatable(parent)
             constructor = getConstructor(parent)
 
             if constructor then return constructor(self, ...) end
-        end
+        end)
 
         constructor(obj, ...)
     end
 
-    obj.super = nil
+    rawset(obj, 'super', nil)
 
     if next(obj.private) then
         local private = table.clone(obj.private)