chore: class new is now generic

lua/nvim-tree/class.lua

@@ -1,22 +1,24 @@
 ---Generic class, useful for inheritence.
 ---@class (exact) Class
----@field private __index? table
 local Class = {}
 
----@param o Class?
----@return Class
+---@generic T
+---@param self T
+---@param o T|nil
+---@return T
 function Class:new(o)
   o = o or {}
 
   setmetatable(o, self)
-  self.__index = self
+  self.__index = self ---@diagnostic disable-line: inject-field
 
   return o
 end
 
 ---Object is an instance of class
 ---This will start with the lowest class and loop over all the superclasses.
----@param class table
+---@generic T
+---@param class T
 ---@return boolean
 function Class:is(class)
   local mt = getmetatable(self)
@@ -32,7 +34,7 @@ end
 ---Return object if it is an instance of class, otherwise nil
 ---@generic T
 ---@param class T
----@return `T`|nil
+---@return T|nil
 function Class:as(class)
   return self:is(class) and self or nil
 end