Best way to implement something like an abstract base class?

I'm working on a framework where users of it implement a kind of module that mixes their provided logic with some optional event handlers.

Here is a simple example

-- provided by framework
---@class Base
---@field OnClick fun(self: Base, x: number, y: number)
local base = {}

---@generic T: Base
---@param name `T`
---@return T
function New(name)
	return setmetatable({}, {__index = base})
end

-- usage of framework by user

---@class MyImpl: Base
local foo = New("MyImpl")

function foo:OnClick(x, y) -- x and y are inferred as any instead of number :(
end

function foo:myHelperFunction()
end

So I expect the user to implement OnClick and fill it with their logic. My goal here is that the user automatically gets the correct types on the parameters for foo:OnClick. Here in this simple example it's just two numbers, but my real app has like > 10 such methods and some of these take complex types as parameters.

With the code above it doesn't know anything about the parameters in OnClick and shows them as any. Maybe I got something wrong with the generics, but even without all the fancy generic stuff (just @return base on New) it's the same problem.

The only work-around I found was to not use @class on the user-defined class and not define a generic, this makes the parameters on the OnCLick function definition correct! However, it now triggers injected-field on all user-defined values not defined in the base class like the myHelperFunction method :(

重現 issue #2453 中附有註解的 Lua 範例，並檢查 language server 如何處理泛型回傳值、繼承的方法以及使用者新增的欄位。完成標準是：被覆寫的 OnClick 參數會被推斷為 number，而使用者定義的方法（例如 myHelperFunction）不會產生注入欄位診斷。