How to allow the injection of new fields to avoid "fields cannot be injected" error?

[Dennis1000]

How to allow the injection of a new field to a predefined class?

---@class A
---@type A
local a={}

function a:newfunc() end  -- <- Error, "Fields cannot be injected"

Is there a better way instead of redefining and casting to a new extended class like this:

---@class A
---@type A
local a={}

---@class B : A
---@field newfunc function
---@cast a B

function a:newfunc() end

How about adding a @inject or something

---@class A
---@type A
local a={}

---@inject
function a:newfunc() end 

or is there an alternative that I haven't found yet? Thanks

[carsakiller]

There are a few options:

1. You are allowed to inject directly into a class definition:

---@class A
local a = {}

function a:myFunction() end

2. Define the injected field:

---@class A
---@field myFunction? fun(self: A, a: string): boolean

---@type A
local a = {}

function a:myFunction(a)
	return true
end

[Dennis1000]

2.) was what I've searched for - injecting a function AFTER the class function was made in another file by declaring the new functions as optional. Thanks!

[Dennis1000]

Works multiple times as well:

---@class A
...

---@type A
local a = {}

---@class A
---@field myFunction? fun(self: A, a: string): boolean
function a:myFunction(a)
	return true
end

...

---@class A
---@field myFunction2? fun(self: A, a: string): boolean
function a:myFunction2(a)
	return true
end

a:myFunction('test1')    <-- no error now shown
a:myFunction2('test2')   <-- no error now shown