Class Inheritance Triggers Typing Issues

[chadvandy]

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

Windows

What is the issue affecting?

Type Checking, Diagnostics/Syntax Checking

Expected Behaviour

To put it in plain terms, this is for a system of UserControls for a settings-panel system. There is a single Superclass, called "MCT.Option", which houses all of the unified behavior of all the UserControls. Then there are subclasses, for each type of UserControl - checkbox, dropdown, etc.

There's an abstracted method on the UserControl "holders", holder:get_option_by_key("user_control_key') that I have annotated as returning an MCT.Option. In reality, that superclass is never actually returned in practice - it's purely abstracted, and any option is one of the several subclasses.

So when I call:

---@type MCT.Option.Checkbox
local option = holder:get_option_by_key("i_know_this_is_a_checkbox")

I'm expecting to very easily call a conversion from superclass -> subclass.

I have all that (I think) I need to tell the debugger that it's a subclass: initial definition of the subclass is ---@class MCT.Option.Checkbox : MCT.Option, Class to tell it its parents, and it reads from the higher methods and properties completely fine.

But when I call ---@type like that, the debugger doesn't let me simply convert from one to another.

I can of course use ---@cast option MCT.Option.Checkbox after the variable is defined, but that's a bit clunkier in my opinion than having the type defined above the variable, and it ends up requiring me to reference the variable in the annotation, so it takes a bit longer to write up (and I have a lot of these!)

Actual Behaviour

Reproduction steps

1. Create a superclass:

   ---@class MySuperclass 
   local o = {}

2. Create a subclass:

   ---@class MySubclass : MySuperclass 
   local o = {}

3. Create a function that returns MySuperclass
4. Try to direct the type that returns from that function into MySublass

Additional Notes

Thank you for all the hard work you've done over the years - I've been using this extension for a very very long time and it's truly a lifesaver.

Log File

file_s%3A_modding_warhammer_3_groovy_mct.log

[sumneko]

I think it is normal.

---@class Animal
---@class Cat: Animal

---@return Animal
local function getRandomAnimal() end

---@type Cat
local cat

cat = getRandomAnimal() -- can not assign `Animal` to `Cat`