LuaLS / LuaLS/lua-language-server

When the subclass inherits the constructor of the parent class, generics do not work (the type of `self` cannot be used for annotation)

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Dominant language
Lua
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Description

How are you using the lua-language-server?

Other

Which OS are you using?

Windows

What is the issue affecting?

Annotations, Type Checking

Expected Behaviour

---@class Vehicle
Vehicle = {}

---comment
---@generic T
---@param self `T`
---@param o? T
---@return T
function Vehicle:new(o)
  o = o or {}
  setmetatable(o, self)
  self.__index = self
  return o
end

---@class Plane: Vehicle
Plane = {}

setmetatable(Plane, { __index__ = Vehicle })

local obj = Plane.new()

图片

图片

The code prompt given when calling a constructor annotated with generic parameters that is inherited by a subclass is incorrect.

The prompt message should be

 function Plane.new(self: Plane, o?: Plane)

And the type of the obj variable in the code hint should be Plane instead of unknown

Actual Behaviour
---@param o? self
---@return self
function Vehicle:new(o)
  o = o or {}
  setmetatable(o, self)
  self.__index = self
  return o
end

self should be used to refer to the type of the method caller. And the self method should replace the generic method to annotate the type in this use case

Such type annotations should work, and code completion should show self as the caller's type

Reproduction steps
  1. Copy example to editor
  2. Call code prompt
  3. The prompt result is not as expected
Additional Notes

No response

Log File

No response

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the provided Vehicle and Plane example in the editor and trace constructor generic and self-type inference for inherited methods. Verify the code prompt shows function Plane.new(self: Plane, o?: Plane) and that the inferred type of obj is Plane rather than unknown.

Written by the indexing model from the issue text.

Assessment

Tech stack
lua
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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