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()
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
- Copy example to editor
- Call code prompt
- The prompt result is not as expected
Additional Notes
No response
Log File
No response
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- 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