LuaLS / LuaLS/lua-language-server
Class generics produce unusable and wrong union types
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Description
How are you using the lua-language-server?
Visual Studio Code Extension (sumneko.lua)
Which OS are you using?
MacOS, Windows
What is the issue affecting?
Completion
Expected Behaviour
Methods Peek,Push,Pop have proper type hints
Actual Behaviour
While types of a, b, c are correct the
type hints of methods are unusable with unnecessary union types.
If Push is removed from superclass, then type hints go to normal without unions but still with <T> in many places
local _lua_setmetatable = setmetatable
Stack = {}
--- @generic T
--- @class Stack<T> : {
--- Pop: (fun(self: Stack<T>): T),
--- Peek: (fun(self: Stack<T>): T),
--- Push: (fun(self: Stack<T>, value: T): Stack<T>),
--- }
--- @field protected _stack any[]
--- @field protected _count integer
Stack.__index = {}
--- Creates a new, empty stack.
--- @generic T
--- @return Stack<T>
function Stack.New()
local this = {
_stack = {},
_count = 0,
}
return _lua_setmetatable(this, Stack)
end
local st = Stack.New() --[[@as Stack<{ num: integer }>]]
local a = st:Peek()
local b = st:Pop()
local c = st:Push({})
Reproduction steps
Analyze specified code in VSCode with luals installed
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
Reproduce the issue by analyzing the Lua snippet in VS Code with lua-language-server installed, focusing on completion hints for Stack.New and the Peek, Pop, and Push methods. Compare the inferred types of a, b, and c with the expected non-union method hints; done means the methods no longer show unusable or unnecessary union types or stray generic placeholders.
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