LuaLS / LuaLS/lua-language-server

Wrong type for generic

Open
#2,194 1 comment 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

enhancement
Dominant language
Lua
Stars
4.4k
Forks
442
PR merge metrics
No merged PRs in 30d

Description

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

MacOS

What is the issue affecting?

Type Checking

Expected Behaviour
---@class lanes.Lane<TResult...> : { [integer] : TResult... }

---Arg must be a fun!
---@generic TReturn..., TParams...
---@param func fun(...: TParams...): TReturn...
---@return fun(...: TParams...): lanes.Lane<TReturn...>
function lanes.gen(func) end


---@param a number
---@param b number
---@return number
local function add(a, b)
    return a + b
end

local test = lanes.gen(add)
local x = test(1, 2)[1]

that x show up as a number

Actual Behaviour

x is <TResult...>

Screenshot 2023-07-04 at 20 50 11
Reproduction steps

Use the code above

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 with the Lua snippet in the report and reproduce the type-checking result in the Visual Studio Code extension. Trace how generic return types are inferred for lanes.gen and verify the inferred type of x. Done means the example reports x as a number rather than <TResult...>.

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

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.