Ipairs with generic

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?

Annotations

Expected Behaviour

Should have got a correct type inference in a generic function.

Actual Behaviour

1. could not specify a V-related type for result in the generic function
2. ipairs will be inferred as unknown
3. returns of the generic function will be inferred as a strange type

Reproduction steps

---@class Test
---@field name string

---@type Test[]
local tests = {
    { name = "test1" },
    { name = "test2" },
    { name = "test3" },
}

--[[
CORRECT:
    function group_by(rows: <V>[], key: string)
    -> table<string, <V>[]>
]]
---@generic V
---@param rows V[]
---@param key string
---@return table<string, V[]>
local function group_by(rows, key)
    --[[
        ---@type table<string, V[]>
        GOT: Undefined type or alias `V`.
    ]]
    local result = {}
    -- WRONG: local v: unknown
    for i, v in ipairs(rows) do
        local k = v[key]
        if not result[k] then
            result[k] = {}
        end
        table.insert(result[k], v)
    end
    return result
end

--[[
WRONG:
    local groups: table<string, <V>[]> | { [<K>]: Test }
EXPECTED:
    local groups: table<string, Test[]>
]]
local groups = group_by(tests, "name")

Additional Notes

No response

Log File

No response

Commencez par reproduire l’extrait Lua de l’issue et examinez les chemins d’annotation générique, d’accès indexé et d’inférence de types de ipairs du serveur de langage. Le travail est terminé lorsque V est accepté dans l’annotation du résultat local, que ipairs fournit le type d’élément générique et que group_by(tests, "name") est inféré comme table<string, Test[]>.