Generics don't expand alias types/don't work with other parameters

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?

Type Checking

Expected Behaviour

With a code sample like this:

---@alias TestFunction fun(abc: string): integer

---@generic T
---@param name `T`
---@param func T
local function testSecond(name, func) end

testSecond("TestFunction", function(abc) end)

I would expect abc to have a type of string, and the function to be type checked and require a return.

Actual Behaviour

Instead, abc has the any type and the function requires no return.
I further tested with a different code sample:

---@alias TestFunction fun(abc: string): integer

---@generic T
---@param name `T`
---@return T
local function testSecond(name, func) return function(abc) end end

local cool = testSecond("TestFunction", function(abc) end)
cool()

This shows no warnings and does not require me to pass any arguments to cool(), which is incorrect. Hovering over cool provides a type of 'TestFunction' and does not show the full expanded type of the alias, unlike other variables with a type of an alias. That rings the same with this code sample I also tested:

---@alias TestFunction fun(abc: string): integer

---@generic T
---@param name `T`
---@param func fun(cool: T)
local function testSecond(name, func) end

testSecond("TestFunction", function(abc) end)

where hovering over abc provides me with a 'TestFunction' unexpanded type.
However, correct behavior is seen with the following code sample using the base string type;

---@alias TestFunction fun(abc: string): integer

---@generic T
---@param name `T`
---@param func fun(cool: T)
---@return T
local function testSecond(name, func) end

local cool = testSecond("string", function(abc) abc.cool = "hi" end)
local testfind = cool:find("test")

Autocomplete is provided for :find() and abc.cool = "hi" throws the correct warning for field injection.
And most confusing of all, this code sample behaves in line with expected behavior, and the alias is fully expanded.

---@alias TestFunction fun(abc: string): integer

---@generic T
---@param name `T`
---@param func fun(cool: T)
---@return T
local function testSecond(name, func) end

local cool = testSecond("TestFunction",
    ---@param abc TestFunction
    function(abc)
        abc()
    end
)

This also doesn't work, which I kind of expected. (no warnings)

Reproduction steps

1. Paste code into project with Lua LSP on, see issue

Additional Notes

No response

Log File

No response

首先，在使用 LuaLS 的 Visual Studio Code Extension 中重现这些示例，重点关注泛型参数和 aliased function types 的类型检查。比较使用 TestFunction 的情况与使用基础 string 类型的情况。完成的标准是：别名能够一致地展开，回调参数能够获得预期类型，并且无效调用或缺少返回值时会产生警告。