Function wrapper that changes the return value

[Periapsises]

I'm trying to make a wrapper for a function that changes the return value of the function passed.
Here is an example of what I'm trying to achieve.

---@class Result<T>: { value: T, error: string }

---@generic T
---@param func fun(): T
---@return fun(): Result<T>
local function wrap(func) end

---@return boolean
local function myFunc() end

local myFuncWrapped = wrap(myFunc)

print( myFuncWrapped().value ) -- `value` should be a boolean

I don't know if I'm just doing it wrong or if it's not possible given the current state of generics.

[CppCXY]

Are you referring to this? LuaLS indeed does not have a well-implemented generic system.

[Periapsises]

Yes!
That's how I would be expecting it to work, is that preview using LuaLS?

[CppCXY]

No, the author doesn't have time to update it in the near future; this is a different plugin.

[Periapsises]

Oh, I see!
Thank you for the fast reply 👍

Proper generics would be really powerful, but I understand how it must be hard to implement.

At least now I know!

[CppCXY]

Proper generics would be really powerful, but I understand how it must be hard to implement.

The implementation of generics is indeed very complex. If you are interested, you can follow my language server.

[tomlau10]

In the current state of LuaLS, the workaround that I can come up with is to inline the { value: T, error: string } into the ---@return

---@generic T
---@param func fun(): T
---@return fun(): { value: T, error: string }
local function wrap(func) end

---@return boolean
local function myFunc() end

local myFuncWrapped = wrap(myFunc)

print( myFuncWrapped().value ) -- `value` is now boolean

Or you may try another plugin with better generics support as suggested by the above comment. 😃