Request/How-to: Get return type of generic function

[BribeFromTheHive]

I have a function which accepts a generic function as its parameter. It does stuff with that function, then returns that function's return value(s) as its own. I would like for the returned properties to cascade from the generic function and propogate accordingly for type information.

In TypeScript, I would do:

const foo = <T extends Function>(func: T): ReturnType<T> => func(...)

[carsakiller]

It seems that the language server is unable to infer the return type when doing this:

---@generic T : function
---@param f T
local function acceptFun(f)
    return f()
end

local function theFun(a, b)
    return tostring(a + b)
end

local result = acceptFun(theFun)

It seems we do need a @return to somehow specify it is the return of T. Something like ReturnType<T> like you showed in TypeScript.

The server is able to keep track of the types here, but obviously this is not what is needed here:

---@generic T : function
---@param f T
---@return T
local function acceptFun(f)
    return f()
end

local function theFun(a, b)
    return tostring(a + b)
end

local result = acceptFun(theFun)