Possibility to "resolve" a functions return type?

[snwflake]

Given the following scenario:

---@class thing
local thing = {}

---@class subThing
thing.subThing = {

  ---@class amazingTbl
  ---@field a number
  ---@field b number
  ---@field c number
  ---@return amazingTbl
  doStuff = function ()
    return {
      a = 1,
      b = 2,
      c = 3,
    }
  end,
}

thing.subThing.doStuff()

while I guess it is working as expected (hence why this is posted in discussions rather than as an issue) to just have the generic type displayed as the return value, I was wondering if there is an option to make that more elaborate.

My use-case is a configuration table, with a multitude of keys, subtables and whatnot.

I'd like something akin to:

function doStuff()
  -> table {
       a: number,
       b: number,
       c: number
     }

as the docstring, is that possible?

I have tried to define amazingTbl in a multitude of ways, and also tried annotating doStuff() with ---@type fun(), ---@param;@return to no avail.

[carsakiller]

Your return value is { a: number, b: number, c: number}, it is just presented as the alias amazingTbl. You should receive correct completions and type checking. Is this question mainly just about the alias name being displayed when hovering instead of the value the alias represents?

[snwflake]

Yes, pretty much. I'm primarily struggling with semantics to be fair.

Consider the following RGB type:

---@class RGB
---@field r number
---@field g number
---@field b number
---
---@param hex string
---@return RGB
function foo:hexToRgb(hex)
  local hex = hex:gsub('#', '')

  return {
    r = tonumber("0x" .. hex:sub(1, 2)) / 255,
    g = tonumber("0x" .. hex:sub(3, 4)) / 255,
    b = tonumber("0x" .. hex:sub(5, 6)) / 255
  }
end

The general type-checking, completions and whatnot will all work, but how do you deduce what RGB really is by just bringing up the function definition in the auto-complete? You only see the type. Is it a table? Is it just 3 values? Named table?

I can omit the type definition for RGB, which in turn will then just display table as the return type, which compared to this, is actually better, because that's a known type.

[carsakiller]

Yeah, until you assign a value, there is no real way to know what the return type is

You could instead define an alias that will instead display its values when hovering:

---@alias RGB {r: number, g: number, b: number}

---@param hex string
---@return RGB
function foo:hexToRgb(hex)
  local hex = hex:gsub('#', '')

  return {
    r = tonumber("0x" .. hex:sub(1, 2)) / 255,
    g = tonumber("0x" .. hex:sub(3, 4)) / 255,
    b = tonumber("0x" .. hex:sub(5, 6)) / 255
  }
end

local val = foo:hexToRgb("#ffffff")

Perhaps the hover popup should show the type as RGB{}, similar to how TypeScript will show string[], for example, for a function that returns an array of strings. This would be its own issue.

[snwflake]

An alias would definitely work for above use case, but not for my actual use case. Imagine how a table with ~30 odd keys nested over 4 levels would look x)

I agree that the type should show up. Maybe this can overall get some love.
I'll create an issue from this discussion and edit my initial post, seeing that I did not explain my intentions very well, which was probably due to sleep deprivation (much like it is now).