How to get children of an instance using typecheck

[LerpSoh]

So I want to be able to get a children of an instance by typechecking but when doing that it return the properties of the instance too and I don’t know how to filter it out. I have tried doing HTTP api but it take too long to do and much code to solve

local Service = game:GetService("ServerScriptService")
type Server = typeof(Service)

local Part = Instance.new("Part")
Part.Parent = Service

local Table : Server = {}
Table. --Show all the properties and children

[LerpSoh]

Found a soultion

How to 'trick' Luau Typechecking into returning Instance classes based on function arguments?

You can actually typeof the Instance.new function and override your function with it. type __new = typeof(Instance.new) local Create: __new = function(Name: string) return Instance.new(Name) end :: any -- Unneeded, but using for Forward-Compatibility Create("Part") -- Now it works! -- Do note, we lose the argument names with this

[LerpSoh]

Turn out there something different between a period and a colon

[gertkeno (Gert)]

You can use typeof(child) and child:IsA("type") to determine the types of children at run-time. If you just want the linter to assume a type you can use child :: type but it won’t do any conversions.

If this doesn’t solve your problem could you explain more about what you are trying to do? A code snippet of iterating over children and how you want types to interact with said children?

[LerpSoh]

I’m trying to replica the solution made by MagmaBurnsV but with the FindFirstChild function but it somehow doesn’t work like it supposed to. I assumed it because of the period and the colon. The purpose of doing this is to autofill a specific function parameter like the Create function from MagmaBurnsV post.

[LerpSoh]

And also some how work with

type __new = typeof(function(a:"b"|"c") end)

local Create: __new = function(Name: string)
	return Instance.new(Name) -- Doesn't matter
end :: any

Create("b") --auto fill "b" and "c"

[gertkeno (Gert)]

Yeah Luau is evolving quickly, that post from last year is definitely out of date.

So you need a function to return a Instance.new and have the type checker know what type it is? It might be best to declare the type of the variable at it’s call site

local new_part: Part = Create("Part")

[gertkeno (Gert)]

That is because string literals are acceptable types, the result of that Create function is missing type annotations though.

Type checking

[LerpSoh]

Well… sort of but with FindFirstChild function. Here the current code I can came up with

local Service = game:GetService("ServerScriptService")
type Server = typeof(Service.FindFirstChild) --Set typeof for FindFirstChild function

local Part = Instance.new("Part")
Part.Parent = Service

local Find: Server = function(Name:string) -- Should automatically set the FindFirstChild parameters to the functions
 return Service:FindFirstChild(Name)
end

Find("") -- No autofill showing

[gertkeno (Gert)]

Aha, yeah Luau doesn’t currently support that. It would be an engine-level thing, or you would have to type out all the string literals you want. The autofill for children is a relative new feature to begin with!

You might notice hovering over game:GetService objects and relative paths from script.Parent are all typed with any but still get auto-fill for properties and children. This is a pretty hacky feature at the moment, Luau can decay these to just any without autofill in a number of situations.

[LerpSoh]

Ooh thanks for explaining me everything. Now I just realized it like that one old post I posted that is related to OOP but work the same thing am trying to achieve above just different approach Function as variable should work like it should