Conditional-based Type Checking

Help and Feedback Scripting Support
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#1

  1. What do you want to achieve? Be able to have a custom type whose definition is based on a conditional system.

  2. What is the issue? I don’t know how to do it (or if it’s even possible).

  3. What solutions have you tried so far? Research on the topic and trying to implement it through different operations (assertions, functions), but no luck so far.

For example, let’s say I want to have a specific type called FolderChild for Models that are children of a specific Folder.

local model = game.Workspace.Model
local folder = game.Workspace.Folder

How may I insert this condition:

(model.Parent ~= folder)

implicitly into this type definition?:

type FolderChild = Model

.
In other words, ‘embed’ this condition:

if model.Parent == folder then
    -- type of model may be FolderChild
else
    -- type of model may NOT be FolderChild (compiler throws warning)
end

Into a type, something like this (obviously this is conceptual, not actually correct)

type FolderChild = Model -> ([Parent] = folder) -- FolderChild = «a Model whose Parent property is set to Folder»

.
Yeah, I know this may be implemented easily through an external conditional system, yet I want to know if there’s a way to implicitly embed it into the type’s root definition.

Let me know if I expressed myself clearly.
Thanks in advance!

Edit: typo.