In type-checking, what are generic functions?

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#1

I tried my best to understand what they are but couldn’t get a single hint of what it is.

My hypothesis that they are just the equivalent of typeof(“function parameter here”) put in <> but I’m obviously wrong

#2

Generics let you specify a type which is passed down as a parameter to wherever that parameter may be used. They exist so that you don’t have to create a new type for every single type annotation that you need to use.

So instead of

type numberArray = {number}
type stringArray = {string}
type boolArray = {boolean}

local function test1(arg: numberArray)
	-- insert code
end

local function test2(arg: stringArray)
	-- insert code
end

local function test3(arg: boolArray)
	-- insert code
end

you can just do:

type array<T> = {T}

local function test1(arg: array<number>)
	-- insert code
end

local function test2(arg: array<string>)
	-- insert code
end

local function test3(arg: array<boolean>)
	-- insert code
end

And as for generic functions, I’m not totally sure. But from what I can see, it allows you to pass down specific types for function parameters (if the function returns a value).

local function test<T>(array: {T}): {T}
	-- do stuff with array
	
	return array
end

local num: {string} = test({5, 3}) -- Type `{number}` could not be converted to `{string}`

You can read more about them in these posts:
Generic’s in Lua, how to use them? - Help and Feedback / Scripting Support - DevForum | Roblox
Typechecking generics don’t make sense - Help and Feedback / Scripting Support - DevForum | Roblox